tnqq event selection

Pre-Pre-Selection (the same as e/mnqq events)

• CLASS 16
• Anti-qq cut: missing energy E_mis> 0, missing momentum P_mis > 0, E_mis+P_mis > 35 GeV
• Anti-qqg cut: longitudinal missing momentum P_zmis < (s-M_z²)/(2E_CM)-27.5 GeV OR P_zmis+sqrt(E_mis²-P_tmis²) < (s-M_z²)/E_CM-6 GeV where P_tmiss is the transverse missing momentum.

Pre-Selection

• Charged track multiplicity > 6: where the considered tracks are good tracks with |cosq|<0.95
• No isolated energy flow neutrals with no energy flow charged tracks in a 30 degrees cone and no energy flow neutrals between 5 and 30 degrees.

In addition to the above pre-selection events can be selected by the e/m selection if they fulfill the following additional pre-selection.

e/m Pre-Selection

• The event has to fulfill the e/mnqq pre-selection

Selection

Two different selection criteria are applied to select the tnqq events, depending on which pre-selection has been fulfilled.

Hadronic Selection

The following pre-NN cuts has to be fulfilled

• e/mnqq veto: the event has not to be selected as e/mnqq
• Visible mass: M_vis > 50 GeV
• Invariant mass of the hadronic jets: M_W > 5 GeV
• Missing transverse momentum: P_t > 10 GeV
• Acollinearity of the two hemispheres created by the thrust axis: q_acol < 175 degrees

The following variables are computed and used as input arguments for a NN discriminating function. The events are selected by applying a cut on the function output value

• [variable list to be added]

e/m Selection

• e/mnqq veto: the event has not to be selected as e/mnqq
• Number of good charged tracks N_trks > 5

The following variables are computed and used as input arguments for a NN discriminating function. The events are selected by applying a cut on the function output value. These variables are the same used for the e/mnqq selection

• Transverse momentum P_t
• Lepton momentum P_lcorr corrected for the bremsstrahlung energy loss if it is identified as an electron
• log(tan(q_ACL/2))+log(tan(q_AFL/2)) where the angles q_ACL q_AFL are defined as:
  • q_ACL: the maximum angle of a cone around the lepton candidate which includes less than 200 MeV of good charged track energy.
  •   q_AFL: the maximum angle of a cone around the lepton candidate which includes less than 5 GeV of energy flow object energy.

Details and practical advices about the discriminating functions and how to use them can be found here.

08/10/03