1. PheniX, STAr AND AN EIC E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

2. The Physics we want to study
What is the role of gluons and gluon self-interactions in nucleons and nuclei?
Observables in eA / ep:
diffractive events: rapidity gap events, elastic VM production, DVCS
structure functions F2A, FLA, F2cA, FLcA, F2p, FLp,………
What is the internal landscape of the nucleons?
What is the nature of the spin of the proton?
Observables in ep
inclusive, semi-inclusive Asymmetries
electroweak Asymmetries (g-Z interference, W+/-)
What is the three-dimensional spatial landscape of nucleons?
Observables in ep/eA
semi-inclusive single spin asymmetries (TMDs)
cross sections, SSA of exclusive VM, PS and DVCS (GPDs)
What governs the transition of quarks and gluons into pions and nucleons?
Observables in ep / eA
semi-inclusive c.s., ReA, azimuthal distributions, jets
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

3. Kinematic Plane E.C. Aschenauer EIC INT Program, Seattle 2010, Week 10
Need to study hadronic method
to increase y acceptance
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

4. Lepton Kinematics Follow Hera Convention:
Hadron beam positive z (=> q = 0o)  Lepton beam negative z => q = 180o)
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

5. Hadron Kinematics E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

6. Kinematics of elastic diffraction
no cuts:
4x100
4x50
4x250
cuts: Q2 > 0.1 GeV && y < 0.9 GeV
decay products of r & J/ψ
go more and more
forward with
increasing
asymmetry in
beam energies
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

7. Diffractive Physics: p’ kinematics
t=(p4-p2)2 = 2[(mpin.mpout)-(EinEout - pzinpzout)]
4 x 50 ?
Diffraction:
recoil protons and break-up particles from Au need dedicated forward detectors
4 x 100
4 x 250
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

8. IP configuration for eRHIC
Nice design for protons from exclusive reactions and nuclear breakup particles
pt > 1.5GeV  main detector
0.1 MeV < pt < 1GeV after dipole
4.5 cm
pc/2.5
neutrons
90 mm
q=44 mrad
6 mrad
3.5 m
pc/2.5
11.2 cm
2.5 m
15.7 cm
5.75 m
q=18 mrad
4.5 m
ZDC
6.3 cm
q=10 mrad IP 2 4 6 8 10 12 14 16
Dipole:
2.5 m, 6Tm
q=18 mrad
Estimated b*≈ 8 cm
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

9. IR Design
eRHIC - Geometry high-lumi IR with β*= 8cm, l*=4.5 m and 10 mrad crossing angle
Dipole to separate p/A beam
from “recoil”/breakup particles
q= mrad Q4 Q5 D5
325 GeV p
Or 125 GeV/u ions
4 m
11.9 m
q=18 mrad
5.75 m m m m
10 mrad
30 GeV e-
5.75 cm
4.5 10 20 30
17.65 m m m
© D.Trbojevic
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

10. Current PHENIX Detector at RHIC
MPC < | h | < 3.9
2.5o < Q < 5.2o
Muon Arms < | h | < 2.4
South: o < Q < 37o
North: o < Q < 37o
Central Arms | h | < 0.35
60o < Q < 110o
electrons will not make it
to the south muon arm
 to much material
p/A e-
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

11. What will the current PheniX see
pe: 0-1 GeV
pe: 1-2 GeV
pe: 2-3 GeV
pe: 3-4 GeV
4x100
Current PheniX detector
not really useable for
DIS
acceptance not matched to DIS kinematics
4x100
4x100
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

12. The New PheniX Spectrometer
Design completely driven by AA, dA and pp physics program
p/A e-
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

13. What can we detect pe: 0-1 GeV pe: 1-2 GeV pe: 2-3 GeV pe: 3-4 GeV
No dependence on hadron beam energy
Q2>0.1GeV2
4GeV  >5o
10GeV  >2o
20GeV  >1o
New PheniX has close to full coverage for scattered lepton
4x50
Forward upgrade
identified hadrons
5 GeVx50GeV
20 GeV x 250 GeV
4x100
central arm
unidentified
North m arm
only muons
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

14. Electromagnetic Calorimetry:
The STAR Detector
Tracking: TPC
Particle ID: TOF
Electromagnetic Calorimetry:
BEMC+EEMC+FMS
(-1 ≤  ≤ 4)
Upgrades:
Muon Telescope Detector
Roman Pots Phase 2
Forward Upgrade
Heavy Flavor Tracker (2013)
Forward Gem Tracker
(2011)
Full azimuthal particle identification
over a broad range in pseudorapidity
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

15. STAR Experiment as of 2014 MTD EMC Barrel MRPC ToF Barrel EMC End Cap
FMS
BBC
FPD
TPC
Roman Pots
Phase 2
computing
DAQ1000
COMPLETE
Trigger and DAQ
Upgrades
HFT
FGT
Ongoing
R&D
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

16. STAR Forward Upgrade
proton
nucleus
Positive η: Drell Yan
High precision tracking and background rejection using calorimetry
Optimized for p+A and p+p
High momentum scale
Negative η: eRHIC
Optimized for low energy electrons (~1 GeV)
Triggering, tracking, identification
R&D necessary for optimal technology choice
Switch colors of the beams
nucleus
electron
To fully investigate cold QCD matter, STAR will move forward
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

17. Energy loss in cold QCD matter
RAπ
Hermes, Nucl. Phys.B 780, 1 (2007)
Lc ∝ ν: Lc up to few 100 fm
Complementary probe of mechanism of energy loss
HERMES: mixture of hadronic absorption and partonic loss
Hadrons can form partially inside the medium
eRHIC: light quarks form far outside medium
Heavy quarks: unexplored to date. Low β: short formation time
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

18. STAR and eRHIC Phase I
Current detector matches quite well to kinematics of eRHIC
Particle ID, sufficent pT resolution, etc. at mid-rapidity
Upgrades in forward direction: increase capability at lower momentum
Developing plan for effective and compelling use of e+A
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

19. Longer term: STAR and eRHIC
Forward region critical for higher energy options
Major upgrades in forward direction would be needed
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10

20. Summary
Both, the new PheniX and STAR have reasonable capabilities for ep/eA collisions
inclusive measurements
some initial semi-inclusive measurements as well as for heavy quarks
BUT no replacement for a dedicated detector
using STAR and/or PHENIX might help to release some of the requirements on the dedicated detector
need still to resolve all the details how to bring the lepton beam with 10mrad in the detectors for collisions and the non-colliding beams around.
STAR seems easier than PHENIX
E.C. Aschenauer
EIC INT Program, Seattle 2010, Week 10