CERN Accelerating science

Article
Report number	arXiv:1706.02428
Title	The Cylindrical GEM Inner Tracker of the BESIII experiment: prototype test beam results
Author(s)	Lavezzi, L. (Beijing, Inst. High Energy Phys. ; INFN, Turin) ; Alexeev, M. (INFN, Turin) ; Amoroso, A. (INFN, Turin ; Turin U.) ; Baldini Ferroli, R. (Beijing, Inst. High Energy Phys. ; Frascati) ; Bertani, M. (Frascati) ; Bettoni, D. (INFN, Ferrara) ; Bianchi, F. (INFN, Turin ; Turin U.) ; Calcaterra, A. (Frascati) ; Canale, N. (INFN, Ferrara) ; Capodiferro, M. (Frascati ; INFN, Rome ; Rome U.) ; Carassiti, V. (INFN, Ferrara) ; Cerioni, S. (Frascati) ; Chai, JY. (Beijing, Inst. High Energy Phys. ; INFN, Turin ; Turin Polytechnic) ; Chiozzi, S. (INFN, Ferrara) ; Cibinetto, G. (INFN, Ferrara) ; Cossio, F. (INFN, Turin ; Turin Polytechnic) ; Cotta Ramusino, A. (INFN, Ferrara) ; De Mori, F. (INFN, Turin ; Turin U.) ; Destefanis, M. (INFN, Turin ; Turin U.) ; Dong, J. (Frascati) ; Evangelisti, F. (INFN, Ferrara) ; Farinelli, R. (INFN, Ferrara ; Ferrara U.) ; Fava, L. (INFN, Turin) ; Felici, G. (Frascati) ; Fioravanti, E. (INFN, Ferrara) ; Garzia, I. (INFN, Ferrara ; Ferrara U.) ; Gatta, M. (Frascati) ; Greco, M. (INFN, Turin ; Turin U.) ; Leng, CY. (Beijing, Inst. High Energy Phys. ; INFN, Turin ; Turin Polytechnic) ; Li, H. (Beijing, Inst. High Energy Phys. ; INFN, Turin) ; Maggiora, M. (INFN, Turin ; Turin U.) ; Malaguti, R. (INFN, Ferrara) ; Marcello, S. (INFN, Turin ; Turin U.) ; Melchiorri, M. (INFN, Ferrara) ; Mezzadri, G. (INFN, Ferrara ; Ferrara U.) ; Mignone, M. (INFN, Turin) ; Morello, G. (Frascati) ; Pacetti, S. (INFN, Perugia ; Perugia U.) ; Patteri, P. (Frascati) ; Pellegrino, J. (INFN, Turin ; Turin U.) ; Pelosi, A. (Frascati ; INFN, Rome ; Rome U.) ; Rivetti, A. (INFN, Turin) ; Rolo, M.D. (INFN, Turin) ; Savrié, M. (INFN, Ferrara ; Ferrara U.) ; Scodeggio, M. (INFN, Ferrara ; Ferrara U.) ; Soldani, E. (Frascati) ; Sosio, S. (INFN, Turin ; Turin U.) ; Spataro, S. (INFN, Turin ; Turin U.) ; Tskhadadze, E. (Frascati ; Dubna, JINR) ; Verma, S. (Ferrara U.) ; Wheadon, R. (INFN, Turin) ; Yan, L. (INFN, Turin)
Publication	2017-07-27
Imprint	2017-06-07
Number of pages	6
Note	Proceedings for "Instrumentation for Colliding Beam Physics" (INSTR17) Conference, 27 February - 3 March 2017, Novosibirsk, Russia (prepared for submission to JINST)
In:	JINST 12 (2017) C07038
In:	Instrumentation for Colliding Beam Physics, Novosibirsk, Russia, 27 Feb - 3 Mar 2017, pp.C07038
DOI	10.1088/1748-0221/12/07/C07038
Subject category	physics.ins-det ; Detectors and Experimental Techniques
Accelerator/Facility, Experiment	BEPC ; BES III CERN SPS CERN SPS
Test beam	H4
Abstract	A cylindrical GEM detector is under development, to serve as an upgraded inner tracker at the BESIII spectrometer. It will consist of three layers of cylindrically-shaped triple GEMs surrounding the interaction point. The experiment is taking data at the e+e- collider BEPCII in Beijing (China) and the GEM tracker will be installed in 2018. Tests on the performances of triple GEMs in strong magnetic field have been run by means of the muon beam available in the H4 line of SPS (CERN) with both planar chambers and the first cylindrical prototype. Efficiencies and resolutions have been evaluated using different gains, gas mixtures, with and without magnetic field. The obtained efficiency is 97-98% on single coordinate view, in many operational arrangements. The spatial resolution for planar GEMs has been evaluated with two different algorithms for the position determination: the charge centroid and the micro time projection chamber (mu-TPC) methods. The two modes are complementary and are able to cope with the asymmetry of the electron avalanche when running in magnetic field, and with non-orthogonal incident tracks. With the charge centroid, a resolution lower than 100 micron has been reached without magnetic field and lower than 200 micron with a magnetic field up to 1 T. The mu-TPC mode showed to be able to improve those results. In the first beam test with the cylindrical prototype, the detector had a very good stability under different voltage configurations and particle intensities. The resolution evaluation is in progress.
Copyright/License	arXiv nonexclusive-distrib. 1.0

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