1. ePHENIX Letter of Intent
Kieran Boyle ( )

2. sPHENIX Upgrade Workfest--August 2, 2013
Outline
ePHENIX LOI charge letter
Main physics goals at eRHIC
Helicity structure, TMDs, GPDs, Saturation and Hadronization
Physics requirements for the different measurements
ePHENIX detector concept
Why this design
sPHENIX Upgrade Workfest--August 2, 2013

3. Charge for Letter of Intent – Part 1
Charge to PHENIX and STAR Collaborations: LOI for Transition to eRHIC
In 2010 the PHENIX and STAR collaborations each generated decadal plans laying out proposed science goals and detector upgrade paths for the period At the request of ALD Vigdor, the Decadal Plan documents provided by both collaborations included conceptual ideas for utilizing these detectors for the study of ep and eA collisions in an early stage of the eRHIC program. In the case of PHENIX, the subsequent sPHENIX proposal includes a more extensive discussion of a possible ePHENIX upgrade through inclusion of additional particle identification and forward detectors.
We now have an EIC White Paper with a comprehensive outline of the physics questions for an Electron Ion Collider, a rapidly maturing machine design for eRHIC, and a clearer view of a possible path to an early-stage eRHIC program leading to first measurements in the mid-2020s. Therefore, the PHENIX and STAR Collaboration are now being asked to consider their role in a transition from RHIC to eRHIC on this time scale, and to provide specific plans (i.e. Letters of Intent) to upgrade/reconfigure the detectors from their present form to first-generation eRHIC detectors. These Letters of Intent (LOI) will be an important part of BNL’s strategic planning as we move toward the next Nuclear Physics Long Range Plan. They should include an assessment of how the collaborations may evolve through this transition, and of the size and breadth of the scientific staffing required to carry out these plans.
Forward sPHENIX Workshop--May 21, 2013

4. Charge for Letter of Intent– Part 2
In preparing these LOI the collaborations should assume an eRHIC machine with an electron beam energy up to 10 GeV, hadron beam energies as provided by the current RHIC machine (255 GeV for p and 100 GeV/nucleon for Au), and design luminosities of 1033 cm-2 s-1 for 10 GeV on 255 GeV ep collisions and the equivalent of 6×1032 cm-2 s-1 for 10 GeV on 100 GeV/ nucleon eA collisions.
The LOI should include a description of the physics reach of the upgraded detectors, based on their detection capabilities, taking into consideration the key measurements identified in the EIC White Paper for Stage 1 (but now for 10 GeV electrons instead of 5 GeV). Further details of the desired detector requirements will be soon posted by the eRHIC Task Force on a Wiki page.
The technical details of the proposed upgrades should be given in sufficient detail to make a preliminary cost estimate. We assume that the upgrades may come in stages, with some elements implemented during the on-going RHIC heavy ion operations. Sufficient detail should be provided for each step to allow a rough outline of the overall construction schedule, assuming a 2-3 year shut-down of collider operations before the commencement of eRHIC operations, and an estimate of the required funding profile.
The Letters of Intent should be submitted by September 30, A brief statement of progress by each collaboration at the time of the June 2013 PAC meeting would be appreciated.
August 31
Forward sPHENIX Workshop--May 21, 2013

5. sPHENIX Upgrade Workfest--August 2, 2013
LOI Writing Group
PHENIX Management set up Writing Group:
Sasha Bazilevsky (co-chair), KB (co-chair), Abhay Deshpande, Jin Huang, Tom Hemmick, Itaru Nakagawa, Craig Woody
Also Jamie Nagle, Dave Morrison and John Haggerty
Goal is finish by August 31 so BNL has a month before sending it to DOE on Oct. 1
LOI plan
As much of physics case laid out in EIC White Paper (WP), only briefly in LOI
Focus on detector requirements, layout and cost
sPHENIX Upgrade Workfest--August 2, 2013

