The Muon g-2 Experiment at Fermi National Accelerator Laboratory set out to measure the muon anomalous magnetic moment, $a_{\mu}$, with a target precision of 140 parts-per-billion (ppb), representing a four-fold improvement over the predecessor measurement at Brookhaven National Laboratory in the 2000s. The Muon g-2 collaboration recently published the analysis of the final three of a total of...
In my talk, I will present the latest advances in the theoretical study of medium and heavy muonic atoms. I will discuss the four largest QED contributions, current uncertainties, and the limitations in determining nuclear radii, illustrated by the case of the doubly magic nucleus 208Pb. Finally, I will address the feasibility of obtaining model-independent values of nuclear radii.
The Universe and its history are at the same time very well understood and a big mystery. We have amazing tools from satellites to observatories to weight the universe as it is today and also as it was in the past. But the content of the Universe can simply not be explained by physicists. To get the full picture, we need to identify and understand the interactions at play throughout the life...
The extreme electronic properties of highly charged ions (HCI) render them highly sensitive probes for testing fundamental physical theories. The same properties reduce systematic frequency shifts, making HCI excellent optical clock candidates. The technical challenges that hindered the development of such clocks have now all been overcome, starting with their extraction from a hot plasma and...
The quest for an optical nuclear frequency standard, the ‘nuclear clock’ based on the elusive and uniquely low-energetic ‘thorium isomer’ $^{229m}$Th, has increasingly triggered experimental and theoretical research activities in numerous groups worldwide in the last decade. Today’s most precise timekeeping is based on optical atomic clocks. How-ever, those could potentially be outperformed by...
Ultracold neutrons (UCN) are neutrons with kinetic energies below approximately 340 neV—low enough to be confined using material or magnetic bottles. These unique properties make UCN an essential tool for precision experiments in fundamental physics, such as probing the Standard Model and searching for new physics beyond it.
At Los Alamos National Laboratory, we operate a UCN source that...
SuperSUN: A high-density Source of Ultracold Neutrons at ILL
SuperSUN is a newly commissioned superthermal high-density ultracold neutron (UCN) source at the Institut Laue-Langevin (ILL). It employs isotopically pure superfluid helium-4, cooled below 0.6 K, to convert a broad-spectrum cold neutron beam into UCN via inelastic scattering. The source has demonstrated a continuous, reliable...
We report on a precision measurement of the neutron electric charge using the QNeutron apparatus. It consists of a Talbot-Lau interferometer for cold neutrons in the ballistic regime. The setup employs three identical absorption gratings and a differential two-beam geometry to detect potential beam deflections induced by a strong transverse electric field. During an 84-hour data-taking...
Parity-conjugated copies of standard model particles, so-called mirror particles, could provide answers for several standing issues in physics.
Since they would at first only interact with ordinary matter gravitationally, they can be viable candidates for dark matter. If mixing between standard model and mirror particles was possible, they could contribute to baryon number violation.
The...
The search for neutrinoless double-beta decay is currently one of the
most compelling challenges in physics, with the potential to reveal the origin of the neutrino’s mass, demonstrate lepton number violation, and provide hints of the mechanism behind the matter anti-matter asymmetry we observe in our universe. Detecting this ultra-rare process, however, requires us to build very large...
Corrected transition rates ($\mathcal{F}t^{0^+→0^+}$ values) of superallowed $0^+ \rightarrow 0^+$ beta decays have served as a benchmark for validating the conserved vector current (CVC) hypothesis in weak interactions. They now provide the most precise value of $V_{ud}$, the dominant top-row element of the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. By imposing stringent constrains...
In this talk I will discuss measurements of the $2\,^3$S$_1 \rightarrow 2\,^1$P$_1$ ($\nu_F$) transition in positronium (Ps). Although this transition is strictly forbidden by charge conjugation symmetry (C), it becomes observable in the presence of a magnetic field. Ps atoms were produced using a pulsed positron beam and optically excited to the radiatively metastable $2\,^3$S$_1$ state....
Positronium and muonium, as purely leptonic atoms without internal structure, provide ideal systems for high-precision tests of quantum electrodynamics (QED) [1] and measurements of fundamental constants. Here, we present the recent results we obtained at ETH on the $\text{1}^\text{3}\text{S}_\text{1} \to \text{2}^\text{3}\text{S}_\text{1}$ transition in positronium, measured via two-photon...
Antihydrogen—a bound state of an antiproton and a positron—offers a platform for precision tests of fundamental symmetries in nature. Over the past two decades, experimental progress has transformed antihydrogen studies from the demonstration phase into the precision measurement phase.
In this talk, I will review recent advances in antihydrogen research, with a focus on results from the...
ASACUSA plans to measure the ground-state hyperfine structure of antihydrogen at low magnetic field using the Rabi method, for which a slow atomic beam ($v < 1500\,\mathrm{m/s}$) is needed. We make antihydrogen by slowly combining large amounts of positrons and antiprotons in a Penning-Malmberg trap. The antiprotons are "mixed" with the positrons for $60\,\mathrm{s}$, during which time about...
