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A.De RoeckCERN

SLAC, MDI meeting, January 2005

Physics Options Overviewfor the ILC

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Physics Case for New High Energy Machines

Reminder: The Standard Model - tells us how but not why (contains 19 parameters!) 3 flavour families? Mass spectra? Hierarchy? - needs fine tuning of parameters to level of 10-30 ! - no unification of the forces at high energy

If a Higgs field exists: - Supersymmetry - Extra space dimensions If there is no Higgs below ~ 700 GeV - Strong electroweak symmetry breaking around 1 TeV Other ideas: more gauge bosons/quark & lepton substructure, Little Higgs models…

SM

SUSY

Understand the mechanism Electroweak Symmetry Breaking

Discover physics beyond the Standard Model

Most popular extensions these days

What is the origin of mass of the fundamental particles?

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The ILC• ILC world wide consensus for a baseline linear collider with a

centre of mass energy up to 500 GeV and a luminosity above 1034cm-2s-1

• However the ILC will be much more – Its required flexibility/tunability in CMS energy, and additional options will greatly enhance its physics potential for precision EWSB studies, or disentangling the new physics– The baseline & options have been outlined in the document parameters for the linear collider

Special studies and/or R&D for these options is required (and ongoing) We do not know for sure what path Nature has chosen, hence the priority and importance these options will become clear with the data of the LHC and first data of the ILC. The implications of these options on machine, MDI and detectors should be taken into account –where possible - from the start.

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ILC Parameters & options

• Baseline ILC– Minimum energy of 500 GeV, with int. luminosity of 500 fb-1 in the first 4 years– Scan energies between from LEP2 till new energy range: 200-500 GeV with a

luminosity ~ s. Switch over should be quick (max 10% of data taking time)– Beam energy stability should be to less than 0.1%.– Electron beam polarization with at least 80%– Two interaction regions should be planned for– Should allow for calibration running at the Z (s = 90 GeV)– Upgrade: Energy upgrade up to ~ 1 TeV with high luminosity should be

planned

• Options beyond the baseline: enhance the physics reach– Running as an e-e- collider– Running as a e or collider– Polarization of the positron beam– Running at Z0 with a luminosity of several 1033cm-2s-1 (GigaZ)– Running at WW mass threshold with a luminosity of a few times 1033cm-2s-1

– (not in the document) Extendability to multi-TeV??

Several years of intense physics studies have led to:

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Interaction Regions

baseline recommendation for the ILC parameters for two interaction regions

(KEK)

November 04

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Interaction regions

• How symmetric should these interaction regions be (for physics)?• High versus low energy IR?• Simultaneous or staged running? As an experimentalist on LEP, HERA, LHC I believe that

– Both experiments will want to measure e+e- collisions at the maximum ILC energy

– Both experiments will want to have data as soon as they are ready (even before)

• Simultaneous like running will be preferred if not a technically nightmare and if the efficiency to collect good data is acceptable, especially at the start. (Moenig/Stahl: worry about polarization?)

So I would not give up on that option (yet).• Ideally: experiments have a specialization. Eg. one may include

gamma-gamma in its baseline design, or may optimize detector more for Z runs

May help to decide on which experiment goes to what IR• Cost of 2nd interaction region? (~10%?)

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e-e- collisions

Advantages of e-e-: Large polarization for both beams: eL,eR

Large polarization of the e- beam Work with fundamental fields of particles with well defined handiness Exotic quantum numbers (H--) Larger sensitivity in some processes Some very clean processes

No s-channel, lower luminosity

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e-e- optionHiggs production

Supersymmetry

measurementof CP violatingphases

Note: before detector simulation, IR, beamstrahlung, selectron width…

Heusch

Minkowski

Mass reconstructedfrom tagged electronsneeds good forwarddetector coveragedown to a few degrees

Thomas

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e-e-option

Non-Commutative QED Sensitivity to contact interactions

…Majorana neutrinos

…for equal luminosities

Hewett, Petriollo, Rizzo

Heusch Minkowski

Barklow

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e-e- optionParameters (Snowmass 2001)Study for TESLA (S. Schreiber)

Luminosity 5-(10)•1033 cm-2 s-1

L e-e- = 1/6 –(1/3) L e+e-

Stability ~OK with intra-train feedback system

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e-e- option

Clem Heusch’s dream:Future control room at the ILC??

No ‘major’ changesrequired in IPor accelerator butneed to include spent beam kicker magnets? feedback system second e-source …

e-e- is the optionwhich should beeasy to realize

Has to be revisitedduring the MDI discussions to keep on the roadmap

S. Schreiber

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The photon collider option

and e option

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Gamma-gamma and e-gamma

Compton backscattering on laser photons Peaked but smeared energy spectrum Highly polarised photon beams

However: needs extra effort Is it worthwile? Jeju LCWS02 panel discusion: Yes!

Examples of advantages Higher cross sections for charg. particles Different JPC state than in e+e- Higgs s-channel produced! Higher mass reach in some scenarios Pure QED interaction (in e+e- also Z exchange) Higher polarization of initial state (>80%/beam) CP analysis opportunities (linear polarization…)

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Parameters for the TESLA design

Since in collisionsthe electron beams do not meet (and self-destroy)one can reach highergeometrical luminositiesby focusing stronger andhave a smaller emittance(round beams) than in e+e-/e-e- optics

Only the high energy part is of interest for the luminosity!

z=W/2Ebeam

V. Telnov

Both beams are e-

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Golden Processes for a Photon Collider

Higgs

SUSY

EDs,…

Trilin.coupl.

Top

QCD

Boos et al.,hep-ph/0103090

ADR (ECFA/DESY) hep-ph/0311138

Added value to an e+e- collider

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Example: Higgs

The precise measurement of the 2-photon width of the Higgs isvery important.It is affected by all charged particles that can occur in the loop Very sensitive to new physics

New physics effects are few % to 10%

QCD bb in suppression: V. Khoze,…

Krawczyk et al., Moenig et al.

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Example: MSSM Higgses H,A

e+e- collider: H,A produced in pairs, hence MA reach is see/2 collider: s-channel production, hence MA reach is 0.8•see

Photon collider only option to close the wedge for masses up to ~800GeV

Minimal Supersymmetric SM: 5 Higgses: h,H (CP even), A (CP odd) and H

PC: Measurement of / to 10-20% (1 year running)

Krawczyk et al

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SUSY example

e+e-: reach is s/2e: reach is 0.8s - M(LSP)

Can extend the mass range by 100-200 GeV if LSP is light

M(LSP) = 100 GeV

Extended reach for sleptons Watanabe et al.

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The Photon Collider Option

Special requirements for a Photon Collider at the ILC• Crossing angle between the beams should be O(25-30mrad), for the

removal of the disrupted beams, (angle > disruption + Rquad/L ~0.01+6/400 ~ 0.025)

• Product of horizontal and vertical emittance should be as small as possible to allow for high luminosity

• Final focus: as small as possible spot size at IR (reduce horizontal function by order of magnitude compared to e+e-)

• Beam dump: cannot deflect photon beam narrow photon beam in a straight line from the IR

• Modified detector in the region < 100 mrad, including the vacuum pipe and vertex detector

• Space needed for laser beam lines and housing

Summary letter sent to the ISCLC in July 04, after LCWS04

Proposal of the PC study contact persons and workgroup convenors Design the 2nd IR optimized for a PC, but keep full compatibility of the FFS to allow to run also in e+e- mode (horizontal function). Detector to be designed to operate in both modes, with easy transition

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Interaction region

Mask and laser optical paths designs

Study of beam related background: e+e- pairs, overlap events, neutrons

# of hits in the layers of pixel detector Incoherent pair production: essentially the same as for e+e- Coherent pair production: High! but ok, similar to e+e- (Moenig,Sekaric)

same vertex detector as for e+e- Neutrons? Under study (V. Telnov)

K. Moenig et al.

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G. KlemzOptical cavityto storelaserpulses(TESLA)

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Beam Dump Design

V. TelnovSee talk tomorrow

Angular divergences of disrupted beams

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PC R&D• Photon collider IP introduces new challenges

– Laser & Optics– Stability/control in IR (1nm), cavity length control, alignment,

feedback…– Extraction line, beam dumps… Opportunities also for university projects/contributions

• Important to involve laser expert community (LLNL, others)– Some collaboration established but need intensifying– Hardware e.g. (reduced size) cavity or focus region needs to be

tested– Suitable lasers (prototypes) need to be tested

• Some related activities – LLNL plan to work on cavities to generate sufficient laser power for

making a positron source via Compton scattering; Gain experience with high power issues, critical for PC lasers

– Orsay: build a laser resonator for a polarimeter, as part of EuroTeVWorld wide organized R&D for this option is needed

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Polarized Positrons

• Polarization of the electron beam in base-line program– Techniques have been already succesfully (SLC)– Allows to reduce background/enhance signal for s-channel

processes– Allows e.g. for LR measurements in s-channel processes, single

spin asymmetries, measurements of couplings…• Polarization of the positron beam

– Techniques in R&D phase (helical undulator, Compton scattering)– Increases the effective polarization– Reduce the uncertainty of the polarization

• By error propagation (factor 3-4) eg. for Pe-=80% and Pe+=-60% Peff=95% Peff/Peff~1/3P/P

• By using the Blondel scheme

See K. Moeing talk

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Polarized Positrons: Physics Topic Examples

• High precision analysis in the SM– Triple gauge couplings in e+e-Z– Anomalous couplings in e+e- W+W-– Transversely polarized beams in e+e- W+W-, graviton

effects– GigaZ (see later)– Sensitivity to CP violation the SM

• Revealing the structure of SUSY– Quantum numbers in e+e- selectron pairs– Stop mixing angle in e+e- stop pairs– Study of the chiral structure of the Gaugino/Higgsino sector polarization (large tan case)– CP phase determination in stau sector– Identification of extended susy scenarios

• Enhancing reach for extra dimensions in e.g. e+e-G, etc, etc..Report from the POWER group being released soon

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Polarized Positrons: ExamplesTest if the sparticles have the same chiral quantum numbers as their SM partners

Disentangle

from

with polarized e+

Discovery:Look for kinematicedges in inclusivemuon distribution! WW background !

G. Moortgat-pick

U. Nauenberg et al

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Polarized Positrons: Examples

Z’ couplings from e+e-ff Backgroundno polarizatione+ polarizatione+ and e- polar

ADD eeG cross section

ADD effects in e+e-ff

Transverse polarizationPT=0.8 P’T=0.6

cos cos

e+e-cc e+e-bb

G. WilsonCasalbuoni et al.

T. Rizzo

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Polarization and MDI

• Polarimeters for longitudinal (and transverse) polarized beams• Polarimeters before and after the IR?

– Polarimeter after the IR only possible with crossing angle (?)– Depolarization effects: so far expected to be in control for

0.5-1 TeV but is large for e.g. for CLIC– Redundancy is not a luxury for precision measurements so if

we can have data to check, so much the better. But what can we really learn from this measurement?

– Use also other physics processes to check, see talk of Klaus• Precision of the polarimeters 0.5-0.25% adequate for

everything?– High statistics channels (Z’, TGCs) require O(0.1)%– GigaZ requires 10-4, needs polarized e+ (Blondel Method)

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GigaZ option

• Measure to a precision of O(10-5) from left-right asymmetries

• Z-lineshape: improve Z-width with a factor two, cross section ratios by a factor three ( factor two on and a factor 3 on s)

• Zbb couplings improved by factor 5-10 wrt. LEP• B-physics: Factor 10 improvement in Electro-weak b-quark physics

possible, CP violation effects, rare B-decays (maybe need 1010 Zs)Imposes stringent requirement on the control of the beam energy andbeam energy spread, polarization, luminosity precision, detector (b-tagging)…

Luminosity ~ 51033cm-2s-1 at Z pole 109Zs in less than a year 100 x more statistics than LEP (1000x SLC for polarized studies)

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Measurement of sin2

• Stat. error with 109 Zs: ALR/ALR=4.10-5 (Pe-=80%,Pe+=0%)

• Error from the polarization ALR/ALR= P/P

• With positon polarization (Pe-=80%,Pe+=60%)– Gain a factor 3-4 with error propagation – Apply Blondel scheme

Need to understand polarization differences between the two helicity states to the level of 10-4. Need to take into account correlations between the polarizations of the two beams. Track time dependencies of the polarization.

