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B-physics trigger: update fit procedure for cascade decays of the B_c+

Vladimir Lyubushkin requested to merge lyubushk/athena:master-bBmumux into master

This MR introduces a new approach for the cascade decays of B_c+:

  • B_c+ -> J/psi(-> mu+ mu-) D_s+(->phi(-> K+ K-) pi+)
  • B_c+ -> J/psi(-> mu+ mu-) D+(-> K- pi+ pi+) now are

There is no possibility to run cascade vertex fitter at HLT level due to the CPU limitations. So that, three tracks from D+/D_s+ are fitted to the standalone secondary vertex. The combined momentum of D+/D_s+ candidate is constrained to point to the dimuon vertex. We found that simplified approach is efficient enough to select requested decay topologies.

Affected chains:

  • 'HLT_2mu4_bBmumux_BcmumuDsloose_L12MU3V'
  • 'HLT_2mu4_bBmumux_BcmumuDploose_L12MU3V'

CC: @abarton

Edited by Vladimir Lyubushkin

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