Magnetic Moment Of Proton Research Articles

An algebraic approach to the calculation of the magnetic moment of the Δ+ +

A fully relativistic, gauge invariant, and nonperturbative calculation of the Δ++ magnetic moment, μΔ++, is made using equal-time commutation relations (ETCRs) and the dynamical concepts of asymptoticSUF(2) flavor symmetry and asymptotic level realization. Physical masses of the Δ and nucleon are used in this broken-symmetry calculation. It is found that μΔ++=2.04μp, where μp is the proton magnetic moment. This result is very similar to that obtained by usingSU(6)⊗O(3) symmetry or the static quark model.

Wavefunction-independent relations between the nucleon axial-coupling gA and the nucleon magnetic moments

We calculate the proton's magnetic moment μ p and its axial-vector coupling g A as a function of its Dirac radius R 1 using a relativistic three-quark model formulated on the light-cone. The relationship between μ p and g A is found to be independent of the assumed form of the light-cone wavefunction. At the physical radius R 1 = 0.76 fm, one obtains the experimental values for both μ p and g A , and the helicity carried by the valence u and d quarks are each reduced by a factor ∽ 0.75 relative to their non-relativistic values. At large proton radius, μ p and g A are given by the usual non-relativistic formulae. At small radius, μ p becomes equal to the Dirac moment, as demanded by the Drell-Hearn-Gerasimov sum rule. In addition, as R 1 → 0, the constituent quark helicites become completely disoriented and g A → 0.

Hadron electromagnetic structure: Shedding light on models and their mechanisms

Strange quark contributions to the proton magnetic moment are estimated from a consideration of baryon magnetic moment sum rules. The environment sensitivity of quark contributions to baryon moments is emphasized. Pion cloud contributions to proton charge radii are examined in the framework of Chiral Perturbation Theory. The absence of scalar-diquark clustering in the nucleon is discussed.

Spin structure of nucleons in a quark model with constituent gluons.

We discuss the spin structure of nucleons in a quark model with gluonic degrees of freedom. The sum rules for polarized protons and neutrons are related to nucleon magnetic moments. In particular, when the ratio of the proton and neutron magnetic moments is larger than $\ensuremath{-}\frac{3}{2}$ the sum rule for polarized neutrons is negative, in agreement with recent experiments.

Determining the Avogadro Constant from Electrical Measurements

It is now possible to obtain indirect values of the Avogadro constant NA having comparatively small combined standard uncertainties by appropriately combining the values of a number of other fundamental physical constants. These constants, whose values in several important cases can be obtained from electrical measurements, include the Rydberg, fine-structure, Josephson, von Klitzing, Planck, and Faraday constants, the molar mass of the proton, the proton-electron mass ratio, and the shielded proton gyromagnetic ratio. This paper gives the expressions that relate NA to these other fundamental constants and the values of NA that can be obtained from these expressions using the currently available data. It also briefly discusses the prospects of obtaining an indirect value of NA with a combined standard uncertainty that is small enough to allow the redefinition of the kilogram.

A CALCULATION OF THE MAGNETIC MOMENT OF THE Δ++

A fully relativistic, gauge-invariant, and non-perturbative calculation of the Δ++ magnetic moment, μΔ++, is made using equal-time commutation relations (ETCRs) and the dynamical concepts of asymptotic SU F(2) flavor symmetry and asymptotic level realization. Physical masses of the Δ and nucleon are used in this broken symmetry calculation. It is found that μΔ++=2.04μp, where μp is the proton magnetic moment. This result is very similar to that obtained by using SU(6) ⊗ O(3) symmetry or the static quark model.

New experimental limits to the time variations of gp(me/mp) and alpha.

A new experimental limit to the possible time variation of the proton gyromagnetic ratio times the electron-to-proton mass ratio has been obtained from the frequency comparison data between Cs and Mg atomic beam standards. The measurements, made over a period of one year, lead to an upper limit for the rate of change of ${\mathit{g}}_{\mathit{p}}$(${\mathit{m}}_{\mathit{e}}$/${\mathit{m}}_{\mathit{p}}$) of 5.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$/yr. This result, based only on the validity of the quantum mechanical theory of the atomic spectra, together with astrophysical data regarding analogous products of atomic fundamental constants, leads also to a new limit for the time stability of the fine structure constant \ensuremath{\alpha} (2.7\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}13}$/yr).

Chiral limit of nucleon lattice electromagnetic form factors.

