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Register a new userLattice QCD investigation of a doubly-bottom $bar{b} bar{b} u d$ tetraquark with quantum numbers $I(J^P) = 0(1^+)$
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We use lattice QCD to investigate the spectrum of the $bar{b} bar{b} u d$ four-quark system with quantum numbers $I(J^P) = 0(1^+)$. We use five different gauge-link ensembles with $2+1$ flavors of domain-wall fermions, including one at the physical pion mass, and treat the heavy $bar{b}$ quark within the framework of lattice nonrelativistic QCD. Our work improves upon previous similar computations by considering in addition to local four-quark interpolators also nonlocal two-meson interpolators and by performing a Luscher analysis to extrapolate our results to infinite volume. We obtain a binding energy of $(-128 pm 24 pm 10) , textrm{MeV}$, corresponding to the mass $(10476 pm 24 pm 10) , textrm{MeV}$, which confirms the existence of a $bar{b} bar{b} u d$ tetraquark that is stable with respect to the strong and electromagnetic interactions.
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We study tetraquark resonances with lattice QCD potentials computed for a static bbar bbar pair in the presence of two lighter quarks u d, the Born-Oppenheimer approximation and the emergent wave method. As a proof of concept we focus on the system with isospin I = 0, but consider different relative angular momenta l of the heavy quarks bbar bbar. For l=0 a bound state has already been predicted with quantum numbers I(JP) = 0(1+). Exploring various angular momenta we now compute the phase shifts and search for S and T matrix poles in the second Riemann sheet. We predict a tetraquark resonance for l =1, decaying into two B mesons, with quantum numbers I(JP) = 0(1-), mass m = 10 , 576^{+4}_{-4} MeV} and decay width Gamma = 112^{+90}_{-103} MeV.
We compare two frequently discussed competing structures for a stable $bar b bar b u d$ tetraquark with quantum numbers $I(J^P) = 0(1^+)$ by considering a meson-meson as well as a diquark-antidiquark creation operator. We treat the heavy antiquarks as static with fixed positions and find diquark-antidiquark dominance for $bar b bar b$ separations $r < 0.2 , text{fm}$, while for $r > 0.5 , text{fm}$ the system essentially corresponds to a pair of $B$ mesons. For the meson-meson to diquark-antidiquark ratio of the tetraquark we obtain around $58%/42%$.
In recent years, the existence of a hadronically stable $bar{b} bar{b} u d$ tetraquark with quantum numbers $I(J^P) = 0(1^+)$ was confirmed by first principles lattice QCD computations. In this work we use lattice QCD to compare two frequently discussed competing structures for this tetraquark by considering meson-meson as well as diquark-antidiquark creation operators. We use the static-light approximation, where the two $bar{b}$ quarks are assumed to be infinitely heavy with frozen positions, while the light $u$ and $d$ quarks are fully relativistic. By minimizing effective energies and by solving generalized eigenvalue problems we determine the importance of the meson-meson and the diquark-antidiquark creation operators with respect to the ground state. It turns out, that the diquark-antidiquark structure dominates for $bar{b} bar{b}$ separations $r < 0.25 , text{fm}$, whereas it becomes increasingly more irrelevant for larger separations, where the $I(J^P) = 0(1^+)$ tetraquark is mostly a meson-meson state. We also estimate the meson-meson to diquark-antidiquark ratio of this tetraquark and find around $60% / 40%$.
We have studied the masses for fully open-flavor tetraquark states $bcbar{q}bar{s}$ and $scbar{q}bar{b}$ with quantum numbers $J^{P}=0^{+},1^{+}$. We systematically construct all diquark-antiquark interpolating currents and calculate the two-point correlation functions and spectral densities in the framework of QCD sum rule method. Our calculations show that the masses are about $7.1-7.2$ GeV for the $bcbar{q}bar{s}$ tetraquark states and $7.0-7.1$ GeV for the $scbar{q}bar{b}$ tetraquarks. The masses of $bcbar{q}bar{s}$ tetraquarks are below the thresholds of $bar{B}_{s}D$ and $bar{B}_{s}^{*}D$ final states for the scalar and axial-vector channels respectively. The $scbar{q}bar{b}$ tetraquark states with $J^{P}=1^{+}$ lie below the $B_{c}^{+}K^{*}$ and $B_{s}^{*}D$ thresholds. Such low masses for these possible tetraquark states indicate that they can only decay via weak interaction and thus are very narrow and stable.
We study tetraquark resonances using lattice QCD potentials for a pair of static antiquarks $bar{b}bar{b}$ in the presence of two light quarks $ud$. The system is treated in the Born-Oppenheimer approximation and we use the emergent wave method. We focus on the isospin $I=0$ channel, but consider different orbital angular momenta $l$ of the heavy antiquarks $bar{b}bar{b}$. We extract the phase shifts and search for $mbox{S}$ and $mbox{T}$ matrix poles on the second Riemann sheet. For orbital angular momentum $l=1$ we find a tetraquark resonance with quantum numbers $I(J^P)=0(1^-)$, resonance mass $m=10576^{+4}_{-4} , textrm{MeV}$ and decay width $Gamma= 112^{+90}_{-103} textrm{MeV}$, which can decay into two $B$ mesons.
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