1 a FOrward CALorimeter Richard Seto Winter Workshop on Nuclear Dynamics Feb 7, 2009 Overview

2 NSAC milestones – Physics Goals Year# MileStone FOCAL 2012DM8Determine gluon densities at low x in cold nuclei via p+ Au or d + Au collisions.Required for direct photon 2013HP12Utilize polarized proton collisions at center of mass energies of 200 and 500 GeV, in combination with global QCD analyses, to determine if gluons have appreciable polarization over any range of momentum fraction between 1 and 30% of the momentum of a polarized proton. Low-x Direct  2014DM10 (new) Measure jet and photon production and their correlations in A≈200 ion+ion collisions at energies from medium RHIC energies to the highest achievable energies at LHC. DM10 captures efforts to measure jet correlations over a span of energies at RHIC and a new program using the CERN Large Hadron Collider and its ALICE, ATLAS and CMS detectors. Marginal without FOCAL 2015HP13 (new) Test unique QCD predictions for relation between single-transverse spin phenomena in p-p scattering and those observed in deep-inelastic lepton scattering New Milestone HP13 reflects the intense activity and theoretical breakthroughs of recent years in understanding the parton distribution functions accessed in spin asymmetries for hard-scattering reactions involving a transversely polarized proton. This leads to new experimental opportunities to test all our concepts for analyzing hard scattering with perturbative QCD. Required  G  -Jet AuAu transverse spin phenomena pA physics – nuclear gluon pdf

3 direct  jets –x resolution forward η (low-x)  Nuclear Gluon PDF’s : DM8 Look for saturation effects at low x Measure initial state of Heavy Ion Collision  measure gluon PDF’s in nuclei! (DM8) x Saturation at low x xG(x)

4 Longitudinal Spin  G,  g(x) : HP12 What is the gluon contribution to the proton spin. Is it at low-x? Phenix and STAR have put constraints on  G

5   g(x) very small at medium x (even compared to GRSV or DNS)  best fit has a node at x ~ 0.1  huge uncertainties at small x DSSV finds Current data is sensitive to  G for x gluon = 0.02  0.3 direct  jets –x resolution forward η (low-x)  0 x RHIC range 0.05 · x · 0.2 small-x · x · 0.05  Longitudinal Spin  G,  g(x) : HP12 EXTEND MEASUREMENTS TO LOW x! Forward Measure x

6 direct  -jet  0 forward η (low-x) large η coverage  Major new Thrust Transverse Spin Phenomena: HP13 use  -jet to measure Sivers Use  0 in jet to measure Collins determination of the process dependence of the Sivers effect in  +jet events So what does Sivers tell us about orbital angular momentum? Sivers

7 EM - shower large η coverage Jet correlations in AuAu  Correlations with jets in heavy Ion collisions: DM10 Study the medium via long range correlations with jets are these correlations from a response by the medium? leading EM shower ? “ridge” “jet” STAR Preliminary for example

8 To meet these goals we must have a detector that measures: direct  and electromagnetic showers jet angles to obtain x 2  0 s forward  to reach low-x has large  coverage now what do we build?

9 Schematic of PHENIX Central Arms |  |<0.3 Tracking PbSc/PbGl(EMC) PID VTX to come MPC 3<|  |<4 Muon arms 1.1<|  |<2.4 magnet tracking  -ID FVTX to come central magnet calorimetry

10 Perfect space for FOCAL! (but tight!) 14EM bricks 14 HAD bricks HAD behind EM FOCAL 40 cm from Vertex 20 cm of space nosecone

11 FOCAL Requirements Ability to measure photons and π 0 ’s to 30 GeV Energy resolution < 25%/  E Compact (20 cm depth) Ability to identify EM/hadronic activity Jet angular measurement High granularity ~ similar to central arms small mollier radius ~1.4 cm large acceptance – rapidity coverage x 2 ~ Densest calorimeter -> Si W We wanted large  coverage what sort of coverage if we put a detector where the nosecones are?

12 Muon tracking VTX & FVTX MPC rapidity  coverage 2  EMC FOCAL a large acceptance calorimeter FOCAL tracking What’s missing?FORward CALorimetery

13 reach in x 2 for  g(x) and G A (x) log(x 2 ) EMC+VTX EMC+VTX+FOCAL EMC+VTX+FOCAL+MPC X 2  10 -3

14 FOCAL Design

15 Overall Detector – stack the bricks “brick” 85 cm Note this ledge may not be in the final design supertower 17 cm 6cm

16 Design Tungsten-Silicon Silicon “pads” 4 planes of x-y “strips” (8 physical planes) Particle Direction 4 mm W Supertower γ/π 0 Discriminator= EM0 EM1 EM2 segments= Pads Silicon Design Pads: 21 layers 535  m silicon 16 cells: 15.5mmx15.5mm X and Y Strips: 4 layers x-y high resolution strip planes 128 strips: 6.2cmx0.5mm 6cm

17 Vital statistics ~17 cm in length 22 X0 ~ 0.9 Strips – read out by SVX-4 8 layer *128 strips=1024 strips/super-tower 1024 strips/super-tower*160 super-towers/side = 163,840 strips/side strips/side (1detector/128 strips) = 1280 Strip Detectors/side 163,840 strips /(128 channels/chip)= 1280 chips/side Pads – read out by ADC– 3 longitudinal readouts 160 supertowers/side*21 detectors/supertower= 3360 Si pad detectors/side 3360 detector*16channels/detector= pads/side readout channels (pads) 160 supe-rtowers/side *16 pads/tower*3 towers = 7680 readouts/side Bricks 2x4 supertowers: 4 2x6 supertowers: 6 2x7 supertowers: 4 EM0=  /  0, EM1, EM2 segments

