Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userLimits on the Existence of sub-MeV Sterile Neutrinos from the Decay of $^7$Be in Superconducting Quantum Sensors
70
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Sterile neutrinos are natural extensions to the standard model of particle physics and provide a possible portal to the dark sector. We report a new search for the existence of sub-MeV sterile neutrinos using the decay-momentum reconstruction technique in the decay of $^7$Be. The experiment measures the total energy of the $^7$Li daughter atom from the electron capture decay of $^7$Be implanted into sensitive superconducting tunnel junction (STJ) quantum sensors. This first experiment presents data from a single STJ operated at a low count rate for a net total of 28 days, and provides exclusion limits on sterile neutrinos in the mass range from 100 to 850 keV that improve upon previous work by up to an order of magnitude.
rate research
Read More
The existence of light sterile neutrinos, as predicted in several models, can help to explain a number of observations starting from dark mater to recent anomalies in short baseline experiments. In this paper we consider two models - Left-Right Symmetric Zee model and Extended Seesaw model, that can naturally accommodate the presence of light sterile neutrinos in the eV to MeV mass scale. We perform a detailed study on the neutrinoless double beta decay process which receives major contributions from diagrams involving these light sterile neutrinos. Considering a number of theoretical and experimental constraints, including light neutrino masses and mixings, unitarity of the mixing matrix etc., we compare our predicted values of the half-life of neutrinoless double beta decay with the experimental limits. This can put significant constraints on the neutrino mass, active-sterile neutrino mixing and several other important parameters in these models.
A detailed discussion is given of the analysis of recent data to obtain improved upper bounds on the couplings $|U_{e4}|^2$ and $|U_{mu 4}|^2$ for a mainly sterile neutrino mass eigenstate $ u_4$. Using the excellent agreement among ${cal F}t$ values for superallowed nuclear beta decay, an improved upper limit is derived for emission of a $ u_4$. The agreement of the ratios of branching ratios $R^{(pi)}_{e/mu}=BR(pi^+ to e^+ u_e)/BR(pi^+ to mu^+ u_mu)$, $R^{(K)}_{e/mu}$, $R^{(D_s)}_{e/tau}$, $R^{(D_s)}_{mu/tau}$, and $R^{(D)}_{e/tau}$, and the branching ratios $BR(B^+rightarrow e^+ u_e)$ and $BR(B^+rightarrow mu^+ u_mu)$ decays with predictions of the Standard Model, is utilized to derive new constraints on $ u_4$ emission covering the $ u_4$ mass range from MeV to GeV. We also discuss constraints from peak search experiments probing for emission of a $ u_4$ via lepton mixing, as well as constraints from pion beta decay, CKM unitarity, $mu$ decay, leptonic $tau$ decay, and other experimental inputs.
Discovering neutrino decay would be strong evidence of physics beyond the Standard Model. Presently, there are only lax lower limits on the lifetime $tau$ of neutrinos, of $tau/m sim 10^{-3}$ s eV$^{-1}$ or worse, where $m$ is the unknown neutrino mass. High-energy cosmic neutrinos, with TeV-PeV energies, offer superior sensitivity to decay due to their cosmological-scale baselines. To tap into it, we employ a promising method, recently proposed, that uses the Glashow resonance $bar{ u}_e + e to W$, triggered by $bar{ u}_e$ of 6.3 PeV, to test decay with only a handful of detected events. If most of the $ u_1$ and $ u_2$ decay into $ u_3$ en route to Earth, no Glashow resonance would occur in neutrino telescopes, because the remaining $ u_3$ have only a tiny electron-flavor content. We turn this around and use the recent first detection of a Glashow resonance candidate in IceCube to place new lower limits on the lifetimes of $ u_1$ and $ u_2$. For $ u_2$, our limit is the current best. For $ u_1$, our limit is close to the current best and, with the imminent detection of a second Glashow resonance, will vastly surpass it.
IceCube has observed a flux of cosmic neutrinos, with a bump in the energy range $10 lesssim E/{rm TeV} lesssim 100$ that creates a $3sigma$ tension with gamma-ray data from the Fermi satellite. This has been interpreted as evidence for a population of hidden cosmic-ray accelerators. We propose an alternative explanation of this conundrum on the basis of cold dark matter which decays into sterile neutrinos that after oscillations produce the bump in the cosmic neutrino spectrum.
Improved upper bounds are presented on the coupling $|U_{e4}|^2$ of an electron to a sterile neutrino $ u_4$ from analyses of data on nuclear and particle decays, including superallowed nuclear beta decays, the ratios $R^{(pi)}_{e/mu}=BR(pi^+ to e^+ u_e)/BR(pi^+ to mu^+ u_mu)$, $R^{(K)}_{e/mu}$, $R^{(D_s)}_{e/tau}$, and $B^+_{e 2}$ decay, covering the mass range from MeV to GeV.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
