PHENIX Spin Program Recent results

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PHENIX Spin ProgramRecent results
A.Bazilevsky Brookhaven National Laboratory for
the PHENIX Collaboration XXXXth Rencontres de
Moriond - March 12-19, 2005       QCD and
Hadronic interactions at high energy
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Proton Spin Structure
Quark Spin
Gluon Spin
Spin
Orbital Angular Momentum

• Polarized DIS contribution of quarks to proton
  spin is amazingly small DS?0.25
• Main candidate to carry proton spin - Gluons

Gluon polarization (?G) remains poorly
constrained ? ?G measurements main RHIC-Spin
goal
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Polarised PDFAsymmetry Analysis Collaboration
M. Hirai, S. Kumano and N. Saito, PRD (2004)

• Valence Dists are determined well
• Sea Distribution poorly constrained
• Gluon can be either pos, 0, neg!

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PHENIX Spin Program
? Production
Prompt Photon
Heavy Flavors
Utilizing high energy polarized proton beams of
RHIC
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RHIC as polarized proton collider
Absolute Polarimeter (H jet)
RHIC pC Polarimeters
Siberian Snakes
Spin Rotators
2 ? 1011 Pol. Protons / Bunch e 20 p mm mrad
Partial Siberian Snake
LINAC
BOOSTER
Pol. Proton Source 500 mA, 300 ms
AGS
AGS Internal Polarimeter
200 MeV Polarimeter
Rf Dipoles
RHIC accelerates heavy ions to 100 GeV/A and
polarized protons to 250 GeV
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Spin Running at RHIC-PHENIX

• Run2 2001-2002
• Transversely polarized pp collisions
• Average polarization of 15
• Integrated luminosity 0.15 pb-1
• Run3 2003
• Longitudinally polarized pp collisions achieved
• Average polarization of 27
• Integrated luminosity 0.35 pb-1
• Run4 2004
• Longitudinally polarized pp collisions
• Polarization of 40-45
• Integrated luminosity 0.15 pb-1

• Run5 starting next month
• Expected Longitudinally polarized pp collisions
• Expected P 50
• Expected L gt 10 pb-1

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?0 Cross Section in pp at ?s200 GeV
Phys. Rev. Lett. 91, 241803 (2003)

• NLO pQCD consistent with data within theoretical
  uncertainties
• PDF CTEQ5M
• Fragmentation functions
• Kniehl-Kramer-Potter (KKP)
• Kretzer
• Spectrum constrains D(gluon?p) fragmentation
  function

?lt0.35
9.6 normalization error not shown
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?0 ALL
(P) Polarization (R) Relative Luminosity (N)
Number of pi0s
Preliminary PRL 93, 202002
?0 ALL small (or consistent with zero)
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?0 ALL ?G constrain
Fractional contribution to pp??0X at ?s200 GeV
at mid-rapidity
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?0 ALL ?G constrain
B.Jager et al., PRD67, 054005 (2003)

• Note considerable contribution of soft physics in
  the lowest pT point (?50)
• Comparison with theory
• GRSV-std
• 21-24 (pTgt1 GeV/c)
• 27-29 (pTgt2 GeV/c)
• GRSV-max
• 0.00-6 (pTgt1 GeV/c)
• 0.01-13 (pTgt2 GeV/c)

Run34
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
Consistent with GRSV-std Less consistent with
GRSV-max
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Prompt photons and ?G

• Gluon Compton Dominates
• At LO no fragmentation function
• Small (?15) contamination from annihilation

• NLO pQCD describes data well ? can be used to
  interpret ALL(?)
• ALL(?) needs large luminosity results expected
  in 2007-08

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Transverse Single-Spin Asymmetries
left

• Observed in p0 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

right
AN for both charged hadrons and neutral pions
consistent with zero.
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Future
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Summary

• RHIC has been successful as the worlds 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

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Backup slides
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Brazil University of São Paulo, São
Paulo China Academia Sinica, Taipei,
Taiwan China Institute of
Atomic Energy, Beijing Peking
University, Beijing France 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, Nantes Germany University of Münster,
Münster Hungary Central Research Institute for
Physics (KFKI), Budapest
Debrecen University, Debrecen
Eötvös Loránd University (ELTE), Budapest India
Banaras Hindu University, Banaras
Bhabha Atomic Research Centre,
Bombay Israel Weizmann Institute,
Rehovot Japan 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,
Seoul Russia 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.
Petersburg Sweden Lund University, Lund
12 Countries 57 Institutions 460 Participants
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


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PHENIX Detector

• Philosophy
• High rate capability granularity
• Good mass resolution and particle ID
• Sacrifice acceptance

• Central Arms
• ?lt0.35, ??2?900
• Charged particle ID and tracking
• photon ID
• Muon Arm
• 1.2lt?lt2.4
• Muon ID and tracking
• Global Detectors
• Collision trigger
• Collision vertex characterization
• Relative luminosity
• Local Polarimetry

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?G other experiments

• 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

GRSV-max
HERMES
GRSV-std
SMC
So far all results are consistent with GRSV-std
PHENIX x-range
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?G Prompt Photons ALL
Statistics with full design luminosity and
polarization ( ?Ldt320 pb-1, P70 )
x?G
GS95
prompt photon
x
GRSV Frixione and Vogelsang, Nucl. Phys.
B56860 (2000) GS95 Gehrmann and Stirling,
PRD53, 6100 (1996)
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AN
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?G Heavy Flavor
Open heavy flavor production

• Decay channels
• ee-, mm-, em, e, m, eD, mD

H. Sato

• Provides more independent ?G measurements in
  PHENIX
• Helps control experimental and theoretical
  systematic errors
• Different channels cover different kinematic
  regions

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Flavor Decomposition

• Drell-Yan production of lepton pairs
• Maximal parton level asymmetry aLL -1
• Possible severe background from semi-leptonic
  decays of open charm productions

• 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

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W Production
800 pb-1
W dominates for muon pTgt20 GeV/c
W
Z
quark x from parton kinematics
x1gtgtx2 AL(W) ? ?u/u(x1)
_ x2gtgtx1 AL(W) ? - ?d/d(x1)
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PHENIX Local Polarimeter

• Forward neutron transverse asymmetry (AN)
  measurements
• SMD (position) ZDC (energy)

f distribution
SMD
Vertical ? f ?p/2 Radial ? f 0 Longitudinal
? no asymmetry
ZDC
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Neutron Asymmetry
Y. Fukao

• Unexpectedly large asymmetry found
• EMCal ZDC results are consistent

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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

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Silicon Vertex Detector
Barrel Two layers of pixels (2.5, 5cm) Two
layers of strips (10, 14cm) Endcap Four sets of
mini-strip lampshades
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Physics with Silicon VTX

• Jet-axis for photonjet-axis ? constraint on x
• c?e,m displaced vertex low-x S/B, D?Kp high-x
• b?displaced J/y low/high-x, b?e, displaced vertex
  high -x