Search results for "dipole"
showing 10 items of 982 documents
The two-loop supersymmetric corrections to lepton anomalous magnetic and electric dipole moments
2006
Using the effective Lagrangian method, we analyze the electroweak corrections to the anomalous dipole moments of lepton from some special two-loop topological diagrams which are composed of neutralino (chargino) - slepton (sneutrino) in the minimal supersymmetric extension of the standard model (MSSM). Considering the translational invariance of the inner loop momenta and the electromagnetic gauge invariance, we get all dimension 6 operators and derive their coefficients. After applying equations of motion to the external leptons, the anomalous dipole moments of lepton are obtained. The numerical results imply that there is a parameter space where the two-loop supersymmetric corrections to …
New ISR Cross Section Results on e + e − → π + π − π 0 π 0 and e + e − → π + π − η from BaBar
2017
Abstract Two new hadronic cross sections measured by the BaBar experiment are presented: e + e − → π + π − π 0 π 0 and e + e − → π + π − η . For both channels, the contribution to the anomalous magnetic moment of the muon is calculated.
Initial State Radiation Measurements at BESIII
2019
Precision measurements of the hadronic cross sections e+ e−→ π+ π− , π+π−π0, π+π−2π0, ωπ0 and π+π−3π0 are performed at the BESIII experiment located in Beijing, China. These cross section measurements are needed as input for the Standard Model prediction of the anomalous magnetic moment of the muon, (g − 2)µ.The initial state radiation method is used to access the energy regions of interest for (g − 2)µ. Our results will improve the precision of the Standard Model prediction of (g − 2)µ .
Tau anomalous magnetic moment form factor at Super B/Flavor factories
2008
The proposed high-luminosity B/Flavor factories offer new opportunities for the improved determination of the fundamental physical parameters of standard heavy leptons. Compared to the electron or the muon case, the magnetic properties of the $\tau$ lepton are largely unexplored. We show that the electromagnetic properties of the $\tau$, and in particular its magnetic form factor, may be measured competitively in these facilities, using unpolarized or polarized electron beams. Various observables of the $\tau$'s produced on top of the $\Upsilon$ resonances, such as cross-section and normal polarization for unpolarized electrons or longitudinal and transverse asymmetries for polarized beams,…
The role of pions and kaons in τ decays, (gμ − 2), the running of αQED and the muonium hyperfine splitting
2003
Abstract We make use of recent accurate results obtained for the pion and kaon vector form factors within a chiral unitary approach in order to calculate the decay widths of the τ lepton to these mesons and also to evaluate the contribution of this two mesons to the anomalous magnetic moment of the muon, the running of the fine structure constant and the muonium hyperfine splitting, without fitting to the experimental data.
Vector form factor of the pion : A model-independent approach
2003
4 páginas, 2 figuras, 3 tablas.-- Comunicación presentada a la 9ª High-Energy Physics International Conference on Quantum ChromoDynamics (QCD 02) celebrada del 2 al 9 de Julio de 2002 en Montpellier (Francia).-- arXiv:hep-ph/0209224v1
Collider probes of axion-like particles.
2017
Axion-like particles (ALPs), which are gauge-singlets under the Standard Model (SM), appear in many well-motivated extensions of the SM. Describing the interactions of ALPs with SM fields by means of an effective Lagrangian, we discuss ALP decays into SM particles at one-loop order, including for the first time a calculation of the $a\to\pi\pi\pi$ decay rates for ALP masses below a few GeV. We argue that, if the ALP couples to at least some SM particles with couplings of order $(0.01-1) \mbox{TeV}^{-1}$, its mass must be above 1 MeV. Taking into account the possibility of a macroscopic ALP decay length, we show that large regions of so far unconstrained parameter space can be explored by se…
The two-photon physics program at BESIII
2017
Abstract One of the main aspects of the two-photon physics program of the BESIII Collaboration is the determination of electromagnetic transition form factors (TFF). Precision measurements of TFF are needed as input to the calculations of the contribution of hadronic light-by-light scattering to the anomalous magnetic moment of the muon a μ . Data acquired with the BESIII detector allow for the determination of TFF of light pseudoscalar mesons at momentum transfers below 2 GeV2, the region of highest relevance for a μ . The measurements of the TFF of π 0 , η and η ′ mesons, as well as pion pairs, are presented, and the potential for a first double-tagged measurement of the pion transition f…
Pion and kaon vector form factors and their role in π decay and the anomalous magnetic moment of the muon
2003
Abstract The pion and kaon coupled-channel vector form factors are described by making use of the resonance chiral Lagrangian results together with a suitable unitarization method in order to take care of the final state interactions. A very good reproduction of experimental data is accomplished for the vector form factors up to √s ⩽ 1.2 GeV. We then apply these form factors to calculate the width of τ decay to two pions and to two kaons and also to evaluate the contribution of these mesons to the anomalous magnetic moment of the muon.
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.