Neutrino Mass Searches Research Articles

Operation modes of the KATRIN experiment Tritium Loop System using 83mKr

The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to search for the effective electron antineutrino mass with a sensitivity of 0.2 eV (90 % C.L.).In order to achieve this goal, KATRIN measurement phases focusing on the neutrino mass search are alternated with phases of investigations of systematic effects.During these phases, metastable 83mKr is used as a calibration source.The monoenergetic conversion electrons emitted accompanying the decay of 83mKr allow a direct access to the starting conditions of β-electrons produced inside the windowless gaseous tritium source (WGTS) of KATRIN.To make use of 83mKr in the WGTS, the Tritium Loop System, which provides a stable flow of tritium to the WGTS, needs to be operated in special modes.This paper focuses on the technical implementation of these modes and their performance with regard to the achievable 83mKr-rates, gas densities, and gas compositions inside the WGTS.

Absolute ν Mass Measurement with the DUNE Experiment.

Time of flight delay in the supernova neutrino signal offers a unique tool to set model-independent constraints on the absolute neutrino mass. The presence of a sharp time structure during a first emission phase, the so-called neutronization burst in the electron neutrino flavor time distribution, makes this channel a very powerful one. Large liquid argon underground detectors will provide precision measurements of the time dependence of the electron neutrino fluxes. We derive here a new ν mass sensitivity attainable at the future DUNE far detector from a future supernova collapse in our galactic neighborhood, finding a sub-eV reach under favorable scenarios. These values are competitive with those expected for laboratory direct neutrino mass searches.

High-precision measurement of a low Q value for allowed β−-decay of 131I related to neutrino mass determination

The ground-state-to-ground-state β−-decay 131I (7/2+) → 131Xe (3/2+) Q value was determined with high precision utilizing the double Penning trap mass spectrometer JYFLTRAP at the IGISOL facility. The Q value of this β−-decay was found to be Q = 972.25(19) keV through a cyclotron frequency ratio measurement with a relative precision of 1.6 × 10−9. This was realized using the phase-imaging ion-cyclotron-resonance technique. The new Q value is more than 3 times more precise and 2.3σ higher (1.45 keV) than the value extracted from the Atomic Mass Evaluation 2020. Our measurement confirms that the β−-decay to the 9/2+ excited state at 971.22(13) keV in 131Xe is energetically allowed with a Q value of 1.03(23) keV while the decay to the 7/2+ state at 973.11(14) keV was found to be energetically forbidden. Nuclear shell-model calculations with established two-body interactions, alongside an accurate phase-space factor and a statistical analysis of the logft values of known allowed β decays, were used to estimate the partial half-life for the low-Q-value transition to the 9/2+ state. The half-life was found to be (1.97−0.89+2.24) ×107 years, which makes this candidate feasible for neutrino mass searches.

Integral Equations in Neutrino Mass Searches from Beta Decay

A new mathematical model for elucidating neutrino mass from beta decay is proposed. It is based upon the solutions of transformed Fredholm and Abel integral equations. In principle, theoretical beta-particle spectra can consist of several neutrino-mass eigenstates. Integration of the beta spectrum with a normalized instrumental response function results in the Fredholm integral equation of the first kind. This equation is then transformed to yield a solution in a form of superposition of Heaviside step-functions, one for each neutrino mass eigenstate. A series expansion leading to matrix linear equations is then derived to solve the transformed Fredholm equation. Another approach is derived when the theoretical beta spectrum is obtained by a separate deconvolution of the observed spectrum. It is then proven that the transformed Fredholm equation reduces to the Abel integral equation. The Abel equation has a general integral solution, which is proven in this work by using a specific equation for the beta spectrum. Several examples of numerical solutions of the Abel equation are provided, which show a fractional sensitivity of about 10-3 for subtle neutrino eigenstate searches and can distinguish from the beta-spectrum discrepancies, such as minute shape and energy nonlinearities.

