Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 53

Geant4 simulation of INTT Phase-2 Test Beam at Fermilab
C. Shih,∗3 Y. Akiba,∗1 D. Cacace,∗2 K. Cheng,∗3 E. Desmond,∗2 T. Hachiya,∗1,∗4 S. Hasegawa,∗5 T. Kondo,∗6C. Kuo,∗3 M. Lenz,∗2 E. Mannel,∗2 C. Miraval,∗2 M. Morita,∗4 I. Nakagawa,∗1 R. Nouicer,∗2 R. Pisani,∗2
M. Shibata,∗4 A. Suzuki,∗4 T. Todoroki,∗1 X. Wei,∗7 and R. Xiao∗7
The INTermediate Tracker (INTT) is the tracker system between the Time Projection Chamber (TPC) andthe MAPS - based Vertex Detector (MVTX). It makes
up the gap between the TPC and the MVTX, and it
can produce the track reconstruction of charged particles
more precisely. To check the performance of the INTT
modules, a beam test of INTT phase-2 was conducted inFermilab in May 2019. Protons at 120 GeV were used in
the test beam. Geant4 is applied to check the analysis
results. The geometry of the INTT beam test in simulation is shown in Fig. 1. There are 4 layers of INTT
modules, each of which is formed by 2 silicon sensors,
HDI, and a cooling system. The air gap between twolayers is 35 mm. The INTT modules are sandwiched bytrigger scintillators, one in the front and one in the back.
The readout chips and glue layers are not considered in
the simulation.
The beam is set to be perpendicular to the modules
in the ﬁrst simulation. To be consistent with the actual
data analysis of the beam test, only events that ﬁre asingle strip in layer 1 were selected in MC. A comparisonof energy deposit distributions is shown in Fig. 2. Thehorizontal scale for MC is adjusted to match the MIP
peak position. The result shows that MC is wider thanthe data. In order to investigate the discrepancy, the injection angle theta of the beam is scanned from 0 to 2.81
degree with 0.01 degree step in the second simulation.
For most cases, the distribution of energy deposit is similar to that of the ﬁrst simulation. However, we foundthat the shape of the distribution changes once the an-Fig. 3. Left: Distribution of energy deposit, beam theta angle
is 1.26 degree. Right: the schematic of event display.

Fig. 4. Beam spot distribution of INTT Test beam.

Fig. 5. Real energy deposit distribution.

Fig. 1. Geometry of INTT Test Beam in simulation.

Fig. 2. Distribution of energy deposit, the beam direction isset to be perpendicular to modules.
∗1
∗2
∗3
∗4
∗5
∗6
∗7

RIKEN Nishina Center
Brookhaven National Laboratory
National Central University
Nara Women’s University
Japan Atomic Energy Agency
Tokyo Metropolitan Industrial Technology Research InstitutePurdue University

gle passes a threshold, as illustrated in the right panel ofFig. 3. The proton starts to ﬁre multiple strips, and thepass length of the primary strip becomes shorter than in
the perpendicular case. Consequently, the MIP peak of
the MC shrinks and leads to better agreement with thedata, as demonstrated in the left panel of Fig. 3. The
beam information of the phase-2 beam test is recordedby three wire chambers, and the beam spot is in Fig. 4,
the sigma is 0.0025 degree. Thus, the beam information
is optimized.
The second step is to reproduce the most probablevalue (MPV) of energy deposit. The function to convert
data from mV to KeV is 0.075 * mV = KeV. The MPV
ratio of the data and MC is 56.5%, the plot is shown inFig. 5.
In conclusion, the simulation indicated that the beam
was not injected at a perfectly perpendicular condition tothe INTT modules. The next step is to feed the beamspot distribution to a simulation with a diﬀerent angle
and to ﬁnd the angle between the beam direction andmodules. In the phase-3 INTT test beam, the gain andtiming setting needs to be checked.
Reference1) Conceptual Design Report of sPHENIX (2018).

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