NeuLAND - FAIR

exemplarily, the strength of 5% TRK sum rule is represented by a Gaussian distribution
with Em = 8 MeV and a width of σ = 1 MeV. The Coulomb cross section distribution is
calculated for 136 Sn projectiles impinging on a Pb-target with 1000 AMeV. According to
the energy-differential Coulomb cross section distribution, events were simulated within
a statistical-model approach, detailing the decay channels (1 to 4 neutrons), the neutron
and fragment momenta and the γ-transitions below the particle thresholds on an eventby-event
basis. Figure 4.18 presents the total excitation-energy-distribution input to the
NeuLAND simulation, together with its one- to four-neutron contributions.
events
15000
10000
5000
1 n
2 n
3 n
4 n
0
0 10 20 30
E* (MeV)
Figure 4.18.: The input excitation-energy distribution is shown for a combination of PDR
and GDR in 136 Sn (Coulomb excitation on a Pb target at 1000 AMeV). The
overall distribution is displayed (black line), together with the composition
into the 1 neutron (red), 2 neutron (cyan), 3 neutron (blue), and 4 neutron
channels (magenta). The distribution is calculated for excitation energies
from the one-neutron threshold up to 20 MeV.
Approximately 7×10 5 events were collected into the input for the R 3 BRoot simulation of
the NeuLAND response. NeuLAND is located at a distance of 23.5 m to the target in this
simulation. Neutrons were reconstructed from the NeuLAND tracking algorithm output.
Together with the momentum of the fragment and the γ-transitions, the excitation
energy was reconstructed using the invariant-mass method. Since our aim is to study
the performance of the response of NeuLAND, γ-transitions and the heavy fragment
were treated as ideal.
Figure 4.19 displays the comparison of the excitation-energy-distribution input to the
response of NeuLAND from the R 3 BRoot simulation. For the reconstruction, neutron
multiplicities of 1 to 4 were taken into account. The mass of the projectile fragment
is used as a cross check for the detection of the each neutron channel. Thus, only
channels with the correctly identified neutron multiplicities (diagonal elements of the
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