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Designing a detector for a future e - e + linear collider

Precision measurements based on Particle Flow & high granularity calorimeters. Designing a detector for a future e - e + linear collider. News of particle physics. From the report of the High Energy Physics Advisory Panel (2004).

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Designing a detector for a future e - e + linear collider

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  1. Precision measurements based on Particle Flow & high granularity calorimeters. Designing a detector for a future e-e+ linear collider 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? 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. 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’, …) Philippe Doublet

  5. Why linear ? • Energy losses per orbit via synchrotron radiation : E αγ4/R • For a given energy and radius, Eloss,e- / Eloss,proton = (mproton/me-)4 ~ 1013 • To compensate, need R~1013R ! • If E  2 E, then E  16 E ! • LEP : Emax,e- ~ 104 GeV, R = 4.3 km : maximum radius considering energy losses  go to linear 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 = 1034 cm-2s-1 • Expected after 4 years : L = 500fb-1 at 500 GeV • 80% polarised electrons : • Left – right production asymmetries • Suppress backgrounds 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, AFBt , ALRt • WW scattering at 1 TeV • SUSY mass spectrum • Other BSM scenarios : • Z’ • 4th generation • … Higgs-Strahlung process to study the Higgs Top quark production Philippe Doublet

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

  9. My next study : top production • Top mass : combining semileptonic decays and hadronic decays of the W give mt ~ 30 MeV (stat.) • Top cross section : 0.4% uncertainty (stat.) ILD LOI Wlv (leptonic decay of the W) Wqq’ (hadronic decay of the W) Reconstructed top mass (semileptonic events) Philippe Doublet

  10. Structure of the ILD detector 3D view of the proposed ILD detector 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 : σE/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 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) • MW~80GeV, MZ~91GeV, MH>115GeV • Performance depends on mass resolution of the jets • Need to reconstruct ALL the particles ~68%  JETS ~70% Philippe Doublet

  13. Associate charged tracks and clusters (tracker + E/HCAL) Reconstruct the photons (ECAL) Reconstruct neutral hadrons (E/HCAL) Why ? Ejet = 65% charged + 26% photons + 9% neutral h. Need excellent tracker and very good E/HCAL Example of particle separation How to reconstruct all final state particles ? KL HCAL ECAL π+ γ Philippe Doublet

  14. Concept driven by the particle flow Di-jet masses for separation of WW and ZZ di-boson events ALEPH-like detector ILD-like detector 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 : σE/E < 3 to 4% • factor 2 times better than LEP • ~50% less luminosity needed • Impact parameter (b&c-tagging) 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 Philippe Doublet

  17. Calorimeters under testbeams • Testbeam periods at DESY, CERN (2006-07) and FNAL (2008) • Goals : energy, position and angular resolution, validation of hadronic shower models The calorimeters tested at Fermilab in May 2008. Si-W ECAL, Analog HCAL : fibers and scintillating tiles, Tail Catcher : fibers and scintillating strips.  A 120 GeV proton event 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, RM = 0.9 cm • Total depth = 24X0 ~ 1λI • Full containment of EM showers • ~ 2/3 of the hadrons may interact in the ECAL Philippe Doublet

  19. Results for the ECAL • Resolution studies done with electrons • Linearity within 1% • Data & MC agree Energy resolution studies 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 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 Philippe Doublet

  22. Procedure developped • Identify a MIP • Delimit the interaction region • 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, … Philippe Doublet

  23. Going further in using the granularity ? • Count the number of entering particles • See different kind of interactions Figures : • (top) A 2 GeV pion interacting « strongly » in the ECAL • (bottom) A 2 GeV pion with a « bifurcation » in the ECAL Seen for the first time here Philippe Doublet

  24. Comparing shower contents • Once the interaction is found, compare the longitudinal profile of data with Monte Carlo simulations. • Several MC  differences between sets of simulations • We want to optimise them to get the closest to reality. Simulation of 10 GeV pions + real data : longitudinal profile of energy deposition Dots = real dataColours = content of the shower (electromagnetic, protons, mesons, others) 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 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 Philippe Doublet

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