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PHENIX Spin ProgramRecent results
A.Bazilevsky Brookhaven National Laboratoryfor the PHENIX Collaboration
XXXXth Rencontres de Moriond - March 12-19, 2005 QCD and Hadronic interactions at high energy
Proton Spin Structure
pzLG
2
1
2
1Spin zLG
2
1
2
1
Quark Spin Gluon Spin
Orbital Angular Momentum
sdusdu
Polarized DIS: contribution of quarks to proton spin is amazingly small 0.25
Main candidate to carry proton spin - Gluons
Gluon polarization (G) remains poorly constrained G measurements – main RHIC-Spin goal
Polarised PDFAsymmetry Analysis Collaboration
M. Hirai, S. Kumano and N. Saito, PRD (2004)
• Valence Dist’s are determined well
• Sea Distribution poorly constrained
• Gluon can be either pos, 0, neg!
PHENIX Spin Program
Prompt Photon LLA (gq X)
Transverse Spinu u d d , , ,
u u d d
Flavor decomposition
GGluon Polarization
L lA (u d W ) T
,
A p p ( , ) X
I nterference fragmentation:
:Transversity q
NSingle Asymmetries A
Production LLA (gg,gq X) W Production
L lA (u d W )
Heavy Flavors LLA (gg cc,bb X)
TTDrell Yan A
Utilizing high energy polarized proton beams of RHIC
RHIC as polarized proton collider
BRAHMS & PP2PP (p)
STAR (p)
PHENIX (p)
AGS
LINACBOOSTER
Pol. Proton Source500 A, 300 s
GeVs
L
50050
onPolarizati%70
cms102 2132max
Spin Rotators
Partial Siberian Snake
Siberian Snakes
200 MeV Polarimeter AGS Internal PolarimeterRf Dipoles
RHIC pC PolarimetersAbsolute Polarimeter (H jet)
2 1011 Pol. Protons / Bunch = 20 mm mrad
RHIC accelerates heavy ions to 100 GeV/A and polarized protons to 250 GeV
Spin Running at RHIC-PHENIX
Run2: 2001-2002– Transversely polarized p+p collisions– Average polarization of ~15%– Integrated luminosity 0.15 pb-1
Run3: 2003– Longitudinally polarized p+p collisions
achieved– Average polarization of ~27%– Integrated luminosity 0.35 pb-1
Run4: 2004– Longitudinally polarized p+p collisions – Polarization of ~40-45%– Integrated luminosity 0.15 pb-1
Run5: starting next month– Expected Longitudinally
polarized p+p collisions – Expected P ~ 50%– Expected L > 10 pb-1
0 Cross Section in pp at s=200 GeV
9.6% normalization error not shown
Phys. Rev. Lett. 91, 241803 (2003) NLO pQCD consistent with data
within theoretical uncertainties• PDF: CTEQ5M• Fragmentation functions:
• Kniehl-Kramer-Potter (KKP)Kniehl-Kramer-Potter (KKP)• Kretzer
• Spectrum constrains D(gluon) fragmentation function
Important confirmation that pQCD can be used to extract spin dependent pdf’s.
