Nicolas Borghini
Bielefeld University
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Publication
Featured researches published by Nicolas Borghini.
Physical Review C | 2001
Nicolas Borghini; Phuong Mai Dinh; Jean-Yves Ollitrault
We present a new method for analyzing directed and elliptic flow in heavy-ion collisions. Unlike standard methods, it separates the contribution of flow to azimuthal correlations from contributions due to other effects. The separation relies on a cumulant expansion of multiparticle azimuthal correlations, and includes corrections for detector inefficiencies. This new method allows the measurement of the flow of identified particles in narrow phase-space regions, and can be used in every regime, from intermediate to ultrarelativistic energies.
Physical Review C | 2001
Nicolas Borghini; Phuong Mai Dinh; Jean-Yves Ollitrault
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
Physics Letters B | 2005
Rajeev S. Bhalerao; Jean-Paul Blaizot; Nicolas Borghini; Jean-Yves Ollitrault
1/\sqrt{N},
Physics Letters B | 2006
Nicolas Borghini; Jean-Yves Ollitrault
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 measurements of much smaller values of azimuthal anisotropies, down to
Physical Review C | 2000
Nicolas Borghini; Phuong Mai Dinh; Jean-Yves Ollitrault
1/N.
Physical Review D | 2001
Nicolas Borghini; Yves Gouverneur; Michel H. G. Tytgat
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.
Physics Letters B | 2000
Phuong Mai Dinh; Nicolas Borghini; Jean-Yves Ollitrault
Abstract We argue that RHIC data, in particular those on the anisotropic flow coefficients v 2 and v 4 , suggest that the matter produced in the early stages of nucleus–nucleus collisions is incompletely thermalized. We interpret the parameter ( 1 / S ) ( d N / d y ) , where S is the transverse area of the collision zone and d N / d y the multiplicity density, as an indicator of the number of collisions per particle at the time when elliptic flow is established, and hence as a measure of the degree of equilibration. This number serves as a control parameter which can be varied experimentally by changing the system size, the centrality or the beam energy. We provide predictions for Cu–Cu collisions at RHIC as well as for Pb–Pb collisions at the LHC.
Physical Review C | 2002
Nicolas Borghini; Phuong Mai Dinh; Jean-Yves Ollitrault; A. M. Poskanzer; Sergei A. Voloshin
Abstract If the matter produced in ultrarelativistic heavy-ion collisions reaches thermal equilibrium, its subsequent evolution follows the laws of ideal fluid dynamics. We show that general predictions can be made on this basis alone, irrespective of the details of the hydrodynamical model. We derive several scaling rules for momentum spectra and anisotropic flow (in particular the elliptic flow, v 2 , and the hexadecupole flow, v 4 ) of identified particles. Comparison with existing data is briefly discussed, and qualitative predictions are made for LHC.
Journal of Physics G | 2000
Nicolas Borghini; W N Cottingham; R. Vinh Mau
Several heavy ion experiments at SPS have measured azimuthal distributions of particles with respect to the reaction plane. These distributions are deduced from two-particle azimuthal correlations under the assumption that they result solely from correlations with the reaction plane. In this paper, we investigate other sources of azimuthal correlations: transverse momentum conservation, which produces back-to-back correlations, resonance decays, HBT correlations and final state interactions. These correlations increase with impact parameter: most of them vary with the multiplicity N like 1/N. When they are taken into account, the experimental results of the NA49 collaboration at SPS are significantly modified. These correlations might also explain an important fraction of the pion directed flow observed by WA98. Data should be reanalyzed taking into account carefully these non--flow correlations.
European Physical Journal C | 2012
Nicolas Borghini; Clément Gombeaud
The restrictions imposed by anomaly cancellation on the chiral fermion content of nonsupersymmetric gauge theories based on various groups are studied in spacetime dimension D = 6, 8, and 10. In particular, we show that the only mathematically consistent chiral SU(5) theory in D = 6 contains three nonidentical generations.