arXiv subjects

Guillaume Pignol

Publications and source records attributed to Guillaume Pignol.

At least 19 recordsLinked to original sources

arXiv2026

Further search for magnetic-field-induced neutron disappearance in an ultracold neutron beam

We report the results of the second iteration of an experiment searching for neutron-hidden-neutron oscillations in a beam of ultracold neutrons, conducted at the PF2 facility of the Institut Laue Langevin (ILL). Oscillations were tested via neutron disappearance as a function of an applied magnetic field, in the context of a phenomenological two-parameter model assuming zero hidden potentials. The magnetic field was varied in a step-wise manner in order to resonantly enhance the oscillation probability at different mass splittings ($δm$) across a 60--1550 peV range. No evidence for neutron disappearance is observed and conservative limits on the neutron-hidden-neutron oscillation period ($τ_{nn'}$) have been set at 95 % confidence level: $τ_{nn'} > 200$ms for $|δm| \in [60, 400]$ peV and $τ_{nn'} > 100$ ms for $|δm| \in [400, 1550]$ peV

hep-ex↗

arXiv2025

Physics Briefing Book: Input for the 2026 update of the European Strategy for Particle Physics

The European Strategy for Particle Physics (ESPP) reflects the vision and presents concrete plans of the European particle physics community for advancing human knowledge in fundamental physics. The ESPP is updated every five-to-six years through a community-driven process. It commences with the submission of specific proposals and other input from the community at large, outlining projects envisioned for the near-, mid-, and long-term future. All submitted contributions are evaluated by the Physics Preparatory Group (PPG), and a preliminary analysis is presented at a Symposium meant to foster a broad community discussion on the scientific value and feasibility of the various ideas proposed. The outcomes of the analysis and the deliberations at the Symposium are synthesized in the current Briefing Book, which provides an important input in the deliberations of the Strategy recommendations by the European Strategy Group (ESG).

hep-ex↗

arXiv2022

Manipulation of gravitational quantum states of a bouncing neutron with the GRANIT spectrometer

The bouncing neutron is one of the rare system where gravity can be studied in a quantum framework. To this end it is crucial to be able to select some specific gravitational quantum state (GQS). The GRANIT apparatus is the first physics experiment connected to a superthermal helium UCN source. We report on the methods developed for this instrument showing how specific GQS can be favored using a step between mirrors and an absorbing slit. We explore the increase of GQS separation efficiency by increasing the absorber roughness amplitude, and find it is feasible but requires a high adjustment precision. We also quantify the transmission of the absorbing slit leading to a measurement of the spatial extension of the neutron vertical wave function $z_0 = \hbar^{2/3}\left(2m^2g\right)^{-1/3} = 5.9\pm0.3\,μ$m.

hep-ex↗

arXiv2021

The search for the neutron electric dipole moment at PSI

The existence of a nonzero permanent electric dipole moment (EDM) of the neutron would reveal a new source of CP violation and shed light on the origin of the matter--antimatter asymmetry of the Universe. The sensitivity of current experiments using stored ultracold neutrons (UCN) probes new physics beyond the TeV scale. Using the UCN source at the Paul Scherrer Institut, the nEDM collaboration has performed the most sensitive measurement of the neutron EDM to date, still compatible with zero ($|d_n|<1.8\times 10^{-26} \, e {\rm cm}$, C.L.90%). A new experiment designed to improve the sensitivity by an order of magnitude, n2EDM, is currently in construction.

hep-ex↗

arXiv2019

A global perspective on searches for Electric Dipole Moments

Many experiments are underway in the world to search for a non-zero electric dipole moment (EDM) of a particle with spin 1/2 such as the neutron or the electron. Finding an EDM would reveal new sources of CP violation. EDM measurements are motivated by the high sensitivity to new physics beyond the Standard Model. They are relevant to find the explanation for the matter-antimatter asymmetry of the Universe. A variety of programs with different systems are being pursued, with free neutrons, diamagnetic atoms, paramagnetic systems, and charged particles in storage rings. This article presents a basic introduction of the subject and attempts to compile the ongoing projects.

hep-ph↗

arXiv2019

Boron-10 conversion layer for ultra-cold neutron detection

We report on the development of a 10B conversion layer optimized for ultra-cold neutron detection with silicon detectors. The efficiency of this layer is high and roughly uniform over a large ultra-cold neutron velocity range. The designed titanium-boron-nickel multilayer film was deposited on silicon using a microwave plasma-assisted co-sputtering method (first, for test purpose, on silicon wafers, then directly on the surface of a CCD sensor). The obtained sensor was then tested using both cold and ultra-cold neutrons.

