Performance of the LHCb Vertex Locator

Aaij, R.; Laﬀerty, G.; Nikitin, N.; Leﬂat, A.; Ketel, T.; Harrison, J.; Zverev, E.; Hutchcroft, D.; Dossett, D.; Hennessy, K.; Rinnert, K.; Farry, S.; Gong, H.; Noor, A.; Jaeger, A.; Thomas, C.; Needham, M.; Frei, R.; van Lysebetten, A.; Carroll, J.; Gordon, H.; Collins, P.; McNulty, R.; Bates, A.; Silva Coutinho, R.; Gersabeck, M.; Marinho, F.; Appleby, R.B.; Mous, I.; Bay, A.; Casse, G.; van den Brand, J.; Mountain, R.; Behrendt, O.; Borgia, A.; De Capua, S.; Volkov, V.; Schneider, O.; Doets, M.; Schiller, M.; John, M.; Hulsbergen, W.; Borghi, S.; Bogdanova, G.; Mylroie-Smith, J.; Jalocha, P.; Ali, S.; Farinelli, C.; Jans, E.; Kraan, M.; Korolev, M.; Callot, O.; van Beuzekom, M.; Rakotomiaramanana, B.; Parkes, C.; Akiba, K.; Whitehead, M.; Merkin, M.; Lastovicka, T.; Dumps, R.; Webber, A.; Pappagallo, M.; MacGregor, G.; Wang, J.; Ferro-Luzzi, M.; Haefeli, G.; Affolder, A.; Bjornstad, P.M.; Viret, S.; Garofoli, J.; Donleavy, S.; Patel, G.D.; Velthuis, J.; Oblakowska-Mucha, A.; Verlaat, B.; Lefeuvre, G.; Huse, T.; Heijne, V.; Keaveney, J.; Moran, D.; Tobin, M.; Alexander, M.; Brown, H.; Buytaert, J.; Wallace, C.; Saavedra, A.F.; Bowcock, T.J.V.; Redford, S.; Reid, M.; Eklund, L.; Eckstein, D.; Papadelis, A.; Benton, J.; Artuso, M.; Rodrigues, E.; Gong, A.; van Tilburg, J.; Szumlak, T.; Shears, T.; Smith, N.A.; Liles, M.; Gershon, T.; Latham, T.

