Abstract: In this paper we explore possible extensions of interacting dark energy cosmologies, where dark energy and dark matter interact nongravitationally with one another. In particular, we focus on the neutrino sector, analyzing the effect of both neutrino masses and the effective number of neutrino species. We consider the Planck 2018 legacy release data combined with several other cosmological probes, finding no evidence for new physics in the dark radiation sector. The current neutrino constraints from cosmology should therefore be regarded as robust, as they are not strongly dependent on the dark sector physics, once all the available observations are combined. Namely, we find a total neutrino mass g, < 0.15 eV and a number of effective relativistic degrees of freedom N-eff = 3.03(-0.33)(+0.33), both at 95% C.L., which are close to those obtained within the ACDM cosmology, M-v < 0.12 eV and N-eff = (+0.36)(-0.35), for the same data combination.

Abstract: In this paper we perform an amplitude analysis of eta ' -> pi(+)pi(-)gamma and confront it with the latest BESIII data. Based on the final-state interaction theorem, we represent the amplitude in terms of an Omnes function multiplied by a form factor that corresponds to the contributions from left-hand cuts and right-hand cuts in the inelastic channels. We also take into account the isospin violation effect induced by rho-omega mixing. Our results show that the anomaly contribution is mandatory in order to explain the data. Its contribution to the decay width of Gamma(eta ' -> pi pi gamma) is larger than that induced by isospin violation. Finally we extract the pole positions of the rho and omega as well as their corresponding residues.

Abstract: In this paper we study the reaction e(+)e(-) -> (D*(D*) over bar (+/-)pi(-/+) in which the BESIII collaboration has claimed the existence of a 1(+) resonance, named Z(c)(4025), in the (D*(D*) over bar invariant mass spectrum with a mass around 4026 MeV and width close to 26 MeV. We determine the (D*(D*) over bar invariant mass distribution and find that although the explanation considered by the BESIII collaboration is plausible, there are others which are equally possible, like a 2(+) resonance or a bound state. Even more, we find that the data can be explained without the existence of a resonance/bound state. In view of the different possible interpretations found for the BESIII data, we try to devise a strategy which could help in identifying the origin of the signal reported by the BESIII collaboration. For this, we study the dependence of the (D*(D*) over bar spectrum considering the different options as a function of the total center-of-mass energy. We arrive at the conclusion that increasing the center-of-mass energy from 4.26 GeV to 4.6 GeV can be useful to distinguish between a resonance, a bound state or just a pure background as being responsible for the signal found. This information should be useful for future experiments.

Abstract: In this paper we use two different but complementary approaches in order to study the ghost propagator of a pure SU(3) Yang-Mills theory quantized in the linear covariant gauges, focusing on its dependence on the gauge-fixing parameter xi in the deep infrared. In particular, we first solve the Schwinger-Dyson equation that governs the dynamics of the ghost propagator, using a set of simplifying approximations, and under the crucial assumption that the gluon propagators for xi > 0 are infrared finite, as is the case in the Landau gauge (xi = 0). Then we appeal to the Nielsen identities, and express the derivative of the ghost propagator with respect to xi in terms of certain auxiliary Green's functions, which are subsequently computed under the same assumptions as before. Within both formalisms we find that for xi > 0 the ghost dressing function approaches zero in the deep infrared, in sharp contrast to what happens in the Landau gauge, where it is known to saturate at a finite (nonvanishing) value. The Nielsen identities are then extended to the case of the gluon propagator, and the xi-dependence of the corresponding gluon masses is derived using as input the results obtained in the previous steps. The result turns out to be logarithmically divergent in the deep infrared; the compatibility of this behavior with the basic assumption of a finite gluon propagator is discussed, and a specific Ansatz is put forth, which readily reconciles both features.

Abstract: In this paper, analogies between multiparticle production in high-energy collisions and the time evolution of the early Universe are discussed. A common explanation is put forward under the assumption of an unconventional early state: a rapidly expanding universe before recombination (last scattering surface), followed by the cosmic microwave background, later evolving up to present days, versus the formation of hidden/dark states in hadronic collisions followed by a conventional QCD parton shower yielding final-state particles. In particular, long-range angular correlations are considered pointing out deep connections between the two physical cases potentially useful for the discovery of new physics.