The anticharmed exotic baryon Theta_c and its relatives

TL;DR

This paper predicts the existence and estimates the masses of exotic baryons Theta_c and Theta_b^+ with heavy quarks, based on a novel pentaquark model inspired by the Theta^+ discovery.

Contribution

It introduces a new pentaquark model to estimate properties of heavy-quark exotic baryons Theta_c and Theta_b^+.

Findings

Theta_c mass estimated at 2985 ± 50 MeV

Theta_b^+ mass estimated at 6398 ± 50 MeV

States should appear as narrow peaks in specific decay channels

Abstract

Motivated by the recent discovery of the exotic S=+1 narrow baryon resonance Theta^+ at 1540 MeV, with quark content {uudd sbar}, we conjecture the existence of its anti-charmed analogue Theta_c, with quark content {uudd cbar}, and compute its likely properties. We rely on the recently constructed model of a novel kind of a pentaquark with an unusual color structure which provides a good approximation to the Theta^+ mass. We expect that Theta_c is an isosinglet with J^P=1/2^+ and estimate its mass at 2985 \pm 50 MeV. We also discuss another possible exotic baryon resonance containing heavy quarks, the Theta_b^+, a {uudd bbar} state, and estimate m_{Theta_b^+}=6398 \pm 50 MeV. These states should appear as unexpectedly narrow peaks in D^-p, Dbar^0 n, B^0 p and B^+ n mass distributions.