Search for R-parity-violating supersymmetry in a final state containing leptons and many jets with the ATLAS experiment using s√=13 TeV proton–proton collision data

A search for R-parity-violating supersymmetry in final states characterized by high jet multiplicity, at least one isolated light lepton and either zero or at least three b-tagged jets is presented. The search uses 139fb−1 of s√=13 TeV proton–proton collision data collected by the ATLAS experiment during Run 2 of the Large Hadron Collider. The results are interpreted in the context of R-parity-violating supersymmetry models that feature gluino production, top-squark production, or electroweakino production. The dominant sources of background are estimated using a data-driven model, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. Machine-learning techniques are used to reach sensitivity to electroweakino production, extending the data-driven background estimation to the shape of the machine-learning discriminant. No significant excess over the Standard Model expectation is observed and exclusion limits at the 95% confidence level are extracted, reaching as high as 2.4 TeV in gluino mass, 1.35 TeV in top-squark mass, and 320 (365) GeV in higgsino (wino) mass

ATLAS Higgs searches in WW and ZZ channels

The most recent ATLAS results on H->diboson channel searches are presented

Measurement of the decay rate of the radiative K-e3(0) decay

Data from the NA31 experiment at CERN have been used to measure the decay KL → π±e∓vy (K0e3γ). 1384 ± 53 events of this decay type have been observed. The decay rate relative to K0e3 is found to be Γ(K0e3γ, E(Black star)γ ≥ 30 MeV, Θ(Black star)e-γ ≥ 20°)/Γ(K0e3) = (0.934 ± 0.036 (stat.) +0.055-0.039 (syst.))% which corresponds to a branching ratio of BR(K0e3γ, E(Black star)γ ≥ 30 MeV, Θ(Black star)e-γ ≥ 20°) = (0.361 ± 0.014(stat.) +0.021-0.015 (syst.))%. The result is in good agreement with theoretical predictions. The decay KL → π±e∓vγ is found to be dominated by internal bremsstrahlung

Measurement of the decay rate of the radiative K-e3(0) decay

Data from the NA31 experiment at CERN have been used to measure the decay KL → π±e∓vy (K0e3γ). 1384 ± 53 events of this decay type have been observed. The decay rate relative to K0e3 is found to be Γ(K0e3γ, E(Black star)γ ≥ 30 MeV, Θ(Black star)e-γ ≥ 20°)/Γ(K0e3) = (0.934 ± 0.036 (stat.) +0.055-0.039 (syst.))% which corresponds to a branching ratio of BR(K0e3γ, E(Black star)γ ≥ 30 MeV, Θ(Black star)e-γ ≥ 20°) = (0.361 ± 0.014(stat.) +0.021-0.015 (syst.))%. The result is in good agreement with theoretical predictions. The decay KL → π±e∓vγ is found to be dominated by internal bremsstrahlung

Measurement of the K-S mean lifetime from pi(+)pi(-) and pi(0)pi(0) decays using K-L decays to determine the acceptance

A precision measurement of the KS mean lifetime has been performed by comparing, in the same experimental setup, the distributions of two-pion decays of neutral kaons produced by high energy proton-beryllium interactions in two targets at a relative distance variable between 112 and 160 m. The value obtained combining the results from π+π- and π0π0 decays is τS = (0.8971 ± 0.0021) 10-10 s. © Springer-Verlag 1997

SEARCH FOR THE DECAY K(L)-]PI(0)PI(0)GAMMA

Data from the NA31 experiment at CERN have been used for a search for the decay mode KL → π0π0γ. After all cuts, three events remain in the signal region with an estimated background of 2.2 ± 0.9 events. The upper limit for the branching ratio of KL→π0π0γ is 5.6×10-6 at the 90% confidence level

A TEST OF CHIRAL PERTURBATION-THEORY FROM THE MEASUREMENT OF THE DECAY KS-]GAMMA-GAMMA

Data from NA31 experiment at CERN have been used to measure the decay KS → γγ. From 69 candidate events of the type K0 → γγ, 52 events can be attributed to KL → γγ and one event is expected from background processes. The ratio of the relative decay widths R = Γ(KS → γγ) Γ(KL → γγ) is measured to be R = 2.2 ± 1.0(stat.) ± 0.3(syst.) ± 0.2(ext.) where the external systematic error is due to the experimental uncertainty in the branching ratio of the decay KL → γγ. This translates into a branching ratio of BR(KS → γγ) = (2.2 ± 1.1) × 10-6. If these data are combined with the published data from an earlier data taking period with the same experiment, the ratio R is determined to be R = 2.35 ± 0.75(stat.) ± 0.4(syst.) + 7.5 · (1 - BR(KL → γγ) 5.86 × 10-4) where the last term accounts for the dependence on the measured KL → γγ branching ratio. The corresponding branching ratio for KS → γγ is BR(KS → γγ) = (2.4 ± 0.9) × 10-6. The measurement is a sensitive test of chiral perturbation theory and in good agreement with theoretical predictions. © 1995

SEARCH FOR THE DECAY K(S)-]PI(0)E+E-

The full data set of the experiment NA31 at CERN has been used to search for the decay Ks→π0e+e-. The rate of this decay may be used to determine the magnitude of the state mixing contribution to the CP violating amplitude of the decay KL→π0e+e-. No candidate events for the decayKs→π0e+- were seen. This leads to a branching ratio upper limit of 1.1 × 10-6 at the 90% confidence level. © 1993

Search for the decay KL→3γK_{L} \rightarrow 3\gamma

Data from the NA31 experiment at the CERN SPS have been used for the first search for the decay mode KL → 3γ. Seven events have been found with an estimated background of 6.7 ± 1.5 events. The corresponding upper limit for the branching ratio is Γ(KL → 3γ) Γ(KL → all) = 2.4 × 10-7 at the 90% confidence level, assuming a phase-space decay distribution. © 1995