The GBAR experiment at the Extra Low Energy Antiproton ring ELENA at CERN aims to produce positive antihydrogen ions (Hbar+), the pure antimatter bound state of two positrons together with one antiproton, and the charge conjugate to the (fragile) H- ion. The production of such ions requires an experimentally challenging two step formation process, but it will open the door for next generation...
The Mainz Energy-recovering Superconducting Accelerator (MESA) is a cutting-edge facility designed to push the frontiers of particle, hadron, and nuclear physics. It will enable high-precision measurements, including the weak mixing angle at low energies, and contribute to the search for physics beyond the Standard Model. MESA’s two flagship experiments, P2 and MAGIX, will offer crucial...
Rapid progress in the experimental control and interrogation of molecules is enabling new opportunities to investigate the violation of fundamental symmetries. In particular, molecules containing heavy, octupole-deformed nuclei, such as radium, can offer enhanced sensitivity for measuring parity- and time-reversal violating nuclear properties. In this talk, I will present recent results and...
Recent progress in both theory and experiment has left the unitarity of the quark mixing matrix (CKM) somewhat of an open question. The Nab experiment at the Spallation Neutron Source is designed to improve precision of the extraction of the first matrix element and shed light on experimental tensions within the neutron beta decay dataset. Nab’s asymmetric spectrometer allows coincident...
The Fundamental Neutron Physics Beamline at the Spallation Neutron Source provides intense, pulsed, cold-neutron beams dedicated to fundamental physics. With the termination of the nEDM@SNS experiment, we are proposing a new strategy to develop the beamline into a multi-user facility. This would include upgrades to allow measurements of correlations in the decay of polarized neutrons with the...
Very slow neutrons are excellent probes for fundamental physics at the precision frontier.
In recent years, the Institut Laue-Langevin (ILL) has been strengthening its corresponding infrastructure: The superthermal UCN source SuperSUN has been commissioned and successfully put into user operation. The work-horse of UCN physics, the instrument PF2, has been modernized, and its VCN-port...
The TUCAN collaboration is building a world-leading ultracold neutron (UCN) source at TRIUMF (Canada Particle Accelerator Center) to conduct a measurement of the neutron’s electric dipole moment (nEDM) with a sensitivity of 10^(-27) ecm. If discovered, it would be a new source of CP violation and contribute to our understanding of the Baryon Asymmetry of the universe as well as theories beyond...
This presentation details recent developments from the Ultra-Cold Neutron (UCN) Physics group at the TRIGA research reactor in Mainz, Germany. We report on the operational performance of the UCN sources, the advancement of various detector systems, and on the implementation and improvement of a dedicated UCN simulation framework supporting the τSPECT neutron lifetime experiment. The novel...
Recoil-order and radiative corrections to neutron decay correlations enter at the 10$^{-3}$ level, important at the precision of recent and future experiments, especially when comparing results for $\lambda = G_A / G_V$. The aCORN experiment obtains the neutron electron-antineutrino correlation ($a$-coefficient) from an asymmetry in proton-electron coincidence events, in contrast to previous...
Baryon asymmetry of the Universe offers one of the strongest hints for physics Beyond the Standard Model (BSM). Remarkably, in the general two Higgs Doublet Model (g2HDM) that possesses a second set of Yukawa matrices, one can have electroweak baryogenesis (EWBG), while the electron EDM is evaded by a natural flavor tuning that echoes SM. We show that eEDM may first emerge around 10^−30 𝑒 cm...
The MEG II experiment is being carried out in the PSI, piE5 area in the experimental hall west. The MEG II aims to search for the charged lepton flavor violation process, $\mu^{+}\rightarrow e^{+}\gamma$. The physics run started in 2021 and will be planned by the end of 2026 with the target sensitivity of branching ratio of $6\times10^{-14}$). In 2025, we published the result with the data...
A large enhancement of parity-violation via the weak interaction has been observed in nuclear reactions for several nuclei [1]. The enhancement is explained by the mixing of parity-unfavored partial amplitudes in the entrance channel of the compound nuclear states, s-p mixing [2]. The s-p mixing occurs between resonances with the same spin. Therefore, the spin of resonances is an important...
The nEDM Collaboration at PSI presents a novel method for extracting the energy spectrum of ultracold neutrons from magnetically induced spin depolarization measurements using the n2EDM apparatus. This method is also sensitive to the storage properties of the materials used to trap ultracold neutrons, specifically, how specular or diffuse is the surface. We highlight the sensitivity of this...
We present a detailed analytic evaluation of the soft-photon bremsstrahlung radiative corrections to the unpolarized elastic lepton-proton scattering cross-section within the framework of low-energy chiral effective field theory. Our study is motivated by the precision goals of the MUSE experiment, which aims to resolve the proton radius puzzle via simultaneous measurements of $e^\pm p$ and...
