Magnetic Moment Of Proton Research Articles

Quark and proton anomalous magnetic moments in confining models

We compute the one-loop quark-photon vertex and the quark magnetic moment in three different models with an infrared-modified gluon propagator, namely: the massive (Curci-Ferrari-like) model, the Gribov-Zwanziger model, and the refined Gribov-Zwanziger model. We show results for the F2 form factor and analyze the role played by the mass parameters associated with the confined gluon in these models. Using the framework of the constituent quark model, we further construct the observable proton magnetic moment including the effects of quantum chromodynamics (QCD) interactions generated by the different confining models. Our results show that there is no qualitative observable difference stemming from the presence of complex-conjugated poles. On the other hand, quantitative differences between the various confining models can be sizable, so that observable constraints would in principle be possible, provided one has sufficient information about the constituent quark mass and the QCD running coupling. Published by the American Physical Society 2024

Proton and neutron electromagnetic radii and magnetic moments from lattice QCD

We present results for the electromagnetic form factors of the proton and neutron computed on the (2 + 1)-flavor Coordinated Lattice Simulations (CLS) ensembles including both quark-connected and -disconnected contributions. The Q2-, pion-mass, lattice-spacing, and finite-volume dependence of our form factor data is fitted simultaneously to the expressions resulting from covariant chiral perturbation theory including vector mesons amended by models for lattice artefacts. From these fits, we determine the electric and magnetic radii and the magnetic moments of the proton and neutron, as well as the Zemach radius of the proton. To assess the influence of systematic effects, we average over various cuts in the pion mass and the momentum transfer, as well as over different models for the lattice-spacing and finite-volume dependence, using weights derived from the Akaike Information Criterion (AIC).

The carted quarks-based equations for the proton magnetic moment, its countless configurations and a supposed spin propelling engine.

The carted quarks-based equations for the proton magnetic moment, its countless configurations and a supposed spin propelling engine.

BASE—high-precision comparisons of the fundamental properties of protons and antiprotons

The BASE collaboration at the antiproton decelerator/ELENA facility of CERN compares the fundamental properties of protons and antiprotons with ultra-high precision. Using advanced Penning trap systems, we have measured the proton and antiproton magnetic moments with fractional uncertainties of 300 parts in a trillion (p.p.t.) and 1.5 parts in a billion (p.p.b.), respectively. The combined measurements improve the resolution of the previous best test in that sector by more than a factor of 3000. Very recently, we have compared the antiproton/proton charge-to-mass ratios with a fractional precision of 16 p.p.t., which improved the previous best measurement by a factor of 4.3. These results allowed us also to perform a differential matter/antimatter clock comparison test to limits better than 3,%. Our measurements enable us to set limits on 22 coefficients of CPT- and Lorentz-violating standard model extensions (SME) and to search for potentially asymmetric interactions between antimatter and dark matter. In this article, we review some of the recent achievements and outline recent progress towards a planned improved measurement of the antiproton magnetic moment with an at least tenfold improved fractional accuracy.Graphic

The Proton and Occam’s Razor

Otto Stern’s 1933 measurement of the unexpectedly large proton magnetic moment indicated to most physicists that the proton is not a point particle. At that time, many physicists modeled elementary particles as point particles, and therefore Stern’s discovery initiated the speculation that the proton might be a composite particle. In this work, we show that despite being an elementary particle, the proton is an extended particle. Our work is motivated by the experimental data, which we review in section 1.By applying Occam’s Razor principle, we identify a simple proton structure that explains the origin of its principal parameters. Our model uses only relativistic and electromagnetic concepts, highlighting the primary role of the electromagnetic potentials and of the magnetic flux quantum Φ M = h/e. Unlike prior proton models, our methodology does not violate Maxwell’s equation, Noether’s theorem, or the Pauli exclusion principle.Considering that the proton has an anapole (toroidal) magnetic moment, we propose that the proton is a spherical shaped charge that moves at the speed of light along a path that encloses a toroidal volume. A magnetic flux quantum Φ M = h/e stabilizes the proton’s charge trajectory. The two curvatures of the toroidal and poloidal current loops are determined by the magnetic forces associated with Φ M . We compare our calculations against experimental data.

