Quantum Numbers JPC Research Articles

The Genuine Resonance of Full-Charm Tetraquarks

In this work, the genuine resonance states of full-charm tetraquark systems with quantum numbers JPC=0++,1+−,2++ are searched in a nonrelativistic chiral quark model with the help of the Gaussian Expansion Method. In this calculation, two structures, meson-meson and diquark–antidiquark, as well as their mixing with all possible color-spin configurations, are considered. The results show that no bound states can be formed. However, resonances are possible because of the color structure. The genuine resonances are identified by the stabilization method (real scaling method). Several resonances for the full-charm system are proposed, and some of them are reasonable candidates for the full-charm states recently reported by LHCb.

Excited and exotic bottomonium spectroscopy from lattice QCD

We explore the spectrum of excited and exotic bottomonia using lattice QCD. Highly excited states are identified with masses up to 11,000 MeV, many of which can be grouped into supermultiplets matching those of the quark model while exotic spin-parity-charge-conjugation quantum numbers JPC = 0+−, 1−+, 2+− that cannot be formed from overline{q}q alone are also identified. Single-meson operator constructions are used that have good JPC in the continuum, these are found to overlap well onto heavy quark states up to J ≤ 4. A continuum JPC is assigned to each level, based on the distribution amongst lattice irreps and dominant operator overlaps. States with a dominant gluonic component are identified and form a hybrid supermultiplet with JPC = (0, 1, 2)−+, 1−−, approximately 1500 MeV above the ground-state ηb, similar to previous computations with light, strange and charm quark systems.

Magnetic moment of Zc(3900) as molecular state

Employing light-cone QCD sum rule, we have acquired the magnetic moment of the Zc(3900) resonance by considering it as the molecular form of D(D^* ) ̅ and D^* D ̅ resonance with quantum numbers JPC = 1+−. The magnetic moment contains crucial knowledge about the internal organization of particles and their geometric configuration. Measurement of the magnetic moment of the Zc(3900) resonance in future experiments can be quite useful comprehension the inner organization of exotic resonances. A comparison of our numerical values on the magnetic moment with those estimated by the other theoretical models existing in literature is carried out.

Mass Prediction for the Last Discovered Member of the Axial-Vector Nonet with Quantum Numbers JPC = 1+−

In this paper, we have shown that the novel mass relation among the vector states, ϕ(1020) and ϕ(1680), with quantum numbers JPC = 1−− and axial-vector strangeonium state \({h_1}\left( {s\overline s } \right)\) with quantum numbers 1+− is also valid for nonzero current quark mass. This relation predicts the mass of recently discovered \({h_1}\left( {s\overline s } \right)\) state by the BESIII Collaboration within experimental accuracy.

Probing axial-vector charmonia χc1(1P) and χc1(2P)

We investigate the ground state heavy quarkonium χc1(1P) and its first excited state χc1(2P) with quantum numbers JPC = 1++. The masses and decay constants of these charmonium states are computed using the two-point QCD sum rule method by including quark, gluon and mixed condensates up to dimension-8. We compare our numerical results with the available experimental data as well as existing theoretical predictions in the literature.

Direct production of χc1 at BESIII

The production of resonances in electron-positron annihilation has only been observed for states with quantum numbers JPC = 1−−, while C = +1 resonances appear only among the decay products. The direct production of the 1++ states could happen through two-photon or neutral current. Due to the smallness of the production rate, this process has never been verified experimentally. With the high luminosity and good performance of the BESIII experiment, a search of the direct production of the 1++ state in charmonium region, χc1, is undergoing with dedicated data samples around the χc1 mass. An overview of the data analysis will be presented.

