How accurately can flow be measured in nucleus-nucleus collisions?

doi:10.1016/0375-9474(92)90204-W

Nuclear Physics A

Volume 540, Issues 1–2, April 1992, Pages 275-290

https://doi.org/10.1016/0375-9474(92)90204-W Get rights and content

Abstract

Monte Carlo simulations of the reaction ⁴⁰Ar at 45 MeV/u on an ²⁷Al target were used to study the limitations associated with measuring the transverse momentum flow using the technique of Danielewicz and Odyniec. In order to disentangle the effects coming from the method itself and from the detector limitations, the study was made first by assuming perfect detection of all products. Then, the study was done with the limitations of a typical 4π detector (Mur+Tonneau at GANIL) included. Those limitations caused by the method itself are more important than the limitations caused by the detector. The measured value of the flow parameter will be less than the real value, especially when the flow approaches zero. The sensitivity of the experimental flow parameter to the recoil velocity correction has also been studied.

References (16)

J.P. Sullivan et al.
Phys. Lett.
(1990)
J.J. Molitoris et al.
Phys. Lett.
(1985)
J.J. Molitoris et al.
Nucl. Phys.
(1986)
A. Bonasera et al.
Nucl. Phys.
(1988)
F. Sébille et al.
P. Danielewicz et al.
Phys. Rev.
(1988)
M. Demoulins
V. de la Mota et al.
D. Krofcheck et al.
Phys. Rev. Lett.
(1989)

There are more references available in the full text version of this article.

Cited by (27)

Scaling of anisotropy flows in intermediate energy heavy ion collisions
2007, Nuclear Physics A
Anisotropic flows ( $v_{1}$ , $v_{2}$ and $v_{4}$ ) of light nuclear clusters are studied by a nucleonic transport model in intermediate energy heavy ion collisions. The number-of-nucleon scalings of the directed flow ( $v_{1}$ ) and elliptic flow ( $v_{2}$ ) are demonstrated for light nuclear clusters. Moreover, the ratios of $v_{4} / v_{2}^{2}$ of nuclear clusters show a constant value of 1/2 regardless of the transverse momentum. The above phenomena can be understood by the coalescence mechanism in nucleonic level and are worthy to be explored in experiments.
Scaling of anisotropic flow and momentum-space densities for light particles in intermediate energy heavy ion collisions
2006, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Anisotropic flows ( $v_{2}$ and $v_{4}$ ) of light nuclear clusters are studied by isospin-dependent quantum molecular dynamics model for the system of ⁸⁶Kr + ¹²⁴Sn at intermediate energy and large impact parameters. Number-of-nucleon scaling of the elliptic flow ( $v_{2}$ ) are demonstrated for the light fragments up to $A = 4$ , and the ratio of $v_{4} / v_{2}^{2}$ shows a constant value of 1/2. In addition, the momentum-space densities of different clusters are also surveyed as functions of transverse momentum, in-plane transverse momentum and azimuth angle relative to the reaction plane. The results can be essentially described by momentum-space power law. All the above phenomena indicate that there exists a number-of-nucleon scaling for both anisotropic flow and momentum-space densities for light clusters, which can be understood by the coalescence mechanism in nucleonic degree of freedom for the cluster formation.
Effects of the mean-field dynamics and the phase-space geometry on the cluster formation
1997, Nuclear Physics A
A model allowing to simulate the production of clusters is developed and applied to heavy-ion reactions at intermediate energies. The model investigates the geometrical properties of the dynamically generated one-body phase space. The collision process is entirely governed by the Landau-Vlasov model, which provides the time evolution of the one-body phase-space distribution. Particles emitted during successive time intervals of the dynamics are gathered together into subensembles to which a clusterization procedure is applied. Comparison with the experimental data for the Ar(65 MeV/nucleon) + Al reaction shows that the average behaviour of particle-dependent global observables is correctly reproduced within this framework. These results point out that the studied global properties of heavy-ion collisions greatly rely on the dynamical effects of the primary non-steady stage of the nuclear reaction.
Directed collective flow and azimuthal distributions in 36Ar + 27Al collisions from 55 to 95 MeV/u
1997, Nuclear Physics A
A 4π charged particle detector array with a low velocity threshold has been used to detect the products from reactions induced by ³⁶Ar on ²⁷Al at energies ranging from 55 to 95 MeV/u. Well characterized events were selected and sorted as a function of the impact parameter. Two methods were used for sorting these events with respect to their impact parameters and three methods were compared to determine the reaction plane. The transverse momentum analysis has been found to be the best method to extract the direction of the reaction plane for this system and for the experimental set-up used here. The energy of vanishing flow for central collisions has been found to be around 90–95 MeV/u. The azimuthal distributions of mid-rapidity particles exhibit a preferential in-plane emission and no squeeze-out effect.
Disappearance of flow and the in-medium nucleon-nucleon cross section for 64Zn+27Al collisions at intermediate energies
1996, Nuclear Physics A
Light charged particles emitted from the reactions ⁶⁴Zn+²⁷Al at beam energies 49, 57, 69 and 79 MeV/u have been measured with a 4π multidetector array. The collective transverse momentum in the reaction plane (in-plane flow) is observed to vary strongly with the impact parameter and the emitted fragments. The flow parameter decreases monotonically from 49 to 79 MeV/u and falls to zero at a beam energy about 79 MeV/u in central collisions. This energy of vanishing flow increases with impact parameter and may be the same for different fragments. The disappearance of flow is also studied with the Boltzmann-Uehling-Uhlenbeck equation and it is demonstrated that the flow parameter and E_VF are very sensitive to the in-medium cross section σ_NN and weakly sensitive to the nuclear compressibility in central collisions. Comparisons with experimental data indicate that σ_NN is around 35 to 45 mb in central collisions.
Azimuthal correlation functions and the energy of vanishing flow in nucleus-nucleus collisions
1995, Nuclear Physics, Section A
A method is proposed for estimating the energy of vanishing flow (also called balance energy, E_bal) without reconstructing the reaction plane. This method is based on the shapes of experimental particle-particle azimuthal correlation functions. It is used for determining E_bal for three systems: Ar + Al, Zn + Ti, Zn + Ni. The results are compared with estimations using flow-parameter analysis and with theoretical expectations.

View all citing articles on Scopus

¹: Present address: P2 Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.

²: We thank Guy Bizard for critical comments.

View full text

Article preview

Nuclear Physics A

Abstract

References (16)

Phys. Lett.

Phys. Lett.

Nucl. Phys.

Nucl. Phys.

Phys. Rev.

Phys. Rev. Lett.

Cited by (27)

Scaling of anisotropy flows in intermediate energy heavy ion collisions

Scaling of anisotropic flow and momentum-space densities for light particles in intermediate energy heavy ion collisions

Effects of the mean-field dynamics and the phase-space geometry on the cluster formation

Directed collective flow and azimuthal distributions in <sup>36</sup>Ar + <sup>27</sup>Al collisions from 55 to 95 MeV/u

Disappearance of flow and the in-medium nucleon-nucleon cross section for <sup>64</sup>Zn+<sup>27</sup>Al collisions at intermediate energies

Azimuthal correlation functions and the energy of vanishing flow in nucleus-nucleus collisions