PhD students meeting 01/27/2010 Philippe Doublet 1 Designing a detector for a future e - e + linear collider Precision measurements based on Particle Flow & high granularity calorimeters.

PhD students meeting 01/27/2010 Philippe Doublet 2 News of particle physics From the report of the High Energy Physics Advisory Panel (2004) 1 Are there undiscovered principles of nature : new symmetries, new physical laws? 2 How can we solve the mystery of dark energy? 3 Are there extra dimensions of space? 4 Do all the forces become one? 5 Why are there so many kinds of particles? 6 What is dark matter? How can we make it in the laboratory? 7 What are neutrinos telling us? 8 How did the universe come to be? 9 What happened to the antimatter?

PhD students meeting 01/27/2010 Philippe Doublet 3 An e - e + collider at the Terascale New discoveries are expected at the Terascale i.e. energies O(1 TeV) : –WW scattering Historically, combining results of proton colliders with electron colliders has led to great progresses and discoveries. –An e-e+ collider will precisely measure what will be discovered at LHC 12 August 1999 Scientific panels charged with studying future directions for particle physics in Europe, Japan, and the United States have concluded that there would be compelling and unique scientific opportunities at a linear electron- positron collider in the TeV energy range. Such a facility is a necessary complement to the LHC hadron collider now under construction at CERN. Experimental results over the last decade from the electron-positron colliders LEP and SLC combined with those from the Tevatron, a hadron collider, have led to this worldwide consensus.

PhD students meeting 01/27/2010 Philippe Doublet 4 Why an e - e + collider ? Excellent knowledge of the initial state Direct probe of the couplings and/or new particles (via loops, Z’, …)

PhD students meeting 01/27/2010 Philippe Doublet 5 Why linear ? Energy losses per orbit via synchrotron radiation :  E α γ 4 /R For a given energy and radius, E loss,e- / E loss,proton = (m proton /m e- ) 4 ~ To compensate, need R  ~10 13 R ! If E  2 E, then  E  16  E ! LEP : E max,e- ~ 104 GeV, R = 4.3 km : maximum radius considering energy losses  go to linear

PhD students meeting 01/27/2010 Philippe Doublet 6 Properties of the International Linear Collider √s up to 500 GeV (possible upgrade at 1TeV ) –Range of energy : 90 GeV  500 GeV –Use of superconductive technology Must be able to tune energy : –top threshold scan –Higgs –SUSY particles Luminosity L = cm -2 s -1 –Expected after 4 years : L = 500fb -1 at 500 GeV 80% polarised electrons : –Left – right production asymmetries –Suppress backgrounds

PhD students meeting 01/27/2010 Philippe Doublet 7 Physics goal of an e - e + collider Higgs –Mass, width, couplings (branching ratios), spin –Also study of ZHH Top quark –Mass, cross-section, A FB t, A LR t WW scattering at 1 TeV SUSY mass spectrum Other BSM scenarios : –Z’ –4 th generation –… Higgs-Strahlung process to study the Higgs Top quark production

PhD students meeting 01/27/2010 Philippe Doublet 8 Example for the Higgs Study of Higgs-Strahlung –L = 250fb -1, √s = 250 GeV, m H = 120 GeV Higgs recoil mass with Z  µ + µ - Hengne Li, LAL ~600 MeV expected mass resolution (µ + e channels, model independant, 30 MeV precision) ~2% precision on the cross-section S/N ~ 2.3 S/√(S+N) ~ 48

PhD students meeting 01/27/2010 Philippe Doublet 9 My next study : top production Top mass : combining semileptonic decays and hadronic decays of the W give  m t ~ 30 MeV (stat.) Top cross section : 0.4% uncertainty (stat.) W  lv (leptonic decay of the W) W  qq’ (hadronic decay of the W) Reconstructed top mass (semileptonic events) ILD LOI

PhD students meeting 01/27/2010 Philippe Doublet 10 Structure of the ILD detector 3D view of the proposed ILD detector

PhD students meeting 01/27/2010 Philippe Doublet 11 Requirements for subdetectors Tracking (vertex detector + main tracker) –Excellent measure of p of charged tracks, do b(c)-tagging –Momentum : δp/p² < 5x10 -5 GeV -1 Calorimetry (ECAL + HCAL ) –Measure energy of the particles via their energy deposition (especially photons and neutral hadrons) –Energy : σ E /E < 3 to 4% (combining tracker + calorimeters) Magnetic field (coil + return yoke) –3.5 Tesla magnetic field ( ~ CMS coil) What drives the requirements ? Particle flow

PhD students meeting 01/27/2010 Philippe Doublet 12 Using the Particle Flow approach Final states at ILC : –mainly multi-boson (ZH, WW, ZZ, ZHH, ZWW, ZZZ) –or fermions + bosons (eeH, eeZ, tt, ttH, ννWW, ννZZ) M W ~80GeV, M Z ~91GeV, M H >115GeV –Performance depends on mass resolution of the jets –Need to reconstruct ALL the particles ~68% ~70%  JETS

