Conveners
Exotic hadrons and candidates: Session 1
- Feng-Kun Guo (Institute of Theoretical Physics, Chinese Academy of Sciences)
Exotic hadrons and candidates: Session 2
- Malte Albrecht (Jefferson Lab)
Exotic hadrons and candidates: Session 3
- Adam Szczepaniak (Indiana University)
Exotic hadrons and candidates: Session 4
- Ryan Mitchell (Indiana University)
Exotic hadrons and candidates: Session 5
- Elisabetta Spadaro Norella (Istituto Nazionale di Fisica Nucleare)
Exotic hadrons and candidates: Session 6
- Alessandro Giachino
Exotic hadrons and candidates: Session 7
- Alessandro Pilloni (UniME & CT)
Exotic hadrons and candidates: Session 8
- Nicola Neri (University and INFN Milano)
The decay rates of the X Y Z exotics discovered in the heavy quarkonium sector are crucial observables for identifying the nature of these states. Based on the framework of nonrelativistic effective field theory, we calculate the rates of semi-inclusive decays of heavy quarkonium hybrids into standard heavy quarkonia. We compute the contributions to the decay rates at leading and subleading...
In this talk, I will report our recent applications of XEFT to the study of decays of exotic hadrons near threshold: including the decay of \chi_{c1}(3872) and the strong decay of Tcc^+ and the consistency of their hadronic molecular description.
Using the data sets above 4.0 GeV collected by the BESIII detector on the Beijing Positron Electron Collider, which corresponds a total integrated luminosity greater than 1.5fb-1, the hexaquark or di-baryon state is searched through e+ e- -> 2(p pbar)and e+ e- -> p p pbar nbar pi- + c.c.. We observed these two final states for the first time, and the Born cross sections ofe+ e- -> 2(p...
In this presentation, we will discuss our benchmark test calculations of tetraquark states using several different few-body methods. These include the diffusion Monte Carlo (DMC), Gaussian expansion method (GEM), and resonant group method (RGM), within various nonrelativistic quark models such as Silvestre-Brac-Semay models and Salamanca chiral quark models. To investigate resonance states...
We have a look at the $P_{cs}$ states generated from the interaction of $\bar D^{(*)} \Xi^{(\prime*)}_c$ coupled channels.
We consider the blocks of pseudoscalar-baryon $({\frac12}^+, {\frac32}^+)$ and vector-baryon $({\frac12}^+, {\frac32}^+)$,
and find $10$ resonant states coupling mostly to $\bar D \Xi_c, \bar D^* \Xi_c,\bar D \Xi'_c, \bar D^* \Xi'_c,\bar D \Xi^*_c$ and
$\bar D^*...
Based on a sample of 10 billion J⁄ψ events collected with the BESIII detector, a partial wave analysis of the decay J⁄ψ □(→) γηη' is performed. An isoscalar state with exotic J^PC=1^(-+) quantum numbers, denoted as η_1 (1855), has been observed for the first time with statistical significance larger than 19σ. Its mass is consistent with the predicted mass of 1^(-+) hybrid from Lattice QCD....
We present a simple alternative to the relativistic Breit–Wigner distribution that (i) contains left-threshold effects, (ii) is properly normalized for any decay width, (iii) can be obtained as an appropriate limit in which the decay width is a constant, (iv) is easily generalized to the multi-channel case (v) as well as to a convoluted form in case of a decay chain and (vi) is simple to deal...
In this work, we interpret the newly observed $\eta_1(1855)$ resonance with exotic $J^{PC}=1^{-+}$ quantum numbers in the $I=0$ sector, reported by the BESIII Collaboration, as a dynamically generated state from the interaction between the lightest pseudoscalar mesons and axial-vector mesons. The interaction is derived from the lowest order chiral Lagrangian from which the Weinberg-Tomozawa...
Glueballs are still an experimentally undiscovered expectation of QCD. Various theoretical approaches (most famously Lattice QCD) predict a spectrum of glueballs. The tensor ($J^{PC}=2^{++}$) glueball is the second lightest, behind the scalar glueball.
Here, using a chiral hadronic model, we compute decay ratios of the tensor glueball into various meson decay channels. We find the tensor...
Using the world’s largest samples of J/psi and psi(3686) events produced in e+e- annihilation, BESIII is uniquely positioned to study light hadrons in radiative and hadronic charmonium decays. In particular, exotic hadron candidates including multiquark states, hybrid mesons and glueballs can be studied in high detail. Recent highlights on the light exotics searches, including the observation...