physics.ins-det↗

arXiv2019

Design and test of a compact and high-resolution time-of-flight measurement device for cold neutron beams

A time-of-flight device was developed to characterize wavelength distribution and uniformity of a cold neutron beam. This device is very compact -- the distance of flight is $60$ cm -- but achieves very high resolution -- the intrinsic resolution $Δλ/λ=2.4\cdot 10^{-3}$ at $λ=0.89$ nm. The time-of-flight device is composed of a fixed slit, a disk rotating up to $216$ Hz and a neutron detector with a thin spherical conversion layer with the chopper slit in its focus. The device accepts the complete angular divergence of the initial neutron beam. The efficiency of neutron detection is constant over the detector area. Systematic corrections caused by neutron scattering in air are minimized due to the reduction of the time-of-flight length. Measurements have been performed on the beamline of the GRANIT experiment at ILL (part of the H172 beamline) on level C, and the first order diffraction peak of the crystal monochromator used for the GRANIT beamline was found to be at $λ=0.8961(11)$ nm, and having a width of $σ=0.0213(13)$ nm.

physics.ins-det↗

arXiv2019

Acoustic Rabi oscillations between gravitational quantum states and impact on symmetron dark energy

The standard model of cosmology provides a robust description of the evolution of the universe. Nevertheless, the small magnitude of the vacuum energy is troubling from a theoretical point of view. An appealing resolution to this problem is to introduce additional scalar fields. However, these have so far escaped experimental detection, suggesting some kind of screening mechanism may be at play. Although extensive exclusion regions in parameter space have been established for one screening candidate - chameleon fields - another natural screening mechanism based on spontaneous symmetry breaking has also been proposed, in the form of symmetrons 11. Such fields would change the energy of quantum states of ultra-cold neutrons in the gravitational potential of the earth. Here we demonstrate a spectroscopic approach based on the Rabi resonance method that probes these quantum states with a resolution of E=2 x 10^(-15) eV. This allows us to exclude the symmetron as the origin of Dark Energy for a large volume of the three-dimensional parameter space.

hep-ph↗

arXiv2019

Wigner-Eckart Theorem and the False EDM of $^{199}$Hg

In neutron electric dipole moment experiments, 199Hg is used as a comagnetometer. The comagnetometer suffers from a false EDM arising in leading order from a gradient dBz/dz in the magnetic field. Our work concerns higher-order multipole corrections to the false EDM of 199Hg. We show that for spherical traps, all higher-order multipole are identically zero. We further show that for the usual cylindrical traps used in EDM experiments, selection of quasi-spherical dimensions for the trap can reduce the higher-order contributions. The results are another indication that trap geometry is an important consideration for experiments desiring to control this systematic effect.

nucl-th↗

arXiv2017

Bounding Quantum Dark Forces

Dark sectors lying beyond the Standard Model and containing sub-GeV particles which are bilinearly coupled to nucleons would induce quantum forces of the Casimir-Polder type in ordinary matter. Such new forces can be tested by a variety of experiments over many orders of magnitude. We provide a generic interpretation of these experimental searches and apply it to a sample of forces from dark scalars behaving as $1/r^3$, $1/r^5$, $1/r^7$ at short range. The landscape of constraints on such quantum forces differs from the one of modified gravity with Yukawa interactions, and features in particular strong short-distance bounds from molecular spectroscopy and neutron scattering.

hep-ph↗

arXiv2016

Search for passing-through-walls neutrons constrains hidden braneworlds

In many theoretical frameworks our visible world is a $3$-brane, embedded in a multidimensional bulk, possibly coexisting with hidden braneworlds. Some works have also shown that matter swapping between braneworlds can occur. Here we report the results of an experiment - at the Institut Laue-Langevin (Grenoble, France) - designed to detect thermal neutron swapping to and from another braneworld, thus constraining the probability $p^2$ of such an event. The limit, $p<4.6\times 10^{-10}$ at $95 \%$ C.L., is $4$ orders of magnitude better than the previous bound based on the disappearance of stored ultracold neutrons. In the simplest braneworld scenario, for two parallel Planck-scale branes separated by a distance $d$, we conclude that $d>87$ in Planck length units.

