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.
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.
121138073
BESII detector simulation
A Monte Carlo program based on GEANT3 has been developed for BESII detector simulation. The organization of the program is outlined, and the digitization procedure for simulating the response of various sub-detectors is described. Comparisons with data show that the performance of the program is generally satisfactory.
209843256
Search for branons at LEP
Abstract We search, in the context of extra-dimension scenarios, for the possible existence of brane fluctuations, called branons . Events with a single photon or a single Z-boson and missing energy and momentum collected with the L3 detector in e + e − collisions at centre-of-mass energies 2 = 189 – 209  GeV are analysed. No excess over the Standard Model expectations is found and a lower limit at 95% confidence level of 103  GeV is derived for the mass of branons, for a scenario with small brane tensions. Alternatively, under the assumption of a light branon, brane tensions below 180 GeV are excluded.
120497934
Measurement of the cross section for open-beauty production in photon–photon collisions at LEP
Abstract The cross section for open-beauty production in photon–photon collisions is measured using the whole high-energy and high-luminosity data sample collected by the L3 detector at LEP. This corresponds to 627 pb −1 of integrated luminosity for electron–positron centre-of-mass energies from 189 to 209 GeV. Events containing b quarks are identified through their semi-leptonic decay into electrons or muons. The e + e − → e + e − b b ¯ X cross section is measured within our fiducial volume and then extrapolated to the full phase space. These results are found to be in significant excess with respect to Monte Carlo predictions and next-to-leading order QCD calculations.
18308235
Search for new particles in hadronic events with isolated photons
Abstract A search for the neutral Higgs boson in the processes e + e − → Z → H 0 γ → q q γ and e + e − → Z → Z ∗ H 0 → q q γγ has been performed using 2.8 million hadronic Z decays collected with the L3 detector at LEP from 1991 through 1994. No evidence for these processes has been observed. Upper limits at 95% confidence level for the corresponding cross sections have been set and the results have been compared with theoretical predictions beyond the Standard Model.
208868872
Measurement of the cross section of W-boson pair production at LEP
The cross section of W-boson pair-production is measured with the L3 detector at LEP. In a data sample corresponding to a total luminosity of 629.4 pb-1, collected at centre-of-mass energies ranging from 189 to 209 GeV, 9834 four-fermion events with W bosons decaying into hadrons or leptons are selected. The total cross section is measured with a precision of 1.4% and agrees with the Standard Model expectation. Assuming charged-lepton universality, the branching fraction for hadronic W-boson decays is measured to be: Br(W→hadrons)=67.50±0.42(stat.)±0.30(syst.)%, in agreement with the Standard Model. Differential cross sections as a function of the W- production angle are also measured for the semi-leptonic channels qqeν and qqμν. © 2004 Published by Elsevier B.V.