Abstract
The analysis of the heavy and very heavy nuclei with, particularly, an extension into the domain of exotic and superheavy nuclei is in the center of the contemporary research in low energy subatomic physics. This research program, currently going on the biggest laboratories in the world, is motivated from the theoretical calculations which predict the existence of an island of...
The spectroscopy of light muonic atoms offers a powerful tool for probing nuclear structure with high precision. By studying X-ray transitions, particularly low-lying states such as the 2p–1s transitions, it is possible to extract absolute nuclear charge radii with high accuracy.
However, measuring these transitions for low-Z nuclei in the 20–150 keV energy range remains challenging,...
A Multi-Pixel Photon Counter (MPPC) sensitive to vacuum ultraviolet (VUV) light, called VUV-MPPC, is used in the liquid xenon (LXe) gamma-ray detector for the MEG II experiment. In the MEG II runs with high intensity muon beam, the degradation of VUV-MPPC's photon detection efficiency (PDE) to VUV light was observed. The cause of PDE degradation is considered due to a surface damage of...
The concept of “mirror matter” has been postulated in various terms since the 1950s. The modern formulation supposes that every Standard Model particle has a partner with opposite chirality, in order to restore parity symmetry in the weak interaction. Neutrons are of particular interest because their lack of electric charge allows for the possibility of mixing between the ordinary and mirror...
Medium-energy, short-baseline neutrino experiments play a crucial role in testing both the Standard Model and physics beyond it. In recent years, pulsed neutron spallation sources have emerged as promising venues for such investigations. The Swiss Spallation Neutron Source (SINQ) at PSI presents another bright neutrino source, however, with almost continuous neutrino production due to the 50...
The impact of earth's gravity on neutral mesons dynamics is analyzed. The main effect of a Newtonian potential is to couple the strangeness and bottomness flavor oscillations with the quarks zitterbewegung oscillations (arXiv:2503.09465). This coupling is responsible of the observed CP violations in the three types of experiments analyzed here: (i)indirect violation in the mixing, (ii) direct...
The muEDM collaboration is aiming at measuring the electric dipole moment of the muon with unprecedented sensitivity of $\sigma (d_\mu) = 6 \cdot 10 ^{23} \space \mathrm{e\space cm}$ at the Paul Scherrer Institute. The experiment uses the frozen-spin technique inside a 3-T superconducting solenoid magnet. One of the key parts of the experiment is the superconducting injection channels. They...
Positronium, a bound state composed of an electron and a positron, is a pure lepton system. Depending on the total spin, there are para-positronium (p-Ps) and ortho-positronium (o-Ps), which eventually annihilate into two photons and three photons, respectively. Due to minimal hadronic effects, experimental measurement of the continuous spectrum of three-photon annihilation of o-Ps can be used...
The MEG II experiment, conducted at PSI from 2021 and planned through 2026, targets a $\mu\to e\gamma$ search with a sensitivity of $6\times 10^{-14}$ to the muon branching ratio. While the experiment has already demonstrated the potential to reach the target sensitivity, improvements in the reconstruction and analysis techniques will enhance the sensitivity beyond the target value.
This...
McMule (Monte Carlo for Muons and other Leptons) is a powerful tool for fully differential higher-order QED calculations of scattering and decay processes involving leptons. It provides different type of observables such as cross-sections and branching ratios.
In this work, we use McMule to study the process of lepton-proton scattering up to and including next-to-next-to-leading order (NNLO)...
The decay of free neutrons is a powerful tool for precision tests of the Standard Model of particle physics. Correlation coefficients - such as the beta asymmetry $A$ and the Fierz interference term $b$ - serve as input for the determination of the CKM matrix element $V_{ud}$ and for searches for (effective) scalar and tensor as well as right-handed couplings.
The neutron decay spectrometer...
The search for neutrinoless double beta decay (0νββ) is fundamental for investigating lepton-number violation, probing new physics beyond the Standard Model, and determining whether neutrinos are Majorana particles. CUORE, a cryogenic calorimetric experiment at LNGS, studies 0νββ in $^{130}$Te using 988 TeO₂ crystals, reaching a tonne-scale mass and operating below 15 mK. Since 2017, CUORE has...
BRAND is a precision experiment that will investigate free polarized neutron beta-decay [1] at the PF1B cold neutron beamline of the Institut Laue-Langevin (ILL), which offers the world’s highest cold neutron flux [2]. The experiment will perform simultaneous measurements of 11 correlation coefficients in neutron beta-decay [3], including five that have never been measured before. This enables...
The process $\mu \to e\gamma$ is a charged lepton flavor violating (CLFV) decay that is forbidden in the Standard Model, but its measurable branching ratio is predicted by several new physics models. The current experimental limit on this decay has been set by the MEG II experiment at PSI, which will continue data collection until the end of 2026 with the target sensitivity of $Br < 6 \times...
