# Presentation: 312240

## The Higgs search at the Tevatron University of the TevatronMarch 27, 2002

**John Womersley**
**Fermilab**

## The Higgs Mechanism

**The Higgs Mechanism**

**In the Standard Model **
**Electroweak symmetry breaking ****occurs through introduction of a ****scalar field ******** ******** masses of W and Z**
**Higgs field permeates space with ****a finite vacuum expectation value = 246 GeV**
**If ******** also couples to fermions ******** generates fermion masses**
**An appealing picture: is it correct?**
**One clear and testable prediction: there exists a ****neutral scalar particle ****which is an excitation of the Higgs field**
**All its properties (production and decay rates, couplings) are fixed except its own mass**
**Highest priority of worldwide high energy physics program: find it!**

## God particle disappears down £6billion drain

**God particle disappears down ****£6billion drain**

**This field need not result from a single, elementary, scalar boson**
**There can be more than one particle**
**e.g. SUSY**
**Composite particles can play the role of the Higgs**
**e.g. technicolor, topcolor**
**We do know that**
**EW symmetry breaking occurs, so something is coupling to ****the W and Z**
**Precision EW measurements imply that this thing looks very much like a Standard Model Higgs **
**though its fermion couplings are less constrained**
**WW cross sections violate unitarity at ~ 1 TeV without H**
**A real LHC experiment:**

## Searching for the Higgs

**Searching for the Higgs**

**Over the last decade, the focus has been on ****experiments at the LEP e****+****e****–**** ****collider at CERN **
**precision measurements of parameters ****of the W and Z bosons, combined with ****Fermilab’s top quark mass measurements, ****set an upper limit of m****H**** ~ 200 GeV **
**direct searches for Higgs production exclude ****m****H**** < 114 GeV**
**Summer and Autumn 2000: Hints of a Higgs?**
**the LEP data may be giving some indication of a Higgs with mass 115 GeV (right at the limit of sensitivity)**
**despite these hints, CERN management decided to shut off LEP operations in order to expedite construction of the LHC**
*	**“**The resolution of this puzzle is now left to Fermilab's Tevatron and the LHC.”*
*– *Luciano Maiani

## The Fermilab Tevatron Collider

**Main Injector**
** ****& Recycler**

**Tevatron**

**Chicago**
****

******p source**

**Booster**

**CDF**

**DØ**

******p **

**p **

**p **

******p **

**1.96 TeV **

**CDF**

**DØ**

## Higgs at the Tevatron

**The search for the mechanism of EWSB motivated the construction of supercolliders (SSC and LHC)**
**After the demise of the SSC, there was a resurgence of ****interest in what was possible with a “mere” 2 TeV**
**Ideas from within accelerator community (“TeV33”)**
**Stange, Marciano and Willenbrock paper 1994**
**TeV2000 Workshop November 1994**
**Snowmass 1996**
**TeV33 committee report to Fermilab director**
**Run II Higgs and Supersymmetry Workshop, November 1998**
**A convergence of**
**technical ideas about possible accelerator improvements**
**clear physics motivation **
**Plan for integrated luminosities, before LHC turn-on, ****much larger than the (then) approved 2fb****-1**** **

## Higgs decay modes

**The only unknown parameter of the SM Higgs sector is the mass**
**For any given Higgs mass, the production cross section and decays are all calculable within the Standard Model**

**One Higgs**

**H ********bb**

**H ******** WW**

## Higgs Production at the Tevatron

**Higgs Production at the Tevatron**

**Inclusive Higgs cross section is ****quite high: ~ 1pb**
**for masses below ~ 140 GeV,****the dominant decay mode H ******** bb ****is swamped by background**
**at higher masses, can use inclusive****production plus WW decays**
**The best bet below ~ 140 GeV appears ****to be associated production of H plus ****a W or Z**
**leptonic decays of W/Z help give ****the needed background rejection**
**cross section ~ 0.2 pb**

