Calo Alley

Introduction

For the time being this alley requires one track and one calorimeter object (electron or photon) above a Pt or Et threshold, respectively. There is clearly room for improvement and therefore everything below is to be taken as provisional.

Many things are missing:

  • L0 confirmation: this isn't in yet but it is definitely important: for instance the distinction between photon and electron will be much more efficient when the electron will be confirmed by the matching to a track. In addition this will help in making the trigger more vertical
  • higher level objects: must look into J/psi->ee and pi0; this might lead to a change in the alley logic or at least in the addition of one or more separate parallel sub-alleys (electron, photon, dielectron, diphoton...)
  • algorithms for determining thresholds on real data and their implementation: the final thresholds will obviously depend on the physics/financial requirements (i.e. how much bandwidth this alley and its sub-alleys will be allocated) but also on the internal logic of the alley.

Calo Alley: Conditions

The general strategy of this alley is to add one calorimeter object (electron or photon) to a track. The selection and reconstruction of the tracks follows the same steps of the Hadron Alley, and so it needs in principle the same variables (cuts on IP and Pt thresholds). For simplicity, for the time being only one track is implemented- but we will have to decide whether we want to add a second track, as done in the Hadron Alley.

In general we should have the possibility to use different thresholds in pretrigger and trigger, especially until we get more or less stable conditions and a well understood trigger. So everything should be duplicated, as detailed below. Probably at some point one will want to use the same threshold in pretrigger and trigger.

HltCalPreTrigger:

IP window cuts: I am not sure whether these should ever be different from those introduced in the Hadron alley, probably not. And also it is still under discussion whether it makes sense to have upper boundaries.

  • IPmin2D: minimum IP for 2D Velo tracks which have to be reconstructed as 3D Velo tracks

  • IPmax2D: maximum IP for 2D Velo tracks which have to be reconstructed as 3D Velo tracks

  • IPmin3D: minimum IP for 3D Velo tracks which have to be reconstructed as VeloTT tracks

  • IPmax3D: maximum IP for 3D Velo tracks which have to be reconstructed as VeloTT tracks

Et and Pt Thresholds:

  • PT1Cut: threshold for highest Pt track

  • ETCutPhot : threshold for highest Et photon

  • ETCutElec : threshold for highest Et electron

requirement: The PreTrigger requires to have one track and one photon or one electron such that:

((PtTrack > PT1Cut) && (EtPhoton > ETCutPhot)) OR ((PtTrack > PT1Cut) && ( EtElectron > ETCutElec ))

HltCalTrigger:

IP window cuts: see comments for the pretrigger

  • IPmin3D: minimum IP for 3D Velo tracks which have to be reconstructed as long tracks

  • IPmax3D: maximum IP for 3D Velo tracks which have to be reconstructed as long tracks

Et and Pt Thresholds:

  • PT1Cut: threshold for highest Pt track

  • ETCutPhot : threshold for highest Et photon

  • ETCutElec : threshold for highest Et electron

requirement: The trigger requires to have one track and one photon or one electron such that:

((PtTrack > PT1Cut) && (EtPhoton > ETCutPhot)) OR ((PtTrack > PT1Cut) && ( EtElectron > ETCutElec ))

Calo Alley: Summary Box Content

All quantities which are used to take the trigger decision:

HltCalPreTrigger:

  • IP1: Impact Parameter of the highest Pt track

  • Pt1: Pt of the highest Pt track

  • EtPhot: Et of the highest Et photon candidate

  • EtElec: Et of the highest Et electron candidate

HltCalTrigger:

  • IP1: Impact Parameter of the highest Pt track

  • Pt1: Pt of the highest Pt track

  • EtPhot: Et of the highest Et photon candidate

  • EtElec: Et of the highest Et electron candidate

Calo Alley: Variables to be monitored

  • All variables in the summary box:
    • For HltCalPreTrigger: IP1, Pt1, EtPhot, EtElec
    • For PreTrigger: IP1, Pt1, EtPhot, EtElec

  • All optimal conditions, i.e. all thresholds listed above, recomputed periodically via the yet unspecified routines.

  • Other more "inclusive" variables. I am not sure here, maybe one would want to histogram all the following variables (also) by lowering all respective thresholds to values significantly lower than the actual cuts to have an idea of the distributions before selections are applied and allow an estimate of the efficiency and retention rates: something similar will probably be needed to re-compute the optimal thresholds...
    • NTracks: number of tracks above the Pt threshold (PT1Cut)
    • PtTracksAll: Pt of all tracks above the Pt threshold (PT1Cut)
    • NPhot: number of photons above the Et threshold (EtCutPhot)
    • EtPhotAll: Et of all photons above the Et threshold (EtCutPhot)
    • NElec: number of electrons above the Et threshold (EtCutElec)
    • EtElecAll: Et of all electrons above the Et threshold (EtCutElec)

-- StefanoVilla - 28 Jun 2006

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Topic revision: r7 - 2007-10-29 - StephenWotton
 
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