The BRAND experiment is designed to search for hints of physics beyond the Standard Model. This objective is achieved through the precise study of neutron beta decay. Generally, in neutron beta decay, the emitted electron is longitudinally polarized due to the vector and axial couplings inherent in the Weak decay theory. Any deviation from the electron's longitudinal polarization...
The Mu3e experiment at the Paul Scherrer Institute (PSI) will search for the charged lepton flavour violating decay µ⁺ → e⁺e⁻e⁺, improving the current best limit set by the SINDRUM experiment by four orders of magnitude.
Mu3e will be conducted in two phases. Phase I, currently under construction at the πE5 beamline at PSI, will utilise an intense DC surface muon beam of 10⁸ µ⁺/s to reach a...
The Mu3e experiment, searching for charged lepton flavor violation in the µ⁺ → e⁺e⁻e⁺ channel with 2*10^-15 sensitivity in Phase I, is under commissioning at PSI PiE5 beamline. To achieve this, Mu3e, operating with the world’s most intense continuous muon beam, must handle multi-terabit-per-second data streams from millions of detector channels. Meeting this challenge requires a triggerless...
Ultracold neutron (UCN) experiments suffer from low counting statistics, especially in precision measurements such as searches for the neutron electric dipole moment (nEDM). In-situ experimental designs, where all measurement and detection steps occur within a superthermal UCN source, have the potential to significantly increase the usable UCN density. Such approaches require novel detector...
The P2 Experiment at the new Mainz Energy-Recovering Superconducting Accelerator (MESA), which is currently under construction in Mainz, will measure the weak mixing angle in elastic electron-proton scattering at low momentum transfer with unprecedented precision.
A key parameter for the analysis, the momentum transfer Q², is measured by a tracking detector designed for high rates,...
At PSI a high-precision experiment is being set up to search for the muon electric dipole moment (muEDM) employing the frozen-spin technique. A muEDM larger than the Standard Model prediction would be a sign of new physics. The search will eventually improve the current best direct limit by three orders of magnitude to $6\cdot 10^{-23}$ e$\cdot$cm. The EDM signal is measured by detecting the...
The n2EDM experiment of an international collaboration at the Paul Scherrer Institute (PSI) aims to improve the sensitivity of the measurement of the neutron electric dipole moment by a factor of ten with respect to its predecessor. A most efficient neutron spin transport is vital to achieve such a sensitivity. We present an overview of the spin transport coil system, the three main channels...
The Mu3e experiment is designed to search for
the lepton flavor violating decay $\mu^+ \rightarrow e^+e^-e^+$.
The aim of the experiment
is to reach a branching ratio sensitivity of $10^{-16}$.
The experiment is located at the Paul Scherrer Institute (Switzerland)
and an existing beam line providing $10^8$ muons per second will allow
to reach a sensitivity of a few $10^{-15}$ in the...
Charge conjugation symmetry (C symmetry) still remains a fundamental symmetry in the realm of physics. It is well-known to be maximally violated in weak interactions. However, its validity is yet to be tested in Electromagnetic (EM) and Strong interactions. With the aim to test this symmetry in EM interactions, the forbidden decay channel of the triplet Positronium state - the...
Designing high-precision particle physics experiments involves optimizing over complex, computationally expensive simulations, often under significant uncertainty—particularly in inputs such as magnetic field maps. In the Muon EDM experiment at PSI – which aims to measure the Electric Dipole Moment (EDM) of the muon using the frozen spin technique – the injection of muons into the experiment...
Observables of neutron decay are, among others, the $\beta$-asymmetry $A$ and the Fierz interference term $b$. Through precision measurements of $A$ we have access to the CKM matrix element $V_{ud}$, while a non-zero Fierz term $b$ would imply the existence of scalar or tensor interactions beyond the V-A theory of the Standard Model.
The currently most precise direct determinations of $A$...
Nuclear charge radii can be determined utilizing muonic atom spectroscopy. Muonic atoms are easily formed by directly stopping negative muons inside a material. Muons are 207 times heavier than electrons and consequently orbit 207 times closer to the nucleus, making them highly sensitive to nuclear properties.
The muX experiment aims to determine the absolute nuclear charge radius of...
The PanEDM experiment, coupled to the new ultracold neutron source SuperSUN at the Institut Laue-Langevin, aims to measure the neutron electric dipole moment (nEDM) with a sensitivity of $4 \times 10^{-27}$ e·cm after 100 beam-days in its first phase.
The search for a CP-violating electric dipole moment is among the most powerful and long-standing precision tests of the Standard Model, and...
The goal of the Mu3e experiment is to search for charged LFV in the muon decay $\mu^+ \to e^+ e^- e^+$. The improvement of the sensitivity by 4 orders of magnitude compared to the limit set by the PSI SINDRUM collaboration 40 years ago, drives the need to suppress all sources of backgrounds to a level well below $10^{-16}$. Accidental backgrounds can be strongly rejected by requiring very...
