Effects of confinement on the permanent electric-dipole moment of Xe atoms in liquid Xe

Searches for permanent electric-dipole moments (EDM) of atoms provide important constraints on competing extensions to the standard model of elementary particles. Recently proposed experiment with liquid $^{129}$Xe [M.V. Romalis and M.P. Ledbetter, Phys. Rev. Lett. \textbf{87}, 067601 (2001)] may significantly improve present limits on the EDMs. To interpret experimental data in terms of CP-violating sources, one must relate measured atomic EDM to various model interactions via electronic-structure calculations. Here we study density dependence of atomic EDMs. The analysis is carried out in the framework of the cell model of the liquid coupled with relativistic atomic-structure calculations. We find that compared to an isolated atom, the EDM of an atom of liquid Xe is suppressed by about 40%

Molecular CP-violating magnetic moment

A concept of CP-violating (T,P-odd) permanent molecular magnetic moments $\mu^{CP}$ is introduced. We relate the moments to the electric dipole moment of electron (eEDM) and estimate $\mu^{CP}$ for several diamagnetic polar molecules. The moments exhibit a steep, Z^5, scaling with the nuclear charge Z of the heavier molecular constituent. A measurement of the CP-violating magnetization of a polarized sample of heavy molecules may improve the present limit on eEDM by several orders of magnitude.Comment: 4 pages, no figures, submitted to PR

Anthropogenic and natural drivers of a strong winter urban heat island in a typical Arctic city

The Arctic has rapidly urbanized in recent decades with 2 million people currently living in more than a hundred cities north of 65∘&thinsp;N. These cities have a harsh but sensitive climate and warming here is the principle driver of destructive thawing, water leakages, air pollution and other detrimental environmental impacts. This study reports on the urban temperature anomaly in a typical Arctic city. This persistent warm anomaly reaches up to 11&thinsp;K in winter with the wintertime mean urban temperature being 1.9&thinsp;K higher on average in the city center than in the surrounding natural landscape. An urban temperature anomaly, also known as an urban heat island (UHI), was found using remote sensing and in situ temperature data. High-resolution (1&thinsp;km) model experiments run with and without an urban surface parameterization helped to identify the leading physical and geographical factors supporting a strong temperature anomaly in a cold climate. The statistical analysis and modeling suggest that at least 50&thinsp;% of this warm anomaly is caused by the UHI effect, driven mostly by direct anthropogenic heating, while the rest is created by natural microclimatic variability over the undulating relief of the area. The current UHI effect can be as large as the projected, and already amplified, warming for the region in the 21st century. In contrast to earlier reports, this study found that the wintertime UHI in the Arctic should be largely attributed to direct anthropogenic heating. This is a strong argument in support of energy efficiency measures, urban climate change mitigation policy and against high-density urban development in polar settlements. The complex pattern of thermal conditions, as revealed in this study, challenges urban planners to account for the observed microclimatic diversity in perspective sustainable development solutions.</p

Observations of the urban boundary layer in a cold climate city

Cold environment supports a large diversity of local climates. Among them, urban climates in northern cities stand out for their pronounced warm temperature anomaly known as the Urban Heat Island (UHI). UHI in northern cities has been already studies through satellite images and in-situ observations in the urban canopy layer (UCL). Yet, the vertical structure of the urban atmospheric boundary layer (UBL) has not been studied there. This work presents new observations of UBL in Nadym – a sub-Arctic Siberian city. During several intensive observing periods we run simultaneous registration of urban and rural meteorological parameters with unmanned drones, a microwave temperature profiler and a dense network of ground-based sensors. The data analysis reveals details of UHI development in the UCL and UBL, and links together horizontal urban-rural canopy-layer temperature differences, boundary layer stability, and UHI vertical extent. We show that during strong temperature inversions, UBL is less stratified than its rural counterpart, but it still remains very thin and limited in height by a few tens of meters. The observations disclose that the ground-based (50 m – 100 m above ground) temperature inversion is one of the strongest control factors for UHI in cold climate conditions in winter

Modeling geoelectric fields in Ireland and the UK for space weather applications

Geoelectric fields at the Earth’s surface caused by geomagnetic storms have the potential to disrupt and damage ground-based infrastructure such as electrical power distribution networks, pipelines, and railways. Here we model geoelectric fields in Ireland and the UK during both quiet and active time intervals of geomagnetic conditions using measurements from magnetic observatories and electromagnetic tensor relationships. The analysis focused on (1) defining periods of the magnetic field variations that are largely affected by the geomagnetic storms, between 30 and 30,000 s; (2) constraining the electromagnetic tensor relationships that defines the Earth’s response to magnetic field variations; (3) implementing and validating two approaches for modeling geoelectric fields based on measurements from magnetic observatories and local and interstation electromagnetic transfer functions; and (4) estimating uncertainties when modeling geoelectric fields. The use of interstation tensor relationships allowed us to differentiate between regional and local geomagnetic sources. We found coherence values of 0.5–0.95, signal-to-noise ratio of 1–15 dB, normalized root-mean-square values of 0.8–3.4, and root-mean-square values of 0.7–84 mV/km. Within these ranges of values, sites in close proximity (<100 km) to a magnetic observatory and not affected by local storms will provide the most accurate results, while sites located at further distances and affected by spatially localized features of the storm will be less accurate. These methods enable us to more accurately model geomagnetically induced currents, and their associated uncertainties, in the British and Irish power networks

Feasibility studies of the time-like proton electromagnetic form factor measurements with PANDA at FAIR

The possibility of measuring the proton electromagnetic form factors in the time-like region at FAIR with the \PANDA detector is discussed. Detailed simulations on signal efficiency for the annihilation of $\bar p +p$ into a lepton pair as well as for the most important background channels have been performed. It is shown that precision measurements of the differential cross section of the reaction $\bar p +p \to e^++ e^-$ can be obtained in a wide angular and kinematical range. The individual determination of the moduli of the electric and magnetic proton form factors will be possible up to a value of momentum transfer squared of $q^2\simeq 14$ (GeV/c)$^2$. The total $\bar p +p\to e^++e^-$ cross section will be measured up to $q^2\simeq 28$ (GeV/c)$^2$. The results obtained from simulated events are compared to the existing data. Sensitivity to the two photons exchange mechanism is also investigated.Comment: 12 pages, 4 tables, 8 figures Revised, added details on simulations, 4 tables, 9 figure

Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR

Simulation results for future measurements of electromagnetic proton form factors at \PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel $\bar p p \to e^+ e^-$ is studied on the basis of two different but consistent procedures. The suppression of the main background channel, $\textit{i.e.}$ $\bar p p \to \pi^+ \pi^-$, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance