37916668
Renormalization of bilinear quark operators for overlap fermions
We present nonperturbative renormalization constants of fermionic bilinears on the lattice in the quenched approximation at {beta}=6.1 using an overlap [H. Neuberger, Phys. Lett. B 417, 141 (1998)] 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 schemes and compared to perturbative calculations.
16381056
Lattice QCD calculation of form factors describing the rare decays $B \to K^* \ell^+ \ell^-$ and $B_s \to \phi \ell^+ \ell^-$
The rare decays $B^0 \to K^{*0} \mu^+ \mu^-$ and $B_s \to \phi \mu^+ \mu^-$ are now being observed with enough precision to test Standard Model predictions. A full understanding of these decays requires accurate determinations of the corresponding hadronic form factors. Here we present results of lattice QCD calculations of the $B \to K^*$ and $B_s \to \phi$ form factors; we also determine the form factors relevant for the tree-level decays $B_s \to K^* \ell \nu$. We use full-QCD configurations including 2+1 flavors of sea quarks using an improved staggered action, and we employ lattice non-relativistic QCD to describe the bottom quark.
118596020
Light baryon masses with dynamical twisted mass fermions
We present results on the mass of the nucleon and the $\ensuremath{\Delta}$ using two dynamical degenerate twisted mass quarks and the tree-level Symanzik improved gauge action. The evaluation is performed at four quark masses corresponding to a pion mass in the range of about 300\char21{}600 MeV on lattices of 2.1\char21{}2.7 fm at three lattice spacings less than 0.1 fm. We check for cutoff effects by evaluating these baryon masses on lattices of spatial size 2.1 fm at $\ensuremath{\beta}=3.9$ and $\ensuremath{\beta}=4.05$ and on a lattice of 2.4 fm at $\ensuremath{\beta}=3.8$. The values we find are compatible within our statistical errors. Lattice results are extrapolated to the physical limit using continuum chiral perturbation theory. Performing a combined fit to our lattice data at $\ensuremath{\beta}=3.9$ and $\ensuremath{\beta}=4.05$ we find a nucleon mass of $963\ifmmode\pm\else\textpm\fi{}12(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}8(\mathrm{syst})\text{ }\text{ }\mathrm{MeV}$ where we used the lattice spacings determined from the pion decay constant to convert to physical units. The systematic error due to the chiral extrapolation is estimated by comparing results obtained at $\mathcal{O}({p}^{3})$ and $\mathcal{O}({p}^{4})$ heavy baryon chiral perturbation theory. The nucleon mass at the physical point provides an independent determination of the lattice spacing. Using heavy baryon chiral perturbation theory at $\mathcal{O}({p}^{3})$ we find ${a}_{\ensuremath{\beta}=3.9}=0.0889\ifmmode\pm\else\textpm\fi{}0.0012(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.0014(\mathrm{syst})\text{ }\text{ }\mathrm{fm}$, and ${a}_{\ensuremath{\beta}=4.05}=0.0691\ifmmode\pm\else\textpm\fi{}0.0010(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.0010(\mathrm{syst})\text{ }\text{ }\mathrm{fm}$, in good agreement with the values determined from the pion decay constant. Using results from our two smaller lattices spacings at constant ${r}_{0}{m}_{\ensuremath{\pi}}$ we estimate the continuum limit and check consistency with results from the coarser lattice. Results at the continuum limit are chirally extrapolated to the physical point. Isospin violating lattice artifacts in the $\ensuremath{\Delta}$-system are found to be compatible with zero for the values of the lattice spacings used in this work. Performing a combined fit to our lattice data at $\ensuremath{\beta}=3.9$ and $\ensuremath{\beta}=4.05$ we find for the masses of the ${\ensuremath{\Delta}}^{++,\ensuremath{-}}$ and ${\ensuremath{\Delta}}^{+,0}$ $1315\ifmmode\pm\else\textpm\fi{}24(\mathrm{stat})\text{ }\text{ }\mathrm{MeV}$ and $1329\ifmmode\pm\else\textpm\fi{}30(\mathrm{stat})\text{ }\text{ }\mathrm{MeV}$, respectively. We confirm that in the continuum limit they are also degenerate.
