LCWS05 - SLAC

1
Trilinear ?WW Couplings at a ?? collider at ILC
K.Mönig, J.Sekaric DESY-Zeuthen
2
Introduction
Dominating diagram for ?? ? WW- Two initial
states
Ambiguities in 4-jet events (cos?1,2,f1,2) ?
(-cos?1,2,f1,2p)
q
?
y
WBACKWARD
?1
x
x
?1
?2
z
?2
z
?
y
WFORWARD
q
?
3
Total Cross-Section vs. CMS
notation
Denner, Dittmaier, Schuster, hep-ph/9503442
4
Total Cross-Section (??, ??) - Whizard
On-shell Ws at cme 400 GeV, 100 polarized beams
5
Diff. Cross-Section (??, ??) - Whizard
Relative deviations of diff. cross-section from
the SM in presence of anomalous couplings
WLWL masked by dominating WTWT fraction
6
Analysis

• Signal (???WW) and (background, pile-up) samples
  at detector level WHIZARD W. Kilian CIRCE2
  T. Ohl (Telnovs spectra)
  (variable energy spectra, 85 polarized e- and
  100 ? beams)
• - pileup low-energy ?? ? qq (1.8 ev/BX)
• - background ?? ? qq ? 4 jets (OMega)
• JZ2 ? s(QCD) (1 ias/p), JZ0 ?s(QCD)
  (1jas/p) iO(1) lt j
• (for JZ0 QCD contribution O(a2) via
  ?? ? qqgg and ?? ? qq(g?)qq ) (MadGraph)
• Response of a detector simulated with SIMDET V4
• Ws are reconstructed from hadronic final states
• Estimated errors of measurement of ?? and ??
  parameters, obtained by fit (binned Likelihood )

7
Pileup rejection
track selection via impact parameter I (xy, z)
pileup
clean
Reconstructed PV of an event as the momentum
weighted average impact parameter IZ of all
tracks, using the information from VTX
Reconstructed IZ of each good/bad track
normalized to its error
Separation efficiency

• All neutral accepted
• neutral tracks with ? gt 7º

8
After impact parameter IXY lt 2sXY condition
signal pileup tracks
pileup tracks
signal tracks
signal with pileup

• All neutral accepted
• neutral tracks with ? gt 7º

clean signal
9
?? ? qq ? 4jets Background
- used luminosity spectra (with mixed JZ0 and
JZ2 states ? smix)
Born Level s2 gtgt s0 JZ2 s2 JZ0 s0 s2(m2/s)
? suppression
J2 contribution for dominating J0
NLO corrections k2QCD lt k0QCD JZ2 k2QCD
(1ias/p) JZ0 k0QCD (1jas/p) i lt j
J0J2
J0 ? J2
1-loop non-Sudakov form factor
Corrections to the Born Level s JZ2 ?? ? qq
(OMega) QCD (4-5) parton shower well
described by Lund model (q ? qg soft gluons)
J0 (? 0) and J2 ? dominates in smix JZ0 ?? ?
qq (OMega) s0Born ltlt s2Born ? J2 dominates in
smix but
OMega s0Born ? 0 due to the (m2/s) suppression
10
Correction to s?? ? qq in the JZ 0 state
s0QCD ? 0 (m2/s) suppression canceled by
double-logarithms (two-loop)
QCD corrections to the Born Level s in JZ 0 gt
s2QCD Pure JZ0 (whole spectrum) MadGraph ? ??
? qqgg qq(g ? qq) (OMega does not calc. QCD)
MINV(3,5,6,9,10,12) gt 30 GeV
MINV(3,5,6,9,10,12) gt 30 GeV
and added to ?? ? qq (OMega) with JZ 0
11
Selection
eff 97
eff 47
Accepted events NENFLO gt 40, NCT gt 20
40º lt accepted events lt 140º
eff 11
eff 88
WF cos? gt 0 WB cos? lt 0
J1,J2 ? WF J3,J4 ? WB
12
eff 53
eff 1.8
(MW1MW2) gt 125 GeV 60 GeV lt MW1,MW2 lt 100 GeV
eff 52
eff 1.9
13
Final angular distributions for JZ0
WF
WB
similar distributions for JZ2
Events made of pileup tracks only
pileup
14
Monte Carlo Fit

• Each event described with 5 kinematical variables
  (sensitive to TGC)
• - W production angle, cos? of W boson
• - W polar decay angles, cos?1,2 (sensitive to the
  different W helicity states)
• azimuthal decay angles, ?1,2 (sensitive to the
  interference between different W helicity
  states)

