Lepton/Photon 2003, Batavia, IL, USA August 11 th – 16 th
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CDF n/Photon 2003, Batavia, IL, USA August 11 th – 16 th Measurement of b Branching Ratios in Modes Containing a c are the b branching fractions interesting? tle is known about the properties of b-baryons. surement of b branching fractions provides a way to test Heavy Quark Theory. rently the b-baryons are only produced at the Tevatron. atron luminosity increase + Silicon Vertex Trigger = large b sample Why measure the ratio of branching fractions? We measure the ratios of branching fractions in kinematically similar decay modes. Same triggers are used both for the signal and normalization modes. Systematic errors from the acceptance, trigger and reconstruction efficiency cancel. What ratios do we measure? ) π D BR(B f ) π Λ BR(Λ f 0 d c b baryon ) π D BR(B )/f π Λ BR(Λ f 0 d c b baryon ) π Λ ν)/BR(Λ μ Λ BR(Λ c b c b How do we measure the branching fraction? b X f u,d,s,baryon X BR X = N signal What do we know about b decays? 2003 Particle Data Group ) π c Λ b BR(Λ ν) μ c Λ b BR(Λ c + p K - + and D - K + - - fully reconstruct decays We could extract ratio of production fractions if combined with other analysis large uncertainty from BR( c pK) There are backgrounds from the feed-down of excited charm, other B-hadrons and fake muons. A slightly different formula : R BR = R X (R yield – R physics -R fake ) We choose one control sample: B 0 D* and B 0 D* to understand the backgrounds and systematic uncertainties. Figure 1: Reconstructed B 0 D - + , D - K + - - . The data are fitted with a signal Gaussian, a satellite Gaussian and a broad Gaussian (background). 2 /N=0.92 Sources of reflections in b c Four-prong B meson decays and all the other B meson decays b c K and other b decays Normalized the reflections with the measured B 0 D - + yield in the b mass window, production fractions and relative BR of four- prong to other B decays and Shin-Shan Yu, University of Pennsylvania for the CDF Collaboration Systematic uncertainties We measure 0.18(BR) 0.09(syst) 0.11(stat) 0.66 ) π D BR(B f ) π Λ BR(Λ f 0 d b baryon c ) π * D 0 BR(B ν) μ * D 0 BR(B Figure 4: Reconstructed B 0 D* Data are fitted with double Gaussian (signal) and a constant background. 2 /N=21.11/31 Figure 3: Reconstructed B 0 D* Data are fitted with a single Gaussian (signal) and a exponential background. 2 /N=29.26/22 ta are collected from the two-track trigger. trigger: a trigger that requires a pair of opposite-charged tracks with 120 m impact parameters 1 mm, momentum 2GeV/c, scalar sum of the transverse momenta 5.5GeV/c, 2 angle between two tracks 90 degrees, the ce between the beam spot and the intersection point of two tracks 200 m . Physics backgrounds from the feed-down of excited D mesons Physics backgrounds are estimated from predicted branching ratios and the efficiencies from the Monte Carlo. Backgrounds contributing 1% are not included. Fake muons from the B hadronic decays Backgrounds from fake muons are estimated b weighting the K/ Pt spectra from B mix D*X hadro Monte Carlo by the measured muon fake rate. See Figure 5. Systematic uncertainties 85% 9% 6% 1 2 3 1. B 0 ->D* 2. B + ->D*X backgrounds 3. B 0 ->D*X backgrounds We BR) ured 1.1(unmeas BR) ed 0.5(measur sys.) (internal 1.3 0.8 7.1(stat) 22.9 ) π D 0 BR(B ν) μ - * D 0 BR(B * Note: The systematic error from the unmeasured BR is calculated by assigning 5% uncertainty to the charm decays and 100% uncertainty to the B decays. Result agrees with 2003 PDG within 0.4. proceed with b analysis Figure 5: muon fake rate and + Pt spectrum : total reconstruction efficiency N signal : measured event yield b : b-quark production cross section f u,d,s,baryon : probability for the b- quark to hadronize to B u,d,s, baryon Figure 2: Reconstructed b c , c pK. The data are fitted with a Gaussian (signal). The background shape is obtained from the Monte Carlo. 2 /N=167/116 There are two sources of backgrounds: 1. combinatorial 2. reflections. See below. Normalization Mode Signal Mode Normalization Mode Signal Mode Yi Le, Bruce Barnett, Petar Maksimovic, Matthew Marti Rick Tesarek Shin-Shan Yu, Nigel Lockyer Efficiency ratio b )/B 0 ) University of Pennsylvania Fermilab Johns Hopkins University
description
Measurement of b Branching Ratios in Modes Containing a c. Johns Hopkins University. Fermilab. University of Pennsylvania. Rick Tesarek. Yi Le, Bruce Barnett, Petar Maksimovic, Matthew Martin. Shin-Shan Yu, Nigel Lockyer. What do we know about b decays? - PowerPoint PPT Presentation
Transcript of Lepton/Photon 2003, Batavia, IL, USA August 11 th – 16 th
CDF
Lepton/Photon 2003, Batavia, IL, USA August 11th – 16th
Measurement of b Branching Ratios
in Modes Containing a c Why are the b branching fractions interesting? Little is known about the properties of b-baryons. Measurement of b branching fractions provides a way to test Heavy Quark Theory. Currently the b-baryons are only produced at the Tevatron. Tevatron luminosity increase + Silicon Vertex Trigger = large b sample
Why measure the ratio of branching fractions? We measure the ratios of branching fractions in kinematically similar decay modes. Same triggers are used both for the signal and normalization modes. Systematic errors from the acceptance, trigger and reconstruction efficiency cancel. What ratios do we measure?
