203 research outputs found
Lattice renormalisation of O(a) improved heavy-light operators: an addendum
The analytical expressions and the numerical values of the renormalisation
constants of dimension 3 static-light currents are given at one-loop order of
perturbation theory in the framework of Heavy Quark Effective Theory and with
an improved gauge action: the static quark is described by the HYP-smeared
action and the light quark is of Wilson kind. This completes a work started few
years ago and is actually an intermediate step in the measurement of the decay
constants and by the European Twisted Mass Collaboration
[arXiv:1107.1441[hep-lat]].Comment: 5 pages, no figure
Fermion Masses and Mixings in a Minimal SO(10)X A_4 SUSY GUT
A SUSY SO(10) GUT model is constructed for fermion masses and
mixing by introducing a minimal set of low dimensional Higgs representations
needed to break the guage symmetry down to . The
hierarchy of fermion masses can be understood in the framework of
symmetry. From the -invariant superpotential, the "double lopsided" mass
matrices for the charged leptons and the down quarks are obtained. It is shown
that this structure leads to bi-large neutrino mixings simultaneously with
small CKM mixing angles. An excellent fit to the masses and mixings of the
quarks and leptons as well as to CP violation parameter is obtained. Moreover,
the model predicts the neutrino mixing angle .Comment: 19 pages, 4 figure
The continuum limit of the static-light meson spectrum
We investigate the continuum limit of the low lying static-light meson
spectrum using Wilson twisted mass lattice QCD with N_f = 2 dynamical quark
flavours. We consider three values of the lattice spacing a ~ 0.051 fm, 0.064
fm, 0.080 fm and various values of the pion mass in the range 280 MeV < m_PS <
640 MeV. We present results in the continuum limit for light cloud angular
momentum j = 1/2, 3/2, 5/2 and for parity P = +, -. We extrapolate our results
to physical quark masses, make predictions regarding the spectrum of B and B_s
mesons and compare with available experimental results.Comment: 18 pages, 3 figure
Lattice renormalisation of O(a) improved heavy-light operators
The analytical expressions and the numerical values of the renormalisation
constants of improved static-light currents are given at one-loop
order of perturbation theory in the framework of Heavy Quark Effective Theory:
the static quark is described by the HYP action and the light quark is
described either with the Clover or the Neuberger action. These factors are
relevant to extract from a lattice computation the decay constants ,
and the set of bag parameters associated with
mixing phenomenology in the Standard Model and beyond.Comment: 16 pages, 2 figures, 4 tables; few comments and references added;
version to be published in Phys Rev
Semileptonic decays in Lattice QCD : a feasibility study and first results
We compute the decays and with finite
masses for the and quarks. We first discuss the spectral properties of
both the meson as a function of its momentum and of the and
at rest. We compute the theoretical formulae leading to the decay
amplitudes from the three-point and two-point correlators. We then compute the
amplitudes at zero recoil of which turns out not to be
vanishing contrary to what happens in the heavy quark limit. This opens a
possibility to get a better agreement with experiment. To improve the continuum
limit we have added a set of data with smaller lattice spacing. The vanishes at zero recoil and we show a convincing signal but only
slightly more than 1 sigma from 0. In order to reach quantitatively significant
results, we plan to fully exploit smaller lattice spacings as well as another
lattice regularization.Comment: 31 pages with 15 figures ; sections 5 and 6 revised and update
Low-lying Baryons with spin 1/2 in Two-flavor Lattice QCD
Low-lying baryons with spin 1/2 are analyzed in full (unquenched)
lattice QCD. We construct cross correlators from flavor SU(3)
"octet" and "singlet" baryon operators, and diagonalize them so as to extract
information of two low-lying states for each parity. The two-flavor CP-PACS
gauge configurations are used, which are generated in the renormalization-group
improved gauge action and the -improved quark action. Three
different 's, , 1.95 and 2.10, are employed, whose
corresponding lattice spacings are , 0.1555 and 0.1076 fm. For each
cutoff, we use four hopping parameters, (),
which correspond to the pion masses ranging about from 500 MeV to 1.1 GeV.
Results indicate that there are two negative-parity states nearly
degenerate at around 1.6 GeV, while no state as low as is
observed. By decomposing the flavor components of each state, we find that the
lowest (1st-excited) negative-parity state is dominated by flavor-singlet
(flavor-octet) component. We also discuss meson-baryon components of each
state, which has drawn considerable attention in the context of multi-quark
pictures of .Comment: 11 pages, 11 figures, 3 tables; version to appear in Phys. Rev.
B_s-\bar{B_s} mixing with a chiral light quark action
We study the mixing amplitude in Standard Model by
computing the relevant hadronic matrix element in the static limit of lattice
HQET with the Neuberger light quark action. In the quenched approximation, and
after matching to the scheme in QCD, we obtain .Comment: 6 pages, 3 figures, talk presented at Lattice 2005 (Heavy quark
physics
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