Ralf Seidl
(RIKEN)
PHENIX upgrades past
 PHENIX has a history of
constant detector
improvements
 Some detectors recently
removed for latest
upgrades
 Reaction plan
 Hadron Blind Detector
2006
2007
2008
2009
2010
MPC
2011
2012
2013
2014
Reaction Plane
HBD
VTX
Muon Trigger
10/3/2012
forward sPHENIX
FVTX
MPC-EX
2
Why do we need to move forward?
 Longitudinal asymmetries will be measured well in the
next few years:
 Gluon spin at intermediate x
 First access towards lower x via MPC(+EX upgrade)
 Sea quark polarizations via W measurements
 Transverse spin effects largest at forward rapidities
 Cold Nuclear Matter studies in dAu (possibly also pAu,pU)
require lowest xA accessible  most forward
 Some ideas about diffractive J/Psis to access GPDs
 Heavy Ion people also start thinking about forward physics
10/3/2012
forward sPHENIX
3
Physics motivations – Spin (I)
PHENIX, Chiu et al., nucl-ex/0701031
STAR
Can we understand the
origin of these
asymmetries?
BRAHMS Preliminary
 Large forward single spin asymmetries observed from
ZGS, E704 to RHIC in all 3 spin experiments
PRL 101 (2008) 222001
 Origins from either initial state (Sivers-like: QiuSterman, Koike-Kanazawa, Kang) or final state
(Collins-like: Koike,Kang-Yuan-Zhou )
10/3/2012
forward sPHENIX
4
Separating
Sivers and Collins
 L-R Asymmetry on
parton level jet,
photon asymmetries
10/3/2012
forward sPHENIX
 L-R Asymmetry from
fragmentation hadrons
in jet
5
What do we need?
 Good Jet reconstruction to be
able to measure Sivers
cleanly
 Electromagnetic and
hadronic calorimetry
 Particle ID to measure
Collins effect
 Collins effect different for
different hadrons RICH
 B Field to determine charge
sign of hadrons
10/3/2012
forward sPHENIX
6
IFF measurements
 STAR has first nonzero
IFFs seen in pp
 FFs from Belle
 IFF evolution known 
cleaner access to
transversity
 No TMD so factorization
not an issue
 Need to extend to most
forward region for highest
x
Tensor charge
10/3/2012
forward sPHENIX
7
Physics motivations – Spin (II)
 Transversly polarized Drell Yan as important test of TMD
QCD formalism:
SIDIS
DY
 At first glance, SIDIS and Drell-Yan appear to be similar
processes with just the photon and quark legs reversed
 However, color interaction between the initial or final state
quark and the proton remnant cause a specific type of
factorization breaking:
SiversSIDIS = -SiversDrellYan
 Therefore, measuring Drell-Yan Sivers is a test of our
understanding of QCD
10/3/2012
forward sPHENIX
8
Drell Yan
 Want to study
asymmetries overlapping
SIDIS data slightly
forward
 Extend range to
unmeasured higher x 
most forward
10/3/2012
forward sPHENIX
9
Drell Yan
 Expectations show maximal
signal at y≥3
 Current Muon arms only go
out to h=2.4
 3<h<4 is also more difficult:
 Need field, how large?
 How do we get particles
cleanly (low material budget
at shallow angle)
 Background however die
faster than DY
10/3/2012
forward sPHENIX
(Roughly) PHENIX muon arms
sPHENIX coverage
10
Sivers DY with TMD evolution
 Kang’s result from recent
QCD evolution workshop
 If Sivers function would
really evolve so fast
asymmetries would be
much smaller than
anticipated
 However, currently not too
much known about it
need to measure it anyway,
but sign change might be
more challenging
10/3/2012
forward sPHENIX
11
Other DY measurements
 Upol: u x ubar Boer Mulders
 Single spin:
 Transversity x Boer Mulders (combination of u and
ubar)
 Sivers (mostly u)
 Double spin:
 u x ubar Transversity (small due to sea)
 u x ubar Helicity
10/3/2012
forward sPHENIX
12
Physics motivations – Cold nuclear
matter (I)
 So far mostly unknown: Heavy Ion initial state
General interest:
• Extend Understanding
of QCD into the nonperturbative regime of
high field strengths and
large gluon densities.
