the lhc/lc synergy

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

WWWh

fffh

gMgv

mg

clGeVM h %95@114

clGeVM h %95@196

Precision measurements:

G. Mylett, Moriond02

LHCHiggs 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

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Higgs properties at LHC• LHC measures B

– Eg, ggh 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/H10-20%

• Not all channels possible

• tth, h+- critical

Belyaev & Reina, hep-ph/0205270

200 fb-1

300 fb-1 (tth,h, Wh,hbb)

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% (ggh)– 5% (WBF)– 10% (pptth)

Belyaev & Reina, hep-ph/0205270200 fb-1

• Well determined initial state– Precision masses with

recoil technique– Higgs mass independent of

Higgs decay – Model independent Higgs

BRs

yrHiggsGeVM h

/000,40120

Zhee

22 2 ZZh MEssM

Van Kooten

Coupling Constant Measurements at LC

Battaglia & Desch,

hep-ph/0101165

LC

%21WWhg

%2bbhg

L=500 fb-1, s=350 GeV

Compare LHC:

gbbh40-50%

WBF, 600 fb-1

gbbh 10-20%

Piccinini & Polosa, hep-ph/0211170

At LC, largest uncertainty is theory from mb!

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

MeVMfbGeVM

h

h

50500,120 1

h

MeVMfbGeVM

h

h

100300,150 1

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

gghhW+W-W+W-(jjl)(jjl) ghhh=Mh2/2v

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

%24

1000 1

hhh

hhh

fb

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 HAHh ,,, 000

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/0209210Logan & 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

2/1~2/1~2/1~ 5.2,4.,8.1

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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

• M0 limits extraction of other masses

• Fit to SUGRA parameters

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LC makes precision mass measurements

• Chargino pair production, S-wave

• Rises steeply near threshold• This example:

Blair, hep-ph/99910416

%1.mm

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

Feng, hep-ph/0210390

LC mass measurements from endpoint spectra

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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 M0/M0 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, gbbh1.5%

• Top mass and width measured, Mt150 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 massat 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 measurementsWindow 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:

%2.1.~~ 012,1

%21~~~, gue LRR

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

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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• 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 <Xh2<.21

Requires m1/2>300-400 GeVM(+

)>240 GeVM(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 bs

• Similar allowed region from dark matter

• Does this picture persist for more complicated SUSY models?

1.8 x 10-4<B(bs) <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

MeVMfb

t 20040 1

Groote , Yakovlov, hep-ph/0012237

QCD effects well understood

NNLO ~20% scale uncertaintyGeVMfb

t 2150 1

2Mt (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+etth• Theoretically clean s=700 GeV, L=1000 fb-1

• Large scale dependence in tth rate at LHC

• L=300 fb-1

%5.6tth

tth

gg

Baer, Dawson, Reina, hep-ph/9906419

Juste, Merino, hep-ph/9910301

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

Beenacker, hep-ph/0107081

% 16 tth

tth

gg

tth at LC

• 20 % measurement of gtth to mh=200 GeV using hWW 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, T0

Without Higgs, effective theory

• For new physics at 3 TeV scale, EW fits give a,b1

• Models which satisfy EW constraints without Higgs tend to have new Z’ or light t’s

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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