7,340 research outputs found
Combined Relativistic and static analysis for all Delta B=2 operators
We analyse matrix elements of Delta B=2 operators by combining QCD results
with the ones obtained in the static limit of HQET. The matching of all the QCD
operators to HQET is made at NLO order. To do that we have to include the
anomalous dimension matrix up to two loops, both in QCD and HQET, and the one
loop matching for all the Delta B=2 operators. The matrix elements of these
operators are relevant for the prediction of the B-\bar B mixing, B_s meson
width difference and supersymmetric effects in Delta B=2 transitions.Comment: 3 pages, 1 figure. Lattice2001(heavyquark
Non-perturbative Renormalization of the Complete Basis of Four-fermion Operators and B-parameters
We present results on the B-parameters , and , at
, with the tree-level Clover action. The renormalization of the
complete basis of dimension-six four-fermion operators has been performed
non-perturbatively. Our results for and are in reasonable
agreement with those obtained with the (unimproved) Wilson action. This is not
the case for . We also discuss some subtleties arising from a
recently proposed modified definition of the B-parameters.Comment: Talk presented at Lattice '97, Edinburgh (UK), July 1997. LaTeX 3
pages, uses espcrc
K^0-\bar{K}^0 Mixing Beyond the SM from Nf=2 tmQCD
We present preliminary results on the of neutral kaon oscillations in
extensions of the Standard Model. Using Nf=2 maximally twisted sea quarks and
Osterwalder-Seiler valence quarks, we achieve both O(a)-improvement and
continuum-like renormalization pattern for the relevant four-fermion operators.
We perform simulations at three values of the lattice spacing and
extrapolate/interpolate our results to the continuum limit and physical
light/strange quark mass. The calculation of the renormalization constants of
the complete operator basis is performed non- perturbatively in the RI-MOM
scheme.Comment: 7 pages, 2 figures; presented at the XXVIII International Symposium
on Lattice Field Theory Villasimius, Sardinia, Ital
K^0-\bar{K}^0 mixing in the Standard Model from Nf=2+1+1 Twisted Mass Lattice QCD
We present preliminary results at {\beta} = 1.95 (a = 0.077 fm) on the first
unquenched N_f=2+1+1 lattice computation of the B_K parameter which controls
the neutral kaon oscillations in the Standard Model. Using N_f=2+1+1 maximally
twisted sea quarks and Osterwalder-Seiler valence quarks we achieve O(a)
improvement and a continuum-like renormalization pattern for the four-fermion
operator. Our results are extrapolated/interpolated to the physical
light/strange quark mass but not yet to the continuum limit. The computation of
the relevant renormalization constants is performed non perturbatively in the
RI'-MOM scheme using dedicated simulations with N_f=4 degenerate sea quark
flavours produced by the ETM collaboration.
We get B_K^{RGI} (a = 0.077) = 0.747(18), which when compared to our previous
unquenched N_f=2 determination and most of the existing results, suggests a
rather weak B_K^{RGI} dependence on the number of dynamical flavours. We are at
the moment analysing lattice data at two additional {\beta} values which will
allow us to perform an extrapolation to the continuum limit.Comment: 7 pages, 8 figures, Proceedings of Lattice 2011, XXIX International
Symposium on Lattice Field Theory, Squaw Valley, Lake Tahoe, Californi
The Mass of the Convective Zone in FGK Main Sequence Stars and the Effect of Accreted Planetary Material on Apparent Metallicity Determinations
The mass of the outer convective zone in FGK main sequence stars decreases
dramatically with stellar mass. Therefore, any contamination of a star's
atmosphere by accreted planetary material should affect hotter stars much more
than cool stars. If recent suggestions that high metal abundances in stars with
planets are caused by planetesimal accretion are correct, then metallicity
enhancements in earlier-type stars with planets should be very pronounced. No
such trend is seen, however.Comment: Submitted ApJ Letters March 26th; accepted April 30th. 12 pages, 2
figure
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
Recent results from lattice calculations
Recent results from lattice QCD calculations relevant to particle physics
phenomenology are reviewed. They include the calculations of strong coupling
constant, quark masses, kaon matrix elements, and D and B meson matrix
elements. Special emphasis is on the recent progress in the simulations
including dynamical quarks.Comment: 13 pages, 8 figures, plenary talk at the 32nd International
Conference on High-Energy Physics (ICHEP 2004), August 16-22, 2004, Beijing,
Chin
- …