XYZ States Research Articles

Interference effect as resonance killer of newly observed charmoniumlike states Y(4320) and Y(4390)

In this letter, we decode the newly observed charmoniumlike states, Y(4320) and Y(4390), by introducing interference effect between psi (4160) and psi (4415), which plays a role of resonance killer for Y(4320) and Y(4390). It means that two newly reported charmoniumlike states are not genuine resonances, according to which we can naturally explain why two well-established charmonia psi (4160) and psi (4415) are missing in the cross sections of e^+e^- rightarrow pi ^+ pi ^- J/psi and pi ^+ pi ^- h_c simultaneously. To well describe the detailed data of these cross sections around sqrt{s}=4.2 GeV, our study further illustrates that a charmoniumlike structure Y(4220) must be introduced. As a charmonium, Y(4220) should dominantly decay into its open-charm channel e^+e^- rightarrow D^0 pi ^+ D^{*-}, which provides an extra support to psi (4S) assignment to Y(4220). In fact, this interference effect introduced to explain Y(4320) and Y(4390) gives a typical example of non-resonant explanations to the observed XYZ states, which should be paid more attention especially before identifying the observed XYZ states as genuine resonances.

XYZ States at BESIII

The BESIII experiment have collected about 9 [Formula: see text] luminosity data samples above 3.8 GeV. Recent result on the XYZ states, which are also called exotic states, from BESIII experiment is presented in this talk, including the measurement of resonance parameters of vector [Formula: see text] states, the establishment of two isospin triplets of [Formula: see text] states, and the determination of spin-parity of [Formula: see text].

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.

Dynamical picture for the exotic XYZ states

We present a dynamical approach for description of the multi-quark states that is based on an effective interaction Lagrangian describing the coupling of hadrons to their constituent quarks. First, we explore the consequences of treating the X(3872) meson as a tetraquark bound state. We calculate the decay widths of the observed channels and conclude that for reasonable values of the size parameter of the X(3872) one finds consistency with the available experimental data. Then we have critically checked the tetraquark picture for the Zc(3900) state by analyzing its strong decays. We found that Zc(3900) has a much more stronger coupling to DD* than to J/Ψπ that is in discord with experiment. As an alternative we have employed a molecular-type four-quark current to describe the decays of the Zc(3900) state as the charged particle in the isotriplet. We found that a molecular-type current gives the values of the above decays in accordance with the experimental observation. By using moleculartype four-quark currents for the recently observed resonances Zb(10610) and Zb(10650), we have calculated their two-body decay rates into a bottomonium state plus a light meson as well as into B-meson pairs.

Heavy quarkonium hybrids: Spectrum, decay, and mixing

We present a largely model independent analysis of the lighter Heavy Quarkonium Hybrids based on the strong coupling regime of Potential Non-Relativistic QCD (pNRQCD). We calculate the spectrum at leading order, including the mixing of static hybrid states. We use potentials that fulfill the required short and long distance theoretical constraints and fit well the available lattice data. We argue that the decay width to the lower lying Heavy Quarkonia can be reliably estimated in some cases, and provide results for a selected set of decays. We also consider the mixing with Heavy Quarkonium states. We establish the form of the mixing potential at $O(1/m_Q)$, $m_Q$ being the mass of the heavy quarks, and work out its short and long distance constraints. The weak coupling regime of pNRQCD and the effective string theory of QCD are used for that goal. We show that the mixing effects may indeed be important and produce large spin symmetry violations. Most of the isospin zero XYZ states fit well in our spectrum, either as a Hybrid or standard Quarkonium candidates.

Amplitude analysis and the nature of the Zc(3900)

The microscopic nature of the XYZ states remains an unsettled topic. We show how a thorough amplitude analysis of the data can help constraining models of these states. Specifically, we consider the case of the Zc(3900) peak and discuss possible scenarios of a QCD state, virtual state, or a kinematical enhancement. We conclude that current data are not precise enough to distinguish between these hypotheses, however, the method we propose, when applied to the forthcoming high-statistics measurements should shed light on the nature of these exotic enhancements.

