Study Of Charmonium Research Articles

Study of charmonium(-like) spectroscopy and decay at BESIII

The recent results on Charmonium and Charmonium-like states at BESIII are reviewed, including the observation of \rm Z_{cs}(3985) state, the study of the new decay modes of \psi_2(3823)ψ2(3823) state, observation of resonance structure in \rm e^+e^- \to \pi^+\pi^-\psi_2(3823) process, the study of the \rm e^+e^- \to K^+K^-J/\psi process, cross section measurement of \rm e^+e^- \to \omega\pi^0 and \omega\etaωη process, branching fraction measurement of \psi(3686)\to\bar{\Sigma}^0\Lambda + c.c.ψ(3686)→Σ‾0Λ+c.c. process. Decay channels for \chi_{cJ} \to \Lambda\bar{\Lambda}χcJ→ΛΛ‾, \chi_{cJ} \to \Lambda\bar{\Lambda}\etaχcJ→ΛΛ‾η, \psi(3686) \to \Lambda\bar{\Lambda}\omegaψ(3686)→ΛΛ‾ω and \eta_c(2S)\to3(\pi^+\pi^-)ηc(2S)→3(π+π−) are also discussed. The property of the spin singlet P wave Charmonium state, \rm h_c is also reported.

Charmonium studies at Belle

A review of recent charmonium studies at Belle is presented.

Perspective study of charmonium and exotics above the D $$\bar D$$ threshold

The spectroscopy of exotic states with hidden charm is discussed. Together with charmonium, these provide a good tool for testing theories of the strong interactions including both perturbative and nonperturbative QCD, lattice QCD, potential and other phenomenological models. An elaborated analysis of exotics spectrum is given, and attempts to interpret recent experimentally observed states with masses above the D $$\bar D$$ threshold region are considered. Experimental results from different collaborations (BES, BaBar, Belle, LHCb) are analyzed with special attention given to recently discovered hidden charm states. Some of these states can be interpreted as higher-lying charmonium states and others as tetraquarks with hidden charm. It has been shown that charged/neutral tetraquarks must have their neutral/charge partners with mass values differing by at most a few MeV. However, measurements of different decay modes are needed before firm conclusions can be made. These data can be derived directly from the experiments using a high quality antiproton beam with momentum up to 15 GeV/c and proton–proton collisions with momentum up to 26 GeV/c.

Study of the XYZ states at the BESIII

With its unique data samples at energies of 3.8–4.6 GeV, the BESIII experiment made a significant contribution to the study of charmonium and charmonium-like states, i.e., the XYZ states.We review the results for observations of the Z c (3900) and Z c (4020) states, the X(3872) in e + e - annihilation, and charmonium ?(1 3 D 2) state, as well as measurements of the cross-sections of ?? cJ and ?J/?, and the search for e + e - ? ?? cJ and ?Y (4140). We also present data from BESIII that may further strengthen the study of the XYZ and conventional charmonium states, and discuss perspectives on future experiments.

Prospects of charmonium studies in the Belle-II experiment

TheBelle-II experiment at the SuperKEKB super-B factorywill begin data acquisition in 2016, the expected integrated luminosity being 50 ab-1. A statistical data sample of record volume 50 times as large as that of the statistical data sample accumulated earlier at the Belle detector will make it possible to measure precisely the parameters of new exotic states discovered recently at B factories and to clarify the origin of these states.

Physics with antiprotons at [formula omitted]ANDA

The P¯ANDA collaboration (anti-Proton ANnihilations at DArmstadt) is a next generation hadron physics experiment to be operated at the future Facility for Antiproton and Ion Research (FAIR) at Darmstadt, Germany. It will use intensive cooled antiproton beams with a momentum between 1.5 GeV/c and 15 GeV/c. The P¯ANDA detector is a state-of-the-art internal target detector allowing the detection and identification of neutral and charged particles almost in the whole solid angle.One of the major goal of the experiment is the comprehensive study of charmonium and candidates to the hybrids, molecules and other exotics. Charmonium states with different quantum numbers can be reached via the decay of these resonances. The P¯ANDA will scan the parameters of the resonances in formation mode with the use of the excellent momentum resolution Δp/p=104 – 105 of the HESR beam. The precision measurements of light mesons mass and width will be fulfilled as well as glueball search.Study of double hyperon production including their spin properties is another important item of the P¯ANDA experiment.