Feasibility study for precisely measuring the EIC He3 beam polarization with the Polarized Atomic Hydrogen Gas Jet Target polarimeter at RHIC

The Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is used to measure the absolute proton beam polarization, $\sigma_P^\text{syst}/P\!\lesssim\!0.5\%$, at the Relativistic Heavy Ion Collider. Here I consider the possibility of employing HJET to measure the ${}^3\text{He}$ ($h$) beam polarization at the Electron-Ion Collider (EIC). The dominant contribution to the ratio of the $h^\uparrow{p}$ and $p^\uparrow{h}$ analyzing powers, which is needed for such measurements, can be easily calculated using well-known values of the proton and helion magnetic moments, but some corrections should be applied to achieve the required accuracy. It was found that corrections due to absorption and ${}^3\text{He}$ breakup effectively cancel in the ratio and a correction due to hadronic spin-flip amplitudes can be derived from the proton beam measurements. As a result, the anticipated systematic uncertainty in the measured ${}^3\text{He}$ beam polarization can satisfy the EIC requirement $\sigma_P^\text{syst}/P\!\lesssim\!1\%$.

Thermomagnetic modification of the anomalous magnetic moment of quarks using the NJL model

The effective photon-quark-antiquark ($\gamma q \overline{q}$) vertex function is evaluated at finite temperature in the presence of an arbitrary external magnetic field using the two-flavor gauged Nambu--Jona-Lasinio (NJL) model in the mean field approximation. The lowest order diagram contributing to the magnetic form factor and the anomalous magnetic moment (AMM) of the quarks is calculated at finite temperature and external magnetic field using the imaginary time formalism of finite temperature field theory and the Schwinger proper time formalism. The Schwinger propagator including all the Landau levels with non-zero AMM of the dressed quarks is considered while calculating the loop diagram. Using sharp as well as smooth three momentum cutoff, we regularize the UV divergences arising from the vertex function and the parameters of our model are chosen to reproduce the well known phenomenological quantities at zero temperature and zero magnetic field, such as pion-decay constant ($f_\pi$), vacuum quark condensate, vacuum pion mass ($m_\pi$) as well as the magnetic moments of proton and neutron. We then study the temperature and magnetic field dependence of the AMM and constituent mass of the quark. We found that, the AMM as well as the constituent quark mass are large at the chiral symmetry broken phase in the low temperature region. Around the pseudo-chiral phase transition they decrease rapidly and at high temperatures both of them approach vanishingly small values in the symmetry restored phase.

How Alfvén waves energize the solar wind: heat vs work.

A growing body of evidence suggests that the solar wind is powered to a large extent by an Alfvén-wave (AW) energy flux. AWs energize the solar wind via two mechanisms: heating and work. We use high-resolution direct numerical simulations of reflection-driven AW turbulence (RDAWT) in a fast-solar-wind stream emanating from a coronal hole to investigate both mechanisms. In particular, we compute the fraction of the AW power at the coronal base (P AWb) that is transferred to solar-wind particles via heating between the coronal base and heliocentric distance r, which we denote χ H(r), and the fraction that is transferred via work, which we denote χ W(r). We find that χ W(r A) ranges from 0.15 to 0.3, where r A is the Alfvén critical point. This value is small compared to one because the Alfvén speed v A exceeds the outflow velocity U at r < r A, so the AWs race through the plasma without doing much work. At r > r A, where v A < U, the AWs are in an approximate sense "stuck to the plasma," which helps them do pressure work as the plasma expands. However, much of the AW power has dissipated by the time the AWs reach r = r A, so the total rate at which AWs do work on the plasma at r > r A is a modest fraction of P AWb. We find that heating is more effective than work at r < r A, with χ H(r A) ranging from 0.5 to 0.7. The reason that χ H ⩾ 0.5 in our simulations is that an appreciable fraction of the local AW power dissipates within each Alfvén-speed scale height in RDAWT, and there are a few Alfvén-speed scale heights between the coronal base and r A. A given amount of heating produces more magnetic moment in regions of weaker magnetic field. Thus, paradoxically, the average proton magnetic moment increases robustly with increasing r at r > r A, even though the total rate at which AW energy is transferred to particles at r > r A is a small fraction of P AWb.

On quarks and the origin of QCD: Partons and baryons from intrinsic states

We create quarks from baryons in stead of constituting baryons from quarks. The quantum fields of QCD are generated via the exterior derivative (momentum form) of baryon wave functions on an intrinsic configuration space, the Lie group U(3). Local gauge transformations correspond to coordinate translations in the intrinsic space. A proton spin structure function and a proton magnetic moment are derived. We show how the spectrum of unflavoured baryons, the N and Delta resonances, can be understood from a mass Hamiltonian on the intrinsic space and note how our model resolves the problem of colour confinement. We calculate an approximate value for the relative neutron-to-proton mass shift and give an exact value for the neutron mass. We predict neutral charge singlets that may be interpreted as neutral pentaquarks at LHCb.

