G. Ruggiero

Performance of the Totem Detectors at the LHC

The TOTEM Experiment is designed to measure the total proton–proton cross-section with the luminosity-independent method and to study elastic and diffractive pp scattering at the LHC. To achieve optimum forward coverage for charged particles emitted by the pp collisions in the interaction point IP5, two tracking telescopes, T1 and T2, are installed on each side of the IP in the pseudorapidity region 3.1≤|η|≤6.5, and special movable beam-pipe insertions — called Roman Pots (RP) — are placed at distances of ±147 m and ±220 m from IP5. This article describes in detail the working of the TOTEM detector to produce physics results in the first three years of operation and data taking at the LHC.

Planar edgeless silicon detectors for the TOTEM experiment

Roman pot silicon detectors for the LHC TOTEM experiment require a highly reduced insensitive area at the edge where, for electrical stability, a terminating structure is required. This work provides an innovative approach based on standard planar fabrication technology which reduces the conventional width of the terminating structure to less than 100 micrometers. The approach decouples the electric behaviour of the surface and the sensitive volume. Beam test measurements demonstrate that detectors with this new structure are fully operational and fully efficient in less than 60 micrometers from the die cut. Detailed results are provided in the paper.

LHC Optics Measurement with Proton Tracks Detected by the Roman Pots of the TOTEM Experiment

Precise knowledge of the beam optics at the LHC is crucial to fulfill the physics goals of the TOTEM experiment, where the kinematics of the scattered protons is reconstructed with near-beam telescopes—so-called Roman pots (RP). Before being detected, the protons’ trajectories are influenced by the magnetic fields of the accelerator lattice. Thus precise understanding of the proton transport is of key importance for the experiment. A novel method of optics evaluation is proposed which exploits kinematical distributions of elastically scattered protons observed in the RPs. Theoretical predictions, as well as Monte Carlo studies, show that the residual uncertainty of the optics estimation method is smaller than .

Diamond detectors for the TOTEM timing upgrade

This paper describes the design and the performance of the timing detector developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the Time-Of-Flight (TOF) of the protons produced in central diffractive interactions at the LHC. The measurement of the TOF of the protons allows the determination of the longitudinal position of the proton interaction vertex and its association with one of the vertices reconstructed by the CMS detectors. The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD) diamond plates and is designed to measure the protons TOF with about 50 ps time precision. This upgrade to the TOTEM apparatus will be used in the LHC run 2 and will tag the central diffractive events up to an interaction pileup of about 1. A dedicated fast and low noise electronics for the signal amplification has been developed. The digitization of the diamond signal is performed by sampling the waveform. After introducing the physics studies that will most profit from the addition of these new detectors, we discuss in detail the optimization and the performance of the first TOF detector installed in the LHC in November 2015.

Advanced model of silicon edgeless detector operation

The progress in silicon edgeless strip detectors became evident recently when the current terminating structure was proposed and successfully realized in p-on-n Si edgeless detectors for the TOTEM experiment at CERN. In this study the key characteristics of the structure - potential and electric field distributions at the detector sensitive diced edge are considered within the framework of two models — the resistive and amorphous edge layers. The surface potential distributions predicted by these models are compared to the experimental profiles measured by two methods — Conductive MicroProbe Technique and Scanning Transient Current Technique. It is shown that the experimental distributions correspond closely to the amorphous edge model. This advanced model of edgeless detector operation is applied to make predictions on irradiated detector characteristics and will be used for the development of the radiation hard version of edgeless detectors for the TOTEM experiment.

Simulation of irradiated edgeless detectors

In this work, results of simulation of irradiated edgeless detectors for close to beam experiments are presented. The charge collection efficiency at the sensitive cut for minimal ionizing particles was numerically simulated in the frame of amorphous silicon model of heavily damaged cut surface. It is shown that the charge collection reduction for non- irradiated detectors is expected in the region adjacent to the cut of 50 μm width that well correlates to the experiment. The detector irradiation reduces the collected charge at the bulk and at the surface in close extent. In irradiated detectors however the charge collected within the layer which is in direct contact with the damaged cut may be higher than before irradiation.