CERN Accelerating science

The LHCb experiment started in 2015 a pioneering fixed-target program studying the collisions between LHC protons and gas targets injected into the LHC beam pipe through a system called SMOG. The gas was free to spread between a wide area covering the pp luminous region, limiting the injectable gas species to noble ones. Fixed-target data were mostly acquired during special runs of limited duration to avoid interfering with the $pp$ physics program. The upgrade of the SMOG program, SMOG2, will mainly consist in the installation of a confinement cell for the gas covering a 20 cm long region upstream the nominal $pp$ interaction point. This will allow to increase the gas density by up to two orders of magnitude and to potentially extend the gas species to be injected. Moreover, the large separation between the $pp$ and SMOG2 regions opens the scenario of a simultaneous data-taking, provided that the reconstruction performance of both fixed-target and $pp$ events is not significantly affected and the tight time constraints for the online reconstruction and selection are met. This poster contains some preliminary results for the efficiencies of the Run3 tracking sub-detectors: the performance are demonstrated to be comparable between $pp$ and SMOG2 collisions and they do not degrade for $pp$ when adding Helium or Argon gas targets.

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