What to Optimize Calorimetry at the ILC

What to Optimize  Calorimetry at the ILC www.phwiki.com

What to Optimize Calorimetry at the ILC

Hale, Mike, Features Editor & Food Writer has reference to this Academic Journal, PHwiki organized this Journal Concepts, Calorimetry in addition to PFA Mark Thomson University of Cambridge This Talk: ILC Physics/Detector Requirements Detector Concepts in addition to optimisation Calorimetry at the ILC Particle Flow Status PFA in near future Conclusions ILC Physics / Detector Requirements Precision Studies/Measurements Higgs sector SUSY particle spectrum SM particles (e.g. W-boson, top) in addition to much more Detector optimized as long as precision measurements in difficult environment Only 2 detectors (1) – make sure we choose the right options Small cross-sections High Multiplicity final states often 6/8 jets Many final states have“missing” energy neutrinos + neutrilinos()/gravitinos() + Difficult Environment: ILC Detector Requirements Momentum: s1/p < 7x10-5/GeV (1/10 x LEP) (e.g. Z mass reconstruction from charged leptons) Impact parameter: sd0 < 5mmÅ5mm/p(GeV) (1/3 x SLD) (c/b-tagging in background rejection/signal selection) Jet energy : dE/E = 0.3/E(GeV) (1/2 x LEP) (W/Z invariant mass reconstruction from jets) Hermetic down to : q = 5 mrad ( as long as missing energy signatures e.g. SUSY) Sufficient timing resolution to separating events from different bunch-crossings Must also be able to cope with high track densities due to high boost in addition to /or final states with 6+ jets, there as long as e require: High granularity Good pattern recognition Good two track resolution Sacramento Center CA www.phwiki.com

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Currently 3 detector concepts Detector Concepts COMPACT: Silicon Detector (SiD) TESLA-like: Large Detector Concept : (LDC) LARGE : GLD What is the purpose of the Concepts Relevance to CALICE SiW ECAL is not cheap ! big cost driver as long as overall detector Can it be justified are the physics benefits worth the cost do we need such high granularity would very high granularity help MAPS These are important questions. The concept studies will hopefully provide the answers Explore phase space as long as ILC detector design Produce costed “conceptual design reports” by end of 2006 Place detector R&D (e.g. CALICE) in context of a real detector Per as long as m some level of cost-per as long as mance optimisation Possible/likely to be nucleus around which real collaborations as long as m What to Optimize The Big Questions (to first order): CENTRAL TRACKER TPC vs Si Detector Samples vs. granularity – pattern recognition in a dense track environment with a Si tracker

ECAL Widely (but not unanimously) held view that a high granularity SiW ECAL is the right option BUT it is expensive Need to demonstrate that physics gains outweigh cost + optimize pad size/layers HCAL SIZE Higher granularity digital (e.g. RPC) vs lower granularity analog option (e.g. scint-steel) Physics argues as long as : large + high granularity Cost considerations: small + lower granularity What is the optimal choice Aside: the GLD ECAL Initial GLD ECAL concept: Strips : 1cm x 20cm x 2mm Tiles : 4cm x 4cm x 2mm Achieve effective ~1 cm x 1cm segmentation using strip/tile arrangement Ultimate design needs to be optimised as long as particle flow per as long as mance + question of pattern recognition in dense environment Calorimetry at the ILC Much ILC physics depends on reconstructing invariant masses from jets in hadronic final states Kinematic fits won’t necessarily help – Unobserved particles (e.g. n), + (less important ) Beamstrahlung, ISR Aim as long as jet energy resolution ~ GZ as long as “typical” jets – the point of diminishing return Jet energy resolution is the key to calorimetry The Energy Flow/Particle Flow Method The visible energy in a jet (excluding n) is: Reconstruct momenta of individual particles avoiding double counting Need to separate energy deposits from different particles

Reconstruction of two di-jet masses allows discrimination of WW in addition to ZZ final states THIS ISN’T EASY ! Often-quoted Example: Jet energy resolution directly impacts physics sensitivity EQUALLY applicable to any final states where want to separate Wgqq in addition to Zgqq ! granularity more important than energy resolution sjet2 = sx±2 + sg2 + sh02 + sconfusion2 + sthreshold2 Best resolution achieved as long as TESLA TDR : 0.30Ejet morgunov Single particle resolutions not the dominant contribution to jet energy resolution ! In addition, have contributions to jet energy resolution due to “confusion” = assigning energy deposits to wrong reconstructed particles (double-counting etc.) Will come back to this later Calorimeter Requirements Some COMMENTS/QUESTIONS: RMoliere ~ 9mm as long as solid tungsten – gaps between layers increase effective RMoliere – an engineering/electronics issue RMoliere is only relevant scale once shower has developed – in first few radiation lengths higher/much higher lateral segmentation should help + Many optimisation issues !

