# Presentation: 126598

## THE LHC/LC SYNERGY

- 		            S. Dawson, BNL
- 		            December, 2002
-  Why we need both the LC and the LHC
-  Examples:  EWSB, SUSY, top quark
-  The cosmological connection

## Why are we here?

***Not*** to compare/ contrast LHC/LC
- Rather to see how physics info from one machine can influence physics results from the other
***Goal:***  Working group document, Spring 03

*Weiglein, Oreglia*

## What do we want to know?

- What is the origin of EWSB?
- Is it a Higgs?
- Is it something else?
- What is the origin of fermion masses?
- Understanding the top quark
- Is there physics at an intermediate scale? (and what is the scale?)
- Is it SUSY?
- Is it little Higgs?
- Is it extra dimensions?
- .....

## Is mass due to a Higgs boson?

- Production rates at LEP, Tevatron, LHC fixed in terms of mass
- Direct search limit from LEP
- Higgs contributions to precision measurements calculable

- Precision measurements:

- G. Mylett, Moriond02

- LHC

***Higgs Discovery at Tevatron or LHC***

- Tevatron

*Carena, Conway, Haber, Hobbs, hep-ph/0010338*

*ATLAS TDR*

## Is it a Higgs?

- How do we verify role in EWSB?
- Measure Yukawa couplings
- Measure spin/parity
- Reconstruct Higgs potential

## Higgs properties at LHC

- LHC measures B
- Eg,  ggh depends on ggh and h couplings
- Result is combination of coupling constants
- Significant PDF uncertainties
- Cancel in ratios
- Weak boson fusion depends on SU(2) assumption about WWh and ZZh couplings
- Precision measurement for Mh>140 GeV from WBF

- Zeppenfeld, Belyaev, Reina

## Higgs Measurements at LHC

- Mh<140 GeV, H/H10-20%
- Not all channels possible
- tth, h+- critical

*Belyaev & Reina, hep-ph/0205270*

*200 fb**-1*
*300 fb**-1** *
*(tth,h****, Wh,h****bb)*

## Untangle Higgs Couplings

- PDF uncertainties cancel in ratios
- Improved precision by fixing bbh/h coupling to SM value
- Note lousy precision on bbh
- Theory systematic error:
- 20% (ggh)
- 5% (WBF)
- 10% (pptth)

*Belyaev & Reina, hep-ph/0205270*

*200 fb**-1*

## Well determined initial state
Precision masses with recoil technique
Higgs mass independent of Higgs decay       

Model independent Higgs BRs

- Precision masses with recoil technique
- Higgs mass independent of Higgs decay
- Model independent Higgs BRs

- Van Kooten

## Coupling Constant Measurements at LC 

*Battaglia & Desch, *
*hep-ph/0101165*

- LC

*L=500 fb**-1**, ****s=350 GeV*

*Compare LHC:**  *
*	**g**bbh****40-50% *
*WBF, 600 fb**-1**** *
*            **g**bbh**** 10-20%*

*Piccinini & Polosa, hep-ph/0211170*

*At LC, largest uncertainty is theory from m**b**!*

## Who cares about Higgs Couplings?And how well do we need to do?

- SUSY models, gbbh enhanced at large tan , small MA ...info about SUSY parameters
- Little Higgs, topcolor models, new physics in gtth

*Logan*

## Higgs mass measurements

- LC:
- LHC:
- 	Direct reconstruction of

-              LC @ 350 Gev

*Conway, hep-ph/0203206*

*Primarily interesting for comparison with precision EW measurements*

## Angular correlations of decay products distinguish scalar/pseudoscalar

- Miller, hep-ph/0102023

- Threshold behavior measures spin

- [20 fb-1 /point]

