5,591 research outputs found
Observation of hypersonic phononic crystal effects in porous silicon superlattices
Brillouin light scattering experiments were carried out on porous silicon superlattices with modulation wavelengths in the range 37–167 nm. Phonon frequencies deduced from the Brillouin spectra show good agreement with those obtained from an elastic continuum model for a system with one-dimensional periodicity. Evidence for the existence of a hypersonic phononic bandgap and zone-folded longitudinal acoustic phonons is reported
New physics effects to the lepton polarizations in the B -> K l^+ l^- decay
Using the general, model independent form of the effective Hamiltonian, the
general expressions of the longitudinal, normal and transversal polarization
asymmetries for (l^-) and (l^+) and combinations of them for the exclusive (B
-> K l^+ l^-) decay are found. The sensitivity of lepton polarizations and
their combinations on new Wilson coefficients are studied. It is found that
there exist regions of Wilson coefficients for which the branching ratio
coincides with the Standard Model result while the lepton polarizations differ
substantially from the standard model prediction. Hence, studying lepton
polarization in these regions of new Wilson coefficients can serve as a
promising tool for establishing new physics beyond the Standard Model.Comment: 18 pp, 14 figures (postscript formatted), LaTex formatte
Double-Lepton Polarization Asymmetries and Branching Ratio of the B\rar \gamma l^+ l^- transition in Universal Extra Dimension
We study the radiative dileptonic B \rar \gamma l^+ l^- transition in the
presence of a universal extra dimension in the Applequist-Cheng-Dobrescu model.
In particular, using the corresponding form factors calculated via light cone
QCD sum rules, we analyze the branching ratio and double lepton polarization
asymmetries related to this channel and compare the results with the
predictions of the standard model. We show how the results deviate from
predictions of the standard model at lower values of the compactification
factor () of extra dimension.Comment: 20 Pages and 8 Figure
Lepton polarization correlations in
In this work we will study the polarizations of both leptons () in the
decay channel . In the case of the dileptonic inclusive
decay , where apart from the polarization asymmetries
of single lepton , one can also observe the polarization asymmetries of
both leptons simultaneously. If this sort of measurement is possible then we
can have, apart from decay rate, FB asymmetry and the six single lepton
polarization asymmetries (three each for and ), nine more
double polarization asymmetries. This will give us a very useful tool in more
strict testing of SM and the physics beyond. We discuss the double polarization
asymmetries of leptons in the decay mode within
the SM and the Minimal Supersymmetric extensions of it.Comment: 21 pages, 21 figures; version to match paper to appear in PR
Strong Coupling Constants of Decuplet Baryons with Vector Mesons
We provide a comprehensive study of strong coupling constants of decuplet
baryons with light nonet vector mesons in the framework of light cone QCD sum
rules. Using the symmetry arguments, we argue that all coupling constants
entering the calculations can be expressed in terms of only one invariant
function even if the symmetry breaking effects are taken into
account. We estimate the order of symmetry violations, which are
automatically considered by the employed approach.Comment: 19 Pages, 4 Figures and 5 Table
Shot Noise in Magnetic Tunnel Junctions: Evidence for Sequential Tunneling
We report the experimental observation of sub-Poissonian shot noise in single
magnetic tunnel junctions, indicating the importance of tunneling via impurity
levels inside the tunnel barrier. For junctions with weak zero-bias anomaly in
conductance, the Fano factor (normalized shot noise) depends on the magnetic
configuration being enhanced for antiparallel alignment of the ferromagnetic
electrodes. We propose a model of sequential tunneling through nonmagnetic and
paramagnetic impurity levels inside the tunnel barrier to qualitatively explain
the observations.Comment: 5 pages, 5 figure
The CP asymmetry for B--> K^* l^+ l^- decay in the general two Higgs doublet model
We study CP asymmetry for the exclusive decay B --> K^* l^+ l^- in the two
Higgs doublet model with three level flavor changing neutral currents (model
III). We analyse the dependency of this quantity to the new phase coming from
the complex Yukawa couplings in the theory and we find that there exist a
considerable CP violation for the relevant process. Further, we see that the
sign of the Wilson coefficient C_7^{eff} can be determined by fixing dilepton
mass. Therefore, the future measurements of CP asymmetry for B --> K^* l^+ l^-
decay will give a powerful information about the sign of Wilson coefficient
C_{7}^{eff} and the new physics beyond the SM.Comment: 22 pages, 8 figure
The Forward-Backward Asymmetry in the Decay
Using the most general effective Hamiltonian comprising scalar,vector and
tensor type interactions, we have written the branching ratio, the
forward-backward (FB) asymmetry and the normalized FB asymmetry as functions of
the new Wilson coefficients. It is found that the branching ratio depends on
all new coefficients,but the dependence of asymmetries on coefficients could be
analyzed only for one Wilson coefficient.Comment: 14 pp, 7 figure
Pseudoscalar--meson decuplet--baryon coupling constants in light cone QCD
Taking into account the breaking effects, the strong coupling
constants of the , and mesons with decuplet baryons are
calculated within light cone QCD sum rules method. It is shown that all
coupling constants, even in the case of breaking, are described in
terms of only one universal function. It is shown that for transition violation of symmetry is very large
and for other channels when symmetry is violated, its maximum value
constitutes .Comment: 17 Pages, one Figure and 3 Table
- …