Sean P Fleming

Interests

No activities entered.

Courses

Scholarly Contributions

Journals/Publications

• Fleming, S. P., Makris, Y., & Mehen, T. (2019). An effective field theory approach to quarkonium at small transverse momentum. Journal of High Energy Physics.
• , J. B., , S. F., & , U. v. (2021). Nonrelativistic Effective Field Theory with a Resonance Field.
  More info

  We discuss shallow resonances in the nonrelativistic scattering of twoparticles using an effective field theory (EFT) that includes an auxiliaryfield with the quantum numbers of the resonance. We construct the manifestlyrenormalized scattering amplitude up to next-to-leading order in a systematicexpansion. For a narrow resonance, the amplitude is perturbative except in theimmediate vicinity of the resonance poles. It naturally has a zero in thelow-energy region, analogous to the Ramsauer-Townsend effect. For a broadresonance, the leading-order amplitude is nonperturbative almost everywhere inthe regime of validity of the EFT. We regain the results of an EFT without theauxiliary field, which is equivalent to the effective-range expansion withlarge scattering length and effective range. We also consider an additionalfine tuning leading to a low-energy amplitude zero even for a broad resonance.We show that in all cases the requirement of renormalizability when theauxiliary field is not a ghost ensures the resonance poles are in the lowerhalf of the complex momentum plane, as expected by other arguments. Thesystematic character of the EFT expansion is exemplified with a toy modelserving as underlying theory.[Journal_ref: ]
• , Z. L., , B. M., , M. N., , X. W., & , S. F. (2021). Renormalization and Scale Evolution of the Soft-Quark Soft Function.
  More info

  Soft functions defined in terms of matrix elements of soft fields dressed byWilson lines are central components of factorization theorems for crosssections and decay rates in collider and heavy-quark physics. While in manycases the relevant soft functions are defined in terms of gluon operators, atsubleading order in power counting soft functions containing quark fieldsappear. We present a detailed discussion of the properties of the soft-quarksoft function consisting of a quark propagator dressed by two finite-lengthWilson lines connecting at one point. This function enters in the factorizationtheorem for the Higgs-boson decay amplitude of the $h\to\gamma\gamma$ processmediated by light-quark loops. We perform the renormalization of this softfunction at one-loop order, derive its two-loop anomalous dimension and discusssolutions to its renormalization-group evolution equation in momentum space, inLaplace space and in the "diagonal space", where the evolution is strictlymultiplicative.[Journal_ref: ]
• , J. B., , S. S., , S. F., & , U. v. (2020). Effective Field Theory for Two-Body Systems with Shallow S-Wave Resonances. Annals Phys..
  More info

  Resonances are of particular importance to the scattering of compositeparticles in quantum mechanics. We build an effective field theory for two-bodyscattering which includes a low-energy $S$-wave resonance. Our starting pointis the most general Lagrangian with short-range interactions. We demonstratethat these interactions can be organized into various orders so as to generatea systematic expansion for an $S$ matrix with two low-energy poles. The polepositions are restricted by renormalization at leading order, where the commonfeature is a non-positive effective range. We carry out the expansionexplicitly to next-to-leading order and illustrate how it systematicallyaccounts for the results of a toy model -- a spherical well with a delta shellat its border.[Journal_ref: Annals Phys. 422 (2020) 168283]
• , S. F., & , T. M. (2020). Hadronic Decays of the X(3872) to chi_{cJ} in Effective Field Theory. Phys.Rev.D, 78.
  More info

  The decays of the X(3872) to P-wave quarkonia are calculated under theassumption that it is a shallow bound state of neutral charmed mesons. TheX(3872) is described using an effective theory of nonrelativistic D mesons andpions (X-EFT). We calculate X(3872) decays by first matching heavy hadronchiral perturbation theory (HHchiPT) amplitudes for D^0 bar{D}^{*0} -> chi_{cJ}+ (pi^0,pi+pi) onto local operators in X-EFT, and then using these operators tocalculate the X(3872) decays. This procedure reproduces the factorizationtheorems for X(3872) decays to conventional quarkonia previously derived usingthe operator product expansion. For single pion decays, we find nontrivialdependence on the pion energy from HHchiPT diagrams with virtual D mesons. Thisnontrivial energy dependence can potentially modify heavy quark symmetrypredictions for the relative sizes of decay rates. At leading order, decays tofinal states with two pions are dominated by the final state chi_{c1} + pi^0 +pi^0, with a branching fraction just below that for the decay to chi_{c1} +pi^0. Decays to all other final states with two pions are highly suppressed.[Journal_ref: Phys.Rev.D78:094019,2008]
• , S. F., , A. K., & , T. M. (2020). Resumming the color-octet contribution to e+ e- -> J/psi + X. Phys.Rev.D, 68.
  More info

  Recent observations of the spectrum of J/psi produced in e+ e- collisions atthe Upsilon(4S) resonance are in conflict with fixed-order calculations usingthe Non-Relativistic QCD (NRQCD) effective field theory. One problem is thatleading order color-octet mechanisms predict an enhancement of the crosssection for J/psi with maximal energy that is not observed in the data.However, in this region of phase space large perturbative corrections (Sudakovlogarithms) as well as enhanced nonperturbative effects are important. In thispaper we use the newly developed Soft-Collinear Effective Theory (SCET) tosystematically include these effects. We find that these correctionssignificantly broaden the color-octet contribution to the J/psi spectrum. Ourcalculation employs a one-stage renormalization group evolution rather than thetwo-stage evolution used in previous SCET calculations. We give a simpleargument for why the two methods yield identical results to lowest order in theSCET power counting.[Journal_ref: Phys.Rev.D68:094011,2003]
• Fleming, S. P. (2020). The Large Energy Expansion for B Decays: Soft Collinear Effective Theory. ECONF C, 030603.
  More info

  I this talk I give an introduction to the soft collinear effective theory byconsidering in detail the decay rate for $B \to X_s \gamma$ near the endpoint.[Journal_ref: ECONF C030603:MEC03,2003]
• Mehen, T., Makris, Y., & Fleming, S. (2020). An effective field theory approach to quarkonium at small transverse momentum. Journal of High Energy Physics, 2020(4). doi:10.1007/jhep04(2020)122
  More info

  In this work we apply effective field theory (EFT) to observables in quarkonium production and decay that are sensitive to soft gluon radiation, in particular measurements that are sensitive to small transverse momentum. Within the EFT framework we study χQ decay to light quarks followed by the fragmentation of those quarks to light hadrons. We derive a factorization theorem that involves transverse momentum distribution (TMD) fragmentation functions and new quarkonium TMD shape functions. We derive renormalization group equations, both in rapidity and virtuality, which are used to evolve the different terms in the factorization theorem to resum large logarithms. This theoretical framework will provide a systematic treatment of quarkonium production and decay processes in TMD sensitive measurements.
• Fleming, S. P. (2018). The role of Glauber Exchange in Soft Collinear Effective Theory and the Balitsky-Fadin-Kuraev-Lipatov Equation.
  More info

  In soft collinear effective theory (SCET) the interaction between high energyquarks moving in opposite directions involving momentum transfer much smallerthan the center-of-mass energy is described by the Glauber interaction operatorwhich has two-dimensional Coulomb-like behavior. Here, we determine this$n$-$\bar{n}$ collinear Glauber interaction operator and consider itsrenormalization properties at one loop. At this order a rapidity divergenceappears which gives rise to an infrared divergent (IR) rapidity anomalousdimension commonly called the gluon Regge trajectory. We then go on to considerthe forward quark scattering cross section in SCET. The emission of real softgluons from the Glauber interaction gives rise to the Lipatov vertex. Squaringand adding the real and virtual amplitudes results in a cancelation of IRdivergences, however the rapidity divergence remains. We introduce a rapiditycounterterm to cancel the rapidity divergence, and derive a rapidityrenormalization group equation which is the Balitsky-Fadin-Kuraev-LipatovEquation. This connects Glauber interactions with the emergence of Reggebehavior in SCET.[Journal_ref: ]
• Fleming, S. P., & Zhang-Labun, O. (2016). Rapidity regulators in the semi-inclusive deep inelastic scattering and Drell-Yan processes. Physics. Rev. D, 41.
• Labun, O. Z., & Fleming, S. (2017). Rapidity regulators in the semi-inclusive deep inelastic scattering and Drell-Yan processes. Physical Review D, 95(11). doi:10.1103/physrevd.95.114020
  More info

