6,422 research outputs found
Lattice quark masses: a non-perturbative measurement
We discuss the renormalization of different definitions of quark masses in
the Wilson and the tree-level improved SW-Clover fermionic action. For the
improved case we give the correct relationship between the quark mass and the
hopping parameter. Using perturbative and non-perturbative renormalization
constants, we extract quark masses in the \MSbar scheme from Lattice QCD in
the quenched approximation at , and for both
actions. We find: \bar{m}^{\MSbar}(2 GeV)=5.7 \pm 0.1 \pm 0.8 MeV,
m_s^{\MSbar}(2GeV)= 130 \pm 2 \pm 18 MeV and m_c^{\MSbar}(2 GeV) = 1662\pm
30\pm 230 MeV.Comment: 21 pages, 4 figures, typos corrected, no result change
Quark masses and the chiral condensate with a non-perturbative renormalization procedure
We determine the quark masses and the chiral condensate in the MSbar scheme
at NNLO from Lattice QCD in the quenched approximation at beta=6.0, beta=6.2
and beta=6.4 using both the Wilson and the tree-level improved SW-Clover
fermion action. We extract these quantities using the Vector and the Axial Ward
Identities and non-perturbative values of the renormalization constants. We
compare the results obtained with the two methods and we study the O(a)
dependence of the quark masses for both actions.Comment: LATTICE98(spectrum), 3 pages, 1 figure, Edinburgh 98/1
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
Teaching Nanoscience and thinking nano at the macroscale: Nanocapsules of wisdom
One of the challenges for Nanotechnology is education, which is considered as a bottleneck for Nanotechnology development and implementation. This work contributes to nanoscale education by designing a wide variety of cutting-edge documentaries which assist high-educational level students in learning the underlying concepts of Nanoscience, the last advances and furure prospects. In addition, documentaries seek to bring and disseminate the scientific activity of Nanotechnology to society. In this sense, the secondary goals of the proposed approach nanotech activity are: 1) Transfer of knowledge generated in the nanotechnology field and 2) The promotion of scientific culture and innovation between the public objectives. Based on the results observed in students's assessment and You Tube metrics, it was concluded that the developed of nanoscale based documentaries enabled a fast and efficent comprehension of complex concepts related to Nanoscience and Nanotechnology. In addition, the opinion of You Tube audience is highly promising and shows that You Tube and documentaries are an excellent channel to disseminate Nanoscience to society
Next-to-leading order renormalization of the operators in the static theory
The renormalization, at the next-to-leading order in , of the
operators at the lowest order in the heavy quark expansion, namely
in the static theory, is computed taking into account previously missed
contributions. These operators are relevant for the calculation of the
-- mixing on the lattice.Comment: Latex, 8 pages, 1 figur
Kaon oscillations in the Standard Model and Beyond using Nf=2 dynamical quarks
We compute non-perturbatively the B-parameters of the complete basis of
four-fermion operators needed to study the Kaon oscillations in the SM and in
its supersymmetric extension. We perform numerical simulations with two
dynamical maximally twisted sea quarks at three values of the lattice spacing
on configurations generated by the ETMC. Unwanted operator mixings and O(a)
discretization effects are removed by discretizing the valence quarks with a
suitable Osterwalder-Seiler variant of the Twisted Mass action. Operators are
renormalized non-perturbatively in the RI/MOM scheme. Our preliminary result
for BK(RGI) is 0.73(3)(3).Comment: 7 pages, 3 figures, 1 table, proceedings of the XXVII Int'l Symposyum
on Lattice Field Theory (LAT2009), July 26-31 2009, Peking University,
Beijing (China
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
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
Delta M_K and epsilon_K in SUSY at the Next-to-Leading order
We perform a Next-to-Leading order analysis of Delta S=2 processes beyond the
Standard Model. Combining the recently computed NLO anomalous dimensions and
the B parameters of the most general Delta S=2 effective Hamiltonian, we give
an analytic formula for Delta M_K and epsilon_K in terms of the Wilson
coefficients at the high energy scale. This expression can be used for any
extension of the Standard Model with new heavy particles. Using this result, we
consider gluino-mediated contributions to Delta S=2 transitions in general SUSY
models and provide an improved analysis of the constraints on off-diagonal mass
terms between the first two generations of down-type squarks. Finally, we
improve the constraints on R-violating couplings from Delta M_K and epsilon_K.Comment: 20 pages, 1 figure, uses JHEP.cls; the magic numbers in eq. (2.7),
previously given in the basis (13) of hep-ph/9711402, are now given in the
basis (2.3) of this work. All numerical results are unchange
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