A broad pseudovector glueball from holographic QCD

We study the decay of a pseudovector glueball with quantum numbers JPC=1+−, the lightest glueball with spin different from zero or two, in the top–down holographic Witten–Sakai–Sugimoto model. This glueball is dual to the string-theoretic Kalb–Ramond tensor field, which completely fixes all its couplings by gauge invariance and D-brane anomaly inflow. The dominant decay channels are determined by a Chern–Simons-like action for the flavor branes; couplings from the Dirac–Born–Infeld action turn out to be subdominant. While the resulting width is parametrically of order Nc−2λ−1 for Nc colors and 't Hooft coupling λ, when extrapolated to Nc=3 and with λ matched to experimental data, the prediction is that the pseudovector glueball is an extremely broad resonance.

An improved limit for [formula omitted] of [formula omitted] and [formula omitted] measurement of [formula omitted

Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e+e−→γISRX(3872)→γISRπ+π−J/ψ via the Initial State Radiation technique. The production of a resonance with quantum numbers JPC=1++ such as the X(3872) via single photon e+e− annihilation is forbidden, but is allowed by a next-to-leading order box diagram. We do not observe a significant signal of X(3872), and therefore give an upper limit for the electronic width times the branching fraction ΓeeX(3872)B(X(3872)→π+π−J/ψ)<0.13 eV at the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the ψ(3686) to be Γeeψ(3686)=2213±18stat±99sys eV.

Production of the spin partner of the [formula omitted] in [formula omitted] collisions

We study the production of the spin partner of the X(3872), which is a D⁎D¯⁎ bound state with quantum numbers JPC=2++ and named X2(4012) here, with the associated emission of a photon in electron–positron collisions. The results show that the ideal energy region to observe the X2(4012) in e+e− annihilations is from 4.4 GeV to 4.5 GeV, due to the presence of the S-wave D¯⁎D1(2420) and D¯⁎D2(2460) thresholds, respectively. We also point out that it will be difficult to observe the γX(4012) at the e+e− center-of-mass energy around 4.26 GeV.

Lattice QCD and QCD sum rule determination of the decay constants of [formula omitted], [formula omitted] and [formula omitted] states

We compute the decay constants of the lowest cc¯-states with quantum numbers JPC=0−+ (ηc), 1−− (J/ψ), and 1+− (hc) by using lattice QCD and QCD sum rules. We consider the coupling of J/ψ to both the vector and tensor currents. Lattice QCD results are obtained from the unquenched (Nf=2) simulations using twisted mass QCD at four lattice spacings, allowing us to take the continuum limit. On the QCD sum rule side we use the moment sum rules. The results are then used to discuss the rate of ηc→γγ decay, and to comment on the factorization in B→Xcc¯K decays, with Xcc¯ being either ηc or J/ψ.

J/ψγ and ψ(2S)γ decay modes of the X(3872)

The X(3872) with quantum numbers JPC = 1++ is considered as a composite state containing both molecular hadronic and a component. Based on this structure assumption we first constrain model parameters in order to reproduce the predictions for the radiative decay widths of X(3872) → J/ψγ and X(3872) → ψ(2S)γ as obtained in potential models. Depending on these predictions we find that further inclusion of the molecular component can in principle lead to an improved description of the radiative X(3872) decays. We also show that strong decay modes of the X(3872) and, in particular, the ratio of radiative (J/ψγ) to strong (J/ψπ+π−) decays hint toward a subleading role of the component in the X(3872).

S-WAVE MESON SCATTERING UP TO 2 GeV AND ITS SPECTROSCOPY

We report here on recent advances that shed light on the topic of scalar meson sector, which is controversial up to date. We study the scattering and spectroscopy of the strongly interacting mesons in coupled channels with quantum numbers JPC = 0++ and I = 0 and I = 1/2, up to a center of mass energy [Formula: see text]. Our framework is based on Unitary Chiral Perturbation Theory, but extended now to include many more channels. The resonant content of our fits is discussed, with the appearence of σ, f0(980), f0(1310), f0(1500), f0(1710) and f0(1790) for I = 0 and the κ and the [Formula: see text] for I = 1/2.

