# Presentation: 090485

## Progress in Electroweak Symmetry Breaking

- It’s not just the Higgs....
-           Weak Interactions and Neutrinos 03
-                             Sally Dawson
-                                  BNL
-                            October, 2003

- http://quark.phy.bnl.gov/~dawson/win03.pdf

## SM works well

- LEP EWWG 2003

- Any new physics severely constrained by precision measurements

- Fit assumes Mh=150 GeV

## The Job:

- Note:  Poor quality of fit

*The Job:*

- Mh < 219 GeV

- Precision EW Measurements:

-     See talk by B. Claire

-    NuTeV questions don’t change Higgs   conclusions

**Notes:**
Heavier Mtop pushes mh limit up

## The Tevatron will point the way....

- D0 preliminary:
-  Mt=180.13.64.0 GeV

***Increasing M******t ******by 5 GeV increases upper bound on  M******h ******by 35 GeV!***

## Why are we so sure this isn’t the whole story?

***   ******Why not just have a Standard Model Higgs with M******h******<200 GeV?***
- Boring!
- Leaves many questions unanswered
- Origin of fermion mass
- Higgs mechanism accommodates fermion masses, but doesn’t explain them
- What about CP?
- No gauge unification
- .....

## Light Scalars are unnatural

- Higgs mass grows with cut-off, 

- h

- h

## Solutions:

- Remove Higgs completely
- Dynamical symmetry breaking
- Higgsless models in extra D
- Lower cut-off scale
- Large extra dimensions
- Force cancellations
- SUSY
- Little Higgs
- Make Higgs component of gauge field in extra D

- Which way to go?

***Symmetries maintain cancellations at higher order!***

***Ultimate answer will come from data***!

##                       Why the TeV Scale?  

- We expect new physics on very general grounds

- Standard Model  inconsistent
- without Higgs unless new
- physics around 1.3 TeV

***Either a light Higgs, or strong WW Scattering***

- Kolda & Murayama, hep-ph/0003170

- Fits to EW data with non-zero S&T

## SUSY....Our favorite model*

- Quadratic divergences cancelled automatically if SUSY particles at TeV scale
- Cancellation result of ***supersymmetry***, so happens at every order

- * Spires: 7421 papers after 1990 with title supersymmetry or supersymmetric!

## MSSM requires light Higgs

- Tension:  stop should be **TeV scale** to cancel quadratic divergences in MH from top loops
- Stop needs to be **heavy** so that lightest Higgs mass satisfies LEP bound,
- 		MH>114 GeV
- Reasonable to consider expanding model by adding Higgs triplets and singlets

- Degrassi,Heinemeyer, Holliuk, Slavich, Weiglein, hep-ph/0212020

- tan=3

- Xt=At-cot

**Notes:**
Plots has mstop=m_A=mu=1 TeV

Check rho parameter and triplets

## LEP MSSM Higgs Bound

- Degrassi-Heinemeyer-Hollik-Slavich-Weiglein

- Boundaries of theoretically inaccessible region  (“the nose”) have shifted due to 2- loop calculations of MSSM Higgs mass

## Add Scalars to MSSM

- Add  Higgs singlet S, triplets T0,T1
- Superpotential,
- At tree level, lightest Higgs mass bound becomes,
- Higgs mass bound depends on particle content
- Assume couplings perturbative to MGUT and SUSY scale 1 Tev
-                       Mh < 150 –200 GeV with singlet and triplet Higgs
- Singlets and  triplets can be consistent with precision measurements

- Espinosa & Quiros, hep-ph/9809269,Kobe & Wells, 2002

## Beyond the MSSM (NMSSM)

- Add singlet Higgs (doesn’t spoil gauge unification)
- S3 term necessary to avoid PQ axion
- <S>  gives  term of MSSM
- W=HuHd in MSSM
- Why is  weak scale?
- Higgs phenomenology very different than MSSM:
- 3 Neutral Higgs, 2 pseudoscalar Higgs
- Many scenarios have h0, A at EW scale

- See talk by D. Miller

- Miller, Nevzorov, Zerwas, hep-ph/0304049

**Notes:**
S^3 term to avoid PQ axion

## MSSM, hAA excluded Experimentally

- hAA important discovery channel in NMSSM
-  h can be SM-like and A light in   NMSSM
- Look for
-  W+W--hAA  +- jj
- Statistically significant at LHC with 300 fb-1/detector

- Look for enhancement at low mass

- Not Gold-Plated!

