Plans for Linear Collider Calorimetry Test Beam Work at Fermilab
Physics Requirements for Calorimetry at a Linear Collider André S. Turcot
description
Transcript of Physics Requirements for Calorimetry at a Linear Collider André S. Turcot
![Page 1: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/1.jpg)
June 28, 2002 UCSC Linear Collider Retreat
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
![Page 2: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/2.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 3: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/3.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 4: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/4.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 5: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/5.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 6: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/6.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
Higgs Physics
ZH WW
• 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
![Page 7: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/7.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 8: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/8.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 9: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/9.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 10: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/10.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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 ?
![Page 11: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/11.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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)
vvWW
vvZZ
evWZ
![Page 12: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/12.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
Gauge Boson Identification
Videau, Calor2002
![Page 13: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/13.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 14: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/14.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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
![Page 15: Physics Requirements for Calorimetry at a Linear Collider André S. Turcot](https://reader036.fdocuments.us/reader036/viewer/2022081512/56814dbe550346895dbb147a/html5/thumbnails/15.jpg)
June 28, 2002 UCSC Linear Collider Retreat
André S. Turcot
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