Parity Nonconservation Effects Research Articles

Modeling of Local Strong Parity Non-Conservation Effects in Relativistic Heavy-Ion Collisions

Modeling of Local Strong Parity Non-Conservation Effects in Relativistic Heavy-Ion Collisions

How to Experimentally Determine the Influence of the Weak Nuclear Force in Promoting Molecular Chirality via Heavy–Metal Promoted Autocatalytic Synthesis of Amino Acids

AbstractThe potential impact of the parity non‐conserving (PNC) weak nuclear interaction on the chirality of a nascent chiral carbon center has previously been examined in the context of evolutionary models for enantiomeric selectivity in the formation of natural amino acids and nucleic acids. Since the PNC effect is the only inherently handed property in nature, it is an obvious candidate to consider in those cases where there is a natural selectivity for a specific enantiomer, including the molecular building blocks of the molecules of life. Over geological timeframes, the potential impact of the PNC weak nuclear force on chiral preference appears feasible. Key requirements included an autocatalytic reaction cycle and involvement of metal‐ion catalysts. While prior studies offer no feasible path to experimentally test the hypothesis; the Z5‐dependence of the PNC interaction does suggest that catalysis by heavy elements could yield observable chiral preferences within an experimentally accessible timeframe. Calculations of the magnitude of the effect are presented for select heavy‐elements and it is shown that chiral preference could be observed within a time span of weeks to months when such metals are used to promote amino acid synthesis via an autocatalytic Strecker reaction.

Influence of the Weak Nuclear Force on Metal-Promoted Autocatalytic Strecker Synthesis of Amino Acids: Formation of a Chiral Pool of Precursors for Prebiotic Peptide and Protein Synthesis.

Natural chiral amino acids typically adopt an L structural configuration. While a preference for specific molecular chiralities is observed throughout biology and cellular chemistry, the origins of this preference are unclear. In a previous report the origin of enantiomeric selectivity was analyzed in terms of an "RNA World" model, and a pathway to a chiral preference for d-ribose was proposed based on the autocatalytic transformation of glyceraldehyde as a precursor to the formation of sugars. Metal-ion-promoted catalysis allows the parity non-conserving (PNC) weak nuclear interaction to influence the chirality of a nascent chiral carbon center. Since the PNC effect is the only natural property with an inherent handedness, it is an obvious candidate to influence enantiomeric preference from a catalytic reaction performed over geologically relevant time scales. The PNC influence requires and emphasizes the important role of catalytic metal ions in primordial chemistry. In this study, the impact of geologically available divalent calcium and higher Z alkaline earth elements are examined as mediators of chiral preference. Detailed calculations of the magnitude of the effect are presented, including the influence of time, temperature, pH, and metal ion identity. It is concluded that metal ions can direct chiral preference for amino acid synthesis via a metal-promoted autocatalytic Strecker reaction within a relatively short geological timeframe, thereby providing a pool of l-amino acids for catalytic chemistry evolving either from an RNA-world model of molecular evolution or alternative pathways to protein synthesis.

P,T -odd energy shifts of the YbOH173 molecule

The energy shift in molecular spectra due to interaction of nuclear magnetic quadrupole moment ($M$) with electrons is equal to $\delta E_M = MW_M P_{ M}$, where $W_M$ is a constant determined by the electronic structure of the molecule and $P_{ M}$ is a dimensionless constant. We extended the method for calculation of parity nonconservation effects in triatomic molecules developed in Ref. [A. Petrov and A. Zakharova, Phys. Rev. A ${\bf 105}$, L050801 (2022)] to the case of $P_{ M}$ constant and applied it to $^{173}$YbOH in the first excited $v=1$ bending mode. Results of our calculations are required for the extraction of the $M$ value from the YbOH experiment.

