Catherine Vander Velde

Study of hadronic decays of the Z0 boson

Abstract Hadronic decays of Z 0 bosons are studied in the Delphi detector. Global event variables and singel particles inclusive distributions are compared with QCD-based predictions. The mean charged multiplicity is found to be 20.6±1.0 (stat+syst). The mean values of the sphericity, aplanarity, thrust, minor value, p in T and p out T are compared with values found at lower energy e + e − colliders.

Limits on neutrino oscillations from a study of νe charged current interactions

Abstract We have fully analysed all events with a single electron obtained in an exposure of BEBC to the 350 GeV wide-band neutrino beam at CERN. The data agrees well with expectations based on the calculated ν e flux and assuming μ−e universality. Using both the rate and the kinematic distributions, improved limits are set on ν e → ν X , ν μ → ν e , ν μ → ν τ mixing.

First observation of the production and decay of the Σc

Abstract An event with the decay chain Σ c + → Λ c + + π 0 , Λ c + → K − + p + π + , has been observed in an exposure of BEBC, equipped with a track sensitive target, to the wide band neutrino beam from the SPS at CERN. The event has a unique three constraint kinematic fit to the ΔS = − ΔQ reaction v + p → μ − + p + K − + π + + π + + π 0 with both gammas from the π 0 decay detected. The proton and other final state particles are identified. The masses are M ( Λ c + ) = 2290 ± 3 MeV/ c 2 , M ( Σ c + ) = 2457 ± 4 MeV/ c 2 and M ( Σ c + ) − M ( Λ c + ) = 168 ± 3 MeV/ c 2 . Including other data one obtains M ( Σ c ++ ) − M ( Σ c + ) = 0 ± 4 MeV/ c 2 .

Positron production by muon neutrinos BEBC filled with a neon-hydrogen mixture

Abstract For e + energy > 0.3 GeV and 10 GeV ƒ = (v μ + Ne → μ − e + )/(v μ + Ne → μ − ) = (0.41 ± 0.15)% ; (ii) 1.2 ± 0.5 neutral strange particles are produced per μ − e + event; (iii) the lifetime of possible positron-parent particles is −10 s (90% C.L.); (iv) the cross section for direct e + production via the neutral current is + , decaying into e + … is −3 times that for μ − production, implying M (L + ) > 10 GeV.

Measurement of the tt̄ production cross section in the dilepton channel in pp collisions at √s = 8 TeV

The top-antitop quark (tt) production cross section is measured in proton-proton collisions at √ s = 8 TeV with the CMS experiment at the LHC, using a data sample corresponding to an integrated luminosity of 5.3 fb−1. The measurement is performed by analysing events with a pair of electrons or muons, or one electron and one muon, and at least two jets, one of which is identified as originating from hadronisation of a bottom quark. The measured cross section is 239± 2 (stat.)± 11 (syst.)± 6 (lum.) pb, for an assumed top-quark mass of 172.5 GeV, in agreement with the prediction of the standard model. Published in the Journal of High Energy Physics as doi:10.1007/JHEP02(2014)024. c

Measurement of the ZZ production cross section and Z → ℓ+ℓ−ℓ′+ℓ′− branching fraction in pp collisions at s=13 TeV

A bstractThis paper describes the search for a high-mass narrow-width scalar particle decaying into a Z boson and a photon. The analysis is performed using proton-proton collision data recorded with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 fb−1, respectively. The Z bosons are reconstructed from opposite-sign electron or muon pairs. No statistically significant deviation from the standard model predictions has been found in the 200-2000 GeV mass range. Upper limits at 95% confidence level have been derived on the product of the scalar particle production cross section and the branching fraction of the Z decaying into electrons or muons, which range from 280 to 20 fb for resonance masses between 200 and 2000 GeV.

Search for massive resonances decaying into pairs of boosted bosons in semi-leptonic final states at (Formula presented.) = 8 TeV

A bstractA search for new resonances decaying to WW, ZZ, or WZ is presented. Final states are considered in which one of the vector bosons decays leptonically and the other hadronically. Results are based on data corresponding to an integrated luminosity of 19.7 fb−1 recorded in proton-proton collisions at s

Search for B 0 s →μ + μ − and B 0 →μ + μ − decays

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