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Register a new userA Search for Charged Excitation of Dark Matter with the KamLAND-Zen Detector
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There are many theories where a dark matter particle is part of a multiplet with an electrically charged state. If WIMP dark matter ($chi^{0}$) is accompanied by a charged excited state ($chi^{-}$) separated by a small mass difference, it can form a stable bound state with a nucleus. In supersymmetric models, the $chi^{0}$ and the $chi^{-}$ could be the neutralino and a charged slepton, such as the neutralino-stau degenerate model. The formation binding process is expected to result in an energy deposition of {it O}(1--10 MeV), making it suitable for detection in large liquid scintillator detectors. We describe new constraints on the bound state formation with a xenon nucleus using the KamLAND-Zen 400 Phase-II dataset. In order to enlarge the searchable parameter space, all xenon isotopes in the detector were used. For a benchmark parameter set of $m_{chi^{0}} = 100$ GeV and $Delta m = 10$ MeV, this study sets the most stringent upper limits on the recombination cross section $langlesigma vrangle$ and the decay-width of $chi^{-}$ of $2.0 times 10^{-31}$ ${rm cm^3/s}$ and $1.1 times 10^{-18}$ GeV, respectively (90% confidence level).
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A search for double-beta decays of 136Xe to excited states of 136Ba has been performed with the first phase data set of the KamLAND-Zen experiment. The 0+1, 2+1 and 2+2 transitions of 0{ u}{beta}{beta} decay were evaluated in an exposure of 89.5kg-yr of 136Xe, while the same transitions of 2{ u}{beta}{beta} decay were evaluated in an exposure of 61.8kg-yr. No excess over background was found for all decay modes. The lower half-life limits of the 2+1 state transitions of 0{ u}{beta}{beta} and 2{ u}{beta}{beta} decay were improved to T(0{ u}, 0+ rightarrow 2+) > 2.6times10^25 yr and T(2{ u}, 0+ rightarrow 2+) > 4.6times10^23 yr (90% C.L.), respectively. We report on the first experimental lower half-life limits for the transitions to the 0+1 state of 136Xe for 0{ u}{beta}{beta} and 2{ u}{beta}{beta} decay. They are T (0{ u}, 0+ rightarrow 0+) > 2.4times10^25 yr and T(2{ u}, 0+ rightarrow 0+) > 8.3times10^23 yr (90% C.L.). The transitions to the 2+2 states are also evaluated for the first time to be T(0{ u}, 0+ rightarrow 2+) > 2.6times10^25 yr and T(2{ u}, 0+ rightarrow 2+) > 9.0times10^23 yr (90% C.L.). These results are compared to recent theoretical predictions.
This Letter reports results from a haloscope search for dark matter axions with masses between 2.66 and 2.81 $mu$eV. The search excludes the range of axion-photon couplings predicted by plausible models of the invisible axion. This unprecedented sensitivity is achieved by operating a large-volume haloscope at sub-kelvin temperatures, thereby reducing thermal noise as well as the excess noise from the ultra-low-noise SQUID amplifier used for the signal power readout. Ongoing searches will provide nearly definitive tests of the invisible axion model over a wide range of axion masses.
NEWAGE is a direction-sensitive dark matter search using a low-pressure gaseous time projection chamber. A low alpha-ray emission rate micro pixel chamber had been developed in order to reduce background for dark matter search. We conducted the dark matter search at the Kamioka Observatory in 2018. The total live time was 107.6 days corresponding to an exposure of 1.1 kg${cdot}$days. Two events remained in the energy region of 50-60 keV which was consistent with 2.5 events of the expected background. A directional analysis was carried out and no significant forward-backward asymmetry derived from the WIMP-nucleus elastic scatterings was found. Thus a 90% confidence level upper limit on Spin-Dependent WIMP-proton cross section of 50 pb for a WIMP mass of 100 GeV/c2 was derived. This limit is the most stringent yet obtained from direction-sensitive dark matter search experiments.
The Dark Matter Time Projection Chamber (DMTPC) is a low pressure (75 Torr CF4) 10 liter detector capable of measuring the vector direction of nuclear recoils with the goal of directional dark matter detection. In this paper we present the first dark matter limit from DMTPC. In an analysis window of 80-200 keV recoil energy, based on a 35.7 g-day exposure, we set a 90% C.L. upper limit on the spin-dependent WIMP-proton cross section of 2.0 x 10^{-33} cm^{2} for 115 GeV/c^2 dark matter particle mass.
We report the result of a search for neutrinos in coincidence with solar flares from the GOES flare database. The search was performed on a 10.8 kton-year exposure of KamLAND collected from 2002 to 2019. We found no statistical excess of neutrinos and established 90% confidence level upper limits of $8.4 times 10^7$,cm$^{-2}$ ($3.0 times 10^{9}$,cm$^{-2}$) on electron anti-neutrino (electron neutrino) fluence at 20,MeV normalized to the X12 flare, assuming that the neutrino fluence is proportional to the X-ray intensity. The 90% C.L. upper limits from this work exclude the entire region of parameter space associated with the Homestake event excess for the large solar flare in 1991.
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