Transcript Weak Mixing Angle and EIC Yingchuan Li INT Workshop on Pertubative and Non-Pertubative Aspects of QCD at Collider Energies Sep.

Weak Mixing Angle and EIC
Yingchuan Li
INT Workshop on Pertubative and Non-Pertubative Aspects of QCD at Collider Energies
Sep. 17th 2010
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BNL LDRD
Electroweak Physics with an Electron-Ion Collider
Deshpande, Kumar, Marciano, Vogelsang
STUDY GOALS
• DIS & Nuclear Structure Functions (,Z,W) (Beyond HERA)
• ARL, sin2W(Q2), Radiative Corrections, “New Physics”
• Lepton Flavor Violation: eg epX
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Outline
• Why is EW precision physics important?
• The past, present, and future (EIC) of
• Summary.
sin W
2
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Standard Model
• SM of particle physics
SU(3)C  SU(2) L U (1)Y
Higgs
mechanism
U (1) EM
 Strong sector: right and complete, hard to solve;
 EW sector: still not sure about how EW symmetry
breaking happens
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Scenarios of Higgs mechanism
• Fundamental Higgs: hierarchy problem
 SUSY;
 Extra Dim;
• Higgsless models;
 Technicolor;
• Composite Higgs as a PGB;
 Georgi-Kaplan model;
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To ping down the EW symmetry breaking
• Direct search at high energy collider
 SM Higgs;  SUSY particles;  KK modes;  other exotics;
Major motivation for LHC!
See talk by Del Duca on Wed.
• Indirect searchs via precision tests
 Z-pole measurements;
 Low energy tests of neutral current;
What can EIC do on this?
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EW sector with SM Higgs
• Three para. (g,g’,v) determine properties of EW gauge bosons
 Masses: M W 
 EM coupling:
ev
ev
; MZ 
2 sin W
2 sin W cosW
e  g sin W
 Charged current:
g
2
2e2
1
GF 

8MW2 sin 2 W
2v 2
g

2

(
T

2
Q
sin
W  T3 5 )
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 Neutral current:
2 cosW
Higgs and top mass enters at loop level !
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EW precision tests: three best measured
• Fine structure constant:   1 / 137.035999084
(51)
Electron anomalous magnetic moment
• Fermi constant:
GF  1.166364(5) 105 GeV -2
Muon life time
• Z boson mass:
M Z  91.1876 0.0021GeV
LEP
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2
sin
W
The hunt for
• Prediction within SM
sin 2 W (M Z ) ms 
4
2G M Z2 [1  r (M H )]
• Z-pole experiment measurements:
SLAC :
sin 2 W ( M Z ) ms  0.23070(26)
CERN :
sin W ( M Z ) ms  0.23193(29)
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WorldAverage: sin 2 W ( M Z ) ms  0.23125(16)
3 sigma difference!
Correct?
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The implications of sin 2 W
• World average: sin 2 W (M Z )ms  0.23125(16)
M H  8539
28 GeV; S  0.13(10)
Consistent with
LEP bound
(MH>114 GeV)
Suggestive for
SUSY
(MH<135 GeV)
Rule out most
technicolor models
Satisfied and happy?
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The implications of sin 2 W
• SLAC result:
sin 2 W (M Z )ms  0.23070(26)
+ mW=80.398(25) GeV
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M H  3018
GeV; S  0.12
Ruled out by
LEP bound
(MH>114 GeV)
• CERN result:
Suggestive for
SUSY
sin 2 W (M Z )ms  0.23193(29)
+ mW=80.398(25) GeV
300
M H  450190
GeV; S  0.45
Consistent with
LEP bound
(MH>114 GeV)
Suggestive for
technicolor models
Very different implication! We failed to nail weak mixing angle!
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2
sin
W
Other evidence of
• Low energy measurements probe 4-fermion interactions:
 - hardron:  L,R
 -e:
gV,e A
e - hardron: C1u , 2u ,1d , 2 d
e-e:
C2 e
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Other evidence of sin 2 W : neutrino scattering
• Neutrino-lepton elastic scattering: R    e /   e
 probe
 - e couplings: gV,e A
 CHARM II: sin 2 W (M Z )  0.2324(84)
ms
• Neutrino-nucleon DIS:
NC
NC