Cold and stable antimatter for fundamental physics.

The field of cold antimatter physics has rapidly developed in the last 20 years, overlapping with the period of the Antiproton Decelerator (AD) at CERN. The central subjects are CPT symmetry tests and Weak Equivalence Principle (WEP) tests. Various groundbreaking techniques have been developed and are still in progress such as to cool antiprotons and positrons down to extremely low temperature, to manipulate antihydrogen atoms, to construct extremely high-precision Penning traps, etc. The precisions of the antiproton and proton magnetic moments have improved by six orders of magnitude, and also laser spectroscopy of antihydrogen has been realized and reached a relative precision of 2 × 10−12 during the AD time. Antiprotonic helium laser spectroscopy, which started during the Low Energy Antiproton Ring (LEAR) time, has reached a relative precision of 8 × 10−10. Three collaborations joined the WEP tests inventing various unique approaches. An additional new post-decelerator, Extra Low ENergy Antiproton ring (ELENA), has been constructed and will be ready in 2021, which will provide 10–100 times more cold antiprotons to each experiment. A new era of the cold antimatter physics will emerge soon including the transport of antiprotons to other facilities.

All-Optical Magnetometric Sensor for Magnetoencephalography and Ultralow Field Tomography

A variant of the scheme of a magnetometric sensor based on cesium atomic vapor is proposed and experimentally investigated. The sensor uses magnetic resonance excitation by modulated light of an hyperfine optical pumping that is transverse to the magnetic field. It is shown that, for a cell with a volume of 0.125 cm3, the variational sensitivity of such a scheme, estimated from the ratio of the steepness of the signal in the center of the magnetic resonance to the shot noise of the detecting radiation, reaches a level of <10 fT/Hz1/2 in the frequency band width of the order of 850 Hz. The sensor, which does not emit radio frequency fields, is designed for use in magnetoencephalographic complexes. Possible ways to improve the performance of the scheme for detecting relatively fast (~4.2 kHz in a field of 0.1 mT) signals of the precession of proton magnetic moments in promising ultra-weak field tomography schemes are considered.

Precision Measurements of the Fundamental Properties of the Proton and Antiproton

Precision measurements comparing the fundamental properties of conjugate particles and antiparticles constitute stringent tests of CPT invariance. We review recent precision measurements of the BASE collaboration, which improved the uncertainty of the proton and antiproton magnetic moments and the comparison of the proton-to-antiproton charge-to-mass ratio. These measurements constitute the most stringent tests of CPT invariance with antiprotons. Further, we discuss the improved limit on the antiproton lifetime based on the storage of a cloud of antiprotons in the unique BASE reservoir trap. Based on these recent advances, we discuss ongoing technical developments which comprise a coupling trap for the sympathetic cooling of single (anti-)protons with laser-cooled beryllium ions, a transportable trap to relocate antiproton measurements into a high-precision laboratory, and a new experiment to measure the magnetic moment of helium-3 ions, which will improve absolute precision magnetometry.

Полностью оптический магнитометрический датчик для задач магнитоэнцефалографии и томографии сверхслабого поля

A version of the scheme of an atomic cesium vapour magnetometric sensor using magnetic resonance excitation by modulated radiation transverse to the magnetic field of hyperfine optical pumping is proposed and experimentally studied. It is shown that when using a cell with a volume of 0.125 cm3, the variational sensitivity of the sensor, estimated from the ratio of the steepness of the signal at the center of the magnetic resonance to the shot noise of the detecting radiation, reaches a level of less than 10 fT/Hz1/2 in the frequency band determined by the magnetic resonance line width (of the order of 800 Hz). The sensor, which does not use and does not emit resonant radio-frequency fields, is designed to operate in magnetoencephalographic complexes. Possible ways to increase the frequency response of the circuit for detecting relatively fast (~ 4.2 kHz in a field of 0.1 mT) proton magnetic moment precession signals in promising ultralow field tomography schemes are considered.

