43,848 research outputs found
A Theoretical Reappraisal of Branching Ratios and CP Asymmetries in the Decays and Determination of the CKM Parameters
We present a theoretical reappraisal of the branching ratios and CP
asymmetries for the decays , with , taking
into account current theoretical uncertainties in the description of the
inclusive decay amplitudes from the long-distance contributions, an improved
treatment of the renormalization scale dependence, and other parametric
dependencies. Concentrating on the partial branching ratios , integrated over the invariant dilepton mass region , we calculate theoretical precision on the
charge-conjugate averaged partial branching ratios , CP asymmetries in partial decay rates
, and the ratio of the
branching ratios .
For the central values of the CKM parameters, we find , , , , and . The dependence of and on the CKM parameters is worked out and the resulting constraints on
the unitarity triangle from an eventual measurement of are
illustrated.Comment: 18 pages, 7 figures (require epsf.sty
Evolution of galaxy groups in the Illustris simulation
We present the first study of evolution of galaxy groups in the Illustris
simulation. We focus on dynamically relaxed and unrelaxed galaxy groups
representing dynamically evolved and evolving galaxy systems, respectively. The
evolutionary state of a group is probed from its luminosity gap and separation
between the brightest group galaxy and the center of mass of the group members.
We find that the Illustris simulation, over-produces large luminosity gap
galaxy systems, known as fossil systems, in comparison to observations and the
probed semi-analytical predictions. However, this simulation is equally
successful in recovering the correlation between luminosity gap and luminosity
centroid offset, in comparison to the probed semi-analytic model. We find
evolutionary tracks based on luminosity gap which indicate that a large
luminosity gap group is rooted in a small luminosity gap group, regardless of
the position of the brightest group galaxy within the halo. This simulation
helps, for the first time, to explore the black hole mass and its accretion
rate in galaxy groups. For a given stellar mass of the brightest group
galaxies, the black hole mass is larger in dynamically relaxed groups with a
lower rate of mass accretion. We find this consistent with the latest
observational studies of the radio activities in the brightest group galaxies
in fossil groups. We also find that the IGM in dynamically evolved groups is
hotter for a given halo mass than that in evolving groups, again consistent
with earlier observational studies.Comment: 10 pages, 10 figures. Accepted for publication in Ap
A Comparative Study of the Decays in Standard Model and Supersymmetric Theories
Using improved theoretical calculations of the decay form factors in the
Light Cone-QCD sum rule approach, we investigate the decay rates, dilepton
invariant mass spectra and the forward-backward (FB) asymmetry in the decays () in the standard
model (SM) and a number of popular variants of the supersymmetric (SUSY)
models. Theoretical precision on the differential decay rates and FB-asymmetry
is estimated in these theories taking into account various parametric
uncertainties. We show that existing data on and the
experimental upper limit on the branching ratio provide interesting bounds on the coefficients of the underlying
effective theory. We argue that the FB-asymmetry in
constitutes a precision test of the SM and its measurement in forthcoming
experiments may reveal new physics. In particular, the presently allowed
large- solutions in SUGRA models, as well as more general
flavor-violating SUSY models, yield FB-asymmetries which are characteristically
different from the corresponding ones in the SM.Comment: 36 pages, 12 figures (require epsfig.sty), 8 Tables, LaTeX2e;
subsection 6.4 corrected, minor changes in numerical results, Figures 3 and 9
to 12 modified; submitted to Physical Review
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Fuzzy image segmentation of generic shaped clusters
The segmentation performance of any clustering algorithm is very sensitive to the features in an image, which ultimately restricts their generalisation capability. This limitation was the primary motivation in our investigation into using shape information to improve the generality of these algorithms. Fuzzy shape-based clustering techniques already consider ring and elliptical profiles in segmentation, though most real objects are neither ring nor elliptically shaped. This paper addresses this issue by introducing a new shape-based algorithm called fuzzy image segmentation of generic shaped clusters (FISG) that incorporates generic shape information into the framework of the fuzzy c-means (FCM) algorithm. Both qualitative and quantitative analyses confirm the superiority of FISG compared to other shape-based fuzzy clustering methods including, Gustafson-Kessel algorithm, ring-shaped, circular shell, c-ellipsoidal shells and elliptic ring-shaped clusters. The new algorithm has also been shown to be application independent so it can be applied in areas such as video object plane segmentation in MPEG-4 based coding
Corrections to Decay in the 2HDM
QCD corrections to the inclusive decay are
investigated within the two - Higgs doublet extension of the standard model
(2HDM). The analysis is performed in the so - called off-resonance region; the
dependence of the obtained results on the choice of the renormalization scale
is examined in details. It is shown that corrections can suppress
the decay width up to times (depending on the
choice of the dilepton invariant mass and the low - energy scale ). As
a result, in the experimentally allowed range of the parameters space, the
relations between the branching ratio and the new physics
parameters are strongly affected. It is found also that though the
renormalization scale dependence of the branching is
significantly reduced, higher order effects in the perturbation theory can
still be nonnegligible.Comment: 16 pages, latex, including 6 figures and 3 table
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