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Forward Calorimeter Upgrades in PHENIX: Past and Future

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

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

  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 g-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 h Richard Hollis 8th January 2010 ● 3

  4. Muon Arms Central Arms Onset of Gluon Saturation d+Au collisions • Nuclear modification factor: • Increasing suppression with h • 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 Richard Hollis 8th January 2010 ● 4

  5. Proton spin contribution from gluon polarization p+p collisions xDg • Spin contribution from gluon polarization • derived from measured ALL • currently over a narrow region of x • Large uncertainty at low-x • Need to measure ALL over a broader region of x • forward h • measure direct photons RHIC range 0.05 < x < 0.2 Richard Hollis 8th January 2010 ● 5

  6. Building detectors to suit physics needs • Need: • Forward rapidities • Direct photons • Well defined energy scale for g measurements Richard Hollis 8th January 2010 ● 6

  7. mTr mTr 0 f coverage 2p (F)VTX -3 -2 -1 0 1 2 3 h EMC 0 f coverage 2p -3 -2 -1 0 1 2 3 h PHENIX Acceptance • Tracking • Central region and forward muon arms • Calorimetry • Very limited acceptance • In f and h • What do we need for the future? • and how can we obtain it? Richard Hollis 8th January 2010 ● 7

  8. mTr mTr 0 f coverage 2p (F)VTX -3 -2 -1 0 1 2 3 h EMC 0 f coverage 2p -3 -2 -1 0 1 2 3 h PHENIX Acceptance • Staged Calorimeter Upgrades • Muon Piston Calorimeter (MPC) • 3.1<|h|<3.9 MPC MPC Richard Hollis 8th January 2010 ● 8

  9. Counts Muon Piston Calorimeter (MPC) MPC(N) • Lead Scintillator (PbW04) • 18cm long ~20X0 • 2.2x2.2cm transverse • 220 (196) Crystals in N (S) • South Arm: -3.7<h<-3.1 • North Arm: 3.1<h< 3.9 • Measure p0’s up to 17 GeV • pT~1.7 GeV/c • pT>1.7GeV/c – measure single “clusters” Raw Signal Mixed-event Background Yield 12 < E < 15 GeV Richard Hollis 8th January 2010 ● 9

  10. Mid-rapidity p0 Trigger Forward Associates Physics Application • Two-particle correlations • Correlation of central arm p0 and h with MPCp0 • Measure jet modification in d+Au collisions dN df Df Richard Hollis 8th January 2010 ● 10

  11. Mid-rapidity p0 Trigger Forward Associates Physics Application • Two-particle correlations • Correlation of central arm p0 and h with MPCp0 • Measure jet modification in d+Au collisions • Probe low-x (0.006<x<0.1) • IdA suppression – a signature of CGC Richard Hollis 8th January 2010 ● 11

  12. p+p0+X at s=62.4 GeV/c2 3.0<<4.0 Physics Application • Calorimeters are versatile • Measurements using identified cC and h 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 DG – the gluon contribution to proton spin • Would like to measure direct gs Richard Hollis 8th January 2010 ● 12

  13. mTr mTr 0 f coverage 2p -3 -2 -1 0 1 2 3 h (F)VTX EMC 0 f coverage 2p -3 -2 -1 0 1 2 3 h PHENIX Acceptance • Staged Calorimeter Upgrades • Muon Piston Calorimeter (MPC) • 3.1<|h|<3.9 • Forward Calorimeter (FoCal) • 1<|h|<3 MPC MPC Richard Hollis 8th January 2010 ● 13

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

  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 Richard Hollis 8th January 2010 ● 15

  16. FoCal Transverse View • Silicon-Tungsten sampling calorimeter • 21 layers ~21X0 • Each Arm:1<|h|<3 • Expect good resolution in E and h/f • Active readout ~1.5x1.5cm • Distinct 2-shower p0 up to pT~3 GeV/c (h~1) Longitudinal View 6.1cm Richard Hollis 8th January 2010 ● 16

  17. FoCal x Coverage p+p collisions • x coverage: • Weak pT dependence x versus pT (p+p, 500 GeV) (FoCal Acceptance) Richard Hollis 8th January 2010 ● 17

  18. FoCal x Coverage p+p collisions • x coverage: • Weak pT dependence • Strong h dependence x versus h (p+p, 500 GeV) (FoCal Acceptance) Richard Hollis 8th January 2010 ● 18

  19. FoCal x Coverage p+p collisions • x coverage: • Weak pT dependence • Strong h dependence • FoCal complementary to MPC x versus h (p+p, 500 GeV) (FoCal & MPC Acceptance) Richard Hollis 8th January 2010 ● 19

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

  21. FoCal (Expected) Performance d+Au collisions • 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 Richard Hollis 8th January 2010 ● 21

  22. What about direct g identification? • Important for our measurements in the next decade in • Spin • d+Au • Au+Au Richard Hollis 8th January 2010 ● 22

  23. Identifying p0 and g p+p collisions • First: use physics • Direct g typically are alone • Whilst p0 are produced as part of a hadronic jet • Measurement of accompanying energy can reduce background at minimal expense to g • Still, this does not provide full decontamination • Need direct p0 identification Ratio of background/signal (NLO calculation) Richard Hollis 8th January 2010 ● 23

  24. High energy p0 shower p+p collisions • Origin of all shower particles (red) • Shown with effective resolution of pads • Individual tracks not distinguishable Richard Hollis 8th January 2010 ● 24

  25. High energy p0 shower p+p collisions • Finer resolution could “see” individual tracks from p0 • Up to ~50GeV • Make the whole detector with finer resolution!! • Not realistic → what can be designed? Richard Hollis 8th January 2010 ● 25

  26. x y x y x y x y High energy p0 shower p+p collisions • Finer resolution could “see” individual tracks from p0 • 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 g tracks EM0 EM1 EM2 ~70 strips ~2 towers Richard Hollis 8th January 2010 ● 26

  27. High energy p0 shower • Finer resolution could “see” individual tracks from p0 • 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 g tracks Track showers Merge Tracks are visibly Separable Catch the shower, before it’s too late Richard Hollis 8th January 2010 ● 27

  28. High energy p0 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 Richard Hollis 8th January 2010 ● 28

  29. Performance of FoCal Reconstruction Reconstruction of p0 (p+p 500 GeV minimum bias pythia) Signal reconstruction (d+Au 200 GeV minimum bias + embedded pythia g+jet signal) Richard Hollis 8th January 2010 ● 29

  30. Summary • PHENIX Calorimeter upgrades (will) provide much extended coverage for a variety of physics topics • Proven p0 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 Richard Hollis 8th January 2010 ● 30

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

  32. MPC x Coverage x versus h (p+p, 500 GeV) (MPC Acceptance) Richard Hollis 8th January 2010 ● 32

  33. d+Au collisions • Correlation of central arm p0 and h with MPCp0 • Measured associate yields relative to pp • Systematic suppression with centrality • No appreciable trigger dependence • Probe low-x (0.006<x<0.1) Richard Hollis 8th January 2010 ● 33