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- Electroweak corrections to higgs boson decays in a complex singlet extension of the SM and their phenomenological impactPublication . Egle, Felix; Mühlleitner, Margarete; Santos, Rui; Viana, JoãoThe complex singlet extension CxSM of the Standard Model (SM) is a simple extension of the SM with two visible Higgs bosons in the spectrum and a Dark Matter (DM) candidate. In this paper we complete the computation of the next-to-leading (NLO) electroweak (EW) corrections to on-shell and non-loop-induced Higgs decays. Our calculations are implemented in the code EWsHDECAY which also includes the relevant QCD corrections. Performing an extensive parameter scan in the model and including all relevant theoretical and experimental single- and di-Higgs as well as DM constraints, we obtain a viable parameter sample. We find that current DM constraints are able to test the model in DM mass regions where collider searches are not sensitive. The relative EW corrections turn out to be large for scenarios with relatively large couplings, threshold effects or small leading-order (LO) widths. Otherwise, they are of typical EW size and can amount up to about 20-25%. The theory uncertainty derived from the change of the renormalization scheme dependence then is of a few per cent. While the NLO corrections applied in the constraints due to single- and di-Higgs searches impact the validity of specific parameter points, the overall shape of the allowed parameter region is not yet sensitive to the EW corrections. This picture will change with further increased experimental precision in the future and necessitates precise predictions on the theory side as presented in this paper.
- Wide-angle seismic imaging of divergente and transform segments of the Pará-Maranhão-Barreirinhas-Ceará margin, NW BrazilPublication . Schnürle, Philippe; Gallais, Flora; Afilhado, Alexandra; Moulin, Maryline; Dias, Nuno; Soares, José; Loureiro, Afonso; Fuck, Reinhardt; Cupertino, José António; Viana, Adriano; Aslanian, DanielThe structure of the North-East equatorial Brazilian margin was investigated during the MAGIC (Margins of brAzil, Ghana and Ivory Coast) seismic wide-angle experiment. This study focuses on the MC5 profile, that spans NW-SE 720 km in length, from the São Paulo Double Fracture Zone to the Barreirinhas margin and continental Borborema province. Its main objective is to understand the fundamental processes which lead to the thinning and finally to the breakup of the continental crust in a specific context of a divergent pull-apart system with two strike-slip borders. The experiment was devised to obtain the 2D structure along this profiles from joint pre-stack depth migration of streamer data and travel-time inversion by forward modeling of 43 Ocean Bottom Seismometers and 21 Land Seismic Stations records. Along the MC5 wide-angle transect, 4 major sectors are identified: 1) the São Paulo Double Fracture Zone presenting a 4.5 km thick volcano-sedimentary Basin on top of a 5.5 km thick basement; 2) a volcanic alignment and intermediate domain SE-ward, formed by the 4.5 km thick Basin III; 3) the 7.5 km thick Basin II, and the 5.5 km thick Basin I composing the continental slope and shelf. While all the offshore basement remains about 6 km thick in the deep-sea domains, acoustic velocity evolves from two-layer 4.8–6 km/s and 6.1–6.8 km/s beneath Basin III to two-layer high velocity 6.1–6.8 km/s and 7.2–7.4 km/s beneath Basin II and I, The necking zone, forming the Parnaiba Platform and associated Piaui-Camocim and Ceará Basins, is 50 km wide; 4) the Médio Coreaú and Ceará Central thrust belt, where the un-thinned continental crust thickness reaches 32 km. Finally, a schematic kinematic reconstruction that satisfies these observation is argumented.
- Neutrino physics: experimental and theoretical challengePublication . Gonzalez Felipe, RicardoThe existence of massive neutrinos is the first solid evidence of physics beyond the standard model of particle physics. A remarkable progress has been achieved in solar, atmospheric, reactor, and accelerator neutrino experiments during the last decades. On the theoretical side, several questions are being addressed, namely the Dirac or Majorana nature of neutrinos, the mechanisms for neutrino mass generation, and the relation between neutrinos and the matter-antimatter asymmetry observed in the Universe, among others. This article provides a brief overview on some of the current experimental and theoretical aspects in neutrino physics.
