the pfa approach to ilc calorimetry steve magill argonne national laboratory multi-jet events at the...
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The PFA Approach to ILC CalorimetryThe PFA Approach to ILC Calorimetry
Steve Magill
Argonne National Laboratory
Multi-jet Events at the ILCPFA ApproachPFA Goals
PFA Requirements on ILC Calorimetry
PFA-motivated Detector Models
PFA Results
Detector Optimization with PFAs
Summary
Precision Physics at the Precision Physics at the ILCILC
ZHH500 events
• e+e- : background-free but can be complex multi-jet events
• Includes final states with heavy bosons W, Z, H
• But, statistics limited so must include hadronic decay modes (~80% BR) -> multi-jet events
• In general no kinematic fits -> full event reconstruction
Parton Measurement via Jet Reconstruction
From J. Kvita at CALOR06
Cal Jet -> large correction -> Particle Jet -> small correction -> Parton Jet
The Particle Flow Approach to Jet ReconstructionPFA Goal : 1 to 1 correspondence between measured detector objects and particle 4-vectors -> best jet (parton) reconstruction (energy and momentum of parton)
-> combines tracking and 3-D imaging calorimetry :
good tracking for charged particles (~60% of jet E)-> p (tracking) <<< E for photons or hadrons in CAL
good EM Calorimetry for photon measurement (~25% of jet E)
-> E for photons < E for neutral hadrons-> dense absorber for optimal longitudinal separation of photon/hadron showers
good separation of neutral and charged showers in E/HCAL-> CAL objects == particles-> 1 particle : 1 object -> small CAL cells
adequate E resolution for neutrals in HCAL (~13% of jet E)-> E < minimum mass difference, e.g. MZ – MW
-> still largest contribution to jet E resolution
fluctuations
Jet Energy Resolution – “Perfect” PFA
Dilution factor vs cut :integrated luminosity equivalent
• Want mZ - mW = 3σm (dijets) -> dijet mass resolution of ~3.5 GeV or 3-4% of the mass
• Better resolution is worth almost a factor 2 in useable luminosity – or running cost
/M ~ 3%
Dijet masses in WW and ZZ events
PFA Goal – Particle-by-Particle W, Z ID
/M ~ 6%
102 GeV Higgs?!!
PFA Goal – Jet Energy Resolution Dependence
For a pair of jets have:
Assuming a single jet energy resolution of
+ term due to 12 uncertainty
For a Gauge boson mass resolution of order
(Ej) < 0.03 Ejj(GeV)
~3%
Ejj/GeV (Ej)
91 < 29 %
200 < 42 %
360 < 57 %
500 < 67 %Jet energy resolution requirement depends on energy
tt event at 500 GeV-
PFAs and Detector DesignPFAs and Detector Design
PFA key -> complete separation of charged and neutral hadron showers
-> hadron showers NOT well described analytically, fluctuations dominate -> average approach -> E resolutions dominated by fluctuations-> shower reconstruction algorithms -> sensitive to fluctuations on a shower-by-shower basis -> better E resolution - PFA approach
Calorimeter designed for optimal 3-D hadron shower reconstruction :
-> granularity << shower transverse size (number of "hits")-> segmentation << shower longitudinal size ("hits")-> digital or analog readout?-> dependence on inner R, B-field, etc.
uses optimized PFA to test detector model variations
-> Need a dense calorimeter with optimal separation between the starting depth of EM and Hadronic showers. If I/X0 is large, then the longitudinal separation between starting points of EM and Hadronic showers is large
-> For electromagnetic showers in a dense calorimeter, the transverse size is small
-> small rM (Moliere radius)-> If the transverse segmentation is of size rM or smaller, get optimal transverse separation of electromagnetic clusters.
