Guido Tonelli

The pion form factor has been measured in the space-like q2 region 0.014 to 0.26 (GeV/c)2 by scattering 300 GeV pions from the electrons of a liquid hydrogen target. A detailed description is given of the apparatus, data analysis and corrections to the data. The mean square charge radius extracted from the data is model-dependent. We find that a form which includes a realistic description of the form factor phase gives a similar results to the naive pole form, and conclude 〈r2π〉 = 0.438±0.008 fm2.

We discuss the physics potential and the experimental challenges of an upgraded LHC running at an instantaneous luminosity of 1035 cm-2s-1. The detector R&D needed to operate ATLAS and CMS in a very high radiation environment and the expected detector performance are discussed. A few examples of the increased physics potential are given, ranging from precise measurements within the Standard Model (in particular in the Higgs sector) to the discovery reach for several New Physics processes.

The negative kaon electromagnetic form factor has been measured in the space-like q2 range 0.015–0.10 (GeV/c)2 by the direct scattering of 250 GeV kaons from electrons at the CERN SPS. It is found that the kaon mean square charge radius 〈r2K〉 = 0.34 ± 0.05 fm2. From data collected simultaneously for πe scattering, the difference between the charged pion and kaon mean square radii (which is less sensitive to systematic errors) is found to be 〈r2π〉 − 〈r2K = 0.1 0 ± 0.045 fm2.

The CDF central and endwall hadron calorimeter covers the polar region between 30° and 150° and a full 2π in azimuth. It consists of 48 steel-scintillator central modules with 2.5 cm sampling and 48 steel-scintillator endwall modules with 5.0 cm sampling. A general description of the detector is given. Calibration techniques and performance are discussed. Some results of the test beam studies are shown.

We report a measurement of the negative pion electromagnetic form factor in the range of space-like four-momentum transfer 0.014 < q2 < 0.122 (GeV/c)2. The measurement was made by the NA7 collaboration at the CERN SPS, by observing the interaction of 300 GeV pions with the electrons of a liquid hydrogen target. The form factor is fitted by a pole form with a pion radius of 〈r2〈12 = 0.657 ± 0.012 fm.

The EM form factor of the pion has been studied in the time-like region by measuring σ(e+e− → π+π−) normalized to σ(e+e− → μ+μ−). Results have been obtained for q2 down to the physical threshold.

An asynchronous version of a binary pixel readout circuit has been implemented in an array with 16 columns at 500 mu m pitch and 63 rows at 75 mu m pitch. This readout chip has been bonded with solder bumps to a silicon detector with matching pixel elements. Event information in a pixel can be strobed into a local memory by a trigger signal and subsequently read out. Without a strobe the information in this memory is continuously cleared. The complete hybrid detector has been successfully tested with ionizing particles from a radioactive source. Three such devices have been used in the CERN heavy ion experiment WA94 in the Omega spectrometer where they recorded particle tracks from high multiplicity /sup 32/S interactions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Large double-sided readout silicon strip detectors have been fabricated for the Aleph minivertex. We have tested them with a β-source and have observed charge collection and capacitive charge division both on the junction side and on the ohmic side. A charge correlation has been observed between the two faces and can be used to reduce ambiguities in the case of two particles crossing the same wafer.

The Compact Muon Solenoid (CMS) is one of the experiments at the Large Hadron Collider (LHC) under construction at CERN. Its inner tracking system consist of the world largest Silicon Strip Tracker (SST). In total it implements 24,244 silicon sensors covering an area of 206m2. To construct a large system of this size and ensure its functionality for the full lifetime of 10 years under LHC condition, the CMS collaboration developed an elaborate design and a detailed quality assurance program. This paper describes the strategy and shows first results on sensor qualification.

The purpose of this work is to study layout solutions aimed at increasing the breakdown voltage in silicon micro-strip detectors. Several structures with multiple floating guards in different configurations have been designed and produced on high-resistivity silicon wafers. The main electrical characteristics of these devices have been measured before and after irradiation. Both radiation-induced surface and bulk damage effects were considered as well. The highest breakdown voltage was found on devices featuring p/sup +/ guards without field plates. A simulation study has been carried out on simplified structures to evaluate the distribution of the breakdown field as a function of the guard layout. The aim was design optimization.

The ϱ− radiative decay width has been measured by studying the production of ϱ− via the Primakoff effect by 200 GeV incident π− on Cu and Pb targets. This width was obtained by fitting the measured dσ/dt for ϱ production with the theoretical coherent differential cross section including both the electromagnetic and strong contributions. The measured radiative width value is 81 ± 4 ± 4 keV: it is consistent with the ratio Γ(ϱ → πγ)/Γ(ω → πγ) ∼ case:19 as expected from the vector dominance and the quark model.

