In this work, we investigate the decay widths and the line shapes of the open-charm radiative and pionic decays of Y(4274) with the $D_s\bar{D}_{s0}(2317)$ molecular charmonium assignment. Our calculation indicates that the decay widths of $Y(4274)\to D^{+}_{s}D^{*-}_{s}γ$ and $Y(4274)\to D^+_{s}D^-_{s}π^0$ can reach up to 0.05 keV and 0.75 keV, respectively. In addition, the result of the line shape of the photon spectrum of $Y(4274)\to D_s^+ {D}_s^{*-} γ$ shows that there exists a very sharp peak near the large end point of photon energy. The line shape of the pion spectrum of $Y(4274)\to D_s^+ {D}_s^{*-} π^0$ is similar to that of the pion spectrum of $Y(4274)\to D_s^+ {D}_s^{*-} γ$, where we also find a very sharp peak near the large end point of pion energy. According to our calculation, we suggest further experiments to carry out the search for the open-charm radiative and pionic decays of Y(4274).
We consider transitions from the resonance X(3872) to the chi_{cJ} states of charmonium with emission of one or two pions as a means of studying the structure of the X resonance. We find that the relative rates for these transitions to the final states with different J significantly depend on whether the initial state is a pure charmonium state or a four-quark/molecular state.
We propose to investigate various charmonium states using their common decay channel to p pbar at LHC. Having the branching ratios for charmonium decaying into the p pbar final state measured or calculated, we propose to measure the charmonium production rate for both hadroproduction including soft-diffraction and inclusive production from b-hadron decays. We discuss the theoretical impacts in QCD of measuring different charmonium production rates and also the experimental prospects at LHCb, in particular, those for yet unmeasured eta_c and h_c.
The linearity and parallelism of Regge trajectories is combined with a hyperfine splitting relation in multiplet to study charmonium spectrum. It is found that predictions to the spectrum of 1D multiplet could be made once another 1D state is confirmed. The newly observed X(3872), Y(3940), X(3940), Y(4260) and Z(3930) are studied within the charmonium framework.
Recent data on charmonium production in B-meson decays suggest that charmonium hybrid mesons with mass ~4 GeV may be produced in B-decay via c\bar{c} colour octet operators. Some of these states are likely to be narrow with clean signatures to J/ψpi^+ pi^- final states. Experimental signatures and search strategies for existing B-factories are described.
The open-charm strong decays of higher charmonium states up to the mass of the $6P$ multiplet are systematically studied in the $^3P_0$ model. The wave functions of the initial charmonium states are calculated in the linear potential (LP) and screened potential (SP) quark model. The decay widths for most of the well-established charmonium states above the open-charm thresholds can be reasonably described. By comparing our quark model calculations with the experimental observations we also discuss the nature of some of the newly observed charmonium-like states. It is found that (i) the $ψ(4415)…
Using a sample of 102 million $Υ(1S)$ events collected with the Belle detector, we report on the first search for charge-parity-even charmonium and charmonium-like states in $Υ(1S)$ radiative decays. No significant $χ_{cJ}$ or $η_c$ signal is observed and 90% C.L. limits on $\BR(Υ(1S)\to γχ_{c0})<6.5 \times 10^{-4}$, $\BR(Υ(1S)\to γχ_{c1})<2.3\times 10^{-5}$, $\BR(Υ(1S)\to γχ_{c2})<7.6 \times 10^{-6}$, and $\BR(Υ(1S)\to γη_c)<5.7\times 10^{-5}$ are obtained. The product branching fraction limits $\BR(Υ(1S)\to γX(3872)) \BR(X(3872)\toπ^+π^-\jpsi)< 1.6 \times 10^{-6}$, $\BR(Υ(1S)\to γX(3872)) \B…
Identification of charmonium states at hadron colliders has mostly been limited to leptonic decays of the J/ψ. In this paper we present and algorithm to identify hadronic decays of charmonium states (J/ψ, ψ(2S), χ_{c0,1,2}) which make up the large majority of all decays. The algorithm is able to identify hadronic $J/ψ$ decays with an efficiency of 36\% while suppressing a background of quark and gluon jets by a factor 100.
