149 research outputs found
The rare decays B --> K(*) anti-K(*) and R-parity violating supersymmetry
We study the branching ratios, the direct CP asymmetries in decays and the polarization fractions of decays by employing the QCD factorization in the minimal
supersymmetric standard model with R-parity violation. We derive the new upper
bounds on the relevant R-parity violating couplings from the latest
experimental data of , and some of these constraints
are stronger than the existing bounds. Using the constrained parameter spaces,
we predict the R-parity violating effects on the other quantities in decays which have not been measured yet. We find that the
R-parity violating effects on the branching ratios and the direct
asymmetries could be large, nevertheless their effects on the longitudinal
polarizations of decays are small. Near future
experiments can test these predictions and shrink the parameter spaces.Comment: 31 pages with 10 figure
Flavor Changing Effects in Family Nonuniversal Z' Models
Flavor-changing and CP-violating interactions of Z' to fermions are generally
present in models with extra U(1) gauge symmetry that are string-inspired or
related to broken gauged family symmetry. We study the consequences of such
couplings in fermion electric dipole moments, muon g-2, and K and B meson
mixings. From experimental limits or measured values, we constrain the
off-diagonal Z' couplings to fermions. Some of these constraints are comparable
or stronger than the existing constraints obtained from other observables.Comment: 17 pages, 2 figure
Dispersion Theory and the Low Energy Constants for Neutral Pion Photoproduction
The relativistic amplitudes of pion photoproduction are evaluated by
dispersion relations at t=const. The imaginary parts of the amplitudes are
taken from the MAID model covering the absorption spectrum up to center-of-mass
energies W = 2.2 GeV. For sub-threshold kinematics the amplitudes are expanded
in powers of the two independent variables \nu and t related to energy and
momentum transfer. Subtracting the loop corrections from this power series
allows one to determine the counter terms of covariant baryon chiral
perturbation theory. The proposed continuation of the amplitudes into the
unphysical region provides a unique framework to derive the low-energy
constants to any given order as well as an estimate of the higher order terms
by global properties of the absorption spectrum.Comment: 13 pages, 6 figures, 5 table
Power-law running of the effective gluon mass
The dynamically generated effective gluon mass is known to depend
non-trivially on the momentum, decreasing sufficiently fast in the deep
ultraviolet, in order for the renormalizability of QCD to be preserved. General
arguments based on the analogy with the constituent quark masses, as well as
explicit calculations using the operator-product expansion, suggest that the
gluon mass falls off as the inverse square of the momentum, relating it to the
gauge-invariant gluon condensate of dimension four. In this article we
demonstrate that the power-law running of the effective gluon mass is indeed
dynamically realized at the level of the non-perturbative Schwinger-Dyson
equation. We study a gauge-invariant non-linear integral equation involving the
gluon self-energy, and establish the conditions necessary for the existence of
infrared finite solutions, described in terms of a momentum-dependent gluon
mass. Assuming a simplified form for the gluon propagator, we derive a
secondary integral equation that controls the running of the mass in the deep
ultraviolet. Depending on the values chosen for certain parameters entering
into the Ansatz for the fully-dressed three-gluon vertex, this latter equation
yields either logarithmic solutions, familiar from previous linear studies, or
a new type of solutions, displaying power-law running. In addition, it
furnishes a non-trivial integral constraint, which restricts significantly (but
does not determine fully) the running of the mass in the intermediate and
infrared regimes. The numerical analysis presented is in complete agreement
with the analytic results obtained, showing clearly the appearance of the two
types of momentum-dependence, well-separated in the relevant space of
parameters. Open issues and future directions are briefly discussed.Comment: 37 pages, 5 figure
Obtaining CKM Phase Information from B Penguin Decays
We discuss a method for extracting CP phases from pairs of B decays which are
related by flavor SU(3). One decay (B0 -> M1 M2) receives a significant bbar ->
dbar penguin contribution. The second (B' -> M1' M2') has a significant bbar ->
sbar penguin contribution, but is dominated by a single amplitude. CP phase
information is obtained using the fact that the B' -> M1' M2' amplitude is
