# Presentation: 089816

## LHC ILC Interplay

- Klaus Desch
- University of Bonn
- Fermilab, April 13, 2007

## Slide 2

## The Terascale

- Very good reasons to explore the TeV-scale:
-  Evidence for light Higgs
-  SM without Higgs violates unitarity at ~1.3 TeV
-  Hierarchy between mweak and mPlanck to be protected at TeV scale
-  Dark matter consistent with sub-TeV-scale WIMP (e.g. SUSY-LSP)
-  2mtop = 350 GeV

## Driving Physics Questions

- Broad and rich spectrum of fundamental questions
- are awaiting answers at the Terascale:
- Electroweak Symmetry Breaking
- New Symmetries and Unification of Forces
- Space-Time Structure
- +     Connecting Cosmology and Particle Physics

- and surprises...

**Notes:**
Add “Logos” Higgs-Potential, Unification Plot, XD-Picture, Surprises (Grupen plot)

## Complementarity of tools

- Electron positron collisions at high energy provide a powerful tool to explore TeV-scale physics complementary to the LHC
- Due to their point-like structure and absence of strong interactions there are clear advantages of e+e- collisions:
-  known and tunable centre-of-mass energy
-  clean, fully reconstructable events
-  polarized beams
-  moderate backgrounds    no trigger

- broad consensus for a
-   Linear Collider with up to
-   at least ~500 GeV

**Notes:**
`Vergleichender – LHC: broadband, high mass reach, ILC: defined initial state, clean

## Complementarity of tools

- EPP2010 report

**Notes:**
`Vergleichender – LHC: broadband, high mass reach, ILC: defined initial state, clean

## Interplay and Synergy

**LCWS Korea 2002**

- LHC/ILC Study group
- Phys. Rept. 426 (2006) 47

## Getting excited

- With first collisions at 14 TeV next year, it is obvious that we have to
- start understanding implications of LHC discoveries for the ILC in much
- more detail

**Barish**

## Getting excited

-  general physics case of the ILC does not depend on the LHC
-     (no matter what LHC will see, ILC has an important additional value)
- Advanced (2002-2006): Explore the synergies if LHC and ILC
-  both machines, if analyzed (and ideally running) simultaneously,
-      will provide added value
- Facing the real thing (2007-): Optimizing the ILC choices in the light of LHC discoveries
-  no reason to get nervous but a reason to get excited
- Abe Seiden @ SLAC : “It could be that the physics is not in the ILC reach”
- could that really be the case? under which circumstances?
- Burt Richter @ SLAC: “How interesting will 500 GeV be in 2020?”
- are there scenarios where the initial ILC parameters (energy,luminosity)
- need revisiting?
- Need good answers to this scepticism a.s.a.p.!

## The LHC Early Phase for the ILC

- Workshop charge

- What could be the impact of early LHC results on the choice of the ultimate ILC energy range and the ILC upgrade path? Could there be issues that would need to be implemented into the ILC machine and detectors design from the start?
- Could there be cases that would change the consensus about the physics case for an ILC with an energy of about 500 GeV?
- What are the prospects for LHC/ILC interplay based on early LHC data?

## Strategy

- Largely signal-driven (not so much model driven)
- 1. The detection of only one state with properties that are    compatible with those of a Higgs boson
- 2. No experimental evidence for a Higgs boson at the early stage     of LHC
- 3. The detection of new states of physics beyond the Standard    Model.	a. Missing Energy (+nothing, leptons, jets) signals
- 	b. Leptonic resonances
- 	c. Multi-Gauge-Boson signals
- 	d. Everything else.

## From a maze to a decision tree

- Here, the artist might have failed:
- There is more than one path from the
- LHC to the ILC!

## LHC

- start

- commision&understanddetectors

- Higgslike
- state

- Excess in
- missing ET
- (plus leptons?)

- Leptonic
- resonances

- Multi-gauge
- bosons

- Something
- Else

- No Higgs
- (yet?)

