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 PT suppression

Thermal photon

• Our activities

PHENIX upgrade

ALICE at LHC

OUTLINEOUTLINE

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:Tc = 170 15% MeV (~ 2 x 1012 K)

RHIC’s Experiments

STARSTAR

High pT particle production

proton-proton collision : hard scattered partons fragment into jets of hadrons

hadrons

hadrons

jet

nucleus-nucleus collision : parton energy loss if partonic matter supprssion of high pT hadrons no suppression of high pT photons

At RHIC, most of high pT particles are from jets.

High pT suppression or jet quenching

• Compare high pT distribution of p+p and Au+Au after scaling with the number of nucleon-nucleon binary collisions (Ncoll).

• 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 pT particles in Au+Au compared to p+p would indicate the existence of a partonic matter.

100% 0 %

Ncoll can be calculated by looking at ET or multiplicity of produced particles

direct / 0 in p+p at s = 200 GeV

(Run 2003 data: PRL 98 (2007) 012002)

Run 2005:preliminary

Agreement with pQCD: Prerequisite for jet quenching calculations in A+A

p+p at s = 200 GeV

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 Ncoll

Data exhibits suppression: RAA= red/blue < 1

Blue lines: Ncoll 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)

ppTcoll

AATAA dpdNN

dpdNR

/

/

Time

Initial hard parton-partonscatterings ( hard )

Thermalizedmedium (QGP!?), T0 > Tc ,Tc 170 - 190 MeV ( thermal )

Phase transitionQGP → hadron gas

Freeze-out

Thermal photons in nucleus-nucleus collisions

q

qg

Thermal photons (theory prediction)

• High pT (pT>3 GeV/c) pQCD photon

• Low pT (pT<1 GeV/c)

photons from hadronic gas• Themal photons from QGP is

the dominant source of direct photons for 1<pT<3 GeV/c

• Measurement is difficult since the expected signal is only 1/10 of photons from hadron decays

S.Turbide et al PRC 69 014903 S.Turbide et al PRC 69 014903

q

qg

Hadron decayphotons

11

Virtual Photon Measurement

Case of hadrons (0, ) (Kroll-Wada)

S = 0 at Mee > Mhadron

Case of direct *

If pT2>>Mee

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.

dNpMSMM

m

M

m

dM

Ndtee

eeee

e

ee

e

ee

),(12

14

13

22

2

2

22

Process dependent factor

3

2

222 1

hadron

eeee M

MMFS

0

Direct

dN

dNpMS tee

*

),(

0 Dalitz decay

Compton

fdirect : direct photon shape with S = 1

arXiv:0804.4168arXiv:0912.0244

• Interpret deviation from hadronic cocktail (, , , ’, ) as signal from virtual direct photons

• Fit in 120-300MeV/c2 (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 (pT>4GeV)

– virtual (1<pT<5GeV)

• pQCD consistent with p+p down to pT=1GeV/c

• Au+Au = “scaled p+p” + “expon”:

exp + TAA scaled pp

NLO pQCD (W. Vogelsang)

Fit to pp

arXiv:0804.4168arXiv:0912.0244

fAu Au

( pT

)N

coll

NNinel f

p p( p

T)

Be

pT

T

The inverse slope TAuAu > Tc ~ 170 MeV

Press release

WHEN: Monday, February 15, 2010, 9:30 a.m.

WHERE: The American Physical Society (APS) meeting, Marriott WardmanPark Hotel, Washington, D.C., Press Room/Briefing Room, Park Tower8222

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

2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

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 programp-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 1st 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 pT photon

EM Shower in W-Si Sandwich calorimeter

20cm, 20X0, 1λ

15mm, RM

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

Eresolution

%22

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

Eresolution

%20

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 pT 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 pT 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

750m² 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

1st 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: Tini > Tavg = 220 MeV From hydrodynamical models: Tini = 300 to 600 MeV, t0 = 0.15 to 0.6 fm/c

Lattice QCD predicts a phase transition to quark gluon plasma at Tc ~ 170 MeV

TC from Lattice QCD ~ 170 MeV

Tave(fit) = 221 MeV

Further discussions?

38

Blue line: Ncoll scaled p+p cross-section

Direct Photons in Au+Au

Au+Au data consistent with pQCD calculation scaled by Ncoll

Direct photon is measured as “excess” above hadron decay photonsMeasurement at low pT difficult since the yield of thermal photons is only 1/10 of that of hadron decay photons

PRL 94, 232301 (2005)

• Direct production in p+p

One of the best known QCD process…

Hard photon : Higher order pQCDSoft 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, andsignal intensity as function of drift time.

(Plastic fiber + Air)