Search Results (10)

This paper comprehensively reports experimental proof of parity violation in the ground and photoexcited states of three mirror-symmetric Si–Si bond polymers in homogeneous solutions of achiral molecules under non-stirring conditions by analyzing 370 chiroptical datasets relating to multiple second-order helix–helix transitions in the circular dichroism (CD) of poly(di-i-butylsilane) (iBS), poly(di-i-pentylsilane) (iPS), and poly(di-i-hexylsilane) (iHS) in achiral alkanols and p-dioxane-h₈/-d₈. Particularly large (–)-CD of g_abs = −3.1 × 10⁻² at 290 nm was found for iBS in i-pentanol at 25 °C. Notably, iPS in n-propanol at −5 °C generated (–)-CD with g_abs = −0.48 × 10⁻² at 300 nm, but (+)-circularly polarized luminescence (CPL) with g_lum = +0.84 × 10⁻² at 326 nm. In contrast, iHS in n-octanol at 0 °C showed only very weak (–)-CD of g_abs ~−0.03 × 10⁻² at 310 nm. The H/D isotopes of p-dioxane-h₈/-d₈ weakly affected the helix–helix transition characteristics of iBS. (–)-Sign vibrational CD signals assigned to the handed symmetric and asymmetric bending modes of the CH₃ and CH₂ groups of the solvents and other achiral molecules were observed. We assumed (i) three ¹H nuclear-spin-1/2 induced handed motions of CH₃ rotors at i-alkyl side chains and achiral alkanols, and (ii) helical main-chain Si atoms (δ⁺) coordinated by handed lone pairs at oxygen (δ⁻) in gauche-containing n- and i-alkanols induced by the CH₃ rotors. A possible origin of biomolecular handedness is proposed based on the first observation of far-UV CD and UV spectra of zwitterionic glycine bearing H₃N⁺ rotor in neutral H₂O. Full article

We consider the implications of the recent measurement of the W-boson mass $M_W=\mathrm{80,433.5}\pm 9.4\mathrm{MeV}/{\mathrm{c}}^2$ for atomic parity violation experiments. We show that the change in $M_W$ shifts the Standard Model prediction for the ${}^{133}$Cs nuclear weak charge to $Q_W\left({}^{133}\mathrm{Cs}\right)=-73.11\left(1\right)$, i.e., by $8.5\sigma$ from its current value, and the proton weak charge by 2.7%. The shift in $Q_W\left({}^{133}\mathrm{Cs}\right)$ ameliorates the tension between existing determinations of its value and motivates more accurate atomic theory calculations, while the shift in $Q_W\left(p\right)$ inspires next-generation atomic parity violation experiments with hydrogen. Using our revised value for $Q_W\left({}^{133}\mathrm{Cs}\right)$, we also readjust constraints on parameters of physics beyond the Standard Model. Finally, we reexamine the running of the electroweak coupling for the new W boson mass. Full article

We present an experimental and theoretical investigation of the spectroscopy of dilute alkali atoms in a solid matrix of inert gases at cryogenic temperatures, specifically Rubidium atoms in a solid Argon or Neon matrix, and related aspects of the interaction energies between the alkali atoms and the atoms of the solid matrix. The system considered is relevant for matrix isolation spectroscopy, and it is at the basis of a recently proposed detector of cosmological axions, exploiting magnetic-type transitions between Zeeman sublevels of alkali atoms in a magnetic field, tuned to the axion mass, assumed in the meV range. Axions are one of the supposed constituents of the dark matter (DM) of the Universe. This kind of spectroscopy could be also relevant for the experimental search of new physics beyond the Standard Model, in particular the search of violations of time-reversal or parity-charge-conjugation (CP) symmetry. In order to efficiently resolve the axion-induced transition in alkali-doped solid matrices, it is necessary to reduce as much as possible the spectral linewidth of the electronic transitions involved. The theoretical investigation presented in this paper aims to estimate the order of magnitude of the inhomogeneous contribution to the linewidth due to the alkali–matrix interactions (Coulomb/exchange and dispersion), and to compare the theoretical results with our experimental measurements of spectra of dilute Rubidium atoms in Argon and Neon solid matrix. The comparison of the expected or measured spectral linewidths will be important for selecting the most appropriate combination of alkali atoms and matrix inert elements to be used in the proposed axion detection scheme. It is finally suggested that dilute Lithium atoms diffused in a cold parahydrogen solid matrix could be, overall, a good system upon which the proposed detector could be based. Full article