Neutrino masses

The various experiments on neutrino oscillation evidence that neutrinos have indeed non‐zero masses but cannot provide the absolute neutrino mass scale. This scale of neutrino masses is very important for understanding the evolution and the structure formation of the universe as well as for nuclear and particle physics beyond the present Standard Model. Complementary to deducing constraints on the sum of all neutrino masses from cosmological observations, two different methods to determine the neutrino mass scale in the laboratory are pursued: the search for neutrinoless double β‐decay and the direct neutrino mass search by investigating single β‐decays or electron captures. The former method is not only sensitive to neutrino masses but also probes the Majorana character of neutrinos and thus lepton number violation with high sensitivity. Currently quite a few experiments using different techniques are being constructed, commissioned, or are even running, which aim for a sensitivity on the neutrino mass of (100) meV. The principal methods and these experiments are discussed in this short review.

Characterization of the Superconducting Transition of Thin Ir Films for TES

We are currently producing iridium based TESs for a wide variety of applications such as single photon detection of the visible and infrared light, X-ray spectroscopy and low energy nuclear beta and electron capture spectroscopy for neutrino mass search experiment. We present a study of the TES performance related to the superconductivity properties of the Ir film as function of the production processes, that depend on substrate type: Si or SiN, and of the operating electrical parameters. Moreover we developed a finite element model of thin superconducting film, by which we obtain qualitative agreement between experimental and simulated data.

A UV LED-based fast-pulsed photoelectron source for time-of-flight studies

We report on spectroscopy and time-of-flight measurements using an 18 keV fast-pulsed photoelectron source of adjustable intensity, ranging from single photoelectrons per pulse to 5 photoelectrons per μs at pulse repetition rates of up to 10 kHz. Short pulses between 40 ns and 4 μs in length were produced by switching light emitting diodes with central output wavelengths of 265 and 257 nm, in the deep ultraviolet (or UV-C) regime, at kHz frequencies. Such photoelectron sources can be useful calibration devices for testing the properties of high-resolution electrostatic spectrometers, like the ones used in current neutrino mass searches.

Improved limit onθ13and implications for neutrino masses in neutrinoless double beta decay and cosmology

We analyze the impact of a measurement, or of an improved bound, on theta_{13} for the determination of the effective neutrino mass in neutrino-less double beta decay and cosmology. In particular, we discuss how an improved limit on (or a specific value of) theta_{13} can influence the determination of the neutrino mass spectrum via neutrino-less double beta decay. We also discuss the interplay with improved cosmological neutrino mass searches.

Beta decay in the field of electromagnetic wave and neutrino mass search

The results of the investigation of electromagnetic field effects on the process of beta decay are used for analyzing experimental data on direct neutrino mass search. It is shown that electromagnetic wave can affect beta spectrum by shifting its end point towards higher energy values region. The phenomenon is of purely classical nature and is connected with the electron acceleration in the radiation field. The magnetic fields of substantial strength exist in the setups for the neutrino mass precise measurement, thus the above field can arise due to the synchrotron radiation mechanism. The phenomenon under study can explain the observed anomalies in the spectrum of decay electrons, in particular the effect of “negative neutrino mass squared”.

Beta decay in the field of electromagnetic wave and neutrino mass search

The results of the investigation of electromagnetic field effects on the process of beta decay are used for analyzing experimental data on direct neutrino mass search. It is shown that electromagnetic wave can affect beta spectrum by shifting its end point towards higher energy values region. The phenomenon is of purely classical nature and is connected with the electron acceleration in the radiation field. The magnetic fields of substantial strength exist in the setups for the neutrino mass precise measurement, thus the above field can arise due to the synchrotron radiation mechanism. The phenomenon under study can explain the observed anomalies in the spectrum of decay electrons, in particular the effect of “negative neutrino mass squared”.

