Study of the Quark Gluon Plasma with Hadronic Jets

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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

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Quark-Gluon Plasma (QGP)

• Lattice QCD - hadronic systems undergo a double
  phase transition
• at TC160 -170 MeV
• deconfined quarkgluon matter (QGP) long range
  confining force screened
• chiral symmetry restoration quarks become
  massless

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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.)
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The Relativistic Heavy Ion Collider (RHIC) at BNL
Runs 1 - 6 (2000 2006) AuAu _at_ 200, 130,
62, 22 GeV CuCu _at_ 200, 62 GeV dAu _at_ 200
GeV pp _at_ 200, 62, 22 GeV (polarized)
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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)ltlt1) produced early (?lt1fm) - 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.
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Hadronic Jet Suppression Partonic Energy Loss
nuclear modification factor
Explained by (and only by) final state
partonic energy loss models dNgluon/dy 1100 e
15 GeV/fm3 (consistent with value from dNch/d?
meas.)
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Why do I (we) believe that (a) QGP was formed at
RHIC

• Dense e15GeV/fm3 (ec1GeV/fm3), dNg/dy1100
  from nuclear modification factors and global
  measurements
• Hot Tave360MeV (Tc160MeV) from thermal
  photon spectra
• Debye screening of J/? (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?

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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 (?f0) from
  parton fragmentation away side (?fp) from
  fragmentation of opposite parton
• Dijets in AuAu are expected to be strongly
  modified by the medium

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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!
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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 gt15 GeV/fm3
• gluon density dNg/dy gt 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

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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

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Dilepton Tagged Jets with the CMS detector (LHC)
We replace one jet in the di-jet with an
electromagnetic probe (Z0/??ll-), hence
dilepton-tagged jet Why? Electromagnetic probes
dont 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.
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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