1 / 15

Physics Requirements for Calorimetry at a Linear Collider André S. Turcot

Physics Requirements for Calorimetry at a Linear Collider André S. Turcot Brookhaven National Lab Santa Cruz Linear Collider Retreat June 27-30 2002. Overview. There are key physics processes that set the performance requirements for the Linear Collider Calorimetry

iniko
Download Presentation

Physics Requirements for Calorimetry at a Linear Collider André S. Turcot

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physics Requirements for Calorimetry at a Linear Collider André S. Turcot Brookhaven National Lab Santa Cruz Linear Collider Retreat June 27-30 2002 UCSC Linear Collider Retreat

  2. Overview • There are key physics processes that set the performance requirements for the Linear Collider Calorimetry • In many cases, measurements will be statistics limited • To fully exploit the physics potential of the machine we will have to consider fully hadronic final states • In the following, I will try to give an overview of those processes where calorimetry will play a key role UCSC Linear Collider Retreat

  3. Physics Benchmarks • Higgs: • Precision Higgs physics will be statistics limited • Use of hadronic Z decays will be necessary • ElectroWeak: • Separation of Hadronic Gauge Boson Decays • Why? We must adopt the paradigm that the W/Z is a fundamental particle equivalent to the photon • Top Quark: • Reconstruction of 6 jet final states • Jet Energy Resolution/Reconstruction • SUSY Searches: Hermiticity, Missing ET Resolution • Precision EW: Luminosity Profile UCSC Linear Collider Retreat

  4. Energy Resolution? • Energy Resolution is not the true figure of merit • Physics is driven by jet resolution • e.g. D0 U/AR e/h = 1 • (EM) = 15%/E • (pion)  50%/E • Yet (jet)  80%-100%/E Calorimeter design should be guided by Jet Energy Resolution Current State of the Art is Energy Flow Analysis Requires highly segmented tracking calorimetry UCSC Linear Collider Retreat

  5. Hermeticity • Hermeticity enters in two key roles • Determination of the event missing energy • Tagging of scattered beam particles • SUSY drives the hermeticity issue • Two photon, ee -> eeff backgrounds will be problematic • Scattered e(s) in ee -> ee X can easily produce missing ET • ET(max) = EBEAM x sin  where  defines calorimeter fiducial • For 500 GeV and 40 mrad coverage, ETMISS can be up to 10 GeV Hermeticity in forward region will be crucial UCSC Linear Collider Retreat

  6. ZH WW Higgs Physics • Measurement of the hWW coupling requires separation vvh and Zh production channels • Missing mass is discriminating variable • e.g. BR(h->WW*) • Degrading the jet resolution from 30% to 60% corresponds to a factor 2 in luminosity • hZ production with hadronic Z final states have a large impact UCSC Linear Collider Retreat

  7. Higgs Physics Self Coupling • Flagship measurement for a Linear Collider • Verify shape of potential • Does the Higgs generate its own mass? • Critically depends on the calorimeter performance • 6j final state with 4 b jets • For 1 ab-1 and 60%/E jet resolution -> 3 sigma signal, • For 30%/E -> 6 sigma signal • Evidence vs. a measurement UCSC Linear Collider Retreat

  8. SUSY and Calorimetry • Consider two possible SUSY scenarios • “High” tan scenarios • multiple soft tau leptons • Tau ID could be a driving issue • Hermeticity will be critical as the ee xsec is enormous • Measurement of the tau polarization in cascade decays will provide a key insight • “Small” Gaugino mass differences: O(5) GeV • Small visible mass in final states! • Hermeticity in forward region again will be the critical issue • Irreducible eeqq bckgnds will require excellent visible mass resolution to isolate signal UCSC Linear Collider Retreat

  9. Further SUSY Considerations • Given that the SUSY breaking mechanism is a black box, we must be prepared for surprises • GMSB scenarios can produce non-pointing photons • Rely on calorimeter to determine Impact Parameter • Measure Gaugino lifetime (key input to any theory) • Quasi-degenerate Gauginos • Small visible mass, hermeticity will be essential UCSC Linear Collider Retreat

  10. Tau Physics • The Tau lepton will be a sensitive polarimeter for LC physics • However, most processes will be statistics limited • LEP expts. had 200K tau pairs, we will not be so blessed • Need ability to cleanly separate v and v final states • Could be critical depending on physics scenario that is realized • Tests of CP violation in Higgs decays • Stau NLSP scenarios • High tan solutions • Z’ effects for 3rd generation • More mundane level, tau ID and controlling jet fake rates • What is acceptable fake rate? 10-3 ? UCSC Linear Collider Retreat

  11. Gauge Boson Scattering • Measurement of the WL WL scattering amplitudes • Must cleanly distinguish between evWZ, vvZZ and vvWW using purely hadronic final states • relying on leptonic final states is not possible • Uninteresting evWZ 4x larger • Going from 30%/E to 60%/E corresponds to loosing 45% of the integrated L (Brient) evWZ vvWW vvZZ UCSC Linear Collider Retreat

  12. Gauge Boson Identification Videau, Calor2002 UCSC Linear Collider Retreat

  13. Top Quark Physics • Precise measurement of the Top Quark mass • There are two complementary techniques • Direct measurement above threshold (pole mass) • Requires good jet reconstruction efficiency • “Bootstrap” reconstruction • find jet pairs -> W, W+b -> top • Hadronic W mass resolution is important • Suppress 6-f final states and combinatorics • Recall LEP W mass measurement (4 jets -> 3 pairings) • Threshold scan requires precise dL/dE spectrum • Places premium on small angle bhabha scattering UCSC Linear Collider Retreat

  14. Timing Considerations • Depending on choice of machine technology timing information from the calorimeter may be necessary • Consider beam bunch structure • Tesla: 300 ns spacing in 1 ms trains @ 5 Hz • NLC/JLC: 2ns spacing in 300 ns trains @ 180 Hz • May need to suppress contribution from 2-photon events in different bunches • Topologies such at () ETmiss require ability to veto cosmics • Depends details of signal integration times • Time-of-flight may be useful for quasi-stable massive charged particles UCSC Linear Collider Retreat

  15. Conclusions • To fully realize the physics potential of a linear collider we will have to rely reconstructing fully hadronic final states • Given the fundamental nature of the W and Z bosons we must accept a new paradigm that they must be fully reconstructable and distinguishable in complex events • In many key physics processes, the figure of merit is the jet energy resolution • Our current understanding of jet energy resolution points to a solution relying upon an Energy Flow Algorithm • Any proposed calorimeter must be amenable to the implementation of an Energy Flow analysis UCSC Linear Collider Retreat

More Related