Physics objects for top quark physics in ATLAS

Top quark physics measurements performed using data from the ATLAS detector at the LHC rely on efficient reconstruction and precise calibration of leptons, jets and missing transverse energy. A review of the techniques used to reconstruct such objects is given, with an emphasis on the uncertainties achieved for energy calibration and efficiency measurements, illustrated with their impact on key top quark physics results.Comment: 5 pages, 3 figures, proceedings of Top2016 conferenc

Inclusive ttˉt\bar{t} cross-section measurements at LHC

A review of ATLAS and CMS measurements of the inclusive $t\bar{t}$ production cross-section in $pp$ collisions at $\sqrt{s}=$7-13 TeV is presented, focusing on the most precise results in the dilepton and lepton+jets final states. The measurements are in good agreement with state-of-the-art QCD predictions, and have been used to determine the top quark pole mass and provide constraints on proton parton distribution functions.Comment: 5 pages, 3 figures, proceedings of the Top2017 conferenc

Electroweak and CP violation physics at a Linear Collider Z-factory

A future linear collider such as TESLA may be able to run on the Z0 resonance with very high luminosity and polarised electron and positron beams. The possibilities of measuring electroweak quantities with high precision are investigated. Huge improvements with respect to the present precision can be expected, especially for the asymmetries A_LR and A_b where beam polarisation can be exploited. The very large sample of Z to bbbar events also allows studies of various CP-violating b decays. The precision achievable on the CKM unitarity triangle angles is comparable to experiments at b factories and future hadron colliders.Comment: 26 pages, 11 figures. To be submitted to European Journal of Physics Direc

Theoretical models of helicopter rotor noise

For low speed rotors, it is shown that unsteady load models are only partially successful in predicting experimental levels. A theoretical model is presented which leads to the concept of unsteady thickness noise. This gives better agreement with test results. For high speed rotors, it is argued that present models are incomplete and that other mechanisms are at work. Some possibilities are briefly discussed

Ice sheets as a significant source of highly reactive nanoparticulate iron to the oceans

The Greenland and Antarctic Ice Sheets cover ~\n10% of global land surface, but are rarely considered as active components of the global iron cycle. The ocean waters around both ice sheets harbour highly productive coastal ecosystems, many of which are iron limited. Measurements of iron concentrations in subglacial runoff from a large Greenland Ice Sheet catchment reveal the potential for globally significant export of labile iron fractions to the near-coastal euphotic zone. We estimate that the flux of bioavailable iron associated with glacial runoff is 0.40–2.54?Tg per year in Greenland and 0.06–0.17?Tg per year in Antarctica. Iron fluxes are dominated by a highly reactive and potentially bioavailable nanoparticulate suspended sediment fraction, similar to that identified in Antarctic icebergs. Estimates of labile iron fluxes in meltwater are comparable with aeolian dust fluxes to the oceans surrounding Greenland and Antarctica, and are similarly expected to increase in a warming climate with enhanced melting

Physics at International Linear Collider (ILC)

International Linear Collider (ILC) is an electron-positron collider with the initial center-of-mass energy of 500 GeV which is upgradable to about 1 TeV later on. Its goal is to study the physics at TeV scale with unprecedented high sensitivities. The main topics include precision measurements of the Higgs particle properties, studies of supersymmtric particles and the underlying theoretical structure if supersymmetry turns out to be realized in nature, probing alternative possibilities for the origin of mass, and the cosmological connections thereof. In many channels, Higgs and leptonic sector in particular, ILC is substantially more sensitive than LHC, and is complementary to LHC overall. In this short article, we will have a quick look at the capabilities of ILC.Comment: To appear in JPSJ Vol76 No1

Predictions for Lepton Flavour Violation in Z decays

Recent experimental results suggest that the neutrinos of the Standard Model are massive, though light. Therefore they may mix with each other giving rise to lepton flavour or even lepton number violating processes, depending on whether they are Dirac or Majorana particles. Furthermore, the lightness of the observed neutrinos may be explained by the existence of heavy ones, whose effects on LFV would be very sizeable. We present an analysis of the effect of massive neutrinos on flavour-changing decays of the Z boson into leptons, at the one-loop level, independent of neutrino mass models. Constraints from present experiments are taken into account.Comment: 6 pages, 2 figures, uses npb.sty. Talk given by J.I.I. at Loops and Legs 2000, Bastei, Germany, April 9-14. Typos corrected, Figure 2 replaced. Conclusions unchange

Virtual effects of light gauginos and higgsinos: a precision electroweak analysis of split supersymmetry

We compute corrections to precision electroweak observables in supersymmetry in the limit that scalar superpartners are very massive and decoupled. This leaves charginos and neutralinos and a Standard Model-like Higgs boson as the only states with unknown mass substantially affecting the analysis. We give complete formulas for the chargino and neutralino contributions, derive simple analytic results for the pure gaugino and higgsino cases, and study the general case. We find that in all circumstances, the precision electroweak fit improves when the charginos and neutralinos are near the current direct limits. Larger higgsino and gaugino masses worsen the fit as the theory predictions asymptotically approach those of the Standard Model. Since the Standard Model is considered by most to be an adequate fit to the precision electroweak data, an important corollary to our analysis is that all regions of parameter space allowed by direct collider constraints are also allowed by precision electroweak constraints in split supersymmetry.Comment: 22 pages, 5 figures, v2: typos fixed and note adde