119452157
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.
118450238
Oscillatory behavior of the domain wall fermions revisited
In the generic domain wall fermion formulation of chiral fermions on the lattice, the zero modes of the four-dimensional Wilson fermion operator with the negative mass parameter -M-5 introduce unphysical massive modes propagating in the four-dimensional spacetime. In the free fermion case, the pole mass of this kind of unphysical modes is given by (E) over bar = ln(1-M-5), which acquires an imaginary part, i pi, when M-5 > 1 and results in an oscillatory behavior of the domain wall fermion propagator in time. The existence of the unphysical modes in the presence of gauge fields is investigated in the mean field approximation, and their physical consequences are discussed. In addition, we also give a semiquantitative criterion for tuning M-5 in the realistic numerical study.
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
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.
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.
55815228
Muon Collider Higgs Factory for Snowmass 2013
Author(s): Alexahin, Y; Ankenbrandt, CM; Cline, DB; Conway, A; Cummings, MA; Benedetto, VD; Eichten, E; Gatto, C; Grinstein, B; Gunion, J; Han, T; Hanson, G; Hill, CT; Ignatov, F; Johnson, RP; Lebedev, V; Lipton, R; Liu, Z; Markiewicz, T; Mazzacane, A; Mokhov, N; Nagaitsev, S; Neuffer, D; Palmer, M; Purohit, MV; Raja, R; Striganov, S; Summers, D; Terentiev, N; Wenzel, H | Abstract: We propose the construction of, and describe in detail, a compact Muon Collider s-channel Higgs Factory.
125773108
A Measurement of J / psi decay widths
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.
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.
122052372
Angular multiplicity fluctuations in hadronic Z decays and comparison to QCD models and analytical calculations
Abstract Local multiplicity fluctuations in angular phase space intervals are studied using factorial moments measured in hadronic events at s ≃91.2 GeV , which were collected by the L3 detector at LEP. Parton shower Monte Carlo programs agree well with the data. On the other hand, first-order QCD calculations in the Double Leading Log Approximation and the Modified Leading Log Approximation are found to deviate significantly from the data.