Relativistic Heavy Ion Experiments at Yonsei Ju Hwan Kang (Yonsei University) the 4th Stanford-Yonsei Workshop (HEP session) February, 26, 2010

Introduction De-confinement and Quark-Gluon Plasma (QGP) Relativistic Heavy Ion Collider (RHIC) at BNL Highlights of RHIC results High P T suppression Thermal photon Our activities PHENIX upgrade ALICE at LHC OUTLINE

Deconfinement & RHIC QCD : established theory of the strong interaction Quarks and gluons deconfined at high temperatures, at least from Lattice QCD RHIC : Relativistic Heavy Ion Collider (√s = 200 GeV/nucleon) To make a hot QCD matter by colliding heavy ions Lattice Calculations: T c = 170 ± 15% MeV  (~ 2 x K)

RHIC’s Experiments STAR

High p T particle production  proton-proton collision : hard scattered partons fragment into jets of hadrons hadrons jet  nucleus-nucleus collision : parton energy loss if partonic matter  supprssion of high p T hadrons  no suppression of high p T photons At RHIC, most of high p T particles are from jets.

High p T suppression or jet quenching Compare high p T distribution of p+p and Au+Au after scaling with the number of nucleon-nucleon binary collisions (N coll ). If the properties of the medium produced after the collision is the same for both cases, the two distributions should be identical. The suprression of high p T particles in Au+Au compared to p+p would indicate the existence of a partonic matter. 100% 0 % N coll can be calculated by looking at E T or multiplicity of produced particles

 direct /  0 in p+p at  s = 200 GeV (Run 2003 data: PRL 98 (2007) ) Run 2005: preliminary Agreement with pQCD: Prerequisite for jet quenching calculations in A+A p+p at  s = 200 GeV 00  direct

 direct /  0 in Au+Au at  s = 200 GeV Au+Au   0 + X (peripheral) Au+Au   0 + X (central) Strong suppression Peripheral spectra agree well with p+p (data & pQCD) scaled by N coll Data exhibits suppression: R AA = red/blue < 1 Blue lines: N coll scaled pQCD p+p cross-section Au+Au   direct + X

Evidence for Parton Energy Loss? Energy loss for quark and gluon jets No energy loss for  ‘s  0 ’s and  ’s are suppressed, direct photons are not: Evidence for parton energy loss (jet quenching, indicating production of deconfined state or QGP)

Time Initial hard parton-parton scatterings (  hard  ) Thermalized medium (QGP!?), T 0 > T c, T c  MeV (  thermal  ) Phase transition QGP → hadron gas Freeze-out Thermal photons in nucleus-nucleus collisions q qg 

Thermal photons (theory prediction) High p T (p T >3 GeV/c) pQCD photon Low p T (p T <1 GeV/c) photons from hadronic gas Themal photons from QGP is the dominant source of direct photons for 1<p T <3 GeV/c Measurement is difficult since the expected signal is only 1/10 of photons from hadron decays S.Turbide et al PRC q qg      Hadron decay photons 11

Virtual Photon Measurement  Case of hadrons (  0,  ) (Kroll-Wada) S = 0 at M ee > M hadron  Case of direct  * If p T 2 >>M ee 2 S = 1  For m>m ,  0 background (~80% of background) is removed  S/B is improved by a factor of five Any source of real  can emit  * with very low mass. Relation between the  * yield and real photon yield is known. Process dependent factor 00  Direct   0 Dalitz decay Compton

f direct : direct photon shape with S = 1 arXiv: arXiv: Interpret deviation from hadronic cocktail ( , , ,  ’,  ) as signal from virtual direct photons Fit in MeV/c 2 (insensitive to  0 yield) r = direct  * /inclusive  * Extraction of the direct  signal A. Adare et al., PRL accepted

Direct photon spectra Direct photon measurements –real (p T >4GeV) –virtual (1<p T <5GeV) pQCD consistent with p+p down to p T =1GeV/c Au+Au = “scaled p+p” + “expon”: exp + T AA scaled pp NLO pQCD (W. Vogelsang) Fit to pp arXiv: arXiv: The inverse slope T AuAu > T c ~ 170 MeV

Press release WHEN: Monday, February 15, 2010, 9:30 a.m. WHERE: The American Physical Society (APS) meeting, Marriott Wardman Park Hotel, Washington, D.C., Press Room/Briefing Room, Park Tower 8222 DETAILS: The Relativistic Heavy Ion Collider (RHIC) is a 2.4-mile-circumference particle accelerator/collider that has been operating at Brookhaven Lab since 2000, delivering collisions of heavy ions, protons, and other particles to an international team of physicists investigating the basic structure and fundamental forces of matter. In 2005, RHIC physicists announced that the matter created in RHIC's most energetic collisions behaves like a nearly "perfect“ liquid in that it has extraordinarily low viscosity, or resistance to flow. Since then, the scientists have been taking a closer look at this remarkable form of matter, which last existed some 13 billion years ago, a mere fraction of a second after the Big Bang. At this press event, scientists will present new findings, including the first measurement of temperature very early in the collision events, and their implications for the nature of this early- universe matter.

