Abstract
Low-mass dimuon production, including light vector mesons ρ, ω, ϕ, provides key information on the hot and dense state of strongly interacting matter produced in high-energy heavy-ion collisions. In particular, strangeness production can be studied via ϕ meson measurements, while the detailed description of the full dimuon mass spectrum down to the kinematic threshold can be used to reveal in-medium modifications of hadron properties and the thermal emission arising from the medium. Measurements in pp and p-A systems, in absence of hot nuclear matter effects, must be used as a reference to test our knowledge of the processes expected to contribute to dilepton production. Dimuon production is studied with the ALICE apparatus at the LHC at forward rapidity (2.5 < y < 4) with the Muon Spectrometer. In this contribution, results on low-mass dimuon production are shown, for various center-of-mass energies per nucleon pair, in pp, p-Pb, and Pb-Pb collisions.
Highlights
Low-mass dimuon production at the LHC energies is dominated by the 2-body and Dalitz decays of the light neutral mesons η, ρ, ω, η and φ — the so-called “hadronic cocktail” — with dimuons from open charm and open beauty decay processes contributing to the invariant mass continuum
Describing the observed low-mass dimuon production in pp collisions allows for the study of particle production mechanisms in elementary hadronic interactions in the light quark sector, while observations in p-A collisions are sensitive to initial state effects affecting particle production in cold nuclear matter
Low-mass dimuon measurements in heavy-ion collisions, in particular, allow the identification of hot nuclear matter effects related to the creation of an extended volume of quark-gluon plasma (QGP), to its hydrodynamical evolution, and to the chiral symmetry restoration expected to occur within the deconfined system
Summary
Low-mass dimuon production at the LHC energies is dominated by the 2-body and Dalitz decays of the light neutral mesons η, ρ, ω, η and φ — the so-called “hadronic cocktail” — with dimuons from open charm and open beauty decay processes contributing to the invariant mass continuum. Low-mass dimuon measurements in heavy-ion collisions, in particular, allow the identification of hot nuclear matter effects related to the creation of an extended volume of quark-gluon plasma (QGP), to its hydrodynamical evolution, and to the chiral symmetry restoration expected to occur within the deconfined system. In this case, key-observables are strangeness production via φ meson measurement, the spectral function modification of the short-lived ρ meson, and the observation of direct thermal radiation from the QGP phase. In all the measurements presented in the following, the combinatorial background is evaluated using an event mixing technique [5] and subtracted from the raw dimuon invariant mass spectrum
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