Proton reconstruction with the CMS-TOTEM Precision Proton Spectrometer

Abstract

The Precision Proton Spectrometer (PPS) of the CMS and TOTEM experiments collected 107.7 fb-1 in proton-proton (pp) collisions at the LHC at 13 TeV (Run 2). This paper describes the key features of the PPS alignment and optics calibrations, the proton reconstruction procedure, as well as the detector efficiency and the performance of the PPS simulation. The reconstruction and simulation are validated using a sample of (semi)exclusive dilepton events. The performance of PPS has proven the feasibility of continuously operating a near-beam proton spectrometer at a high luminosity hadron collider.

Development of the CMS detector for the CERN LHC Run 3

“…The detectors are enclosed in movable stations, referred to as "roman pots", within which the detectors can be positioned as close as a few millimeters from the proton beam. The PPS first started in Run 2 as a joint project (CT-PPS) with the TOTEM Collaboration [12]. The initial PPS system consisted of two tracking and one timing station on each side.…”

“…The cables are cut in half to create "pigtails", which form the basic units for assembly into the ODU. Each HB (HE) pigtail has up to 18 (12) fibers. The routing and connections of the fibers are shown in figure 30 (left).…”

“…In Run 3 the "220 near" horizontal unit is used in place of the "210 near". Reproduced from [12]. The Author(s).…”

“…All vertical RPs remain reserved for the TOTEM physics program. However, their role is crucial for PPS operations at the beginning of each data-taking period, when the tracking detectors they host are used in special runs, in conjunction with those in the horizontal RPs, to determine the global alignment parameters [12].…”

“…The energy loss of protons can be measured, through detailed knowledge of the LHC optics parameters and dedicated calibrations [12], from the parameters of their reconstructed tracks. In order to obtain the needed accuracy in 𝜉, a resolution of few tens of µm is required on the coordinates of the track impact point.…”