19 research outputs found
Search for New Physics in CP-violating B Decays
We consider three possible scenarios of new physics in B^0_d-\bar{B}^0_d
mixing and propose a simple framework for analyzing their effects. This
framework allows us to study the CP asymmetry in semileptonic B_d decays ({\cal
A}_{SL}) and those in nonleptonic transitions such as B_d \to J/\psi K_S and
B_d \to \pi^+\pi^-. Numerically we find that new physics may enhance the
magnitude of {\cal A}_{SL} up to the percent level within the appropriate
parameter space. So measurements of {\cal A}_{SL} and its correlation with
other CP asymmetries will serve as a sensitive probe for new physics in
B^0_d-\bar{B}^0_d mixing.Comment: Latex 18 page
In Pursuit of New Physics with B_s Decays
The presence of a sizeable CP-violating phase in B_s^0-B_s^0-bar mixing would
be an unambiguous signal of physics beyond the Standard Model. We analyse
various possibilities to detect such a new phase considering both tagged and
untagged decays. The effects of a sizeable width difference Delta Gamma between
the B_s mass eigenstates, on which the untagged analyses rely, are included in
all formulae. A novel method to find this phase from simple measurements of
lifetimes and branching ratios in untagged decays is proposed. This method does
not involve two-exponential fits, which require much larger statistics. For the
tagged decays, an outstanding role is played by the observables of the
time-dependent angular distribution of the B_s -> J/psi [-> l^+ l^-] \phi [->
K^+K^-] decay products. We list the formulae needed for the angular analysis in
the presence of both a new CP-violating phase and a sizeable Delta Gamma, and
propose methods to remove a remaining discrete ambiguity in the new phase. This
phase can therefore be determined in an unambiguous way.Comment: minor changes, lattice prediction of Delta Gamma updated, appears in
PR
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
Enhanced contribution to quark and neutron electric dipole moments with small mixing of right-handed currents and CKM CP violation
We study the light quark and the neutron electric dipole moments (EDMs) under
the assumptions that the CP source is still in the usual CKM matrix and that
there is a small mixing of right-handed charged currents in the quark sector.
We find that the EDMs arise already at two loop order that are much larger than
the standard model (SM) result even for a small mixing.Comment: 9 pages, revtex, axodraw.sty, 1 figure, published version in Phys.
Rev. D. References updated, minor corrections and typos fixe
Charm and Bottom Semileptonic Decays
We review the present status of theoretical attempts to calculate the
semileptonic charm and bottom decays and then present a calculation of these
decays in the light--front frame at the kinematic point . This allows us
to evaluate the form factors at the same value of , even though the
allowed kinematic ranges for charm and bottom decays are very different. Also,
at this kinematic point the decay is given in terms of only one form factor
. For the ratio of the decay rates given by the E653 collaboration we
show that the determination of the ratio of the Cabibbo--Kobayashi--Maskawa
(CKM) matrix elements is consistent with that obtained from the unitarity
constraint. At present, though, the unitarity method still has greater
accuracy. Since comparisons of the semileptonic decays into and either
electrons or muons will be available soon from the E791 Fermilab experiment, we
also look at the massive muon case. We show that for a range of the
symmetry breaking is small even though the contributions of the
various helicity amplitudes becomes more complicated. For decays, the decay
at involves an extra form factor
coming from the photon contribution and so is not amenable to the same kind of
analysis, leaving only the decay as a
possibility. As the mass of the decaying particle increases we note that the
symmetry becomes badly broken at .Comment: Latex, 19 pages, two figures are attached, a minor change in the
manuscript related to thi
The Physics of Heavy Flavours at SuperB
This is a review of the SuperB project, covering the accelerator, detector,
and highlights of the broad physics programme. SuperB is a flavour factory
capable of performing precision measurements and searches for rare and
forbidden decays of , , and
particles. These results can be used to test fundamental symmetries and
expectations of the Standard Model, and to constrain many different
hypothesised types of new physics. In some cases these measurements can be used
to place constraints on the existence of light dark matter and light Higgs
particles with masses below . The potential impact of the
measurements that will be made by SuperB on the field of high energy physics is
also discussed in the context of data taken at both high energy in the region
around the \Upsilon({\mathrm{4S}})$, and near charm threshold.Comment: 49 pages, topical review submitted to J. Phys
Spontaneous CP violation in Supersymmetric theories
We study the minimal version of the supersymmetric standard model with
spontaneous CP breaking. In this model, the KM matrix is real and contributions
to arise from box diagrams involving squarks. We analyze the
region of the parameter space which corresponds to values for ,
and the neutron electric dipole moment (NEDM)
in agreement with the experimental data. We show that the CP violating phases
must be of \calo (10^{-2}) and the NEDM lies near its present experimental
limit.Comment: 17 pages, 5 figures (no included), SCIPP-92/30, PHYZZX fil
Possible Large Direct CP Violations in Charmless B-Decays
We discuss the perturbative QCD approach for the exclusive two body B-meson
decays to light mesons. We briefly review its ingredients and some important
theoretical issues on factorization approach. We show numerical results which
are compatible with present experimantal data for the charmless B-meson decays.
Specailly we predict the possibility of large direct CP violation effects in
and .
In the last section we investigate two methods to determine the weak phases
and from processes. We obtain bounds on
and from present experimental measurements.Comment: 18 pages, latex, 8 figures and 8 tables, typos corrected and added
more tables and references. Presented at the 3rd workshop on Higher
Luminosity B Factory, 6-7 August 2002, Kanagawa, Japan; Submitted to Phys.
Rev.
Exploring CP Violation through Correlations in B --> pi K, B_d --> pi^+pi^-, B_s --> K^+K^- Observable Space
We investigate allowed regions in observable space of B --> pi K, B_d -->
pi^+pi^- and B_s --> K^+K^- decays, characterizing these modes in the Standard
Model. After a discussion of a new kind of contour plots for the
system, we focus on the mixing- induced and direct CP asymmetries of the decays
B_d --> pi^+pi^- and B_s--> K^+K^-. Using experimental information on the
CP-averaged B_d --> pi^{+/-}K^{+/-} and B_d --> pi^+pi^- branching ratios, the
relevant hadronic penguin parameters can be constrained,implying certain
allowed regions in observable space. In the case of B_d --> pi^+pi^-, an
interesting situation arises now in view of the recent B-factory measurements
of CP violation in this channel, allowing us to obtain new constraints on the
CKM angle gamma as a function of the B^0_d--\bar{B^0_d} mixing phase
phi_d=2beta, which is fixed through A_{CP}^{mix}(B_d --> J/psi K_S) up to a
twofold ambiguity. If we assume that A_{CP}^{mix}(B_d --> pi^+pi^-) is
positive, as indicated by recent Belle data, and that phi_d is in agreement
with the ``indirect'' fits of the unitarity triangle, also the corresponding
values for gamma around 60 degrees can be accommodated. On the other hand, for
the second solution of phi_d, we obtain a gap around gamma ~ 60 degrees. The
allowed region in the space of A_{CP}^{mix}(B_s --> K^+K^-) and
A_{CP}^{dir}(B_s --> K^+K^-) is very constrained in the Standard Model, thereby
providing a narrow target range for run II of the Tevatron and the experiments
of the LHC era.Comment: 34 pages, LaTeX, 12 figures. More detailed introduction and a few
Comments added, conclusions unchanged. To appear in Phys. Rev.