Master student Projects

Projects for Master students in the Nikhef B-physics (LHCb) group

date: May 2015

This is an overview with all available Master student projects in the Nikhef B-physics (LHCb) group.

If you have your own research proposal, need more detailed information on the (availability) of individual proposals or would like to discuss about other available projects in the group you are always welcome to contact either the contact person for the project and/or the Nikhef B-physics group leader:

Marcel Merk [e-mail: i93_at_nikhef.nl, Tel 020-5925107, Nikhef room N2xx]

For an overview of the theses written in the Nikhef B-physics group you can look at the Nikhef LHCb theses page

Master projects in the Nikhef B-physics group

J/psi phi is a flagship analysis in the LHCb experiment. However, no-one in LHCb has tested whether CPT symmetry is violated. CPT symmetry is tightly connected to the principle of Lorentz invariance. Lorentz invariantz violation would become visible if the decay rate would show any dependency to a fixed direction in space. In this project the CP violation analysis is extended to test for Lorentz Invariance violation.

For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. This is a project that is closely related to the larger effort at Nikhef (~5 people) of measuring phi_s with Bs->J/psiPhi decays. Weekly video meetings with CERN coordinate the efforts within the LHCb collaboration.

Relevant information:

Belle Collaboration: arXiv:1203.0930v2, Search for Time-Dependent CPT Violation in Hadronic and Semileptonic B Decays

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1) Detector Electronics & Data acquisition for the LHCb Scintillating Fiber Tracker

Supervisors: Antonio Pellegrino (physicist), Wilco Vink (engineer)

Research description:

The large-acceptance tracker of LHCb will be replaced by a detector with increased rate capabilities during next LHC long shutdown in 2019. The new detector will be based on arrays of scintillating fibers (SciFi) with 0.25 mm diameters, read out by silicon photo-multipliers (SiPMs). The processing of the SiPM signals (the whole detector will consist of 589,824 SiPM channels) in the on-detector electronics will proceed in two stages: first an application-specific integrated circuit will amplify and shape the signal and a set of comparators will digitize a two-bits information per channel; then dedicated FPGAs will reduce the data size and suppress noise through a data-clustering algorithm.

The Nikhef group is responsible for this second stage, namely for the implementation of the clusterization algorithm and for the design, production and testing of the on-detector PCBs hosting the FPGAs running the algorithm. This master project will contribute to this R&D in two main ways. On the one hand, supporting the Nikhef electronics department in the development of the code for the clusterization FPGA, providing a computer emulation of the algorithm based on C++ code and a test bench capable of processing the same data processed by the FPGA and of comparing the results. On the other, participating to the design of an automated test system to diagnose and characterize the SciFi on-detector electronics through the injection of SiPM-like current pulses, in particular writing control software and ROOT software to analyze the test data and diagnose faults.

For this project computing skills are needed (C++ and ROOT); an interest for digital electronics is welcome (with the option of learning the basic of VHDL programming). The student will perform his research in a group consisting of two seniors, one Ph.D. student and an electronic engineer.

Relevant information:

LHCb Tracker Upgrade Technical Design Report CERN-LHCC-2014-001

2) Measurement of BR(B0->pi-Ds+) and BR(Bs->Ds-*pi+)/BR(Bs->Ds-pi+)

Supervisors: Niels Tuning (staf), Lennaert Bel (PhD), Mick Mulder (PhD)

Research description:

This project aims to measure the branching fraction of the decay B0->pi-Ds+. The decay B0->pi-Ds+ is quite rare, because it occurs through the transition of a b-quark to a u-quark. It has been measured at the B-factories only at modest precision (~12%). This decay is interesting, because
1) It is sensitive to the CKM-element Vub, which determination is heavily debated.
2) It can be used to determine the ratio r_pi=B0->pi-D+/B0->D-pi+ which in turn is needed for CP violation measurements.
3) It can quantify non-factorisable QCD effects in certain B-decays.

The experimental challenge is to understand the background from e.g. Bs->Ds*pi decays. The aim is to also determine the relative branching fraction of Bs->Ds*pi relative to Bs->Dspi decays. This can is useful, because
1) It helps in the measurement of B0->pi-Ds+
2) It might quantify the magnitude of the ratio of form factors F(Bs->Ds*)/F(Bs->Ds*)

For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. This is a project that is closely related to three important analyses in the group:
1) Measurements of fs/fd with hadronic Bs->DsPi decays,
2) Time dependent CP violation analysis of Bs->DsK decays.
Weekly video meetings with CERN coordinate the efforts with in the LHCb collaboration.

Relevant information:

[1] R.Aaij et al. [LHCb Collaboration], ``Determination of the branching fractions of B0s->DsK and B0->DsK, Submitted to JHEP [arXiv:1412.7654 [hep-ex]].

[2] R. Fleischer, N. Serra and N. Tuning, ``Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States, Phys. Rev. D 83, 014017 (2011) [arXiv:1012.2784 [hep-ph]].

[3] K. de Bruyn, R. Fleischer, R. Knegjens, M. Merk, M. Schiller and N. Tuning, ``Exploring Bs -> Ds(*)K Decays in the Presence of a Sizable Width Difference ??s, Nucl. Phys. B 868, 351 (2013) [arXiv:1208.6463 [hep-ph]].