The search for the neutrino mass by direct method in the tritium beta-decay and perspectives of study it in the project KATRIN

The updated results of the search for neutrino mass in the tritium beta-decay on the Troitsk nu-mass and Neutrino Mainz set-ups are presented. Both groups give an upper limit for the neutrino mass at 95% m v < 2.05 eV/ c 2 in Troitsk and m v < 2.2 V/ c 2 in Mainz. Further improvement is limited both by statistic and systematic errors. In order to enter in the cosmologically important sub-electronvolt area the collaboration of groups from Karlsruhe Forschungszentrum, Mainz, Troitsk et al. proposed a new advanced project KATRIN. The status of the project is presented.

Can long range anomalous neutrino interactions account for the measured tritium beta decay spectrum?

Recent experimental searches for neutrino mass in tritium beta decay yield a negative value for the neutrino ( mass) 2. If this effect is genuine, then it is hard to understand it using conventional particle physics ideas as embodied in (say) the standard electroweak model. We discuss the possibility that there is a hidden anomalous long range interaction of neutrinos that is responsible for this effect and study the phenomenological consistency as well as tests of this idea. We also discuss how such interactions may arise in extensions of the standard model.

Update on neutrino mass search at ISIS

Karmen , the Karlsruhe-Rutherford Medium Energy Neutrinoexperiment at the pulsed spallation neutron facility ISIS uses the beam stop neutrinos ν μ and ν e , #x003BD; μ from π + and μ + decay at rest to search for neutrino oscillations in the appearance channels ν μ → ν e and #x003BD; μ → #x003BD; e . The signature for both oscillations is based on charged current neutrino nuclear interaction spectroscopy in a high resolution 56t liquid scintillator calorimeter. This report describes the results based on data acquired from June 1990 to August 1995.

Overview of Neutrino Mass Measurements

We review the results of searches for neutrino mass from beta spectra, double beta decay and neutrino oscillations.

The case for a kilometer-scale high energy neutrino detector

Doing astronomy with photons of energies in excess of a GeV has turned out to be extremely challenging. Efforts are underway to develop instruments that may push astronomy to wavelengths smaller than $10^{-14}$~cm by mapping the sky in high energy neutrinos instead. Neutrino astronomy, born with the identification of thermonuclear fusion in the sun and the particle processes controlling the fate of a nearby supernova, will reach outside the galaxy and make measurements relevant to cosmology. The field is immersed in technology in the domains of particle physics to which many of its research goals are intellectually connected. To mind come the search for neutrino mass, cold dark matter (supersymmetric particles?) and the monopoles of the Standard Model. While a variety of collaborations are pioneering complementary methods by building telescopes with effective area in excess of 0.01~km$^2$, we show here that the natural scale of a high energy neutrino telescope is 1~km$^2$. With several thousand optical modules and a price tag unlikely to exceed 100 million dollars, the scope of a kilometer-scale instrument is similar to that of experiments presently being commissioned such as the SNO neutrino observatory in Canada and the Superkamiokande experiment in Japan.

Direct searches for neutrino mass

At present there is no positive experimental evidence that neutrinos have mass. Nevertheless, searches for neutrino mass continue, largely because the consequences of neutrinos having mass would be quite profound. In particular, the discovery of a non-zero neutrino mass would be a clear indication of physics beyond the current particle-physics standard model. In addition, neutrinos, if they have mass, remain viable candidates for the non-baryonic dark matter known to permeate galaxies. The current status of the experimental efforts searching for neutrino mass will be reviewed. In particular, it will be shown that the most recent tritium beta decay searches for neutrino mass clearly rule out the non-zero neutrino mass result first reported in 1980 by the Institute for Theoretical and Experimental Physics (ITEP) in Moscow. However, a troubling feature of these same recent results is that they all have best fits to neutrino mass squared that are negative. The significance of these negative neutrino mass squared results will be explored.

On low-energy nuclear electron capture

The atomic states formed in electron capture beta decay (EC) have a finite width, so that decays can take place even with energies far from the resonance energies. Here, the lineshape deviates considerably from the normally assumed Breit-Wigner form. The lineshapes far from resonance are discussed and are shown to be important in calculations of total decay rates when the Q value is low or the emitted atomic radiation is of low energy. The implications for neutrino mass searches employing electron capture decays are also discussed.