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Brambilla, Nora; Tormo, Xavier Garcia i; Soto, Joan; Vairo, Antonio

doi:10.1103/physrevd.75.074014

Cited by 55 publications

(44 citation statements)

References 27 publications

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“…This model assumes that the nonperturbative dynamics leaves unchanged the quantum numbers of the perturbative quark-antiquark pair, which are the same as those of the physical bound state. It is curious to note that the analogous corrections to the hadronic decay width of a colorsinglet 3 S 1 state, which involve exactly the same diagrams, have been available for a long time [7] and play an important role in the extraction of α S from Υ decays [8]. Our calculation for the inclusive decay rate at NLO provides the first independent confirmation of those results.…”

supporting

confidence: 72%

“…However, the corresponding short distance coefficients might compensate this suppression, either by having leading order contributions starting at α 2 S compared to the α 3 S of the singlet and/or by kinematic enhancements due to a different scaling of the differential cross section with the p T . In particular it is easy to verify that the partonic differential cross sections at LO behave as 1/p 6 T for CP-even color-octet states and 1/p 4 T for the 3 S [8] 1 , compared to the 1/p 8 T scaling of the colorsinglet. In the case of charmonium production at the Tevatron, the 1/p 4 T and 1/p 6 T behaviors are clearly seen in the data [9] and the introduction of the contribution from the octets allows an explanation of the observed p T spectrum [10].…”

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confidence: 99%

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QCD Corrections toJ/ψandΥProduction at Hadron Colliders

2007

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We calculate the cross section for hadroproduction of a pair of heavy quarks in a 3 S1 color-singlet state at next-to-leading order in QCD. This corresponds to the leading contribution in the NRQCD expansion for J/ψ and Υ production. The higher-order corrections have a large impact on the pT distributions, enhancing the production at high pT both at the Tevatron and at the LHC. The total decay rate of a 3 S1 into hadrons at NLO is also computed, confirming for the first time the result obtained by Mackenzie and Lepage in 1981.PACS numbers: 12.38.Bx,13.25.Gv 1. Charmonium and bottomonium states are certainly among the most interesting systems to test our understanding of the strong interactions, both at the perturbative and non-perturbative level. More than thirty years after the discovery of the first charm-anticharm resonance, the J/ψ, the study of their properties, including production and decay mechanisms, is still the subject of considerable interest [1].From the theoretical point of view, a rigorous framework, based on the use of non-relativistic QCD (NRQCD) [2], has been introduced that allows consistent theoretical predictions to be made and to be systematically improved. However, despite theoretical developments and successes, not all the predictions of the NRQCD factorization approach have been firmly established. Recent measurements in e + e − collisions have shown that production rates for single and double charmonium production are in general much larger than those predicted by leading order calculations [3]. Measurements at the Tevatron in proton-antiproton collisions are not fully compatible with those obtained at HERA in electron-proton collisions [4] and in fixed-target experiments [5], suggesting the possibility that charmonium might be too light for the NRQCD factorization and/or scaling rules to work. In this context, a real challenge is offered by measurements of the J/ψ polarization at the Tevatron. NRQCD predicts a sizeable transverse polarization for J/ψ 's at high-p T , in contrast with the latest data that now clearly indicate that J/ψ's are not transversely polarized [6].In view of such a puzzling scenario, it is worth to re-examine in detail the theoretical predictions and try to systematically improve on them. In this Letter we report on the calculation of the next-to-leading order correction to the hadroproduction of a pair of heavy quarks in a color-singlet 3 S 1 state. This is the leading term in the NRQCD expansion for a J/ψ or a Υ and it is equivalent to the "color-singlet model" approximation. This model assumes that the nonperturbative dynamics leaves unchanged the quantum numbers of the perturbative quark-antiquark pair, which are the same as those of the physical bound state. It is curious to note that the analogous corrections to the hadronic decay width of a colorsinglet 3 S 1 state, which involve exactly the same diagrams, have been available for a long time [7] and play an important role in the extraction of α S from Υ decays [8]. Our calculation for the inclusive decay r...

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supporting

confidence: 72%

mentioning

confidence: 99%

QCD Corrections toJ/ψandΥProduction at Hadron Colliders

2007

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“…In order to extract α s , a sensible determination of the NRQCD hadronic matrix elements is needed. Using a combination of lattice and continuum inputs, the most recent analysis obtains [58] …”

Section: Quarkoniummentioning

confidence: 99%

Review of alpha_s determinations

Pich¹

2013

Proceedings of XTH Quark Confinement and the Hadron Spectrum — PoS(Confinement X)

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The present knowledge on the strong coupling is briefly summarized. The most precise determinations of α s , at different energies, are reviewed and compared at the Z mass scale, using the predicted QCD running. The impressive agreement achieved between experimental measurements and theoretical predictions constitutes a beautiful and very significant test of Asymptotic Freedom, establishing QCD as the fundamental theory of the strong interaction. The world average value of the strong coupling is found to be α s (M 2 Z ) = 0.1186 ± 0.0007. Xth Quark Confinement and the Hadron Spectrum

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“…3.2.2), together with a theoretical description of the photon spectrum [231], has made it possible to obtain a precise determination of α s from Υ(1S) decays [232]. A convenient observable is the parton-level ratio…”

Section: αS Determinationsmentioning

confidence: 99%

Heavy quarkonium: progress, puzzles, and opportunities

Brambilla¹,

Eidelman²,

Heltsley³

et al. 2011

Advances in the Physics of Particles and Nuclei

103

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A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the B-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations at BESIII, the LHC, RHIC, FAIR, the Super Flavor and/or Tau-Charm factories, JLab, the ILC, and beyond. The list of newly-found conventional states expanded to include hc(1P ), χc2(2P ), B + c , and η b (1S). In addition, the unexpected and still-fascinating X(3872) has been joined by * Editors † Section coordinators ‡ Corresponding author: bkh2@cornell.edu more than a dozen other charmonium-and bottomonium-like "XY Z" states that appear to lie outside the quark model. Many of these still need experimental confirmation. The plethora of new states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of cc, bb, and bc bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. Lattice QCD has grown from a tool with computational possibilities to an industrialstrength effort now dependent more on insight and innovation than pure computational power. New effective field theories for the description of quarkonium in different regimes have been developed and brought to a high degree of sophistication, thus enabling precise and solid theoretical predictions. Many expected decays and transitions have either been measured with precision or for the first time, but the confusing patterns of decays, both above and below open-flavor thresholds, endure and have deepened. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hotand cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.

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Extraction ofαsfrom radiativeΥ(1S)decays

Abstract: We improve on a recent determination of α s from Γ(Υ(1S) → γ X)/Γ(Υ(1S) → X) with CLEO data by taking into account color octet contributions and avoiding any model dependence in the extraction. We obtain α s (M Υ(1S) ) = 0.184

Cited by 55 publications

References 27 publications

QCD Corrections toJ/ψandΥProduction at Hadron Colliders

QCD Corrections toJ/ψandΥProduction at Hadron Colliders

Review of alpha_s determinations

Heavy quarkonium: progress, puzzles, and opportunities

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