O. Pooth

A detector prototype based on a fast plastic scintillator read out with silicon photomultipliers is presented. All studies have been done with cosmic muons and focus on parameter optimization such as coupling the SiPM to the scintillator or wrapping the scintillator with reflective material. The prototype shows excellent results regarding the light-yield and offers a detection efficiency of 99.5% with a signal purity of 99.9% for cosmic muons.

Correlations among hadrons with the same electric charge produced in Z0 decays are studied using the high statistics data collected from 1991 through 1995 with the OPAL detector at LEP. Normalized factorial cumulants up to fourth order are used to measure genuine particle correlations as a function of the size of phase space domains in rapidity, azimuthal angle and transverse momentum. Both all-charge and like-sign particle combinations show strong positive genuine correlations. One-dimensional cumulants initially increase rapidly with decreasing size of the phase space cells but saturate quickly. In contrast, cumulants in two- and three-dimensional domains continue to increase. The strong rise of the cumulants for all-charge multiplets is increasingly driven by that of like-sign multiplets. This points to the likely influence of Bose–Einstein correlations. Some of the recently proposed algorithms to simulate Bose–Einstein effects, implemented in the Monte Carlo model Pythia, are found to reproduce reasonably well the measured second- and higher-order correlations between particles with the same charge as well as those in all-charge particle multiplets.

The subsystems of the CMS silicon strip tracker were integrated and commissioned at the Tracker Integration Facility (TIF) in the period from November 2006 to July 2007. As part of the commissioning, large samples of cosmic ray data were recorded under various running conditions in the absence of a magnetic field. Cosmic rays detected by scintillation counters were used to trigger the readout of up to 15\,\% of the final silicon strip detector, and over 4.7~million events were recorded. This document describes the cosmic track reconstruction and presents results on the performance of track and hit reconstruction as from dedicated analyses.

The CMS Silicon Strip Tracker will be equipped with 16000 silicon microstrip detector modules covering a surface of approximately 200m2. The APV Readout Controller system was developed at RWTH Aachen, III. Physikalisches Institut in order to perform full readout tests of hybrids and modules at each production step. From the experience derived from initial module production, an automated fault finding algorithm has been developed which uses the full correlations between different electrical tests. The results of a recent production of over 250 Tracker Outer Barrel and 25 Tracker End Cap modules at UCSB demonstrate that the testing protocols are sufficient to find all known faults and that electrical module components produced have a high quality. The results are typical of all CMS tracker assembly and bonding sites.

Abstract For the CMS tracker Phase-2 upgrade new modules with silicon strip sensors are being developed.Each module features a Service Hybrid (SEH), which is responsible for the distribution of low voltages to the module components using a two-stage DC-DC conversion scheme.For modules equipped with the latest generation of SEHs an increase in module noise has been observed.A setup for inducing radiative noise with external magnetic fields that are frequency- and location-dependent is presented.Measurements carried out on modules from different prototyping phases show that the sensitivity is similar across generations, which indicates that radiative coupling into the sensor or readout electronics is not responsible for the observed noise increase.

Abstract The CMS tracker will be equipped with 16,000 silicon microstrip detector modules covering a surface of approximately 220 m 2 . For quality control, a compact and inexpensive DAQ system is needed to monitor the mass production in industry and in the CMS production centres. To meet these requirements a set-up called APV Readout Controller (ARC) system was developed and distributed among all collaborating institutes to perform full readout tests of hybrids and modules at each production step. The system consists of all necessary hardware components, C++ based readout software using LabVIEW 1 as graphical user interface and provides full database connection to track every single module component during the production phase. Two preseries of Tracker End Cap (TEC) silicon detector modules have been produced by the TEC community and tested with the ARC system at Aachen. The results of the second series are presented.