- Ellwanger, Gunion, Hugonie, Moretti, hep-ph/0305109

- Curves are different models

**Notes:**
Points are different models

H->aa in mssm only possible with light a.  But then Z-> ah excludes it.

## CP Violation in MSSM

- mSUGRA type models [m0, m1/2, A0, tan , sign()] can have ***phases in m******1/2******, A******0***
- Phases change Higgs mass spectrum, couplings
- Could suppress hZZ coupling
***Light Higgs (M******h************60 GeV) could have escaped LEP detection***
- New signatures
- Can arrange large branching ratio Hh0W

- See talk by S. Mrenna

- Computational Progress:  CPSUPERH has MSSM masses with CP violation.  (hep-ph/0307377)

## Little Higgs Models

- New particles at scale f ~  cancel SM quadratic divergences
- Cancellation from same spin particles
- Need symmetry to enforce cancellation

- Heavy WH,ZH,AH cancel gauge loops
- Scalar triplet cancels Higgs loop
- Vector-like charge 2/3 quark cancels top loop

- Arkani-Hamed, Cohen, Katz, Nelson, hep-ph/0206021

## More on little Higgs

- Broken to subgroup H (SO(5))
-  Higgs is Goldstone Boson of broken symmetry
- Effective theory below symmetry breaking scale
-  Gauged subgroups of G ([SU(2)xU(1)]2) contain SM
-   Higgs gets mass at 2 loops (naturally light)
- Freedom to arrange couplings of 1st 2 generations of fermions (their quadratic divergences small)

- Heavy W’s, Z’s, ’s
- Heavy top
- Extended Higgs sector

**Notes:**
Littlest higgs has 14 gbs

## Little Higgs & Precision EW

- Mixing of heavy-light gauge bosons leads to problems with precision measurements
- Many models
- Typically,

- See talk by G. Kribs

## New Phenomenology in Little Higgs Models

- Drell-Yan production of ZH
- EW precision limits prefer  cot .2 (Heavy-light gauge mixing parameter)
- BRs very different from SM
- Look for heavy tops
- Look for non-SM 3 gauge boson vertices

- Scale down by  cot2 .04

-      Han,Logan,McElrath, Wang,  hep-ph/0301040

**Notes:**
Tevatron limit on ZH interesting

## Higgs production & decay in Little Higgs Models

- Rate  could be reduced by 25%
- Later....could see same type of effect in radion models
- How to tell the difference?
- Have to see new particles
-  ZH, WH, H

- LHC

- Han, Logan, McElrath, Wang, hep-ph/0302188

- ggh

***Growing realization that EWSB isn’t just Higgs discovery, but requires finding spectrum of new particles!***

- This is theoretically allowed region

## Look for Higgs Triplets

- Present in little Higgs models
- Easy to add to SUSY models
- Left-Right models
- Triplet VEVs contribute to  parameter
- Model with one real Higgs triplet: 4v’2/v2
- Complex triplets give H++ (unique signal for triplets)
- Lots of new signals
- Z*H++H—
- W-W- H---

- See talk by M.-C. Chen

- D0 limit:  M(H++) > 116 GeV

## Can We Evade Higgs mass Bounds?

- Higgs self-coupling scales with energy
-   at scale   
- Heavier the Higgs (=MH2/2v2)
- The smaller the scale 
- Relatively low scale of new physics
-                         ***Consider SM as effective theory***

## Higgs can be heavy with new physics

- Non-zero S and/or T required for heavy Higgs
- Mh  450-500 GeV allowed with large T
- Include all operators allowed by symmetries to construct effective theory

