The PFA Approach to ILC Calorimetry Steve Magill Argonne National Laboratory Multi-jet Events at the ILC PFA Approach PFA Goals PFA Requirements on ILC Calorimetry PFA-motivated Detector Models PFA Results Detector Optimization with PFAs Summary

Precision Physics at the ILC ZHH 500 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 Reconstruction PFA 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. M Z – M W -> still largest contribution to jet E resolution

fluctuations Jet Energy Resolution – “Perfect” PFA

Dilution factor vs cut : integrated luminosity equivalent Want m Z - m W = 3σ m (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  (E j ) < 0.03  E jj (GeV) ~3% E jj /GeV  (E j ) 91< 29 % 200< 42 % 360< 57 % 500< 67 % Jet energy resolution requirement depends on energy 

tt event at 500 GeV -

PFAs 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 /X 0 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 r M (Moliere radius) -> If the transverse segmentation is of size r M or smaller, get optimal transverse separation of electromagnetic clusters. ECAL Requirements for Particle-Flow Material I (cm) I (cm) X 0 (cm) I /X 0 I /X 0 W Au Pt Pb U Material I (cm) I (cm) X 0 (cm) I /X 0 I /X 0 Fe (SS) Cu Dense, Non-magneticLess Dense, Non-magnetic... use these for ECAL

cone mean (GeV) rms  /mean 222 cone mean (GeV) rms  /mean 222 SSW 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  HCAL Requirements for Particle-Flow

Digital HCAL? Analog linearityDigital 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 AnalogDigital Landau Tails + path length Gaussian  /mean ~22%  /mean ~19% E (GeV)Number of Hits

Occupancy 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 features Large B-field with solenoid outside calorimeter Suppress backgrounds Separate charged hadrons Dense (W), fine-grained (Silicon pixels) ECAL High granularity and segmented HCAL digital and analog readouts

SiD Pictures, short descriptions LDC GLD SiD Detector Model Si Strip Tracker W/Si ECAL, IR = 125 cm 4mm X 4mm cells SS/RPC Digital HCAL 1cm X 1cm cells 5 T B field (CAL inside)

PFA 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)

 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 E JET  E /E =  √(E/GeV) |cos|< GeV GeV GeV GeV rms90

PFA Results - Angular Dependence PandoraPFA v01-01 Fairly flat until next to beam pipe Evidence for shower leakage at cos  = 0?

RMS = GeV RMS90 = GeV [66.7%/sqrt(E)] RMS = GeV RMS90 = 8.45 GeV [~59%/sqrt(E)] Removing events with shower leakage PFA Results : qq at 200 GeV Barrel Events

RMS = GeV RMS90 = 21.4 GeV [~97%/sqrt(E)] RMS = GeV RMS90 = GeV [127.%/sqrt(E)] Removing events with 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 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 segmentation  Investigated HCAL Depth (interaction lengths) Generated Z  uds 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 3x35x510x10  Analogue scintillator tile HCAL : change tile size 1x1  10x10 mm 2 “Preliminary Conclusions”  3x3 cm 2 cell size  No advantage  1x1 cm 2 physics ? algorithm artefact ?  5x5 cm 2 degrades PFA Does not exclude coarser granularity deep in HCAL

Radius vs Field Radius 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 Granularity Use Mokka to generate Z  uds 200 GeV with different ECAL segmentation: 5x5, 10x10, 20x20 [mm 2 ] For 100 GeV jets, not a big gain going from 10x10  5x5mm 2 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 -Status MIPP E907 took data in 2005 is busy analyzing 18 million events—Results expected soon. MIPP E907 took data in 2005 is busy analyzing 18 million events—Results expected soon. MIPP Upgrade proposal P-960 MIPP Upgrade proposal P-960 –was deferred in October 2006 till MIPP publishes existing data –Obtains new collaborators-(10 additional institutions have joined) MIPP Upgrade will speed up DAQ by a factor of 100 and will obtain data on 30 nuclei. This will benefit hadronic shower simulator programs enormously—See Dennis Wright’s talk at the ILC test beam workshop. MIPP Upgrade will speed up DAQ by a factor of 100 and will obtain data on 30 nuclei. This will benefit hadronic shower simulator programs enormously—See Dennis Wright’s talk at the ILC test beam workshop. MIPP Upgrade will provide tagged neutral beams for ILC calorimeter usage. MIPP Upgrade will provide tagged neutral beams for ILC calorimeter usage.

Models (MARS, PHITS, Geant4) disagree with each other and data when 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 tungsten thick target-Before and after the Hadronic shower simulation workshop 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 million events/day on the following nuclei The A-List The A-List H 2,D 2,Li,Be,B,C,N 2,O 2,Mg,Al,Si,P,S,Ar,K,Ca,,Fe,Ni,Cu,Zn,Nb,Ag,Sn,W,Pt,Au,Hg,Pb,Bi,U H 2,D 2,Li,Be,B,C,N 2,O 2,Mg,Al,Si,P,S,Ar,K,Ca,,Fe,Ni,Cu,Zn,Nb,Ag,Sn,W,Pt,Au,Hg,Pb,Bi,U The B-List The B-List Na, Ti,V, Cr,Mn,Mo,I, Cd, Cs, Ba Na, Ti,V, Cr,Mn,Mo,I, Cd, Cs, Ba With this data, for beam energies ranging from 1 GeV/c-120 GeV/c for 6 beam species, one can change the quality of hadronic shower simulations enormously— Net conclusion of HSSW06. With this data, for beam energies ranging from 1 GeV/c-120 GeV/c for 6 beam species, one can change the quality of hadronic shower simulations enormously— Net conclusion of HSSW06.

Tagged neutron and K-long beams in MIPP-For ILC Particle flow algorithm studies MIPP Spectrometer permits a high statistics neutron and K-long beams generated on the LH2 target that can be tagged by constrained fitting. The neutron and K-long momenta can be known to better than 2%. The energy of the neutron (K-long) can be varied by changing the incoming proton(K + ) momentum. The reactions involved are MIPP Spectrometer permits a high statistics neutron and K-long beams generated on the LH2 target that can be tagged by constrained fitting. The neutron and K-long momenta can be known to better than 2%. The energy of the neutron (K-long) can be varied by changing the incoming proton(K + ) momentum. The reactions involved are See R.Raja-MIPP Note 130. Expected tagged neutral rates/day of running An expression of support from the ILC community will help speed up the approval process 

Summary

Much “cleaner” environment for jets in e+e- collisions than in ppbar - at the LHC, jet E resolution is dominated by contributions from underlying events and 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? ~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