L. Malgeri

A bstract The discovery by the ATLAS and CMS experiments of a new boson with mass around 125 GeV and with measured properties compatible with those of a Standard-Model Higgs boson, coupled with the absence of discoveries of phenomena beyond the Standard Model at the TeV scale, has triggered interest in ideas for future Higgs factories. A new circular e + e − collider hosted in a 80 to 100 km tunnel, TLEP, is among the most attractive solutions proposed so far. It has a clean experimental environment, produces high luminosity for top-quark, Higgs boson, W and Z studies, accommodates multiple detectors, and can reach energies up to the $$ \mathrm{t}\overline{\mathrm{t}} $$ threshold and beyond. It will enable measurements of the Higgs boson properties and of Electroweak Symmetry-Breaking (EWSB) parameters with unequalled precision, offering exploration of physics beyond the Standard Model in the multi-TeV range. Moreover, being the natural precursor of the VHE-LHC, a 100 TeV hadron machine in the same tunnel, it builds up a long-term vision for particle physics. Altogether, the combination of TLEP and the VHE-LHC offers, for a great cost effectiveness, the best precision and the best search reach of all options presently on the market. This paper presents a first appraisal of the salient features of the TLEP physics potential, to serve as a baseline for a more extensive design study.

This document a outlines a set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these simplified models have when applied to dark matter searches at the LHC, and to provide a number of useful expressions for reference. The list of models includes both s-channel and t-channel scenarios. For s-channel, spin-0 and spin-1 mediations are discussed, and also realizations where the Higgs particle provides a portal between the dark and visible sectors. The guiding principles underpinning the proposed simplified models are spelled out, and some suggestions for implementation are presented.

The two-jet invariant mass spectrum as measured in the UA2 experiment is used to search for additional heavy vector bosons decaying to two-jets. The mass of an additional W boson that couples to fermions with a V+A form is constrained to be greater than 261 GeV to the 90% confidence level. A limit on the production cross section of additional W and Z bosons is given as a function of the boson mass. A limit on the production of excited quarks is also given as a function of the excited quark mass.

An initial measurement of the lifetime of the positive muon to a precision of 16 parts per million (ppm) has been performed with the FAST detector at the Paul Scherrer Institute. The result is tau_mu = 2.197083 (32) (15) microsec, where the first error is statistical and the second is systematic. The muon lifetime determines the Fermi constant, G_F = 1.166353 (9) x 10^-5 GeV^-2 (8 ppm).

A measurement of the cross-sections for single and double prompt photon production in pp interactions at s = 630GeV is presented. The data sample corresponds to an integrated luminosity of 13.2 pb−1. The results are in good agreement with the predictions of perturbative QCD. The signal from double prompt photon production has a statistical significance of 4.3 standard deviations.

The process t→H+b, H+→τ+v, τ+→hadrons+v and its charge conjugate are investigated by seeking an excess in number of observed τ's beyond that expected from the standard model under the assumption of e-τ universality. No such excess is found and new regions of the mH−mt plane are excluded for B(H+→τv) = 0.5 and 1.0. In addition, the ratio of couplings of the τ and e to the W is precisely measured as gwτ/gwe = 1.02 ± 0.04(stat.)±0.04(syst.).

A measurement of the gluon structure fusion using direct photon events observed with the UA2 detector in pp collisions at √s=630 GeV is presented. The x-range covered by this analysis is between 0.049 and 0.207 and the Q2 range is between 280 GeV2 and 3670 GeV2. The data sample corresponds to an integrated luminosity of 7.14 pb−1. The results are found to be in good agreement with the gluon distributions measured in deep inelastic scattering experiments extrapolated to the UA2 Q2 values.

The CMS Electromagnetic crystal Calorimeter (ECAL) must be precisely inter-calibrated if its full potential performance is to be realized.In this note, a detailed Monte Carlo study of in-situ intercalibration of the ECAL crystals using isolated electrons is described.The achievable precision depends on the quality and number of available electrons per crystal.This in turn depends upon the position of the crystals and the corresponding thickness of material in front of the ECAL.

The CMS CERN Analysis Facility (CAF) was primarily designed to host a large variety of latency-critical workflows. These break down into alignment and calibration, detector commissioning and diagnosis, and high-interest physics analysis requiring fast-turnaround. In addition to the low latency requirement on the batch farm, another mandatory condition is the efficient access to the RAW detector data stored at the CERN Tier-0 facility. The CMS CAF also foresees resources for interactive login by a large number of CMS collaborators located at CERN, as an entry point for their day-by-day analysis. These resources will run on a separate partition in order to protect the high-priority use-cases described above. While the CMS CAF represents only a modest fraction of the overall CMS resources on the WLCG GRID, an appropriately sized user-support service needs to be provided. We will describe the building, commissioning and operation of the CMS CAF during the year 2008. The facility was heavily and routinely used by almost 250 users during multiple commissioning and data challenge periods. It reached a CPU capacity of 1.4MSI2K and a disk capacity at the Peta byte scale. In particular, we will focus on the performances in terms of networking, disk access and job efficiency and extrapolate prospects for the upcoming LHC first year data taking. We will also present the experience gained and the limitations observed in operating such a large facility, in which well controlled workflows are combined with more chaotic type analysis by a large number of physicists.