- See talk by W. Kilian

- Chivukula, Holbling, hep-ph/0110214

## Hard to construct explicit models

- Models are complicated
- Tend to have replicated weak gauge structure
- SU(2) x SU(2)
- non-commuting extended TC
- topflavor
- ununified SM
- U(1) x U(1)
- topcolor-assisted TC
- topflavor-seesaw
- General analysis of limits from precision measurements
- Fermion charge assignments have major effect
-  ***None of these models give better fits to EW precision data than SM***

- Topcolor, NCETC, UUM
- new physics scale bounded 10 TeV.....Extra gauge bosons too heavy to be observed at LHC
- Topflavor bounds  few TeV

- 95% cl bound on new physics scale

- Chivukula, He, Howard, Simmons, hep-ph/0307209

## Solving naturalness problem with low scale extra dimensions

- Flat:

- Warped:

- Where does Higgs live?  On the brane?  In the bulk?

- Maybe electroweak symmetry breaking through boundary conditions on the brane?

- See talk by B. Dobrescu

- Can Higgs be 5th component of gauge field in 5D?

## Models with Extra Dimensions provide another good comparison point for SM

- Extra-D Models have towers of new Kaluza Klein Gravitons
- Graviton emission can measure the number of hidden dimensions
- Graviton exchange affects precision measurements,
- 	Drell-Yan production, missing ET measurements....

## Once we find something, we want to know what it is....

- Warped extra D has radion: 
-  couples like Higgs, but with strength /TeV instead of h/v
- Higgs- mixing suppresses standard channel, ggh
- How do you know it’s a radion?
-   Have to find both Higgs & radion

- Higgs-Radion Mixing Parameter

- Battaglia, DeCurtis, DeRoeck, Dominici,& Gunion, hep-ph/030425
- Dominici, Grzadkowski, Gunion, Toharia, hep-ph/0206192
- Hewett & Spiropulu, hep-ph/0205100

- SM  Limit

- Is it a Higgs or is it a radion?

**Notes:**
To tell this model from SUSY model, you need to find phi.  You must know bk pretty well
Radion corresponds to fluctuations in size of extra dimensions.

Need to know gamma gamma background very well

## If we find a “Higgs-like” object, what then?

- We need to:
- Measure Higgs couplings to fermions & gauge bosons
- Measure Higgs spin/parity
- Reconstruct Higgs potential
- Reminder: Many models have other signatures:
- New gauge bosons (little Higgs)
- Other new resonances (Extra D)
- Scalar triplets (little Higgs, NMSSM)
- Colored scalars (MSSM)
- etc

## Coupling Constant Measurements

- Duehrssen

- LHC measures  BR for Higgs production and decay

- Individual measurements depend on combinations of coupling constants
- Do global fit to relative couplings
- How well do we need to do?

## How well do we need Higgs couplings?

- MSSM example:

- Note rapid approach to decoupling limit

- 21% deviation from SM

- 5.4% deviation from SM

- MSUSY=1.5 TeV

- Guasch, Hollik, Penaranda, hep-ph/0307012

**Notes:**
R has large renormalization scheme independent corrections in MSSM

## Absolute measurements of Higgs couplings

-  e+e- LC at s=350 GeV
-  L=500 fb-1, MH=120 GeV

- Battaglia, Desch, hep-ph/0101165

- Duhrssen, ATL-PHYS-2003-030

**Notes:**
Note LHC numbers normalized to HW coupling

## Can we reconstruct the Higgs potential?

- Fundamental test of model!

