The observation of two pentaquark resonances and the proof of the resonant nature of the Zc state opened to the search for the many isospin partner of these multi-quark states. We review the studies of these states and discuss the prospects for the analyses of the LHCb Run2 data,
I will present some recent lattice QCD studies of charmonia and exotic hadrons.
Belle experiment found an alternative candidate $X^*(3860)$ for the excited scalar charmonium $\chi_{c0}(2P)$ in 2017. I will report on the preliminary results on the related scalar resonance obtained by simulating $D\bar D$ scattering on the CLS lattice ensembles. D0 experiment claimed the evidence for an exotic...
I will discuss recent progress in studying the spectra of mesons using first-principles lattice QCD calculations. In particular, some results on excited mesons, resonances and related phenomena in the light and heavy sectors will be highlighted, including work relevant for puzzling/exotic states such as the Ds(2317). I will also comment on future prospects.
Implications of heavy-quark spin-symmetry (HQSS) are investigated for the isoscalar charmonium-like state $X(3872)$ and the isovector bottomonium-like states $Z_b(10610)$ and $Z_b(10650)$ under the assumption of the latter being bound states of the nearby heavy meson-antimeson pairs (see Refs. [1,2] for more details). We formulate and solve a system of the integral equations for a...
Heavy hadrons interacting via pion exchange can form bound states (hadronic molecules), analogous to conventional nuclei. A large number of possible states is controlled by the same interaction potential, and although the binding energy in a given channel depends sensitively on the details of the potential, the overall pattern of binding does not. In particular, bound states arise only for a...
In the past decade many charmonium-like states were observed experimentally, including many charmonium-like XYZ states and the hidden-charm pentaquark states Pc(4380) and Pc(4450). We systematically investigate their mass spectra using the method of QCD sum rules. Especially, we pay attention to their internal structure by constructing all the relevant local hidden-charm tetraquark and...
The BESIII Experiment at the Beijing Electron Positron Collider (BEPC2) has accumulated the world's largest samples of e+e- collisions in the tau-charm region. Cross sections of e+e- --> pi+pi- psi(2S) above 4.0 GeV, and a charged structure has been observed in the pi psi(2S) mass spectrum. Cross sections of e+e- --> KKbar J/psi between 4189 and 4600 MeV. Compared with pi+ pi- J/psi, more...
The BESIII Experiment at the Beijing Electron Positron Collider (BEPC2) has accumulated the world's largest samples of e+e- collisions in the tau-charm region. Based on these data samples, some new results from the Y(4260) decays will be shown.
The $u\overline{u}c\overline{c}$, $u\overline{u}b\overline{b}$, and $u\overline{u}s\overline{s}$ $J^{PC}=1^{--}$ states are investigated by a coupled-channel two-meson model. We used the complex scaling method with 14 two-meson channels with an effective hadron interaction originated from interaction between quarks. The coupling between channels is obtained from the quark rearrangement.
We...
We review the status of searches and measurements of exotic hadron states at ATLAS. Among them: the search for the beauty partner of $X(3872)$ charmonium state, the measurement of differential cross-section of the prompt and non-prompt production of $X(3872)$ in the $J/\psi \pi \pi$ final states, the search for the structure in the $B_s \pi$ invariant mass, reported by D0 experiment, search...
Using the Fixed Center Approximation to Faddeev equations we have investigated the $DKK$ and $DK\bar{K}$ three-body systems, with the input of two-body interactions obtained from the chiral unitary approach, and considering that the $D^*_{s0}(2317)$, generated from the $DK$ interaction, acts as the heavy cluster. For the $DK\bar{K}$ system we have found evidence of a state with...
In this work, we investigate the ground states and their radial excitations which couple to scalar, axial vector and tensor, molecular and diquark-antidiquark currents via QCD sum rules. In operator product expansion, we considered quark, gluon and mixed condansates up to dimension eight. For the ground states coupling to these currents, we estimated degenerate masses within 10 MeV...
The measured properties of the $X(3915)$ and $X(3930)$ make difficult their theoretical
description. These charmonium resonances, firstly detected by the
Belle and BaBar Collaborations in $\gamma\gamma$ fusion process, were measured
in different final channels: the $X(3915)$ was discovered in the $\omega
J/\psi$ [1, 2] invariant mass distribution whereas the $X(3930)$ was seen in the...
In this talk we will study the implications on heavy hadron molecules (containing one constituent heavy quark) of heavy quark spin-flavor and chiral symmetries (together with unitarity). We start by studing the $D\pi$, $D\eta$ and $D_s \bar{K}$ scattering with $(I,J^P) = (1/2,0^+)$ quantum numbers. In this sector there appears the so far only known charmed non-strange scalar meson, namely...
The observation of the unexpected $XYZ$ resonances has challenged the ordinary heavy quarkonium framework, and their microscopic nature remains an unsettled topic.
We review the status of the multiquark phenomenology, and show how the large prompt production cross-section of the $X(3872)$, compared with the light nuclei production data, disfavors loosely-bound molecules, and calls for other...
