Measurements of ψ(2S) and X(3872) → J/ψπ + π − production in pp collisions at s = 8 $$ \sqrt{s}=8 $$ TeV with the ATLAS detector

Abstract

Measurements of ψ(2S) and X(3872) → J/ψπ + π − production in pp collisions at √ s = 8 TeV with the ATLAS detectorThe ATLAS collaboration E-mail: atlas.publications@cern.ch Abstract: Differential cross sections are presented for the prompt and non-prompt production of the hidden-charm states X(3872) and ψ(2S), in the decay mode J/ψπ + π − , measured using 11.4 fb −1 of pp collisions at √ s = 8 TeV by the ATLAS detector at the LHC. The ratio of cross-sections X(3872)/ψ(2S) is also given, separately for prompt and nonprompt components, as well as the non-prompt fractions of X(3872) and ψ(2S). Assuming independent single effective lifetimes for non-prompt X(3872) and ψ(2S) production gives= (3.95 ± 0.32(stat) ± 0.08(sys)) × 10 −2 , while separating short-and long-lived contributions, assuming that the short-lived component is due to B c decays, gives R B = (3.57 ± 0.33(stat) ± 0.11(sys)) × 10 −2 , with the fraction of non-prompt X(3872) produced via B c decays for p T (X(3872)) > 10 GeV being (25 ± 13(stat) ± 2(sys) ± 5(spin))%. The distributions of the dipion invariant mass in the X(3872) and ψ(2S) decays are also measured and compared to theoretical predictions. A Spin-alignment 21The ATLAS collaboration 26 IntroductionThe hidden-charm state X(3872) was discovered by the Belle Collaboration in 2003 [1] through its decay to J/ψπ + π − in the exclusive decay B ± → K ± J/ψπ + π − . Its existence was subsequently confirmed by CDF [2] through its production in pp collisions, and its production was also observed by the BaBar [3] and D0 [4] experiments shortly after. CDF determined [5] that the only possible quantum numbers for X(3872) were J P C = 1 ++ and 2 −+ . At the LHC, the X(3872) was first observed by the LHCb Collaboration [6], which finally confirmed its quantum numbers to be 1 ++ [7]. A particularly interesting aspect of the X(3872) is the closeness of its mass, 3871.69 ± 0.17 MeV [8], to the D 0D * 0 threshold, such that it was hypothesised to be a D 0D * 0 molecule with a very small binding energy [9]. A cross-section measurement of promptly produced X(3872) was performed by CMS [10] as a function of p T , and showed the non-relativistic QCD (NRQCD) prediction [11] for prompt X(3872) production, assuming a D 0D * 0 molecule, to be too high, although the shape of the p T dependence was described fairly well. A later interpretation of X(3872) as a mixed χ c1 (2P )-D 0D * 0 state, where the X(3872) is produced predominantly through its χ c1 (2P ) component, was adopted in conjunction with the next-to-leading-order (NLO) NRQCD model and fitted to CMS data, showing good agreement [12].-1 -

X(3872) as virtual companion pole of the charm–anticharm state χc1(2P)

“…The scenario proposed in our work merges quite well both the charmonium and the molecular behavior of the arXiv:1903.06926v2 [hep-ph] 24 Oct 2019…”

Production of X(3872) accompanied by a soft pion at hadron colliders

“…Estimates of the ratio of the cross sections for producing Xπ 0 and Xπ ± in the peak from the charmmeson triangle singularity to the cross section for producing X without an accompanying pion are given in Eqs. (21).…”

“…It is only logarithmically sensitive to the binding energy |E X |, but it depends strongly on the unknown momentum scale Λ of order m π . The inclusive prompt production of X in pp collisions has been studied at the Large Hadron Collider (LHC) by the CMS [20] and ATLAS [21] collaborations. The inclusive production of X in pp collisions has also been studied at the LHC by the LHCb [19], but they did not separate the prompt production from production from decay of bottom hadrons.…”

“…The inclusive production of X in pp collisions has been studied at the Tevatron by the CDF [12] and D0 [18] collaborations. The inclusive production of X in pp collisions has been studied at the Large Hadron Collider (LHC) by the LHCb [19], CMS [20], and ATLAS [21] collaborations. At a high energy hadron collider, X is produced by the weak decays of bottom hadrons, and it is also produced promptly through QCD mechanisms that create charm quarks and antiquarks.…”

Study of the X±(5568) state with semileptonic decays of the BsAbazov1, Abbott2, Acharya3 et al. 2018Phys. Rev. DSelf Cite341130View full textAdd to dashboardCite

“…The 2003 discovery by the Belle experiment [7] of the Xð3872Þ in the channel B AE → K AE Xð→ π þ π − J=ψÞ was the first candidate exotic meson in which heavy flavor quarks participate. This state was subsequently confirmed in several production and decay modes by ATLAS [8], BABAR [9], BES III [10], CDF [11], CMS [12], D0 [13] and LHCb [14] Collaborations. Several additional four-quark candidate exotic mesons have since been found, though in many cases not all experiments have been able to confirm their existence.…”