The open charm effects via intermediate hadron loop transitions seem to play a crucial role in the understanding of several existing "puzzles" in charmonium exclusive decays, such as the $ψ(3770)$ non-$D\bar{D}$ decays, and "$ρπ$ puzzle" etc. In the charmonium energy region, non-perturbative mechanisms could be still sizeable, and as a consequence the intermediate hadron loop transitions also provide a mechanism for the helicity-selection-rule (HSR) violation. We report our recent progress on those existing puzzles.
Studies of charmonium properties and production mechanism started with the discovery of $J/ψ$ meson. Since more than 40 years the charmonium production mechanism is still not entirely understood. Following the era of investigations at $e^+e^-$ machines, nowadays, charmonium states are copiously produced at hadron colliders, that allows systematic studies of their resonance parameters, production observables and decays. Despite large production rates, many charmonium states are barely studied due to the complications of their reconstruction against a large background level. The LHCb experiment …
Here we discuss three separate topics in charmonium physics. (1) The Omicron \OMC as $1^{--}$ trigluonia, and the charmonium puzzle; the $η_c' (3600)$ search. (2) The decay $ψ(^1P_1) \to π^o + J/ψ$ and isospin violating charmonium decays. (3) How to search for $χ_c' = χ_c(2P)$ charmonium states.
The radiative transitions from the neutral exotic $Z_c(4020)^0$ resonance to $X(3872)$ with emission of a photon and the pionic transitions from the charged $Z_c(4020)^\pm$ to $X(3872)$ and a charged pion $π^\pm$ are considered for both charmoniumlike states being charmed meson-antimeson molecules. The underlying processes for these transitions are the decays of the charmed vector meson to pseudoscalar plus a photon or a pion. It is found that the discussed transition rates typically amount to a branching fraction of several permil with a peak at the vector meson pair threshold.
Based on the updated data of charmoniumlike state $Y(4220)$ reported in the hidden-charm %and open-charm channels of the $e^+e^-$ annihilation, we propose a $4S$-$3D$ mixing scheme to categorize $Y(4220)$ into the $J/ψ$ family. We find that the present experimental data can support this charmonium assignment to $Y(4220)$. Thus, $Y(4220)$ plays a role of a scaling point in constructing higher charmonia above 4 GeV. To further test this scenario, we provide more abundant information on the decay properties of $Y(4220)$, and predict its charmonium partner $ψ(4380)$, whose evidence is found by ana…
To illustrate the campaign to extend our knowledge of the charmonium spectrum, I focus on a puzzling new state, $X(3872) \to π^+π^- J/ψ$. Studying the influence of open-charm channels on charmonium properties leads us to propose a new charmonium spectroscopy: additional discrete charmonium levels that can be discovered as narrow resonances of charmed and anticharmed mesons. I call attention to open issues for theory and experiment.
The analysis of the mass spectrum and the calculation of the strong decay of P-wave charmonium states strongly support to explain the newly observed X(3915) and X(4350) as new members in P-wave charmonium family, i.e., $χ_{c0}^\prime$ for X(3915) and $χ_{c2}^{\prime\prime}$ for X(4350). Under the P-wave charmonium assignment to X(3915) and X(4350), the $J^{PC}$ quantum numbers of X(3915) and X(4350) must be $0^{++}$ and $2^{++}$ respectively, which provide the important criterion to test P-wave charmonium explanation for X(3915) and X(4350) proposed by this letter. The decay behavior of the re…
This report discusses some recent investigations of the heavy hadron spectra using lattice QCD. The first half addresses multiple precision determinations of the masses of charm (and bottom) baryons. Recent lattice results in the tetraquark and the dibaryon sectors are also presented. The second half focuses on new exploratory studies of the excited charmonium spectra in the vector and scalar channels. Along the way, lattice results are compared with the experimental results, wherever they are available.
