Session QQ02: V: Neutrinos and New Particles

Demonstrating Cyclotron Radiation Emission Spectroscopy using a Cavity: The Cavity CRES Apparatus

The Project 8 experiment aims to measure the effective mass of the electron antineutrino.

In order to achieve this, Project 8 uses Cyclotron Radiation Emission Spectroscopy (CRES) to detect the faint RF radiation of single tritium beta-decay electrons in a magnetic field. Using RF cavities instead of free space antennas for CRES promises to bring advantages in signal-to-noise ratio and compatibility with atom traps.

In order to explore the use of cavities for the future phases of the Project 8 experiment, a Cavity CRES Apparatus (CCA) is currently under development. Using a small mode-filtered cavity operating at 26 GHz in a 1-T magnetic field, it will demonstrate the CRES detection of conversion electrons from the decay of meta-stable ^83mKr. Furthermore, the CCA will be used to test the calibration of CRES using an electron gun for the first time.

In this contribution I will present the current CCA design and planned measurements.   

Measurements of Neutron-Induced Gamma Ray Background of 100Mo for CUPID

CUPID (CUORE with Upgraded Particle IDentification), an update to CUORE (Cryogenic Underground Observatory for Rare Events), is an experiment designed to search for neutrinoless double beta decay using the candidate isotope ¹⁰⁰Mo. To estimate the neutron-induced gamma ray background of ¹⁰⁰Mo, an experiment was conducted at TUNL (Triangle Universities Nuclear Laboratory) in which neutron beams ranging from 4-8 MeV were targeted at varying samples of ¹⁰⁰Mo, ⁵⁶Fe, and Cu. We present neutron-¹⁰⁰Mo gamma production cross sections for decays of interest to the background estimations of CUPID, and set a limit on production of gamma-events within the region of interest.   

MAGNETO-ν: Searching for keV-scale sterile neutrino in 241Pu beta decays

Sterile neutrino of a keV-scale mass is one of strong low mass dark matter candidates. The MAGNETO-ν experiment is a search for keV neutrino signatures in 241Pu beta decays using magnetic quantum sensors. Non-zero mixing of the keV neutrino with the electron neutrino can result in emission of sterile neutrinos in nuclear beta decays, reducing maximum energies carried by electrons and nuclear recoils and producing the “kink” structure in beta decay spectra. 241Pu has a single beta decay branch to the ground state of 241Am with the 20.78(17) keV Q-value and the 14.329(29) y half-life, therefore is very suitable for searching for sterile neutrinos in the 1 keV – 20 keV mass range. MAGNETO-ν uses enriched 241Pu sources and Decay Energy Spectrometry (DES) technique with magnetic quantum sensors for high resolution, low background, and high statistics measurement of 241Pu beta spectrum. Our first result of 241Pu measurement and experiment plan as well as systematics of the experiment will be presented.

    

IceCube MEOWS Working Group Update

This talk presents recent results from the IceCube experiment on new physics searches using a very pure sample of up-going muon tracks produced by TeV-scale atmospheric neutrino interactions beneath the detector.  Results on searches for sterile neutrinos in complex models that include a non-zero ??₃₄ mixing angle and decay will be presented along with results on non-standard interactions and on neutrino decoherence.  Future upgrades of the analysis will also be discussed.   

Analysis of MAGNETO-ν data and a preliminary limit to keV-sterile neutrino mixing

Sterile neutrino in the keV scale is a potential dark matter candidate. A non-zero mixing of sterile neutrino with the electron-antineutrino can cause a discontinuity in the beta spectrum. Thus, a precise beta spectrum measurement in the keV region is a test of presence of the keV-scale sterile neutrino. The MAGNETO-ν experiment measures the total beta decay spectrum of ²⁴¹Pu, including the daughter nuclear recoils, with high resolution magnetic microcalorimeters (MMCs). The ²⁴¹Pu sources are fully embedded into the detector to achieve total energy absorption with ~100% detection efficiency. This approach has allowed us to achieve O(0.01) sensitivity for the sterile neutrino mixing |U_e4|² in the 10 keV mass region with only 24 hours of measurement and a single detector with a 1 Bq ²⁴¹Pu source. We are presenting the experimental setup, the data processing, and the preliminary analysis for sterile neutrino probing with current dataset taken for 10 days with a 100 Bq source.

    

Testing neutrality of matter by measuring magnetic fields

Possible existence of minicharges questions charge conservation, thereby also the neutrality of neutrons, and by extension the neutrality of matter. The charge of the neutron is extremely well measured, and is consistent with zero: q_n = (-0.2+-0.8)*10^{-21} e. This measurement comes from testing for neutrality of SF6 molecules using acoustic oscillations (sound). Furthermore, charge conservation in conjunction with the asymmetry between the proton and electron charges further confirms the neutrality of the neutron: (q_p + q_e) <10^{-21} e. Other techniques for testing neutrality of matter in the past has involved, suspended macro-particles falling, deflection of beams of neutrons, atoms, and molecules, both under the influence of electromagnetc fields, and by measuring potential differences upon gas efflux.

In the presence of small minicharges, a flowing cryogenic fluid generates measurable constant magnetic field. Current state of the art DC-SQUID magnetometers have achieved a precision of better than 100 aT, and can already provide a pathway to testing neutrality of matter at the level of 10^{-21} e. The technique, pioneered by the ABRACADABRA collaboration, of characterizing oscillating magnetic fields with the help of SQUIDs, provides robust background noise rejection. An oscillating density mimics an alternating flow-direction, both of which generate oscillating magnetic fields in the presence of minicharges. Alternating flow-direction can be generated by alternating pumping, and oscillating density can be generated by thermal acoustic oscillation. The sensitivity of both these techniques towards testing neutrality of matter will be presented.   

Search for new heavy resonances decaying to two Standard Model bosons with semi-leptonic final states using the full Run 2 ATLAS dataset

We present preliminary results of a combined search for new particles decaying to a vector boson and a Higgs boson, as well as to two vector bosons, focusing on semi-leptonic final states and using 139 fb$^{-1}$ of proton-proton collisions at the LHC. Two important models that predict such particles are the Heavy Vector Triplet (HVT) model and the two-Higgs-doublet model (2HDM), which address important deficiencies of the Standard Model related to the Higgs sector: the naturalness problem and the possibility of an extended scalar sector. The analysis will set limits on the production cross-sections of a new heavy vector boson predicted by the HVT model and of a new pseudoscalar boson A predicted by the 2HDM model, as well as constrain the respective models' parameters. Improvements in sensitivity with respect to previous iterations of the analysis using novel deep learning techniques will be discussed, with particular focus on a multi-class boosted jet classifier for the identification of the particle origin of the hadronic decay as coming from a top quark, a W boson, a Z boson, a Higgs boson, or multi-jet production.