6. eRHIC eRHIC design presented yesterday
For ePHENIX LOI, consider eRHIC with:
Ee =2-10 GeV
Ep = GeV
Lep = 1033 cm-2s-1 for 10x250 configuration
LeA 6×1032 cm-2 s-1 for 10x100 GeV/nucleon
For ePHENIX, consider 10 fb-1 for all measurements
(equiv. to a few months of running at each setting)
sPHENIX Upgrade Workfest--August 2, 2013

7. sPHENIX Upgrade Workfest--August 2, 2013
DIS Kinematics
sPHENIX Upgrade Workfest--August 2, 2013

8. sPHENIX Upgrade Workfest--August 2, 2013
eRHIC Physics
Abhay discussed the physics case yesterday:
Understanding spin, transvers momentum and spatial structure
Understanding gluons at high density
TMDs
GPDs
Gluon Helicity
Understanding how hadronization is modified in a nuclear medium
sPHENIX Upgrade Workfest--August 2, 2013

9. ePHENIX detector concept
sPHENIX Upgrade Workfest--August 2, 2013

10. ePHENIX Detector Concept
Use BABAR magnet
-1<h<1:
Keep sPHENIX EMCal and HCal
Add m-TPC and DIRC
-4<h<-1:
Crystal calorimeter with good (2%) Energy resolution
GEM Trackers (+ m-TPC)
No PID
Next two talks:
Tracking & Magnetic Field: Jin Huang
PID: Itaru Nakagawa
1<h<4:
HCal (1<h<5)
EMCal
PbSc restack?
GEM Trackers (+ m-TPC)
PID requires good resolution
Aerogel (1<h<~2)
RICH
sPHENIX Upgrade Workfest--August 2, 2013

11. Measurement Requirements
DIS (Gluon helicity)
Calorimetry
e-p separation
SIDIS (Sea quark helicity, TMDs, Hadronization)
p, K, p PID at high momentum
DVCS (GPDs)
Calorimetry & tracking over wide range in h
Forward particle tagging (Roman pots, ZDC)
Diffractive (Saturation)
(Hadronic) Calorimetry over large range in h
sPHENIX Upgrade Workfest--August 2, 2013

12. DIS: Where does the electron go?
10x250
Need to measure electron in e-going direction and barrel.
e-going and central EMCal
For electron scattered in h-going direction, will need to use Jaques-Blondel (hadron) method
h-going EMCal, HCal, tracking
sPHENIX Upgrade Workfest--August 2, 2013

13. DIS: Getting the (correct) electron
Photons
DIS Electron
Ee<2GeV
Ee<1GeV
5x50
Issue at low Ee’
Hadron contamination is large
Need rejection of ~103 at Ee’=1 (2) GeV for electron beam energy of 5 (10) GeV
Crystal EMCal give ~10
Tracking: E/p from tracking gives ~5
Electrons from p0 (conversion and Dalitz)
Tracking can remove some conversions
Dalitz contrib. is small (will add for LOI)
sPHENIX Upgrade Workfest--August 2, 2013

14. Impact on Physics: Gluon Helicity
Apply realistic cuts on y:
0.01<y<0.8
x-Q2 coverage very good
Will show impact on DG based on 10 fb-1 simulated in PYTHIA
sPHENIX Upgrade Workfest--August 2, 2013

15. DVCS: Catching the electron, g and p
10x250
Electron:
Similar to DIS
No vertex, so p resolution worse
Photon:
Reasonable EMCal for -4<h<1
Minimum separation angle 9 degrees
Proton (neutron)
Roman Pots and ZDC
y (rad)
photon e y g
p/2 p
photon h
qe (rad)
sPHENIX Upgrade Workfest--August 2, 2013

16. Impact on Physics: GPDs
Same capabilities as dedicated detector
Remake x-Q2 plot with relevant kinematic range
No plans to remake “physics” plots
Just reference them
sPHENIX Upgrade Workfest--August 2, 2013

