J/ ψ ( ψ (2s)) vetoes
1
J/ψ(ψ(2s)) vetoes Fit • Unbinned maximum likelihood fit is performed in m ES and ΔE (m ES , ΔE and m Kπ ) to extract signal yields of B Kl → + l - (BK → * l + l - ) • Other signal parameters fixed to values from simulation or charmonium control samples • Peaking background: same shape as signal with yields fixed • Combinatorial background: empirical shape fitted to data with a floating normalization Results •B Kl → + l - Significance ~8σ •BK → * l + l - • Assume BF(BK → * e + e - )/ BF(BK → * µ + µ - ) = 1.33 to account for contribution from photon penguin pole near m ll = 0 [Ali et al. PRD 66 034002 (2002)] 44 . 0 07 . 3 9 . 4 2 . 4 27 . 0 20 . 0 2 . 10 6 . 0 12 . 0 86 . 0 4 . 6 5 . 4 12 . 0 11 . 1 6 . 13 4 . 12 17 . 0 63 . 1 7 . 8 9 . 5 08 . 0 21 . 0 1 . 20 8 . 1 02 . 0 07 . 0 5 . 8 7 . 0 08 . 0 05 . 1 2 . 19 7 . 24 ) 10 ( (%) 58 . 2 78 . 1 5 . 3 4 . 2 * 34 . 1 87 . 0 8 . 3 5 . 2 * 79 . 0 58 . 0 1 . 4 0 . 3 0 * 56 . 0 47 . 0 3 . 6 2 . 5 0 * 82 . 0 63 . 0 0 . 3 3 . 2 0 23 . 0 16 . 0 0 . 2 4 . 1 0 19 . 0 11 . 0 0 . 2 2 . 1 25 . 0 22 . 0 9 . 5 2 . 5 6 K e e K K e e K K e e K K e e K BF Yield Mode Introduction • The branching fraction for B Kl → + l - (BK → * l + l - ) is predicted to be around 0.5×10 -6 (1.5×10 -6 ) with an accuracy of 35% • 8 decay modes studied: B + K → + l + l - , B 0 K l → + l - , B + K → *+ l + l - and B 0 K l → + l - (l=e or μ) • A data sample of 122.9×10 6 BB decays is used • Run 3 (2002-2003) data included Event selection • B-candidates are formed by combining an oppositely charged lepton pair with a K ± or K , and for the BK → * l + l - modes, a π ± to form a K * candidate • Photons from Bremsstrahlung are recovered for electron tracks • The K + are identified using the DIRC and dE/dx B-reconstruction • The B-candidates are peaked strongly in two kinematic variables: where E b is the beam energy in the centre of mass frame and, m i and p i are the masses and three- momenta of the B-candidate’s daughters Background • Non-peaking background arises from random combinations of particles from BB and qq events • Peaking background in m ES and ΔE arises from: • B J/ → ψ(ψ(2s))K (*) • BK → * γ followed by photon conversion • Hadronic B-decays in which a π + π - pair is identified as a µ + µ - pair • The inclusive branching fractions for BX → s l + l - , where l is either an e or µ, are predicted to be (4.2±0.7) ×10 -6 for m ll >0.2 GeV/c 2 [Ali, hep- ph/0210183] • Sample of 88.9 ×10 6 BB events used • Reconstruct ~50% of all final states by selecting oppositely charged electron or muon pairs combined with a K ± or K , and up to 2 pions, one of which may be a π 0 • Event selection is optimized in 3 regions of m(X s ) to enhance background rejection at higher m(X s ) • Similar peaking backgrounds to BK → (*) l + l - • Unbinned extended maximum likelihood fit is performed to extract signal yields, and shape and yield of combinatorial background • The distribution of m(X s ) for e and µ shows states beyond the K * (892) contribute to the total yield • Signal yield 41.4±10.3±1.5, with a statistical significance of 4.6σ • Dominant systematic uncertainties from the measured exclusive BFs and the Fermi motion model used for the b-quark in the meson • With improved measurements of exclusive mode BFs and the Fermi motion the systematic uncertainty will decrease significantly Jim Libby (SLAC) surements of Rare Flavour Changing Neutral Current B-decays FCNC B decays B K → (*) l + l - BX → s l + l - • Flavour changing neutral current (FCNC) decays appear only at the 1-loop level in the Standard Model • Examples are the Penguin and W-box b sl → + l - decays (right) and pure Penguin bs → γ decay (below) • Excellent place to search for new physics because it appears at the same order as the Standard Model • Some SUSY examples are shown in the figure below • Theoretical predictions are more precise for inclusive modes than exclusive, due to hadronic uncertainties in the latter, however they are more challenging experimentally • Measurement of the bs → γ photon energy spectrum leads to a more accurate simulation of the b ul → ν lepton momentum spectrum, which is a major uncertainty in the determination of V ub •Preliminary results from BABAR are presented on BK → (*) l + l - , B X → s l + l - and B K (1430) → γ 6 34 . 0 29 . 0 * 10 ) 11 . 0 89 . 0 ( ) ( l l K B BF 6 15 . 0 13 . 0 10 ) 06 . 0 69 . 0 ( ) ( l Kl B BF 6 8 . 1 5 . 1 10 ) 6 . 1 3 . 6 ( ) ( l l X B BF s BK → 2 (1430) γ • Branching fractions for the processes B + K → *+ (1430) γ and B 0 K → *0 (1430) γ have been measured • Sub-modes K *0 K → + π - and K *+ K → + π 0 , K 0 π + • The spin-2 state is isolated from spin-1 background by fitting to the cosine of the helicity angle (cosθ H ) as well as ΔE and m ES Signal projections in m Kπ and |cosθ H |- B 0 K → *0 (1430) γ Combinatorial Comb. + Peaking bkg Signal + bkg 5 * 2 5 0 * 2 0 10 ) 13 . 0 40 . 0 44 . 1 ( ) ( 10 ) 11 . 0 25 . 0 22 . 1 ( ) ( K B BF K B BF Simulation after cuts * 2 * 2 2 2 * ES ) ( b i i i i * i b E m E E m p p Signal Background * 2 s 0 s 0 s *0 * * s 0 * 2 2 2 2 s 2
description
*. 2. s. *0. s. s. s. 0. 0. 0. Signal Background. Signal + bkg. Comb. + Peaking bkg. J/ ψ ( ψ (2s)) vetoes. Combinatorial. B→X s l + l -. FCNC B decays. - PowerPoint PPT Presentation
Transcript of J/ ψ ( ψ (2s)) vetoes
J/ψ(ψ(2s)) vetoes
Fit• Unbinned maximum likelihood fit is performed in
mES and ΔE (mES, ΔE and mKπ) to extract signal yields of B→Kl+l- (B→K*l+l-)
• Other signal parameters fixed to values from simulation or charmonium control samples
• Peaking background: same shape as signal with yields fixed
• Combinatorial background: empirical shape fitted to data with a floating normalization
Results
• B→Kl+l-
Significance ~8σ• B→K*l+l-
• Assume BF(B→K*e+e-)/ BF(B→K*µ+µ-) = 1.33 to account for contribution from photon penguin pole near mll = 0 [Ali et al. PRD 66 034002 (2002)]
Significance ~3.3σ (including systematics)
44.007.39.42.427.020.02.106.012.086.04.65.412.011.16.134.1217.063.17.89.508.021.01.208.1
02.007.05.87.008.005.12.197.24
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56.047.0
3.62.5
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0.33.2
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23.016.0
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6
KeeK
KeeK
KeeK
KeeK
BFYieldMode
Introduction• The branching fraction for B→Kl+l- (B→K*l+l-) is
predicted to be around 0.5×10-6 (1.5×10-6) with an accuracy of 35%
• 8 decay modes studied: B+→K+l+l-, B0→K l+l-, B+→K*+l+l- and B0→K l+l- (l=e or μ)
• A data sample of 122.9×106 BB decays is used• Run 3 (2002-2003) data included
Event selection• B-candidates are formed by combining an
