192 research outputs found
Prospects For Identifying Dark Matter With CoGeNT
It has previously been shown that the excess of events reported by the CoGeNT
collaboration could be generated by elastically scattering dark matter
particles with a mass of approximately 5-15 GeV. This mass range is very
similar to that required to generate the annual modulation observed by
DAMA/LIBRA and the gamma rays from the region surrounding the Galactic Center
identified within the data of the Fermi Gamma Ray Space Telescope. To
confidently conclude that CoGeNT's excess is the result of dark matter,
however, further data will likely be needed. In this paper, we make projections
for the first full year of CoGeNT data, and for its planned upgrade. Not only
will this body of data more accurately constrain the spectrum of nuclear recoil
events, and corresponding dark matter parameter space, but will also make it
possible to identify seasonal variations in the rate. In particular, if the
CoGeNT excess is the product of dark matter, then one year of CoGeNT data will
likely reveal an annual modulation with a significance of 2-3. The
planned CoGeNT upgrade will not only detect such an annual modulation with high
significance, but will be capable of measuring the energy spectrum of the
modulation amplitude. These measurements will be essential to irrefutably
confirming a dark matter origin of these events.Comment: 6 pages, 6 figure
CoGeNT Interpretations
Recently, the CoGeNT experiment has reported events in excess of expected
background. We analyze dark matter scenarios which can potentially explain this
signal. Under the standard case of spin independent scattering with equal
couplings to protons and neutrons, we find significant tensions with existing
constraints. Consistency with these limits is possible if a large fraction of
the putative signal events is coming from an additional source of experimental
background. In this case, dark matter recoils cannot be said to explain the
excess, but are consistent with it. We also investigate modifications to dark
matter scattering that can evade the null experiments. In particular, we
explore generalized spin independent couplings to protons and neutrons, spin
dependent couplings, momentum dependent scattering, and inelastic interactions.
We find that some of these generalizations can explain most of the CoGeNT
events without violation of other constraints. Generalized couplings with some
momentum dependence, allows further consistency with the DAMA modulation
signal, realizing a scenario where both CoGeNT and DAMA signals are coming from
dark matter. A model with dark matter interacting and annihilating into a new
light boson can realize most of the scenarios considered.Comment: 24 pages, 12 figs, v2: published version, some discussions clarifie
Cosmological parameter estimation using Very Small Array data out to â= 1500
We estimate cosmological parameters using data obtained by the Very Small Array (VSA) in its extended configuration, in conjunction with a variety of other cosmic microwave background (CMB) data and external priors. Within the flat Î cold dark matter (ÎCDM) model, we find that the inclusion of high-resolution data from the VSA modifies the limits on the cosmological parameters as compared to those suggested by the Wilkinson Microwave Anisotropy Probe (WMAP) alone, while still remaining compatible with their estimates. We find that Ωbh2= 0.0234+0.0012â0.0014, Ωdmh2= 0.111+0.014â0.016, h= 0.73+0.09â0.05, nS= 0.97+0.06â0.03, 1010AS= 23+7â3 and Ï= 0.14+0.14â0.07 for WMAP and VSA when no external prior is included. On extending the model to include a running spectral index of density fluctuations, we find that the inclusion of VSA data leads to a negative running at a level of more than 95 per cent confidence ( nrun=â0.069 ± 0.032 ), something that is not significantly changed by the inclusion of a stringent prior on the Hubble constant. Inclusion of prior information from the 2dF galaxy redshift survey reduces the significance of the result by constraining the value of Ωm. We discuss the veracity of this result in the context of various systematic effects and also a broken spectral index model. We also constrain the fraction of neutrinos and find that fÎœ < 0.087 at 95 per cent confidence, which corresponds to mÎœ < 0.32 eV when all neutrino masses are equal. Finally, we consider the global best fit within a general cosmological model with 12 parameters and find consistency with other analyses available in the literature. The evidence for nrun < 0 is only marginal within this model
Evolutionary Entropy: A Predictor of Body Size, Metabolic Rate and Maximal Life Span
Body size of organisms spans 24 orders of magnitude, and metabolic rate and life span present comparable differences across species. This article shows that this variation can be explained in terms of evolutionary entropy, a statistical parameter which characterizes the robustness of a population, and describes the uncertainty in the age of the mother of a randomly chosen newborn. We show that entropy also has a macroscopic description: It is linearly related to the logarithm of the variables body size, metabolic rate, and life span. Furthermore, entropy characterizes Darwinian fitness, the efficiency with which a population acquires and converts resources into viable offspring. Accordingly, entropy predicts the outcome of natural selection in populations subject to different classes of ecological constraints. This predictive property, when integrated with the macroscopic representation of entropy, is the basis for enormous differences in morphometric and life-history parameters across species