The armed invasion of Ukraine by the Russian Federation has adversely affected the relations between Russia and Western countries. Among other aspects, it has put scientific cooperation and collaboration into question and changed the scientific landscape significantly. Cooperation between some Western institutions and their Russian and Belarusian partners were put on hold after February 24, 2022. The CERN Council decided at its meeting in December 2023 to terminate cooperation agreements with Russia and Belarus that date back a decade. CERN is an international institution with UN observer status, and has so far played a role in international cooperation which was independent of national political strategies. We argue that the Science4Peace idea still has a great value and scientific collaboration between scientists must continue, since fundamental science is by its nature an international discipline. A ban of scientists participating in international cooperation and collaboration is against the traditions, requirements and understanding of science. We call for measures to reactivate the peaceful cooperation of individual scientists on fundamental research in order to stimulate international cooperation for a more peaceful world in the future. Specifically, we plead for finding ways to continue this cooperation through international organizations, such as CERN and JINR.

The ALEPH silicon vertex detector is the first detector operating in a colliding beam environment that uses silicon strip detectors which provide readout on both sides and hence a three-dimensional point measurement for the trajectory of charged particles. The detector system was commissioned successfully at the e+e− collider LEP at the research centre CERN, Switzerland, during the year 1991 while taking data at the Z0 resonance. The achieved spatial resolution of the complete 73 728 channel device (intrinsic plus alignment) is 12 μm in the r-f view and 12 μm in the z view. The design and construction of the entire detector system are discussed in detail and the experience gained in running the detector will be described with special emphasis on the uses of this novel tracking device for the physics of short-lived heavy particles produced in the decays of the Z0 resonance.

Microstrip silicon detectors with orthogonal readout on opposite sides have been designed and fabricated. The active area of each device is 25 cm2 and the strip pitch is 25 μm on the junction side and 50 μm on the opposite ohmic side. A space resolution of 15 μm on the junction side (100 μm readout pitch) and 24 μm on the ohmic side (200 μm readout pitch) has been measured. We also report on AC-coupling chips, designed and fabricated in order to allow AC connection of the strips to the amplifiers. These chips are 6.4 × 5.0 mm2 and have 100 μm pitch. Both AC-couplers and detectors have been installed as part of the ALEPH minivertex.

Successive versions of high speed, active silicon pixel detectors with integrated readout electronics have been developed for particle physics experiments using monolithic and hybrid technologies. Various matrices with binary output as well as a linear detector with analog output have been made. The hybrid binary matrix with 1024 cells (dimension 75 μm×500 μm) can capture events at ∼5 MHz and a selected event can then be read out in < 10 μs. In different beam tests at CERN a precision of 25 μm has been achieved and the efficiency was better than 99.2%. Detector thicknesses of 300 μm and 150 μm of silicon have been used. In a test with a 109Cd source a noise level of 170 e− r.m.s. (1.4 keV fwhm) has been measured with a threshold non-uniformity of 750 e− r.m.s. Objectives of the development work are the increase of the size of detecting area without loss of efficiency, the design of an appropriate readout architecture for collider operation, the reduction of material thickness in the detector, understanding of the threshold non-uniformity, study of the sensitivity of the pixel matrices to light and low energy electrons for scintillating fiber detector readout and last but not least, the optimization of cost and yield of the pixel detectors in production.

Results of tests performed on a series of prototype silicon detectors with double side readout are presented. Electrical characteristics and particle data analysis indicate that these detectors can be operated in capacitive charge division with good spatial resolution on two orthogonal coordinates.

Vertex detectors allow high precision reconstruction of particle tracks and therefore make possible the investigation of the decay topology of short-lived particles in collider experiments. In the ALEPH experiment at LEP a minivertex detector will be installed. It consists of silicon microstrip detectors arranged on two concentric “cylindrical” surfaces around the interaction point. With this geometry it will be possible to measure the r − ϕ − z coordinates of particles traversing the detector. The expected position resolution is 10 μm in r − ϕ and 20 μm in r − z. For optimum signal processing monolithic CMOS readout electronics are under development. Each chip consists of 60 charge sensitive preamplifiers, multiplexed into one output channel. Fast power switching will reduce heat dissipation. Details about construction and expected device performance will be described.