N
N
 Paschos-Wolfenstein ratio R   CC
 N   CC
N
 probe  - hardron couplings:  L,R (u, d )
 NuTeV: sin
2
W (M Z )ms  0.236(2)
Rad. Corr.? Nuclear charge symmetry breaking?
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Other evidence of sin 2 W : Atomic PV
• Weak charge: QW (Z , N )  PV (Z (1  4 PV sin 2 W )  N )
 SM:
QW (Cs) SM  73.19(3)
 1990:
QW (Cs)exp.  71.04(1.38)(0.88)
 1999:
QW (Cs)exp.  72.06(28)(34)
 2008:
QW (Cs)exp.  72.69(28)(39)
 2009:
QW (Cs)exp.  73.16(28)(20)
sin 2 W (M Z )ms  0.2312(16)
Consistent with Z pole measurement!
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Other evidence of sin 2 W : Moller scattering
• E158 at SLAC:
 Pol. Electron (E=50 GeV) on fixed target: Q  0.02 GeV
2
2
 Meaure ALR to 12%, extract sin 2 W to 0.6%
sin 2 W (M Z )ms  0.2329(13)
Establish the running of mixing angle (together with APV) to 6 sigma.
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Future effort to nail sin W
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• QWEAK exp. At JLAB: ep
• Polarized Moller at JLAB: ee
ep;
ee;
• Polarized eD (fixed target) DIS at JLAB (6 & 12 GeV);
• Polarized ep & eD collider;
Goal: 0.1% accuracy
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Future effort: QWEAK & Moller
• QWEAK at JLAB:
 Electron (E=1.1 GeV) on fixed target: Q  0.03 GeV
2
2
 Polarized electron beam: Pe  0.80  1%
 Meaure ALR (ep) to 4%, extract sin 2 W to 0.3%
• Moller at JLAB:
 Electron on fixed target after 12 GeV upgrade;
 MeasureALR (ee  ee) to 2.5%, extract sin 2 W to 0.1%
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0.250
2
sin ^ W (
0.240
AFB(lep) [Tevatron]
Moller [SLAC]
-DIS
APV(Cs)
0.235
sc
re
en
ing
Moller [JLab]
Qweak [JLab]
0.230
0.225
PV-DIS [JLab]
ant
iscr
een
ing
0.245
SM
current
future
ALR(had) [SLC]
AFB(b) [LEP]
0.0010.010.11101001000
[ GeV]
Plot taken from proposal for JLAB Moller scattering
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Future effort: eD DIS
• eD (fixed target) DIS:
 Advantage: extract C2u,2d
e
ALR
(eD  eX )  Q2[(C1u  C1d / 2)  f ( y)(C2u  C2d / 2)]
 High luminosity: 1038 cm-2 sec-1
• eD(p) collision DIS:
 Larger asymmetry at higher Q-square; A  Q2 , N  1/ Q2 , A2 N  Q2
 Lower luminosity (1033,34,35 cm-2 sec-1 );
 Both electron and deuteron (proton) are polarized;
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E-Ion collider: double asymmetry
 RR   RL   LR   LL
 Pe
 RR   RL   LR   LL
 RR   RL   LR   LL
p,D
 Pp , D
• Polarized p or D: ALR 
 RR   RL   LR   LL
 RR   LL
ep
A

 Peff .
• Both e & p (D) polarized:
LLRR
 RR   LL
e
• Polarized e: ALR 
 Effective polarization: Peff . 
Pe  Pp
1  Pe Pp
Pe  0.85, Pp  0.70  Peff .  0.972
Peff . / Peff .  0.17Pe / Pe  0.08Pe / Pe
Larger!
Smaller!
Pe  0.85 0.004, Pp  0.70  0.014 Peff .  0.972 0.0018
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Summary
• Precision tests are very important in revealing the physics
behind EW symmetry breaking among other things.
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• The most precise (0.1%) measurement at Z pole of sin W
still has 3 sigma difference.
• Another future measurement of sin 2 W with 0.1%
precision is demanded.
• The EIC may add new twist to it!
Thank you !!!