Radiative events as a probe of dark forces at GeV-scale <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> colliders

High-luminosity e ⁺ e ⁻ colliders at the GeV scale (flavor factories) have been recently recognized to be an ideal environment to search for a light weakly coupled vector boson U (dark photon) emerging in several new physics models. At flavor factories a particularly clean channel is the production of the U boson in association with a photon, followed by the decay of the U boson into lepton pairs. Beyond the approximations addressed in previous works, we perform an exact lowest order calculation of the signal and background processes of this channel. We also include the effect of initial- and final-state QED corrections neglected so far, to show how they affect the distributions of experimental interest. We present new results for the expected statistical significance to a dark photon signal at KLOE/KLOE-2 and future super-B factories. The calculation is implemented in a new release of the event generator BabaYaga@NLO, which is available for full event simulations and data analysis.     

A logical characterization of coherence for imprecise probabilities

Whilst supported by compelling arguments, the representation of uncertainty by means of (subjective) probability does not enjoy a unanimous consensus. A substantial part of the relevant criticisms point to its alleged inadequacy for representing ignorance as opposed to uncertainty. The purpose of this paper is to show how a strong justification for taking belief as probability, namely the Dutch Book argument, can be extended naturally so as to provide a logical characterization of coherence for imprecise probability, a framework which is widely believed to accommodate some fundamental features of reasoning under ignorance. The appropriate logic for our purposes is an algebraizable logic whose equivalent algebraic semantics is a variety of MV-algebras with an additional internal unary operation representing upper probability (these algebras will be called UMV-algebras).     

Cytotoxicity and physico-chemical evaluation of acetylated and pegylated cellulose nanocrystals

The high hydrophilicity of cellulose nanocrystals (CNC) may result in poor dispersion in some matrices and solvents. So in this work, two different methodologies were used to reduce the hydrophilicity of CNC. In the first methodology, CNC were acetylated (CNC-Ac) in a mixture of acetic and hydrochloric acid, and in the second methodology, polyethylene glycol (PEG) was adsorbed onto CNC surface (CNC-PEG) under stirring in aqueous solution. CNC obtained by both methods were characterized by transmission electron microscopy (TEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta potential, and thermogravimetric analysis (TGA). Images of TEM showed that the intrinsic morphology of cellulose was preserved after both treatments. FTIR confirmed acetylation reaction by the presence of a new band at 1732 cm^?1 (acetate groups) and the consumption of OH groups. XRD showed a reduction in the crystallinity index for both applied methodologies. DLS showed reduced stability in water for CNC-Ac and CNC-PEG. Values of zeta potential changed after acetylation, from ??45 mV (CNC) to ??1 mV (CNC-Ac), and after adsorption of PEG, to ??26.7 mV (CNC-PEG). TGA showed a reduction in the thermal stability after both treatments and a change in the main degradation behavior for CNC-PEG. MTT assays showed that both proposed functionalizations induce cell proliferation, being even more evident for acetylation because, in addition to viability increase with time, it increased with the sample concentration.     

Homogeneous line width in a zinc borate glass activated by Eu

In this work we report on the temperature depedence of the homogeneous line width (Γ_h) in 4ZnO · 3B₂O₃:Eu³⁺ glass in the region between 30 K and room temperature. The time resolved resonant fluorescence line narrowing technique was applied to the ⁷F₀ ↔ ⁵D₀ transition of Eu³⁺. We obtain that Γ_h follows the commonly found behaviour T² in the whole range of temperature (30–300 K). The Γ_h is comparable to that measured in borate glasses with a small amount of network modifier. This result, together with a linear increase of Γ_h with the excitation energy within the inhomogeneous profile, is indicative of a specific local environment around the Eu³⁺ ion in the zinc borate glass.     

A path integral way to option pricing

An efficient computational algorithm to price financial derivatives is presented. It is based on a path integral formulation of the pricing problem. It is shown how the path integral approach can be worked out in order to obtain fast and accurate predictions for the value of a large class of options, including those with path-dependent and early exercise features. As examples, the application of the method to European and American options in the Black–Scholes model is illustrated. A particularly simple and fast semi-analytical approximation for the price of American options is derived. The results of the algorithm are compared with those obtained with the standard procedures known in the literature and found to be in good agreement.     

A Note on Relative Efficiency of Axiom Systems

We introduce a notion of relative efficiency for axiom systems. Given an axiom system A_β for a theory T consistent with S¹₂, we show that the problem of deciding whether an axiom system A_α for the same theory is more efficient than A_β is II₂-hard. Several possibilities of speed-up of proofs are examined in relation to pairs of axiom systems A_α, A_β, with A_α ? A_β, both in the case of A_α, A_β having the same language, and in the case of the language of A_α extending that of A_β: in the latter case, letting Pr_α, Pr_β denote the theories axiomatized by A_α, A_β, respectively, and assuming Pr_α to be a conservative extension of Pr_β, we show that if A_α — A_β contains no nonlogical axioms, then A_α can only be a linear speed-up of A_β; otherwise, given any recursive function g and any A_β, there exists a finite extension A_α of A_β such that A_α is a speed-up of A_β with respect to g. Mathematics Subject Classification: 03F20, 03F30.     

Recent results on antiproton annihilation in 4He

With experimental data of ${\bar p}$ annihilation at rest on nuclei of ⁴He, collected by the Obelix spectrometer (LEAR, CERN), we have studied a number of reactions with 4 and 5 charged particles in the final state, distinguishing the annihilations on more than one nucleon, and with strangeness production. The main results of our observations are: (a) a higher (up to 20 times) strangeness production in ⁴He than in H; (b) the evidence of a possible signature of a $\overline{K}pp$ ( $\overline{K} ppn$ ) bound state; (c) a measurement of a double strangeness production (2K ⁺) and a hint for some production yields of double-strange bound systems like 2K ^?2n; (d) a signal compatible with the baryonic $\Theta^+(1530)$ resonance, interpreted as a pentaquark system.