This proposal focuses on the experimental study of the phase diagram of Quantum Chromo Dynamics (QCD), the fundamental theory of the strong interaction and one of the pillars of the Standard Model, at extreme values of energy and particle density. The goal of this research project is to quantitatively characterise the physical properties of two QCD "media": the "Quark-Gluon-Plasma" (QGP) and the "Color-Class-Condensate" (CGC), via the study of the modifications suffered by "hard" probes (particles with larg e transverse momentum and/or high mass) produced in nucleus-nucleus and proton-nucleus collisions at ultra-relativistic energies, compared to their production in reference proton-proton collisions ("QCD vacuum") at the same energies. More specifically, the proposal focuses on the development of the heavy-ion physics programme of the "Compact Muon Solenoid" (CMS) experiment, the largest physics collaboration at the CERN "Large Hadron Collider" (LHC). The detailed characterization of the QGP will be basicall y done exploiting the excellent experimental capabilities of CMS for full jet reconstruction, and for the identification of the family of Upsilon resonances. Indeed, the two strongest signals of QGP formation are: (i) the "absorption" of hard-scattered par tons (jets) in the dense medium formed in nucleus-nucleus reactions ("jet quenching"), and (ii) the "melting" of quark-antiquark resonances at high plasma temperatures ("quarkonia suppression"). The discovery and study of possible gluon-saturation (CGC) ef fects will be possible via the unique coverage of the CMS detector in a kinematic regime at very forward rapidities (very small angles) where the fraction of the transverse momentum carried by the colliding gluons (low-x) will be the smallest ever probed i n high-energy hadronic collisions in the laboratory.
Call for proposal
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