ECAL Granularity : is the RMol the correct scale Personal View: e.g. electrons in SiW with 1 mm x 1 mm segmentation Moliere radius is only relevant towards shower max At start of shower (ECAL front) much higher granularity may help MAPS . At end of shower can probably reduce granularity Higher granularity clearly helps particularly at shower start H.Videau (Snowmass) General view now leaning towards higher granularity IF SiW ECAL cost driven mainly by Si cost – no problem Another example: t+ r+ n p+ p0 Two(+) Options: Tile HCAL (Analogue readout) Steel/Scintillator s in addition to wich Lower lateral segmentation 5×5 cm2 (motivated by cost) Digital HCAL High lateral segmentation 1×1 cm2 digital readout (granularity) RPCs, wire chambers, GEMS Semi-Digital option Highly Segmented – as long as Energy Flow Longitudinal: ~10 samples ~5 lhad (limited by cost – coil radius) Would like fine (1 cm2 ) lateral segmentation (how fine ) For 5000 m2 of 1 cm2 HCAL = 5×107 channels – cost ! Hadron Calorimeter Energy depositions in active region follow highly asymmetric L in addition to au distribution OPEN QUESTION

Particle Flow Status Particle flow in an ILC highly granular ECAL/HCAL is very new No real experience from previous experiments We all have our personal biases/beliefs about what is important BUT at this stage, should assume we know very little Real PFA algorithms vital to start learning how to do this type of “calorimetry” Example: Often quoted F.O.M. as long as jet energy resolution: BR2/s (R=RECAL; s = 1D resolution) i.e. transverse displacement of tracks/“granularity” B-field just spreads out energy deposits from charged particles in jet – not separating collinear particles Size more important – spreads out energy deposits from all particles R more important than B Used to justify ( in addition to optimise) SiD parameters BUT it is almost certainly wrong ! So where are we Until recently we did not have the software tools to optimise the detector from the point of view of Particle Flow This has changed ! The basic tools are mostly there: Mokka : now has scalable geometry as long as the LDC detector MARLIN: provides a nice ( in addition to simple) reconstruction framework LCIO: provides a common as long as mat as long as worldwide PFA studies SLIC: provides a G4 simulation framework to investigate other detector concepts (not just GLD, LDC in addition to SiD) Algorithms: in MARLIN framework already have ALGORITHMS as long as TPC tracking, clustering + PFA Some Caution: This optimisation needs care: can’t reach strong conclusions on the basis of a single algorithm A lot of work to be done on algorithms + PFA studies Not much time : aim to provide input to the detector outline We are now in the position to start to learn how to optimise the detector as long as PFA BUT : real progress as long as Snowmass (mainly from DESY group) Perfect Particle Flow What contributes to jet energy resolution in ideal “no confusion” case (i.e. use MC to assign hits to correct PFOs) Missed tracks not a negligible contribution !

Example : full PFA results in MARLIN (Alexei Raspereza) NOTE: currently achieving 0.40/E During Snowmass attempted to investigate PFA per as long as mance vs B-field as long as LDC 4 Tesla 2 Tesla 6 Tesla Not yet understood – more confusion in ECAL with higher field But could just be a flaw in algorithm .

PFA Studies in Near Future (Steve Magill, Felix Sefkow, Mark Thomson in addition to Graham Wilson) Proposal: Arrange monthly PFA phone conferences Forum as long as people as long as m to present/discuss recent progress Goal : realistic PFA optimisation studies as long as Bangalore ( in addition to beyond) Try in addition to involve all regions : need to study EACH detector per as long as mance with multiple algorithms First xday of each month 1600-1800 (CET) not ideal as long as all regions but probably the best compromise I will start to set up an email list next week We can make real in addition to rapid progress on underst in addition to ing what really drives PFA Provide significant input into the overall optimisation of the ILC detector concepts UK perspective: we could make a big impact here BUT need to start soon To date, UK input to detector concepts very limited ! At Snowmass, identified the main PFA questions Prioritised PFA list The A-List (in some order of priority) The B-List B-field : is BR2 the correct per as long as mance measure (probably not) ECAL radius TPC length Tracking efficiency How much HCAL – how many interactions lengths 4, 5, 6 Longitudinal segmentation – pattern recognition vs sampling frequency as long as calorimetric per as long as mance 7) Transverse segmentation 8) Compactness/gap size 9) HCAL absorber : Steel vs. W, Pb, U 10) Circular vs. Octagonal TPC (are the gaps important) 11) HCAL outside coil – probably makes no sense but worth demonstrating this (or otherwise) 12) TPC endplate thickness in addition to distance to ECAL 13) Material in VTX – how does this impact PFA Impact of dead material Impact (positive in addition to negative) of particle ID – (e.g. DIRC) How important are conversions, V0s in addition to kinks 4) Ability to reconstruct primary vertex in z (from discussions + LDC, GLD, SiD joint meeting) Goals as long as Vienna: Study HCAL granularity vs depth already started (AR) how many interaction lengths really needed ECAL granularity how much ultra-high granularity really helps granularity vs depth B-field dependence: Requires realistic as long as ward tracking (HIGH PRIORITY) Complete study of “perfect particle flow” Radial in addition to length dependence: Ideally with > 1 algorithm Try to better underst in addition to confusion term Breakdown into matrix of charged-photon-neutral hadron

Hale, Mike Monterey County Herald Features Editor & Food Writer www.phwiki.com

What can we do . LDC Franken-C Possible to make rapid progress ! Developing PFA algorithms isn’t trivial ! BUT to approach the current level Started writing generic PFA “framework” in MARLIN Designed to work on any detector concept Conclusions Calorimetry at ILC is an interesting problem Design driven by Particle Flow Only just beginning to learn what matters as long as PFA Significant opportunity as long as UK to make a big impact BUT need to start very soon

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