Beam energy ALR/ s = 2 10-2/GeV from Z interference need to know s ~ 1 MeV relative to the MZ (spectrometer with 10-5 relative precision)

Beamstrahlung: need to be controlled to a few %

Challenging requirements!!

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Z-scan observables

• If relative beam energy measurement of 10-5 can be reached then /=0.410-3 (compared to 0.910-3 at LEP)

• Assume the selection efficiency for leptons to be improved by a factor 3 w.r.t. LEP detectors improve the leptonic to the hadronic cross section ratio Rlep/Rlep=0.310-3 (1.210-3 at LEP)

• With luminosity measurement improvements w.r.t LEP: improve the hadronic pole cross section 0

Beam energy spread should be kept below 0.1% and understood to the level of a few% for the 0 and measurements

In principle both are in reach of the Bhabha acolinearity measurement.

Improvements on line shaperelated quantities

Z properties affected by new physics: e.g. Z’ like objects in hep-ph/0303107

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WW factory

Revisiting the W mass Threshold scan: a six point scan with

100 fb-1 (1 year)• Efficiencies and purities as at LEP• Beam polarization used to measure

the background/enhance the signal– Need P/P < 0.25%– If polarized positrons are available,

can use the Blondel scheme• Beam energy needs to be controlled

to 510-5 between mZ and 2mW

• Can reach a precision of 6 MeV on MW (compare: 15 MeV at the LHC)

G. Wilson

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Multi-TeV collider• CLIC two beam acceleration presently thought to be only feasible way

to multi-TeV region CTF3 under construction/operation at CERN • MDI related issues to keep in mind if one plans for a facility that should be upgradable to a multi-TeV collider in future

– crossing angle needed of ~20 mrad (multi-bunch kink stability; see tomorrow)

– Present desing: Long collimator syst. (2 km on each side) and final focus (0.5 km)

– Energy collimators most important. Fast kicker solution not applicable. Maybe rotating collimators …– Gentle bending to reduce SR & beam spot growth construct the linacs

already under an angle of ~ 20 mrad– Internal geometry differences of the collimation system and final focus,

allow for enough space in the tunnels (O(m))

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Multi-TeV physics: Examples

New Z’ resonance

Heavy Higgs

ADD Extra Dimensions

Supersymmetric particles:# of higgses, sleptonsgauginos, squarks detected for benchmark scenarios (hep-ph/0306219)

s=5

s=3

MH=900 GeV

CLIC physics studyCERN-2004-005 & hep-ph/0412251

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Importace of the Options: Eg. SUSY

Supersymmetry: Study of benchmark point (SPS1a or B)

To fully exploit the ILC potential and measure the new sparticle masses weneed: e+e- up to 1 TeV, e-e-, polarized positrons (60% assumed here), anda PC to measure the heavy Higgses.. (H,A)…

From the documentLHC/ILC complementarityhep-ph/0410364

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Summary

• Additional options to the ILC will certainly increase the physics reach of the ILC. All have their merits

Today we do not know which one of these will have the highest impact on the physics program

• The options have consequences for the MDI With the WG4 recommendation it looks natural to suggest to

study in detail the IR with large crossing angle (15-20) mrad is kept compatible for a PC option (or even multi-TeV) from the start

What would we loose if the crossing has to be 25 mrad?– Affects small angle tagging efficiency of electrons from

backgrounds SUSY: eg. reduced efficiency for stau’s in stau- degenerate mass scenarios (CDM studies). Perhaps affordable?

– Some luminosity reduction– Are there additional technical risks?

• Should include all options & their requirements in the MDI studies