The a1(1260) as a    Resonance in Nuclear Matter

Abstract

We present a theoretical study of the properties of the a1(1260) axial-vector resonance in a cold nuclear medium. In the vacuum, the a1(1260) resonance is generated dynamically from the interactions of a pseudoscalar and vector meson (ρπ and KK * ) in a coupled channel chiral unitary approach. Medium effects are implemented through the modification of the ρ and π propagators at finite nuclear density from well established microscopic many-body calculations. The in-medium pion spectral function accounts for the coupling to N -hole and ∆-hole excitations including short range correlations, whereas the in-medium ρ incorporates modifications of its virtual pion cloud as well as direct resonance-hole excitations. The resulting in-medium a1(1260) exhibits significant broadening with increasing density as reflected in the ρπ scattering amplitude. The possible relation of our results with partial restoration of chiral symmetry in nuclear matter is discussed in terms of in-medium Weinberg sum rules. * ) See, however, Ref. 13) for an alternative interpretation in terms of the so-called vector manifestation.* * ) Recently a method to test whether dynamically described states can be interpreted as quasibound states of hadrons has been proposed in Ref. 42).

Sum rule analysis of vector and axial-vector spectral functions with excited states in vacuum

“…Rather than using the vacuum spectral function from an effective hadronic model (see, e.g., Refs. [38][39][40][41][42][43][44]), we employ a generic Breit-Wigner form,…”

Theoretical description of the J/ψ→η(η′)hWu1, Sakai2, Oset3 2019Phys. Rev. D11190View full textAdd to dashboardCite

“…The behavior of a 1 ð1260Þ resonance in a nuclear medium from the perspective of its ρπ main component was also studied in Ref. [42].…”

Scattering of unstable particles in a finite volume: The case ofπρscattering and thea1(1260)resonance

“…(See a more extended discussion on this zero in Ref. [44]). From the scattering amplitudes we can get the phase shift, δ, that is well defined for stable particle an which in our normalization it is related to the amplitude via…”