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:
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 !!!