Experimental investigation of the residues produced in the ${}^{136}\mathrm{Xe}+\mathrm{Pb}$ and ${}^{124}\mathrm{Xe}+\mathrm{Pb}$ fragmentation reactions at $1A$ GeV

The nuclide cross sections and longitudinal velocity distributions of residues produced in the reactions of ${}^{136}\mathrm{Xe}$ and ${}^{124}\mathrm{Xe}$ at $1A$ GeV in a lead target were measured at the high-resolution magnetic spectrometer, the fragment separator (FRS) of GSI. The data cover a broad range of isotopes of the elements between $Z=3$ and $Z=56$ for ${}^{136}\mathrm{Xe}$ and between $Z=5$ and $Z=55$ for ${}^{124}\mathrm{Xe}$, reaching down to cross sections of a few microbarns. The velocity distributions exhibit a Gaussian shape for masses above $A=20$, while more complex behavior is observed for lighter masses. The isotopic distributions for both reactions preserve a memory on the projectile $N/Z$ ratio over the whole residue mass range.

Figure 1

Schematic view of the FRS and the associated detector equipment.

Figure 2

Velocity distribution of the isotope ${}^{31}\mathrm{P}$ measured in the ${}^{136}\mathrm{Xe}+\mathrm{Pb}$ experiment. Different parts of this distribution measured in neighboring settings of the magnetic fields are marked by full and dashed histograms.

Figure 3

Identification plots from the ${}^{136}\mathrm{Xe}+\mathrm{Pb}$ experiment: (a) light-fragment settings; (b) heavy-fragment settings. The vertical scale corresponds approximately to the atomic number $Z$.

Figure 4

Same as Fig. 3, but from the ${}^{124}\mathrm{Xe}+\mathrm{Pb}$ experiment.

Figure 5

Measured longitudinal velocity distributions in the projectile frame for several nuclides measured in the ${}^{136}\mathrm{Xe}+\mathrm{Pb}$ (full red histogram) and the ${}^{124}\mathrm{Xe}+\mathrm{Pb}$ (dashed blue histogram) experiments. Note the different horizontal scales for different subgroups of data.

Figure 6

Angular- acceptance-integrated production cross sections for isotopes of elements $Z=3\text{−}56$ and $Z=5\text{−}55$ measured in the ${}^{136}\mathrm{Xe}+\mathrm{Pb}$ and ${}^{124}\mathrm{Xe}+\mathrm{Pb}$ experiments, respectively, presented on the chart of nuclides. Missing isotopes close to the projectile in the ${}^{124}\mathrm{Xe}+\mathrm{Pb}$ chart are due to more restrictive slit settings in this experiment (see the text).

Figure 7

Angular-acceptance-integrated isotopic cross sections measured in ${}^{136}\mathrm{Xe}+\mathrm{Pb}$ (full red symbols) and ${}^{124}\mathrm{Xe}+\mathrm{Pb}$ (open blue symbols), for $Z=3\text{−}22$. The dashed lines serve to guide the eye. Statistical error bars are smaller than the size of the symbols.

Figure 8

Same as Fig. 7, but for $Z=23\text{−}42$.

Figure 9

Same as Fig. 7, but for $Z=43\text{−}56$.

Figure 10

Mass and nuclear-charge distributions measured in the ${}^{136}\mathrm{Xe}+\mathrm{Pb}$ and ${}^{124}\mathrm{Xe}+\mathrm{Pb}$ experiments. Statistical error bars are smaller than the size of the symbols.

Figure 11

Comparison of the $\langle N\rangle /Z$ of final residues determined from the isotopic distributions of the reactions ${}^{136}\mathrm{Xe}$($N/Z=1.52\hspace{0.5em}+\hspace{0.5em}\mathrm{Pb}$) and ${}^{124}\mathrm{Xe}$($N/Z=1.30\hspace{0.5em}+\hspace{0.5em}\mathrm{Pb}$) at $1A$ GeV. Values for $Z<10$ are derived from angular-acceptance-integrated cross sections. The full line represents the $\langle N\rangle /Z$ of the stable isotopes [36]. Statistical error bars are not shown when they are smaller than the size of the symbols. Systematic uncertainties are negligible.