Master student Projects

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

date: August 2013

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

1) Study of long-living particles

Supervisors: Wouter Hulsbergen (staf) and Veerle Heijne (PhD)

Research description:

Supersymmetry is potentially the key to understand the Dark Matter in the Universe. Within the SUSY framework, long-living supersymmetric particles can exist, which can be detected by the LHCb detector. The search for these particles will be performed on the recent data set recorded in 2012, and some work is also needed on the trigger selection, to prepare for data taking in 2015, when the LHC will be running at a higher center-of-mass energy.

For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. You become part of our research group (~5 persons); we have weekly video meetings with colleagues at CERN.

Relevant information:

Master thesis Suzanne Klaver (2013): A Search for Long-lived Neutralinos in LHCb

2) World's best measurement of the Bc+ mass with Bc+ -> Bs pi+

Supervisors: Niels Tuning (staf), Jacco de Vries (PhD)

Research description:

At Nikhef we recently discovered the first weak B-decay with another B-to-B decay: Bc+ -> Bs pi+. The mass difference between the Bc+ and Bs meson is very small (only about 0.9 GeV), and as a result the mass difference can be accurately determined. This will lead to the world's best measurement of the Bc+ mass.

A theoretical component (in collaboration with Robert Fleischer) can be added to this project, by examining the various possible Bc+ decay modes, and make quantitative predictions for the relative branching fractions. Investigating the various decay modes, can lead to a method for determining the absolute production rate of Bc+ mesons at the LHC, which is at present still unknown.

For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. This is a small project, where the student can perform his research in an independent way. The group at Nikhef (~2 persons) collaborates with a small group at CERN that studies the same decay, but with a different Bs final state. This research will likely result in an official LHCb publication.

Relevant information:

Master thesis Jacco de Vries (2013): First observation of the decay Bc+ -> B0s pi+

LHCb collaboration, arXiv:1308.4544 (2013): Observation of the decay Bc+ -> Bs pi+

R. Fleischer, N. Serra and N. Tuning, Phys. Rev. D 83, 014017 (2011) Tests of Factorization and SU(3) Relations in B Decays into Heavy-Light Final States

3) Light Higgs search A0 -> mu+mu-

Supervisors: Wouter Hulsbergen (staf), Pieter Davids (PhD)

Research description:

Supersymmetry is potentially the key to understand the Dark Matter in the Universe. In supersymmetry, there is not just one Higgs boson as in the Standard Model, but there ar five Higgs bosons. Certain SUSY models predict a relatively light A0 Higgs particle. The A0 particle can decay to two muons, which would be clearly detectable at LHCb thanks to its excellent mass resolution, leading to a narrow mass peak in the di-muon invariant mass spectrum.

For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. This is a new project, within the small group at Nikhef (~3 persons). The analysis resembles the search for the decay Bs->mu+mu-, which was discovered this Summer and led to a lot of attention.

Relevant information:

LHCb collaboration, arXiv:1307.5024 Measurement of the B0s->mu+mu- branching fraction and search for B0->mu+mu- decays at the LHCb experiment

4) Understanding 'penguin pollution' in phi_s with Bs -> J/psi K* decays

Supervisors: Gerhard Raven (staf), Vasilis Syropoulos (PhD)

Research description:

The measurement of the CP-violating phase phi_s is a flagship in LHCb. A deviating measurement of phi_s can be a hint of new particles, and can shed light on the mystery why we live in a matter-dominated Universe without anti-matter. However, certain decay diagrams (called 'penguin' diagrams) can affect the measurement of phi_s, which is theoretically difficult to quantify. To solve this problem, measurements on the decay Bs->J/psiK* will provide important constraints on these penguin contributions.

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:

LHCb collaboration, arXiv:1304.2600, Measurement of CP-violation and the Bs0-meson decay width difference with Bs0->J/psiK+K- and Bs0->J/psi pi+pi- decays

5) Search for a light Higgs in the decay Sigma+ -> p mu mu

Supervisors: Francesco Dettori (postdoc), Antonio Pellegrino (staf), Siim Tolk (PhD)

Research description:

The decay Sigma+ -> p mu mu is very rare in the Standard Model. In 2005 the HyperCP experiment has seen first evidence of this decay, but with a very peculiar feature: all the three events seen have the same dimuon invariant mass. This could be due to new particles (a very light Higgs?) giving rise to a decay of the type Sigma -> p X decay, with X decaying into two muons. The search for this decay at LHCb is important both to confirm this very rare process and to search for possible new phenomena.

For this project computer skills are needed. The ROOT programme and C++ and/or Python macros are used. This is a small project, where the student can perform his research in an independent way.

This research will likely result in an official LHCb publication.

Relevant information:

HyperCP Collaboration, Phys. Rev. Lett. 94, 021801 (2005) [http://arxiv.org/abs/hep-ex/0501014 Evidence for the decay Sigma+ -> p mu mu ]

Xiao-Gang He, Jusak Tandean, G. Valencia, Phys. Rev. Lett. 98, 081802 (2007) [http://arxiv.org/abs/hep-ph/0610362 Has HyperCP Observed a Light Higgs Boson? ]