Neutron interferometry, fifth force and axion like particles

Physical Review D, 2007

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.

Physics Letters B

We propose a new approach in the investigation and detection of axion and axion-like particles based on the study of the entanglement for two interacting fermions. We study a system made of two identical fermions with spin −1/2, and we show that fermion-fermion interaction mediated by axions leads to a non-zero entanglement between the fermions. An entanglement measurement can reveal the interaction, providing an indirect evidence of the existence of axions. We discuss how the other interactions affect the entanglement, and how to isolate the axion contribution. Particular care is devoted to the analysis of the magnetic dipole-dipole interaction, which turns out to be, apart from axions, the most relevant contribution to the entanglement, and we show that it can be suppressed by setting opportunely the duration of the observation. We also introduce a two-body correlation function, which could be directly observed in an experiment, and plays the role of an entanglement witness.

Science, 2021

Setting bounds on a fifth force Some extensions to the Standard Model of particle physics posit the existence of a fifth force to complement the existing four fundamental forces. To set bounds on the strength of such an interaction, experiments on vastly different length scales have been performed. Heacock et al . used an unusual method called Pendellösung interferometry to measure the neutron structure factors of silicon. The momentum dependence of the structure factors enabled the researchers to put more stringent bounds on the strength of a type of fifth force called the Yukawa force, as well as measure the charge radius of the neutron. —JS

Physics Letters B, 2012

Recently, the PVLAS collaboration has reported evidence for an anomalously large rotation of the polarization of light generated in vacuum in the presence of a transverse magnetic field. This may be explained through the production of a new light spin-zero particle coupled to two photons. In this Letter of Intent, we propose to test this hypothesis by setting up a photon regeneration experiment which exploits the photon beam of the Vacuum-UltraViolet Free-Electron Laser VUV-FEL, sent along the transverse magnetic field of a linear arrangement of dipole magnets of size B L ≈ 30 Tm. The high photon energies available at the VUV-FEL increase substantially the expected photon regeneration rate in the mass range implied by the PVLAS anomaly, in comparison to the rate expected at visible lasers of similar power. We find that the particle interpretation of the PVLAS result can be tested within a short running period. The pseudoscalar vs. scalar nature can be determined by varying the direction of the magnetic field with respect to the laser polarization. The mass of the particle can be measured by running at different photon energies. The proposed experiment offers a window of opportunity for a firm establishment or exclusion of the particle interpretation of the PVLAS anomaly before other experiments can compete.

WORLD SCIENTIFIC eBooks, 2014

The possible existence of short-range forces between unpolarized and polarized spin-1 2 particles has attracted the attention of physicists for decades. These forces are predicted in various theories and provide a possible new source for parity (P) and time reversal (T) symmetry violation. We use an ensemble of polarized 3 He gas in a cell with a 250 µm thickness glass window to search for a force from pseudoscalar boson exchange over a sub-millimeter ranges. This interaction would produce a NMR frequency shift as an unpolarized mass is moved near and far from the polarized ensemble. We report a new upper bound with a factor of 10-30 improvement on the product gsg n p of the scalar couplings to the fermions in the unpolarized mass, and the pseudoscalar coupling of the polarized neutron in the 3 He nucleus for force ranges from 10 −4 to 10 −2 m, which corresponds to a mass range of 2 × 10 −3 to 2 × 10 −5 eV for the pseudoscalar boson. This represents the most sensitive search that sets a direct limit in the important "axion window".

Physica B+C, 1988

A brief summarizing review is given of all those neutron interferometric experiments performed hitherto which explicitly use the spin-½ particle properties of the neutron. It covers topics as the verification of the 4~-periodicity of spinors, the cooperative action of nuclear phase shift and spin-rotation on the neutron wave function, the demonstration of the quantum mechanical principles of fermion spin-state superposition and the more recent double resonance experiments where the two interfering beams propagate through spatially separated oscillatory magnetic fields. Finally a proposal will be presented also for a so-called "late-choice" experiment with polarized neutrons.

2007

We discuss the experimental techniques used to date for measuring the changes in polarization state of a laser produced by a strong transverse magnetic field acting in a vacuum. We point out the likely artifacts that can arise in such experiments, with particular reference to the recent PVLAS observations and the previous findings of the BFRT collaboration. Our observations are based on studies with a photon-noise limited coherent homodyne interferometer with a polarization sensitivity of 2×10 -8 rad Hz 1/2 mW -1/2 . P. A.C.S. numbers: 42.15.Eq, 14.80.Mz,

Physical Review D, 2016

We present constraints on the nature of axions and axion-like particles (ALPs) by analyzing gamma-ray data from neutron stars using the Fermi Large Area Telescope. In addition to axions solving the strong CP problem of particle physics, axions and ALPs are also possible dark matter candidates. We investigate axions and ALPs produced by nucleon-nucleon bremsstrahlung within neutron stars. We derive a phenomenological model for the gamma-ray spectrum arising from subsequent axion decays. By analyzing 5 years of gamma-ray data (between 60 MeV and 200 MeV) for a sample of 4 nearby neutron stars, we do not find evidence for an axion or ALP signal, thus we obtain a combined 95% confidence level upper limit on the axion mass of 7.9×10 −2 eV, which corresponds to a lower limit for the Peccei-Quinn scale f a of 7.6×10 7 GeV. Our constraints are more stringent than previous results probing the same physical process, and are competitive with results probing axions and ALPs by different mechanisms.

Physical Review D, 2013

The possible existence of short-range forces between unpolarized and polarized spin-1 2 particles has attracted the attention of physicists for decades. These forces are predicted in various theories and provide a possible new source for parity (P) and time reversal (T) symmetry violation. We use an ensemble of polarized 3 He gas in a cell with a 250 µm thickness glass window to search for a force from pseudoscalar boson exchange over a sub-millimeter ranges. This interaction would produce a NMR frequency shift as an unpolarized mass is moved near and far from the polarized ensemble. We report a new upper bound with a factor of 10-30 improvement on the product gsg n p of the scalar couplings to the fermions in the unpolarized mass, and the pseudoscalar coupling of the polarized neutron in the 3 He nucleus for force ranges from 10 −4 to 10 −2 m, which corresponds to a mass range of 2 × 10 −3 to 2 × 10 −5 eV for the pseudoscalar boson. This represents the most sensitive search that sets a direct limit in the important "axion window".

Physical Review D, 1995

We reexamine the axion-photon couplings in various invisible axion models motivated by the recent proposal of using optical interferometry at the ASST facility in the SSCL to search for axion. We illustrate that the assignment of U(1) P Q charges for the fermion fields plays an important role in determining the couplings. Several simple non-minimal invisible axion models with suppressed and enhanced axionphoton couplings are constructed, respectively. We also discuss the implications of possible new experiments to detect solar axions by conversion to X-rays in a static magnetic apparatus tracking the sun.