Nuclear Theory·nucl-th

Monday·July 31, 2017

9 papers—5 primary·4 cross-listed

06
[Submitted on 26 Jul 2017] (cross-list from hep-ph)
Quarkonium Polarization and the Long Distance Matrix Elements Hierarchies using Jet Substructure
Lin Dai🇺🇸 · Prashant Shrivastava🇺🇸
We investigate the quarkonium production mechanisms in jets at the LHC, using the Fragmenting Jet Functions (FJF) approach. Specifically, we discuss the jet energy dependence of the $J / ψ$ production cross section at the LHC. By comparing the cross sections for the different NRQCD production channels ( $^{1} S_{0}^{[8]}$ , $^{3} S_{1}^{[8]}$ , $^{3} P_{J}^{[8]}$ , and $^{3} S_{1}^{[1]}$ ), we find that at fixed values of energy fraction $z$ carried by the $J / ψ$ , if the normalized cross section is a decreasing function of the jet energy, in particular for $z > 0.5$ , then the depolarizing $^{1} S_{0}^{[8]}$ must be the dominant channel. This makes the prediction made in [Baumgart et al., JHEP 1411, 003 (2014)] for the FJF's also true for the cross section. We also make comparisons between the long distance matrix elements extracted by various groups. This analysis could potentially shed light on the polarization properties of the $J / ψ$ production in high $p_{T}$ region.
Comments:
13 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1707.08629 [pdf]
PRD(2017)·10 citations
07
[Submitted on 27 Jul 2017] (cross-list from hep-lat)
Chiral symmetry constraints on resonant amplitudes
Peter C. Bruns🇩🇪 · Maxim Mai🇺🇸
We discuss the impact of chiral symmetry constraints on the quark-mass dependence of meson resonance pole positions, which are encoded in non-perturbative parametrizations of meson scattering amplitudes. Model-independent conditions on such parametrizations are derived, which are shown to guarantee the correct functional form of the leading quark-mass corrections to the resonance pole positions. Some model amplitudes for $π π$ scattering, widely used for the determination of $ρ$ and $σ$ resonance properties from results of lattice simulations, are tested explicitly with respect to these conditions.
Comments:
Version accepted by Phys. Lett. B. Supplemental material include additional proofs
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1707.08983 [pdf]
PLB(2018)·15 citations
08
[Submitted on 28 Jul 2017] (cross-list from hep-ph)
The nucleon as a test case to calculate vector-isovector form factors at low energies
Stefan Leupold (UU)🇸🇪
Extending a recent suggestion for hyperon form factors to the nucleon case, dispersion theory is used to relate the low-energy vector-isovector form factors of the nucleon to the pion vector form factor. The additionally required input, i.e. the pion-nucleon scattering amplitudes are determined from relativistic next-to-leading-order (NLO) baryon chiral perturbation theory including the nucleons and optionally the Delta baryons. Two methods how to include pion rescattering are compared: (a) solving the Muskhelishvili-Omnes (MO) equation and (b) using an N/D approach. It turns out that the results differ strongly from each other. Furthermore the results are compared to a fully dispersive calculation of the (subthreshold) pion-nucleon amplitudes based on Roy-Steiner (RS) equations. In full agreement with the findings from the hyperon sector it turns out that the inclusion of Delta baryons is not an option but a necessity to obtain reasonable results. The magnetic isovector form factor depends strongly on a low-energy constant of the NLO Lagrangian. If it is adjusted such that the corresponding magnetic radius is reproduced, then the results for the corresponding pion-nucleon scattering amplitude (based on the MO equation) agree very well with the RS results. Also in the electric sector the Delta degrees of freedom are needed to obtain the correct order of magnitude for the isovector charge and the corresponding electric radius. Yet quantitative agreement is not achieved. If the subtraction constant that appears in the solution of the MO equation is not taken from nucleon+Delta chiral perturbation theory but adjusted such that the electric radius is reproduced, then one obtains also in this sector a pion-nucleon scattering amplitude that agrees well with the RS results.
Comments:
12 pages, discussion and references added, results unchanged
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1707.09210 [pdf]
EPJA(2018)·84 citations
09
[Submitted on 28 Jul 2017] (cross-list from hep-ph)
Covariant spectator theory of quark-antiquark bound states: Mass spectra and vertex functions of heavy and heavy-light mesons
Sofia Leitão🇵🇹 · Alfred Stadler🇵🇹 · M. T. Peña🇵🇹 · Elmar P. Biernat🇵🇹
We use the covariant spectator theory with an effective quark-antiquark interaction, containing Lorentz scalar, pseudoscalar, and vector contributions, to calculate the masses and vertex functions of, simultaneously, heavy and heavy-light mesons. We perform least-square fits of the model parameters, including the quark masses, to the meson spectrum and systematically study the sensitivity of the parameters with respect to different sets of fitted data. We investigate the influence of the vector confining interaction by using a continuous parameter controlling its weight. We find that vector contributions to the confining interaction between 0% and about 30% lead to essentially the same agreement with the data. Similarly, the light quark masses are not very tightly constrained. In all cases, the meson mass spectra calculated with our fitted models agree very well with the experimental data. We also calculate the mesons wave functions in a partial wave representation and show how they are related to the meson vertex functions in covariant form.
Comments:
23 pages, 10 figures. Minor corrections of previous version. To be published in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1707.09303 [pdf]
PRD(2017)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE

Quarkonium Polarization and the Long Distance Matrix Elements Hierarchies using Jet Substructure

Chiral symmetry constraints on resonant amplitudes

The nucleon as a test case to calculate vector-isovector form factors at low energies

Covariant spectator theory of quark-antiquark bound states: Mass spectra and vertex functions of heavy and heavy-light mesons

Affiliations