Ⅱ-4. Hadron Physics

RIKEN Accel. Prog. Rep. 47 (2014)

RIKEN Accel. Prog. Rep. 00 (0)Development of coordinate oﬀset online calibration system at
RHIC-PHENIX
H. Asano,∗1,∗2 A.Adare,∗3 Y. Akiba,∗2 R. Akimoto,∗4,∗2 A. Dion,∗5 S. Bathe,∗6,∗2 J. Bryslawskyj,∗6D.McGlinchey,∗3 T.Koblesky,∗3 T.Moon,∗7,∗2 T. Hachiya,∗2 M. Kurosawa,∗2 A. Lebedev,∗8 M. McCumber,∗9H. Nakagomi,∗10,∗2 R. Nouicer,∗11,∗2 H. Sako,∗12,∗2 S. Sato,∗12,∗2 M. Shimomura,∗4,∗2 T. Sumita,∗2 H.Torii,∗2A. Taketani,∗2 and the PHENIX VTX group
The PHENIX experiment in the Relativistic Heavy
Ion Collider (RHIC) at Brookhaven National Laboratory has been upgraded by installing a silicon vertex
tracker (VTX)1). The VTX has been developed forheavy-ﬂavor (charm and bottom) measurements and isdedicated to precise tracking for ﬁnding primary andsecondary vertices. The ﬁrst set of physics data including the VTX was recorded for the Au+Au collisions in
RUN 11 (RHIC experiment performed in 2011).
The ﬁrst and second layers of the VTX are comprised of pixel detectors, and the third and the fourthlayers of VTX are comprised of stripixel detectors2),
as shown in Fig. 1. Geometrical calibration is important because precise alignment is required in the VTX
to identify primary and secondary vertices. To analyze
the distance of closest approach (DCA) of tracks to theprimary vertex, we require a drift chamber (DC) trackis associated with the clusters on the VTX, as shownin Fig. 2.

to access the detectors, we need to calibrate the relative positions of the detectors. We developed an onlineand automated system to calibrate the coordinate oﬀset between each of the west and east half barrels of
VTX and DC in the east and west arms. Once we access the detectors, we always take zero-magnetic-ﬁeld
data in which all tracks from the collision point are
assumed to be straight. The online calibration system calculates the beam center position with respect
to DC west/east and VTX west/east coordinate system. Once the zero-ﬁeld data are taken, the online
calibration system runs immediately, and its result issubmitted to a database. This result is used in thetracking analysis. This module outputs QA plots sothat we can conﬁrm that the result is reasonable.
In summary, we developed a coordinate oﬀset online calibration system for RHIC-PHENIX. The system outputs calibration parameters of the coordinate
oﬀset of VTX and DC for the tracking analysis with
VTX and DC data.

Fig. 1. Cross section of the VTX. The VTX is separated
into a west half barrel and an east half barrel.

In the PHENIX apparatus, the west and east halfbarrels of VTX and DC in the east and west arms
are mechanically separated, and their relative positions may shift. After each time we open up the apparatus

Fig. 2. Cross section of the PHENIX detector. The relative
position of VTX west/east and DC west/east can be
moved during the experiment.

∗1Department of Physics, Kyoto University
RIKEN Nishina Center∗3 Department of Physics, University of Colorado Boulder∗4 Center for Nuclear Study, Univ. of Tokyo, Japan∗5 Department of Physics and Astronomy, Stony Brook University∗6 Department of Physics, City University of New York∗7 Department of Physics, Yonsei University∗8 Department of Physics and Astronomy, Iowa State University∗9 Los Alamos National Laboratory∗10 Graduate School of Pure and Applied Sciences, Universityof Tsukuba∗11 Brookhaven National Laboratory∗12 JAEA, Advanced Science Research CenterReferences∗21) M Baker et al, Proposal for a Silicon Vertex Tracker(VTX) for PHENIX Experiment, 2004 BNL72204-2004,
Physics Dept. BNL
2) A. Taketani et al., Nucl. Instr. and Meth. A 623 (2010)374- 84 -1