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Register a new userAn apparatus to search for mirror dark matter via the invisible decay of orthopositronium in vacuum
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Mirror matter is a possible dark matter candidate. It is predicted to exist if parity is an unbroken symmetry of the vacuum. The existence of the mirror matter, which in addition to gravity is coupled to our world through photon-mirror photon mixing, would result in orthopositronium (o-Ps) to mirror orthopositronium (o-Ps) oscillations. The experimental signature of this effect is the invisible decay of o-Ps in vacuum. This paper describes the design of the new experiment for a search for the o-Ps -> invisible decay in vacuum with a sensitivity in the branching ratio of Br(o-Ps -> invisible)simeq 10^{-7}, which is an order of magnitude better than the present limit on this decay mode from the Big Bang Nucleosynthesis. The experiment is based on a high-efficiency pulsed slow positron beam, which is also applicable for other experiments with o-Ps, and (with some modifications) for applied studies. Details of the experimental design and of a new pulsing method, as well as preliminary results on requirements for the pulsed beam components are presented. The effects of o-Ps collisions with the cavity walls as well as the influence of external fields on the o-Ps to o-Ps oscillation probability are also discussed.
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We propose an experiment to search for invisible decays of orthopositronium (o-Ps) with a 90% confidence sensitivity in the branching ratio as low as $10^{-8}$. Evidence for this decay mode would unambigously signal new physics: either the existence of extra--dimensions or fractionally charged particles or new light gauge bosons. The experimental approach and the detector components of the proposed experiment are described.
A search is performed for a new sub-GeV vector boson ($A$) mediated production of Dark Matter ($chi$) in the fixed-target experiment, NA64, at the CERN SPS. The $A$, called dark photon, could be generated in the reaction $ e^- Z to e^- Z A$ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay $A to chi overline{chi}$. The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to $4.3times10^{10}$ electrons on target no evidence of such a process has been found. New stringent constraints on the $A$ mixing strength with photons, $10^{-5}lesssim epsilon lesssim 10^{-2}$, for the $A$ mass range $m_{A} lesssim 1$ GeV are derived. For models considering scalar and fermionic thermal Dark Matter interacting with the visible sector through the vector portal the 90% C.L. limits $10^{-11}lesssim y lesssim 10^{-6}$ on the dark-matter parameter $y = epsilon^2 alpha_D (frac{m_chi}{m_{A}})^4 $ are obtained for the dark coupling constant $alpha_D = 0.5$ and dark-matter masses $0.001 lesssim m_chi lesssim 0.5 $ GeV. The lower limits $alpha_D gtrsim 10^{-3} $ for pseudo-Dirac Dark Matter in the mass region $m_chi lesssim 0.05 $ GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using tree level, exact calculations of the $A$ production cross-sections, which turn out to be significantly smaller compared to the one obtained in the Weizs{a}cker-Williams approximation for the mass region $m_{A} gtrsim 0.1$ GeV.
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.
This paper reports on a cavity haloscope search for dark matter axions in the galactic halo in the mass range $2.81$-$3.31$ ${mu}eV$. This search excludes the full range of axion-photon coupling values predicted in benchmark models of the invisible axion that solve the strong CP problem of quantum chromodynamics, and marks the first time a haloscope search has been able to search for axions at mode crossings using an alternate cavity configuration. Unprecedented sensitivity in this higher mass range is achieved by deploying an ultra low-noise Josephson parametric amplifier as the first stage signal amplifier.
We search for $J/psi$ radiative decays into a weakly interacting neutral particle, namely an invisible particle, using the $J/psi$ produced through the process $psi(3686)topi^+pi^-J/psi$ in a data sample of $(448.1pm2.9)times 10^6$ $psi(3686)$ decays collected by the BESIII detector at BEPCII. No significant signal is observed. Using a modified frequentist method, upper limits on the branching fractions are set under different assumptions of invisible particle masses up to 1.2 $mathrm{ Gekern -0.1em V}/c^2$. The upper limit corresponding to an invisible particle with zero mass is 7.0$times 10^{-7}$ at the 90% confidence level.
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