ESFA/DESY LC Workshop 1 Klaus Mönig and Jadranka Sekaric Klaus Mönig and Jadranka Sekaric DESY - Zeuthen MEASUREMENT OF TGC IN e  COLLISIONS AT TESLA

ESFA/DESY LC Workshop 2 02/04/2003, Amsterdam INTRODUCTIONINTRODUCTION In order to predict the precision of measurement of trilinear gauge couplings (TGC) at a photon collider : (e   W ) 1.signal to background separation study (e   W ) for real and parasitic e  -mode 2.observables sensitive to TGC (angular distributions, cross-sections …)    and   of measurement of   and  parameters, obtained by fit-minimizing the  2 value 3.estimated errors,    and   of measurement of   and  parameters, obtained by fit-minimizing the  2 value - effect of photon beam polarization on   and   measurement T E S L A

ESFA/DESY LC Workshop 3 EVENT SELECTION TOOLS: PYTHIA event generator SIMDET V3 detector simulation  sample of 10 5 mixed signal and background events, generated with PYTHIA at E CM (e  )= 450 GeV background for real and parasitic e  -mode: e   W  qq  T  37 pb e   eZ 0  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 T E S L A

ESFA/DESY LC Workshop 4 sufficientlyhigh W production cross-section allows us to efficiently separate signal from background sufficiently high W production cross-section allows us to efficiently separate signal from background Applied cuts: acceptance of detector - 7° acceptance of detector - 7° 02/04/2003, Amsterdam  angular distributions for signal and bck. hadronic final states e   W e   eZ 0   qq W energy W energy ( ) Gev  hadronic final states energy spectrum T E S L A

ESFA/DESY LC Workshop 5 High efficiency for hadronic channel, 84% with low background 02/04/2003, Amsterdam W mass W mass (60-100) Gev  hadronic final states mass spectrum e   W e   eZ 0   qq  final angular distributions after selection T E S L A

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

ESFA/DESY LC Workshop 7 T E S L A 02/04/2003, Amsterdam W mass W mass (60-100) Gev S/B WW ~ 9:1, purity ~ 90% angular distribution after selection mass distribution WWW qq

ESFA/DESY LC Workshop 8 OBSERVABLES SENSITIVE TO TGC  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 (Bilenky at al.,Nuc.Phys. B(409) (1993)22  WHIZARD Monte Carlo tree–level generator (W.Kilian,University of Karlsruhe) total and differential cross-section 02/04/2003, Amsterdam T E S L A

ESFA/DESY LC Workshop 9 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 T E S L A ANOMALOUS TGC can affect the total production cross-section and the shape of the differential cross-section

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

ESFA/DESY LC Workshop 11  WHIZARD Monte Carlo generator, 10 6 mixed pairs (du-bar and sc-bar) at E CM = 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 – cosθ 1 -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 T E S L A MONTE CARLO FIT

ESFA/DESY LC Workshop 12  2D (over cosθ, cosθ1and 3D(over cosθ, cosθ1,  cross-section distributions are fitted  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 T E S L A

ESFA/DESY LC Workshop 13 real mode/ parasitic mode E CM = 450 GeV, ∫L  t = 110 fb -1 Monte Carlo 2D J  = +1 LL1%0.1%accurate   · /3.71.0/1.00.4/0.4   · / /2.1 Estimated errors of   and  for +1 photon polarization state (P=100%) – single parameter 2D and 3D fit  Estimated errors of   and  for +1 photon polarization state (P=100%) – single parameter 2D and 3D fit real mode/ parasitic mode E CM = 450 GeV, ∫L  t = 110 fb -1 Monte Carlo 3D J  = +1 LL1%0.1%accurate   · /3.11.0/1.00.4/0.4   · /2.9 02/04/2003, Amsterdam T E S L A

ESFA/DESY LC Workshop 14 -  distribution slightly decreases error 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   02/04/2003, Amsterdam   =1.01   =0.99  =0.01  =-0.01 T E S L A 2D3D 22 

ESFA/DESY LC Workshop 15 02/04/2003, Amsterdam T E S L A Polarization influence on   and  - 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 - 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 - sample with 1% different polarization  increased the N ev with P  =-1 for 10%  increase of N ev correspond to the P  =+0.89  test-fit and … -we found : 1% changes in polarization -we found : 1% changes in polarization (accurate fit)    within ~ 12    within ~ 1  Contribution from normalization and from polarization J

ESFA/DESY LC Workshop 16 02/04/2003, Amsterdam T E S L ASUMMARYSUMMARY -Efficient signal to background separation for both e  modes -   ,   ~ (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