The paper describes the technology used for the fabrication of a set of prototypes of microstrip silicon detectors matching the requirements of the CMS inner tracking system. The detectors are single and double-sided devices featuring integrated AC coupling on both sides. Polysilicon resistors are used as bias elements and individual p-stop patterns provide isolation in between the strips on the ohmic side. The design is such that the performance of these detectors will be marginally affected by the heavy irradiation correlated to several years of running at LHC. Different dielectric layers have been used to study rigidity and yield in the integrated capacitors. Different polysilicon implant doses have been used to optimise the uniformity and to increase the reproducibility of the poly resistors. The paper describes the design choices and the results of laboratory tests on a series of devices.

This paper presents a WDM architecture of a photonic analogue to digital converter (ADC) for direct RF sampling in radar and EW digital receiver, the architecture is based on the parallel operation of an array of state-of-the-art electronic ADCs while the photonic sampling is achieved using a mode locked laser (MLL). The parallelisation is implemented through a novel technique for the slicing of the optical spectrum and the time interleaving of the colored pulses. A high dynamic range by bandwidth product of the ADC can be obtained. The MLL overcomes the jitter limitation in conventional electronic quartz references in electronic ADCs and can be also fiber optic distributed as reference clock for the Radar Tx and Rx functions. The test realized on the prototype is reported demonstrating a 5 Gbps sampling rate ADC.

The first observation of neutral pion production in πe inelastic scattering is presented. The cross section at 300 GeV for |t‖>62;10−3 (GeV / c)2 is 2.11 ± 0.47 nb, in good agreement with the theory of PCAC anomalies with 3 quark colours.

We report the results of two beam tests performed in July and September 1995 at CERN using silicon microstrip detectors of various types: single sided, double sided with small angle stereo strips, double sided with orthogonal strips, double sided with pads. For the read-out electronics use was made of Preshape32, Premux128 and VA1 chips. The signal to noise ratio and the resolution of the detectors was studied for different incident angles of the incoming particles and for different values of the detector bias voltage. The goal of these tests was to check and improve the performances of the prototypes for the CMS Central Detector.

Resolution and linearity of the position measurement of Pisa multi-electrode silicon detectors are presented. The detectors are operated in slightly underdepleted mode and take advantage of their intrinsic resistivity for resistive charge partition between adjacent strips. 22 μm resolution is achieved with readout lines spaced 300 μm. Possible applications in colliding beam experiments for the detection of secondary vertices are discussed.

A large system of silicon strip detectors with double sided readout has been successfully commissioned over the course of the last year at the e+e− collider LEP. The readout of this 73 728 channel system is performed with custom designed VLSI charge sensitive amplifier chips (CAMEX64A). An overall point resolution of 12 μm on both sides has been acheived for the complete system. The most important difficulties during the run were beam losses into the detector, and a chemical agent deposited onto the electronics; however, the damage from these sources was understood and brought under control. This and other results of the 1991 data-taking run are described with special emphasis on the operational experience.

Describes the germanium monlithic detector and discusses its performance. The detector is a parallelepiped 5 x 5 x 20 mm in volume with 48 electrodes 20 mm long, 50 microns wide and spaced 50 microns one from the other deposited on one face. Presents a sketch of the detector and its working principle. To obtain a finer granularity, a telescope of 40 layers of silica was substituted with a target made out of a single block of germanium followed by a silicon telescope.

A new GeSi active target is presently used in the NA1 experiment at CERN to study photoproduction of charmed particles and to measure their lifetimes. Some general comments on the active target technique are made.

A non selective method for the isolation of DNA repair-deficient mutants in mammalian cells is discussed.The method requires radioactive labelling of the short DNA sequences synthesized during repair of damaged regions.Mutants should be recognized by the absence of radioactive incorporation into their DNA.A multiwire proportional chamber (MWPC) is proposed as a suitable radioactivity detector.The performance of a MWPC prototype with a cathode coupled delay line read-out is described and is shown to be adequate for this application.The main avantages of a MWPC are reviewed with respect to other methods used for t3-radioactivity counting of biological samples, such as liquid scintillators or autoradiography: the proposed detection method is non destructive for the ceils, which are being kept alive for further biological studies; furthermore many cell clones can be screened within a reasonable time.

A description of the ALEPH Vertex Detector (VDET 91), including the mechanical structure and the improved data acquisition system, is given. The apparatus consists of two complete layers of silicon detectors with double-sided readout which provide a full x, y, z information of the impact points of charged particles. The authors show results on signal-to-noise ratio for minimum ionizing particles and efficiency in hit/track matching. Results on position, impact parameter, and momentum resolution are also shown as measured using high momentum muons. The first preliminary study on vertexing techniques and their impact on physics analysis is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Several 5*5 cm/sup 2/ double-sided readout silicon strip detectors have been fabricated using planar technology. Electrical characteristics (I-V and C-V curves interstrip resistance versus bias voltage) have been measured. Some detectors have been tested with a scanning electron microscope to investigate defects due to the fabrication process. A few of them have been tested with a beta source and with a 50-GeV electron beam. A strong correlation is observed between charges collected on the ohmic side and on the junction side. Preliminary results on capacitive charge division studies are also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A measurement of the lifetime of theΛ c baryon photoproduced coherently off a Germanium-Silicon target is presented. A signal ofΛ c →ΔK*→pKππ0 has been observed and the two different decay diagrams for this process are compared. A sample of 9Λ c decays gives a lifetime of 1.1 −0.4 +0.8 10−13 s.

