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Rare Decays and their sensitivity to New Physics.

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Presentation on theme: "Rare Decays and their sensitivity to New Physics."— Presentation transcript:

1 Rare Decays and their sensitivity to New Physics

2 Klassiker: hep-ph/ mSUGRA Parameter:

3 Light chargino bounds from LEP, Radiative EWSB LSP not neutral hep-ph/

4 < 5.8· % CL 2 fb -1 arXiv: to PRL < 9.3· % CL D0 Note 5344-Conf (2007)

5 Problem: Untergrundunterdrückung Invariante Masse keine ausreichende Diskriminate Multivariate Analyse

6 Lifetime of B Muon Impact Parameter Sign. B s Impact Parameter DOCA between muons Isolation Geometry Likelihood Muon Pion Likelihood ( LL) Muon Kaon Likelihood ( LL) PID Likelihood signal bb inclusive b b B c J/

7 signal bb inclusive 3-dim. Binning: 4 Bins in Geometry LL 3 Bins in PID LL 5 Bin in invarianter Masse Untergrund Ereignisse/Bin Signalereignisse/Bin (BR) Sensitivität

8 BR excluded at 90 % CL, i.e. only background is observed BR observed or discovered. Exclude the interesting region between and SM with little Lumi (~0.5 fb -1 ) Observe (discover) SM BR with 3 (5 ) after ~2 (~6) fb -1

9 Events after preselection cuts in 600 ( 60) MeV mass window


11 Radiative b s decays Standard Model b s (b s ): LH s-quark (RH s-quark) LH (RH) photons BSM physics (SUSY, LR Models) could lead to appreciable RH component photon helicity probes BSM physics Probing photon helicity: (Photon conversion) Time dependent A CP : Parity-odd triple correlations between photon and 2 out of 3 hadrons in B ( K + + ) decays b (X)

12 B 0 s [1] hep-ph/ [2] arXiv:hep-ex/ v1 Erste Beobachtung von B s (Ball et al.)

13 sensitive to NP SMNP polarization predominantly left handed right handed components CPV in decay < 1 % 10%-40% Inclusive decays : theory experiment Exclusive decays theory experiment CPV in interference mixing decay B 0 (B 0 bar) X 0 very small B 0 (B 0 bar) X 0 Could be large Why this decay ?

14 Expected for one year of measurement ( 2 fb -1 ) have to fight background very good PID necessary, 0 rejection proper time resolution (Time dependent CPV polarization) high trigger efficiency good offline selection What do we expect at LHCb ?

15 two body kinematics geometrical cuts on pp-interaction PV and B-decay SV Selection mainly based on Selection criteria maximize with = S: signal evts B: background evts K-K- K+K+ PV SV Reconstruction and Selection

16 Photon selection 2 body kinematics hard E T ( ) spectrum from numerous 0 decay soft Require E T ( ) > 2.8 GeV On the way to the Charged tracks must NOT come from PV ( of B) K + K - should come from SV Some selection criteria…

17 On the way to the B p B = p p should point to PV use B ( allow rather large B as the SV resolution is not good because of Ks !) PV SV B reconstructed p flight path Some selection criteria…

18 large background from B 0 s und B K* 0 use vector meson polarization helicity of for B 0 s for B 0 s define helicity angle H sin 2 H distribution for signals cos 2 H distribution for correlated bkg flat for combinatorial bkg K+K+ K-K- B H Background…

19 Expect 68k signal events for 2 fb -1 with B/S < 0.6 red: true events blue : comb. bkg. And finally one gets… B 0 Expect 11.5k signal events for 2 fb -1 with B/S < 0.6 B s

20 from b s predominantly left-handed (SM: V-A coupling of W boson) e.g. in MSSM can be largely right-handed ( doesnt effect incl. radiative decay rate predicted by SM) helicity measurement via time-dependent CP asymmetry, … Polarization

21 amplitudes Relative amount of wrong photon polarization Weak phases (CP odd)

22 Time dependent decay rate Standard Model:

23 The CP asymmetry From the time dependent decay rate one gets CP Asymmetry The measurement of A determines the fraction of different-polarized photons ! LHCb Toy study:for 2 fb -1



26 Asymmetrie: Interesting observable: Muon forward-backward Asymmetry

27 Zero crossing point: hep-ph/

28 Generator Studie: 6.5 M Ereignisse. Change in order to which Wilson coefficients are calculated.

29 A. Ali et al. hep-ph/ SM SUGRA MIA SUSY (lower lines = pure short distance components) M 2 mass distributiuonForward backward asymmetry SM SUGRA MIA SUSY MIA SUSY C 10 >0 Upper/lower lines C 7 0 MIA = Flavor violating SUSY, mass insertion approx.






35 Non-resonant background: Upper limit: BR < events / 2 fb -1 irreducible Asymmetry In kinematischer Region II erwartet man gleiche Afb wie für K*ll

36 Q 2 Verteilung für Daten-Set von 2 fb -1 : signal Untergrund (fluktuiert), flach in M Bemerkung: Nicht-resonanter Untergrund wird vernachlässigt. Signal Ereignisse: Untergund: (non-res ignoriert)

37 Statistische Signifikanz des Zero-Crossing Punktes: Kein Untergrund: 0.41 GeV 2 Mit Untergrund (kein non-res): 0.46 GeV 2 / 0.27 GeV 2 Standardmodell: s 0 2 = GeV 2 Systematische Effekte sind bisher noch nicht untersucht !! (aus toy Experimenten) A FB s=m 2 [GeV 2 ] 2 fb -1 (s 0 ) = 0.46 (s 0 ) = 0.27 (10 fb -1 )

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