Long-range parity-nonconserving electron-nucleon interaction

As known, electron vacuum polarization by nuclear Coulomb field produces Uehling potential with the range $\hbar/2m_e c$. Similarly, neutrino vacuum polarization by $Z$ boson field produces long range potential $\sim G^2/r^5$ with the large range $\hbar/2m_{\nu}c$. Attempts to measure parity-conserving part of this potential produced only limits on this potential which are several orders of magnitude higher than the standard model predictions. We show that parity non-conserving (PNC) part of the neutrino exchange potential $W_L(r)$ gives a significant fraction of the observed PNC effects. Mixed $Z-\gamma$ electron vacuum polarization produces PNC potential with range $\hbar/2m_e c$, which exceeds the range of the weak interaction by five orders of magnitude. We calculate contribution of the long-range PNC potentials to the nuclear spin independent and nuclear spin dependent PNC effects. The cases of the single-isotope PNC effects and the ratio of PNC effects in different isotopes are considered for Ca, Cs, Ba, Sm, Dy, Yb, Hg, Tl, Pb, Bi, Fr, Ra atoms and ions. Contributions of the long-range PNC potentials ($\sim$1\%) significantly exceed experimental error (0.35\%) for PNC effect in Cs.

Effect of the neutron quadrupole distribution in the TaO+ cation

We estimate the effect of the tensor parity nonconserving (PNC) interaction in the 181TaO+ molecular cation. It can be used to probe the unknown quadrupole distribution of the neutrons inside the Ta nucleus. To this end, we evaluate the constant which characterizes this interaction using the relativistic Fock space coupled cluster theory for electronic structure modelling. The 3Δ1 state of the TaO+ cation which can be used to measure the PNC effect is found to be the ground one in agreement with the previous theoretical study.

Nuclear Spin-Dependent Effects of Parity Nonconservation in Ortho-H2

We report a theoretical treatment of the nuclear spin-dependent spatial parity nonconserving (NSD-PNC) electron–nuclear interaction effect in the diatomic homonuclear ortho-H 2 molecule. The magnetic dipole transition between v = 1 and v = 0 vibrational sublevels of the ground 1 Σ g + state is examined. The orthohydrogen molecule is a unique molecular system where the parity nonconserving (PNC) nuclear spin-dependent interaction due to the neutral weak currents can be directly observed and the corresponding coupling constant can be extracted from the future experiments. The theoretical simulation shows that using the cavity-enhanced scheme in conjunction with the record achievement of the intracavity absorption spectroscopy, the experiment on the observation of the NSD-PNC effect due to the neutral weak current in ortho-H 2 looks feasible.

Dependence of atomic parity-violation effects on neutron skins and new physics

We estimate the relative contribution of nuclear structure and new physics couplings to the parity non-conserving spin-independent effects in atomic systems, for both single isotopes and isotopic ratios. General expressions are presented to assess the sensitivity of isotopic ratios to neutron skins and to couplings beyond standard model at tree level. The specific coefficients for these contributions are calculated assuming Fermi distribution for proton and neutron nuclear densities for isotopes of Cs, Ba, Sm, Dy, Yb, Pb, Fr, and Ra. The present work aims to provide a guide to the choice of the best isotopes and pairs of isotopes for conducting atomic PNC measurements.

Parity non-conservation effect in heavy atomic systems within relativistic many-body perturbation theory: Advanced data

Computing the parity non-conservation (PNC) effect parameters in a few heavy atomic systems has been performed and based on the combined relativistic nuclear mean-field theory and relativistic many-body perturbation theory (PT) formalism with accounting for the interelectron correlation and dominant QED corrections. Results of computing the PNC amplitudes and weak charges for different heavy atoms (caesium, thallium, ytterbium) are presented and compared with available data in the literature.

HfF+ as a candidate to search for the nuclear weak quadrupole moment

Nuclei with a quadrupole deformation such as $^{177}$Hf have enhanced weak quadrupole moment which induces the tensor weak electron-nucleus interaction in atoms and molecules. Corresponding parity non-conserving (PNC) effect is strongly enhanced in the $^3\Delta_1$ electronic state of the $^{177}$HfF$^+$ cation which has very close opposite parity levels mixed by this tensor interaction. In the present paper we perform relativistic many-body calculations of this PNC effect. It is shown that the tensor weak interaction induced by the weak quadrupole moment gives the dominating contribution to the PNC effects in $^{177}$HfF$^+$ which significantly exceeds contributions of the vector anapole moment and the scalar weak charge. The anapole and the weak charge can contribute due to the nonadiabatic mechanism proposed here. Therefore, corresponding experiment will allow one to separate the tensor weak PNC effect from the other PNC effects and to measure the quadrupole moment of the neutron distribution which gives the dominating contribution to the weak quadrupole moment.

