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BESIII Track Extrapolation & Matching. Wang Liangliang EPC IHEP. Outline. Track Extrapolation Track Information Matching (Event assembly) Analysis of MC sample Summary. Track Extrapolation (1). Introduction:. Extrapolation. MDC Tracking. Track Parameter
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BESIIITrack Extrapolation & Matching Wang Liangliang EPC IHEP
Outline • Track Extrapolation • Track Information Matching (Event assembly) • Analysis of MC sample • Summary
Track Extrapolation (1) • Introduction: Extrapolation MDC Tracking Track Parameter & error matrix TOF(2 layers) EMC MUC Expected position, momentum, Corresponding Error matrix, projected error on certain directions
Track Extrapolation (2) • Method: Part1:Extrapolation of track parameters (x, p) Based on some Geant4 codes, we construct the same detectors and magnetic field as simulation, and perform the track extrapolation in small steps, which considered the charged track deflection in the magnetic field, the ionization energy loss in the material of detectors.
Track Extrapolation (3) • Method: Part2:Transformation of Error Matrix for small steps After each step, the infinitesimal propagation of the error matrix is calculated by E′=J∙E ∙JT+Em E′ is the error matrix at the end point of the current step E is the error matrix at the end point of the last step J is the Jacobian for the transformation Emis the multiple scattering effect term of the current step
Track Extrapolation (4) Start a event • Flow diagram (in a event loop): failure Get next MDC track Register results to TDS successful Transform the helix parameters and matrix to (x,p) form End a event Particle is out of BESIII world or it’s energy equals 0 yes no Perform extroplation and propogate matrix in a small step If the track reached a certain sensitive detector’ surface for the first time, its parameters and matrix is recorded.
Track Extrapolation (5) • Some results of an example:
Track Information Matching(Event assembly) • Event model: totalTrks nChr nNeu nVEEs(Ks, Lambda, gamma conversion ) nPi0 EventList : (Global event information) DstTrackListCol: (collectionof tracks belong to a event) trackID DstMdcTrack DstMdcKalTrack DstDedx DstExtTrack DstTofTrack DstEmcTrack DstMucTrack DstTrackList
Track Information Matching (2) • Method: Mdc Track dEdx Kalman Track Track ID Ext Track Tof Muc Track Emc Information Matching: We just simply match one shower to each charged track here. First, we find the smallest angle between the Ext Track’s position vector and the showers’ position vectors; if the corresponding shower’s position locates in our matching window, this shower will be matched to the charged track. These unmatched showers will be treated as neutral tracks.
Track Information Matching (3) • Emc Information Matching Window: using sample Theta: -10º~10º Phi: -15º~15º
Track Information Matching (4) • Emc matching efficiency: Using psi→anything MC sample (50000 events)
Analysis of MC sample(The first example of MC sample analysis in BOSS beta release) Rho0 pi0 RhoPlus RhoMinus
Summary • Track extrapolation is a necessary part of reconstruction and a base work before Event assembly. And this package works well in the BOSS beta release. • Event assembly is also accomplished. And it is the base of physics data analysis, and the start of the more advanced AnalysisEvent Data Model which will be used in data analysis in future.