For radiography applications using fast neutrons simultaneously with gammas we have developed a detector with 16 stilbene crystals in a 4×4 2D array with a 5 mm pitch and a depth of 25 mm. The crystal array is read out by Silicon photomultipliers and custom signal processing electronics. The detector prototype was tested using a custom D-D fast neutron generator at the Paul Scherrer Institute. By applying a pulse shape discrimination algorithm the detector is able to detect and distinguish fast neutrons and gammas simultaneously. Various attenuating samples placed between the source and detector with different materials and thicknesses were tested and the measured macroscopic fast neutron cross sections were compared to what was expected. Deviations were studied with the help of detailed Geant4 simulations. The detection efficiency for D-D fast neutrons was measured to be around 10%.

Abstract Alongside the High Luminosity LHC upgrade, the silicon tracker of the CMS detector will be replaced within the scope of the so-called Phase-2 upgrade. The new tracker will consist of an inner part (Inner Tracker with pixelated modules) and at larger radii the Outer Tracker with two different module types (PS and 2S modules). One hybrid type used on these modules is the 2S service hybrid. It provides the optical link connection of a 2S module via the Low Power Giga Bit Transceiver (lpGBT) and a Versatile Transceiver Plus module (VTRx+). It is also responsible for the module power distribution. The different responsibilities of the hybrid require a complete testing, which is performed by a dedicated custom made test card. After a hybrid has been installed on the test card, all signal connections can be tested and verified. The test system is designed to handle a high throughput during mass production. The requirements and the design for the 2S service hybrid test card are presented together with testing results of the first final 2S service hybrid prototypes.

The CMS silicon strip tracker (SST) is a key element for the discovery potential of the CMS experiment at the Large Hadron Collider. It is designed to work at a bunch crossing frequency of 40 MHz in very high particle fluxes and a harsh radiation environment. The CMS tracker is described and the status of the production of silicon detector modules and larger substructures is discussed.

In order to check the system aspects of the forward–backward MSGC tracker designed for the future CMS experiment at LHC, 38 trapezoidal MSGC counters assembled in six multi-substrates detector modules were built and exposed to a muon beam at the CERN SPS. Results on the gain uniformity along the wedge-shaped strip pattern and across the detector modules are shown together with measurements of the detection efficiency and the spatial resolution.

Bose-Einstein correlations between like-sign charged-particle pairs in e+e− → W+W− events recorded with the OPAL detector at LEP at centre-of-mass energies between 183 GeV and 209 eV are studied. Test variables are used to investigate the presence of correlations between hadrons originating from different W bosons in W+W− → qq events. Within the statistics of the data sample no evidence for inter-WW Bose-Einstein correlations is obtained. The data are also compared with predictions'of a recent implementation of Bose-Einstein correlation effects in the Monte Carlo model PYTHIA. This presentation is based on [1].

The Compact Muon Solenoid (CMS) is one of two general purpose detectors which are foreseen to operate at the Large Hadron Collider (LHC), which is presently being built at the European laboratory for particle physics (CERN) in Switzerland. The Central Tracker of CMS consists of a Pixel System, which is located close to the interaction point and a Silicon Strip Tracker (SST) which instruments the intermediate and outer region. The SST is composed of 15148 Silicon Microstrip Detector Modules which contain the readout electronics (hybrids) and sensors. These modules will be assembled into substructures with control electronics and optics for transmitting data. The substructures will be integrated into the subsystems of the SST. The SST will be operated for up to ten years in the harsh radiation environment of the LHC. The lifetime of the SST will be extended by operating the detector at lowered temperature. The sensors, which are very delicate with respect to radiation damage, will be operated at a maximum temperature of -10/spl deg/C. Since the assembly of the modules as well as the mounting on substructures is done at room temperature, tests in a CMS-like environment are necessary to prove the mechanical and electrical stability.