The paper describes the role of the n+ edge implants in the breakdown process of p+ on n-bulk silicon diodes. Laboratory measurements and simulation studies are presented on a series of test structures aimed at an optimization of the design in the edge region. The dependence of the breakdown voltage on the geometrical parameters of the devices is discussed in detail. Design rules are extracted for the use of n+-layers along the scribe line to avoid surface conduction of current generated by the exposed edges. The effect of neutron irradiation has been studied up to a fluence of 1.8×1015 cm−2.

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.

We present results obtained with full-size wedge silicon microstrip detectors bonded to APV6 (Raymond et al., Proceedings of the 3rd Workshop on Electronics for LHC Experiments, CERN/LHCC/97-60) readout chips. We used two identical modules, each consisting of two crystals bonded together. One module was irradiated with 1.7×1014neutrons/cm2. The detectors have been characterized both in the laboratory and by exposing them to a beam of minimum ionizing particles. The results obtained are a good starting point for the evaluation of the performance of the “ensemble” detector plus readout chip in a version very similar to the final production one. We detected the signal from minimum ionizing particles with a signal-to-noise ratio ranging from 9.3 for the irradiated detector up to 20.5 for the non-irradiated detector, provided the parameters of the readout chips are carefully tuned.

The Aleph silicon vertex detector at the LEP e+e− collider at CERN is described. A detailed information on the various components of the detector is given. Preliminary results obtained during 1990 LEP running are presented.

The major reason for building a vertex detector for CDF is the tagging of decay vertices of particles with lifetime in the 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> 3/10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> 2 sec. range. This is a complementary approach to heavy flavour physics with respect to missing E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> and large P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> leptons. The method can be best applied to tag hadronic decays of heavy flavours, which have the largest branching ratios, but have eluded any specific tagging until now. It also works, although with somewhat reduced efficiency, in events with a semileptonic decay. All in all it promises to be a powerful tool in the search of rather elusive processes like Higgs, top, or fourth generation quark production [1]. The additional information provided by the vertex detector will also improve significantly the resolution of the CDF central tracking system [2].

Hydrogen supported thermal donor (TD) formation was observed in oxygen enriched high resistive float zone (FZ) silicon being used as substrates for detectors in the Large Hadron Collider (CERN). TD formation was provided by a “2-step-process”, consisting of a plasma hydrogenation at 250 °C (60 min) and subsequent annealing at 450 °C in air (typically for 20–30 min). The samples were analyzed by spreading resistance probe (SRP), C(V) and DLTS measurements. Doping by TDs in the oxygen enriched layers of FZ Si samples might be a promising method for the creation of very deep (∼100μm) electrical field gradients for an improved performance of Si radiation detectors.

The behavior of oxygen in oxygen-doped high-resistivity (HR) n-type float-zone (FZ) silicon has been studied using a combination of analytical techniques. In the as-doped material, a large number of deep levels have been observed with deep-level transient spectroscopy. The corresponding parameters (concentration, activation energy, and trap signature) are given, and the possible identity is discussed in view of the presence of oxygen and other impurities in the material. In addition, the impact of a low-temperature hydrogen-plasma preannealing on the formation of oxygen thermal donors (OTDs) and other oxygen-related shallow thermal donors (STDs) at 450°C is described. It is shown that the introduction rate of OTDs in oxygenated HR FZ silicon is much smaller than in Czochralski silicon. In fact, for short anneals at 450°C following a plasma treatment, the STDs are the ones which have been predominantly created near the surface of the samples. © 2003 The Electrochemical Society. All rights reserved.

A proposal for a pixel-based Level 1 trigger for the Super-LHC is presented. The trigger is based on fast track reconstruction using the full pixel granularity exploiting a readout which connects different layers in specific trigger towers. The trigger will implement the current CMS high level trigger functionality in a novel concept of intelligent detector. A possible layout is discussed and implications on data links are evaluated.