We present a recent lattice QCD investigation of charm tetraquarks. After describing some of our new methodology, we demonstrate its use in calculations with unphysically heavy light quarks such that the pion mass is 391 MeV. Spectra in the doubly charmed and hidden charmed sector will be shown including those which are of relevance to the experimentally observed charged $Z_c$ states.
There has been a long-standing puzzle in understanding why the dipion invariant distribution for the $ \Upsilon(3S) \to \Upsilon(1S) \pi \pi$ transition shows a double-bump structure while other analogous transitions have only one. By including the $\pi \pi$ final state interaction and effects from the $Z_b$ states, we show that this phenomenon can be understood. However, this requires the...
After the discovery of X(3872) many new and unexplained X Y Z states have been discovered experimentally in recent times [1]. It has helped in our faith towards the existence of multi quark states. Most of these unknown states consist of hidden heavy quark anti quark pair with combinations of quark/antiquark in the lighter sector (cq$\bar{c}$ $\bar{q}$or bq$\bar{b}$ $\bar{q}$ where q ϵ u, d,...
The evidence for an unexpected narrow Bs pi structure claimed by the D0 Collaboration and named X(5568) has triggered its search in other hadron collider experiments including CMS. Its interest resides in its possible interpretation as a compact hadronic state composed of four different quark flavours (udsb). The CMS search is performed using an integrated luminosity of 19.7fb^-1 of pp...
We describe studies of heavy states with charm and beauty in
the Belle experiment. Particular attention is drawn to production
and decays of heavy quarkonia for which the interpretation is
not yet clear. Also discussed is a search for a pentaquark.
In this talk I would like to present a series of theoretical works
regarding the $\Lambda_b \to J/\psi K^- p$ reaction from where a recent experiment by the LHCb collaboration at CERN claimed the existence of
two hidden charm pentaquarks, $P_c(4380)^+$ and
$P_c(4450)^+$.
We discuss the possible explanations of the pentaquark states found within the picture of a dynamical meson-baryon...
Several new findings in the four, five and six quark systems reheat the interest in the field of multiquark states (beyond trivial $q\bar q$ and qqq). A lot of progress has recently been made in the 6q sector, on both the theoretical and experimental side. A resonance like structure observed in double-pionic fusion to the deuteron, at M=2.38 GeV with $\Gamma=70 MeV$ and $I(J^P )=0(3^+)$ has...
The dibaryon resonance d*(2380) with I(JP) = 0(3+) -- first observed in the
double-pionic fusion to the deuteron [1] -- has meanwhile been detected in all
relevant two-pion production channels in incident neutron-proton collisions
[2]. In addition, its resonance pole has been revealed in neutron-proton
scattering [3].
Theoretical calculations describe this state either as a compact hexaquark...
Recent Lattice QCD predictions for the mass of H-dibaryon pointing to the mass region near $\Lambda\Lambda$ and $\Xi^-p$ thresholds encourage experimental searches. A dedicated experiment (J-PARC E42) has been prepared for hunting the H-dibaryon close to $\Lambda\Lambda$ and $\Xi^-p$ thresholds. The experiment was
designed to measure $\Lambda p\pi^-$, $\Lambda\Lambda$ and ?$\Xi^-p$...
Exotic charmonium-like XYZ states have been targeted by various experiments in the last 15 years,
but their nature still is unknown. Photo-(muo)production, is a new promising instrument to study them.
COMPASS, a fixed target experiment at CERN, analyzed the full set of the data collected with a
muon beam between 2002 and 2011, covering the range from 7 GeV to 19 GeV in the centre-of-mass...
We will present an introduction to the physics of exotic charmonium, describing
the most popular configurations proposed for these states: tetraquark and meson molecules. I will then show how these states can be produced in hadronic collisions and in heavy ion collisions, both in central and peripheral reactions. I
will present our latest results on the production cross sections,...
The future experiment PANDA@FAIR is a fix-target ppbar machine that will run in the energy range [1.5-15.0] GeV, and it is supposed to reach a peak luminosity of about 2 * 10^31 cm-2 s-1 in the first phase of data taking. This will allow to perform a number of analyses which are suppressed or forbidden at e+e- colliders, especially in the sector of charm- and charmonium physics. To investigate...
Large mass, non-relativistic dynamics, large energy level spacing and clear
experimental signature are unique characteristics of the bottomonium states
that make this sector so rich with a wide range of opportunities for new
studies, ranging from the the spin structure of QCD to the extensions of the SM
Lagrangian, from the non-$q\bar{q}$ states and light quarks dynamics to the
gluon...
We study the weak decay of the $\Lambda_b$ baryon into $J/\Psi \phi \Lambda$ states and the possibility of producing exotic hadrons via final state interaction in $J/\Psi \phi$ and $J/\Psi \Lambda$ channels.
The elementary weak transition at the quark level proceeds via the creation of a $J/\Psi (\bar{c} c)$ meson and an excited sud system with I = 0, which upon hadronization leads...
