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A new measurement of the neutron lifetime, carried out with the aid of a large gravitational spectrometer made in Petersburg Institute of Nuclear Physics (PNPI) is presented: τn = 881.5 ± 0.7 ± 0.6 s. In our experiment the measurement of neutron lifetime is carried out using the method of storing ultracold neutrons in a material trap with gravitational barrier. Further improvement of the obtained result can be achieved at the helium temperatures. Here we present our neutron lifetime result, modified installation scheme and the first results of cryogenic tests are discussed.

We give a short overview of the gravity resonance spectroscopy methods used recently by the qBounce experiment. It has been demonstrated that mechanically induced transitions between bound neutron states in the gravitational field can be observed. Applications of this new method test Newton's gravity law, search for extra dimensions of space-time, and study the neutrality of the neutron.

This volume contains the written proceedings of PPNS-2018, the international workshop on “Particle Physics at Neutron Sources” hosted by the LPSC in Grenoble, France from May 24 th –26 th , 2018.

qBounce is using quantum states of ultra-cold neutrons in the gravitational field of the Earth to investigate gravitation in the micrometre range. We present current measurements taken in 2021 at the Institut Laue-Langevin (ILL) to determine energy differences of these states by mechanically induced transitions. This allows a determination of the local acceleration \\(g\\) using a quantum measurement. The data presented here results in \\(g=9.8120(18) m/s^2\\). The classical local value at the experiment is \\(g_c=9.8049 m/s^2\\). We present an analysis of systematic effects that induces shifts of the transition frequency of order 100 mHz. The inferred value for \\(g\\) at the experiment shows a systematic shift of \\(\\delta g\\approx3.9\\sigma\\).

Models that postulate the existence of hidden sectors address contemporary questions, such as the source of baryogenesis and the nature of dark matter. Among the possible mixing processes, neutron-to-hidden-neutron oscillations have been repeatedly tested with ultra-cold neutron storage and passing-through-wall experiments in the range of small (\\( m<2\\) peV) and large mass splitting (\\( m>10\\) neV), respectively. In this work, we present a new constraint in the oscillation parameter space derived from neutron disappearance in ultra-cold neutron beam experiments. The overall limit, which covers the intermediate mass-splitting range, is given by \\(_nn'> 1\\) s for \\(| m| ın [2,69]\\) peV (95\\% C.L.).

The study of the properties of the quantum states of bouncing neutrons requires position sensitive detection with micro-metric spatial resolution. The UCNBoX detector relies on Charge Coupled Devices (CCD) coated with a thin boron-10 conversion layer to detect neutron hits. In this paper, we present an original experimental method to determine the spatial resolution of this device using micrometric masks. The observed resolution is \\(2.0\\pm0.3~\\mu\\)m.

We demonstrate the use of nanodiamond in constructing holographic nanoparticle-polymer composite transmission gratings with large saturated refractive index modulation amplitudes at both optical and slow-neutron wavelengths, resulting in efficient control of light and slow-neutron beams. Nanodiamond possesses a high refractive index at optical wavelengths and large coherent and small incoherent scattering cross sections with low absorption at slow-neutron wavelengths. We describe the synthesis of nanodiamond, the preparation of photopolymerizable nanodiamond-polymer composite films, the construction of transmission gratings in nanodiamond-polymer composite films and light optical diffraction experiments. Results of slow-neutron diffraction from such gratings are also presented.

Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world's brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).

We calculate the chameleon field profile, confined between two parallel plates, filled with air at pressure \\(P = 10^{-4}\\,{\\rm mbar}\\) and room temperature and separated by the distance \\(L\\), in the chameleon field theory with Ratra--Peebles self--interaction potential with index \\(n = 1\\). We give the exact analytical solution in terms of Jacobian elliptic functions, depending on the mass density of the ambient matter. The obtained analytical solution can be used in qBounce experiments, measuring transition frequencies between quantum gravitational states of ultracold neutrons and also for the calculation of the chameleon field induced Casimir force for the CANNEX experiment. We show that the chameleon--matter interactions with coupling constants \\(\\beta \\le 10^4\\) can be probed by qBounce experiments with sensitivities \\(\\Delta E \\le 10^{-18}\\,{\\rm eV}\\). At \\(L = 30.1\\,{\\rm \\mu m}\\) we reproduce the result \\(\\beta < 5.8\\times 10^8\\), obtained by Jenke {\\it et al.} Phys. Rev. Lett. {\\bf 112}, 151105 (2014)) at sensitivity \\(\\Delta E \\sim 10^{-14}\\,{\\rm eV}\\). In the vicinity of one of the plates our solution coincides with the solution, obtained by Brax and Pignol (Phys. Rev. Lett. {\\bf 107}, 111301 (2011)) (see also Ivanov {\\it et al.} Phys. Rev. D {\\bf 87}, 105013 (2013)) above a plate at zero density of the ambient matter.