**H ********bb**

**H ******** WW**

**Dominant decay mode**

## mH < 140 GeV: H bb 

**m****H**** < 140 GeV: H ********bb **

**WH ******** qq’********bb is the dominant decay mode but is overwhelmed by QCD background**** **
**WH ******** ****l****±******** bb ****	****	****backgrounds W********bb, WZ,********tt, single top**
**ZH ******** ****l****+****l****-******** bb****	**** ****	****backgrounds Z********bb, ZZ,********tt**
**ZH ******** ******** bb****	**** ****	****backgrounds QCD, Z********bb, ZZ,********tt **
**powerful but requires relatively soft missing E****T**** trigger (~ 35 GeV)**

**CDF Z ********bb in Run I**

**DØ simulation for 2fb****-1**

**2 ******** 15fb****-1 ****(2 experiments)**

**m****H**** = 120 GeV**

**Higgs**

**Z**

****_**bb mass resolution**_
**Directly influences signal significance**
**Z ********bb will be a calibration**

**~**

## pp  WH 

**Two b-jets from**
**Higgs decay**

**Missing E****T**

**Electron Track**

**EM cluster**

**Calorimeter**
**Towers**

**p ******

******p**

******pp ******** WH **
**	****    ********bb**
**             ******** ****e******

**Hits in Silicon Tracker**
**(for b-tagging)**

## Example: mH = 115 GeV

**Example: m****H**** = 115 GeV**

**~ 2 fb****-1****/expt (2003): exclude at 95% CL**
**~ 5 fb****-1****/expt (2004-5): evidence at 3******** level **
**~ 15 fb****-1****/expt (2007): expect a 5******** signal**
**Events in one experiment with 15 fb****-1****:**
**If we do see something, we will want to test whether it is really a Higgs by measuring:**
**production cross section**
**Can we see H ******** WW? (Branching Ratio ~ 9% and rising w/ mass)**
**Can we see H ******** ********? (Branching Ratio ~ 8% and falling w/ mass)**
**Can we see H******** ********? (not detectable for SM Higgs at the Tevatron)**

**Every factor of **
**two in luminosity**
**yields a lot **
**more physics**

## Associated productiontt + Higgs

**Cross section very low (few fb) ****but signal:background good**
**Major background is********tt + jets**
**Signal at the few event level:**

**H ********bb**

**H ******** WW**

**Tests top quark Yukawa coupling **

**15fb****-1 ****(one experiment)**

## mH > 140 GeV : H  WW(*)

**gg ******** H ******** WW****(*********) ******** ****l****+****l****-**** ********	****    ****	**
**	****Backgrounds ****	****Drell-Yan, WW, WZ, ZZ, tt, tW, ********	****	****Initial signal:background ratio ~ 10****-2 **
**Angular cuts to separate signal from “irreducible” WW background**

**Before tight cuts:**
**verify WW modelling**

**After tight cuts**

**~**

**2 ******** 15fb****-1 **
**(2 experiments)**

**Higgs signal**

**Background **
**(mainly WW)**

## 
No guarantee of success, but certainly a most enticing possibility

**No guarantee of success, but certainly a most enticing possibility**

**15 fb****-1**

**110-190 GeV**

**m****H**** probability ****density, J. Erler****(hep-ph/0010153)**

**Tevatron Higgs mass reach**

## Indirect Constraints on Higgs Mass

**Indirect Constraints on Higgs Mass**

**Future Tevatron W and top mass measurements, per experiment**
**	****	****	********m****W**
**	****2 fb****-1****	****	****±27 MeV**
**	****15 fb****-1**** **** ****	****±15 MeV**
**	****	****	********m****t**
**	****2 fb****-1****	****	****±2.7 GeV**
**	****15 fb****-1**** **** ****	****±1.3 MeV**

**Impact on Higgs mass fit using**
******m****W ****= 20 MeV, ********m****W ****= 1 GeV,**
****** ****= 10****-4****, current central values**
- M. Grünewald et al., hep-ph/0111217

## Supersymmetric Higgs sector

**Expanded Higgs sector: h, H, A, H****±**
**Properties depend on**
**At tree level, two free parameters (usually taken to be m****A****, tan ********)**
**Plus radiative corrections depending on sparticle masses and m****t**** **

