Temporal fluctuations of waves in weakly nonlinear disordered media

We consider the multiple scattering of a scalar wave in a disordered medium with a weak nonlinearity of Kerr type. The perturbation theory, developed to calculate the temporal autocorrelation function of scattered wave, fails at short correlation times. A self-consistent calculation shows that for nonlinearities exceeding a certain threshold value, the multiple-scattering speckle pattern becomes unstable and exhibits spontaneous fluctuations even in the absence of scatterer motion. The instability is due to a distributed feedback in the system "coherent wave + nonlinear disordered medium". The feedback is provided by the multiple scattering. The development of instability is independent of the sign of nonlinearity.Comment: RevTeX, 15 pages (including 5 figures), accepted for publication in Phys. Rev.

Microalgae biorefinery alternatives and hazard evaluation

Biodiesel production based on microalgae and using carbon dioxide as feedstock constitutes an attractive biofuel alternative. Technology development and process optimization are necessary to minimize the overall production cost. Moreover, in the framework of process sustainability, social and environmental impacts should include process safety aspects. In this context, the objective of this work is to develop a biodiesel production process based on microalgae and the subsequent estimation of the associated risks, thus contributing to more sustainable and safe processes. The biodiesel biorefinery is optimized, taking into account alternative configurations for algae cultivation and lipid extraction. Algae cultivation options are open ponds and tubular photobioreactors. Regarding lipid extraction, dewatering and subsequent n-hexane extraction, and combined ethanol/n-hexane extraction are the studied alternatives. Numerical results showed that open ponds and n-hexane extraction provide maximum net present value. However, n-hexane consumption dramatically rises, and industrial hazards have not been considered in the optimization process. To overcome this issue, a preliminary hazard analysis is carried out to identify hazardous materials and operations. Event trees are formulated to derive the frequencies of different accident scenarios, further determining the consequences. The major consequences of accidents involve toxic releases of high quantities of n-hexane. By comparing the proposed alternatives, this work aims to highlight the need to consider not only economic but also safety and environmental objectives in the development of a biodiesel production project.The authors are grateful for the financial support provided by CONICET and the Spanish MICINN under projects CTQ2013-48280-C3-1-R and CTM2014-57833-R. J. Pinedo would also like to thank the financial support provided by “Becas Iberoamérica JPI España 2014”

Phenomenological MSSM interpretation of CMS searches in pp collisions at √s=7 and 8 TeV

Searches for new physics by the CMS collaboration are interpreted in the framework of the phenomenological minimal supersymmetric standard model (pMSSM). The data samples used in this study were collected at root s = 7 and 8 TeV and have integrated luminosities of 5.0 fb(-1) and 19.5 fb(-1), respectively. A global Bayesian analysis is performed, incorporating results from a broad range of CMS supersymmetry searches, as well as constraints from other experiments. Because the pMSSM incorporates several well-motivated assumptions that reduce the 120 parameters of the MSSM to just 19 parameters defined at the electroweak scale, it is possible to assess the results of the study in a relatively straightforward way. Approximately half of the model points in a potentially accessible subspace of the pMSSM are excluded, including all pMSSM model points with a gluino mass below 500 GeV, as well as models with a squark mass less than 300 GeV. Models with chargino and neutralino masses below 200 GeV are disfavored, but no mass range of model points can be ruled out based on the analyses considered. The nonexcluded regions in the pMSSM parameter space are characterized in terms of physical processes and key observables, and implications for future searches are discussed

Forward-backward asymmetry of Drell-Yan lepton pairs in pp collisions at root s=8 TeV

Peer reviewe

Search for massive WH resonances decaying into the l nu b(b)over-bar final state at root s=8 TeV

Peer reviewe

Measurement of the inclusive 3-jet production differential cross section in proton-proton collisions at 7 TeV and determination of the strong coupling constant in the TeV range

This paper presents a measurement of the inclusive 3-jet production differential cross section at a proton–proton centre-of-mass energy of 7 TeV using data corresponding to an integrated luminosity of 5 fb-1 collected with the CMS detector. The analysis is based on the three jets with the highest transverse momenta. The cross section is measured as a function of the invariant mass of the three jets in a range of 445–3270 GeV and in two bins of the maximum rapidity of the jets up to a value of 2. A comparison between the measurement and the prediction from perturbative QCD at next-to-leading order is performed. Within uncertainties, data and theory are in agreement. The sensitivity of the observable to the strong coupling constant αS is studied. A fit to all data points with 3-jet masses larger than 664 GeV gives a value of the strong coupling constant of αS(MZ)=0.1171±0.0013(exp)-0.0047+0.0073(theo)

Search for heavy neutrinos and W bosons with right-handed couplings in proton - proton collisions at \sqrt = 8TeV

A search for heavy, right-handed neutrinos, Nℓ ( ℓ=e,μ ), and right-handed WR bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS experiment. The search was based on a sample of two lepton plus two jet events collected in proton–proton collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb-1 . For models with strict left-right symmetry, and assuming only one Nℓ flavor contributes significantly to the WR decay width, the region in the two-dimensional (MWR,MNℓ) mass plane excluded at a 95 % confidence level extends to approximately MWR=3.0TeV and covers a large range of neutrino masses below the WR boson mass, depending on the value of MWR . This search significantly extends the (MWR,MNℓ) exclusion region beyond previous results. Electronic supplementary material The online version of this article (doi:10.1140/epjc/s10052-014-3149-z) contains supplementary material, which is available to authorized users

Search for lepton flavour violating decays of heavy resonances and quantum black holes to an eμ pair in proton–proton collisions at √s = 8 TeV

A search for narrow resonances decaying to an electron and a muon is presented. The eμ mass spectrum is also investigated for non-resonant contributions from the production of quantum black holes (QBHs). The analysis is performed using data corresponding to an integrated luminosity of 19.7 fb-1 collected in proton-proton collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC. With no evidence for physics beyond the standard model in the invariant mass spectrum of selected eμ pairs, upper limits are set at 95 % confidence level on the product of cross section and branching fraction for signals arising in theories with charged lepton flavour violation. In the search for narrow resonances, the resonant production of τ sneutrino in R-parity violating supersymmetry is considered. The τ sneutrino is excluded for masses below 1.28 TeV for couplings λ132= λ231= λ311′= 0.01 , and below 2.30 TeV for λ132= λ231= 0.07 and λ311′= 0.11. These are the most stringent limits to date from direct searches at high-energy colliders. In addition, the resonance searches are interpreted in terms of a model with heavy partners of the Z boson and the photon. In a framework of TeV-scale quantum gravity based on a renormalization of Newton’s constant, the search for non-resonant contributions to the eμ mass spectrum excludes QBH production below a threshold mass Mth of 1.99 TeV. In models that invoke extra dimensions, the bounds range from 2.36 TeV for one extra dimension to 3.63 TeV for six extra dimensions. This is the first search for QBHs decaying into the eμ final state