*Higgs spin/parity in e**+**e**-****Zh*

## Higgs self couplings difficult at LHC

*Baur, Plehn, Rainwater, hep-ph/021124*

*gg****hh****W**+**W**-**W**+**W**-****(jjl****)(jjl****)*

* **g**hhh**=M**h**2**/2v*

## Measuring Higgs Self Couplings at LC

- Must measure
-              e+e- Zhh
- Small rate
-      .2 fb for Mh=120 GeV large background

- Large effects in SUSY
- Resonances
-  ghhh suppressed  MA < 300 GeV

*Lafaye, hep-ph/0002238*

*Castanier, Gay, Lutz, Orloff, hep-ph/0101028*

## Is the world Supersymmetric?

*Find SUSY particles*
*     **Find  SUSY partners*
*Check impact on precision measurements*
*Measure SUSY couplings*
*Reconstruct underlying GUT  theory*

## Light SUSY consistent with Precision Measurements

- SUSY predicts light Higgs, Mh<130 GeV
- For MA, SUSY Higgs sector looks like SM
- Can we tell them apart?
- Higgs BR are different in SUSY
- Find all SUSY Higgs

- LHC

*Find all the Higgs Bosons*

*Carena, hep ph/9907422*

- Tevatron

*** **collider sensitive*

*Gunion*

*4 years at ****!*

## Into the wedge

-  e+e- H+H-, H0A0
- 	  Observable to  MH=460 GeV
-        at s=1 TeV
- e+e- H+,H+tb
-        L=1000 fb-1, s=500 GeV,
-        3 signal for MH 250 GeV
-  e+e- W+H-
- 	Largest at low tan 
-     s=500 GeV,  .01 fb

*Moretti, hep-ph/0209210*

*Logan & Su, hep-ph/0206135*

## mSUGRA simplest version of SUSY

- 4 parameters, 1 sign
-  m0  (scalar mass at MGUT)
-  m1/2 (gaugino mass at MGUT)
-  A0  (mixing term)
-  tan  (ratio of Higgs VEVs)
- Measure m(gluino) at LHC
- 	predict m(neutralino) at LC

***Very predictive...all masses and couplings predicted***

*Relationships are different for GMSB, AMSB.....*

## LHC/Tevatron will find SUSY

- SUSY mass differences from cascade decays;eg
- M0 limits extraction of other masses
- Fit to SUGRA parameters

- Catania, CMS

*Baer*

## LC makes precision mass measurements

- Chargino pair production, S-wave
- Rises steeply near threshold
- This example:

*Blair, hep-ph/99910416*

*How do we distinguish a chargino from a 4**th** generation lepton?*

*Feng, hep-ph/0210390*

## LC mass measurements from endpoint spectra

## LC can step through Energy Thresholds Run-time Scenario for L=1000 fb-1

| Year | 1 | 2 | 4 | 5 | 6 | 7 |
| --- | --- | --- | --- | --- | --- | --- |
| L (fb-1) | 10 | 40 | 150 | 200 | 250 | 250 |

- SUSY masses to .2-.5 GeV from sparticle threshold scans
- M0/M0 7% (Combine with LHC data)
- 445 fb-1 at s=450-500 GeV
- 180 fb-1 at s=320-350 GeV (Optimal for Higgs BRs)
- Higgs mass and couplings measured, gbbh1.5%
- Top mass and width measured, Mt150 GeV
-                     *Battaglia, hep-ph/0201177*

## LHC:  Fits to SUSY Parameters

*Bachacou, Hinchliffe, Paige,  hep-ph/9907518*

*LC accuracy*

*LHC:  Mass reconstruction limited by LSP mass*
*** **LHC sensitive to mass *
*           ****differences***

***Measurement of LSP mass***
***at LC improves LHC***
*** ******mass resolution***

## SUSY: LC+LHC

- LHC sensitive to heavy squarks
- Use neutralino mass, couplings from LC
- CMS study:10 fb-1 gives squark, gluino masses to 1-2% ***if ***neutralino mass known from LC