We calculate electric and magnetic form factors of protons and neutrons in quenched Monte Carlo lattice QCD on a ${16}^{3}$ \ifmmode\times\else\texttimes\fi{} 24 lattice at $\ensuremath{\beta}=6.0$ using Wilson fermions. We employ a method which characterizes one of the nucleon fields as a fixed zero-momentum secondary source. Extrapolating the overall data set to the chiral limit, we find acceptable fits for either dipole or monopole forms and extract proton and neutron magnetic moments, the magnitude of which are 10 to 15% low compared to experiment. In the extrapolation of the dipole fit of the form factors, we find that the dipole-to-nucleon mass ratio is about 7% low compared to experiment. In addition, we obtain positive values of the neutron electric form factor, which, however, are poorly represented by a popular phenomenological form at intermediate to small $\ensuremath{\kappa}$ values. A zero-momentum technique for extracting hadron magnetic moments is briefly discussed and shown to yield unrealistically small magnetic moment values.

Analyzing power in pion-proton bremsstrahlung, and the Delta ++(1232) magnetic moment.

We report on a first measurement of the polarized-target asymmetry of the pion-proton bremsstrahlung cross section (${\ensuremath{\pi}}^{+}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}p\ensuremath{\gamma}$). As in previous cross section measurements the pion energy (298 MeV) and the detector geometry for this experiment was chosen to optimize the sensitivity to the radiation from the magnetic dipole moment of the ${\ensuremath{\Delta}}^{++}(1232)$ resonance ${\ensuremath{\mu}}_{\ensuremath{\Delta}}$. Comparison to a recent isobar model for pion-nucleon bremsstrahlung yields ${\ensuremath{\mu}}_{\ensuremath{\Delta}}=(1.62\ifmmode\pm\else\textpm\fi{}0.18) {\ensuremath{\mu}}_{p}$, where ${\ensuremath{\mu}}_{p}$ is the proton magnetic moment. Since the asymmetry depends less than the cross section on the choice of the other input parameters for the model, their uncertainties affect this analysis by less than the experimental error. However the theory fails to represent both the cross section and the asymmetry data at the highest photon energies. Hence further improvements in the calculations are needed before the model dependence of the magnetic moment analysis can be fully assessed. The present result agrees with bag-model corrections to the SU(6) prediction ${\ensuremath{\mu}}_{\ensuremath{\Delta}}=2{\ensuremath{\mu}}_{p}$. As a by-product, the analyzing power for elastic ${\ensuremath{\pi}}^{+}p$ scattering at 415 MeV/c was also measured. This second result is in good agreement with phase shift calculations.

Formula omitted], magnetic moments and the spin of the proton

A general proof shows that valence quark spins carry only 70% of the nucleon spin in any model where u and d current-quark spin determine G A G V and the ratio of the nucleon magnetic moments, and their contributions to magnetic moments are proportional to their electric charges. A two-component nucleon model is presented in which a configuration with three valence quarks and a valence gluon is admixed to the standard SU (6) wave function with three valence quarks, and the mixing angle is determined by fitting the experimental value of G A G V . The ratio of the proton and neutron magnetic moments is -1.45, closer to the experimental value -1.46 than the SU (6) value -1.5.

ENDOR study on the position of hydrogens close to the manganese cluster in S 2 state of photosystem II

Proton matrix ENDOR of the manganese multiline in the S 2, state of photosystem II membranes from spinach has been investigated. The spectral structure over a range of frequencies of ± 2 MHz centered on the position for a free proton was analyzed through employing a simulation method based on the dipolar interaction between electron and proton magnetic moments. The 6 pairs of lines resolved were attributed to the surrounding proton populations at distances varying within the range 2.7–6.0 Å from the putative manganese center. Two of the 6 pairs, namely those corresponding to protons at distances of 2.7 and 3.2 Å from the manganese center were eliminated on washing of the membranes with deuterated buffer. This suggests that these protons belong to the water molecules coordinating to the manganese cluster. The presence of ethylene glycol instead of glycerol and sucrose in the buffer broadened both EPR and ENDOR spectra. This suggests that ethylene glycol molecules are also accessible to the two-manganese cluster. A possible model of water association to the manganese ions in the photosynthetic water-oxidation system is proposed.

A low field determination of the proton gyromagnetic ratio in water

The proton gyromagnetic ratio in H/sub 2/O is measured by the low-field method. gamma '/sub p/(low)=2.67513376*10/sup 8/ s/sup -1/ T/sup -1/ (0.11 p.p.m.), leads to a value of the fine structure constant of alpha /sup -1/=137.0359840 (0.037 ppm) and a value for the quantized Hall resistance in SI units of R/sub H/=25812.80460 Omega (0.037 p.p.m.). To achieve this result, the dimensions of a 2.1-m solenoid were measured with an accuracy of 0.04 mu m, and the NMR (nuclear magnetic resonance) frequency of a water sample was measured in the field of the solenoid. >

NBS determination of the fine-structure constant, and of the quantized Hall resistance and Josephson frequency-to-voltage quotient in SI units