ECAL Requirements for Particle-FlowECAL Requirements for Particle-Flow
MaterialMaterial II (cm) (cm) XX00 (cm) (cm) II/X/X00
WW 9.599.59 0.350.35 27.4027.40
AuAu 9.749.74 0.340.34 28.6528.65
PtPt 8.848.84 0.3050.305 28.9828.98
PbPb 17.0917.09 0.560.56 30.5230.52
UU 10.5010.50 0.320.32 32.8132.81
MaterialMaterial II (cm) (cm) XX00 (cm) (cm) II/X/X00
Fe (SS)Fe (SS) 16.7616.76 1.761.76 9.529.52
CuCu 15.0615.06 1.431.43 10.5310.53
Dense, Non-magnetic Less Dense, Non-magnetic
. . . use these for ECAL
conconee
mean mean (GeV)(GeV)
rmrmss
//meanmean
22
.025.025 1.921.92 1.41.444
.78.78 9.369.36
.05.05 2.942.94 1.31.399
.41.41 4.294.29
.075.075 3.593.59 1.21.288
.31.31 2.422.42
.10.10 4.014.01 1.21.233
.25.25 2.352.35
.25.25 4.644.64 1.31.300
.23.23 2.702.70
.50.50 4.774.77 1.21.299
.23.23 2.502.50
.75.75 4.794.79 1.21.288
.23.23 2.412.41
1.001.00 4.804.80 1.21.288
.23.23 2.402.40
conconee
mean mean (GeV)(GeV)
rmrmss
//meanmean
22
.025.025 2.072.07 1.61.622
.79.79 10.6110.61
.05.05 2.962.96 1.61.666
.51.51 4.514.51
.075.075 3.633.63 1.51.566
.38.38 2.742.74
.10.10 4.084.08 1.41.488
.31.31 2.562.56
.25.25 4.764.76 1.41.444
.25.25 2.492.49
.50.50 4.854.85 1.41.433
.25.25 2.422.42
.75.75 4.864.86 1.41.422
.25.25 2.252.25
1.001.00 4.874.87 1.41.422
.25.25 2.452.45
SS W
rms
cone
Energy in fixed cone size :-> means ~same for SS/W-> rms ~10% smaller in W
Tighter showers in W
. . . dense HCAL as well?-> 3-D separation of showers
Single 5 GeV Single 5 GeV
HCAL Requirements for Particle-FlowHCAL Requirements for Particle-Flow
Digital HCAL?
Analog linearity Digital linearity
GEANT 4 Simulation of SiD Detector (5 GeV +)-> sum of ECAL and HCAL analog signals - Analog-> number of hits with 1/3 mip threshold in HCAL - Digital
Analog Digital
Landau Tails+ path length
Gaussian
/mean ~22% /mean ~19%
E (GeV) Number of Hits
Occupancy Event DisplayOccupancy Event Display
All hits from all particles
Hits with >1 particle contributing
PFA-Motivated Detector Models
SiD, LDC, GLD in order of Inner Radius size
Common featuresLarge B-field with solenoid outside calorimeterSuppress backgroundsSeparate charged hadronsDense (W), fine-grained (Silicon pixels) ECALHigh granularity and segmented HCAL digital and analog readouts
SiD
Pictures, short descriptions
LDCGLD
SiD Detector ModelSi Strip TrackerW/Si ECAL, IR = 125 cm 4mm X 4mm cellsSS/RPC Digital HCAL 1cm X 1cm cells5 T B field (CAL inside)
PFA Results at Z Pole in SiDPFA Results at Z Pole in SiD
Average confusion contribution = 1.9 GeV <~ Neutral hadron resolution contribution of 2.2 GeV -> closing in on PFA goal
2.61 GeV 86.5 GeV 59% -> 28%/√E
3.20 GeV 87.0 GeV 59% -> 34%/√E
Energy Sum (GeV) Energy Sum (GeV)
PandoraPFA v01-01 LDC00Sc B = 4 T 3x3 cm HCAL (63 layers) Z uds (no ISR) TrackCheater
√s = 91 GeV
√s = 360 GeV √s = 200 GeV
PFA Results on qqbar LDC00Sc
EEJETJET
EE/E = /E = √(E/GeV)√(E/GeV)
|cos|cos|<0.7|<0.7
45 GeV45 GeV 0.2950.295
100 GeV100 GeV 0.3050.305
180 GeV180 GeV 0.4180.418
250 GeV250 GeV 0.5340.534
rms90
PFA Results - Angular Dependence
PandoraPFA v01-01
• Fairly flat until next to beam pipe• Evidence for shower leakage at cos = 0?
