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 TGC measurements?

  • 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 TGC measurements?

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 TGC measurements?

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 TGC measurements?

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 TGC measurements?

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 TGC measurements?

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 TGC measurements?

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 TGC measurements?

  • 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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