Lowest-lying [formula omitted] and [formula omitted][formula omitted] resonances: From the strange to the bottom sectors

Abstract

We present a detailed study of the lowest-lying 12− and 32−ΛQ resonances both in the heavy quark (bottom and charm) and the strange sectors. We have paid special attention to the interplay between the constituent quark-model and chiral baryon–meson degrees of freedom, which are coupled using a unitarized scheme consistent with leading-order heavy quark symmetries. We show that the Λb(5912) [JP=1/2−], Λb(5920) [JP=3/2−] and the Λc(2625) [JP=3/2−], and the Λ(1520) [JP=3/2−] admitting larger breaking corrections, are heavy-quark spin-flavor siblings. They can be seen as dressed quark-model states with ΣQ(∗)π molecular components of the order of 30%. The JP=12−Λc(2595) has, however, a higher molecular probability of at least 50%, and even values greater than 70% can be easily accommodated. This is because it is located almost on top of the threshold of the Σcπ pair, which largely influences its properties. Although the light degrees of freedom in this resonance would be coupled to spin-parity 1− as in the Λb(5912), Λb(5920) and Λc(2625), the Λc(2595) should not be considered as a heavy-quark spin-flavor partner of the former ones. We also show that the Λ(1405) chiral two-pole pattern does not have analogs in the 12− charmed and bottomed sectors, because the ND(∗) and NB¯(∗) channels do not play for heavy quarks the decisive role that the NK¯ does in the strange sector, and the notable influence of the bare quark-model states for the charm and bottom resonances. Finally, we predict the existence of two Λb(6070) and two Λc(2765) heavy-quark spin and flavor sibling odd parity states.