Measurement of the production cross-section of ψ(2S) → J/ψ(→μ + μ − )π + π − in pp collisions at s $$ \sqrt{s} $$ = 7 TeV at ATLAS

Abstract

Measurement of the production cross-section of ψ(2S) → J/ψ(→ µ + µ − )π + π − in pp collisions at √ s = 7 TeV at ATLASThe ATLAS collaboration E-mail: atlas.publications@cern.ch Abstract:The prompt and non-prompt production cross-sections for ψ(2S) mesons are measured using 2.1 fb −1 of pp collision data at a centre-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. The measurement exploits the ψ(2S) → J/ψ(→ µ + µ − )π + π − decay mode, and probes ψ(2S) mesons with transverse momenta in the range 10 ≤ p T < 100 GeV and rapidity |y| < 2.0. The results are compared to other measurements of ψ(2S) production at the LHC and to various theoretical models for prompt and non-prompt quarkonium production. Keywords: Hadron-Hadron ScatteringArXiv ePrint: 1407.5532Open Access, Copyright CERN, for the benefit of the ATLAS Collaboration. Article funded by SCOAP 3 .doi:10.1007/JHEP09(2014)079 JHEP09(2014)079 A Acceptance correction factors 28The ATLAS collaboration 33 IntroductionThe production of quarkonium states in hadronic collisions has been the subject of intense theoretical and experimental study for many decades, especially since measurements of prompt J/ψ and Υ production at the Tevatron [1-7] exposed order-of-magnitude differences between data and theoretical expectations [8]. Despite these being among the most studied heavy-quark bound states, there is still no satisfactory understanding of the mechanisms of their formation. Quarkonium production acts as a unique and important testing ground for quantum chromodynamics (QCD) in its own right. While the production of a heavy quark pair occurs at a hard scale and is generally well-described by QCD, its subsequent evolution into a bound state includes many non-perturbative effects at much softer scales that pose a challenge to current theoretical methods. With the data obtained from the Large Hadron Collider (LHC), it is possible to perform stringent tests of theoretical models across a large range of momentum transfer. Studies of heavy quarkonia were conducted previously by ATLAS in the J/ψ → µ + µ − [9] and Υ(nS) → µ + µ − [10, 11] decay modes. The measurements described here are based on an analysis of 2.1 fb −1 of pp collision data at √ s = 7 TeV, and study the prompt and non-prompt production of the ψ(2S) meson through its decay to J/ψ(→µ + µ − )π + π − . The prompt production arises from direct QCD production mechanisms and the nonprompt production arises from weak decays of b-hadrons. The J/ψ(→µstate offers improvements in ψ(2S) mass resolution and background discrimination over exclusive dilepton channels. Unlike prompt J/ψ production, which can occur through either direct QCD production of J/ψ or the production of excited states that subsequently decay into J/ψ + X final states, no appreciable prompt production of excited states decaying into ψ(2S) has been established in hadron collisions. In this respect the ψ(2S) is a unique state with no significant feed-down from higher quarkonium resonances, which decay predominantly to DD pairs.The measu...

HELAC-Onia 2.0: An upgraded matrix-element and event generator for heavy quarkonium physics

“…For instance, through a combined fit of d 2 σ/dP T dy to the ATLAS [70], CMS [107], LHCb [108] and CDF [109] data, we obtained κ = 0.543 and λ = 0.118 for prompt ψ(2S) when P T = 4.5 GeV and n = 2, where χ 2 = 242 for total 90 experimental data. The comparisons are shown in Fig.8.…”

Yields and polarizations of prompt J/ψ and ψ(2S) production in hadronic collisions

“…We update our numerical predictions for ψ(2S) yields at the Tevatron and the LHC as several collaborations have released their prompt ψ(2S) yields measurements [26,[31][32][33] in the past a few years. It is worthwhile to mention that one of the main uncertainty in experimental measurement comes from the unknown spin-alignment.…”

“…Comparison of NLO NRQCD (with the default set of CO LDMEs) and CDF [26],CMS [31], LHCb [32] and ATLAS [33] data for prompt ψ(2S) yields. [26],CMS [31], LHCb [32] and ATLAS [33] data for prompt ψ(2S) yields. Comparison of NLO NRQCD (with the default set of CO LDMEs) and CDF [34], CMS [35] and LHCb [36] data for prompt ψ(2S) polarisation λ θ in helicity frame.…”

“…[8,11]. Comparison of NLO NRQCD (with the default set of CO LDMEs) and CDF [26],CMS [31], LHCb [32] and ATLAS [33] data for prompt ψ(2S) yields. [26],CMS [31], LHCb [32] and ATLAS [33] data for prompt ψ(2S) yields.…”

Quarkonium production at the LHC: A data-driven analysis of remarkably simple experimental patterns

“…6, we choose to refer to the standard conjecture of fully transverse 3 S [8] 1 polarization. In the new conjecture, instead, the 3 S [8] 1 term would contribute to both the unpolarized (σ u ) and polarized (σ p ) cross sections, depending on the effective polarization (0 < λ ϑ ( 3 S [8] 1 ) < 1) transmitted by the 3 Unpolarized ψ Polarized ψ Figure 6: Unpolarized (left) and polarized (right) cross sections in the UAU scenario, normalized to unity at p T /M = 2, with uncertainty bands reflecting correlated variations in the fit parameters. The 1 S [8] 0 and 3 S [8] 1 SDCs are also shown, arbitrarily normalized, calculated at NLO with NNLO fragmentation contributions [27].…”