# ICHEP 2020

28 July 2020 to 6 August 2020
virtual conference
Europe/Prague timezone

## Interpretation of LHCb Hidden-Charm Pentaquarks within the Compact Diquark Model

31 Jul 2020, 13:45
3m
virtual conference

#### virtual conference

Poster 06. Strong Interactions and Hadron Physics

### Speaker

Alexander Parkhomenko (P.G. Demidov Yaroslavl State University, Yaroslavl, Russia)

### Description

The LHCb collaboration have recently updated their analysis of the resonant $J/\psi\, p$ mass spectrum in the decay $\Lambda_b^0 \to J/\psi\, p\, K^-$, making use of their combined Run 1 and Run 2 data. In the updated analysis, three narrow states, $P_c (4312)^+$, $P_c (4440)^+$, and $P_c (4457)^+$, are observed. The spin-parity assignments of these states are not yet known. We interpret these narrow resonances as compact hidden-charm diquark-diquark-antiquark pentaquarks. Using an effective Hamiltonian, based on constituent quarks and diquarks, we calculate the pentaquark mass spectrum for the complete $SU (3)_F$ lowest $S$- and $P$-wave multiplets, taking into account dominant spin-spin, spin-orbit, orbital and tensor interactions. The resulting spectrum is very rich and we work out the quark flavor compositions, masses, and $J^P$ quantum numbers of the pentaquarks. However, heavy quark symmetry restricts the observable states in $\Lambda_b$-baryon, as well as in the decays of the other weakly-decaying $b$-baryons, $\Xi_b$ and $\Omega_b$. In addition, some of the pentaquark states are estimated to lie below the $J/\psi\, p$ threshold in $\Lambda_b$-decays (and corresponding thresholds in $\Xi_b$- and $\Omega_b$-decays). They decay via $c \bar c$ annihilation into light hadrons or a dilepton pair, and are expected to be narrower than the $P_c$-states observed. We anticipate their discovery, as well as of the other pentaquark states present in the spectrum at the LHC, and in the long-term future at a Tera-$Z$ factory.

### Primary author

Alexander Parkhomenko (P.G. Demidov Yaroslavl State University, Yaroslavl, Russia)

### Co-authors

Ahmed Ali (DESY) Dr Ishtiaq Ahmed (National Centre for Physics, Islamabad, Pakistan) Muhammed Jamil Aslam (National Centre for Physics) Abdur Rehman (National Centre for Physics, Islamabad)

### Presentation Materials

 Talk-Parkhomenko-ext.pdf Talk-Parkhomenko-ID248.pdf