Suppression of the S-wave production of (3/2)^+ + (1/2)^- heavy meson pairs in e^+e^- annihilation

TL;DR

The paper demonstrates that heavy meson pairs involving an excited (3/2)^+ and a ground state (1/2)^- meson cannot be produced in S-wave in e+e- annihilation due to heavy quark spin symmetry, leading to suppressed production near thresholds.

Contribution

It reveals a fundamental suppression mechanism for certain heavy meson pair productions in e+e- annihilation, challenging previous molecular state interpretations.

Findings

S-wave production of these meson pairs is forbidden by heavy quark spin symmetry.

The suppression affects interpretations of the Y(4260) resonance as a D1 D̄ molecular state.

Production yields near thresholds are significantly reduced.

Abstract

The heavy meson-antimeson pairs, where one is an excited $\bigl ({3 \over 2} \bigr) ^+ $ meson and the other is a ground state $\bigl ({1 \over 2} \bigr) ^-$ meson, namely the pairs ($D_1(2420) \bar D$ + c.c.), ($D_1(2420) \bar D^*$ + c.c.), ($D_2(2460) \bar D^*$ + c.c.) in the charm sector and ($B_1(5721) \bar B$ + c.c.), ($B_1(5721) \bar B^*$ + c.c.), ($B_2(5747) \bar B^*$ + c.c.) in the bottom sector, are allowed, by the quantum numbers, to be produced in the $S$ wave in $e^+e^-$ annihilation. We show, however, that such $S$-wave production is forbidden by the heavy quark spin symmetry. Thus the yield of the considered meson pairs in $e^+e^-$ annihilation should be significantly suppressed near the respective thresholds. In our view, this substantially weakens the arguments for considering the Y(4260) charmonium-like resonance as a $D_1 \bar D$ molecular state.