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arXiv · 1107.0254

Bound state nature of the exotic Z_b states

Martin Cleven·Feng-Kun Guo·Christoph Hanhart·Ulf-G. Meißner
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Abstract

The assumption that the newly observed charged bottomonia states Z_b(10610) and Z_b(10650) are of molecular nature is confronted with the measured invariant mass distributions for the transitions of the Upsilon(5S) to the final states h_b pi^+ pi^- and h_b(2P) pi^+ pi^-. It is shown that the assumption that the Z_b(10610) and Z_b(10650) are B\bar B^*+{\rm c.c.} and B^*\bar B^* bound states, respectively, with very small binding energies is consistent with the data. The calculation is based on a power counting for bottom meson loops, which is explicitly given up to two-loop in the framework of a nonrelativistic effective field theory. We also show that if the Z_b states are of molecular nature, then the data should not be analyzed by using a Breit-Wigner parametrization.

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Martin Cleven, Feng-Kun Guo, Christoph Hanhart, Ulf-G. Meißner. 2011-07-01. Bound state nature of the exotic Z_b states. https://doi.org/10.1140/epja/i2011-11120-6

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