1. Forward Calorimeter Upgrades in PHENIX: Past and Future Richard Hollis for the PHENIX Collaboration University of California, Riverside Winter Workshop on Nuclear Dynamics 8 th January 2010

2. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 2 Overview The next decade at RHIC&PHENIX Motivation and Needs Calorimeter Upgrades Past: MPC – currently operational Future: FoCal – proposal soon Summary

3. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 3 The next decade at PHENIX A biased (to Forward Calorimetry) view: Gluon density at low-x in cold nuclear matter Proton spin contribution from Gluon Polarization Measure  -jet production, correlations in Au+Au collisions Test predictions for the relation between single-transverse spin in p+p and those in DIS For data taking and analysis over the course of the next decade… First step: measurements at high 

4. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 4 Onset of Gluon Saturation Nuclear modification factor: Increasing suppression with  Consistent with the onset of gluon saturation at small- x in the Au nucleus. Need to study this in more detail by identifying particles expanding forward coverage BRAHMS: PRL93 (2009) 242303 d+Au collisions Central Arms Muon Arms

5. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 5 Proton spin contribution from gluon polarization p+p collisions RHIC range 0.05 < x < 0.2 xgxg Spin contribution from gluon polarization derived from measured A LL currently over a narrow region of x Large uncertainty at low- x Need to measure A LL over a broader region of x forward  measure direct photons

6. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 6 Building detectors to suit physics needs Need: Forward rapidities Direct photons Well defined energy scale for  measurements

7. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 7 PHENIX Acceptance Tracking Central region and forward muon arms Calorimetry Very limited acceptance In  and  What do we need for the future? and how can we obtain it? -3 -2 -1 0 1 2 3  0  coverage 2  EMC -3 -2 -1 0 1 2 3  0  coverage 2   Tr (F)VTX

8. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 8 PHENIX Acceptance Staged Calorimeter Upgrades Muon Piston Calorimeter (MPC) 3.1<|  |<3.9 -3 -2 -1 0 1 2 3  0  coverage 2   Tr (F)VTX -3 -2 -1 0 1 2 3  0  coverage 2  EMCMPC

9. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 9 Muon Piston Calorimeter (MPC) Lead Scintillator (PbW0 4 ) 18cm long ~20X 0 2.2x2.2cm transverse 220 (196) Crystals in N (S) South Arm: -3.7<  <-3.1 North Arm: 3.1<  < 3.9 Measure  0 ’s up to 17 GeV p T ~1.7 GeV/c p T >1.7GeV/c – measure single “clusters” 12 < E < 15 GeV Raw Signal Mixed-event Background Yield Counts MPC(N)

10. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 10 Physics Application Two-particle correlations Correlation of central arm  0 and h  with MPC  0 Measure jet modification in d+Au collisions Mid-rapidity  0 Trigger Forward Associates  dN d 

11. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 11 Physics Application Two-particle correlations Correlation of central arm  0 and h  with MPC  0 Measure jet modification in d+Au collisions Probe low- x (0.006< x <0.1) I dA suppression – a signature of CGC Mid-rapidity  0 Trigger Forward Associates

12. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 12 Physics Application Calorimeters are versatile Measurements using identified  C and  are underway Preliminary results on transverse single-spin asymmetries Measurements over a broad phase space will provide quantitative tests for models How do the calorimeters contribute to  G – the gluon contribution to proton spin Would like to measure direct  s 3.0<  <4.0 p  +p  0 +X at  s=62.4 GeV/c 2

13. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 13 PHENIX Acceptance Staged Calorimeter Upgrades Muon Piston Calorimeter (MPC) 3.1<|  |<3.9 Forward Calorimeter (FoCal) 1<|  |<3 -3 -2 -1 0 1 2 3  0  coverage 2   Tr (F)VTX -3 -2 -1 0 1 2 3  0  coverage 2  EMCMPC

14. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 14 Finding space in PHENIX MPC installed ~ 3<|  |<4 MPC FoCal: where could it fit?

15. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 15 Finding space in PHENIX Small space in front of nosecone 40 cm from vertex 20 cm deep Calorimeter needs to be high density Silicon-Tungsten sampling calorimeter

16. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 16 FoCal Silicon-Tungsten sampling calorimeter 21 layers ~21X 0 Each Arm: 1<|  <3 Expect good resolution in E and  /  Active readout ~1.5x1.5cm Distinct 2-shower  0 up to p T ~3 GeV/c (  ~1) Transverse View Longitudinal View 6.1cm

17. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 17 FoCal x Coverage x coverage: Weak p T dependence p+p collisions x versus p T (p+p, 500 GeV) (FoCal Acceptance)

18. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 18 FoCal x Coverage x coverage: Weak p T dependence Strong  dependence p+p collisions x versus  (p+p, 500 GeV) (FoCal Acceptance)

19. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 19 FoCal x Coverage p+p collisions x versus  (p+p, 500 GeV) (FoCal & MPC Acceptance) x coverage: Weak p T dependence Strong  dependence FoCal complementary to MPC

20. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 20 FoCal x Coverage x for  bins (p+p, 500 GeV) (FoCal Acceptance) x coverage: Weak p T dependence Strong  dependence FoCal complementary to MPC Selecting  region probes a specific x range

21. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 21 FoCal (Expected) Performance Can one see jets over the background Sufficiently isolated? Average background Units are measured energy (~2% of total) Single-event background ~20 times higher 30GeV embedded jet Visible over the background d+Au collisions

22. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 22 What about direct  identification? Important for our measurements in the next decade in Spin d+Au Au+Au

23. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 23 Identifying  0 and  First: use physics Direct  typically are alone Whilst  0 are produced as part of a hadronic jet Measurement of accompanying energy can reduce background at minimal expense to  Still, this does not provide full decontamination Need direct  0 identification Ratio of background/signal (NLO calculation) p+p collisions

24. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 24 High energy  0 shower Origin of all shower particles (red) Shown with effective resolution of pads Individual tracks not distinguishable p+p collisions

25. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 25 High energy  0 shower Finer resolution could “see” individual tracks from  0 Up to ~50GeV Make the whole detector with finer resolution!! Not realistic → what can be designed? p+p collisions

26. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 26 High energy  0 shower Finer resolution could “see” individual tracks from  0 Up to ~50GeV Make the whole detector with finer resolution!! Not realistic → what can be designed? Add highly segmented layers of x/y strips into first segment. Measure the development of the shower at its infancy With a resolution to distinguish individual  tracks EM0EM1EM2 x y ~2 towers~70 strips p+p collisions

27. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 27 High energy  0 shower Finer resolution could “see” individual tracks from  0 Up to ~50GeV Make the whole detector with finer resolution!! Not realistic → what can be designed? Add highly segmented layers of x/y strips into first segment. Measure the development of the shower at its infancy With a resolution to distinguish individual  tracks Catch the shower, before it’s too late Tracks are visibly Separable Track showers Merge

28. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 28 High energy  0 shower Using a Hough Transform, Transverse/longitudinal coordinate Find the best track as most frequently occurring Hough- slope Use each track vector, full track energy → calculate invariant mass

29. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 29 Performance of FoCal Reconstruction Reconstruction of  0 (p+p 500 GeV minimum bias pythia) Signal reconstruction (d+Au 200 GeV minimum bias + embedded pythia  +jet signal)

30. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 30 Summary PHENIX Calorimeter upgrades (will) provide much extended coverage for a variety of physics topics Proven  0 reconstruction in the MPC further our understanding of forward jet production in d+Au collisions FoCal complements the MPC in terms of additional phase-space coverage and direct photon identification capabilities at high energies. For p+p, d+Au (and Au+Au) collisions

31. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 31 An energy scale for jet suppression h-h correlations exhibit interesting features … but have limitations: may be subject to surface bias may not reveal the jet energy scale  -h or  -jet could provide an energy scale (assuming) the  is not [energy] suppressed Reduced surface bias as the trigger probe is not modified STAR: NPA830 (2009) 685C STAR: PRL103 (2009) 172301 A+A collisions

32. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 32 MPC x Coverage x versus  (p+p, 500 GeV) (MPC Acceptance)

33. N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 33 Correlation of central arm  0 and h  with MPC  0 Measured associate yields relative to pp Systematic suppression with centrality No appreciable trigger dependence Probe low- x (0.006< x <0.1) d+Au collisions