**Multiple Higgses**

**One of us looks much like the Standard Higgs...**

**~**

## Supersymmetric Higgs Masses

**Over much of the remaining allowed parameter space, **
**m****h**** ~ 130 GeV,**
**m****A**** ~ m****H**** ~ m****H****±**** = “large”**

_**From LEP:**_** **
**m****h**** > 91 GeV, m****A**** > 92 GeV, m****H****±**** > 79 GeV, ****tan******** > 2.4**

## MSSM Higgs Decays

**	****Very rich structure!**
**	**
**	****For most of allowed mass range h behaves very much like H****SM**
**H ******** WW and ZZ modes suppressed compared to SM**
**bb and ******** modes enhanced**
**	****A ********bb and ********      **
** **
**	****H******** ******** ******** and********tb**

## SUSY Higgs Production at the Tevatron

**SUSY Higgs Production at the Tevatron**

**bb(h/H/A) enhanced at large tan ********:**
****** ****~ 1 pb for tan******** = 30 and****m****h**** = 130 GeV**

**bb(h/A) ******** 4b**

**CDF Run 1 analysis (4 jets, 3 b tags) **
**sensitive to tan ******** > 60**

**10 fb****-1**
**m****A**** =150 GeV,**
**tan ******** = 30**

- one
- expt

**Preliminary**

**increasing**
**luminosity**

## SUSY Higgs reach at the Tevatron

**Enhances h ******** ********  ?**

**95% exclusion**

**5******** discovery**

**Exclusion and discovery**
**for maximal stop mixing,**
**sparticle masses = 1 TeV**

**Most challenging scenario:**
**suppressed couplings to bb **

**95% exclusion**

**5******** discovery**

**5 fb****-1**

**5 fb****-1**

**15 fb****-1**

**20 fb****-1**

**15 fb****-1**

**20 fb****-1**

**Luminosity per experiment, CDF + DØ combined**

## What if we see nothing?

**As long as we have adequate sensitivity, exclusion of a Higgs is still a very ****important discovery for the Tevatron**
**In the SM, we can exclude most of the ****allowed mass range**
**In the MSSM, we can potentially exclude **_**all**_** the remaining mass range**
**A light Higgs is a very basic prediction of ****the supersymmetric SM**
**e.g. Strumia, hep-ph/9904247**

** ****LEP limit**

**Still allowed**

**It’s a good thing**

## What if we see something else?

**Alternatives to SUSY: dynamical models like technicolor and topcolor **
**the Higgs is a composite particle: no elementary scalars**
**many other new particles in the mass range 100 GeV - 1 TeV **
**with strong couplings and large cross sections**
**decaying to vector bosons and (third generation?) fermions**

**SM**

******T ********bb**

******T ******** ****l******** ********T **

**At the Tevatron,**
**you have to be lucky,**
**but if you are, you can****win big:**

## Run 2B

**Planning has started on the additional detector enhancements that will be needed to meet the goal of accumulating 15 fb****-1 ****by end 2007 **
**major components are two new silicon detectors to replace the present CDF and D****Ø ****devices which can not survive the radiation dose**
**Technical design reports submitted to the laboratory Oct 2001**
**goal: installed and running by early 2005**

**Proposed D****Ø Run 2B **
**silicon detector**

**Run 2B silicon installed**

## Tevatron plan for 2002

**Only ~ 20pb****-1**** delivered so far, which CDF and D****Ø have used**** to commission their detectors **
**2002 will be the year that serious physics running starts**

**2002 PLAN**

## Slide 25

## By 200x at the Tevatron, if all goes well
We will observe a light Higgs
Test its properties at the gross level
but not able to differentiate SM from MSSM 
Or we will exclude a light Higgs
Interesting impact on SUSY
We will tighten exclusion regions for MSSM charged Higgs and  multi-b jet signals at high tan 
We may even be lucky enough to find something else 
e.g. low scale technicolor

**We will observe a light Higgs**
**Test its properties at the gross level**
**but not able to differentiate SM from MSSM **
_**Or**_** we will exclude a light Higgs**
**Interesting impact on SUSY**
**We will tighten exclusion regions for MSSM charged Higgs and  ****multi-b jet signals at high tan ******
**We may even be lucky enough to find something else **
**e.g. low scale technicolor**

