Transcript Using transversely polarised beams in W pair production for TGC measurements? A very first look Filip Franco-Sollova Wolfgang Menges Klaus Desch ECFA/DESY Workshop Polarisation Session Amsterdam, 01/04/03 • Motivation •

Using transversely polarised beams in W pair
production for TGC measurements?
A very first look
Filip Franco-Sollova
Wolfgang Menges
Klaus Desch
ECFA/DESY Workshop
Polarisation Session
Amsterdam, 01/04/03
• Motivation
• First Plots
• Next Steps
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
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Motivation
• If both beams can be polarised longitudinally, also transverse
polarisation can become useful (insert spin rotators before IP)
• One possible application might be the study of anomalous
Triple Gauge Couplings in e+e-gW+W• Transverse polarisation leads to an azimuthal asymmetry of
the cross section:
• Especially interesting for CP-violating anomalous couplings
(they introduce a phase shift in the phi asymmetry
= new observable not present for LPOL)
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
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Transverse Polarisation
Thoery worked out in
Fleischer,Jegerlehner,Kolodziej PRD49(1994!!)2174.
Probe longitudinal W bosons at
Measure azimuthal asymmetry
s
2 mW
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
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Transverse Polarisation
Both, transverse polarisation and anomalous TGC’s (including
CP violating couplings) are built into the WHIZARD generator.
T. Ohl, W. Kilian
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
- thanks!
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Transverse Polarisation
The Observable:
How big is the asymmetry?
Depends strongly on cosθ cut
(only s-channel exhibits cos2Φ modulation)
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
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Transverse Polarisation
WWgmnqq events
√s = 500 GeV, 500 fb-1
generator level
P(e-) = 0.8, P(e+) = -0.6
all events
only events with
cosθ<0.4
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
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Transverse Polarisation
azimuthal asymmetry as a
function of the cosθ cut:
statistical significance
of the assymetry (for 500 fb-1)
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
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Transverse Polarisation
Switch on anomalous coupling lg
quite dramatic…
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
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Summary&Next Steps
• Tools to perform an experimental study of WW production
with transversely polarized beams are now available (built into
WHIZARD) seems to work
• Azimuthal asymmetry is significant in the SM
• Can be much larger if anomalous TGC’s are present
• Check effect of CPV couplings -> phase shift in phi-distribution?
• Become quantitative (estimate sensitivity to TGC’s)
• If there is increased sensitivity (compared to LPOL),
study detector effects + possible systematics
F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production
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