Transcript `constituent quarks`.

RHIC Experimental Status
&
Future Outlook
Huan Zhong Huang
Department of Physics and Astronomy
University of California, Los Angeles
June 28-29 @ Shanghai Eastern Forum
Topics
1) Deconfined Partonic Matter
2) What Can Heavy Ion Physics Experimentalists
Teach About Lattice QCD?
3) Is There a Phase Transition?
4) Chiral Symmetry Restoration?
5) RHIC as an Exotic Particle Factory
Constituent Quark Scaling
STAR
Baryon
Meson
PHENIX
Constituent (n) Quark Scaling
-- Meson n=2 and Baryon n=3 grouping
Saturation of v2 at Intermediate pT
Partonic v2 and Surface Emission
PRL 92 (2004) 052302; PRL 91 (2003) 182301
At hadron formation time
there is a collective v2
among constituent quarks
Recombination/coalescence
provides a hadronization
scheme
(not necessarily related to
partonic matter, works
for d+Au)
Possible geometrical nature
of v2 saturation
– surface emission
Hadronization of Bulk Partonic Matter
1) At the moment of hadronization in nucleus-nucleus
collisions at RHIC the dominant degrees of freedom
is related to number of constituent quarks.
2) These ‘constituent quarks’ exhibit an angular
anisotropy resulting from collective interactions.
3) Hadrons seem to be formed from coalescence or
recombination of the ‘constituent quarks’, and the
hadron properties are determined by the sum of
‘constituent quarks’.
Conditions at Tc
Empirically,
Partonic matter evolves such that at the
hadronization, the dominant degrees of freedom are
in ‘constituent quarks’/quasi-hadrons. The formation
mechanism could be coalescence or recombination
of these quarks.
Gluon degrees of freedom are not
manifested at hadronization, though at initial stage
of the heavy ion collision, gluons must dominate.
Lattice QCD
LQCD,
Spectral functions of hadrons (J/psi and light
hadrons) survive near TC or somewhat above TC.
Strong correlations persist up to high temperature
above TC!
LQCD e.g. S. Datta et al, hep-lat/0412037
J/y and hC may survive up to 2.25 TC !
Our data indicate that at T=TC even light hadrons
are in quasi-hadron state (strongly
interacting constituent quark state) !
Phase Transition ?
The Initial State from the Collision must be dominated
by gluons (Temperature?) Parton Evolutions (?)
At the Hadronization Stage the dominate degrees of
freedom are constituent quarks (or quasi-hadrons)
(Empirical + LQCD)
What is the parton evolution dynamics??
Empirically the dense matter with collective motions of
constituent quark degrees of freedom must be
preceded with a deconfined partonic matter, BUT
we do not have any experimental indication that this
is a phase transition !
Chiral Symmetry
How Chiral Symmetry has manifested in
nucleus-nucleus collisions?
We must measure vector mesons in
both hadronic and leptonic decay channels!
electron PID  TOF upgrade
HFT – reduce conversion BK
K-pi PID  TOF upgrade
h and h’  EMC + high statistics
Baryonic resonances (D,L(1520),S(1385),X(1530)....)
RHIC Physics in + Years
1) Heavy Quark Production
-- Yield and pT distribution (Energy Loss)
-- Parton Collectivity
2) Thermal Photon Radiation
3) QCD Photons (gamma-jet and QGP Brem.)
4) Chiral Symmetry and low mass di-leptons
5) Exotic Particle Searches
RHIC – Exotic Particle Factory
Clustering and Surface Emission
Volcanic mediate pT – Spatter (clumps)
Enhancement of Clusters
at intermediate pT !
Search for Multi-quark (>3) Cluster State at RHIC !
dAu results
M (GeV/c2)
pK+ and pK- from 18.4 M d+Au at 200 GeV
Background – Combinatorial and Correlated Pairs
dAu results
PeaK?!
Understand the Background!
dAu results
The invariant mass distribution is fitted to a Gaussian plus a linear
function. A 3.5-5.0 sigma signal is seen
Measured mass is about 1.53 GeV/c2. Full width is about 15 MeV
The Puzzle Continues
1) If pK+ peak at 1530 MeV/c2 is a real pentaquark, then
I = 1 likely, there must be a q+. But the recent JLab
null result on q+ casts serious doubt on the observation
of q+.
