22,919 research outputs found
Contribution of through the QCD anomaly in exclusive decays and
We compute the decay rates for the exclusive decays and in a QCD-improved factorization framework by including the
contribution from the process through
the QCD anomaly. This method provides an alternative estimate of the
contribution to these decays as
compared to the one using the intrinsic charm content of the
and mesons determined through the decays . The resulting branching ratios are compared with the CLEO
data on and
and predictions are made for the rest.Comment: 16 pages including 4 postscript figures; uses epsfig. The most recent
branching ratios from CLEO, ref. [5], are taken into account. The theory part
is unchange
Effect of resonance decays on hadron elliptic flows
The influence of resonance decays on the elliptic flows of stable hadrons is
studied in the quark coalescence model. Although difference between the
elliptic flow of pions from resonance decays, except the rho meson, and that of
directly produced pions is appreciable, those for other stable hadrons are
small. Since there are more pions from the decays of rho mesons than from other
resonances, including resonance decays can only account partially the deviation
of final pion elliptic flow from the observed scaling of hadron elliptic flows,
i.e., the hadron elliptic flow per quark is the same at same transverse
momentum per quark. The remaining deviation can be explained by including the
effect due to the quark momentum distribution inside hadrons.Comment: 13 pages and 5 figures, version pubblished in PRC, updated references
and figure
Avalanche-Induced Current Enhancement in Semiconducting Carbon Nanotubes
Semiconducting carbon nanotubes under high electric field stress (~10 V/um)
display a striking, exponential current increase due to avalanche generation of
free electrons and holes. Unlike in other materials, the avalanche process in
such 1D quantum wires involves access to the third sub-band, is insensitive to
temperature, but strongly dependent on diameter ~exp(-1/d^2). Comparison with a
theoretical model yields a novel approach to obtain the inelastic optical
phonon emission length, L_OP,ems ~ 15d nm. The combined results underscore the
importance of multi-band transport in 1D molecular wires
Lymphotoxins and cytomegalovirus cooperatively induce interferon-beta, establishing host-virus détente
Tumor necrosis factor (TNF)-related cytokines regulate cell death and survival and provide strong selective pressures for viruses, such as cytomegalovirus (CMV), to evolve counterstrategies in order to persist in immune-competent hosts. Signaling by the lymphotoxin (LT)-β receptor or TNF receptor-1, but not Fas or TRAIL receptors, inhibits the cytopathicity and replication of human CMV by a nonapoptotic, reversible process that requires nuclear factor κB (NF-κB)-dependent induction of interferon-β (IFN-β). Efficient induction of IFN-β requires virus infection and LT signaling, demonstrating the need for both host and viral factors in the curtailment of viral replication without cellular elimination. LTα-deficient mice and LTβR-Fc transgenic mice were profoundly susceptible to murine CMV infection. Together, these results reveal an essential and conserved role for LTs in establishing host defense to CMV
Identified Hadrons and Jet Chemistry for p+p and Au+Au Collisions at RHIC
The study of hadron spectra at high in p+p collisions provides a good
test of perturbative quantum chromo-dynamic calculations (pQCD) and baseline
for measurements of nuclear modification factors in Au+Au collisions. Using
events triggered by the Barrel Electro-Magnetic Calorimeter, identified charged
hadron transverse momentum () spectra are measured up to 15 GeV/ at
mid-rapidity ( 0.5) and neutral kaon spectra up to 12
GeV/ in p + p collisions at = 200 GeV. The particle ratios
of , and / in p + p
collisions are shown and compared with next-to-leading order pQCD calculations.
In central Au+Au collisions, we report nuclear modification factors ()
for pion, kaon, proton and and discuss several model calculations:
color-charge dependence of jet quenching and jet conversion. Finally,
centrality dependence of at high ( 5.5 GeV/c) for kaon are
compared with that of pion in Au + Au collisions at 200 GeV.Comment: 6 pages, 4 figures, SQM 2009 contributio
Transverse hydrodynamics with sudden hadronization -- production of strangeness
We consider a physical scenario for ultra-relativistic heavy-ion collisions
where, at the early stage, only transverse degrees of freedom of partons are
thermalized, while the longitudinal motion is described by free streaming. When
the energy density of the partonic system drops to a certain critical value,
the partons hadronize and the newly formed hadronic system freezes out. This
sudden change is described with the help of the Landau matching conditions
followed by the simulations done with THERMINATOR. The proposed scenario
reproduces well the transverse-momentum spectra, the elliptic flow coefficient
v2, and the HBT radii of pions and kaons studied at RHIC (Au+Au collisions at
the top beam energy). It also reproduces quite well the transverse-momentum
spectra of hyperons.Comment: talk presented by WF at the Strangeness in Quark Matter Conference,
Buzios, Brazil, Sept. 27 - oct. 2, 200
Forty-Four Pass Fibre Optic Loop for Improving the Sensitivity of Surface Plasmon Resonance Sensors
A forty-four pass fibre optic surface plasmon resonance sensor that enhances
detection sensitivity according to the number of passes is demonstrated for the
first time. The technique employs a fibre optic recirculation loop that passes
the detection spot forty- four times, thus enhancing sensitivity by a factor of
forty-four. Presently, the total number of passes is limited by the onset of
lasing action of the recirculation loop. This technique offers a significant
sensitivity improvement for various types of plasmon resonance sensors that may
be used in chemical and biomolecule detections.Comment: Submitted for publication; patent disclosure submitte
Constraining properties of neutron stars with heavy-ion reactions in terrestrial laboratories
Heavy-ion reactions provide a unique means to investigate the equation of
state (EOS) of neutron-rich nuclear matter, especially the density dependence
of the nuclear symmetry energy . The latter plays an important
role in understanding many key issues in both nuclear physics and astrophysics.
Recent analyses of heavy-ion reactions have already put a stringent constraint
on the around the saturation density. This subsequently allowed
us to constrain significantly the radii and cooling mechanisms of neutron stars
as well as the possible changing rate of the gravitational constant G.Comment: 6 pages. Talk given at the Nuclear Physics in Astrophysics III,
Dresden, Germany, March 26-31, 2007. To appear in a special volume of J. of
Phys.
New Developments in MadGraph/MadEvent
We here present some recent developments of MadGraph/MadEvent since the
latest published version, 4.0. These developments include: Jet matching with
Pythia parton showers for both Standard Model and Beyond the Standard Model
processes, decay chain functionality, decay width calculation and decay
simulation, process generation for the Grid, a package for calculation of
quarkonium amplitudes, calculation of Matrix Element weights for experimental
events, automatic dipole subtraction for next-to-leading order calculations,
and an interface to FeynRules, a package for automatic calculation of Feynman
rules and model files from the Lagrangian of any New Physics model.Comment: 6 pages, 3 figures. Plenary talk given at SUSY08, Seoul, South Korea,
June 2008. To appear in the proceeding
Directed flow of neutral strange particles at AGS
Directed flow of neutral strange particles in heavy ion collisions at AGS is
studied in the ART transport model. Using a lambda mean-field potential which
is 2/3 of that for a nucleon as predicted by the constituent quark model,
lambdas are found to flow with protons but with a smaller flow parameter as
observed in experiments. For kaons, their repulsive potential, which is
calculated from the impulse approximation using the measured kaon-nucleon
scattering length, leads to a smaller anti-flow than that shown in the
preliminary E895 data. Implications of this discrepancy are discussed.Comment: 6 pages, 2 figure
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