Speaker
Prof.
pedro gonzález
(Dep. Física Teórica and IFIC, Fac. Física, Univ. Valencia)
Description
The explanation of the large $e^{+}e^{-}\rightarrow\pi^{+}\pi^{-}%
\Upsilon\left(ns\right) $ $\left( n=1,2,3\right) $ widths at
$\sqrt
{s}=10.866\pm0.002$ GeV near the $\Upsilon\left( 10860\right) $
peak [1], about two orders of magnitude larger than those for $\Upsilon\left(ns\right)$$\rightarrow\pi^{+}\pi^{-}%$
$\Upsilon\left(1s\right)$
$\left( n=2,3,4\right) ,$ has been in recent years a
theoretical challenge (see for example [2]) despite the quite natural
(according to its mass) asignment of
$\Upsilon\left( 10860\right) $ to the
standard $\Upsilon\left( 5s\right) $ quark model state. Moreover, the
experimental production rates of
$\Upsilon\left( 10860\right) \rightarrow
\pi^{+}\pi^{-}h_{b}\left( np\right) $
$\left( n=1,2\right) $ and
$\Upsilon\left( 10860\right) \rightarrow\pi^{+}%
\pi^{-}\Upsilon\left( ns\right) $ are of the same order of magnitude whereas the calculated
$\Upsilon\left( 5s\right) \rightarrow
\pi^{+}\pi^{-}h_{b}\left( np\right) $ rates are suppressed
against
$\Upsilon\left( 5s\right) \rightarrow\pi^{+}\pi^{-}\Upsilon\left(
ns\right) $ ones by Heavy Quark Spin Symmetry.
We show that a good quantitative description of the
$\Upsilon\left(
10860\right) $ mass, its
$e^{+}e^{-}$ leptonic width and its
$\pi^{+}\pi
^{-}\Upsilon\left( ns\right) $ production rates, as well as a qualitative
understanding of its
$\pi^{+}\pi^{-}h_{b}\left( np\right) $ production rates can be obtained under the assumption that
$\Upsilon\left(
10860\right) $ is a mixture of the conventional
$\Upsilon\left( 5s\right) $ quark model state with a small proportion of the lowest
$1^{--}$ hybrid state [3].
[1] M. Tanabashi et al. (Particle Data Group (PDG)), Phys. Rev. D98, 030001 (2018).
[2] L. Olsen, T. Skwarnicki, and D. Zieminska, Rev.Mod.Phys.90,015003 (2018).
[3] R. Bruschini and P. Gonzalez, Pys. Lett. B791,409 (2019).
Primary author
Prof.
pedro gonzález
(Dep. Física Teórica and IFIC, Fac. Física, Univ. Valencia)
Co-author
Mr
Roberto Bruschini
(IFIC, CSIC - Univ. Valencia)
