307 research outputs found
A new simulation algorithm for lattice QCD with dynamical quarks
A previously introduced multi-boson technique for the simulation of QCD with
dynamical quarks is described and some results of first test runs on a
lattice with Wilson quarks and gauge group SU(2) are reported.Comment: 7 pages, postscript file (166 KB
B-physics with Wilson fermions
We report the final results of the ALPHA collaboration for some B-physics
observables: , and . We employ CLS configurations with 2
flavors of improved Wilson fermions in the sea and pion masses ranging
down to 190 MeV. The b-quark is treated in HQET to order . The
renormalization, the matching and the improvement were performed
non-perturbatively, and three lattice spacings reaching fm are used
in the continuum extrapolation
Decay constants of B-mesons from non-perturbative HQET with two light dynamical quarks
We present a computation of B-meson decay constants from lattice QCD
simulations within the framework of Heavy Quark Effective Theory for the
b-quark. The next-to-leading order corrections in the HQET expansion are
included non-perturbatively. Based on Nf=2 gauge field ensembles, covering
three lattice spacings a (0.08-0.05)fm and pion masses down to 190MeV, a
variational method for extracting hadronic matrix elements is used to keep
systematic errors under control. In addition we perform a careful
autocorrelation analysis in the extrapolation to the continuum and to the
physical pion mass limits. Our final results read fB=186(13)MeV, fBs=224(14)MeV
and fBs/fB=1.203(65). A comparison with other results in the literature does
not reveal a dependence on the number of dynamical quarks, and effects from
truncating HQET appear to be negligible.Comment: 16 pages including figures and table
The b-quark mass from non-perturbative Heavy Quark Effective Theory at
We report our final estimate of the b-quark mass from lattice QCD
simulations using Heavy Quark Effective Theory non-perturbatively matched to
QCD at . Treating systematic and statistical errors in a conservative
manner, we obtain GeV after an extrapolation to the physical point.Comment: 15 pages including figures and tables; as published in Phys.Lett.B /
typo in table 4 corrected / footnote 1 expande
Preparing for N(f) = 2 simulations at small lattice spacings
We discuss some large effects of dynamical fermions. One is a cutoff effect, others concern the contribution of multi-pion states to correlation functions and are expected to survive the continuum limit. We then turn to the preparation for simulations at small lattice spacings which we are planning down to around a=0.04fm in order to understand the size of O(a^2)-effects of the standard O(a)-improved theory. The dependence of the lattice spacing on the bare coupling is determined through the Schr'odinger functional renormalized coupling
CP-Violating Asymmetries in Charmless Non-Leptonic Decays in the Factorization Approach
We present estimates of the direct (in decay amplitudes) and indirect
(mixing- induced) CP-violating asymmetries in the non-leptonic charmless
two-body decay rates for , and decays and their
charged conjugates, where P(V) is a light pseudoscalar (vector) meson. These
estimates are based on a generalized factorization approach making use of
next-to-leading order perturbative QCD contributions which generate the
required strong phases. No soft final state interactions are included. We study
the dependence of the asymmetries on a number of input parameters and show that
there are at least two (possibly three) classes of decays in which the
asymmetries are parametrically stable in this approach. The decay modes of
particular interest are: \optbar{B^0} \to \pi^+ \pi^-, \optbar{B^0} \to
K_S^0 \pi^0, \optbar{B^0} \to K_S^0 \eta^\prime, \optbar{B^0} \to K_S^0
\eta and \optbar{B^0} \to \rho^+ \rho^-. Likewise, the CP-violating
asymmetry in the decays \optbar{B^0} \to K_S^0 h^0 with is found to be parametrically stable and large. Measurements
of these asymmetries will lead to a determination of the phases
and and we work out the relationships in these modes in the
present theoretical framework. We also show the extent of the so-called
"penguin pollution" in the rate asymmetry and of the
"tree shadow" in the asymmetry which will effect the
determination of and from the respective
measurements. CP-violating asymmetries in ,
, and are potentially interesting and are studied here.Comment: 42 pages (LaTex) including 19 figures, requires epsfig.sty; submitted
to Phys. Rev.
Dimension-Six Terms in the Standard Model Lagrangian
When the Standard Model is considered as an effective low-energy theory,
higher dimensional interaction terms appear in the Lagrangian. Dimension-six
terms have been enumerated in the classical article by Buchmueller and Wyler
[3]. Although redundance of some of those operators has been already noted in
the literature, no updated complete list has been published to date. Here we
perform their classification once again from the outset. Assuming baryon number
conservation, we find 15 + 19 + 25 = 59 independent operators (barring flavour
structure and Hermitian conjugations), as compared to 16 + 35 + 29 = 80 in
Ref.[3]. The three summed numbers refer to operators containing 0, 2 and 4
fermion fields. If the assumption of baryon number conservation is relaxed, 4
new operators arise in the four-fermion sector.Comment: 16 pages, no figures, v3: Redundant B-violating operator remove
Recalculation of QCD Corrections to Decay
We give a more complete calculation of decay, including
leading log QCD corrections from to in addition to corrections
from to . We have included the full set of dimension-6 operators
and corrected numerical mistakes of anomalous dimensions in a previous
paper\cite{Cho}. Comparing with the calculations without QCD running from
to \cite{Mis}, the inclusive decay rate is found to be enhanced.
At GeV, it results in 12\% enhancement, and for GeV, 15\% is
found. The total QCD effect makes an enhanced factor of 4.2 at GeV,
and 3.2 for GeV.Comment: 16 pages, 7 figures (uuencoded ps files), Changes of description. To
appear in Phys. Rev.
Decay and Right-handed Top-bottom Charged Current
We introduce an anomalous top quark coupling (right-handed current) into
Standard Model Lagrangian. Based on this, a more complete calculation of decay including leading log QCD corrections from to
in addition to corrections from to is given. The inclusive decay
rate is found to be suppressed comparing with the case without QCD running from
to except at the time of small values of . e.g. when
, it is only of the value given before. As
goes smaller, this contribution is an enhancement like standard model case.
From the newly experiment of CLEO Collaboration, strict restrictions to
parameters of this top-bottom quark coupling are found.Comment: 20 Pages, 2 figures( ps file uuencoded)
Radiative B decays to the axial mesons at next-to-leading order
We calculate the branching ratios of at next-to-leading
order (NLO) of where is the orbitally excited axial vector
meson. The NLO decay amplitude is divided into the vertex correction and the
hard spectator interaction part. The one is proportional to the weak form
factor of transition while the other is a convolution between
light-cone distribution amplitudes and hard scattering kernel. Using the
light-cone sum rule results for the form factor, we have \calB(B^0\to
K_1^0(1270)\gamma)=(0.828\pm0.335)\times 10^{-5} and \calB(B^0\to
K_1^0(1400)\gamma)=(0.393\pm0.151)\times 10^{-5}.Comment: 17pages, 4 figures. Minor changes, typos corrected. PRD accepted
versio
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