Gravitationally bound quantum states of neutrons: applications and perspectives

Abele, H.; Bäßler, S.; Börner, Hans G.; Gagarski, A. M.; Nesvizhevsky, V. V.; Petoukhov, A.; Протасов, К. В.; Voronin, A. Yu.; Westphal, Alexander

doi:10.1063/1.2220384

AIP Conference Proceedings

2006

DOI: 10.1063/1.2220384

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Gravitationally bound quantum states of neutrons: applications and perspectives

H. Abele

S. Bäßler

Hans G. Börner³

et al.

Abstract: Gravitationally bound quantum states of matter were observed recently due to unique properties of ultracold neutrons. We discuss here the actual status and possible improvements in this experiment. This phenomenon could be useful for various domains ranging from the physics of elementary particles and fields, to surface studies, or to foundations of quantum mechanics

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Cited by 6 publications

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“…It should also be mentioned that the method used in this experiment (based on position sensitive detectors) to visualize the wave functions of the low lying states [18,20] also revealed no deviation from expected theoretical behavior.…”

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Constraint on the coupling of axionlike particles to matter via an ultracold neutron gravitational experiment

et al. 2007

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We present a new constraint for the axion monopole-dipole coupling in the range of 1 µm -a few mm, previously unavailable for experimental study. The constraint was obtained using our recent results on the observation of neutron quantum states in the Earth's gravitational field. We exploit the ultimate sensitivity of ultra-cold neutrons (UCN) in the lowest gravitational states above a material surface to any additional interaction between the UCN and the matter, if the characteristic interaction range is within the mentioned domain. In particular, we find that the upper limit for the axion monopole-dipole coupling constant is gpgs/( c) < 2 10 −15 for the axion mass in the "promising" axion mass region MA ∼ 1 meV.A vanishing value for the neutron electric dipole moment motivated the introduction of hypothetical light (pseudo) scalar bosons (commonly called axions), as an extension of the Standard Model [1,2,3,4]. According to the suggested theories the axion mass could be in the range of 10 −6 < M A < 10 −1 eV, while its coupling to photons, leptons and nucleons is not fixed by the existing models (though it is extremely weak). Following the theoretical predictions mentioned intensive searches for axions have been performed over recent decades. These studies include testing the astrophysical consequences of the axion theories, QED effects (axion-two photon coupling) and macroscopic forces (spin-matter coupling). They put severe constraints on axion-matter coupling in different axion mass ranges. A detailed review of axion studies can be found in [5,6].The recently reported positive results of the PVLAS experiment on light polarization rotation in a vacuum in the presence of a transverse magnetic field [7] may be seen as evidence of the long sought axion [8]. According to [7], the mass of neutral boson possibly responsible for the observed signal is 1 < M A < 1.5 meV.The value of the axion-photon coupling strength obtained from the PVLAS experiment is in contradiction with recent CAST observations [9]. Several ideas have been discussed recently, in [10,11], capable of explaining this discrepancy.This intriguing result makes it particularly important to carry out independent testing on the axion-matter coupling in the corresponding distance range of 130 < λ < 200 µm.In the present Letter we report on constraints for axion monopole-dipole coupling. Such coupling results in a spin-matter CP violating Yukawa-type interaction potential [12]between spin and matter, where g p g s is the product of couplings at the scalar and polarized vertices and λ is the force range. Here r is the distance between a neutron and a nucleus, n = r/r is a unitary vector, and m is the nucleon mass. Only a few experiments for distances below 100 mm have placed upper limits on the product coupling in a system of magnetized media and test masses [6]. One experiment [13] had peak sensitivity at ∼ 100 mm and two other ones [14,15] had peak sensitivity at ∼ 10 mm.The constraint for the g s g p presented in this article is competitive in the dista...

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Constraint on the coupling of axionlike particles to matter via an ultracold neutron gravitational experiment

et al. 2007

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Everything you always wanted to know about the cosmological constant problem (but were afraid to ask)

Martin¹

2012

Comptes Rendus. Physique

735

832

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This article aims at discussing the cosmological constant problem at a pedagogical but fully technical level. We review how the vacuum energy can be regularized in flat and curved spacetime and how it can be understood in terms of Feynman bubble diagrams. In particular, we show that the properly renormalized value of the zero-point energy density today (for a free theory) is in fact far from being 122 orders of magnitude larger than the critical energy density, as often quoted in the literature. We mainly consider the case of scalar fields but also treat the cases of fermions and gauge bosons which allows us to discuss the question of vacuum energy in supersymmetry. Then, we discuss how the cosmological constant can be measured in cosmology and constrained with experiments such as measurements of planet orbits in our solar system or atomic spectra. We also review why the Lamb shift and the Casimir effect seem to indicate that the quantum zero-point fluctuations are not an artifact of the quantum field theory formalism. We investigate how experiments on the universality of free fall can constrain the gravitational properties of vacuum energy and we discuss the status of the weak equivalence principle in quantum mechanics, in particular the Collela, Overhausser and Werner experiment and the quantum Galileo experiment performed with a Salecker-Wigner-Peres clock. Finally, we briefly conclude with a discussion on the solutions to the cosmological constant problem that have been proposed so far.

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Experiments with ultracold neutrons

Nesvizhevsky

2011

Low Temperature Physics

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Ultracold neutrons (UCN) form a tiny low-energy fraction in Maxwelian spectrum of thermal neutrons in moderators of nuclear reactors and spallation sources. Their energy is extremely small (~10-7 eV), their velocity is a few meters per second, and their effective temperature is as low as ~1 mK. Specific feature of UCN consists of their nearly total elastic reflection from nuclear-optical potential of many materials at any incidence angle; therefore they could be stored in closed traps for many minutes, thus they could be used for extremely sensitive measurements. A fraction of UCN in the thermal neutron flux is as low as 10-11-10-12 , and serious efforts are undertaken all over the world to produce UCN in larger amounts. UCN are widely used in precision particle physics experiments. Applications of UCN are emerging in surface and nanoparticle physics. Here we will focus on recent advances in the field.

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Gravitationally bound quantum states of neutrons: applications and perspectives

Cited by 6 publications

References 2 publications

Constraint on the coupling of axionlike particles to matter via an ultracold neutron gravitational experiment

Constraint on the coupling of axionlike particles to matter via an ultracold neutron gravitational experiment

Everything you always wanted to know about the cosmological constant problem (but were afraid to ask)

Experiments with ultracold neutrons

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