Electroweak precision observables in the LHC epoch

Electroweak Electroweak precision precision

observables in the observables in the LHC epochLHC epoch

A.Zaitsev, ProtvinoA.Zaitsev, Protvino

Gomel, July 2007Gomel, July 2007

EWPOEWPO

High precision measurements of EW parameters give the way to probe new physics via virtual effects of additional objects.

Most of EW precision data were obtained at LEP and SLD.

The progress in accelerators and detectors gives the chance for construction of dedicated Z-factory.

It can provide us with information on new physics

complimentary to that at LHC.

Examples of new physics discovered with Examples of new physics discovered with EWPOEWPO

• Nν =2.984 ± 0.008

• Mt=172 + 10.2 - 7.6 GeV

•

Examples of new physics discovered with Examples of new physics discovered with EWPOEWPO

Dedicated Z - factoryDedicated Z - factory

• Suggested parameters • E GeV 46+46 82+82• R=2,8 km (UNK tunnel C=20,7 km)• Beam-beam tune shift ξy 0,05 0,09• Beta function β*y= 0,02 m• Synchrotron power P=60 MW• Energy loss per turn GeV 0,14 1,4• Luminosity 1034 cm-2s-1 0,5 0,2

LEP D Brandt, H Burkhardt, M. Lamont, S Myers et al

e+e- COLLIDER IN THE VLHC TUNNEL

A.Barcikowski, G. Goeppner, J. Norem et al

A Z-factory in the VLLC tunnel E. Keil

ZF A.Skrinsky et al

Transverse polarizationTransverse polarization

• Transverse polarization at MZ

can reach 55% with polarization time t<1h.

• It gives excellent possibilities for precise energy calibration

From R.Asmann

Polarization at LEP CERN 1988

Longitudinal Longitudinal polarizationpolarization

• Transverse polarization can be transformed to longitudinal one

• Experiment has to be inclined by 10

• Some loss of luminosity: 5·1033 cm-2s-1 → 1·1033 cm-2s-1

Longitudinal polarization at LEP

D.Treille

C.Bovet, H.Burkhardt, F.Couchot et al

StatisticsStatistics• Z peak

0∫5years

L dt = 2.5·1041cm-2

NZ=1010

• Longitudinal polarization in Z peak

0∫1year

L dt = 1·1040cm-2

NZ=4·108

• WW at threshold (164 GeV)

0∫2years

L dt = 4·1040cm-2

NWW = 2.5·105

From P.Wells

Z peakZ peak

• MZ, ΓZ, σhad,

Rl, Rb, Rc,

AlFB, Ab

FB, AcFB, Al(Pτ)

• Energy calibration:

Systematic errors in ESystematic errors in E

• n

ZF goal: δMZsyst< 1 MeV

MonitoringMonitoring • ZF goal:

• Absolute error: δL ≈ 3·10-4

• Relative error: δL ≈ 1·10-4

ZF at Z peakZF at Z peak• δMZ ≈ 1 MeV• δΓZ ≈ 1 MeV• δσhad /σhad ≈5·10-4

• δRl / Rl ≈ 5·10-4

• δRb ≈0,0002• δ Rc ≈0,001• δ Al

FB ≈0,0002• δ Ab ≈0,001• δ Ac ≈0,002• δ Al(Pτ) ≈0,001

• At ZF the precision in EW parameters can be improved significantly in comparison with LEP/SLD owing to:

• 3 orders of statistics• Advanced

technologies in detectors

(especially in vertex detectors)

and data analysis• Better energy

calibration

R. HawkingsK. M¨onig. P.RowsonM.Woods

AALR LR with longitudinal polarizationwith longitudinal polarization

• N=4·108

• P=55%• δL/L= 1·10-4

• δP/P= 1·10-4

↓• δALR= 1,6·10-4 (compare: SLD δALR= 2·10-3 )

• δSin2θW = 1/8 δALR = 2 ·10-5

• ALR = 2(1 − 4 sin2 θeff)/(1 + (1 − 4 sin2 θeff)2)

Blondel scheme

W massW mass

• A

The crossection of WW pair production near the threshold in the region of

2E=164 GeV is very sensitive to W mass:

dσ/dM / σ = 0,5 GeV-1

δMstat= 4 MeV

δMEbeam = 5 MeV

δ M other syst = 5 MeV

δ M W ≈ 8 MeV

EWPO for new physics (1)EWPO for new physics (1)

S

T

J. Erler, S.Heinemeyer, W. Hollik, G.Weiglein, P.M. Zerwas


δsin2θW = 2 ·10-5 → δMH / MH = 5% It requires: δMt<0.4 GeV δΔαhad (MZ)< 0.0001

DecaysDecays• Z →γγγ

• FCNC: Z →eμ, eτ, μτ, s[b

• Z →W f [f

• Z →Q̃]Q̃ γ, Pγ

• γγ →x

• Nb] b= 1.5·109

• Z` M> 200÷1400 GeV → θmix < 10-3 →

V.ObraztsovY.Khokhlov

ZF vs GigaZZF vs GigaZ

ZF GigaZCost x << 10xLum [cm-2s-1] 5·1033 ≈ 5·1033

∫ Lum dt [cm-2] 5·1041 >> 5·1040

δ E [MeV] <1 << >10Beamstrahlung [MeV] <<1 << >10Events/bunch ≈10-6 << ≈10-3

Background x < y ↓ ZF !

TunnelTunnel 20.8 km circumference ~50 m underground 5.1 m diameter

Electroweak precision observables in the LHC epoch

Documents

Transcript of Electroweak precision observables in the LHC epoch