We review selected lattice results on the charmonium spectrum and first attempts to search for the existence of exotic states. The hadro-quarkonium model was proposed to interpret some of the exotic states as a quarkonium core inside a hadron. We present a lattice study of the hadro-quarkonium model in the limit of static quarks. The charm quark decouples in low energy observables and binding energies of charmonium. In a model calculation we are able to evaluate the corrections to decoupling of the charm quark in the continuum.
The cross section value of doubly charmonium production in e+e- annihilations have been estimated at interaction energy 10.6 GeV. The quarkonium wave function shape, as well as the nonzero value of charm quark have been taken into account.
We propose the initial single chiral particle emission mechanism, with which the hidden-charm di-kaon decays of higher charmonia and charmonium-like states are studied. Calculating the distributions of differential decay width, we obtain the line shape of the $J/ψK^+$ invariant mass spectrum of $ψ_i\to J/ψK^+K^-$, where $ψ_i=ψ(4415), Y(4660)$, and $ψ(4790)$. Our numerical results show that there exist enhancement structures with both hidden-charm and open-strange decays, which are near the $D\bar{D}_s^*/D^*\bar{D}_s$ and $D^*\bar{D}_s^*/\bar{D}^*{D}_s^*$ thresholds. These charged charmonium-li…
We analyze the singlet $P$--wave charmonium production at $e^+ e^-$ colliders within the framework of unconstrained supersymmetry. We show that the CP--violating transitions, dominated by the gluino exchange, are typically four orders of magnitude larger than the CP--conserving ones, and former is generated by the electric dipole moment of the charm quark. Our results can be directly tested via the charmonium searches at the CLEO--c experiment.
This contribution briefly discusses some new theoretical results for the properties of charmonium, especially the "higher charmonium" states above open-charm threshold. In particular we discuss the spectrum of states, open-flavor strong decays, and the surprisingly large effects of virtual decay loops of charmed meson pairs.
In this study, the properties of the $J^{PC}=1^{++}$ hidden charm poles are analyzed under the variation of the bare 2P charmonium mass within the effective field theory proposed in Ref.[1]. The main focus of the current work is on the pole trajectory of the $χ_{c1}(2P)$ charmonium dressed by the $D \bar{D}^*$ meson loops. It is shown that the trajectories of the pole change radically for values of the bare charmonium mass above a certain value and also depending on how close the pole is to the threshold.
This talk summarizes the status of the charmonium system, with particular emphasis on outstanding problems in QCD spectroscopy which a tau-charm factory can address.
Recent theoretical progress in calculations of the spectrum and decays of charmonium is reviewed. Traditionally, our understanding of charmonium was based on potential models. This is now being replaced by first principles.
Studying the hidden-charm dipion decays of the charmoniumlike state Y(4360), we show that there exist charged charmoniumlike structures near $D\bar{D}^*$ and $D^*\bar{D}^*$ thresholds in the $J/ψπ^+$, $ψ(2S)π^+$ and $h_c(1P)π^+$ invariant mass spectra of the corresponding hidden-charm dipion decays of Y(4360) using the {\it{Initial Single Pion Emission} mechanism}. We suggest to do further experimental study on these predicted charged enhancement structures, especially by BESIII, Belle, and the forthcoming BelleII.
In this article, we study the two-pion decays in the $P$-wave to $S$-wave charmonium transitions with the heavy meson effective theory, and make qualitative predictions for the ratios among the two-pion decay widths.