Nuclear spin-independent effects of parity nonconservation in molecule of hydrogen

Theoretical concepts and calculation results of the spatial parity nonconserving (PNC) effects of electron-electron and electron-nucleus nuclear spin-independent interactions in diatomic homonuclear molecule H2 of parahydrogen are presented. The magnetic dipole transition between the states with the same rotational number of the vibrational band in the H2 ground electronic state is considered. It is shown that in this situation these effects are of the same order of magnitude. The H2 molecule is therefore the first example of molecular system where the electron-electron PNC interaction can be directly observed. Since the constants of the electron-nucleus PNC interaction have been already accurately measured in atomic experiments, the electron-electron PNC interaction constant also can be extracted from the future experiments. In other atoms and molecules the electron-electron PNC interaction is usually deeply screened by the electron-nucleus one. Since the nuclei of H2 contain no neutrons, in such future experiments on the PNC effect observation one can, in principle, measure the Weinberg angle (free parameter of the standard model) with unprecedented accuracy.

Considerations towards the possibility of the observation of parity nonconservation in highly charged ions in storage rings

The feasibility of an experiment for the observation of parity nonconserving effects using He-like highly charged ions in storage rings is discussed theoretically. The basic idea is the observation of an asymmetry in the emission of the hyperfine quenched transition with respect to the direction of a beam of ions with polarized nuclei. It will be shown, that for such an experiment 151Eu61+ ions with nuclear spin in the excited electronic state with zero total electron angular momentum and polarized nuclei are the best available candidates. The nuclei can be polarized if H-like Eu62+ ions capture an electron from a polarized electron beam which overlays the ion beam on some part of the ring and travels with nearly the same velocity. It is suggested, to monitor steadily the degree of the nuclear polarization by the observation of the selective laser excitation and subsequent decay of the Zeeman sublevels of the excited hyperfine states of the ionic ground state. Estimates for the observation time aiming at an accuracy of PNC measurement of about are given.

Probing Low-Mass Vector Bosons with Parity Nonconservation and Nuclear Anapole Moment Measurements in Atoms and Molecules.

In the presence of P-violating interactions, the exchange of vector bosons between electrons and nucleons induces parity-nonconserving (PNC) effects in atoms and molecules, while the exchange of vector bosons between nucleons induces anapole moments of nuclei. We perform calculations of such vector-mediated PNC effects in Cs, Ba^{+}, Yb, Tl, Fr, and Ra^{+} using the same relativistic many-body approaches as in earlier calculations of standard-model PNC effects, but with the long-range operator of the weak interaction. We calculate nuclear anapole moments due to vector-boson exchange using a simple nuclear model. From measured and predicted (within the standard model) values for the PNC amplitudes in Cs, Yb, and Tl, as well as the nuclear anapole moment of ^{133}Cs, we constrain the P-violating vector-pseudovector nucleon-electron and nucleon-proton interactions mediated by a generic vector boson of arbitrary mass. Our limits improve on existing bounds from other experiments by many orders of magnitude over a very large range of vector-boson masses.

Computational modelling parity nonconservation and electroweak interaction effects in heavy atomic systems within the nuclear-relativistic many-body perturbation theory

Computing the hyperfine coupling constants and parity non-conservation (PNC) effect parameters in a few heavy atomic systems has been performed and based on the combined relativistic nuclear mean-field theory and relativistic many-body perturbation theory (PT) formalism with accounting for the interelectron correlation and dominant QED corrections. Results of estimating hyperfine structure constants and PNC parameters for different heavy atoms (caesium, ion of barium, thallium, ytterbium) are presented and compared with other theoretical and experimental data. The spin-dependent contributions to the PNC amplitude for the caesium are presented too.

