125977653
Lattice study on exotic vector charmonium relevant to X(4260)
In the quenched approximation and with very high statistics, a heavy vector charmonium state, with a mass of 4.33(2)GeV, is disentangled from the conventional charmonium states by using spatially extended hybrid-like interpolating field operators. Through a simultaneous fit of correlation functions built from different operators, the leptonic decay constant this state is estimated to be 31(15)MeV, which gives a much smaller leptonic decay width of 23(20)eV in comparison with that of conventional vector charmonia. The connection of this state with X(4260) is also discussed.
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.
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
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.
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.
209835666
Measurement of the spectroscopy of orbitally excited B mesons at LEP
Abstract We measure the masses, decay widths and relative production rate of orbitally excited B mesons using 1.25 million hadronic Z decays recorded by the L3 detector. B-meson candidates are inclusively reconstructed and combined with charged pions produced at the primary event vertex. An excess of events above the expected background in the B π mass spectrum in the region 5.6–5.8 GeV is interpreted as resulting from the decay B ∗∗ u , d → B (∗) π , where B ∗∗ u , d denotes a mixture of l =1 B-meson states containing a u or a d quark. A fit to the mass spectrum yields the masses and decay widths of the B 1 ∗ and B 2 ∗ spin states, as well as the branching fraction for the combination of l =1 states. In addition, evidence is presented for the existence of an excited B-meson state or mixture of states in the region 5.9–6.0 GeV.
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.
118634976
Decoding the Origin of Dark Matter
We discuss the interplay between LHC signatures and the mechanism by which dark matter is generated in the early universe in supersymmetric theories. The LHC signatures of two of the major mechanisms for such generation of dark matter which are known to be the Stau Coannihilation (Stau‐Co) region and annihilation on the Hyperbolic Branch (HB) are exhibited in detail. By analyzing the various LHC signatures, including multi leptons, hadronic jets, b‐tagging, and missing transverse momentum, one can discriminate between the Stau‐Co region and the HB region for the mSUGRA model. Interestingly, there are some regions of the parameter space which are beyond the current and near future reach of the dark matter direct detection experiments but will be accessible at the LHC, and vise versa.
7825870
Study of inclusive strange-baryon production and search for pentaquarks in two-photon collisions at LEP
Measurements of inclusive production of the Λ, Ξ- and Ξ*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections for Λ and Ξ- are measured as a function of the baryon transverse momentum, pt, and pseudo-rapidity, η. The mean number of Λ, Ξ- and Ξ*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4 GeV<pt<2.5 GeV, |η|<1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive production of the pentaquark θ+(1540) in two-photon collisions through the decay θ+→pK0S is also presented. No evidence for production of this state is found.
15082169
Search for Neutral Charmless B-Decays at Lep
Abstract A search for rare charmless decays of B d 0 and B s 0 mesons has been performed in the exclusive channels B d(s) 0 → ηη , B d(s) 0 → ηπ 0 and B d(s) 0 → π 0 π 0 . The data sample consisted of three million hadronic Z decays collected by the L3 experiment at LEP from 1991 through 1994. No candidate event has been observed and the following upper limits at 90% confidence level on the branching ratios have been set: Br ( B () d → ηη ) x 10 −4 , Br ( B () s → ηη ) x 10 −3 , Br ( B () d → ηφ () ) x 10 −4 , Br ( B () s → ηphi ; () ) x 10 −3 , Br ( B () d → phi ; () phi ; () ) x 10 −5 , Br ( B () s → phi ; () phi ; () ) x 10 −4 . These are the first experimental limits on B d 0 →ηη and on the B s 0 neutral charmless modes.