Charmonium States Research Articles

Bethe-Salpeter wave functions of ηc(1S, 2S) and ψ(1S, 2S) states: local-potential description of the charmonium system revisited

The quark potential models with an energy-independent central potential have been successful for understanding the conventional charmonium states especially below the open charm threshold. As one might consider, however, the interquark potential is in general energy-dependent, and its tendency gets stronger in higher lying states. Confirmation of whether the interquark potential is energy-independent is also important to verify the validity of the quark potential models. In this talk, we examine the energy dependence of the charmonium potential, which can be determined from the Bethe-Salpeter (BS) amplitudes of cc̅ mesons in lattice QCD.We first calculate the BS amplitudes of radially excited charmonium states, the ηc(2S) and ψ(2S) states, using the variational method and then determine both the quark kinetic mass and the charmonium potential within the HAL QCD method. Through a direct comparison of charmonium potentials determined from both the 1S and 2S states, we confirm that neither the central nor spin-spin potential shows visible energy dependence at least up to 2S state.

Charmonium Excitation Functions in $\bar p A$ Collisions

We study the excitation function of the low-lying charmonium state: $\Psi$(3686) in $\bar p$ Au collisions taking into account their in-medium propagation. The time evolution of the spectral functions of the charmonium state is studied with a BUU type transport model. We calculated the excitation function of $\Psi$(3686) production and show that it is strongly effected by the medium. The energy regime will be available for the PANDA experiment.

Vector states above open charm threshold at BESIII

Based on the the large XYZ data sample collected at BESIII detector, we study the vector states above charm threshold, including the traditional charmonium and charmonium-like states, Y in many decay modes. For example, e+e- → hc, π+π-J/Ψ,Ψ(3686); e+e- → η(ή)J/Ψ. Many charmonium and charmonium-like candidates are found, but some of them need to be confirmed further with much larger data.

XYZ states at BESIII

The BESIII experiment has collected about 6 fb-1 luminosity data samples above 3.8 GeV. Recent result on the charmonium(-like) states (or called XYZ states) from BESIII experiment is presented in this talk, including the production and decay of the X(3872) states, the vector Y states, as well as the charged and neutral charmoniumlike Zc states.

Recent heavy-flavour results from ATLAS

The ATLAS heavy-ion program utilizes heavy-flavour hadrons to probe the hot, dense matter formed at the LHC. Quarkonium measurements have been performed in pp, p+Pb and Pb+Pb systems to study medium effects. The Pb+Pb results show a strong suppression of charmonium productions in more central events. Proton-lead interactions show little modification of the 1S charmonium state, but seem to indicate a centrality dependence of the 2S state. Upsilons have been studied in p+Pb and are found to show decreasing behaviour in more central collisions. Inclusive muons with pT above 4 GeV have been studied to provide insight on open-flavour production, and are found to be strongly suppressed in Pb+Pb collisions with a substantial and significant elliptic flow signal. Muon-hadron correlations have also been studied in the 2016 [see formula in PDF] = 8.16 TeV p+Pb data. There are clear indications of a near-side ridge, suggesting that similar mechanisms may be relevant for both the small and large systems.

Understanding X(3862), X(3872), and X(3930) spectrum in a Friedrichs-model-like scheme

In this talk, we review the method we proposed to use the Friedrichs-like model combined with QPC model to include the hadron interaction corrections to the spectrum predicted by the quark model, in particular the Godfrey-Isgur model. This method is then used on the first excited P-wave charmonium states, and X(3862), X(3872), and X(3930) state could be simultaneously produced with a quite good accuracy. The X(3872) state is shown to be a bound state with a large DD* continuum component. At the same time, the hc(2P) state is perdicted at about 3902 MeV with a pole width of about 54 MeV.

Charmonium production in pPb and PbPb collisions at 5.02 TeV with CMS

Charmonium states, such as the J/ψ and ψ(2S) mesons, are excellent probes of the deconfined state of matter, the Quark-Gluon Plasma (QGP) created in heavy ion collisions. In addition, the measurements in pPb collisions allow to study the cold nuclear matter effects, being crucial to disentangle these from the QGP-related effects in PbPb collisions. In this talk the new nuclear modification factor RAA of prompt and nonprompt J/ψ in PbPb collisions at [see formula in PDF] = 5.02 TeV were presented over a wide kinematic range (3 < pT < 50 GeV/c, |y| < 2.4), and fine event-centrality intervals. The results were compared to those at 2.76 TeV over a similar kinematic range. In addition, new prompt ψ(2S) RAA results at 5.02 TeV were reported. Finally the final prompt and nonprompt J/ψ results, as well as preliminary ψ(2S) results, in pPb collisions at 5.02 TeV, were discussed.

