413 research outputs found
Higher dimensional 3-adic CM construction
We find equations for the higher dimensional analogue of the modular curve
X_0(3) using Mumford's algebraic formalism of algebraic theta functions. As a
consequence, we derive a method for the construction of genus 2 hyperelliptic
curves over small degree number fields whose Jacobian has complex
multiplication and good ordinary reduction at the prime 3. We prove the
existence of a quasi-quadratic time algorithm for computing a canonical lift in
characteristic 3 based on these equations, with a detailed description of our
method in genus 1 and 2.Comment: 23 pages; major revie
Quark Masses and Renormalization Constants from Quark Propagator and 3-point Functions
We have computed the light and strange quark masses and the renormalization
constants of the quark bilinear operators, by studying the large-p^2 behaviour
of the lattice quark propagator and 3-point functions. The calculation is
non-perturbatively improved, at O(a), in the chiral limit. The method used to
compute the quark masses has never been applied so far, and it does not require
an explicit determination of the quark mass renormalization constant.Comment: LATTICE99 (Improvement and Renormalization) - 3 pages, 2 figure
First Lattice QCD Study of the Sigma -> n Axial and Vector Form Factors with SU(3) Breaking Corrections
We present the first quenched lattice QCD study of the form factors relevant
for the hyperon semileptonic decay Sigma -> n l nu. The momentum dependence of
both axial and vector form factors is investigated and the values of all the
form factors at zero-momentum transfer are presented. Following the same
strategy already applied to the decay K0 -> pi- l nu, the SU(3)-breaking
corrections to the vector form factor at zero-momentum transfer, f1(0), are
determined with great statistical accuracy in the regime of the simulated quark
masses, which correspond to pion masses above ~ 0.7 GeV. Besides f1(0) also the
axial to vector ratio g1(0) / f1(0), which is relevant for the extraction of
the CKM matrix element Vus, is determined with significant accuracy. Due to the
heavy masses involved, a polynomial extrapolation, which does not include the
effects of meson loops, is performed down to the physical quark masses,
obtaining f1(0) = -0.948 +/- 0.029 and g1(0) / f1(0) = -0.287 +/- 0.052, where
the uncertainties do not include the quenching effect. Adding a recent
next-to-leading order determination of chiral loops, calculated within the
Heavy Baryon Chiral Perturbation Theory in the approximation of neglecting the
decuplet contribution, we obtain f1(0) = -0.988 +/- 0.029(lattice) +/-
0.040(HBChPT). Our findings indicate that SU(3)-breaking corrections are
moderate on both f1(0) and g1(0). They also favor the experimental scenario in
which the weak electricity form factor, g2(0), is large and positive, and
correspondingly the value of |g1(0) / f1(0)| is reduced with respect to the one
obtained with the conventional assumption g2(q**2) = 0 based on exact SU(3)
symmetry.Comment: final version to appear in Nucl. Phys.
Electromagnetic and strong isospin-breaking corrections to the muon from Lattice QCD+QED
We present a lattice calculation of the leading-order electromagnetic and
strong isospin-breaking corrections to the hadronic vacuum polarization (HVP)
contribution to the anomalous magnetic moment of the muon. We employ the gauge
configurations generated by the European Twisted Mass Collaboration (ETMC) with
dynamical quarks at three values of the lattice spacing ( fm) with pion masses between and
MeV. The results are obtained adopting the RM123 approach in the
quenched-QED approximation, which neglects the charges of the sea quarks. Quark
disconnected diagrams are not included. After the extrapolations to the
physical pion mass and to the continuum and infinite-volume limits the
contributions of the light, strange and charm quarks are respectively equal to
, and . At leading order in and we obtain , which is currently the most accurate determination of the
isospin-breaking corrections to .Comment: 23 pages, 7 figures, 5 tables. Version to appear in PRD. A bug in the
update of the strange and charm contributions is removed and an extended
discussion on the identification of the ground-state is included. arXiv admin
note: text overlap with arXiv:1808.00887, arXiv:1707.0301
A Theoretical Prediction of the Bs-Meson Lifetime Difference
We present the results of a quenched lattice calculation of the operator
matrix elements relevant for predicting the Bs width difference. Our main
result is (\Delta\Gamma_Bs/\Gamma_Bs)= (4.7 +/- 1.5 +/- 1.6) 10^(-2), obtained
