Future e e linear colliders - University of Victoriakarlen/talks/lc/york00.pdf · 2009. 10. 27. ·...

Future e+e− linear colliders

IPP Forward Planning MeetingJune 3, 2000

York University

Dean Karlen / Carleton Universitywww.physics.carleton.ca/~karlen/lc

Future linear colliders Dean Karlen / June 3, 2000 2

Outline

• Review of proposals for a TeV scale e+e−

collider:– NLC/JLC, TESLA, CLIC

• Physics opportunities at a future e+e− collider• Detector concepts• International coordination• Canadian activities• Summary


TeV scale e+e− colliders

• NLC/JLC– US/Japan collaboration on a high frequency, warm

accelerating structure• TESLA

– DESY collaboration on a lower frequency, super conducting accelerator

• CLIC– two beam accelerator, capable of higher gradients

• See Tom Mattison’s talk: MO-A5-4


NLC/JLC• SLAC, LLNL, LBNL, FNAL, KEK• NLC R&D budget: $17M• Ecm= 500 GeV, L = 5×1033 cm-2 s-1

– higher lumi (×4) possible– later, increase to 1 TeV by

installing full linac– upgrade routes to 1.5 TeV

• Technology based on results from test facilities

• Incorporates knowledge gained from SLC operation


NLC progress

• Positive Lehman review in May 1999– recommends proceeding to CDR phase– congress stops move to CD

• Since then, further optimization– Cost reduction: $5.1B → $3.5B

• possible timeline:– FY2002: release 2-site CDR– FY2004: construction start


TESLA• Lead institute: DESY• Lower frequency (1.3 GHz),

superconducting cavities• Lower gradient (25 - 34 MV/m)• Initially: Ecm= 500 GeV

L = 3×1034 cm-2 s-1

• Later: Ecm= 800 GeVL = 5×1034 cm-2 s-1

• Lower wakefields• Looser tolerances• Higher luminosity


TESLA plans

• Design and cost optimization underway• Two sites under consideration (DESY, FNAL)• possible timeline:

– 2001: release TDR with accurate costing– 2003: construction start


CLIC

• Lead institution: CERN• Goal: Ecm= 0.5 - 5.0 TeV , L = 1035 cm-2 s-1

• High frequency (30 GHz) normal conducting• Extracts RF power from a high intensity, low

energy, parallel drive beam• High gradient (150 MV/m): 30 km length


CLIC plans


TeV collider summary

• By building prototype test accelerators, the US/Japan and TESLA groups have demonstrated their designs are capable of achieving the necessary gradients.

• Final focus test beam studies at SLAC have demonstrated techniques to focus the beams to nanometer dimensions in order to attain the necessary luminosity.

• The common goal, to build a 0.5-1.5 TeVenergy collider with luminosities exceeding 1034 cm-2 s-1, is within reach.


Physics opportunities• A complementary facility to the LHC

– brings new information to clarify discoveries of the LHC experiments

• A rich physics program of its own– Ecm = 100, 350, > 500 GeV– precision top quark studies– ideal machine for examining a light Higgs– precision electroweak measurements– access to new physics at the TeV scale

•• Unnecessary to wait for LHC results before Unnecessary to wait for LHC results before proceeding with a future linear proceeding with a future linear collidercollider


Examination of the Higgs

• Precision measurements are consistent with a light SM Higgs boson– mH > 108 GeV at 95%CL (direct: searches)– mH < 190 GeV at 95% CL (indirect: radiative corr.)

• no proof that it exists, but if not the SM Higgs, something new (at a similar mass scale) must provide the extra contributions to the observables (and render the physics renormalizable).



