Table of contents

Any future high energy e⁺e⁻ linear collider aims at precision measurements of Standard Model quantities as well as of new, not yet discovered phenomena. In order to pursue this physics programme, excellent detectors at the interaction region have to be complemented by beam diagnostics of unprecedented precision. This article gives an overview of current plans and issues for polarimeters and energy spectrometers at the International Linear Collider, which have been designed to fulfill the precision goals at a large range of beam energies from 45.6 GeV at the Z⁰ pole up to 250 GeV or, as an upgrade, up to 500 GeV.

Systematic measurements on the rate capability of thin MWPCs operated in Xenon, Argon and Neon mixtures using CO₂ as UV-quencher are presented. A good agreement between data and existing models has been found, allowing us to present the rate capability of MWPCs in a comprehensive way and ultimately connect it with the mobilities of the drifting ions.

A numerical study on three dimensional field configuration of a structure based on the concept of Gaseous Electron Multiplier (GEM), namely THick GEM (THGEM) has been carried out using nearly exact Boundary Element Method (neBEM) solver. Various designs of this multiplier device have been studied to examine the effect of the geometrical and electrical properties of the structure on its field configuration.

We have developed a SPEMT (Single Photon Emission MammoTomography) scanner that is made up of two cameras rotating around the pendulous breast of the prone patient, in Vertical Axis of Rotation (VAoR) geometry. Monte Carlo simulations indicate that the device should be able to detect tumours of 8 mm diameter with a tumour/background uptake ratio of 5:1. The scanner field of view is 41.6 mm height and 147 mm in diameter. Each head is composed of one pixilated NaI(Tl) crystal matrix coupled to three Hamamatsu H8500 64-anodes PMT's read out via resistive networks. A dedicated software has been developed to combine data from different PMT's, thus recovering the dead areas between adjacent tubes. A single head has been fully characterized in stationary configuration both in active and dead areas using a point-like source in order to verify the effectiveness of the readout method in recovering the dead regions. The scanner has been installed at the Nuclear Medicine Division of the University of Pisa for its validation using breast phantoms. The very first tomographic images of a breast phantom show a good agreement with Monte Carlo simulation results.

In the framework of the Clear-PEM project for the construction of a high-resolution and high-specificity scanner for breast cancer imaging, a Positron Emission Mammography tomograph has been developed and installed at the Instituto Português de Oncologia do Porto hospital. The Clear-PEM scanner is mainly composed by two planar detector heads attached to a robotic arm, trigger/data acquisition electronics system and computing servers. The detector heads hold crystal matrices built from 2 × 2 × 20 mm³ LYSO:Ce crystals readout by Hamamatsu S8550 APD arrays. The APDs are optically coupled to both ends of the 6144 crystals in order to extract the DOI information for each detected event. Each one of 12288 APD's pixels is read and controlled by Application Specific Integrated Circuits water-cooled by an external cooling unit. The Clear-PEM frontend boards innovative design results in a unprecedented integration of the crystal matrices, APDs and ASICs, making Clear-PEM the PET scanner with the highest number of APD pixels ever integrated so far. In this paper, the scanner's main technical characteristics, calibration strategies and the first spectrometric performance evaluation in a clinical environment are presented. The first commissioning results show 99.7% active channels, which, after calibration, have inter-pixel and absolute gain distributions with dispersions of, respectively, 12.2% and 15.3%, demonstrating that despite the large number of channels, the system is uniform. The mean energy resolution at 511 keV is of 15.9%, with a 8.8% dispersion, and the mean C_DOI⁻¹ is 5.9%/mm, with a 7.8% dispersion. The coincidence time resolution, at 511 keV, for a energy window between 400 and 600 keV, is 5.2 ns FWHM.

Geiger-mode avalanche photodiodes (G-APD) are promising new sensors for light detection in atmospheric Cherenkov telescopes. In this paper, the design and commissioning of a 36-pixel G-APD prototype camera is presented. The data acquisition is based on the Domino Ring Sampling (DRS2) chip. A sub-nanosecond time resolution has been achieved. Cosmic-ray induced air showers have been recorded using an imaging mirror setup, in a self-triggered mode. This is the first time that such measurements have been carried out with a complete G-APD camera.

This paper presents a novel approach to estimate the Standard Model backgrounds based on modifying Monte Carlo predictions within their systematic uncertainties. The improved background model is obtained by altering the original predictions with successively more complex correction functions in signal-free control selections. Statistical tests indicate when sufficient compatibility with data is reached. In this way, systematic effects are absorbed into the new background model. The same correction is then applied on the Monte Carlo prediction in the signal region. Comparing this method to other background estimation techniques shows improvements with respect to statistical and systematic uncertainties. The proposed method can also be applied in other fields beyond high energy physics.

A small prototype of a finely granulated digital hadron calorimeter with Resistive Plate Chambers as active elements was exposed to positive pions of 1–16 GeV energy from the Fermilab test beam. The event selection separates events with mostly non-interacting particles and events with hadronic showers which initiated in the front part of the calorimeter. The data are compared to a Monte Carlo simulation of the set-up. The paper concludes with predictions for the performance of an extended digital hadron calorimeter.

