Experiments:CERN-LHC-LHCb
Deadline: 2017-03-15
Region: Europe
Job description:
Applications are invited for a PhD student position in Centre de Physique des Particules de Marseille (CPPM), France. Applicants must hold a Master degree (or equivalent) in Particle Physics, or expect to hold such a degree by September 2017. The PhD contract will start on October 1st, 2017, for 3 years. The deadline for application is March 15th, 2017.
LHCb is one of the four big experiments installed at the largest proton-proton collider ever built, the LHC, at Cern, Geneva, in Switzerland. The experiment is dedicated to the search for Physics Beyond the Standard Model (BSM) studying beauty and charm hadrons. Since the beginning of data taking in 2010, LHCb has accumulated the largest sample of b-hadrons ever collected and published hundreds of world-leading measurements. The CPPM LHCb group is deeply involved in the experiment since its beginning.
In the past few years, two intriguing anomalies have shown up in the flavour sector. One related to the b → s ll flavour changing neutral current and another one in the b → c τντ charged current. Both effects are ∼ 4σ away from the Standard Model (SM) expectation.
Concerning the second effect, the measured quantities are the ratios of branching fractions R(D(*)) = BR(B → D(*)τ−ντ) / BR(B → D(*)l−νl) , (l = μ,e) . In the Standard Model, the only difference between the numerator and the denominator is the lepton mass.When combining the results of the BaBar, Belle and LHCb experiments, the measurements appear to be 3.9σ away from their SM expectation. This is a striking hint of lepton flavour non-universality (LFNU) which clearly needs to be checked in other modes.
The student will start by working on the existing channel, B → D(*)τντ . If only the branching ratio has been measured so far, the next steps consist in exploiting, in addition, the information brought by the tau polarization, the decay angles and the q2 dependence which bring different sensitivity to BSM effects. The tau meson can be reconstructed using his muonic ( μ−νμντ ) or hadronic (π−π+π−ντ ) final states. Other modes allow to test LFNU and also need to be studied, like Λb→ Λ τντ, B0s→ Ds−τ+ντ, Bc−→ J/ψτ−ντ . During her/his PhD, the student is expected to analyse the full run1 and run2 data, which will give an un-precedented precision and should hopefully allow to clarify the current situation. The student will often travel to Cern, to participate to data taking and to present her/his results.
The ideal candidate would have a strong interest in data analysis, good software skills (C++, python, ROOT) and some experience in experimental particle physics.
Applications with detailed CV, motivation letter and 2 recommendation letters should be sent to: Olivier.Leroy@in2p3.fr
More Information:http://lhcb.web.cern.ch/lhcb/