W Mass Measurements and Electroweak Constraints Chris Parkes Higgs Maxwell Particle Physics Workshop, Ne-SC Edinburgh, February 9 th 2005 •Happy 22 nd Birthday W’s •UA1,UA2 •LEP RIP •W Boson Properties •WW xsec, W BRs, V cs , TGCs •W Mass Higgs mass •The Future •TeVatron Run II, LHC, ILC
W Mass Measurements and Electroweak Constraints. Happy 22 nd Birthday W’s UA1,UA2 LEP RIP W Boson Properties WW xsec, W BRs, V cs , TGCs W Mass Higgs mass The Future TeVatron Run II, LHC, ILC. Chris Parkes. - PowerPoint PPT Presentation
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Perform maximum likelihood fit to data•Calibrate with simulation
•Event by Event Resoultion
LEP W Mass Error Components
0 5 10 15 20 25 30
Statistics
FSI
O()
EBeam
Detector
Hadronisation
LEP Beam Energy Determination
• Spin precession frequency of polarised e+e- beams (EBEAM=200keV)– Polarisation< 60 GeV Calibrate other methods
• Measurement of magnetic field of LEP bending magnets
• Oscillations of beam around ideal orbit (Synchotron tune)
• Spectrometer
Beam
Beam
W
W
EE
MM Correlated between all experiments
MeVMW 10From Ebeam
Final State Interactions• W+W- decay vertices separation typically 0.1fm
• Typical hadronisation scale 1fm
BEC: between final state hadrons – identical bosons (pions) close in phase space – 35 MeVCR: cross-talk between coloured objects in non-perturbative QCD region – 65 MeV
Additional systematic on W Mass for fully-hadronic decays
•Simulation•Measurements
World average W Mass
• Weight of qqqq channel in LEP fit 10%
• Mass difference (no FSI) 2243 MeV
• Stat (no syst.) 21 MeV
• LEP direct determination of W Width– 2.150 0.0068(stat.) 0.0060(syst.) GeV
[0.029(stat.) 0.031 (syst)]
Measuring the Higgs Mass
mHiggs < 260 GeV (95% CL)
Remember LEP 1 predicted the top mass !
GeVmHiggs6945114
SUSY?
• SM MH varied
• MSSM parameters varied
Triple Gauge Couplings
Also QGCs!(WW)And NTGCs
•O(em):• 1-2% xsec•W- production angle becomes more fwd peaked
WW me 2/)1( 2/)( WW meq
C, P conservingemag. gauge invariant
WWZ, WW
The near-ish Future: TeVatron, LHC• LEP+TeVatron Run II MW~30 MeV• LHC MW~15 MeVu
d l
l
W
))cos1(2(2 TT
lTW ppM
•Systematics limited Statistical Error 2 MeV for 10fb-1
–Lepton energy scale, use Zl+l- i.e. measure mW/mZ
–Parton distribution functions W longitudinal plepton acceptance
• Transverse mass– No knowledge of longitudinal
momentum– Transverse momentum from
missing momentumCDF
•Theory: •To obtain error of 1MeV •GENTLE MW=24MeV•Full O() calculation in threshold region,~ 104 Feynman graphs
•Ebeam•Spectrometer, calibrate to Mz
•Z radiative return
•Luminosity•LEP 700pb-1• ILC 107 s, 100fb-1
•Determine Background•At threshold t-channel diagram, eL
+ eR-
Polarised beams can turn off signal !
The Far Future: ILC MW~7MeV
The difficulties:
Measure the cross-section at thresholdmeasure mass
Measurement made at LEP with 10pb-1
Sensitivity ~ same at direct reconstruction
%05.0
Dear All,Having a lovely time in the 2nd nicest town in Scotland.