K. Kumar, W. Marciano, Y. Li

Electroweak physics at EIC- Summary of week 7

INT Workshop on Pertubative and Non-Pertubative Aspects of QCD at Collider Energies

Nov. 19th 2010

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(Talks by M. Gonderinger and A.

Deshpande)

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

Weak mixing angle at EIC(Talks by K. Kumar, W. Marciano, and YL)

13

Scenarios of Higgs mechanism

• Higgsless models;

• Composite Higgs as a PGB;

• Fundamental Higgs: hierarchy problem

Georgi-Kaplan model;

Extra Dim; SUSY;

Technicolor;

1414

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!

151515

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 !

16161616

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

1717171717

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!

181818181818

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?

19191919191919

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!

20202020202020202020

Past and currently planed experiments:

Where does EIC stand?

21212121212121212121

Weak mixing at EIC

• The ugly:

Large uncertainty with the polarized PDFs;

Higher asymmetry at high Q:

• The good:

Both beam polarized;

Low luminosity ( ) compared to fixed target experiments ;

• The bad:

2222 ,/1 , QNAQNQA

-1-235,34,33 sec cm 10

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

22222222222222222222

Weak mixing at EIC

• How to control the systematic error?

• What is the required luminosity to reach specific statistical error?

• What are the good asymmetries?

2323

Single-spin asymmetries

•Simplified for e-d:

PDF drops out for isosinglet

Large x: antiquark contribution negligible,

small uncertainty in PDF

Large uncertainty (5%)

•For e-p collider:

2424

Effective polarization

•Take advantage of effective polarization:

2525

Double-spin asymmetry

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

2626

Good asymmetries

•e-d collider:

•e-p collider:

272727

Preliminary MC simulation results

•single-spin asymmetry in e-p:

282828

Preliminary results on reachable precision

•e-p collider with polarized electron beam:

29292929292929292929

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

303030

Summary and outlook

• Precision tests are very important probe of BSM before and after LHC.

Thank you !!!Thank you !!!

• Many things to do

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

think about other topics;

W2sin

• EIC has good chance to

go beyond HERA on bounds on e-tau conversion;

redo the analysis of signal selection efficiency for e-tau at EIC;

a better understanding of systematic error of PVDIS;