Ⅱ-9. Instrumentation
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

Preliminary results of INTT beam test 2021 at ELPH†
C. W. Shih,∗1 Y. Akiba,∗2 J. Bertaux,∗3 K. Fujiki,∗2,∗4 M. Fujiiwara,∗5 T. Hachiya,∗2,∗5 S. Hasegawa,∗2,∗6M. Hata,∗5 H. Imai,∗2,∗4 M. Kano,∗5 T. Kato,∗2,∗4 T. Kondo,∗7 C. M. Kuo,∗1 R. -S. Lu,∗8 I. Nakagawa,∗2Y. Namimoto,∗2,∗5 R. Nouicer,∗9 G. Nukazuka,∗2 M. Shimomura,∗5 R. Shishikura,∗2,∗4 M. Stojanovic,∗3Y. Sugiyama,∗5 R. Takahama,∗2,∗5 W. -C. Tang,∗1 H. Tsujibata,∗5 M. Watanabe,∗5 and X. Wei∗3The Intermediate silicon Tracker, INTT, is one
among the sub-detectors of sPHENIX tracking system.1) A beam test experiment was performed withINTT ladders at the end of 2021 at ELPH, Japan.
In the experiment, a telescope of 4 INTT ladders wasinstalled, and 3 ladders were operated. The positron
beam with the energy of 1 GeV was delivered. Oneof the goals of this experiment was to demonstrate thedetection eﬃciency of INTT ladder. As the radiation
length of INTT ladder was 1.08% X0 , the track wasassumed to be a straight line.
This study focused on the column with the highestevents.2) The clustering was performed on 3 ladders,the adjacent ﬁred channels in a column were grouped
to form a hit cluster. The cluster position y in vertical direction was determined by y = Σi Ei · yi /Σi Ei ,where E is the energy deposit. The track reconstruction was performed by the upstream ladder, L0, anddownstream ladder, L2, and the detection eﬃciency ofthe middle ladder, L1, was measured. In the reconstruction process, no cluster in the adjacent columnsof all ladders was required, and the number of clusters was required to be one on the same column forL0 and L2. The tracks passing the criteria were considered as track candidates. The residual r is deﬁned
as r ≡ (y + Cy ) − ypred , where ypred is the y positionat L1 predicted by the track candidate, and Cy is anoﬀset term indicating the misalignment. An alignment
correction of −Cy was applied in the study.
Several cuts were applied to maximize the authenticity of the results. For L0 and L2, the single-hit cluster was rejected to minimize the false track candidates
based on accidental noise hits. The track candidates
within ﬁve channels from the edges were rejected tosuppress the misalignment eﬀect (edge eﬀect). In addition, the track candidates with large deviation in theangle (±0.01 radian) from the beam axis were excluded(Slope cut). The track candidates that passed all criteria were considered as good tracks. Subsequently, theclusters in L1 were checked. Three categories were con†

∗1
∗2
∗3
∗4
∗5
∗6
∗7
∗8
∗9Condensed from the article in ELPH Annu. Rep. (2022)
Center for High Energy and High Field Physics and Department of Physics, National Central University
RIKEN Nishina Center
Department of Physics and Astronomy, Purdue University
Department of Physics, Rikkyo University
Department of Mathematical and Physical Sciences, Nara
Women’s University
Japan Atomic Energy Agency
Tokyo Metropolitan Industrial Technology Research InstituteDepartment of Physics, National Taiwan University
Physics Department, Brookhaven National Laboratory

sidered:(1) The closest cluster is close to ypred (Ngood ),(2) The closest cluster is far from ypred (Nfar ),(3) No cluster was found (Nno hit ).
The residual distribution of the ﬁrst two categories isshown in Fig. 1. The ﬁrst category requires |r| <0.234 mm (Residual cut).

Fig. 1. Residual distribution in L1.

The equation of detection eﬃciency of L1 is deﬁned
N
as Nno hit +Ngood×100%. The systematic uncertaingood +Nfar
ties associated with the detection eﬃciency originate
from the determinations of the three cut values, theslope cut, edge eﬀect, and residual cut. Scanning
cut values provides the variation of each source, andthe variation average estimates the uncertainties. The
numerical values are summarized in Table 1.
Table 1. Sources of the systematic uncertainties aﬀecting
the detection eﬃciency calculation.
Sources
Residual cut
Slope cutEdge eﬀect
Total

Scan range
0.164–0.304 mm
0.0088–0.0112 radian
0–10 channels

Uncertainty (%)
0.063
3e-3
4e-40.063

Considering the systematic uncertainty, the detection
eﬃciency of ladder L1 was 99.33 ± 0.04 (stat) ±0.06(syst)%. The performance of INTT ladder is excellent
enough for the sPHENIX experiment.
References
1) Conceptual Design Report of sPHENIX (2018).
2) G. Nukazuka et al., ELPH Annu. Rep. (2022).

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