XYZ states at BESIII

The BESIII Experiment at the Beijing Electron Positron Collider (BEPCII) collected large data samples for electron-positron collisions with center-of-mass above 4 GeV during 2013 and 2014. The analysis of these samples has resulted in a number of surprising discoveries, such as the discoveries of the neutral exotic X states, vector charmonium-like Y states and the electrically charged and neutral Zc states. In this papar, we will review the current status of the analyses of the XYZ states, as well as a number of other interesting features in the new BESIII data samples.

Heavy Hybrids: decay to and mixing with Heavy Quarkonium

We report on a recent QCD based research on hybrid mesons containing $c\bar c$ or $b\bar b$ quarks. We present results for the spectrum, the decay widths to heavy quarkonium, and the role of mixing with the latter. We point out that mixing with heavy quarkonium provides a potentially large source of spin symmetry breaking. We identify candidates to hybrid mesons among the so called XYZ states in the charmonium and bottomonium spectrum.

Modeling new XYZ states at JPAC

The observation of the unexpected XYZP resonances has challenged the usual heavy quarkonium framework. One of the most studied exotic states, the X(3872), happens to be copiously produced in high-energy hadron collisions. We discuss how this large prompt production cross-section, together with the comparison with light nuclei production data, disfavors a loosely-bound molecule interpretation, and calls for a new interpretation for the exotic hadron resonances. We also present the research of the Joint Physics Analysis Center in Hadron Spectroscopy.

Hidden charm octet tetraquarks from a diquark-antidiquark model

Four exotic charmonium-like states, i.e. $X(4140)$, $X(4274)$, $X(4500)$, and $X(4700)$, have been observed very recently by LHCb Collaboration in the decay process $B^+\to J/\psi \phi K^+$ using the 3${\rm fb}^{-1}$ data of $p\bar p$ collision at $\sqrt s= 7$ and $8$ TeV. In this paper, we investigate systematically the properties of hidden charm tetraquark states. The hidden charm tetraquarks form an octet configuration and a singlet configuration according to flavor $SU(3)$ symmetry. Based on a diquark-antidiquark model, the hidden charm tetraquarks spectra are given. The previous XYZ exotic states altogether with the newly ones $X(4140)$, $X(4274)$, $X(4500)$, and $X(4700)$, can be well classified into certain representations. The spin-parities and masses of the XYZ are predicted, most of which are in agreement with the data. We particularly find that $Z_c(4430)$ may be treated as the first radial excitation of $Z_c(3900)$, while the $Y(1^{--})$ states can be obtained by the first orbital excitation of the $X/Z$ states. Besides, we calculate the decay widths of the hidden charm tetraquarks into two charmed mesons. This work gives a general tetraquark description for the XYZ states, which is helpful to uncover their inner structures.

Charm physics and XYZ states at BESIII

The BESIII Experiment at the Beijing Electron Positron Collider (BEPC2) collected large data samples for electron-positron collisions with c.m. energy above 4 GeV/c2 during 2013 and 2014. The analysis of these samples has resulted in a number of surprising discoveries, such as the discoveries of the electrically charged “Zc” structures, which, if resonant, cannot be accommodated in the traditional charm quark and anti-charm quark picture of charmonium. In this talk, we will review the current status of the analyses of the Zc structures, as well as a number of other interesting features in the new BESIII data samples. We'll also present the recent charm physics results from BESIII.

Rashba realization: Raman with RF

We theoretically explore a Rashba spin–orbit coupling scheme which operates entirely in the absolute ground state manifold of an alkali atom, thereby minimizing all inelastic processes. An energy gap between ground eigenstates of the proposed coupling can be continuously opened or closed by modifying laser polarizations. Our technique uses far-detuned ‘Raman’ laser coupling to create the Rashba potential, which has the benefit of low spontaneous emission rates. At these detunings, the Raman matrix elements that link mF magnetic sublevel quantum numbers separated by two are also suppressed. These matrix elements are necessary to produce the Rashba Hamiltonian within a single total angular momentum f manifold. However, the far-detuned Raman couplings can link the three XYZ states familiar to quantum chemistry, which possess the necessary connectivity to realize the Rashba potential. We show that these XYZ states are essentially the hyperfine spin eigenstates of dressed by a strong radio-frequency magnetic field.