17. sPHENIX Upgrade Workfest--August 2, 2013
Semi Inclusive DIS
Highest momentum hadrons in h-going direction
Many hadrons go in central and e-going direction, though with lower momentum
Solenoidal magnet limits central region PID choices
Need to get p-K-p separation over wide range
5x100
p/A e
10x250
sPHENIX Upgrade Workfest--August 2, 2013

18. Central (-1<h<1) PID
5x100
Central Barrel PID (-1<h<1):
Limited space in r, so few technology choices
For LOI, choose DIRC
Maximum p-K separation from past: p<3.5 GeV
Could conceivably get to 4 GeV with different readout (I. Nakagawa)
sPHENIX Upgrade Workfest--August 2, 2013

19. sPHENIX Upgrade Workfest--August 2, 2013
h-going (h>1) PID
5x100
RICH for high p PID
pp>2-4, pK>10-15, pp>20-30
Aerogel for K-p separation for p<~10 GeV
Only 1<h<~2 due to space
Itaru will show details
sPHENIX Upgrade Workfest--August 2, 2013

20. What about z dependence?
p & h depend on x, Q2 and z
How do these detectors do?
Nothing x<10-3 or high y
Moderate y and low z
Low y and full z range
Better at with 5 GeV electron beam
10x250
DIRC
Aerogel
RICH
x = 10-3, Q2 = 10
x = 10-2, Q2 = 10
x = 10-3, Q2 = 1
x = 10-4, Q2 = 1
x = 10-1, Q2 = 100
x = 10-1, Q2 = 10
sPHENIX Upgrade Workfest--August 2, 2013

21. Impact on Physics: TMDs
White Paper plot (not reproducing)
White Paper plot (Alexsi Prokudin willing to reproduce)
Working on a plot to show statistical impact that is clearer than EIC WP plot
Based on Pythia stat, have hadron yields.
Will give to Alexsi and get theory plot
Can consider doing x-Q2 sensitivity plot, but it will depend on z.
Unclear how to show z dependence
sPHENIX Upgrade Workfest--August 2, 2013

22. sPHENIX Upgrade Workfest--August 2, 2013
Diffractive
Define diffractive events by rapidity gap
Look at most forward particle (catch in calorimeter)
Clear that extend HCal to h~5 is best, definitely need h~4
Difference in actual detector size is small (100 cm2) with inner radius of 5 cm instead of 15 cm
Note that HCal is 62 m2
sPHENIX Upgrade Workfest--August 2, 2013

23. Impact on Physics: Saturation
We expect to have same acceptance for diffractive as dedicated EIC detector
Can do measurement as well
Measurement for Stage I is ratio of total diffractive cross section, so only need rapidity gap
Detector acceptance and inefficiencies will cancel in ratio
sPHENIX Upgrade Workfest--August 2, 2013

24. sPHENIX Upgrade Workfest--August 2, 2013
Conclusions
PHENIX charged to write LOI describing how:
PHENIX/sPHENIX  ePHENIX
We have designed a detector that can do much of the physics available with 5-10 GeV electron beams
Realistic estimates for DIS and SIDIS underway
DVCS and Diffractive physics same as in EIC WP
Can have a good eRHIC detector at moderate cost
ePHENIX can be the eRHIC detector
Detector fits in nicely with the evolution of PHENIX
sPHENIX barrel with BABAR magnet is good for ePHENIX, and good step along the way
fsPHENIX physics requires similar detector in forward arm
sPHENIX Upgrade Workfest--August 2, 2013

25. sPHENIX Upgrade Workfest--August 2, 2013
BACKUPS
sPHENIX Upgrade Workfest--August 2, 2013

26. sPHENIX Upgrade Workfest--August 2, 2013
Semi Inclusive DIS
Three PID detectors:
-1<h<1, p<4 GeV: DIRC
h>1, p
sPHENIX Upgrade Workfest--August 2, 2013