This paper summarises the work done by the ATLAS and CMS collaborations, and by the teams of the Large Hadron Collider at CERN, that led to the discovery of a new particle, with mass near 125 GeV and properties consistent with the ones predicted for the Standard Model Higgs boson. An overview of the Standard Model, with a description of the role of the Higgs boson in the theory, and a summary of the searches for this particle prior to the LHC operations is also given. The paper presents the results obtained by ATLAS and CMS from the analysis of the full data set produced in the first physics run of LHC. After a short discussion on the implications of the discovery, the future prospects for the precision study of the new particle are lastly discussed.

This paper describes the main achievements in the development of radiation resistant silicon detectors to be used in the CMS tracker. After a general description of the basic requirements for the operation of large semiconductor systems in the LHC environment, the issue of radiation resistance is discussed in detail. Advantages and disadvantages of the different technological options are presented for comparison. Laboratory measurements and test beam data are used to check the performance of several series of prototypes fabricated by different companies. The expected performance of the final detector modules are presented together with preliminary test beam results on system prototypes.

A low dose technique has been recently proposed for tomographic studies of the lung, which makes use of a gamma camera to detect 90° Compton-scattered photons from external planar gamma source. In this paper, we present a detailed Monte Carlo study of this technique. A 20 × 20 × 20 cm3 water phantom was simulated as a target and a large gamma camera equipped with an imaging collimator as a detector. The multiple scattering contamination of the single scattered signal was studied as a function of the source-detector geometry and of the incident energy in the range 100-500 keV. The multiple to single scatter ratio has an approximate 1/E0.7 dependence and increases almost linearly with the phantom depth and the transversal thickness at 90°. Simulation has been also performed with a 16 × 16 × 10 cm3 sawdust phantom of 0.3 g/cm3 density; the Monte Carlo results agree to within a few percent with experimental data.

Multi-electrode germanium detectors are being used as an active target for decay path measurements of charmed mesons. The procedure used to fabricate such detectors is described and a brief analysis of their performance is given.

The use of multiwire proportional chamber (MWPC) for mapping the incorporation of a radioactive precursor of DNA biosynthesis by aggregates of cells is discussed. The resolving power, sensitivity and linearity of the developed system are shown, together with preliminary “electronic autoradiograms” of 14C-labelled cells.

Abstract In the framework of the CERN detector R&D effort in view of future high luminosity colliders, several pixel detector prototypes, both hybrid and monolithic, are being developed. A hybrid matrix of 16 × 64 pixels with a new readout cell is described here, and it will be first used for a test in a heavy-ion experiment. Preliminary results from the application of SOI processes on high resistivity silicon are also presented.

The authors describe the performance of surface barrier silicon detectors with x,y readout electrodes which have been fabricated and tested with minimum ionizing particles. The impact points of the incoming particles are reconstructed with an accuracy of 52 mu m and 300 mu m, respectively, for the two coordinates, and each detector provides a fully two-dimensional plot of the beam profile. Global efficiency, edge effects, and two-particle resolution in both coordinates are reported. It is concluded that the strong correlation between the charges collected on the two sides is helpful in solving ambiguities in about 80% of the events with two particles.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The paper describes the large silicon tracking system of CMS, one of the two general purpose detectors planned at the Large Hadron Collider of CERN. The system consists of three layers of silicon microstrip detectors instrumenting the interaction region as part of the Inner Tracking Detector of CMS. The expected performance of the system is discussed together with preliminary test beam results on single and double-sided prototype detectors.

Spectral purity and source stability represent two of the primary goals in the design of high performance frequency synthesizer for modern radar systems. This paper presents a new X-band High Stable Synthesizer (HSS) architecture, which combines Phase Lock Loop (PLL), Direct Digital Synthesis (DDS) and multiplier techniques, in order to cope with low phase noise and frequency agility requirements of the next radar generations. This synthesizer offers frequency coverage in X band with a percentage bandwidth of a minimum of 10%, with fast switching time, high digitally-tunable resolution and very low phase noise. The achievement of such performance has been demonstrated by experimental results measured on a laboratory demonstrator: they show a lock-in time within 10 us and a phase noise improvement up to 30 dB compared to the current state of art Frequency Generation Unit (FGU). Moreover, for its versatility, the architecture is able to provide an intermediate output covering the needs for new S-L band application.

