Overview of spin physics results from PHENIX

experiment

The 4th International Workshop of High Energy Physics in the LHC Era

Valparaiso, Chile

January 4-10, 2012

Kiyoshi Tanida (Seoul National University) for the PHENIX Collaboration

Overview of spin physics results from PHENIX

experiment

The 4th International Workshop of High Energy Physics in the LHC Era

Valparaiso, Chile

January 4-10, 2012

Kiyoshi Tanida (Seoul National University) for the PHENIX Collaboration

What are we aiming at?• To study proton’s spin structure• The flagship question:

“Where the proton spin comes from?”– Proton spin puzzle– Helicity distribution of partons in longitudinally polarized

protons, especially gluons– Flavor-decomposed quark helicity distribution using Ws

• What’s there in transversely polarized protons?– dq ≠ Dq– Very hot recently– Needs more than simple

collinear picture to understand

4

The Relativistic Heavy Ion Collideraccelerator complex

at Brookhaven National Laboratory

PHENIXSTAR

Brahmspp2pp

5

RHIC p+p accelerator complex

BRAHMS & PP2PP

STARPHENIX

AGS

LINACBOOSTER

Pol. Proton Source

Spin Rotators

20% Snake

Siberian Snakes

200 MeV polarimeter Rf Dipoles

RHIC pC “CNI” polarimeters

PHOBOS

RHIC

absolute pHpolarimeter

SiberianSnakes

AGS pC “CNI” polarimeter

5% Snake

Coulomb-Nuclear Interference

6

PHENIX Experiment

Pioneering High Energy Nuclear Interaction EXperiment

7

13 Countries; 70 Institutions

Abilene Christian University, Abilene, TX 79699, U.S.Baruch College, CUNY, New York City, NY 10010-5518, U.S.Collider-Accelerator Department, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S.Physics Department, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S.University of California - Riverside, Riverside, CA 92521, U.S.University of Colorado, Boulder, CO 80309, U.S.Columbia University, New York, NY 10027 and Nevis Laboratories, Irvington, NY 10533, U.S.Florida Institute of Technology, Melbourne, FL 32901, U.S.Florida State University, Tallahassee, FL 32306, U.S.Georgia State University, Atlanta, GA 30303, U.S.University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.Iowa State University, Ames, IA 50011, U.S.Lawrence Livermore National Laboratory, Livermore, CA 94550, U.S.Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.University of Maryland, College Park, MD 20742, U.S.Department of Physics, University of Massachusetts, Amherst, MA 01003-9337, U.S. Morgan State University, Baltimore, MD 21251, U.S.Muhlenberg College, Allentown, PA 18104-5586, U.S.University of New Mexico, Albuquerque, NM 87131, U.S. New Mexico State University, Las Cruces, NM 88003, U.S.Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S.Department of Physics and Astronomy, Ohio University, Athens, OH 45701, U.S.RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, NY 11973-5000, U.S.Chemistry Department, Stony Brook University,SUNY, Stony Brook, NY 11794-3400, U.S.Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook, NY 11794, U.S.University of Tennessee, Knoxville, TN 37996, U.S.Vanderbilt University, Nashville, TN 37235, U.S.