  Office of Science, Office of Nuclear Physics of the US Department of Energy [DE-FG02-04ER41338]
• Fleming, S. P., Mereghetti, E., Fickinger, M., & Kim, C. (2016). Effective field theory approach to heavy quark fragmentation. JHEP, 095, 1611. doi:10.1007/JHEP11(2016)095
• Fleming, S. P., & Zhang-Labun, O. (2015). Rapidity Divergences and Deep Inelastic Scattering in the Endpoint Region. Phys. Rev. D, 91, 11.
• Fleming, S. P. (2014). The role of Glauber exchange in soft collinear effective theory and the Balitsky–Fadin–Kuraev–Lipatov Equation. Phys. Lett. B, 735, 6.
• Fleming, S., Leibovich, A. K., Mehen, T., & Rothstein, I. Z. (2013). Anomalous dimensions of the double parton fragmentation functions. Physical Review D - Particles, Fields, Gravitation and Cosmology, 87(7).
  More info

  Abstract: Double parton fragmentation is a process in which a pair of partons produced in the short-distance process hadronize into the final state hadron. This process is important for quarkonium production when the transverse momentum is much greater than the quark mass. Resummation of logarithms of the ratio of these two scales requires the evolution equations for double parton fragmentation functions (DPFF). In this paper we complete the one-loop evaluation of the anomalous dimensions for the DPFF. We also consider possible mixing between the DPFF and single parton power suppressed gluon fragmentation and show that such effects are subleading. © 2013 American Physical Society.
• Fleming, S., & Mehen, T. (2012). Decay of the X(3872) into χ _cJ and the operator product expansion in effective field theory. Physical Review D - Particles, Fields, Gravitation and Cosmology, 85(1).
  More info

  Abstract: We consider a low-energy effective theory for the X(3872) (XEFT) that can be used to systematically analyze the decay and production of the X(3872) meson, assuming that it is a weakly bound state of charmed mesons. In a previous paper, we calculated the decays of X(3872) into χ cJ plus pions using a two-step procedure in which Heavy Hadron Chiral Perturbation Theory (HHχPT) amplitudes are matched onto XEFT operators and then X(3872) decay rates are calculated using these operators. The procedure leads to IR divergences in the three-body decay X(3872)→χ cJππ when virtual D mesons can go on shell in tree level HHχPT diagrams. In previous work, we regulated these IR divergences with the D *0 width. In this work, we carefully analyze X(3872)→χ cJπ0 and X(3872)→χ cJππ using the operator product expansion in XEFT. Forward scattering amplitudes in HHχPT are matched onto local operators in XEFT, the imaginary parts of which are responsible for the decay of the X(3872). Here we show that the IR divergences are regulated by the binding momentum of the X(3872) rather than the width of the D *0 meson. In the operator product expansion, these IR divergences cancel in the calculation of the matching coefficients so the correct predictions for the X(3872)→χ c1ππ do not receive enhancements due to the width of the D *0. We give updated predictions for the decay X(3872)→χ c1ππ at leading order in XEFT. © 2012 American Physical Society.
• Fleming, S., Leibovich, A. K., Mehen, T., & Rothstein, I. Z. (2012). Systematics of quarkonium production at the LHC and double parton fragmentation. Physical Review D - Particles, Fields, Gravitation and Cosmology, 86(9).
  More info

  Abstract: In this paper, we discuss the systematics of quarkonium production at the LHC. In particular, we focus on the necessity to sum logs of the form log(Q/p ≥) and log(p ≥/m Q). We show that the former contributions are power suppressed, while the latter, whose contribution in fragmentation is well known, also arise in the short distance (i.e., nonfragmentation) production mechanisms. Though these contributions are suppressed by powers of m Q/p ≥, they can be enhanced by inverse powers of v, the relative velocity between heavy quarks in the quarkonium. In the limit p ≥m Q, short-distance production can be thought of as the fragmentation of a pair of partons (i.e., the heavy quark and antiquark) into the final state quarkonium. We derive an all-order factorization theorem for this process in terms of double parton fragmentation functions and calculate the one-loop anomalous dimension matrix for the double parton fragmentation functions. © 2012 American Physical Society.
• Fleming, S. (2009). Soft collinear effective theory: An overview. Proceedings of Science.
  More info

  Abstract: In this talk I give an overview of soft collinear effective theory (SCET), including a discussion of some recent advances. First, I briefly cover the foundation upon which SCET is built, namely QCD factorization, and review the theoretical framework of SCET. Next, I cover some recent calculations involving SCET. Since there are more interesting results than I can cover, I have picked four that that I find particularly exciting. The first two topics are dynamical threshold enhancements in Drell-Yan and resummation of higgs production at the LHC. Both topics center on the resummation of large Sudakov logarithms, however, for each there is a twist. In the case of threshold enhancements in Drell-Yan, it is partonic, not hadronic logarithms that are summed. In the case of higgs production at the LHC, the twist is that the logarithms are of a time-like scale. The third topic highlighted is electroweak corrections at high energy. In particular the electroweak Sudakov form factor. Finally, I end by discussing generalized event shapes in e+e- annihilation. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
• Fleming, S. P. (2009). Soft Collinear Effective Theory: An Overview. PoS EFT, 09.
  More info

  In this talk I give an overview of soft collinear effective theory (SCET),including a discussion of some recent advances. First, I briefly cover thefoundation upon which SCET is built, namely QCD factorization, and review thetheoretical framework of SCET. Next, I cover some recent calculations involvingSCET. Since there are more interesting results than I can cover, I have pickedfour that that I find particularly exciting. The first two topics are dynamicalthreshold enhancements in Drell-Yan and resummation of higgs production at theLHC. Both topics center on the resummation of large Sudakov logarithms,however, for each there is a twist. In the case of threshold enhancements inDrell-Yan, it is partonic, not hadronic logarithms that are summed. In the caseof higgs production at the LHC, the twist is that the logarithms are of atime-like scale. The third topic highlighted is electroweak corrections at highenergy. In particular the electroweak Sudakov form factor. Finally, I end bydiscussing generalized event shapes in $e^+e^-$ annihilation.[Journal_ref: PoS EFT09:002,2009]
• Fleming, S., & Mehen, T. (2009). X(3872) in effective field theory. AIP Conference Proceedings, 1182, 491-494.
  More info

  Abstract: If the X(3872) resonance is a shallow boundstate of a the charm mesons D0D̄*0 and D*0D̄0 it can be described by an effective theory of nonrelativistic D mesons coupled to nonrelativistic pions (X-EFT). In this talk, I give a brief overview of the X(3872), followed by a short review of X-EFT. I end my talk with results from calculations of the the next-to-leading-order correction to the partial decay width Γ[X→ D0D̄0π0], and the decay of X(3872) to P-wave quarkonia. © 2009 American Institute of Physics.
• Bauer, C. W., Fleming, S., Lee, C., & Sterman, G. (2008). Factorization of e+e- event shape distributions with hadronic final states in soft collinear effective theory. Physical Review D - Particles, Fields, Gravitation and Cosmology, 78(3).
  More info