The neutron storage experiment $\tau$SPECT aims to measure the free neutron lifetime, an essential input for precision tests of the Standard Model of particle physics and the Big-Bang nucleosynthesis, by confining ultracold neutrons (UCNs) in a three-dimensional magnetic trap. In contrast to material bottles, magnetic storage avoids interactions with the trap wall, eliminating systematic...
The MEG II experiment at PSI searches for the charged lepton flavor violating decay, $\mu\to e\gamma$. The physics run commenced in 2021 and is planned to continue until the end of 2026, aiming at a target sensitivity on the branching ratio of $6\times 10^{−14}$. Based on data from 2021 and 2022, we have set the most stringent upper limit to date on the branching ratio at BR($\mu\to e\gamma$)...
The $\tau$SPECT experiment measures the free neutron lifetime by confining ultracold neutrons (UCN) in magnetic field gradients and counting the remaining neutrons after varying storage times. There are statistical and systematical changes in the yield and energy of the UCN produced by the neutron source, therefore the amount of neutrons filled into the trap in each filling cycle has to be...
Commonly used UCN beam polarizers employ the longitudinal Stern-Gerlach effect due to a strong magnetic field, or spin dependent neutron transmission through a thin magnetized foil, exploiting the combination of the spin independent neutron optical potential and the spin dependent magnetic potential. In contrast to commonly used iron foils, the commercial alloy Hiperco50, consisting of 49%...
The n2EDM experiment at the Paul Scherrer Institute (PSI) aims to improve the sensitivity to the neutron electric dipole moment (nEDM) by an order of magnitude relative to the current best limit ($1.8 \times 10^{-26}~e\cdot\mathrm{cm}$). A key requirement to achieve this goal is the generation and precise control of a highly homogeneous static magnetic field $ B_0 $ within the precession...
The n2EDM experiment at the Paul Scherrer Institute aims to measure the neutron electric dipole moment with a sensitivity of below 1E−27 e⋅cm by observing neutron spin precession in a near perfectly uniform magnetic field. Precise control of systematic effects, particularly those caused by magnetic field non-uniformities, is crucial for achieving this sensitivity. To address this, an array of...
The Mu3e experiment aims to search for the charged lepton flavour violating decay μ⁺ → e⁺e⁻e⁺ with an ultimate sensitivity of 10⁻¹⁶. Its Vertex Detector employs ultra-thin
MuPix11 sensors to provide precise tracking with minimal material. During our beam time at PSI this year, we successfully commissioned the detector.
Through Time over Threshold calibration, signal transmission tuning, and...
The $\tau$SPECT experiment aims to measure the free neutron lifetime
with an uncertainty goal of sub-second by storing ultra-cold neutrons (UCNs)
in a fully magnetic bottle using a spin-flip loading technique. Monte Carlo (MC) simulations of neutron dynamics in the experiment are a key element to study and understand systematic effects, reduce uncertainties, and improve the experimental...
The PIONEER experiment intends to measure rare pion decays at the PSI PiE5 beamline to achieve the most precise test of lepton flavor universality to date. To achieve the necessary statistics for PIONEER, a pion stop rate of more than 300 kHz must be employed; such high beam rates result in significant pileup in the calorimeter used to differentiate between pion and muon decay products, which...
Precision storage ring experiments, such as those testing fundamental symmetries and investigating nuclear structure, rely on precise control of electric and magnetic fields to guide, focus and probe charged particles. This is achieved using various techniques, generally involving distributed systems across large scale rings [1-4].
The frozen-spin technique is a yet-undemonstrated approach...
Understanding the matter-dominated universe requires the discovery of CP violation beyond the Standard Model. A promising approach is to search for time-reversal invariance violation (TRIV), which is equivalent to CP violation, using polarized neutron and polarized target nuclear reactions. Neutron transmission experiments are expected to be a particularly sensitive probe of TRIV effects by...
Ultracold neutrons (UCNs) can be stored in material vessels and magnetic field gradients. This property allows for long observation times and thereby precision measurements of fundamental neutron properties. In the presented detector design, UCNs are converted into an electrical signal by employing a $^{10}\text{B}$ conversion layer stacked with a ZnS(Ag) scintillation layer. The neutron...
We present the performance characterization of a Magnetically Shielded Room (MSR) designed to meet the stringent magnetic requirements of next-generation $^3$He/$^{129}$Xe co-magnetometer experiments, in particular the search for a permanent electric dipole moment (EDM) of $^{129}$Xe. The Xenon EDM experiment aims to probe new sources of CP violation beyond the Standard Model with...
The study of cold antihydrogen for CPT symmetry tests began in 2010 with the first successful demonstration of trapping individual antihydrogen atoms [1]. In the ALPHA experiment, antihydrogen is produced via a three-body recombination process involving one antiproton and two positrons [2]. Antihydrogen is formed by combining cold plasmas of positrons and antiprotons in a specialized...
