122073109
A check of quantum electrodynamics and of electron-muon equivalence
SummaryA study of the timelike reaction e+e-→μ∓μ± and of its comparison with the spacelike dominated reaction e+e−→e±e± allows us to establish the validity of QED in terms of production angular distributions, absolute rates, energy dependence and angular correlations between the pair of final-state leptons, in two very different ranges of invariant four-momentum transfer. No sign of QED break is detected in the electromagnetic interaction of leptons and the muon behaves like a heavy electron, within the accuracy of the present investigation.RiassuntoSi è compiuto uno studio della reazione «timelike» e+e-→μ∓μ± ed un confronto di questa con la reazione e+e−→e±e± nella quale la parte «spacelike» è dominante. Si sono studiate le distribuzioni angolari delle particelle prodotte, la loro dipendenza dall'energia, le correlazioni geometriche fra le coppie di leptoni nello stato finale, i valori assoluti delle sezioni d'urto, al fine di stabilire la validità dell'elettrodinamica quantica in due intervalli diversi di quadrimomento trasferito. Entro gli errori sperimentali (±8%) non si trova alcuna evidenza di violazione della elettrodinamica quantica nell'interazione elettromagnetica dei leptoni, ed il muone si comporta come un elettrone pesante.РезюмеИсследование времениподобной реакции e+e-→μ∓μ± и ее сравнение с пространственноподобной доминирующей реакцией e+e−→e±e± позволяет нам установить справедливость квантовой электродинамики в терминах угловых распределений рождения, авсолютных интенсивностей, энергетической зависимости и углобых корреляций между парами лептонов в конечном состоянии, в двух очень различиых областях инвариантного четырехмерного передаваемого импульса. Не определен знак нарушения квантовой электродинамики и мюон ведет себя подобно тяжелому электрону в пределах точности настоящего исследования.
120972616
A limited-streamer tube electron detector with high rejection power against pions
Abstract The problem of detecting electrons in the 0.5–4.0 GeV energy range, in the presence of a high pion background, has been studied using a new type of electromagnetic shower detector. Its structural properties and the main parameters are given, together with the basic results in terms of energy resolution and of rejection power against pion background. The optimization of this new instrument gives a pion rejection power of ∼ 6 × 10 −4 for energy ≳ 1.2 GeV.
122652831
Results of a search for free quarks with a large avalanche chamber in high-energy neutrino interactions
SummaryA search for free quarks liberated via neutrino-quark coupling using the highest possible available energy was performed at CERN (WA-44 experiment) in the neutrino wide-band beam. The neutrino interactions take place in a 23 ton lead target. A forward large avalanche chamber is triggered when one or more charged particles from the neutrino (antineutrino) interactions cross two sets of counter hodoscopes. Ionization measurements in the avalanche chamber have been performed using two measuring machines: HPD in Bologna and PERPR in Frascati. The 6% expected statistical fluctuations in the ionization measurements have been obtained on one metre long tracks. This allowed an accurate analysis of the data to search in the 1/3 and even in the 2/3 charge regions. About 3.7·105 tracks were observed in the chamber, from about 105 neutrino (antineutrino) interactions. The analysis of the digitized data has selected 20 candidates for fractional charges. After a detailed analysis of both pictures and measurements, and a complete investigation of all possible instrumental effects, one event remains as a fractional charge (+1/3) candidate. This candidate has a small probability to be an edge effect in the apparatus. However this event is at the expected level of candidate events from the rejection power of our detector. Upper limits (90% c.l.) on the flux of quarks produced in both neutrino and antineutrino interactions are at the level of a few 10−5.
14861104
The AMS-02 Time of Flight System. Final Design
The AMS-02 detector is a superconducting magnetic spectrometer that will operate on the International Space Station. The time of flight (TOF) system of AMS-02 is composed by four scintillator planes with 8, 8, 10, 8 counters each, read at both ends by a total of 144 phototubes. This paper describes the new design, the expected performances, and shows preliminary results of the ion beam test carried on at CERN on October 2002.
121671301
A large-area modular electromagnetic shower detector for the CERN intersecting storage rings
Abstract We describe the design and performances of a large-area (13 m 2 ) shower detector built for an experiment at the CERN ISR to detect electrons and gamma rays with energies up to 4 GeV. The main characteristics of the detector are: a) linearity of the energy response from 0.5 to 4 GeV; b) good energy, time and space resolutions; c) modularity of the mechanical assembly; d) low cost of construction.
124305736
Search for fractionally charged particles produced in proton-proton collisions at the highest ISR energy
SummaryThe results of an experiment to search for quarks at the CERN ISR, at a total centre-of-mass energy √s=62.2 GeV, are reported. The experiment was sensitive to fractionally charged particles with 0.035e≤|Q|≤0.67e, β=v/c≥0.1 and masses up to 26 GeV/c2. The 90% confidence level on the ratio «quark flux/charged flux» is 1.78·10−9 forQ=+(1/3)e and 1.05·10−9 forQ=−(1/3)e. These values hold true for production processes with transverse momentap⊥≃0.4 GeV/c.RiassuntoSi presentano i risultati di un esperimento per la ricerca di quarks presso gli ISR del CERN, ad un valore dell'energia totale nel centro di massa √s=62.2 GeV. L'esperimento era sensibile a particelle con carica frazionaria nell'intervallo 0.035e≤|Q|≤0.67e, con β=v/c≧0.1 e masse fino a 26 GeV/c2. Il valore del rapporto «flusso di quarks/flusso di particelle cariche», con un livello di confidenza del 90%, è 1.78·10−9 perQ=+(1/3)e, e 1.05·10−9 perQ=−(1/3)e. Questi valori si applicano a processi di produzione con impulsi trasversip⊥≃0.4 GeV/c.
119968739
CMS Silicon Strip Tracker Commissioning and Preliminary Performances
The Silicon Strip Tracker (SST) of the Compact Muon Solenoid (CMS) Experiment at the CERN Large Hadron Collider (LHC) is the world's largest silicon microstrip detector. The SST is composed of four subdetectors which were integrated into the Tracker Support Tube (TST) at the CERN Tracker Integration Facility (TIF) in March 2007. After the insertion of the TST into CMS in December 2007, the first data taking of CMS with the SST included took place in July 2008 without magnetic field and one month later with a magnetic field of 3.8 Tesla. The SST was ready for the LHC start-up of September 10, 2008. The main aspects of the SST commissioning and a description of the problems encountered and solved so far are summarized here together with some preliminary performance evaluation.
121781476
First performance studies of a pixel-based trigger in the CMS experiment
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.
102340714
CMS Tracker, ECAL and Pixel Optical Cabling: Installation and Performance Verification
The installation of 52304 optical links for the readout and control of the CMS Tracker, ECAL and Pixel detectors is complete. 768 96-way optical cables were installed and tested using an optical time-domain reflectometer. The testing was followed by connections at high density optical fibre patchpanels. Finally, a further round of testing and troubleshooting following feedback from system commissioning with the Tracker Data Acquisition was carried out. Over 90% of the faults found were recovered, resulting overall in only 0.1% of dead optical link channels in the CMS Tracker.
123498730
CMS tracker performance
Abstract The Compact Muon Solenoid (CMS) experiment is a multipurpose high energy physics detector operated at the CERN Large Hadron Collider (LHC) near Geneva, Switzerland. The current status and performance of the CMS silicon tracker after 2 years of p–p collisions at s = 7 TeV are reviewed.