  Abstract: We present a new analysis of two-jet event shape distributions in soft collinear effective theory. Extending previous results, we observe that a large class of such distributions can be expressed in terms of vacuum matrix elements of operators in the effective theory. We match these matrix elements to the full theory in the two-jet limit without assuming factorization of the complete set of hadronic final states into independent sums over partonic collinear and soft states. We also briefly discuss the relationship of this approach to diagrammatic factorization in the full theory. © 2008 The American Physical Society.
• Fleming, S., & Mehen, T. (2008). Hadronic decays of the X(3872) to χcJ in effective field theory. Physical Review D - Particles, Fields, Gravitation and Cosmology, 78(9).
  More info

  Abstract: The decays of the X(3872) to P-wave quarkonia are calculated under the assumption that it is a shallow bound state of neutral charmed mesons. The X(3872) is described using an effective theory of nonrelativistic D mesons and pions (X-EFT). We calculate X(3872) decays by first matching heavy hadron chiral perturbation theory (HHχPT) amplitudes for D0D̄ *0→χcJ(π0,ππ) onto local operators in X-EFT, and then using these operators to calculate the X(3872) decays. This procedure reproduces the factorization theorems for X(3872) decays to conventional quarkonia previously derived using the operator product expansion. For single pion decays, we find nontrivial dependence on the pion energy from HHχPT diagrams with virtual D mesons. This nontrivial energy dependence can potentially modify heavy-quark symmetry predictions for the relative sizes of decay rates. At leading order, decays to final states with two pions are dominated by the final state χc1π0π0, with a branching fraction just below that for the decay to χc1π0. Decays to all other final states with two pions are highly suppressed. © 2008 The American Physical Society.
• Fleming, S., Hoang, A. H., Mantry, S., & Stewart, I. W. (2008). Jets from massive unstable particles: Top-mass determination. Physical Review D - Particles, Fields, Gravitation and Cosmology, 77(7).
  More info

  Abstract: We construct jet observables for energetic top quarks that can be used to determine a short-distance top quark mass from reconstruction in e+e- collisions with accuracy better than ΛQCD. Using a sequence of effective field theories we connect the production energy, mass, and top width scales, QmΓ, for the top jet cross section, and derive a QCD factorization theorem for the top invariant mass spectrum. Our analysis accounts for αs corrections from the production and mass scales, corrections due to constraints in defining invariant masses, nonperturbative corrections from the cross talk between the jets, and αs corrections to the Breit-Wigner line shape. This paper mainly focuses on deriving the factorization theorem for hemisphere invariant mass distributions and other event shapes in e+e- collisions applicable at a future linear collider. We show that the invariant mass distribution is not a simple Breit-Wigner function involving the top width. Even at leading order it is shifted and broadened by nonperturbative soft QCD effects. We predict that the invariant mass peak position increases linearly with Q/m due to these nonperturbative effects. They are encoded in terms of a universal soft function that also describes soft effects for massless dijet events. In a future paper we compute αs corrections to the jet invariant mass spectrum, including a summation of large logarithms between the scales Q, m, and Γ. © 2008 The American Physical Society.
• Fleming, S., Hoang, A. H., Mantry, S., & Stewart, I. W. (2008). Top jets in the peak region: Factorization analysis with next-to-leading-log resummation. Physical Review D - Particles, Fields, Gravitation and Cosmology, 77(11).
  More info

  Abstract: We consider top quarks produced at large energy in e+e- collisions, and address the question of what top mass can be measured from reconstruction. The production process is characterized by well-separated scales: the center-of-mass energy Q, the top mass m, the top decay width Γt, and also ΛQCD; scales which can be disentangled with effective theory methods. In particular we show how the mass measurement depends on the way in which soft radiation is treated, and that this can shift the mass peak by an amount of order QΛQCD/m. We sum large logs for Q Γt>ΛQCD and demonstrate that the renormalization group ties together the jet and soft interactions below the scale m. Necessary conditions for the invariant mass spectrum to be protected from large logs are formulated. Results for the cross section are presented at next-to-leading order with next-to-leading-log (NLL) resummation, for invariant masses in the peak region and the tail region. Using our results we also predict the thrust distribution for massive quark jets at NLL order for large thrust. We demonstrate that soft radiation can be precisely controlled using data on massless jet production, and that in principle, a short-distance mass parameter can be measured using jets with precision better than ΛQCD. © 2008 The American Physical Society.
• Hoang, A. H., Fleming, S., Mantry, S., & Stewart, I. W. (2007). Factorization approach for top mass reconstruction in the continuum. Electronic Proceedings of the 2007 International Linear Collider Workshop, LCWS 2007 and ILC 2007.
  More info

  Abstract: Using effective theories for jets and heavy quarks it is possible to prove that the double differential top-antitop invariant mass distribution for the process e+e- → ttμ in the resonance region for c.m. energies Q much larger than the top mass can factorized into perturbatively computable hard coefficients and jet functions and a non-perturbative soft function. For invariant mass prescriptions based on hemispheres defined with respect to the thrust axis the soft function can be extracted from massless jet event shape distributions. This approach allows in principle for top mass determinations without uncertainties from hadronization using the reconstruction method and to quantify the top mass scheme dependence of the measured top quark mass value.
• Kolck, U. V., Mehen, T., Kusunoki, M., Kolck, U. V., & Fleming, S. (2007). Pion interactions in the X(3872). Physical Review D, 76(3). doi:10.1103/physrevd.76.034006
  More info

  We consider pion interactions in an effective field theory of the narrow resonance X(3872), assuming it is a weakly bound molecule of the charm mesons D{sup 0}D*{sup 0} and D*{sup 0}D{sup 0}. Since the hyperfine splitting of the D{sup 0} and D*{sup 0} is only 7 MeV greater than the neutral pion mass, pions can be produced near threshold and are nonrelativistic. We show that pion exchange can be treated in perturbation theory and calculate the next-to-leading-order correction to the partial decay width {gamma}[X{yields}D{sup 0}D{sup 0}{pi}{sup 0}].
• Fleming, S. (2006). Soft collinear effective theory. AIP Conference Proceedings, 842, 923-928.
  More info

  Abstract: In this talk I review soft collinear effective theory. After a discussion of the formalism and properties of the effective field theory, I turn to phenomenology. I present results on color-suppressed B → D decays, and on the Υ radiative decay spectrum. © 2006 American Institute of Physics.
• Fleming, S. P. (2006). Soft Collinear Effective Theory. AIP Conf.Proc., 842, 923-928.
  More info

  In this talk I review soft collinear effective theory. After a discussion ofthe formalism and properties of the effective field theory, I turn tophenomenology. I present results on color-suppressed B to D decays, and on theUpsilon radiative decay spectrum.[Journal_ref: AIP Conf.Proc.842:923-928,2006]
• Fleming, S., & Mehen, T. (2006). Doubly heavy baryons, heavy quark-diquark symmetry, and nonrelativistic QCD. Physical Review D - Particles, Fields, Gravitation and Cosmology, 73(3).
  More info

  Abstract: In the heavy quark limit, properties of heavy mesons and doubly heavy baryons are related by heavy quark-diquark symmetry. This problem is reanalyzed in the framework of nonrelativistic QCD (NRQCD). We introduce a novel method for deriving potential NRQCD (pNRQCD) Lagrangians for composite fields from vNRQCD, which contains quarks and antiquarks as explicit degrees of freedom and maintains manifest power counting in the velocity via a label formalism. A Hubbard-Stratonovich transformation is used to eliminate four quark interactions in vNRQCD and then quarks and antiquarks are integrated out to get effective Lagrangians for composite fields. This method is used to rederive Lagrangians for the QQ̄ and QQ sectors of pNRQCD and give a correct derivation of the O(1/mQ) prediction for the hyperfine splitting of doubly heavy baryons. © 2006 The American Physical Society.
• Fleming, S., Leibovich, A. K., & Mehen, T. (2006). J/Ψ photo-production at large z in soft collinear effective theory. Proceedings of the Ringberg Workshop on New Trends in HERA Physics 2005, 239-250.
  More info

