Pentaquarks and doubly heavy exotic mesons

Marek Karliner,A Wrońska,C Guaraldo,A Magiera,H Ströher

doi:10.1051/epjconf/201613001003

Abstract

I discuss the experimental evidence for and theoretical interpretation of the new mesons and baryons with two heavy quarks. These include doubly-heavy baryons, exotic hadronic quarkonia and most recently a manifestly exotic pentaquark-like doubly heavy baryon with a minimal quark content uudc discovered by LHCb, whose mass, decay mode and width are in agreement with a prediction based on a physical picture of a deuteron-like Σ c D * “hadronic molecule”.

Highlights

This strongly suggests a parallel with X(3872), whose mass is almost exactly at the D∗Dthreshold
In the bottom system the attraction due to π exchange is essentially the same, but the kinetic energy is much smaller by a factor of ∼m(B)/m(D)≈2.8
The narrow widths of these exotic resonances implies that they are deuteron-like loosely bound states and/or near threshold resonances in the two heavy-meson system

Summary

Introduction

This strongly suggests a parallel with X(3872), whose mass is almost exactly at the D∗Dthreshold. In the charm system the I=1 state is expected to be well above the D∗Dthreshold and the I=0 X(3872) is at the threshold.1 In the bottom system the attraction due to π exchange is essentially the same, but the kinetic energy is much smaller by a factor of ∼m(B)/m(D)≈2.8 . The narrow widths of these exotic resonances implies that they are deuteron-like loosely bound states and/or near threshold resonances in the two heavy-meson system.

Results

Conclusion