- See talks by A. deRoeck and S. Martin

## Higgs self-couplings require careful interpretation

- MSSM, corrections to 3,4 largely absorbed in definition of Higgs mass

- Little Higgs models generate effective Higgs potential from integrating out heavy particles
- At one-loop, quadratic sensitivity to cutoff
- No prediction for 3,4

- Dobado, Herrero, Hollik, Penaranda, hep-ph/0210315

- Genuine corrections to 3, 4 are differences between curves

## Reconstructing the Higgs potential

- 3  requires 2 Higgs production
- Mh<140 GeV, hbbbb
- Overwhelming QCD background
- Easier at higher Mh

- Baur, Plehn & Rainwater, hep-ph/0304015

- Can determine whether 3=0 at 95% cl with 300 fb-1 for 150<Mh<200 GeV

**Notes:**
This is not the best case since br H->bb is smaller at Mh=180 than smaller Mh

Can tell that lambda_3 isn’t zero

## Tri-Linear Higgs Coupling at e+e- Colliders

- Mh<140 Gev, e+e- Zhh
- Dominant decay, hbb
- High efficiency for identifying
-     b’s recoiling from Z
- Mh=120 GeV, s=500 GeV,
-     L=1 ab-1
- Mh>150 GeV, hW+W-
- Phase space suppression
- (Zhh) decreases at higher s; sensitivity to  decreases
- (hh)  << (Zhh)
-  s=500 GeV optimal energy

-  Castanier, hep-ex/0101028
-  Baur,Plehn, Rainwater, hep-ph/0304015

***LHC & LC are complementary:***
***LHC sensitive to M******h******>150 GeV, LC sensitive to lighter M******h***

**Notes:**
Show Uli fig 5
Uli fig 5; Castanier showed only needed to tag one b

## Look for dimension-6 Higgs Interactions

- Barger et al, hep-ph/0301097

- Model independent approach

- Lose connection between Mh and 3 with dimension-6 operators

***Is there a model?***

## What about Quartic Higgs Coupling

- Requires 3 Higgs production
- 10 TeV, e+e- collider has 5 e+e-hhh events with L= 1 ab-1
- Maybe resonant enhancement in gg hhh in MSSM?
- Unfortunately, no sensitivity to quartic coupling

- Cynolter, Lendvai, Pocsik, hep-ph/0003008

- ?

- ?

## Is it new physics?
Extra dimensions
Little Higgs
SUSY
Something really new.....
Or is it QCD?

- Extra dimensions
- Little Higgs
- SUSY
- Something really new.....
- Or is it QCD?

- Effects typically O(v2/2)

- QCD effects O(s) same size

- New Physics Searches require
***Precision Calculations***

- Unless you see a new particle or resonance!

**Notes:**
For years just the Higgs.  Mssm still uses Higgs mechanism.  Now we are thinking outside the box.
Higgs in 4 d; Higgs partly in extra d; maybe symmetry breaking from kk particles...

## (g-2) example of need for higher order corrections

- BNL g-2 experiment latest result from 2000 +  data released 2002

- a********x********

- Soon result of 2001 -data expected
- 	30% error reduction
- Excellent place for new physics
- 	unexplored loop effects ~ m2μ/Λ2
- Supersymmetry is natural candidate at moderate/large tanβ

## Lots of contributions to (g-2)

- Dominated by low energy region, ρ resonance

- 4loop big, never checked!

- Slide from P. Gambini

## New data for hadronic contribution

- Hagiwara et al (HMNT) NEW result:
- aμhad,LO=691.7±5.8exp±2.0r.c.

- Final CMD-2 π π data (2002) 0.6% syst error!

- This translates to a ~2-2.5σ discrepancy

- Using τ data below 1.8 GeV Davier at al (DEHZ)
-  aμhad,LO=709.0±5.1exp±1.2r.c±2.8SU(2)

- Good agreement between Aleph, CLEO, Opal τ data

- Slide from P. Gambini

- My Editorial Comment:  Still can’t make case for new physics!

## Progress in Theoretical Predictions

- NNLO results for inclusive Higgs production, pph

- Harlander & Kilgore, hep-ph/0201206,
- Anastasiou, Melnikov, hep-ph/0207004

- Note reduced scale dependence                 at NNLO

*********  ******Large corrections***

## Higgs Distributions at NLO

- NLO corrections to shape small, 5% at y=0
- Suggests using LO Monte Carlo, weighted by NNLO cross section
- Need case by case study

- Anastasiou, Dixon, &Melnikov, hep-ph/0211141
- Glosser & Schmidt, hep-ph/0209248
- Ravindran, Smith, & van Neervan, hep-ph/021114
- deFlorian, Grazzini, & Kunszt, hep-ph/9902483