• Same comparison fails at lower energies
)()()( /// hchbBbaAa zDdxfxfdcdab
||<0.35
0 ALL
PreliminaryPRL 93, 202002
0 ALL small (or consistent with zero)
L
LR
RNN
RNN
PPALL ;
||
1
21
(P) Polarization (R) Relative Luminosity(N) Number of pi0s
0 ALL: G constrain
gqgq G
G
q
q
qqqq q
q
q
q
gggg G
G
G
G
Fractional contribution to pp0X at s=200 GeV at mid-rapidity
0 production at low/moderate pT’s is sensitive to gluon distribution
0 ALL: G constrain
Note considerable contribution of soft physics in the lowest pT point (50%)
Comparison with theory: GRSV-std
21-24% (pT>1 GeV/c)27-29% (pT>2 GeV/c)
GRSV-max0.00-6% (pT>1 GeV/c)0.01-13% (pT>2 GeV/c)
Run3+4
Consistent with GRSV-stdLess consistent with GRSV-max
B.Jager et al., PRD67, 054005 (2003)
This is the first constrain of gluon polarization using strongly interacting probes; the current sensitivity is comparable to the world set of polarized DIS data
Prompt photons and G
NLO pQCD describes data well can be used to interpret ALL() ALL() needs large luminosity: results expected in 2007-08
• Gluon Compton Dominates– At LO no fragmentation function– Small (15%) contamination from annihilation
2i i 2
i u,d,s
2i i 2
i u,d,s
LL1
1LL
e f (xg(
)
e f (A
x )a (gq
x )
g(x )q )
pol-DIS theory
Unpol. cross section
||<0.35
Transverse Single-Spin Asymmetries • Observed in 0 production at
forward region (E704, STAR)
– Increase with xF
• Origin of AN
– Transversity Spin-dep fragmentation (Collins effect)
– Intrinsic-kT imbalance (Sivers effect)
– Higher-twist effects– Or combination of above
NAleft
rightAN at mid-rapidity (||<0.35)
AN for both charged hadrons and neutral pions consistent with zero.
Future
200910: q-bar from W AL
200507: G from 0 ALL
200708: G from ALL
Summary• RHIC has been successful as the world’s first polarized proton
collider, opening up new kinematic regions for investigating the spin of the proton
• The first spin results from PHENIX are out and stimulating discussion within the theoretical community– AN of neutral pions and non-identified charged hadrons– ALL of neutral pions
Many more years of exciting data and results to look forward to!
• Spin physics at PHENIX planned for 2005 and beyond– Measure gluon polarization via direct photon double longitudinal
asymmetry– Probe gluon polarization from heavy flavor production (gg fusion) via
electrons – Probe polarization of sea quarks via W boson single longitudinal asymmetry
Backup slides
USA Abilene Christian University, Abilene, TX Brookhaven National Laboratory, Upton, NY University of California - Riverside, Riverside, CA University of Colorado, Boulder, CO Columbia University, Nevis Laboratories, Irvington, NY Florida State University, Tallahassee, FL Georgia State University, Atlanta, GA University of Illinois Urbana Champaign, IL Iowa State University and Ames Laboratory, Ames, IA Los Alamos National Laboratory, Los Alamos, NM Lawrence Livermore National Laboratory, Livermore, CA University of New Mexico, Albuquerque, NM New Mexico State University, Las Cruces, NM Dept. of Chemistry, Stony Brook Univ., Stony Brook, NY Dept. Phys. and Astronomy, Stony Brook Univ., Stony Brook, NY Oak Ridge National Laboratory, Oak Ridge, TN University of Tennessee, Knoxville, TN Vanderbilt University, Nashville, TN
Brazil University of São Paulo, São PauloChina Academia Sinica, Taipei, Taiwan China Institute of Atomic Energy, Beijing Peking University, BeijingFrance LPC, University de Clermont-Ferrand, Clermont-Ferrand Dapnia, CEA Saclay, Gif-sur-Yvette IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, Orsay LLR, Ecòle Polytechnique, CNRS-IN2P3, Palaiseau SUBATECH, Ecòle des Mines at Nantes, NantesGermany University of Münster, MünsterHungary Central Research Institute for Physics (KFKI), Budapest Debrecen University, Debrecen Eötvös Loránd University (ELTE), Budapest India Banaras Hindu University, Banaras