The 4th International Workshop of High Energy Physics in the LHC Era
Valparaiso, Chile
January 4-10, 2012
for the PHENIX Collaboration

The 4th International Workshop of High Energy Physics in the LHC Era
Valparaiso, Chile
January 4-10, 2012
for the PHENIX Collaboration

• 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?
– d q ≠ D q
– Very hot recently
– Needs more than simple collinear picture to understand
4

PHENIX
R
H
I
C
5
Brahms pp2pp
STAR

p+p
PHOBOS absolute pH polarimeter
RHIC pC “CNI” polarimeters
BRAHMS
& PP2PP
Siberian
Snakes
PHENIX
RHIC
Spin Rotators
Pol. Proton Source
LINAC
BOOSTER
STAR
AGS
Siberian Snakes
5% Snake
AGS pC “CNI” polarimeter
200 MeV polarimeter
20% Snake
Rf Dipoles
Coulomb-Nuclear
Interference
6

7
P ioneering H igh E nergy N uclear I nteraction E X periment

Universidade de São Paulo, Instituto de Física, Caixa Postal 66318, São Paulo CEP05315-970, Brazil
Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
China Institute of Atomic Energy (CIAE), Beijing, People's Republic of China
Peking University, Beijing, People's Republic of China
Charles University, Ovocnytrh 5, Praha 1, 116 36, Prague, Czech Republic
Czech Technical University, Zikova 4, 166 36 Prague 6, Czech Republic
Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2,
182 21 Prague 8, Czech Republic
Helsinki Institute of Physics and University of Jyväskylä, P.O.Box 35, FI-40014 Jyväskylä, Finland
Dapnia, CEA Saclay, F-91191, Gif-sur-Yvette, France
Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS-IN2P3, Route de Saclay,
F-91128, Palaiseau, France
Laboratoire de Physique Corpusculaire (LPC), Université Blaise Pascal, CNRS-IN2P3,
Clermont-Fd, 63177 Aubiere Cedex, France
IPN-Orsay, Universite Paris Sud, CNRS-IN2P3, BP1, F-91406, Orsay, France
Debrecen University, H-4010 Debrecen, Egyetem tér 1, Hungary
ELTE, Eötvös Loránd University, H - 1117 Budapest, Pázmány P. s. 1/A, Hungary
KFKI Research Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences (MTA KFKI RMKI),
H-1525 Budapest 114, POBox 49, Budapest, Hungary
Department of Physics, Banaras Hindu University, Varanasi 221005, India
Bhabha Atomic Research Centre, Bombay 400 085, India
Weizmann Institute, Rehovot 76100, Israel
Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo,
Tokyo 113-0033, Japan
Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan
KEK, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan
Kyoto University, Kyoto 606-8502, Japan
Nagasaki Institute of Applied Science, Nagasaki-shi, Nagasaki 851-0193, Japan
RIKEN, The Institute of Physical and Chemical Research, Wako, Saitama 351-0198, Japan
Physics Department, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan
Department of Physics, Tokyo Institute of Technology, Oh-okayama, Meguro, Tokyo 152-8551, Japan
Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, Japan
Chonbuk National University, Jeonju, Korea
Ewha Womans University, Seoul 120-750, Korea
Hanyang University, Seoul 133-792, Korea
KAERI, Cyclotron Application Laboratory, Seoul, South Korea
Korea University, Seoul, 136-701, Korea
Myongji University, Yongin, Kyonggido 449-728, Korea
Department of Physocs and Astronomy, Seoul National University, Seoul, South Korea
Yonsei University, IPAP, Seoul 120-749, Korea
IHEP Protvino, State Research Center of Russian Federation, Institute for High Energy Physics,
Protvino, 142281, Russia
INR_RAS, Institute for Nuclear Research of the Russian Academy of Sciences, prospekt 60-letiya Oktyabrya 7a,
Moscow 117312, Russia
Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia
Russian Research Center "Kurchatov Institute", Moscow, Russia
PNPI, Petersburg Nuclear Physics Institute, Gatchina, Leningrad region, 188300, Russia
Saint Petersburg State Polytechnic University, St. Petersburg, Russia
Skobeltsyn 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
13 Countries; 70 Institutions
Feb 2011
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.

