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Predicting the origin of the first hits measured by the Vertex Locator for B(c) → τ + ν

Bruine, Frederiek de (2023) Predicting the origin of the first hits measured by the Vertex Locator for B(c) → τ + ν. Bachelor's Thesis, Physics.


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At the LHCb experiment at CERN, proton beams are collided to study the decays of hadrons that include a beauty quark. To measure these short-lived particles before they decay, one of the detectors at the LHCb experiment, the Vertex Locator (VELO), is placed at only a 5.1 mm distance from the proton-proton collision point to measure the location of charged particles that hit the detector. A way to test the Standard Model is to measure the branching fractions of the B(c) → τ (→ π+π+π−ντ )ντ and B+ → τ (→ π+π+π−ντ )ντ decays. To possibly improve the separation of background decays from these signal decays, the goal of this research is to determine the B(c)-to-τ ratio of first hits measured at the VELO. The origin of the first hits is determined by comparing the location of the firsthits with the location of the decay vertex of the B(c) particle for data simulated with the RapidSim package. For the Bc-decay this resulted in 90.6% of first hits to be classified as τ -hits and 9.4% as Bc hits and for the B+-decay in 30.9% as τ hits and 69.1% as B+ hits. Since the decay vertex of the B(c) particle cannot be determined experimentally, it is also studied whether it is possible to predict the origin of the first VELO hits with only the observed parameters. By implementing a Multivariate Analysis, it is shown that this is possible for both the Bc and B+ decay.

Item Type: Thesis (Bachelor's Thesis)
Supervisor name: Bruyn, K.A.M. de and Jones, S.A.
Degree programme: Physics
Thesis type: Bachelor's Thesis
Language: English
Date Deposited: 12 Jul 2023 09:20
Last Modified: 12 Jul 2023 09:20

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