using transversely polarised beams in w pair production for tgc measurements a very first look
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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. Motivation.

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using transversely polarised beams in w pair production for tgc measurements a very first look
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

motivation
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

transverse polarisation
Transverse Polarisation

Thoery worked out in

Fleischer,Jegerlehner,Kolodziej PRD49(1994!!)2174.

Probe longitudinal W bosons at

Measure azimuthal asymmetry

F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production

transverse polarisation1
Transverse Polarisation

Both, transverse polarisation and anomalous TGC’s (including

CP violating couplings) are built into the WHIZARD generator.

T. Ohl, W. Kilian - thanks!

F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production

transverse polarisation2
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

transverse polarisation3
Transverse Polarisation

WWgmnqq events

√s = 500 GeV, 500 fb-1

generator level

P(e-) = 0.8, P(e+) = -0.6

only events with

cosθ<0.4

all events

F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production

transverse polarisation4
Transverse Polarisation

statistical significance

of the assymetry (for 500 fb-1)

azimuthal asymmetry as a

function of the cosθ cut:

F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production

transverse polarisation5
Transverse Polarisation

Switch on anomalous coupling lg

quite dramatic…

F.Franco-Sollova,W.Menges,K.Desch - Transverse Beam Polarisation for WW Production

summary next steps
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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