Bottom and charm mass determinations from global fits to Qoverline{Q} bound states at N3LO

The bottomonium spectrum up to n = 3 is studied within Non-Relativistic Quantum Chromodynamics up to N3LO. We consider finite charm quark mass effects both in the QCD potential and the overline{mathrm{MS}} -pole mass relation up to third order in the Y-scheme counting. The u = 1/2 renormalon of the static potential is canceled by expressing the bottom quark pole mass in terms of the MSR mass. A careful investigation of scale variation reveals that, while n = 1, 2 states are well behaved within perturbation theory, n = 3 bound states are no longer reliable. We carry out our analysis in the nℓ = 3 and nℓ = 4 schemes and conclude that, as long as finite mc effects are smoothly incorporated in the MSR mass definition, the difference between the two schemes is rather small. Performing a fit to boverline{b} bound states we find {overline{m}}_bleft({overline{m}}_bright) = 4.216 ± 0.039 GeV. We extend our analysis to the lowest lying charmonium states finding {overline{m}}_cleft({overline{m}}_cright) = 1.273 ± 0.054 GeV. Finally, we perform simultaneous fits for {overline{m}}_b and αs finding {alpha}_s^{left({n}_f=5right)}left({m}_Zright)=0.1178pm 0.0051 . Additionally, using a modified version of the MSR mass with lighter massive quarks we are able to predict the uncalculated mathcal{O}left({alpha}_s^4right) virtual massive quark corrections to the relation between the overline{mathrm{MS}} and pole masses.

Charmonia production from b-hadron decays at LHC with k_T-factorization: J/psi , psi (2S) and J/psi + Z

We consider the production of J/psi and psi (2S) mesons originating from the decays of b-flavored hadrons at the LHC using the k_T-factorization approach. Our analysis covers both inclusive charmonia production and production of J/psi mesons in association with Z bosons. We apply the transverse momentum dependent (or unintegrated) gluon density in a proton derived from Catani–Ciafaloni–Fiorani–Marchesini (CCFM) evolution equation and adopt fragmentation functions based on the non-relativistic QCD factorization to describe the inclusive b-hadron decays into the different charmonium states. Our predictions agree well with latest experimental data taken by the CMS, ATLAS and LHCb Collaborations at sqrt{s} = 7, 8 and 13 TeV. The contributions from double parton scattering to the associated non-prompt J/psi + Z production are estimated and found to be small.

Observation of the helicity-selection-rule suppressed decay of the χc2 charmonium state

The decays of χc2→K+K−π0, KSK±π∓, and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K*K¯, χc2→a2±(1320)π∓/a20(1320)π0, and χc2→ρ(770)±π∓ are measured. Here, K*K¯ denotes both K*±K∓ and its isospin-conjugated process K*0K¯0+c.c., and K* denotes the resonances K*(892), K2*(1430), and K3*(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K*(892)K¯ are more than ten times larger than the upper limit of χc2→ρ(770)±π∓, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.Received 18 December 2016DOI:https://doi.org/10.1103/PhysRevD.96.111102© 2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasParticle decaysParticle interactionsParticles & Fields

AdS/QCD duality and the quarkonia holographic information entropy

Bottomonium and charmonium, representing quarkonia states, are scrutinized under the point of view of the information theory, in the AdS/QCD holographic setup. A logarithmic measure of information, comprised by the configurational entropy, is here employed to quantitatively study quarkonia radially excited S-wave states. The configurational entropy provides data regarding the relative dominance and the abundance of the bottomonium and charmonium states, whose underlying information is more compressed, in the Shannon's theory meaning. The derived configurational entropy, therefore, identifies the lower phenomenological prevalence of higher S-wave resonances and higher masses quarkonia in Nature.

B-meson decays into charmonium states in the ATLAS experiment

The paper presents several recent ATLAS results on the analyses of B-meson decays into charmonium states. These include the measurements of B+ mass and the fractions of J/ψ mesons produced in b-hadron decays in pp collisions at $$\sqrt s$$ = 13 TeV in the center of mass system. The measured partial widths and polarizations in B + → J/ψD (*)+ decays and CP-violation parameters in B 0 → J/ψϕ decays in pp collisions at 7 and 8 TeV in the center of mass system are also presented.