**What will we know and when will we know it?**

## The Large Hadron Collider

**The Large Hadron Collider**

**Lake Geneva**
****

**Main CERN site**

**SPS**

**ATLAS**

**p **

** ****p **

**14 TeV **

**CMS**

**ATLAS**

**CMS**

## LHC construction

**Magnet String Test**

**Underground construction at the ATLAS cavern**

**Dipole procurement now approved**
_**but**_** significant delays due to SC cable (~ 9 mos. late)**
****** ****one year delay in official schedule**

## LHC detector construction

**ATLAS tile calorimeter**

**CMS 4T solenoid inside muon iron**

**CMS hadron calorimeter**

## LHC cost problems

**LHC cost review (9/01) concluded there is a 850M CHF cost overrun at CERN (machine cost plus significant extra costs for detectors, computing, etc.)**
**Discussions in council**
**Five internal task forces established, austerity measures being taken:**
**Cost cutting, reduction of scientific activity in 2002 (reduce accelerator operating time by 25%)**
**allow 33.5 MCHF to be reallocated to the LHC this year**
**External review committee established, will examine:**
**LHC accelerator, experimental areas and CERN's share of detector construction**
**CERN's scientific program not directly related to the LHC **
**For the longer term, a series of internal Task Forces has been set up to examine CERN's functioning, thereby allowing for a meaningful analysis of savings. **
**CERN’s commitment to the LHC is not in any way in doubt, but the impact of all this on the start date for physics is not yet clear **

## The Linear Collider

**CDF**

**e****+**** **

**e****-**** **

**0.5-1.0 TeV**

**?**

## A three-stage relay race

**Tevatron**
**Discovery if we’re lucky**
**Fermilab’s role is obvious**
**LHC**
**Guaranteed discovery of one or more Higgs or some other signal of EWSB**
**Measure properties at the 20% level**
**Learn a lot more about physics at the TeV scale ****(SUSY? Extra dimensions?)**
**Fermilab’s role is significant but needs to be consolidated for the physics analysis phase**
**Linear Collider**
**Measure, measure, measure:****Higgs couplings to W, Z, individual fermions, HHH coupling**
**What is Fermilab’s role? **

## Top ten reasons to pursue the Higgs search at Fermilab

**10.****	**** Window of opportunity before LHC startup is not getting shorter  **
**9.****	****The origin of EWSB has been unclear for way too long, and theorists   can’t figure the question out by themselves**
**8.****	****Find it while Mr. Higgs is still alive and can win the Nobel Prize**
**7.****	****Learn if there really are fundamental scalars (SUSY?)**
**6.****	****Learn why the standard model seems to work so well**
**5.****	****We might find something other than a Higgs**
**4.****	****Excluding a light Higgs is almost as interesting as finding it**
**3.****	****Huge potential payback for a (relatively) small investment**
**2.****	****Excitement and discovery move the field forward**
**1.****	****Because we can!**

## What the Higgs search will teach us

**What is the source of mass of the W and Z? **
**Why is the weak force weak?**
**What is the source of mass of the fundamental fermions?**
**Are there fundamental scalars?**
**Is there SUSY?**
**if no light Higgs, no weak scale SUSY...**
**Is there other new physics at the weak scale?**
**New forces like technicolor**
**Are m****W****, m****t**** and m****H**** consistent with precision EW fits?**
**What is the mass scale of new physics?**
**What is the next machine we’ll want to build after the linear collider?**

## What the Higgs search won’t explain

**Why fermion masses have the values they do**
**Why is the top quark so heavy?**
**The origin of all mass in the universe**
**The universe is roughly **
**70% dark energy (???)**
**20% cold dark matter **
- e.g. neutralinos with mass ~100 GeV
**5% neutrinos?**
**5% baryons **
- whose mass is almost all due to QCD
**Flavor**
**What distinguishes a top quark from an up quark?**

