arXiv subjects

Zhaofeng Liu

Publications and source records attributed to Zhaofeng Liu.

65 records · Page 4Linked to original sources

arXiv2013

Non-perturbative renormalization of overlap quark bilinears on domain wall fermion configurations

We present renormalization constants of overlap quark bilinear operators on 2+1-flavor domain wall fermion configurations. Both overlap and domain wall fermions have chiral symmetry on the lattice. The scale independent renormalization constant for the local axial vector current is computed using a Ward Identity. The renormalization constants for the scalar, pseudoscalar and vector current are calculated in the RI-MOM scheme. Results in the MS-bar scheme are obtained by using perturbative conversion ratios. The analysis uses in total six ensembles with lattice sizes 24^3x64 and 32^3x64.

hep-lat↗

arXiv2013

Lattice study on $η_{c2}$ and X(3872)

Properties of $2^{-+}$ charmonium $η_{c2}$ are investigated in quenched lattice QCD. The mass of $η_{c2}$ is determined to be 3.80(3) GeV, which is close to the mass of $D$-wave charmonium $ψ(3770)$ and in agreement with quark model predictions. The transition width of $η_{c2}\to γJ/ψ$ is also obtained with a value $Γ=3.8(9)$ keV. Since the possible $2^{-+}$ assignment to X(3872) has not been ruled out by experiments, our results help to clarify the nature of X(3872).

hep-lat↗

arXiv2011

A lattice calculation of B -> K(*) form factors

Lattice QCD can contribute to the search for new physics in b -> s decays by providing first-principle calculations of B -> K(*) form factors. Preliminary results are presented here which complement sum rule determinations by being done at large q^2 and which improve upon previous lattice calculations by working directly in the physical b sector on unquenched gauge field configurations.

hep-ph↗

arXiv2010

Form factors for rare B decays: strategy, methodology, and numerical study

We investigate the combined use of moving NRQCD and stochastic sources in lattice calculations of form factors describing rare B and B_s decays. Moving NRQCD leads to a reduction of discretisation errors compared to standard NRQCD. Stochastic sources are tested for reduction of statistical errors.

hep-lat↗

arXiv2007

Diquark effects in light baryon correlators from lattice QCD

We study the role of diquarks in light baryons through point to point baryon correlators. We contrast results from quenched simulations with ones with two flavors of dynamical overlap fermions. The scalar, pseudoscalar and axial vector diquarks are combined with light quarks to form color singlets. The quenched simulation shows large zero mode effects in correlators containing the scalar and pseudoscalar diquark. The two scalar diquarks created by gamma_5 and gamma_0gamma_5 lead to different behavior in baryon correlators, showing that the interaction of diquarks with the third light quark matters: we do not see an isolated diquark. In our quark mass range, the scalar diquark created by gamma_5 seems to play a greater role than the others.

hep-ph↗

arXiv2007

Moments of meson distribution functions with dynamical twisted mass fermions

We present our preliminary results on the lowest moment of quark distribution functions of the pion using two flavor dynamical simulations with Wilson twisted mass fermions at maximal twist. The calculation is done in a range of pion masses from 300 to 500 MeV. A stochastic source method is used to reduce inversions in calculating propagators. Finite volume effects at the lowest quark mass are examined by using two different lattice volumes. Our results show that we achieve statistical errors of only a few percent. We plan to compute renormalization constants non-perturbatively and extend the calculation to two more lattice spacings and to the nucleons.

hep-lat↗

arXiv2007

Baryon masses with dynamical twisted mass fermions

We present results on the mass of the nucleon and the $Δ$ using two dynamical degenerate twisted mass quarks. The evaluation is performed at four quark masses corresponding to a pion mass in the range of 690-300 MeV on lattices of size 2.1 fm and 2.7 fm. We check for cutoff effects by evaluating these baryon masses on lattices of spatial size 2.1 fm with lattice spacings $a(β=3.9)=0.0855(6)$ fm and $a(β=4.05)=0.0666(6)$ fm, determined from the pion sector and find them to be within our statistical errors. Lattice results are extrapolated to the physical limit using continuum chiral perturbation theory. The nucleon mass at the physical point provides a determination of the lattice spacing. Using heavy baryon chiral perturbation theory at ${\cal O}(p^3)$ we find $a(β=3.9)=0.0879(12)$ fm, with a systematic error due to the chiral extrapolation estimated to be about the same as the statistical error. This value of the lattice spacing is in good agreement with the value determined from the pion sector. We check for isospin breaking in the $Δ$-system. We find that $Δ^{++,-}$ and $Δ^{+,0}$ are almost degenerate pointing to small flavor violating effects.

hep-lat↗

arXiv2007

Quark condensate in one-flavor QCD

We compute the condensate in QCD with a single quark flavor using numerical simulations with the overlap formulation of lattice fermions. The condensate is extracted by fitting the distribution of low lying eigenvalues of the Dirac operator in sectors of fixed topological charge to the predictions of Random Matrix Theory. Our results are in excellent agreement with estimates from the orientifold large-N_c expansion.

hep-th↗

arXiv2006

Quark condensate in two-flavor QCD

We compute the condensate in QCD with two flavors of dynamical fermions using numerical simulation. The simulations use overlap fermions, and the condensate is extracted by fitting the distribution of low lying eigenvalues of the Dirac operator in sectors of fixed topological charge to the predictions of Random Matrix Theory.

hep-lat↗

arXiv2006

Baryon correlators containing different diquarks from lattice simulations

Point to point vacuum correlators containing diquarks in the color anti-triplet representation are computed both in the quenched approximation and dynamical overlap simulations with two flavors. The scalar, pseudoscalar and axial vector diquarks are combined with light quarks to form color singlets. The scalar ("good") diquark channel shows a stronger attraction than the axial vector ("bad") channel in the quenched data set. The pseudoscalar diquark channel shows a finite volume zero mode artifact: the correlator becomes negative at large distance when the quark mass is small. By separating configurations without zero modes from those with zero modes, we found that the zero modes have an important contribution in both the attraction in the scalar channel and the repulsion in the pseudoscalar channel. In the axial vector diquark channel, we did not find apparent zero mode effects.

hep-lat↗

arXiv2005

Renormalization of Bilinear Quark Operators for Overlap Fermions

We present non-perturbative renormalization constants of fermionic bilinears on the lattice in the quenched approximation at beta=6.1 using an overlap fermion action with hypercubic(HYP)-blocked links. We consider the effects of the exact zero modes of the Dirac operator and find they are important in calculating the renormalization constants of the scalar and pseudoscalar density. The results are given in the RI' and MS bar schemes and compared to the perturbative calculations.

hep-lat↗