contents introduction the experiments (phenix detector) physics highlights conclusion

Hideto En'yo RIKEN/RBRC 1

Italy-Japan Symposium on Heavy Ion Physics

26/Sep/01 RHIC Spin Projectopening a new era of hadron physics

Hideto En’yo Hideto En’yo

RIKEN / RIKEN-BNL Research CenterRIKEN / RIKEN-BNL Research Center

ContentsContents Introduction Introduction The Experiments (PHENIX detector)The Experiments (PHENIX detector) Physics HighlightsPhysics Highlights ConclusionConclusion

ISABELL (abandoned in 1983) to RHIC (started in 2000)

The FirstThe First Heavy Ion Collider Heavy Ion Collider&&

The first Polarized ColliderThe first Polarized Collider

3.83 km circumferenceTwo independent rings

120 bunches/ring106 ns bunch crossing

Can collide ~any nuclei on ~any other nuclei

Top Energy:500 GeV for p-p200 GeV for Au-Au

LuminosityAu-Au: 2 x 1026 cm-2 s-1

p-p : 2 x 1032 cm-2 s-1 (polarized)



26/Sep/01 Year2000 to Year2001

First Collision of Gold beams at 130 GeV/A 10% of Designed Luminosity achieved Successful Physics Run

Successful Spin Commissioning!

First Collision of Gold beams at 200GeV/A !!!

Currently running with Au+Au Beam with ~design luminosity.First Muon Data from PHENIX

First Polarized Proton Collision will take place in November – December, 2001!



26/Sep/01 RHIC Polarized Collider GeVs 50050

Illustrated by Thomas Roser

BRAHMS & PP2PP

STARPHENIX

AGS

LINACBOOSTER

Pol. Proton Source500 A, 300 s

Spin RotatorsPartial Siberian Snake

Siberian Snakes

200 MeV PolarimeterAGS Internal Polarimeter

Rf Dipoles

RHIC pC Polarimeters

Absolute Polarimeter (H jet)

2 1011 Pol. Protons / Bunch = 20 mm mrad

PHOBOS

RHIC

onPolarizati%70 2132max cms102 L

KEK

•



26/Sep/01 Milestones• Naive quark model = 1 = u+d+s• 1973 Ellis-Jaffe sum rule s =0 → g1

pdx,g1ndx 　 predicted

• 1974 Sehgal’s spin crisis s =0 → • 1989 -99 EMC spin crisis s = 0.1 ?

•1989 RHIC project started •1990 Polarized Collider Workshop at Penn State •1992 STAR and then PHENIX, approved for RHIC •1993 RHIC-Spin proposal (Accelerator,STAR,PHENIX)•1995 RIKEN-BNL MoU [Spin construction started]•1997 RIKEN-BNL Research Center established (T.D.Lee)•2000 The first HI collisions & polarized proton acceleration •2001 The first polarized proton collisions

Looking for the OTHER spin Carrier1/2=(1/2)+G+Lq+Lg

Pre-RHICHistory

History toWedding ofHI & SPINat RHIC



26/Sep/01Spin Structure of Nucleon Parton Distribution Function

Quark Distribution

),(

),(

),(

2

2

2

Qxq

Qxq

Qxq

Unpolarized Distribution

Helicity Distribution

Transversity Distribution

Gluon Distribution

),(

),(2

2

Qxg

Qxg

D.I.S.

RHIC

12.0~ sdu



26/Sep/01

Global QCD Analysis

AAC Pre

liminary

AAC Pre

liminary

M. Hirai, H.Kobayashi, M. Miyama et al.

Impact of RHIC Spin on g With RHIC DATA (1year)



26/Sep/01 Spin Physics at RHIC

• Spin Structure of Nucleon– 1/2=(1/2)+G+Lq+Lg

G: gluon polarization q: Anti-quark polarization

– New Structures• h1: transversity

RHIC = polarized parton colliderRHIC = polarized parton collider

•NEW TOOL to study hadronic processes

•W,Z @500GeV•flavor sensitive studies on the structure functions

•cc/bb•Production mechanism

•Spin in the fragmentation•Parity,CP violating interaction?