Abstract Inside the CMS detector 1 charged particles are measured precisely with layers of low-occupancy silicon detectors and Micro Strip Gas Chambers (MSGCs) with pitches of 50 and 200 μm, respectively. Low occupancy is achieved by a high granularity of 3×106 channels for silicon detectors and 11×106 for MSGCs. For the CMS forward tracker we tested a closed MSGC module with wedge-shaped strip patterns on 300 μm DESAG263 2 glass substrates produced by OPTIMASK. Using a 100 GeV μ-beam at CERN we investigated the behaviour of this MSGC module foreseen for four wedge-shaped substrates, 512 strips each.

Silicon photomultipliers (SiPM) are semiconductor photo sensors that have the potential to replace photomultiplier tubes (PMT) in various fields of application. We present detectors consisting of 30 × 30 × 0.5 cm3 fast plastic scintillator tiles read out with SiPMs. The detectors offer great electronic and mechanical advantages over the classical PMT-scintillator combination. SiPMs are very compact devices that run independent of magnetic fields at low voltages and no light guides between the scintillator and the SiPM are necessary in the presented layouts. Three prototypes, two of which with integrated wavelength shifting fibres, have been tested in a proton beam at the COSY accelerator at Forschungszentrum Jülich. The different layouts are compared in terms of most probable pulse height, detection efficiency and noise behaviour as well as timing resolution. The spatial distributions of these properties across the scintillator surface are presented. The best layout can be operated at a mean efficiency of =99.9 % while sustaining low noise rates in the order of 10 Hz with a timing resolution of less than 3 ns. Both efficiency and timing resolution show good spatial homogeneity.

Bose-Einstein Correlations in WW events have been studied by all four LEP experiments.This overview concentrates on the results for the search for Bose-Einstein Correlations between particles originating from different W's in the reaction e + e -→ W + W -→ qqqq, based on data recorded at centre-of-mass energies between 172 and 209 GeV.There is no evidence for Bose-Einstein Correlations between particles originating from different W's.* Speaker.

Triggering on high p t muons at the projected high luminosity LHC (HL-LHC) with an expected instantaneous luminosity of 10 35 /(cm 2 • s) will be one major challenge for the CMS experiment from 2022 on.With the Muon Track fast Tag (MTT) a new detector subsystem is proposed that can help to keep the Level-1 trigger rate low enough without increasing the p t thresholds for single muons.The trigger concept must be extended by combining the information of the inner tracking system with a fast muon tag which is also able to reduce the problem with ambiguities of simultaneously traversing muons leading to so-called ghost hits.Tiles of fast plastic scintillator material read out by silicon photomultipliers (SiPMs) are under investigation to provide the additional detector layer in the very limited space available between the CMS solenoid and the first muon stations.

During the last five years many institutes worldwide produced and tested the individual components for the silicon strip detector. Starting from the main ingredients – sensors, front-end electronics, module frames etc. – the objects being built and under test became more and more complex. Finally after careful shipment of all pre-assembled and tested subdetectors the full silicon strip tracker was assembled and commissioned at the tracker test facility TIF at CERN. In December 2007 the entire object was installed inside CMS in its final position. Final cabling and testing was carried out and finished in spring 2008.

When the experiments at the Large Hadron Collider (LHC) at CERN begin data taking the biggest high energy physics experiments ever will be underway. One of these experiments is the Compact Muon Soleno

The inner tracking system is designed to measure as precisely as possible the trajectories of charged particles with a full silicon based system. Originally CMS was foreseen to use two different detector technologies in the central strip tracking part: silicon based strip detectors and micro strip gas chambers (MSGC, [32]) in the outer regions. Finally in the year 1999 the CMS collaboration decided to use a full silicon solution for the entire tracking device, because of superior radiation hardness and dropping prices for silicon sensors.

To pinpoint the smallest fractions of matter in the universe the largest machine in high energy physics ever is being commissioned at CERN near Geneva in Switzerland. The main motivation of the Large Hadron Collider project LHC is to study the nature of electroweak symmetry breaking for which the Higgs mechanism is presumed to be responsible. The experimental study of the Higgs mechanism will explore the consistency of the Standard Model in particle physics at energy scales above about 1 TeV.

