Instructions for using the Shrinking Cone

The prototype for the Shrinking Cone is

void ShrinkingConeD3PDAlg(TLorentzVector tau,vector* inputtracks20, vector* inputtracks20charge, vector* inputtracks40, vector* inputtracks40charge, vector* outputtracksgood, vector* outputtracksgoodcharge, vector* outputtracksbad, vector* outputtracksbadcharge, int& nProng, int& flag, float& pi0angle, TLorentzVector* barycenter);

All the variables for input and output are declared by the user and passed to the function.

The attached document ShrinkingConeD3PDAlg.h contains all the necessary functions and prototypes. Please copy and paste its contents into your header (.h) file.

Input Variables

• tau : This is the four vector for the reco tau
• inputtracks20: This collection of four vectors contains the tracks with dR < 0.2 w.r.t. the tau.
  • IMPORTANT: The mass of each track must be nonzero! [You can set it to the pi+/- mass (0.13957 GeV)]
• inputtracks20charge: This contains the charges of the tracks in inputtracks20
• inputtracks40: This collection of four vectors contains the tracks with dR < 0.4 w.r.t. the tau.
  • IMPORTANT: The mass of each track must be nonzero! [You can set it to the pi+/- mass (0.13957 GeV)]
• inputtracks40charge: This contains the charges of the tracks in inputtracks40

Output Variables

• outputtracksgood: This collection of four vectors are the tracks which are consistent with tau kinematics
• outputtracksgoodcharge:This contains the charges of the tracks in outputtracksgood
• outputtracksbad: This collection of four vectors are the tracks which are not consistent with tau kinematics
• outputtracksbadcharge:This contains the charges of the tracks in outputtracksbad
• nProng: This value ranges from 0 to 3, and corresponds to the number of tracks in outputtracksgood
  • nProng = 0 correspond to taus classified as fakes
  • nProng = 1 corresponds to 1 prong taus
  • nProng = 2 correspond to taus with only 2 reconstructed tracks (most likely 3 prong taus).
  • nProng = 3 corresponds to 3 prong taus.
• flag: This tells the quality of the classification
  • flag = 0 corresponds to taus which are classified as fakes.
  • flag = 1 corresponds to good taus
  • flag = 2 corresponds to conditional taus.
    • nProng = 1: corresponds to taus with 2 reconstructed tracks in which the lowest pT track has been classified as spurious
    • nProng = 2: corresponds to taus with 3 reconstructed tracks in which the lowest pT track has been classified as spurious
    • nProng = 3: corresponds to taus with 4 reconstructed tracks in which the 3 highest pT tracks have been found consistent with tau kinematics
• pi0angle returns the angle around the barycenter which contains 99% of truth pi0s
  • pi0angle = -99 for fakes ( flag = 0)
• barycenter gives the sum of the four vectors of the good tracks and forms the axis of the cone which contains 99% of the truth pi0s

Other Notes

• Any tau with five (5) or more tracks in the cone of dR < 0.2 w.r.t. the tau axis will automatically be classified as a fake tau. All tracks will be returned in the outputttracksbad collection.
• There is a special case for fakes. Ordinarily, if nProng = 0, then flag = 0 as well. However, taus with three tracks of the same sign ( |tau charge| = 3) which are otherwise consistent with tau kinematics will be saved.
  • They will be denoted by nProng = 3 AND flag = 0