• 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

• 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

• Quark spin carries only 20-30% of the nucleon spin
 spin puzzle (crisis)
• What carries the rest?
– Gluon spin?
– Orbital angular momentum?
1
2

1
2
D
0.2-0.3
 D
G

L

• Photon mediated  sensitive to charge 2
– u : d : s : g = 4 : 1 : 1 : 0
– Gluon is invisible!
(c.f., indirect methods: Q 2 evolution, photon-gluon fusion)
13
• Can we see gluons directly?
 Yes, what we need is a

A
LL



(

)
(

)
 
 
(

)
(

)
~ (parton pol.) 2 × (a
LL in parton reaction)
14

• Typical parton level diagrams （ LO ） gg
 gg gq
 gq qq
 qq
15
 g g g g
 q g q g

D q
D q q q
• What we actually measure are not partons, but fragmented hadrons
– Come from different mix of partons
– Parton information （ e.g., Bjorken x ） is obscured

• Direct photon: g + q  g
+ q
– No fragmentation
– Small contamination (e.g.
` qq  gg
)
• Jet, high-p
T 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
16

with longitudinal polarization
Year
2003 (Run 3)
 s [GeV] Recorded L Pol [%]
200 .35 pb -1 27
2004 (Run 4)
2005 (Run 5)
200
200
.12 pb -1
3.4 pb -1
40
49
2006 (Run 6)
2006 (Run 6)
2009 (Run 9)
2009 (Run 9)
2011 (Run 11)
200
62.4
200
500
500
7.5 pb -1
0.08 pb -1
16 pb -1
10 pb -1
17 pb -1
57
48
55
39
44
FOM
(P 4 L)
1.5 nb -1
3.3 nb -1
0.2 pb -1
0.69 pb -1
5.3 nb -1
1.5 pb -1
0.23 pb -1
0.64 pb -1
17

p
0 A
LL
@200 GeV
18
Run5
Run6
Run9
Precision reaches O(10 -3 ), but still consistent with 0 asymmetry

D
• p
0 s come from quarks and gluons of various x
 Deconvolution necessary
• Are we sure that we understand contribution of partons? YES!
– NLO-pQCD calculation reproduces
 well p 0
@200 GeV, h
~0
19
PRD76:051106,2007

D
• Practical analysis
– Assume functional form: e.g., D g(x)=Cg(x)x a
(1-x) b
– Search optimum parameters using data, including DIS.
• Ex ： GRSV （ M. Gluck et al., PRD 63 (2001) 094005.
）
– Assume D
G, other parameters are determined from DIS.
– Several versions for various D
G （ GRSV-std, max, min, ...
）
• Several other analyses
– For the same integral, D
G,
D g(x) could be very different
– Our measurement mostly constrains D
G
[0.02,0.3]
20

RHIC data
21 D
DSSV analysis
(Run 9 data not taken into account)
Phys. Rev. Lett.
101, 072001(2008)
Uncertainty estimation:
D
2 =1
D
2 /

2 =2%
Node in
D g(x)?

p
0
LL
By S.Taneja et al (DIS2011) ala DSSV with slightly different uncertainty evaluation approach
22
DSSV
A node at x~0.1 ?
DSSV + PHENIX Run9 p
0 A
LL
No node …
Uncertainties decreased



p
0 at | h
|<0.35: x g distribution vs p
T bin
23
 s=62 GeV

2-2.5 GeV/c
4-5 GeV/c
9-12 GeV/c
2-2.5 GeV/c
4-5 GeV/c
9-12 GeV/c
 s=200 GeV
 s=500 GeV

p

p
0: PHENIX, PRD79, 012003

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 A
LL provides measurements at the same x but different scale (p
T
  s=500 GeV A
LL or Q 2 ) results will be available soon (from Run2009 with
L~10 pb -1 and P~0.4)
Charged hadrons
25

Muon Piston Calorimeter (3.1 < |h| < 3.9) : lower x

10 -3
26
Cluster ( p 0 dominant) A
LL
Decay photon
π 0
Direct photon
P
T

A
L
W
 
D u ( x
1
) d ( x u ( x
1
) d ( x
2
2
)  D d ( x
1
) u ( x
)  d ( x
1
) u ( x
2
)
2
)
W   e   e