In decays of the $Z^0$, the dominant mechanism for the direct production of charmonium states is the decay of the $Z^0$ into a charm quark or antiquark followed by its fragmentation into the charmonium state. We calculate the fragmentation functions describing the splitting of charm quarks into S-wave charmonium states to leading order in the QCD coupling constant. Leading logarithms of $M_Z/m_c$ are summed up using Altarelli-Parisi evolution equations. Our analytic result agrees with the complete leading order calculation of the rate for $Z^0 \rightarrow ψc {\bar c}$. We also use our fragment…
The effects of charmed meson loops on the spectrum of charmonium are considered, with special attention paid to the levels above open-charm threshold. It is found that the coupling to charmed mesons generates a structure at the D \bar{D}* threshold in the 1++ partial wave. The implications for the nature of the X(3872) state are discussed.
In this article, we study the radiative decays among the charmonium states with the heavy quark effective theory, and make predictions for the ratios among the radiative decay widths of an special multiplet to another multiplet. The predictions can be confronted with the experimental data in the future and put additional constraints in identifying the $X$, $Y$, $Z$ charmonium-like mesons.
We investigate the spectrum and decay rates of low lying charmonium states within the framework of the non relativistic quark model by employing a Coulomb like potential from the perturbative one gluon exchange and the linear confining potential along with the potential derived from instanton vacuum to account for the hyperfine mass splitting of charmonium states in variational approach. We predict radiative E1, M1, two-photon, leptonic and two-gluon decay rates of low lying charmonium states. An overall agreement is obtained with the experimental masses and decay widths.
We perform numerical comparison of the fragmentation mechanism of charmonium production ($g\,g\to c\,\bar{c}$ followed by $c\toψ\,c$) with the full leading order calculation ($g\,g\toψ\,c\,\bar{c}$ at $Ø (α_s^4)$). We conclude that the non-fragmentation contributions remain important up to $J/ψ$ transverse momenta about as large as 50 GeV, thus making questionable the applicability of the fragmentation approximation at smaller transverse momenta.
Caution is suggested on the comparison of the spin-singlet charmonium P-state with the centre of gravity of triplet states, when the mass splitting is of the order of a few MeV. The physics of new hidden-charm states X and Y is briefly reviewed. Perspectives for producing double-charm baryons and double-charm exotic mesons are discussed.
This paper gives a short summary of some of the aspects of charmonium which can be addressed at BES and CLEO-c and other $e^+e^-$ facilities. These topics include the spectroscopy of charmonium states, radiative transitions, $e^+e^-$ widths, two-photon widths, hadron loop effects and open-flavor strong decays.
The charmonium mass spectrum is considered in the framework of the constituent quark model with the relativistic treatment of the c quark. The obtained masses are in good agreement with the existing experimental data including the mass of eta_c(2S).
We discuss the validity of factorization for exclusive two-body B to charmonium transitions. In particular, we consider the role of non factorizable corrections in selected two-body modes.
A previously introduced reduction of the Dirac equation is used to study the Charmonium spectrum. A regularized vector potential that only depends on the coupling constant and on the regularization radius is adopted, considering the interacting quark as an extended source of the Chromo-electric field. A scalar interaction is also introduced with some constraints for its parameters. A good description of the structure of the Charmonium spectrum is obtained with only three free parameters.
The recent progress in experiments at B-factories suggests an opportunity to search for missing charmonium states $η_{c}'(2^1S_0)$ and $h_c(1^1P_1)$. The feasibility of such a search in B-meson decays are discussed.
We explore the influence of open-charm channels on charmonium properties, and profile the 1:3D2, 1:3D3 and 2:1P1 charmonium candidates for X(3872). The favored candidates, the 1:3D2 and 1:3D3 levels, both have prominent radiative decays. The 1:3D2 might be visible in the $D^{0}\bar{D}^{*0}$ channel, while the dominant decay of the 1:3D3 state should be into $D\bar{D}$. We propose that additional discrete charmonium levels can be discovered as narrow resonances of charmed and anticharmed mesons.
In this paper, Schrodinger equation is numerically applied through non-relativistic potential model for deriving Spectrum, radial wave functions at origin, decay constants, lepton and photon decay widths for radial and orbital excited conventional as well as hybrid charmonium mesons. These calculated results are found in agreement with others theoretical results and with the experimental observations.
