Molecular interpretation of the LHCb pentaquarks from an analysis of J/ψp spectrum

A coupled-channel approach including the ΛcD¯(*) and ηcp channels in addition to the Σc(*)D¯(*) and J/ψp channels, as required by unitarity and heavy quark spin symmetry (HQSS), is applied to the hidden-charm pentaquark Pc states, i.e., Pc(4312), Pc(4440) and Pc(4457), discovered by LHCb Collaboration. It is demonstrated that to obtain cutoff independent results, the one-pion exchange potential in the multichannel systems is to be supplemented with next-leading order counter terms responsible for the S-wave-to-D-wave transitions. We show that the experimental data for the J/ψp mass distributions are fully in line with the ΣcD¯ and ΣcD¯* hadronic molecular interpretation of the Pc(4312) and Pc(4440)/Pc(4457), respectively. A narrow Σc*D¯ molecule around 4.38 GeV is required by the HQSS with the evidence for its existence seen in the J/ψp spectrum. Moreover, we predict the line shapes for the elastic and inelastic channels.

CP violation in charm

The existence of CP violation in the decays of strange and beauty mesons is very well established experimentally. On the contrary, CP violation in the decays of charmed particles has been elusive for a long time and has been observed for the first time in 2019 by the LHCb experiment. Since then several studies have been performed in the charm sector. During the LHC Run 1 and Run 2, the LHCb collaboration has collected large samples containing charm hadron decays, on a scale never seen before. Collected data enabled physicists to obtain several new results, most of which surpassed previous results and became new world’s best measurements. Presently the LHCb spectrometer is being upgraded to enhance readout system, improve subdetector components and increase integrated luminosity to 50 fb−1 by the end of Run 4.

Searching for heavy leptoquarks at a muon collider

The LHCb Collaboration recently gave an update on testing lepton flavour universality with B+→ K+ℓ+ℓ−, in which a 3.1 standard deviations from the standard model prediction was observed. The g-2 experiment also reports a 3.3 standard deviations from the standard model on muon anomalous magnetic moment measurement. These deviations could be explained by introducing new particles including leptoquarks. In this paper, we show the possibility to search for heavy spin-1 leptoquarks at a future TeV scale muon collider by performing studies from three channels: 1) same flavour final states with either two bottom or two light quarks, 2) different flavour quark final states, and 3) a so-called “VXS” process representing the scattering between a vector boson and a leptoquark to probe the coupling between leptoquark and tau lepton. We conclude that a 3 TeV muon collider with 3 ab−1 of integrated luminosity is already sufficient to cover the leptoquark parameter space in order to explain the LHCb lepton flavour universality anomaly.

Masses and strong decays of open charm hexaquark states $$\Sigma _{c}^{(*)}{\Sigma }_{c}^{(*)}$$

Inspired by the recent discovery of the doubly charmed tetraquark state $$T_{cc}^{+}$$ T cc + by the LHCb Collaboration, we perform a systematic study of masses and strong decays of open charm hexaquark states $${\Sigma }_{c}^{(*)}\Sigma _{c}^{(*)}$$ Σ c ( ∗ ) Σ c ( ∗ ) . Taking into account heavy quark spin symmetry breaking, we predict several bound states of isospin $$I=0$$ I = 0 , $$I=1$$ I = 1 , and $$I=2$$ I = 2 in the one boson exchange model. Moreover, we adopt the effective Lagrangian approach to estimate the decay widths of $${\Sigma }_{c}^{(*)}\Sigma _{c}^{(*)} \rightarrow \Lambda _{c}\Lambda _{c}$$ Σ c ( ∗ ) Σ c ( ∗ ) → Λ c Λ c and their relevant ratios via the triangle diagram mechanism, which range from a few MeV to a few tens of MeV. We strongly recommend future experimental searches for the $${\Sigma }_{c}^{(*)}\Sigma _{c}^{(*)}$$ Σ c ( ∗ ) Σ c ( ∗ ) hexaquark states in the $$\Lambda _c\Lambda _c$$ Λ c Λ c invariant mass distributions.

P-wave $\Omega_{b}$ states: masses and pole residues

In this paper, we consider all P-wave $\Omega_{b}$ states represented by interpolating currents with a derivative and calculate the corresponding masses and pole residues with the method of QCD sum rule. Due to the large uncertainties in our calculation compared with the small difference in the masses of the excited $\Omega_{b}$ states observed by the LHCb collaboration, it is necessary to study other properties of the P-wave $\Omega_{b}$ states represented by the interpolating currents investigated in the present work in order to have a better understanding about the four excited $\Omega_{b}$ states observed by the LHCb collaboration. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Strong and electromagnetic decays of the radially excited $$D_s$$ and $$B_s$$ mesons in light cone QCD sum rules

Recently, LHCb Collaboration announced the discovery of radial excitations of $$D_s$$ D s and $$B_s$$ B s mesons. In present work, we calculate the most promising strong and electromagnetic decay widths of radially excited $$D_s(2S)$$ D s ( 2 S ) and $$B_s(2S)$$ B s ( 2 S ) mesons within the light cone QCD sum rules method.

