Search results for "magnetic dipole moment"
showing 10 items of 117 documents
Anomalous magnetic moment of the muon in a dispersive approach
2014
We present a new general dispersive formalism for evaluating the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. In the suggested approach, this correction is related to the imaginary part of the muon's electromagnetic vertex function. The latter may be directly related to measurable hadronic processes by means of unitarity and analyticity. As a test we apply the introduced formalism to the case of meson pole exchanges and find agreement with the direct two-loop calculation.
Dispersive analysis of the γγ⁎ → ππ process
2019
Abstract We present a theoretical study of the γ γ ⁎ → π + π − , π 0 π 0 processes from the threshold through the f 2 ( 1270 ) region in the ππ invariant mass. We adopt the Omnes representation in order to account for rescattering effects in both s- and d-partial waves. For the description of the f 0 ( 980 ) resonance, we implement a coupled-channel unitarity. The constructed amplitudes serve as an essential framework to interpret the current experimental two-photon fusion program at BESIII. They also provide an important input for the dispersive analyses of the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment.
IMPROVED BOUNDS ON THE TAU MAGNETIC MOMENTS
2001
New limits on the tau magnetic couplings to the photon, the Z and the W bosons are obtained from the most general effective Lagrangian. Model independent bounds are set using data for tau pair production and W decay into tau leptons at LEP1, LEP2, SLD and hadron colliders. For the anomalous magnetic moment the bounds are, for the first time, of the order of magnitude of the standard model prediction.
Study of the discovery potential for hidden photon emission at future electron scattering fixed target experiments
2013
Electron scattering fixed target experiments are a versatile tool to explore various physics phenomena. Recently these experiments came into focus to search for $U(1)$ extensions of the Standard Model of particle physics at low energies. These extensions are motivated from anomalies in astrophysical observations as well as from deviations from Standard Model predictions, such as the discrepancy between the experimental and theoretical determination of the anomalous magnetic moment of the muon. They also arise naturally when the Standard Model is embedded into a more general theory. In the considered $U(1)$ extensions a new, light messenger particle $\gamma^\prime$, the hidden photon, couple…
Continuous Stern–Gerlach effect and the magnetic moment of the antiproton
2004
Abstract The measurement of the magnetic moment (or g-factor ) of the antiproton and of the proton is a sensitive test of CPT invariance. We discuss the possibility of applying the continuous Stern–Gerlach effect to detect quantum jumps between the two spin states (spin up and spin down) of the antiproton. The measurement will be performed on a single antiproton stored in a Penning trap. The g -factor of the antiproton is determined by measuring its cyclotron frequency and its spin precession frequency in the magnetic field of the trap. With the double Penning trap method the g -factor of the antiproton can be determined with an accuracy of 1 ppb.
Spin and magnetic moment of25Na by ?-radiation detected optical pumping
1975
25Na (T1/2 = 60 sec) has been produced in a22Ne target by the (α,p) reaction and polarized by means of spin-exchange scattering with optically pumped87Rb. The asymmetry in the β decay of polarized nuclei served to detect rf transitions between hfs Zeeman levels of the atomic ground state, yielding spinI = 5/2 and hyperfine splitting ΔW= 2648.5(3.0) MHz, from which the magnetic moment μI = 3.683(4)nm (corrected for diamagnetism) was deduced.
Singlet-groundstate magnetism in TbP
1979
Elastic neutron scattering and magnetic susceptibility data are reported for temperatures around the Neel-point,TN=7.3 K, and for zero magnetic field. AboveTN, the temperature dependence of the magnetic central peak intensity can adequately be described within the RPA assuming isotropic exchange between nearest and next-nearest neighbours as the only parameters. This two-parameter model is quantitatively confirmed by the susceptibility data. AtTN, magnetic Bragg-intensities arise almost discontinuously (reaching 70% of the saturation within 0.1 K) accompanied by thermal hysteresis. For all temperatures belowTN the sublattice magnetic moment is explained by solutions of meanfield equations, …
An interpolation of the vacuum polarization function for the evaluation of hadronic contributions to the muon anomalous magnetic moment
2001
We propose a simple parameterization of the two-point correlator of hadronic electromagnetic currents for the evaluation of the hadronic contributions to the muon anomalous magnetic moment. The parameterization is explicitly done in the Euclidean domain. The model function contains a phenomenological parameter which provides an infrared cutoff to guarantee the smooth behavior of the correlator at the origin in accordance with experimental data in e+ e- annihilation. After fixing a numerical value for this parameter from the leading order hadronic contribution to the muon anomalous magnetic moment the next-to-leading order results related to the vacuum polarization function are accurately re…
Review of dark photon searches
2016
Dark Photons are hypothetical extra-U(1) gauge bosons, which are motivated by a number of astrophysical anomalies as well as the presently seen deviation between the Standard Model prediction and the direct measurement of the anomalous magnetic moment of the muon, (g − 2)μ . The Dark Photon does not serve as the Dark Matter particle itself, but acts as a messenger particle of a hypothetical Dark Sector with residual interaction to the Standard Model. We review recent Dark Photon searches, which were carried out in a global effort at various hadron and particle physics facilities. We also comment on the perspectives for future invisble searches, which directly probe the existence of Light Da…
Lattice QCD and the timelike pion form factor.
2011
We present a formula that allows one to calculate the pion form factor in the timelike region 2mpi <= sqrt{s} <= 4mpi in lattice QCD. The form factor quantifies the contribution of two-pion states to the vacuum polarization. It must be known very accurately in order to reduce the theoretical uncertainty on the anomalous magnetic moment of the muon. At the same time, the formula constitutes a rare example where, in a restricted kinematic regime, the spectral function of a conserved current can be determined from Euclidean observables without an explicit analytic continuation.