384 research outputs found
1/m_Q Corrections to the Heavy-to-Light-Vector Transitions in the HQET
Within the HQET, the heavy to light vector meson transitions are
systematically analyzed to the order of 1/m_Q. Besides the four universal
functions at the leading order, there are twenty-two independent universal form
factors at the order of 1/m_Q. Both the semileptonic decay B->\rho which is
relevant to the |V_{ub}| extraction, and the penguin induced decay B -> K^*
which is important to new physics discovering, depend on these form factors.
Phenomenological implications are discussed.Comment: RevTeX, 9 pages, no figure
B -> K^* gamma from D -> K^* l nu
The B -> K^* gamma branching fraction is predicted using heavy quark spin
symmetry at large recoil to relate the tensor and (axial-)vector form factors,
using heavy quark flavor symmetry to relate the B decay form factors to the
measured D -> K^* l nu form form factors, and extrapolating the semileptonic B
decay form factors to large recoil assuming nearest pole dominance. This
prediction agrees with data surprisingly well, and we comment on its
implications for the extraction of |Vub| from B -> rho l nu.Comment: 10 page
New Physics with earliest LHC data
We investigate which new physics models could be discovered in the first year of the LHC. Such a âSupermodelâ is a new physics scenario for which the LHC sensitivity with only 10 pbâ1 useful luminosity is greater than that of the
Tevatron with 10 fbâ1. The simplest supermodels involve s-channel resonances in the quark-antiquark and especially in the quark-quark channels. We concentrate on easily visible final states with small standard model backgrounds, and suggest simple searches, besides those for Z
states, which could discover new physics in
early LHC data
Relativistic quantum theories and neutrino oscillations
Neutrino oscillations are examined under the broad requirements of
Poincar\'e-invariant scattering theory in an S-matrix formulation.
This approach can be consistently applied to theories with either field or
particle degrees of freedom. The goal of this paper is to use this general
framework to identify all of the unique physical properties of this problem
that lead to a simple oscillation formula. We discuss what is in principle
observable, and how many factors that are important in principle end up being
negligible in practice.Comment: 21 pages, no figure
The Decay in the Context of Chiral Perturbation Theory
We study the decay , using
chiral perturbation theory for heavy charmed mesons
and vector mesons, in the kinematic regime where (here or ) is much smaller than the chiral symmetry breaking
scale, ( 1 GeV). We present the
leading diagrams and amplitude, and calculate the rate, in the region where, to
leading order in our calculations, the is at zero recoil in the
rest frame. The rate thus calculated is given in terms of a known form
factor and depends on the coupling constant of the heavy
(charmed) meson chiral perturbation theory Lagrangian. A measurement of the
above decay, in the aforementioned kinematic regime, can result in the
extraction of an experimental value for , accurate at the level of our
approximations, and give us a measure of the validity of approaches based on
chiral perturbation theory in studying similar processes.Comment: 17 pages, Latex, 2 embedded postscript figure
Combining exclusive semi-leptonic and hadronic B decays to measure |V_ub|
The Cabibbo-Kobayashi-Maskawa matrix element |V_ub| can be extracted from the
rate for the semi-leptonic decay B -> pi + l + antineutrino_l, with little
theoretical uncertainty, provided the hadronic form factor for the B -> pi
transition can be measured from some other B decay. In here, we suggest using
the decay B -> pi J\psi. This is a color suppressed decay, and it cannot be
properly described within the usual factorization approximation; we use instead
a simple and very general phenomenological model for the b d J\psi vertex. In
order to relate the hadronic form factors in the B -> pi J\psi and B -> pi + l
+ antineutrino_l decays, we use form factor relations that hold for
heavy-to-light transitions at large recoil.Comment: Latex, 7 pages, no figure
Implications of the lepton spectrum for heavy quark physics
The shape of the lepton spectrum in inclusive semileptonic decay is sensitive to matrix elements of the heavy quark
effective theory, and . From CLEO data we extract
GeV and , where
the uncertainty is the statistical error only. Systematic
uncertainties are discussed. These values for and are
used to determine and the bottom and charm quark
masses. We discuss the theoretical uncertainties related to order
effects and higher orders in the perturbative
expansion.Comment: 10 pages revtex + one figure. Corrections from secondary leptons
included, that affect the numerical results. Thus the central values become
and $\lambda_1=-0.19\pm0.10GeV^2
- âŠ