Holographic model for charmonium dissociation

We present a holographic bottom up model for the thermal behavior of cc¯ vector mesons in a finite temperature and density plasma. There is a clear physical interpretation for the three input energy parameters of the model. Two of them are related to the mass spectrum of the heavy meson. Namely the quark mass and the string tension of the quark–anti-quark interaction. The third parameter is a large energy scale associated with the non-hadronic meson decay. In such a process the heavy meson is transformed into a much lighter state by electroweak processes. The corresponding transition amplitude is assumed to depend on the energy scale associated with this large mass variation. With this three parameter model one can fit the masses and decay constants of J/Ψ and three radial excitations with an rms error of 20.7%. Using the geometry of a charged black hole, one finds the spectral function for charmonium states inside a plasma at finite temperature and density. The charmonium dissociation in the medium is represented by the decrease in the height of the spectral function peaks.

Comparison of two Minkowski-space approaches to heavy quarkonia

In this work we compare mass spectra and decay constants obtained from two recent, independent, and fully relativistic approaches to the quarkonium bound-state problem: the Basis Light-Front Quantization approach, where light-front wave functions are naturally formulated; and, the Covariant Spectator Theory (CST), based on a reorganization of the Bethe–Salpeter equation. Even though conceptually different, both solutions are obtained in Minkowski space. Comparisons of decay constants for more than ten states of charmonium and bottomonium show favorable agreement between the two approaches as well as with experiment where available. We also apply the Brodsky–Huang–Lepage prescription to convert the CST amplitudes into functions of light-front variables. This provides an ideal opportunity to investigate the similarities and differences at the level of the wave functions. Several qualitative features are observed in remarkable agreement between the two approaches even for the rarely addressed excited states. Leading-twist distribution amplitudes as well as parton distribution functions of heavy quarkonia are also analyzed.

Heavy flavour production in proton–lead and lead–lead collisions with LHCb

The LHCb experiment offers the unique opportunity to study heavy-ion interactions in the forward region (2<η<5), in a kinematic domain complementary to the other 3 large experiments at the LHC. The detector has excellent capabilities for reconstructing quarkonia and open charm states, including baryons, down to zero pT. It can separate the prompt and displaced charm components. In pPb collisions, both forward and backward rapidities are covered thanks to the possibility of beam reversal. Results include measurements of the nuclear modification factor and forward-backward ratio for charmonium, open charm and bottomonium states. These quantities are sensitive probes for nuclear effects in heavy flavour production. Perspectives are given with the large accumulated luminosity during the 2016 pPb run at the LHC. In 2015, LHCb participated successfully for the first time in the PbPb data-taking. The status of the forward prompt J/ψ nuclear modification factor measurement in lead-lead collisions is discussed.

Measurement of charmonium production in heavy-ion collisions with the ATLAS detector

The suppression of charmonium states in heavy-ion collisions is a phenomenon understood as a consequence of quark gluon plasma formation in the hot, dense system formed in heavy ion collisions at the LHC. In addition to hot matter effects in heavy-ion collisions, so-called cold nuclear effects that modify charmonium production are also present. Therefore, a full assessment requires detailed studies in both A+A and p+A collisions. Based on p+Pb data collected in 2013 and pp and Pb+Pb data collected in 2015 at the LHC, the ATLAS experiment has studied prompt and non-prompt J/ψ and ψ(2S) production via the dimuon decay final states. The production yields and excited-to-ground state yield ratios, measured in p+Pb and Pb+Pb with respect to that measured in pp collision data, are presented in intervals of transverse momentum, rapidity and centrality.

Quarkonium h states as arbiters of exoticity

The mass splitting between the quarkonium spin-singlet state $h$ ($J^{PC} = 1^{+-}$) and the spin average of the quarkonium spin-triplet states $\chi$ ($J^{PC} = 0^{++}, 1^{++}, 2^{++}$) is seen to be astonishingly small, not only in the charmonium and bottomonium cases where the relevant masses have been measured, but in positronium as well. We find, both in nonrelativistic quark models and in NRQCD, that this hyperfine splitting is so small that it can be used as a test of the pure $Q\bar Q$ content of the states. We discuss the $2P$ states of charmonium in the vicinity of $3.9$ GeV, where the putative exotics $X(3872)$ and $X(3915)$ have been seen and a new $\chi_{c0}(2P)$ candidate has been observed at Belle.

Light-by-light forward scattering sum rules for charmonium states

We apply three forward light-by-light scattering sum rules to charmonium states. We show that these sum rules imply a cancellation between charmonium bound state contributions, which are mostly known from the $\gamma \gamma$ decay widths of these states, and continuum contributions above $D \bar D$ threshold, for which we provide a duality estimate. We also show that two of these sum rules allow to predict the yet unmeasured $\gamma^\ast \gamma$ coupling of the $\chi_{c1}(1P)$ state, which can be tested at present high-luminosity $e^+ e^-$ colliders.