Universidade de São Paulo, Instituto de Física, Caixa Postal 66318, São Paulo CEP05315-970, BrazilInstitute of Physics, Academia Sinica, Taipei 11529, TaiwanChina Institute of Atomic Energy (CIAE), Beijing, People's Republic of ChinaPeking University, Beijing, People's Republic of ChinaCharles University, Ovocnytrh 5, Praha 1, 116 36, Prague, Czech RepublicCzech Technical University, Zikova 4, 166 36 Prague 6, Czech RepublicInstitute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech RepublicHelsinki Institute of Physics and University of Jyväskylä, P.O.Box 35, FI-40014 Jyväskylä, FinlandDapnia, CEA Saclay, F-91191, Gif-sur-Yvette, FranceLaboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS-IN2P3, Route de Saclay, F-91128, Palaiseau, FranceLaboratoire de Physique Corpusculaire (LPC), Université Blaise Pascal, CNRS-IN2P3, Clermont-Fd, 63177 Aubiere Cedex, FranceIPN-Orsay, Universite Paris Sud, CNRS-IN2P3, BP1, F-91406, Orsay, FranceDebrecen University, H-4010 Debrecen, Egyetem tér 1, HungaryELTE, Eötvös Loránd University, H - 1117 Budapest, Pázmány P. s. 1/A, HungaryKFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences (MTA KFKI RMKI), H-1525 Budapest 114, POBox 49, Budapest, HungaryDepartment of Physics, Banaras Hindu University, Varanasi 221005, IndiaBhabha Atomic Research Centre, Bombay 400 085, IndiaWeizmann Institute, Rehovot 76100, IsraelCenter for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, JapanHiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, JapanKEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, JapanKyoto University, Kyoto 606-8502, JapanNagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki 851-0193, JapanRIKEN, The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, JapanPhysics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, JapanDepartment of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, JapanInstitute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, JapanChonbuk National University, Jeonju, KoreaEwha Womans University, Seoul 120-750, KoreaHanyang University, Seoul 133-792, KoreaKAERI, Cyclotron Application Laboratory, Seoul, South KoreaKorea University, Seoul, 136-701, KoreaMyongji University, Yongin, Kyonggido 449-728, KoreaDepartment of Physocs and Astronomy, Seoul National University, Seoul, South KoreaYonsei University, IPAP, Seoul 120-749, KoreaIHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, 142281, RussiaINR_RAS, Institute for Nuclear Research of the Russian Academy of Sciences, prospekt 60-letiya Oktyabrya 7a, Moscow 117312, RussiaJoint Institute for Nuclear Research, 141980 Dubna, Moscow Region, RussiaRussian Research Center "Kurchatov Institute", Moscow, RussiaPNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, RussiaSaint Petersburg State Polytechnic University, St. Petersburg, RussiaSkobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Vorob'evy Gory, Moscow 119992, Russia Department of Physics, Lund University, Box 118, SE-221 00 Lund, Sweden

Feb 2011

The PHENIX Detector• Philosophy

– high resolution & high-rate at the cost of acceptance

– trigger for rare events

• Central Arms– |h| < 0.35, Df ~ p– Momentum, Energy, PID

• Muon Arms– 1.2 < |h| < 2.4– Momentum (MuTr)

• Muon piston calorimeter– 3.1 < |h| < 3.9

9

PART 1: Helicity distribution

with longitudinal polarization

Helicity distribution

• Lepton deep inelastic scattering (DIS) experiments– Quasi-elastic scattering of quark and lepton at high

energies where perturbation is applicable– Reaction depends on quark spin spin structure function

Proton spin puzzle• Quark spin carries only 20-30% of the nucleon spin

spin puzzle (crisis)• What carries the rest?

– Gluon spin?– Orbital angular momentum?

LG 2

1

2

1

Our Main Goal

0.2-0.3

What we can’t know from DIS• Photon mediated sensitive to charge2

– u : d : s : g = 4 : 1 : 1 : 0– Gluon is invisible!

(c.f., indirect methods: Q2 evolution, photon-gluon fusion)

• Can we see gluons directly? Yes, what we need is a

　　　　　　 Polarized Proton collider

13

What we measure?

~ (parton pol.)2× (aLL in parton reaction)

)()(

)()(

LLA

14

How can we access gluons?• Typical parton level diagrams （ LO ）

• What we actually measure are not partons, but fragmented hadrons– Come from different mix of partons– Parton information （ e.g., Bjorken x ） is obscured

qqqq gggg

g g

g g

gqgq

q g

q g

q

q

q

q

15

Some examples• Direct photon: g + q g + q

– No fragmentation– Small contamination (e.g.`qq gg)

• Jet, high-pT hadron production– Mix of all subprocesses– LO highest statistics

　　　 Good measurement with lower luminosity• Heavy quarks (charm, bottom)

