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We report here several technical improvements to the HAYSTAC (Haloscope at Yale Sensitive To Axion Cold dark matter) that have improved operational efficiency, sensitivity, and stability.
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We report on the results from a search for dark matter axions with the HAYSTAC experiment using a microwave cavity detector at frequencies between 5.6-5.8$, rm Ghz$. We exclude axion models with two photon coupling $g_{agammagamma},gtrsim,2times10^{-14},rm GeV^{-1}$, a factor of 2.7 above the benchmark KSVZ model over the mass range 23.15$,<,$$m_a ,$<$,$24.0$,murm eV$. This doubles the range reported in our previous paper. We achieve a near-quantum-limited sensitivity by operating at a temperature $T<h u/2k_B$ and incorporating a Josephson parametric amplifier (JPA), with improvements in the cooling of the cavity further reducing the experiments system noise temperature to only twice the Standard Quantum Limit at its operational frequency, an order of magnitude better than any other dark matter microwave cavity experiment to date. This result concludes the first phase of the HAYSTAC program utilizing a conventional copper cavity and a single JPA.
The microwave cavity experiment is the most sensitive way of looking for axions in the 0.1-10 GHz range, corresponding to masses of 0.5 - 40 $mu$eV. The particular challenge for frequencies greater than 5 GHz is designing a cavity with a large volume that contains a resonant mode that has a high form factor, a high quality factor, a wide dynamic range, and is free from intruder modes. For HAYSTAC, we have designed and constructed an optimized high frequency cavity with a tuning mechanism that preserves a high degree of rotational symmetry, critical to maximizing its figure of merit. This cavity covers an important frequency range according to recent theoretical estimates for the axion mass, 5.5 - 7.4 GHz, and the design appears extendable to higher frequencies as well. This paper will discuss key design and construction details of the cavity, present a summary of the design evolution, and alert practitioners of potentially unfruitful avenues for future work.
DANSS is a one cubic meter highly segmented plastic scintillator detector. Its 2500 one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS detector is placed under an industrial 3.1GW reactor of the Kalinin Nuclear Power plant 350km NW from Moscow. The distance to the core ia varied on-line from 10.7m to 12.7m. Recent results on searches for a sterile neutrino are presented as well as measurements of the antineutrino spectrum dependence on the fuel composition. All results are preliminary. PACS: 14.60.Pq, 14.60.St
We present new results of the DANSS experiment on the searches for sterile neutrinos. They are based on 2.1 million of inverse beta decay events collected at 10.7, 11.7 and 12.7 meters from the reactor core of the 3.1 GW Kalinin Nuclear Power Plant in Russia. This data sample is 2.5 times larger than the data sample in the previous DANSS publication. The search for the sterile neutrinos is performed using the ratio of $bar u_e$ spectra at two distances. This method is very robust against systematic uncertainties in the $bar u_e$ spectrum and the detector efficiency. We do not see any statistically significant sign for the $bar u_e$ oscillations. This allows us to exclude further a large and interesting part of the sterile neutrino parameter space. All results are preliminary.
The OPERA experiment aims at the direct confirmation of the leading oscillation mechanism in the atmospheric sector looking for the appearance of $ u_{tau}$ in an almost pure $ u_{mu}$ beam (the CERN CNGS beam). In five years of physics run the experiment collected $17.97 times 10^{19}$ p.o.t. The detection of $tau$s produced in $ u_{tau}$ CC interactions and of their decays is accomplished exploiting the high spatial resolution of nuclear emulsions. Furthermore OPERA has good capabilities in detecting electron neutrino interactions, setting limits on the $ u_{mu} rightarrow u_{e}$ oscillation channel. In this talk the status of the analysis will be presented together with updated results on both oscillation channels.
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