55532447
Nonperturbative renormalization of overlap quark bilinears on 2+1-flavor domain wall fermion configurations
Department of Physics, Zhejiang University, Hangzhou 311027, China(Received 9 January 2014; published 19 August 2014)We present renormalization constants of overlap quark bilinear operators on 2þ 1-flavor domain wallfermion configurations. This setup is being used by the χQCD Collaboration in calculations of physicalquantities such as strangeness in the nucleon and the strange and charm quark masses. The scale-independent renormalization constant for the axial-vector current is computed using the Ward identity.The renormalization constants for scalar, pseudoscalar, and vector currents are calculated in the RI-MOMscheme. Results in the MS scheme are also given. The step scaling function of quark masses in theRI-MOM scheme is computed as well. The analysis uses, in total, six different ensembles of three seaquarks, each on two lattices with sizes 24
119237953
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 scheme are obtained by using perturbative conversion ratios. The analysis uses in total six ensembles with lattice sizes 243×64 and 323×64.
118073401
Observation of $\eta_{c}$ decay into $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$ final states
Using a data sample of $2.25\times10^{8}$ $J/\psi$ events collected with the BESIII detector, we present the first observation of the decays of $\eta_{c}$ mesons to $\Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$. The branching fractions are measured to be $(2.11\pm0.28_{\rm stat.}\pm0.18_{\rm syst.}\pm0.50_{\rm PDG})\times10^{-3}$ and $(0.89\pm0.16_{\rm stat.}\pm0.08_{\rm syst.}\pm0.21_{\rm PDG})\times10^{-3}$ for $\eta_{c} \to \Sigma^{+}\bar{\Sigma}^{-}$ and $\Xi^{-}\bar{\Xi}^{+}$, respectively. These branching fractions provide important information on the helicity selection rule in charmonium-decay processes.
121457351
Boson-Fermion Duality in A2 Toda Field Theory
In this paper, we consider a two-dimensional integrable and conformal invariant field theory with two Dirac spinors and two scalar fields. This model has chiral symmetry and CP-like symmetry. Moreover, this model also has a Neother current depending only on the matter field. At last, we bosonize the spinor fields.
122655890
The $\bar B \bar B$ strong interaction with chiral perturbation theory
We study the strong interaction potentials of up to order with the heavy meson chiral perturbation theory. Besides the leading contributions from the contact terms we also consider the one-loop corrections to the contact diagrams and the contributions from the 2ϕ-exchange diagrams. Hopefully, the analytical structures of our result will be helpful in the extrapolation of the relevant heavy meson interaction in the lattice QCD simulation.
116857589
Inclusive $\pi^0$ and $K^0_{S}$ production in two photon collisions at LEP
The reactions e + e − →e + e − π 0 X and e + e − →e + e − K S 0 X are studied using data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 202 GeV. Inclusive differential cross sections are measured as a function of the particle transverse momentum p t and the pseudo-rapidity. For p t ⩽1.5 GeV, the π 0 and K S 0 differential cross sections are described by an exponential, typical of soft hadronic processes. For p t ⩾1.5 GeV, the cross sections show the presence of perturbative QCD processes, described by a power-law. The data are compared to Monte Carlo predictions and to NLO QCD calculations.
123811747
Double-tag events in two-photon collisions at LEP
Abstract Double-tag events in two-photon collisions are studied using the L3 detector at LEP centre-of-mass energies from s =189  GeV to 209 GeV. The cross sections of the e + e − →e + e − hadrons and γ ∗ γ ∗ → hadrons processes are measured as a function of the product of the photon virtualities, Q 2 = Q 2 1 Q 2 2 , of the two-photon mass, W γγ , and of the variable Y =ln( W 2 γγ / Q 2 ). The average photon virtuality is 〈 Q 2 1 〉=〈 Q 2 2 〉=16 GeV 2 . The results are in agreement with next-to-leading order calculations for the process γ ∗ γ ∗ → q q in the interval 2⩽ Y ⩽5. An excess is observed in the interval 5 Y ⩽7, corresponding to W γγ greater than 40 GeV. This may be interpreted as a contribution of resolved photon QCD processes or the onset of BFKL phenomena.