 

Parity Violation Asymmetry
Clean flavor separation 
W     

A
W
L

A
W
L



D u ( u ( x x
1
,
1
,
M
W
2
M
2
W
)
)
, x
1


D d d (
( x x
1
,
1
,
M
M
2
W
2
W
)
)
, x
1 x
2
( y
W
 x
2
(
 y
W
0 )

0 )


Phys. Rev. Lett. 106, 062001 (2011)

e +
Run 9 data e -
29
Uncertainty is still large
More data in 2011 and from now

ー
Resistive Plate Counter
(RPC) (Φ segmented)
Trigger events with straight track
(e.g.
D strip <= 1)
SG1
30
RPC
FEE
Level 1
Trigger
Board
Trigger
MuTRG
Amp/Discri.
Transmit
Data
Merge
Trigger
5% Optical
MuTRG
ADTX 1.2Gbps
MuTRG
MRG
B
2 planes
95%
MuTr
FEE
Interaction Region
Trigger
RPC / MuTRG data are also recorded on disk.
Rack Room

31
Run11 data under analysis ー results coming soon
More results ... no time to show them all

32

• Transversity d q : Due to Einstein’s relativity, not the same as
D q
– Unexplored leading twist PDF
33
• A
N
： left-right asymmetry wrt transverse polarization
Left x
F
<0 x
F
>0
L 𝑝
Right
R 𝑝
A
N


L

L
 
 
R
R

N
• Helicity flip amplitude & relative phase
• In QCD, helicity is conserved if m q
=0.
 A
N
~ a s m q
/p
T
~ O(10 -3 ) in naive collinear picture

However, large A
N observed in forward pions. WHY??
We need something more
 hot topic
35

(i) Sivers mechanism: correlation between proton spin & parton k
T
S
P
36
(ii) Collins mechanism:
Transversity (quark polarization)
× jet fragmentation asymmetry
S
P
S q p k
T,q p p p
S q k
T, π
Phys Rev D41 (1990) 83; 43 (1991) 261 Nucl Phys B396 (1993) 161
(iii) Twist 3: quark-gluon/gluon-gluon correlation
 A source for Sivers function
Expectation: at large p
T
, A
N
~ 1/p
T
– not observed so far

p 0
A
N
37

Cluster ( p 0 dominant) A
N
38
Same tendency with other energies and experiments

h
N
39

h
N
40 same tendency with p 0

Quite different at high x
F
Due to slightly different kinematic conditions?
Need confirmation/ deconfirmation
41

N
42
• A
N is zero within 0.1%  contrast with forward hadrons

Interference fragmentation function H
1
( ,
 pp
)
J. Collins, S.Heppelmann, G. Ladinsky, Nuclear Physics B, 420 (1994) 565
Quark spin h
1
A
UT
 d q

H
1
□ h
2
 quark
_
 quark h
2 h
1
Collins fragmentation function
J. C. Collins, Nucl. Phys. B396, (1993) 161 h
H
1

A
UT
 d q

H
1

 quark
_
 quark
(courtesy A. Bacchetta) h
FF measurements are ongoing at KEK-BELLE
43

44
Still need more data...
• More results ... again, no time to show them all

45

• Goal:
> 50 pb-1 @ 200 GeV, > 300 pb -1 @ 500 GeV mid rapidity p
0 forward p
0
46
MPC p
0 500 GeV
300 pb -1 P=0.55

 
47

• VTX (from 2011)
• FVTX (from 2012)
• Study of c & b
Gluon polarization via
VTX barrel | h |<1.2
48
• Larger acceptance
 Jet tagging
– q+g  g
+jet
– Theoretically clean channel
– Luminosity hungry
FVTX
More will be discussed by J. Seele this afternoon

49
Compact, hermetic, EM + hadron calorimetry
Forward region is important for spin physics
- A
N in forward regions
-
D g(x) in small x region
Details will be discussed by J. Seele this afternoon

• Gluon polarization
– Significant constraints on D g(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 A
N forward region in
– Access transversity
• More data are still to come
50