Session HB: Neutrinos

Commissioning Measurements of the KATRIN Main Spectrometer

Beginning in May 2013, the KArlsruhe TRItium Neutrino experiment (KATRIN) collaboration began measurements to commission the 10-m diameter main spectrometer. KATRIN utilizes the spectrometer to provide magnetic adiabatic collimation and electrostatic filtering designed to analyze the tritium beta decay spectrum for contributions from the neutrino mass. In order to achieve an order-of-magnitude improvement on previous neutrino mass experiments the desired sensitivity of the apparatus must be 200 meV in the decay endpoint region. Goals of the recent measurements include identification and reduction of backgrounds and determination of the spectrometer transfer function. Backgrounds have been probed by utilizing electromagnetic field configurations to explore decays in the spectrometer, Penning traps and field emission. A 148-pixel PIN diode array is employed to detect particles exiting the spectrometer, which permits angular and radial distributions of particles to be analyzed. This has allowed for high precision comparison between measurements and simulations of expected backgrounds to be investigated in order to commission the spectrometer.   

Status of the Project 8 Detector Prototype

The average mass of the 3 neutrino mass eigenstates has been bound by oscillation experiments and by direct mass measurements to lie in the range $0.02{\rm\ eV} \leq m_\nu \leq 2{\rm\ eV}$. Nonetheless, only the upper decade of this parameter space will be accessible to the most sensitive experiment presently under construction, KATRIN. The Project 8 collaboration has been involved in the development of technology in the form of a prototype detector which may offer sensitivity to neutrino masses over the entire allowed parameter space. The key to this technology is a direct, non-integrated measurement of the energy spectrum of $\beta$ decay electrons very near the endpoint of $^3{\rm H}$ decay by probing the cyclotron frequency of those electrons as they move in a strong background magnetic field. The current generation of the prototype detector is expected to reach 1\,ppm resolution of the cyclotron frequency of the electron. Recent progress and results from the detector prototype will be discussed. This research is supported by DOE under grant DE-FG02-97ER41020.   

Measuring molecular dissociation in tritium beta decay: validating theory used in neutrino mass experiments

The next generation of tritium-based neutrino mass experiments (KATRIN, Project 8) requires a comprehensive understanding of the distribution of molecular states excited in the decay. Recent ab initio calculations predict a dissociation probability that disagrees with two experiments from the 1950s. Further study is needed to resolve the discrepancy and validate the calculations. The Tritium Recoil-Ion Mass Spectrometer is designed to measure the molecular tritium branching ratio to the bound molecular ion $^3\textrm{HeT}^+$ using a time-of-flight spectrometer.   

The Coherent Elastic Neutrino Nucleus Scattering (CENNS) Experiment at Fermilab

Low energy neutrinos ($<$ 50 MeV) with a wavelength larger than target nuclei can engage in coherent elastic scattering with low momentum transfer. This scattering channel has remained unobserved due to low energy deposits and despite a large scattering cross section. Coherent scattering is important for supernovae, low-$Q^2$ weak nuclear form factors, and other low-energy Standard Model tests. Dark matter detector technologies make a first measurement possible with accelerator neutrino sources. The CENNS collaboration is proposing a 1-ton, single-phase, liquid argon detector to measure coherent neutrino scattering near the booster neutrino beam (BNB) at Fermilab. By placing the detector near the beam target in a far off-axis position, a flux of low-energy neutrinos is produced with a similar energy spectrum as stopped pion sources. The proximity to the BNB introduces a potential background of beam-correlated neutrons whose elastic scatters are indistinguishable from the neutrino signal. In this talk, I will describe the proposed detector, recent beam-correlated neutron background measurements, and ongoing shielding studies.   

