Muon+Hadron Alley Parameters (Hugo Ruiz)

Note that all IP and IPS cuts are refered to the minimum value to any primary vertex. The numbers between parentheses inform on the way in which the parameters will be computed online (see below).

  • Cuts applied to the muons found by the Muon Alley (1)
    • pTMin (MeV)
    • IPSMin

  • Cuts applied to the VELO 2D tracks (2)
    • IPMin (mm)

  • Relative cuts between VELO 2D tracks and muon tracks (2)
    • ThetaMax: angle to muon in sqrt(delta phi^2 + delta eta^2)
    • DOCAMax: distance of closest approach to the muon track (mm) (maybe to be removed, as having two cuts makes authomatic computation of the cut value more difficult)

  • Parameters of the VELO2D->VELOSpace reconstruction of hadron candidates (3)

  • Cuts applied to the VELO 3D tracks (2)
    • IPmin (mm)

  • Relative cuts between VELO 3D tracks and muon tracks (1)
    • ThetaMax (see above)
    • DOCAMax (see above)

  • Parameters of the VELOSpace->VELOTT reconstruction of hadron candidates (3)

  • Cuts applied to VELOTT tracks (2)
    • pTMin (MeV)

  • Parameters of the VELOTT->Long reconstruction of hadron candidates (3)

  • Cuts applied to long tracks (1)
    • pTMin (MeV)
    • IPSMin

(1): The value of these parameters needs to be computed online by the optimization of B purity. For that, a sample of high B purity and lower pT/IPS muon cuts is required. Some ideas will be investigated in short:

  • A selection based on two displaced muons and maybe some extra displaced tracks (without requiring a good vertexing, hence aiming for simultaneous B1->mu1X1 B2->mu2X2).

  • Events coming from other B-rich selections (like displaced D*) containing muons.
Selected events undergo a complete reconstruction.

(2): The value of these parameters could be computed by requiring a fixed efficiency on the long tracks required by (1)

(3): Parameters of every step of the reconstruction should probably determiened globally by all HLT alleys. If each alley has different parameters, the accounting of which tracks have been promoted to the next level by other alleys will be complicated.

Muon+Hadron Alley Summary Box Contents

The Muon+Hadron Alley will be implemented as a succession of instances of two algorithms: FilterTracks (blue arrows in the diagram below) and FilterVertices (orange arrows).

The first algorithm is in charge of applying single-track cuts, while the second apply the relative cuts between muon and hadron tracks. Note that, at every filtering stage, only pairs (or "vertices") passing the previous cuts need to be considered. This will ensure the "verticality" of the trigger, making the understanding of the causes of the trigger much simpler.

Note that all track and vertex candidates are considered. In other words, loops are not broken as soon as a first candidate is found, but continued until the end until all combinations are tried. This design makes sure that any track or vertex that 'could have triggered' the event is really triggering it, and its information will be stored in the summary box.

The information that needs to be stored in the summary box is: * List of the tracks and vertices that passed each filtering stage. * The values of the properties computed for each vertex/track for the selection must also be stored. For IP and IPS, the values to any primary vertex should be stored. * The list of primary vertices and their properties.


Muon+Hadron Alley Monitoring

  • Automatically measured values of the parameters in the conditions database (procedures described in the conditions section).
  • For each instance of FilterTracks (blue arrows) or FilterVertices (orange arrows):
    • Distributions of each property on which cuts are done (pT, IPS, IP, DOCA, ThetaMax)
    • Input and output rate
    • Number of input and output tracks/vertices
  • Only for FilterVertices:
    • Number of times a track overlap is found (that is, how many muon/hadron tracks share segments).

-- HugoRuiz - 22 May 2006

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Topic revision: r7 - 2006-06-28 - HugoRuiz
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