  Abstract: One of the outstanding problems in J/Ψ physics is a systematic understanding of the differential photo-production cross section dσ/dz(γ+p → J/Ψ + X), where z = EΨ,/E gamma;/ in the proton rest frame. The theoretical prediction based on the nonrelativistic QCD (NRQCD) factorization formalism has a color-octet contribution which grows rapidly in the endpoint region, z -→ 1, spoiling perturbation theory. In addition there are subleading operators which are enhanced by powers of 1/(1 - z) and they must be resummed to all orders. Here an update of a systematic analysis is presented. The approach used to organize the endpoint behavior of the photoproduction cross section is based on a combination of NRQCD and soft collinear effective theory. While a final result is not yet available, an intermediate result indicates that better agreement between theory and data will be achieved in this framework. Copyright © 2006 by World Scientific Publishing Co. Pte. Ltd.
• Fleming, S., Leibovich, A. K., & Mehen, T. (2006). Resummation of large endpoint corrections to color-octet J/ψ photoproduction. Physical Review D - Particles, Fields, Gravitation and Cosmology, 74(11).
  More info

  Abstract: An unresolved problem in J/ψ phenomenology is a systematic understanding of the differential photoproduction cross section, dσ/dz[γ+p→J/ψ+X], where z=Eψ/Eγ in the proton rest frame. In the nonrelativistic QCD (NRQCD) factorization formalism, fixed-order perturbative calculations of color-octet mechanisms suffer from large perturbative and nonperturbative corrections that grow rapidly in the endpoint region, z→1. In this paper, NRQCD and soft collinear effective theory are combined to resum these large corrections to the color-octet photoproduction cross section. We derive a factorization theorem for the endpoint differential cross section involving the parton distribution function and the color-octet J/ψ shape functions. A one-loop matching calculation explicitly confirms our factorization theorem at next-to-leading order. Large perturbative corrections are resummed using the renormalization group. The calculation of the color-octet contribution to dσ/dz is in qualitative agreement with data. Quantitative tests of the universality of color-octet matrix elements require improved knowledge of shape functions entering these calculations as well as resummation of the color-singlet contribution which accounts for much of the total cross section and also peaks near the endpoint. © 2006 The American Physical Society.
• , S. F., , C. L., & , A. K. (2005). Exclusive Radiative Decays of Upsilon in SCET. Phys.Rev. D.
  More info

  We study exclusive radiative decays of the $\Upsilon$ using soft-collineareffective theory and non-relativistic QCD. In contrast to inclusive radiativedecays at the endpoint we find that color-octet contributions are powersuppressed in exclusive decays, and can safely be neglected, greatlysimplifying the analysis. We determine the complete set of Lorentz structuresthat can appear in the SCET Wilson coefficients and match onto them usingresults from a previous calculation. We run these coefficients from the scale$\mups$ to the scale $\Lambda \sim 1 \textrm{GeV}$, thereby summing largelogarithms. Finally we use our results to predict the ratio of branchingfractions $B(\Upsilon \to \gamma f_2)/B(J/\psi \to \gamma f_2)$, $B(J/\psi \to\gamma f_2)/B(\psi' \to \gamma f_2)$, and the partial rate for $\Upsilon \to\gamma \pi \pi$.[Journal_ref: Phys.Rev. D71 (2005) 074002]
• Fleming, S. (2005). QCD. International Journal of Modern Physics A, 20(14), 3007-3020.
  More info

  Abstract: In this talk I review recent experimental and theoretical results in QCD. Since the topic is too vast to cover within given time constraints I choose to highlight some of the subjects that I find particularly exciting. On the experimental side I focus on measurements made at the Tevatron. Specifically jet production rates, and the cross section for B meson production. In addition I discuss an interesting measurement made by the Belle collaboration of double exclusive charmonium production. On the theory side I quickly review recent advances in computing hadronic cross sections at subleading order in perturbation theory. I then move on to soft-collinear effective theory. After a lightning review of the formalism I discuss recently published results on color-suppressed B → D decays. © World Scientific Publishing Company.
• Fleming, S., Lee, C., & Leibovich, A. K. (2005). Exclusive radiative decays of Υ in soft-collinear effective theory. Physical Review D - Particles, Fields, Gravitation and Cosmology, 71(7), 1-10.
  More info

  Abstract: We study exclusive radiative decays of the Υ using soft-collinear effective theory and nonrelativistic QCD. In contrast to inclusive radiative decays at the endpoint we find that color-octet contributions are power suppressed in exclusive decays, and can safely be neglected, greatly simplifying the analysis. We determine the complete set of Lorentz structures that can appear in the SCET Wilson coefficients and match onto them using results from a previous calculation. We run these coefficients from the scale M Υ to the scale A ∼ 1 GeV, thereby summing large logarithms. Finally we use our results to predict the ratio of branching fractions B(Υ→γf2)/B(J/ψ→f2), B(ψ′→f2), and the partial rate for Υ→γππ. © 2005 The American Physical Society.
• , S. F., & , A. K. (2004). Flavor-singlet light-cone amplitudes and radiative Upsilon decays in SCET. Phys.Rev. D.
  More info

  We study the evolution of flavor-singlet, light-cone amplitudes in thesoft-collinear effective theory (SCET), and reproduce results previouslyobtained by a different approach. We apply our calculation to the color-singletcontribution to the photon endpoint in radiative Upsilon decay. In a previouspaper, we studied the color-singlet contributions to the endpoint, butneglected operator mixing, arguing that it should be a numerically smalleffect. Nevertheless the mixing needs to be included in a consistentcalculation, and we do just that in this work. We find that the effects ofmixing are indeed numerically small. This result combined with previous work onthe color-octet contribution and the photon fragmentation contribution providesa consistent theoretical treatment of the photon spectrum in radiative Upsilondecay.[Journal_ref: Phys.Rev. D70 (2004) 094016]
• Fleming, S. P. (2004). The Resummed Photon Spectrum in Radiative Upsilon Decays (And More). AIP Conf.Proc., 698, 579-582.
  More info

  In this talk I present the results of two calculations that make use ofNon-Relativistic QCD and the newly developed Soft-Collinear Effective Theory.The first process considered is inclusive radiative $\Upsilon$ decay. Thesecond process considered is the leading color-octet contribution to $e^+ e^-\to J/\psi + X$.[Journal_ref: AIP Conf.Proc.698:579-582,2004]
• Fleming, S., & Leibovich, A. K. (2004). Flavor-singlet light-cone amplitudes and radiative Υ decays in the soft-collinear effective theory. Physical Review D - Particles, Fields, Gravitation and Cosmology, 70(9), 094016-1-094016-11.
  More info

  Abstract: We study the evolution of flavor-singlet, light-cone amplitudes in the soft-collinear effective theory, and reproduce results previously obtained by a different approach. We apply our calculation to the color-singlet contribution to the photon endpoint in radiative Υ decay. In a previous paper, we studied the color-singlet contributions to the endpoint, but neglected operator mixing, arguing that it should be a numerically small effect. Nevertheless the mixing needs to be included in a consistent calculation, and we do just that in this work We find that the effects of mixing are indeed numerically small. This result combined with previous work on the color-octet contribution and the photon fragmentation contribution provides a consistent theoretical treatment of the photon spectrum in ΥY → γX.
• , S. F., & , A. K. (2003). The Photon Spectrum in Upsilon Decays. Phys.Rev. D.
  More info

