1,894 research outputs found
V_{us} from hyperon semileptonic decays
A model-independent determination of the CKM matrix element V_{us} from five
measured strangeness-changing hyperon semileptonic decays is performed. Flavor
SU(3) symmetry breaking effects in the leading vector and axial-vector form
factors are analyzed in the framework of the 1/N_c expansion of QCD. A fit to
experimental data allows one to extract the value V_{us}=0.2199\pm 0.0026,
which is comparable to the one from K_{e3} decays. This reconciliation is
achieved through second-order symmetry breaking effects of a few percent in the
form factors f_1, which increase their magnitudes over their SU(3) predictions.Comment: 23 pages, Revtex4, 12 tables, no figure
Semileptonic Hyperon Decays and CKM Unitarity
Using a technique that is not subject to first-order SU(3) symmetry breaking
effects, we determine the element of the CKM matrix from data on
semileptonic hyperon decays. We obtain =0.2250(27). This value is of
similar precision to the one derived from , but higher and in better
agreement with the unitarity requirement, .Comment: 3 pages, 1 tabl
The electromagnetic effects in decay
The final state interaction of pions in decay allows one to obtain
the value of the isospin and angular momentum zero scattering length
.We take into account the electromagnetic interaction of pions and
isospin symmetry breaking effects caused by different masses of neutral and
charged pions and estimate the impact of these effects on the procedure of
scattering length extraction from decay.Comment: 8 pages,1 figur
Non-leptonic B-decays, CP violation & the UT
We study the implication of the time-dependent CP asymmetry in
decays on the extraction of weak phases taking into account
the precise measurement of , obtained from the ``gold-plated''mode
. Predictions and uncertainties for the hadronic parameters
are investigated in QCD factorization. Furthermore, independent theoretical and
experimental tests of the factorization framework are briefly discussed.
Finally, a model-independent bound on the unitarity triangle from CP violation
in and is derived.Comment: 4 pages; 4 figures (requires epsfig, psfrag); To appear in the
proceedings of the 11th International Conference on Quantum Chromodynamics
(QCD 04), Montpellier, France, 5--10th July 200
Size of Isospin Breaking in Charged K(L4) Decay
We evaluate the size of isospin breaking corrections to form factors and
of the decay process which
is actually measured by the extended NA48 setup at CERN. We found that, keeping
apart the effect of Coulomb interaction, isospin breaking does not affect
modules. This is due to the cancelation between corrections of electromagnetic
origin and those generated by the difference between up and down quark masses.
On the other hand, electromagnetism affects considerably phases if the infrared
divergence is dropped out using a minimal subtraction scheme. Consequently, the
greatest care must be taken in the extraction of phase shifts from
experiment.Comment: 29 pages, LaTeX, 7 postscript figure
Study of SU(3) vortex-like configurations with a new maximal center gauge fixing method
We present a new way of fixing the gauge to (direct) maximal center gauge in
SU(N) Yang-Mills theory and apply this method to SU(3) configurations which are
vortex-like. We study the structure of the Z_3 configurations obtained after
center-projecting the SU(3) ones.Comment: 11 pages, 2 figures. To appear in PL
Matrix Elements without Quark Masses on the Lattice
We introduce a new parameterization of four-fermion matrix elements which
does not involve quark masses and thus allows a reduction of systematic
uncertainties in physical amplitudes. As a result the apparent quadratic
dependence of e'/e on m_s is removed. To simplify the matching between lattice
and continuum renormalization schemes, we express our results in terms of
Renormalization Group Invariant B-parameters which are renormalization-scheme
and scale independent. As an application of our proposal, matrix elements of
DeltaI=3/2 and SUSY DeltaF=2 () four-fermion operators have been
computed.Comment: LATTICE99(Matrix Elements), 3 pages, 1 figure, BUHEP-99-2
The isospin symmetry breaking effects in decays
The Fermi-Watson theorem is generalized to the case of two coupled channels
with different masses and applied to final state interaction in
decays. The impact of considered effect on the phase of the scattering
is estimated and shown that it can be crucial for scattering lengths extraction
from experimental data on decays
Semileptonic Hyperon Decays
We review the status of hyperon semileptonic decays. The central issue is the
element of the CKM matrix, where we obtain . This
value is of similar precision, but higher, than the one derived from ,
and in better agreement with the unitarity requirement,
. We find that the Cabibbo model gives an
excellent fit of the existing form factor data on baryon beta decays ( for 3 degrees of freedom) with , , and no indication of flavour-SU(3)-breaking effects. We
indicate the need of more experimental and theoretical work, both on hyperon
beta decays and on decays.Comment: 37 pages, 8 figures, 4 tables, Final version of this material is
scheduled to appear in the Annual Review of Nuclear and Particle Science Vol.
5
A Quark-Antiquark Condensate in Three-Dimensional QCD
Three-dimensional lattice QCD is studied by Monte Carlo simulations within
the quenched approximation. At zero temperature a quark-antiquark condensate is
observed in the limit of vanishing quark masses. The condensate vanishes
continuously at the finite-temperature deconfinement phase transition of the
theory. A natural interpretation of this phenomenon in the full theory with
dynamical quarks is in terms of the spontaneous flavor symmetry breaking
. In addition, the spectrum of low-lying
Dirac operator eigenvalues is computed and found to be consistent with a flat
distribution at zero temperature, in agreement with analytical predictions.Comment: Extensive revision of the original version. 11 pages, 6 figures
included as EPS files. The problem with figure encapsulation fixe
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