Quarkonium Results in PbPb Collisions at CMS

We summarize the results from the study of charmonium and bottomonium via the dimuon decay channel in PbPb collisions with the CMS experiment. We discuss the observation of sequential suppression of the Υ states. We present preliminary results of prompt J/ψ and ψ' production, as well as of non-prompt J/ψ's coming from the weak decay of b-quarks. This latter measurement is sensitive to b-quark energy loss. We discuss the results and compare to model predictions.

Prospects for quarkonia production studies in U + U collisions

Collisions of deformed uranium nuclei provide a unique opportunity to study the spatial dependence of charmonium in-medium effects. By selecting the orientations of the colliding nuclei, different path lengths through the nuclear medium could be selected within the same experimental environment. In addition, higher energy densities can be achieved in U + U collisions relative to Au+Au collisions. In this paper, we investigate the prospects for charmonium studies with U + U collisions. We discuss the effects of shadowing and nuclear absorption on the $J/\ensuremath{\psi}$ yield. We introduce a new observable which could help distinguish between different types of $J/\ensuremath{\psi}$ interactions in hot and dense matter.

RECENT RESULTS ON CHARMONIUM DECAYS AT CLEO-c

The CLEO-c Experiment has made several recent contributions to the study of charmonium decays. This review briefly outlines the CLEO-c analyses of charmonium that were completed or made public during 2010. Special attention is given to the discovery of the process e+ e- → π+ π- hc at a center of mass energy of 4170 MeV.

Charmonium production in pp collisions at LHC with the ALICE Muon Spectrometer

The Forward Muon Spectrometer of the ALICE experiment is designed for the study of quarkonium resonances and open heavy flavour particles coming from the strongly interacting matter produced in nucleus-nucleus collisions at the LHC, where the formation of the Quark Gluon Plasma is expected. Muon pairs are detected at forward rapidity (−4 < y < −2.5) and in a wide transverse momentum range (from 0 to tens of GeV/c). The proton-proton physics program of the Muon Spectrometer has the aim to define a proper normalization for nuclear collision studies and to deal with some open issues such as quarkonium production mechanism and polarization. The physics performances of the Muon Spectrometer for charmonium studies are presented and the progress of the data taking with the first LHC high energy run is shown.

Recent results in charm and charmonium physics

The experiments at the B-factories offer excellent opportunities for charmed mesons and charmonium studies. The recent observation of new states with masses in the D s and the charmonium regions, whose properties are not fully understood, revived the interest in this field. More experimental results are needed, to discriminate between interpretations based on different models that have been proposed. A selection of recent BaBar results is presented.

Study of charmonium(-like) states via ISR at Belle**Talk given at the BES-Belle-CLEO-BaBar joint workshop on charm physics, Beijing, Chnia, November 26–27, 2007. Supported by National Natural Science Foundation of China (10775142) and 100 Talents Program of CAS (U-25)

The cross sections for e+e− → π+π−J/ψ, π+π−ψ(2S), K+K−J/ψ, DD̄, D0D−π++c.c., D*D̄+c.c., and D*D̄* are measured using data sample collected on or near the Υ(4S) resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c2, corresponding to the so called Y(4260), is observed in π+π−J/ψ final state. In addition, there is another cluster of events at around 4.05 GeV/c2. Two resonant structures are observed in the π+π−ψ(2S) invariant mass distribution, one at 4361±9±9 MeV/c2 with a width of 74±15±10 MeV/c2, and another at 4664±11±5 MeV/c2 with a width of 48±15±3 MeV/c2. The rich structures observed in all these final states indicate that our understanding of the vector charmonium states above the open charm threshold is still poor, let alone the other possible dynamics such as charmonium hybrids or final state re-scattering and so on.

ϒ cross section in p+p collisions at STAR

The main focus of the heavy flavour programme at RHIC is to investigate the properties of the dense matter produced in heavy-ion collisions by studying its effect on open heavy flavour and quarkonia production. This in turn requires a detailed understanding of their production in elementary p+p collisions so that the dense matter effects can be later unfolded. In this paper, we present the first midrapidity cross section measurement of bottomonium at with the STAR experiment. We compare our results with perturbative QCD calculations. A brief status on the study of charmonium in STAR is given.

