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Special Option #1 and #3 Summary + Precision EW & e Polarization
E3 - Linear Collider Plenary Snowmass 2001 July 17th, 2001 Snowmass, Colorado Eric Torrence University of Oregon З Giga-Z З Beam Energy З Polarimetry

Please note: I am a virtual expert...
http://www.cern.ch/torrence/talks/SM01_SO13
Eric Torrence Snowmass July 2001


Giga-Z Potential
2 20 2000 LC 15

10

5

[Experimental Only] 0 10
2

10 Higgs Mass [GeV]

3

[R. Hawkings, R. M?nig, 2000]

З sin W : 0.00017 0.00001 З mW : 35 MeV 6 MeV З mt : 3 GeV 0.2 GeV mH 5 %
Eric Torrence

2

(also b-physics)

Snowmass

July 2001


MSSM Potential

[S. Heinemeyer, G. Weiglein, 2001]

SM Uncertainty: Higgs Mass MSSM Uncertainty: SUSY particles

Eric Torrence

Snowmass

July 2001


Giga-Z Uncertainties Experimental Instrumental

Theoretical

Experimental З Selection Efficiency З Background Estimation Instrumental З Beam Energy З Beam Polarization Theoretical З Standard Model Processes З Electroweak Interpretation No Straight Answers!

Eric Torrence

Snowmass

July 2001


Theory Constraints Interpretation Quantity m m m
t

Uncertainty 130 MeV 50 MeV 0.001 2.1 MeV 5 з10
-5

sin

2 eff W

[ppm]

m

W

[MeV]

4

1

H s Z

14 18 30

2.5 1 3

had

Estimate

[S. Heinemeyer, G. Weiglein, 2001]

WW Threshold
Event Rate / Cross Section

1.05 1.04



WW

/

WW

2%

80.31 GeV

1.03 1.02 1.01 1.00 0.99 0.98 0.97 0.96 0.95
160 162 164 166 168 170

80.39 GeV

З No DPA ЗO() 4f+ needed Need ~ 0.1% on shape

Theor y 80.47 GeV Uncer tainty

Centre-of-mass Energy (GeV)

Eric Torrence

Snowmass

July 2001


Instrumentation Weak Mixing Angle
sin
2 eff W

E

beam

[MeV]

E

beam

[ppm]

SLD e- only Blondel e- only

0.00027 0.00005 0.00002

25 ~5 ~2

500 100 40

З 50M events З P e - = 80 %, P Blondel scheme З ~100M events З P e - = 80 %, P

e

+

= 0%

З P e / P e = 0.25 %

e

+

= 50 %

W Threshold E
beam

< 5 MeV [50 ppm]

Eric Torrence

Snowmass

July 2001


Prior Knowledge Predicted Improvements
sin
2 eff W

m

W

[MeV]

Today Run IIa (2 fb-1) Run IIb (30 fb-1) LHC Cumulative Giga-Z

0.00017 0.00050 0.00013 0.00021 ~ 0.00010 0.00002

34 30 15 15 ~ 10 6

[J. Erler et. al., hep-ph/0005024]

Further improvements at Run II/LHC possible!

Giga-Z Outlook З Substantial improvement in sin З Modest improvement in m W З Dramatic improvement in W ?
2 W

Giga-Z provides unique systematics...
Eric Torrence Snowmass July 2001


Beam Energy Needs Weak Mixing Angle e- only: E
beam

< 5 MeV [100 ppm] < 2 MeV [40 ppm]

Blondel: E WW Threshold E
beam

beam

< 5 MeV [50 ppm]

Low beamstrahlung needed Top Mass 40 MeV in 10fb-1 [230 ppm] Higgs Mass ~ 50 MeV (Direct Reconstruction) 100-200 ppm `adequate' for HE running

Eric Torrence

Snowmass

July 2001


Meet the WISRD
Spectrometer Magnet Quadrupole Vertical Doublet eHorizontal Bends for Synchrotron Radiation

E

beam

l = -- B dl x



Dump Synchrotron Light Monitor

e+

SLC Parameters at 50 GeV



B dl = 3.05 Tesla meters x = 27 cm at 50 GeV

l = 15 meters

Systematic Errors per Beam
B dl : Alignment: 190 ppm Detector - IP: 135 ppm Total: 250 ppm 12.5 MeV at 50 GeV 1998 SLC mZ scan implies a ~ 40 Б 20 MeV offset in ECM



100 ppm

Eric Torrence

Snowmass

July 2001


WISRD Limits Magnetic Field
З B dl : 100 ppm achieved at SLC З Error is relative: Not affected by increasing З Dominated by absolute scale error s



Relative accuracy of ~ 30 ppm achieved at LEP

Detector Alignment
З Magnet to Detector distance irrelevant: dl / l = 17 ppm З Transverse detector precision dominates: Wire Screen #1 Wire Screen #2

p

d Pitch Error: p = 10 Еm

Relative detector distance: d = 25 Еm 93 ppm at 50 GeV (d=27 cm) 370 ppm at 500 GeV! (assuming single screen) Better detector possible for high energy/small d? Intrinsic Synchrotron stripe width ~1mm at SLC...
Eric Torrence Snowmass July 2001