doi:10.1088/1748-0221/9/09/P09007

Article
Report number	arXiv:1405.7808 ; CERN-LHCB-DP-2014-001
Title	Performance of the LHCb Vertex Locator
Related title	Performance of the LHCb Vertex Locator
Author(s)	Aaij, R. (Nikhef, Amsterdam) ; Affolder, A. (Liverpool U.) ; Akiba, K. (UFRJ, Rio de Janeiro) ; Alexander, M. (Glasgow U.) ; Ali, S. (Nikhef, Amsterdam) ; Appleby, R.B. (Manchester U.) ; Artuso, M. (Syracuse U. (main)) ; Bates, A. (Glasgow U.) ; Bay, A. (Ecole Polytechnique, Lausanne) ; Behrendt, O. (CERN) ; Benton, J. (Bristol U.) ; van Beuzekom, M. (Nikhef, Amsterdam) ; Bjornstad, P.M. (Manchester U.) ; Bogdanova, G. (SINP, Moscow) ; Borghi, S. (Manchester U.) ; Borgia, A. (Syracuse U. (main)) ; Bowcock, T.J.V. (Liverpool U.) ; van den Brand, J. (Nikhef, Amsterdam) ; Brown, H. (Liverpool U.) ; Buytaert, J. (CERN) ; Callot, O. (Orsay, LAL) ; Carroll, J. (Liverpool U.) ; Casse, G. (Liverpool U.) ; Collins, P. (CERN) ; De Capua, S. (Manchester U.) ; Doets, M. (Nikhef, Amsterdam) ; Donleavy, S. (Liverpool U.) ; Dossett, D. (Warwick U.) ; Dumps, R. (CERN) ; Eckstein, D. (DESY) ; Eklund, L. (Glasgow U.) ; Farinelli, C. (Nikhef, Amsterdam) ; Farry, S. (Liverpool U.) ; Ferro-Luzzi, M. (CERN) ; Frei, R. (Ecole Polytechnique, Lausanne) ; Garofoli, J. (Syracuse U. (main)) ; Gersabeck, M. (Manchester U.) ; Gershon, T. (Warwick U.) ; Gong, A. (Tsinghua U., Beijing, CHEP) ; Gong, H. (Tsinghua U., Beijing, CHEP) ; Gordon, H. (CERN) ; Haefeli, G. (Ecole Polytechnique, Lausanne) ; Harrison, J. (Manchester U.) ; Heijne, V. (Nikhef, Amsterdam) ; Hennessy, K. (Liverpool U.) ; Hulsbergen, W. (Nikhef, Amsterdam) ; Huse, T. (Oslo U.) ; Hutchcroft, D. (Liverpool U.) ; Jaeger, A. (Heidelberg U. ; Lyon, IPN) ; Jalocha, P. (Oxford U.) ; Jans, E. (Nikhef, Amsterdam) ; John, M. (Oxford U.) ; Keaveney, J. (Vrije U., Brussels) ; Ketel, T. (Nikhef, Amsterdam) ; Korolev, M. (SINP, Moscow) ; Kraan, M. (Nikhef, Amsterdam) ; Lastovicka, T. (Prague, Inst. Phys.) ; Laﬀerty, G. (Manchester U.) ; Latham, T. (Warwick U.) ; Lefeuvre, G. (Syracuse U. (main)) ; Leﬂat, A. (SINP, Moscow) ; Liles, M. (Liverpool U.) ; van Lysebetten, A. (Nikhef, Amsterdam) ; MacGregor, G. (Manchester U.) ; Marinho, F. (UFRJ, Rio de Janeiro) ; McNulty, R. (University Coll., Dublin) ; Merkin, M. (SINP, Moscow) ; Moran, D. (U. Autonoma, Madrid (main)) ; Mountain, R. (Syracuse U. (main)) ; Mous, I. (Nikhef, Amsterdam) ; Mylroie-Smith, J. (Liverpool U.) ; Needham, M. (Edinburgh U.) ; Nikitin, N. (SINP, Moscow) ; Noor, A. (Liverpool U.) ; Oblakowska-Mucha, A. (AGH-UST, Cracow) ; Papadelis, A. (Nikhef, Amsterdam) ; Pappagallo, M. (Glasgow U.) ; Parkes, C. (Manchester U.) ; Patel, G.D. (Liverpool U.) ; Rakotomiaramanana, B. (Ecole Polytechnique, Lausanne) ; Redford, S. (CERN) ; Reid, M. (Warwick U.) ; Rinnert, K. (Liverpool U.) ; Rodrigues, E. (Manchester U.) ; Saavedra, A.F. (Sydney U.) ; Schiller, M. (Nikhef, Amsterdam) ; Schneider, O. (Ecole Polytechnique, Lausanne) ; Shears, T. (Liverpool U.) ; Silva Coutinho, R. (Warwick U.) ; Smith, N.A. (Liverpool U.) ; Szumlak, T. (AGH-UST, Cracow) ; Thomas, C. (Oxford U.) ; van Tilburg, J. (Nikhef, Amsterdam) ; Tobin, M. (Ecole Polytechnique, Lausanne) ; Velthuis, J. (Bristol U.) ; Verlaat, B. (Nikhef, Amsterdam) ; Viret, S. (Lyon, IPN) ; Volkov, V. (SINP, Moscow) ; Wallace, C. (Warwick U.) ; Wang, J. (Syracuse U. (main)) ; Webber, A. (Manchester U.) ; Whitehead, M. (Warwick U.) ; Zverev, E. (SINP, Moscow)
Collaboration	LHCb VELO Group
Publication	2014
Imprint	30 May 2014
Number of pages	61
Note	61 pages, 33 figures Minor typographical changes made during journal review are implemented in this version
In:	JINST 9 (2014) P09007
DOI	10.1088/1748-0221/9/09/P09007
Subject category	physics.ins-det ; Detectors and Experimental Techniques ; Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; LHCb
Abstract	The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the proton-proton interaction region in the LHCb experiment. The performance of the detector during the first years of its physics operation is reviewed. The system is operated in vacuum, uses a bi-phase CO2 cooling system, and the sensors are moved to 7 mm from the LHC beam for physics data taking. The performance and stability of these characteristic features of the detector are described, and details of the material budget are given. The calibration of the timing and the data processing algorithms that are implemented in FPGAs are described. The system performance is fully characterised. The sensors have a signal to noise ratio of approximately 20 and a best hit resolution of 4 microns is achieved at the optimal track angle. The typical detector occupancy for minimum bias events in standard operating conditions in 2011 is around 0.5%, and the detector has less than 1% of faulty strips. The proximity of the detector to the beam means that the inner regions of the n+-on-n sensors have undergone space-charge sign inversion due to radiation damage. The VELO performance parameters that drive the experiment's physics sensitivity are also given. The track finding efficiency of the VELO is typically above 98% and the modules have been aligned to a precision of 1 micron for translations in the plane transverse to the beam. A primary vertex resolution of 13 microns in the transverse plane and 71 microns along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 microns is achieved for particles with transverse momentum greater than 1 GeV/c.
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