- Aging effects on the rheology of LC solutions of hydroxypropylcellulosePublication . Leal, Catarina R.; Godinho, M. H.; Martins, A. F.; Fried, F.We apply the recently developed continuum theory of liquid crystalline polymers1 to interpret the behavior of the shear viscosity η(γ.) and the first normal-stress difference N1(γ.) measured for liquid crystalline solutions (c = 37%, c > c*) of HPC (Aldrich, Mw = 100,000) in acetic acid (AA) with different ages: 1 day, 1 month and 2 years. η(γ.) and N1(γ.) were measured over four decades in γ. N1(γ.) is observed to change from positive to negative and again to positive, as the shear rate γ. increases. η(γ.) shows a small newtonian plateau at low shear rates and a strong shear-thinning at higher values of γ. The rate of decrease of η(γ.) in this region is not monotonous, as usual, but shows an “hesitation” similar to one previously observed in a different system2. The aging effect promotes a “depolymerization”3 of HPC. This, in turn, should have a strong influence on the behavior of Nl(γ.) and η(γ.) which is indeed observed4. All these observations can be rationalized within the framework of the theory1.
- Rheological properties of lyotropic solutions of acetoxypropylcellulose in dimethylacetamide. A comparision with the thermotropic casePublication . Cidade, M. T.; Leal, Catarina R.The rheological properties of a thermotropic acetoxypropylcellulose (APC) were already described in previous works [1,2]. In this work we present the rheo logical properties, viscosity, Z, and first normal stress difference, N1, of lyotropic solutions of APC in dimethylacetamide (DMAc). The flow curve of the lyotropic solution presents the typical behavior for this type of system (Onogi and Asada Curve) [3] however, contrary to what happens with that other lyotropic system [4–7], the APC/DMAc system presents a con tinuous increase of N1 in function of the shear rate, which we attribute to the fact that APC has higher flexibility than the other liquid crystalline polymers studied so far—namely hydroxypropylcellulose and poly-benzyl-L-glutamate— that present a negative N1 region, as well as a low molecular weight. We will also present some remarks concerning rheo-optical studies preformed with APC/DMAc, by comparison with previous studies on thermotropic APC [8,9].
- Experimental Results for the Rheological and Rheo-Optical Behavior of Poly(ethylene terephthalate)/ Liquid-Crystalline Polymer BlendsPublication . Cidade, M. T.; Menon, A. R.; Leal, Catarina R.; Pillai, C. K. S.The use of thermoplastic/liquid-crystalline polymer (LCP) blends is recognized as a good strategy for reducing viscosity and improving mechanical properties relative to pure thermoplastics. This improvement, how ever, is only noticeable if the LCP fibrillates, in situ, during processing and the fibrils are kept in the solid state. In this article, we report a morphological, rheological, and rheo optics study performed with two blends of poly(ethylene terephthalate) with a LCP, Rodrun LC3000 (10 and 25 wt % LCP content), and we show that the obtained droplet shape relaxation time (the time the deformed droplet took to regain its spherical form after the cessation of flow) allowed for the explanation of the morphological observa tions. In fact, the droplet-shape relaxation time was higher for the blend with higher LCP content, for the higher experimentally accessible shear rates, and still increased at the highest shear rate, which explained the fibrils of the LCP dispersed phase observed in this blend, whereas for the lower LCP content blend, the droplet-shape relaxation time reached a low-value plateau for higher shear rates, which explained the absence of fibrillation in this blend.
- Temperature dependence of the rheological properties of acetoxypropylcellulose in the thermotropic chiral nematic phasePublication . Cidade, M. T.; Leal, Catarina R.; Godinho, M. H.; Navard, P.The rheological behaviour of two different molecular weights of a thermotropic liquid crystalline cellulose derivative, acetoxypropylcellulose (APC), at T=I2OoC, has already been reported [ l]. In this work we present the temperature dependence of the rheological properties of two molecular weights of APC. The shear viscosity, q, and first normal stress difference, N,, were measured at temperatures T=120, 130 and 140°C. for Mciw = 94000 g/mole, and T=120 and 140°C for Mw = 129000 g/mole, and for shear rates, +, between 0.01 and 10 s-’. The shear viscosity q(+) decreases with increasing T, for both samples, showing a strong shear thinning behaviour at all temperatures and over the whole range of + studied, except for shear rates between about 0.2 and 1 s-’ (depending on IGiw and T), where a quasi-Newtonian plateau is observed. The first normal stress difference N1 (+) also decreases with increasing T at a given +. It increases with shear rate over the whole + range studied, and shows an inflection at + values slightly above + = 1/r, where z is the relaxation time of the polymer memory function. The temperature dependence of the shear viscosity was fitted to an Arrhenius law, giving an apparent activation energy (E,) in the order of 8-15 kcaUmole, depending on molecular weight and shear rate. The activation energy was found to increase with molecular weight (at a given + ). The variation of E, with +, , for Mw = 94000 g/mole, shows a minimum at ;i x 2 s-l. Using a continuum theory for nematic polymers, proposed by Martins [2], some fundamental parameters were obtained from the fit of the theory to the experimental data. Using these parameters it was possible to construct a “master curve” for the viscosity, q(+), in good agreement with the experimental data.
