Discovery potential of stable and near-threshold doubly heavy tetraquarks at the LHC

Abstract

We study the LHC discovery potential of the double-bottom tetraquarks $bb\bar{u}\bar{d}$, $bb\bar{u}\bar{s}$ and $bb\bar{d}\bar{s}$, the lightest of which having $J^P=1^{+}$, called $T_{[\bar{u}\bar{d}]}^{\{bb\}}$, $T_{[\bar{u}\bar{s}]}^{\{bb\}}$ and $T_{[\bar{d}\bar{s}]}^{\{bb\}}$, are expected to be stable against strong decays. Employing the Monte Carlo generators MadGraph5$\_$aMC@NLO and Pythia6, we simulate the process $pp\to \bar{b}b\bar{b}b$ and calculate the $bb$-diquark jet configurations, specified by the invariant mass interval $m_{bb}<M_{T_{[\bar{q}{\bar{q}}^{\prime }]}^{\{bb\}}}+\Delta M$. Estimates of $\Delta M$ from the measured product $\sigma (pp\to B_c^{+}+X)\mathcal{B}(B_c^{+}\to J/\psi {\pi }^{+})$ are presented and used to to get the $bb$-diquark jet cross sections in double-bottom hadrons $\sigma (pp\to H_{\{bb\}}+X)$, where $H_{\{bb\}}$ represent tetraquarks and baryons. This is combined with the LHCb data on the fragmentation $b\to {\Lambda }_b$ and $b\to B$ to obtain $\sigma (pp\to T_{[\bar{u}\bar{d}]}^{\{bb\}}+X)=(2.4_{-0.6}^{+0.9})\text{nb}$, and about a half of this for the $T_{[\bar{u}\bar{s}]}^{\{bb\}}$ and $T_{[\bar{d}\bar{s}]}^{\{bb\}}$. We also present estimates of the production cross sections for the mixed bottom-charm tetraquarks, $bc\bar{u}\bar{d}$, $bc\bar{u}\bar{s}$ and $bc\bar{d}\bar{s}$, obtaining $\sigma (pp\to T_{[\bar{u}\bar{d}]}^{[bc]}+X)=(48_{-12}^{+19})\mathrm{nb}$, and the related ones having $T_{[\bar{u}\bar{s}]}^{[bc]}$ and $T_{[\bar{d}\bar{s}]}^{[bc]}$. They have excellent discovery potential at the LHC, as their branching ratios in various charge combinations of $B{D}_{(s)}(\gamma )$ are anticipated to be large.

Comments: 6 pages, 4 figures; v2: Revised to incorporate referee remarks, version accepted for publication in Physics Letters B