Nuclear Theory·nucl-th

Friday·July 29, 2022

11 papers—8 primary·3 cross-listed

09
[Submitted on 27 Jul 2022] (cross-list from hep-ph)
Contact interaction analysis of octet baryon axialvector and pseudoscalar form factors
Peng Cheng🇨🇳 · Fernando E. Serna🇨🇴 · Zhao-Qian Yao🇨🇳 · Chen Chen🇨🇳 · Zhu-Fang Cui🇨🇳 · Craig D. Roberts🇨🇳
Octet baryon axial, induced pseudoscalar, and pseudoscalar form factors are computed using a symmetry-preserving treatment of a vector $\times$ vector contact interaction (SCI), thereby unifying them with an array of other baryon properties and analogous treatments of semileptonic decays of pseudoscalar mesons. The baryons are treated as quark--plus--interacting-diquark bound states, whose structure is obtained by solving a Poincaré-covariant Faddeev equation. The approach is marked by algebraic simplicity, involves no free parameters, and since it is symmetry preserving, all consequences of partial conservation of the axial current are manifest. It is found that SCI results are consistent with only small violations of SU $(3)$ -flavour symmetry, an outcome which may be understood as a dynamical consequence of emergent hadron mass. The spin-flavour structure of the Poincaré-covariant baryon wave functions is expressed in the presence of both flavour-antitriplet scalar diquarks and flavour-sextet axialvector diquarks and plays a key role in determining all form factors. Considering neutral axial currents, SCI predictions for the flavour separation of octet baryon axial charges and, therefrom, values for the associated SU $(3)$ singlet, triplet, and octet axial charges are obtained. The results indicate that at the hadron scale, $ζ_{H}$ , valence degrees-of-freedom carry roughly 50% of an octet baryon's total spin. Since there are no other degrees-of-freedom at $ζ_{H}$ , the remainder may be associated with quark+diquark orbital angular momentum.
Comments:
20 pages, 6 figures, 15 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2207.13811 [pdf]
PRD(2022)·26 citations
10
[Submitted on 28 Jul 2022] (cross-list from hep-ph)
Possible $Λ_{c} Λ ˉ_{c}$ molecular states and their productions in nulceon-antinulceon collision
Lin-Qing Song🇨🇳 · Dan Song🇨🇳 · Jun-Tao Zhu🇨🇳 · Jun He🇨🇳
In this work, a study of possible molecular states from the $Λ_{c} Λ ˉ_{c}$ interaction and their productions in nucleon-antinucleon collision is performed in a quasipotential Bethe-Salpeter equation approach. Two bound states with quantum numbers $J^{P C} = 0^{-+}$ and $1^{--}$ are produced with almost the same binding energy from the $Λ_{c} Λ ˉ_{c}$ interaction which is described by the light meson exchanges. However, the result does not support the assignment of experimentally observed $Y (4630)$ as a $Λ_{c} Λ ˉ_{c}$ molecular state because it is hard to obtain a peak near experimental mass of the $Y (4630)$ which is far above the $Λ_{c} Λ ˉ_{c}$ threshold. The possibility to search these states in nucleon-antinucleon collision is studied by including couplings to $N N ˉ$ and $D^{(*)} D ˉ^{(*)}$ channels. The peaks can be found obviously near the $Λ_{c} Λ ˉ_{c}$ threshold in the $D^{*} D ˉ^{*}$ channel at an order of amplitude of 10 $μ$ b. Too small width of state with $0^{-+}$ may lead to the difficulty to be observed in experiment. Based on the results in the current work, search for the $Λ_{c} Λ ˉ_{c}$ molecular state with $1^{--}$ is suggested in process $N N ˉ \to D^{*} D ˉ^{*}$ , which is accessible at $P ˉ ANDA$ .
Comments:
4 pages, 4 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2207.13957 [pdf]
PLB(2022)·15 citations
11
[Submitted on 28 Jul 2022] (cross-list from hep-ph)
Sensitivity of the $η^{(')} \to π^{0} γ γ$ and $η^{'} \to η γ γ$ decays to a sub-GeV leptophobic $U (1)_{B}$ boson
Rafel Escribano🇪🇸 · Sergi Gonzàlez-Solís🇺🇸 · Emilio Royo🇪🇸
The sensitivity of the rare decays $η^{(')} \to π^{0} γ γ$ and $η^{'} \to η γ γ$ to signatures of a leptophobic $B$ boson in the MeV-GeV mass range is analyzed in this work. By adding an explicit $B$ -boson resonance exchange, $η \to B γ \to π^{0} γ γ$ , to the Standard Model contributions from vector and scalar meson exchanges, and employing experimental data for the associated branching ratios, it allows us to improve the current constraints on the $B$ -boson mass $m_{B}$ and coupling to Standard Model particles $α_{B}$ . From these constraints and the analysis of the available experimental $γ γ$ invariant mass distribution, we show that a $B$ -boson signature in the resonant mass range $m_{π^{0}} ≲ m_{B} ≲ m_{η}$ is strongly suppressed and would be very difficult to experimentally identify, assuming that the leptophobic $B$ boson only decays to Standard Model particles. In contrast, the limits outside this mass window are less stringent and the corresponding $t$ - and $u$ -channel signatures may still be observable in the data, as it occurs with the nonresonant Standard Model $ρ$ , $ω$ and $ϕ$ meson exchanges. In addition, we make use of experimental data from the $η^{'} \to π^{0} γ γ$ and $η^{'} \to η γ γ$ decays to explore larger $B$ -boson masses. Our results are relevant for the $B$ -boson search programs at existing and forthcoming light-meson facilities, such as KLOE(-II) and Jefferson Lab Eta Factory experiments.
Comments:
15 pages, 12 figures, 1 table; v2 includes a discussion of the uncertainty of the Standard Model estimate and an improvement in the overall presentation
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2207.14263 [pdf]
PRD(2022)·12 citations

Affiliations

first authorsco-authorsvia INSPIRE

Contact interaction analysis of octet baryon axialvector and pseudoscalar form factors

Possible Λc​Λˉc​ molecular states and their productions in nulceon-antinulceon collision

Sensitivity of the η(′)→π0γγ and η′→ηγγ decays to a sub-GeV leptophobic U(1)B​ boson

Affiliations

Possible $Λ_{c} Λ ˉ_{c}$ molecular states and their productions in nulceon-antinulceon collision

Sensitivity of the $η^{(')} \to π^{0} γ γ$ and $η^{'} \to η γ γ$ decays to a sub-GeV leptophobic $U (1)_{B}$ boson