Angular distributions in multifragmentation

Angular distributions are reported for ${}^{37}\mathrm{Ar}$ and ${}^{127}\mathrm{Xe}$ from 381-GeV ${}^{28}\mathrm{Si}+\text{Au}$ interactions and for products between ${}^{24}\mathrm{Na}$ and ${}^{149}\mathrm{Gd}$ from 28-GeV ${}^1\mathrm{H}+\text{Au}$. Sideward peaking and forward deficits for multifragmentation products are significantly enhanced for heavy ions compared with protons. Projectile kinetic energy does not appear to be a satisfactory scaling variable. The data are discussed in terms of a kinetic-focusing model in which sideward peaking is due to transverse motion of the excited product from the initial projectile-target interaction.

Figure 1

Angular distributions of ${}^{37}\mathrm{Ar}$ and ${}^{127}\mathrm{Xe}$ from the fragmentation of Au by heavy ions. Filled points are from the present work; open ones are from Refs. 20, 21. Solid curves are normalized cubic polynomials in $\cos {\theta }_{\mathrm{lab}}$; dashed ones are fits to a kinetic focusing model. Arrows indicate the direction of the cascade recoil (see text).

Figure 2

Angular distributions for products of the fragmentation of Au by 28-GeV protons. Solid curves are normalized cubic polynomials in $\cos {\theta }_{\mathrm{lab}}$; dashed ones are fits to a kinetic focusing model. Arrows indicate the direction of the cascade recoil (see text).

Figure 3

The $0^{°}$ to ${180}^{°}$ intensity ratio as a function of projectile energy for MF reactions yielding products with A = 37–48. Open triangles are from Ref. 12 for Sc isotopes produced in p + U interactions. A solid curve indicates their trend. Open circles are for p + Au $\to$${}^{48}\mathrm{Sc}$ and ${}^{48}\mathrm{V}$ from the present work. Filled circles are for HI + Au $\to$${}^{37}\mathrm{Ar}$ from the present work and Refs. 20, 21. Their trend is shown by the dashed curve.

Figure 4

Dependence of KFM parameters on product mass. Filled points are from the present work for 28-GeV p + Au open ones are from Refs. 20, 21 for 25-GeV ${}^{12}\mathrm{C}+\text{Au}$. Values of V in the uppermost panel were obtained from Ref. 24. Smooth curves show data trends.