Abstract: Low-energy partial-wave N scattering data is reexamined with the help of the production representation of partial-wave S matrix, where branch cuts and poles are thoroughly under consideration. The left-hand cut contribution to the phase shift is determined, with controlled systematic error estimates, by using the results of O(p(3)) chiral perturbative amplitudes obtained in the extended-onmass- shell scheme. In S-11 and P-11 channels, severe discrepancies are observed between the phase shift data and the sum of all known contributions. Statistically satisfactory fits to the data can only be achieved by adding extra poles in the two channels. We find that a S-11 resonance pole locates at zr = (0:895-0:081)-(0:164-0:023)i GeV, on the complex s-plane. On the other hand, a P-11 virtual pole, as an accompanying partner of the nucleon bound-state pole, locates atzv = (0:966-0:018) GeV, slightly above the nucleon pole on the real axis below threshold. Physical origin of the two newly established poles is explored to the best of our knowledge. It is emphasized that the O(p(3)) calculation greatly improves the fit quality comparing with the previous O(p(2)) one.

Abstract: We investigate the possibility of probing the hot and dense nuclear matter-created in relativistic heavyion collisions (HICs)-with strange vector mesons (K*, (K) over bar*). Our analysis is based on the nonequilibrium parton-hadron-string dynamics (PHSD) transport approach which incorporates partonic and hadronic degrees of freedom and describes the full dynamics of HIC on a microscopic level-starting from the primary nucleon-nucleon collisions to the formation of the strongly interacting quark gluon plasma (QGP), followed by dynamical hadronization of (anti)quarks as well as final hadronic elastic and inelastic interactions. This allows us to study the K* and (K) over bar* meson formation from the QGP as well as the in-medium effects related to the modification of their spectral properties during the propagation through the dense and hot hadronic environment in the expansion phase. We employ relativistic Breit-Wigner spectral functions for the K*, (K) over bar* mesons with self-energies obtained from a self-consistent coupled-channel G-matrix approach to study the role of in-medium effects on the K* and (K) over bar* meson dynamics in heavy-ion collisions from FAIR/NICA to LHC energies. According to our analysis most of the final K* /(K) over bar*'s, that can be observed experimentally by reconstruction of the invariant mass of pi + K((K) over bar) pairs, are produced during the late hadronic phase and originate dominantly from the K((K) over bar) + pi -> K*( (K) over bar*) formation channel. The amount of K*/ (K) over bar*'s, originating from the QGP channel is comparatively small even at LHC energies and those K* /(K) over bar*'s can hardly be reconstructed experimentally due to the rescattering of final pions and (anti)kaons. This mirrors the results from our previous study on the strange vector-meson production in heavy-ion collisions at RHIC energies. We demonstrate that K* /(K) over bar* in-medium effects should be visible at FAIR/NICA and BES RHIC energies, where the production of K* /(K) over bar*'s occurs at larger net-baryon densities. Finally, we present the experimental procedures to extract the information on the resonance masses and widths by fitting the final mass spectra at LHC energies.

Abstract: Dark matter interactions with massless or very light standard model particles, as photons or neutrinos, may lead to a suppression of the matter power spectrum at small scales and of the number of low mass haloes. Bounds on the dark matter scattering cross section with light degrees of freedom in such interacting dark matter (IDM) scenarios have been obtained from e.g., early time cosmic microwave background physics and large scale structure observations. Here we scrutinize dark matter microphysics in light of the claimed 21 cm EDGES 78 MHz absorption signal. IDM is expected to delay the 21 cm absorption features due to collisional damping effects. We identify the astrophysical conditions under which the existing constraints on the dark matter scattering cross section could be largely improved due to the IDM imprint on the 21 cm signal, providing also an explicit comparison to the WDM scenario.

Abstract: We propose here a novel method which singles out the a priori unavoidable dependence on the underlying cosmological model when extracting parameter constraints, providing robust limits which only depend on the considered dataset. Interestingly, when dealing with several possible cosmologies and interpreting the Bayesian preference in terms of the Gaussian statistical evidence, the preferred model is much less favored than when only two cases are compared. As a working example, we apply our approach to the cosmological neutrino mass bounds, which play a fundamental role not only in establishing the contribution of relic neutrinos to the dark matter of the Universe but also in the planning of future experimental searches of the neutrino character and of the neutrino mass ordering.

Abstract: .We perform a calculation of the -M1M2, with M1,M2 either pseudoscalar or vector mesons using the basic weak interaction and angular momentum algebra to relate the different processes. The formalism also leads to a different interpretation of the role played by G-parity in these decays. We also observe that, while PPp-wave production is compatible with chiral perturbation theory and experiment, VP and VVp-wave production is clearly incompatible with experiment and we develop the formalism also in this case, producing the VP or VV pairs in s-wave. We compare our results with experiment and other theoretical approaches for rates and invariant mass distributions and make predictions for unmeasured decays. We show the value of these reactions, particularly if the M1M2 mass distribution is measured, as a tool to learn about the meson-meson interaction and the nature of some resonances, coupling to two mesons, which are produced in such decays.