165 research outputs found
Molecular CP-violating magnetic moment
A concept of CP-violating (T,P-odd) permanent molecular magnetic moments
is introduced. We relate the moments to the electric dipole moment
of electron (eEDM) and estimate 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∘ 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 K in winter with the wintertime mean urban temperature
being 1.9 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 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 % 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
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 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 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 (GeV/c). The total cross section will be measured up to (GeV/c).
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 is studied on the basis
of two different but consistent procedures. The suppression of the main
background channel, , 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
Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR
This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented
Study of doubly strange systems using stored antiprotons
Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the P‾ANDA experiment at FAIR. For the first time, high resolution γ-spectroscopy of doubly strange ΛΛ-hypernuclei will be performed, thus complementing measurements of ground state decays of ΛΛ-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Ξ−-atoms will be feasible and even the production of Ω−-atoms will be within reach. The latter might open the door to the |S|=3 world in strangeness nuclear physics, by the study of the hadronic Ω−-nucleus interaction. For the first time it will be possible to study the behavior of Ξ‾+ in nuclear systems under well controlled conditions
Recommended from our members
Heavy ion fusion science research for high energy density physics and fusion applications
During the past two years, the U.S. heavy ion fusion science program has made significant experimental and theoretical progress in simultaneous transverse and longitudinal beam compression, ion-beam-driven warm dense matter targets, high brightness beam transport, advanced theory and numerical simulations, and heavy ion target designs for fusion. First experiments combining radial and longitudinal compression of intense ion beams propagating through background plasma resulted in on-axis beam densities increased by 700X at the focal plane. With further improvements planned in 2007, these results will enable initial ion beam target experiments in warm dense matter to begin next year at LBNL. We are assessing how these new techniques apply to low-cost modular fusion drivers and higher-gain direct-drive targets for inertial fusion energy
- …