229 research outputs found
Nonfactorization and the decays and
In six chosen scenarios for the dependence of the form factors involved
in transition, we have determined the allowed domain
of and from the experimentally measured
ratios and in a scheme that uses the value of the phenomenological parameter and includes nonfactorized
contribution. We find that the experimentally measured values of and
from semileptonic decays of favor solutions which have significant
nonfactorized contribution, and, in particular, favors solutions in
scenarios where is either flat or decreasing with .Comment: 15 pages, Latex, four figure (available on request)
Nonfactorization and Color-Suppressed Decays
Using value of the parameter but including a modest
nonfactorized amplitude, we show that it is possible to understand all data,
including polarization, for color-suppressed
decays in all commonly used models of form factors. We show that for decay one can define an effective , which is process-dependent and,
in general, complex; but it is not possible to define an effective for
decay. We also explain why nonfactorized amplitudes do not
play a significant role in color-favored B decays.Comment: 13 pages, Latex, one figure (not included
Exclusive processes in electron - ion collisions
The exclusive processes in electron-ion () interactions are an important
tool to investigate the QCD dynamics at high energies as they are in general
driven by the gluon content of the target, which is strongly subject to parton
saturation effects. In this paper we compute the cross sections for the
exclusive vector meson production as well as the deeply virtual Compton
scattering (DVCS) relying on the color dipole approach and considering the
numerical solution of the Balitsky-Kovchegov equation including running
coupling corrections (rcBK). The production cross sections obtained with the
rcBK solution and bCGC parametrization are very similar, the former being
slightly larger.Comment: 6 pages, 4 figure
Software Company Centric Roles, Responsibilities and Higher Positions of Software Tester in Software Development Life Cycle
ABSTRACT: Traditional Software Development Life Cycle is still most popular and used in many software companies. During each phase specialist team member/members are used to fulfill the requirement of user. In the same way the software Testers are also used at various phases depends on the company's strategies. So this paper is largely focuses on the Software Testers complete environment including its roles, responsibilities and future higher position that pusses by him/her
Probing the Color Glass Condensate in an electron-ion collider
Perturbative Quantum Chromodynamics (pQCD) predicts that the small- gluons
in a hadron wavefunction should form a Color Glass Condensate (CGC),
characterized by a saturation scale which is energy and atomic
number dependent. In this paper we study the predictions of CGC physics for
electron - ion collisions at high energies. We consider that the nucleus at
high energies acts as an amplifier of the physics of high parton densities and
estimate the nuclear structure function , as well as the
longitudinal and charm contributions, using a generalization for nuclear
targets of the Iancu-Itakura-Munier model which describes the HERA data
quite well. Moreover, we investigate the behavior of the logarithmic slopes of
the total and longitudinal structure functions in the kinematical region of the
future electron - ion collider eRHIC.Comment: 18 pages, 9 figures. Version to be published in the European Physical
Journal
Long Distance Contribution to and Implications for and
We estimate the long distance (LD) contribution to the magnetic part of the
transition using the Vector Meson Dominance approximation
. We find that this contribution may be significantly
larger than the short distance (SD) contribution to and could
possibly saturate the present experimental upper bound on the decay rate, eV. For the decay , which is driven by as well, we obtain an upper bound on the branching ratio from . Barring the possibility that the Quantum Chromodynamics
coefficient be much smaller than 1, also implies the approximate relation .
This relation agrees quantitatively with a recent independent estimate of the
l.h.s. by Deshpande et al., confirming that the LD contributions to are small. We find that these amount to an increase of in
the magnitude of the transition amplitude, relative to the SD
contribution alone.Comment: 16 pages, LaTeX fil
Standard Model CP violation in Polarised b->d l^+ l^-
In the standard model, we study CP violating rate asymmetries in the decay
b->d l^+ l^- when one of the leptons is polarised. We find an asymmetry of (5
-- 15)% in the polarised decay spectrum which is comparable to known results
for the unpolarised case. In the kinematic region separating the rho-omega and
resonances, which is also theoretically cleanest, the polarised
contribution to the asymmetry is larger than the unpolarised results. In order
to observe a 3 sigma signal for direct CP violation in the polarised spectrum,
assuming 100% efficiency, about 10^10 pairs are required at a B
factory. Our results indicate an asymmetric contribution from the individual
polarisation states to the unpolarised CP asymmetry. Taking advantage of this,
one can attribute any new physics to be most sensitive to a specific
polarisation state.Comment: 23 pages, one reference adde
The lifetime of B_c-meson and some relevant problems
The lifetime of the B_c-meson is estimated with consistent considerations on
all of the heavy mesons () and the double
heavy meson B_c. In the estimate, the framework, where the non-spectator
effects for nonleptonic decays are taken into account properly, is adopted, and
the parameters needed to be fixed are treated carefully and determined by
fitting the available data. The bound-state effects in it are also considered.
We find that in decays of the meson B_c, the QCD correction terms of the
penguin diagrams and the main component terms c_1O_1, c_2O_2 of the effective
interaction Lagrangian have direct interference that causes an enhancement
about 3 ~ 4% in the total width of the B_c meson.Comment: 27 pages, 0 figur
Effective Lagrangian for and Vertices in the mSUGRA model
Complete expressions of the and vertices are
derived in the framework of supersymmetry with minimal flavor violation. With
the minimal supergravity (mSUGRA) model, a numerical analysis of the
supersymmetric contributions to the Wilson Coefficients at the weak scale is
presented.Comment: 12 pages + 7 ps figures, Late
Nuclear shadowing in Glauber-Gribov theory with Q2-evolution
We consider deep inelastic scattering off nuclei in the Regge limit within
the Glauber-Gribov model. Using unitarized parton distribution functions for
the proton, we find sizeable shadowing effects on the nuclear total and
longitudinal structure functions, and , in the low-x limit.
Extending a fan-diagram analysis for the large-mass region of coherent
diffraction off nuclei to high Q2, we also find significant shadowing effects
in this kinematical regime. Finally, we discuss shortcomings of our approach
and possible extensions of the model to other kinematical regimes.Comment: 16 pages, 9 figure
- …