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a FO rward CAL orimeter. Overview. Richard Seto Winter Workshop on Nuclear Dynamics Feb 7, 2009. NSAC milestones – Physics Goals. pA physics – nuclear gluon pdf. G. -Jet AuAu. transverse spin phenomena. Look for saturation effects at low x - PowerPoint PPT Presentation
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a
FOrward CALorimeter
Richard SetoWinter Workshop on Nuclear Dynamics
Feb 7, 2009
Overview
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NSAC milestones – Physics Goals
Year # MileStone FOCAL
2012
DM8 Determine gluon densities at low x in cold nuclei via p+ Au or d + Au collisions.
Required for direct photon
2013
HP12 Utilize 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-xDirect
2014
DM10(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
2015
HP13 (new)
Test unique QCD predictions for relation between single-transverse spin phenomena in p-p scattering and those observed in deep-inelastic lepton scatteringNew 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
transversespin phenomena
pA physics – nuclear gluon pdf
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pA physics – nuclear gluon pdf
direct jets –x resolutionforward 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)
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2
( )
( )
T Jet
T Jet
px e e
sp
x e es
xSaturation 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
0
LLA
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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 xgluon= 0.020.3
direct jets –x resolutionforward η(low-x)0 0
x RHIC range0.05· x · 0.2
small-x0.001· x · 0.05
Longitudinal Spin G, g(x) : HP12
EXTEND MEASUREMENTS TO LOW x!Forward
Measure x
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direct -jet0
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
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EM - showerlarge 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?
leadingEM shower
?
“ridge”
“jet”
STAR Preliminary
for example
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To meet these goals we must have a detector that measures:
direct and electromagnetic showers
jet angles to obtain x2
0 s forward to reach low-x has large coverage
now what do we build?
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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
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Perfect space for FOCAL! (but tight!)
14 EM bricks14 HAD bricksHAD behind EM
FOCAL
40 cm from Vertex
20 cm of space
nosecone
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FOCAL Requirements Ability to measure photons and π0’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 x2 ~
0.001 Densest calorimeter -> Si W
We wanted large coveragewhat sort of coverage if we put a detector where the nosecones are?
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Mu
on
tra
ckin
g
Mu
on
tra
ckin
g
VTX & FVTX MP
C
MP
C
-3 -2 -1 0 1 2 3 rapidity
cove
rage
2
EM
CE
MC
FOCAL a large acceptance calorimeter
FOCALFOCAL
trac
kin
g
trac
kin
g
What’s missing? FORward CALorimetery
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reach in x2 for g(x) and GA(x)
log(x2)EMC+VTXEMC+VTX+FOCALEMC+VTX+FOCAL+MPC X2 10-3
2~s Q
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FOCAL Design
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Overall Detector – stack the bricks
“brick”
85 cm Note thisledge may not bein the final design
supertower
17 cm6cm
6cm
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Design Tungsten-Silicon
Silicon “pads”4 planes of x-y “strips” (8 physical planes)
ParticleDirection
4 mm W
Supertower
γ/π0 Discriminator=EM0 EM1 EM2segments=
Pads SiliconDesign
Pads: 21 layers 535 m silicon 16 cells:
15.5mmx15.5mmX and Y Strips: 4 layers
x-y high resolution strip planes
128 strips: 6.2cmx0.5mm
6cm
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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 163840 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= 53760 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
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Detection – how it works
Some detector performance examples
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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
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It’s a tracking device
vertex
EM0 EM1 EM2A 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.
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Energy Resolution (Geant4)
Excludes Stripsno sampling fraction correction
0.00+0.20/√E
New Geometry
adequate: we wanted ~ 0.25/√E
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pt=2.-2.5y=1-1.5 pt=4.-4.5
y=1-1.5
pt=1.-1.5y=1-1.5
/0 identification: pp 2 track 0 pT<5 GeV
E=6-10 GeV
pt=0.5-1.0y=2-2.5pt=0.5-1.0
y=1.5-2.0
pt=1.5-2.0y=1.5-2.0
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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 50-50 split as a first algorithm
invariant mass
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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 identification: single track /0tested at various energies and angles, so far at pp multiplicities
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Longitudinal Spin G, g(x) : HP12
150/pb, P=0.7
GSC, Response + Background
FOCAL Direct Gamma ALLnext step: use -jet to constrain x
RHICregion
ALL
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DSSV
GSC
Selecting x with rapidity cuts 0
0
Use 0 as a stand in for jets and do a correlation require 1st 0 pT>2.5 GeV, =1-3 (into focal) Choose 2nd 0 to be opposite side in and to go to low
x2
Longitudinal Spin Goal
log(x2)
(2nd 0)
0
LLA
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“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/0802.0139
( )
( )Pb
p
G x
G x
GluonSeaValence
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Resolutions EM shower
energy – 20%/E angular – 6mr
Jet angular resolution 60 mr @ pt=20 GeV
pT
jet angularresolution
( )JetTgluon
px e e
s
x2~ resolution 15%
2 2/x x
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Expected Error for GA(x)/Gp(x) :DM8
G(x)Au/G(x)p
Log(x2)
d+Au: Ldt = 0.45 pb -1 x 0.25 effp+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
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hadrons
q
q
hadrons leading particle suppressed
leading particle suppressed
Studying the medium through jet “tomography” DM10
hadrons
q
q
hadrons
leadingparticle
leading particle
“ridge”
“jet”
STAR Preliminary
ridgejet
pTtrig>2.5 GeV/c, pT
assoc > 20 MeV/c, Au+Au 0-30%
E. Wenger (PHOBOS), QM2008
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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
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backgroundassumingpp high ptrates
/0 trigger eff, AuAu b=3.2 fm =[1.,1.5] Ecut> ~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 Nσ
Strategy:
2
measE EN
RMS
E
ERMS
/0
tri
gg
er
eff
high pT em showerembedded inhijing
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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 x2
has large rapidity coverage and can probe x2 10-3
We now have a have design Prototype in April