The n2EDM experiment at the Paul Scherrer Institute searches for the electric dipole moment (EDM) of the neutron with a baseline sensitivity of approximately $1×10^{−27}$ e·cm. Precise monitoring of the average magnetic field experienced by the neutrons is essential to prevent systematic shifts in the EDM measurement that cannot be otherwise mitigated. This magnetic field monitoring is...
The LEMING experiment is designing the next generation of laser spectroscopy and gravity experiments using a novel atomic beam of muonium (Mu = μ⁺ + e⁻). Cold atomic muonium beams are generated in vacuum and subsequently undergo self-interference using newly engineered, self-aligned diffraction gratings. The setup allows for nanometer-sensitive measurements of muonium displacements due to...
The muEDM experiment aims to measure the electric dipole moment (EDM) of the muon with unprecedented sensitivity, providing a powerful probe for physics beyond the Standard Model. Utilizing the frozen spin technique, the experiment is designed to isolate EDM-induced spin precession while suppressing magnetic moment (g−2) effects. This poster presents a technical overview of the experimental...
The HyperMu experiment at PSI aims at the first measurement of the ground state hyperfine splitting in muonic hydrogen (μp) with 1 ppm precision using pulsed laser spectroscopy. This accuracy allows for a precise extraction of the proton structure contributions, including the Zemach radius and the proton polarizability.
To measure the ground state hyperfine splitting in μp, we are...
The PanEDM experiment aims to measure the neutron electric dipole moment, using ultracold neutrons (UCN) produced by the superfluid-helium UCN source SuperSUN at the Institut Laue-Langevin (ILL). UCN will be stored in double-chamber spectrometer for spin-precession measurements, with a sensitivity of $4 \times 10^{-27}\,e \,\mathrm{cm}$ anticipated after 100 days of measurement time.
A...
The qBounce experiment investigates the quantum states of ultracold neutrons in the gravitational field of the Earth. This offers a unique opportunity to study gravity at a microscopic level with great accuracy. When neutrons are confined above a horizontal mirror, ultracold neutrons form discrete quantum energy levels arising from the interplay between gravitational and quantum effects. This...
The n2EDM experiment at the Paul Scherrer Institut seeks to measure the neutron electric dipole moment with a sensitivity below 10^(−27) e . cm, which demands an extremely well-controlled magnetic environment. To track down tiny magnetic contaminants that could mimic an EDM signal, we built a mobile gradiometer based on optically pumped cesium magnetometers operating in the Mx configuration....
The Muon $g-2$ experiment at Fermilab has measured the anomalous magnetic moment of the muon ($a_{\mu} \equiv (g_{\mu} -2)/2$) to a precision of 127 parts-per-billion. During the experiment, `fills' of $\mathcal{O}\left( 10^5 \right)$ $3.1\,\text{GeV}/\text{c}$ muons were injected into the $g-2$ storage ring, of which $\approx 5{\small,}000$ muons were stored and decay over the course of...
The Mu3e experiment is designed to search for the Charged Lepton Flavor Violation (cLFV) through the rare decay μ+ → e+e−e+, targeting a branching ratio sensitivity of 10^-15 using the PSI piE5 beamline in Phase I, scheduled for 2026.
To cope with the exceptionally high muon rate of 10^8/s (equivalent to ~80 Gbps raw data rate), a triggerless, GPU-based online event selection algorithm is...
for the nEDM Collaboration at PSI
The n2EDM project, aiming for a most sensitive measurement of the electric dipole moment of the neutron hosted by PSI, takes advantage of extensive Monte Carlo simulations of the ultracold neutron storage and transport. This includes modelling of the UCN spin transport system, which also allows the study of depolarization effects in the guides during...
We provide an overview of the capabilities of the modernized Ultra-Cold and Very-Cold Neutron beam ports of the PF2 instrument at the Institut Laue-Langevin.
Experiments using UCN and VCN are important tools to investigate fundamental physics and beyond. Experiments range from dark sector searches over cross-section measurements to neutron instrumentation.
The PF2 instrument serves as...
We describe a concept for a quantum computer based on an abundant number of energy eigenstates. These states form Q-bits or, ad libitum, higher dimensional Q-Nits with N > 2, allowing gate operations according to the quantum computing requirements of DiVincenzo. This system with higher dimensional Q-Nits offers potential advantages over traditional Q-Bit-based quantum computing. It provides a...
Neutron Interferometry was introduced by H. Rauch and U. Bonse in 1974. It opened the path to matter wave interferometry, allowing many direct precision tests of quantum mechanics and fundamental physics and the precise measurement of scattering lengths. A thermal neutron interferometer uses perfect crystals as optical elements (beam splitters, mirrors, and recombiner), where all acting...
The ``neutron lifetime puzzle'' arises from the discrepancy between neutron lifetime measurements obtained using the beam method, which measures decay products, and the bottle method, which measures the disappearance of neutrons.