18 Detection – how it works Some detector performance examples

19 Status of simulations Stand alone done w/ GEANT3/G4 to study  /  0 separation, single track  0 (G4) EM shower energy/angle resolutions (G4) Full PISA jet resolution (G3/PISA) 2 track  0 (G3/PISA) Several levels Statistical errors, backgrounds, resolutions folded into Pythia level calculations Full PISA simulation using old configuration Transverse spin physics – task force formed – simulations in progress (early step is to put models etc into simulations) *PISA – PHENIX Geant3 simulation

20 It’s a tracking device vertex EM0 EM1 EM2 A 10 GeV photon “track” Pixel-like tracking: 3 layers + vertex Each “hit” is the center of gravity of the cluster in the segment Iterative pattern recognition algorithm uses a parameterization of the shower shape for energy sharing among clusters in a segment and among tracks in the calorimeter.

21 Energy Resolution (Geant4) Excludes Strips no sampling fraction correction /√E New Geometry adequate: we wanted ~ 0.25/√E

22 pt= y=1-1.5 pt= y=1-1.5 pt= y=1-1.5  /  0 identification: pp 2 track  0 p T <5 GeV E=6-10 GeV pt= y=2-2.5 pt= y= pt= y=

23 X-view Y-view 50 GeV pi0 4-x, 2x 4-y, 3y  /  0 identification: Single track  /  0 for pt>5 GeV showers overlap use x/y + vertex to get opening angle Energy from Calorimeter Energy Asymmetry – assume split as a first algorithm invariant mass

24 10 GeV  ~1.65 (Geant4-pp events) Fake  reconstruction: 20% Real  0 reconstruction: 50-60% Real  reconstruction: ~ 60% Fake  0 reconstruction ~ 5% Assumed  0 region Assumed  region 00   /  0 identification: single track  /  0 tested at various energies and angles, so far at pp multiplicities

25 Longitudinal Spin  G,  g(x) : HP12 150/pb, P=0.7 GSC, Response + Background FOCAL Direct Gamma ALL next step: use  -jet to constrain x RHIC region A  LL

26 DSSV GSC Selecting x with rapidity cuts  0  0 Use  0 as a stand in for jets and do a correlation require 1 st  0 p T >2.5 GeV,  =1-3 (into focal) Choose 2 nd  0 to be opposite side in  and  to go to low x 2 Longitudinal Spin Goal log(x 2 )  (2 nd  0)

27 “Direct” Constraint of G(x) in Nuclei:DM8 q qg  q q g  Compton Annihilation G(x) in nuclei almost unconstrained at low x Proposal: Measure  -jet in d+Au collisions to extract G(x) in nuclei unknown Eskola et al, JHEP0807:102,2008 hep-ph/ Gluon Sea Valence

28 Resolutions EM shower energy – 20%/  E angular – 6mr Jet angular resolution 60 pt=20 GeV pTpT jet angular resolution Full PISA simulation x2~ resolution 15%

29 Expected Error for G A (x)/G p (x) :DM8 G(x) Au /G(x) p Log(x 2 ) d+Au:  Ldt = 0.45 pb -1 x 0.25 eff p+p:  Ldt = 240 pb-1 x 0.25 eff pT jet>4 GeV, ptgamma>2 Current uncertainty Possibility for a dramatic improvement in understanding of G(x) in nuclei Impact is widespread Errors are statistical only

30 hadrons q q leading particle suppressed Studying the medium through jet “tomography” DM10 hadrons q q leading particle leading particle “ridge” “jet” STAR Preliminary ridge jet p T trig >2.5 GeV/c, p T assoc > 20 MeV/c, Au+Au 0-30% E. Wenger (PHOBOS), QM2008

31 Jet correlation studies with the FoCal DM10 Need higher-pT triggers, Extended  reach large  How: trigger on high-energy  in FoCal study associated particles in central and muon arms What: Extended  reach and  range (  ~6) Study particle composition of correlated particles using central/muon arm PID detectors including photons Heavy-quark studies via leptons in central/muon arms

32 background assuming pp high pt rates  /  0 trigger eff, AuAu b=3.2 fm  =[1.,1.5] E cut > ~15 GeV S:B~10:1 Parameterize background by studying average energy deposited in the detector (E) and its fluctuations (RMS) Study efficiency and contamination for set values of N σ Strategy: EE E RMS  /  0 trigger eff high pT em shower embedded in hijing

33 Conclusion We want to address the following NSAC milestones measure  G at low-x to see if the gluon contributes to the proton spin measure the nuclear gluon pdf’s to study the effects of transverse spin and its connection to the orbital angular momentum of the constituents of the proton Study long range correlations between jets and secondary particles as a means to understand the medium created in heavy ion collisions at RHIC These goals can addressed by calorimeter which can identify and measure  s and  0 can measure the jet angular resolution and together with the information from the  can lead to a reasonable measurement of x 2 has large rapidity coverage and can probe x 2  We now have a have design Prototype in April