Charmonium-like States Research Articles

Radiative open charm decay of the Y(3940) , Z(3930) , X(4160) resonances

We determine the radiative decay amplitudes for the decay into D* and \( \bar{{D}}\) \( \gamma\) , or D * s and \( \bar{{D}}_{s}^{}\) \( \gamma\) of some of the charmonium-like states classified as X , Y , Z resonances, plus some other hidden charm states which are dynamically generated from the interaction of vector mesons with charm. The mass distributions as a function of the \( \bar{{D}}\) \( \gamma\) or \( \bar{{D}}_{s}^{}\) \( \gamma\) invariant mass show a peculiar behavior as a consequence of the D * \( \bar{{D}}^{*}_{}\) nature of these states. The experimental search of these magnitudes can shed light on the nature of these states.

Charmonium physics in the belle experiment

At the present time, charmonium physics experiences renaissance. Among many discoveries made within the past six years, the majority do not have an unambiguous interpretation and do not comply with traditional theoretical expectations. This review article is devoted to experimental results obtained by the members of the Belle Collaboration from the Institute of Theoretical and Experimental Physics (ITEP, Moscow) in the realms of charmonium spectroscopy and the production and decays of charmonia and charmonium-like states.

Exotic Charmoniumlike States

A review of recent experimental results concerning the XYZ charmoniumlike mesons is presented.

Observation of a Charmoniumlike Enhancement in theγγ→ωJ/ψProcess

We report the results of a search for a charmonium-like state produced in the process gamma gamma --> omega J/psi in the 3.9-4.2 GeV/c^2 mass region. We observe a significant enhancement, which is well-described by a resonant shape with mass M = (3915 +/- 3 +/- 2) MeV/c^2 and total width Gamma = (17 +/- 10 +/- 3) MeV. This enhancement may be related to one or more of the three charmonium-like states so far reported in the 3.90-3.95 GeV/c^2 mass region.

Central diffraction at the LHCb

The LHCb experiment is shown to be ideal for studies of exclusive final states from central diffractive reactions. The gluon-rich environment of the central system allows detailed QCD studies and searches for exotic meson states, such as glueballs, hybrids and new charmonium-like states. It would also provide a good testing ground for detailed studies of heavy quarkonia. Due to its distinct design features, the LHCb can accurately measure the low-mass central systems with good purity. The efficiency of the Forward Shower Counter (FSC) system for detecting rapidity gaps is shown to be adequate for the proposed studies. With this detector arrangement, valuable new data can be obtained by tagging central diffractive processes.

Nature ofX(3872)from data

Properties of the charmoniumlike state X(3872) are investigated and its nature is discussed as based on the existing experimental data. In particular, we analyze the new data from Belle and BABAR Collaborations and argue that, while the BABAR data prefer the dynamically generated virtual state in the DD* system, the new Belle data clearly indicate a sizable cc 2{sup 3}P{sub 1} component in the X wave function.

New States and Charmonium Spectroscopy at BaBar

Several charmonium-like states above D D ¯ threshold have been discovered at the Belle and BaBar B -factories. Some are produced via Initial State Radiation (e.g. Y ( 4260 ) and Y ( 4350 ) ), and some are observed in B meson decays (e.g. X ( 3872 ) , Y ( 3940 ) , and Z ( 4430 ) − ). The Z ( 4430 ) − state has generated a great deal of interest, having minimum quark content ( c c ¯ d u ¯ ) and, thus, representing the unequivocal manifestation of a four-quark meson state. Here we summarize recent BaBar results on the Y ( 4260 ) , X ( 3872 ) , Y ( 3940 ) , and on a search for the Z ( 4430 ) − .

Coupled-channel and screening effects in charmonium spectrum

Using the same quenched limit as input, we compare the charmonium spectra predicted by two different models, i.e., the coupled-channel model and the screened potential model in the mass region below 4 GeV, in which the contributions from decay channels involving $P$-wave (as well as even higher excited) $D$ mesons can be neglected. We find that the two models have similar global features in describing the charmonium spectrum since they approximately embody the same effect of the vacuum polarization of dynamical light quark pairs. Adopting these models will be helpful to clarify the nature of the newly discovered charmonium or charmoniumlike states; and the coupled-channel model is more adept in investigating the influences of open-charm thresholds on the charmonium spectrum. In particular, we show the $S$-wave decay coupling effect on lowering the ${\ensuremath{\chi}}_{c1}(2P)$ mass toward the $D{\overline{D}}^{*}$ threshold, in support of the assignment of the $X(3872)$ as a ${\ensuremath{\chi}}_{c1}(2P)$-dominated charmonium state.

Charmonium 2007: New experimental results

The most important experimental results in charmonium physics in the energy region above the threshold for open-charm production that were obtained in recent years are surveyed. The first measurements of the exclusive cross sections for e + e − → D \( \bar D \), D \( \bar D \)*, and D* \( \bar D \)* processes are discussed along with the discovered decay ψ(4415) → \( \bar D_2^* \)(2460). The properties of charmonium-like states, including the group of states Y (4260), Y (4325), and Y (4660) with quantum numbers of J PC = 1−−; the X(3940) and X(4160) states discovered in the process of double charmonium production in e + e − annihilation; and the X(3872), Y(3940), and Z ±(4430) states found in B-meson decays, are presented.

