28,190 research outputs found
Scavi e ricerche nell'antica Plestia
in particolare pp. 213-231, 252-27
\Delta S=2 and \Delta C=2 bag parameters in the SM and beyond from Nf=2+1+1 twisted-mass LQCD
We present unquenched lattice QCD results for the matrix elements of
four-fermion operators relevant to the description of the neutral K and D
mixing in the Standard Model and its extensions. We have employed simulations
with Nf = 2 + 1 + 1 dynamical sea quarks at three values of the lattice
spacings in the interval 0.06 - 0.09 fm and pseudoscalar meson masses in the
range 210 - 450 MeV. Our results are extrapolated to the continuum limit and to
the physical pion mass. Renormalization constants have been determined
non-perturbatively in the RI-MOM scheme. In particular, for the Kaon
bag-parameter, which is relevant for the \overline{K}^0-K^0 mixing in the
Standard Model, we obtain B_K^{RGI} = 0.717(24).Comment: Added comments to error budget discussion; fig.19 corrected. Version
to appear in PR
Strong coupling expansion of chiral models
A general precedure is outlined for an algorithmic implementation of the
strong coupling expansion of lattice chiral models on arbitrary lattices. A
symbolic character expansion in terms of connected values of group integrals on
skeleton diagrams may be obtained by a fully computerized approach.Comment: 2 pages, PostScript file, contribution to conference LATTICE '9
Singular limits of a coupled elasto-plastic damage system as viscosity and hardening vanish
The paper studies the asymptotic analysis of a model coupling elastoplasticity and damage depending on three parameters—governing viscosity, plastic hardening, and convergence rate of plastic strain and displacement to equilibrium—as they vanish in different orders. The notion of limit evolution obtained is proven to coincide in any case with a notion intro- duced by Crismale and Rossi (SIAM J Math Anal 53(3):3420–3492, 2021), moreover, such solutions are closely related to those obtained in the vanishing-viscosity limit by Crismale and Lazzaroni (Calc Var Part Differ Equ 55(1):17, 2016), for the analogous model where only the viscosity parameter was present
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
Electron beam transfer line design for plasma driven Free Electron Lasers
Plasma driven particle accelerators represent the future of compact
accelerating machines and Free Electron Lasers are going to benefit from these
new technologies. One of the main issue of this new approach to FEL machines is
the design of the transfer line needed to match of the electron-beam with the
magnetic undulators. Despite the reduction of the chromaticity of plasma beams
is one of the main goals, the target of this line is to be effective even in
cases of beams with a considerable value of chromaticity. The method here
explained is based on the code GIOTTO [1] that works using a homemade genetic
algorithm and that is capable of finding optimal matching line layouts directly
using a full 3D tracking code.Comment: 9 Pages, 4 Figures. A related poster was presented at EAAC 201
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
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