To resolve this puzzle, we conducted an experiment using a pulsed cold neutron beam at J-PARC. In this experiment, the neutron lifetime is determined from the ratio...
Particle physics today faces the challenge of explaining the mystery of
dark matter, the origin of matter over anti-matter in the Universe, the origin of the neutrino masses, the apparent fine-tuning of the electro-weak scale, and many other aspects of fundamental physics.
Perhaps the most striking frontier to emerge in the search for answers involves new physics at mass scales comparable to...
Ultra-low-mass bosonic particles produced non-thermally in the early Universe may form a coherently oscillating classical field that can comprise the observed cold dark matter. The very high number density of such particles can give rise to characteristic wave-like signatures that are distinct from the particle-like signatures considered in more traditional searches for WIMP dark matter. In...
Searches for charged lepton flavor violation in the muon sector stand out among the most sensitive and clean probes for physics beyond the Standard Model. Currently, $\mu^+ \to e^+ \gamma$ experiments provide the best constraints in this field and, in the coming years, new experiments investigating the processes of $\mu^+ \to e^+e^+e^-$ and $\mu \to e$ conversion in the nuclear field are...
The MUonE experiment at CERN is motivated by longstanding questions surrounding the muon's anomalous magnetic moment, which would be sensitive to contributions from new physics. However, the precision of its Standard Model theory value is limited primarily by the leading-order hadronic vacuum polarization term. MUonE will determine this term using a new approach, by measuring the shape of...
Recent work of our group and collaborators will be described, including the progress towards measuring parity violation in chiral molecules [1] and a novel type of nuclear-spin oscillators [2].
[1] Erik Van Dyke, James Eills, Kirill Sheberstov, John Blanchard, Manfred Wagner, Robert Graf, Andrés Emilio Wedenig, Konstantin Gaul, Robert Berger, Rudolf Pietschnig, Denis Kargin, Danila A....
Studies of fundamental symmetries violations in atoms and molecules provide some of the most confronting tests of the standard model and sensitive searches for new physics beyond. In this talk, I will review the current status and key challenges of the theory related to atomic parity violation and electric dipole moments. I will also discuss how atoms may be used to deduce improved nuclear...
One of the most striking mysteries in our visible universe is the origin of the large asymmetry between matter and antimatter which our standard model, despite the observed charge-parity (CP) violation, seems to be unable to explain. At MPIK we are currently developing the Lepton Symmetry (LSym) experiment. There, we will store a single positron and an electron in a deep-cryogenic Penning...
Muonium is a pure leptonic binary system that consists of a bound state of a positive muon and an electron. Its energy level structure can be calculated with high precision within the framework of bound-state quantum electrodynamics (QED). Muonium serves as an ideal probe of the electroweak interaction to rigorously test the Standard Model and search for additional unknown interactions between...
The LEMING experiment aims for measuring the gravitational acceleration of muonium, and to carry out next generation laser spectroscopy experiments in search for beyond SM physics. We developed a novel cold muonium source by converting conventional (sub)surface muons in a thin layer of superfluid helium, resulting in a high brightness atomic beam. Most recently, we verified the horizontal Mu...
Muonic atom spectroscopy is a well-established technique to measure absolute nuclear charge radii with exceptional precision, successfully utilized for nuclei throughout the entire nuclear chart – from protons and the lightest elements to medium-mass, heavy and radioactive isotopes. These precise measurements serve as critical benchmarks for ab initio nuclear theory, important input in atomic...
I will present our latest results [1], implementing pure quantum state preparation, coherent manipulation, and non-destructive state readout of the hydrogen molecular ion H$_2^+$.
H$_2^+$ is the simplest stable molecule, and its structure can be calculated ab initio with high precision using quantum electrodynamics. By comparing the calculations with experimental data, fundamental constants...
Neutrons exhibit significant quantum mechanical wave properties in the low-energy region. This optical characteristic not only makes neutron beam transport practical but also allows for precision measurements. One well-known example in fundamental physics is neutron confinement using the total reflection phenomenon of neutrons at a material surface, resulting in a well-known experiment...
The European Spallation Source (ESS), currently under construction in
Lund, Sweden, will soon become the world’s most powerful pulsed neutron
source and simultaneously the brightest pulsed neutrino source. Its unique capabilities open unprecedented opportunities for a precision particle physics program, complementing other facilities worldwide. Neutron sources, when combined with precision...
The PIENU experiment at TRIUMF has provided, to date, the most precise experimental determination of R$^{e/\mu}_\pi$ , the ratio of pions decaying to positrons relative to muons. While more than an order
of magnitude less precise that the Standard Model (SM) calculation, the PIENU result is a precise test of the universality of charged leptons interaction, a key principle of the Standard...
The neutron lifetime is a key parameter in nuclear physics and cosmology, yet two world-leading techniques—the “bottle” and “beam” methods—disagree by almost 10 seconds. This talk will survey the experimental strategies, highlight recent advances, and discuss efforts to resolve this long-standing puzzle.
