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Study of the Quark Gluon Plasma with Hadronic Jets

Study of the Quark Gluon Plasma with Hadronic Jets. What : the Quark Gluon Plasma Where : the Relativistic Heavy Ion Collider at BNL How : hadronic jets Summary Outlook : the Large Hadron Collider at CERN. q. q. q. q. q. q. q. q. q. q. q. q. q. q. q. q. q. q. q. q. q. q.

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Study of the Quark Gluon Plasma with Hadronic Jets

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  1. Study of the Quark Gluon Plasma with Hadronic Jets • What: the Quark Gluon Plasma • Where: the Relativistic Heavy Ion Collider at BNL • How: hadronic jets • Summary • Outlook: the Large Hadron Collider at CERN

  2. q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q q Quark-Gluon Plasma (QGP) • Lattice QCD - hadronic systems undergo a double phase transition • at TC~160 -170 MeV: • deconfined quark&gluon matter (QGP) – long range confining force screened • chiral symmetry restoration – quarks become massless

  3. 250 200 150 QGP (hot&baryon free) RHIC 100 SPS deconfinement chiral restauration Temperature (MeV) AGS thermal freeze-out 50 hadron gas SIS 0 nuclei neutron stars 0 200 400 600 800 1000 1200 Baryonic Potential B (MeV) QCD Phase Diagram However, the QGP hadronizes very quickly: one can observe only signatures of its existence (jet quenching, J/ suppression, strangeness enhancement, large collective flow, thermal electromagnetic radiation, etc.)

  4. PHENIX The Relativistic Heavy Ion Collider (RHIC) at BNL Runs 1 - 6 (2000 – 2006): Au+Au @ 200, 130, 62, 22GeV Cu+Cu @ 200, 62 GeV d+Au @ 200 GeV p+p @ 200, 62, 22 GeV (polarized)

  5. Jet event in a hot QCD medium Hadronic Jets as Tools for QGP Study Bulk (soft) QCD particle production: - low-Q2, long range strong processes, well described by hydro-/thermo-dynamical models; - ~90% of all final state particles are from vacuum ! Jet (hard) QCD particle production : -from partonic hard scattering (primarily gluons); - high-Q2 processes with calculable cross section (S(Q2)<<1) produced early (<1fm); - interact strongly with the bulk QGP:loose energy (radiate gluons)  jet quenching and broadening Observed via: - leading (high pT) hadron spectra; - two-particle azimuthal correlations.

  6. Vitev & Gyulassy, PRL 89 (2002) 252301 Hadronic Jet Suppression – Partonic Energy Loss nuclear modification factor Explained by (and only by) final state partonic energy loss models: dNgluon/dy ~ 1100 ε ~ 15 GeV/fm3 (consistent with value from dNch/dη meas.)

  7. Why do I (we) believe that (a) QGP was formed at RHIC… • Dense: ε~15GeV/fm3 (εc~1GeV/fm3), dNg/dy~1100 – from nuclear modification factors and global measurements • Hot: Tave~360MeV (Tc~160MeV) – from thermal photon spectra • Debye screening of J/Ψ(suppression and recombination) • Strongly coupled: large collective flow coefficients (v2) of all (light and heavy) mesons – quark number scaling • Thermal & chemical equilibrium: wide range of particle ratios are in agreement with statistical models • Next phase: what kind of QGP? What are its properties? • Equation of state? Transition order? • Transport coefficients? • Speed of sound?

  8. d-Au p-p PHENIX Preliminary I. Vitev Phys.Lett. B630 (2005) 78 Back to (Di-)Jets: What happens with the dissipated energy? • Hard partons loose energy. What happens to the lost energy? • Look at angular distributions of lower pT fragments… • Dijets in pp and dAu: near side (Δφ~0) from parton fragmentation; away side (Δφ~π) from fragmentation of opposite parton • Dijets in AuAu are expected to be strongly modified by the medium

  9. Away-side peak is displaced from Δφ = π: away Mach shock wave: A supersonic parton will generate a conic shock wave at a Mach angle D = acos(cs) D near D D D away Shuryak J.Phys. G31 (2005) L19 Di-Jet Shape Modification in Heavy Ion Collisions Displacement is dependent on collision centrality and independent on collision energy. IF it is indeed a Mach cone, D measures directly the speed of sound in the plasma!

  10. Summary: Probing partonic state of dense matter • RHIC has produced a dense, hot, strongly interacting, partonic state of matter at thermal and chemical equilibrium • We now have started probing the properties of the matter • energy density e >15 GeV/fm3 • gluon density dNg/dy > 1100 • initial state temperature T0ave = 300-400 MeV • More differential measurements, like angular particle correlations, are employed to gain deeper information about the properties of this state of matter

  11. Outlook: RHIC II at BNL and LHC at CERN • RHIC II: improved luminosity, new/upgraded detectors • LANL is an important part of it: a large part of our team builds a new forward silicon vertex PHENIX detector; prototype funded through a LDRD-DR grant • LHC at CERN (starts 2008): longer lived, hotter plasma • LANL is also involved: a smaller part of our team is funded through a LDRD-ER grant to study the feasibility of using dileptons to tag the hadronic jets

  12. Dilepton Tagged Jets with the CMS detector (LHC) We replace one jet in the di-jet with an electromagnetic probe (Z0/γ*l+l-), hence dilepton-tagged jet… Why? Electromagnetic probes don’t interact with the QCD medium  they measure the initial kinematics of the back-to-back jet. LDRD-ER team: Gerd J. Kunde (PI), Camelia Mironov, Maria Castro, P.C.

  13. Ratios of hadron yields consistent with system at chemical equilibrium • Global fit to relative particle abundances with 4 parameters: • chemical freezeout temperature (Tchem ~ Tcrit • baryon chemical potential for light & strange quarks (μq, μs) • strangeness saturation factor, S (S =1 is strangeness fully equilibriated) Kaneta, Xu nucl-th/0405068 Braun-Munzinger, Redlich, Stachel nucl-th/0304013

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