Search results for "HIDDEN"
showing 10 items of 210 documents
The width of the omega meson in the nuclear medium
2013
We evaluate the width of the omega meson in nuclear matter. We consider the free decay mode of the omega into three pions, which is dominated by rho IEuro decay, and replace the rho and pi propagators by their medium-modified ones. We also take into account the quasielastic and inelastic processes induced by a vector-baryon interaction dominated by vector meson exchange, as well as the contributions coming from the mechanism with medium-modified K , propagators. We obtain a substantial increase of the omega width in the medium, reaching a value of 121 +/- 10 MeV at normal nuclear matter density for an omega at rest, which comes mainly from omega N -> pi pi N, omega NN -> pi NN processes ass…
Charmed hadrons in nuclear medium
2010
5th International Conference on Quarks and Nuclear Physics (QNP09).Inst High Energy Phys Chinese Acad Sci, Beijing, PEOPLES R CHINA, SEP 21-25, 2009
Search for K+ decays to a muon and invisible particles
2021
The NA62 experiment at CERN reports searches for $K^+\to\mu^+N$ and $K^+\to\mu^+\nu X$ decays, where $N$ and $X$ are massive invisible particles, using the 2016-2018 data set. The $N$ particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of ${\cal O}(10^{-8})$ of the neutrino mixing parameter $|U_{\mu4}|^2$ for $N$ masses in the range 200-384 MeV/$c^2$ and lifetime exceeding 50 ns. The $X$ particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for $X$ masses in the range 10-370 MeV/$c^2$ are reported for the first time, ranging from ${\cal O}(10^{-5})$ t…
The search for dark matter gauge bosons with the Mainz Microtron
2011
Abstract A pilot experiment in the search for light gauge bosons at the spectrometer setup of the A1 collaboration at MAMI is presented. Light gauge bosons arise naturally in a wide range of theoretical approaches beyond the standard model and are in accordance with several pieces of experimental evidence not yet understood in the standard model. A first test measurement at MAMI showed that existing limits on the coupling of such a light gauge boson can be improved by nearly an order of magnitude by fixed target experiments at existing electron accelerators.
isotracer: An R package for the analysis of tracer addition experiments
2021
AbstractTracer addition experiments, particularly using isotopic tracers, are becoming increasingly important in a variety of studies aiming at characterizing the flows of molecules or nutrients at different levels of biological organization, from the cellular and tissue levels, to the organismal and ecosystem levels.We present an approach based on Hidden Markov Models (HMM) to estimate nutrient flow parameters across a network, and its implementation in the R package isotracer.The isotracer package is capable of handling a variety of tracer study designs, including continuous tracer drips, pulse experiments, and pulse-chase experiments. It can also take into account tracer decay when radio…
Case in favor of the N*(1700)(3/2(-))
2013
Using an interaction extracted from the local hidden-gauge Lagrangians, which brings together vector and pseudoscalar mesons, and the coupled channels rho N (s wave), pi N (d wave), pi Delta (s wave), and pi Delta (d wave), we look in the region ofv root s = 1400-1850 MeV and find two resonances dynamically generated by the interaction of these channels, which are naturally associated to N*(1520)(3/2(-)) and N*(1700)(3/2(-)). N*(1700)(3/2(-)) appears neatly as a pole in the complex plane. The free parameters of the theory are chosen to fit the pi N (d-wave) data. Both the real and imaginary parts of the pi N amplitude vanish in our approach in the vicinity of this resonance, which is simila…
Observational constraints on decoupled hidden sectors
2016
We consider an extension of the Standard Model with a singlet sector consisting of a real (pseudo)scalar and a Dirac fermion coupled with the Standard Model only via the scalar portal. We assume that the portal coupling is weak enough for the singlet sector not to thermalize with the Standard Model allowing the production of singlet particles via the freeze-in mechanism. If the singlet sector interacts with itself sufficiently strongly, it may thermalize within itself, resulting in dark matter abundance determined by the freeze-out mechanism operating within the singlet sector. We investigate this scenario in detail. In particular, we show that requiring the absence of inflationary isocurva…
Reheating the Standard Model from a hidden sector
2016
We consider a scenario where the inflaton decays to a hidden sector thermally decoupled from the visible Standard Model sector. A tiny portal coupling between the hidden and the visible sectors later heats the visible sector so that the Standard Model degrees of freedom come to dominate the energy density of the Universe before Big Bang Nucleosynthesis. We find that this scenario is viable, although obtaining the correct dark matter abundance and retaining successful Big Bang Nucleosynthesis is not obvious. We also show that the isocurvature perturbations constituted by a primordial Higgs condensate are not problematic for the viability of the scenario.
Icecube/DeepCore tests for novel explanations of the MiniBooNE anomaly
2019
While the low-energy excess observed at MiniBooNE remains unchallenged, it has become increasingly difficult to reconcile it with the results from other sterile neutrino searches and cosmology. Recently, it has been shown that non-minimal models with new particles in a hidden sector could provide a better fit to the data. As their main ingredients they require a GeV-scale $Z'$, kinetically mixed with the photon, and an unstable heavy neutrino with a mass in the 150 MeV range that mixes with the light neutrinos. In this letter we point out that atmospheric neutrino experiments (and, in particular, IceCube/DeepCore) could probe a significant fraction of the parameter space of such models by l…
Los prejuicios no percibidos y el caso Sócrates: un ejemplo paradigmático
2021
En un trabajo anterior defendimos que no se había prestado suficiente atención al procedimiento utilizado en el juicio contra Sócrates, sin que examináramos las causas de esa desatención. Ahora, tras analizarlas, llegamos a la conclusión de que ese procedimiento se habría malentendido completamente al haberse implementado un prejuicio no percibido. Habríamos extrapolado a ese procedimiento los presupuestos individualistas de los procedimientos vigentes hoy en día y, en consecuencia, habríamos estado sordos a lo que nos dice la tradición. Un ejemplo de sordera que podría ser muy útil para detectar otros casos semejantes de implementación de prejuicios no percibidos. In a previous work, we de…