W and Z Cross Sections at the Tevatron

The CDF and D0 experiments at the Tevatron have used p-pbar collisions at sqrt(s)=1.96 TeV to measure the cross section of W and Z boson production using several leptonic final states. An indirect measurement of the total W width has been extracted, and the lepton charge asymmetry in Drell-Yan production has been studied up to invariant masses of 600 GeV/c^2.Comment: 4 pages, 6 figures, proceedings of Moriond QCD 2003, Les Arcs 22-29 march 2003, to be published by World Scientific (ed. T.T.Vanh

Recent Results of the CMS Experiment

The CMS collaboration has recently produced results of a number of searches for new physics processes using data collected during the 2011 run of the Large Hadron Collider. Up to 5 inverse femtobarns of proton-proton collisions at 7 TeV centre-of-mass energy have been used to search for the standard model Higgs boson in five different decay modes, divided in 42 independent sub-channels. The combination of the results has allowed CMS to set 95% confidence-level limits on the Higgs boson mass, constraining it to lay in the region 114.4600 GeV. An excess of events with a local significance of 3.1 standard deviations is observed for M(H)=124 GeV; the global significance of observing such an effect anywhere in the search range 110-600 GeV is estimated to be 1.5 standard deviations. A number of signatures of supersymmetric particles have also been investigated, significantly restricting the parameter space of natural low-scale theories. A search for the rare decays of neutral bottom mesons to muon pairs, Bs to mu mu and Bd to mu mu, has achieved the tightest limits to date, and is approaching the sensitivity to measure the standard model branching ratios. As it happens, though, the highly informative results extracted from 2011 data produce more questions than answers; this doubles expectations for the 2012 run of LHC, which will conclusively answer several of them.Comment: 33 pages, 20 figures. Contribution to the Proceedings of the 50th International Winter Meeting on Nuclear Physics, Bormio (Italy) 23-27 January 201

Observation of Z Decays to b Quark Pairs at the Tevatron Collider

A search for Z boson decays to pairs of b-quark jets has been performed in the full dataset collected with the CDF detector at the Tevatron proton-antiproton collider. After the selection of a pure sample of bb events by means of the identification of secondary vertices from b-quark decays, we have used two kinematic variables to further discriminate the electroweak bb production from QCD processes, and sought evidence for the Z decay in the dijet invariant mass distribution. An absolute background prediction allows the extraction of an excess of events inconsistent with the background predictions by 3.23 sigma but in good agreement with the amount and characteristics of the expected signal. We then fit the mass distribution with an unbinned likelihood technique, and obtain a Z -> bb signal amounting to 91+-30+-19 events.Comment: 12 pages, 8 .eps figure

Recent CMS Results

The CMS experiment obtained a large number of groundbreaking results from the analysis of 7- and 8-TeV proton-proton collisions produced so far by the Large Hadron Collider at CERN. In this brief summary only a sample of those results will be discussed. A new particle with mass m(H) = 125.3 +- 0.4(stat.) +- 0.5(syst.) GeV and characteristics compatible with those expected for a standard model Higgs boson has been observed in its decays to photon pairs, WW pairs, and ZZ pairs. Searches for the rare decays B_d -> mu mu and B_s -> mu mu have allowed to set limits on the branching fractions which are close to standard model predictions, strongly constraining new physics models. The top quark has been studied with great detail, obtaining among other results the world's best measurement of its mass as m(top) = 173.49 +- 0.43(stat. + JES) +- 0.98(syst.) GeV. New physics models have been strongly constrained with the available data.Comment: 13 pages. Proceedings of the 1st International Conference on Frontier Physics, Kolymbari, Crete (GR) June 201

The Inverse Bagging Algorithm: Anomaly Detection by Inverse Bootstrap Aggregating

For data sets populated by a very well modeled process and by another process of unknown probability density function (PDF), a desired feature when manipulating the fraction of the unknown process (either for enhancing it or suppressing it) consists in avoiding to modify the kinematic distributions of the well modeled one. A bootstrap technique is used to identify sub-samples rich in the well modeled process, and classify each event according to the frequency of it being part of such sub-samples. Comparisons with general MVA algorithms will be shown, as well as a study of the asymptotic properties of the method, making use of a public domain data set that models a typical search for new physics as performed at hadronic colliders such as the Large Hadron Collider (LHC).Comment: 8 pages, 5 figures. Proceedings of the XIIth Quark Confinement and Hadron Spectrum conference, 28/8-2/9 2016, Thessaloniki, Greec

Geometry optimization of a muon-electron scattering detector

Abstract A high-statistics determination of the differential cross section of elastic muon-electron scattering as a function of the transferred four-momentum squared, d σ e l ( μ e → μ e ) / d q 2 , has been argued to provide an effective constraint to the hadronic contribution to the running of the fine-structure constant, Δ α h a d , a crucial input for precise theoretical predictions of the anomalous magnetic moment of the muon. An experiment called ''MUonE'' is being planned at the north area of CERN for that purpose. We consider the geometry of the detector proposed by the MUonE collaboration and offer a few suggestions on the layout of the passive target material and on the placement of silicon strip sensors, based on a fast simulation of elastic muon-electron scattering events and the investigation of a number of possible solutions for the detector geometry. The employed methodology for detector optimization is of general interest as it may be applied to the design of task-specific detectors for high-energy physics, nuclear physics, and astro-particle physics applications

Hadron Collider Searches for Diboson Resonances

This review covers results of searches for new elementary particles that decay into boson pairs (dibosons), performed at the CERN Large Hadron Collider in proton-proton collision data collected by the ATLAS and CMS experiments at 7-, 8-, and 13-TeV center-of-mass energy until the year 2017. The available experimental results of the analysis of final states including most of the possible two-object combinations of W and Z bosons, photons, Higgs bosons, and gluons place stringent constraints on a variety of theoretical ideas that extend the standard model, pushing into the multi-TeV region the scale of allowed new physics phenomena.Comment: 76 pages, 16 figures. To be published in Progress of Particle and Nuclear Physic