LHCb RICH Upgrade: an overview of the photon detector and electronics system

TL;DR

The paper discusses the upgrade of the LHCb RICH detector's photon detection system, focusing on new MaPMTs and CLARO electronics to maintain high particle identification performance at increased collision rates.

Contribution

It introduces the new photon detectors and readout electronics, including the CLARO chip, designed to operate efficiently at high photon rates with low power and cross-talk.

Findings

Successful testing of prototypes in charged particle beams

Implementation of CLARO chip for high-rate photon counting

Enhanced detector performance at increased luminosity

Abstract

The LHCb experiment is one of the four large detectors operating at the LHC at CERN and it is mainly devoted to CP violation measurements and to the search for new physics in rare decays of beauty and charm hadrons. The data from the two Ring Image Cherenkov (RICH-1 and RICH-2) detectors are essential to identify particles in a wide momentum range. From 2019 onwards 14 TeV collisions with luminosities reaching up to $2\cdot10^{33}$ cm$^{-2}$ s$^{-1}$ with 25 ns bunch spacing are planned, with the goal of collecting 5 fb$^{-1}$ of data per year. In order to avoid degradation of the PID performance at such high rate (40 MHz), the RICH detector has to be upgraded. New photodetectors (Multi-anode photomultiplier tubes, MaPMTs) have been chosen and will be read out using a 8-channels chip, named CLARO, designed to sustain a photon counting rate up to 40 MHz, while minimizing the power consumption and the cross-talk. A 128-bit digital register allows selection of thresholds and attenuation values and provides features useful for testing and debugging. Photosensors and electronics are arranged in basic units, the first prototypes of which have been tested in charged particle beams in autumn 2014. An overview of the CLARO features and of the readout electronics is presented.