– gg→`qq is the main process at RHIC• W ： sensitive to quark flavors

– e.g., 　 W+ comes from`du

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Accumulated data

Year Ös [GeV] Recorded L Pol [%]FOM (P4L)

2003 (Run 3) 200 .35 pb-1 27 1.5 nb-1

2004 (Run 4) 200 .12 pb-1 40 3.3 nb-1

2005 (Run 5) 200 3.4 pb-1 49 0.2 pb-1

2006 (Run 6) 200 7.5 pb-1 57 0.69 pb-1

2006 (Run 6) 62.4 0.08 pb-1 48 5.3 nb-1

2009 (Run 9) 200 16 pb-1 55 1.5 pb-1

2009 (Run 9) 500 10 pb-1 39 0.23 pb-1

2011 (Run 11) 500 17 pb-1 44 0.64 pb-1

with longitudinal polarization

17

Results18

Run5Run6Run9

Precision reaches O(10-3), but still consistent with 0 asymmetry

p0 ALL@200 GeV

How to extract Dg(x)? (1)• p0s come from quarks and gluons of various x

Deconvolution necessary• Are we sure that we understand contribution of

partons? YES!– NLO-pQCD calculation

reproduces s well

p0 @200 GeV, h~0

PRD76:051106,2007

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How to extract Dg(x)? (2)• Practical analysis

– Assume functional form: e.g., Dg(x)=Cg(x)xa(1-x)b

– Search optimum parameters using data, including DIS.• Ex ： GRSV （ M. Gluck et al., PRD 63 (2001) 094005. ）

– Assume DG, other parameters are determined from DIS.– Several versions for various DG （ GRSV-std, max,

min, ... ）• Several other analyses

– For the same integral, DG, Dg(x) could be very different– Our measurement mostly constrains DG[0.02,0.3]

20

G: Global Fit21

RHIC data DSSV analysis (Run 9 data not taken into account)

Phys. Rev. Lett. 101, 072001(2008)

Uncertainty estimation:

2=12/2=2%

Node in Dg(x)?

Global Fit including Run9 0 ALL By S.Taneja et al (DIS2011)

ala DSSV with slightly different uncertainty evaluation approach

DSSV DSSV + PHENIX Run9 0 ALL

No node …Uncertainties decreased

A node at x~0.1 ?

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Extend x-range different s

2-2.5 GeV/c4-5 GeV/c9-12 GeV/c

2-2.5 GeV/c4-5 GeV/c9-12 GeV/c

0 at ||<0.35: xg distribution vs pT bin

s=500 GeV

s=62 GeV

s=200 GeV

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at s=62 GeV

Charged hadrons

Very limited data sample (0.04 pb-1, compared 2.5 pb-1 from Run2005 s=200 GeV)

Clear statistical improvement at larger x; extends the range to higher x (0.06<x< 0.4)

Overlap with 200 GeV ALL provides measurements at the same x but different scale (pT or Q2)

s=500 GeV ALL results will be available soon (from Run2009 with L~10 pb-1 and P~0.4)

0: PHENIX, PRD79, 012003

25

Forward Calorimetry: MPCMuon Piston Calorimeter (3.1 < |h| < 3.9) : lower x10-3

26

Cluster (p0 dominant) ALLDecay photon

π0

Direct photon

PT

Fra

ctio

n of

clu

ster

s

ALW

u(x1)d(x2) d(x1)u(x2)

u(x1)d(x2) d(x1)u(x2)

Parity Violation AsymmetryClean flavor separationw/o fragmentation uncertainty

)0( , ),(

),(

)0( , ),(

),(

2121

21

2121

21

WW

WWL

WW

WWL

yxxMxd

MxdA

yxxMxu

MxuA

W e e

W

W measurement

We in mid-rapidity

Phys. Rev. Lett. 106, 062001 (2011)

W asymmetry29

e+ e-

Uncertainty is still large

More data in 2011 and from now

Run 9 data

30

Forward ー New Trigger System

MuTRGADTX

MuTRGMRG

Level 1TriggerBoard

MuTrFEE

Resistive Plate Counter(RPC) (Φ segmented)

B

2 planes

5%

95%

Trigger

Trigger

Trigger

Interaction Region Rack Room

Optical

1.2Gbps

Amp/Discri.Transmit

DataMerge

MuTRG

RPCFEE

Trigger events with straight track(e.g. Dstrip <= 1)

RPC / MuTRG data arealso recorded on disk.

