Heavy light tetraquarks from Lattice QCD

TL;DR

This paper reports preliminary lattice QCD calculations indicating the existence of both shallow and deeply bound heavy-light tetraquark states in charm and bottom sectors, using advanced fermion actions on MILC ensembles.

Contribution

First lattice QCD study to investigate heavy-light tetraquarks in multiple flavor sectors with detailed analysis of bound states.

Findings

Shallow bound states in double charm sector.

Deeply bound states in double bottom sector.

Evidence of tetraquark states below relevant thresholds.

Abstract

We present preliminary results from a lattice calculation of tetraquark states in the charm and bottom sector of the type $ud\bar{b}\bar{b}$, $us\bar{b}\bar{b}$, $ud\bar{c}\bar{c}$ and $sc\bar{b}\bar{b}$. These calculations are performed on $N_f = 2 + 1 + 1$ MILC ensembles with lattice spacing of $a = 0.12~\mathrm{fm} $ and $a=0.06~\mathrm{fm} $. A relativistic action with overlap fermions is employed for the light and charm quarks while a non-relativistic action with non-perturbatively improved coefficients is used in the bottom sector. Preliminary results provide a clear indication of presence of energy levels below the relevant thresholds of different tetraquark states. While in double charm sector we find shallow bound levels, our results suggest deeply bound levels with double bottom tetraquarks.