Related papers: Four-quark operators in hadrons
We have measured some simple matrix elements for pseudoscalar and vector mesons made of Wilson valence quarks and staggered sea quarks at $\beta=5.6$ at sea quark masses $am_q=0.01$ and 0.025. Our measurements include the decay constants of…
The role of 5-quark components in the pion and electromagnetic decays and transition form factors of the N(1440) is explored. The $qqqq\bar q$ components, where the 4-quark subsystem has the flavor-spin symmetries $[4]_{FS}[22]_F[22]_S$ and…
We propose a theoretical framework for evaluating the effect of four-fermion operators on the mass of composite particles in confining strongly-coupled gauge theories. The confining sector is modelled by a non-local Nambu-Jona Lasinio…
We report a proof-of-principle lattice QCD simulation of the electric and magnetic polarizabilities for a neutral pion in the four-point function method. The results are based on the same quenched Wilson ensembles on a $24^3\times 48$…
We present results for the nucleon electromagnetic form factors using an ensemble of maximally twisted mass clover-improved fermions with pion mass of about 130 MeV. We use multiple sink-source separations and three analysis methods to…
We determine the chiral corrections to the matrix elements of the Delta B=0 four-quark operators which are relevant to the studies of the ratios of lifetimes of heavy-light mesons as well as to the power corrections to the inclusive…
We describe the calculation of the $B\rightarrow \pi$ hadronic matrix element from operator product expansion near the light-cone in QCD. In the resulting sum rules, the form factors $f^+$ and $F_0$ determining this matrix element are…
We present the status of our calculation of the first few moments of the nucleon structure functions. Our calculations are done using domain wall fermions in the quenched approximation with the DBW2 gauge action at 1.3GeV inverse lattice…
We calculate the perturbative corrections to fermion bilinears that are used in numerical simulations when extracting weak matrix elements using staggered fermions. This extends previous calculations of Golterman and Smit, and Daniel and…
We match continuum and lattice heavy-light four-fermion operators at one loop in perturbation theory. For the heavy quarks we use nonrelativistic QCD and for the massless light quarks the highly improved staggered quark action. We include…
High luminosity accelerators have greatly increased the interest in semi-exclusive and exclusive reactions involving nucleons. The relevant theoretical information is contained in the nucleon wavefunction and can be parametrized by moments…
We consider the vector space of $n \times n$ matrices over $\mathbb C$, Fermi operators and operators constructed from these matrices and Fermi operators. The properties of these operators are studied with respect to the underlying…
We analyze the electromagnetic form factors of the nucleon to fourth order in relativistic baryon chiral perturbation theory. We employ the recently proposed infrared regularization scheme and show that the convergence of the chiral…
Considering Ginsparg-Wilson type fermions dynamically in lattice QCD simulations is a challenging task. The hope is to be able to approach smaller pion masses and to eventually reach physical situations. The price to pay is substantially…
Matrix elements of six-quark operators are needed to extract new physics constraints from experimental searches for neutron-antineutron oscillations. This work presents in detail the first lattice quantum chromodynamics calculations of the…
Higher-twist effects in the low-order moments of the longitudinal and transverse structure functions of proton and deuteron have been analyzed using available phenomenological fits of existing data in the Q**2 range between 1 and 20…
We present results for the non-perturbative renormalisation of four-fermion operators with two flavours of dynamical quarks. We consider both fully relativistic left current-left current operators, and a full basis for $\Delta B=2$…
We report on recent results for the pion and nucleon matrix element of the twist-2 operator corresponding to the average momentum of non-singlet quark densities. We discuss finite size effects for the nucleon matrix element and present…
The standard hybrid Monte Carlo algorithm uses the second order integrator at the molecular dynamics step. This choice of the integrator is not always the best. Using the Wilson fermion action, we study the performance of the hybrid Monte…
$\pi$-$N$ $\sigma$ term and proton axial vector matrix elements are calculated including disconnected contributions with a variant wall source method using the Wilson quark action at $\beta=5.7$ in quenched QCD. For the $\sigma$ term, we…