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Rare Decays Bs Bs 0 B K 0 and their sensitivity to New Physics Klassiker: Bs B(Bs ) 106 tan6 M12/ 2 GeV4 (M12/ 2 M02 )3 hep-ph/0108037 SM : BR (3.4 0.4) 10-9 mSUGRA Parameter: M1/ 2 , M0 , (MA ) A0 , tan , sign B(Bs ) 106 tan6 M12/ 2 GeV4 (M12/ 2 M02 )3 Light chargino bounds from LEP, Radiative EWSB LSP not neutral hep-ph/0108037 arXiv:0712.1708 to PRL < 9.3·10-8 95% CL 2 fb-1 < 5.8·10-8 95% CL D0 Note 5344-Conf (2007) Problem: Untergrundunterdrückung B0 B Invariante Masse keine ausreichende Diskriminate Multivariate Analyse Bs Impact Parameter Lifetime of B Muon Impact Parameter Sign. DOCA between muons Muon Pion Likelihood (LL) Muon Kaon Likelihood (LL) Isolation Geometry Likelihood PID Likelihood signal bb inclusive b b BcJ/ M 3-dim. Binning: signal bb inclusive 18MeV • 4 Bins in Geometry LL • 3 Bins in PID LL • 5 Bin in invarianter Masse Untergrund Ereignisse/Bin Signalereignisse/Bin (BR) Sensitivität BR excluded at 90 % CL, i.e. only background is observed Exclude the interesting region between 10-8 and SM with little Lumi (~0.5 fb-1) BR observed or discovered. Observe (discover) SM BR with 3 (5) after ~2 (~6) fb-1 Events after preselection cuts in 600 (60) MeV mass window Radiative bs decays Standard Model bs (bs): • 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 ACP: Bs • Parity-odd triple correlations between photon and 2 out of 3 hadrons in B (K+p+p) decays • b(X) B0s F Erste Beobachtung von Bs 5.5 BR(Bs ) (5.711..58 1.2 5 1.7 ) 10 SM : (3.94 1.19) 105 (Ball et al.) [1] hep-ph/0607258 [2] arXiv:hep-ex/0607071v1 Why this decay ? SM polarization CPV in decay NP predominantly right handed left handed components <1% 10%-40% Inclusive decays : theory experiment Exclusive decays theory experiment B0 (B0bar)X0 CPV in very small interference mixingdecay B0 (B0bar)X0 Could be large sensitive to NP What do we expect at LHCb ? Expected for one year of measurement ( 2 fb-1 ) • have to fight background • very good PID necessary, p0 rejection • proper time resolution (Time dependent CPV polarization) • high trigger efficiency • good offline selection Reconstruction and Selection Selection mainly based on • two body kinematics • geometrical cuts on pp-interaction PV and B-decay SV Selection criteria maximize with SV S = S+B S: signal evts B: background evts F PV KK+ Some selection criteria… Photon selection • 2 body kinematics hard ET() spectrum • from numerous p0 decay soft Require ET() > 2.8 GeV On the way to the • Charged tracks must NOT come from PV (t of B) • K+K- should come from SV Some selection criteria… On the way to the B • pB = p p should point to PV • use qB ( allow rather large qB as the SV resolution is not good because of K’s !) flight path SV qB reconstructed p PV Background… • large background from B0s Fp0 und BK*p0 use vector meson polarization helicity of F 0 for B0s Fp0 F 1 for B0s F • define helicity angle qH K+ B qH • sin2qH distribution for signals F cos2qH distribution for correlated bkg flat for combinatorial bkg K- And finally one gets… 13 min B0 K0 B0 K0 Expect 68k signal events for 2 fb-1 with B/S < 0.6 Bs Expect 11.5k signal events for 2 fb-1 with B/S < 0.6 • red: true events • blue : comb. bkg. Polarization • from bs predominantly left-handed (SM: V-A coupling of W boson) • e.g. in MSSM can be largely right-handed ( doesn’t effect incl. radiative decay rate predicted by SM) • helicity measurement via time-dependent CP asymmetry, … Polarization B(t ) M 0 amplitudes A(B M 0 L ) A cos e iL A(B M 0 R ) A sin e iR A(B M 0 R ) A cos e iL A(B M 0 L ) A sin e iR tan A(B M R ) A(B M L ) R , L Relative amount of „wrong photon polarization“ Weak phases (CP odd) Time dependent decay rate (Bq (Bq ) M ) e 0 qt qt qt cosh A sinh 2 2 C cos(mqt ) S sin(mqt ) Standard Model: S sin 2 sin A sin 2 cos M R L 1 A sin 2 C 0 CP Asymmetry The CP asymmetry From the time dependent decay rate one gets The measurement of A determines the fraction of ‘different-polarized’ photons ! LHCb Toy study: A 0.2 for 2 fb-1 B0 K 0 sˆ s mb ˆ , m b mB2 mB Interesting observable: Muon forward-backward Asymmetry Asymmetrie: M 2 hep-ph/9910221 sˆ „Zero crossing point:“ s mB2 Generator Studie: 6.5 M Ereignisse. Change in order to which Wilson coefficients are calculated. M2 mass distributiuon SM SUGRA MIA SUSY (lower lines = pure short distance components) MIA = Flavor violating SUSY, mass insertion approx. Forward backward asymmetry SM SUGRA MIA SUSY MIA SUSY C10 >0 Upper/lower lines C7 < 0 / C7 > 0 A. Ali et al. hep-ph/9910221 K p K 0 B0 B RMS 33m K p K 0 B 0 RMS 97m B sel rec sel rec 6.1% 20.6% 1.3% Trigger L0 L1 93% 95% 89% S 1012 2 0.398 BR(B0 K 0) BR(K 0 K p ) tot 1.22 106 0.67 Non-resonant background: Upper limit: BR < 4 10-7 B Kp 173075 events / 2 fb-1 irreducible Asymmetry In kinematischer Region II erwartet man gleiche Afb wie für K*ll Q2 Verteilung für Daten-Set von 2 fb-1: signal Untergrund (fluktuiert), flach in M Bemerkung: Nicht-resonanter Untergrund wird vernachlässigt. Signal Ereignisse: 37001200 Untergund: 1100 250 (non-res ignoriert) 4m2 q2 9 GeV2 Statistische Signifikanz des Zero-Crossing Punktes: (aus 10000 toy Experimenten) Kein Untergrund: 0.41 GeV2 Mit Untergrund (kein non-res): 0.46 GeV2 / 0.27 GeV2 Systematische Effekte sind bisher noch nicht untersucht !! s02 = 4.2 0.6 GeV2 AFB Standardmodell: 2(10) fb1 2 fb-1 (s0) = 0.46 (s0) = 0.27 (10 fb-1) s=m2 [GeV2]