## Conclusions

**For as long as I have done high energy physics, we have known that we needed something like a Higgs, and it has been the highest priority of the field to explore this question experimentally**
**That is about to change dramatically: the next few years will see the Higgs become a discovery or set of discoveries to be understood and measured**
**and, we hope, the first window on to a new domain of ****physics at the TeV scale**
**Personally, I can’t wait to see what’s behind the curtain**

## Conclusions

**For as long as I have done high energy physics, we have known that we needed something like a Higgs, and it has been the highest priority of the field to explore this question experimentally**
**That is about to change dramatically: the next few years will see the Higgs become a discovery or set of discoveries to be understood and measured**
**and, we hope, the first window on to a new domain of ****physics at the TeV scale**
**Personally, I can’t wait to see what’s behind the curtain**

**?**

## Backup slides:LHC, linear collider

## Higgs at LHC

**Production cross section and luminosity both ****~ 10 times higher at LHC than at Tevatron**
**Can use rarer decay modes of Higgs **

## “Precision Channels”

**Both LHC detectors have invested heavily in precision EM calorimetry and muon systems in order to exploit these channels**

**H ******** ******** **
**for m****H**** = 120 GeV, 100fb****-1****, CMS**

**H ******** ZZ****(*********)**** ******** 4****l**** **
**for m****H**** = 300 GeV, 10fb****-1****, ATLAS**

## Associated productionttH at LHC

## Vector boson fusion channels

**Use two forward jets to “tag” the VB fusion process**
**Improves the S/B for large Higgs masses**
**Example: H ******** WW ******** l********jj**

**Two jets with E ~ 300 GeV and**
**2 < |********| < 4**

**ATLAS**
**m****H**** = 600 **
**100fb****-1**

**Also useful **
**for lower**
**Higgs masses**
**(~10% of total**
**cross section)**
**H ******** ******
**m****H**** = 120 GeV**
**ATLAS**

## Tagging jets work well in GEANT simulation
But life at  =  4 is always going to be hard 

**Tagging jets work well in GEANT simulation**
**But life at ******** = ******** 4 is ****always going to be hard **

**D****Ø Run 1 data**

## LHC Discovery Potential

**Significance for 100 fb****-1**

**Luminosity required for 5******

**The whole range of SM Higgs masses is covered**

## SM Higgs parameter determination at LHC

**Mass**

**Width**

******·****B**

**0.1% to 1% accuracy**
**in measurement of m****H**

**5 to 10% measurement **
**of the width for m****H**** > 300 GeV**

******·****B measured to the**
**level of the luminosity**
**uncertainty (~5%?)**

- ATLAS TDR

## Higgs coupling measurements

**Can measure various ratios of Higgs couplings and branching fractions by comparing rates in different processes **
**CMS estimates of uncertainties with 300 fb****-1**
**	**Luminosity uncertainties largely cancel in ratios
- 	Errors are dominated by statistics of the rarer process

**Can we verify that the Higgs actually provides a) vector bosons and b) fermions **
**With their masses?**

**qq ******** qqH process very important here**

## SUSY Higgs production at the LHC

**Cross sections at the 10 pb level and ******** as tan ******** ******** **
**(H/A)********bb enhanced as tan ******** ******** but VB fusion suppressed**

**tan ******** = 3**

**tan ******** = 30**

**tan ******** = 3**

**tan ******** = 30**

**h, H**

**A**

## SUSY Higgs discovery channels

**The best SM channel (H ******** ZZ****(*********)******** 4****l****) is suppressed**
**Good bets:**
**h ******** ******
**h ********bb**
**H/A ******** ******
**H******** ******** ******
**In certain regions of parameter space:**
**H/A ******** ******
**H ******** hh**
**A ******** Zh**
**H******** ******** tb**
**SUSY masses permitting**
**H/A ******** neutralino pairs**
**h production in SUSY ****cascades ********0****2 ******** ********0****1****h**

**h discovery modes**

## Importance of tau modes

**A/H ******** ******

**H******** ******** ******
**	****For lower masses, search in top decays (t ******** ******** rate enhanced)**
**	****For higher masses, associated production  ****pp ******** tH****±******** t******
**Signal is a peak in transverse mass of ******** jet and E****T****miss**
**tt background suppressed by jet veto and cut on mass ****of ********, E****t****miss ****and jet (= m****t**** for t ******** bW****±******** b********)**

