4,937 research outputs found
Factorization in B -> K pi e+e- decays
We derive factorization relations for the transverse helicity amplitudes in
the rare decays B-> K\pi l+l- at leading order in Lambda/m_b, in the
kinematical region with an energetic kaon and a soft pion. We identify and
compute a new contribution of leading order in Lambda/m_b to the B->K\pi l+l-
amplitude, which is not present in the one-body decay B-> K*l+l-. As an
application we study the forward-backward asymmetry (FBA) of the lepton
momentum angular distribution in B-> K\pi l+l- decays away from the K*
resonance. The FBA in these decays has a zero at q0^2 = q0^2(M_{Kpi}), which
can be used, in principle, for determining the Wilson coefficients C_{7,9} and
testing the Standard Model. We point out that the slope of the q0^2(M_{Kpi}^2)
curve contains the same information about the Wilson coefficients as the
location of the zero, but is less sensitive to unknown nonperturbative
dynamics. We estimate the location of the zero at leading order in
factorization, and using a resonant model for the B -> K\pi l+l-
nonfactorizable amplitude.Comment: 16 pages, 5 figures. Version to appear in Physical Review D. One new
observable introduced and considered - the slope of the zero of the
forward-backward asymmetry as function of the K\pi invariant mas
Heavy Meson Physics: What have we learned in Twenty Years?
I give a personal account of the development of the field of heavy quarks.
After reviewing the experimental discovery of charm and bottom quarks, I
describe how the field's focus shifted towards determination of CKM elements
and how this has matured into a precision science.Comment: This talk was presented during the ceremony awarding the Medalla 2003
of the Division of Particles and Fields of The Mexican Phsyical Society, at
the IX Mexican Workshop on Particles and Fields; submitted for proceedings; 9
pages, 9 figures; replacement: fix multiple typo
Lepton non-universality in decays and fermion mass structure
We consider the possibility that the neutral-current anomalies are due to
radiative corrections generated by Yukawa interactions of quarks and leptons
with new vector-like quark and lepton electroweak doublets and new Standard
Model singlet scalars. We show that the restricted interactions needed can
result from an underlying Abelian family symmetry and that the same symmetry
can give rise to an acceptable pattern of quark and charged lepton masses and
mixings, providing a bridge between the non-universality observed in the
B-sector and that of the fermion mass matrices. We construct two simple models,
one with a single singlet scalar in which the flavour changing comes from quark
and lepton mixing and one with an additional scalar in which the flavour
changing can come from both fermion and scalar mixing. We show that for the
case the new quarks are much heavier than the new leptons and scalars the
anomalies can be due to box diagrams with couplings in the perturbative regime
consistent with the bounds coming from , and mixing as well as other lepton family number violating processes. The
new states can be dark matter candidates and, in the two scalar model with a
light scalar of O(60) GeV and vector-like lepton of O(100) GeV, there can be a
simultaneous explanation of the B-anomalies, the muon anomalous magnetic moment
and the dark matter abundance.Comment: Replacement contains few additional reference
Recommended from our members
An introduction to the theory of heavy mesons and baryons
Introductory lectures (delivered at TASI, June 1994) on heavy quarks and heavy quark effective field theory. Applications to inclusive semileptonic decays and to interactions with light mesons are covered in detail
Massive Vector Scattering in Lee-Wick Gauge Theory
We demonstrate that amplitudes describing scattering of longitudinally
polarized massive vector bosons present in non-Abelian Lee-Wick gauge theory do
not grow with energy and, hence, satisfy the constraints imposed by
perturbative unitarity. This result contrasts with the widely-known violation
of perturbative unitarity in the standard model with a very heavy Higgs. Our
conclusions are valid to all orders of perturbation theory and depend on the
existence of a formulation of the theory in which all operators are of
dimension four or less. This can be thought of as a restriction on the kinds of
higher dimension operator which can be included in the higher derivative
formulation of the theory.Comment: 11 pages, no figure
Magnetic Wormholes and Vertex Operators
We consider wormhole solutions in Euclidean dimensions. A duality
transformation is introduced to derive a new action from magnetic wormhole
action of Gupta, Hughes, Preskill and Wise. The classical solution is
presented. The vertex operators corresponding to the wormhole are derived.
Conformally coupled scalars and spinors are considered in the wormhole
background and the vertex operators are computed. ( To be published in Phys.
Rev. D15)Comment: 18 pages of RevTex, preprint IP/BBSR/94-2
Driven Diffusive Systems: An Introduction and Recent Developments
Nonequilibrium steady states in driven diffusive systems exhibit many
features which are surprising or counterintuitive, given our experience with
equilibrium systems. We introduce the prototype model and review its unusual
behavior in different temperature regimes, from both a simulational and
analytic view point. We then present some recent work, focusing on the phase
diagrams of driven bi-layer systems and two-species lattice gases. Several
unresolved puzzles are posed.Comment: 25 pages, 5 figures, to appear in Physics Reports vol. 299, June 199
Exclusive rare B -> K*e+e- decays at low recoil: controlling the long-distance effects
We present a model-independent description of the exclusive rare decays B->
K* e+e- in the low recoil region (large lepton invariant mass q^2 ~ m_b^2). In
this region the long-distance effects from quark loops can be computed with the
help of an operator product expansion in 1/Q, with Q={m_b, \sqrt{q^2}}.
Nonperturbative effects up to and including terms suppressed by Lambda/Q and
mc^2/mb^2 relative to the short-distance amplitude can be included in a
model-independent way. Based on these results, we propose an improved method
for determining the CKM matrix element |V{ub}| from a combination of rare and
semileptonic B and D decays near the zero recoil point. The residual
theoretical uncertainty from long distance effects in this |V{ub}|
determination comes from terms in the OPE of order alpha_s(Q)\Lambda/mb,
alpha_s^2(Q), mc^4/mb^4$ and duality violations and is estimated to be below
10%.Comment: 21 pages RevTex, 2 figures; v3: extensive numerical changes in the
NLL analysis, with improved stability under scale dependence. Typos fixed,
version to appear in Phys.Rev.
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