Observation of J/ψϕ Structures Consistent with Exotic States from Amplitude Analysis of B^{+}→J/ψϕK^{+} Decays

Observation of Exotic J/ψϕ Resonant Structure in Diffractive Processes in Proton-Proton Collisions

The first study of J/ψϕ production in diffractive processes in proton-proton collisions is presented. The study is based on an LHCb dataset recorded at center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5  fb^{-1}. The data disfavor a nonresonant J/ψϕ production but are consistent with a resonant model including several resonant states observed previously only in B^{+}→J/ψϕK^{+} decays. The χ_{c0}(4500) state is observed with a significance over 6σ and the χ_{c1}(4274) is confirmed with a significance of more than 4σ.

Observation of New Resonances Decaying to J/ψK^{+} and J/ψϕ

The first observation of exotic states with a new quark content cc[over ¯]us[over ¯] decaying to the J/ψK^{+} final state is reported with high significance from an amplitude analysis of the B^{+}→J/ψϕK^{+} decay. The analysis is carried out using proton-proton collision data corresponding to a total integrated luminosity of 9  fb^{-1} collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The most significant state, Z_{cs}(4000)^{+}, has a mass of 4003±6_{-14}^{+4}  MeV, a width of 131±15±26  MeV, and spin parity J^{P}=1^{+}, where the quoted uncertainties are statistical and systematic, respectively. A new 1^{+}  X(4685) state decaying to the J/ψϕ final state is also observed with high significance. In addition, the four previously reported J/ψϕ states are confirmed and two more exotic states, Z_{cs}(4220)^{+} and X(4630), are observed with significance exceeding 5 standard deviations.

Predicting the D‾s(*)Ds(*) bound states as the partners of X(3872)

In this work, we investigate the SU(3) flavor symmetry, heavy quark spin symmetry and their breaking effects in the di-meson systems. We prove the existence of the [Formula: see text] , [Formula: see text] , and [Formula: see text] bound states as the consequence of two prerequisites in the SU(3) flavor symmetry and heavy quark spin symmetry. The first prerequisite, the X(3872) as the weakly D‾^∗D/D‾D^∗ bound state is supported by its mass and decay branching ratios. The second prerequisite, the existence of the [Formula: see text] bound state is supported by the lattice QCD calculation and the observation of χ_c0(3930) by the LHCb Collaboration. We hope the future experimental analyses can search for these bound states in the B→D_(s)^(*)D‾_(s)^(*)h processes (h denotes the light hadrons). The [Formula: see text] bound state is also expected to be reconstructed in the J/ψϕ final state in the B→J/ψϕK decay.

Recent results on hadronic spectroscopy at LHCb

The LHCb experiment is optimized to make precision measurements in the flavour sector. The large datasets collected between 2010 and 2016 allow to study the properties of heavy hadrons with unprecedented precision. In these proceedings recent results related to three topics are discussed: studies of charmonium production and properties using inclusive b → φφX decays, the observation of charmed pentaquarks and exotic mesons, and the observation of five new excited Ωc baryons.

Heavy mesons in the Quark Model

Since the discovery of theJ/ψ, the quark model was very successful in describing the spectrum and properties of heavy mesons including only q̄ components. However since 2003, with the discovery of theX(3872), many states that can not be accommodated on the naive quark model have been discovered, and they made unavoidable to include higher Fock components on the heavy meson states. We will give an overview of the success of the quark model for heavy mesons and point some of the states that are likely to be more complicated structures such as meson-meson molecules.

Tetra and pentaquarks from the molecular perspective

We present results for the analysis of the B+ → J/ψϕK+ which shows the contribution of two resonances, the X(4140) and X(4160) and a cusp at the $D_s^*\bar D_s^*$ threshold tied to the molecular character of the X(4160) resonance. In the second part we present the results for the theoretical approach to the new Ωcstates from the molecular perspective. In both cases we compare with results of the LHCb collaboration.

Heavy flavour spectroscopy and hadron properties from LHCb

The LHCb experiment is designed to study the properties and decays of heavy flavored hadrons produced in pp collisions at the LHC. The data collected enables precision spectroscopy studies of beauty and charm hadrons. The latest results on spectroscopy of conventional and exotic hadrons are reviewed.

Hadron spectroscopy in LHCb

The LHCb experiment is designed to study the properties and decays of heavy flavored hadrons produced in pp collisions at the LHC. The data collected in the LHC Run I enables precision spectroscopy studies of beauty and charm hadrons. The latest results on spectroscopy of conventional and exotic hadrons are reviewed. In particular the discovery of the first charmonium pentaquark states in theJ/Ψpsystem, the possible existence of four-quark states decaying toJ/ΨΦand the confirmation of resonant nature of theZc(4430)−mesonic state are discussed. In the sector of charmed baryons, the observation of five new Ωcstates, the observation of the Ξcc+and the study of charmed baryons decaying toD0pare presented.

Threshold effects in hadron spectrum: a new spectroscopy?

The exploration of energies above the open-flavor threshold in the meson spectra has led to the appearance of unexpected states difficult to accommodate in the naive picture of a bound state of a quark and an antiquark. Many of such states are located close to meson-meson thresholds, which suggests that molecular structures may be a relevant component in the total wave function of such resonances. In this work, the state of meson-meson molecules calculations is reviewed, using a nonrelativistic constituent quark model that has been applied to a wide range of hadronic observables, and therefore all model parameters are completely constrained. The model has been able to reproduce, among others, the properties of the X(3872), described as a mixture of cc and DD* states, or the spectrum of the P-wave charm-strange mesons, which are well reproduced only if DK and D*K structures are taken into account. We show that such constituent quark model, which is able to describe the ordinary heavy meson spectra, is also capable of providing a good description of many new states recently reported.