SG1

31

OK: plateau eff. 92%

Trigger efficiency

Run11 data under analysis ー results coming soon

More results ... no time to show them all

Part 2:Transverse spin physics

32

Transverse spin physics• Transversity dq: Due to Einstein’s relativity, not the

same as Dq – Unexplored leading twist PDF

• AN ： left-right asymmetry wrt transverse polarization

xF<0 xF>0

R

L

Left

Right

33

RL

RLNA

Requirements for AN

• Helicity flip amplitude & relative phase

• In QCD, helicity is conserved if mq=0.

AN ~ asmq/pT ~ O(10-3)

in naive collinear picture

Reality

However, large AN

observed in forward

pions. WHY??

We need somethingmore

hot topic

35

(ii) Collins mechanism: Transversity (quark polarization) × jet fragmentation asymmetry

(i) Sivers mechanism:

correlation between proton spin & parton kT SP

p

p

Sq kT,π

Possible mechanisms (ex.)

SP

kT,qp

p

Sq

Phys Rev D41 (1990) 83; 43 (1991) 261 Nucl Phys B396 (1993) 161

36

(iii) Twist 3: quark-gluon/gluon-gluon correlation A source for Sivers function Expectation: at large pT, AN ~ 1/pT – not observed so far

Forward -- MPC 37

p0 AN

MPC @ 200 GeV

Same tendency with other energies and experiments

38

Cluster (p0 dominant) AN

Forward h AN

39

Forward h AN

40

same tendency with p0

Comparison with STAR

Quite different

at high xF

Due to slightly different kinematic conditions?

Need confirmation/deconfirmation

41

Midrapidity hadrons AN

• AN is zero within 0.1% contrast with forward hadrons

42

43IFF and Collins FF

Collins fragmentation function 1H

Interference fragmentation function

1 ( , )H z M

h1

h1

h2

quark

h2

quark

_Quark spin

J. Collins, S.Heppelmann, G. Ladinsky, Nuclear Physics B, 420 (1994) 565

h

quark

h

quark

_

(courtesy A. Bacchetta)

J. C. Collins, Nucl. Phys. B396, (1993) 161

□1HqAUT

1HqAUT

FF measurements are ongoing at KEK-BELLE

Asymmetry result

• More results ... again, no time to show them all

44

Still need more data...

Part 3:Future measurements

45

More data!• Goal:

> 50 pb-1 @ 200 GeV, > 300 pb-1 @ 500 GeV

46

mid rapidity 0

MPC 0 500 GeV300 pb-1 P=0.55

forward 0

Wm in forward47

48

More detectors – (F)VTX• VTX (from 2011)• FVTX (from 2012)• Study of c & b

Gluon polarization via • Larger acceptance

Jet tagging– q+g g+jet– Theoretically clean channel– Luminosity hungry

VTX barrel |h|<1.2

FVTX

More will be discussed by J. Seele this afternoon

49Even further upgrade -- sPHENIX

Details will be discussed by J. Seele this afternoon

Forward region is important forspin physics- AN in forward regions- Dg(x) in small x region

Compact, hermetic, EM + hadron calorimetry

Summary• Gluon polarization

– Significant constraints on Dg(x) for 0.02<x<0.3– Extension toward lower x is important

higher energy, forward region

• Flavor decomposed quark distribution via W– W e observed in central arm, muon arm follows

• Transverse spin physics– Trying to find the mechanism to produce large AN in

forward region– Access transversity

• More data are still to come

50