Search

There are various tests of the Standard Model aimed at probing new physics. One such test is to check the unitarity of the Cabbibo-Kobayashi-Masakawa matrix, with the most precise result given by the normalization of the top row. The precision of this result is limited by the uncertainty of the Vud and Vus elements. The most precise result for Vud is currently derived from the ensemble of superallowed 0+ → 0+ nuclear β decays, but the determination from other transitions is desirable to check theoretical calculations and the potential presence of unknown systematic contributions. Other candidates include neutron decay, pion decay, and the ensemble of nuclear mirror decays. While the neutron and pion decay present their own unique experimental challenges, the group of mirror decays require the precise determination of the Fermi to Gamow-Teller mixing ratio. This value can be extracted from a measurement of the β-ν angular correlation parameter, αβν, which is currently only known for five mirror decays. A new ion trapping system, St. Benedict (Superallowed Transition Beta-Neutrino Decay-Ion-Coincidence Trap), to be located in the Nuclear Science Laboratory at the University of Notre Dame is currently under construction and will ultimately aim to extract αβν for more mirror decays. The focus of this work is on simulations that will guide the design of the Paul trap which will be used for the measurement.

In the low-energy regime, precision measurements in nuclear β −decay continue to be a sensitive tool to search for new physics beyond the standard model (SM). The primary goal of the Texas A&M University Penning trap facility (TAMUTRAP) is to improve the limits on non-SM processes in the weak interaction. In particular, scalar currents, by measuring the β − ν angular correlation parameter (aβν), for T = 2, super-allowed β −delayed proton emitters. The precise measurement of energy Doppler shift of the proton following β+ −decay is sensitive to β − ν angular correlation coefficient, which is unity (aβν= 1) for pure Fermi transition in the absence of scalar currents. The experiments will be performed in a unique large bore cylindrical Penning trap with an inner radius of 90 mm, which is larger than any existing Penning trap across the world. The TAMUTRAP facility has been commissioned off-line and has demonstrated the ability to perform high precision mass measurements. We describe here the facility overview and summarize the current status towards the first measurement of β − ν angular correlation for T = 2, beta delayed proton emitters using a large bore cylindrical Penning trap with closed end caps.

The Beta-decay Paul Trap (BPT) at Argonne National Laboratory has proven to be an extremely effective tool for high-precision tests of the Standard Model via measurements of the β − ν correlation in mass-8 isotopes. Using four double-sided silicon strip detectors (DSSDs) backed by plastic scintillators and surrounding the ions confined by the BPT, the kinematics of the decays of the mirror nuclei lithium-8 and boron-8 are overdetermined when all charged decay products are measured. The most stringent low-energy limit on an intrinsic tensor current in the weak interaction was set using the BPT in 2015 (Sternberg, M.G., et al., Phys. Rev. Lett. 115, 182501 2015) utilizing trapped lithium-8. Since then, similar data for boron-8 and higher statistics data for lithium-8 have been collected and are currently being analyzed. With the elimination of radio-frequency (RF) pickup from the DSSDs and a detailed investigation of experimental systematic errors, the uncertainty is now dominated by the contribution from recoil-order terms in the decay rate. Our eventual goal is to limit tensor currents in the weak interaction with relative precision at or below 0.1%.

We review the current status of the radioisotopes program at the Soreq Applied Research Accelerator Facility (SARAF), where we utilize an electrostatic-ion-beam trap and a magneto-optical trap for studying the nuclear $\beta$-decay from trapped radioactive atoms and ions. The differential energy spectra of $\beta$'s and recoil ions emerging from the decay is sensitive to beyond standard model interactions and is complementary to high energy searches. The completed facility SARAF-II will be one of the world's most powerful deuteron, proton and fast neutron sources, producing light radioactive isotopes in unprecedented amounts, needed for obtaining enough statistics for a high precision measurement.

The positronium ground state hyperfine splitting (hfs) has long been of interest as a high-precision test of our understanding of binding in QED. The positronium hfs is particularly sensitive to recoil effects (because the ratio of masses is one) and to virtual electron-positron annihilation, but positronium is insensitive to strong and weak interaction effects. Consequently, the comparison between theory and experiment for the positronium hfs, and more generally the positronium spectrum, tests different aspects of the theory compared to comparisons in other exotic atoms. For the past fifteen years there has been a persistent discrepancy between predicted and measured values of the positronium hfs of about four standard deviations (although a new experimental result is consistent with present theory). Recent experimental work is leading to new high-precision measurements, and the calculation of order- α 3 corrections has begun. The status of the positronium hfs problem and a discussion of recent progress is the topic of this contribution.

