Takeo Higuchi Institute of Particle and Nuclear Studies, KEK Jan 21, 2004 Hawaii, USA Super B Factory Workshop Charged Higgs Search with B  D   

Physics Motivation Branching ratio:, is sensitive to the charged Higgs mass (M H ). The sensitivity depends on vacuum expectation of two Higgs fields: tan  = v u /v d. Probe for minimal SUSY SM. Br (B  D l  ) = (2.14±0.20) % (PDG2003) Br (B  D   ) = ??? %

Decay of B  D    u/d cb   BD B  D     = ~0.8% (SM) H/WH/W Heavier lepton has better sensitivity to H ±

Analysis Overview signal B D    B B  (4S) B B    h  , l  l  Decay of signal B includes 2 or more neutrinos. Tag B should be fully reconstructed to identify signal B. Signal B is searched for in the remained particles using kinematic selection. tag B full reconstruction

MC Sample Fast simulated MC-sample with fully-reconstructed B – Charged B: 3.0 ab  1 (3.2×10 6 events) – Neutral B: 6.1 ab  1 (3.2×10 6 events) Signal B: Generic decay Tag B: Already ‘fully-reconstructed’ – We ‘fully-reconstruct’ tag B seeing generator information. – Reconstruction efficiency of tag B in this sample = 100%. – Statistics can be increased while saving processing time.

B Decays We Search for (1) signal B D0D0    (4S) BB BB BB BB tag B D 0  K    4%  K     0 13%  K        7%  K         0 4%  K S  0 1%  K S     2%  K S      0 4% Total35%      11%    25%    35% Total71% Tag B decay products are tagged using generator information. Searched for in generic B decays. C.C. implicitly included

B Decays We Search for (2) signal B DD    (4S) BB BB BB BB tag B D   K      9%  K       0 6%  K S   1% Total16%      11%    25%    35% Total71% Tag B decay products are tagged using generator information. Searched for in generic B decays. C.C. implicitly included

B  D    : Event Selection (1) Particle selection – Kaon: PID(K) > 0.4. – Pion: PID(  ) > 0.6. – Photon: ECL cluster energy, E  > 50 MeV.   reconstruction –. D 0 reconstruction –.

B  D    : Event Selection (2) Event rejection by signal-B decay products – Events with proton or K L in signal-B decay are rejected. B   D* 0    event rejection – If D* 0 is reconstructed, reject the event. Constraints on remained particles – Neither charged particle nor  0 is allowed after signal B and tag B reconstruction. – Residual ECL energy sum < 100 MeV.

B  D    : Event Selection (3) D   (h    )  modes – Angle between two neutrinos:  1.0 < cos  < 0.8. – Missing mass squared: | p B  p D  p h | 2 > 0.1 (GeV/c 2 ) 2 cos  | p B  p D  p h | 2 (GeV/c 2 ) 2

B  D    : Event Selection (4) D   (    )  modes – Missing mass squared: | p B  p D  p | 2 > 1.2 (GeV/c 2 ) 2

Reconstruction Efficiencies Full-recon. efficiency is not included.

Statistical Significance Assuming B  D     = ~0.8% B  D     is measurable in 12  significance at 5 ab  1.

Dominating Background Modes For modes 45% 58% 20%

Constraint on Charged Higgs Mass R = M W tan  / M H as a function of integrated luminosity  is a parameter, which dominates an uncertainty of the hadron form factor. The  can be experimentally determined by semi-leptonic B decays. may be given with 5 ab  1 data. systematic error not included

Summary B  D    is one of sensitive decays to the charged Higgs. Because other-side-B should be fully-reconstructed, this mode calls for the statistical power of the SuperB factory. The reconstruction efficiency and S/N of this mode are studied using large number of fast simulated MC samples. At the integrated luminosity of 5 ab  1, Br(charged B  D    ) can be measured in the statistical significance of 12 . At the limit of no systematic uncertainty of Br(charged B  D    ) measurement, M H > M W tan  / 11 may be constrained with 5 ab  1 data.