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B s → D s ± K ±

ﺇﻞﻫﺎﺳﻲﺑﻲ. B s → D s ± K ±. Besma M’charek Jeroen van Tilburg. Introduction. Understanding the decay of the B 0 s -meson and its antiparticle into D s ± K ± . This decay channel allows an observation of CP violation. Selection of the B 0 s → D s ± K ± events. Plans.

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B s → D s ± K ±

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  1. ﺇﻞﻫﺎﺳﻲﺑﻲ Bs→ Ds±K± Besma M’charek Jeroen van Tilburg

  2. Introduction • Understanding the decay of the B0s-meson and its antiparticle into Ds±K±. • This decay channel allows an observation of CP violation. • Selection of the B0s→Ds±K± events. • Plans

  3. Decay of the Bso -meson to a Ds and a K particle • Neutral B-mesons mix and oscillate and decay after a certain time • After the B-meson is created it decays in a final state f or anti (f). • This gives: Bs→ f Bs→anti(f) anti (Bs)→ f anti (Bs) → anti (f)

  4. Topology π K K Ds Bs p p K

  5. Af u Vus K+ s W+ b c Bs D-s V*cb s s Bs→ Ds-K+

  6. Af s V*us K- u W- b c Bs D+s Vcb s s Bs→ Ds+K-

  7. Af c D+s Vcs s W+ b u Bs V*ub K- s s Bs→ Ds+K-

  8. Af s V*cs D-s c W- b u K+ Bs Vub s s s s Bs→ Ds-K+

  9. CP violation in the interference between decay and mixing • In our case there is an interference between mixing and decay amplitudes • Only one diagram contributes to each of the decay amplitudes (no penguin pollution) • The two parameters, λ and anti(λ) defined as:

  10. CP violation in the interference between decay and mixing • Because of the interference term a phase arises in the expression of the λ’s; λDsK • Which gives us:

  11. Bs→DsK event selection: preselection cuts • Track selection: momentum criterium; particles originating from the Bs particle have relatively high momentum p and have a Σp above 2GeV ) • Ds vertex selection: constrained mass fit, reconstructed Ds mass approximately 3σclose to 1969MeV and a good significance for the impact parameter for the track reconstructions of the products (all particles have SIP >1) • Bs vertex selection: large bachelor-Ds opening angle and the reconstructed Bs should point back to the primary vertex, SIP >4 for the bachelor and SIP <4 for the Bs • Cuts applied also as for the selection of background.

  12. All products p Ds products pt Ds products Σpt SIP(Ds products) SIP(Ds) Ds mass window SIP(Bs product) SIP(Ds) Bs mass window Cos(θ) Bachelor K:ΔLKπ Bachelor K: ΔLke 2 GeV 200 MeV 0 0 1 50MeV 1 20 500MeV 0.998 -5 -5 Bs→DsK event selection: preselection cuts

  13. Nevents Bsmass Nevents GeV/c2 Dsmass GeV/c2 Bs→DsK event selection:results • Bs→DsK signals and background (Bs→Dsπ and bbinclusive) • Number of events 5000. • # Bs→DsK selected = 477 • # Bs→Ds π selected = 143 • # bbinclusive selected = 78 (oops we did it again!!)

  14. Bs→DsK event selection :other interesting cuts • Cosine(θ) • χ2 of the Bs vertex fit. • χ2 of the Ds vertex fit (mass constrained fit).

  15. Cosine(θ) χ2 of Bs χ2 of Ds Further cuts

  16. Efficiencies ε in Bs→DsK events selection #events = 10000 events

  17. Plans

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