Results of US National Bureau of Standards (NBS) experiments to realize the ohm and the watt, to determine the proton gyromagnetic ratio by the low-field method, to determine the time dependence of the NBS representation of the ohm using the quantum Hall effect, and to maintain the NBS representation of the volt using the Josephson effect, are appropriately combined to obtain an accurate value of the fine-structure constant and of the quantized Hall resistance in SI units, and values in SI units of the Josephson frequency-to-voltage quotient, Planck constant and elementary charge.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Errors in the measurement of the terrestrial magnetic field with a proton magnetometer

Typical errors in the measurement of the precession frequency of the magnetic moment of protons when using the periodometer, are discussed and methods are proposed to minimize it’s influence. Important conclusions are made with regard to the time of measurement and polarization and the properties of the sensor fluid.

A quark model based on QCD scale anomaly

We consider a quark model based on QCD scale anomaly in which the quarks move in the field of an effective glueball field. Hadrons correspond to solitonic bags of higher energy density in a nonperturbative sea of condensed gluons. We calculate the static properties of nucleon in this model and find that the nucleon mass is far too large (2.4–4 GeV) and the proton charge radius (0.37–0.54 fm) is low. The proton gyromagnetic ratio and gA/gv are in reasonable agreement with the experimental numbers.

Chiral colour dielectric model of the nucleon

Abstract We apply the colour dielectric model to the nucleon including the chiral symmetry by the linear sigma model. The results of numerical calculations show that as the quark-meson coupling becomes stronger, the chiral symmetry breaking phase inside the bag changes to the restoring phase. The hedgehog solution is projected onto the spin-isospin eigenstate by means of the collective coordinate method, and we study some static properties of the nucleon. Except for the proton magnetic moment, the observed static properties favour strong quark-meson coupling and light glueball mass (∼1 GeV) giving a “chiral bag” like solution. The calculated values of the observables are similar to those of the chiral soliton bag model with the topological number: Z = 1.

Electronic structure of synthetic iron(III) porphyrins in pyridine and pyridine [sbnd]water solutions: A proton magnetic resonance study

The results of variable temperature proton nuclear magnetic resonance, ESR and magnetic moment measurements on tetraphenylporphyrin iron(III) Cl and octaethylporphyrin iron(III) Cl in pure dry pyridine and in pyridine water mixtures are reported. In pure dry pyridine both Fe(TPP)Cl and Fe(OEP)Cl exist as undissociated adducts. The temperature dependence of the isotropic shifts and magnetic moments in pyridine water solutions is explained in terms of thermal equilibrium between high spin S = 5/2 and low spin S = 1/2 states with low spin state lying lower.

The damping of interplanetary Alfvénic fluctuations and the heating of the solar wind

The theoretical model of Tu et al. (1984) describing the radial variation of the power spectra of interplanetary Alfvénic fluctuations has been extended to explain the radial variations of Alfvénic fluctuations between 0.3 and 5 AU and of the solar wind proton temperature observed by Helios between 0.3 and 1 AU. The extended model predicts that the fluctuations have the following features. (1) If the lifetime of two wave packets in the fluctuations is less than their correlation time, their interaction time is determined by the lifetime. In this case, the spectral index in the high‐frequency range is close to −5/3. (2) The shape of the power spectrum evolves as the fluctuations propagate away from the Sun in the distance range between 0.3 and 1 AU; however, it remains approximately unchanged between 1 and 5 AU. The extended model also predicts that the proton magnetic moment increases with increasing heliocentric distance and that this increase for high‐speed streams from 0.35 to 0.95 AU is about 2×104K/nT. All these results are consistent with observations, indicating that the extended model proposed in the present paper can account for both the damping of Alfvénic fluctuations and the heating of the solar wind protons simultaneously. A relationship between the thermal speed of solar wind protons and the variance of the solar wind velocity components is also predicted for further comparison of the present model with Helios data.

Hadronic Parameters of Deformed MIT Bags

We carry out the analytical computation of the proton mean square radius and magnetic moment in a deformed MIT bag model. The results show that a quite good estimate of these parameters is given by a simple, geometrical approximation relating their values to those of the spherical bag model.

The low-field proton gyromagnetic ratio γ′p experiment at the ETL

The low-field proton gyromagnetic ratio γ′ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> (low) experiment at the Electrotechnical Laboratory (ETL) has been continuing with the construction of a new nonmagnetic building, precision solenoid, and dimensional measuring apparatus. A tentative value of γ′ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> (low) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ETL86</inf> and its uncertainty are given: γ′ <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> (low) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ETL86</inf> = 2.6 751 289(59) × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> T <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ETL</inf> (2.2 ppm). The sources of uncertainty have been carefully investigated. The irregularity of the solenoid diameter and the resistance calibration mainly caused the large uncertainty. In order to reduce the uncertainties some improvements have been done or are planned.