Modular Localization of Massive Particles with "Any" Spin in d=2+1

We discuss a concept of particle localization which is motivated from quantum field theory, and has been proposed by Brunetti, Guido and Longo and by Schroer. It endows the single particle Hilbert space with a family of real subspaces indexed by the space-time regions, with certain specific properties reflecting the principles of locality and covariance. We show by construction that such a localization structure exists also in the case of massive anyons in d=2+1, i.e. for particles with positive mass and with arbitrary spin s in the reals. The construction is completely intrinsic to the corresponding ray representation of the (proper orthochronous) Poincare group. Our result is of particular interest since there are no free fields for anyons, which would fix a localization structure in a straightforward way. We present explicit formulas for the real subspaces, expected to turn out useful for the construction of a quantum field theory for anyons. In accord with well-known results, only localization in string-like, instead of point-like or bounded, regions is achieved. We also prove a single-particle PCT theorem, exhibiting a PCT operator which acts geometrically correctly on the family of real subspaces

The complex X-ray spectrum of NGC 4507

XMM-Newton and Chandra/HETG spectra of the Compton-thin (NH 4x10^{23} cm^{-2}) Seyfert 2 galaxy, NGC 4507, are analyzed and discussed. The main results are: a) the soft X-ray emission is rich in emission lines; an (at least) two--zone photoionization region is required to explain the large range of ionization states. b) The 6.4 keV iron line is likely emitted from Compton-thick matter, implying the presence of two circumnuclear cold regions, one Compton-thick (the emitter), one Compton-thin (the cold absorber). c) Evidence of an Fe xxv absorption line is found in the Chandra/HETG spectrum. The column density of the ionized absorber is estimated to be a few x10^{22} cm^{-2}.Comment: accepted for publication in A&

Study on cosmogenic activation above ground for the DarkSide-20k project

The activation of materials due to the exposure to cosmic rays may become an important background source for experiments investigating rare event phenomena. DarkSide-20k is a direct detection experiment for galactic dark matter particles, using a two-phase liquid argon time projection chamber filled with 49.7 tonnes (active mass) of Underground Argon (UAr) depleted in 39Ar. Here, the cosmogenic activity of relevant long-lived radioisotopes induced in the argon and other massive components of the set-up has been estimated; production of 120 t of radiopure UAr is foreseen. The expected exposure above ground and production rates, either measured or calculated, have been considered. From the simulated counting rates in the detector due to cosmogenic isotopes, it is concluded that activation in copper and stainless steel is not problematic. Activation of titanium, considered in early designs but not used in the final design, is discussed. The activity of 39Ar induced during extraction, purification and transport on surface, in baseline conditions, is evaluated to be 2.8% of the activity measured in UAr from the same source, and thus considered acceptable. Other products in the UAr such as 37Ar and 3H are shown to not be relevant due to short half-life and assumed purification methods

Hydrocarbon measurements in the spring Arctic troposphere during the ARCTOC 95 campaign

The hydrocarbon measurements made during the ARCTOC 95 field campaign (16 April – 10 June 1995) at Ny Ålesund, Spitsbergen (78°55''N, 11°56'E) allow the estimation of Cl and Br atom concentrations during periods of low ozone concentrations in the lower troposphere. In-situ analyses for nonmethane hydrocarbons and selected halocarbons were carried out with two GC-FID/ECD systems allowing a time resolution of about 2 hours and detection limits in the lower ppt range. A third GC was used to monitor the CO mixing ratio with a 5 min time resolution. Additionally, about 70 whole air samples were collected in stainless steel canisters and analysed for hydrocarbons (C2-C8), some halocarbons, methane, CO, and CO2 at the laboratory in Jülich. 15 of those samples were taken at the measurement site, the others were collected on top of Zeppelin Mountain (474 m a.s.l., distance from measurement site 1000 m). In-situ measurements as well as canister samples showed that all nonmethane hydrocarbons were present at low mixing ratios. CO levels were found to be between 100 and 140 ppb showing a nearly constant decrease from April to June. During an ozone depletion event (18-24 April) the hydrocarbon pattern changed drastically. The mixing ratios of alkanes and ethyne decreased together with ozone, whereas benzene, chloromethane, and CO mixing ratios remained nearly constant. From the ratio of NMHC background mixing ratios and those during low ozone periods the time integrated Cl and Br atom concentrations were calculated to some 1010 moleculesċsċcm−3 and 5ċ1012 moleculesċsċcm−3, respectively

The indirect determination of chlorine atom concentration in the troposphere from changes in the patterns of non-methane hydrocarbons

About 200 measurements of C2–C9 hydrocarbons were made during a ship cruise (NATAC 91) in the western Mediterranean Sea, the eastern Mid- and North Atlantic and the North Sea in April and May 1991. The changes in the ratios of several pairs of hydrocarbons are used to investigate the possible impact of Cl-atom reactions on the atmospheric removal processes of hydrocarbons. In order to minimize the potential bias from atmospheric mixing processes, a careful selection of suitable hydrocarbon sets is essential. The NMHC mixing ratios observed during NATAC 91 are generally well above those typical for air in the remote marine background and the observed changes in the hydrocarbon patterns agree very well with those predicted from OH-radical chemistry. No significant evidence for an impact of chlorine atoms could be found in this data set. The best estimate for the average [Cl]/[OH] ratio is in the range of 10−3. However, within the various uncertainties associated with such estimates, this value is not significantly different from zero. The upper limit is in the range of 2–7·10−3. Based on an average OH-radical concentration of 106 cm−3, this corresponds to some 103 Cl-atoms cm−3. This is far below the Cl-atom concentrations found during the tropospheric ozone depletion events in arctic spring. Our values are also far below those derived in some other studies for the marine boundary layer but are still compatible with recent model calculations. Our findings support the conclusion of Rudolph and coworkers that on average, Cl-atoms are of limited importance for the chemistry of the troposphere. It is important that the major part of the uncertainty of the Cl-atom concentration estimates results from errors in the rate constants for the reactions of the hydrocarbons with OH-radicals. A reliable and consistent set of the relevant rate constants would further improve the accuracy of the Cl-atom concentration estimates or their upper limits derived from changes in the hydrocarbon patterns