In this work we study the implications of light-quark pionic matter at finite temperatures on the properties of open and hidden charm mesons. The meson-meson interactions are described by means of a chiral unitary approach accounting for coupled channels effects. The in-medium Lippmann-Schwinger Equations, which consider the change in self-energy that the mesons acquire from interacting with the surrounding pionic matter, are solved self-consistently, and the spectral functions of the mesons in the hot pion bath are obtained. It is observed that the charmed mesons develop a quite substantial p…
In this work, the charm quark mass is obtained from a QCD sum rule analysis of the charmonium system. In our investigation we include results from nonrelativistic QCD at next-to-next-to-leading order. Using the pole mass scheme, we obtain a value of $M_c=1.70\pm 0.13$ GeV for the charm pole mass. The introduction of a potential-subtracted mass leads to an improved scale dependence. The running ${\rm \bar{MS}}$-mass is then determined to be $m_c(m_c) = 1.23 \pm 0.09$ GeV.
The mass spectra of charmonium are investigated using a Coulomb plus linear (Cornell) potential. Gaussian wave function in position space as well as in momentum space are employed to calculate the expectation value of potential and kinetic energy respectively. Various experimental states ($X(4660)(5^{3}S_{1})$, $X(3872)(2^{3}P_{1})$, $X(3900)(2^{1}P_{1})$, $X(3915)(2^{3}P_{0})$ and $X(4274)(3^{3}P_{1})$ etc.) are assigned as charmonium states. We also study the Regge trajectories, pseudoscalar and vector decay constants, the Electric and Magnetic dipole transition rates and the annihilation de…
Assuming that $X(3872)$ is a mixture between $2P$ charmonium and $\bar{D}D^{*}$ molecular states with $J^{PC}=1^{++}$, an analysis of $X(3872)$ radiative decays into $J/ψγ$ and $ψ(2S)γ$ is presented. The modification of the radiative branching ratio due to possible constructive or destructive interferences between the meson-loop and the short-distance contact term, which is modeled by a charm quark loop, is shown. The model predictions are shown to be compatible with the experimentally determined ratio of the mentioned branching fractions for a wide range of the $X(3872)$ charmonium content. I…
The elaborate analysis of spectrum of charmonium states and charmed hybrids in the mass region over DD-threshold is given. The combined approach based on the potential model and relativistic spherical symmetric top model for decay products has been proposed. The experimental data from different collaborations were analyzed. Especial attention was given to the new states with the hidden charm discovered recently. Eight of these states may be interpreted as higher laying radial excited charmoniumstates. Butmuchmore data on different decay modes are needed for deeper analysis. These data can be d…
In this work, we predict two charged charmonium-like structures close to the $D^\ast\bar{D}$ and $D^\ast\bar{D}^\ast$ thresholds, where the Initial Single Pion Emission mechanism is introduced in the hidden-charm dipion decays of higher charmonia $ψ(4040)$, $ψ(4160)$, $ψ(4415)$ and charmonium-like state Y(4260). We suggest BESIII to search for these structures in the $J/ψπ^+$, $ψ(2S)π^+$ and $h_b(1P)π^+$ invariant mass spectra of the $ψ(4040)$ decays into $J/ψπ^+π^-$, $ψ(2S)π^+π^-$ and $h_b(1P)π^+π^-$. In addition, the experimental search for these structures in the $J/ψπ^+$, $ψ(2S)π^+$ and $h…
If the $X(3872)$ is described by the picture as a mixture of the charmonium and molecular $D^{\ast} D$ states; $Y(3940)$ as a mixture of the $χ_{c0}$ and $D^\ast D^\ast$ states; and $X(4260)$ as a mixture of the tetra-quark and charmonium sates, their orthogonal combinations should also exist. We estimate the mass and residues of the states within the QCD sum rules method. We find that the mass splitting among $X$, $Y$ and their orthogonal states is at most $200MeV$. Experimental search of these new states can play critical role for establishing the nature of the new charmonium states.
