Performance of the LHCb vertex detector alignment algorithm determined with beam test data

Gersabeck, M.; Viret, S.; Parkes, C.; Artuso, M.; Borel, J.; Bowcock, T. J. V.; Buytaert, J.; Collins, P.; Dumps, Raphael; Dwyer, L.; Eckstein, D.; Eklund, L.; Ferro‐Luzzi, M.; Frei, R.; Haefeli, G.; Hennessy, K.; Huse, T.; Jans, E.; John, M.; Ketel, T.; Keune, A.; Laštovička, T.; Mountain, R.; Neufeld, N.; Papadelis, A.; Stone, S.; Szumlak, T.; Beuzekom, M. van; Lysebetten, A. Van; Versloot, T. W.; Vries, H. de; Wang, J.C.

doi:10.1016/j.nima.2008.07.154

Cited by 15 publications

(6 citation statements)

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“…A comprehensive overview of the performance of the alignment software with beam test data is given in Ref. [6]. A first indication of the quality of the alignment algorithms can be obtained by studying residual distributions.…”

Section: Beam Test Resultsmentioning

confidence: 99%

Alignment of the LHCb Vertex Locator

Gersabeck

2008

Preprint

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LHCb will commence data taking as the first dedicated heavy flavour experiment at a hadron collider in 2008. A very high hit precision from its vertex detector (VELO) is essential to meet the tight requirements of vertex reconstruction in B-physics. The single hit precision of the VELO is better than 10 µm. However, the VELO is operated only 8 mm from the beam and must be retracted and reinserted each LHC fill. Hence, the detector places unique demands on its alignment algorithm. The partially assembled VELO system has already been tested in a beam test. The novel software alignment methods are presented together with their interplay with the metrology measurements. Results from Monte Carlo simulation studies are discussed and recent beam test results are shown that prove the method's precision at the micron level.

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Section: Beam Test Resultsmentioning

confidence: 99%

Alignment of the LHCb Vertex Locator

Gersabeck

2008

Preprint

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“…The first method [34,35] performs the Φ sensor alignment by fitting an analytical form to the residuals as a function of φ , and performs the remaining alignment stages using a matrix inversion method, based on Millepede [36], which performs a χ 2 minimisation that depends upon both the track and alignment parameters. This alignment method is fast but the implementation fits straight line tracks in the VELO.…”

Section: Track-based Alignment Methodsmentioning

confidence: 99%

Performance of the LHCb Vertex Locator

Bjørnstad

2011

J. Inst.

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The Vertex Locator (VELO) is a silicon microstrip detector that surrounds the protonproton 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 CO 2 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 µm 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 µm for translations in the plane transverse to the beam. A primary vertex resolution of 13 µm in the transverse plane and 71 µm along the beam axis is achieved for vertices with 25 tracks. An impact parameter resolution of less than 35 µm is achieved for particles with transverse momentum greater than 1 GeV/c.

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“…The performance of this algorithm has also been demonstrated with beam test data and is reported in Ref. [10].…”

Section: Simulation Studiesmentioning

confidence: 99%