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Register a new userA new experiment to search for the invisible decay of the orthopositronium
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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.
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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.
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.
The existence of dark matter has been established in astrophysics. However, there is no candidate for DM in the Stand Model (SM). In SM, the Higgs boson can only decay invisibly via $Hrightarrow ZZ^ast rightarrow ubar{ u} ubar{ u}$ or DM, so any evidence of invisible Higgs decay that exceeds BR (H$rightarrow$inv.) will immediately point to a phenomenon that is beyond the standard model (BSM). In this paper, we report on the upper limit of BR (H$rightarrow$invisible) estimated for three channels, including two leptonic channels and one hadronic channel, under the assumption predicted by SM. With the SM ZH production rate, the upper limit of BR (H$rightarrow$inv.) could reach 0.24% at the 95% confidence level.
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.
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