**WG1**

**WG4**

**WG2**

**WG3**

**WG3**

**WG4**

## When we talk about the first 10 fb-1 we have to account for

- start

- commision&understanddetectors

- Higgslike
- state

- Excess in
- missing ET
- (plus leptons?)

- Leptonic
- resonances

- Multi-gauge
- bosons

- Something
- Else

- No Higgs
- (yet?)

**WG1**

**WG4**

**WG2**

**WG3**

**WG3**

**WG4**

- When we talk about the first 10 fb-1 we have to account for
- additional time to get the detectors into a state where they are ready
- for discoveries.
- This time certainly depends on the complexity of the signal but
- ATLAS + CMS deserve some patience from the community
- Solid results are better than fast results

## Before discovery: work hard

- Energy dependence of dN/d ?
- Vital for tuning Underlying Event model, Important of Jet-Energy, Etmiss
- Only requires a few thousand events but needs to be accounted for in subsequent searches

- The first three minutes of
- data taking...

## Before discovery: work hard

- Establish the major SM signals: Z, W, top

- No one will believe in a discovery if Z+jets, W+jets, tt+jets are not observed in agreement with SM predictions and well modelled

- also: hadronic W-mass peak(jet E-scale)

- example top:

| Channel | events/100 pb-1 |
| --- | --- |
| W | ~106 |
| Z | ~105 |
| ttbjjb | ~104 |
| jets w pT>1TeV | ~103 |

## Before discovery: work hard

- Understand and
- calibrate Jets & Etmiss

- To understand the major backgrounds at the LHC
- (Z+jets, W+jets, tt+jets,...) we need Monte Carlo simulations beyond the
- classical LO+ parton shower approach.
- Recent developments
- MC@NLO (1 additional jet at full NLO)
- ALPGEN, SHERPA, ... (n additional jets as LO matrix element +                              „matching“ of ME and PS
- Here, the Tevatron is an important training camp...

## mH

- start

- commision&understanddetectors

- Higgslike
- state

- Excess in
- missing ET
- (plus leptons?)

- Leptonic
- resonance(s)

- Multi-gauge
- bosons

- Something
- Else

- Nothing
- (yet)

- mH

- <160

- 160-350

- >350

- preferred by prec. data

## Higgs at LHC

- SM Higgs discovery assured for ~10 fb-1 over full mass range if nothing
- goes wrong
- - rather easy (and fast) for mH > 140 GeV
- - more involved for light Higgs mH < 140 GeV

## Higgs signals at the LHC

- ATLAS30 fb-1

- WBF, H

- CMS HZZ4l

## MSSM Higgs at LHC

- ATLAS preliminary

- 30 fb-1

- Weak Boson Fusion can cover
- whole parameter space for
- lightest MSSM Higgs boson with 30 fb-1

- With more luminosity heavier MSSM
- Higgses are accessible only for large tan, some indirect sensitivity from
- light h:

## ILC: if mH < 160 GeV

- Full program of Higgs precision measurements can (and must) be done

-  decay-mode-independent observation
-  mass (50 MeV)
-  absolute couplings (Z,W,t,b,c,) (1-5%)
-  total width (model-independent)
-  spin, CP
-  top Yukawa coupling (~5%)
-  self coupling (~20%, 120-140 GeV)
-   at photon collider (2%)

- fully establish Higgs mechanism!