•Test of pQCD •Use asymmetries sensitive ONLY to the higher orders (AN at high PT etc.)

?QCD triumph? or

?beyond ?



26/Sep/01 Asymmetries Measurements

• ALL: Double Longitudinal Spin Asymmetry– Useful in extracting quark/gluon helicity distributions

)()(

)()(

LLA

ATT: Transversity AN:Twist-3 or TAL:Parity Violation



26/Sep/01

Asymmetry Measurements

Effect of Background

data = Asignal [ 1/(1+) ]+ Aback [ /(1+) ]

=Nback/Nsignal

Keys Luminocity (STATISTIC !) Polarization (>70% expected at RHIC) Large Partonic Asymmetry (Choose good channel) Low 　 Background (Clean signal and/or clean analysis) Low 　 Background 　 Asymmetry (better measured within the same experiment)

Remarks in the Asymmetry Measurements

LNLN

LNLN

PPA

BBLL

21

1exp

　ｇｇ→ QQ

Dilution Fake Asymmetry

STAR AcceptanceSTAR Acceptance

STAR PHENIX



26/Sep/01PHENIX

DETECTOR

South muon Arm

North muon Arm

West Arm

East Arm

Central ArmsCoverage (E&W) -0.35< y < 0.35 30o <||< 120o

M(J/)= 20MeVM() =160MeV

Muon ArmsCoverage (N&S) -1.2< |y| <2.3 - < <M(J/)=105MeVM() =180MeV

3 station CSC5 layer MuID (10X0)p()>3GeV/c

GlobalsMVD/BB/ZDC



26/Sep/01EM-calorimeter (gift from HI physics)

• Fine segmentation <0.01 – finest in the collider history separation up to 25GeV

• linearity <2% up to 80GeV • Resolution 1.9% 8.2%/E

30/25/20/15/10 GeV/c Pt of opening angle

PHENIX Segmentation



26/Sep/01MuonArms

Double Muon Arm solution is Major Upgrade in PHENIX for SPINWorks as Up-Down counters for -decay of polarized W

W

3 stations

5 layer Muon Identifier



26/Sep/01

• Measurements with Central Arms– Direct photon inclusive 0

– J/e+eW±e±– inclusive high Pt e±

• Measurements with Muon Arms– inclusive high Pt ± J/+

– Z/* + W±±• Measurements with both Arms

– cc/bb±e+X (unlike sign pair)

leptons penetrating Quark Matter also probe pQCD insite Polarized proton Delivered from RHIC

1-Year Ldt =320/pb at 200GeV 800/pb at 500GeV, (10weeks/y) High polarization ~70% expected ( KEK pol. source ) Y2001: 6 weeks L~1/10 Pol~50%

PHENIX Spin Physics Probes

Y. Goto (RBRC)A. Vazilevsky(RBRC)N. Saito (RIKEN/RBRC)H. Torii(Kyoto/RIKEN-JRA)

N. Saito (RIKEN/RBRC)H. D.Sato(Kyoto/RIKEN-JRA)N. Hayashi(RIKEN)A. Taketani(RIKEN)K. Kurita (RIKEN)



26/Sep/01 Jet Production

Mixture of gg/gq/qq scatteringsVery sensitive to gluon polarization

gggg

gqgq

qqqq

G

G

G

G

G

G

q

q

q

q

q

q



26/Sep/01

10 times more yield than fromGluon Compton Process

• convolution of all the partonic asymmetry

• Model dependent but G sensitive from g+q, g+g scatterings

• Accessible with 1/10 Luminosity.