  We present a theoretical prediction for the photon spectrum in radiativeUpsilon decay. Parts of the spectrum have already been understood, but anunderstanding of the endpoint region has remained elusive. In this paper weprovide the missing piece, and resolve a controversy in the literature. Wetreat the endpoint region of Upsilon -> X gamma decay within the framework ofthe soft-collinear effective theory (SCET). Within this approach the Upsilonstructure function arises naturally, and kinematic logarithms are summed byrunning operators using renormalization group equations. In a previous paper westudied the color-octet contribution to the decay. Here we treat thecolor-singlet contribution. We combine our result with previous results toobtain the Upsilon -> X gamma spectrum. We find that resumming thecolor-singlet contribution in the endpoint gives a result that is in muchbetter agreement with the data than the leading order prediction.[Journal_ref: Phys.Rev. D67 (2003) 074035]
• , S. F., & , A. K. (2003). The Resummed Photon Spectrum in Radiative Upsilon Decays. Phys.Rev.Lett..
  More info

  We present a theoretical prediction for the photon spectrum in radiativeUpsilon decay including the effects of resumming the endpoint region, E_\gamma-> M_\Upsilon/2. Our approach is based on NRQCD and the soft collineareffective theory. We find that our results give much better agreement with datathan the leading order NRQCD prediction.[Journal_ref: Phys.Rev.Lett. 90 (2003) 032001]
• Fleming, S., & Leibovich, A. K. (2003). Resummed photon spectrum in radiative Y decays. Physical Review Letters, 90(3), 032001/1-032001/4.
  More info

  Abstract: The radiative decay Y→Xγ was first investigated about a quarter century ago. The conventional wisdom was that this process was computable in perturbative QCD due to the large b mass. The current method for calculating the direct radiative decay of the γ was by using the operator product expansion (OPE), with the operators scaling as some power of the relative velocity of the heavy quarks, given by the power counting of nonrelativistic QCD (NRQCD).
• Fleming, S., & Leibovich, A. K. (2003). The photon spectrum in Y decays. Physical Review D, 67(7).
  More info

  Abstract: We present a theoretical prediction for the photon spectrum in radiative Y decay. Parts of the spectrum have already been understood, but an understanding of the end point region has remained elusive. In this paper we provide the missing piece, and resolve a controversy in the literature. We treat the end point region of Y →Xγ decay within the framework of the soft-collinear effective theory (SCET). Within this approach the Y structure function arises naturally, and kinematic logarithms are summed by running operators using renormalization group equations. In a previous paper we studied the color-octet contribution to the decay. Here we treat the color-singlet contribution. We combine our result with previous results to obtain the Y→Xγ spectrum. We find that resumming the color-singlet contribution in the end point gives a result that is in much better aoreement with the data than the leading order prediction. © 2003 The American Physical Society.
• Fleming, S., Leibovich, A. K., & Mehen, T. (2003). Resumming the color-octet contribution to e⁺e-→J/ψ+X. Physical Review D, 68(9).
  More info

  Abstract: Recent observations of the spectrum of J/ψ produced in e+e- collisions at the Υ(4S) resonance are in conflict with fixed-order calculations using the nonrelativistic QCD effective field theory. One problem is that leading order color-octet mechanisms predict an enhancement of the cross section for J/ψ with a maximal energy that is not observed in the data. However, in this region of phase space large perturbative corrections (Sudakov logarithms) as well as enhanced nonperturbative effects are important. In this paper we use the newly developed soft-collinear effective theory (SCET) to systematically include these effects. We find that these corrections significantly broaden the color-octet contribution to the J/ψ spectrum. Our calculation employs a one-stage renormalization group evolution rather than the two-stage evolution used in previous SCET calculations. We give a simple argument for why the two methods yield identical results to lowest order in the SCET power counting. © The American Physical Society.
• Bauer, C. W., Fleming, S., Pirjol, D., Rothstein, I. Z., & Stewart, I. W. (2002). Hard scattering factorization from effective field theory. Physical Review D - Particles, Fields, Gravitation and Cosmology, 66(1 II), 140171-1401723.
  More info

  Abstract: In this paper we show how gauge symmetries in an effective theory can be used to simplify proofs of factorization formulas in highly energetic hadronic processes. We use the soft-collinear effective theory, generalized to deal with back-to-back jets of collinear particles. Our proofs do not depend on the choice of a particular gauge, and the formalism is applicable to both exclusive and inclusive factorization. As examples we treat the π-γ form factor (γγ*→π0), light meson form factors (γ*M→M), as well as deep inelastic scattering (e-p→e-X), the Drell-Yan process (pp→Xl+l-), and deeply virtual Compton scattering (γ*p →γ(*)p).
• Bauer, C. W., Chiang, C., Fleming, S., Leibovich, A. K., & Low, I. (2001). Resumming the color-octet contribution to radiative Y decay. Physical Review D, 64(11).
  More info

  Abstract: At the upper end point of the photon energy spectrum in Y→Xγ, the standard NRQCD power counting breaks down and the OPE gives rise to color-octet structure functions. Furthermore, in this kinematic regime large Sudakov logarithms appear in the octet Wilson coefficients. The end point spectrum can be treated consistently within the framework of a recently developed effective field theory of collinear and soft particles. Here we show that within this approach the octet structure functions arise naturally and that Sudakov logarithms can be summed using the renormalization group equations. We derive an expression for the resummed energy spectrum and, using a model light cone structure function, investigate the phenomenological importance of the resummation. ©2001 The American Physical Society.
• Leibovich, A. K., Fleming, S., & Braaten, E. (2001). Nonrelativistic QCD analysis of bottomonium production at the Fermilab Tevatron. Physical Review D, 63(9). doi:10.1103/physrevd.63.094006
  More info

  Recent data from the CDF Collaboration on the production of spin-triplet bottomonium states at the Fermilab Tevatron $p\overline{p}$ collider are analyzed within the NRQCD factorization formalism. The color-singlet matrix elements are determined from electromagnetic decays and from potential models. The color-octet matrix elements are determined by fitting the CDF data on the cross sections for $\ensuremath{\Upsilon}(1S),$ $\ensuremath{\Upsilon}(2S),$ and $\ensuremath{\Upsilon}(3S)$ at large ${p}_{T}$ and the fractions of $\ensuremath{\Upsilon}(1S)$ coming from ${\ensuremath{\chi}}_{b}(1P)$ and ${\ensuremath{\chi}}_{b}(2P).$ We use the resulting matrix elements to predict the cross sections at the Tevatron for the spin-singlet states ${\ensuremath{\eta}}_{b}(\mathrm{nS})$ and ${h}_{b}(\mathrm{nP}).$ We argue that ${\ensuremath{\eta}}_{b}(1S)$ may be observable in run II through the decay ${\ensuremath{\eta}}_{b}\ensuremath{\rightarrow}J/\ensuremath{\psi}+J/\ensuremath{\psi}.$
• Stewart, I. W., Pirjol, D., Fleming, S., & Bauer, C. W. (2001). An Effective field theory for collinear and soft gluons: Heavy to light decays. Physical Review D, 63(11). doi:10.1103/physrevd.63.114020
  More info

  We construct the Lagrangian for an effective theory of highly energetic quarks with energy Q, interacting with collinear and soft gluons. This theory has two low energy scales, the transverse momentum of the collinear particles, ${p}_{\ensuremath{\perp}},$ and the scale ${p}_{\ensuremath{\perp}}^{2}/Q.$ The heavy to light currents are matched onto operators in the effective theory at one loop and the renormalization group equations for the corresponding Wilson coefficients are solved. This running is used to sum Sudakov logarithms in inclusive $\stackrel{\ensuremath{\rightarrow}}{B}{X}_{s}\ensuremath{\gamma}$ and $\stackrel{\ensuremath{\rightarrow}}{B}{X}_{u}l\overline{\ensuremath{\nu}}$ decays. We also show that the interactions with collinear gluons preserve the relations for the soft part of the form factors for heavy-to-light decays found by Charles et al. [Phys. Rev. D 60, 014001 (1999)], establishing these relations in the large energy limit of QCD.
• Fleming, S., Mehen, T., & Stewart, I. W. (2000). NN scattering ³S₁-³D₁ mixing angle at next-to-next-to-leading order. Physical Review C - Nuclear Physics, 61(4), 440051-440059.
  More info

