high density matter and searches for exotics @rhic
DESCRIPTION
High Density Matter and Searches for Exotics @RHIC. Huan Z. Huang Department of Physics and Astronomy University of California, Los Angeles. The STAR Collaboration. Outline. High Density Matter and Its Hadronization at RHIC Pentaquark Searches in STAR - PowerPoint PPT PresentationTRANSCRIPT
High Density Matter and
Searches for Exotics @RHIC
Huan Z. Huang Department of Physics and Astronomy University of California, Los Angeles
The STAR Collaboration
Outline
• High Density Matter and Its Hadronization at RHIC
• Pentaquark Searches in STAR
• The Puzzle Continues
RHIC – Exotic Particle Factory
RHIC – Dense Partonic Matter andRapid Hadronization
Unique Collision Environment for Possible Exotic Particles Formation
Exotic Mesons, Pentaquarks, Di-baryons [ and Strangelets
Formation of Dense Matter at RHIC
1) Suppression of high pT hadrons in central Au+Au collisions
2) Disappearance of back-to-back high pTjet correlations and the energy dissipation
in soft particle production
Empirical Quark Scaling in RAA and v2
STAR
PHENIX
Baryon
Meson
Constituent (n) Quark Scaling-- Meson n=2 and Baryon n=3 grouping
Saturation of v2 at Intermediate pT
Very different from fragmentation formation scheme !!
Hadronization of Bulk Partonic Matter
PR
L 92
(20
04
) 05
23
02
; PR
L 91
(20
03
) 18
23
01
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
Clustering and Surface Emission
Volcanic mediate pT – Spatter (clumps)
Enhancement of Clustersat intermediate pT !(baryons and hyperons)
Search for Multi-quark (>3) Cluster State at RHIC !
Au + Au Collisions at RHIC
STARSTAR
Central Event
(real-time Level 3)
STAR Pentaquark Searches
+ p + KS
++ p + K+
Data Set:Au + Au 200 GeV run 2 (~1.7 M, 30-80%) p + p data 200 GeV run 2 (~8 M, Z<75cm)d + Au 200 GeV run 3 (18.4 M)Au + Au 63 GeV run 4 (5.1 M)Cu + Cu 63 GeV run 5 (15.6 M)
Particle identification
Particle Identification: dE/dx from TPC
dAu results
M (GeV/c2)
pK+ and pK- from 18.4 M d+Au at 200 GeVBackground – Combinatorial and Correlated Pairs
dAu results
Understand the Background!
PeaK?!
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
Possible Sources of Background
Double Conversion of 0 photons
0 e+e- e+e-
Same-sign e’s within the K and p bands
mostly in the low mass region opening angle cut very effective
Associated production K+ p
These background sources contribute to the residuals in the event-mixing. But they do not produce a narrow peak !
+++p and using as K
K
Other PID Cuts
Kaon 0.2<p&pt<0.7, Proton 0.3<p&pt<1.0, no opening angle cut
Other PID Cuts
Kaon 0.2<p&pt<0.8, Proton 0.3<p&pt<1.0, no opening angle cut
Other PID Cuts
Kaon 0.2<p&pt<0.8, Proton 0.3<p&pt<1.5, no opening angle cut
Other PID Cuts
Kaon 0.2<p&pt<1.0, Proton 0.3<p&pt<1.5, no opening angle cut
Spectrum?
Spectrum includes ++ and -- Mt-exponential fit yields:dN/dy = 0.0012 +- 0.0006T = 315 +- 30 MeV
Yields for some particles in dAuKs: 0.321 +- 0.006 +- 0.03L+Lbar: 0.339 +- 0.007Xi+Xibar: 0.0251 +- 0.0006Phi: 0.0642
After acceptance and efficiency correction
Assuming 100% branching ratio
++/ ~ 2%
AuAu 62.4 GeV Results
o A nice signal is also seen in AuAu 62.4 GeV data from 20-80% centrality bin, 5.1 M events.o --/++ = 0.47 +- 0.2
++ --
++ plus --
A Stringent Limit from HERA-B
HERA-B hep-ex/0408048sqrt(s) 42 GeVpA (C,Ti,W) 200 M inelastic events+/ <0.92%; 95%CL+/(1520) <2.7%; 95% CL
Our Estimate in STARd+Au sqrt(s) 200 GeV/ ~ 0.35%
Does this imply (1520)/ ~ 34%?
STAR(1520)/ ~ 10% !
The Puzzle Continues1) If pK+ peak at 1530 MeV/c2 is a real pentaquark, then
I = 1 likely, there must be a +. But the recent JLab null result on + casts serious doubt on the observation
of +.
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 significantpeak 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)?
STAR – Exciting Physics Program A full TOF and Heavy Flavor Tracker upgrade will greatly enhance STAR’s capability !!
RHIC – Exotic Particle Factory
Heavy Flavor TrackerUsing Active Pixel Sensor
two layers of thin silicon detector 1.5 cm and 4 cm radius Charmed Exotics?!Full Barrel TOF Using MRPC
Exotic Particles Hadrons with internal structure beyond existing
QCD qqq and q-qbar framework !!
pp pA
AA
pppA
AA
Exotic
RHIC – Dedicated QCD Machine & Beyond
(spin) (CGC,EMC)
(Deconfinement Phase Transition)
The End