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Introduction Context of the measurement Status of documentation Analysis overview Open issues

A Study of Charged Kaons Produced in Association with Mesons Godparent Kick-Off Meeting Matthew Jones/ Niharika Ranjan. Introduction Context of the measurement Status of documentation Analysis overview Open issues. Introduction.

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Introduction Context of the measurement Status of documentation Analysis overview Open issues

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  1. A Study of Charged Kaons Produced in Association with MesonsGodparent Kick-Off MeetingMatthew Jones/NiharikaRanjan • Introduction • Context of the measurement • Status of documentation • Analysis overview • Open issues Godparent meeting

  2. Introduction • This analysis studies the charge-flavor correlations that are present in the early stages of heavy quark fragmentation • The two-track trigger provides large samples of fully reconstructed charm mesons • The TOF and COT (dE/dx) allow statistical discrimination between kaons, pionsand protons. • More directly associated with fragmentation process rather than correlations due to strong decays such as . Godparent meeting

  3. Context • We know that heavy quarks need a harder fragmentation function • Fragmentation parameters tuned to inclusive properties of jets. • What about quarks produced in the next fragmentation branch? Godparent meeting

  4. Context • Of practical importance for B flavor tagging • Effectiveness of same side kaon tag predicted using string fragmentation model in Pythia • Can we check this with other heavy quarks? Godparent meeting

  5. Documentation • Technical notes: • Note 10662: Analysis description • Note 10272: Universal curve parametrization • Note 10209: TOF residual parametrization • Note 9749: Prompt/secondary discrimination • Blessed results: • Blessing presentation:February 2nd, 2012 • Questions and Answers • Public web page • Note 10704: Public note • Older results: • B+/B0/Bs-Kaon correlations: Note 8137 Godparent meeting

  6. Analysis Overview • Data sample: xbhd0d (360 pb-1) • Select Ds+/D+ φπ+, φK+K- • Same final state, common systematics • Fit mass distribution separately in each pT range. • Fitted pdf is later used to calculate the likelihood that a decay is in each of the 4 categories. Godparent meeting

  7. Analysis Overview • Two sources of Ds+/D+ mesons: • Charm fragmentation • Decays of bottom hadrons • Discriminate between them using their impact parameter measurement: Ds+K+K-π+ Ds+K+K-π+ p.v. B-decay p.v. Charm fragmentation Non-zero impact parameter (d0) Godparent meeting

  8. Analysis Overview • Prompt component: impact parameter distribution determined by d0 resolution (double Gaussian function). • Secondary component: distribution in b-decays convoluted with resolution • Approximately Lorentz invariant, insensitive to spectator quarks in B decays • Simulate exclusive B decays, apply trigger and event selection. • Parametrize generator-level impact parameter distribution with sum of two exponentials. Godparent meeting

  9. Analysis Overview • Impact parameter pdf is fit separately in five ranges of pT • Likelihood for prompt component of Ds+/D+/background determined from product of mass and impact parameter pdf’s. Godparent meeting

  10. Particle Identification • Use TOF to measure particle fractions by fitting pion Δt residual distribution. • TOF resolution function calibrated using pure sample of pionsfrom D*+D0π+ decays. Godparent meeting

  11. TOF Resolution Function • Un-binned likelihood fit to Δtπ and Δm. • Kaon and proton response assumed to be the same, but shifted in time. Godparent meeting

  12. dE/dx Response • Analyze charged tracks in a cone around the D*+ candidates. • Fit parameters in universal curve and resolution function. • Constrain particle fractions using TOF • Fit fractions using likelihood function constructed from the product of TOF and z(dE/dx) pdf’s. Godparent meeting

  13. Calibration Samples • D*+D0π+ decays provide a pure sample of pions. • φK+K- decays provide pure sample of kaons. • Biases in particle fraction measurements parametrized using • Measured fractions corrected using measured biases in calibration samples • Statistical uncertainty in bias coefficients propagated as systematic uncertainties. Godparent meeting

  14. Associated Particle Production • Consider charged particles produced in a cone of radius ΔR < 0.7 around the Ds+/D+ candidate • Select the track with maximum pT • In 77% of the cases there is only one charged track • In the remaining 23% we have to pick one out of two or three tracks in the cone • Measure particle fractions around prompt/secondary Ds+/D+/background components for same-sign and opposite-sign charge combinations. Godparent meeting

  15. Results • As expected based on our naïve model for fragmentation, opposite sign kaon production is enhanced around Ds+ compared to D+. • Like-sign kaon production is similar around Ds+ and D+. • PYTHIA and HERWIG both have similar trends. Godparent meeting

  16. Results Godparent meeting

  17. Open Issues • Is the structure of the PRD draft clear? • Is each section clear? • Are there additional figures that would be useful? Eg. φK+K- mass distribution. • Additional quantitative information regarding efficiencies, acceptance, … • What is the main result? How can we strengthen the conclusions? • Suggestions? Godparent meeting

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