Speaker
Description
The LHCb RICH detectors will introduce timing information $\mathcal{O}(100\,$ps) for every detected photon during the LHC Run 4. Using the RICH time information, the primary vertex time (PV t$_0$) can be estimated for the first time in LHCb, which is a key input parameter for exploiting fast-timing techniques in the experiment. In the RICH reconstruction algorithm, an object called a photon object (PO) is created for each combination of a detector hit and particle track that passes a set of initial spatial constraints. Using the LHCb tracking systems, tracks can be associated with different PVs. The multitude of POs (on average, hundreds of signal photons are detected per PV) in the RICH detectors allows the PV t$_0$ to be determined with high precision. The key challenge is to determine, out of all generated POs and in the presence of signal pile-up and background hits, which PO has a correct association from detector hit to track to PV. Simulation studies show that approximately 20% of the initial POs have a correct association to the PV. Therefore, new techniques in the reconstruction algorithm have been explored to identify a subset of POs with the highest probability to have a correct PV association. New results, generated using the LHCb experiment simulation framework, will be presented. The proposed techniques provide a 85±2 ps (FWHM) time resolution for 94% of the PVs, starting from an initial PV time spread of 450 ps (FWHM) at the simulated bunch crossings. Additionally, the use of additional information from a first iteration of the RICH reconstruction likelihood-maximisation algorithm is being explored. The benefit of such a likelihood iteration and other techniques will be weighed against the cost in extra computation.
