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
virtual conference

virtual conference

Poster 06. Strong Interactions and Hadron Physics Strong Interactions and Hadron Physics - Posters


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


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)


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