Gauge Boson Self Couplings and four fermion final states at LEP

Four-fermion productions measured in the LEP2 data are reviewed. The total and differential cross-section yields represent the first clear evidence for the existence of gauge boson self couplings, in support of the non-abelian SU(2)xU(1) structure of the electroweak model, at the percent level.Comment: 4 pages, 3 figures. To appear in the Proceedings of 'XV IFAE - Incontri sulla Fisica delle Alte Energie', 23-26 April 2003, Lecce, Ital

Studies of Fragmentation and Colour Reconnection at LEP

Hadronic events at the Z pole have been investigated in search for Colour Reconnection effects and QCD coherence. Colour Reconnection effects are searched for in three-jet events and the data results are compared to the predictions of different Monte Carlo models. QCD colour coherence effects are tested through the multiplicity distributions of hadrons with restricted momenta, and the LEP1 e+e- data is compared to HERA e+p data under the equivalence assumption of the e+e- hemisphere with the current region of the Breit frame of reference.Comment: 4 pages, 4 figures, contribution to ICHEP06 proceeding

Four-fermion final states in e+e- collisions at LEP2

The measurements of four-fermion production rates performed at LEP2 in e+e- collisions at centre-of-mass energies ranging from 161 to 209 GeV are presented. The focus is put on processes that involve the production and decay of W or Z electroweak bosons. Results on W decay rates and couplings are also discussed.Comment: 5 pages, 3 figures. To appear in the Proceedings of 'XIV IFAE - Incontri sulla Fisica delle Alte Energie', 3-5 April 2002, Parm

Physics Behind Precision

This document provides a writeup of contributions to the FCC-ee mini-workshop on "Physics behind precision" held at CERN, on 2-3 February 2016.Comment: https://indico.cern.ch/event/469561

Measurements of the properties of the Higgs-like boson with the CMS experiment at the LHC

Measurements of the properties of the recently discovered Higgs-like boson are presented using data samples recorded by the CMS experiment corresponding to integrated luminosities of up to 5.1 fb−1 at 7TeV and up to 12.2 fb−1 at 8TeV in proton proton collisions at the LHC. The results combine decay modes in pairs of photons, Z bosons, W bosons, tau leptons and b quarks. The mass of the boson is determined to be 125.8 ± 0.4 (stat.) ± 0.4 (syst.)GeV, and the signal strength at the measured mass is μ = 0.88 ± 0.21, normalized to the standard model expectation. Combined results on couplings, spin and parity reveal a broad agreement with the expectations of a standard model Higgs boson

Dark matter searches at LHC

Besides Standard Model measurements and other Beyond Standard Model studies, the ATLAS and CMS experiments at the LHC will search for Supersymmetry, one of the most attractive explanation for dark matter. The SUSY discovery potential with early data is presented here together with some first results obtained with 2010 collision data at 7 TeV. Emphasis is placed on measurements and parameter determination that can be performed to disentangle the possible SUSY models and SUSY look-alike and the interpretation of a possible positive supersymmetric signal as an explanation of dark matter.Comment: 15 pages, 14 figures, Invited plenary talk given at DISCRETE 2010: Symposium On Prospects In The Physics Of Discrete Symmetries, 6-11 Dec 2010, Rome, Ital

Precision measurements of the top quark mass from the Tevatron in the pre-LHC era

The top quark is the heaviest of the six quarks of the Standard Model. Precise knowledge of its mass is important for imposing constraints on a number of physics processes, including interactions of the as yet unobserved Higgs boson. The Higgs boson is the only missing particle of the Standard Model, central to the electroweak symmetry breaking mechanism and generation of particle masses. In this Review, experimental measurements of the top quark mass accomplished at the Tevatron, a proton-antiproton collider located at the Fermi National Accelerator Laboratory, are described. Topologies of top quark events and methods used to separate signal events from background sources are discussed. Data analysis techniques used to extract information about the top mass value are reviewed. The combination of several most precise measurements performed with the two Tevatron particle detectors, CDF and \D0, yields a value of \Mt = 173.2 \pm 0.9 GeV/$c^2$.Comment: This version contains the most up-to-date top quark mass averag

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s) = 1.96 TeV

We present a measurement of the top quark pair production cross section in ppbar collisions at sqrt(s)=1.96 TeV using 318 pb^{-1} of data collected with the Collider Detector at Fermilab. We select ttbar decays into the final states e nu + jets and mu nu + jets, in which at least one b quark from the t-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of 178 GeV/c^2, we measure a cross section of 8.7 +-0.9 (stat) +1.1-0.9 (syst) pb. We also report the first observation of ttbar with significance greater than 5 sigma in the subsample in which both b quarks are identified, corresponding to a cross section of 10.1 +1.6-1.4(stat)+2.0-1.3 (syst) pb.Comment: Accepted for publication in Physics Review Letters, 7 page