1. ｓPHENIX　 Spin physics
Ralf Seidl
(RIKEN)

2. PHENIX upgrades past
PHENIX has a history of constant detector improvements
Some detectors recently removed for latest upgrades
Reaction plan
Hadron Blind Detector
11/27/2012
forward sPHENIX

3. 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 ( some addressed already by MPC (clusters) and MPC-EX (p0,photons)
Cold Nuclear Matter studies in dAu (possibly also pAu,pU) require lowest xA accessible  most forward
Some ideas about diffractive J/y to access GPDs
Heavy Ion people also start thinking about forward physics
11/27/2012
forward sPHENIX

4. Physics motivations – Spin (I)
PHENIX, Chiu et al., nucl-ex/
STAR
Can we understand the origin of these asymmetries?
Pol Beam direction
x-Axis
Spin Axis
BRAHMS Preliminary
Large forward single spin asymmetries observed from ZGS, E704 to RHIC in all 3 spin experiments
Origins from either initial state (Sivers-like: Qiu-Sterman, Koike-Kanazawa, Kang) or final state (Collins-like: Koike,Kang-Yuan-Zhou )
PRL 101 (2008)
11/27/2012
forward sPHENIX

5. Separating Sivers and Collins
Jet
HadronPID
Separating Sivers and Collins
L-R Asymmetry on parton level jet, photon asymmetries
L-R Asymmetry from fragmentation hadron asymmetries in jet
11/27/2012
forward sPHENIX

6. Jet
HadronPID
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
11/27/2012
forward sPHENIX

7. 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 (xBj Integral of quark transversities)
11/27/2012
forward sPHENIX

8. Physics motivations – Spin (II)
e/m ID
Transversly polarized Drell Yan (p↑pg*l+l- X ) as important test of TMD QCD formalism:
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
SIDIS DY
11/27/2012
forward sPHENIX

9. e/m ID
Drell Yan
Want to study asymmetries overlapping SIDIS data slightly forward
Extend range to unmeasured higher x  most forward
11/27/2012
forward sPHENIX

10. Drell Yan Expectations show maximal signal at y≥3 (~6 degrees)
e/m ID
Drell Yan
Expectations show maximal signal at y≥3 (~6 degrees)
Current Muon arms only go out to h=2.4 (~10 degrees)
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
(Roughly) PHENIX muon arms
sPHENIX coverage
11/27/2012
forward sPHENIX

11. Sivers DY with TMD evolution
e/m ID
Sivers DY with TMD evolution
Kang’s result from 2012 QCD evolution workshop suggests large evolution effect
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
11/27/2012
forward sPHENIX

12. Other DY measurements Upolarized pp: u x ubar Boer Mulders
e/m ID
Other DY measurements
Upolarized pp: u x ubar Boer Mulders
Single spin p↑p:
Transversity x Boer Mulders (combination of u and ubar)
Sivers (mostly u)
Double spin p↑p↑ , p→p→:
u x ubar Transversity (small due to sea)
u x ubar Helicity
11/27/2012
forward sPHENIX

13. The detectors
11/27/2012
forward sPHENIX

14. The sPHENIX Detector Upgrade
Jet
PHENIX Collaboration arXiv: v1
led by Jamie Nagle, David Morrison & John Haggerty
New PHENIX central arms
keep VTX inner tracking
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
eventual ePHENIX
11/27/2012
forward sPHENIX

15. sPHENIX Forward Physics
Jet
e/m ID
HadronPID
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: v1)
(4) Survey cold nuclear matter effects in
the transition region to the saturation
regime. Quantify the initial state for
HI-Collisions.
TMD framework: inclusion of final and
initial state gluon radiation via gauge link
integrals gives rise to large
transverse spin effects and
process dependence.
Unique measurements at forward
rapidity using jet observables
and the Drell-Yan process!
11/27/2012
forward sPHENIX 15 15

16. Experimental Requirements Driven by p-p Goals
Jet
e/m ID
HadronPID
MuID
RICH
HCal
EMCal
Tracker
Good Jet reconstruction to be able to measure Sivers cleanly
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
11/27/2012
forward sPHENIX
from Kieran Boyle, DIS – April 2012 16

17. Forward Detector Rely on central magnet field
Jet
e/m ID
HadronPID
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 technology
Interest of HI in forward direction may influence choices based on expected multiplicity.
PbSc restack
MPC restack
=12x12 towers
1 tower is 5.5cm2
= 2.2cm2
11/27/2012
forward sPHENIX

18. Detector Layout for Physics Studies
Jet
e/m ID
HadronPID
Detector Layout for Physics Studies
Studies for detector components led by
GEM-trackers: Los Alamos, RBRC
RICH: Stony Brook/RIKEN
EMC: RBRC/RIKEN, ISU
HCAL: UIUC
Magnet: Los Alamos, RBRC, UCR
B field might not be enough at highest rapidities  additional magnets needed?
11/27/2012
forward sPHENIX 18

19. Jet
e/m ID
HadronPID
A dipole detector?
Requires beam shielding which might limit acceptance
Compensation also necessary
Other possibilities? Split dipole like Phobos
or similar to LHCb?
11/27/2012
forward sPHENIX

20. Particle identification
e/m ID
HadronPID
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
11/27/2012
forward sPHENIX

21. 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
11/27/2012
forward sPHENIX

22. Next Steps for forward sPHENIX
o Detector and sensitivity simulations in progress
o RBRC workshop on “Forward Physics at RHIC”
 July 30 to August 1st 2012 (
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
 March 2013
o Explore funding possibilities: external funds, staging c
11/27/2012
forward sPHENIX 22

23. Rough x Q2 map for pol. EIC and pp
Full eRHIC
Transversity and Collins,
Sivers:
Q2 evolution,
Flavor decomposition
1st phase eRHIC
High x transversity,
High x Sivers
pp factorization?
D d sign change?
Dubar – D dbar,
Sivers, Boer Mulders at lower x
Forward pp
Currend pol DIS
JLAB12
Dg via g1 scaling
Ds,
D sbar 1
10-4
10-3
10-2
0.4 1
xBJ
11/27/2012
forward sPHENIX

24. 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, re-use current central PHENIX EM calorimetry
Golden Spin measurements:
Drell Yan Sivers single spin asymmetries
Jet (Sivers) and hadron in jet (Collins) single spin asymmetries
11/27/2012
forward sPHENIX