linear collider physics

David J. Miller UCL; Linear Collider Physics. ICHEP Beijing 22/8/04 1

Linear Collider Physics


We need the LHC asap, for lots of very good reasons.

We need 2 LCs

The TeV International Linear Collider, also asap.

Then a multi-TeV CLIC

+ (maybe) a Larger Hadron Collider


The TeV ILC planned for 2015, overlaps with LHC.

Parameters defined by ILCSC scope-panel for ITRPhttp://www.fnal.gov/directorate/icfa/LC_parameters.pdf

Baseline s = 200-500 GeV, integrated uminosity 500 fb-1 over 1st 4 years80% electron polarisation2 interaction regions with easy switching

Upgrade Anticipate s 1 TeV, = 1 ab-1 over 4 years

Options e-e- collisions, 50% positron polarisation,“GigaZ”; high at Z and at WW threshold,Laser backscatter for and e collisions,Doubled at 500 GeV.

Choice among options to be guided by physics needs.

ITRP wants highest possible


Physics case for LHC has been made and accepted.It will look into the whole region where newphysics should be.

Physics AND cosmology say “expect strong new signals at the scale of 1 TeV”.

Physics case for the TeV ILC has been made. (LCWS series, TESLA TDR, JLC/GLC reports, Snowmass black book, European+ACFA+ALCPG workshops etc. etc.

+ work in progress; see LHC/LC Study Group report at http://www.ippp.dur.ac.uk/~georg/lhclc/).

At least 2700 physicists support ILC (http://sbhep1.physics.sunysb.edu/~grannis/lc_consensus.html)

I will present some of the case here.(Or see Peskin at Victoria 31 July; http://www.linearcollider.ca:8080/lc/vic04/plenary/m_peskin.pdf)

Physics cases for CLIC (and Larger HC?) will follow results from LHC and TeV ILC.


Programme for the TeV ILC - will depend on what appears, but ILC isneeded in every scenario .

1. Definite; mt<100MeV

2. If there is a light Higgs

3. and extra particles

4. If LHC sees nothing newbelow ~ 500 GeV mass


1. Definite job to be done.Measure mt to < 100 MeV

Why?

2001; mt=174.3 5.1; PDG

2004; mt=178.0 4.3

Moves best fit mh

by > 20 GeV. Very sensitive.

Recent illustration; D0’s new mt measurement

Because precision on mt limits current SM fit.


Precise mt championed by Heinemeyer et al (hep-ph/0306181, and LHC/LC report)

current MW

A couple of their examples

a) What it does forThe Standard Model

“Unless mt < 100MeV,it is the dominant erroron many precision measurements.”


b) what precise mt would do for MSSM

(Heinemeyer et al)


Can we get mt < 100MeV with a real ILC ?

We think so. Doing R&D on spectrometry and detector-based measurement. Lots of work for ITRP – see Victoria workshop:Barklow, Torrens, Woods, DJM: http://www.linearcollider.ca:8080/lc/vic04/abstracts/detector/ipbi/ E.g. new work by Boogert* on fitting mt at threshold

with beamstrahlung and Initial State Radiation, using Bhabha acollinearity+.

*reported by DJM athttp://www.linearcollider.ca:8080/lc/vic04/abstracts/physics/topqcd/;+ Frary+DJM, Kurihara et al, Cinabro, Moenig.

Realistic fit givesshift of mt by only48 Mev; can surely correct to ~ 10 MeV


2. If there is a light Higgs of any kind, seen or unseen at LHC.

The ILC will see it and pin it down.Does it have standard model couplings?What is its precise mass?Does it have light scalar partners?Many scenarios investigated (see LHC/LC report etc.)


Higgs mass measurement (TESLA TDR; newer work confirms)

500 fb-1 at350 GeV

Constrained fits to final states

0

120HM GeV

H Z bbqq

0

120HM GeV

H Z bbl l

0

150HM GeV

H Z W W qq

0

150HM GeV

H Z W W l l


Precision on Higgs branching ratios with LC and

TESLATDR

David J. Miller UCL; Linear Collider Physics. ICHEP Beijing 22/8/04 13Both machines needed to get complete picture.

For new work on combined LHC/LC see next slide

TESLATDR c.f. SphicasVienna 2004,for LHC.

top Yukawa

Sphicas Vienna


New work on top Yukawa coupling Dawson, Juste, Reina and Wackeroth, LHC/LC report.