2) The STAR observed yield is so small such that many
experiments would not have the sensitivity to see it.
3) Within the STAR data we have not seen any significant
peak signal in p+p (8M) data and Au+Au at
200 GeV (~10M).
What do these null observations mean?
Production dynamics or data set bias unknown to us?
What is so special about d+Au 200 GeV (18.4 M events)
and Au+Au 62.4 GeV (5.1 M events)?
Other Exotic Particles
Gluon Balls
Exotic mesons (uds)(ud) (uds)s
Pentaquarks
Dibaryons
H (uuddss)
[W-W] (ssssss)
RHIC – Exotic Particle Factory
STAR – Exciting Physics Program
A full TOF and Heavy Flavor Tracker upgrade will
greatly enhance STAR’s capability !!
Full Barrel TOF Using MRPC
Heavy Flavor Tracker
Using Active Pixel Sensor
two layers of thin silicon detector
1.5 cm and 4 cm radius
Charmed Exotics?!
eRHIC Inevitable ?! But When?
RHIC II – Machine Upgrade
-- Tandem
-- Electron Cooling
Electron – LINAC 10 GeV
Natural Physics Direction from RHIC/JLAB
20 Years ?
RHIC Beyond +5 Years
Hadrons with internal structure beyond existing
QCD qqq and q-qbar framework !!
RHIC –
Dedicated QCD Machine &
Beyond
Exotic
AA
pp
(spin)
(Deconfinement
Phase Transition)
pA
(CGC,EMC)
The End
Identified Particles
No Clear Idea on what to measure for
phase transition signatures !
Particle Flavor Fluctuations
Strangeness
Baryon numbers
Baryon Formation Mechanism?
Hadronization time scale?
STAR Full TOF Upgrade will open a new
window. Is it sufficient to see a clear
picture? ??
Deconfined Matter at RHIC
Coalescence/Recombination Mechanism
IS not key argument for deconfinement !
It works in d+Au and perhaps p+p as well !
Deconfined –
Constituent quark degree of freedom
Matter –
Collective interaction  partonic v2
strange/charm dynamics in the deconfined
medium
Is There a Q++ Pentaquark State?
d+Au
 Require the opening angle of the two daughters to be greater
than 30 degree, and change the proton p&pt cut to be within 0.3
and 1.5 GeV
 A clear peak is seen with a 5-6.4 sigma significance
  S / N  2902 / 211200  6.4
Is Q Isospin One ?
If both q+ and q++ exist as the lowest pentaquark state –
Isospin >= 1
Chiral Soliton Model
Di-quark model
Quark cluster model
???
If q state has isospin I = 1, there will be
q 0  n + KS
Critical confirmation for I = 1 !!
RHIC’s Uniqueness
Multi-Strange Exotic Particles:
RHIC: Large Strangeness
Production
Strangeness gs ~ 1
baryon and anti-baryon
~ symmetric
NA49 Pentaquark ?
X- - X- + pM  [1890-180*Y] MeV
What Are Required
High Detection Efficiency for Weak Decays
-- Intermediate Tracking R~10 cm up
-- Continuous Tracking a plus
Large Acceptance
-- Ks, Lambda, Xi, Omega
-- Multi-particle Correlations
Neutral Detectors
-- Neutron (anti-neutron!)
-- p0
PID – TOF and trigger capability
Micro-Vertex– for Charmed Exotic Particles
High Rate Capability and DAQ Rate
New Experiment
Affordable Neutron Detector
Tracking of V0 near primary vertex
Excellent Particle Identification (TOF)
Upgradeable with Heavy Flavor Tracker
STAR versus New Experiment
STAR:
Existing detector
Large Acceptance
Reasonable Data Rate
V0 Capability not ideal
-- lack of continuous tracking
at intermediate R
No Neutron detection
PID – TOF will do
Limited high rate (distortion)
Large Inertial in STAR