RMS = 15.89 GeVRMS90 = 9.632 GeV[66.7%/sqrt(E)]
RMS = 11.44 GeVRMS90 = 8.45 GeV[~59%/sqrt(E)]
Removing eventswith shower leakage
PFA Results : qq at 200 GeV
Barrel Events
RMS = 30.25 GeVRMS90 = 21.4 GeV[~97%/sqrt(E)]
RMS = 43.88 GeVRMS90 = 28.11 GeV[127.%/sqrt(E)]
Removing eventswith shower leakage
• Shower leakage affects PFA performance at high energy• Events with heavy shower leakage could be identified by hits in the muon detectors• Use hits in the muon detectors to estimate shower leakage?
PFA Results : qq at 500 GeV
Z
Z
W,Z Separation in Physics Events with PFA
Detector Optimisation Detector Optimisation Studies Studies
From point of view of detector design – what do we want to know ?
Optimise performance vs. cost
Main questions (the major cost drivers):• Size : performance vs. radius• Granularity (longitudinal/transverse): ECAL and HCAL• B-field : performance vs. B
To answer them use MC simulation + PFA algorithm
!• Need a good MC simulation• Need realistic PFA algorithm (want/need results from multiple algorithms)
These studies are interesting but not clear how seriously they should be taken
how much is due to the detector how much due to imperfect algorithm
Caveat Emptor
4.3 I 5.3 I
HCAL Depth and Transverse HCAL Depth and Transverse segmentationsegmentation Investigated HCAL Depth (interaction lengths)
• Generated Zuds events with a large HCAL (63 layers)• approx 7 I
• In PandoraPFA introduced a configuration variable to truncate the HCAL to arbitrary depth• Takes account of hexadecagonal geometry
NOTE: no attempt to account for leakage – i.e. using muon hits - this is a worse case
HCAL leakage is significant for high energy Argues for ~ 5 I HCAL
1x1 3x3 5x5 10x10
Analogue scintillator tile HCAL : change tile size 1x1 10x10 mm2
“Preliminary Conclusions”
3x3 cm2 cell size No advantage 1x1 cm2
• physics ?• algorithm artefact ?
5x5 cm2 degrades PFA• Does not exclude coarser
granularity deep in HCAL
Radius vs FieldRadius vs Field
100 GeV jets
LDC00Sc
180 GeV jets
Radius more important than B-field
Radius more important at higher energies
B-field studies on the way…
ECAL Transverse GranularityECAL Transverse Granularity• Use Mokka to generate Z uds events @ 200 GeV with different ECAL segmentation: 5x5, 10x10, 20x20 [mm2]
• For 100 GeV jets, not a big gain going from 10x10 5x5mm2
With PandoraPFA
[ for these jet energies the contributions from confusion inside the ECAL is relatively small – need ]
• 20x20 segmentation looks too coarse
100 GeV jets
PFA + Full Simulations -> LC detector design
- unique approach to calorimeter design
- requires generation of e+e- physics processes as well as single particles
- needs good simulation of the entire LC detector
- requires flexible simulation package -> fast variation of many parameters
- huge reliance on correct! simulation of hadron showers
-> importance of timely test beam results!
PFA Reliance on Simulation
PFA Calorimeters in Test Beam – Hadron Shower Model Comparisons
For upgrade we will add the plastic ball detector (GSI, Darmstadt) as a recoil detector. This will help with the tagged neutrons
MIPP Experiment and Upgrade -StatusMIPP Experiment and Upgrade -Status
• MIPP E907 took data in 2005 is busy analyzing 18 MIPP E907 took data in 2005 is busy analyzing 18 million events—Results expected soon.million events—Results expected soon.
• MIPP Upgrade proposal P-960 MIPP Upgrade proposal P-960 – was deferred in October 2006 till MIPP publishes was deferred in October 2006 till MIPP publishes
existing dataexisting data– Obtains new collaborators-(10 additional Obtains new collaborators-(10 additional
institutions have joined)institutions have joined)• MIPP Upgrade will speed up DAQ by a factor of 100 MIPP Upgrade will speed up DAQ by a factor of 100
and will obtain data on 30 nuclei. This will benefit and will obtain data on 30 nuclei. This will benefit hadronic shower simulator programs enormously—hadronic shower simulator programs enormously—See Dennis Wright’s talk at the ILC test beam See Dennis Wright’s talk at the ILC test beam workshop.workshop.
• MIPP Upgrade will provide tagged neutral beams MIPP Upgrade will provide tagged neutral beams for ILC calorimeter usage.for ILC calorimeter usage.
