1 / 11

Advanced Vertexing Techniques for Precise Lxy Determination in LBLB Group Decays

This document outlines a detailed three-step process for determining the vertex from tracks in LBLB group decays, emphasizing the challenges in accurately computing secondary vertex positions. It highlights the application of beamline constraints and the systematic uncertainties involved, including variations observed in Monte Carlo simulations. Additionally, the analysis addresses the scale factors affecting secondary vertex measurements, providing insights into the impact parameter pulls, and the dependency of the scale factor on decay modes. The conclusions suggest an approach to assess all scale factors accurately.

kasie
Download Presentation

Advanced Vertexing Techniques for Precise Lxy Determination in LBLB Group Decays

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EbE Vertexing for Mixing Alex For the LBLB group

  2. Decay Lxy Determination A 3 step process: • Determine vertex from tracks in the event (~25m-ish) • Apply beamline constraint (~25m-ish) • Compute secondary vertex position At each step, pulls of the new ingredient must be 1!!! PV PV beam + Combined PV Lxy

  3. PV Scale Factor (no beam constr.) • Scale factor in data is O(1.38) • Montecarlo after L00 reweighting shows consistent numbers • Systematics from fit model and across samples available [effect is O(10%)] • Pull after beamline constraint? • Apply beam constraint • Look at d0 of fully reco’d candidates WRT EbE vertex • Affected by: • EbE (PV + beam) • Secondary Vertex

  4. Beamline Constraint • Impact Parameter Pull w.r.t. beamline/beamline constrained EbE: • d0beam shows ~10-15% deviation from 1 • d0EbE Shows O(20%) deviation • Where do these come from? • Beamline [constraint] • Secondary Vertex res.

  5. Secondary Vertex Scale factor from B decays • Example: BK+ • Fit  to a single vertex • “point”  back to K • Measure Lxy wrt B vertex • Pull is a proxy for a “seconday vertex” pull!   “Two” K B “One” Primary Vertex

  6. The SV scale factor problem • Re-analyzed all samples • Fixed a couple of bugs… • Pull grows as a function of lifetime? • No clear dependency on any other variable spotted • How does this compare to montecarlo?

  7. Montecarlo • We compare/complement data with: • Toy montecarlo to study pull of fixed kinematics vs Lxy • Several samples: • As many of the modes we study on data as possible • , K+, K*,D+ • Pythia (preferable to evaluate the PV pulls) • Bgen (suitable for most SV studies)

  8. L00 Reweighting on SV • L00 reweighting has a larger effect on SV than PV • Effect consistently reproduces our ‘problem’ on Montecarlo!!! • If we find consistency with data, we can dissect the MC and get another tool to investigate the problem! • In the short term we can just use MC to assess the scale factor, with a systematic uncertainty of few %! • We can confirm this looking at the impact parameter, rather than Lxy

  9. Cross check: ‘B’ pion IP Picture is consistent with what we see on Lxy !!!

  10. Bottomline • SV scale factor depends on mode (kinematics/topology) • Montecarlo reproduces the behavior • We can measure the appropriate scale factor comparing measured-truth

  11. Conclusions • We now have a way of assessing all the scale factors involved [O(10-20%) different from 1] • Aart’s measurement of the beamline ‘growth’ with time needs to be incorporated as well [O(10-15%) effect] • Putting all together should allow us to obtain a consistent picture with a reasonable systematic [O(10%)] • Plan is to verify this and document everything!

More Related