PHYSICS WITH HADRONIC PROBES AT COMPASS

This paper describes the methods and goals of the spectroscopy programme of COMPASS using hadron beams, and reports on first results from a short pilot run using a 190 GeV/c pion beam, carried out in 2004. A partial wave analysis of the reaction π-N → π-π-π+ N' shows significant production of a state with spin-exotic quantum numbers JPC = 1-+ at 1.6 GeV/c2.

Estimate of the charmed0--hybrid meson spectrum from quenched lattice QCD

We compute from quenched lattice QCD the ground state masses of the charmed hybrid mesons cbar c g, with exotic quantum numbers JPC=1-+, 0+- and 0--. The 0-- hybrid meson spectrum has never been provided by lattice simulations due to the difficulties to extract high gluonic excitations from noise. We employ improved gauge and fermion actions on the anisotropic lattice, which reduce greatly the lattice artifacts, and lead to very good signals. The data are extrapolated to the continuum limit, with finite size effects under well control. For 1-+ and 0+- hybrid mesons, the ground state masses are 4.405(38) GeV and 4.714(52) GeV. We predict for the first time from lattice QCD, the ground state mass of 0-- to be 5.883(146) GeV.

Discrete spectrum of the graviton in the AdS5 black hole background

The discrete spectrum of fluctuations of the metric about an AdS5 black hole background are found. These modes are the strong coupling limit of so-called glueball states in a dual 3-d Yang–Mills theory with quantum numbers JPC=2++,1−+,0++. For the ground state modes, we find the mass relation m(0++)<m(2++)<m(1−+). Contrary to expectation, the mass of our new 0++ state (m2=5.4573) associated with the graviton is smaller than the mass of the 0++ state (m2=11.588) from the dilaton. In fact the dilatonic excitations are exactly degenerate with our tensor 2++ states. We find that variational methods gives remarkably accurate mass estimates for all three low-lying levels while a WKB treatment describes the higher modes well.

The 2++ Three-Gluon Tensor Glueball in Quantum Chromodynamics Sum Rules

The three-gluon tensor current of quantum numbers JPC = 2++ is constructed. The corresponding two-point function is calculated by including not only the perturbative contribution but also the non-perturbative ones resulting from condensates of dimensions up to six. In a usual "resonance plus continuum" model of the spectral function of the current, the quantum chromodynamics sum rules for the 2++ three-gluon tensor glueball are deduced, and the mass of that glueball is determined to be 2.0 GeV approximately.

φφ excitation function at LEAR

The cross sections of the reactions pp → φφ, φK+K− and 4K± have been measured by the JETSET (PS202) experiment at CERN in the invariant mass range from 2.15 to 2.43 GeV/c2. A spin-parity analysis of the φφ system has been performed. The absolute value of the φφ cross section and the ratios σ(φφ)/σ(φK+K−), σ(φφ)/σ(4K±) are large, in marked violation of the OZI rule. Waves of quantum numbers JPC = 2++ give the dominant contribution near threshold.

Hybrid mesons and instantons

The scalar quark—gluon current for describing hybrids with quantum numbersJ PC=0 ++ is studied by the method of QCD sum rules. The contribution of direct instantons to the correlation function of this current instantonfluid model is calculated. It is shown that in the mass rangeM R≥5 GeV the QCD sum rule in this channel admits the existence of resonance structure, which at lower masses is destroyed by instanton interactions.

The H′-meson in the framework of QCD sum rule method

The QCD sum rules are used for the determination of the parameters of the meson nonet with quantum numbersJPC = 1+−. We predict the mass of the experimentally unobserved H′-meson to be (1.40 ÷ 1.45) GeV.

Hybrid quarkonia from QCD sum rules

We present calculations of the vacuum polarization functions in QCD induced by heavy-quark qqG currents with the quantum numbers JPC = 1+−, 0++, 1−+ and 0−−. In the framework of QCD sum rules we investigate the possible resonance structure in these channels. We obtain definite predictions for the masses of resonances in the channels 0−−, 0++ and 1+−, but not in the exotic 1−+ channel. The resulting mass values are unexpectedly high.