1,959 research outputs found
The e+ e- -> P1 P2 gamma processes close to the Phi peak: toward a model-independent analysis
We discuss the general decomposition and possible general parameterizations
of the processes , where , , or , for .
Particular attention is devoted to the amplitude where the two pseudoscalar
mesons are in a state, where we propose a general
parameterization which should help to shed light on the nature of light scalar
mesons.Comment: 12 pages, Late
On lattice chiral gauge theories
The Smit-Swift-Aoki formulation of a lattice chiral gauge theory is presented. In this formulation the Wilson and other non invariant terms in the action are made gauge invariant by the coupling with a nonlinear auxilary scalar field, omega. It is shown that omega decouples from the physical states only if appropriate parameters are tuned so as to satisfy a set of BRST identities. In addition, explicit ghost fields are necessary to ensure decoupling. These theories can give rise to the correct continuum limit. Similar considerations apply to schemes with mirror fermions. Simpler cases with a global chiral symmetry are discussed and it is shown that the theory becomes free at decoupling. Recent numerical simulations agree with those considerations
B Physics on the Lattice: , , , , mixing, \fb and all that
We present a short review of our most recent high statistics lattice
determinations in the HQET of the following important parameters in B physics:
the B--meson binding energy, and the kinetic energy of the
b quark in the B meson, , which due to the presence of power
divergences require a non--perturbative renormalization to be defined; the
running mass of the b quark,
; the -- mass splitting, whose
value in the HQET is determined by the matrix element of the chromo--magnetic
operator between B meson states, ; the B parameter of the
-- mixing, , and the decay constant of the B meson,
. All these quantities have been computed using a sample of gauge
field configurations on a lattice at . For
and , we obtain our
estimates by combining results from three independent lattice simulations at
, and on the same volume.Comment: 3 latex pages, uses espcrc2.sty (included). Talk presented at
LATTICE96(heavy quarks
The post-Higgs MSSM scenario: Habemus MSSM?
We analyze the Minimal Supersymmetric extension of the Standard Model that we
have after the discovery of the Higgs boson at the LHC, the hMSSM (habemus
MSSM?), i.e. a model in which the lighter boson has a mass of approximately
125 GeV which, together with the non-observation of superparticles at the LHC,
indicates that the SUSY-breaking scale is rather high, TeV. We
first demonstrate that the value GeV fixes the dominant
radiative corrections that enter the MSSM Higgs boson masses, leading to a
Higgs sector that can be described, to a good approximation, by only two free
parameters. In a second step, we consider the direct supersymmetric radiative
corrections and show that, to a good approximation, the phenomenology of the
lighter Higgs state can be described by its mass and three couplings: those to
massive gauge bosons and to top and bottom quarks. We perform a fit of these
couplings using the latest LHC data on the production and decay rates of the
light boson and combine it with the limits from the negative search of the
heavier and states, taking into account the current
uncertainties.Comment: 1+12 pages, pdflatex, 7 figure
Plasma antioxidants from chocolate
There is some speculation that dietary flavonoids from chocolate, in particular (-)epicatechin, may promote cardiovascular health as a result of direct antioxidant effects or through antithrombotic mechanisms. Here we show that consumption of plain, dark chocolate results in an increase in both the total antioxidant capacity and the (-)epicatechin content of blood plasma, but that these effects are markedly reduced when the chocolate is consumed with milk or if milk is incorporated as milk chocolate. Our findings indicate that milk may interfere with the absorption of antioxidants from chocolate in vivo and may therefore negate the potential health benefits that can be derived from eating moderate amounts of dark chocolate
Two-body non-leptonic decays on the lattice
We show that, under reasonable hypotheses, it is possible to study two-body
non-leptonic weak decays in numerical simulations of lattice QCD. By assuming
that final-state interactions are dominated by the nearby resonances and that
the couplings of the resonances to the final particles are smooth functions of
the external momenta, it is possible indeed to overcome the difficulties
imposed by the Maiani-Testa no-go theorem and to extract the weak decay
amplitudes, including their phases. Under the same assumptions, results can be
obtained also for time-like form factors and quasi-elastic processes.Comment: 15 pages, 1 Postscript figur
Commissioning of the ATLAS Muon Trigger System with early data
An overview of the early results on commissioning and performance of the ATLAS Muon Trigger System is shown. The ATLAS Muon Trigger has been designed to cope with the high interaction rate expected at the LHC. The presented
performance studies have been obtained using both cosmic-ray and 900GeV collision data
Results from a Non-Perturbative Renormalization of Lattice Operators
We propose a general renormalization method, which avoids completely the use
of lattice perturbation theory. We present the results from its numerical
applications to two-fermion operators on a lattice, at
.Comment: 3 pages postscript file. Contribution to Lattice '9
Chiral behaviour of the lattice -parameter with the Wilson and Clover Actions at
We present results for the kaon -parameter from a sample of
configurations using the Wilson action and configurations using the
SW-Clover action, on a lattice at . We compare
results obtained by renormalizing the relevant operator with different
``boosted" values of the strong coupling constant . In the case of
the SW-Clover action, we also use the operator renormalized non-perturbatively.
In the Wilson case, we observe a strong dependence of on the prescription
adopted for , contrary to the results of the Clover case which are
almost unaffected by the choice of the coupling. We also find that the matrix
element of the operator renormalized non-perturbatively has a better chiral
behaviour. This gives us our best estimate of the renormalization group
invariant -parameter, .Comment: LaTeX, 17 pages, 3 postscript figures uuencode
Model independent determination of the shape function for inclusive B decays and of the structure functions in DIS
We present a method to compute, by numerical simulations of lattice QCD, the
inclusive semileptonic differential decay rates of heavy hadrons and the
structure functions which occur in deep inelastic scattering. The method is
based on first principles and does not require any model assumption. It allows
the prediction of the differential rate in B semileptonic decays for values of
the recoiling hadronic mass W ~ sqrt(M_B Lambda_QCD), which is in the relevant
region to extract |V_ub| from the end-point of the lepton spectrum in inclusive
decays.Comment: 16 pages, LaTeX fil
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