Multifragmentation of Au induced by 14.6 GeV ${}^4\mathrm{He}$

The multifragmentation reaction channel was investigated in 14.6 GeV ${}^4\mathrm{He}$+Au interactions. The experimental setup enabled event-by-event analysis. An internal correlation study suggests a nearly simultaneous emission of fragments. The velocities ($V{}_{\mathrm{c.m.}}$) of the center-of-mass system of correlated fragments were calculated. The transverse component of $V{}_{c.m.}$ with respect to the beam direction has higher values than the longitudinal one, which corresponds to large recoil angles of the source. The angular distributions of fragments are sideways peaked. The peak angle is dependent on the atomic number of fragment and multiplicity. Our results show that the heaviest fragment in one event corresponds, on average, to the largest emission angle, the second heaviest fragment corresponds to the second largest emission angle, and so on.

Figure 1

(a) Transverse ($V{}_T$) versus parallel ($V{}_{\left|\right|}$) component of the laboratory velocity of the lightest fragment relative to the direction of the center-of-mass system of two heavier fragments ($V{}_{c.m.23}$; direction $+v{}_{\left|\right|}$). (b) Transverse versus parallel component of the velocity of the lightest fragment in the scission frame of two heavier fragments. (c) Distribution of angles ($\Theta {}_R$) between the velocity of the lightest fragment in event and the relative velocity of two heavier fragments.

Figure 2

(a) Velocity ($V{}_{c.m.}$) of the center-of-mass system of fragments and its components ($V{}_{c.m.\left|\right|}$ and $V{}_{c.m.T}$) with respect to the beam direction as a function of $Z{}_{\mathrm{bound}}$. (b) Angle between $V{}_{c.m.}$ and beam direction versus $Z{}_{\mathrm{bound}}$.

Figure 3

Angular distributions of (a) the lighter (1) and the heavier (2) fragments from $M{}_{\mathrm{IMF}}=2$ events and (b) the lightest (1), the medium (2), and the heaviest (3) fragments from $M{}_{\mathrm{IMF}}=3$ events.