Nuclear Theory·nucl-th

Friday·June 14, 2019

5 papers—4 primary·1 cross-listed

01
[Submitted on 12 Jun 2019]
Nucleon Resonances with Hidden Charm in $γ p$ reactions
Jia-Jun Wu🇨🇳 · T.-S. H. Lee🇺🇸 · Bing-Song Zou🇨🇳
The excitations of nucleon resonances with hidden charm, $N_{c c ˉ}^{*}$ , in the $γ p$ reactions are investigated by using the predictions from the available meson-baryons (MB) coupled-channel models. For the $γ p \to J / ψ p$ process, we first calculate the Pomeron-exchange amplitudes with the parameters determined from fitting the available total cross section data up to invariant mass $W = 300$ GeV. We then add the resonant amplitudes to examine the effects of $N_{c c ˉ}^{*}$ excitations on the cross sections of $γ p \to J / ψ p$ in the near threshold energy region. The $N_{c c ˉ}^{*} \to M B$ transition matrix elements are determined from the partial decay widths predicted by the meson-baryons coupled-channel models. The $γ p \to N_{c c ˉ}^{*}$ transition amplitudes are calculated from the Vector Meson Dominance (VMD) model. The total $γ p \to J / ψ p$ amplitudes then depend on an off-shell form factor, parameterized as $F_{V} (q^{2}) = Λ^{4} / (Λ^{4} + (q^{2} - m_{V}^{2})^{2})$ with $Λ = 550$ MeV. We then demonstrate that the $N_{c c ˉ}^{*}$ can be most easily identified in the differential cross sections at large angles of outgoing $J / ψ$ where the contribution from Pomeron-exchange becomes negligible. With the same VMD model and the same coupled-channel models of $N_{c c ˉ}^{*}$ , we also calculate the resonant amplitudes for the $γ p \to V p \to N_{c c ˉ}^{*} \to D ˉ^{0} Λ_{c}^{+} (D ˉ^{* 0} Λ_{c}^{+})$ processes. By adding the non-resonant amplitudes due to the exchange of $D ˉ^{* 0}$ ( $D ˉ^{0})$ , we then predict the cross sections of $γ p \to D ˉ^{0} Λ_{c}^{+} (D ˉ^{* 0} Λ_{c}^{+})$ for additional experimental tests of the available meson-baryon coupled-channel models of $N_{c c ˉ}^{*}$ .
Comments:
23 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1906.05375 [pdf]
PRC(2019)·61 citations
02
[Submitted on 12 Jun 2019]
Prompt Neutron Multiplicity Distributions Inferred from $γ$ -ray and Fission Fragment Energy Measurements
A.E. Lovell · I. Stetcu · P. Talou · G. Rusev · M. Jandel
We propose a novel method to extract the prompt neutron multiplicity distribution, $P (ν)$ , in fission reactions based on correlations between prompt neutrons, $γ$ rays, and fragment kinetic energy arising from energy conservation. In this approach, only event-by-event measurements of the total $γ$ -ray energy released as a function of the total kinetic energy (TKE) of the fission fragments are performed, and no neutron detection is required. Using the $CGMF$ fission event generator, we illustrate the method and explore the accuracy of extracting the neutron multiplicity distribution when taking into account the energy resolution and calibration of the energy measurements. We find that a TKE resolution of under 2 MeV produces reasonably accurate results, independent of typical $γ$ -ray energy measurement resolution.
Comments:
5 pages, 4 figures, published in PRC
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1906.05418 [pdf]
PRC(2019)·0 citations
03
[Submitted on 13 Jun 2019]
Do Delta Baryons Play a Role in Neutron Stars?
T. F. Motta🇦🇺 · A. W. Thomas🇦🇺 · P. A. M. Guichon🇫🇷
The presence of exotic hadrons, such as hyperons and $Δ$ isobars, in the dense nuclear matter in their cores has been shown to produce important changes in the properties of neutron stars. Within the quark-meson coupling model, we show that the many-body forces generated by the change in the internal quark structure of the baryons in the strong scalar mean fields generated in dense nuclear matter prohibit the appearance of $Δ$ isobars.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1906.05459 [pdf]
PLB(2020)·33 citations
04
[Submitted on 13 Jun 2019]
Polarization of tau in quasielastic (anti)neutrino scattering: the role of spectral functions
J.E. Sobczyk🇪🇸 · N. Rocco🇺🇸 · J.Nieves🇪🇸
We present a study of the $τ$ polarization in charged-current quasielastic (anti)neutrino-nucleus scattering. The spectral function formalism is used to compute the differential cross section and the polarization components for several kinematical setups, relevant for neutrino-oscillation experiments. The effects of the nuclear corrections in these observables are investigated by comparing the results obtained using two different realistic spectral functions, with those deduced from the relativistic global Fermi gas model, where only statistical correlations are accounted for. We show that the spectral functions, although they play an important role when predicting the differential cross sections, produce much less visible effects on the polarization components of the outgoing $τ$ .
Comments:
16 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1906.05656 [pdf]
PRC(2019)·23 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nucleon Resonances with Hidden Charm in γp reactions

Prompt Neutron Multiplicity Distributions Inferred from γ-ray and Fission Fragment Energy Measurements

Do Delta Baryons Play a Role in Neutron Stars?

Polarization of tau in quasielastic (anti)neutrino scattering: the role of spectral functions

Affiliations

Nucleon Resonances with Hidden Charm in $γ p$ reactions

Prompt Neutron Multiplicity Distributions Inferred from $γ$ -ray and Fission Fragment Energy Measurements