Prospects for Using Coherent Elastic Neutrino-Nucleus Scattering to Measure the Nuclear Neutron Form Factor

We suggest coherent elastic neutrino-nucleus scattering (CENNS) as a method for measuring the neutron part of the nuclear form factor. Using an expansion into moments of the form factor, we show that the second moment (the neutron radius), as well as the fourth moment can be probed using neutrinos from a stopped pion source. We use Monte Carlo techniques to demonstrate that the neutron radius could be found with an uncertainty of a few percent in tonne scale detectors of argon, germanium, and xenon. The effects of detector shape uncertainty and detector size were also studied to determine the prospects of such a measurement. We find that in order to measure the neutron radius to 5\%, the the spectral shape uncertainty of the detector needs to be known to 1\% or better.   

Development of a Low Energy Threshold Germanium Detector for Measuring Neutrino Magnetic Moments

Since it is understood that the neutrino has mass, it is also evident that the neutrino will have a magnetic moment proportional to its mass. Current experimental reports indicate that the neutrino magnetic moment ($u_{\nu })$ will be greater than or around 10$^{\mathrm{-20}}u_{B}$. This number, however, is a lower bound, and extensions from the Standard Model yield larger possible magnetic moments. We can potentially measure the neutrino magnetic moment (NMM) by studying the electron recoil energy in a given detector. The NMM contribution to the differential scattering cross section for electron neutrinos or antineutrinos occurs at very low recoil energies. In order to detect this electromagnetic reaction, it is beneficial to use an experiment where the measurable electronic recoils are below 100 eV. In this project, we show the development of a low energy threshold germanium detector with internal amplification that will measure the NMM at Homestake, using a large artificial neutrino source.   

Analysis of the nuclear dependence of the $\nu_{\mu}$ charged-current inclusive cross section with MINERvA

Neutrino experiments use heavy nuclei (Fe, Pb, C) to achieve necessary statistics. However, the use of heavy nuclei exposes these experiments to the nuclear dependence of neutrino-nucleus cross sections, which are poorly known and difficult to model. The MINERvA (Main INjector ExpeRiment for $\nu$-A), a few-GeV neutrino nucleus scattering experiment at Fermilab, seeks to remedy the situation by directly studying the A-dependence of exclusive and inclusive channels. The MINERvA detector contains an 8 ton fully active fine-grained scintillator tracking core and targets of carbon, iron, lead, water and liquid helium which sit upstream of the tracking core. We present results from our first analysis using the nuclear targets: ratios of the $\nu_{\mu}$ charged-current inclusive cross section in carbon, iron, lead and plastic.   

Neutral pion production by charged-current antineutrino-nucleus interactions in MINERvA

MINERvA is a neutrino scattering experiment at the NuMI beamline of FNAL. It is a high resolution, fully active detector designed to study the interaction of neutrinos with nuclei. In addition to plastic scintillator, there are several other nuclear targets such as 4He, Fe, Pb, C, and H20 which allow detailed studies of the A dependence of neutrino cross sections. We present the preliminary results of the measurement of single neutral pion production by charged-current interactions of anti-neutrinos in plastic scintillator.   

A tricky method for indirect measurement of electron Antineutrino mass

During beta decay of rest neutron, an electron anti neutrino is also emitted. $n_o\to p^++e^-+ \overline\nu_e$ by detecting momentum of proton and electron after decay and by using conservation laws of einstein's theory of relativity, i realized (indirectly) that electron anti neutrino is photon-like particle $E=\vec {P}c=\vec {P_e}c=\vec {P_p}c$ and its mass is $\overline\nu_e=\frac {E}{c^2} =0.545626\frac {Mev}{c^2}$ Essential Results: $n_o=E_p+E_e+(E=\vec{P}c)=\sqrt{\vec{P_p}^2c^2+p_o^2}+\sqrt{\vec{P_e}^2c^2+e_o^2}+ E_{\overline\nu_e}$ where the $p_o$ denotes Energy of rest proton and $e_o$ denotes Energy of rest electron. $(E=\vec{P}c)$ denotes photon-like anti-neutrino. $\alpha_w=\frac{\vec{P_e}c}{E_e}=\frac{1}{1.370073665}$ This is electron weak-structure constant (it is almost $100.0$ times stronger than fine-structure constant)