  Abstract: The 3S1-3D1 mixing angle for nucleon-nucleon scattering ∈1 is calculated to next-to-next-to-leading order in an effective field theory with perturbative pions. Without pions, the low energy theory fits the observed ∈1 well for momenta less than∼50 MeV. Including pions perturbatively significantly improves the agreement with data for momenta up to ∼150 MeV with one less parameter. Furthermore, for these momenta the accuracy of our calculation is similar to an effective field theory calculation in which the pion is treated nonperturbatively. This gives phenomenological support for a perturbative treatment of pions in low energy two-nucleon processes. We explain why it is necessary to perform spin and isospin traces in d dimensions when regulating divergences with dimensional regularization in higher partial wave amplitudes.
• Fleming, S., Mehen, T., & Stewart, I. W. (2000). NNLO corrections to nucleon-nucleon scattering and perturbative pions. Nuclear Physics A, 677(1-4), 313-366.
  More info

  Abstract: The 1S0, 3S1, and 3D1 nucleon-nucleon scattering phase shifts are calculated at next-to-next-to-leading order (NNLO) in an effective field theory. Predictions for the 1P1, 3P0,1,2, 1D2, and 3D2,3 phase shifts at this order are also compared with data. The calculations treat pions perturbatively and include the NNLO contributions from order Qr3 and Qr4 radiation pion graphs. In the 3S1, 3D1 and 3P0,2 channels we find large disagreement with the Nijmegen partial-wave analysis at NNLO. These spin triplet channels have large corrections from graphs with two potential pion exchange which do not vanish in the chiral limit. We compare our results to calculations within the Weinberg approach, and find that in some spin triplet channels the summation of potential pion diagrams seems to be necessary to reproduce the observed phase shifts. In the spin singlet channels the nonperturbative treatment of potential pions does not afford a significant improvement over the perturbative approach. © 2000 Elsevier Science B.V.
• Luke, M., Fleming, S., & Bauer, C. W. (2000). Summing Sudakov logarithms in B ---> X(s gamma) in effective field theory. Physical Review D, 63(1). doi:10.1103/physrevd.63.014006
  More info

  We construct an effective field theory valid for processes in which highly energetic light-like particles interact with collinear and soft degrees of freedom, using the decay B → Xs near the endpoint of the photon spectrum, x = 2Eγ/mb → 1, as an example. Below the scale µ = mb both soft and collinear degrees of freedom are included in the effective theory, while below the scale µ = mb √ x − y, where 1 − y is the lightcone momentum fraction of the b quark in the B meson, we match onto a theory of bilocal operators. We show that at one loop large logarithms cancel in the matching conditions, and that we recover the well known renormalization group equations that sum leading Sudakov logarithms.
• Stewart, I. W., Mehen, T., & Fleming, S. (2000). NN scattering 3 S 1 − 3 D 1 mixing angle at next-to-next-to-leading order. Physical Review C, 61(4). doi:10.1103/physrevc.61.044005
  More info

  The ${}^{3}{S}_{1}{\ensuremath{-}}^{3}{D}_{1}$ mixing angle for nucleon-nucleon scattering ${\ensuremath{\epsilon}}_{1}$ is calculated to next-to-next-to-leading order in an effective field theory with perturbative pions. Without pions, the low energy theory fits the observed ${\ensuremath{\epsilon}}_{1}$ well for momenta less than \ensuremath{\sim}50 MeV. Including pions perturbatively significantly improves the agreement with data for momenta up to \ensuremath{\sim}150 MeV with one less parameter. Furthermore, for these momenta the accuracy of our calculation is similar to an effective field theory calculation in which the pion is treated nonperturbatively. This gives phenomenological support for a perturbative treatment of pions in low energy two-nucleon processes. We explain why it is necessary to perform spin and isospin traces in d dimensions when regulating divergences with dimensional regularization in higher partial wave amplitudes.
• Braaten, E., Lee, J., & Fleming, S. (1999). Associated production of γ and weak gauge bosons in hadron colliders. Physical Review D - Particles, Fields, Gravitation and Cosmology, 60(9), 1-5.
  More info

  Abstract: We calculate the rate of production of W± + γ and Z0+γ in hadron colliders. We find the cross sections for W± + γ and Z0 + γ to be roughly 0.45 pb and 0.15 pb at the Fermilab Tevatron and roughly 4 pb and 2 pb at the CERN Large Hadron Collider (LHC). The dominant production mechanism involves the binding of a color-octet bb̄ pair into a P-wave bottomonium state which subsequently decays into γ. The purely leptonic decay modes of γ, W±, and Z0 provide signatures with small backgrounds. These events may be observable in run II at the Tevatron, and they should certainly be observable at the LHC. ©1999 The American Physical Society.
• Fleming, S., & Mehen, T. (1998). Leptoproduction of J/ψ. Physical Review D - Particles, Fields, Gravitation and Cosmology, 57(3), 1846-1857.
  More info

  Abstract: We study leptoproduction of J/ψ at large Q2 within the nonrelativistic QCD (NRQCD) factorization formalism. The cross section is dominated by color-octet terms that are of order αs. The color-singlet term, which is of order α2s, is shown to make a small contribution to the total cross section. We also calculate the tree diagrams for color-octet production at order α2s in a region of phase space where there is no leading color-octet contribution. We find that in this regime the color-singlet contribution dominates. We argue that nonperturbative corrections arising from diffractive leptoproduction, higher twist effects, and higher order terms in the NRQCD velocity expansion should be suppressed as Q2 is increased. Therefore, the color-octet matrix elements 〈script O signψ8(1S0)〉 and 〈script O signψ8(3P0)〉 can be reliably extracted from this process. Finally, we point out that an experimental measurement of the polarization of leptoproduced J/ψ will provide an excellent test of the NRQCD factorization formalism.
• Fleming, S., & Mehen, T. (1998). Photoproduction of h_c. Physical Review D - Particles, Fields, Gravitation and Cosmology, 58(3), 0375031-0375034.
  More info

  Abstract: Using the NRQCD factorization formalism, we calculate the total cross section for the photoproduction of hc mesons. We include color-octet and color-singlet mechanisms as well as next-to-leading order perturbative QCD corrections. The theoretical prediction depends on two nonperturbative matrix elements that are not well determined from existing data on charmonium production. For reasonable values of these matrix elements, the cross section is large enough that the hc may be observable at the E831 experiment and at the DESY HERA experiments.
• Mehen, T., & Fleming, S. (1998). Photoproduction of (Formula Presented). Physical Review D, 58(3). doi:10.1103/physrevd.58.037503
• Amundson, J., Fleming, S., & Maksymyk, I. (1997). Photoproduction of J/ψ in the forward region. Physical Review D - Particles, Fields, Gravitation and Cosmology, 56(9), 5844-5850.
  More info

  Abstract: We study the phenomenology of fixed-target elastic J/ψ photoproduction in the nonrelativistic QCD (NRQCD) factorization formalism. Our goal is to test an essential feature of this formalism - the color-octet mechanism. We obtain an order-of-magnitude estimate for a certain linear combination of NRQCD color-octet matrix elements. Our estimate is consistent with other empirical determinations and with the v-scaling rules of NRQCD.
• Fleming, S. (1997). Determining color-octet ψ-production matrix elements from γp and ep processes. International Journal of Modern Physics A, 12(22), 3995-4004.
  More info

