Search results for "form factor"
showing 10 items of 261 documents
Reinterpretation of Classic Proton Charge Form Factor Measurements
2020
In 1963, a proton radius of $0.805(11)~\mathrm{fm}$ was extracted from electron scattering data and this classic value has been used in the standard dipole parameterization of the form factor. In trying to reproduce this classic result, we discovered that there was a sign error in the original analysis and that the authors should have found a value of $0.851(19)~\mathrm{fm}$. We additionally made use of modern computing power to find a robust function for extracting the radius using this 1963 data's spacing and uncertainty. This optimal function, the Pad\'{e} $(0,1)$ approximant, also gives a result which is consistent with the modern high precision proton radius extractions.
Measurement of the Charge-Averaged Elastic Lepton-Proton Scattering Cross Section by the OLYMPUS Experiment
2020
Physical review letters 126(16), 162501 (1-6) (2021). doi:10.1103/PhysRevLett.126.162501
Measurement of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII
2021
Physics letters / B 817, 136328 (2021). doi:10.1016/j.physletb.2021.136328
Muon capture in11B
1971
In this paper the partial-capture rates of muons in11B going to11Be(g.s.) and11Be (320 keV), as well as the hyperfine effect in the transition to11Be*, are studied. Comparing these results with the beta-decay of11Be and the electromagnetic transition11Be* →11Be, we can derive some conclusions on the nuclear structure of the bound states of11Be. We also discuss some possible experiences which can give information on the pseudoscalar form factor in weak interactions.
Measurement of the decay rate and form factor parameter in the decay KL→e+e−γ
1999
Abstract The decay rate of the neutral K meson KL→e+e−γ has been measured with the NA48 detector at the CERN SPS. A total of 6864 events has been observed with an estimated background of 10 events. The branching ratio is Γ(KL→e+e−γ)/Γ(KL→all) = (1.06±0.02stat±0.02sys±0.04calc)×10−5. The parameter α K ∗ describing the relative strength of the two contributing amplitudes to this decay through intermediate pseudoscalar or vector mesons was measured to be α K ∗ =−0.36±0.06stat±0.02sys.
Measurement of the π0, η, η′ Transition Form Factors at BABAR
2013
Abstract Measurements of the transition form factors of the pseudoscalar mesons π 0 , η, η ′ have been carried out by the BABAR collaboration at the SLAC B-factory PEP-II. The form factors F ( Q 2 ) were measured in two-photon processes covering the kinematic range 4 GeV 2 Q 2 40 GeV 2 . For the π 0 form factor, results are significantly higher than predicted by Brodsky and Lepage assuming an asymptotic distribution amplitude. Data also suggest that the asymptotic regime of QCD is reached only at relatively high Q 2 . We also report on measurements of the η and η ′ transition form factors, which happen to feature a significantly different Q 2 behaviour than the one of the neutral pion.
ElectromagneticN→N*(1535)transition in the relativistic constituent-quark model
1990
We study a light-cone model of the nucleon and the ${S}_{11}(1535)$ resonance which provides a relativistic generalization of the constituent-quark model in the nonperturbative low-${Q}^{2}$ regime. The two parameters of the model, namely, the size parameter $\ensuremath{\alpha}$ and the constituent-quark mass ${m}_{q}\ensuremath{\approx}300$ MeV, are fixed by the axial form factor. We find good agreement for the electromagnetic form factors of the nucleon up to ${Q}^{2}\ensuremath{\approx}1\ensuremath{-}2$ Ge${\mathrm{V}}^{2}$. All static properties of the nucleon, except for the neutron charge radius, are reproduced within 10%. In addition, we show that the electromagnetic current of the …
Pion electroproduction, partially conserved axial-vector current, chiral Ward identities, and the axial form factor revisited
2003
We reinvestigate Adler's partially conserved axial-vector current relation in the presence of an external electromagnetic field within the framework of QCD coupled to external fields. We discuss pion electroproduction within a tree-level approximation to chiral perturbation theory and explicitly verify a chiral Ward identity referred to as the Adler-Gilman relation. We critically examine soft-momentum techniques and point out how inadmissable approximations may lead to results incompatible with chiral symmetry. As a result we confirm that threshold pion electroproduction is indeed a tool to obtain information on the axial form factor of the nucleon.
Coherent elastic neutrino-nucleus scattering on 40Ar from first principles
2019
Coherent elastic neutrino scattering on the 40Ar nucleus is computed with coupled-cluster theory based on nuclear Hamiltonians inspired by effective field theories of quantum chromodynamics. Our approach is validated by calculating the charge form factor and comparing it to data from electron scattering. We make predictions for the weak form factor, the neutron radius, and the neutron skin, and estimate systematic uncertainties. The neutron-skin thickness of 40Ar40 is consistent with results from density functional theory. Precision measurements from coherent elastic neutrino-nucleus scattering could potentially be used to extract these observables and help to constrain nuclear models.
Measurement of the hadronic form factor inD0→K−e+νedecays
2007
We present a preliminary measurement of the q2 dependence of the D0 --> K- e+ nu_e decay rate. This rate is proportional to the hadronic form factor squared, specified by a single parameter. This is either the mass in the simple pole ansatz m_pole = (1.854 +- 0.016 +- 0.020) GeV/c2 or the scale in the modified pole ansatz alpha_pole = 0.43 +- 0.03 +- 0.04. The first error refers to the statistical, the second to the systematic uncertainty.