相关论文: The Roper Puzzle

Assuming that the 125 GeV particle observed at the LHC is a composite scalar and responsible for the electroweak gauge symmetry breaking, we consider the possibility that the bound state is generated by a non-Abelian gauge theory with…

The origin of the low-lying nature of the $N$*(1440), or Roper resonance, has been the subject of significant interest for many years, including several investigations using lattice QCD. The majority of lattice studies have not observed a…

We calculate the Sivers function of $\bar{u}$ and $\bar{d}$ quarks using the overlap representation within the light-cone formalism. The light-cone wave functions of the proton is obtained in terms of the $|\bar{q} q B\rangle$ Fock states…

The confining strength or model parameters and constituent quark masses are reparametrized for predicting the ground state meson masses. We analyzed these from the hyperfine splitting of $S$-wave heavy-flavored, heavy-light and light…

We present a new method for extracting excited states from a single two-point correlation function calculated on the lattice. Our method simply combines the correlation function evaluated at different time slices so as to ``subtract'' the…

We present a technique which permits the calculation of two-point functions of operators containing one heavy quark and an arbitrary number of light quarks as analytic functions of the heavy-quark mass. It is based on the standard Jacobi…

We study excited states of the nucleon in quenched lattice QCD with the spectral analysis using the maximum entropy method. Our simulations are performed on three lattice sizes $16^3\times 32$, $24^3\times 32$ and $32^3\times 32$, at…

Using automated perturbation theory techniques, we have computed the one-loop mass of Fermilab fermions, with an improved gluon action. We will present the results of these calculations, and the resulting predictions for the charm and…

Results for the excited meson and baryon spectrum with two flavors of Chirally Improved sea quarks are presented. We simulate several ensembles with pion masses ranging from 250 to 600 MeV and extrapolate to the physical pion mass. Strange…

We report results on hadron masses, fitting of the quenched chiral log, and quark masses from Neuberger's overlap fermion on a quenched $20^4$ lattice with lattice spacing $a = 0.15$ fm. We used the improved gauge action which is shown to…

We present results for the light, strange and charm quark masses using $N_f=2+1+1$ twisted mass fermion ensembles at three values of the lattice spacing, including two ensembles simulated with the physical value of the pion mass. The…

In this article we describe our studies of the sigma meson, f_0(500), using two-pion correlation functions. We use lattice quantum chromodynamics in the quenched approximation with so-called clover fermions. By working at unphysical pion…

We calculate the electromagnetic form factor of the pion in quenched lattice QCD. The non-perturbatively improved Sheikoleslami-Wohlert lattice action is used together with the ${\mathcal O}(a)$ improved current. We calculate form factor…

We calculate electromagnetic mass difference of mesons using a method proposed by Duncan {\it et al}. The RG-improved gauge action and the non-compact Abelian gauge action are employed to generate configurations. Quark propagators in the…

We study the quark mass function on hypercubic lattices, in a large range of physical volumes and cutoffs. To avoid the very large Wilson term artefact, we exploit the relation between the quark mass function and the pseudoscalar vertex in…

We present results of a quenched QCD simulation with overlap fermions on a lattice of volume V = 16^3X32 at beta=6.0, which corresponds approximatively to a lattice cutoff of 2 GeV and an extension of 1.4 fm. From the two-point correlation…

Cross-section and angular distributions for hadronic and lepton-pair final states in e+e- collisions at centre-of-mass energies between 189 GeV and 209 GeV, measured with the OPAL detector at LEP, are presented and compared with the…

We investigate the mass of the $1^{-+}$ exotic meson, created with hybrid interpolating fields. Access to light quark masses approaching 25 MeV is facilitated by the use of the Fat-Link Irrelevant Clover (FLIC) fermion action, and large…

We present estimates of light quarks masses using lattice data. Our main results are based on a global analysis of all the published data for Wilson and Staggered fermions, both in the quenched approximation and with $n_f=2$ dynamical…

We study the proton and the Roper resonance together with the meson cloud model, by constructing a Hamiltonian matrix and solving the eigenvalue equation. The proton sea quark flavour asymmetry and some properties of the Roper resonance are…