Relativistic description of heavy tetraquarks

The masses of the ground-state and excited heavy tetraquarks with hidden charm and bottom are calculated within the relativistic diquark-antidiquark picture. The dynamics of the light quark in a heavy-light diquark is treated completely relativistically. The diquark structure is taken into account by calculating the diquark-gluon form factor. New experimental data on charmonium-like states above the open charm threshold are discussed. The obtained results indicate that X(3872), Y(4260), Y(4360), Z(4433), and Y(4660) can be tetraquark states with hidden charm.

Excited heavy tetraquarks with hidden charm

The masses of the excited heavy tetraquarks with hidden charm are calculated within the relativistic diquark-antidiquark picture. The dynamics of the light quark in a heavy-light diquark is treated completely relativistically. The diquark structure is taken into account by calculating the diquark-gluon form factor. New experimental data on charmonium-like states above open charm threshold are discussed. The obtained results indicate that X(3872), Y(4260), Y(4360), Z(4248), Z(4433) and Y(4660) could be tetraquark states with hidden charm.

RECENT RESULTS ON B DECAYS AT BELLE

We present the recent B decay results from BELLE experiment operated at the asymmetric e+e− KEKB collider in the energy of ϒ(4S) resonance. In this report, we mainly mention the B decays including multineutrinos sensitive on beyond Standard Model, and new charged charmonium-like state from B hadronic decays, which should be explained in the future.

Spectroscopy of Mesons with Heavy Quarks

I will give a concise overview of mesons with heavy quarks including p-wave charmed mesons and charmonium (or charmonium-like) states such as X(3872), Y(4260), X(3940), Y(3940), Z(3930) etc. The effect from the nearby S-wave open channels on the quark model spectrum is emphasized.

New Charmonium-like States

In recent years the B-factories and other machines have found evidence for a large number of new states with hidden charm: candidate h_c(1P), eta_c(2S), and chi_{c2}(2P) states; the well-established X(3872); enhancements called X(3940), Y(3940), and Y(4260); and a new structure at 4350 MeV. Various conventional-charmonium and more exotic interpretations of these data have been proposed. In this talk we review the current state of the experimental evidence and the prospects for clarifying the spectrum.

Results on Charmonium-like States from Belle

We present results from the Belle experiment on various charmonium-like states: X(3872), Y(3940), X(3940), Z(3930), and Y(4260). Several of these are difficult to interpret within the conventional quark model and may represent new types of hadronic structure.

The XYZs of cc̄

In this invited contribution I summarize the status of the new charmonium-like states near and above 3.9 GeV, which are the X(3872), X(3943), Y(3943), Z(3931), Y(4260) and ψ(4320). First I review the spectrum of conventional charmonium states in the context of a potential model, following which I discuss the status of these new states and consider whether they might be charmonia or charmonium hybrids, and how these possibilities might be tested in future.

Potential model calculations and predictions for heavy quarkonium

(Dated: February 2, 2008)We investigate the spectroscopy and decays of the charmonium and upsilon systems in a potentialmodel consisting of a relativistic kinetic energy term, a linear confining term including its scalarand vector relativistic corrections and the complete perturbative one-loop quantum chromodynamicshort distance potential. The masses and wave functions of the various states are obtained usinga variational technique, which allows us to compare the results for both perturbative and nonper-turbative treatments of the potential. As well as comparing the mass spectra, radiative widths andleptonic widths with the available data, we include a discussion of the errors on the parameterscontained in the potential, the effect of mixing on the leptonic widths, the Lorentz nature of theconfining potential and the possible c¯cinterpretation of recently discovered charmonium-like states.1. INTRODUCTION

Double charmonium production in annihilation at

The observation of the processes e + e − → J / ψ η c , J / ψ χ c 0 , and J / ψ η c ( 2 S ) is confirmed using a dataset more than three times larger than that of Belle's previous report, and no evidence for the process e + e − → J / ψ J / ψ is found. An angular analysis for J / ψ ( c c ¯ ) res production is performed and an upper limit on the production of J / ψ J / ψ is set. Processes of the type e + e − → ψ ( 2 S ) ( c c ¯ ) res have been observed for the first time; their rates are found to be comparable to those of e + e − → J / ψ ( c c ¯ ) res processes. The first observation of a new charmonium-like state at a mass of (3.943 ± 0.006 ± 0.006) GeV/c2is reported. This state, denoted as X(3940), is observed in the spectrum of masses recoiling from the J / ψ in the inclusive process e + e − → J / ψ + anything.

Masses of heavy tetraquarks in the relativistic quark model

The masses of heavy tetraquarks with hidden charm and bottom are calculated in the framework of the relativistic quark model. The tetraquark is considered as the bound state of a heavy–light diquark and antidiquark. The light quark in a heavy–light diquark is treated completely relativistically. The internal structure of the diquark is taken into account by calculating the diquark–gluon form factor in terms of the diquark wave functions. New experimental data on charmonium-like states above open charm threshold are discussed. The obtained results indicate that the X(3872) can be the tetraquark state with hidden charm. The masses of ground state tetraquarks with hidden bottom are found to be below the open bottom threshold.

Observation of a narrow charmoniumlike state in exclusive B+/--->K+/-pi+pi-J/psi decays.

We report the observation of a narrow charmoniumlike state produced in the exclusive decay process B+/--->K+/-pi(+)pi(-)J/psi. This state, which decays into pi(+)pi(-)J/psi, has a mass of 3872.0+/-0.6(stat)+/-0.5(syst) MeV, a value that is very near the M(D0)+M(D(*0)) mass threshold. The results are based on an analysis of 152M B-Bmacr; events collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The signal has a statistical significance that is in excess of 10sigma.