Klaus Mönig and Jadranka Sekaric

1ESFA/DESY LC Workshop

Klaus Mönigand

Jadranka Sekaric

Klaus Mönigand

Jadranka SekaricDESY - ZeuthenDESY - Zeuthen

MEASUREMENT OF TGC IN

e COLLISIONS AT TESLA

MEASUREMENT OF TGC IN

e COLLISIONS AT TESLA

2ESFA/DESY LC Workshop02/04/2003,Amsterdam

INTRODUCTIONINTRODUCTIONINTRODUCTIONINTRODUCTION

In order to predict the precision of measurement of In order to predict the precision of measurement of trilinear gauge couplings (TGC) at a photon collider trilinear gauge couplings (TGC) at a photon collider ::

1. signal to background separation study ((ee WW ) )

for real and parasitic for real and parasitic ee -mode -mode

2. observables sensitive to TGC

(angular distributions, cross-sections …)(angular distributions, cross-sections …)

3. estimated errors, and and of measurement of of measurement of and and

parameters, obtained by fit-minimizing the parameters, obtained by fit-minimizing the 22 valuevalue

- effect of photon beam polarization on - effect of photon beam polarization on and and measurement measurement

T E S L A


EVENT SELECTIONEVENT SELECTIONEVENT SELECTIONEVENT SELECTIONTOOLSTOOLS::

PYTHIAPYTHIA event generatorevent generatorSIMDETSIMDET V3V3 detector simulationdetector simulation

sample of 10sample of 1055 mixed mixed signalsignal and and backbackgroundground events, generated with PYTHIA at events, generated with PYTHIA at EECM CM (e(e))= 450 = 450 GeV GeV background for real and parasitic e-mode:

ee WW qqqq TT 37 pb 37 pb

ee eZ eZ0 0 eqq eqq T T 3.5 pb 3.5 pb

qqqq T T 137 pb 137 pb

WW WW l lqqqq T T 82 pb 82 pb

qqqq T T 128 pb 128 pb response of a detector simulated with SIMDET V3response of a detector simulated with SIMDET V3 WWs are reconstructed from s are reconstructed from hadronic final stateshadronic final states

02/04/2003,Amsterdam

T E S L A


sufficientlysufficiently high W production cross-section high W production cross-section allows us to efficiently separate signal from allows us to efficiently separate signal from

backgroundbackgroundApplied cuts:Applied cuts:

• acceptance acceptance of detector - of detector - 77°°


angular distributions for signal and bck. hadronic final states

ee WW e eZ0 qq

• W energyW energy(100-250) Gev(100-250) Gev

hadronic final states energy spectrum

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High High efficiency efficiency

for hadronicfor hadronic

channel,channel, 84%84%

with low with low backgrounbackgroundd


• W massW mass(60-100) Gev(60-100) Gev

hadronic final states mass spectrum

ee WW e eZ0 qq

final angular distributions after selection

T E S L A


Background for parasitic e mode : WW lqqsame cuts as previous qq

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ee WW WWWW qqqq

angular distribution

energy distribution02/04/2003,Amsterdam

• W energyW energy(100-250) Gev(100-250) Gev

Applied cuts:Applied cuts:

• acceptance acceptance of detector - of detector - 77°°


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• W massW mass(60-100) Gev(60-100) Gev

S/BWW~ 9:1, purity ~ 90%

angular distribution after selection

mass distribution

WW WWWW qqqq


OBSERVABLES SENSITIVE TO TGCOBSERVABLES SENSITIVE TO TGCOBSERVABLES SENSITIVE TO TGCOBSERVABLES 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


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DCS in presence of anomalous coupling for J

= ± 1 statenormalized to its SM value

DCS for J = ±1 state in SM


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ANOMALOUS TGC can affect the total production cross-section and the shape of the differential cross-section


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Contribution of each helicity state of the W boson affects the distribution of their decay products

1

2

1

2

1

112

1

4

3coscos

)(cosd

d

)(cosd

d

)(cosd)(cosd

d LT


WHIZARDWHIZARD Monte Carlo generator Monte Carlo generator,, 101066 mixedmixed pairs (pairs (dudu-bar and -bar and scsc-bar)-bar) at at EECM CM = 450 GeV, fixed photon-= 450 GeV, fixed photon-beam energy, polarized beams (P=100%), anomalous beam energy, polarized beams (P=100%), anomalous couplingscouplings

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 Monte Carlo SM events are reweighted with function RR(()) (( and and are free parameters) are free parameters)

RR(() = 1 + A·) = 1 + A· + + BB·· + C·( + C·())22 + D·( + D·())22 + E · + E ·


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MONTE CARLO FITMONTE CARLO FITMONTE CARLO FITMONTE CARLO FIT


2D (over 2D (over coscosθθ, , coscosθθ11 ) and 3Dand 3D (over (over coscosθθ, , coscosθθ1,1, ) cross-sectioncross-section distributions are fitted distributions are fitted

LL-error on the luminosity -error on the luminosity measurementmeasurementnormnorm-normalization constant-normalization constant

n

i

n

j

n

k )L(

)norm()norm)k,j,i(N)k,j,i(N(

)k,j,i(

)(ACCACC

1 12

2

2

2

1

2 10


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real mode/parasitic

mode

ECM = 450 GeV, ∫Lt = 110 fb-1

Monte Carlo 2DJ = +1

L 1% 0.1% accurate

·10-3 3.6/3.7 1.0/1.0 0.4/0.4

·10-3 1.5/2.2 1.5/2.2 1.4/2.1

Estimated errors of Estimated errors of andand for for +1+1 photon photon polarization state (P=100%) – single parameter polarization state (P=100%) – single parameter

2D and 3D fit 2D and 3D fit

real mode/parasitic

mode

ECM = 450 GeV, ∫Lt = 110 fb-1

Monte Carlo 3DJ = +1

L 1% 0.1% accurate

·10-3 3.0/3.1 1.0/1.0 0.4/0.4

·10-4 2.6/2.9 2.6/2.9 2.6/2.9


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- 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


=1.01

=0.99

=0.01

=-0.01

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2D 3D2


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- Polarization influence on Polarization influence on and and

variation of laser polarization in the laser wave beam field influences the photon polarizationsample with Psample with P=+0.9 polarized photons=+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 polarizationsample 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 :we found : 1% changes in polarization1% changes in polarization (accurate fit)

within ~ 12within ~ 12

withinwithin ~ 1~ 1Contribution from normalization and from Contribution from normalization and from

polarizationpolarization

J


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SUMMARYSUMMARYSUMMARYSUMMARY-Efficient signal to background separation for 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

Klaus Mönig and Jadranka Sekaric

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