Recent empirical developments in the study and understanding of XYZ states

Exotic hadronic states beyond the conventional quark model (called charmoniumlike/bottomoniumlike states or XYZ particles) have been searched for and many candidates were proposed including glueballs, hybrids, multi-quark states, hadron molecules, etc. Dramatic progress was made in the study of the exotic states after the running of the two B -factories, i.e., Belle at KEK and BaBar at SLAC. In my review report, I present the most recent results on the study of the XYZ states from the BESIII, Belle, BaBar, LHCb, CMS experiments, etc., including (1) X states: the observation of the X(3872) in e + e − → γX (3872) at around 4.26 GeV; searches for the X b state; (2) Y states including the updated results for the Y (4008), Y (4260), Y (4360), Y (4660), etc; (3) Z states including the observations of the Z (4430), Z 1 (4050), Z 2 (4250), Z c (3900), Z c (4020), Z c (4200); the evidence for the Z c (4050) ± → π ± ψ (2 S ); search for the Z cs in e + e − → K + K − J/ψ .

XYZ physics at BESIII

Recent progress on the charmonium-like states (or called XYZ states) from BESIII experiment based on large data samples above DD‾ threshold is presented in this talk, including the observation of X(3823) in the process e+e−→π+π−X(3823)→π+π−γχc1, the observation of X(3872) from radiative decay of the Y(4260), the study of the Y states from the e+e−→π+π−hc, ωχc0, ηJ/ψ and η′J/ψ, and the observation of the Zc states.

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.

Recent results, status and prospects for the BESIII experiment

We report the measurement of the asymmetry ACP of the branching fractions of D0 → K-π+ in the CP-odd and CP-even eigenstates using a data sample of 2.92 fb-1 collected with the BESIII detector at the center-of-mass energy √s = 3.773 GeV. With the measured ACP, the strong phase difference δKπ between the doubly Cabibbo-suppressed process D̄0 → K−π+ and the Cabibbo-favored process D0 → K−π+ is extracted. Using world- average values of external parameters, we obtain the most precise measurement of δKπ to date: cos δKπ = 1.02 ± 0.11 ± 0.06 ± 0.01. The first and second uncertainties are statistical and systematic, respectively, while the third arises from external input. Based on the same data sample a preliminary results of the parameter yCP in D0D̄0 oscillation is obtained. Finally, a summary of the recent results from charmonium spectroscopy is reported. The high statistics accumulated at the Y(4260) and Y(4360) energies help us to understand the nature and the proprieties of the XYZ states.

Probing the nature of [formula omitted] states via the [formula omitted] decay

The nature of the so-called XYZ states is a long-standing problem. It has been suggested that such particles may be described as compact four-quark states or loosely bound meson molecules. In the present work we analyze the Zc(′)→ηcρ decay using both approaches. Such channel might provide useful insights on the nature of the Zc(′), helping discriminating between the two different models.

Recent highlights from BESIII: XYZ states

In this contribution we review recent results from the BESIII experiment. We focus on the investigation of XYZ states and the discovery of new charged charmonium - like structures. Two isospin triplets Z(3900) and Z(4020) have been discovered, decaying into π± J/ψ and π± hc, respectively. Structures with compatible parameters have been found decaying to DD̄∗ and D∗D̄∗, respectively, suggesting that these structures might be of the same origin. Furthermore, we have investigated the transition Y(4260) → γX(3872). This is the first observation of a radiative transition between XYZ states.

Recent highlights from BESIII: XYZ states

In this contribution we review recent results from the BESIII experiment. We focus on the investigation of XYZ states and the discovery of new charged charmonium - like structures. Two isospin triplets Z(3900) and Z(4020) have been discovered, decaying into π± J/ψ and π± hc , respectively. Structures with compatible parameters have been found decaying to DD ∗ and D ∗ D ∗, respectively, suggesting that these structures might be of the same origin. Furthermore, we have investigated the transition Y (4260) → γX (3872). This is the first observation of a radiative transition between XYZ states.

A Study of One S- and One P-Wave Heavy Meson Interaction in a Chiral Quark Model

The analytical forms of the interaction potentials between one pseudo-scalar/vector and one scalar/tensor/axial-vector heavy mesons are deduced based on a chiral quark model. Our results explicitly show the attractive property between the two heavy mesons. Consequently, a series of possible molecular states are obtained. It is expected that our study might shed some light on the popular discussions of the newly observed XYZ states.