775 research outputs found
Phase space constraints and statistical jet studies in heavy-ion collisions
The effect of the correlation induced by global momentum conservation on the
two-particle distribution in nucleus-nucleus collisions is discussed, with a
focus on the generic case of collisions with a non-vanishing impact parameter.Comment: 5 pages, invited talk at the RHIC & AGS Annual Users' Meeting,
Brookhaven Nat. Lab. (USA) and at the EPS HEP 2007 Conference, Manchester
(UK
Analysis of directed flow from three-particle correlations
We present a new method for analysing directed flow, based on a
three-particle azimuthal correlation. It is less biased by nonflow correlations
than two-particle methods, and requires less statistics than four-particle
methods. It is illustrated on NA49 data.Comment: Contribution to Quark Matter 2002, Nantes, July 18-24, 200
Elliptic flow in proton-proton collisions at 7 TeV
The angular correlations measured in proton-proton collisions at 7 TeV are
decomposed into contributions from back to back emission and elliptic flow.
Modeling the dominant term in the correlation functions as a momentum
conservation effect or as an effect of the initial transverse velocity of the
source, the remaining elliptic flow component can be estimated. The elliptic
flow coefficient extracted from the CMS Collaboration data is 0.04-0.08. No
additional small-angle, ridge-like correlations are needed to explain the
experimental data
Anisotropic flow from Lee-Yang zeroes: a practical guide
We present a new method to analyze anisotropic flow from the genuine
correlation among a large number of particles, focusing on the practical
implementation of the method.Comment: 4 pages; contribution to Quark Matter 2004, Oakland, January 11-17,
200
Improved quality check procedures of XBT profiles in MFS-VOS
International audienceSippican T4/DB XBT profiles, collected in the framework of Mediterranean Forecasting System ? Toward Environmental Prediction, are analysed, namely the possible influence of launching position height, ship speed and of probes' characteristics. Comparison of XBT vs CTD profiles have suggested some changes in quality control procedures and, more important, in the values of fall rate coefficients customised for the Mediterranean. The effects of these new procedures on the overall uncertainty on depth and on temperature measurements are estimated
Factors affecting the quality of XBT data - results of analyses on profiles from the Western Mediterranean Sea
EXpendable BathyThermograph (XBT) temperature profiles collected in the framework of the Mediterranean Forecasting System - Toward Environmental Prediction (MFS-TEP) project have been compared with CTD measurements. New procedures for the quality control of recorded values have been developed and checked. Some sources of possible uncertainties and errors, such as the response time of the apparatus (XBT probe, thermistor and readout chain), or the influence of initial conditions are also analysed. To deal with the high homogeneity of Mediterranean waters, a new technique to compute the fall rate coefficients, that give a better reproduction of the depth of thermal structures, has been proposed, and new customized coefficients have been calculated. After the application of a temperature correction, the overall uncertainties in depth and in temperature measurements have been estimated
Jet multiplicities as the QGP thermometer
It is proposed to use the energy behavior of mean multiplicities of jets
propagating in a nuclear medium as the thermometer of this medium during the
collision phases. The qualitative effects are demonstrated in the framework of
the fixed coupling QCD with account of jet quenching.Comment: Modify version of hep-ph/0509344, 3 figure
The mechanical design of a gas supply and mixing system for the AMS-02 particle detector onboard the international space station
Abstract The Alpha Magnetic Spectrometer 02 is a particle physics experiment that will search for antimatter, dark matter, and measure cosmic rays in space aboard the International space station for 3 years . It is comprised of an array of sub-detectors: Transition Radiation Detector (TRD); Time of Flight detector; Anti-Coincidence Counter; Silicon Tracker; Ring Imaging Cherenkov counter; Electromagnetic Calorimeter and requires the operation of a cryogenic super conducting magnet at its core. It is built by an international collaboration of more than 100 scientists spread all over Europe, USA and the far East. The TRD that is located above the Cryomagnet and Upper Time of Flight, consists of several layers of straw modules interleaved with a fiber fleece material and arranged in a conical octagon structure built out of a carbon fiber/aluminum honeycomb sandwich. A charged particle traversing this detector produces characteristic electromagnetic radiation in each layer that is measured in the gas filled array of straw tubes. From this, the mass and momentum of the particle can be measured provided the tubes are filled with the proper gas mixture. The TRD gas supply stores 50 kg of gas corresponding to 8100 l Xe and 2000 l CO2 at 1 atm , filters, mixes, recirculates, and purges a daily supply of Xe/CO2 (80%/20%) gaseous mixture, thus supplying the TRD with clean, mixed gas for the 3-year ISS mission. Designing and building this reliable, weight optimised system to withstand launch loads and the harsh space environment presented a formidable engineering challenge. Adding to the complexity of the system was that a flexible valve/pump arrangement was needed to control mixture ratio, circulation flow and pressure, and purging. These studies are presented in the paper
Effect of flow fluctuations and nonflow on elliptic flow methods
We discuss how the different estimates of elliptic flow are influenced by
flow fluctuations and nonflow effects. It is explained why the event-plane
method yields estimates between the two-particle correlation methods and the
multiparticle correlation methods. It is argued that nonflow effects and
fluctuations cannot be disentangled without other assumptions. However, we
provide equations where, with reasonable assumptions about fluctuations and
nonflow, all measured values of elliptic flow converge to a unique mean
v_{2,PP} elliptic flow in the participant plane and, with a Gaussian assumption
on eccentricity fluctuations, can be converted to the mean v_{2,RP} in the
reaction plane. Thus, the 20% spread in observed elliptic flow measurements
from different analysis methods is no longer mysterious.Comment: one typo in Table I correcte
Buda-Lund hydro model for ellipsoidally symmetric fireballs and the elliptic flow at RHIC
The ellipsoidally symmetric extension of Buda-Lund hydrodynamic model is
shown here to yield a natural description of the pseudorapidity dependence of
the elliptic flow , as determined recently by the PHOBOS experiment
for Au+Au collisions at and 200 GeV. With the same set of
parameters, the Buda-Lund model describes also the transverse momentum
dependence of of identified particles at mid-rapidity. The results
confirm the indication for quark deconfinement in Au+Au collisions at RHIC,
obtained from a successful Buda-Lund hydro model fit to the single particle
spectra and two-particle correlation data, as measured by the BRAHMS, PHOBOS,
PHENIX and STAR collaborations.Comment: 16 pages, 2 figures, 1 table added, discussion extended and an
important misprint in the caption of Fig. 1 is correcte
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