  Abstract: We calculate, within the NRQCD factorization formalism, the leading color-octet contributions to ψ production in photon-nucleon and electron-nucleon collisions. The expressions we obtaine depend on the NRQCD matrix elements 〈O 8ψ( 1S 0)〉 and (O 8ψ( 3P 0)〉. These matrix elements can be determined by fitting to experimental data. The color-octet contribution to ψ photoproduction is in the forward region of phase space, where there may be large corrections to the NRQCD result from higher twist terms. As to ψ leptoproduction we point out that the theoretical uncertainties plaguing the photoproduction calculation vanish in the large momentum transfer limit. In this region of phase space the NRQCD formalism should be valid, making ψ leptoproduction an ideal laboratory for testing the theory. © World Scientific Publishing Company.
• Fleming, S., Hernández, O. F., Maksymyk, I., & Nadeau, H. (1997). NRQCD matrix elements in polarization of J/ψ produced from b decay. Physical Review D - Particles, Fields, Gravitation and Cosmology, 55(7), 4098-4104.
  More info

  Abstract: We present the nonrelativistic QCD (NRQCD) prediction for the polarization of the J/ψ promptly produced in b→J/ψ+X, as well as the helicity-summed production rate. We propose that these observables can be of avail in measuring the three most important color-octet NRQCD matrix elements involved in J/ψ production. Anticipating the measurement of the polarization parameter α, we determine its expected range given current experimental bounds on the color-octet matrix elements. We find that the leading-order NRQCD prediction for the polarization parameter α is expected to lie in the range -0.33 to 0.05 whereas the color-singlet model prediction is -0.40±0.04.
• Braaten, E., Fleming, S., & Yuan, T. C. (1996). Production of heavy quarkonium in high-energy colliders. Annual Review of Nuclear and Particle Science, 46(1), 197-235.
  More info

  Abstract: Recent data from the Tevatron collider have revealed that the production rate of prompt charmonium at large transverse momentum is orders of magnitude larger than die best theories of a few years ago had predicted. These surprising results can be understood by taking into account two recent developments that have dramatically revised the theoretical description of heavy-quarkonium production. The first is the realization that fragmentation must dominate at large transverse momentum, which implies that most charmonium in this kinematic region is produced by the hadronization of individual high-pT partons. The second is the development of a factorization formalism for quarkonium production based on nonrelativistic QCD that allows the formation of charmonium from color-octet cc̄ pairs to be treated systematically. This review summarizes these theoretical developments and their implications for quarkonium production in high-energy colliders.
• Fleming, S., & Maksymyk, I. (1996). Can light Nambu-Goldstone boson loops counter the "S argument" against technicolor?. Physical Review D - Particles, Fields, Gravitation and Cosmology, 53(5), 2781-2788.
  More info

  Abstract: We examine the oblique correction phenomenology of one-family technicolor with light pseudo Nambu-Goldstone bosons. From loop calculations based on a gauged chiral Lagrangian for technicolor we are led to conclude that even though loops with light Nambu-Goldstone bosons give a negative contribution to S measured at the Z pole, this effect is not sufficiently large to unambiguously counter the "S argument" against one-family technicolor. This result cannot be guessed a priori, but must be explicitly calculated. Our analysis entails an extended version of the STU oblique parametrization of Peskin and Takeuchi. In principle, this extended formalism (STUVWX) must be used when there are light new particles in loops.
• Fleming, S., & Maksymyk, I. (1996). Extending the STU formalism for electroweak oblique corrections to the case of light new physics. Annals of Physics, 251(1), 26-44.
  More info

  Abstract: The STU formalism, which parametrizes oblique electroweak corrections due to heavy new physics, has recently been extended to the case of light new physics. In principle, this extended formalism, which involves the six parameters STUVWX, must be used if loop contributions to the oblique corrections entail light new particles with masses in the range ∼~MZ or less. Applying classical equations of motion to manipulate the effective lagrangian, we present here a thorough introductory discussion of the STUVWX formalism, elucidating such subtleties as the connection between S - X and the star formalism of Kennedy and Lynn, the connection between S - X, and the ε parameters of Altarelli and Barbieri, and the loss of definite symmetry properties which S and U undergo as the STU parameter set is extended to the case of light new physics. This paper provides a significantly more detailed, expanded, and pedagogic presentation than previous expositions of the STUVWX parameters. © 1996 Academic Press, Inc.
• Fleming, S., & Maksymyk, I. (1996). Hadronic J/ψ production calculated in the NRQCD factorization formalism. Physical Review D - Particles, Fields, Gravitation and Cosmology, 54(5), 3608-3618.
  More info

  Abstract: The NRQCD factorization formalism of Bodwin, Braaten, and Lepage prescribes how to write quarkonium production rates as a sum of products of short-distance coefficients times nonperturbative long-distance NRQCD matrix elements. We present a calculation of the inclusive cross section for hadronic ψ production within the framework of the factorization formalism. Our method applies to the case in which the helicity of the ψ is not measured. In addition to the well-known color-singlet production mechanisms, there are equally important mechanisms in which the cc̄ pair that forms the Jl ψ is initially produced in a color-octet state, in either a 3S1. 1S0, 3P0, or 3P2 angular-momentum configuration. In our presentation, we faithfully follow the "matching" procedure, thereby shedding light on the NRQCD factorization formalism. We determine the short-distance coefficients appearing in the factorization formula, and we point out how one may systematically include relativistic corrections in these calculations.
• Phillips, R. J., Phillips, R. J., Fleming, S., & Barger, V. (1996). Double gluon fragmentation to J/ψ pairs at the Tevatron. Physics Letters B, 371(1), 111-116. doi:10.1016/0370-2693(95)01592-2
  More info

  Abstract It has been proposed that the large cross sections for prompt ψ, ψ′, aand χ c production at the Fermilab Tevatron p p collider can be explained by a dominant color-octet term in the fragmentation function for a gluon to split into quarkonium. We show that this mechanism makes testable predictions for double-quarkonium ψψ, ψψ′, ψχ c , ψϒ and ψχ b production , as well as for Wψ production, using color-octet matrix elements previously determined from charmonium production data. The ψψ signal would already be measurable at the Tevatron, while the ψχ c and Wψ signals would be on the edge of present detectability.
• Yuan, T. C., Fleming, S., & Braaten, E. (1996). PRODUCTION OF HEAVY QUARKONIUM IN HIGH-ENERGY COLLIDERS. Annual Review of Nuclear and Particle Science, 46(1), 197-235. doi:10.1146/annurev.nucl.46.1.197
  More info

  ▪ Abstract Recent data from the Tevatron collider have revealed that the production rate of prompt charmonium at large transverse momentum is orders of magnitude larger than the best theories of a few years ago had predicted. These surprising results can be understood by taking into account two recent developments that have dramatically revised the theoretical description of heavy-quarkonium production. The first is the realization that fragmentation must dominate at large transverse momentum, which implies that most charmonium in this kinematic region is produced by the hadronization of individual high-pT partons. The second is the development of a factorization formalism for quarkonium production based on nonrelativistic QCD that allows the formation of charmonium from color-octet pairs to be treated systematically. This review summarizes these theoretical developments and their implications for quarkonium production in high-energy colliders.
• Braaten, E., & Fleming, S. (1995). Color-octet fragmentation and the ψ + ′ surplus at the fermilab tevatron. Physical Review Letters, 74(17), 3327-3330.
  More info

  Abstract: The production rate of prompt ψ + ′'s at large transverse momentum at the Fermilab Tevatron is larger than theoretical expectations by about a factor of 30. As a solution to this puzzle, we suggest that the dominant ψ + ′ production mechanism is the fragmentation of a gluon into a cc̄ pair in a pointlike color-octet S-wave state, which subsequently evolves nonperturbatively into a ψ + ′ plus light hadrons. This contribution to the fragmentation function is enhanced by a short-distance factor of 1/αs2, which may compensate for its suppression by υ4, where υ is the relative momentum of the charm quark in the ψ + ′.
• Braaten, E., & Fleming, S. (1995). QCD radiative corrections to the leptonic decay rate of the Bc meson. Physical Review D, 52(1), 181-185.
  More info

