Search results for "form factor"
showing 10 items of 261 documents
Electromagnetic Structure of the Neutron from Annihilation Reactions
2022
The investigation of the fundamental properties of the nucleon is one of the most important topics in the modern hadron physics. Its internal structure and dynamics can be studied through the measurement of electromagnetic form factors which represent the simplest structure observables and serve as a test ground for our understanding of the strong interaction. Since the first attempt to measure the time-like form factors of the neutron, only four experiments published results on its structure from annihilation reactions. Due to the lack of statistics and experimental challenges, no individual determination of the form factors of the neutron has been possible so far. Modern developments of e…
Precise Measurement of the Neutron Magnetic Form FactorGMnin the Few-GeV2Region
2009
The neutron elastic magnetic form factor was extracted from quasielastic electron scattering on deuterium over the range Q;{2}=1.0-4.8 GeV2 with the CLAS detector at Jefferson Lab. High precision was achieved with a ratio technique and a simultaneous in situ calibration of the neutron detection efficiency. Neutrons were detected with electromagnetic calorimeters and time-of-flight scintillators at two beam energies. The dipole parametrization gives a good description of the data.
A measurement of |Vcb| from
1995
Abstract From approximately 3 million hadronic decays of Z bosons recorded with the aleph detector at lep , a sample of 410 ± 32 B 0 → D ∗+ l − ν l candidates is selected, where l is either an electron or a muon. The differential decay rate dΓ ( B 0 → D ∗+ l − ν l ) dω from this sample is fitted, yielding a value for the product of the CKM matrix element |Vcb| and the normalisation of the decay form factor at the point of zero recoil of the D∗+ meson F (ω = 1)|Vcb| = (31.4 ± 2.3stat ± 2.5syst) × 10−3. A value for |Vcb| is extracted using theoretical calculations of the form factor normalisation, with the result |Vcb| = (34.5 ± 2.5stat ± 2.7syst ± 1.5theory) × 10−3. From the integrated s the…
Classical form factor for nlm→n′l′m transitions in the hydrogen atom
2000
Abstract The form factor for nlm → n ′ l ′ m transitions in the hydrogen atom is deduced on the basis of kinematics of the classical mechanics. The consistency of this approach is verified by derivation of the known result for the transition probability averaged over m . The classical transition probability as a function of the final state energy and angular momentum is investigated comprehensively in the case of l = m =0.
Line shape and D(*)D¯(*) probabilities of ψ(3770) from the e+e−→DD¯ reaction
2019
We have performed a calculation of the DD¯, DD¯*, D*D¯, D*D¯* components in the wave function of the ψ(3770). For this we make use of the P03 model to find the coupling of ψ(3770) to these components, that with an elaborate angular momentum algebra can be obtained with only one parameter. Then we use data for the e+e-→DD¯ reaction, from where we determine a form factor needed in the theoretical framework, as well as other parameters needed to evaluate the meson-meson self-energy of the ψ(3770). Once this is done we determine the Z probability to still have a vector core and the probability to have the different meson components. We find Z about 80%–85%, and the individual meson-meson compon…
Baryon Properties with Three-Quark Forces
1987
The Constituent Quark Model (CQM) is very useful for the description of many baryon properties, leading to a fair agreement with the experimental data, especially in the case of the baryon spectrum 1) and of the electromagnetic processes involving baryons2,3). The model is based on a non relativistic QCD-inspired dynamics, which includes a confinement potential and a spin-dependent short-range part, the so called hyperfine interaction4,1). The confinement potential contains as its major part a harmonic oscillator (h.o.) interaction, which has however a too degenerate spectrum with respect to the experimental one and leads to an unreasonable damping of the form factors even at moderate momen…
Axial, induced pseudoscalar, and pion-nucleon form factors in manifestly Lorentz-invariant chiral perturbation theory
2006
We calculate the nucleon form factors G_A and G_P of the isovector axial-vector current and the pion-nucleon form factor G_piN in manifestly Lorentz-invariant baryon chiral perturbation theory up to and including order O(p^4). In addition to the standard treatment including the nucleon and pions, we also consider the axial-vector meson a_1 as an explicit degree of freedom. This is achieved by using the reformulated infrared renormalization scheme. We find that the inclusion of the axial-vector meson effectively results in one additional low-energy coupling constant that we determine by a fit to the data for G_A. The inclusion of the axial-vector meson results in an improved description of t…
form factor at order of chiral perturbation theory
2001
Abstract This paper describes the calculation of the electromagnetic form factor of the K 0 meson at order p 6 of chiral perturbation theory which is the next-to-leading order correction to the well-known p 4 result achieved by Gasser and Leutwyler. On the one hand, at order p 6 the chiral expansion contains 1- and 2-loop diagrams which are discussed in detail. Especially, a numerical procedure for calculating the irreducible 2-loop graphs of the sunset topology is presented. On the other hand, the chiral Lagrangian L (6) produces a direct coupling of the K 0 current with the electromagnetic field tensor. Due to this coupling one of the unknown parameters of L (6) occurs in the contribution…
Relativistic corrections in quasi-free electro-disintegration of the deuteron
1992
The role of relativistic effects in deuteron break-up by electrons is investigated for quasi-free kinematics by including the lowest-order relativistic corrections beyond the nonrelativistic limit to electromagnetic operators and by wave-function boost. In particular, the dependence of form factors and structure functions on the frame in which they are calculated is studied. It is found that the inclusion of these corrections leads to observables that are less frame-dependent than for a pure nonrelativistic description. The boost contributions show a decisive influence even though they are small in absolute size. Furthermore, the dependence on the parametrization of the nucleon current in t…
Measurement of the neutrino neutral-current elastic differential cross section on mineral oil atEν∼1 GeV
2010
We report a measurement of the flux-averaged neutral-current elastic differential cross section for neutrinos scattering on mineral oil (CH{sub 2}) as a function of four-momentum transferred squared, Q{sup 2}. It is obtained by measuring the kinematics of recoiling nucleons with kinetic energy greater than 50 MeV which are readily detected in MiniBooNE. This differential cross-section distribution is fit with fixed nucleon form factors apart from an axial mass M{sub A} that provides a best fit for M{sub A}=1.39{+-}0.11 GeV. Using the data from the charged-current neutrino interaction sample, a ratio of neutral-current to charged-current quasielastic cross sections as a function of Q{sup 2} …