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Background Filter Information

This page descibes the background filter information available for your analysis. All the variables are of type bool, and can be obtained by the names in the tables below.

At the bottom of this page there are some useful lines of code needed to declare appropriate variables and retrieve the bits, and write the variables to a ntuple.

On the Trigger and Filter Efficiency AWG Homepage you can find links to pages in development describing the various filters. Currently, the filter names on these pages are the old ones, but they are similar enough to the actual names that one can make an easy correspondance.

Digi Filter Flags


These flags are set at the digitization (digi) level.
Nano-Database Variable Name Description
DigiFL1Prescale A sample of events that have passed Level-1 trigger, with no other requirement. For example, these events do not have to pass the Level-3 trigger, so they events can be used to study the Level-3 trigger (e.g., for efficiency and bias).
DigiFL3OutDchEmcPreVetoPrescale Events that pass the L3 Dch or Emc selection *before* the Bhabha veto is applied
DigiFL3Prescale A sample of events that have passed Level-3 trigger, with no other requirement. These events do not have to pass any of the physics filters, so they can be used to study those filters.
DigiFRandomPrescale  
DigiFBhabhaFlat Bhabha events that have been flattened in theta, to provide a more uniform theta distribution. This is done to reduce the number of Bhabha events with small angles, since they are extrememly copius.
DigiFRadiativeBhabha A filter designed to pass radiative Bhabha events.

Background Filter Flags

These flags are set after part of the reconstruction code has run on the event. They are designed to prevent overloading the PR (prompt reconstruction system. An event must have one of these flags set true in order to be fully reconstructed and written to the Event Store.

NB: The ChargedTracks and CalorNeutral lists that most analysts know well are not available at this stage of the reconstruction, so the cuts below cannot be replicated in your analysis (at least for now). The charged tracks and neutral objects used to create the flags are similar to, but not identical to, the final reconstruction objects.

P1 and P2 correspond to the highest and 2nd highest momentum charged tracks. E1 and E2 correspond to the highest and 2nd highest energy neutral clusters.

Nano-Database Variable Name Description
BGFMultiHadron # Charged Tracks > 2
R2 < 0.98
BGFMuMu P1>4 GeV
P2>2 GeV
2.8>Theta1+Theta2>3.5
E1+E2<2.0 GeV
BGFTau # Charged Tracks = 2
Event Charge = 0
P1+P2<9 GeV
E1+E2<5 GeV
E1/P1 or E2/P2 < 0.8
energyCM-P1-P2>0
(Pt1+Pt2)/(energyCM-P1-P2)>0.07
BGFTwoProng # Charged Tracks = 2
Event Charge = 0
P1 or P2>1 GeV
E1 and E2<3 GeV
cosmic rejection:
|cosThetaP1+cosThetaP2|>0.1
require EMC for high momentum track:
cosThetaP1>-0.75
high momentum track or Pt balance:
P1 or P2 > 4 Gev OR |Pt1-Pt2|<0.3
BGFGammaGamma # Charged Tracks = 0
# EMC Clusters >= 2
E1 > 4 GeV
E2 > 2 GeV
|thetaE1 + thetaE2 - Pi| < 0.2
|Sin(PhiE1-PhiE2)| < 0.2
BGFGammaGammaPrescale  
BGFPhiGamma 2 < # Charged Tracks < 5
1 Isolated Photon:
__ 4 GeV < Ephoton < 6 GeV
__ all tracks satisfy: cos( TrkPhi - PhotonPhi) < 0.8
2 tracks in opposite hemisphere with invariant mass consistent with Kshort->PiPi or Phi->KK

Example code to obtain the variables listed on this page:

In your module's event(AbsEvent *anEvent) function:
AbsEventTag* tag = Ifd<AbsEventTag>::get( anEvent );

bool l3Prescale(false);
bool l1Prescale(false);
bool rndPrescale(false);
bool bhaPrescale(false);
bool radBhabha(false);

bool hadron(false);
bool mumu(false);
bool tau(false);
bool twoProng(false);
bool gammaGamma(false);
bool phiGamma(false);

tag->getBool(l3Prescale,"DigiFL3Prescale");
tag->getBool(l1Prescale,"DigiFL1Prescale");
tag->getBool(rndPrescale,"DigiFRandomPrescale");
tag->getBool(bhaPrescale,"DigiFBhabhaFlat");
tag->getBool(radBhabha,"DigiFRadiativeBhabha");

tag->getBool(hadron,"BGFMultiHadron");
tag->getBool(mumu,"BGFMuMu");
tag->getBool(tau,"BGFTau");
tag->getBool(twoProng,"BGFTwoProng");
tag->getBool(gammaGamma,"BGFGammaGamma");
tag->getBool(phiGamma,"BGFPhiGamma");


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