Mapping the material in the LHCb vertex locator using secondary hadronic interactions

Alexander, M.; Barter, W.; Bay, A.; Bel, L. J.; Beuzekom, M. Van; Bogdanova, G.; Borghi, S.; Bowcock, T. J. V.; Buchanan, E.; Buytaert, J.; Akiba, K. Carvalho; Chen, S.; Coco, V.; Collins, P.; Crocombe, A.; Marinho, F. Da Cunha; Dall'Occo, E.; Capua, S. De; Dean, C. T.; Dettori, F.; Dossett, D.; Dreimanis, K.; Dujany, G.; Eklund, L.; Evans, T.; Ferro-Luzzi, M.; Gersabeck, M.; Gershon, T.; Hadavizadeh, T.; Harrison, J.; Hennessy, K.; Hulsbergen, W.; Hutchcroft, D.; Ilten, P.; Jans, E.; John, M.; Kopciewicz, P.; Koppenburg, P.; Lafferty, G.; Latham, T.; Leflat, A.; Majewski, M. W.; Mcnulty, R.; Mylroie-Smith, J.; Oblakowska-Mucha, A.; Parkes, C.; Pearce, A.; Poluektov, A.; Pritchard, A.; Qian, W.; Redford, S.; Richards, S.; Rinnert, K.; Rodrigues, E.; Sarpis, G.; Schiller, M.; Schindler, H.; Smith, M.; Smith, N. A.; Szumlak, T.; Velthuis, J. J.; Volkov, V.; Wallace, C.; Wark, H. M.; Webber, A.; Williams, M. R. J.; Williams, M.

doi:10.1088/1748-0221/13/06/P06008

Precise knowledge of the location of the material in the LHCb vertex locator (VELO) is essential to reducing background in searches for long-lived exotic particles, and in identifying jets that originate from beauty and charm quarks. Secondary interactions of hadrons produced in beam-gas collisions are used to map the location of material in the VELO. Using this material map, along with properties of a reconstructed secondary vertex and its constituent tracks, a p-value can be assigned to the hypothesis that the secondary vertex originates from a material interaction. A validation of this procedure is presented using photon conversions to dimuons.