18642908
Moments of meson distribution functions with dynamical twisted mass fermions
We present our preliminary results on the lowest moment hxi 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.
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.
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.
118634793
Lattice study on $\eta_{c2}$ and X(3872)
Properties of 2(-+) charmonium eta(c2) are investigated in quenched lattice QCD. The mass of eta(c2) is determined to be 3.80(3) GeV, which is close to the mass of D-wave charmonium psi(3770) and in agreement with quark model predictions. The transition width of eta(c2) -> gamma J/psi is also obtained with a value of Gamma = 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). DOI: 10.1103/PhysRevD.87.014501
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.
121811137
Standard model Higgs boson with the L3 experiment at LEP
Abstract Final results of the search for the standard model Higgs boson are presented for the data collected by the L3 detector at LEP at centre-of-mass energies up to about 209 GeV. These data are compared with the expectations of standard model processes for Higgs boson masses up to 120 GeV. A lower limit on the mass of the standard model Higgs boson of 112.0 GeV is set at the 95% confidence level. The most significant high mass candidate is a Hν ν event. It has a reconstructed Higgs mass of 115 GeV and it was recorded at s =206.4  GeV .
117349439
Probing supergravity unified theories at the Large Hadron Collider
The discovery of supersymmetry is one of the major goals of the current experiments at the Tevatron and in proposed experiments at the Large Hadron Collider (LHC). However when sparticles are produced the signatures of their production will to a significant degree depend on their hierarchical mass patterns. Here we investigate hierarchical mass patterns for the four lightest sparticles within one of the leading candidate theories - the SUGRA model. Specifically we analyze the hierarchies for the four lightest sparticles for the mSUGRA as well as for a general class of supergravity unified models including nonuniversalities in the soft breaking sector. It is shown that out of nearly $10^4$ possibilities of sparticle mass hierarchies, only a small number survives the rigorous constraints of radiative electroweak symmetry breaking, relic density and other experimental constraints. The signature space of these mass patterns at the LHC is investigated using a large set of final states including multi-leptonic states, hadronically decaying $\tau$s, tagged $b$ jets and other hadronic jets. In all, we analyze more than 40 such lepton plus jet and missing energy signatures along with several kinematical signatures such as missing transverse momentum, effective mass, and invariant mass distributions of final state observables. It is shown that a composite analysis can produce significant discrimination among sparticle mass patterns allowing for a possible identification of the source of soft breaking. While the analysis given is for supergravity models, the techniques used in the analysis are applicable to wide class of models including string and brane models.
120858051
Parafermion Fields Constructed by Current Algebra
In this letter, the parafermion fields constructed by current algebra are considered. It is proved that there must be a parafermion field with respect to each form of current algebra. We also obtain the corresponding representation and unitary relation of the parafermion field from any current algebra.
117839544
Search for a Higgs boson decaying into two photons at LEP
A Higgs particle produced in association with a Z boson and decaying into two photons is searched for in the data collected by the L3 experiment at LEP. All possible decay modes of the Z boson are investigated. No signal is observed in 447.5 pb^-1 of data recorded at centre-of-mass energies up to 209 GeV. Limits on the branching fraction of the Higgs boson decay into two photons as a function of the Higgs mass are derived. A lower limit on the mass of a fermiophobic Higgs boson is set at 105.4 GeV at 95% confidence level.
197473721
Measurements of J/psi decays into omega K anti-K pi and phi K anti-K pi and eta K0(S) K+- pi-+