Semileptonicand leptonic B decay results from early Belle ... · Integrated luminosity during early...
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Semileptonic and leptonic B decay results from early Belle II data Andrea Fodor, on behalf of the Belle II collaboration McGill University, Canada Belle II detector EM Calorimeter: CsI(Tl), waveform sampling electronics K long and muon detector: Resistive Plate Counter for barrel Scintillator + Si-PM for end-caps Vertex detector: 2 layers pixel sensors + 4 layers double- sided silicon strip detectors Central Drift Chamber: Small cells, fast electronics Particle Identification: New Time Of Propagation counter (barrel) Proximity focusing Aerogel RICH (fwd) Belle II run in 2019 →ℓ ℓ − untagged reconstruction →ℓ ℓ − hadronic FEI tagging Hadronic FEI tagging performance → ∗ ℓ ℓ − untagged reconstruction -meson reconstruction and Full Event Interpretation • First Belle II official data taking run with the full detector installed from March to July 2019 • Reached an instantaneous luminosity of 5.5 × 10 ,, cm -2 s -1 Integrated luminosity during early 2019 run: 6.49 fb -1 of data collected, approximately 7.1 × 10 - . -pairs • 0 1 collided at the Υ 4 resonance which decays almost exclusively to B-meson pairs • B-mesons produced almost at rest in the CoM frame • Several approaches in the analysis depending on the treatment of the companion B-meson, B tag ← 29 and 26 hadronic B + and B 0 tag-side decay modes reconstructed • Can be used to measure | 78 | and | 98 | CKM matrix elements • Current measurements show disagreement of | 78 | / | 98 | in inclusive and exclusive final states • Belle II has completed its first physics run and collected 6.5 fb-1 of data • First data analyzed to validate the detector performance • FEI hadronic tagging performance tested with → ℓ ℓ decay mode • Validation of Monte Carlo simulation using → ∗ ℓ ℓ untagged analysis • Untagged →ℓ ℓ measurements under preparation Belle II Performance B-meson detection: Data/MC comparison of R2, ratio of second and zeroth Fox-Wolfram moment – a good indicator of collisions at Υ(4) resonance Particle Identification: Identification efficiency for electrons and muons tested using J/ → ℓ 0 ℓ 1 decays • Untagged reconstruction – signal reconstruction without full B tag reconstruction • Tagged approach – reconstruction of the B tag first using semileptonic or hadronic decay modes and attributing the remaining detected depositions to the B sig • Full Event Interpretation – tagging approach implemented by Belle II that uses Machine Learning and reconstructs B tag from more than 200 different decay modes, improving the B tag reconstruction efficiency; enables precise determination of the energy carried by undetected neutrinos ↑ Determine the correctly reconstructed tag-side yield by fitting the mass of the reconstructed B tag 89 = 8BCD E /4 − ∗ G HIJ E • Evaluate hadronic FEI tagging performance in early data • Highest momentum lepton selected from the remaining tracks not associated with B tag • ℓ ∗ > 0.6 GeV/c, 89 KLM > 5.27 GeV/c 2 • The missing neutrino momentum is equivalent to the missing mass squared, reconstructed using: N E ≡ DPQQ E = BB − RCS − ℓ − T E • Analysis of the lepton spectrum close to the kinematic endpoint to be used to separate between 9 ℓ ℓ and 7 ℓ ℓ decay modes • Untagged analysis; suppression of continuum processes using multi-variative methods • Off-resonance data available to describe continuum Conclusion • ∗ ± candidates reconstructed from the ∗ ± → V ± decays; V mesons reconstructed in the decay mode ± ∓ • Electrons/muons paired with the ∗ ± to form signal candidates • Signal events identified using the missing mass squared and the angle between the B-meson and the ∗ ℓ system: DPQQ E = Z [[ E − \ E , cos G\ = Ea b ∗ a c ∗ 1d b e 1D c e EZ b ∗ Z c ∗ , where Y indicates the ∗ ℓ system • To be used for |V cb | measurements ↑ B classifier value, P tag , discriminates correctly reconstructed tag-sides from background 0 1 0 1 V 1 V 1 V 1 V 1 0 1 0 1 ∗0 1 g N sig = 63 ± 10 ∗0 1 g N sig = 63 ± 10 ∗0 1 B N sig = 80 ± 12 ∗0 1 B N sig = 80 ± 12 B Comput. Softw. Big Sci. (2019) 3: 6
Transcript of Semileptonicand leptonic B decay results from early Belle ... · Integrated luminosity during early...