Baryon number violation is a key ingredient of baryogenesis. It has been hypothesized that there could also be a parity-conjugated copy of the standard model particles, called mirror particles. The existence of such a mirror universe has specific testable implications, especially in the domain of neutral particle oscillation, viz. the baryon number violating neutron to mirror-neutron ($n-n^{\prime }$) oscillation. Consequently, there were many experiments that have searched for $n-n^{\prime }$ oscillation, and imposed constraints upon the parameters that describe it. Recently, further analysis on some of these results have identified anomalies which could point to the detection of $n-n^{\prime }$ oscillation. All the previous efforts searched for $n-n^{\prime }$ oscillation by comparing the relative number of ultracold neutrons that survive after a period of storage for one or both of the two cases: (i) comparison of zero applied magnetic field to a non-zero applied magnetic field, and (ii) comparison where the orientation of the applied magnetic field was reversed. However, $n-n^{\prime }$ oscillations also lead to variations in the precession frequency of polarized neutrons upon flipping the direction of the applied magnetic field. Precession frequencies are measured, very precisely, by experiments searching for the electric dipole moment. For the first time, we used the data from the latest search for the neutron electric dipole moment to constrain $n-n^{\prime }$ oscillation. After compensating for the systematic effects that affect the ratio of precession frequencies of ultracold neutrons and cohabiting ${}^{199}$Hg-atoms, chief among which was due to their motion in non-uniform magnetic field, we constrained any further perturbations due to $n-n^{\prime }$ oscillation. We thereby provide a lower limit on the $n-n^{\prime }$ oscillation time constant of ${\tau }_{n{n}^{\prime }}/\sqrt{|cos(\beta \left)\right|}>5.7s,0.36{\mathrm{T}}^{\prime }<B^{\prime }<1.01{\mathrm{T}}^{\prime }$ (95% C.L.), where $\beta$ is the angle between the applied magnetic field and the ambient mirror magnetic field. This constraint is the best available in the range of $0.36{\mathrm{T}}^{\prime }<B^{\prime }<0.40{\mathrm{T}}^{\prime }$. Full article

The energy and structural parameters were obtained for all forms of the carbonyl complex of osmium Os₃(CO)₁₂ with D_3h and D₃ symmetries using density functional theory (DFT) methods. The calculations took into account various levels of relativistic effects, including those associated with nonconservation of spatial parity. It was shown that the ground state of Os₃(CO)₁₂ corresponds to the D₃ symmetry and thus may be characterized either as left-twisted (D_3S) or right-twisted (D_3R). The D_3S↔D_3R transitions occur through the D_3h transition state with an activation barrier of ~10^–14 kJ/mol. Parity violation energy difference (PVED) between D_3S and D_3R states equals to ~5 × 10⁻¹⁰ kJ/mol. An unusual three-center exchange interaction was found inside the {Os₃} fragment. It was found that the cooperative effects of the mutual influence of osmium atoms suppress the chirality of the electron system in the cluster. Full article

We present an extension and a deepened analysis of a suggested experimental scheme for detecting atomic parity violation, previously published in Phys. Rev. A 2019, 100, 050101. The experimental concept is described in more detail and we compute new ab initio data necessary for assessing the plausibility of the approach. Original theoretical data for transition matrix elements on the electric dipole forbidden transition in caesium $6\mathrm{s}{}^2{\mathrm{S}}_{1/2}$ – $5\mathrm{d}{}^2{\mathrm{D}}_{3/2}$ are reported, as are a range of electric dipole matrix elements connected to the ground state 6s. The latter is used for an analysis of the wavelength-dependent light shift in Cs. A range of experimental details is presented, combined with a survey of realistic lasers parameters. These are adopted to project the feasibility of the scheme to eventually be capable of delivering data beyond the standard model of particle physics. Full article