- Higgs pT spectrum at NLO QCD:

## Large Mt limit and QCD corrections

- NLO, NNLO use effective theory:

- 

- Effective theory is extremely accurate approximation

## Does effective theory work for SUSY?

- Harlander and Steinhauser, hep-ph/0307346

- Use effective theory only for small tan where b loop is suppressed
- Include stop, gluino loops

***No decoupling for heavy gluino with SUSY couplings maintained***

- ggh at NNLO

- Dawson, Djouadi, Spira, hep-ph/9603423

- Omitted this   one

- SUSY effects tend to suppress rate

## Tremendous progress in automated programs

-   GRACE collaboration: Automated system for 1-loop electroweak processes
- General non-linear gauge:  check gauge independence
- Also check ultraviolet  and infrared finiteness
- 22 processes at one loop EW:
-  e+e-, e+e-, W+W-, ZZ, hZ
-  tbW+,W+Z, W+h,....
-  etc
- Uses finite photon mass
- Not easily generalized to QCD
- Start on automating 2 3 1-loop EW
-  e+e-  tth
-  e+e- h
-  e+e- Zhh
- Many new multi-loop calculations....
- Review by Dittmaier , hep-ph/0308070

- GRACE collaboration, Belanger et al, hep-ph/0308080

## NNLO QCD and NLO EW Corrections to Wh and Zh production

- Two loop O(s2) corrections to Wh  and Zh production at Tevatron and LHC
- Increase rate 5-10%
- Theoretically very clean
- Almost no scale dependence at NNLO

-     Brein, Djouadi, Harlander, hep-ph/0307206

- Complete EW corrections
- Decrease rate
- Opposite sign from QCD !

-  Ciccolini, Dittmaier, Kramer, hep-ph/0306234

**Notes:**
10% increase at Tevatron, smaller at LHC
QCD NNLO also has gg->wh, zh box

## NLO QCD &EW Corrections to tth Production

- Cancellation of QCD & EW corrections at high s

- Belanger et al, hep-ph/0301040
- Denner, Dittmaier, Roth, Weber, hep-ph/0309274

- QCD correction to tth production large at LHC

- Dawson, Jackson, Orr, Reina, Wackeroth,hep-ph/0305087
- Beenakker et al, hep-ph/0211352

##  bbh in MSSM

- NNLO:  Harlander & Kilgore, hep-ph/0304035

- NLO: Maltoni, Sullivan, & Willenbrock, hep-ph/0301033

- Only relevant in SUSY with large tan 

-  bbh

- When is the b quark a parton????
-   Leads to new signatures with single b’s:  gbbh

- Reduced theoretical error from reduced  dependence

## What is the dominant process?

***Answer depends on whether you tag outgoing b’s***

-  b densities enhanced:  b(x)  s ln(Q2/mb2) g(x)

## Exclusive cross section for 

- Use high pT b-quarks to suppress background:  need NLO

- Dittmaier, Kramer, Spira, hep-ph/0309204
- S. Dawson, C. Jackson, L. Reina, D. Wackeroth

**Notes:**
Comment on scheme dependence

## Tevatron Check Sheet:  Tevatron can probe EWSB!

- Measure Mt:
- 5 GeV in Mt is 35 GeV in Higgs limit
- Measure MW:
- Precision measurements are critical constraint on models of new physics
- Measure Drell-Yan:
-  Probes heavy Z of Little Higgs, Extra-D
- Search for Non-SM Higgs (You don’t know they’re not there until you look!)
- CP violating MSSM, NMSSM, triplets,  2HDM...
- Search for new particles:
- Models of new physics have lots of new particles
***Workshop Goal:  FILL IN MORE ENTRIES!***

- It’s not just the Higgs!

## Conclusions

- Explosion of new models
- Models strongly impacted by precision measurements
- Think outside the box....
- Look for Higgs triplets, singlets, new gauge bosons, heavy fermions....
- Calculational progress vital to distinguish new physics from radiative corrections