1. BESIII Track Extrapolation & Matching Wang Liangliang EPC IHEP

2. Outline Track ExtrapolationTrack Extrapolation Track Information MatchingTrack Information Matching (Event assembly) Analysis of MC sampleAnalysis of MC sample SummarySummary

3. Track Extrapolation (1) Introduction:Introduction: MDC Tracking Track Parameter & error matrix TOF(2 layers)EMCMUC Extrapolation Expected position, momentum, Corresponding Error matrix, projected error on certain directions

4. Track Extrapolation (2) Method: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. 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.

5. Track Extrapolation (3) Method: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 ∙J T +E m 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 E m is the multiple scattering effect term of the current step

6. Track Extrapolation (4) Flow diagramFlow diagram (in a event loop): Get next MDC track Transform the helix parameters and matrix to (x,p) form Perform extroplation and propogate matrix in a small step Particle is out of BESIII world or it’s energy equals 0 If the track reached a certain sensitive detector’ surface for the first time, its parameters and matrix is recorded. no yes successful End a event failure Start a event Register results to TDS

7. Track Extrapolation (5) Some results of an example:Some results of an example:

8. Track Information Matching (Event assembly) Event model:Event model: DstTrackList trackID DstMdcTrack DstMdcKalTrack DstDedx DstExtTrack DstTofTrack DstEmcTrack DstMucTrack DstTrackListCol: ( collectionof tracks belong to a event) DstTrackListCol: ( collection of tracks belong to a event) EventList : (Global event information) totalTrksnChrnNeu nVEEs(Ks, Lambda, gamma conversion ) nPi0

9. Track Information Matching (2) Mdc Track dEdx Kalman Track Ext Track Tof Muc Track Track ID Method:Method: 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.

10. Track Information Matching (3) Emc Information Matching Window:Emc Information Matching Window: using sample using sample Theta: -10º~10º Phi: -15º~15º

11. Track Information Matching (4) Emc matching efficiency:Emc matching efficiency: Using psi→anything MC sample (50000 events)

12. Analysis of MC sample (The first example of MC sample analysis in BOSS beta release) pi0 Rho0 RhoPlus RhoMinus

13. 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.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 Analysis Event Data Model which will be used in data analysis in future.Event assembly is also accomplished. And it is the base of physics data analysis, and the start of the more advanced Analysis Event Data Model which will be used in data analysis in future.

14. Thank you!