Matrix element calculations (OMega) ? weights to
reweight SM events (???0, ???0) as functions of
anomalous TGC by
Weight/event R(???,???) 1 A??? B(???)2
C??? D(???)2 E ??? ???
6-th dimension ? cme
NDNSM- data sample (SM), NMC- Monte Carlo
sample NSMR(???,???), ?L error on
luminosity measurement
15
Error Estimations
Estimated errors for ?? and ?? - two-parameter
n 6D fit
6D FIT Jz 0 Jz 0 Jz 0
6D FIT without pileup / with pileup / background without pileup / with pileup / background without pileup / with pileup / background
?L 1 0.1 accurate
??? 10-4 19.9 / 26.9 / 27.8 5.5 / 5.8 / 5.9 2.6 / 3.0 / 3.1
??? 10-4 3.7 / 5.4 / 5.7 3.7 / 5.2 / 5.6 3.7 / 5.2 / 5.6
6D FIT Jz 2 Jz 2 Jz 2
6D FIT without pileup / with pileup / background without pileup / with pileup / background without pileup / with pileup / background
?L 1 0.1 accurate
??? 10-4 29.9 / 37.4 / 37.8 6.2 / 6.8 / 7.0 3.7 / 4.6 / 4.8
??? 10-4 3.1 / 4.6 / 4.8 3.1 / 4.6 / 4.8 3.1 / 4.6 / 4.8
16
2-dimensional contour plots
JZ0 1s
JZ0
JZ2
?L 0.1 95 CL
?L 0.1
?L 1
17
400 GeV 800 GeV
Estimated errors for ?? and ?? - two-parameter
n (5D fit) (generator level, fixed beam energy)
5D FIT Jz 0 Jz 0 Jz 0 JZ 2 JZ 2 JZ 2
400 GeV / 800 GeV (110 fb-1) 400 GeV / 800 GeV (110 fb-1) 400 GeV / 800 GeV (110 fb-1) 400 GeV / 800 GeV (110 fb-1) 400 GeV / 800 GeV (110 fb-1) 400 GeV / 800 GeV (110 fb-1)
?L 1 0.1 accurate 1 0.1 accurate
??? 10-4 14.4/7.2 5.4 / 4.5 2.6 / 2.4 20.1/8.1 6.2/4.6 3.8/2.6
??? 10-4 3.0 / 1.3 3.0 / 1.3 3.0 / 1.3 1.6/0.63 1.6/0.58 1.6/0.56
18
500 GeV ?e ?L?t 160/230 fb-1 ?? ?L?t 1000 fb-1 ee- ?L?t 500 fb-1
?L 0.1 0.1 (1) -
???10-4 10.0 / 11.0 7.0 / 5.9 (28) 3.6¹
???10-4 4.9 / 6.7 4.8 / 5.6 (5.7) 11.0¹
?e Real / Paras.
1000GeV ee-(800) ?L?t 1000 fb-1 ?? ?L?t 1000 fb-1
?L - (0.1) / (1)
???10-4 2.1¹ 5.2 / 13.9
???10-4 3.3¹ 1.7 / 2.5
?? JZ2 / JZ0
¹ generator level e- e pol.
Scaled for bkg., spectrum, pileup
19
Systematic Errors

• Polarization influence on ?? and ??
• Data sample - 1 changed polarization JZ2/JZ0
  in the sample with P0,2 0.90 JZ0/JZ2
• (realized increasing Nev with JZ 2,0 for 10 ?
  increase of Nev corresponds to the P0,2 0.89)
• fit (with MC) JZ0 (?L 1) ? ??,?? shifted lt
  1?
• JZ2 (?L 0.1) ? ?? shifted lt 3?, ?? shifted lt
  1?

• Effect of the background
• Data sample
• Estimated background per bin is changed for both
  modes, fit (with MC)
• (?L 0.1)
• JZ2 ? for ?? shifted by 1s ? bck. at level of lt
  0.8, for ?? lt 4
• JZ0 ? for ?? shifted by 1s ? bck. at level of lt
  1.1, for ?? lt 0.6
• (?L 1) for ?? shifted by 1s ? bck. at level of
  15, for ?? lt 0.6

20
Conclusions

• Pileup rejection is difficult (still has a large
  contribution decrease to enlarge b)
• Good signal / background separation
• Information on ??? in the cross-section (via n)
• Information on ??? in the shape of the
  distributions
• Statistical error estimations ???, ??? 10-4
• Systematic errors ? background