from the ratio of matrix elements, R(m_b)=/<\bar
B_s^0|Q_L|B_s^0>=-0.93(3)^(+0.00)_(-0.01). R(m_b) was evaluated from the two
relevant B-parameters, B_S^{MSbar}(m_b)=0.86(2)^(+0.02)_(-0.03) and
B_Bs^{MSbar}(m_b) = 0.91(3)^(+0.00)_(-0.06), which we computed in our
simulation.Comment: 21 pages, 7 PostScript figure
Continuum Determination of Light Quark Masses from Quenched Lattice QCD
We compute the strange and the average up/down quark masses in the quenched
approximation of lattice QCD, by using the O(a)-improved Wilson action and
operators and by implementing the non-perturbative renormalization. Our
computation is performed at four values of the lattice spacing, from which we
could extrapolate to the continuum limit. Our final result for the strange
quark mass (in the MSbar scheme) is ms(2 GeV) = (106 +/- 2 +/- 8) MeV. For the
average up/down quark mass we have ml(2 GeV) = (4.4 +/- 0.1 +/- 0.4) MeV. The
ratio ms/ml = (24.3 +/- 0.2 +/- 0.6).Comment: 14 pages, 3 PostScript figure
Perturbative and non-perturbative renormalization results of the Chromomagnetic Operator on the Lattice
The Chromomagnetic operator (CMO) mixes with a large number of operators
under renormalization. We identify which operators can mix with the CMO, at the
quantum level. Even in dimensional regularization (DR), which has the simplest
mixing pattern, the CMO mixes with a total of 9 other operators, forming a
basis of dimension-five, Lorentz scalar operators with the same flavor content
as the CMO. Among them, there are also gauge noninvariant operators; these are
BRST invariant and vanish by the equations of motion, as required by
renormalization theory. On the other hand using a lattice regularization
further operators with will mix; choosing the lattice action in a
manner as to preserve certain discrete symmetries, a minimul set of 3
additional operators (all with ) will appear. In order to compute all
relevant mixing coefficients, we calculate the quark-antiquark (2-pt) and the
quark-antiquark-gluon (3-pt) Green's functions of the CMO at nonzero quark
masses. These calculations were performed in the continuum (dimensional
regularization) and on the lattice using the maximally twisted mass fermion
action and the Symanzik improved gluon action. In parallel, non-perturbative
measurements of the matrix element are being performed in simulations
with 4 dynamical () twisted mass fermions and the Iwasaki improved
gluon action.Comment: 7 pages, 1 figure, 3 tables, LATTICE2014 proceeding
Strange and charm HVP contributions to the muon ( including QED corrections with twisted-mass fermions
We present a lattice calculation of the Hadronic Vacuum Polarization (HVP)
contribution of the strange and charm quarks to the anomalous magnetic moment
of the muon including leading-order electromagnetic corrections. We employ the
gauge configurations generated by the European Twisted Mass Collaboration
(ETMC) with dynamical quarks at three values of the lattice
spacing ( fm) with pion masses in the range
MeV. The strange and charm quark masses are tuned at
their physical values. Neglecting disconnected diagrams and after the
extrapolations to the physical pion mass and to the continuum limit we obtain:
,
and
,
for the strange
and charm contributions, respectively.Comment: 34 pages, 10 figures, 5 tables; version to appear in JHE
Leading isospin-breaking corrections to pion, kaon and charmed-meson masses with Twisted-Mass fermions
We present a lattice computation of the isospin-breaking corrections to
pseudoscalar meson masses using the gauge configurations produced by the
European Twisted Mass collaboration with dynamical quarks at
three values of the lattice spacing ( and fm)
with pion masses in the range MeV. The strange and
charm quark masses are tuned at their physical values. We adopt the RM123
method based on the combined expansion of the path integral in powers of the
- and -quark mass difference () and of the
electromagnetic coupling . Within the quenched QED approximation,
which neglects the effects of the sea-quark charges, and after the
extrapolations to the physical pion mass and to the continuum and infinite
volume limits, we provide results for the pion, kaon and (for the first time)
charmed-meson mass splittings, for the prescription-dependent parameters
, \epsilon_\gamma(\overline{MS}, 2~\mbox{GeV}),
\epsilon_{K^0}(\overline{MS}, 2~\mbox{GeV}), related to the violations of the
Dashen's theorem, and for the light quark mass difference (\widehat{m}_d -
\widehat{m}_u)(\overline{MS}, 2~\mbox{GeV}).Comment: 47 pages, 20 figures, 4 tables; comments on QED and QCD splitting
prescriptions added; version to appear in PR
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