Yingchuan Li

Electroweak physics at EIC

Brookhaven National Lab

Feb. 3rd 2011, BNL

Outline

2

• Conclusion

• Lepton flavor violation at EIC

• Weak mixing angle at EIC

• Introduction: symmetry of SM

3

Standard Model: symmetry and symmetry breaking

3

• Symmetries breaking:

EW gauge symmetry breaking;

Many accidental global symmetries L, B, B-L, LF…;

QCD and EW gauge symmetries;

• Symmetries:

Broken discrete symmetries C, P, CP;

Dynamical chiral symmetry breaking;

4

LFV: e-tau conversion at EIC

(Based on talks by M. Gonderinger and A. Deshpande in INT workshop)

5

Accidental symmetries of SM

• violated by irrelevant operators – induced by new physics

• L, B, B-L, LF…

• respected by relevant operators in SM - specific quantum numbers of SM fields

• global symmetries (may or may not be gauged);

• violated in extension of SM - new fields carrying new quantum numbers

Search for BSM by search for violation of these symmetries

6

7

Flavor & CP problem for BSM

• What about the new physics scale?

high enough to suppress flavor and CP violations;

low enough to stabilize the EW breaking scale;

Hunted for long time but not found (mostly involving first-two

generations).

Solution: treat the 3rd generation differently

“More minimal SUSY”, Cohen, Kaplan, Nelson 1996;“Warped Extra Dim.”, Randall, Sundrum 1999;

Large FV and CPV associated with 3rd generation

88

LFV of tau

• Various processes:

Magnetic moment operator ;

e-tau conversion (e p->tau, X);

tau -> 3 e;

• Various operators:

4-fermion operators;

tau -> e, gamma;

9

10

11

Theoretical and experimental analysis

12

Waiting for Ahbay’s update on experimental aspects.

Please stay tuned!

13

Weak mixing angle at EIC

14

Scenarios of Higgs mechanism

• Higgsless models;

• Composite Higgs as a PGB;

• Fundamental Higgs: hierarchy problem

Georgi-Kaplan model;

Extra Dim; SUSY;

Technicolor;

So many models, need experimental evidence!

1515

To ping down the EW symmetry breaking

• Indirect searchs via precision tests

• Direct search at high energy collider

KK modes; SM Higgs;

Low energy tests of neutral current;

SUSY particles; other exotics;

What can EIC do on this?

Z-pole measurements;

Major motivation for LHC!

161616

EW sector with SM Higgs

• Three para. (g,g’,v) determine properties of EW gauge bosons

Neutral current:

Wge sin

WWZ

WW

evM

evM

cossin2 ;

sin2

2

g

)sin2(cos2 53

23

TQT

gW

W

Masses:

EM coupling:

Charged current:222

2

2

1

sin8

2

vM

eG

WWF

Higgs and top mass enters at loop level !

17171717

EW precision tests: three best measured

• Z boson mass: GeV 0021.01876.91 ZM

Muon life time

• Fine structure constant:Electron anomalous magnetic

moment

)51(035999084.137/1

• Fermi constant: -25 GeV 10)5(166364.1 FG

LEP

1818181818

The hunt for

Correct?

• Prediction within SM

)16(23125.0)(sin :Average World

)29(23193.0)(sin :CERN

)26(23070.0)(sin :SLAC

2

2

2

msZW

msZW

msZW

M

M

M

• Z-pole experiment measurements:

W2sin

)](1[2

4)(sin

2

2

HZmsZW

MrMGM

3 sigma difference!

191919191919

The implications of

• World average:

W2sin

)10(13.0 GeV; 85 3928

SM H

)16(23125.0)(sin 2 msZW M

Rule out most technicolor

models

Consistent with LEP

bound (MH>114

GeV)

Suggestive for SUSY

(MH<135 GeV)

Satisfied and happy?

20202020202020

The implications of

• CERN result:

W2sin

45.0 GeV; 450 300190

SM H

)29(23193.0)(sin2 msZW M

Suggestive for technicolor

models

Consistent with LEP

bound (MH>114

GeV)

• SLAC result:

12.0 GeV; 30 3318

SM H

)26(23070.0)(sin2 msZW M

Suggestive for SUSY

Ruled out by LEP bound (MH>114

GeV)

+ mW=80.398(25) GeV

+ mW=80.398(25) GeV

Very different implication! We failed to nail weak mixing angle!

21212121212121212121

Past and currently planed experiments:

Where does EIC stand?

22222222222222222222

Weak mixing at EIC

• The ugly:

Large uncertainty with the polarized PDFs;

High energy:

higher asymmetry, wide coverage of Q.

• The good: Both beam polarized;

Low luminosity ( ) compared to fixed target experiments ;

• The bad:-1-235,34,33 sec cm 10

Large uncertainty (5%) with the hadron beam polarization;

23232323232323232323

Weak mixing at EIC

• How to control the systematic error?

• What is the statistical error with reasonable luminosity?

• What are the good asymmetries?

2424

Single-spin asy. with polarized electron

•Simplified for ed-DIS:

PDF drops out for isosinglet

•For ep-DIS:

2525

Single-spin asy. with polarized hadron

•For ed-DIS:

•For ep-DIS:

Large uncertainty with hadron polarization and polarized PDF

2626

Effective polarization: the trick learned from Moller scattering

•Take advantage of effective polarization:

2727

Double-spin asymmetry

•Simplified for e-d at kinematic region with y->1:

•Double-spin asymmetry:

2828

Good asymmetries

•e-d collider:

•e-p collider:

292929

Monte Carlo simulation: asymmetries

•single-spin asymmetry in ep-DIS:

303030

Monte Carlo simulation: asymmetries

•single-spin asymmetry in ed-DIS:

313131

Monte Carlo simulation: Figure of merit

•Figure of merit for ep-DIS:

323232

Monte Carlo simulation: Figure of merit

•Figure of merit for ed-DIS:

333333

Monte Carlo simulation: statistical error

•Statistical error for ep-DIS:

343434

Monte Carlo simulation: statistical error

•Statistical error for ed-DIS:

35353535353535353535

Past, currently planed, and EIC experiments:• Weak mixing probed at wide range of Q at EIC:

363636

Summary

• Precision tests are very important probe of BSM complementary to LHC.

Thank you !!!Thank you !!!

measure over a wide range of Q with statistical error similar to the Z-pole experiments and other planed low-Q experiments (JLab) ;

W2sin

• EIC has good chance to

go beyond HERA on bounds on e-tau conversion;