esfa/desy lc workshop 1 klaus mönig and jadranka sekaric klaus mönig and jadranka sekaric desy -...
TRANSCRIPT
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
3ESFA/DESY LC Workshop
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
4ESFA/DESY LC Workshop
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°°
02/04/2003,Amsterdam
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
T E S L A
5ESFA/DESY LC Workshop
High High efficiency efficiency
for hadronicfor hadronic
channel,channel, 84%84%
with low with low backgrounbackgroundd
02/04/2003,Amsterdam
• 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
6ESFA/DESY LC Workshop
Background for parasitic e mode : WW lqqsame cuts as previous qq
T E S L A
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°°
7ESFA/DESY LC Workshop
T E S L A
02/04/2003,Amsterdam
• W massW mass(60-100) Gev(60-100) Gev
S/BWW~ 9:1, purity ~ 90%
angular distribution after selection
mass distribution
WW WWWW qqqq
8ESFA/DESY LC Workshop
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
02/04/2003,Amsterdam
T E S L A
9ESFA/DESY LC Workshop
DCS in presence of anomalous coupling for J
= ± 1 statenormalized 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
10ESFA/DESY LC Workshop02/04/2003,Amsterdam
T E S L A
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
11ESFA/DESY LC Workshop
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 ·
02/04/2003,Amsterdam
T E S L A
MONTE CARLO FITMONTE CARLO FITMONTE CARLO FITMONTE CARLO FIT
12ESFA/DESY LC Workshop
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
02/04/2003,Amsterdam
T E S L A
13ESFA/DESY LC Workshop
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
02/04/2003,Amsterdam
T E S L A
14ESFA/DESY LC Workshop
- 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
2D 3D2
15ESFA/DESY LC Workshop02/04/2003,Amsterdam
T E S L A
- Polarization influence on Polarization influence on and and
variation of laser polarization in the laser wave beam field influences the photon polarization- sample 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
16ESFA/DESY LC Workshop02/04/2003,Amsterdam
T E S L A
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