Two-loop ultrasoft running of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>O</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:msup><mml:mi>v</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:mo stretchy="false">)</mml:mo></mml:math>QCD quark potentials

Hoang, André H.; Stahlhofen, Maximilian

doi:10.1103/physrevd.75.054025

Cited by 18 publications

(39 citation statements)

References 22 publications

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“…A discussion on the v 2 -suppressed vNRQCD potentials is given in Refs. [20,38,39]. We note that there are also potentials generated by the electroweak interactions.…”

Section: A Basicsmentioning

confidence: 97%

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Phase space matching and finite lifetime effects for top-pair production close to threshold

2010

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The top-pair t " t production cross section close to threshold in e þ e À collisions is strongly affected by the small lifetime of the top quark. Since the cross section is defined through final states containing the top decay products, a consistent definition of the cross section depends on prescriptions of how these final states are accounted for the cross section. Experimentally, these prescriptions are implemented, for example, through cuts on kinematic quantities such as the reconstructed top quark invariant masses. As long as these cuts do not reject final states that can arise from the decay of a top and an antitop quark with a small off-shellness compatible with the nonrelativistic power counting, they can be implemented through imaginary phase space matching conditions in nonrelativistic QCD. The prescription-dependent cross section can then be determined from the optical theorem using the e þ e À forward scattering amplitude. We compute the phase space matching conditions associated to cuts on the top and antitop invariant masses at next-to-next-to-leading logarithmic order and partially at next-to-next-to-next-toleading logarithmic order in the nonrelativistic expansion accounting also for higher order QCD effects. Together with finite lifetime and electroweak effects known from previous work, we analyze their numerical impact on the t " t cross section. We show that the phase space matching contributions are essential to make reliable nonrelativistic QCD predictions, particularly for energies below the peak region, where the cross section is small. We find that irreducible background contributions associated to final states that do not come from top decays are strongly suppressed and can be neglected for the theoretical predictions.

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“…A discussion on the v 2 -suppressed vNRQCD potentials is given in Refs. [20,38,39]. We note that there are also potentials generated by the electroweak interactions.…”

Section: A Basicsmentioning

confidence: 97%

“…Partial results for the NNLL order anomalous dimension of the current have been computed in Refs. [4,20]. At the present stage, renormalization group improved results have a normalization uncertainty of 6%-10% [19,21].…”

Section: Introductionmentioning

confidence: 98%

Phase space matching and finite lifetime effects for top-pair production close to threshold

2010

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“…[29]. Recently the full set of ultrasoft mixing corrections from the subleading RG evolution of the potential coefficients [30][31][32] has become available [32]. 3 The results show that the ultrasoft mixing and non-mixing NNLL corrections to the evolution of the production current are both anomalously large, but that there are substantial cancellations between them.…”

Section: Jhep05(2014)121mentioning

confidence: 99%

The top-antitop threshold at the ILC: NNLL QCD uncertainties

Hoang

Stahlhofen²

2014

J. High Energ. Phys.

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Abstract:We discuss the top-antitop production cross section near threshold at a future linear collider accounting for the NNLL QCD corrections to the anomalous dimension of the leading S-wave production current computed recently within renormalization-groupimproved NRQCD perturbation theory. We argue that the still unknown soft NNLL mixing corrections are negligible so that the NNLL QCD corrections to the total cross section can be considered complete for practical purposes. Based on combined variations of the renormalization and matching scales and the overall size of the perturbative corrections we estimate that the NNLL QCD total cross section has a normalization uncertainty of dσ/σ = 5% at threshold. We present results for the total cross section and also for the experimentally more relevant case, when moderate cuts are imposed on the reconstructed top and antitop invariant masses.

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“…Those resummations, which were originally only done in the framework of velocity NRQCD, have now been calculated within pNRQCD [260]. The terms at next-to-nextto-leading logarithmic accuracy are not yet completely known [261]. Consistent inclusion of all effects related to the instability of the top quark is needed.…”

Section: Mt Determinationmentioning

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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Two-loop ultrasoft running of theO(v2)QCD quark potentials

Cited by 18 publications

References 22 publications

Phase space matching and finite lifetime effects for top-pair production close to threshold

Phase space matching and finite lifetime effects for top-pair production close to threshold

The top-antitop threshold at the ILC: NNLL QCD uncertainties

Heavy quarkonium: progress, puzzles, and opportunities

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