We report on progress towards performing precision measurements of parity violation in Yb, in which the theoretical prediction for a strong weak-interaction-induced effect in the 6s^{2} ^{1}S_{0} \rightarrow 5d6s ^{3}D_{1} optical transition at 408 nm has already been confirmed, with a measurement of the effect at the \approx 10 % level of accuracy. With a new atomic-beam apparatus offering enhanced sensitivity, we are aiming at precisely determining the parity violation observable in Yb, which will allow us to probe the distributions of neutrons in different isotopes, investigate physics beyond the Standard Model, as well as to study intra-nucleus weak interactions, through an observation of the anapole moment of Yb nuclei with nonzero spin. We present the experimental principle employed to probe atomic parity violation, describe our new apparatus, and discuss the attained experimental sensitivity as well as the methods for characterizing systematics in these measurements.

The NPDGamma experiment measures the parity-violating (PV) gamma asymmetry from polarized cold neutrons captured on protons at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The (PV) neutron spin asymmetry A γ of photons from polarized cold neutron capture on protons is proportional to the ΔI=1 long range weak meson coupling $h_{\pi }^{1}$ between nucleons in the hadronic weak interaction (HWI). Liquid para-hydrogen production data taking concluded in April 2014 and once the background aluminum asymmetry measurements are complete, the PV asymmetry A γ can be extracted. Preliminary results of the analysis of A γ are presented.

The PIENU experiment aims to measure the branching ratio of the charged pion decay with precision of < 0.1 %. This measurement is much sensitive to search for massive neutrinos coupled to electrons in ${\pi }^{+}{\rightarrow }e^{+}{\nu }_{e}$ decay. The initial analysis was completed and the upper limit on the neutrino mixing parameter |U e i |2 in the neutrino mass range of 0 to 55 MeV/c 2 was improved by a factor of 1.5, and the sensitivity for the mass range of 68 to 129 MeV/c 2 was improve by a factor of up to 4.

Precision measurements in nuclear beta decay provide sensitive means to determine the fundamental coupling of charged fermions to weak bosons and to test discrete symmetries in the weak interaction. The main motivation of such measurements is to find deviations from Standard Model predictions as possible indications of new physics. I focus here on two topics related to precision measurements in beta decay, namely: (i) the determination of the V ud element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix from nuclear mirror transitions and (ii) selected measurements of time reversal violating correlations in nuclear and neutron decays. These topics complement those presented in other contributions to this conference.

The main goal of the NPDGamma experiment is to measure the gamma-ray asymmetry with respect to the neutron spin direction in the nuclear reaction $\overrightarrow{n}+ p \rightarrow d + \gamma$ . The up-down asymmetry A γ has a predicted size of the order of 5 ·10 − 8 , and the NPDGamma experiment is designed to measure it with an uncertainty of about 10 − 8. To test the entire apparatus the gamma-ray asymmetry from neutron capture was measured using a Cl target followed by measurements on Al to establish the relevant background levels. At present the experiment is taking data with a liquid H 2 target to measure the parity violation on the $\overrightarrow{n} + p \rightarrow d + \gamma$ reaction and extract the ΔI = 1 part of the hadronic weak interaction.

An experiment to observe the bound beta-decay (BOB) of the free neutron into a hydrogen atom and an electron anti-neutrino is described. The hyperfine spin state population of the monoenergetic hydrogen atom yields the neutrino left-handedness or possible right-handed admixture as well as possible small scalar and tensor contributions to the weak force. The BOB H(2s) hyperfine states can be separated with a Lamb-Shift Spin Filter. These monoenergetic H(2s) atoms are ionised into H− by charge exchanging within an argon cell. These ions are then separated using an adaptation of a MAC-E Filter. A first experiment is proposed at the FRMII high thermal-neutron flux beam reactor SR6 through-going beam tube, where we will seek to observe this rare neutron decay-mode for the first time and determine the branching ratio. After successful completion, the hyperfine spin state population will be determined, possibly at the ILL high-flux beam reactor through-going beam tube H6–H7, where the thermal neutron flux is a factor of four larger.