The ALEPH experiment [1] at LEP is equipped with a vertex detector [2] using two layers of double-sided silicon strip detectors. These detectors allow a real two-dimensional measurement of charged particle tracks. The present (1991) detector has the inner layer at a radius of 6.5 cm and the outer layer at 11.5 cm. The theta angle coverage is ±33° for the inner layer and ±50° for the outer layer. The inner layer is made out of 9 faces with four silicon detectors each, the outer layer has 15 such faces. We use silicon detectors of 5 × 5 cm2 and 300 μm thickness. The readout pitch is 100 μm at both sides and using capacitive charge division a resolution in the order of 10 μm can be achieved. The signals from 256 readout strips are integrated, amplified and multiplexed using four CAMEX64 chips. An early version of this detector was already installed in spring 1990. Although the detector was not complete and in addition was accidentally damaged by malfunctions of the external electronics, it took data during the 1990 ALEPH run. For the first time double sided silicon detectors were used in a physics experiment. In 1991 the beampipe was replaced by a smaller one. This allowed us to move the inner layer to a radius of 6.5 cm. A completely new detector has been built. This new detector has been installed in spring 1991. Most of the results quoted in this paper refer to this detector.

20 The Higgs boson is an unstable particle, living for only the tiniest fraction of a second. But it plays a major role in particle physics and in shaping the cosmos. The particle can be seen as a manifestation of an invisible field that fills every corner of our universe, assigning a distinctive mass to each elementary particle through its interaction with the field. Heavy particles, like super-massive top quarks, experience strong couplings with the Higgs field, while massless particles, like photons, can fly through it unaffected. As a consequence of the mechanism, the chaotic ingredients of the early universe at a certain moment started eventually Researchers of the ATLAS and CMS experiments at CERN, have announced the discovery of a new particle whose characteristics seem to be consistent with the ones expected for the long sought Higgs boson. Are we there at last? And what could be the implications of this historical discovery? l Guido Tonelli CERN, Geneva, Switzerland;

A measurement of the lifetime of D0-mesons photoproduced coherently off a germanium target is presented. Signals have been observed for the production of D0 into several channels and for D*+ → D0π+. A sample of 58 D0 decays gives a lifetime of (3.4−0.5+0.6 ± 0.3) · 10−13 s.

High-voltage operation can be a solution to obtain full charge collection in strongly irradiated silicon detectors. The maximum bias voltage which can be applied is limited by the breakdown point of the junction. We show how multiguard structures can enhance the breakdown voltage in p+–n silicon devices designed for applications in the LHC environment.

The most recent developments in fabrication and performance of double-sided microstrip silicon detectors are described in view of applications for beauty physics at e+e− and hadron colliders.

In the last years several hundreds of large (∼25 cm2) double-sided silicon strip detectors have been designed and tested in our Pisa-INFN laboratory. These detectors are currently used in ALEPH and L3 vertices, and in other field of applications as well. We present the tests performed on a single detector, and we discuss some results on the test structures inserted in each wafer in order to measure the relevant, process-dependent, quantities which determine the detector performances.

A prototype of the barrel Tracking Detector of the Compact Muon Solenoid (CMS) experiment proposed for LHC was built and tested in a beam and in a magnetic field of up to 3 T. It contained six microstrip gas chambers, 25 cm long, and three double-sided silicon microstrip detectors, 12.5 cm long. We report some preliminary results on the performance of the chambers.

The digital imaging of carbohydrate consumption in myocardial tissue has been performed by using a deposit tracer of glucose metabolism (3H-deoxyglucose) and a specially designed Multiwire Proportional Chamber (MWPC) that acts as a position sensitive radioactivity detector. The resolving power (≃1.5 mm FWHM), sensitivity (≃10-1Bq/cm2), efficiency (≃10%) and uniformity (±4%) of the system are shown and MWPC digital autoradiographs of canine heart in different pathophysiological conditions are presented.

Keine Kultur kann existieren ohne eine Erzählung von den Ursprüngen. Der italienische Teilchenphysiker und Bestsellerautor Guido Tonelli erzählt in "Genesis" die große Geschichte von der Entstehung unseres Universums, angefangen vom Big Bang und den allerersten Augenblicken danach bis zu unserem Sonnensystem. Sein Buch ist der meisterhafte Versuch, aus dem Wissen der heutigen Astrophysik heraus eine Erzählung von den Ursprüngen zu entwickeln, die nie die Grenzen der Wissenschaft verlässt, sich aber an den großen Mythen messen lassen kann.

Four position sensitive silicon detectors have been tested inside the Tevatron beam pipe at Fermilab. The system is the prototype of the small angle silicon spectrometer designed to study primarily pp elastic and diffractive cross-sections at the Collider of Fermilab (CDF). Particles in the beam halo during p-p storage tests were used to study the performance of the detectors. Efficiency, linearity of response and spatial resolution are shown. Measurements performed at different distances from the beam axis have shown that the detectors could be operated at 8.5 mm from the beam with low rates and no disturbance to the circulating beams. This distance corresponds to about 11 times the standard half-width of the local beam envelope. The behaviour of the detectors with the radiation dose has also been investigated.