Weak production of strange Ξ baryons off the nucleon

The charged current Cabibbo-supressed associated $K \Xi$ production off the nucleon induced by anti-neutrinos is studied at low and intermediate energies. The non-resonant terms are obtained using a microscopical model based on the SU(3) chiral Lagrangian. The basic parameters of the model are $f_\pi$, the pion decay constant, Cabibbo's angle, the proton and neutron magnetic moments and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. In addition, we also consider $\Sigma^\ast(1385)$ resonance, which can decay in $K \Xi$ final state when this channel is open. The studied mechanism is the prime source of $\Xi$ production at anti-neutrino energies around $2$ GeV and the calculated cross sections at these energies can be measured at the current and future neutrino experiments.

Consistency of local and astrophysical tests of the stability of fundamental constants

Tests of the stability of nature's fundamental constants are one of the cornerstones of the ongoing search for the new physics which is required to explain the recent acceleration of the universe. The two main settings for these tests are high-resolution spectroscopy of astrophysical systems (mainly in low-density absorption clouds along the line of sight of bright quasars) and laboratory comparisons of pairs of atomic clocks. Here we use standard chi-square techniques to perform a global analysis of all currently available data, studying both the consistency of tests of stability of different constants (specifically the fine-structure constant $\alpha$, the proton-to-electron mass ratio $\mu$ and the proton gyromagnetic ratio $g_p$) and the consistency between local laboratory and astrophysical tests. We start by doing a model-independent analysis (studying the internal consistency of the various available datasets) but also explore specific phenomenological models motivated by string theory and grand unification. Overall there is weak (one to two sigma) evidence of variations, at the level of up to a few parts per million, and reasonable agreement between laboratory and astrophysical tests. This result holds even if one removes from the analysis the Webb {\it et al.} archival dataset of $\alpha$ measurements. Forthcoming astrophysical facilities, such as the ESPRESSO spectrograph, should be able to confirm or rule out these hints.

A Novel Penning‐Trap Design for the High‐Precision Measurement of the 3He2 + Nuclear Magnetic Moment

AbstractA new experiment is constructed aiming at the first direct high‐precision measurement of the helium‐3 nuclear magnetic moment with a relative precision of parts‐per‐billion or better. Methods similar to those used in proton and antiproton magnetic moment measurements are applied. As those techniques rely on the challenging detection of single spin‐flips, a novel Penning trap design optimized for nuclear spin‐flip detection is developed.

Discovery of OH Absorption from a Galaxy at z ∼ 0.05: Implications for Large Surveys with SKA Pathfinders

Abstract We present the first detection of OH absorption in diffuse gas at z &gt; 0, along with another eight stringent limits on OH column densities for cold atomic gas in galaxies at 0 &lt; z &lt; 0.4. The absorbing gas detected toward Q0248+430 (z q = 1.313) originates from a tidal tail emanating from a highly star-forming galaxy G0248+430 (z g = 0.0519) at an impact parameter of 15 kpc. The measured column density is N(OH) = (6.3 ± 0.8) × 1013 cm−2, where and T ex are the covering factor and the excitation temperature of the absorbing gas, respectively. In our Galaxy, the column densities of OH in diffuse clouds are of the order of N(OH) ∼ 1013–14 cm−2. From the incidence (number per unit redshift; n 21) of H i 21 cm absorbers at 0.5 &lt; z &lt; 1 and assuming no redshift evolution, we estimate the incidence of OH absorbers (with log N(OH) &gt; 13.6) to be n OH = at z ∼ 0.1. Based on this we expect to detect such OH absorbers from the MeerKAT Absorption Line Survey (MALS). Using H i 21 cm and OH 1667 MHz absorption lines detected toward Q0248+430, we estimate (ΔF/F) = (5.2 ± 4.5) × 10−6, where , α is the fine structure constant, μ is the electron–proton mass ratio, and g p is the proton gyromagnetic ratio. This corresponds to Δα/α(z = 0.0519) = (1.7 ± 1.4) × 10−6, which is among the stringent constraints on the fractional variation of α.

Surface-Mediated Hyperpolarization of Liquid Water from Parahydrogen

Summary This article reports the discovery of surface-mediated parahydrogen-induced alignment of the proton magnetic moments in liquid water as well as methanol and ethanol. In this SWAMP (surface waters are magnetized by parahydrogen) effect, the spin polarization of the solvent protons is enhanced simply by the bubbling of parahydrogen through a suspension of Pt 3 Sn intermetallic nanoparticles (iNPs) encapsulated within a protectective mesoporous silica shell (Pt 3 Sn@mSiO 2 ). The conversion of singlet spin order into magnetization is mediated by symmetry-breaking interactions on the surface of the iNPs. Stimulated emission NMR signals of the exchangeable hydroxy protons are observed. Non-exchangeable methyl or methylene protons are also hyperpolarized, an observation that provides insight into the molecular mechanism. SWAMP has a myriad of potential applications, ranging from low-field MRI to drug discovery.