On July 4, 2012, the discovery of a new boson, with mass around 125 GeV/c2 and with properties compatible with those of a standard-model Higgs boson, was announced at CERN. In this context, a high-luminosity electron-positron collider ring, operating in the LHC tunnel at a centre-of-mass energy of 240 GeV and called LEP3, becomes an attractive opportunity both from financial and scientific point of views. The performance and the suitability of the CMS detector are evaluated, with emphasis on an accurate measurement of the Higgs boson properties. The precision expected for the Higgs boson couplings is found to be significantly better than that predicted by Linear Collider studies.

The Fibre Active Scintillator Target (FAST) experiment at the Paul Scherrer Institute (PSI) is designed for a high-precision measurement of the μ+ lifetime, in the order of a few parts per million. This paper describes the design, construction and performance of the FAST detector and its readout electronics, trigger and data acquisition system.

The four LEP experiments ALEPH, DELPHI, L3 and OPAL successfully recorded e+e- collision data during the years 1989 to 2000. As part of the ordinary evolution in High Energy Physics, these experiments can not be repeated and their data is therefore unique. This article briefly reviews the data preservation efforts undertaken by the four experiments beyond the end of data taking. The current status of the preserved data and associated tools is summarised.

This note presents a combination of published and preliminary electroweak results from the four LEP collaborations and the SLD collaboration which were prepared for the 2004 summer conferences. Averages from Z resonance results are derived for hadronic and leptonic cross sections, the leptonic forward-backward asymmetries, the {tau} polarization asymmetries, the b{bar b} and c{bar c} partial widths and forward-backward asymmetries and the q{bar q} charge asymmetry. Above the Z resonance, averages are derived for di-fermion cross sections and forward-backward asymmetries, photon-pair, W-pair, Z-pair, single-W and single-Z cross sections, electroweak gauge boson couplings, W mass and width and W decay branching ratios. Also, an investigation of the interference of photon and Z-boson exchange is presented, and colour reconnection and Bose-Einstein correlation analyses in W-pair production are combined. The main changes with respect to the experimental results presented in summer 2003 are updates to the W branching fractions and four-fermion cross sections measured at LEP-2, and the SLD/LEP heavy-flavour results measured at the Z pole. The results are compared with precise electroweak measurements from other experiments, notably the final result on the electroweak mixing angle determined in neutrino-nucleon scattering by the NuTeV collaboration, the latest result in atomic parity violation in Caesium, and the measurement of the electroweak mixing angle in Moller scattering. The parameters of the Standard Model are evaluated, first using the combined LEP electroweak measurements, and then using the full set of high-Q{sup 2} electroweak results.

The Fibre Active Scintillator Target (FAST) experiment is a novel imaging particle detector currently operating in a high-intensity π+ beam at the Paul Scherrer Institute (PSI), Villigen, Switzerland. The detector is designed to perform a high precision measurement of the μ+ lifetime, in order to determine the Fermi constant, Gf, to 1 ppm precision. A dedicated second level (LV2) hardware trigger system has been developed for the experiment. It performs an online analysis of the π/μ decay chain by identifying the stopping position of each beam particle and detecting the subsequent appearance of the muon. The LV2 trigger then records the muon stop pixel and selectively triggers the Time-to-Digital Converters (TDCs) in the vicinity. A detailed description of the trigger system is presented in this paper.

The Fiber Active Scintillator Target (FAST) is an imaging particle detector intended for high precision muon lifetime measurement. This measurement will lead to a determination of the Fermi coupling constant (C,) with an uncertainty of Ippm, one order of magnitude better than the current world average. This contribution presents a description of the detector instrumentation and the first results, which have validated the design of the system.

The four LEP experiments ALEPH, DELPHI, L3 and OPAL successfully recorded e+e- collision data during the years 1989 to 2000. As part of the ordinary evolution in High Energy Physics, these experiments can not be repeated and their data is therefore unique. This article briefly reviews the data preservation efforts undertaken by the four experiments beyond the end of data taking. The current status of the preserved data and associated tools is summarised.

In five years of running at energies above WW and ZZ production thresholds, LEP-II provided each experiment an integrated luminosity of ∼ 700 pb−1. The collected statistics allows to measure with high precision the total e+e− → WW, ZZ, and γγ cross sections. Derived quantities as leptonic and hadronic branching fractions of the W boson, differential distributions of the polar scattering angle and constraints on new physics are also herein reported. All results, unless differently stated, have to be considered preliminary.

The measurements of W-pair cross sections performed by the L3 experiment at the LEP collider are herein reported. The statistics collected in the period 1996-2000 amounts to more than 8000 events distributed over a large center-of-mass energy range: 161–208 GeV. From the cross section measurements, also the W branching fractions in leptons and hadrons are derived with a percent precision: BR ( W → qq) = 68.47 ± 0.49 ± 0.33% and BR ( W → ℓν) = 10.51 ± 0.16 ± 0.11%. The improving statistical accuracy of the measurements is now approaching the systematic uncertainties. Further studies, necessary also for the W mass determination, will be needed in the near future to keep them under control.

The reaction e + e -→ e + e -γ * γ * → e + e -hadrons for quasi-real photons is studied at LEP using data from √ s = 130 GeV up to 202 GeV.Results on the total cross sections σ(e + e -→ e + e -hadrons) and σ(γγ → hadrons) are obtained for the two-photon centre-of-mass energies ranging in 5 GeV ≤ W γγ ≤ 185 GeV.A steeper rise with the twophoton centre-of-mass energy as compared to the hadron-hadron and the photon-proton cross sections is observed.Several theoretical models have also been tested.