Heavy Ion Physics with PID

1. Heavy Ion Physics with PID Tatsuya Chujo University of Tsukuba

2. Some notes: In this presentation, I will talk about some of the basics physics motivations for the PID upgrade in PHENIX. Mid-term is for the next 5 years (2011-2015), and long term is for the another next 5 years (2016-2020). “PID” means the charged particle identification from (relatively) lower pT to intermediate pT region (~0.1 – 4.0 GeV/c) in this presentation. I assume that R&D/installation period for forward rapidity region in mid-term, and aiming to have a mid rapidity coverage in long term. I also assumed that there is still much interest on the study of QCD Critical Point (QCP) on QCD phase diagram, not only for the mid-term but also for long term upgrade.

3. Reminder: Importance of PID in Heavy Ion Physics • Sensitive to the collective phenomena (e.g. radial flow, v2) • Sensitive to the baryon chemical property of the matter, one can explore QCD phase diagram. • Sensitive to the dynamical evolution of matter (HBT) • Sensitive to the novel features at RHIC: • Baryon enhancement at intermediate pT. • Quark number scaling of v2. • CP violation. • Would be sensitive to signatures of QCD Critical Point (QCP). • Main observables by PID detectors: • Spectra • Flow (v2, v3, v4 (v1)) • HBT • Fluctuations • D pK, B J/y +X, e+X, Resonances (L, W, f, etc…) • Medium response to hard probes (e.g. jets)

4. As an example: √s dep. of mB, T, <b> STAR, arXiv:0808.2041 • μB: falls monotonically. • Tch: rapidly rises at SIS and AGS energy, saturates at SPS and RHIC energies (a unique Tch ~ Tc from lattice QCD). • Tkin: decoupled at √sNN~10 GeV from Tch. Due to the strong collective flow, matter is cooled  prolong period of chemical freeze-out and kinetic freeze-out. • <bT> : rapid increase from SIS to AGS, increasing slowly from SPS to RHIC. Change in Tch / Tkin properties around √sNN~10 GeV ?

5. 3 < pt,trig< 4 GeV/c pt,assoc. > 2 GeV/c Au+Au 0-10% STAR preliminary Medium response to hard probe V.S. Pantuev, arXiv:hep-ph/0701.1882v1 • Key to determine the medium property. e.g.) • Speed of sound (mach cone, triangular flow). • Long range correlations (like ridge structure).

6. h-jet correlations & role of PID Key to understand in medium properties: (1) correlations, (2) fully reconstructed jet • Full jet reconstruction by calorimeters. • Trigger high pT hadron, and look at recoil jet in away side, measure conditional yield in (Au+Au / p+p). • STAR: observed stronger suppression for lower recoil jet energy, indicating broadening of recoil jet cone size. • “Controlled” surface bias • Interesting to see these with PID: (1) Particle composition in jets, (2) Path length dependence of energy loss for different flavor (u, d, s, c, (b)).

7. T. Hatsuda, K. Fukushima, arXiv:1005.4814v2 M. A. Stephanov, arXiv:hep-lat/0701002 Lattice QCD, effective model prediction of QCP EXPLORING THE QCD PHASE DIAGRAM AT RHIC

8. From C. Nonaka (JPS2008 fall) • PRC71:044904,2005, • arXiv:0803.2449 • Relativistic Dynamical Model • (3D Hydro + UrQMD) • Focusing effect near the QCD coital point in isentropic trajectories on the T-mB plane. • Emission time dependence. • High pT particles emit at earlier time. A proposed observable: pbar/p vs. pT. (or Tinv for p and pbar)

9. List of potential observables for QCP study via PID • p/pbar ratio as a function of pT. • Fluctuations: • K/p, <pT> of pions, net proton (p-pbar), … • Global observables; • p/p ratio?, break of quark number scaling? • Measurements with PID charged hadrons should give an crucial role for QCP study.

10. sPHENIX layout At mid rapidity, very strong for jet, photon, lepton pair measurements, but missing PID detector.

11. 10ps TOF as PID detector (M. Chu et al.) K. Inami et al., NIM A 560 (2006) 303-308 Figure from M. Chu’s proposal • Also having HCal & EMCal in current sPHENIX, it is ideal to study medium response by the PID detector at mid rapidity. • We might also perform some complementary measurements on chiral symmetry restoration via hadronic channel, e.g. f KK, or rpp? • MCP-PMT (w/ waveform digitizer) based 10 ps TOF. • Proposed by M. Chu et al. • 2010-2015: R&D and planning installation at forward rapidity region. • Key physics: • Ridge, jet, long range correlations. • Direct reconstruction of D. • Parity violation study (K0s asymmetry at forward-y) • Transversity dq of quarks (p+p) • <10 ps TOF is also ideal for mid-rapidity, and can identify K/p < 4 GeV/c (4 s) @ 1 m flight path length, with low occupancy (<10%) in HIC.

12. Layout of FOTOF (forward 10ps TOF, by M. Chu) 0.8 < |h| < 1.5 See M. Chu’s talk Figure from M. Chu’s proposal

13. Summary PID detector at forward and mid rapidity in upgraded PHENIX setup gives un an significant advantage to explore the QCD phase diagram. From the experience of RHIC data, interplay between soft and hard is the key to understand the hot and dense medium, so that PID detector should play an important role to determine the medium property with hard probes (together with HCal and EMCal). PID detector is also sensitive to novel features at RHIC. In longer term, for any new colliding systems (e.g. U+U, e+A, p+A) and new energies, we need basic measurements, e.g. spectra, v2, HBT with PID, in order to characterize the bulk properties of matter. (I am personally interested in the R&D and collaboration for the 10 ps TOF project.)