Since the potential of mirror beta transitions to provide an independent determination of the $V_{ud}$ quark-mixing matrix element was pointed out, about 15 years ago [1], many measurements of spectroscopic quantities have been performed and more detailed theoretical corrections have been addressed. These significantly improved the precision on the Ft-values of these transitions [2, 3]. In...
Precision spectrum shape measurements in nuclear beta decay can be used for testing the Standard Model and physics beyond it with accuracy being competitive with high-energy collider experiments. Such a comparison can be carried out in the framework of effective field theory. The most prominent and poorly known effect in the Standard Model is weak magnetism, the higher-order recoil correction...
Precision mass measurements of stable as well as long-lived nuclides have numerous applications among others in atomic-, nuclear-, neutrino- and particle physics. Technical developments in the manipulation and detection of radionuclides and stable species in high-precision Penning-trap mass spectrometry have boosted the field and allow for relative mass uncertainties at the level of 10-11 and...
We will report on our progress to measure the fine-structure constant 𝛼 with improved accuracy to resolve the currently unexplained discrepancy between recent 𝛼 measurements [1,2]. The fine-structure constant 𝛼 characterizes the strength of electromagnetic interactions. Precision measurement of 𝛼 with atom interferometry combined with precision measurement of 𝛼 with electron g - 2 enables one...
The GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment seeks to measure the gravitational acceleration of antimatter with precision better than 1% using ultracold antihydrogen atoms. To obtain ultracold antihydrogen atoms, a multi-step process is used: first, antihydrogen ions are formed and sympathetically cooled using $\mathrm{Be^+}$ ions. Afterward, the extra positron is...
On behalf of the AEgIS collaboration
The Antimatter Experiment: Gravity, Interferometry, Spectroscopy (AEgIS) at CERN's antimatter factory has achieved remarkable performance in trapping antiprotons for the pulsed creation of antihydrogen, as well as other antimatter-bound systems, such as positronium. Currently, a new technique is being developed using the AEgIS infrastructure to...
Electric dipole moments (EDM) of fundamental particles inherently violate the combined symmetry of charge-conjugation and parity inversion (CP) .
At PSI we plan to measure the EDM of the muon using the frozen-spin technique within a compact storage trap. This method exploits the high effective electric field, E = 165 MV/m, experienced in the muon’s rest frame with a momentum of about 23 MeV/c...
The Standard Model of Particle Physics is a versatile and well-tested theory. However, it does not explain the extreme imbalance of matter over antimatter observed in our Universe. A possible mechanism that could explain this asymmetry includes new sources of CP violation, which could result in the existence of a permanent electric dipole moment in fundamental particles such as the...
Status and progress of the NL-eEDM experiment
Jelmer Levenga, on behalf of the NL-eEDM collaboration
Within the Standard Model fundamental particles are predicted to have a permanent electric dipole moment (EDM). An EDM is a CP-violating signature which is small within the standard model, but can be greatly enhanced in Beyond the Standard Model (BSM) physics. EDM experiments are...
The characterization of size and structure of hadrons and nuclei has been the focus of a large work effort over multiple decades. Recently, this topic garnered new interest for various reasons, including the proton charge radius puzzle and advances in determinations of the gravitational form factors. The accurate extraction of quantities does not only rely on precise data, but also on...
The charge radii of the isotopes of hydrogen and helium serve as important benchmarks for understanding of nucleon and nuclear structure, and are essential input the QED tests or determinations of fundamental constants via high-precision laser spectroscopy of ordinary atoms.
Our laser spectroscopy of muonic H through He-4 has provided precision measurements of the 4 lightest nuclei. I will...
Kaon physics has played a foundational role in particle physics, from the discovery of strangeness and CP violation to some of the most precise tests of the Standard Model (SM). Today, it continues to provide a uniquely sensitive probe of potential new physics through the study of rare processes and flavor-changing neutral currents. This talk will present an overview of the current status and...
The rate for $\mu\to e$ conversion in nuclei is set to provide one of the most stringent tests of lepton-flavor symmetry and a window into physics beyond the Standard Model. However, to disentangle new lepton-flavor-violating interactions, in combination with information from $\mu\to e\gamma$ and $\mu\to 3e$, it is critical that uncertainties at each step of the analysis be controlled and...
The Mu3e experiment searches for the charged lepton-flavour violating decay of a muon into two positrons and one electron. Due to the negligible Standard Model branching ratio, any observation would provide unequivocal evidence of new physics. A first phase of the experiment aims for a single-event sensitivity of one in $2 \cdot 10^{15}$ muon decays.
To reach this goal, the collaboration...
Precision measurements capture an increasing amount of attention in probing physics beyond the Standard Model (BSM). Worldwide, a multitude of experiments aim at reaching high precision, ~0.1% , and will have comparable control over systematic uncertainties. By this, these experiments will augment LHC constraints on models of BSM physics.
These efforts entail a need in Standard-Model...
