7 research outputs found
Determination of the chiral condensate from 2+1-flavor lattice QCD
We perform a precise calculation of the chiral condensate in QCD using
lattice QCD with 2+1 flavors of dynamical overlap quarks. Up and down quark
masses cover a range between 3 and 100 MeV on a 16^3x48 lattice at a lattice
spacing around 0.11 fm. At the lightest sea quark mass, the finite volume
system on the lattice is in the epsilon-regime. By matching the low-lying
eigenvalue spectrum of the Dirac operator with the prediction of chiral
perturbation theory at the next-to-leading order, we determine the chiral
condensate in 2+1-flavor QCD with strange quark mass fixed at its physical
value as Sigma (MS-bar at 2 GeV) = [242(04)(^+19_-18}) MeV}]^3, where the
errors are statistical and systematic, respectively.Comment: 4 pages, 3 figures, errors in table 1 and fig.3 corrected. Published
in PR
Ward Identities, B-> \rho Form Factors and |V_ub|
The exclusive FCNC beauty semileptonic decay B-> \rho is studied using Ward
identities in a general vector meson dominance framework, predicting vector
meson couplings involved. The long distance contributions are discussed which
results to obtain form factors and |V_ub|. A detailed comparison is given with
other approaches.Comment: 30 pages+four postscript figures, an Appendix adde
Minimal Flavour Violation Waiting for Precise Measurements of Delta M_s, S_{psi phi}, A^s_SL, |V_ub|, gamma and B^0_{s,d} -> mu+ mu-
We emphasize that the recent measurements of the B^0_s - bar B^0_s mass
difference Delta M_s by the CDF and D0 collaborations offer an important model
independent test of minimal flavour violation (MFV). The improved measurements
of the angle gamma in the unitarity triangle and of |V_ub| from tree level
decays, combined with future accurate measurements of Delta M_s, S_{psi K_S},
S_{psi phi}, Br(B_{d,s} -> mu+ mu-), Br(B -> X_{d,s} nu bar nu), Br(K+ -> pi+
nu bar nu) and Br(K_L -> pi^0 nu bar nu) and improved values of the relevant
non-perturbative parameters, will allow to test the MFV hypothesis in a model
independent manner to a high accuracy. In particular, the difference between
the reference unitarity triangle obtained from tree level processes and the
universal unitarity triangle (UUT) in MFV models would signal either new
flavour violating interactions and/or new local operators that are suppressed
in MFV models with low tan(beta), with the former best tested through S_{psi
phi} and K_L -> pi^0 nu bar nu. A brief discussion of non-MFV scenarios is also
given. In this context we identify in the recent literature a relative sign
error between Standard Model and new physics contributions to S_{psi phi}, that
has an impact on the correlation between S_{psi phi} and A^s_SL. We point out
that the ratios S_{psi phi}/A^s_SL and (Delta M_s)/(Delta Gamma_s) will allow
to determine (Delta M_s)/(Delta M_s)^SM. Similar proposals for the
determination of (Delta M_d)/(Delta M_d)^SM are also given.Comment: 22 pages, 8 figures, 1 table. Extended discussion of the correlation
between S_{psi phi} and A^s_SL and new proposals to determine Delta
M_q/(Delta M_q)^SM from future measurements, with respect to the first
version. Minor changes and few references adde
Measurement of the K_L \to \pi\mu\nu form factor parameters with the KLOE detector
Using 328 pb^{-1}of data collected at DAFNE corresponding to 1.8
million decays, we have measured the form factor
parameters. The structure of the vector-current provides information
about the dynamics of the strong interaction; its knowledge is necessary for
evaluation of the phase-space integral required for measuring the CKM matrix
element and for testing lepton universality in kaon decays. Using a
new parametrization for the vector and scalar form factors, we find
=\pt(25.7\pm 0.6),-3, and =\pt(14.0\pm 2.1),-3,. Our
result for , together with recent lattice calculations of ,
and , satisfies the Callan-Trieman relatio