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
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
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
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) d+Au collisions Central Arms Muon Arms
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 xgxg 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
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
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? 0 coverage 2 EMC 0 coverage 2 Tr (F)VTX
N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 8 PHENIX Acceptance Staged Calorimeter Upgrades Muon Piston Calorimeter (MPC) 3.1<| |< 0 coverage 2 Tr (F)VTX 0 coverage 2 EMCMPC
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)
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
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
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
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<| |< 0 coverage 2 Tr (F)VTX 0 coverage 2 EMCMPC
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?
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
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
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)
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)
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
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
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
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
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
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
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
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
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
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
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)
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
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) A+A collisions
N UCLEARDYNAMICS WINTER●WORKSHOP Richard Hollis 8 th January 2010 ● 32 MPC x Coverage x versus (p+p, 500 GeV) (MPC Acceptance)
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