Study of charmonium production in {b} -hadron decays and first evidence for the decay {{{B}} ^0_{{s}}} !rightarrow phi phi phi

Using decays to phi -meson pairs, the inclusive production of charmonium states in {b} -hadron decays is studied with pp collision data corresponding to an integrated luminosity of 3.0 {,mathrm{fb}}^{-1} , collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. Denoting by {mathcal {B}} _C equiv {mathcal {B}} ( {{b}} !rightarrow C X ) times {mathcal {B}} ( C!rightarrow phi phi ) the inclusive branching fraction of a {{b}} hadron to a charmonium state C that decays into a pair of phi mesons, ratios R^{C_1}_{C_2}equiv {mathcal {B}} _{C_1} / {mathcal {B}} _{C_2} are determined as R^{{upchi _{{{c}} 0}}}_{{eta _{{c}}} (1S)} = 0.147 pm 0.023 pm 0.011, R^{{upchi _{{{c}} 1}}}_{{eta _{{c}}} (1S)} = 0.073 pm 0.016 pm 0.006, R^{{upchi _{{{c}} 2}}}_{{eta _{{c}}} (1S)} = 0.081 pm 0.013 pm 0.005, R^{{upchi _{{{c}} 1}}}_{{upchi _{{{c}} 0}}} = 0.50 pm 0.11 pm 0.01, R^{{upchi _{{{c}} 2}}}_{{upchi _{{{c}} 0}}} = 0.56 pm 0.10 pm 0.01 and R^{{eta _{{c}}} (2S)}_{{eta _{{c}}} (1S)} = 0.040 pm 0.011 pm 0.004. Here and below the first uncertainties are statistical and the second systematic. Upper limits at 90% confidence level for the inclusive production of X(3872), X(3915) and {upchi _{{{c}} 2}} (2P) states are obtained as R^{X(3872)}_{{upchi _{{{c}} 1}}} < 0.34, R^{X(3915)}_{{upchi _{{{c}} 0}}} < 0.12 and R^{{upchi _{{{c}} 2}} (2P)}_{{upchi _{{{c}} 2}}} < 0.16. Differential cross-sections as a function of transverse momentum are measured for the {eta _{{c}}} (1S) and chi _c states. The branching fraction of the decay {{{B}} ^0_{{s}}} !rightarrow phi phi phi is measured for the first time, {mathcal {B}} ( {{{B}} ^0_{{s}}} !rightarrow phi phi phi ) = (2.15 pm 0.54 pm 0.28 pm 0.21_{{mathcal {B}}}) times 10^{-6}. Here the third uncertainty is due to the branching fraction of the decay {{{B}} ^0_{{s}}} !rightarrow phi phi , which is used for normalization. No evidence for intermediate resonances is seen. A preferentially transverse phi polarization is observed. The measurements allow the determination of the ratio of the branching fractions for the {eta _{{c}}} (1S) decays to phi phi and {{p}} {overline{{{p}}}} as {mathcal {B}} ( {eta _{{c}}} (1S)!rightarrow phi phi )/{mathcal {B}} ( {eta _{{c}}} (1S)!rightarrow {{p}} {overline{{{p}}}} ) = 1.79 pm 0.14pm 0.32.

Charmonium production in Pb–Pb collisions measured by ALICE at the LHC

The ALICE experiment is dedicated to the study of the Quark-Gluon Plasma (QGP), a state of matter where, due to high temperature and density, quarks and gluons are deconfined. One of the probes studied to investigate this state of matter is the production of charmonium states, such as the J/ψ and the ψ(2S). Indeed, the presence of the QGP is expected to modify the charmonium production yields, due to a balance between the color screening of the charm quark potential and a recombination mechanism. A suppression of the production yields in heavy ion collisions with respect to pp collisions scaled by the mean number of binary nucleon-nucleon collisions was observed by ALICE in Pb-Pb collisions at a centre-of-mass energy per nucleon pair sNN=2.76 TeV. The observed suppression is smaller than the one found by PHENIX at an order of magnitude lower collision energy. This behavior can be explained by a stronger contribution from recombination processes at LHC than at lower energies. In this presentation, we report on new results for the charmonium production in Pb-Pb collisions measured at forward rapidity with the the muon spectrometer of ALICE at sNN=5.02 TeV and their comparison with previous results and model predictions.