**Garcia-Abia **

## Many motivations for precise measurements...

- distinguish models

- indirect mass determination of
- heavy Higgses, if there (MSSM):

- mA = 30% for mA = 800 GeV
- also in parameter regions whereLHC is blind

**Yamashita**

**Zivkovic et al**

## LHC-ILC interplay on Higgs couplings

**KD,Dührssen,Heinemyer,Logan,Rainwater,Weiglein,Zeppenfeld - preliminary**

- LHC+
- mild model
- assumptions

- LHC+ILC model independent

## mH>~160 GeV

- Here we need more work for the ILC
- Shopping list:
- - couplings to WW, ZZ still measurable (but how much better than LHC?)
-     improve precision (include hadronic Z?, more luminosity?)
- - fully explore WW-Fusion
- - Yukawa couplings hard to access
-     BR(Hbb) measurable up to ~ 220 GeV
-     Htt* below threshold ?
-     ttH needs high energy (studied        up to mH= 200 GeV so far...)
- - explore total width measurement   from WWHWW!
- - total width from threshold scan?
- - selfcoupling from HHWWWW   (energy, luminosity)?

- upper limit on sensitivity...

## mH>~160 GeV: SM precision measurements

- If there is a heavy SM-like Higgs we need precision measurements
- to test quantum structure  indication for new physics close by.
- We will need:
-  precise mtop (100 MeV)   from tt-threshold
-  precise mW (6 MeV)   from WW threshold
-  precise sin2w   from Giga-Z
-  e+e-ff, WW, ...

**Heinemeyer,Kraml,Porod,Weiglein**

## Summary on Higgs-like state

-  excellent discovery prospects at the LHC
-  discovery of heavier SM-like Higgs (140, >160) may be very fast
-  light Higgs (<160) discovery calls for ILC precision Higgs program
-   immediately (even w/o further new physics observed yet)
-  heavier Higgs (>160) likely also calls for ILC precision   Higgs program + SM precision program (needs more activity)!

## LHC

- start

- commision&understanddetectors

- Higgslike
- state

- Excess in
- missing ET

- Leptonic
- resonance(s)

- Multi-gauge
- bosons

- Something
- Else

- Nothing
- (yet)

- + many jets,
- no leptons

- + many jets
- + leptons

- + few jets

- + few jets
- + leptons

- + jets
- + photons

- + no jets
- + 1,3leptons

## Huge variety of possible models with large MET

**S.Asai**

- in addition to model-driven searches, topology-driven searches required

## SUSY at LHC

- OS dileptons

- SS dileptons

- 1 fb-1, m(squark,gluino) ~ 1 TeV

## SUSY at LHC

- mSugra discovery reach with 10 fb-1

## MET signal at LHC

- after observation of an excess:
- need estimate of thresholds at ILC

- Fast estimate of m(gluino),m(squark) is not enough!
- need to get estimates of masses
- of the cascading particles!

## SUSY at LHC

- Dileptons:

- A sharp edge in the
- dilepton mass spectrum
- is a “go” for the ILC

## `MET signal at LHC

- what we need is a model-independent estimate
- of the particle masses in cascade decays, which end in an
- invisible massive particle (DM candidate)
- Full kinematic reconstruction is tough
- see e.g. **Kawagoe,Nojiri,Polesello ****hep-ph/0410160**
- Need more effort here...
- Fully exploit
-  pT spectra of visible objects and MET
-  invariant masses
-  rates!

## SUSY at ILC

- precise masses of color-neutral states(50 MeV to 1 GeV)

- spin (angular distributions)

- chiral quantum numbers (polarisation!)

-  prove that it is SUSY
-  no model assumptions
-  learn about SUSY breaking

- once a few thresholds are in reach, the ILC is the place to reveal SUSY

**G.Moortgat-Pick**

**U.Martyn**

**ACFA study**

## SUSY at ILC + LHC

- ILC and LHC together can likely measure precisely
-  the parameters of constrained models (mSugra...)
-  determine the underlying SUSY parameters w/o model assumptions
-  determine the properties of the LSP  dark matter density
-  test more complex realisations (e.g. NMSSM)

**Hesselbach,Moortgat-Pick**

**Bechtle,KD,Wienemann**
**also SFITTER: Plehn ea**

**LHC-ILC report**

## mX

- start

- commision&understanddetectors

- Higgslike
- state

- Excess in
- missing ET
- (plus leptons?)

