7 Role of Mass Asymmetry on the Energy of Peak …
83
In case of asymmetric reactions various experimental and theoretical attempts
have also been done. On the experimental front, Bowmann et al. studied fragment
distribution of various asymmetric reactions of
129 Xe projectile with
12 C,
27 Al,
51 V,
nat Cu,
89 Y, and
197 Au using 4π detector. They observed that the fragment multiplicity
distributions and charge distributions are target independent [27]. In another study,
the ALADIN collaborators performed study on asymmetric reactions of
129 Xe,
197 Au,
and
238 U projectiles with Be, C, Al, Cu, In, Au, and U targets and reported a linear rise
in the energy of maximum fragment production with the projectile mass [20]. Very
recently, Puri et al. investigated the mass dependence of < E
max
c.m. > and < N
max
I M Fs >
in various mass asymmetric reactions and successfully reproduced the experimental
data using the IQMD model. They found that the slope of the linear rise decreases
on shifting from mass symmetric to asymmetric reactions. The study also showed
the immense capability of < E
max
c.m. > of the asymmetric reactions to constrain the
density dependence of the symmetry energy at subsaturation densities [28]. In earlier
studies, the role of mass asymmetry on the energy of vanishing flow (EVF), geometry
of vanishing flow (GVF) and transition energy were also reported [29–31].
The rise and fall behavior of IMFs is also observed with impact parameter for
symmetric and asymmetric reactions. This behavior is heavily explored in many
experimental and theoretical fronts at fixed incident energies. For instance, the SIS
facility at GSI reported the rise and fall in multiplicity of IMFs in symmetric reactions
of
197 Au +
197 Au at energy of 100, 250, and 400 MeV/nucleon . They observed
maximum multiplicity of IMFs is shifting from central to peripheral geometries with
increase in incident energy [16]. In another study by ALADIN group, the rise and fall
behavior is observed for various reactions of
197 Au on Be, C, Al, and Au at different
energies of 400, 600, 800, and 1000 MeV/nucleon. They reported that on decreasing
the target mass, maximum fragment multiplicity is shifting toward central collisions
and its dependence on the bombarding energy increases [20]. On theoretical front, it
was observed that the < E
max
c.m. > as well as < N
max
I M Fs > decreases with increase in
impact parameter for both symmetric and asymmetric reactions but later has greater
slope compared to former [32].
The present study is mainly dedicated to investigate the reaction dynamics of
asymmetric reactions at their peak energy of IMFs (5≤A≤A total /6) production. The
study is carried out by exploring the mass dependence of peak energy of IMFs
production for fixed targets of
124 Sn and
197 Au and by varying the projectile mass
from
44 Ca to
197 Au. Further, in our study we will explore the behavior of different
fragments such as free nucleons (FNs) [A=1], A=2, light charge particle (LCPs)
[2≤A≤4], medium mass fragments (MMFs) [5≤A≤9] and heavy mass fragments
(HMFs) [10≤A≤A tot /6] with total system mass at the energy of peak fragment production. Here, we also plan to investigate the behavior of various observables related
to nuclear dynamics such as average and maximum central density, temperature,
collision number and participant and spectator matter at the energy of peak fragment
production which is never been investigated at peak energy of fragmentation. The
present study is done within the framework of Isospin-dependent Quantum Molecular
Dynamics (IQMD) model which is described in detail in [33].
83
In case of asymmetric reactions various experimental and theoretical attempts
have also been done. On the experimental front, Bowmann et al. studied fragment
distribution of various asymmetric reactions of
129 Xe projectile with
12 C,
27 Al,
51 V,
nat Cu,
89 Y, and
197 Au using 4π detector. They observed that the fragment multiplicity
distributions and charge distributions are target independent [27]. In another study,
the ALADIN collaborators performed study on asymmetric reactions of
129 Xe,
197 Au,
and
238 U projectiles with Be, C, Al, Cu, In, Au, and U targets and reported a linear rise
in the energy of maximum fragment production with the projectile mass [20]. Very
recently, Puri et al. investigated the mass dependence of < E
max
c.m. > and < N
max
I M Fs >
in various mass asymmetric reactions and successfully reproduced the experimental
data using the IQMD model. They found that the slope of the linear rise decreases
on shifting from mass symmetric to asymmetric reactions. The study also showed
the immense capability of < E
max
c.m. > of the asymmetric reactions to constrain the
density dependence of the symmetry energy at subsaturation densities [28]. In earlier
studies, the role of mass asymmetry on the energy of vanishing flow (EVF), geometry
of vanishing flow (GVF) and transition energy were also reported [29–31].
The rise and fall behavior of IMFs is also observed with impact parameter for
symmetric and asymmetric reactions. This behavior is heavily explored in many
experimental and theoretical fronts at fixed incident energies. For instance, the SIS
facility at GSI reported the rise and fall in multiplicity of IMFs in symmetric reactions
of
197 Au +
197 Au at energy of 100, 250, and 400 MeV/nucleon . They observed
maximum multiplicity of IMFs is shifting from central to peripheral geometries with
increase in incident energy [16]. In another study by ALADIN group, the rise and fall
behavior is observed for various reactions of
197 Au on Be, C, Al, and Au at different
energies of 400, 600, 800, and 1000 MeV/nucleon. They reported that on decreasing
the target mass, maximum fragment multiplicity is shifting toward central collisions
and its dependence on the bombarding energy increases [20]. On theoretical front, it
was observed that the < E
max
c.m. > as well as < N
max
I M Fs > decreases with increase in
impact parameter for both symmetric and asymmetric reactions but later has greater
slope compared to former [32].
The present study is mainly dedicated to investigate the reaction dynamics of
asymmetric reactions at their peak energy of IMFs (5≤A≤A total /6) production. The
study is carried out by exploring the mass dependence of peak energy of IMFs
production for fixed targets of
124 Sn and
197 Au and by varying the projectile mass
from
44 Ca to
197 Au. Further, in our study we will explore the behavior of different
fragments such as free nucleons (FNs) [A=1], A=2, light charge particle (LCPs)
[2≤A≤4], medium mass fragments (MMFs) [5≤A≤9] and heavy mass fragments
(HMFs) [10≤A≤A tot /6] with total system mass at the energy of peak fragment production. Here, we also plan to investigate the behavior of various observables related
to nuclear dynamics such as average and maximum central density, temperature,
collision number and participant and spectator matter at the energy of peak fragment
production which is never been investigated at peak energy of fragmentation. The
present study is done within the framework of Isospin-dependent Quantum Molecular
Dynamics (IQMD) model which is described in detail in [33].