PhD students meeting 01/27/2010 Philippe Doublet 13 How to reconstruct all final state particles ? 1)Associate charged tracks and clusters (tracker + E/HCAL) 2)Reconstruct the photons (ECAL) 3)Reconstruct neutral hadrons (E/HCAL) Why ? –E jet = 65% charged + 26% photons + 9% neutral h. Need excellent tracker and very good E/HCAL Example of particle separation ECAL HCAL γ π+π+ KLKL

PhD students meeting 01/27/2010 Philippe Doublet 14 Concept driven by the particle flow Di-jet masses for separation of WW and ZZ di-boson events ALEPH-like detectorILD-like detector

PhD students meeting 01/27/2010 Philippe Doublet 15 Challenges for an ILC detector Measure bosons very well (tt  bWbW, ZH, ZHH, ννWW, ννZZ, ttH, …) Particle Flow concept –Reconstruct every particle –Associate the particles to jets Need an excellent W/Z separation –Momentum : δp/p² < 5x10 -5 GeV -1 –Energy : σ E /E < 3 to 4% factor 2 times better than LEP ~50% less luminosity needed –Impact parameter (b&c-tagging)

PhD students meeting 01/27/2010 Philippe Doublet 16 What about prototypes ? Principle : –high granularity to separate showers on a topological basis (see neutrals’ contributions inside the shower) Goal : –build prototypes to validate high granularity concept Huge energy fluctuations in showers e/h ratio not well known : don’t fully rely on energy but geometry Validate models of hadronic showers Prototypes exist and have been intensively used under testbeams

PhD students meeting 01/27/2010 Philippe Doublet 17 Calorimeters under testbeams Testbeam periods at DESY, CERN ( ) and FNAL (2008) Goals : energy, position and angular resolution, validation of hadronic shower models The calorimeters tested at Fermilab in May Si-W ECAL, Analog HCAL : fibers and scintillating tiles, Tail Catcher : fibers and scintillating strips.  A 120 GeV proton event

PhD students meeting 01/27/2010 Philippe Doublet 18 The Si-W ECAL prototype Sandwich structure of W (absorber) and Si (detector) 30 layers 1 cm x 1 cm Si pixels –9720 channels 3 W depths  3 stacks –Molière radius, R M = 0.9 cm Total depth = 24X 0 ~ 1λ I –Full containment of EM showers –~ 2/3 of the hadrons may interact in the ECAL

PhD students meeting 01/27/2010 Philippe Doublet 19 Results for the ECAL Resolution studies done with electrons Linearity within 1% Data & MC agree Energy resolution studies

PhD students meeting 01/27/2010 Philippe Doublet 20 Why study hadronic showers in the ECAL ? Bad knowledge of hadronic showers, very complex environment 1 x 1 cm² pixels –Tracking possibilities –Look inside showers

PhD students meeting 01/27/2010 Philippe Doublet 21 Using the granularity of the ECAL Applied to hadrons –Identify MIPs i.e. particles passing through the ECAL with a minimum deposited energy (easy) –Find hadronic interactions (medium) –Disentangle several kinds of hadronic interactions (hard) My work : pions, 1 GeV < E < 10 GeV 2D views of a pion interacting in the ECAL. Structure : MIP – interaction - cluster

PhD students meeting 01/27/2010 Philippe Doublet 22 Procedure developped 1.Identify a MIP 2.Delimit the interaction region 3.Define the structure of the shower Work done so far : Development of an algorithm : « MipFinder » Getting the interaction layer Describe the shower (ongoing) Learning : C++, SM, extra dimensions, …

PhD students meeting 01/27/2010 Philippe Doublet 23 Benchmark for the MipFinder Count the number of entering particles Done with muon and pion runs, data & MC Figures : 1.(top) Efficiency of the MipFinder with 10 GeV simulated muons 2.(bottom) Fraction of events of 0, 1, 2 and 3+ particles entering the ECAL at FNAL Algorithm validated

PhD students meeting 01/27/2010 Philippe Doublet 24 Finding the interaction region First step : find the interaction layer –3 physics lists used (~30,000 events each for every energy) –Data selected among TB done at FNAL (>100,000 events per energy) *not shown here* –Discrepancies seen at 2 GeV (bad hadronic models at low energies) Simulation of 2 GeV pions Interaction layer found by the algorithm for 3 different physics list of Geant4

PhD students meeting 01/27/2010 Philippe Doublet 25 My future work & one step beyond Describe the interaction region and further Work on simulated events for ILD : e - e +  tt for the search of extra dimensions Get PhD ! About the ECAL, ILD, ILC : –New technological prototype of the ECAL being developed « the EUDET module » –ILD concept validated, now moving towards detailed design with more realistic simulations

PhD students meeting 01/27/2010 Philippe Doublet 26 For you to remember Future e - e + linear collider for precision measurements and discoveries Studies of WW scattering, top quark, Higgs, new physics Detector based on the particle flow approach (reconstruct every particle to form jets) Successful runs of particle flow Si-W ECAL with potential for hadronic shower studies