- Leptonic
- resonance(s)

- Multi-gauge
- bosons

- Something
- Else

- Nothing
- (yet)

- mX

- <500 GeV

- <1000 GeV

- >1000GeV

## Leptonic Resonances at LHC

- CMS 100 pb-1
- With initial (misaligned)
- detector

- SSM Z’ 1 TeV

- can possibly be seen very early...

- Discovery reach 3-4 TeV with 10 fb-1

- CMS

## Resonances: ILC consequences

-  Not very likely, that a <500 GeV   ll-Resonance appears
-   (but ILC would of course    study it in s-channel )
-  A resonance within the direct   reach of an upgraded ILC would  probably call for a fast upgrade   path (still would like to do the
-   precision Higgs (if there) and   SM program)
-  A resonance beyond the direct   ILC reach: ILC+LHC can determine   coupling structure from interference
-   with /Z exchange to determine its   nature

- E6  model
- LR symmetric
- Littelest Higgs (LH)
- Simplest Little Higgs (SLH)
- KK excitations in ED

**Godfrey et al, hep-ph/0511335**

- 95% contours, MZ’= 1,2,3,4 TeV

## LHC

- start

- commision&understanddetectors

- Higgslike
- state

- Excess in
- missing ET
- (plus leptons?)

- Leptonic
- resonance(s)

- Multi-gauge
- bosons

- Something
- Else

- Nothing
- (yet)

## Multigauge bosons at LHC

- Rich field
-  Measure TGCs in WW,WZ,ZZ
-  Measure QGCs in WWZ, WW
- Crucial test of EWSB: Weak boson fusion at high mass: e.g. qq jjWWjjll
- Needs more attention at LHC (did I miss something?)
- Important for ILC planning!

- WHIZARD **(Kilian,Reuter,Ohl)**

**Mertens(Dipl thesis),Schumacher**

- effective Lagrangian approach valid
- at m(WW)>1.2 TeV??
- exclusion potential?

**see also Kilian,Reuter**
**hep-ph/0507099**

- preliminary

## LHC

- start

- commision&understanddetectors

- Higgslike
- state

- Excess in
- missing ET
- (plus leptons?)

- Leptonic
- resonance(s)

- Multi-gauge
- bosons

- Something
- Else

- Nothing
- (yet)

## Something else

- Not unlikely, but hard to prepare for
- Important that ATLAS+CMS are open-minded enough and perform broadband searches...

**Grupen**

## LHC

- start

- commision&understanddetectors

- Higgslike
- state

- Excess in
- missing ET
- (plus leptons?)

- Leptonic
- resonance(s)

- Multi-gauge
- bosons

- Something
- Else

- Nothing
- (yet)

## Nothing yet...

- With 10-30 fb-1 analysed at the LHC, many of our favourite
- scenarios can be excluded:
- - SM Higgs
- - MSSM Higgs
- - MSSM indirect: absence of light Higgs, direct: up to ~1.5 TeV
- - ...
- Major focus then: EWSB
- 1. has the LHC missed the Higgs(es)?   (e.g. invisible, Higgs continuum, Hjets, ...)
-   ILC can discover the Higgs in these scenarios.
- 2. there is really no Higgs
-    Technicolor/Higgsless models
-    Signals might show up with higher luminosity
-    (WW scattering at high masses crucial)
-    if this scenario can be excluded at LHC, revisit option 1.

## Conclusions

- The LHC Early Phase will be exciting!
- The LHC Early Phase will confront our ideas about Terascale
- physics with real data
- We will have to demonstrate that there is indeed a strong case for the ILC in the light of these data: that’s no free lunch! (but I’m not nervous...)
- Some possible signals at LHC (light Higgs, SUSY-like signals, leptonic resonances,...) are clear “go ahead” signs for ILC
- Others (e.g. heavier Higgs) need more studies to assess the ILC
- physics potential within the various physics scenarios
- Optimal ILC run plan and upgrade path have to be inferred from LHC data