Branching ratios and couplings from 500 GeV ILC improve LHC result

Mh Mh

600

800

-

Direct tth with ILC at ~ 800 GeVmakes a big difference

Mh

tth

-

s (GeV)


Cosmic Microwave

BackgroundT

hen

Now

WMAPconstrains M

Higher precision can give discoveries.

Wouldn’t know it’sthere from COBE

AND Planckis coming; more

precise still

WITHPolarisationIf ILC measures the wrong Higgs mass (using S.M. fits

with ILC value of mt) it has discovered the new physics.LHC precision on mh may not be enough to do this.


3. If there is a light Higgs and extra particles

LC at s=400 GeV,

= 200 fb-1.

Clear endpoints give, for example,

(some others come fromthreshold scans). lepton energy (GeV)

0 01 1L R R Re e

E.g. the Minimal Supersymmetric Standard Model*, then LHC expects to see squarks and gluinos.

ILC good for sleptons and especially for LightestSupersymmetric Particle ( LSP is favoured candidatefor Dark Matter).

New studies at point SPS1a in LHC/LC report (Martyn).

01

*(+ new work on NMSSM and others in LHC/LC report, at Victoria, here)

MeVmmR

20001

~~


Global fits to MSSM (LHC/LC report, Lafaye, Plehn and D.Zerwas)

LC alone, ~1/100 of LHC erroron LSP

* Needs > 500 GeV. (Also < 500 study in LHC/LC)

+ e+e- threshold scan.- e-e- threshold scan (s-wave allowed)

*

*+

++

+ **

- -

+

***


SUSY Partners in e-e- and e-

- the natural habitat of the selectron

• Dotted lines are perfect beams •Solid for flat beams with ISR, beamstrahlung, and energy spread.

• Dashed is for round beam e-e-.

• Need 1/100 luminosity in e-e- compared with e+e-

to measure selectron mass to 100 MeV.

Similar big cross-section advantages in

R R R Re e e e

R Re e e e

150Rem GeV

01,2e e

S wave


Sensitivity of pMSSM parameters to experimental inputs (Lafaye, for SPA project, Beijing 17/8/04)


IF we have a self consistent SUSYpicture, can extrapolate fundamental couplings in mSUGRA (say) to the GUT scale,via renormalisation group equations.

Allanach, Blair, Kraml, Martyn, Polesello, Porod,Zerwas

LC+ GigaZ solid bands, LHC outer lines.

LC constrains more tightly at GUT scale.


Global fits to MSSM (LHC/LC report, Lafaye, Plehn and D.Zerwas)

LC alone, ~1/100 of LHC erroron LSP

Combined ½ error from LC alone.Uses dilepton mass from LHC (see next).


But look-out! Warning from Michael Peskin at Victoria.

“The differences between these scenarios are very subtle.

But they are the whole game.”

LC can confirm which one it is.

mll

02

Sharp edgegives mass(CMS study)

02

01


4. If LHC sees nothing new below ~ 500 GeV mass

Peskin again, at Victoria:


(Lots being done about these in the LHC/LC study)


em


ILC includes GigaZ(Z-Z’ mixing) and 1 TeV LC(interference)[Richard,hep-ph/0303107]

Sensitivity to heavy Z’ in different models

-(e+e- f f )(direct)

ILC


e+e- WW scattering amplitudes sensitive even to Low Energy Theorem effects. 15 s.d. for 1.9 TeV resonance. (Barklow, Snowmass)

500 GeV500 fb-1

Or WLWL Resonances; LHC sees direct up to ~1.5 TeV

1.9 TeV resonance parameters; above direct threshold for both colliders.

LHC fit,100fb-1

LC 1 TeV 1 ab-1

Imposing a1=1 (S.M. coupling)get blue bar from LHC,red from ILC.

ILC resolves single resonance from LET point up to 2.5 TeV (s = 500), 4.1 TeV (s = 1000 GeV).Well beyond LHC


Summary of the case for the TeV ILC

1. Definite; mt<100MeV

2. If there is a light Higgs

3. and extra particles

4. If LHC sees nothing newbelow ~ 500 GeV mass

Vital constraint.Increasingly sure

it can be done.

LHC probably sees.ILC shows what it is.

LHC and ILC needed topin down model, identify DM(?),

extrapolate to GUT scale.

Then LHC + ILC point to CLIC, andmaybe superLHC

ILC looks beyondLHC’s direct reach


EWSB

2004. Is there a structure here?


LHC

EWSB

2010. It’s taking shape.


2015. Looks like a gateway!

LHC

LC

EWSB


LHC

LC

EWSB

2020. Both pillars needed to see to the Temple of Unification

linear collider physics

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