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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
Richard Hollis8th January 2010 ● 2
NUCLEARDYNAMICSWINTER●WORKSHOP
Overview
The next decade at RHIC&PHENIXMotivation and Needs
Calorimeter UpgradesPast: MPC – currently operationalFuture: FoCal – proposal soon
Summary
Richard Hollis8th January 2010 ● 3
NUCLEARDYNAMICSWINTER●WORKSHOP
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
Richard Hollis8th January 2010 ● 4
NUCLEARDYNAMICSWINTER●WORKSHOP
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) 242303
d+Au collisions
CentralArms
MuonArms
Richard Hollis8th January 2010 ● 5
NUCLEARDYNAMICSWINTER●WORKSHOP
Proton spin contribution from gluon polarization
p+p collisions
RHIC range0.05 < x < 0.2
xg 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 measure direct photons
Richard Hollis8th January 2010 ● 6
NUCLEARDYNAMICSWINTER●WORKSHOP
Building detectors to suit physics needs
Need:Forward rapiditiesDirect photonsWell defined energy scale for measurements
Richard Hollis8th January 2010 ● 7
NUCLEARDYNAMICSWINTER●WORKSHOP
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?
-3 -2 -1 0 1 2 3
0
c
over
age
2
EMC
-3 -2 -1 0 1 2 3
0
c
over
age
2
Tr Tr
(F)VTX
Richard Hollis8th January 2010 ● 8
NUCLEARDYNAMICSWINTER●WORKSHOP
PHENIX Acceptance
Staged Calorimeter Upgrades
Muon Piston Calorimeter (MPC) 3.1<||<3.9
-3 -2 -1 0 1 2 3
0
c
over
age
2
Tr Tr
(F)VTX
-3 -2 -1 0 1 2 3
0
c
over
age
2
EMCMPC MPC
Richard Hollis8th January 2010 ● 9
NUCLEARDYNAMICSWINTER●WORKSHOP
Muon Piston Calorimeter (MPC)
Lead Scintillator (PbW04)
18cm long ~20X0
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 pT~1.7 GeV/c
pT>1.7GeV/c – measure single “clusters”
12 < E < 15 GeV
Raw Signal
Mixed-eventBackground
Yield
Cou
nts
MPC(N)
Richard Hollis8th January 2010 ● 10
NUCLEARDYNAMICSWINTER●WORKSHOP
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
dNd
Richard Hollis8th January 2010 ● 11
NUCLEARDYNAMICSWINTER●WORKSHOP
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)
IdA suppression – a signature of CGC
Mid-rapidity 0 Trigger
Forward Associates
Richard Hollis8th January 2010 ● 12
NUCLEARDYNAMICSWINTER●WORKSHOP
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+p0+X at s=62.4 GeV/c2
Richard Hollis8th January 2010 ● 13
NUCLEARDYNAMICSWINTER●WORKSHOP
PHENIX Acceptance
Staged Calorimeter Upgrades
Muon Piston Calorimeter (MPC) 3.1<||<3.9
Forward Calorimeter (FoCal) 1<||<3
-3 -2 -1 0 1 2 3
0
c
over
age
2
Tr Tr
(F)VTX
-3 -2 -1 0 1 2 3
0
c
over
age
2
EMCMPC MPC
Richard Hollis8th January 2010 ● 14
NUCLEARDYNAMICSWINTER●WORKSHOP
Finding space in PHENIX
MPC installed ~ 3<||<4
MPC
FoCal: where could it fit?
Richard Hollis8th January 2010 ● 15
NUCLEARDYNAMICSWINTER●WORKSHOP
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 Hollis8th January 2010 ● 16
NUCLEARDYNAMICSWINTER●WORKSHOP
FoCal
Silicon-Tungsten sampling calorimeter 21 layers ~21X0
Each Arm: 1<|<3
Expect good resolution in E and / Active readout
~1.5x1.5cm
Distinct 2-shower 0 up to pT~3 GeV/c (~1)
Transverse View
Longitudinal View
6.1cm
Richard Hollis8th January 2010 ● 17
NUCLEARDYNAMICSWINTER●WORKSHOP
FoCal x Coverage
x coverage: Weak pT dependence
p+p collisions
x versus pT (p+p, 500 GeV)(FoCal Acceptance)
Richard Hollis8th January 2010 ● 18
NUCLEARDYNAMICSWINTER●WORKSHOP
FoCal x Coverage
x coverage: Weak pT dependence
Strong dependence
p+p collisions
x versus (p+p, 500 GeV)(FoCal Acceptance)
Richard Hollis8th January 2010 ● 19
NUCLEARDYNAMICSWINTER●WORKSHOP
FoCal x Coverage
p+p collisions
x versus (p+p, 500 GeV)(FoCal & MPC Acceptance)
x coverage: Weak pT dependence
Strong dependence FoCal complementary to MPC
Richard Hollis8th January 2010 ● 20
NUCLEARDYNAMICSWINTER●WORKSHOP
FoCal x Coverage
x for bins (p+p, 500 GeV)(FoCal Acceptance)
x coverage: Weak pT dependence
Strong dependence FoCal complementary to MPC
Selecting region probes a specific x range
Richard Hollis8th January 2010 ● 21
NUCLEARDYNAMICSWINTER●WORKSHOP
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
Richard Hollis8th January 2010 ● 22
NUCLEARDYNAMICSWINTER●WORKSHOP
What about direct identification?
Important for our measurements in the next decade in Spin d+Au Au+Au
Richard Hollis8th January 2010 ● 23
NUCLEARDYNAMICSWINTER●WORKSHOP
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
Richard Hollis8th January 2010 ● 24
NUCLEARDYNAMICSWINTER●WORKSHOP
High energy 0 shower
Origin of all shower particles (red) Shown with effective
resolution of pads
Individual tracks not distinguishable
p+p collisions
Richard Hollis8th January 2010 ● 25
NUCLEARDYNAMICSWINTER●WORKSHOP
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
Richard Hollis8th January 2010 ● 26
NUCLEARDYNAMICSWINTER●WORKSHOP
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
EM0 EM1 EM2
x y x y x y x y
~2 tow
ers
~70 strips
p+p collisions
Richard Hollis8th January 2010 ● 27
NUCLEARDYNAMICSWINTER●WORKSHOP
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 tracksCatch the shower, before it’s too late
Tracks are visiblySeparable
Track showersMerge
Richard Hollis8th January 2010 ● 28
NUCLEARDYNAMICSWINTER●WORKSHOP
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
Richard Hollis8th January 2010 ● 29
NUCLEARDYNAMICSWINTER●WORKSHOP
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)
Richard Hollis8th January 2010 ● 30
NUCLEARDYNAMICSWINTER●WORKSHOP
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
Richard Hollis8th January 2010 ● 31
NUCLEARDYNAMICSWINTER●WORKSHOP
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) 685CSTAR: PRL103 (2009) 172301
A+A collisions
Richard Hollis8th January 2010 ● 32
NUCLEARDYNAMICSWINTER●WORKSHOP
MPC x Coverage
x versus (p+p, 500 GeV)(MPC Acceptance)
Richard Hollis8th January 2010 ● 33
NUCLEARDYNAMICSWINTER●WORKSHOP
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