• Search for universal
properties of nuclear
matter at low x and high
energies.
10/3/2012
forward sPHENIX
Heavy Ion Collisions:
• Understand the initial state
to obtain quantitative
description of the final state
in HI-collisions.
• Establish theoretical
framework to describe initial
state of HI-collisions based
on measurements of GA (x)
in p/d-A or e-A.
13
J/ψ: Cold Nuclear Matter Effects in the Initial
State
(I) Shadowing (from fits to DIS
data or model calculations)
RGPb
(II) Dissociation of cc
into two D mesons by
nucleus or co-movers
cc
D
co-movers
D
(III) Gluon saturation from non-linear
gluon interactions for the high
gluon densities at small x
K. Eskola H. Paukkumen, C. Salgado
JHEP 0807:102,2008
 DGLAP LO analysis of nuclear pdfs
GPb (x,Q2)=RGPb(x,Q2) Gp (x,Q2)
10/3/2012
forward sPHENIX
low x
high x
J/ψ : Some of the Suppression in A-A is from Cold
Nuclear Matter Effects found in d-A Collisions
EKS shadowing + dissociation:
use d-Au data to determine
break-up cross section
PRC 77,024912(2008)
10/3/2012
forward sPHENIX
EKS shadowing + dissociation:
from d-Au vs Au-Au data
at mid-rapidity
forward-rapidity
The Color Glass Condensate
see for example, F. Gelis, E. Iancu, J. JalilianMarian, R. Venugopalan, arXiv:1002.0333
gluon density n(Y , kT ) saturates for
CGC:
effective
large an
densities
at field
smalltheory:
x:
Small-x gluons are described as the
Non-linear
evolution
color
fields radiated
byeqn.
fast color
sources
at higher rapidity. This EFT
n
2
2 2
 the
n



n

μα
describes
saturated
gluons
S
S t
S n(slow
Y
partons)
as a Color Glass Condensate.
diffusion
g-ginvariant,
merging
g emission
The EFT
provides a gauge
universal distribution, W(ρ):
 1a
g-g merging
large if αtoS nfind
W(ρ) ~ probability
configuration ρ of color sources
in a nucleus.
saturation
scale
QS in kT of
so W(ρ)
that nis
(Y described
, kT )  1 by
The evolution
αS
the JIMWLK equation.
QS, nuclear enhancement ~ A1/3
10/3/2012
forward sPHENIX
CNM measurements
The various CNM effects are difficult to disentangle experimentally – multiple
probes, types & energies of collisions, wide kinematic coverage are key
• open-heavy suppression – isolates initial-state effects
• other probes of shadowing & gluon saturation – forward hadrons, etc.
• Drell-Yan to constrain parton energy loss in CNM
And strong theoretical guidance & analysis – not just for certain measurements
but for the ensemble of measurements
anti-shadowing
dE / dx

q
q
shadowing
Dilute
parton
system
(deuteron)
10/3/2012
forward sPHENIX
Drell-Yan

PT is balanced
by many gluons
Dense gluon
field (Au)
17
10/3/2012
forward sPHENIX
18
The sPHENIX Detector Upgrade
PHENIX Collaboration arXiv:1207.6378v1
led by Jamie Nagle, David Morrison & John Haggerty
10/3/2012
forward sPHENIX
Magnetic Solenoid: 2 Tesla, 70 cm radius
Compact Tungsten-Fiber EMCal
Steel-Scintillator Hadronic Calorimeter
Open geometry at forward angles for next
stage upgrades for transverse spin and
19
eventual ePHENIX
sPHENIX Forward Physics
The study of transverse spin asymmetries
has led to an advanced understanding of
scattering processes involving the strong
interaction:
The PHENIX forward upgrade aims to
(1) quantitatively confirm TMD
framework including decomposition
of AN observed in pp, process
dependence and evolution.