oppositely charged lepton pair with a K± or K , and for the B→K*l+l- modes, a π± to form a K*
candidate • Photons from Bremsstrahlung are recovered for
electron tracks• The K+ are identified using the DIRC and dE/dx
B-reconstruction• The B-candidates are peaked strongly in two
kinematic variables:
where Eb is the beam energy in the centre of mass frame and, mi and pi are the masses and three-momenta of the B-candidate’s daughters
Background• Non-peaking background arises from random
combinations of particles from BB and qq events • Peaking background in mES and ΔE arises from:• B→J/ψ(ψ(2s))K(*)
• B→K*γ followed by photon conversion • Hadronic B-decays in which a π+π- pair is
identified as a µ+µ- pair
• After cuts peaking background less than ≤ 0.7 events in each mode
• The inclusive branching fractions for B→Xsl+l-, where l is either an e or µ, are predicted to be (4.2±0.7) ×10-6 for mll>0.2 GeV/c2 [Ali, hep-ph/0210183]
• Sample of 88.9 ×106 BB events used• Reconstruct ~50% of all final states by selecting
oppositely charged electron or muon pairs combined with a K± or K , and up to 2 pions, one of which may be a π0
• Event selection is optimized in 3 regions of m(Xs) to enhance background rejection at higher m(Xs)
• Similar peaking backgrounds to B→K(*)l+l-
• Unbinned extended maximum likelihood fit is performed to extract signal yields, and shape and yield of combinatorial background
• The distribution of m(Xs) for e and µ shows states beyond the K*(892) contribute to the total yield
• Signal yield 41.4±10.3±1.5, with a statistical significance of 4.6σ
• Dominant systematic uncertainties from the measured exclusive BFs and the Fermi motion model used for the b-quark in the meson
• With improved measurements of exclusive mode BFs and the Fermi motion the systematic uncertainty will decrease significantly
Jim Libby (SLAC)Measurements of Rare Flavour Changing Neutral Current B-decays
FCNC B decays
B→K(*)l+l-
B→Xsl+ l-
• Flavour changing neutral current (FCNC) decays appear only at the 1-loop level in the Standard Model
• Examples are the Penguin and W-box b→sl+l-
decays (right) and pure Penguin b→sγ decay (below)
• Excellent place to search for new physics because it appears at the same order as the Standard Model
• Some SUSY examples are shown in the figure below• Theoretical predictions are more precise for inclusive modes
than exclusive, due to hadronic uncertainties in the latter, however they are more challenging experimentally
• Measurement of the b→sγ photon energy spectrum leads to a more accurate simulation of the b→ulν lepton momentum spectrum, which is a major uncertainty in the determination of Vub• Preliminary results from BABAR are
presented on B→K(*)l+l-, B→ Xs l+l- and B→K (1430)γ
634.029.0
* 10)11.089.0()(
llKBBF
615.013.0 10)06.069.0()(
lKlBBF
68.15.1 10)6.13.6()(
llXBBF s
B→K2 (1430)γ• Branching fractions for the processes
B+→K*+(1430) γ and B0→K*0(1430) γ have been measured
• Sub-modes K*0→ K+π- and K*+→ K+π0, K0π+
• The spin-2 state is isolated from spin-1 background by fitting to the cosine of the helicity angle (cosθH) as well as ΔE and mES
Signal projections in mKπ and |cosθH|- B0→K*0(1430) γ
Combinatorial
Comb. +Peaking bkg
Signal +bkg
5*2
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10)11.025.022.1()(
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Simulation after cuts
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