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Charm HLT2 rate reduction

Lorenzo Pica requested to merge charm-hlt2-rate-reduction into master

Implements few changes to reduce the bandwidth of Charm HLT2 lines:

  • tighten the requirements of the cross-section lines, and adding a small prescale for all of them
  • tighten the IPCHI2 on the lepton and add a 10% prescale to all lines in
  • replaces persistreco with selective persistence in a cone for
  • tighten the selection requirements of (inclusive selection of Lc and Xic baryons), which has persistreco activated. TODO: Note that the new IPCHI2 requirement on the baryons significantly reduces the rates at the price of removing also charmed baryons from b-hadron decays. The impact on spectroscopy measurements is expected to be small, but this should be checked in the future and maybe some workarounds should be developed (e.g. a prescaled line without IPCHI2 cut, or a non-prescaled line without IPCHI2 cut and no persistreco activated)

In addition, the general event cut (GEC) is deactivated for all charm lines. A non-optimal tuning of the GEC in previous tests was responsible for the ~65% increase in the charm bandwidth observed by Ross in the RTA meeting of 2023.03.08. Analysts are currently checking that the increase in bandwidth corresponds to an equal increase in signal efficiency (preliminary studies are consistent with this assumption). The GEC will be activated only on a line-by-line basis when needed, as done in the other WGs.

To be tested with DaVinci!1053 (closed) and LHCbIntegrationTests!65 (closed)

FYI @fbetti @dmitzel @tpajero @aanelli @cacochat @fsouzade @roneil

Edited by Lorenzo Pica

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