Our activities in PHEMIX PHENIX upgrades and NCC –NCC is W-Si Sandwich calorimeter –NCC measures  /  0 to study  /jet correlations Our activities for NCC –Silicon pad sensor production –Micromodule production –Cosmic muon test –Beam test at CERN

PHENIX & RHIC upgrade plans RHIC baseline program Au-Au ~ 250  b -1 at 200 GeV Species scan at 200 GeV Au-Au energy scan Polarized protons  150 nb -1 Full utilization of RHIC opportunities: Studies of QGP with rare probes: jet tomography, open flavor, J/ ,  ’,  c,  (1s),  (2s),  (3s) Complete spin physics program p-A physics Near term detector upgrades of PHENIX TOF-W, HBD, VTX,  Trig 40x design luminosity for Au-Au via electron cooling Commissioning Long term upgrades FVTX, TPC/GEM, NCC Extended program with 1 st detector upgrades: Au-Au ~ 1.5 nb -1 at 200 GeV Polarized p at 500 GeV (start p-A program) Analysis of data on tape PHENIX upgrades RHIC luminosity upgrade Near term: Base line Long term: full detector and RHIC upgrades Medium term: first upgrades

NoseCone Calorimeter (NCC, or ForCal) EM (W-Si) calorimeter in the forward rapidity good  -  0 separation with reasonable energy resolution Measurement of  /jet correlations and high p T photon

EM Shower in W-Si Sandwich calorimeter  20cm,  20X 0,  1λ 15mm,  R M

Exercise for silicon pad sensor production

Micromodule (Packaging)

Cosmic  test setup (sensor & electronics) Bridge board Micromodule(Sensor) Preamp card 8Ch. fADC(100MHz)

Beam test at CERN Preamp hybrid 7 vertical channels grouped (cost issue) 8 pad sensors in one carrier board PS for below 6GeV, and SPS for up to 100GeV

Production and test results ~ 100 sample micro-module production has completed. Mechanical and electrical issues have been checked Total yield = 102/141 = 73% (most loss from sensor fabrication) Beam test results : & good linearity 24

ALICE (A Large Ion Collider Experiment) at CERN LHC To study even hotter QCD matter...

SPS LHC ALICE

Our activities in ALICE R&D for Forward EM calorimeter –To measure high p T photon in forward rapidity –Discussing a similar type of detector as NCC –Presented the results from our NCC efforts TRD participation –TRD measures electrons and low p T photons –Participating in TRD integration and taking TRD shifts –Plan to analysis TRD data for photon physics

TRD (Transition Radiation Detector) | η |<0.9, 45°< θ <135° 18 supermodules in Φ sector 6 Radial layers 5 z-longitudinal stack  total 540 chambers  750m ² active area  28m³ of gas In total 1.18 million read-out channels

Student at CERN Participating in TRD integration

FoCAL in AliROOT PHENIX at RHIC PHENIX upgrade plans NCC Involvement ALICE at LHC R&D for ForCal Participation in TRD

Hosted ALICE upgrade workshop

1 st Paper

Please find below the outcome of a meeting to define the LHC running schedule for the next few years. We will have a long run spanning 2010 and most of 2011 at 7 TeV (presumably with a short technical stop again during Christmas 2010, but this has still to be decided), followed by a long shutdown starting mid to end 2011 to bring the machine up to its design Energy. A long run now is the right decision for the LHC and for the experiments. It gives the machine people the time necessary to prepare carefully for the work that’s needed before allowing 14 TeV, or 5.5 TeV/nucleon. “Current” plan for LHC

Backups

Input hadron spectra for cocktail Fitting with a modified Hagedorn function for pion, for all other mesons assume m_T scaling by replacing p_T by

Virtual photon emission rate Real photon yield Turbide, Rapp, Gale PRC69,014903(2004)

Initial temperature From data: T ini > T avg = 220 MeV From hydrodynamical models: T ini = 300 to 600 MeV, t 0 = 0.15 to 0.6 fm/c Lattice QCD predicts a phase transition to quark gluon plasma at Tc ~ 170 MeV T C from Lattice QCD ~ 170 MeV T ave (fit) = 221 MeV

Further discussions? 38

Blue line: N coll scaled p+p cross-section Direct Photons in Au+Au Au+Au data consistent with pQCD calculation scaled by N coll Direct photon is measured as “excess” above hadron decay photons Measurement at low p T difficult since the yield of thermal photons is only 1/10 of that of hadron decay photons PRL 94, (2005)

Direct  production in p+p  One of the best known QCD process… Hard photon : Higher order pQCD Soft photon : Initial/final radiation, Fragmentation function  Leading order diagram in perturbation theory Really? Motivation : Direct  production

Transition radiation (TR) is produced if a highly relativistic (γ>900) particle traverses many boundaries between materials with different dielectric properties. Electrons can be identified using total deposited charge, and signal intensity as function of drift time. (Plastic fiber + Air)