)πDBR(Bf
)πΛBR(Λf0
d
cbbaryon
)πDBR(B)/fπΛBR(Λf 0dcbbaryon
)πΛν)/BR(ΛμΛBR(Λ cbcb
How do we measure the branching fraction? b X fu,d,s,baryon X BR X = Nsignal
What do we know about b decays?2003 Particle Data Group
)πcΛbBR(Λ
ν)μcΛbBR(Λ
c+ p K- + and D- K+ - -
fully reconstruct decays We could extract ratio of production fractions if combined with other analysis large uncertainty from BR(c pK)
There are backgrounds from the feed-down of excited charm, other B-hadrons and fake muons. A slightly different formula : RBR = R X (Ryield – Rphysics-Rfake) We choose one control sample: B0 D* and B0 D* to understand the backgrounds and systematic uncertainties.
Figure 1: Reconstructed B0 D-+, D- K+-
-. The data are fitted with a signal Gaussian, a satellite Gaussian and a broad Gaussian (background). 2/N=0.92
Sources of reflections in b c Four-prong B meson decays and all the other B meson decays b cK and other b decays Normalized the reflections with the measured B0 D-+ yield in the b mass window, production fractions and relative BR of four-prong to other B decays
and
Shin-Shan Yu, University of Pennsylvania for the CDF Collaboration
Systematic uncertainties
We measure
0.18(BR)0.09(syst)0.11(stat)0.66)πDBR(Bf
)πΛBR(Λf0
d
bbaryon c
)π*D0BR(B
ν)μ*D0BR(B
Figure 4: Reconstructed B0D*Data are fitted with double Gaussian (signal) and a constant background. 2/N=21.11/31
Figure 3: Reconstructed B0D*Data are fitted with a single Gaussian (signal) and a exponential background. 2/N=29.26/22
Both data are collected from the two-track trigger. Two-track trigger: a trigger that requires a pair of opposite-charged tracks with 120 m impact parameters 1 mm, transverse momentum 2GeV/c, scalar sum of the transverse momenta 5.5GeV/c, 2 angle between two tracks 90 degrees, the 2-D distance between the beam spot and the intersection point of two tracks 200 m .
Physics backgrounds from the feed-down of excited D mesons Physics backgrounds are estimated from predicted branching ratios and the efficiencies from the Monte Carlo. Backgrounds contributing 1% are not included.
Fake muons from the B hadronic decaysBackgrounds from fake muons are estimated byweighting the K/Pt spectra from BmixD*Xhadron
Monte Carlo by the measured muon fake rate. See Figure 5.Systematic uncertainties
85%
9%
6%
1
2
3
1. B0->D*2. B+->D*X backgrounds3. B0->D*X backgrounds
We measure
BR) ured1.1(unmeasBR) ed0.5(measursys.) (internal1.30.87.1(stat)22.9
)πD0BR(B
ν)μ-*D0BR(B
*
Note: The systematic error from the unmeasured BR is calculated by assigning 5% uncertainty to the charm decays and 100% uncertainty to the B decays.
Result agrees with 2003 PDG within 0.4. proceed with b analysis
Figure 5: muon fake rate and + Pt spectrum
: total reconstruction efficiency Nsignal : measured event yield
b : b-quark production cross section fu,d,s,baryon: probability for the b-quark to hadronize to Bu,d,s, baryon
Figure 2: Reconstructed b c, c pK. The data are fitted with a Gaussian (signal). The background shape is obtained from the Monte Carlo. 2/N=167/116There are two sources of backgrounds: 1. combinatorial 2. reflections. See below.
Normalization Mode Signal Mode
Normalization Mode Signal Mode
Yi Le, Bruce Barnett,Petar Maksimovic, Matthew MartinRick TesarekShin-Shan Yu, Nigel Lockyer
Efficiency ratiob)/B0)
University of Pennsylvania Fermilab Johns Hopkins University
