arXiv subjects

R. Bradford

Publications and source records attributed to R. Bradford.

23 records · Page 2Linked to original sources

arXiv2007

Extraction of the Axial Nucleon Form Factor from Neutrino Experiments on Deuterium

We present new parameterizations of vector and axial nucleon form factors. We maintain an excellent descriptions of the form factors at low momentum transfers ($Q^2$), where the spatial structure of the nucleon is important, and use the Nachtman scaling variable $ξ$ to relate elastic and inelastic form factors and impose quark-hadron duality constraints at high $Q^2$ where the quark structure dominates. We use the new vector form factors to re-extract updated values of the axial form factor from $\numu$ experiments on deuterium. We obtain an updated world average value from $\numu$d, $\numubar$H and pion electroproduction experiments of $M_{A}$ = $1.014 \pm 0.014 GeV/c^2$. Our parameterizations are useful in modeling $ν$ interactions at low energies (e.g. for $\numu$ oscillations experiments). The predictions for high $Q^2$ can be tested in the next generation electron and $\numu$ scattering experiments.

hep-ex↗

arXiv2007

Modeling Atmospheric Neutrino Interactions: Duality Constrained Parameterization of Vector and Axial Nucleon Form Factors

We present new parameterizations of vector and axial nucleon form factors. We maintain an excellent descriptions of the form factors at low momentum transfers, where the spatial structure of the nucleon is important, and use the Nachtman scaling variable ξto relate elastic and inelastic form factors and impose quark-hadron duality constraints at high momentum transfers where the quark structure dominates. We use the new vector form factors to re-extract updated values of the axial form factor from neutrino experiments on deuterium. We obtain an updated world average value from neutrino and pion electroproduction experiments of M_A = 1.0144 +- 0.0136 GeV/c2. Our parameterizations are useful in modeling atmospheric neutrino interactions (e.g. for neutrino oscillations experiments)

hep-ex↗

arXiv2006

First Measurement of Beam-Recoil Observables Cx and Cz in Hyperon Photoproduction

Spin transfer from circularly polarized real photons to recoiling hyperons has been measured for the reactions $\vecγ+ p \to K^+ + \vecΛ$ and $\vecγ+ p \to K^+ + \vecΣ^0$. The data were obtained using the CLAS detector at Jefferson Lab for center-of-mass energies $W$ between 1.6 and 2.53 GeV, and for $-0.85<\cosθ_{K^+}^{c.m.}< +0.95$. For the $Λ$, the polarization transfer coefficient along the photon momentum axis, $C_z$, was found to be near unity for a wide range of energy and kaon production angles. The associated transverse polarization coefficient, $C_x$, is smaller than $C_z$ by a roughly constant difference of unity. Most significantly, the {\it total} $Λ$ polarization vector, including the induced polarization $P$, has magnitude consistent with unity at all measured energies and production angles when the beam is fully polarized. For the $Σ^0$ this simple phenomenology does not hold. All existing hadrodynamic models are in poor agreement with these results.

nucl-ex↗

arXiv2006

A new parameterization of the nucleon elastic form factors

The nucleon elastic form factors are generally interpreted as a mapping of the charge and magnetic current distributions of the proton and neutron. New high Q^2 measurements have opened up fundamental questions about G_ep that remain to be answered. This talk will summarize current developments surrounding the nucleon form factors and explain why they are important to neutrino physicists. New parameterizations of the nucleon form factors, suitable for use by neutrino physicists, will be introduced and discussed.

hep-ex↗

arXiv2005

Differential Cross Sections for gamma + p --> K+ + Y for Lambda and Sigma0 Hyperons

High-statistics cross sections for the reactions gamma + p --> K^+ + Lambda and gamma + p --> K^+ + Sigma^0 have been measured using CLAS at Jefferson Lab for center-of-mass energies W between 1.6 and 2.53 GeV, and for -0.85 < cos theta_{K^+}^{c.m.}< +0.95. In the K^+ Lambda channel we confirm a resonance-like structure near W=1.9 GeV at backward kaon angles. The position and width of this structure change with angle, indicating that more than one resonance is likely playing a role. The K^+ Lambda channel at forward angles and all energies is well described by a t-channel scaling characteristic of Regge exchange, while the same scaling applied to the K^+ Sigma^0 channel is less successful. Several existing theoretical models are compared to the data, but none provide a good representation of the results.

nucl-ex↗