Models (MARS, PHITS, Geant4) Models (MARS, PHITS, Geant4) disagree with each other and data disagree with each other and data when tested on thick Al targetwhen tested on thick Al target
Proton production from thick aluminum target at 67 GeV/c Ratio of calculated and measured cross sections
Energy deposition in cylindrical Energy deposition in cylindrical tungsten thick target-Before and after tungsten thick target-Before and after the Hadronic shower simulation the Hadronic shower simulation workshopworkshop
Before workshop
After workshop
1 GeV protons on 10cm tungsten rod (1cm radius)
10 GeV protons on 10cm tungsten rod (1cm radius)
MIPP Upgrade will acquire 5 MIPP Upgrade will acquire 5 million events/day on the million events/day on the following nucleifollowing nuclei• The A-ListThe A-List
• HH22,D,D22,Li,Be,B,C,N,Li,Be,B,C,N22,O,O22,Mg,Al,Si,P,S,Ar,K,Ca,,Fe,Ni,C,Mg,Al,Si,P,S,Ar,K,Ca,,Fe,Ni,Cu,Zn,Nb,Ag,Sn,W,Pt,Au,Hg,Pb,Bi,Uu,Zn,Nb,Ag,Sn,W,Pt,Au,Hg,Pb,Bi,U
• The B-ListThe B-List
• Na, Ti,V, Cr,Mn,Mo,I, Cd, Cs, BaNa, Ti,V, Cr,Mn,Mo,I, Cd, Cs, Ba
• With this data, for beam energies ranging from With this data, for beam energies ranging from 1 GeV/c-120 GeV/c for 6 beam species, one can 1 GeV/c-120 GeV/c for 6 beam species, one can change the quality of hadronic shower change the quality of hadronic shower simulations enormously—Net conclusion of simulations enormously—Net conclusion of HSSW06.HSSW06.
Tagged neutron and K-long Tagged neutron and K-long beams in MIPP-For ILC Particle beams in MIPP-For ILC Particle flow algorithm studiesflow algorithm studies• MIPP Spectrometer permits MIPP Spectrometer permits
a high statistics neutron and a high statistics neutron and K-long beams generated on K-long beams generated on the LH2 target that can be the LH2 target that can be tagged by constrained tagged by constrained fitting. The neutron and K-fitting. The neutron and K-long momenta can be known long momenta can be known to better than 2%. The to better than 2%. The energy of the neutron (K-energy of the neutron (K-long) can be varied by long) can be varied by changing the incoming changing the incoming proton(Kproton(K++) momentum. The ) momentum. The reactions involved arereactions involved are
pnpp
pKpK
pKpK
pnpp
L
L
0
0
See R.Raja-MIPP Note 130.
Expected tagged neutral rates/day of running
Beam Mom entum Proton Beam K+ beam K- beam Antiproton beam
GeV/c n/day K-Long/day K-Long/day anti-n/day
10 20532 4400 4425 665020 52581 9000 9400 1145030 66511 12375 14175 1350060 47069 15750 14125 1355090 37600
An expression of support from the ILC community will help speed up the approval process
Summary
Much “cleaner” environment for jetsin e+e- collisions than in ppbar - at theLHC, jet E resolution is dominated bycontributions from underlying eventsand final state gluon radiation
Without large UE and FSR contributions, CAL resolution dominates-> An obvious goal – W/Z ID with dijet mass measurement? Current calorimeters - M ~ 9 GeV at Z-Pole PFA potential improvement - M ~ 3 GeV -> in addition to leptonic decay modes, can use >80% of hadronic decays as well
PFAs for LC Detectors?PFAs for LC Detectors?~13% for CMS
PFA vs Compensation? Hardware compensation – for high energy particles (ZEUS 35%/E for > ~3 GeV) but for jets resolution degrades. Software compensation - requires knowledge of the particle type and/or particle energy, + reliance on shower and/or jet models Particle Flow works as long as "mistakes" < E of neutral hadrons (10%)
ppbar -> qqbar -> hadrons + photons -> large calorimeter cells traditional jet measurement
Z -> qqbar -> hadrons + photons = small 3D cal cells
PFA jet measurement
Dijet event in CDF Detector
One jet in Z -> qqbar event in a LC Detector