**b-tagging associated jets is a powerful way to enhance the signal**

****** ******** ****l**** + ********-jet**

**t H****± ******** t ******** ******

## Combined Coverage

**Discovery Regions**

**Problematic region:**
**Only h visible, looks like SM Higgs**
**Need to observe SUSY particles**

**Do I look like SUSY to you?**

**Note that 95% exclusion is more forgiving:****m****A**** = 450, tan ********=10 can be ruled out by A ******** ******

## Determination of parameters

**First question: do we have a SM H or a SUSY h?**
**Note: often this will be moot at the LHC because squarks and gluons will have been observed before any Higgs – but there is always the possibility of more complicated Higgs sectors**
**Second question: where are we in SUSY parameter space (or 2HDM space?)**
**Use masses, widths and branching ratios**
**If more than one Higgs is observed, more straightforward**
**Example of tan ******** determination from ATLAS TDR:**

## Additional SUSY decay modes

**If we are lucky, beautiful signals may be observable**
**Higgs ******** sparticles or sparticles ******** Higgs**
**h ********bb in cascade decays from squark and gluon production**

**(H/A) ******** ********0****2********0****2**** ******** 4****l**

**H ********bb in cascade****decays of squarks and****gluinos**

**Region of observability**

## Technicolor

******T**** ******** ********T****Z ******** bq ****l****+****l****-**

**Yellow = Z+jets**
**Green =********tt**
**Blue = technicolor signal**
**   ****(m********, m********) = (500, 300) GeV**
**   ****(m********, m********) = (800, 500) GeV**

******T**** ******** ********T****W ******** bq ****l******

******T**** ******** ********T******** ******** ********bb**

**Yellow = Z+jets**
**Green =********tt**
**Blue = technicolor signal**
**   ****(m********, m********) = (500, 300) GeV**
**   ****(m********, m********) = (800, 250) GeV**
**   ****(m********, m********) = (800, 500) GeV**

**Yellow = ********+jets**
**Blue = technicolor signal**
**   ****(m********, m********) = (500, 300) GeV**
**   ****(m********, m********) = (800, 500) GeV**

## Topcolor see-saw model

**Topcolor see-saw model**

**Composite Higgs (top plus new isosinglet quark ********)**
**Can be significantly more massive than in SM as long as other new physics exists (********T)**
**topgluons, Z’**

**LHC will see the Higgs ****(400 - 500 GeV)**

**LHC probably won’t see the ********(> 6 TeV)**

**m****H**

**m******

- Chivukula, He, Hoelbling

## Strong WW scattering

**Strong WW scattering**
**Will be possible to establish a signal as an excess of W****+****W****+**** events, but measurements will be hard**

**ATLAS 300 fb****-1**
**__ K-matrix**
**--- 1 TeV H**

## Higgs at a Linear Collider

**No longer about discovery; about precision**
**Plays the role that LEP did to the SPS for W/Z **
**Psychology very different!**
**Exploit**
**Aggressive detector technology (charm tagging, calorimetry)**
**Polarization**
**Higgs production at a LC:**

**For ********s = 500 GeV  (few********100fb****-1**** per year)**
**m****H**** = 120 GeV, ******** ~ 80fb****	**** **
**m****H**** = 240 GeV, ******** ~ 40fb**
**   ****(cf. total e****+****e****-**** ********qq cross section few pb)**
**HZ process allows H reconstruction**
**in a model independent way (from Z)**
**For an 800 GeV machine, ****HZ is suppressed, H******** dominant**

**H**

**Z**

****

**H**

****

- Jim Brau at Snowmass:*“Just finding the Higgs is of limited value”*

## Higgs couplings to W and Z

**Use Z ******** ****l****+****l****-**** together with known ********s to reconstruct mass of Higgs ****(= whatever the Z recoils against) **
**Flavor blind, includes invisible decays (e.g. neutralinos)**
**	******** ********(HZ) (few %/500fb****-1****) ******** HZZ coupling determined to few %**
**	****Provides simple test of whether this is the only Higgs: does it account for all of the mass of the Z?**
**	****e.g. in the MSSM g****hZZ****= g****Z****M****Z****sin(********–********)**
**	****	****	**** ****g****HZZ****= g****Z****M****Z****cos(********–********)**
**Use H******** process with H********bb and reconstruct missing mass**
**	******** ********(H********)  (few %/500fb****-1****)******** HWW coupling determined to few %**
**	****Also get total width to a few % from ********(H********) and BR(H********WW) **