Tracked pellets — a way to improve the efficiency of charmonium studies

We investigate the possibility of tracking individual hydrogen micro-spheres from an internal pellet target. Such a method aims to provide the primary vertex of a reaction to within about 100 μ m , without utilizing any detector response. Apart from background considerations the knowledge of the reaction vertex may be essential for the reconstruction of many physics channels. This is in particular true for the study of the Ψ ( 3770 ) decay into D-mesons planned at the PANDA detector at the future FAIR facility. Here, the reconstruction of displaced vertices is especially difficult since neutral particles are involved. Studies with a pellet target at The Svedberg Laboratory, Uppsala, show the technical feasibility of a tracking system utilizing fast CCD line-scan cameras. Simulations for the reaction p ¯ p → Ψ ( 3770 ) → D + D - prove the large impact such a system would have on the data taking and reconstruction at PANDA.

Physics with the P̄ANDA detector at GSI

The P̄ANDA experiment, which will be installed at the High-Energy Storage Ring (HESR) of the recently approved FAIR facility at GSI in Darmstadt, Germany, has a rich experimental program of hadron spectroscopy which includes the study of charmonium, the search for glueballs and hybrids and the investigation of in-medium modifications of hadrons as they interact with nuclear matter.

Experiment E835 at Fermilab

We provide a comprehensive description of experiment E835 at Fermilab, a high-precision experimental study of charmonium bound states. The c ̄ c states are formed in p ̄ p annihilations of cooled antiprotons stored in the Fermilab Antiproton Accumulator using a dense internal hydrogen gas-jet target. We describe the experimental strategies adopted for detecting the tiny c ̄ c resonant signals in the huge non-resonant hadronic background, and for measuring resonance parameters with high precision.

Experimental review of charmonium spectroscopy

Charmonium spectroscopy is one of the best means of making precision study of QCD, the strong-interaction component of the Standard Model of particle physics. Recent progress in the study of charmonium, the need for additional precision data, and the opportunities that the new facilities offer, are discussed.

Quarkonium Production at LEP with the OPAL Detector

Evidence for the production of ϒ mesons in hadronic Z0 decays has recently been reported by the OPAL experiment at LEP. ϒ mesons are identified from their decays into e+e- and μ+μ- pairs. These decays provide a clear signature, since the e+e- and μ+ μ- background with invariant mass around 10 GeV/c2 is found to be small. In the first part of this report, a summary of the ϒ analysis is presented and possible production mechanisms are discussed. In the second part, studies on charmonium production are presented. Charmonium studies are based on an inclusive sample of J/ψ candidates, used to derive inclusive J/ψ and ψ′ rates, and the prompt J/ψ rate as well. Finally, since prompt J/ψ mesons are expected to be produced at LEP by the same production mechanisms as for the ϒ, a more general discussion on quarkonium production via fragmentation processes is presented.

On the possibility of constructing a high luminosity 2 × 5 GeV photon collider at SLC

Physical principles of the operation of high-energy photon linear colliders (PLC's) based on the Compton backscattering of laser photons on high-energy electrons are discussed. The main emphasis is on analyzing the possibility of constructing a PLC with a center-of-mass energy of 3–10 GeV at the Stanford Linear Collider (SLC). It can be done with minor modifications of the existing facility by installing a new injector, kicker magnet and a two-stage free-electron laser (FEL). The proposed FEL system would consist of a tunable FEL oscillator ( λ ∼ 10–30 μm, output power ∼ 10 MW) with subsequent amplification of the master signal in an FEL amplifier up to a power of ∼ 3 × 10 11W. The FEL parameters are optimized, restrictions on the electron beam and FEL magnetic system parameters are formulated, and the means of possible technical realization are discussed. The FEL-based photon collider at SLC, providing a luminosity of colliding γγ beams L γγ of about 10 34 cm −2 s −1, may be constructed at the present level of acceleration technique R&D. It would be a unique instrument for precise study of charmonium and bottomonium physics as well as τ-lepton physics providing ∼ 10 2 polarized τ leptons per second. At the same time, the Photon Linear Collider at SLC would serve as a reliable test base for constructing future TeV-range photon linear colliders.