The paper presents the results of an extensive set of measurements performed on silicon microstrip sensors produced by STMicroelectronics for the CMS Tracker. 5″ and 6″ technologies were used to process several series of detector prototypes. Detectors 300μm thick were produced on 5″ wafers and fully characterized. A new design on 500μm thick wafers with 6″ technology has been recently implemented. The performance of three different layouts has been investigated in terms of macroscopic electrical parameters and radiation resistance.

For the construction of the silicon microstrip detectors for the Tracker of the CMS experiment, two different substrate choices were investigated: A high-resistivity (6 k cm) substrate with (111) crystalorientation and a low-resistivity (2k cm) one with (100) crystalorientation. The interstrip and backplane capacitances were measured before and after the exposure to radiation in a range of strip pitches from 60 μm to 240 μm and for values of the width-over-pitch ratio between 0.1 and 0.5.

Tritium labelled mammalian cells with defective repair of UV-induced damage have been identified by using a MWPC as a position sensitive radioactivity detector.The resolving power (~1.5mmFWHM), sensitivity (~10 1Bq/cm2),efficiency (~10%)and uniformity (~4%)of the detection system are shown and "electronic autoradiograins" of normal and mutant cultures are presented; cells, rescued after the radioactivity measurement, retain their cloning ability.

Abstract A large quantity of silicon microstrip detectors is foreseen to be used as part of the CMS tracker. A specific research and development program has been carried out with the aim of defining layouts and technological solutions suitable for the use of silicon detectors in high radiation environment. Results presented here summarise this work on many research areas such as techniques for device manufacturing, pre- and post-irradiation electrical characterization, silicon bulk defects analysis and simulations, system performance analytical calculations and simulations and test beam analysis. As a result of this work we have chosen to use single-sided, AC-coupled, poly silicon biased, 300 μm thick, p + on n substrate detectors. We feel confident that these devices will match the required performances for the CMS tracker provided they can be operated at bias voltages as high as 500 V. Such high-voltage devices have been succesfully manufactured and we are now concentrating our efforts in enhancing yield and reliability.

The breakdown performance of CMS barrelmodule prototype detectors and test devices with single and multi-guard structures were studied before and after neutron irradiation up to 2·1014 1 MeV equivalent neutrons. Before irradiation avalanche breakdown occurred at the guard ring implant edges. We measured 100–300 V higher breakdown voltage values for the devices with multi-guard than for devices with single-guard ring. After irradiation and type inversion the breakdown was smoother than before irradiation and the breakdown voltage value increased to 500–600 V for most of the devices.

The decision taken by the CMS experiment to build a tracker entirely based on silicon detectors has made necessary the use of thicker sensors instead of the usual 300-/spl mu/m sensors for the outer part of the detector. We first present results on the performance of 500-/spl mu/m-thick detectors, before and after neutron irradiation, bonded to the CMS tracker front-end electronics. Laboratory measurements show that the total collected charge scales linearly with thickness when compared with a 300-/spl mu/m module, and the measured noise is in good agreement with expectations. The results obtained confirm the feasibility of large-area silicon trackers.

We present the status of the CMS experiment at the LHC and the highlights of its first physics results.Using pp collisions at centre-of-mass energy of 7 TeV, about 303nb -1 of integrated luminosity have been collected by CMS out of a total of about 346nb -1 delivered by LHC.We report on the performance of the trigger and the data acquisition systems, on the commissioning of the main detector components and on the physics objects and tools.The first physics measurements performed on these data are then described.We present results on charged hadrons multiplicities, inclusive jet cross section and measurements of the J/ψ and ϒ differential cross section as a function of p T .We then show results on W and Z bosons, including measurements of their production cross sections.Lastly we present the first observation of top quark pairs produced at the LHC and identified both in single-lepton and di-lepton decay channels.

Double-sided silicon detector prototypes produced for the CMS inner tracker are described which divide the n-side into pads rather than strips. The signal routing to the readout electronics is made on a separate flexible z-print which is glued on the detector and then wire-bonded to the pads.

This paper investigates the performance of 500μm thick silicon microstrip detectors before and after heavy irradiation. Prototype sensors, produced by STMicroelectronics, have been extensively studied using laboratory measurements, a radioactive source and a beam of minimum ionising particles. The comparison with a standard 300μm sensor shows that the collected charge in thick devices scales linearly with thickness. By over-depleting the irradiated devices, the pre-irradiated charge collection efficiency is fully recovered. The measured noise is in good agreement with expectations. Although more work is needed, the paper shows that 500μm thick devices are a promising technology for very large tracking systems.

