Yingchuan Li

Weak Mixing Angle at Electron-Ion Collider

DIS 2011, Newport News, VA

Collaboration with William Marciano

Outline2

• Conclusion

• Prospects of measuring weak mixing angle at EIC

• Introduction

3

EW symmetry breaking: still a big puzzle !

• So many models:

Higgsless: Technicolor

Composite Higgs: Georgi-Kaplan model, Little Higgs, Gauge-Higgs Unification

Hungary for Experimental Data!

Fundamental Higgs: SUSY, Extra Dim., RS…

44

To ping down the EW symmetry breaking

• Indirect searchs via precision electroweak

• Direct search at high energy collider KK modes; SM Higgs;

Vital role in the establishment of the next model;

SUSY particles; other exotics;

What can EIC do on this?

Play important role in the establishment of SM;

Major motivation for LHC!

55555

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 measurements:

W2sin

)](1[24)(sin

22

HZmsZW MrMG

M

3 sigma difference!

666666

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?

7777777

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 33

18 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!

8888888888

Past and currently planed experiments:

Where does EIC stand?

9999999999

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;

10101010101010101010

Weak mixing at EIC

• How to control the systematic error?

• What is the statistical error with reasonable luminosity?

• What are the good asymmetries?

1111

Single-spin asy. with polarized electron

•Simplified for ed-DIS:

PDF drops out for isosinglet

•For ep-DIS:

1212

Single-spin asy. with polarized hadron

•For ed-DIS:

•For ep-DIS:

Large uncertainty with hadron polarization and polarized PDF

1313

Effective polarization: the trick learned from Moller scattering

•Take advantage of effective polarization:

1414

Double-spin asymmetry

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

•Double-spin asymmetry:

1515

Good asymmetries

•e-d collider:

•e-p collider:

171717

Monte Carlo simulation: asymmetries

•single-spin asymmetry in ed-DIS:

191919

Monte Carlo simulation: Figure of merit

•Figure of merit for ed-DIS:

212121

Monte Carlo simulation: statistical error

•Statistical error for ed-DIS:

22222222222222222222

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

232323

Summary

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

Thank you !!!Thank you !!!

W2sin• EIC has good chance to measure over a wide

range of Q with statistical error similar to Z-pole experiments.

• It is highly desirable to have another experiment on weak mixing angle given the 3 sigma difference in two Z-pole experiments.