M?ller Scattering
Silicon Microstrip Detector (SMD) Hydrogen Gas Jet (GJT) Scattered electron 1 LEP beam Recoil Proton Tracker 2 Electromagnetic Calorimeter (ECAL) E1

L

E2

E

beam

8 me 1 = ----------------------------------------- -------------- - m ( tan 1 + tan 2 ) 2 1 - 2

e

tan 1 - tan 2 E1 - E2 = --------------------------------- or = -----------------tan 1 + tan 2 E1 + E2 З Use angles only (need IP position) З Use energy and angles (independent of IP position)

LEP II Study

[LEP II Yellow Report]

l = 30 meters = 2 - 6 mRad angular acceptance E / E = 3.37 / E ( GeV ) 1 / 4 % resolution

E E

stat syst

= 2 MeV in 30 minutes (~600 Hz) 2 MeV (dominated by Fermi motion)

Complete study for LC needed... (also Compton)
Eric Torrence Snowmass July 2001


Radiative Returns f e+e- Е f f Statistics
Channel Ebeam

1 f
Number of Events / 1 GeV

2

sin 1 + sin 2 - sin ( 1 + 2 ) s' -- = -----------------------------------------------------------------------sin 1 + sin 2 + sin ( 1 + 2 ) s

300

Data qq M.C. reweighted M.C. background 183 GeV Data MZ = 91.172 Б 0.098 GeV

L3

qq ЕЕ ee

~ 18 MeV ~ 40 MeV ~ 70 MeV

200

LEP Potential Statistics Only 2.7 fb-1

100

0 70

80

90

100

110

m

inv

[ GeV]
Estimates Ebeam ~ 70 MeV Ebeam ~ 20 MeV Ebeam ~ 80 MeV
July 2001

Systematics
З Theoretical Description З Hadronization Uncertainties З Detector Understanding Need absolute measurement!
Eric Torrence Snowmass

Opal qq ЕЕ ee


Polarimetry Overview Production З Electrons: ~ 80% (strained GaAs cathode) З Positrons: 0 - 60% (not so simple...) P
eff

P- + P+ = --------------------- ~ 93% [80%/50%] 1 + P- P+ P / P SLD 0.40% 0.20% 0.10% 0.20% 0.50% 0.15% P / P LC 0.20% 0.10% 0.10% 0.05% 0.25% < 0.05

Detection Uncertainty Source Analyzing Power Detector Linearity Laser Polarization Electronic Noise Total Uncertainty IP Corrections High Energy Needs З P / P ~ 0.25% adequate З P e + makes many things easier З Direct measurement possible in WW
Eric Torrence Snowmass July 2001


Polarized Positrons Tesla/JLC production

Polarized 's Target

e+e- Pairs

P = f(E)

З Circularly polarized photons З Thin target converts to e+eЗ Large energy-polarization correlation Tesla: helical undulator JLC: Compton scattering Lots of R&D needed New Idea [R. Partridge]
Polarized 's RF cavity

Unpolarized e+

Polarized e+

З Compton scattering (2 GeV e+ + 2 eV ) З Must restore energy loss (~4%) Ridiculous laser power needed?
Eric Torrence Snowmass July 2001


Polarized Positron Physics Slepton Production e e
-

Z/
+

~ e ~ e
L

e e

- +

~

~ e
0

~ e

~~ s-channel: e L e ~~ t-channel: e L e

or

R

~ e ~ and e

RR RL

~ e ~ e

only also

1000

1000

100

100

10

10

-1

-0.5

0

0.5

1

-1

-0.5

0

0.5

1

[G. Moortgat-Pick, H. Steiner, 2000]

Unique manipulation of helicity states

Eric Torrence

Snowmass

July 2001


Direct Polarization
W W W

Z/

W



= 12 - 7 pb at s = 350 - 500 GeV
ALR

1

0.8

s = 800 GeV

0.6

= 1.007 Z = 1.01 SM

0.4

-1

-0.5

0

0.5

1 cos

[K. M?nig, Snowmass 2001]

P / P < 0.1 % for 500 fb-1 at 350 GeV (9/1 L ratio) Similar with e- only
Eric Torrence Snowmass July 2001


Summary Giga-Z
2 З e- only: sin W

~ 0.00005

2 З e+ also: sin W ~ 0.00002 З Threshold: m W ~ 6 MeV

Need E

beam

< 50 ppm!

Beam Energy Needs З WISRD spectrometer for general operation З Need detector ideas/R&D for Giga-Z З Radiative returns interesting for WW

Polarization З З З e+ production needs lots of work WW provides P / P < 0.1 % e+ improves most analyses ~~ Some are probably crucial ( e e ) Expect the Unexpected!
Eric Torrence Snowmass July 2001