The explanation of some exotic states in the $$cs{\bar{c}}{\bar{s}}$$ tetraquark system

Inspired by the recent observation of $$\chi _{c0}(3930)$$ χ c 0 ( 3930 ) , X(4685) and X(4630) by the LHCb Collaboration and some exotic resonances such as X(4350), X(4500), etc. by several experiment collaborations, the $$cs{\bar{c}}{\bar{s}}$$ c s c ¯ s ¯ tetraquark systems with $$J^{PC}=0^{++}$$ J PC = 0 + + , $$1^{++}$$ 1 + + , $$1^{+-}$$ 1 + - and $$2^{++}$$ 2 + + are systematically investigated in the framework of the quark delocalization color screening model(QDCSM). Two structures, the meson–meson and diquark–antidiquark structures, as well as the channel-coupling of all channels of these two configurations are considered in this work. The numerical results indicate that the molecular bound state $$D^{-}_{s}D_{s}^{+}$$ D s - D s + with $$J^{PC}=00^{++}$$ J PC = 00 + + can be supposed to explain the $$\chi _{c0}(3930)$$ χ c 0 ( 3930 ) . Besides, by using the stabilization method, several resonant states are obtained. Among these states, X(4350), X(4500) and X(4700) can be explained as the compact tetraquark states with $$J^{PC}=00^{++}$$ J PC = 00 + + , and the X(4274) is possible to be a candidate of the compact tetraquark state with $$J^{PC}=1^{++}$$ J PC = 1 + + . Apart from that, the $$J^{PC}=0^{++}$$ J PC = 0 + + resonance state with energy range 4028–4033 MeV, the two $$J^{PC}=2^{++}$$ J PC = 2 + + resonance states with energy range of 4394–4448 MeV and 4526–4536 MeV are possible to be new exotic states, which are indeed worthy of attention. More experimental tests are expected to check the existence of all these possible resonance states.

Newly observed X(4630): a new charmoniumlike molecule

Very recently, the LHCb Collaboration at the Large Hadron Collider at CERN observed new resonance X(4630). The X(4630) is decoded as a charmoniumlike molecule with hidden-strange quantum number well in the one-boson-exchange mechanism. Especially, the study of its hidden-charmed decays explicitly shows the dominant role of $$J/\psi \phi $$ J / ψ ϕ among all allowed hidden-charmed decays of the X(4630), which enforces the conclusion of X(4630) as a charmoniumlike molecule. The discovery of the X(4630) is a crucial step of constructing charmoniumlike molecule zoo.

Prompt production of the hidden charm pentaquarks in the LHC

Motivated by the observation of the first hidden charm pentaquarks by the LHCb collaboration in 2015 and the updated analysis with an order-of-magnitude larger data set in 2019, we estimate their cross sections for the prompt production as well as their heavy quark spin partners, in the $$\Sigma _c^{(*)}\bar{D}^{(*)}$$ Σ c ( ∗ ) D ¯ ( ∗ ) hadronic molecular picture, at the center-of-mass energy $$7~\text {TeV}$$ 7 TeV in the pp collision. Their cross sections are several $${\mathrm {nb}}$$ nb and we would expect several tens hidden charm pentaquark events in the LHC based on its current integrated luminosity. The cross sections show a sizable deviation of the cross sections for hidden charm pentaquarks with the third isospin component $$I_z=+\frac{1}{2}$$ I z = + 1 2 ($$P_c^+$$ P c + ) from those with $$I_z=-\frac{1}{2}$$ I z = - 1 2 ($$P_c^0$$ P c 0 ). The cross sections decrease dramatically with the increasing transverse momentum. Our study can also tell where to search for the missing hidden charm pentaquarks. The confirmation of the complete hidden charm pentaquarks in the heavy quark symmetry would further verify their $$\Sigma _c^{(*)}\bar{D}^{(*)}$$ Σ c ( ∗ ) D ¯ ( ∗ ) molecular interpretation. In addition, the relative strength among these cross sections for pentaquarks can help us to identify the quantum numbers of the $$P_c(4440)$$ P c ( 4440 ) and $$P_c(4457)$$ P c ( 4457 ) .

Threshold effects as the origin of $$Z_{cs}(4000)$$, $$Z_{cs}(4220)$$ and X(4700) observed in $$B^+\rightarrow J/\psi \phi K^+$$

We investigate the $$B^+\rightarrow J/\psi \phi K^+$$ B + → J / ψ ϕ K + decay via various rescattering diagrams. Without introducing genuine exotic resonances, it is shown that the $$Z_{cs}(4000)$$ Z cs ( 4000 ) , $$Z_{cs}(4220)$$ Z cs ( 4220 ) and X(4700) reported by the LHCb collaboration can be simulated by the $$J/\psi K^{*+}$$ J / ψ K ∗ + , $$\psi ^\prime K^+$$ ψ ′ K + and $$\psi ^\prime \phi $$ ψ ′ ϕ threshold cusps, respectively. These cusps are enhanced by some nearby triangle singularities. The X(4685) with $$J^P=1^+$$ J P = 1 + cannot be well simulated by the threshold effects in our model, which implies that it may be a genuine resonance.