3,646 research outputs found
Evaluation of linear ozone photochemistry parametrizations in a stratosphere-troposphere data assimilation system
This paper evaluates the performance of various linear ozone photochemistry parametrizations using the stratosphere-troposphere data assimilation system of the Met Office. A set of experiments were run for the period 23 September 2003 to 5 November 2003 using the Cariolle (v1.0 and v2.1), LINOZ and Chem2D-OPP (v0.1 and v2.1) parametrizations. All operational meteorological observations were assimilated, together with ozone retrievals from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). Experiments were validated against independent data from the Halogen Occultation Experiment (HALOE) and ozonesondes. Additionally, a simple offline method for comparing the parametrizations is introduced. <br><br> It is shown that in the upper stratosphere and mesosphere, outside the polar night, ozone analyses are controlled by the photochemistry parametrizations and not by the assimilated observations. The most important factor in getting good results at these levels is to pay attention to the ozone and temperature climatologies in the parametrizations. There should be no discrepancies between the climatologies and the assimilated observations or the model, but there is also a competing demand that the climatologies be objectively accurate in themselves. Conversely, in the lower stratosphere outside regions of heterogeneous ozone depletion, the ozone analyses are dominated by observational increments and the photochemistry parametrizations have little influence. <br><br> We investigate a number of known problems in LINOZ and Cariolle v1.0 in more detail than previously, and we find discrepancies in Cariolle v2.1 and Chem2D-OPP v2.1, which are demonstrated to have been removed in the latest available versions (v2.8 and v2.6 respectively). In general, however, all the parametrizations work well through much of the stratosphere, helped by the presence of good quality assimilated MIPAS observations
A New Limit on the Antiproton Lifetime
Measurements of the cosmic ray pbar/p ratio are compared to predictions from
an inhomogeneous disk-diffusion model of pbar production and propagation within
the Galaxy, combined with a calculation of the modulation of the interstellar
cosmic ray spectra as the particles propagate through the heliosphere to the
Earth. The predictions agree with the observed pbar/p spectrum. Adding a finite
pbar lifetime to the model, we obtain the limit tau_pbar > 0.8 Myr (90 % C.L.).Comment: 13 pages, 3 encapsulated Postscript figures, uses AASTeX; accepted by
Astrophysical Journal; minor change
A Farey tale for N=4 dyons
We study exponentially suppressed contributions to the degeneracies of
extremal black holes. Within Sen's quantum entropy function framework and
focusing on extremal black holes with an intermediate AdS3 region, we identify
an infinite family of semi-classical AdS2 geometries which can contribute
effects of order exp(S_0/c), where S_0 is the Bekenstein-Hawking-Wald entropy
and c is an integer greater than one. These solutions lift to the extremal
limit of the SL(2,Z) family of BTZ black holes familiar from the "black hole
Farey tail". We test this understanding in N=4 string vacua, where exact dyon
degeneracies are known to be given by Fourier coefficients of Siegel modular
forms. We relate the sum over poles in the Siegel upper half plane to the Farey
tail expansion, and derive a "Farey tale" expansion for the dyon partition
function. Mathematically, this provides a (formal) lift from Hilbert modular
forms to Siegel modular forms with a pole at the diagonal divisor.Comment: 31 page
Heavy quark production via leptoquarks at a neutrino factory
The proposed neutrino factory (NF) based on a muon storage ring (MSR) is an
ideal place to look for heavy quark production via neutral current (NC) and
charged current (CC) interactions. In this article, we address the issue of
contribution coming from mediating leptoquarks (LQ) in interactions leading to the production of at a
MSR and investigate the region where LQ interactions are significant in the
near-site experiments.Comment: 12 pages latex, 10 ps figures, uses axocolour.sty, Slightly revised
version to appear in PR
On the complementarity of Hyper-K and LBNF
The next generation of long-baseline experiments is being designed to make a
substantial step in the precision of measurements of neutrino-oscillation
probabilities. Two qualitatively different proposals, Hyper-K and LBNF, are
being considered for approval. This document outlines the complimentarity
between Hyper-K and LBNF.Comment: 5 pager
Initial report from the ICFA Neutrino Panel
In July 2013 ICFA established the Neutrino Panel with the mandate "To promote
international cooperation in the development of the accelerator-based
neutrino-oscillation program and to promote international collaboration in the
development a neutrino factory as a future intense source of neutrinos for
particle physics experiments". This, the Panel's Initial Report, presents the
conclusions drawn by the Panel from three regional "Town Meetings" that took
place between November 2013 and February 2014.
After a brief introduction and a short summary of the status of the knowledge
of the oscillation parameters, the report summarises the approved programme and
identifies opportunities for the development of the field. In its conclusions,
the Panel recognises that to maximise the discovery potential of the
accelerator-based neutrino-oscillation programme it will be essential to
exploit the infrastructures that exist at CERN, FNAL and J-PARC and the
expertise and resources that reside in laboratories and institutes around the
world. Therefore, in its second year, the Panel will consult with the
accelerator-based neutrino-oscillation community and its stakeholders to:
develop a road-map for the future accelerator-based neutrino-oscillation
programme that exploits the ambitions articulated at CERN, FNAL and J-PARC and
includes the programme of measurement and test-beam exposure necessary to
ensure the programme is able to realise its potential; develop a proposal for a
coordinated "Neutrino RD" programme, the accelerator and detector R&D programme
required to underpin the next generation of experiments; and to explore the
opportunities for the international collaboration necessary to realise the
Neutrino Factory.Comment: ICFA Neutrino Panel 2014(01
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