Identified Hadrons and Their Role at RHIC Camelia Mironov Kent State University 2 Action: wherewhywhat.bnl.gov 3 Relativistic Heavy Ions Collider Where? USA - Long Island Brookhaven - RHIC 4 System s (GeV) Au + Au20, 62, 130, 200 d + Au200 p + p200 Cu +Cu20,62, 200 different energy: vary energy density different A : vary the size of the system have the p+p baseline WHAT? COLLISIONS! Au+Au collisions dense medium hadrons detector Au+Au, p+p, d+Au hadronization mechanisms Theory vs Experiment Future measurements High p T hadrons unidentified identified 6 Geometry of the collision N part number of nucleons in the overlap region Collisions Participants Binary Collisions Participants b (fm) N part, N binary Central peripheral N bin ( N coll ): number of inelastic nucleon - nucleon collisions (# binary collisions) b Im pa ct Pa ra m et er 7 How A+A differs from a bunch of p+p? Initial Final p+p A+A 8 hadrons leading particle a b c d Hard-scattering cross-sectionFragmentation Function pQCD particle production: p+p (pT>2GeV/c) InitialFinal Parton Distribution Functions p p 9 c d hadrons a b pQCD particle production: Au+Au (pT>2GeV/c) InitialFinal Parton Distribution FunctionsIntrinsic k T PDF modification (shadowing) Hard-scattering cross-sectionFragmentation Function leading particle suppressed Partonic Energy Loss 10 Au+Au vs. p+p Au+Au : initial +final state effects pp : simple We NEED ALSO A collision system to disentangle the initial-final states effects p (d) + Au no final state effects 11 pQCD particle production: d+Au (pT>2GeV/c) InitialFinal Parton Distribution Functions Intrinsic kT PDF Modification (shadowing) Fragmentation Function c d hadrons a b 12 Quantify deviations of A+A from p+p ? !!! Simplest: divide AA spectra to pp spectra!!!! NUCLEAR MODIFICATION FACTORS 13 Quantify deviations of A+A from p+p NUCLEAR MODIFICATION FACTORS Need one collision system systematic errors cancel out ASSUMPTION: both ratios exhibit the same behavior because of the same underlying physics 14 Information via R XX R ~1 -- no nuclear effects: A+B = C * (p+p) deviation from 1 indicate presence of nuclear effects: R>1 enhancement (usual explanation: soft scatters before hard collision) R