In a series of measurements performed at the IGISOL facility at the Accelerator Laboratory of the University of Jyvaskyla, the half-lives of 26Si, 29P, 30,31S, 42Ti and 62Ga were measured with high precision. These half-lives are important ingredients for tests of the weak-interaction standard model and allow, together with other experimental inputs and theoretical correction terms, the determination of the vector coupling constant of the weak interaction. The IGISOL method used in Jyvakyla is an ideal tool for these measurements as it allows to access all elements without distinction of their chemical properties.

In 1956 Lee and Yang suggested that parity might be violated and, if nature were so, they further described a recipe on how to exploit that broken symmetry to measure the muon’s magnetic moment. Of course parity violation was very soon confirmed in the weak interactions and many generations of experiments since then have led to a determination of μμ to better than part-per-billion precision. A new experiment proposed for Fermilab is planned to push this precision further still, being motivated by the sensitive comparison of measurement to exquisite theory. We report on the current comparison, which exceeds three standard deviations, and the plans and promise for the future experimental effort.

An overview is given of the present status of parity violation tests in neutron decay and nuclear beta decay. Prospects for improved and new measurements are discussed as well.

We present two experiments measuring the parity-violating asymmetry (P-odd) of tritons emission in the reaction 6Li(n,α)3H and γ-quanta emission in the reaction 10B(n,α)7Li* → 7Li + γ with polarized cold neutrons, aiming at estimation of the weak meson-nucleon coupling constants. These experiments started in the PNPI, Gatchina and continued in the ILL, Grenoble. We describe an integral method to measure P-odd asymmetry and the two experiments. The results of our measurements are: $\alpha{}_{P-odd}^{6Li}=(-8.8\pm2.1)\cdot10^{-8}$ and $\alpha{}_{P-odd}^{10B}=(0.8\pm3.9)\cdot10^{-8}$ .

The A4 collaboration at the MAMI accelerator at Mainz investigates the contribution of strange quarks to the form factors of the nucleon by measuring the parity violating asymmetry APV in the cross section of elastic scattering of longitudinally polarized electrons off hydrogen and deuterium. Recently, measurements at backward angles at a four momentum transfer of Q2 = 0.22 GeV2 were completed. Together with previous results at forward angles at the same momentum transfer, the strange electric and magnetic form factors \(G_E^s\) and \(G_M^s\) can be disentangled.

The international workshop on “Application of Lasers and Storage Devices in Atomic Nuclei Research” held during 2009 in Poznan gave an excellent overview on the latest experimental and theoretical results regarding the investigation of radionuclides by atomic physics techniques and the extraction of ground state properties of exotic nuclei. This publication intends to summarize the progress recently achieved by laser spectroscopy and mass spectrometry as well as by weak interaction studies using atomic physics techniques. Furthermore, it tries to point to some areas requiring urgent improvements and to indicate some routes of future research and challenging opportunities.

Since 2006 the ISOLTRAP mass spectrometer has provided high-precision masses of many short-lived nuclides located all across the nuclear chart with half-lives down to a few 10 ms. These nuclides range from the two-proton halo candidate 17Ne, via the neutron-rich magic 80Zn and 132Sn, up to 229Rn which was identified for the first time. The results show that ISOLTRAP is a versatile tool well suited to address physics topics such as nuclear structure, stellar nucleosynthesis, or the weak interaction.

At KVI the technical structures for the TRI mu P facility are nearly all in place. The aim of the project is to use radioactive ions to study fundamental interactions and symmetries. We will measure beta-recoil correlations in nuclear beta decay. There the V,A structure of the Weak interaction may be violated. The second line of research is the search for a permanent electric dipole moment in Ra, with a magnitude forbidden by the Standard Model. By trapping these radioactive nuclei in atom traps a pure sample that can be manipulated facilitates these searches. The TRI mu P facility consists of a production target and magnetic separator on the high energy side and a Radio-Frequency Quadrupole (RFQ) cooler and buncher on the low energy side. An ion catcher stops the fast product nuclides and transport them into the RFQ cooler. New technological approaches were implemented for several of these devices.

Francium combines a heavy nucleus (Z = 87) with the simple atomic structure of alkalis and is a very promising candidate for precision tests of fundamental symmetries such as atomic parity non-conservation measurements. Fr has no stable isotopes, and the ISAC radioactive beam facility at TRIUMF, equipped with an actinide target, promises to provide record quantities of Fr atoms, up to 1010/s for some isotopes. We discuss our plans for a Fr on-line laser trapping facility at ISAC and experiments with samples of cold Fr atoms. We outline our plans for a measurement of the nuclear anapole moment — a parity non-conserving, time-reversal conserving moment that arises from weak interactions between nucleons — in a chain of Fr isotopes. Its measurement is a unique probe for neutral weak interactions inside the nucleus.

