IFAE

About: IFAE is a other organization based out in Barcelona, Spain. It is known for research contribution in the topics: Large Hadron Collider & Galaxy. The organization has 664 authors who have published 1270 publications receiving 51097 citations. The organization is also known as: Instituto de Fisica de Altas Energias & IFAE.

Measurements of differential cross-sections in four-lepton events in 13 TeV proton-proton collisions with the ATLAS detector

Abstract: Measurements of four-lepton differential and integrated fiducial cross-sections in events with two same-flavour, opposite-charge electron or muon pairs are presented. The data correspond to 139 fb−1 of s = 13 TeV proton-proton collisions, collected by the ATLAS detector during Run 2 of the Large Hadron Collider (2015–2018). The final state has contributions from a number of interesting Standard Model processes that dominate in different four-lepton invariant mass regions, including single Z boson production, Higgs boson production and on-shell ZZ production, with a complex mix of interference terms, and possible contributions from physics beyond the Standard Model. The differential cross-sections include the four-lepton invariant mass inclusively, in slices of other kinematic variables, and in different lepton flavour categories. Also measured are dilepton invariant masses, transverse momenta, and angular correlation variables, in four regions of four-lepton invariant mass, each dominated by different processes. The measurements are corrected for detector effects and are compared with state-of-the-art Standard Model calculations, which are found to be consistent with the data. The Z → 4l branching fraction is extracted, giving a value of (4.41 ± 0.30) × 10−6. Constraints on effective field theory parameters and a model based on a spontaneously broken B − L gauge symmetry are also evaluated. Further reinterpretations can be performed with the provided information. [Figure not available: see fulltext.]

MAGIC very large zenith angle observations of the Crab Nebula up to 100 TeV

Abstract: Aims. We measure the Crab Nebula γ -ray spectral energy distribution in the ~100 TeV energy domain and test the validity of existing leptonic emission models at these high energies.Methods. We used the novel very large zenith angle observations with the MAGIC telescope system to increase the collection area above 10 TeV. We also developed an auxiliary procedure of monitoring atmospheric transmission in order to assure proper calibration of the accumulated data. This employs recording optical images of the stellar field next to the source position, which provides a better than 10% accuracy for the transmission measurements.Results. We demonstrate that MAGIC very large zenith angle observations yield a collection area larger than a square kilometer. In only ~ 56 h of observations, we detect the γ -ray emission from the Crab Nebula up to 100 TeV, thus providing the highest energy measurement of this source to date with Imaging Atmospheric Cherenkov Telescopes. Comparing accumulated and archival MAGIC and Fermi /LAT data with some of the existing emission models, we find that none of them provides an accurate description of the 1 GeV to 100 TeV γ -ray signal.

Shedding light on the t\overline{t} asymmetry: the photon handle

Abstract: We investigate a charge asymmetry in $ t\overline{t}\gamma $ production at the LHC that provides complementary information to the measured asymmetries in $ t\overline{t} $ production. We estimate the experimental uncertainty in its measurement at the LHC with 8 TeV and 14 TeV. We argue that, for new physics models that simultaneously reproduce the asymmetry excess in $ t\overline{t} $ production at the Tevatron and the SM-like asymmetry at the LHC, the measurement in $ t\overline{t}\gamma $ production at the LHC is likely to deviate from the SM prediction. In two new physics models studied in detail we find that the deviations could be significant and observable at the 14 TeV run.

Search for heavy long-lived multicharged particles in proton-proton collisions at √s =13 TeV using the ATLAS detector

Abstract: A search for heavy long-lived multicharged particles is performed using the ATLAS detector at the LHC. Data with an integrated luminosity of 36.1 fb(-1) collected in 2015 and 2016 from proton-proto ...