\newcommand{\ksks}{$K_S^0 K_S^0$\xspace}
\newcommand{\Ks}{$K_S^0$\xspace}
\newcommand{\ffa}{$f_{2}(1270)/a_{2}^{0}(1320)$\xspace}
\newcommand{\ffb}{$f_{2}^{'}(1525)$\xspace}
\newcommand{\ffc}{$f_{0}(1710)$\xspace}
 
Title:
Inclusive \ksks resonance production in $ep$ collisions at HERA

Speaker:
Changyi Zhou
on behalf of ZEUS Collaboration
McGill University
czhou@physics.mcgill.ca


The lightest glueball is predicted to have $J^{PC}=0^{++}$ \cite{1 and 2}
and a mass in the range 1450--1750 MeV.
Thus, it can mix with $q\overline{q}$ states
from the scalar meson nonet, which have
$I=0$ and similar masses.
In the literature, the
state \ffc is  frequently considered to be a state
with a possible glueball or tetraquark composition (see for example the reviews
\cite{Klempt:2007cp,*Oller}).

Inclusive \ksks production in $ep$ collisions dominated by photoproduction with
exchanged photon virtuality, $Q^2$,  below 1 $\gev^2$.
at HERA has been studied with the ZEUS detector using an integrated luminosity of 0.5 fb-1 from "HERAI and HERAII" combined. \Ks mesons were identified through the charged-decay mode,
$K_s^0 \to\pi^{+}\pi^{-}$, and reconstructed with various track quality cuts for selection. The \ksks invariant mass distribution was reconstructed by combining two \Ks candidates.
 Enhancements in the mass spectrum have been observed attributed to the production of f2(1270)/a02(1320), f'2(1525) and f0(1710). The three states $f_{2}(1270)$, $a_{2}^{0}(1320)$ 
and 
\ffb are all of $J^P = 2^+$ and so their interference is seen in the total 
cross-section. The intensity is the modulus-squared of the sum of these 
three amplitudes plus the incoherent addition of \ffc and the 
non-resonant background. The amplitudes for $f_{2}(1270)$, $a_{2}^{0}(1320)$
and \ffb production were 
fixed at the SU(3) ratios of $5:-3:2$ as expected for production via an 
electromagnetic process~\cite{Althoff,lipkin}. 
Very competitive measurements on peak position and width for \ffb and \ffc are done with interference fit and the overall fit describes the data very well. Complete systematic checks have been performed. The final values with statistical and systematical uncertainties were compared well with the PDG values~\cite{7.PDG}.

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