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Klaus Mönig and Jadranka Sekaric

Klaus Mönig and Jadranka Sekaric. DESY - Zeuthen. MEASUREMENT OF TGC IN e  COLLISIONS AT TESLA. T E S L A. INTRODUCTION. In order to predict the precision of measurement of trilinear gauge couplings (TGC) at a photon collider : signal to background separation study ( e  W )

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Klaus Mönig and Jadranka Sekaric

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  1. Klaus Mönig and Jadranka Sekaric DESY - Zeuthen MEASUREMENT OF TGC IN e COLLISIONS AT TESLA

  2. T E S L A INTRODUCTION In order to predict the precision of measurement of trilinear gauge couplings (TGC) at a photon collider : • signal to background separation study(e W) for real and parasitic e -mode • observables sensitive to TGC (angular distributions, cross-sections …) • estimated errors, and of measurement of and  parameters, obtained by fit-minimizing the 2value - effect of photon beam polarization on  and  measurement 02/04/2003, Amsterdam

  3. T E S L A EVENT SELECTION TOOLS: PYTHIAevent generator SIMDETV3detector simulation • sample of 105 mixed signal and background events, generated with PYTHIA at ECM (e)= 450 GeV background for real andparasitice-mode: e  W qqT  37 pb e  eZ0  eqqT  3.5 pb  qqT  137 pb   WW  lqq T  82 pb   qq T  128 pb • response of a detector simulated with SIMDET V3 • Ws are reconstructed from hadronic final states 02/04/2003, Amsterdam

  4. T E S L A sufficientlyhigh W production cross-section allows us to efficiently separate signal from background • Applied cuts: • acceptance of detector - 7°  qq e  W e  eZ0 • angular distributions for signal and bck. hadronic final states • W energy • (100-250) Gev • hadronic final states energy spectrum 02/04/2003, Amsterdam

  5. T E S L A  qq e  W e  eZ0 • W mass • (60-100) Gev High efficiency for hadronic channel,84% with low background • hadronic final states mass spectrum • final angular distributions after selection 02/04/2003, Amsterdam

  6. T E S L A Background for parasitic e mode :   WW  lqq same cuts as previous qq • Applied cuts: • acceptance of detector - 7° e  W   qq   WW angular distribution • W energy • (100-250) Gev energy distribution 02/04/2003, Amsterdam

  7. T E S L A • W mass • (60-100) Gev qq W WW mass distribution S/BWW~ 9:1, purity ~ 90% angular distribution after selection 02/04/2003, Amsterdam

  8. T E S L A OBSERVABLES SENSITIVE TO TGC total and differential cross-section • analytic formula for total (differential) cross-section (A. Denner, A.Dittmaier, Nucl.Phys. B398 (1993)239 • helicity amplitudes for different initial photon and final W states (E.Yehudai, Phys.Rev. D11(44)1991)) • differential cross-section distribution over the decay angle (Bilenkyat al.,Nuc.Phys. B(409) (1993)22 • WHIZARD Monte Carlo tree–level generator (W.Kilian,University of Karlsruhe) 02/04/2003, Amsterdam

  9. T E S L A ANOMALOUS TGC can affect the total production cross-section and the shape of the differential cross-section DCS in presence of anomalous coupling for J= ± 1 state normalized to its SM value DCS for J = ±1 state in SM 02/04/2003, Amsterdam

  10. T E S L A Contribution of each helicity state of the W boson  affects the distribution of their decay products 02/04/2003, Amsterdam

  11. T E S L A MONTE CARLO FIT • WHIZARD Monte Carlo generator,106mixed pairs (du-bar and sc-bar)at ECM = 450 GeV, fixed photon-beam energy, polarized beams (P=100%), anomalous couplings • for each event we observe 3 kinematic variables • -W production angle with respect to the e- beam direction -cosθ • -W polar decay angle - angle of the fermion with respect to the W flight direction measured in the W rest frame –cosθ1 • -azimuthal decay angle  of the fermion with respect to a plane defined by W and the beam axis • Monte Carlo SM events are reweighted with function R()(and  are free parameters) R() = 1 + A· + B· + C·()2 + D·()2 + E ·  02/04/2003, Amsterdam

  12. T E S L A • 2D (over cosθ, cosθ1)and 3D(over cosθ, cosθ1,)cross-section distributions are fitted L-error on the luminosity measurement norm-normalization constant 02/04/2003, Amsterdam

  13. T E S L A • Estimated errors of andfor +1 photon polarization state (P=100%) – single parameter 2D and 3D fit 02/04/2003, Amsterdam

  14. T E S L A =1.01 • - distribution slightly decreaseserror of (L = 1%) and of  • for a factor 7 ! •  shape sensitivity in phi distribution •  phi distribution influences much more on  • 3D - Mean error on comes from • L, not case for  • - Good agreement between 2 modes for and  =0.01 =-0.01 =0.99 2 2D 3D  02/04/2003, Amsterdam

  15. T E S L A • Polarization influence on  and  •  variation of laser polarization in the laser wave •  beam field influences the photon polarization • sample with P=+0.9 polarized photons •  mixing the events with P=+1 and P=-1 in order to get preferred polarization (95:5) •  errors obtained from the fit are in a good agreement with previous ones • sample with 1% different polarization •  increased the Nev with P=-1 for 10%  increase of Nev correspond to the P=+0.89  test-fit and … • we found :1% changes in polarization(accurate fit) •  within ~ 12 •   within~ 1 • Contribution from normalization and from polarization J 02/04/2003, Amsterdam

  16. T E S L A SUMMARY • -Efficient signal to background separationfor both e modes • -,~ 10-3(error on luminosity measurement, L, • is included) • - Main contribution to the error ofcomes from L • Shape sensitivity for anomalous  in phi distribution decreases error of • Variable polarization (1%) affects the measurement • Future plans : • Variable photon-beam energy in WHIZARD • Resolution on reconstructed variables • Background influences on error predictions 02/04/2003, Amsterdam

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