State of the art laser technology and modern spectroscopic methods allow to address issues of fundamental symmetries and fundamental interactions in atoms with high precision experiments. In particular the discrete symmetries Parity (P), Charge Conjugation (C), Time Reversal (T) as well as their combinations CP and CPT are in the center of interest at present. Actual projects are concerned with Parity Violation in atoms, Time Reversal Violation in beta-decays and searches for permanent Electric Dipole Moments (EDMs), and tests of CPT conservation in particle-antiparticle properties, in particular antiprotonic atoms.

An overview of the experimental approaches to study weak interactions using traps is given. Both charged and neutral weak currents are considered.

An overview of the experimental approaches to study weak interactions using traps is given. Both charged and neutral weak currents are considered.

New developments in ion cooling and ion bunching allow the trapping of radioactive ions from a low energy beam, in a very short time scale and with very good efficiency. The performances of Radio Frequency Quadrupole (RFQ) coolers, recently developed in several laboratories in Europe and USA, are now better known. In the present study, a RFQ device will be used to inject 6He+ ions in a transparent Paul trap. The ion beam will be delivered by the SPIRAL facility at GANIL. The careful measurement of the β-recoil ion coincidence spectrum is sensitive to the angular correlation parameter a, which depends on the coupling constants of the weak hamiltonian. It should be equal to −1/3 if the interaction is only of axial vector type (V-A theory). Deviation from this value would imply a new tensor-like interaction involving a new exchange boson thus introducing new physics beyond the Standard Model.

Two experiments to search for new physics beyond the standard model for electroweak interactions by measuring correlations between different spin and momentum vectors in nuclear β-decay are discussed. In the first experiment the correlation between the emission asymmetry and the longitudinal polarisation of positrons emitted by polarised nuclei is determined. This type of measurement is sensitive to the presence of right-handed currents but also to possible scalar and tensor-type currents in the weak interaction. The aim of the second experiment is to determine the βν-correlation in β-decay by measuring the energy spectrum of the recoil ions, using a Penning trap and a retardation spectrometer. In this case the focus is on the search for scalar currents in the weak interaction. The results of the experiments presented here are complementary to results from experiments in muon decay and at high-energy colliders.

Laser trapping and cooling techniques are now being applied to the study of nuclear beta-decay at several labs. A magneto-optical trap (MOT) provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and be detected in coincidence with the beta. This allows reconstruction of the neutrino momentum, and the deduction of the beta-nu correlation in a more direct fashion than previously possible. In addition, the nuclei can be polarized by atomic techniques, opening a new class of spin-correlation measurements to test the degree to which parity is maximally violated in the weak interaction. Our present experiment has detected several hundred thousand recoil-beta(+) coincidences from the 0(+) --> 0(+) pure Fermi decay of K-38m, produced at the on-line isotope separators TISOL and ISAC at TRIUMF. Our goal is to set constraints on non-Standard Model scalar bosons competitive with high-energy colliders and more conventional beta-nu correlation experiments.

The techniques of laser cooling and trapping now make it possible to observe large samples of stable atoms in a small volume at low temperature. This capability was recently extended to radioactive isotopes. This opens up new opportunities for the investigation of fundamental symmetries through measurements using radioactive atoms. In this paper we will discuss several fundamental measurements in atomic systems and how the ability to trap radioactive atoms will play an important role in improving the precision of such measurements. Measurements of the effects of the weak interaction are of particular note since they are becoming quite precise. In particular, we will describe in detail the system developed at Stony Brook to trap radioactive alkali atoms and measure weak interaction effects in francium isotopes.

The essence and main features of muon-catalyzed fusion are exposed. Some important and interesting applications of muon-catalyzed fusion in fundamental physics are presented: nuclear physics, quantum electrodynamics, weak interaction physics, the Coulomb three-body problem and the physics of exotic atoms.