(2) measure quark transversity dis.
including large x  tensor charge !
(3) measure valence and sea-quark
Sivers distributions
 explore connection to Lz
(M. Burkhard arXiv: 1205.2916v1)
TMD framework: inclusion of final and
initial state gluon radiation via gauge link
integrals gives rise to large
transverse spin effects and
process dependence.
10/3/2012
forward sPHENIX
(4) Survey cold nuclear matter effects in
the transition region to the saturation
regime. Quantify the initial state for
HI-Collisions.
Unique measurements at forward
rapidity using jet observables
and the Drell-Yan process!
20 20
A-Dependence of Nucleon
Structure  Goals
p-A
(I)
Study the transition region near the saturation scale!
(II)
Measure GA(x) and quantify initial state for HI collisions
at RHIC: heavy flavor, jets, jet-correlations, direct photon,
Drell-Yan, different nuclei, beam energy.
(III)
Search for onset of gluon saturation and verify CGC
framework as an effective field theory at high field
strengths in QCD.
For example: can we determine color configurations
W(ρ) from RHIC data and use the JIMWLK
evolution to evolve them to
LHC energies?
(IV) Explore similarities between TMD and CGC formalisms.
21
Experimental Requirements
Driven by p-p Goals
 Good Jet reconstruction to be able
to measure Sivers cleanly
Tracker
 Electromagnetic and hadronic
calorimetry
 Particle ID to measure Collins
effect and IFF
 Collins effect different for
different hadrons RICH
 B Field and tracker to determine
charge sign of hadrons
 Electron ID (Preshower) and
Muon Id for DY/Quarkonia
 Vertex detector for heavy flavor
tagging
10/3/2012
forward sPHENIX
RICH
EMCal
HCal MuID
from Kieran Boyle, DIS – April 2012
22 22
Forward Detector
 Rely on central magnet field
 Studying other field/magnet
possibilities
 EMCal based on restack of
current PHENIX calorimetry
 PbSc from central arm (5.52
cm2)
 MPC forward arm (2.2 cm2)
 For tracker considering GEM
PbSc restack
technology
 Interest of HI in forward
direction may influence choices
based on expected multiplicity.
10/3/2012
forward sPHENIX
MPC restack
=12x12 towers
1 tower is 5.5cm2
= 2.2cm2
23
Detector Layout for Physics Studies
Studies for detector components led by
GEM-trackers:
RICH:
EMC:
HCAL:
Magnet:
Los Alamos, RBRC
Stony Brook/RIKEN
RBRC/RIKEN, ISU
UIUC
Los Alamos, RBRC, UCR
B field might not be enough at highest rapidities 
10/3/2012
forward sPHENIX
additional magnets
needed?
24 24
A dipole detector?
 Requires beam shielding which might limit acceptance
 Compensation also necessary
 Other possibilities? Split dipole like Phobos
or similar to LHCb?
10/3/2012
forward sPHENIX
25
Particle identification
 Electron reasonable using
preshower as photon veto, E/P
measurement from EMCAL +
tracking
 Muon identification relatively easy
with HCAL + MUID/RPC stations
downstream, however reasonable
tracking necessary to discard decays
 Hadron momenta of up to 100 GeV
make hadron id difficult with
conventional methods, long
radiators with low refractive indices
necessary, Cherenkov light of
difficult wavelength for mirrors and
readout
10/3/2012
forward sPHENIX
26
Other aspects of upgrade
 Potential of polarized He3 beams
 Clean access to neutron, but only if
protons can be tagged
 New ideas with ultraperipheral J/Psi
production which relates to GPD E,
requires scattered proton detection
Roman pots :
Currently being developed by pp2pp
at RHIC
10/3/2012
forward sPHENIX
27
Next Steps
o Detector and sensitivity simulations in progress
o RBRC workshop on “Forward Physics at RHIC”
 July 30 to August 1st 2012
(https://indico.bnl.gov/conferenceDisplay.py?confId=533)
o Initiate exploratory R&D
GEM-trackers at Los Alamos (LDRD)
EMC at RBRC (RIKEN)
HCAL at UIUC (NSF)
RICH at SBU/RIKEN
o Report on Physics and Design Studies
 November 2012
o Explore funding possibilities: external funds, staging
10/3/2012
forward sPHENIX
28 28
Summary
 Most interesting transverse spin physics and cold
nuclear matter effects require detectors with rapidities
up to 4 (at RHIC energies)
 Measurements clearly layed out, currently studying
requirements in Simulations
 R&D phase for several detectors under preparation, reuse current central PHENIX EM calorimetry
10/3/2012
forward sPHENIX
29
From pp to g p/A
 Get quasi-real photon from one proton
 Ensure dominance of g from one identified proton
by selecting very small t1, while t2 of “typical hadronic
size”
small t1  large impact parameter b (UPC)
 Final state lepton pair  timelike compton scattering
 timelike Compton scattering: detailed access to GPDs
including Eq;g if have transv. target pol.