The theoretical explanations about the ``Rho-pi puzzle'' in charmonium decays are reviewed extensively, and the comparison of theoretical predications with experimental data is made whenever possible. Three methods to estimate the ratio of the branching fractions of J/psi and psi' decays are also discussed. It is pointed out that in order to understand the Rho-pi puzzle, and the dynamics of charmonium decays, systematic studies should be made in theory, phenomenology and experiment aspects.
I briefly review Non-Relativistic QCD and related effective theories, and discuss applications to heavy quarkonium decay, and production in electron-positron colliders.
The production of charmonium in heavy-ion collisions is investigated based on Boltzmann-type transport model for charmonium evolution and langevin equation for charm quark evolution. Charmonium suppression and regeneration in both quark-gluon plasma (QGP) and hadron phase are considered. Charm quarks are far from thermalization, and regeneration of charmonium in QGP and hadron gas is neglectable at SPS and FAIR. At peripheral collisions, charmonium suppression with hadron gas explains the experimental data well. But at central collisions, additional suppression from deconfined matter (QGP) is …
We consider the non-relativistic limit of the QCD Hamiltonian in the Coulomb gauge, to describe radiative transitions between conventional charmonium states and from the lowest multiplet of $c\bar{c}$ hybrids to charmonium mesons. The results are compared to potential quark models and lattices calculations.
We investigate the decays of the charmed baryons aiming at the systematic understanding of hadron internal structures based on the quark model by paying attention to heavy quark symmetry. We evaluate the decay widths from the one pion emission for the known excited states, Λ_c^*(2595), Λ_c^*(2625), Λ_c^*(2765), Λ_c^*(2880) and Λ_c^*(2940), as well as for the ground states Σ_c(2455) and Σ_c^*(2520). The decay properties of the lower excited charmed baryons are well explained, and several important predictions for higher excited baryons are given. We find that the axial-vector type coupling of t…
We investigate charmonium production in the hot medium created by heavy-ion collisions by setting up a framework in which in-medium charmonium properties are constrained by thermal lattice QCD (lQCD) and subsequently implemented into kinetic approaches. A Boltzmann transport equation is employed to describe the time evolution of the charmonium phase space distribution with the loss and gain term accounting for charmonium dissociation and regeneration (from charm quarks), respectively. The momentum dependence of the charmonium dissociation rate is worked out. The dominant process for in-medium …
In calculations of the hyperfine splitting in charmonium, the contributions of the disconnected diagrams are considered small and are typically ignored. We aim to estimate nonperturbatively the size of the resulting correction, which may eventually be needed in high precision calculations of the charmonium spectrum. We study this problem in the quenched and unquenched QCD cases. On dynamical ensembles the disconnected charmonium propagators contain light modes which complicate the extraction of the signal at large distances. In the fully quenched case, where there are no such light modes, the …
Charmonium properties at high temperatures from lattice QCD
Fakultät für Physik, Universität Bielefeld（比勒费尔德大学物理系）；Physics Department, Brookhaven National Laboratory（布鲁克海文国家实验室物理系）；Institut für Kernphysik, Technische Universität Darmstadt（达姆施塔特工业大学核物理研究所）；Werner-Heisenberg-Gymnasium Bad Dürkheim（巴特迪尔凯姆维尔纳·海森堡中学）
We study the effect of thermal charm production on charmonium regeneration in high energy nuclear collisions. By solving the kinetic equations for charm quark and charmonium distributions in Pb+Pb collisions, we calculate the global and differential nuclear modification factors $R_{AA}(N_{part})$ and $R{AA}(p_t)$ for $J/Ψ$s. Due to the thermal charm production in hot medium, the charmonium production source changes from the initially created charm quarks at SPS, RHIC and LHC to the thermally produced charm quarks at Future Circular Collider (FCC), and the $J/Ψ$ suppression ($R_{AA}<1$) observe…