– Good start for 1st-year physics

– Immediate answer if ⊿ ｇ is large

Measurements of G (gg,gq,qq→X)

One-Month statisticwith full luminosity

Y. GotoN.Saito



26/Sep/01

Measurements of G (gq→X)

The primary goal of the RHIC spin project

• Clean elementary process

• Background– qq annihilation (~10%, not rejectable)

– Bremsstrahlung from jet frangments

– Hadronic Decays

• YieldPhenix1-yearsensitivity

)(cos),(),(

),()( *2

12

2

LLqp

g

gTLL aQxA

QxG

QxGpA

320 pb-1 800 pb-1

120K events 1,160K events

A. VazilevskyY. Goto



26/Sep/01

x ・ G(x) derived from prompt measurementsonly statistical error for;

sqrt(s)=200GeV 320pb-1

sqrt(s)=500GeV 800pb-1

crude assumptions as;xg=xT=2pT/sqrt(s)

cos(

Convolution over xBJ space and NLO consideration are required.

global structure can be seen immediately

Gluon Polarization SensitivityGluon Polarization Sensitivity Y. Goto

Decay background ~20%



26/Sep/01 Measurements of G ｇｇ→ QQ → e

• e coincidence enhance the leptons from heavy quarks

• 320/pb provides 120k bb,100k cc,100k hadronic decays

• Like sign pair (also includes signal from bb) gives fine estimation for the background effects

KK　　DecaysDecays

KK　　 DecaysDecays

bb

cc

total

H.D.SatoKyoto /JSPS



26/Sep/01Measurements of Gｇｇ→ QQ → (J/)

• Gluon fusion is the major production channel (agreed)

• Details are questionable over 20 years.– Color evaporation– Color octet – Color singlet

– Decay from c　

pT()>2GeV/c

bottom

J/ （ color singlet model ）

/K

320pb-1

H.D.SatoKyoto /JSPS

NJ/ (pT>2GeV)~120k events

→ALLJ/ (stat.)~ 0.006

→Error from Back ground ~ 0.001Precise ALL measurements

first to verify the production models

GeV/C2

Color octet modelALL prediction



26/Sep/01 Kinematical Coverage: (x,Q2)• @200GeV

Similarly to DIS region

• @500GeV

Coverage Enlarged!

• Advantageous in Global QCD Analysis!

200GeV γ

200GeV eμ

200GeV e(cc)



26/Sep/01 Weak Boson Detection at PHENIX• W production is

– Flavor sensitive

– helicity fixed (V-A)

Kinematics (realized by N.Saito )

• power of the polarized collider with Muon Endcaps

N.Saito

Yield in 1-RHIC year at 500GeV



26/Sep/01Measurements of q, q at PHENIX

– d small at high x u/u (d/d for W) flavor selected valence quark polarization

d/d (u/u for W) determination

Major background is Z decay (20%)

systematic error will be minimized (~1%) with AL

Z (~20%)and (Z) measurements

N.Saito

Au x M d x M d x M u x M

u x M d x M d x M u x MLW a W b W a W b W

a W b W a W b W

( , ) ( , ) ( , ) ( , )

( , ) ( , ) ( , ) ( , )

2 2 2 2

2 2 2 2

Parity violating single Asymmetry unpolarized distribution polarized distribution



26/Sep/01Flavor Structure of Nucleon

• No reason to assume d = u in nucleon– d u is natural

• RHIC– W+/W Yield comparison– p+p then p+He3 ?

FNAL-E866 resultsPRL 80 (1998) 3715

J.C.Peng,G.T.Garvey

PHENIX We

PHENIX WPHENIX W

d=u du

Recent FNAL Data shows 50% difference in p+p/p+d (D.Y.)



26/Sep/01 Searches for New Physics

• Anomalous Parity Violation in Jet Production – Contact Interaction (Scale )

• CDF>1.8 TeV

• D0 >2.4 TeV

• RHIC Spin Reach ~3.3 TeV

– New Gauge Boson Z’



26/Sep/01

pC CNI Polarimeterproton Carbon Elastic Scattering

• Designed Basing on Successful AGS-E950 Measurement

• Installed in Blue Ring– 4 detectors: 45o,135o,225o,315o

Si #1

Si #2 Si #4

Si #3

left right

down

up

J. Tojo et al.

pC CNI Polarimeter Testin AGS E950 & Kyoto Tandem

G=46.5 Injection energySnake OFF Vertical polarization

left right

down

up

Si #1

Si #2 Si #4

Si #3

G=48 Acceleration with Snake OFFPolarization lost

G=48 Acceleration with Snake ONHorizontal polarization

Polarization withSnake magnetON/OFF

G=46.5 Injection energySnake ON Horizontal polarization



26/Sep/01 Conclusions

• RHIC Spin program is very unique.• Y2000 Polarized proton commissioning was very successful.