Early carboniferous brachiopod faunas from the Baoshan block, west Yunnan, southwest China
38 brachiopod species in 27 genera and subgenera are described from the Yudong Formation in the Shidian-Baoshan area, west Yunnan, southwest China. New taxa include two new subgenera: Unispirifer (Septimispirifer) and Brachythyrina (Longathyrina), and seven new species: Eomarginifera yunnanensis, Marginatia cylindrica, Unispirifer (Unispirifer) xiangshanensis, Unispirifer (Septimispirifer) wafangjieensis, Brachythyrina (Brachythyrina) transversa, Brachythyrina (Longathyrina) baoshanensis, and Girtyella wafangjieensis. Based on the described material and constraints from associated coral and conodont faunas, the age of the brachiopod fauna from the Yudon Formation is considered late Tournaisian (Early Carboniferous), with a possibility extending into earlyViseacutean.<br /
Superação de dormĂȘncia de sementes como estratĂ©gia para restauração florestal de pastagem tropical
O objetivo deste trabalho foi avaliar a influĂȘncia de tratamentos de superação da dormĂȘncia de sementes sobre a taxa e o tempo de emergĂȘncia de espĂ©cies arbĂłreas de Fabaceae, e sobre seu estabelecimento, quando reintroduzidas em pastagem, no Cerrado. Foram realizados experimentos em casa de vegetação e em campo (pastagem de Urochloa brizantha), com as espĂ©cies Mimosa caesalpiniifolia, Peltophorum dubium, Pterogyne nitens, Dimorphandra mollis, Copaifera langsdorffii e Hymenaea stigonocarpa, submetidas ou nĂŁo aos seguintes tratamentos de superação de dormĂȘncia: D. mollis e H. stigonocarpa, escarificação mecĂąnica; C. langsdorffii e M. caesalpiniifolia, escarificação quĂmica com H2SO4; P. nitens, punção do tegumento; e P. dubium, imersĂŁo em ĂĄgua a 80ÂșC. O estabelecimento em campo foi monitorado por 21 meses. A superação de dormĂȘncia promoveu, em casa de vegetação, maior emergĂȘncia de quatro das seis espĂ©cies avaliadas, e, no campo, de cinco espĂ©cies. AlĂ©m disso, reduziu o tempo de emergĂȘncia das espĂ©cies e aumentou o recrutamento de M. caesalpiniifolia, P. nitens, D. mollis e H. stigonocarpa, aos 127 dias, e de H. stigonocarpa aos 659 dias. Os tratamentos de superação de dormĂȘncia podem aumentar a eficiĂȘncia da semeadura direta, em projetos de restauração de ĂĄreas degradadas no Cerrado, ao promover maior emergĂȘncia das sementes e o estabelecimento das plantas
Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology
notes: As the primary author, OâMalley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. âMacrobeâ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes â the dominant life form on the planet, both now and throughout evolutionary history â will transform some of the philosophy of biologyâs standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology â including biofilm formation, chemotaxis, quorum sensing and gene transfer â that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations
Measurement of the branching ratio Î(Îbâ° â Ï(2S)Î0)/Î(Îbâ° â J/ÏÎ0) with the ATLAS detector
An observation of the decay and
a comparison of its branching fraction with that of the decay has been made with the ATLAS detector in
proton--proton collisions at TeV at the LHC using an integrated
luminosity of fb. The and mesons are
reconstructed in their decays to a muon pair, while the decay is exploited for the baryon reconstruction. The
baryons are reconstructed with transverse momentum GeV and pseudorapidity . The measured branching ratio of
the and decays is , lower than the expectation from the
covariant quark model.Comment: 12 pages plus author list (28 pages total), 5 figures, 1 table,
published on Physics Letters B 751 (2015) 63-80. All figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2013-08
Measurement of the View the tt production cross-section using eÎŒ events with b-tagged jets in pp collisions at âs = 13 TeV with the ATLAS detector
This paper describes a measurement of the inclusive top quark pair production cross-section (ÏttÂŻ) with a data sample of 3.2 fbâ1 of protonâproton collisions at a centre-of-mass energy of âs = 13 TeV, collected in 2015 by the ATLAS detector at the LHC. This measurement uses events with an opposite-charge electronâmuon pair in the final state. Jets containing b-quarks are tagged using an algorithm based on track impact parameters and reconstructed secondary vertices. The numbers of events with exactly one and exactly two b-tagged jets are counted and used to determine simultaneously ÏttÂŻ and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section is measured to be:
ÏttÂŻ = 818 ± 8 (stat) ± 27 (syst) ± 19 (lumi) ± 12 (beam) pb,
where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, the integrated luminosity and the LHC beam energy, giving a total relative uncertainty of 4.4%. The result is consistent with theoretical QCD calculations at next-to-next-to-leading order. A fiducial measurement corresponding to the experimental acceptance of the leptons is also presented
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