Two different impulse approximations are provided for the problem of fast positron collisions with hydrogen-like ions. One of the impulse approximations is formulated by making a consistent expansion of the scattering wave function in powers of the weak interaction to the strong. The other impulse approximation is formulated by making a consistent expansion of theT-matrix in powers of the weak interaction to the strong. In this impulse approximation, the opposite limits of the target nuclear charge tending to zero and to infinity are examined. Differential and angle-integrated cross sections are computed for ground-state positronium formation from hydrogen within the impulse approximations. The full peaking approximation is employed in the evaluation of theT-matrix. By 300 eV, the impulse approximations for the angle-integrated cross section are in close agreement with the strong potential Born and the exact second Born calculations.

T1 spin relaxation of muonium in KCl has been studied at low temperatures (20 mK to 2 K), where the motion is believed to be band-like, i.e. the mean free path is longer than the lattice constant. The Celio model, based on the assumption of stochastic hopping of muonium, accurately describes the field dependence ofT1 at higher temperatures but fails below 4 K. The measuredT1 spin relaxation rates vary weakly with temperature below 2 K even thoughkBT at the lowest temperature is well below the estimated muonium bandwidth obtained from the data at higher temperatures. This is taken as evidence that muonium is not completely thermalized on the time-scale of the muon lifetime due to the weak interaction with phonons at low temperatures.

Studies of nuclear magnetic moments and nuclear weak interactions discussed in this Conference are reviewed. The importance of configuration mixing and meson exchange currents is examined, and it is emphasized that the second order configuration mixing (tensor correlation) is essential for the understanding of these phenomena. Recent results concerning nuclear quadrupole moments reported in this Conference are also discussed. Finally, the pairing effect in metal clusters is pointed out and the importance of measuring their spins and magnetic moments is mentioned.

We have measured the thermal dependence of thef factor and the line shift of the title compounds, in order to determine the (−2) and (+2) moments of the Fe frequency spectrum. The latter is approximated by a superposition of an acoustic-wave band and an intramolecular optical mode. Our results show that both frequency bands are well separated, owing to a relatively weak interaction between tetrahedral units. Optical frequencies thus determined are consistent with Raman data. Debye temperatures were obtained for the low-frequency vibrations of both crystals.

Possibilities of using negative muons are discussed: (i) for understanding the behaviour of wave functions of outer electron shells in the vicinity of a nucleus and (ii) for investigation of the exchange effects in solid state physics. It is noticed that the effective life time of μ bound in light atoms (nuclear spin i≠O) depends on the state of the outer electron shell. This fact can be used for measurement ofK-capture rates from different components of hyperfine structure of a mesic atom and for estimation of the weak interaction constant.

There are two independent reasons to expect the existence of a new type of weak interaction, involving elastic scattering of electrons and nucleons, e+N→e+N. One is the successful development of unified theories of weak and electromagnetic interactions, based on isospin multiplets of leptons, hadrons and vector mesons. The other is the experimental discovery of the elastic scattering of high energy neutrinos from nucleons, ν+N→ν+N. Together, these developments provide strong motivation to the search for weak electron-nucleon interactions in ordinary atoms, through a breakdown of Laporte's rule. I will present a review of recent developments in this field, including a qualitative discussion of this type of weak interaction and a short summary of the experiments in progress. I will also give a more detailed discussion of one particular experiment at Michigan, involving microwave transitions in a metastable hydrogen beam.

The hyperfine interaction of a system containing two weakly coupled paramagnetic ions is investigated. It is shown that even a very weak interaction cannot be broken by a large magnetic field, if the Zeeman interaction of the two paramagnetic centers is identical. Small differences in theg-values, however, yield immediately a quite different hyperfine pattern which corresponds to two isolated paramagnetic centers in the case of a large external magnetic field. Mossbauer experiments on reduced bacterial ferredoxin where one molecule contains two iron clusters withS=1/2 each are used to analyze the interaction of two paramagnetic centers.

Perturbed angular distribution measurements in a tin target have been performed for the121, 123 Te (7/2+) and115Te (11/2−) isomeric levels subject to a combined magnetic and electric quadrupole interaction. Strong quadrupole interactions attributed to nearby defects, as well as weak interactions due to further located defects, were observed. The ratio of the electric quadrupole moments |Q|(7/2+,121Te)/ |Q|(11/2−,115Te)=1.1(2) was also obtained.

The two-body neutron β-decay into a hydrogen atom and an electron antineutrino is investigated. The hyperfine-state population of the monoenergetic hydrogen atoms (326.5 eV) yields the neutrino left-handedness or a possible right-handed admixture and possible small scalar and tensor contributions to the weak force. The constraints on the neutrino helicity and the scalar and tensor coupling constants of weak interaction can be improved considerably.