The silicon strip tracker of the CMS experiment is currently the largest silicon based detector system worldwide. The production and commissioning has been successfully completed in 2007 and the entire system was inserted into the CMS detector in its final position. In spring 2008 the connection of all cooling pipes and cables to the readout components, high voltage supplies and control systems was finalised. Presently the silicon strip tracker is ready for data taking as soon as the Large Hadron Collider will be switched on.

Particle detectors based on semiconducting materials are used in a wide range of applications in various physics fields. The two main applications are tracking of charged particles and the precise energy spectroscopy of photons. Since the 1950s p-n junctions are used to detect signals from charged particles and photons traversing the depletion zone between an n-doped and p-doped material. For 25 years in coincidence with the detection of short lived mesons containing charm and bottom quarks and the study of decaying tau leptons, the particle physics community developed great interest in very fast particle detectors with high resolution. First applications of semiconducting particle detectors in high energy physics experiments date back to the 1970s. Today nearly every large scale high energy physics experiment makes use of silicon strip and/or silicon pixel detectors to precisely determine the trajectories of traversing charged particles. The tracking device of the CMS experiment with a sensitive silicon area of approximately 200m2 is the largest project of this type today.

For simultaneous imaging with fast neutrons and gammas we have developed a 16-pixel detector that uses the organic scintillator stilbene as active material. Sixteen stilbene cuboids of size 5×5×25mm3 are arranged in a 4 × 4 grid and read out by silicon photomultipliers. The usage of stilbene allows to distinguish neutron and gamma signals via pulse shape discrimination techniques. In this paper, attenuation measurements and first tomographies of objects containing aluminum and PMMA are presented. Fast neutrons and gammas are delivered by an Americium–Beryllium source. The performance of the tomographic reconstructions with neutrons and gammas is evaluated. It is shown that the combination of the two images can improve the material distinction in the reconstructed object.

The CMS MF1 milestone was set in order to evaluate system aspects of the CMS forward–backward MSGC tracker, to check the design and feasibility of mass production and to set up all assembly and test procedures. We describe the construction and the experiences gained with the operation of a complete system of 38 MSGC detectors assembled in six multi-substrate detector modules corresponding to the geometry of the forward–backward MSGC tracker in CMS. Corresponding to various possible designs, the detector modules were equipped with MSGCs mounted side by side without dead space (wall less ϕ crack) forming a continuous detector surface of about 0.2 m2. Operation conditions for these 38 MSGCs are reported from an exposure to a muon beam at the CERN SPS. Gain uniformity along the wedge-shaped strip pattern and across the detector modules will be shown.

The CMS experiment at the Large Hadron Collider LHC will face a new era after Long Shutdown 3, which is scheduled to take place between 2024 and 2026.The challenge of running a tracking detector at the High Luminosity LHC will be the high instantaneous luminosity of 5 × 10 34 s -1 cm -2 , leading to a total integrated luminosity of 3000 fb -1 .Due to the high instantaneous luminosity a particle flux of up to 1 × 10 15 n eq cm -2 is expected in the outer tracker region.To cope with this challenge the existing CMS Outer Tracker has to be replaced by a completely new subdetector system.This Phase-2 tracker will have an increased granularity with ≤ 1% occupancy in all regions and less material compared to the current detector.In addition the CMS Phase-2 tracker will contribute to the level-1 trigger with specialized detector modules with onboard transverse momentum discrimination.The Phase-2 Outer Tracker will consist of 5616 PS modules with a macro-pixel and a strip sensor on top of each other, and 7680 2S modules with two strip sensors on top of each other.In the next years standardized production lines for precise module building and testing are going to be installed in all 2S module production centers in the USA, Germany, Belgium, Pakistan, and India.The current plan foresees to integrate PS and 2S modules on tracker substructures starting 2022 and to start integrating the complete Phase-2 tracker in CMS in 2024 for the operation at the High Luminosity LHC.