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New HLT2 trigger lines for dark photon search from charm decays

Carlos Eduardo Cocha Toapaxi requested to merge charm_dst_to_dee_cocha into master

Description of the lines

Definition of HLT2 lines for the dark photon search A'(-> e+ e-) produced in a D* decay.

Prompt lines:

  1. D*0 -> D0 e+ e- with D0 -> K- pi+
  2. D*0 -> D0 e+ e- with D0 -> K- pi- pi+ pi+
  3. Ds*+ -> D(s)+ e+ e- with D(s)+ -> K- K+ pi+
  • K, pi and D are built inspired by the charm builders defined in d0_to_hh, d0_to_hhhh and d_to_hh. In the future, the cuts are expected to be tuned after a better understanding of the detector/data.
  • The dielectron pairs e+ e- are built including bremsstrahlung correction.
  • The range of the dark photon mass values is accessible within m(D*) - m(D) which is below 140 MeV, but extended to 250 MeV in the D* maker for background fitting.
  • The lines also preserve photons near the dielectron candidates to reconstruct, later, {pi0, eta} -> e+ e- gamma, for background studies. This is done using WeightedRelTableAlg, see Rec!2750 (merged), where a gamma E_T larger 100 MeV and combined mass m(e+e-gamma) below 600 MeV are desired.

Efficiency and rates

The efficiency is calculated using MC signal:

- MagDown : "/MC/Upgrade/27184010/Beam7000GeV-Upgrade-MagDown-Nu7.6-25ns-Pythia8/Sim10aU1/XDIGI"
- MagUp   : "/MC/Upgrade/27184010/Beam7000GeV-Upgrade-MagUp-Nu7.6-25ns-Pythia8/Sim10aU1/XDIGI"

and the rates using minbias:

- MagDown : /MC/Upgrade/30000000/Beam7000GeV-Upgrade-MagDown-Nu7.6-Pythia8/Sim10aU1/XDIGI
- MagUp   : /MC/Upgrade/30000000/Beam7000GeV-Upgrade-MagUp-Nu7.6-Pythia8/Sim10aU1/XDIGI

A minimum electron p_T value of 50 MeV is chosen for all the trigger lines as it provides rates around 100 Hz with a minimal impact on the efficiency. The following table summarizes the results.

Line (cut at min p_T(e) = 50 MeV ) Rate [Hz] Expected signal rate [Hz] TrueSim Efficiency [%]
D*0 -> D0 e+ e-, D0 -> K- pi+ 102.32 61.4 6.2
D*0 -> D0 e+ e-, D0 -> K- pi- pi+ pi+ 55.66 - -
Ds*+ -> D(s)+ e+ e-, D(s)+ -> K- K+ pi+ 6.5 - -

Note: Both D+ and Ds+ are used because the Ds*+ rate is very small.

Besides, the following plot shows the tradeoff between the TrueSim efficiency (red curve) and rate for the different trigger lines as a function of the minimum electron p_T.

eff_rates

Analysis

The trigger line is in the charm repository and gets inspired by some charm makers, but this analysis should also belong to QEE.

Contact people

Edited by Carlos Eduardo Cocha Toapaxi

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