 Challenging to suppress all backgrounds
Z2
A2
 Final state lepton pair not from g* but from J/ψ
 Done already in AuAu
 Estimates for J/ψ (hep-ph/0310223)
 transverse target spin asymmetry  calculable with GPDs
t - t Im(E * H )
AUT (t ,t) ~ 0
mp
|H |
2
M J/Y
t=
s
 information on helicity-flip distribution E for gluons
golden measurement for eRHIC
Gain in statistics doing polarized p↑A
10/3/2012
forward sPHENIX
30
Separating Collins and Sivers
10/3/2012
forward sPHENIX
31
jets
 Most important
measured property: jet
axis
s = 200 GeV
y=3.3 jets
twist
3
Fit of SIDIS
SIDIS old
10/3/2012
forward sPHENIX
32
Direct photon+jet AN
 Initially direct photon
AN thought as clean
Sivers channel
 However, factorization
not clear anymore
 Sign and size
expectations based on
SIDIS Sivers vary
significantly
10/3/2012
forward sPHENIX
33
Some TPPMC output
Developed by J. Lajoie and extended by T. Burton and A. Dion
 Used Soffer bound for






transversity
Collins FF from Torino
analysis
LO
Unpol GRV98
Pol DSSV
FF DSS(*)
No Sivers for now
 Kinematics:
 Hadron Pt >1 GeV
 Rapidity 1-4
10/3/2012
forward sPHENIX
x1 x2 distribution for
selected pi+
34
Transversity x Collins FF
Torino global analysis of
Transversity and Collins FF
 Current measurements
in SIDIS via Collins FF
still very limited in x
 Evolution too not well
known
 Need different hadrons
for flavor decomposition
jet  h+X
10/3/2012
forward sPHENIX
35
Collins asymmetries
(first look via tppmc)
 Resulting asymmetries are
sizeable, but due to glue BG not
very large
 Ordering as expected
 Asymmetries not too sensitive to
smearing
10/3/2012
forward sPHENIX
36
Other hadron in jet measurements
10/3/2012
forward
sPHENIX
What about
predictions,
also for di-hadrons?
37
Polarized He3
 Timeline: polarized He3
as early as 2015,
significantly higher
luminosities not before
2018
 Pol He3 is mostly
polarized neutron +
unpol (pp)
10/3/2012
forward sPHENIX
38
Zhangbo Kang (RBRC)
10/3/2012
forward sPHENIX
39
Marco Stratman (BNL)
pros
polarized 3He mainly a neutron target: 0.865 n + 2*(-0.027) p
 important information for flavor
separation complementary to pp
cons
is the maximum possible c.m.s. energy for p 3He collisions sufficient ?
