1 / 20

Trilinear γ WW Couplings at a γγ – collider at ILC

Trilinear γ WW Couplings at a γγ – collider at ILC. K.M önig, J.Sekaric DESY-Zeuthen. Introduction. Dominating diagram for γγ  W + W - Two initial states. Ambiguities in 4-jet events: ( cos θ 1,2 , φ 1,2 ) ↔ (- cos θ 1,2 , φ 1,2 + π ). q. . y. W BACKWARD.  1. x.  2. x.  1.

gillian-castillo
Download Presentation

Trilinear γ WW Couplings at a γγ – collider at ILC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Trilinear γWW Couplings at a γγ– collider at ILC K.Mönig, J.Sekaric DESY-Zeuthen

  2. Introduction Dominating diagram for γγ W+W- Two initial states Ambiguities in 4-jet events: (cosθ1,2,φ1,2) ↔ (-cosθ1,2,φ1,2+π) q  y WBACKWARD 1 x 2 x 1 z 2 z  y WFORWARD q 

  3. Total Cross-Section vs. CMS notation Denner, Dittmaier, Schuster, hep-ph/9503442

  4. Total Cross-Section (κγ, λγ) - Whizard On-shell Ws at cme = 400 GeV, 100% polarized beams

  5. Diff. Cross-Section (κγ, λγ) - Whizard Relative deviations of diff. cross-section from the SM in presence of anomalous couplings WLWL masked by dominating WTWT fraction

  6. Analysis • Signal (γγ→WW) and (background, pile-up) samples at detector level WHIZARD – W. Kilian & CIRCE2 – T. Ohl (Telnov’s spectra) (variable energy spectra, 85% polarized e- and 100% γbeams) - pileup : low-energy γγ qq (1.8 ev/BX) - background : γγ qq  4 jets (O’Mega) JZ=2  σ(QCD) ~ (1+ iαs/π), JZ=0 σ(QCD) ~ (1+jαs/π) i[O(1)] < j (for JZ=0 + QCD contribution O(α2) via γγ qqgg andγγ qq(g)qq ) (MadGraph) • Response of a detector simulated withSIMDET V4 • Ws are reconstructed fromhadronic final states • Estimated errorsof measurement ofand parameters,obtained by fit (binned Likelihood )

  7. Pileup rejection track selection via impact parameterI (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 θ > 7º

  8. After impact parameter IXY < 2σXYcondition signal + pileup tracks pileup tracks signal tracks signal with pileup • All neutral accepted • neutral + tracks with θ > 7º clean signal

  9. γγ qq  4jetsBackground - used luminosity spectra (with mixed JZ=0 and JZ=2 states  σmix) Born Level σ2 >> σ0 JZ=2: σ2 JZ=0: σ0 ~ σ2∙(m2/s)  suppression J2 contribution for dominating J0 NLO corrections k2QCD < k0QCD JZ=2: k2QCD ~ (1+iαs/π) JZ=0: k0QCD ~ (1+jαs/π) i < j J0+J2 J0 ↔J2 1-loop non-Sudakov form factor Corrections to the Born Level σ JZ=2: γγ qq (O’Mega)+ QCD (4-5%) parton shower well described by Lund model (q  qg soft gluons); J0 ( 0) and J2  dominates in σmix JZ=0: γγ qq(O’Mega) σ0Born << σ2BornJ2 dominates in σmixbut… O’Mega σ0Born 0 due to the (m2/s) suppression

  10. Correction toσγγ qq in the JZ = 0 state σ0QCD→ 0 (m2/s) suppression canceled by double-logarithms (two-loop) QCD corrections to the Born Level σin JZ = 0 > σ2QCD Pure JZ=0 (whole spectrum): MadGraph  γγ qqgg + qq(g  qq) (O’Mega does not calc. QCD) MINV(3,5,6,9,10,12)> 30 GeV MINV(3,5,6,9,10,12)> 30 GeV … and added to γγqq (O’Mega) with JZ =0

  11. Selection εff ≈ 97% εff ≈ 47% Accepted events: NENFLO > 40, NCT > 20 40º < accepted events < 140º εff ≈ 11% εff ≈ 88% WF cosθ > 0 WB cosθ < 0 J1,J2  WF J3,J4  WB

  12. εff ≈ 53% εff ≈ 1.8% (MW1+MW2) > 125 GeV + 60 GeV < MW1,MW2 < 100 GeV εff ≈ 52% εff ≈ 1.9%

  13. Final angular distributions for JZ=0 WF WB similar distributions for JZ=2 Events made of pileup tracks only pileup

  14. Monte Carlo Fit Each event described with 5 kinematical variables (sensitive to TGC) : • - W production angle,cosθof W boson • - W polar decay angles,cosθ1,2 (sensitive to the different W helicity states) • azimuthal decay angles,1,2(sensitive to the interference between different W helicity states) Matrix element calculations (O’Mega)  weights to reweight SM events (Δκγ=0, Δλγ=0) as functions of anomalous TGC by Weight/event: R(,) = 1 + A· + B·()2 + C· + D·()2 + E ·  + 6-th dimension  cme ND=NSM-data sample (SM),NMC- Monte Carlo sample[NSM·R(,)],L– error on luminosity measurement

  15. Error Estimations Estimated errors for and - two-parameter + n6D fit

  16. 2-dimensional contour plots JZ=0 JZ=0 1σ JZ=2 ΔL = 0.1% ΔL = 0.1% 95% CL ΔL = 1%

  17. 400 GeV % 800 GeV Estimated errors for and - two-parameter + n (5D fit) (generator level, fixed beam energy)

  18. γe: Real / Paras. γγ :JZ=2/ JZ=0 ¹ generator level e- & e+ pol. Scaled for bkg., spectrum, pileup

  19. Systematic Errors • Polarization influence on  and  • Data sample- 1% changed polarization JZ=2/JZ=0 in the sample with P0,2= + 0.90 JZ=0/JZ=2 (realized increasing Nev with JZ= 2,0 for 10%  increase of Nev corresponds to the P0,2 = + 0.89) fit (with MC): JZ=0 (L= 1%)  ,λγshifted <1 JZ=2 (L= 0.1%)  shifted <3, shifted < 1 • Effect of the background Data sample Estimated background per bin is changed for both modes, fit (with MC): (L= 0.1%) JZ=2→ for κγshifted by 1σ→ bck. at level of < 0.8%, for λγ< 4% JZ=0 → for κγ shifted by 1σ→ bck. at level of < 1.1%, for λγ< 0.6% (L= 1%) for κγ shifted by 1σ→bck. at level of ~ 15%,for λγ< 0.6%

  20. Conclusions • Pileup rejection is difficult (still has a large contribution – decrease: to enlarge ‘b’) • Good signal / background separation • Information on Δκγ in the cross-section (via n) • Information on Δλγin the shape of the distributions • Statistical error estimations Δκγ, Δλγ ~ 10-4 • Systematic errors  background

More Related