hep-ex↗

arXiv2015

Constraining short-range spin-dependent forces with polarized $^3$He

We have searched for a short-range spin-dependent interaction using the spin relaxation of hyperpolarized $^3$He. Such a new interaction would be mediated by a hypothetical light scalar boson with \CP-violating couplings to the neutron. The walls of the $^3$He cell would generate a pseudomagnetic field and induce an extra depolarization channel. We did not see any anomalous spin relaxation and we report the limit for interaction ranges $λ$ between $1$ and $100~\rm{μm}$: $g_sg_p λ^2 \leq 2.6\times 10^{-28}~\mathrm{m^2}\, ( 95~\%\, \mathrm{C.L.})$, where $g_s$($g_p$) are the (pseudo)scalar coupling constant, improving the previous best limit by 1 order of magnitude.

hep-ex↗

arXiv2015

Probing the braneworld hypothesis with a neutron-shining-through-a-wall experiment

The possibility for our visible world to be a 3-brane embedded in a multidimensional bulk is at the heart of many theoretical edifices in high-energy physics. Probing the braneworld hypothesis is thus a major experimental challenge. Following recent theoretical works showing that matter swapping between braneworlds can occur, we propose a neutron-shining-through-a-wall experiment. We first show that an intense neutron source such as a nuclear reactor core can induce a hidden neutron flux in an adjacent hidden braneworld. We then describe how a low-background detector can detect neutrons arising from the hidden world and quantify the expected sensitivity to the swapping probability. As a proof of concept, a constraint is derived from previous experiments.

hep-ph↗

arXiv2015

Search for a new short-range spin-dependent force with polarized Helium 3

Measuring the depolarization rate of a $^3$He hyperpolarized gas is a sensitive method to probe hypothetical short-range spin-dependent forces. A dedicated experiment is being set up at the Institute Laue Langevin in Grenoble to improve the sensitivity. We presented the status of the experiment at the 10th PATRAS Workshop on Axions, WIMPs and WISPs.

hep-ex↗

arXiv2014

Status of the GRANIT facility

The GRANIT facility is a follow-up project, which is motivated by the recent discovery of gravitational quantum states of ultracold neutrons. The goal of the project is to approach the ultimate accuracy in measuring parameters of such quantum states and also to apply this phenomenon and related experimental techniques to a broad range of applications in particle physics as well as in surface and nanoscience studies. We overview the current status of this facility, the recent test measurements and the nearest prospects.

physics.ins-det↗

arXiv2013

Probing Strongly Coupled Chameleons with Slow Neutrons

We consider different methods to probe chameleons with slow neutrons. Chameleon modify the potential of bouncing neutrons over a flat mirror in the terrestrial gravitational field. This induces a shift in the energy levels of the neutrons which could be detected in current experiments like GRANIT. Chameleons between parallel plates have a field profile which is bubble-like and which would modify the phase of neutrons in interferometric experiments. We show that this new method of detection is competitive with the bouncing neutron one, hopefully providing an efficient probe of chameleons when strongly coupled to matter.

quant-ph↗

arXiv2012

Experimental limits on neutron disappearance into another braneworld

Recent theoretical works have shown that matter swapping between two parallel braneworlds could occur under the influence of magnetic vector potentials. In our visible world, galactic magnetism possibly produces a huge magnetic potential. As a consequence, this paper discusses the possibility to observe neutron disappearance into another braneworld in certain circumstances. The setup under consideration involves stored ultracold neutrons - in a vessel - which should exhibit a non-zero probability p to disappear into an invisible brane at each wall collision. An upper limit of p is assessed based on available experimental results. This value is then used to constrain the parameters of the theoretical model. Possible improvements of the experiments are discussed, including enhanced stimulated swapping by artificial means.

hep-ph↗

arXiv2012

Electric dipole moment searches: reexamination of frequency shifts for particles in traps

In experiments searching for a nonzero electric dipole moment of trapped particles, frequency shifts correlated with an applied electric field can be interpreted as a false signal. One such effect, referred to as the geometric phase effect, is known to occur in a magnetic field that is nonperfectly homogeneous. The increase in sensitivity of experiments demands improved theoretical description of this effect. In the case of fast particles, like atoms at room temperature and low pressure, the validity of established theories was limited to a cylindrical confinement cell in a uniform gradient with cylindrical symmetry. We develop a more general theory valid for an arbitrary shape of the magnetic field as well as for arbitrary geometry of the confinement cell. Our improved theory is especially relevant for experiments measuring the neutron electric dipole moment with an atomic comagnetometer. In this context, we have reproduced and extended earlier numerical studies of the geometric phase effect induced by localized magnetic impurities.

nucl-ex↗