related by SU(3) to a piece of the B0 -> M1 M2 amplitude. The leading-order
SU(3)-breaking effect (~25%) responsible for the main theoretical error can be
removed. For some decay pairs, it can be written in terms of known decay
constants. In other cases, it involves a ratio of form factors. However, this
form-factor ratio can either be measured experimentally, or eliminated by
considering a double ratio of amplitudes. In all cases, one is left only with a
second-order effect, ~5%. We find twelve pairs of B decays to which this method
can be applied. Depending on the decay pair, we estimate the total theoretical
error in relating the B' -> M1' M2' and B0 -> M1 M2 amplitudes to be between 5%
and 15%. The most promising decay pairs are Bd -> pi+ pi- and Bu+ -> K0 pi+,
and Bd -> D+ D- and Bd -> Ds+ D- or Bu+ -> Ds+ D0bar.Comment: 38 pages, JHEP format, no figures. Comments added to text regarding
most promising decay pairs; references added; conclusions unchange
Aerogel Track Morphology: Measurement, Three Dimensional Reconstruction and Particle Location using Confocal Laser Scanning Microscopy
The Stardust spacecraft returned the first undoubted samples of cometary dust, with many grains embedded in the silica aerogel collector . Although many tracks contain one or more large terminal particles of a wide range of mineral compositions , there is also abundant material along the track walls. To help interpret the full particle size, structure and mass, both experimental simulation of impact by shots and numerical modeling of the impact process have been attempted. However, all approaches require accurate and precise measurement of impact track size parameters such as length, width and volume of specific portions. To make such measurements is not easy, especially if extensive aerogel fracturing and discoloration has occurred. In this paper we describe the application and limitations of laser confocal imagery for determination of aerogel track parameters, and for the location of particle remains
Rare K and B Decays in the Littlest Higgs Model without T-Parity
We analyze rare K and B decays in the Littlest Higgs (LH) model without
T-parity. We find that the final result for the Z^0-penguin contribution
contains a divergence that is generated by the one-loop radiative corrections
to the currents corresponding to the dynamically broken generators. Including
an estimate of these logarithmically enhanced terms, we calculate the branching
ratios for the decays K^+ -> pi^+ nu bar nu, K_L -> pi^0 nu bar nu, B_{s,d} ->
mu^+ mu^- and B -> X_{s,d} nu bar nu. We find that for the high energy scale
f=O(2-3) TeV, as required by the electroweak precision studies, the enhancement
of all branching ratios amounts to at most 15% over the SM values. On the
technical side we identify a number of errors in the existing Feynman rules in
the LH model without T-parity that could have some impact on other analyses
present in the literature. Calculating penguin and box diagrams in the unitary
gauge, we find divergences in both contributions that are cancelled in the sum
except for the divergence mentioned above.Comment: 39 pages, 8 figures, typos corrected, comment on (2.17) and (2.18)
added, references added, results unchange
Present and Future CP Measurements
We review theoretical and experimental results on CP violation summarizing
the discussions in the working group on CP violation at the UK phenomenology
workshop 2000 in Durham.Comment: 104 pages, Latex, to appear in Journal of Physics
Dark Matter And With Minimal Soft SUSY Breaking II
We update and extend to larger masses our previous analysis of the MSSM with
minimal [MSOSM] soft SUSY breaking boundary conditions. We
find a well--defined, narrow region of parameter space which provides the
observed relic density of dark matter, in a domain selected to fit precision
electroweak data, including top, bottom and tau masses. The model is highly
constrained which allows us to make several predictions. We find the light
Higgs mass GeV and also upper bounds on the mass of the
gluino \mgluino\lsim3.1 TeV and lightest neutralino \mchi\lsim450 GeV. As
the CP odd Higgs mass increases, the region of parameter space consistent
with WMAP data is forced to larger values of and smaller values of
. Hence, we find an upper bound m_A \lsim 1.3 TeV. This in turn leads to
lower bounds on (assuming minimal
flavor violation) and on the dark matter spin independent detection cross
section \sigsip > 10^{-9} pb. Finally, we extend our previous analysis to
include WIMP signals in indirect detection and find prospects for WIMP
detection generally much less promising than in direct WIMP searches.Comment: 24 page
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