2,054 research outputs found
Spin-dependent energy distribution of B-hadrons from polarized top decays considering the azimuthal correlation rate
In our previous work, we studied the polar distribution of the scaled energy
of bottom-flavored hadrons from polarized top quark decays
, using two different helicity
coordinate systems. Basically, the energy distributions are governed by the
unpolarized, polar and azimuthal rate functions which are related to the
density matrix elements of the decay . Here we
present, for the first time, the analytical expressions for the radiative corrections to the differential azimuthal decay rates
of the partonic process in two helicity
systems, which are needed to study the azimuthal distribution of the energy
spectrum of the B-hadron produced in polarized top quark decays. Our
predictions of the hadron energy distributions enable us to deepen our
knowledge of the hadronization process and to determine the polarization states
of top quarks
Heavy quark fragmentation functions at next-to-leading perturbative QCD
It is well-known that the dominant mechanism to produce hadronic bound states
with large transverse momentum is fragmentation. This mechanism is described by
the fragmentation functions (FFs) which are the universal and
process-independent functions. Here, we review the perturbative FFs formalism
as an appropriate tool for studying these hadronization processes and detail
the extension of this formalism at next-to-leading order (NLO). Using the
Suzuki's model, we calculate the perturbative QCD FF for a heavy quark to
fragment into a S-wave heavy meson at NLO. As an example, we study the LO and
NLO FFs for a charm quark to split into the S-wave -meson and compare our
analytic results both with experimental data and well-known phenomenological
models
How Should Governments Address High Levels of Natural Radiation and Radon--Lessons from the Chernobyl Nuclear Accident and Ramsar, Iran
The authors discuss the high levels of natural background radiation in Ramsar, Iran, and offer data indicating that this has had little effect on the health of Ramsar\u27s inhabitants. The authors then examine the implications their research could have for public health policy
Indirect search for light charged Higgs bosons through the dominant semileptonic decays of top quark
In this work we introduce a new channel to indirect search for the light
charged Higgs bosons, which are predicted in several extensions of the standard
model (SM) such as the two-Higgs-doublet models (2HDMs). We calculate the
QCD radiative corrections to the energy distribution of
bottom- and charmed-flavored hadrons () produced in the dominant decays of
the polarized top quark in the 2HDM, i.e. . %This analysis is studied in a
specific helicity coordinate system where the polarization vector of the top
quark is evaluated with respect to the momentum direction of the bottom quark.
Generally, the energy distribution of hadrons is governed by the unpolarized
rate and the polar and the azimuthal correlation functions which are related to
the density matrix elements of the decay . In our
proposed channel, any deviation of the -meson energy spectrum from its
corresponding SM predictions can be considered as a signal for the existence of
charged Higgs at the LHC. We also calculate, for the first time, the azimuthal
correlation rate at next-to-leading order which vanishes at the
Born level.Comment: 10 pages, 5 figures, published in NPB 932 (2018) 50
Protective role of cyclosporine on the model simulated the rotational nodal arrhythmia (AVNRT) by using extracellular field potential recordings of isolated atrioventricular-node of rabbit
Introduction: Recent studies have shown acute cardioprotective effects of cyclosporine. The aim of the present study was to determine the protective role of cyclosporine on the model simulated the rotational nodal arrhythmia (AVNRT) by using extracellular field potential recordings of isolated atrioventricular-node (AV-node) of rabbit. Methods: This study was performed on isolated double-perfused AV-node of male New Zealand rabbits (1.5-2.5 kg) in one group (n=7). Basic and rate-dependent stimulation protocols (recovery, facilitation, fatigue) and arrhythmia threshold (index of refractoriness) and % Gap incidence were measured for assessment of electrophysiological properties of the AV- node. All stimulation protocols were repeated in control step and in the presence of various cumulative concentrations of cyclosporine (0.5 - 10 μm). Results: Cyclosporine prolonged the effective refractory period from 114.3±7.9 to 142±7.3 msec at the concentration of 10 μm. It also prolonged the functional refractory period from 162±3.3 to 178.6±5 msec and increased the time of Wenckebach at the concentrations of 5 - 10 μM. Various concentrations of cyclosporine increased fatigue and reached a significant level at 10 μm. Gap incidence was 82%, 16.6% and 20% in the control and treatments with 0.5 and 10 μm of cyclosporine, respectively. Conclusion: Block of MPTP by cyclosporine caused inhibition of basic and rate-dependent properties of atrioventricular node. Cyclosporine, by raising the threshold of arrhythmia, could be possibly considered as an anti- AVNRT drug
Heat transfer at the interface of graphene nanoribbons with different relative orientations and gaps
Because of their high thermal conductivity, graphene nanoribbons (GNRs) can be employed as fillers to enhance the thermal transfer properties of composite materials, such as polymer-based ones. However, when the filler loading is higher than the geometric percolation threshold, the interfacial thermal resistance between adjacent GNRs may significantly limit the overall thermal transfer through a network of fillers. In this article, reverse non-equilibrium molecular dynamics is used to investigate the impact of the relative orientation (i.e., horizontal and vertical overlap, interplanar spacing and angular displacement) of couples of GNRs on their interfacial thermal resistance. Based on the simulation results, we propose an empirical correlation between the thermal resistance at the interface of adjacent GNRs and their main geometrical parameters, namely the normalized projected overlap and average interplanar spacing. The reported correlation can be beneficial for speeding up bottom-up approaches to the multiscale analysis of the thermal properties of composite materials, particularly when thermally conductive fillers create percolating pathways
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