Bhabha Atomic Research Centre, BombayIsrael Weizmann Institute, RehovotJapan Center for Nuclear Study, University of Tokyo, Tokyo Hiroshima University, Higashi-Hiroshima KEK, Institute for High Energy Physics, Tsukuba Kyoto University, Kyoto Nagasaki Institute of Applied Science, Nagasaki RIKEN, Institute for Physical and Chemical Research, Wako RIKEN-BNL Research Center, Upton, NY University of Tokyo, Bunkyo-ku, Tokyo Tokyo Institute of Technology, Tokyo University of Tsukuba, Tsukuba Waseda University, Tokyo S. Korea Cyclotron Application Laboratory, KAERI, Seoul Kangnung National University, Kangnung Korea University, Seoul Myong Ji University, Yongin City System Electronics Laboratory, Seoul Nat. University, Seoul Yonsei University, SeoulRussia Institute of High Energy Physics, Protovino Joint Institute for Nuclear Research, Dubna Kurchatov Institute, Moscow PNPI, St. Petersburg Nuclear Physics Institute, St. Petersburg St. Petersburg State Technical University, St. PetersburgSweden Lund University, Lund
12 Countries; 57 Institutions; 460 Participants
PHENIX Detector
• Central Arms: ||<0.35, =2900
Charged particle ID and tracking; photon ID
• Muon Arm:1.2<||<2.4Muon ID and tracking
• Global Detectors Collision triggerCollision vertex characterizationRelative luminosityLocal Polarimetry
Philosophy: High rate capability & granularity Good mass resolution and particle ID Sacrifice acceptance
G: other experiments
GRSV-max
GRSV-std
HERMES
SMC
PHENIX x-range
Theory curves from W.Vogelsang
HERMES: high pt hadron pairs (PRL84, 2584, 2000)
Consistent with both GRSV-max and GRSV-std
SMC: high pt hadron pairs (hep-ex/0402010)
Consistent with GRSV-std
PHENIX: 0 ALL
Consistent with GRSV-std
So far all results are consistent with GRSV-std
G: Prompt Photons ALL
Statistics with full design luminosity and polarization ( Ldt=320 pb-1, P=70% )
prompt photon
GS95xG
x
GRSV: Frixione and Vogelsang, Nucl. Phys. B568:60 (2000)
GS95: Gehrmann and Stirling, PRD53, 6100 (1996)
G: Heavy Flavor
Provides more independent G measurements in PHENIX» Helps control experimental and theoretical systematic errors
» Different channels cover different kinematic regions
bbeX
direct
cceX
H. Sato
gg QQA BLL LL
A B
G(x ) G(x ) ˆA aG(x ) G(x )
Decay channels:» e+e-, +-, e, e, , eD, D
Open heavy flavor productionOpen heavy flavor production
Flavor DecompositionDrell-Yan production of lepton pairs
– Maximal parton level asymmetry: aLL= -1 – Possible severe background from semi-leptonic
decays of open charm productions
qq qqA BLL LL
A B
q(x ) q(x )ˆA a
q(x ) q x
W production» Produced in parity violating V-A process
— Chirality / helicity of quarks defined» Couples to weak charge
— Flavor almost fixed: flavor analysis possible— Flavor ID reduces uncertainty in current pol-PDF models.
» PHENIX-Muon Arms
W a b a bL
a b a b
u(x )d(x ) d(x )u(x )A
u(x )d(x ) d(x )u(x )
W Production
x1>>x2: AL(W+) → u/u(x1) _x2>>x1: AL(W+) → - d/d(x1)
W
Z
800 pb-1
W dominates for muon pT>20 GeV/c
quark x from parton kinematics
PHENIX Local Polarimeter
SMD
Forward neutron transverse asymmetry (AN) measurements SMD (position) + ZDC (energy)
ZDC
Vertical ~ /2Radial ~ 0Longitudinal no asymmetry
distribution
Neutron Asymmetry
» Unexpectedly large asymmetry foundUnexpectedly large asymmetry found» EMCal & ZDC results are consistentEMCal & ZDC results are consistent
Y. Fukao
Upgrades
•Upgrades•Muon Trigger for W Bosons
•Measure sea quark polarization•Nose Cone Calorimeter
+ jet G, extends x-range•Silicon Vertex Tracker
•heavy flavor and jet reconstruction
Silicon Vertex Detector
13cm
20cm
Barrel: Two layers of pixels (2.5, 5cm) Two layers of strips (~10, 14cm)
Endcap: Four sets of mini-strip lampshades
Physics with Silicon VTX• Jet-axis for photon+jet-axis constraint on x
• ce, displaced vertex low-x S/B, DKhigh-x
• bdisplaced J/low/high-x, be, displaced vertexhigh -x
