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

Precision Calculations for Future Colliders

I discuss the motivations for, and the status of, precision calculations for the Large Hadron Collider (LHC) and the planned International Linear Collider (ILC).Comment: latex, uses ws-ijmpe.cls, 19 pages, 9 figures, 1 table, based on a talk given at the symposium "50 Years of High Energy Physics at UB", to appear in International Journal of Modern Physics

Top quark physics at ATLAS and CMS

The LHC will be a top quark factory, producing large numbers of top quarks even at the initial low luminosities. This will allow the detailed investigation of its production and decay properties, providing both stringent tests of the Standard Model and opportunities for new physics searches. Recent studies from ATLAS and CMS will be presented, with an emphasis on initial measurements of top quark pair and single top production cross-sections, and the use of top quarks in detector commissioning and calibration. The potential for the study of top quark properties will also be 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

b Quark Physics with 2 .10^9 Z Bosons

It has been suggested to realize a factory for 10^9 Z^0 through a linear e^+e^- collider with polarized beams. Very likely the relevant CP studies for B mesons will already have been performed at the B factories by that time, hence GIGA-Z will be a third generation b physics experiment. Yet such a facility would provide us with unique opportunities in the domain of beauty physics that would be of essential significance even in 2010: (1) Production and decay of polarized beauty baryons; (2) searching for and probing transitions driven by b --> q \nu \bar{\nu}; (3) detailed and comprehensive studies of inclusive semileptonic B_s decays

Master integrals for massive two-loop Bhabha scattering in QED

We present a set of scalar master integrals (MIs) needed for a complete treatment of massive two-loop corrections to Bhabha scattering in QED, including integrals with arbitrary fermionic loops. The status of analytical solutions for the MIs is reviewed and examples of some methods to solve MIs analytically are worked out in more detail. Analytical results for the pole terms in epsilon of so far unknown box MIs with five internal lines are given.Comment: 23 pages, 5 tables, 12 figures, references added, appendix B enlarge

Contemporary (1951–2001) Evolution of Lakes in the Old Crow Basin, Northern Yukon, Canada: Remote Sensing, Numerical Modeling, and Stable Isotope Analysis

This study reports on changes in the distribution, surface area, and modern water balance of lakes and ponds located in the Old Crow Basin, northern Yukon, over a 50-year period (1951–2001), using aerial photographs, satellite imagery, a numerical lake model, and stable O-H isotope analysis. Results from the analysis of historical air photos (1951 and 1972) and a Landsat-7 Enhanced Thematic Mapper (ETM+) image (2001) show an overall decrease (-3.5%) in lake surface area between 1951 and 2001. Large lakes typically decreased in extent over the study period, whereas ponds generally increased. Between 1951 and 1972, approximately 70% of the lakes increased in extent; however, between 1972 and 2001, 45% decreased in extent. These figures are corroborated by a numerical lake water balance simulation (P-E index) and stable O-H isotope analysis indicating that most lakes experienced a water deficit over the period 1988–2001. These observed trends towards a reduction in lake surface area are mainly attributable to a warmer and drier climate. The modern decrease in lake levels corresponds well to changes in regional atmospheric teleconnection patterns (Arctic and Pacific Decadal oscillations). In 1977, the climate in the region switched from a predominantly cool and moist regime, associated with the increase in lake surface area, to a hot and dry one, thus resulting in the observed decrease in lake surface area. Although some lakes may have drained catastrophically by stream erosion or bank overflow, it is not possible to determine with certainty which lakes experienced such catastrophic drainage, since an interval of two decades separates the two air photo mosaics, and the satellite image was obtained almost30 years after the second mosaic of air photos.La présente étude fait état des changements caractérisant la répartition, l’étendue et le bilan hydrique contemporain des lacs et des étangs situés dans le bassin Old Crow, dans le nord du Yukon, sur une période de 50 ans (1951–2001). L’étude s’est appuyée sur des photographies aériennes, l’imagerie satellitaire, un modèle numérique des lacs et l’analyse des isotopes stables O-H. D’après les résultats de l’analyse des photos aériennes historiques (1951 et 1972) et d’une image par capteur ETM+ (Enhanced Thematic Mapper) de Landsat-7 (2001), il y a eu rétrécissement général ( 3,5 %) de la surface des lacs entre 1951 et 2001. D’un point de vue général, l’étendue des grands lacs a diminué au cours de la période visée par l’étude, tandis que celle des étangs a augmenté. Entre 1951 et 1972, l’étendue d’environ 70 % des lacs s’est accrue, mais entre 1972 et 2001, l’étendue de 45 % des lacs a diminué. Ces données ont été corroborées au moyen de la simulation numérique du bilan hydrique des lacs (indice P-E) et de l’analyse des isotopes stables O-H, qui ont laissé entrevoir que la plupart des lacs ont enregistré un déficit en eau au cours de la période allant de 1988 à 2001. Les tendances de réduction de la surface des lacs qui ont été observées sont principalement attribuables à un climat plus chaud et plus sec. La diminution contemporaine du niveau des lacs correspond bien aux changements caractérisant les modèles régionaux de téléconnexion atmosphérique (oscillations décadaires arctiques et pacifiques). En 1977, le climat de la région est passé d’un régime à prédominance fraîche et humide (associé à l’augmentation de la surface des lacs de la région) à un régime chaud et sec, ce qui s’est traduit par la diminution de la surface des lacs qui a été observée. Bien que certains lacs puissent avoir été drainés de manière catastrophique en raison de l’érosion des cours d’eau ou du débordement des rives, il est impossible de déterminer avec certitude quels lacs ont été la cible d’un assèchement si catastrophique puisqu’un intervalle de deux décennies sépare les deux mosaïques de photographies aériennes, et que l’image satellitaire a été obtenue presque une trentaine d’années après la deuxième mosaïque de photo aérienne

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

Chemical sensors for in situ data collection in the cryosphere

Glaciers and ice sheets are recognised as important components of global biogeochemical cycles. Chemical sensors have great potential for in situ monitoring in the cryosphere and are available for many analytes of interest, but they are frequently unsuitable for deployment since meltwaters are cold, turbid, experience freeze-thaw cycles and display low ionic strength and concentrations of target analytes. Here, we review in situ chemical sensors currently available for measurement of biogeochemically important analytes and assess their suitability for deployment. These include standard parameters such as dissolved oxygen and pH, along with macronutrients (nitrate/nitrite and phosphate), micronutrients (iron and manganese) and biogenic gases (methane). Where no commercial alternatives are available, we discuss sensors currently in development, and their applicability to these extreme environments. The information presented has great relevance for future science in polar environments, and for the ultimate goal of obtaining in situ data from extreme, inaccessible subglacial environments