First studies of event discrimination with a Broad-Energy Germanium (BEGe) detector are presented. A novel pulse shape method, exploiting the characteristic electrical field distribution inside BEGe detectors, allows to identify efficiently single-site events and to reject multi-site events. The first are typical for neutrinoless double beta decays (0νββ) and the latter for backgrounds from gamma-ray interactions. The obtained survival probabilities of backgrounds at energies close to Q_ββ(⁷⁶Ge) = 2039 keV are (0.93 ± 0.08)% for events from ⁶⁰Co, (21 ± 3)% from ²²⁶Ra and (40 ± 2)% from ²²⁸Th. This background suppression is achieved with (89 ± 1)% acceptance of ²²⁸Th double escape events, which are dominated by single site interactions. Approximately equal acceptance is expected for 0νββ-decay events. Collimated beam and Compton coincidence measurements demonstrate that the discrimination is largely independent of the interaction location inside the crystal and validate the pulse-shape cut in the energy range of Q_ββ. The application of BEGe detectors in the GERDA and the Majorana double beta decay experiments is under study.

The properties of the THick Gas Electron Multiplier (THGEM) operated with soft X-rays in Kr at room temperature, are presented. Charge gains ranging from 10⁴ to 3 × 10² and from 4 × 10⁴ to 10³ were reached with single- and double-THGEM detectors in a pressure range of 0.5–3.0 bar, respectively, for operation voltages in the range of 800–2600 V. The gain was limited by photon- and ion-feedback effects, and by electron field-emission from the Cu-electrodes at THGEM operation voltages above 2000 V. Energy resolutions in the range of 21–34% FWHM were measured with 5.9 keV X-rays. Other characteristics, including pulse-shape and electric fields in THGEM structures, are discussed.

The CMS experiment will collect data from the proton-proton collisions delivered by the Large Hadron Collider (LHC) at a centre-of-mass energy up to 14 TeV. The CMS trigger system is designed to cope with unprecedented luminosities and LHC bunch-crossing rates up to 40 MHz. The unique CMS trigger architecture only employs two trigger levels. The Level-1 trigger is implemented using custom electronics, while the High Level Trigger (HLT) is based on software algorithms running on a large cluster of commercial processors, the Event Filter Farm. We present the major functionalities of the CMS High Level Trigger system as of the starting of LHC beams operations in September 2008. The validation of the HLT system in the online environment with Monte Carlo simulated data and its commissioning during cosmic rays data taking campaigns are discussed in detail. We conclude with the description of the HLT operations with the first circulating LHC beams before the incident occurred the 19^th September 2008.

The new type of ring-imaging Cherenkov detector technology called DIRC (an acronym for Detection of InternallyReflected Cherenkov Light) has been used successfully for hadronic particle identification in the BABAR experiment at the B Factory (PEP-II) located at the SLAC National Accelerator Laboratory. This paper describes the R&D for and the construction of the DIRC radiator bars and the performance of the DIRC during more than eight years of B Factory operation.

A common situation in experimental physics is to have a signal which can not be separated from a non-interfering background through the use of any selection criteria. In this paper, we describe a procedure for determining, on an event-by-event basis, a quality factor (Q-factor) that a given signal candidate originated from the signal sample. This procedure generalizes the ``side-band'' subtraction method to higher dimensions without requiring the data to be divided into bins. The Q-factors can then be used as event weights in subsequent analysis procedures, allowing one to more directly access the true spectrum of the signal.

Monte Carlo simulations were performed to investigate the possibility to add a DIRC detector to the WASA detector at the COSY accelerator. A statistical method for pattern recognition is presented and the possible angle resolution and velocity precision achieved are discussed.

A rapidity gap program with great potential can be realised at the Large Hadron Collider, LHC, by adding a few simple forward shower counters (FSCs) along the beam line on both sides of the main central detectors, such as CMS. Measurements of single diffractive cross sections down to the lowest masses can be made with an efficient level-1 trigger. Exceptionally, the detectors also make feasible the study of Central Diffractive Excitation, and in particular the reaction g+g→g+g, in the color singlet channel, effectively using the LHC as a gluon-gluon collider.

We present the FP420 R&D project, which has been studying the key aspects of the development and installation of a silicon tracker and fast-timing detectors in the LHC tunnel at 420 m from the interaction points of the ATLAS and CMS experiments. These detectors would measure precisely very forward protons in conjunction with the corresponding central detectors as a means to study Standard Model (SM) physics, and to search for and characterise new physics signals. This report includes a detailed description of the physics case for the detector and, in particular, for the measurement of Central Exclusive Production, pp→p+ϕ+p, in which the outgoing protons remain intact and the central system ϕ may be a single particle such as a SM or MSSM Higgs boson. Other physics topics discussed are γγ and γp interactions, and diffractive processes. The report includes a detailed study of the trigger strategy, acceptance, reconstruction efficiencies, and expected yields for a particularpp→pHp measurement with Higgs boson decay in theb mode. The document also describes the detector acceptance as given by the LHC beam optics between the interaction points and the FP420 location, the machine backgrounds, the new proposed connection cryostat and the moving (``Hamburg'') beam-pipe at 420 m, and the radio-frequency impact of the design on the LHC. The last part of the document is devoted to a description of the 3D silicon sensors and associated tracking performances, the design of two fast-timing detectors capable of accurate vertex reconstruction for background rejection at high-luminosities, and the detector alignment and calibration strategy.