No Arabic abstract
Sterile neutrino ($ u_s$) conversion in meter scale baselines can be sensitively probed using mono-energetic, sub-MeV, flavor pure $ u_e$s from an artificial MCi source and the unique technology of the LENS low energy solar $ u_e$ detector. Active-sterile {em oscillations} can be directly observed in the granular LENS detector itself to critically test and extend results of short baseline accelerator and reactor experiments.
The recent analysis of the normalization of reactor antineutrino data, the calibration data of solar neutrino experiments using gallium targets, and the results from the neutrino oscillation experiment MiniBooNE suggest the existence of a fourth light neutrino mass state with a mass of O(eV), which contributes to the electron neutrino with a sizable mixing angle. Since we know from measurements of the width of the Z0 resonance that there are only three active neutrinos, a fourth neutrino should be sterile (i.e., interact only via gravity). The corresponding fourth neutrino mass state should be visible as an additional kink in beta-decay spectra. In this work the phase II data of the Mainz Neutrino Mass Experiment have been analyzed searching for a possible contribution of a fourth light neutrino mass state. No signature of such a fourth mass state has been found and limits on the mass and the mixing of this fourth mass states are derived.
We present a reactor model independent search for sterile neutrino oscillation using 2,509,days of RENO near detector data and 180 days of NEOS data. The reactor related systematic uncertainties are significantly suppressed as both detectors are located at the same reactor complex of Hanbit Nuclear Power Plant. The search is performed by electron antineutrino,($overline{ u}_e$) disappearance between six reactors and two detectors with baselines of 294,m,(RENO) and 24,m,(NEOS). A spectral comparison of the NEOS prompt-energy spectrum with a no-oscillation prediction from the RENO measurement can explore reactor $overline{ u}_e$ oscillations to sterile neutrino. Based on the comparison, we obtain a 95% C.L. excluded region of $0.1<|Delta m_{41}^2|<7$,eV$^2$. We also obtain a 68% C.L. allowed region with the best fit of $|Delta m_{41}^2|=2.41,pm,0.03,$,eV$^2$ and $sin^2 2theta_{14}$=0.08$,pm,$0.03 with a p-value of 8.2%. Comparisons of obtained reactor antineutrino spectra at reactor sources are made among RENO, NEOS, and Daya Bay to find a possible spectral variation.
We comment on the claimed observation [arXiv:arXiv:2005.05301] of sterile neutrino oscillations by the Neutrino-4 collaboration. Such a claim, which requires the existence of a new fundamental particle, demands a level of rigor commensurate with its impact. The burden lies with the Neutrino-4 collaboration to provide the information necessary to prove the validity of their claim to the community. In this note, we describe aspects of both the data and analysis method that might lead to an oscillation signature arising from a null experiment and describe additional information needed from the Neutrino-4 collaboration to support the oscillation claim. Additionally, as opposed to the assertion made by the Neutrino-4 collaboration, we also show that the method of coherent summation using the $L/E$ parameter produces similar results to the methods used by the PROSPECT and the STEREO collaborations.
The low-x gluon density in the proton and, in particular, in nuclei is only very poorly constrained, while a better understanding of the low-x structure is crucial for measurements at the LHC and also for the planning of experiments at future hadron colliders. In addition, deviations from linear QCD evolution are expected to appear at low x, potentially leading to gluon saturation and a universal state of hadronic matter, the color-glass condensate. However, these effects have not been unambiguously proven to date. Fortunately, data from the LHC can be used directly to provide better constraints of the parton distribution functions (PDFs). In this context, a Forward Calorimeter (FoCal) is proposed as an addition to the ALICE experiment, to be installed in the Long Shutdown 3. The main goal of the FoCal proposal is to measure forward direct photons in pp and p-Pb collisions to obtain experimental constraints on proton and nuclear PDFs in a new region of low x. Based on the current knowledge from DIS experiments and first results from LHC, we will discuss the physics case for this proposed detector. While open charm measurements do provide important constraints, a photon measurement would provide additional unique information. The direct photon measurement requires a new electromagnetic calorimeter with extremely high granularity. The corresponding innovative design principle of a high-resolution Si-W sandwich calorimeter is discussed.
Light sterile neutrinos have been introduced as an explanation for a number of oscillation signals at $Delta m^2 sim 1$ eV$^2$. Neutrino oscillations at relatively short baselines provide a probe of these possible new states. This paper describes an accelerator-based experiment using neutral current coherent neutrino-nucleus scattering to strictly search for active-to-sterile neutrino oscillations. This experiment could, thus, definitively establish the existence of sterile neutrinos and provide constraints on their mixing parameters. A cyclotron-based proton beam can be directed to multiple targets, producing a low energy pion and muon decay-at-rest neutrino source with variable distance to a single detector. Two types of detectors are considered: a germanium-based detector inspired by the CDMS design and a liquid argon detector inspired by the proposed CLEAR experiment.