9 research outputs found
Updated constraints on new physics in rare charm decays
Motivated by recent experimental results on charm physics we investigate
implications of the updated constraints of new physics in rare charm meson
decays. We first reconsider effects of the MSSM in constrained
by the recent experimental evidence on and find, that due to the
dominance of long distance physics, decay rates cannot be
modified by MSSM contributions. Then we consider effects of the extra heavy up
vector-like quark models on the decay spectrum of and
decays. We find a possibility for the tiny increase of
the differential decay rate in the region of large dilepton mass. The R-parity
violating supersymmetric model can also modify short distance dynamics in decays. We constrain relevant parameters using current upper
bound on the decay rate and investigate impact of that
constraint on the differential decay dilepton
distribution. Present bounds still allow small modification of the standard
model differential decay rate distribution.Comment: 15 pages, 4 figure
The controversy in the process: potential scattering or resonance ?
The reaction shows a broad peak at 1.5
GeV in the channel which has no counterpart in the
channel. This "resonance" is considered as a candidate for a
state in the "s-channel". We show, however, that it can also
be explained by potential scattering of via the -
exchange in the "t-channel".Comment: 12 pages, latex, 3 postscript figures, to appear in Zeitschrift fur
Physi
On the mass differences between the scalar and pseudoscalar heavy-light mesons
We discuss the recent experimental observation which suggested that the mass
difference between the scalar and pseudoscalar heavy-light mesons is larger for
the non-strange states than for the strange ones. After computing the chiral
corrections in the heavy quark limit we show that, contrary to experiment, the
mass difference in the non-strange case should be smaller.Comment: 10 pages, 2 figure
B --> pi and B --> K transitions in partially quenched chiral perturbation theory
We study the properties of the B-->pi and B-->K transition form factors in
partially quenched QCD by using the approach of partially quenched chiral
perturbation theory combined with the static heavy quark limit. We show that
the form factors change almost linearly when varying the value of the sea quark
mass, whereas the dependence on the valence quark mass contains both the
standard and chirally divergent (quenched) logarithms. A simple strategy for
the chiral extrapolations in the lattice studies with Nsea=2 is suggested. It
consists of the linear extrapolations from the realistically accessible quark
masses, first in the sea and then in the valence quark mass. From the present
approach, we estimate the uncertainty induced by such extrapolations to be
within 5%.Comment: Published versio
B-->pi and B-->K transitions in standard and quenched chiral perturbation theory
We study the effects of chiral logs on the heavy-->light pseudoscalar meson
transition form factors by using standard and quenched chiral perturbation
theory combined with the static heavy quark limit. The resulting expressions
are used to indicate the size of uncertainties due to the use of the quenched
approximation in the current lattice studies. They may also be used to assess
the size of systematic uncertainties induced by missing chiral log terms in
extrapolating toward the physical pion mass. We also provide the coefficient
multiplying the quenched chiral log, which may be useful if the quenched
lattice studies are performed with very light mesons.Comment: 33 pages, 8 PostScript figures, version to appear in PR
Toward the quark mass dependence of from lattice QCD
The scattering phase shifts in the channel are extracted from lattice QCD for five different charm quark masses and a fixed light-quark mass corresponding to 280 MeV. The phase shifts are analyzed employing two approaches: effective range expansion and Lippmann-Schwinger equation derived in the effective field theory. In the latter case, the results imply an attraction at short range parametrized by contact terms and a slight repulsion at long range mediated by one-pion exchange with . The poles in the amplitude across the complex energy plane are extracted and their trajectories are discussed as the charm quark mass is varied. Two complex conjugate poles corresponding to a resonance below threshold are found for close to the physical value. They turn into a pair of virtual states at the largest studied. With further increasing , one virtual pole representing is expected to move towards the two-body threshold and turn into a bound state. The light-quark mass dependence of the pole is briefly discussed using the data on scattering from other lattice collaborations