Transcript Electroweak physics at EIC - Summary of week 7 K. Kumar, W.

Electroweak physics at EIC
- Summary of week 7
K. Kumar, W. Marciano, Y. Li
INT Workshop on Pertubative and Non-Pertubative Aspects of QCD at Collider Energies
Nov. 19th 2010
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Outline
• Introduction: symmetry of SM
• Lepton flavor violation at EIC
• Weak mixing angle at EIC
• Conclusion
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Standard Model:
symmetry and symmetry breaking
• Symmetries:
 QCD and EW gauge symmetries;
 Many accidental global symmetries L, B, B-L, LF…;
• Symmetries breaking:
 Broken discrete symmetries C, P, CP;
 Dynamical chiral symmetry breaking;
 EW gauge symmetry breaking;
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LFV: e-tau conversion
(Talks by M. Gonderinger and A. Deshpande)
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Accidental symmetries of SM
• L, B, B-L, LF…
• global symmetries (may or may not be gauged);
• respected by relevant operators in SM
- specific quantum numbers of SM fields
• violated in extension of SM
- new fields carrying new quantum numbers
• violated by irrelevant operators – induced by new physics
Search for BSM by search for violation of these symmetries
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Flavor & CP problem for BSM
• What about the new physics scale?
 high enough to suppress flavor and CP violations;
Hunted for long time but not found (mostly
involving first-two generations).
 low enough to stabilize the EW breaking scale;
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
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LFV of tau
• Various operators:
 Magnetic moment operator ;
• Various processes:
 tau -> e, gamma;
 tau -> 3 e;
 e-tau conversion (e p->tau, X);
 4-fermion operators;
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Theoretical and experimental analysis
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Weak mixing angle at EIC
(Talks by K. Kumar, W. Marciano, and YL)
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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!
• 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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Past and currently planed experiments:
Where does EIC stand?
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Weak mixing at EIC
• The good:
 Higher asymmetry at high Q: A  Q , N  1/ Q , A N  Q
2
2
2
2
 Both beam polarized;
• The bad:
 Low luminosity (1033,34,35 cm-2 sec-1 ) compared to fixed
target experiments ;
• The ugly:
 Large uncertainty (5%) with the hadron beam polarization;
 Large uncertainty with the polarized PDFs;
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Weak mixing at EIC
• What are the good asymmetries?
• How to control the systematic error?
• What is the required luminosity to reach specific
statistical error?
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Single-spin asymmetries
• For e-p collider:
• Simplified for e-d:
Large x: antiquark contribution negligible,
small uncertainty in PDF
PDF drops out for isosinglet
Large uncertainty (5%)
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Effective polarization
• Take advantage of effective polarization:
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Double-spin asymmetry
• Simplified for e-d at kinematic region with y->1:
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Good asymmetries
• e-p collider:
• e-d collider:
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Preliminary MC simulation results
• single-spin asymmetry in e-p:
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Preliminary results on
reachable precision
• e-p collider with polarized electron beam:
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Past, currently planed, and EIC experiments:
• Weak mixing probed at wide range of Q at EIC:
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Summary and outlook
• Precision tests are very important probe of BSM
before and after LHC.
• EIC has good chance to
 go beyond HERA on bounds on e-tau conversion;
 measure sin 2 W over a wide range of Q with statistical error similar to
the Z-pole experiments and other planed low-Q experiments (JLab) ;
• Many things to do
 redo the analysis of signal selection efficiency for e-tau at EIC;
 a better understanding of systematic error of PVDIS;
 think about other topics;
Thank you !!!