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A Proposed FOrward CALorimeter Upgrade in PHENIX

A Proposed FOrward CALorimeter Upgrade in PHENIX. Richard Hollis for the PHENIX Collaboration University of California, Riverside CAARI 2010 12 th August 2010. Overview. The next decade at RHIC&PHENIX Motivation and Needs Overview of Current PHENIX Detector Future: FOCAL

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A Proposed FOrward CALorimeter Upgrade in PHENIX

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  1. A ProposedFOrward CALorimeterUpgrade in PHENIX Richard Hollis for the PHENIX Collaboration University of California, Riverside CAARI 2010 12th August 2010

  2. Overview • The next decade at RHIC&PHENIX • Motivation and Needs • Overview of Current PHENIX Detector • Future: FOCAL • Event Reconstruction and Expected Impact • Summary Richard Hollis 12th August 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 12th August 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 (2004) 242303 Richard Hollis 12th August 2010 ● 4

  5. Theoretical Guidance EPS09: NPA830 (2010) 599c • Current theoretical description of nuclear pdfs (at small x) is unconstrained • How to reduce the uncertainty? • We can directly access the gluon pdf from direct-g • Direct-g is a simple measurement as there is no fragmentation function • Access to low-x at high rapidity Richard Hollis 12th August 2010 ● 5

  6. Building detectors to suit physics needs • Need: • Forward rapidities • Direct photons • Well defined energy scale for g measurements Richard Hollis 12th August 2010 ● 6

  7. Current PHENIX Detector

  8. The PHENIX Detector General features • Central region: • E-M Calorimeter • Electron/photon energy measurements • Tracking • Charged particle momenta • Time of Flight • Charged particle identification • Forward region: • Muon Tracker • Muon identification and momentum • Calorimeter • Very forward photons Richard Hollis 12th August 2010 ● 8

  9. Muon Tracker Muon identification and momentum Calorimeter Very forward photons Trigger BBC and ZDC MPC The PHENIX Detector E-M Calorimeter Electron/photon energy measurements Tracking Charged particle momenta Time of Flight Charged particle identification Richard Hollis 12th August 2010 ● 9

  10. 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 12th August 2010 ● 10

  11. 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 12th August 2010 ● 11

  12. 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) • 1.6<h<2.5 • d-going side in d+Au collisions MPC MPC Richard Hollis 12th August 2010 ● 12

  13. MPC Finding space in PHENIX MPC installed ~ 3<||<4 FoCal: where could it fit? Richard Hollis 12th August 2010 ● 13

  14. 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 12th August 2010 ● 14

  15. FoCal Transverse View • Silicon-Tungsten sampling calorimeter • 21 layers ~21X0 • d-side Arm:1.6<h<2.5 • Expect good resolution in E and h/f • Active readout ~1.5x1.5cm • Distinct 2-shower p0 up to pT~2 GeV/c (h~1.6) Instrumented region 1 “brick” Longitudinal View 6.1cm S0 S1 S2 Richard Hollis 12th August 2010 ● 15

  16. FOCAL Technology • Tungsten • High density for compactness • Silicon • Compact • Segmentation is easy/versatile • Can be built in stackable blocks • Read-out: • 163 pads per brick • 12824 strips per brick Test-beam setup (CERN 2009) Beam S0 S1 S2 Richard Hollis 12th August 2010 ● 16

  17. FoCal x Coverage p+p collisions • Remember: we need low-x • x coverage: • Weak pT dependence x versus pT (p+p, 200 GeV) (FoCal Acceptance) Richard Hollis 12th August 2010 ● 17

  18. FoCal x Coverage p+p collisions • Remember: we need low-x • x coverage: • Weak pT dependence • Strong h dependence x versus h (p+p, 200 GeV) (FoCal Acceptance) Richard Hollis 12th August 2010 ● 18

  19. FoCal x Coverage p+p collisions • Remember: we need low-x • x coverage: • Weak pT dependence • Strong h dependence • FoCal complementary to MPC x versus h (p+p, 200 GeV) (FoCal & MPC Acceptance) Richard Hollis 12th August 2010 ● 19

  20. FoCal x Coverage • Remember: we need low-x • 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, 200 GeV) (FoCal Acceptance) 1.6<h<2.0 2.0<h<2.5 Richard Hollis 12th August 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 Note: Simulation of fully-instrumented FOCAL Richard Hollis 12th August 2010 ● 21

  22. What about direct g identification? • Important for our measurements in the next decade in • Spin • d+Au • Au+Au Richard Hollis 12th August 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 12th August 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 12th August 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 12th August 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 12th August 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 12th August 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 12th August 2010 ● 28

  29. High energy p0 reconstruction Single Particle Simulation • Reconstruction of single g and p0’s with FOCAL • Observe: good separation of g peak and p0 mass peak • Low mass peak from p0’s due to: • Large-angle decays • One g (from p0→gg) dominating (asymmetric energy) • Only one conversion g g p0 Richard Hollis 12th August 2010 ● 29

  30. Understanding the background sources Full PYTHIA Simulation • For each track • Found the closest primary particle • Sorted into 4 categories: p0 – is a p0 g hit – but not p0, h, or dir-g Hadron – any h – is an h Richard Hollis 12th August 2010 ● 30

  31. Currently Expected Sensitivity • Lines: nuclear pdf fits • based on current data • EPS09 • Colors represent nuclear pdfs fits with respect to FOCAL uncertainties • B lue: within 1s • Purple: 2s • Cyan: 3s Richard Hollis 12th August 2010 ● 31

  32. Summary • PHENIX Forward Calorimeter upgrade (will) provide much extended coverage for a variety of physics topics • FoCal complements the existing detectors in terms of additional phase-space coverage and direct photon identification capabilities at high energies. • Novel design integrates a calorimeter and a tracking device • For p+p, d+Au (and Au+Au) collisions Richard Hollis 12th August 2010 ● 32

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