CERN Accelerating science

A view of the LHCb detector \cite{LHCb-TDR-009}. The proton-proton interaction point is on the extreme left at $z=0$~m.

The optical system of (a) \richone and (b) \richtwo~\cite{LHCb-TDR-009}.

The optical system of (a) \richone and (b) \richtwo~\cite{LHCb-TDR-009}.

The focusing optics of an HPD~\cite{LHCb-TDR-009}. A photoelectron generated at the photocathode is accelerated to the silicon sensor chip.

The number of hits from two HPDs (blue and red points) read out by the same L0 board and the combination (black points) for data taken with differing trigger offsets in steps of 1\ns. Each step integrates the number of photons detected over 10\,000 bunch crossings.

(a) The air contamination in \richone as a function of time (black circles), and the correction factor applied to the refractive index (blue crosses). The axis for the correction factor is reversed. (b) The relative difference in the refractive index used in the reconstruction after the calibration, and the true refractive index of the radiator in \richone for differing levels of contamination by air.

The efficiency of selecting kaons (a and b), protons (c, d, e and f), with the associated leakage from misidentifying pions (a, b, c d) and kaons (e and f) in data taken during 2018. (a, c and e)~The efficiency curves are shown for positively (black, solid) and negatively (red, dotted) charged particles. (b, d and f)~The efficiency curves are shown for \textit{Up} (red, dotted) and \textit{Down} (black, solid) magnetic field polarities. Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a and b), protons (c, d, e and f), with the associated leakage from misidentifying pions (a, b, c d) and kaons (e and f) in data taken during 2018. (a, c and e)~The efficiency curves are shown for positively (black, solid) and negatively (red, dotted) charged particles. (b, d and f)~The efficiency curves are shown for \textit{Up} (red, dotted) and \textit{Down} (black, solid) magnetic field polarities. Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a and b), protons (c, d, e and f), with the associated leakage from misidentifying pions (a, b, c d) and kaons (e and f) in data taken during 2018. (a, c and e)~The efficiency curves are shown for positively (black, solid) and negatively (red, dotted) charged particles. (b, d and f)~The efficiency curves are shown for \textit{Up} (red, dotted) and \textit{Down} (black, solid) magnetic field polarities. Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a and b), protons (c, d, e and f), with the associated leakage from misidentifying pions (a, b, c d) and kaons (e and f) in data taken during 2018. (a, c and e)~The efficiency curves are shown for positively (black, solid) and negatively (red, dotted) charged particles. (b, d and f)~The efficiency curves are shown for \textit{Up} (red, dotted) and \textit{Down} (black, solid) magnetic field polarities. Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a and b), protons (c, d, e and f), with the associated leakage from misidentifying pions (a, b, c d) and kaons (e and f) in data taken during 2018. (a, c and e)~The efficiency curves are shown for positively (black, solid) and negatively (red, dotted) charged particles. (b, d and f)~The efficiency curves are shown for \textit{Up} (red, dotted) and \textit{Down} (black, solid) magnetic field polarities. Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a and b), protons (c, d, e and f), with the associated leakage from misidentifying pions (a, b, c d) and kaons (e and f) in data taken during 2018. (a, c and e)~The efficiency curves are shown for positively (black, solid) and negatively (red, dotted) charged particles. (b, d and f)~The efficiency curves are shown for \textit{Up} (red, dotted) and \textit{Down} (black, solid) magnetic field polarities. Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a), protons (b and c), with the associate leakage from misidentifying pions (a and b) and kaons (c). The efficiency curves are shown for 2015 (blue, dashed), 2016 (green, dash-dotted), 2017 (red, dotted), 2018 (black solid). Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a), protons (b and c), with the associate leakage from misidentifying pions (a and b) and kaons (c). The efficiency curves are shown for 2015 (blue, dashed), 2016 (green, dash-dotted), 2017 (red, dotted), 2018 (black solid). Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a), protons (b and c), with the associate leakage from misidentifying pions (a and b) and kaons (c). The efficiency curves are shown for 2015 (blue, dashed), 2016 (green, dash-dotted), 2017 (red, dotted), 2018 (black solid). Uncertainties are statistical only, and are highly correlated between points on the same curve.

The efficiency of selecting kaons (a), protons (b and c), with the associate leakage from misidentifying pions (a and b) and kaons (c) as a function of momentum. Two selections are made, a loose selection (hollow circles) and a tight selection (solid circles).

The efficiency of selecting kaons (a), protons (b and c), with the associate leakage from misidentifying pions (a and b) and kaons (c) as a function of momentum. Two selections are made, a loose selection (hollow circles) and a tight selection (solid circles).

The efficiency of selecting kaons (a), protons (b and c), with the associate leakage from misidentifying pions (a and b) and kaons (c) as a function of momentum. Two selections are made, a loose selection (hollow circles) and a tight selection (solid circles).

The effect of applying hadron PID selections to suppress the dominant kaon mode (a) to measure the CKM suppressed pion mode (b), in rare $B$ decays~\cite{LHCb-PAPER-2015-035}. Here 82~\% of pion events are retained, suppressing the kaons by a factor of 80 relative to the pions, leaving a clear peak from the pion mode.

The effect of applying hadron PID selections to suppress the dominant kaon mode (a) to measure the CKM suppressed pion mode (b), in rare $B$ decays~\cite{LHCb-PAPER-2015-035}. Here 82~\% of pion events are retained, suppressing the kaons by a factor of 80 relative to the pions, leaving a clear peak from the pion mode.

The effect of applying hadron PID selections to suppress the dominant pion mode (a) to measure the CKM suppressed kaon mode (b), in CP violation analyses~\cite{LHCb-PAPER-2019-044}.

The effect of applying hadron PID selections to suppress the dominant pion mode (a) to measure the CKM suppressed kaon mode (b), in CP violation analyses~\cite{LHCb-PAPER-2019-044}.

The effect of applying hadron PID selections to distinguish between \mbox{$B_c^+ \to J/\psi \pi^+ \pi^- \pi^+$} (a) and $B_c^+ \to J/\psi p \bar{p} \pi^+$ (b) decay modes~\cite{LHCb-PAPER-2020-003}.

The effect of applying hadron PID selections to distinguish between \mbox{$B_c^+ \to J/\psi \pi^+ \pi^- \pi^+$} (a) and $B_c^+ \to J/\psi p \bar{p} \pi^+$ (b) decay modes~\cite{LHCb-PAPER-2020-003}.