• Produced by Higgs-strahlung and Fusion

– Z0 provides tag of Higgs-strahlung process– recoil mass peak gives model independent signal– Ecm = 350 GeV well suited for light Higgs studies

ZHZee →→−+ * νν→ −+−+ HeHeee ,


Recoil masses

XHZee −+−+ µµ→→ 00 bbqqHZee →→−+ 00

with 5C fitδmH ~ 50 MeV

Ecm = 350 GeVL = 500 fb−1


Examination of the Higgs• If Higgs not seen at the LHC/Tevatron:

– A light Higgs in non-SM scenarios could have substantially reduced production rates or difficult (eg. invisible) decay modes

– A linear collider could solve the puzzle by observing the recoil mass peak from H0Z0 events

• If Higgs discovered at the LHC/Tevatron:– SM, SUSY, or other sort of Higgs?– Measure Higgs branching ratios to test if its

coupling is proportional to mass– SUSY Higgs BRs depend on SUSY parameters

• indirect sensitivity to mA up to 700 GeV


Precision of Higgs BRs



• Total width:– use:

• check that H0-V-V coupling follows SM by comparing Higgs-strahlung (and Fusion) cross sections to SM predictions

• Higgs self coupling: – σ(ZHH) ≈ 0.3 fb

• Higgs - top Yukawa coupling:– 10% measurement possible

)()( *0*00 WWHBRWWHSMH →→Γ=Γ

ZHHZHZee →→→−+ **

Httee →−+


Multiple Higgs

• No reason not to have several scalar fields responsible for the Z and W masses.

• Experiments at a linear collider can discover the complete set, and show that they alone are responsible for the Z and W masses:– If the process has a cross

section fi times the SM cross section then one knows that the full set of scalars have been observed once

0*iZhZee →→−+

1=∑i

if


Top quark physics

• important to measure top quark as accurately as possible:– necessary to accurately calculate virtual top quark

contributionsδmtop ≈150 MeV achievable in 50 fb-1

– c.f. 1 - 2 GeV at LHCδΓtop / Γtop ≈10%

• Static parameters:– magnetic moment, EDM, decay structure

(V+A / V-A): measurable to a few percent


Precision electroweak measurements

• Fermion pair production– sensitive to Z´, W´, R-parity violation, leptoquarks– sensitivity reaches beyond √s

• for example, LC is sensitive to Z´ if mZ´ < 5 -10 √s

– can distinguish mechanism with AFB, ALR, t & τ pol.• W pair production

– a gain by 2 orders in magnitude in the sensitivity to anomalous couplings in the gauge sector

• Return to the Z0 peak and W W threshold– 30 fb−1 at Z0 peak → 109 Z0 in a few months– with 80% (60%) e− (e+) pol. → δsin2θeff ≈ 0.00001

mtop (GeV)165 170 175 180 185

sin2

θ eff

0.2300

0.2305

0.2310

0.2315

0.2320

0.2325

SMMSSMNow+LHC+LC+GIGA Z

Now +LHC +LC +Z0,W+

δMW 30 MeV 15 MeV 15 MeV 6 MeV

δsin2θeff 0.00017 0.00017 0.00017 0.00001

δmt 5 GeV 2 GeV 0.2 GeV 0.2 GeV

68% C.L.


Supersymmetry• If superpartners are discovered at LHC, the

powerful measurements from a linear collider will be required to fully understand the new Supersymmetric Standard Model.– cross section measurements verify the spins and

SU(2)xU(1) quantum numbers of the new states– through adjustment of Ecm and polarisation,

specific states can be preferentially selected– mixing angles determined by varying polarisation– blind spots in LHC could be uncovered:

• mass degenerate scenarios• GMSB models with semi-stable sparticles


Detector concepts

• Physics– ZH: b-tag, c-tag, recoil and jet-jet mass resolution– SUSY: missing pt, isolated photons

• hermetic coverage down to 100 mrad important

• Technology– not a primary issue: not as challenging as LHC– LEP/SLD experiments work well at Ecm = 200 GeV

• Collider design:– timing information: avoid event overlap from

separate BX: TESLA 300 ns, NLC 3 ns– backgrounds


Vertex detector

• charm tagging (light Higgs, W) is a challenge– prime motivator for bringing in vertex detector as

close as possible• leading candidate: CCDs (success at SLD)