(W cross section might be too small for anticipated RHIC luminosities)
unpolarized 3He a combination of p and n
 no longer probing Δq/q as in pp; but irrelevant “complication“ in a global analysis
need significant running time/luminosity for both pp and p 3He
O(few hundred pb-1) each; but some “synergy effects” of combined set in global fit
10/3/2012
forward sPHENIX
40
Marco Stratman (BNL)
3He p @ 432 GeV
pp @ 500 GeV
caveat: AL study assumes 216 GeV 3He beam
but 325 GeV × Z/A was too optimistic
conservative: 250 GeV × 2/3 = 166 GeV
does not affect AL much but cross section smaller
10/3/2012
forward sPHENIX
41
Other transverse spin studies
 Regular ANs still quite interesting to test if general
picture of asymmetries is correct:
 either Sivers-like or Collins-like should produce clear
prediction for He3 case
 If completely different mechanism different
asymmetries
 He3 asymmetries will be diluted by two unpolarized
protons unless tagged neutron asymmetries available
 IFF with He3 will allow flavor separation based on
RHIC results
10/3/2012
forward sPHENIX
42
Rough x Q2 map for pol. EIC and pp
Q2
1
104
10/3/2012
Transversity
and Collins,
High x
Sivers:
transversit
Dubar – D Q2 evolution,
y,
Flavor
dbar,
High x
Forwar
decomposition
Sivers,
Sivers
d pp
Boer
pp
Currend
Ds, Mulders at
factorizati
pol DISJLAB12 on?
Dg via g1 D sbar
lower
x
st
Full eRHIC
scaling1 phase
D d sign
eRHIC
change?
10100.
1
3
2
4
xBJ
forward sPHENIX
43
Summary
 DY Sivers measurement sign change is most
interesting,
 Same regions as in SIDIS  forward
 other DY measurements lead to further TMDs
 Jet related ANs,
 Sivers, for factorization studies
 Hadrons
10/3/2012
forward sPHENIX
44
Some more kinematics
 not as large z as I would
have thought, some
backscattered events
seen as well
x z distribution for selected pi+
10/3/2012
forward sPHENIX
 Z – pt correlation needs
to be looked at
 Look at parton fractions
45
Z dependence
(folded by unpol pdfs)
z distribution for selected pi+
 Even though unpol gluons
dominating pdfs, high z
behavior seems wrong! (in DSS
glue falls off faster than u)
 Disfavored small for pi+,
substantial for pi- as expected
10/3/2012
forward sPHENIX
46
Collins angle (generated, defined
by real quark spin orientation)
 Favored, disfavored
qualitatively as expected
(need to check
quantitatively)
 Glue does not contribute to
asymmetries (but to
denominator)
 Sum of all processes very
small asymmetries, but
without quark
polarizations not
meaningful
10/3/2012
forward sPHENIX
47
Transverse polarized distribution
 Calculate the asymmetry
of parton spins
(anti)parallel to proton
spin for selected hadrons
(ie folded with FFs)
 Favored and disfavored
separated only, ie diluted
by corresponding sea pol
 High x behavior seems
quite wrong even with
Soffer bound
10/3/2012
forward sPHENIX
48
TMD factorization
 Initially assumption, later LO, one loop proof for some
processes (Metz), that factorization holds also for TMDs
 However, especially with more than 2 hadrons in initial and
final state gauge links with many different color factors
 Bomhof, Mulders 1 loop level: different color factors, but ok
 Rogers and Mulders, Kang, … : not any more ok at higher
loops, some diagrams break factorization – no universal
functions. However not known whether breaking is large or
zero
10/3/2012
forward sPHENIX
49
Collins angles around quark axis
 Very similar to generated
Collins angle
 Introduced some
artificial angle gaussian
smearing of 0.5 rad to
simulated jet axis
reconstruction, etc
10/3/2012
forward sPHENIX
50
 Single (proton) spin
asymmetries calculated
using the quark axis
angles mentioned
 Fit cosine modulations
10/3/2012
forward sPHENIX
51
Collins asymmetries
(using quark axis)
 Resulting asymmetries are
sizeable, but due to glue BG not
very large
 Ordering as expected
 Asymmetries not too sensitive to
smearing
10/3/2012
forward sPHENIX
52
Traditional AN from
transversity x Collins
10/3/2012
forward sPHENIX
53