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Register a new user$Omega_c gamma rightarrowOmega_c^ast$ transition in lattice QCD
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We study the electromagnetic $Omega_c gamma rightarrowOmega_c^ast$ transition in 2+1 flavor lattice QCD, which gives access to the dominant decay mode of $Omega_c^ast$ baryon. The magnetic dipole and the electric quadrupole transition form factors are computed. The magnetic dipole form factor is found to be mainly determined by the strange quark and the electric quadrupole form factor to be negligibly small, in consistency with the quark model. We also evaluate the helicity amplitudes and the decay rate.
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We evaluate the electromagnetic $Xi_c gamma rightarrowXi_c^prime$ transition on 2+1 flavor lattices corresponding to a pion mass of $sim 156$ MeV. We extract the magnetic Sachs and Pauli form factors which give the $Xi_c$-$Xi_c^prime$ transition magnetic moment and the decay rates of $Xi_c^prime$ baryons. We did not find a signal for the magnetic form factor of the neutral transition $Xi_c^0 gamma rightarrowXi_c^{prime 0}$, which is suppressed by the U-spin flavor symmetry. As a byproduct, we extract the magnetic form factors and the magnetic moments of $Xi_c$ and $Xi_c^prime$ baryons, which give an insight to the dynamics of $u/d$, $s$ and $c$ quarks having masses at different scales.
The $DeltaDelta$ dibaryon resonance $d^ast (2380)$ with $(J^P, I)=(3^+, 0)$ is studied theoretically on the basis of the 3-flavor lattice QCD simulation with heavy pion masses ($m_pi =679, 841$ and $1018$ MeV). By using the HAL QCD method, the central $Delta$-$Delta$ potential in the ${}^7S_3$ channel is obtained from the lattice data with the lattice spacing $asimeq 0.121$ fm and the lattice size $Lsimeq 3.87$ fm. The resultant potential shows a strong short-range attraction, so that a quasi-bound state corresponding to $d^ast (2380)$ is formed with the binding energy $25$-$40$ MeV below the $DeltaDelta$ threshold for the heavy pion masses. The tensor part of the transition potential from $DeltaDelta$ to $NN$ is also extracted to investigate the coupling strength between the $S$-wave $DeltaDelta$ system with $J^P=3^+$ and the $D$-wave $NN$ system. Although the transition potential is strong at short distances, the decay width of $d^ast (2380)$ to $NN$ in the $D$-wave is kinematically suppressed, which justifies our single-channel analysis at the range of the pion mass explored in this study.
We investigate the $D_{s0}^ast(2317)$ meson using lattice QCD and considering correlation functions of several $bar{c} s$ two-quark and $bar{c} s (bar{u} u + bar{d} d)$ four-quark interpolating fields. These interpolating fields generate different structures in color, spin and position space including quark-antiquark pairs, tetraquarks and two-meson scattering states. For our computation we use an ensemble simulated with pion mass $m_pi approx 0.296 , textrm{GeV}$ and spatial volume of extent $2.90 , textrm{fm}$. We find in addition to the expected spectrum of two-meson scattering states another state around $60 , textrm{MeV}$ below the $D K$ threshold, which we interpret as the $D_{s0}^ast(2317)$ meson. This state couples predominantly to a quark-antiquark interpolating field and only weakly to a $D K$ two-meson interpolating field. The coupling to the tetraquark interpolating fields is essentially zero, rendering a tetraquark interpretation of the $D_{s0}^ast(2317)$ meson rather unlikely. Moreover, we perform a scattering analysis using Luschers method and the effective range approximation to determine the $D_{s0}^ast(2317)$ mass for infinite spatial volume. We find this mass $51 , textrm{MeV}$ below the $D K$ threshold, rather close to both our finite volume result and the experimentally observed value.
State-of-the-art lattice QCD studies of hot and dense strongly interacting matter currently rely on extrapolation from zero or imaginary chemical potentials. The ill-posedness of numerical analytic continuation puts severe limitations on the reliability of such methods. Here we use the more direct sign reweighting method to perform lattice QCD simulation of the QCD chiral transition at finite real baryon density on phenomenologically relevant lattices. This method does not require analytic continuation and avoids the overlap problem associated with generic reweighting schemes, so has only statistical but no uncontrolled systematic uncertainties for a fixed lattice setup. This opens up a new window to study hot and dense strongly interacting matter from first principles. We perform simulations up to a baryochemical potential-temperature ratio of $mu_B/T=2.5$ covering most of the RHIC Beam Energy Scan range in the chemical potential. We also clarify the connection of the approach to the more traditional phase reweighting method.
Lattice simulations of QCD have produced precise estimates for the masses of the lowest-lying hadrons which show excellent agreement with experiment. By contrast, lattice results for the vector and axial vector form factors of the nucleon show significant deviations from their experimental determination. We present results from our ongoing project to compute a variety of form factors with control over all systematic uncertainties. In the case of the pion electromagnetic form factor we employ partially twisted boundary conditions to extract the pion charge radius directly from the linear slope of the form factor near vanishing momentum transfer. In the nucleon sector we focus specifically on the possible contamination from contributions of higher excited states. We argue that summed correlation functions offer the possibility of eliminating this source of systematic error. As an illustration of the method we discuss our results for the axial charge, gA, of the nucleon.
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