ALICE Upgrade 2 (Silicon Physicist post)

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Quantum-ChromoDynamics (QCD) is the theory of the strong force and understanding its properties has been the focus ofintense World-wide research over the past half century. QCD forms a major part of the Standard Model and itsunderstanding is crucial in producing an overall theory to describe the properties of matter and the fundamental forces ofnature including a grand unification theory to explain how the Universe evolved from the Big Bang.The principal purpose of our research is to use ultra-relativistic heavy-ion interactions to study QCD at extreme energydensities. Theoretical models predict that under very extreme conditions of high energy densities the quarks, which areconfined in normal nuclear matter, will be freed and nuclear matter will undergo a phase transition into a hot, dense plasmaof free quarks and gluons known as a Quark-Gluon Plasma (QGP). It is thought that such a state of matter would haveexisted until about 10^-5 seconds after the Big Bang, after which time the Universe would have cooled sufficiently forprotons and neutrons to form.The physics aim of this research is to study the strong force under these extreme conditions and, in particular, explore theproperties of this exotic state of matter. By studying the QGP, we hope to address the fundamental questions of quarkconfinement and how quarks gain a large effective mass in hadrons due to the strong force (accounting for 99% of atomicmass).In order to create the conditions required to produce a QGP we must collide heavy nuclei together at the highest possibleenergies, creating tiny hot (~10^13K) and dense fireballs. As the resulting QGP will only last for about 10-22 seconds,before condensing in to thousands of elementary particles, we must also use the most sophisticated detectors to analysethese collisions.The LHC collides lead ions at centre-of-mass energies of 2.76 TeV in ALICE. We also collide protons together as this formsan excellent reference data set. Moreover, the excellent particle identification and tracking make ALICE an ideal detectorto study the global aspects of proton-proton collisions in their own right.This field of research employs about two thousand physicists around the world and ALICE is the most sophisticatedexperiment ever built in the field, studying heavy-ion collisions at centre-of-mass energies over an order of magnitudegreater than its nearest rival. It hence represents the pinnacle of research in this field.The ALICE collaboration is now preparing for the second LHC Upgrade scheduled to start in 2018. These upgrades arerequired to cope with the anticipated increase in lead beam luminosity which will increase beam intensities by an order ofmagnitude. The main motivation for the luminosity upgrade is to achieve a precise, quantitative understand of theproperties of the QGP by focusing on rare probes both at low and high transverse momenta as well as on multidimensionalanalysis of such probes with respect to centrality, event plane, multi-particle correlations, etc.