*R. Van Kooten:  “Bands, not blobs”*

## Combine LC/LHC mass measurementsWindow to high scales?

- LC  measures chargino, neutralino, selectron masses from thresholds
- LC extracts mixing parameters from cross section measurements
- LHC measures gluino, squark masses
- RGE evolve parameters to GUT scale

-   Sample mass measurements
-                 (SPS#1A):
- LC:
- LHC:

## Do gaugino & Scalar masses unify in mSugra?

*Freitas, hep-ph/0211076*

*Gaugino masses*

*Scalar masses*

## SUSY Couplings:

- Compare rates at NLO:
- Lowest order,
- Super-oblique corrections sensitive to higher scales

- Masses from endpoints
- Assume
- Tests           coupling to 1% with 20 fb-1

- Feng

*Probes mechanism of SUSY breaking*

## Are we being too simplistic?

- Many possibilities beyond MSSM
- Suppose explicit CP violation
- Complex tri-linear mixing
- Instead of h,H, and A
-  3 states which mix
- Holes in LEP limits on Higgs search
- New phenomenology

- Carena, Mrenna

## Cosmic Connections

*Cosmic Connections*

- LC/LHC can give insight into origin of dark matter
- SUSY provides dark matter candidate, LSP
- LSP is weakly interacting, neutral and stable

##  

- mSUGRA predicts everything in terms of 5 parameters
- Calculate  0 relic density
- Assume 2 around central value

***.07 <************X******h******2******<.21***

***Requires ***
***m******1/2******>300-400 GeV***
***M(************+****** ******)>240 GeV***
***M(************o******)>120 GeV***

*Arnowitt and Dutta, hep-ph/0204187*

*Assume Dark Matter is ****0** *

**Forbidden by 3********  g-2**

## Dark Matter at large tan 

- CLEO bound from bs
- Similar allowed region from dark matter
*Does this picture persist for more complicated SUSY models?*

*1.8 x 10**-4**<B(b****s****)*
*  **<4.5 x 10**-4*

## Understanding the Top Quark

- Why is  Mt  v/2 ?
- Kinematic reconstruction of  tt threshold gives pole mass at LC
- Compare LHC

- Groote , Yakovlov, hep-ph/0012237

- QCD effects well understood
- NNLO ~20% scale uncertainty

*2M**t **(GeV)*

**

## Who cares about precision Mt?

- Precision Mt, MW  test consistency of SM
- Limits Higgs mass, SUSY parameters

## Top Yukawa coupling tests models

-  tth coupling sensitive to strong dynamics
- Above tth threshold
-             e+etth
- Theoretically clean
- s=700 GeV, *L*=1000 fb-1

- Large scale dependence in tth rate at LHC
*L*=300 fb-1

- Baer, Dawson, Reina, hep-ph/9906419
- Juste, Merino, hep-ph/9910301

- Reina, Dawson, Orr, Wackeroth, hep-ph/0211438
- Beenacker, hep-ph/0107081

##  tth at LC

- 20 % measurement of gtth to mh=200 GeV using hWW decay
- Needs s=800 GeV

*Gay, 02*

## What if the LHC doesn’t find a Higgs????

- Still have to understand MW, precision measurements
- Fit to  S, T0
- 	Without Higgs, effective theory
- For new physics at 3 TeV scale, EW fits give a,b1
- Models which satisfy EW constraints without Higgs tend to have new Z’ or light t’s

*Bagger, Falk, & Schwartz, hep-ph/9908327*

*Hill & Simmons, hep-ph/0203079*

## Exciting physics ahead

- LHC/Tevatron finds Higgs
-           LC makes precision measurements of
-               couplings to determine underlying model
- LHC finds evidence for SUSY, measures mass differences
-          LC untangles spectrum, finds sleptons
-          LHC/LC  combination makes precision
-              measurements of  couplings and masses;
- 	         Untangles GUT theory

## Slide 41