- The influence of polymer molecular weight on the first normal-stress difference and shear-viscosity of LC solutions of hydroxypropylcellulosePublication . Martins, A. F.; Leal, Catarina R.; Godinho, M. H.; Fried, F.first normal-stress difference Ni(+) and the shear viscosity V(?) have been measured for liquid crystalline solutions of HFC in acetic acid (AA) as functions of the shear rate i. and the molecu lar mass of HPC. The measurements were done over four decades in +, for two samples of HPC with M, =6O,OOO and 100,OOO (Klucel E and L, respectively) and solution concentration c = 37% (c > c*). N1(+) is observed to change from positive to negative and again to positive, as the shear rate + increases. The 7 values at which N, changes sign depend on M,. The viscosity q(+) shows a small Newtonian plateau at low shear rates and a strong shear-thinning at higher values of +, includ ing an “hesitation” similar to one previously observed in LC solutions of PBUj [2]. All these obser vations are rationalized within the framework of the constitutive equations for liquid crystalline polymers recently proposed by one of us [l]. Expressions for q(+) and Nl(+) derived from this theory fit very well (quantitatively) to the experimental data and some fundamental viscoelastic parameters of the system are thereby obtained for the first time.
- Some Aspects of the Rheo-Nmr Behavior of the Lyotropic Liquid Crystal Poly(γ-BENZYL-L GLUTAMATE) in m-CresoPublication . Leal, Catarina R.; Klink, Jacques; Martins, AssisWe report the use of 2 H NMR spectroscopy to study the director orientation in two nematic solutions of poly(c-benzyl-L-glutamate) (PBLG) in m-cresol during simple shear flow and after its sudden cessation. In the range of applied shear rates ðc_ ¼ 5 ... 150 s 1Þ, a steady-state NMR line shape is reached after a deformation of a few hundred units. Two different line shapes occur that can be related to distinct shear responses in mechanical rheology: the tumbling=wagging and the flow-aligning regimes. The relaxation after cessation of the shear is similar for both cases and essentially follows the ‘‘inhomogeneous reorientation’’ regime known from sudden-rotation NMR experiments. A fit of the relaxation curves indicates that the tumbling parameter k is (slightly) less than one, as expected for a tumbling system.
- Reversible photorheology in solutions of cetyltrimethylammonium bromide, salicylic acid, and trans-2,4,40 -trihydroxychalconePublication . Pereira, M.; R. Leal, Catarina; Parola, A. J.; Sheven, U. M.We show photorheology in aqueous solutions of weakly entangled wormlike micelles prepared with cetyltrimethyl-ammonium bromide (CTAB), salicylic acid (HSal), and dilute amounts of the photochromic multistate compound trans-2,4,40 -trihydroxychalcone (Ct). Different chemical species of Ct are associated with different colorations and propensities to reside within or outside CTAB micelles. A light-induced transfer between the intra- and intermicellar space is used to alter the mean length of wormlike micelles and hence the rheological properties of the fluid, studied in steady-state shear flow and in dynamic rheological measurements. Light-induced changes of fluid rheology are reversible by a thermal relaxation process, at relaxation rates which depend on pH and which are consistent with photochromic reversion rates measured by UV-vis absorption spectroscopy. Parameterizing viscoelastic rheological states by their effective relaxation time τc and corresponding response modulus Gc, we find the light and dark states of the system to fall onto a characteristic state curve defined by comparable experiments conducted without photosensitive components. These reference experiments were prepared with the same concentration of CTAB, but different concentrations of HSal or sodium salicylate (NaSal), and tested at different temperatures.