1 / 19

Background rejection in P326 (NA48/3)

Background rejection in P326 (NA48/3). Giuseppe Ruggiero CERN K-Rare 2005 Workshop Frascati 26 / 05 / 2005. Overview. Characterization of the background Kinematics and background rejection capability Muon rejection and Muon ID Requirements and results from simulations Photon rejection

kalia-cantrell
Télécharger la présentation

Background rejection in P326 (NA48/3)

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. Background rejection in P326 (NA48/3) Giuseppe Ruggiero CERN K-Rare 2005 Workshop Frascati 26 / 05 / 2005 Giuseppe Ruggiero - CERN

  2. Overview • Characterization of the background • Kinematics and background rejection capability • Muon rejection and Muon ID • Requirements and results from simulations • Photon rejection • Requirements and results from simulations • Electron ID • Results from NA48 studies on data • Results about background rejection • Some thoughts about Charged Veto • Conclusions Giuseppe Ruggiero - CERN

  3. Background rejection • Main task of a pnn experiment • All the K+ decay modes are potentially dangerous • Goal of P326: S/B = 10~10-12 rejection • 2-Steps: • Kinematic rejection • Veto and Particle ID • g, m, charged particles • m – p - e separation As better as possible resolution in charged particle reconstruction High hermeticity Giuseppe Ruggiero - CERN

  4. Background kinematically constrained Pion track hyp. 92% of total background Allows us to define the signal region Giuseppe Ruggiero - CERN

  5. Background not kinematically constrained Pion track hyp. 8% of total background Spoils the signal region Giuseppe Ruggiero - CERN

  6. Kinematics: Gigatracker + Double Spectrometer • Tracking systems operating in vacuum • Gigatracker: pixels • Spectrometer: Straw tubes • Gigatracker: • 4x10-3 X0 per station • PK measurement • qK measurement • Spectrometer: • 5x10-3 X0 per chamber • 2 Ptrack measurements • qtrack measurement • Resolution limited by MS Giuseppe Ruggiero - CERN

  7. Kinematic reconstruction Total qpK qp PK Ptrack qK Two independent measurements of the downstream track momentum m2miss resolution ~1.1×10-3 GeV2/c4 Main contribution from QpK measurement Giuseppe Ruggiero - CERN

  8. Kinematic rejection CUTS: Against Km2, p+p0 and p+p+p- Gaussian background < 10-6 Against Km2 RICH operational reasons Simulation and results p+p0 • Simulation of the tracking systems • GEANT - based • Accidental PileUp in Gigatracker • (150 ps resolution per station) • Kinematic rejection inefficiency: • (Limited by non gaussian tails from MS) • Km2~5 x 10-6(Region I mainly) • p+p0~2 x 10-4 • Reconstruction: • Room for ×3 gain in rejection power • (loss in signal acceptance) Cuts on Ptrack Giuseppe Ruggiero - CERN

  9. Sources of m rejection inefficiency: “Catastrophic” m energy losses m bremsstrahlung e+e- pair production high Q2m+ e- scattering m decay in flight Deep inelastic m – nucleon scattering m+ + N  m+ + hadrons (<10-6) electromagnetic shower(10-5) Muon rejection: Physics EM showers (from ICARUS) Hadronic shower (from ICARUS) Giuseppe Ruggiero - CERN

  10. Muon rejection: MAMUD • Detector: Sampling Calorimeter (m rejection) + Magnet (beam deflection) • Goal: m rejection inefficiency < 10-5 • Sensitivity to minimum ionizing particles (MIP) • Distinguishhadronic and electromagneticshowers (longitudinal segmentation) • Bending power:5 Tm 75 GeV/c beam deflected by ~18 mrad Giuseppe Ruggiero - CERN

  11. Simulation of muon rejection: results • Complete GEANT simulation of MAMUD • Rejection: • MAMUD + LKr calorimeter • Rejected events: • MIP deposition in last section only • EM cluster shape • Inefficiency ~10-5 (>90% signal acceptance) • (Inefficiency ~10-6with50% signal acceptance) Giuseppe Ruggiero - CERN

  12. Muon – Pion ID Detector: RICH Goal: Muon – Pion separation with 10-2 ineff. over a wide momentum range As low X0 as possible (RICH before LKr) 1st option:P.S. Cooper – FERMILAB-CONF-05-015-CD Some Brain – Storming : O. Ullaland (CERN) 0.1 ~1 in 2 m Ar : ~22 pe and c=23.7 mrad Argon 0.01 Helium Dq m / p (rad) 0.001 ~1 in 15 m He : ~21 pe and c=8.2 mrad 0.0001 5 10 15 20 25 30 35 40 Giuseppe Ruggiero - CERN Momentum (GeV/c)

  13. Photon Rejection • Detectors: lead-scint sandwich (ANTI), LKr, lead-scint sandwich (IRC, SAC) • Goal: 10-8 level of veto inefficiency on p0 (requirement from p+p0) • Decays with p0: energy correlation between gs’ from p0 decay • Decays with single photon (radiative): hermeticity (0 - 50 mr coverage) Energy of photons from p0 in p+p0 events ANTI LKr Eg > 1 GeV IRC / SAC Eg > 6 GeV 0 1 2 0 1 2 3 4 5 6 0 1 2 3 4 5 6 7 8 9 10 Eg (GeV) Eg (GeV) Eg (GeV) Giuseppe Ruggiero - CERN

  14. Simulation of photon rejection: results • Simulation of geometrical layout • Parametrization of the g inefficiencies • Inefficiency: 2 x 10-8 on p0 from p+p0 • 5 x 10-8 on p0 from Kl3 • 10-3 on g from radiative • GEANT simulation of each • device started • Simulation results validating on • existing detector configurations • where data are available 2mm lead / 6mm Scintillator DATA: S. Ajimura et al., NIM A435 (1999) 408 MC: Our GEANT4 simulation Inefficiency 10-4 10-5 200 400 600 800 1000 Giuseppe Ruggiero - CERN Photon Energy (MeV)

  15. Electron ID • Detector: LKr • Inefficiency of e ID studied in • NA48 with e from p0 Dalitz decay. • Background from hadronic • showers • hID = 1% for E/p < 0.9. • Improvement of a factor 10 if • E/p < 0.85 (about 2% signal lost) • Room for improvements using • E/p + other informations about • clusterization (NN technique). • We assume hID = 10-3 Giuseppe Ruggiero - CERN

  16. Signal acceptance and Kaon flux • Fast simulation of the complete layout • Signal acceptance(Geometry, kinematic cuts, FF): • Region I: 4.5% • Region II: 14.5% • Assumed signal BR = 10-10 • Detailed simulation of the beam line • Expected kaon decays in fiducial region per year: 4.8 x 1012 Giuseppe Ruggiero - CERN

  17. RESULTS: Events collected per year Without Form Factor Giuseppe Ruggiero - CERN

  18. Thoughts about Charged Vetoes • Goal:at least 5 x 10-3 on a single track • Reject Ke4, Km4, p+p+p- • The most dangerous one: Ke4 Task at high angle 2 Gigatracker stations Giuseppe Ruggiero - CERN

  19. Conclusions • The experimental layout is being finalised • Background estimation almost complete • Region I: well understood, a RICH is needed for m background rejection. • S/B = ~5, but room for improvements. • Region II: • S/B > 10, (but with Ke4 and Kp3 contributions missing) • Charged vetoes to be optimised • Once dead-time and selection cuts are taken into account, a 10% signal acceptance is plausible (i.e. 40 events/year for Br~10-10) Giuseppe Ruggiero - CERN

More Related