The spectrum of QCD is expected to contain, besides bound states of quarks, also bound states of gluons. These glueballs can mix with other states that have the same quantum number. For pure Yang-Mills theory, on the other hand, glueballs are the only physical degrees of freedom which makes the picture much clearer. Using state-of-the-art, parameter-free solutions for the propagators and...
The COMPASS experiment at CERN's Super Proton Synchrotron has been a key player in the quest for understanding the spectrum of light mesons. Using a high-energy pion beam, an unprecedented data set on diffractively produced isovector mesons was recorded. In addition to extending our knowledge on ordinary mesons, the data also allow us to search for exotic states not fitting the ordinary quark...
A simple constituent model of gluodynamics that is motivated by lattice field theory and the QCD Hamiltonian in Coulomb gauge is applied to descriptions of hybrid meson flavor mixing and vector hybrid configuration mixing. Good agreement with lattice gauge computations is obtained for flavor multiplet masses, while mixing angles are in approximate agreement, given large errors. The...
The theoretical description of the strong interaction between quarks and gluons that form hadrons is provided by Quantum Chromodynamics. However, the impact of gluonic excitations on the characteristics of hadrons and their role in hadronic structure is yet to be determined.
Recent discoveries of several possibly exotic hadrons highlight the significance of precise spectroscopic measurements...
The $Y(2175)$, recently renamed to $\phi(2170)$, is one of the rare exotic candidates connected to strangeonium instead of the heavier charmonium-like and bottomonium-like exotic states. Originally observed in initial-state radiation by the BaBar experiment in 2006, it is could be a strange partner of the famous charmonium-like exotic vector state $Y(4260)$. Various interpretations exist in...
The identification of exotic states in the charmed quark sector has generated great interest in the hadron physics community. Despite some very clear signals, many questions now arise, particularly with regard to the exact nature of as well as the existence of specific states. A hindrance to this is the fact that almost all of the states are only seen in single production mechanisms,...
The near threshold region of heavy quarkonium has received a lot of attention with possible applications to a wide breadth of physics. I will discuss the recent JPAC analysis of new Jefferson Lab data from the GlueX and Jpsi-007 experiments. I will discuss the still wide array of physics scenarios that may underpin the near threshold data including strong coupled channel effects to open charm...
The famous exotic hadron $X(3872)$ (a.k.a. $\chi_{c1}(3872)$) is observed not only in $J/\psi \pi \pi$ but also in $D^0\bar{D}^{*0}$, and the observed mass and width are larger in the latter decay mode with sizable uncertainties. In this presentation, we report a new measurement on
$X(3872) \to D^0\bar{D}^{*0}$ decay using the full data of the Belle experiment and show the result of an...
The talk will report on the new results on fully-charmed exotic states in $J/\psi J/\psi$ final state by ATLAS and CMS
QCD supports the existence of hadrons with a structure richer than quark-antiquark mesons and three-quark baryons that are conventionally referred to as exotic. Many candidates for such states have been discovered experimentally in the spectrum of heavy quarks, with their minimal quark content being four-quark: two heavy plus two light quarks. In addition, recent results of the LHCb...
LHCb results on four-charm quark tetraquarks - abstract to be determined
I will review studies of exotic meson states in the charmonium region (the XYZ states) performed by the BESIII experiment. Recent results include new decay modes of the X(3872), new e+e- cross sections in the region of the Y(4230), and updates on studies of the isospin-one Zc and isospin-half Zcs states. I'll also preview ongoing and future efforts, which will be much enhanced by an upcoming...
With LHC Run2 data becoming available, a plethora of new states was discovered at LHCb. Among those, are the open
charm exotic states, namely, tetraquarks with quark content of ($c\bar{c}qq$) and pentaquarks with quark
content ($c\bar{c}qqq$). More recently, in 2021 an open-double-charm tetraquark state, named, $T_{cc}{}^+$ was discovered,
with a quark content of ($c\bar{u}c\bar{d}$). This...
I would present results based on the papers: PRD 104, 114015, Arxiv 2304.01870,Arxiv 2303.06078, shared with the collaborators: A. Feijoo, W.H. Liang, I. Vidana, L.R. Dai, L. Abreu, M. Albaladejo and J. Nieves.
I would show how the Tcc appears naturally within an extension of the local Hidden gauge approach, with the correct mass and width and isospin I=0 nature. Then expose a general...
The recent experimental observation of the first doubly charm exotic state Tcc(3875)+ by the LHCb collaboration has triggered the enormous interest in the community. Indeed, this state has very peculiar properties, since it is located just a few hundreds keV below the $D^0D^{*+}$ threshold and its width stems almost entirely from the only available strong decay channel $DD\pi$, as a...