• Y2001, The first measurements of helicity asymmetry will SOON be performed @200GeV. Sizable G generates surprises in the High p

T 0 , High pT Jdata.• Y2002+, Statistics will be much improved @200GeV, ensuring the d

etermination of G in direct and e- coincidence data. “Spin Crisis” will hopefully be solved by them.

• Y200?, Weak Bosons will be produced at RHIC, the NEW “flavor sensitive” tool for the anti-quark/quark polarization and unpolarized structure function of anti-quark measurements.

• And beyondbeyond…



26/Sep/01 L and E Upgrades

• Luminosity Upgrades: 25 Times– 8 Times by Ion Source– 3 Times by increasing number of bunches:

• 120 bunches 360 bunches

• 106 nsec bunch spacing to 35.3 nsec

• Energy Upgrades: 500 GeV 650 GeV– RHIC Dipoles: 30% Margin – RHIC DX Magnets: 10% Margin– With DX Magnet Upgrade, 650 GeV Collision i

s possible



26/Sep/01

Background reductionsegmenttation

0isolatemerged

prompt +decay 　 mass reconstruction 0

isolation cut R=0.4, E-fraction=5%

Measurements of G (gq→X)



26/Sep/01Measurements of G

ｇｇ QQ (μsingle)

• Large statistics but with significant background bb is 0.7b in PYTHIA < a few b expected

• Source of background – Decays before Central Magnet– Punch-through hadrons– g+g, g+q dominant– ALL fake ~ ALL signal

• Background evaluation – 5 layer MuID for punch through estim

ation– Decay muon control with vertex positi

on

Asymmetry may well be sizableGood exercise for the 1st year run

b→

320pb-1

c→

→

pTmin 2GeV/c 4GeV/c 6GeV/c

charmALL

4106

10-36104

0.012103

0.05bottomALL

4106

10-32105

410-32104

0.015

H.D.SatoKyoto /JRA



26/Sep/01

Drell-Yan in PHENIX

FNAL E886

q measurements ALL

h1 measurements ATT

Statistics are not great at high mass (>10GeV)where listed amplitude will be sizable. (not well studied yet)un-polarized structure function is not well determined ( revealed by the FNAL data)p+He3 might be the way to go @200GeV x1 0.1-0.5 vs x20.001-0.01



26/Sep/01

x1 x2

x1P

CentralArm

Muon Arm

x2P

Pｂ→ e

ｂ→

e coincidence in PHENIX

ALLpp→bb Ｘ

GS-A

GS-B

GS-C

AL

L

μe

Me(GeV)

H.D.SatoKyoto/RIKEN-JRA



26/Sep/01 World Competition of g/g(x)

RHIC Spin is THE BEST MEASUREMENTamong currently running experiments,even only with 1EXPT&1 CHANNEL.

GS-C



26/Sep/01PHENIX G sensitivity at a glance

Channel typical

ALL errors background

xregion stat xregion stat

Pt>10GeV 1100k 110k G/G~4% 20-30% bremsh, merging

(Pt>5GeV) wide 5M wide 500k ALL<0. gg,gq,qq mixed up

bb/cc→ ~0.2 vs ~0.03 8M 4M cc,4M bb hadron decays

bb/cc→ e study on going

J→ <0.01 120k ALL< 6%(b-decays)

J→ ee 0.01-0.05 120k study on going

cc→ e ~0.2 vs ~0.03 100k ALL< hadronic decays S/N~2

bb→ e ~0.2 vs ~0.03 120k ALL< hadronic decays S/N~6

500GeV

800/pb

200GeV

320/pb

High Statistic Probes (1st year + later detail studies)Cleaner Probes (2nd Year and later) Global approach to G from many probes available

contents introduction the experiments (phenix detector) physics highlights conclusion

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