1 / 17

Rare and Forbidden Charm Meson Decays in FOCUS

Rare and Forbidden Charm Meson Decays in FOCUS. Angel M. López University of Puerto Rico at Mayaguez DPF Meeting August 10, 2000. Three Categories of Decays. FCNC D +  K + l + l – D +   + l + l – D s +  K + l + l – D s +   + l + l – D 0  l + l –. LFNV

patch
Télécharger la présentation

Rare and Forbidden Charm Meson Decays in FOCUS

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. Rare and Forbidden Charm Meson Decays in FOCUS Angel M. López University of Puerto Rico at Mayaguez DPF Meeting August 10, 2000 DPF2000

  2. Three Categories of Decays FCNC D+  K+l + l – D+  +l + l – Ds+  K+l + l – Ds+  +l + l – D0  l + l – LFNV D+  K+± e D+   +± e Ds+  K+± e Ds+   +± e D0  ± e LNV D+  K-l + l + D+   -l + l + Ds+  K-l + l + Ds+   -l + l + Talk will present D0  + - analysis of complete FOCUS data set as an example of our rare decay reach. Will show preliminary evaluations of sensitivity for these decays. DPF2000

  3. FOCUS has reconstructed over one million charm decays from the Fermilab 1997 fixed target run An excellent vertex detector but also great particle id including full muon detection and E&M calorimetry . DPF2000

  4. Event Selection Criteria • Vertexing (Candidate driven) • Secondary vertex • Confidence Level • Isolation - No other tracks come from that vertex. • Primary vertex • Require consistent with D track from secondary • Confidence Level • Require a minimum multiplicity • Isolation - No tracks from secondary are consistent with coming from the primary. • In target (z position) • Detachment (L/) DPF2000

  5. More Event Selection Criteria • Muon Identification • Number of Muon Planes with Hits (Mupl) • Confidence Level • Not consistent with being a kaon. • Hadron identification – Triple Cerenkov System • Log likelihood for consistency between Cerenkov hits and a particular particle id hypothesis • Compare log likelihoods for different species (Kaonicity) DPF2000

  6. Fixed (loose) Cuts • Vertexing • CLP and CLS > 1% • Primary Multiplicity > 2 • L/ > 3 • Muon Identification • Mupl 4 • Confidence Level > 1% DPF2000

  7. Mass Distributions with Fixed Cuts Fairly clean even with loose cuts but can be improved. Signal area (±2) has been masked in data (blind analysis). DPF2000

  8. Optimization of Cuts – Blind Analysis • Only sidebands are used to study background. • First determine cut ranges by looking at individual variable histograms. • Vertexing • CLS > 1%, 5%, 10% • ISOS < 10-4, 10-3, 10-2 • ISOP < 10-4, 10-3, 10-2 • Distance of primary outside target edge < 0, 2 • Muon Identification • Mupl 4, 5, 6 • Confidence Level > 1%, 3%, 5% • Kaonicity < 2, 5, 8 DPF2000

  9. More Blind Analysis • Determine a baseline set of cuts with the best (lowest) “sensitivity”. (Branching Ratio) (Sensitivity) NL is the average of the 90% upper limit for an ensemble of experiments with zero signal and the background rate estimated from the sidebands. DPF2000

  10. 90% Confidence Intervals Table Including Uncertainty in Background Estimate From hep/ph0005187. The number of events in the signal region is x. The background is estimated as y /  from an observation of y sideband events. This table is for the case  = 2. DPF2000

  11. Optimum Set of Cuts and Sensitivity The sensitivity is more than a factor of 2 lower than the existing limit. DPF2000

  12. Mass Distributions for Optimized Cuts There are two events in the sidebands. DPF2000

  13. Effects of Background from Meson Misid Doubly mis-identified D0 K- + needs to be studied to determine the ratio () of the background in the sidebands to the background under the peak. The preliminary sensitivity was found by assuming a linear background which is justified for most backgrounds such as Bethe-Heitler pairs. A significant effect from D0  K- + would mean  is larger and the actual sensitivity is smaller. Can be studied with data and Monte Carlo. DPF2000

  14. Background from D0  - + is negligible. Doubly misid-ed D0  - + is a worry because it peaks in the signal! A Monte Carlo study with statistics equal to ten times FOCUS finds no events that survive all the baseline cuts. No event survives all cuts. DPF2000

  15. Monte Carlo simulates pion misid well. DPF2000

  16. Studies of D+ or Ds+ h   For now, preliminary estimates. • Vertex cuts (not optimized) • L /  > 20 • CLS > 1% • Efficiencies (conservative estimates) • Assume efficiencies cancel except particle id. • Cerenkov cut on kaon ~ 80% • Muon Id ~ 95% • ISOP < 1% • Relative trigger efficiency ~ 80% DPF2000

  17. DPF2000

More Related