We extend the theoretical framework used of describe the $T_{cc}$ state as a molecular state of $D^* D$ and make predictions for the $D^*D^*$ and $D^*_s D^*$ systems, finding that they lead to bound states only in the $J^P=1^+$ channel. Using input needed to describe the $T_{cc}$ state, basically one parameter to regularize the loops of the Bethe-Salpeter equation, we find bound states with...
The AdS/QCD correspondence allows to compute the quark-antiquark potential. We use this result, the Salpeter equation and a hyperfine splitting potential to determine masses of tetraquarks and pentaquarks containing at least two heavy quarks, based on the hypothesis of a diquark-antidiquark and antiquark-diquark-diquark structure.
The existence of pentaquarks with strangeness content zero and one are major discoveries of the latest years in hadron physics. Most of these states can be understood as hadronic molecules and were predicted prior to their discovery within a model based on unitarized meson-baryon amplitudes obtained from vector meson exchange interactions. Contrary to earlier statements, we show this model to...
The new Facility for Antiproton and Ion Research (FAIR) is under construction at GSI in Darmstadt (Germany). Antiprotons are planned to be provided by the High Energy Storage Ring, at which the PANDA experiment will directy be located. It represents the central part of the hadron physics programme. The field of hadron spectroscopy has gained new momentum by the discovery of the so-called...
Recent LHCb's amplitude analysis on $B^+\to J/\psi \phi K^+$ suggests the existence of exotic $X$ and $Z_{cs}$ hadrons, based on an assumption that Breit-Wigner resonances describe all the peak structures. However, all the peaks and also dips in the spectra are located at relevant meson-meson thresholds where threshold kinematical cusps might cause such structures. This points to the...
The $Z_{cs}$(3985) state was reported as a new exotic state by BESIII collaboration. After its discovery, the $Z_{cs}$(4000) and $Z_{cs}$(4220) states were observed at LHCb. We study the $Z_{cs}$(3985) state based on the $\bar D_s D^*$ with the coupled channels of the vector-pseudoscalar mesons [1]. We find that we can explain this state by the threshold effect from the coupled-channel...
Study of exotic hadrons provides an important perspective on the nature of QCD. Using the pp interaction dataset collected during the Run1 and Run2 data-taking periods, corresponding to an integrated luminosity of 9 fb$^{-1}$, LHCb established the first evidence of pentaquark with strangeness, $P_{\psi s}^{\Lambda}$(4459)$^0$, in $\Xi_b^- \to J/\psi \Lambda K^-$ decays, and further made the...
The last few years have seen the observation of a series of hidden-charm pentaquarks by the LHCb collaboration. The most recent one is the $P_{\psi s}^{\Lambda}(4338)$, which has the quantum numbers of a $\Lambda$ baryon. Most of these pentaquarks are close to a meson-baryon threshold and have been readily interpreted as bound (or molecular) states. Here we explore what are the consequences of...
Photocouplings of pentaquarks are crucial ingredients for photoproduction experiments at JLab which aim to confirm the existence of the hidden-charm pentaquarks reported by the LHCb Collaboration using electromagnetic probes. Photocouplings of ground- and excited-state hidden-charm pentaquarks are analyzed in a quark model approach in which we distinguish between light ($u$, $d$ and $s$) and...
We construct the effective potentials of the $P_c$ and $P_{cs}$ states based on the SU(3)$_{\text{f}}$ symmetry and heavy quark symmetry. Then we perform the coupled-channel analysis of the lowest isospin $P_c$ and $P_{cs}$ systems. The coupled-channel effects play different roles in the $P_c$ and $P_{cs}$ systems. In the $P_c$ systems, this effect gives minor corrections to the masses of the...
A search for potential tetraquarks decaying into a pair of charmonium states will be presented. Two different decay channels, J/psi + J/psi --> 4mu and J/psi + psi(2S) --> 4mu, are studied. Backgrounds are estimated with a hybrid data-driven and MC-based approach. The statistical significance of possible excesses in the di-J/psi and J/psi+psi(2S) channels will be discussed in detail.
We calculate the Sivers function of $\bar{u}$ and $\bar{d}$ quarks using the overlap representation within the light cone formalism. The light-cone wave functions of the proton are obtained in terms of the $|q\bar{q}B\rangle$ Fock states motivated by the meson-baryon fluctuation model. We consider the final-state interaction at the level of one gluon exchange. In a simplified scenario, the...
