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High Density Matter and Searches for Exotics @RHIC

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

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High Density Matter and Searches for Exotics @RHIC

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  1. High Density Matter and Searches for Exotics @RHIC Huan Z. Huang Department of Physics and Astronomy University of California, Los Angeles The STAR Collaboration

  2. Outline • High Density Matter and Its Hadronization at RHIC • Pentaquark Searches in STAR • The Puzzle Continues

  3. RHIC – Exotic Particle Factory • RHIC – Dense Partonic Matter and • Rapid Hadronization • Unique Collision Environment for Possible Exotic Particles Formation • Exotic Mesons, Pentaquarks, Di-baryons [WW] and Strangelets

  4. Formation of Dense Matter at RHIC • Suppression of high pT hadrons in • central Au+Au collisions • 2) Disappearance of back-to-back high pT • jet correlations and the energy dissipation • in soft particle production

  5. STAR PHENIX Empirical Quark Scaling in RAA and v2 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 !!

  6. PRL 92 (2004) 052302; PRL 91 (2003) 182301 Hadronization of Bulk Partonic Matter 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

  7. Volcanic mediate pT – Spatter (clumps) Clustering and Surface Emission Enhancement of Clusters at intermediate pT ! (baryons and hyperons) Search for Multi-quark (>3) Cluster State at RHIC !

  8. Au + Au Collisions at RHIC STAR Central Event (real-time Level 3)

  9. STAR Pentaquark Searches Q+  p + KS Q++  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)

  10. Particle identification Particle Identification: dE/dx from TPC

  11. pK+ and pK- from 18.4 M d+Au at 200 GeV Background – Combinatorial and Correlated Pairs dAu results M (GeV/c2)

  12. dAu results PeaK?! Understand the Background!

  13. 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

  14. Possible Sources of Background Double Conversion of p0 photons p0 gg  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 LK+ pp- + K+ These background sources contribute to the residuals in the event-mixing. But they do not produce a narrow peak !

  15. D++p+p and using p as K Q p  K Q D D

  16. Other PID Cuts Kaon 0.2<p&pt<0.7, Proton 0.3<p&pt<1.0, no opening angle cut

  17. Other PID Cuts Kaon 0.2<p&pt<0.8, Proton 0.3<p&pt<1.0, no opening angle cut

  18. Other PID Cuts Kaon 0.2<p&pt<0.8, Proton 0.3<p&pt<1.5, no opening angle cut

  19. Other PID Cuts Kaon 0.2<p&pt<1.0, Proton 0.3<p&pt<1.5, no opening angle cut

  20. Spectrum? After acceptance and efficiency correction Assuming 100% branching ratio Spectrum includes ++and -- Mt-exponential fit yields: dN/dy= 0.0012 +- 0.0006 T= 315 +- 30 MeV Yields for some particles in dAu Ks: 0.321 +- 0.006 +- 0.03 L+Lbar: 0.339 +- 0.007 Xi+Xibar: 0.0251 +- 0.0006 Phi: 0.0642 Q++/f ~ 2%

  21. AuAu 62.4 GeV Results -- ++ ++ plus -- • A nice signal is also seen in AuAu 62.4 GeV data from 20-80% centrality bin, 5.1 M events. • --/++ = 0.47 +- 0.2

  22. A Stringent Limit from HERA-B HERA-B hep-ex/0408048 sqrt(s) 42 GeV pA (C,Ti,W) 200 M inelastic events q+/L <0.92%; 95%CL q+/L(1520) <2.7%; 95% CL Our Estimate in STAR d+Au sqrt(s) 200 GeV q++/L ~ 0.35% Does this imply L(1520)/L ~ 34%? STAR L(1520)/L ~ 10% !

  23. The Puzzle Continues • 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+. • The STAR observed yield is so small such that many • experiments would not have the sensitivity to see it. • 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)?

  24. RHIC – Exotic Particle Factory STAR – Exciting Physics Program A full TOF and Heavy Flavor Tracker upgrade will greatly enhance STAR’s capability !! Heavy Flavor Tracker Using Active Pixel Sensor two layers of thin silicon detector 1.5 cm and 4 cm radius Charmed Exotics?! Full Barrel TOF Using MRPC

  25. Exotic Particles Hadrons with internal structure beyond existing QCD qqq and q-qbar framework !! RHIC – Dedicated QCD Machine & Beyond Exotic (Deconfinement Phase Transition) AA AA pp pA pp pA (CGC,EMC) (spin)

  26. The End

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