Effects of parity nonconservation in a molecule of oxygen

This paper is devoted to the calculation of parity nonconserving (PNC) effects in the diatomic homonuclear molecule of oxygen O2. For this purpose the magnetic dipole transition was considered. It was believed that the weak electron–electron interaction prevails over the weak interaction of electrons with nuclei in this case. This idea appeared not to be justified for molecular oxygen. As it turns out from our calculations, the parity nonconservation degree for the weak electron–nucleus interaction is of the order and for the weak electron–electron interaction is by two orders smaller . Nevertheless, a PNC experiment for the observation of the weak electron–nucleus interaction looks sufficiently feasible (previously, such experiments were carried out only with atoms).

Relativistic coupled-cluster analysis of parity nonconserving amplitudes and related properties of the 6s2 S1/2 − 5d2 D3/2; 5/2 transitions in 133Cs

ABSTRACTWe present the results of our calculations of the parity nonconserving electric dipole amplitudes(E1PNC) for the 6s2S1/2 − 5d2D3/2; 5/2 transitions of 133Cs employing a relativistic coupled-cluster (RCC) method. E1PNC values for the nuclear spin-independent and nuclear spin-dependent (NSD) parity non-conservation (PNC) effects for different hyperfine levels of the 6s2S1/2 − 5d2D3/2 transition and only due to the NSD PNC interaction Hamiltonian for all possible hyperfine levels of the 6s2S1/2 − 5d2D5/2 transition are given. We have also performed calculations of several properties that are relevant for assessing the reliability of the calculations of the amplitudes of the above-mentioned transitions. We highlight the importance of correlation effects by giving the results of both the Dirac–Fock and RCC contributions. Approximate contributions to these properties from the Breit and quantum electrodynamic interactions have also been evaluated. Plausible experimental schemes to measure these transition amplitudes by light shift techniques and interference involving induced Stark shifts are outlined.

Virginia Ruth Brown

Virginia Ruth Brown died on 8 February 2016 in Chevy Chase, Maryland, after a long battle with cancer. She was a wonderful colleague, friend, and distinguished theoretical nuclear physicist. During her long career, Virginia made important contributions to our understanding of the nucleon–nucleon interaction, nuclear reaction theory, and nuclear structure, among other accomplishments. She loved physics and had a deep commitment to getting to the heart of things.Virginia Ruth BrownPPT|High resolutionBorn on 11 March 1934 in Massachusetts, Virginia received her PhD, under the supervision of Bernard Margolis, from McGill University in 1964. She was a postdoctoral fellow at Yale University and then worked at Lawrence Livermore National Laboratory (LLNL) from 1964 until 1995. She was an NSF program officer for nuclear theory from 1995 to 1998. Following that, she was a visiting professor in the physics department of the University of Maryland in College Park and a visiting scientist in the Laboratory for Nuclear Science at MIT.During Virginia’s early work on nucleon–nucleon bremsstrahlung, she explored the effects of parity nonconservation and demonstrated the importance of meson exchange in neutron–proton bremsstrahlung. Her calculations showed that meson exchange currents contributed a factor of 2 and were not dominated by one-pion exchange. Throughout her career she continued refining and extending her calculations, including for relativistic effects and noncoplanarity. She compared her results with experiment, most notably with the data on neutron–proton bremsstrahlung that Stephen Wender, June Matthews, and their colleagues obtained at the Los Alamos Neutron Science Center. When Virginia was at MIT she interacted frequently with Matthews’s group and directed the research of several of Matthews’s undergraduate and graduate students.Virginia’s collaboration with experimentalists started soon after she joined LLNL; most prominently, she worked with John Anderson on charge-exchange reactions in nuclei.Around 1973 Virginia also began her long partnership with theorist Victor Madsen. They developed the nuclear-structure and reaction theory needed to understand charge-exchange reactions; their breakthroughs included a model for mixing giant resonance states with the low-lying states that had been experimentally observed at the time. Their most important contribution was the systematic inclusion of isospin degrees of freedom that were required to understand the data. It was successfully applied to inelastic scattering processes without any additional modifications.One of us (Bernstein) remembers how stimulating it was to work with Virginia. In the mid 1970s, he received a letter from her about how Madsen’s and her isospin-dependence calculations could explain the puzzles and regularities that he had observed in inelastic alpha-particle scattering. Their collaboration started in their first meeting, and over many years it yielded a productive series of papers. They covered electromagnetic tests of the accuracy of the observed neutron and proton transition matrix elements and their observation using different hadronic probes and electromagnetic methods such as electron scattering and Coulomb excitation. He remembers with great pleasure his annual spring-break trip to the University of California, Berkeley, and LLNL to work with Virginia and to enjoy great dinners with her in Berkeley and San Francisco. Their friendship and collaboration were reinforced while she was working as a visiting scientist at MIT from 1998 until her death.Virginia was a deeply involved member of the American Physical Society (APS), including as secretary/treasurer of the division of nuclear physics (DNP) from 1986 to 1995. Because of her numerous contributions, her colleagues chose her in 2003 to receive the division’s first Distinguished Service Award.Another of us (Gibson) saw firsthand Virginia’s remarkable contributions to APS. He first met Virginia when he was a postdoctoral fellow at LLNL in 1968. Their closest connection came through the DNP, when he succeeded her as secretary/treasurer in 1995, and she mentored him in that time-consuming position.Virginia’s efforts as part of the DNP leadership strengthened the division’s fall meetings, assisted in funding APS’s Hans Bethe and Herman Feshbach Prizes and the division’s Nuclear Physics Dissertation Award, initiated the Department of Energy and NSF’s Nuclear Science Advisory Committee Long Range Plan town meetings, and established the DNP archive and historical record.While at NSF, Virginia suggested exploring a joint meeting with the nuclear physicists of the Physical Society of Japan. She chaired the first of the resulting series of successful international physics meetings in 2001 and remained instrumental in their success through the 2014 joint meeting. After Virginia left NSF, she was a visiting scientist at Los Alamos National Laboratory, where she conducted research and shared meals with Gibson and another of us (Seestrom). During one visit, she and Gibson drafted a history of the DNP. Virginia’s imprint on the division is indelible, and the DNP owes her a great debt of gratitude.With her contagious enthusiasm and laughter, Virginia was a dear friend who will be sorely missed.© 2016 American Institute of Physics.

