Recoil effects in peripheral nucleus-nucleus collisions at E/A=84 MeV

doi:10.1016/0370-2693(87)90797-0

Physics Letters B

Volume 196, Issue 4, 15 October 1987, Pages 439-443

https://doi.org/10.1016/0370-2693(87)90797-0 Get rights and content

Abstract

Azimuthal angular correlations between projectile fragments and light particles have been measured in ¹⁸O induced reactions on ^58.64Ni and ¹⁹⁷Au targets at E/A=84 MeV. Neither sequential projectile decay nor evaporation from an equilibrated target-like recoil can explain the observed correlations. The data are well described in terms of a sideways-moving source suggesting emission of midrapidity light particles from a subset of nucleons which carries a major part of the transverse recoil momentum imparted by the projectile fragment.

References (14)

J. Mougey
Phys. Lett. B
(1981)
A.S. Goldhaber
Phys. Lett. B
(1974)
N. Brummund
Nucl. Phys. A
(1986)
H. Ho
Nucl. Phys. A
(1985)
J. Pochodzalla
Phys. Lett. B
(1986)
M.B. Tsang
Phys. Rev. Lett.
(1986)
C.B. Chitwood
Phys. Rev. C
(1986)

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

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¹: Present address: Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA.

²: Present address: Cyclotron Institute, Texas A&M University, College Station, TX 77843, USA.

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Physics Letters B

Abstract

References (14)

Phys. Lett. B

Phys. Lett. B

Nucl. Phys. A

Nucl. Phys. A

Phys. Lett. B

Phys. Rev. Lett.

Phys. Rev. C

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