We propose that gravitational interactions of cosmic neutrinos with the statistically homogeneous and isotropic fluctuations of space-time lead to decoherence. This working hypothesis, which we describe by means of a Lindblad operator, is applied to the system of two- and three-flavour neutrinos undergoing vacuum oscillations and the consequences are investigated. As a result of this decoherence we find that the neutrino entropy would increase as a function of initial spectral distortions, mixing angles and charge-parity (CP)-violation phase. Subsequently we discuss the chances to discover such an increase observationally (in principle). We also present the expected flavour composition of the cosmic neutrino background after decoherence is completed. The physics of two- or three-flavour oscillation of cosmological neutrinos resembles in many aspects two- or three-level systems in atomic clocks, which were recently proposed by Weinberg for the study of decoherence phenomena. Full article

Searches for permanent electric dipole moments (EDMs) of fundamental particles, atoms and molecules are promising experiments to constrain and potentially reveal beyond Standard Model (SM) physics. A non-zero EDM is a direct manifestation of time-reversal (T) violation, and, equivalently, violation of the combined operation of charge-conjugation (C) and parity inversion (P). Identifying new sources of CP violation can help to solve fundamental puzzles of the SM, e.g., the observed baryon-asymmetry in the Universe. Theoretical predictions for magnitudes of EDMs in the SM are many orders of magnitude below current experimental limits. However, many theories beyond the SM require larger EDMs. Experimental results, especially when combined in a global analysis, impose strong constraints on CP violating model parameters. Including an overview of EDM searches, I will focus on the future neutron EDM experiment at TRIUMF (Vancouver). For this effort, the TUCAN (TRIUMF Ultra Cold Advanced Neutron source) collaboration is aiming to build a strong, world leading source of ultra cold neutrons (UCN) based on a unique combination of a spallation target and a superfluid helium UCN converter. Another focus will be the search for an EDM of the diamagnetic atom ${}^{129}$ Xe using a ${}^3$ He comagnetometer and SQUID detection. The HeXeEDM collaboration has taken EDM data in 2017 and 2018 in the magnetically shielded room (BMSR-2) at PTB Berlin. Full article

Accurate values for atomic dipole matrix elements are useful in many areas of physics, and in particular for interpreting experiments such as atomic parity violation. Obtaining accurate matrix element values is a challenge for both experiment and theory. A new technique that can be applied to this problem is tune-out spectroscopy, which is the measurement of light wavelengths where the electric polarizability of an atom has a zero. Using atom interferometry methods, tune-out wavelengths can be measured very accurately. Their values depend on the ratios of various dipole matrix elements and are thus useful for constraining theory and broadening the application of experimental values. To date, tune-out wavelength measurements have focused on zeros of the scalar polarizability, but in general the vector polarizability also contributes. We show here that combined measurements of the vector and scalar polarizabilities can provide more detailed information about the matrix element ratios, and in particular can distinguish small contributions from the atomic core and the valence tail states. These small contributions are the leading error sources in current parity violation calculations for cesium. Full article

We study a system represented by a Bose-Einstein condensate interacting with a cavity field in presence of a strong off-resonant pumping laser. This system can be described by a three-mode Gaussian state, where two are the atomic modes corresponding to atoms populating upper and lower momentum sidebands and the third mode describes the scattered cavity field light. We show that, as a consequence of the collective atomic recoil instability, these modes possess a genuine tripartite entanglement that increases unboundedly with the evolution time and is larger than the bipartite entanglement in any reduced two-mode bipartition. We further show that the state of the system exhibits genuine tripartite nonlocality, which can be revealed by a robust violation of the Svetlichny inequality when performing displaced parity measurements. Our exact results are obtained by exploiting the powerful machinery of phase-space informational measures for Gaussian states, which we briefly review in the opening sections of the paper. Full article