Central tracking– Drift chamber considered by Asian LC group– Experience with DC at SLC: occupancy can be

intolerable: a TPC can cope much better• TESLA and NLC “L” designs specify a large TPC

– All silicon tracking considered for NLC “S” design• SDD or µstrip• 4-6 T field

NLC S design

NLC L design


Detector concepts

• Calorimetry– high granularity 3D imaging design favoured– eg. European design:

• EM cal: Si-W 1×1 cm2 with 40 layers • Had cal: Fe tiles, 5×5 cm2 with

– excellent energy flow measurements• Trigger

– no trigger necessary: Record everything.– (no gating of TPC)


International Coordination

• Three collider projects will be proposed for the near future (JLC, NLC, TESLA)– at most one of these will be built… LC community

expected to participate at whichever one it is– Physicists from the different regions collaborate to

define physics case and design detector


Workshops in 2000

• International and regional meetings are being held frequently to work towards CDR, TDR

• International:– October 22 - 27, Fermilab

• North America:– March 29 - 31, LBL

• Europe:– May 5 - 8, Padova; September 22 - 25, DESY

• Asia:– August 9 - 11, Taipai


Canadian activities

• NSERC IOF grant supports Canadian participation in linear collider workshops:– R. Carnegie, M. Dixit, S. Godfrey, D. Karlen,

P. Kalyniak, H. Mes (Carleton)– T. Mattison (UBC)

• Magnet vibration control system:– T. Mattison (UBC)

• TPC readout using gas electron multipliers:– R. Carnegie, M. Dixit, D. Karlen, M. Losty, H. Mes

(Carleton)


Vibration control system

• The small vertical beam sizes (few nm) necessitate an accurate vibration control system for the linear collider magnets near the interaction point.

• Tom Mattison (UBC) is studying the feasibility of a 10 m baseline laser interferometer to control the vibration of heavy objects at the nanometer scale– is receiving support from NSERC and SLAC


Vibration control system

• Optical anchor setup


Vibration control system• Labview program

fits the observed interference pattern

• Simulation of 1nm oscillations

• Fitting algorithm correctly tracks the motion


GEM readout for the TPC

• GEM consists of thin insulating sheet with both sides metalized, holes etched through

• A voltage difference applied across the two surfaces provides gas gain of up to 1000



• Advantages of GEM readout:– improved transverse resolution: no E × B effects– improved two track separation:

• smaller pad structures, smaller region of induced signals• faster pulses

– can operate in ungated mode with little positive ion feedback into the TPC

• necessary for untriggered data acquisition

– reduced material in endcap (no wires under tension)



• Electrons drift to one or more pads, and short signals are induced in the neighbouring pads– fast preamplifiers are necessary– to achieve optimal resolution, the position is

determined by weighting the direct and induced pulses

• Test set up:– A double GEM strip and pad readout is under study

at Carleton University– a collimated x-ray source provides primary ionization


GEM test setup• Data from strip readout (1.5 mm pitch)

– averaged to cancel noise

time (s)

-5.0e-7 -2.5e-7 0.0 2.5e-7 5.0e-7 7.5e-7 1.0e-6

sign

al

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

Centre strip

1st neighbour

2nd neighbour


Next 5 years and beyond...

• Vibration control work will continue (NSERC and SLAC funding received)

• GEM readout of TPC will continue if funding awarded

• Once the linear collider project is approved, expect to see great interest in IPP community to participate:– natural follow up to the OPAL experiment– potential to become the 2nd largest IPP collider

experiment (after ATLAS)


Summary

• LC technology to build a 0.5 - 1 TeV e+e−

collider has been demonstrated– expect detailed, costed designs over next 2 years

• Strong physics case exists• Canadians are participating now

– to ensure some key roles in this important project• A first phase LC (500 GeV) may be near

– construction could begin before LHC turn on – plan phase 2 in conjunction with LHC results

• See www.physics.carleton.ca/~karlen/lc

Future e e linear colliders - University of Victoriakarlen/talks/lc/york00.pdf · 2009. 10. 27. ·...

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