******s = 350 GeV**

**HZ**

**H******

## Higgs couplings to fermions

**Requires b, c, tagging based on vertex**
**Requires tau-ID based on hadronic jet multiplicity and kinematics**
**H ******** ******** **
**BR ~ 10****-4**** but clean**
**H ******** tt**
**indirectly (through H ******** gg)**
**through ttH if ********s sufficient**
**Bottom line for ********(g****2****)  ****Snowmass**
**	****m****H**** = 120 GeV, 500 fb****-1**** @ 500 GeV**
**hbb ~ 4 %**
**htt ~ 10 % ****[@ 800GeV]**** **
****** ****topcolor?**
**h******** ~ 7 %**
**hcc ~ 7 %**
**h******** ~ 30 %**

**c coupling/SM**

**b coupling/SM**

**Distinguish MSSM with****m****A**** up to ~ 600 GeV**

## Quantum numbers of the Higgs

**H ******** ******** at LHC already excludes J =1 and requires C even**
**Angular dependence of e****+****e****-**** ******** ZH and of the Z ********ff decay products can cleanly separate CP-even H and odd A**
**sensitive to a 3% admixture of CP-odd A in the “H” signal **

***ZH***

***ZA***

***ZZ***

*cos***

## Higgs self-coupling

**Shape of the Higgs potential can be tested if the HHH coupling is determined**
**Extract from ZHH production (******** 6 jets)**
**Cross section ****tiny**** ~ 0.2 fb ******** requires O(1 ab****-1****)**
**g****HHH**** at the 20 - 30% level**

**g/g(SM)**

**246 GeV/********2**

## MSSM 

**How can the LC help in the moderate tan ******** “problem region” for the LHC?**
**Charged H****±**** only visible in top decays (m****A**** < 150 GeV or so)**
**H and A not visible at all **
**At the LC, direct observation**
**e****+****e****-**** ******** H****+****H****-**** ******** tb tb**
**e****+****e****-**** ******** HA ******** 4b **
**Both cover ~ all m****A**** < 350 GeV****for ********s = 800 GeV**
**Indirectly**
**Distinguish h from H****SM**** up to m****A**** ~ 600 GeV**

**H****±**
**300 GeV**

## No Higgs

**An LC would be an excellent machine to explore the rich spectrum of technihadrons in low-scale technicolor**
**If the LHC sees an excess in WW ******** WW scattering, the LC can measure the form factor of the resonance from e****+****e****- ******** WW **
**LC can probe WW masses far beyond its ********s, measure real and imaginary parts of form factor**
**LC can explore other final states hard to see at LHC**
**WW ******** tt, WW ******** ZZ**
**Worst cases are just that ****— a bad outcome for all**
**The LC potentially makes a bad outcome less bad **
**Provides additional information needed in order to choose the next steps**

## ... leading to a Very Large Hadron Collider?

_**Phase 1**_** – complete our study of the TeV scale**
**heavy superpartners,  isosinglet quarks, few TeV WW resonances . . .**
**Physics that can be simulated and described**
_**Phase 2**_** - Explore the next higher energy scale 10-100 TeV**
**SUSY breaking scale?**
**Deep inelastic WW scattering (see constituents?)**
**This physics is much harder to simulate or describe, but potentially much more interesting and important**

**In many cases (inverted heirarchy SUSY, topcolor...) there can be new ****particles at the few TeV scale that are not visible at the LHC**
**Often the only way to know whether a new collider has high enough energy****to see them is from precision measurements of the Higgs, or whatever ****plays its role; this is the only thing that is guaranteed to be visible (********s!)**
**Without that knowledge, could we go to ****a funding agency to ask for a VLHC? **