32,294 research outputs found
Partonic effects on higher-order anisotropic flows in relativistic heavy-ion collisions
Higher-order anisotropic flows and in heavy ion collisions at
the Relativistic Heavy Ion Collider are studied in a multiphase transport model
that has previously been used successfully for describing the elliptic flow
in these collisions. We find that the same parton scattering cross
section of about 10 \textrm{mb} used in explaining the measured can also
reproduce the recent data on and from Au + Au collisions at
\textrm{AGeV}. It is further found that the is a more
sensitive probe of the initial partonic dynamics in these collisions than
. Moreover, higher-order parton anisotropic flows are nonnegligible and
satisfy the scaling relation , which
leads naturally to the observed similar scaling relation among hadron
anisotropic flows when the coalescence model is used to describe hadron
production from the partonic matter.Comment: 5 pages, 3 figures, version to appear in PRC as a Rapid Communicatio
A numerical study of diffusive shock acceleration of cosmic rays in supernova shocks
The evolution of the energy spectrum of cosmic rays accelerated by the first order Fermi mechanism, by a supernova remnant shock wave, including adiabatic deceleration effects behind the front, is carried out by means of a time-dependent numerical code. The calculations apply to the adiabatic stage (or Sedov stage) of the supernova explosion, and the energetic particle spectrum is calculated in the test particle limit (i.e., the back reaction of the cosmic rays on the flow is not included). The particles are injected mono-energetically at the shock. The radial distribution, The radial distribution, and the spectrum of the accelerated and decelerated particles is shown
First axion dark matter search with toroidal geometry
We firstly report an axion haloscope search with toroidal geometry. In this
pioneering search, we exclude the axion-photon coupling
down to about GeV over the axion mass range from 24.7
to 29.1 eV at a 95\% confidence level. The prospects for axion dark matter
searches with larger scale toroidal geometry are also considered.Comment: 5 pages, 5 figures, 1 table and to appear in PRD-R
Hadron production from quark coalescence and jet fragmentation in intermediate energy collisions at RHIC
Transverse momentum spectra of pions, protons and antiprotons in Au+Au
collisions at intermediate RHIC energy of GeV are studied in
a model that includes both quark coalescence from the dense partonic matter and
fragmentation of the quenched perturbative minijet partons. The resulting
baryon to meson ratio at intermediate transverse momenta is predicted to be
larger than that seen in experiments at higher center of mass energies.Comment: 6 pages, 2 figures. Figures replaced to differentially address the
high-pT behavior of baryon versus antibaryon to meson ratio
The muon g-2 discrepancy: errors or new physics?
After a brief review of the muon g-2 status, we discuss hypothetical errors
in the Standard Model prediction that could explain the present discrepancy
with the experimental value. None of them looks likely. In particular, an
hypothetical increase of the hadroproduction cross section in low-energy e^+e^-
collisions could bridge the muon g-2 discrepancy, but is shown to be unlikely
in view of current experimental error estimates. If, nonetheless, this turns
out to be the explanation of the discrepancy, then the 95% CL upper bound on
the Higgs boson mass is reduced to about 130 GeV which, in conjunction with the
experimental 114.4 GeV 95% CL lower bound, leaves a narrow window for the mass
of this fundamental particle.Comment: 4 pages. Invited talk at 16th International Conference on
Supersymmetry and the Unification of Fundamental Interactions (SUSY08), June
16-21 2008, Seoul, Kore
LFV in semileptonic decays and conversion in nuclei in SUSY-seesaw
Here we review the main results of LFV in the semileptonic tau decays (), (), and () as well as in conversion in nuclei within SUSY-seesaw scenarios,
and compare our predictions with the present experimental boundsComment: Talk given by M. J. Herrero in SUSY08 conference, Seou
Application of fracture mechanics and half-cycle method to the prediction of fatigue life of B-52 aircraft pylon components
Stress intensity levels at various parts of the NASA B-52 carrier aircraft pylon were examined for the case when the pylon store was the space shuttle solid rocket booster drop test vehicle. Eight critical stress points were selected for the pylon fatigue analysis. Using fracture mechanics and the half-cycle theory (directly or indirectly) for the calculations of fatigue-crack growth ,the remaining fatigue life (number of flights left) was estimated for each critical part. It was found that the two rear hooks had relatively short fatigue life and that the front hook had the shortest fatigue life of all the parts analyzed. The rest of the pylon parts were found to be noncritical because of their extremely long fatigue life associated with the low operational stress levels
Kinetic Roughening in Deposition with Suppressed Screening
Models of irreversible surface deposition of k-mers on a linear lattice, with
screening suppressed by disallowing overhangs blocking large gaps, are studied
by extensive Monte Carlo simulations of the temporal and size dependence of the
growing interface width. Despite earlier finding that for such models the
deposit density tends to increase away from the substrate, our numerical
results place them clearly within the standard KPZ universality class.Comment: nine pages, plain TeX (4 figures not included
- …