Semileptonic and leptonic B decay results from early Belle II dataAndrea Fodor, on behalf of the Belle II collaboration
McGill University, CanadaBelle II detector
EM Calorimeter: CsI(Tl), waveform sampling electronics
Klong and muon detector:Resistive Plate Counter for barrelScintillator + Si-PM for end-caps
Vertex detector:2 layers pixel sensors +4 layers double-sided silicon strip detectors
Central Drift Chamber:Small cells,fast electronics
Particle Identification:New Time Of Propagation counter (barrel)Proximity focusing Aerogel RICH (fwd)
Belle II run in 2019
𝐵 → 𝑋 ℓ 𝜈ℓ − untagged reconstruction 𝐵 → 𝑋 ℓ 𝜈ℓ − hadronic FEI tagging
Hadronic FEI tagging performance
𝐵 → 𝐷∗ ℓ 𝜈ℓ − untagged reconstruction
𝐵-meson reconstruction and Full Event Interpretation
• First Belle II official data taking run with the full detector installed from March to July 2019
• Reached an instantaneous luminosity of 5.5 × 10,, cm-2s-1
Integrated luminosity during early 2019 run: 6.49 fb-1 of data collected, approximately 7.1 × 10- 𝐵 .𝐵-pairs
• 𝑒0𝑒1 collided at the Υ 4𝑆 resonance which decays almost exclusively to B-meson pairs
• B-mesons produced almost at rest in the CoM frame
• Several approaches in the analysis depending on the treatment of the companion B-meson, Btag
← 29 and 26 hadronic B+ and B0 tag-side decay modes reconstructed
• Can be used to measure |𝑉78| and |𝑉98| CKM matrix elements• Current measurements show disagreement of |𝑉78| / |𝑉98| in inclusive
and exclusive final states
• Belle II has completed its first physics run and collected 6.5 fb-1 of data• First data analyzed to validate the detector performance• FEI hadronic tagging performance tested with 𝐵 → 𝑋 ℓ𝜈ℓ decay mode• Validation of Monte Carlo simulation using 𝐵 → 𝐷∗ ℓ 𝜈ℓ untagged analysis• Untagged 𝐵 → 𝑋 ℓ 𝜈ℓ measurements under preparation
Belle II PerformanceB-meson detection:Data/MC comparison of R2, ratio of second and zeroth Fox-Wolfram moment – a good indicator of collisions at Υ(4𝑆) resonanceParticle Identification:Identification efficiency for electrons and muons tested using J/𝜓 → ℓ0ℓ1 decays
• Untagged reconstruction – signal reconstruction without full Btag reconstruction
• Tagged approach – reconstruction of the Btag first using semileptonic or hadronic decay modes and attributing the remaining detected depositions to the Bsig
• Full Event Interpretation – tagging approach implemented by Belle II that uses Machine Learning and reconstructs Btag from more than 200 different decay modes, improving the Btag reconstruction efficiency; enables precise determination of the energy carried by undetected neutrinos
↑ Determine the correctly reconstructed tag-side yield by fitting the mass of the reconstructed Btag
𝑚89 = 𝐸8BCDE /4 − 𝑝∗GHIJE
• Evaluate hadronic FEI tagging performance in early data• Highest momentum lepton selected from the remaining tracks not
associated with Btag
• 𝑝ℓ∗ > 0.6 GeV/c, 𝑚89KLM > 5.27 GeV/c2
• The missing neutrino momentum is equivalent to the missing mass squared, reconstructed using:
𝑝NE ≡ 𝑚DPQQE = 𝑝BB − 𝑝RCS − 𝑝ℓ − 𝑝T
E
• Analysis of the lepton spectrum close to the kinematic endpoint to be used to separate between 𝑋9ℓ𝜈ℓ and 𝑋7ℓ𝜈ℓ decay modes
• Untagged analysis; suppression of continuum processes using multi-variative methods
• Off-resonance data available to describe continuum
Conclusion
• 𝐷∗± candidates reconstructed from the 𝐷∗± → 𝐷V𝜋±decays; 𝐷V mesons reconstructed in the decay mode 𝐾±𝜋∓
• Electrons/muons paired with the 𝐷∗± to form signal candidates
• Signal events identified using the missing mass squared and the angle between the B-meson and the 𝐷∗ℓ system:
𝑚DPQQE = Z[[
E− 𝑝\
E, cos 𝜃G\ =
E ab∗ac
∗ 1dbe1Dc
e
E Zb∗ Zc
∗ ,where Y indicates the 𝐷∗ℓ system
• To be used for |Vcb| measurements
↑ B classifier value, Ptag, discriminates correctly reconstructed tag-sides from background
𝐵0𝜇1 𝐵0𝜇1
𝐵V𝜇1 𝐵V𝜇1 𝐵V𝑒1 𝐵V𝑒1
𝐵0𝑒1 𝐵0𝑒1
𝐷∗0𝜇1 𝜈gNsig = 63 ± 10
𝐷∗0𝜇1 𝜈gNsig = 63 ± 10
𝐷∗0𝑒1 𝜈BNsig = 80 ± 12
𝐷∗0𝑒1 𝜈BNsig = 80 ± 12
𝑋 𝑒 𝜈B
Comput. Softw. Big Sci. (2019) 3: 6