In principio era il vuoto. Che non e il nulla, ma uno stato di energia minima, in cui non c’e alcuna forma di materia, che non e attraversato da particelle elementari e non contiene campi di alcun genere, ma che passa attraverso una sequenza interminabile di fluttuazioni, piccole oscillazioni casuali che lo fanno brulicare incessantemente. L’insieme delle osservazioni effettuate negli ultimi decenni sembra convergere verso la conclusione, tutt’altro che scontata, che tutto ha avuto origine proprio da una di queste minuscole fluttuazioni del vuoto.

Chronos, die personifizierte Zeit, ist ein Rätsel, nicht nur für Physiker. Von Newton bis Hamlet, von Einstein bis Dalí ist sie der Protagonist so faszinierender wie schwindelerregender Spekulationen. Können wir das unaufhaltsame Voranschreiten der Zeit jemals zum Stillstand bringen? Lässt sich der Zeitpfeil umdrehen? Hat die Zeit tatsächlich eine eigene Existenz oder ist sie nur eine riesige Illusion? Der Physiker und Schriftsteller Guido Tonelli erzählt in einem spektakulären Buch die lange Geschichte der Zeit, ihre rasende Geburt und bizarre Entwicklung.

Abstract Two small dimension multicell Cherenkov counters have been built for FRAMM-NA1 multiparticle spectrometer to identify pions and kaons in the momentum range between 5 and 22 GeV/c. The performances achieved and the construction details are reported.

Abstract A large use of silicon microstrip detectors is foreseen for the intermediate part of the CMS tracker. A specific research and development program has been carried out with the aim of finding design layouts and technological solutions for allowing silicon microstrip detectors to be reliably used on a high radiation level environment. As a result of this work single sided, AC-coupled, polysilicon biased, 300 μ m thick, p + on n substrate detectors were chosen. Irradiation tests have been performed on prototypes up to fluence 2×10 14  n/cm 2 . The detector performances do not significantly change if the detectors are biased well above the depletion voltage. S / N is reduced by less than 20%, still enough to insure a good efficiency and space resolution. Multiguard structures has been developed in order to reach high voltage operation (above 500 V).

We report the results of test beams performed at CERN using irradiated microstrip silicon detectors. The detectors were single- and double-sided devices, produced by different manufacturers and irradiated with neutrons at various fluences up to 3.6 × 1013 n/cm2. Signal-to-noise ratio, resolution and efficiency were studied for different values of the incidence angle, of the detector temperature and of the read-out pitch, as a function of the detector bias voltage. The goal of these tests was to optimize the design of the final prototypes for the CMS Silicon Strip Tracker.

and buildup factors for l-Mev-source gamma rays in water and 6-Mev-source gamma rays in tin at various penetration depths. These calculations were done both with and without inclusion of the importance sampling. Comparisons were made with moments- method solutions for the same problems; the agreement was good at shallow penetrations in both cases. In addition, deep penetration results, at 7 and l0 source energy relaxation lengths, obtained by importance sampling also agreed well with moments-method solutions. A low-energy spectral peak was observed in the Monte Carho calculation for the case of 6-Mev gamma rays in tin; this is due to gamma rays from pair-production positron annihilation and is not present in the momentsmethod results, which do not include the effects of pair production. Calculations of neutron number spectra for 6-Mevsource neutrons at various penetration depths in water showed good agreement with nioments-method results. Importance sampling became necessary to produce reasonable agreement at penetration distances greater than 30 centimeters. Monte Carlo results were rehiabhe to as deep a penetration as 90 centimeters, or 12 source energy mean free paths. (auth)

An important tool for the discovery of new physics at LHC is the design of a low level trigger with an high power of background rejection. The contribution of pixel detector to the lowest level trigger at CMS is studied focusing on low-energy jet identification, matching the information from calorimeters and pixel detector. In addition, primary vertex algorithms are investigated. The performances are evaluated in terms of, respectively, QCD rejection and multihadronic jets final states efficiency.

Many implications of the discovery of the Higgs boson are discussed, together with a short overview of the new challenges in particle physics. The paper also presents a non-exhaustive review of the current plans in the quest for physics beyond the Standard Model at high-energy accelerators.

Condividere i risultati con gli altri, attenersi ai fatti, essere pronti a cambiare idea, premiare chi ammette di aver sbagliato: sono le regole di base dell’impresa scientifica, specie quando parliamo di esperimenti enormi, che coinvolgono migliaia di ricercatori in tutto il mondo. Come quello che ha portato alla scoperta del bosone di Higgs, di cui era responsabile l’italiano Guido Tonelli. Che dopo molti anni di lavoro, grandi successi ma anche qualche difficolta, confessa: “Mi diverto ancora moltissimo”.