Aurigaia: mock Gaia DR2 stellar catalogues from the Auriga cosmological simulations

We present and analyse mock stellar catalogues that match the selection criteria and observables (including uncertainties) of the Gaia satellite data release 2 (DR2). The source are six cosmological high-resolution magneto-hydrodynamic ΛCDM zoom simulations of the formation of Milky Way analogues from the AURIGA project. Mock data are provided for stars with V 20 deg. The mock catalogues are made using two different methods: the public SNAPDRAGONS code, and a method based on that of Lowing et al. (2015) that preserves the phase-space distribution of the model stars. These publicly available catalogues contain five-parameter astrometry, radial velocities, multiband photometry, stellar parameters, dust extinction values, and uncertainties in all these quantities. In addition, we provide the gravitational potential and information on the origin of each star. By way of demonstration, we apply the mock catalogues to analyses of the young stellar disc and the stellar halo. We show that (i) the young outer stellar disc exhibits a flared distribution that is detectable in the height and vertical velocity distribution of A - and B -dwarf stars up to radii of ∼15 kpc, and (ii) the spin of the stellar halo out to 100 kpc can be accurately measured with Gaia DR2 RR Lyrae stars. These catalogues are well suited for comparisons with observations and should help to (i) develop and test analysis methods for the Gaia DR2 data, (ii) gauge the limitations and biases of the data, and (iii) interpret the data in the light of theoretical predictions from realistic ab initio simulations of galaxy formation in the ΛCDM cosmological model

Cooling down the world oceans and the earth by enhancing the North Atlantic Ocean current

The world is going through intensive changes due to global warming. It is well known that the reduction in ice cover in the Arctic Ocean further contributes to increasing the atmospheric Arctic temperature due to the reduction of the albedo effect and increase in heat absorbed by the ocean’s surface. The Arctic ice cover also works like an insulation sheet, keeping the heat in the ocean from dissipating into the cold Arctic atmosphere. Increasing the salinity of the Arctic Ocean surface would allow the warmer and less salty North Atlantic Ocean current to flow on the surface of the Arctic Ocean considerably increasing the temperature of the Arctic atmosphere and release the ocean heat trapped under the ice. This paper argues that if the North Atlantic Ocean current could maintain the Arctic Ocean ice-free during the winter, the longwave radiation heat loss into space would be larger than the increase in heat absorption due to the albedo effect. This paper presents details of the fundamentals of the Arctic Ocean circulation and presents three possible approaches for increasing the salinity of the surface water of the Arctic Ocean. It then discusses that increasing the salinity of the Arctic Ocean would warm the atmosphere of the Arctic region, but cool down the oceans and possibly the Earth. However, it might take thousands of years for the effects of cooling the oceans to cool the global average atmospheric temperature

Mapping the potential for pumped storage using existing lower reservoirs

The increasing utilization of wind and solar power sources to lower CO2 emissions in the electric sector is causing a growing disparity between electricity supply and demand. Consequently, there is a heightened interest in affordable energy storage solutions to address this issue. Pumped Hydropower Storage (PHS) emerges as a promising option, capable of providing both short and long-term energy storage at a reasonable cost, while also offering the advantage of freshwater storage. To identify potential PHS locations in Brazil existing hydroelectric reservoirs as the lower reservoirs, we employed an innovative methodology that combines (i) plant-siting model that leverages high-resolution topographical and hydrological data to identify the most promising sites for further studies. (ii) An economic methodology was applied to configure PSH projects identified by the plant-siting model in terms of their installed capacity and discharge time, and to select the most attractive projects. (iii) A comprehensive analysis of the socio-environmental impacts of the projects was carried out, which enables the elimination of projects with severe impacts. Results created a ranking of 5600 mutually exclusive projects by net present value (NPV). The highest NPV is 2145 USD which refers to a PHS plant in the Doce Basin and Salto Grande dam as the lower reservoir. The upper reservoir stores 0.36 km3 of water and a 75 m high dam, the PHS has a 2 km tunnel, a 1 GW power capacity and discharge rate of 220 h. The paper shows a vast potential for weekly, monthly, and seasonal PHS with existing lower reservoirs in Brazil

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV

A search is presented for physics beyond the standard model (BSM) in final states with a pair of opposite-sign isolated leptons accompanied by jets and missing transverse energy. The search uses LHC data recorded at a center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to an integrated luminosity of approximately 5 inverse femtobarns. Two complementary search strategies are employed. The first probes models with a specific dilepton production mechanism that leads to a characteristic kinematic edge in the dilepton mass distribution. The second strategy probes models of dilepton production with heavy, colored objects that decay to final states including invisible particles, leading to very large hadronic activity and missing transverse energy. No evidence for an event yield in excess of the standard model expectations is found. Upper limits on the BSM contributions to the signal regions are deduced from the results, which are used to exclude a region of the parameter space of the constrained minimal supersymmetric extension of the standard model. Additional information related to detector efficiencies and response is provided to allow testing specific models of BSM physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.Comment: Submitted to Physics Letters