Heavy flavour as QGP probe in heavy-ion collisions at the LHC
IDPASC Portugal - PHD Programme 2016
2016 / 2017
Theoretical Particle Physics | Experimental Particle Physics
Instituto Superior Técnico
Laboratório de Instrumentação e Física Experimental de Partículas
Heavy favor particles are excellent probes of the properties of the hot and dense QCD medium created in heavy-ion collisions. The subject of this thesis is to explore heavy flavour signals in collisions involving heavy-ions at the LHC, studying the suppression of different states, and thereby characterising the primordial QGP medium. Quarkonia, bound states of a quark and antiquark, are known to be excellent probes of the QGP. In the first operation stage of the LHC (Run1), LIP has led the quarkonium measurements. Taking advantage of the excellent capabilities of the CMS detector, the Y(ns) family of states has been reconstructed for the first time in collisions involving heavy ions. We have used this capability to deliver what is arguably the most spectacular indication of QGP formation at the LHC, and established for the first time the experimental pattern of sequential suppression. The work program involves the extended study of quarkonium states, including the measurement of production and suppression rates as well as angular momenta induced distributions and observables. b-hadrons offer additional probes of the medium, which shall be exclusively reconstructed for the first time in collisions involving heavy ions, and which provide unique information of the flavour dependence of energy loss of hadrons while traversing the medium. This program takes advantage of unique expertise acquired in the group, and has the potential to deliver further ground breaking results towards a more complete characterisation of the QGP medium. Remarks: - LIP has a leading involvement in this physics research area. The proposed supervisor of this thesis is the co-ordinator of the overall CMS-wide heavy flavour physics analysis group (PAG). - LIP members have led quarkonium production measurements (cross sections and polarisations) in Run I at CMS, in pp and PbPb collisions. The discovery of quarkonia sequential suppression is a flagship of the LHC Run1; a LIP member has led this measurement and wrote the paper PRL 109 (2012) 222301 which was highlighted by the journal (editor choice and physics viewpoint 'New temperature probe for QGP'). - Solid computing skills (C++) are a plus. Availability to travel to CERN for short periods is expected, in order to participate in data taking, and in PAG and analysis team meetings.