Enhanced spin-dependent parity-nonconservation effect in the7sS1/22→6dD5/22transition in Fr: A possibility for unambiguous detection of the nuclear anapole moment

Employing the relativistic coupled-cluster method, comparative studies of the parity non-conserving electric dipole amplitudes for the $7s \ ^2S_{1/2} \rightarrow 6d \ ^2D_{5/2}$ transitions in $^{210}$Fr and $^{211}$Fr isotopes have been carried out. It is found that these transition amplitudes, sensitive only to the nuclear spin dependent effects, are enhanced by more than 3 orders compared to the low-lying $S-D_{5/2}$ transitions in Ba$^+$ and Ra$^+$ owing to the very large contributions from the electron core-polarization effects in Fr. This translates to a relatively large and, in principle, measurable induced light shift, which would be a signature of nuclear spin dependent parity nonconservation that is dominated by the nuclear anapole moment in a heavy atom like Fr. A plausible scheme to measure this quantity using the Cyclotron and Radioisotope Center (CYRIC) facility at Tohoku University has been outlined.

Parity nonconservation effect in the resonance elastic electron scattering on heavy He-like ions

We investigate the parity nonconservation effect in the elastic scattering of polarized electrons on heavy He-like ions, being initially in the ground state. The enhancement of the parity violation is achieved by tuning the energy of the incident electron in resonance with quasidegenerate doubly-excited states of the corresponding Li-like ion. We consider two possible scenarios. In the first one we assume that the polarization of the scattered electron is measured, while in the second one it is not detected. For the second scenario we propose a scheme of a modified electron beam ion source (EBIS) experiment where the detection of a parity violation in the electron scattering seems possible.

Weak- and hyperfine-interaction-induced 1s2s 1S0 → 1s2 1S0 E1 transition rates of He-like ions**Project supported by the National Natural Science Foundation of China (Grant Nos. 11274254, 11147108, 10979007, U1331122, and U1332206) and in part by the National Basic Research Program of China (Grant No. 2013CB922200).

Weak- and hyperfine-interaction-induced 1s2s 1S0 → 1s2 1S0 E1 transition rates for the isoelectronic sequence of He-like ions have been calculated using the multi-configuration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction methods. The results should be helpful for the future experimental investigations of parity non-conservation effects.