Yingchuan Li

Weak Mixing Angle and EIC

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

Sep. 17th 2010

22

BNL LDRDElectroweak Physics with an Electron-Ion

ColliderDeshpande, Kumar, Marciano, Vogelsang

STUDY GOALS

• DIS & Nuclear Structure Functions (,Z,W) (Beyond HERA)

• ARL, sin2W(Q2), Radiative Corrections, “New Physics”

• Lepton Flavor Violation: eg epX

Outline

3

• Summary.

• Why is EW precision physics important?

• The past, present, and future (EIC) of W2sin

4

Standard Model

4

• SM of particle physics

EMU )1(

EW sector: still not sure about how EW symmetry breaking happens

Strong sector: right and complete, hard to solve;

YLC USUSU )1()2()3( Higgs

mechanism

5

Scenarios of Higgs mechanism

• Higgsless models;

• Composite Higgs as a PGB;

• Fundamental Higgs: hierarchy problem

Georgi-Kaplan model;

Extra Dim; SUSY;

Technicolor;

66

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!

See talk by Del Duca on Wed.

777

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 !

8888

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

99999

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!

101010101010

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?

11111111111111

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!

121212121212

Other evidence of

• Low energy measurements probe 4-fermion interactions:

e

dduu

Cee

Ce

ge

2

2,1,2,1

eAV,

RL,

:-

:hardron-

:-

:hardron-

W2sin

131313131313

Other evidence of : neutrino scattering

• Neutrino-nucleon DIS:

• Neutrino-lepton elastic scattering:

W2sin

eeR /

CHARM II:

eAV,g :couplings - e probe

)84(2324.0)(sin 2 msZW M

Paschos-Wolfenstein ratio CCN

CCN

NCN

NCNR

)2(236.0)(sin2 msZW M NuTeV:

Rad. Corr.? Nuclear charge symmetry breaking?

),( :couplingshardron - RL, du probe

14141414141414

Other evidence of : Atomic PV

• Weak charge:

W2sin

)20)(28(16.73)Cs( .exp WQ

SM:

2009:

Consistent with Z pole measurement!

))sin41((),( 2 NZNZQ WPVPVW

)3(19.73)Cs( SMWQ

1990: )88.0)(38.1(04.71)Cs( .exp WQ

)34)(28(06.72)Cs( .exp WQ 1999:

)39)(28(69.72)Cs( .exp WQ 2008:

)16(2312.0)(sin 2 msZW M

1515151515151515

Other evidence of : Moller scattering

• E158 at SLAC:

W2sin

Meaure to 12%, extract to 0.6%

Establish the running of mixing angle (together with APV) to 6 sigma.

22 GeV 02.0Q

LRA W2sin

)13(2329.0)(sin 2 msZW M

Pol. Electron (E=50 GeV) on fixed target:

16

171717171717171717

Future effort to nail W2sin

Goal: 0.1% accuracy

• Polarized ep & eD collider;

• QWEAK exp. At JLAB: ep ep;

• Polarized Moller at JLAB: ee ee;

• Polarized eD (fixed target) DIS at JLAB (6 & 12 GeV);

181818181818181818

Future effort: QWEAK & Moller

• Moller at JLAB:

Measure to 2.5%, extract to 0.1%

%180.0 eP

W2sin

Polarized electron beam:

Electron on fixed target after 12 GeV upgrade;

22 GeV 03.0Q

• QWEAK at JLAB:

Electron (E=1.1 GeV) on fixed target:

Meaure to 4%, extract to 0.3%

)( eeeeALR

)(epALR

W2sin

19

0 .0 0 1 0 .0 1 0 .1 1 1 0 1 0 0 1 0 0 0 [GeV]

0 .2 2 5

0 .2 3 0

0 .2 3 5

0 .2 4 0

0 .2 4 5

0 .2 5 0si

n2W^

(

AP V(C s)

Q w eak [ J Lab ]

Mo ller [S LAC ]

-D IS

A L R (h ad ) [S LC ]

A F B (b ) [LE P ]

A F B ( lep ) [T ev atro n ]

screening

antis

cree

ning

Mo ller [ J Lab ]

P V-D IS [ J Lab ]

S Mcurrentfuture

Plot taken from proposal for JLAB Moller scattering

20202020202020202020

Future effort: eD DIS

• eD(p) collision DIS:

High luminosity:

duC 2,2

-1-235,34,33 sec cm 10

Larger asymmetry at higher Q-square;

Lower luminosity ( );

Both electron and deuteron (proton) are polarized;

• eD (fixed target) DIS:

Advantage: extract

2222 ,/1 , QNAQNQA

)]2/)(()2/[()( 22112

dudueLR CCyfCCQeXeDA

-1-238 sec cm 10

2121212121212121212121

E-Ion collider: double asymmetry

• Both e & p (D) polarized:

pe

peeff PP

PPP

1.

• Polarized p or D:

• Polarized e:

eLLLRRLRR

LLLRRLRReLR PA

DpLLLRRLRR

LLLRRLRRDpLR PA ,

,

.effLLRR

LLRRepLLRR PA

Effective polarization:

eeeeeffeff PPPPPP /08.0/17.0/ ..

0018.0972.0014.070.0 ,004.085.0 . effpe PPP

972.070.0 ,85.0 . effpe PPP

Smaller!

Larger!

222222

Summary

• The EIC may add new twist to it!

• Another future measurement of with 0.1% precision is demanded.

• The most precise (0.1%) measurement at Z pole of still has 3 sigma difference.

W2sin

• Precision tests are very important in revealing the physics behind EW symmetry breaking among other things.

W2sin

Thank you !!!Thank you !!!