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Phys. Rev. C 60, 034609 (1999) [10 pages]

Exclusive studies of angular distributions in GeV hadron-induced reactions with 197Au

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W.-c. Hsi, K. Kwiatkowski *, G. Wang †, D. S. Bracken *, E. Cornell ‡, D. S. Ginger §, and V. E. Viola
Departments of Chemistry, Physics and IUCF, Indiana University, Bloomington, Indiana 47405

R. G. Korteling
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A I56

K. B. Morley
Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545

R. Huang, W. G. Lynch, M. B. Tsang, and H. Xi
Department of Physics and NSCL, Michigan State University, East Lansing, Michigan 48824

F. Gimeno-Nogues, E. Ramakrishnan, D. Rowland, and S. J. Yennello
Department of Chemistry and Cyclotron Institute, Texas A & M University, College Station, Texas 77843

H. Breuer
Department of Physics, University of Maryland, College Park, Maryland 20740

S. Gushue and L. P. Remsberg
Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973

A. Botvina **
Department of Physics, University of Bologna, Bologna I-40126, Italy

W. A. Friedman
Department of Physics, University of Wisconsin, Madison, Wisconsin 53706

Received 28 April 1999; published 11 August 1999

Exclusive studies of angular distributions for intermediate-mass fragments (IMFs) produced in GeV hadron-induced reactions have been performed with the Indiana Silicon Sphere (ISiS) 4π detector array. Special emphasis has been given to understanding the origin of sideways peaking, which becomes prominent in the angular distributions for beam momenta above about 10 GeV/c. Both the magnitude of the effect and the peak angle increase as a function of fragment multiplicity and charge. When gated on IMF kinetic energy, the angular distributions evolve from forward-peaked to near isotropy as the fragment kinetic energy decreases. Fragment-fragment angular-correlation analyses show no obvious evidence for a dynamic mechanism that might signal shock wave effects or the breakup of exotic geometric shapes such as bubbles or toroids. Moving-source and intranuclear cascade simulations suggest that the observed sideways peaking is of kinematic origin, arising from significant transverse momentum imparted to the heavy recoil nucleus during the fast cascade stage of the collision. A two-step cascade and statistical multifragmentation calculation is consistent with this assumption.


©1999 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevC.60.034609
DOI: 10.1103/PhysRevC.60.034609
PACS: 25.40.Ve, 21.65.+f, 25.70.Pq, 25.75.-q

* Present address: Los Alamos National Lab, Los Alamos, NM 87545.
† Present address: Epsilon, Inc., Dallas, TX 75240.
‡ Present address: Lawrence Berkeley Laboratory, Berkeley, CA 94720.
§ Present address: Department of Physics, Cambridge University, Cambridge, United Kingdom.
** On leave from Institute for Nuclear Research, RU-117312 Moscow, Russia.

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