  Abstract: The QCD radiative corrections to the leptonic decay rate of the Bc meson are calculated using the formalism of nonrelativistic QCD (NRQCD) to separate short-distance and long-distance effects. The Bc decay constant is factored into a sum of NRQCD matrix elements each multiplied by a short-distance coefficient. The short-distance coefficient for the leading matrix element is calculated to order αs by matching a perturbative calculation in full QCD with the corresponding perturbative calculation in NRQCD. This short-distance correction decreases the leptonic decay rate by approximately 15%. © 1995 The American Physical Society.
• Braaten, E., Cheung, K., Fleming, S., & Yuan, T. C. (1995). Perturbative QCD fragmentation functions as a model for heavy-quark fragmentation. Physical Review D, 51(9), 4819-4829.
  More info

  Abstract: The perturbative QCD fragmentation functions for a heavy quark to fragment into heavy-light mesons are studied in the heavy-quark limit. The fragmentation functions for S-wave pseudoscalar and vector mesons are calculated to next-to-leading order in the heavy-quark mass expansion using the methods of heavy-quark effective theory. The results agree with the mb→ limit of the perturbative QCD fragmentation functions for b̄ into Bc and Bc*. We discuss the application of the perturbative QCD fragmentation functions as a model for the fragmentation of heavy quarks into heavy-light mesons. Using this model we predict the fraction PV of heavy-light mesons that are produced in the vector meson state as functions of the longitudinal momentum fraction z and the transverse momentum relative to the jet axis. The fraction PV is predicted to vary from about 1/2 at small z to almost 3/4 near z=1. © 1995 The American Physical Society.
• Braaten, E., Doncheski, M. A., Fleming, S., & Mangano, M. L. (1994). Fragmentation production of J/ψ and ψ′ at the Tevatron. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 333(3-4), 548-554.
  More info

  Abstract: We present a calculation of the charm and gluon fragmentation contributions to inclusive J/ψ and ψ′ production at large transverse momentum at the Tevatron. For ψ production, we include both fragmentation directly into ψ and fragmentation into χc followed by the radiative decay χc → ψ + γ We find that fragmentation overwhelms the leading-order mechanisms for prompt ψ production at large pT, and that the dominant contributions come from fragmentation into χc- Our results are consistent with recent data on ψ production from the CDF and D0 experiments. In the case of prompt ψ′ production, the dominant mechanism at large pT is charm fragmentation into ψ′. We find serious disagreement between our theoretical predictions and recent ψ′ data from the Tevatron.
• Fleming, S. (1994). J/ψ production from electromagnetic fragmentation in Z0 decay. Physical Review D, 50(9), 5808-5815.
  More info

  Abstract: The rate for Z0→J/ψ+l+l- is surprisingly large with about one event for every million Z0 decays. The reason for this is that there is a fragmentation contribution that is not suppressed by a factor of Mψ2/MZ2. In the fragmentation limit MZ→ with Eψ/MZ fixed, the differential decay rate for Z0→J/ψ+l+l- factors into electromagnetic decay rates and universal fragmentation functions. The fragmentation functions for lepton fragmentation and photon fragmentation into J/ψ are calculated to the lowest order in α. The fragmentation approximation to the rate is shown to match the full calculation for Eψ greater than about 3Mψ. © 1994 The American Physical Society.
• Fleming, S. (1993). Electromagnetic production of quarkonium in Z0 decay. Physical Review D, 48(5), R1914-R1916.
  More info

  Abstract: The decay Z0Q+l+l-, where Q is a JPC=1 - quarkonium state, has a very clean final state which should make it easy to detect. The branching ratio of this mode is greater than 10-6 for, and, indicating that these processes may be detectable at CERN LEP. © 1993 The American Physical Society.

Proceedings Publications

• Fleming, S. (2016). Glauber Gluons in SCET and the BFKL Equation. In Proceedings of QCD Evolution 2015 — PoS(QCDEV2015).
• Fleming, S. P. (2015, May). Glauber Gluons in SCET and the BFKL Equation. In QCD Evolution 2015.
• Fleming, S. P. (2015, May). Glauber Gluons in SCET and the BFKL Equation. In QCD Evolution Workshop (QCD 2015).
• Fleming, S. (2009). Soft Collinear Effective Theory: An Overview. In Proceedings of International Workshop on Effective Field Theories: from the pion to the upsilon — PoS(EFT09).
  More info

  In this talk I give an overview of soft collinear effective theory (SCET), including a discussion of some recent advances. First, I briefly cover the foundation upon which SCET is built, namely QCD factorization, and review the theoretical framework of SCET. Next, I cover some recent calculations involving SCET. Since there are more interesting results than I can cover, I have picked four that that I find particularly exciting. The first two topics are dynamical threshold enhancements in Drell-Yan and resummation of higgs production at the LHC. Both topics center on the resummation of large Sudakov logarithms, however, for each there is a twist. In the case of threshold enhancements in Drell-Yan, it is partonic, not hadronic logarithms that are summed. In the case of higgs production at the LHC, the twist is that the logarithms are of a time-like scale. The third topic highlighted is electroweak corrections at high energy. In particular the electroweak Sudakov form factor. Finally, I end by discussing generalized event shapes in e+e− annihilation.
• Mehen, T., Marshak, M. L., & Fleming, S. (2009). X(3872) in Effective Field Theory. In AIP Conference Proceedings, 1182, 491-494.
  More info

  If the X (3872) resonance is a shallow boundstate of a the charm mesons D0D*0 and D*0D0, it can be described by an effective theory of nonrelativistic D mesons coupled to nonrelativistic pions (X‐EFT). In this talk, I give a brief overview of the X (3872), followed by a short review of X‐EFT. I end my talk with results from calculations of the the next‐to‐leading‐order correction to the partial decay width Γ[X→D0D0π0], and the decay of X (3872) to P‐wave quarkonia.
• Fleming, S. (2004). The Resummed photon spectrum in radiative $\upsilon$ decays (and more). In AIP Conference Proceedings, 698, 579-582.
  More info

  In this talk I present the results of two calculations that make use of Non‐Relativistic QCD and the newly developed Soft‐Collinear Effective Theory. The first process considered is inclusive radiative Υ decay. The second process considered is the leading color‐octet contribution to e+e− → J/ψ + X.
• Fleming, S. (2002). Production & decay of quarkonium. In AIP Conference Proceedings, 618, 405-414.
  More info

  In this talk I review NRQCD predictions for the production of charmonium at the Tevatron. After a quick presentation of the NRQCD factorization formalism for production and decay I review some old results and discuss how they compare to recent data. Following this I discuss some recent work done with Adam Leibovich and Ira Rothstein.
• Mehen, T., & Fleming, S. (1998). Photoproduction of hc. In AIP Conference Proceedings, 452, 101-107.
  More info

  Using the NRQCD factorization formalism, we calculate the total cross section for the photoproduction of hc mesons. We include color-octet and color-singlet mechanisms as well as next-to-leading order perturbative QCD corrections. The theoretical prediction depends on two nonperturbative matrix elements that are not well determined from existing data on charmonium production. For reasonable values of these matrix elements, the cross section is large enough that the hc may be observable at the E831 experiment and at the HERA experiments.

Presentations

• Fleming, S. P. (2015, March). The Glauber Interaction in SCET. SCET2015 Workshop. Santa Fe, NM: LANL.
• Fleming, S. P. (2015, May). Glauber Gluons in SCET and the BFKL Equation. QCD Evolution 2015. Jefferson Lab, Newport News, VA: JLAB.
• Fleming, S. P. (2014, December). Forward Scattering in SCET: Glauber exchange and the BFKL Equation. Seminar at Brookhaven National Lab.
• Fleming, S. P. (2015, February). Effective Theories and the Strong Interactions. Seminar at Temple University.