Data on p slowing down and capture in helium at 1 and 0.2 mb at room temperature are presented and compared to the corresponding previously publicated data in molecular hydrogen and deuterium. A ...Monte Carlo simulation containing a low-energy extrapolation of measured p electronic stopping power in helium gas, screened Rutherford collisions, and simple cascade mechanisms is able to reproduce the gross features of the data, but cannot explain some nontrivial details of the measured distributions.
We reanalize data collected with the DarkSide-50 experiment and recently used to set limits on the spin-independent interaction rate of weakly interacting massive particles (WIMPs) on argon nuclei ...with an effective field theory framework. The dataset corresponds to a total (16660 \(\pm\) 270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We obtain upper limits on the effective couplings of the 12 leading operators in the nonrelativistic systematic expansion. For each effective coupling we set constraints on WIMP-nucleon cross sections, setting upper limits between \(2.4 \times 10^{-45} \, \mathrm{cm}^2\) and \(2.3 \times 10^{-42} \, \mathrm{cm}^2\) (8.9 \(\times 10^{-45} \, \mathrm{cm}^2\) and 6.0 \(\times 10^{-42} \, \mathrm{cm}^2\)) for WIMPs of mass of 100 \(\mathrm{GeV/c^2}\) (1000 \(\mathrm{GeV/c^2}\)) at 90\% confidence level.
The p¯ stopping power in helium from 1 keV kinetic energy is evaluated. Contrary to the effect observed around and below the maximum, Obelix data indicate a p¯ stopping power higher than that for ...proton, the difference being of the order of 15±5% at ≈700 keV. The result contributes to assert the fundamental difference between p¯ stoppings in the simplest gases (He, H2) and in solid targets below some MeV.
We report measurements of the charged daughter fraction of \(^{218}\)Po as a result of the \(^{222}\)Rn alpha decay, and the mobility of \(^{218}\)Po\(^+\) ions, using radon-polonium coincidences ...from the \(^{238}\)U chain identified in 532 live-days of DarkSide-50 WIMP-search data. The fraction of \(^{218}\)Po that is charged is found to be 0.37\(\pm\)0.03 and the mobility of \(^{218}\)Po\(^+\) is (8.6\(\pm\)0.1)\(\times\)10$^{-4}$$\frac{\text{cm}^2}{\text{Vs}}$.
Phys. Rev. Lett. 122, 082003 (2019) The adapted DIRAC experiment at the CERN PS accelerator observed for the
first time long-lived hydrogen-like $\pi^+\pi^-$ atoms, produced by protons
hitting a ...beryllium target. A part of these atoms crossed the gap of 96~mm and
got broken up in the 2.1~\textmu{}m thick platinum foil. Analysing the observed
number of atomic pairs, $n_A^L= \left.436^{+157}_{-61}\right|_\mathrm{tot}$,
the lifetime of the 2$p$ state is found to be
${\tau_{2p}=(\left.0.45^{+1.08}_{-0.30}\right|_\mathrm{tot}) \cdot10^{-11}}$s,
not contradicting the corresponding QED $2p$ state lifetime
${\tau_{2p}^\mathrm{QED}=1.17 \cdot 10^{-11}}$s. This lifetime value is three
orders of magnitude larger than our previously measured value of the
$\pi^+\pi^-$ atom ground state lifetime
$\tau=(\left.3.15^{+0.28}_{-0.26}\right|_\mathrm{tot})\cdot 10^{-15}$s. Further
studies of long-lived $\pi^+\pi^-$ atoms will allow to measure energy
differences between $p$ and $s$ atomic states and so to determine $\pi\pi$
scattering lengths with the aim to check QCD predictions.
The DarkSide-50 direct-detection dark matter experiment is a dual-phase argon time projection chamber operating at Laboratori Nazionali del Gran Sasso. This paper reports on the blind analysis of a ...(16,660+-270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We find no events in the dark matter selection box and set a 90% C.L. upper limit on the dark matter-nucleon spin-independent cross section of 1.14E-44 cm^2 (3.78E-44 cm^2, 3.43E-43 cm^2) for a WIMP mass of 100 GeV/c^2 (1 TeV/c^2, 10 TeV/c^2).
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