Proton-Based Ultrafast Magic Angle Spinning Solid-State NMR Spectroscopy.

Protons are vastly abundant in a wide range of exciting macromolecules and thus can be a powerful probe to investigate the structure and dynamics at atomic resolution using solid-state NMR (ssNMR) spectroscopy. Unfortunately, the high signal sensitivity, afforded by the high natural-abundance and high gyromagnetic ratio of protons, is greatly compromised by severe line broadening due to the very strong 1H-1H dipolar couplings. As a result, protons are rarely used, in spite of the desperate need for enhancing the sensitivity of ssNMR to study a variety of systems that are not amenable for high resolution investigation using other techniques including X-ray crystallography, cryo-electron microscopy, and solution NMR spectroscopy. Thanks to the remarkable improvement in proton spectral resolution afforded by the significant advances in magic-angle-spinning (MAS) probe technology, 1H ssNMR spectroscopy has recently attracted considerable attention in the structural and dynamics studies of various molecular systems. However, it still remains a challenge to obtain narrow 1H spectral lines, especially from proteins, without resorting to deuteration. In this Account, we review recent proton-based ssNMR strategies that have been developed in our laboratory to further improve proton spectral resolution without resorting to chemical deuteration for the purposes of gaining atomistic-level insights into molecular structures of various crystalline solid systems, using small molecules and peptides as illustrative examples. The proton spectral resolution enhancement afforded by the ultrafast MAS frequencies up to 120 kHz is initially discussed, followed by a description of an ensemble of multidimensional NMR pulse sequences, all based on proton detection, that have been developed to obtain in-depth information from dipolar couplings and chemical shift anisotropy (CSA). Simple single channel multidimensional proton NMR experiments could be performed to probe the proximity of protons for structure determination using 1H-1H dipolar couplings and to evaluate the changes in chemical environments as well as the relative orientation to the external magnetic field using proton CSA. Due to the boost in signal sensitivity enabled by proton detection under ultrafast MAS, by virtue of high proton natural abundance and gyromagnetic ratio, proton-detected multidimensional experiments involving low-γ nuclei can now be accomplished within a reasonable time, while the higher dimension also offers additional resolution enhancement. In addition, the application of proton-based ssNMR spectroscopy under ultrafast MAS in various challenging and crystalline systems is also presented. Finally, we briefly discuss the limitations and challenges pertaining to proton-based ssNMR spectroscopy under ultrafast MAS conditions, such as the presence of high-order dipolar couplings, friction-induced sample heating, and limited sample volume. Although there are still a number of challenges that must be circumvented by further developments in radio frequency pulse sequences, MAS probe technology and approaches to prepare NMR-friendly samples, proton-based ssNMR has already gained much popularity in various research domains, especially in proteins where uniform or site-selective deuteration can be relatively easily achieved. In addition, implementation of the recently developed fast data acquisition approaches would also enable further developments in the design and applications of proton-based ultrafast MAS multidimensional ssNMR techniques.

Stability of fundamental couplings: A global analysis

Astrophysical tests of the stability of fundamental couplings are becoming an increasingly important probe of new physics. Motivated by the recent availability of new and stronger constraints we update previous works testing the consistency of measurements of the fine-structure constant $\alpha$ and the proton-to-electron mass ratio $\mu=m_p/m_e$ (mostly obtained in the optical/ultraviolet) with combined measurements of $\alpha$, $\mu$ and the proton gyromagnetic ratio $g_p$ (mostly in the radio band). We carry out a global analysis of all available data, including the 293 archival measurements of {\it Webb et al.} and 66 more recent dedicated measurements, and constraining both time and spatial variations. While nominally the full datasets show a slight statistical preference for variations of $\alpha$ and $\mu$ (at up to two standard deviations), we also find several inconsistencies between different sub-sets, likely due to hidden systematics and implying that these statistical preferences need to be taken with caution. The statistical evidence for a spatial dipole in the values of $\alpha$ is found at the 2.3 sigma level. Forthcoming studies with facilities such as ALMA and ESPRESSO should clarify these issues.