349 research outputs found
New method for measuring azimuthal distributions in nucleus-nucleus collisions
The methods currently used to measure azimuthal distributions of particles in
heavy ion collisions assume that all azimuthal correlations between particles
result from their correlation with the reaction plane. However, other
correlations exist, and it is safe to neglect them only if azimuthal
anisotropies are much larger than 1/sqrt(N), with N the total number of
particles emitted in the collision. This condition is not satisfied at
ultrarelativistic energies. We propose a new method, based on a cumulant
expansion of multiparticle azimuthal correlations, which allows to measure much
smaller values of azimuthal anisotropies, down to 1/N. It is simple to
implement and can be used to measure both integrated and differential flow.
Furthermore, this method automatically eliminates the major systematic errors,
which are due to azimuthal asymmetries in the detector acceptance.Comment: final version (misprints corrected), to be published in Phys.Rev.
Charged Particle Pseudorapidity Distributions in Au+Al, Cu, Au, and U Collisions at 10.8 AGeV/c
We present the results of an analysis of charged particle pseudorapidity
distributions in the central region in collisions of a Au projectile with Al,
Cu, Au, and U targets at an incident energy of 10.8~GeV/c per nucleon. The
pseudorapidity distributions are presented as a function of transverse energy
produced in the target or central pseudorapidity regions. The correlation
between charged multiplicity and transverse energy measured in the central
region, as well as the target and projectile regions is also presented. We give
results for transverse energy per charged particle as a function of
pseudorapidity and centrality.Comment: 31 pages + 12 figures (compressed and uuencoded by uufiles), LATEX,
Submitted to PR
Very Small Strangelets
We study the stability of small strangelets by employing a simple model of
strange matter as a gas of non-interacting fermions confined in a bag. We solve
the Dirac equation and populate the energy levels of the bag one quark at a
time. Our results show that for system parameters such that strange matter is
unbound in bulk, there may still exist strangelets with that are stable
and/or metastable. The lifetime of these strangelets may be too small to detect
in current accelerator experiments, however.Comment: 13 pages, MIT CTP#217
Proton and Pion Production Relative to the Reaction Plane in Au + Au Collisions at AGS Energies
Results are presented of an analysis of proton and charged pion azimuthal
distributions measured with respect to the reaction plane in Au + Au collisions
at a beam momentum of about 11 AGeV/c. The azimuthal anisotropy is studied as a
function of particle rapidity and transverse momentum for different
centralities of the collisions. The triple differential (in rapidity,
transverse momentum, and azimuthal angle) distributions are reconstructed. A
comparison of the results with a previous analysis of charged particle and
transverse energy flow as well as with model predictions is presented.Comment: 23 pages (LaTeX), 12 figure
Two-Proton Correlations from 14.6A GeV/c Si+Pb and 11.5A GeV/c Au+Au Central Collisions
Two-proton correlation functions have been measured in Si+Pb collisions at
14.6A GeV/c and Au+Au collisions at 11.5A GeV/c by the E814/E877 collaboration.
Data are compared with predictions of the transport model RQMD and the source
size is inferred from this comparison. Our analysis shows that, for both
reactions, the characteristic size of the system at freeze-out exceeds the size
of the projectile, suggesting that the fireball created in the collision has
expanded. For Au+Au reactions, the observed centrality dependence of the
two-proton correlation function implies that more central collisions lead to a
larger source sizes.Comment: RevTex, 12 pages, 5 figure
Expanding Paramedicine in the Community (EPIC): study protocol for a randomized controlled trial.
BackgroundThe incidence of chronic diseases, including diabetes mellitus (DM), heart failure (HF) and chronic obstructive pulmonary disease (COPD) is on the rise. The existing health care system must evolve to meet the growing needs of patients with these chronic diseases and reduce the strain on both acute care and hospital-based health care resources. Paramedics are an allied health care resource consisting of highly-trained practitioners who are comfortable working independently and in collaboration with other resources in the out-of-hospital setting. Expanding the paramedic's scope of practice to include community-based care may decrease the utilization of acute care and hospital-based health care resources by patients with chronic disease.Methods/designThis will be a pragmatic, randomized controlled trial comparing a community paramedic intervention to standard of care for patients with one of three chronic diseases. The objective of the trial is to determine whether community paramedics conducting regular home visits, including health assessments and evidence-based treatments, in partnership with primary care physicians and other community based resources, will decrease the rate of hospitalization and emergency department use for patients with DM, HF and COPD. The primary outcome measure will be the rate of hospitalization at one year. Secondary outcomes will include measures of health system utilization, overall health status, and cost-effectiveness of the intervention over the same time period. Outcome measures will be assessed using both Poisson regression and negative binomial regression analyses to assess the primary outcome.DiscussionThe results of this study will be used to inform decisions around the implementation of community paramedic programs. If successful in preventing hospitalizations, it has the ability to be scaled up to other regions, both nationally and internationally. The methods described in this paper will serve as a basis for future work related to this study.Trial registrationClinicalTrials.gov: NCT02034045. Date: 9 January 2014
Quantum corrections for pion correlations involving resonance decays
A method is presented to include quantum corrections into the calculation of
two-pion correlations for the case where particles originate from resonance
decays. The technique uses classical information regarding the space-time
points at which resonances are created. By evaluating a simple thermal model,
the method is compared to semiclassical techniques that assume exponential
decaying resonances moving along classical trajectories. Significant
improvements are noted when the resonance widths are broad as compared to the
temperature.Comment: 9 pages, 4 figure
Boundary and expansion effects on two-pion correlation functions in relativistic heavy-ion collisions
We examine the effects that a confining boundary together with hydrodynamical
expansion play on two-pion distributions in relativistic heavy-ion collisions.
We show that the effects arise from the introduction of further correlations
due both to collective motion and the system's finite size. As is well known,
the former leads to a reduction in the apparent source radius with increasing
average pair momentum K. However, for small K, the presence of the boundary
leads to a decrease of the apparent source radius with decreasing K. These two
competing effects produce a maximum for the effective source radius as a
function of K.Comment: 6 pages, 5 Eps figures, uses RevTeX and epsfi
Lambda-proton correlations in relativistic heavy ion collisions
The prospect of using lambda-proton correlations to extract source sizes in
relativistic heavy ion collisions is investigated. It is found that the strong
interaction induces a large peak in the correlation function that provides more
sensitive source size measurements than two-proton correlations under some
circumstances. The prospect of using lambda-proton correlations to measure the
time lag between lambda and proton emissions is also studied.Comment: 4 pages, 3 figure, revtex style. Two short paragraphs are added at
referees' recommendations. Phys. Rev. Lett. in pres
Baryon phase-space density in heavy-ion collisions
The baryon phase-space density at mid-rapidity from central heavy-ion
collisions is estimated from proton spectra with interferometry and deuteron
coalescence measurements. It is found that the mid-rapidity phase-space density
of baryons is significantly lower at the SPS than the AGS, while those of total
particles (pion + baryon) are comparable. Thermal and chemical equilibrium
model calculations tend to over-estimate the phase-space densities at both
energies.Comment: 5 pages, 2 tables, no figure. RevTeX style. Accepted for publication
in Phys. Rev. C Rapid Communicatio
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