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;