\documentstyle[12pt,epsf]{article}
%\documentstyle[12pt,epsf,epsfig]{article}
\topmargin=-1cm
\oddsidemargin=0cm
\evensidemargin=0cm
\textwidth=16cm
\textheight=24cm
\raggedbottom
\sloppy
\begin{document}
%%% put your own definitions here:
\begin{titlepage}
\pagenumbering{arabic}
\begin{tabular}{l r}
ICHEP'98 \#155 & \hspace{6cm} DELPHI 98-99 CONF 167 \\
Submitted to Pa 5, 7, 9 & 22 June, 1998 \\
\hspace{2.4cm} Pl 7, 11 & \\
\end{tabular}
\vspace*{1.0cm}
\begin{center}
\Huge {\bf The \boldmath $\eta_{c}(2980)$ formation in
two-photon collisions \\at LEP1 energies}\\
\vspace*{0.8cm}
\centerline{\large Preliminary}
\vspace*{1.0cm}
\large {DELPHI Collaboration \\}
\vspace*{0.6cm}
\normalsize {
%===================> DELPHI note author list =====> To be filled <=====%
% {\bf P.~Abreu} $^1$,
% {\bf 2nd author} $^2$,
% {\bf 3rd author} $^{1,3}$,
% {\bf 4th author} $^3$
{B.Muryn} $^1$ and
{G.Polok} $^2$
%========================================================================%
}
\vspace*{1cm}
\end{center}
\begin{abstract}
\noindent
%===================> DELPHI note abstract =====> To be filled <=====%
% The $\eta_{c}(2980)$ production in $\gamma\gamma$ interactions
% its decays into $K^{0}_{s}K\pi$, 4K and
% $\rho_{0}\rho_{0}\rightarrow 4\pi$ has been observed in the data
% taken with the DELPHI detector at LEP1. No direct decay channel
% $\eta_c\rightarrow 4\pi$ has been detected. The two-photon
% radiative width of the $\eta_{c}$ has been determined to be
% $??????\pm ????(stat)\pm ??????(syst)$ keV.
%===================> DELPHI note abstract =====> To be filled <=====%
The $\eta_{c}(2980)$ production in $\gamma\gamma$ interactions via
its decays into $K^{0}_{s}K\pi$, 4K and
$\rho^{0}\rho^{0}\rightarrow 4\pi$ has been observed in the data
taken with the DELPHI detector at LEP1. No direct decay channel
$\eta_c\rightarrow 4\pi$ has been detected. The two-photon
radiative width of the $\eta_{c}$ charmonium state
has been determined providing
$\Gamma_{\gamma\gamma} = 12.2 \pm 2.7 (stat.) \pm 6.3(syst.)keV$
for $\eta_c \rightarrow K^{0}_{s}K\pi$
decay and $\Gamma_{\gamma\gamma} = 6.0 \pm 3.0 (stat.)
\pm 2.5 (syst.)keV$ for
$\eta_c \rightarrow \rho^0\rho^0$. A combined value for
$BR(\eta_c \rightarrow 4K) \times \Gamma_{\gamma\gamma}$ is
also determined yielding $0.94 \pm 0.59 (stat.) \pm 0.69
(syst.)keV$
% pisz keV po kazdej liczbie
% $??????\pm ????(stat)\pm ??????(syst)$ keV.
%=========================================================================%
\end{abstract}
\vspace{\fill}
\begin{center}
Paper submitted to the ICHEP'98 Conference \\
Vancouver, July 22-29
\end{center}
\vspace{\fill}
\par {\footnotesize $^1$ University of Mining and Metallurgy, Cracow, Poland}
\par {\footnotesize $^2$ Institut of Nuclear Physics, Cracow, Poland \\
This work was supported in part by the KBN Grant 2P03B03311}
%\par {\footnotesize $^3$ 3rd Institute address...}
\end{titlepage}
\pagebreak
%==================> DELPHI note text =====> To be filled <======%
\newpage
\vskip 5cm
%\begin{center}
%\large\bf {Introduction}
%\end{center}
\section{Introduction}
Among $\gamma \gamma$ induced final states those with exclusive meson resonance
production play
an important role, since the measurement of the radiative width via corresponding
production cross section provides an information on quark-gluon structure of the
investigated particle. The mesonic resonances built up of heavy quarks are additionally
interesting objects due to a possibility of description of such $\eta_{c}$
bound states by
nonrelativistic models. The very first estimations of the $\eta_c$
partial width $\Gamma_{\gamma\gamma}(\eta_c)$, were obtained from its ratios
to the known widths for $\psi \rightarrow \mu^+\mu^-$ and $\eta_c
\rightarrow
\gamma\gamma$
giving respectively values 8 keV and 4 keV ~\cite{kwong}.
Different models and corrections to them
were applied later providing numbers from 3 to 14 keV, see ~\cite{rein} and
references therein.
Even bigger discrepancy
is observed comparing values obtained by numerous experimental groups. In spite
of large error the results span the $\Gamma_{\gamma\gamma}(\eta_c)$ interval
(4 - 27 ) keV. A precise measurement of two-photon partial width
for charmonium states would provide valuable information on QCD corrections to
$c\bar{c}$ quarkonium. \\
In this paper we report on the production and decays of $\eta_c$
resonance using data collected by DELPHI detector in 1994 and 1995 at $Z^0$ energies,
corresponding to an integrated luminosity of 73 $pb^{-1}$. This resonance state has
been
observed in many experiments where two interacting photons were radiated by electron
and positron beams ~\cite{PLUT} - ~\cite{CLEO2}.
%However there are some
%disagreements
%among results
%presented by different experimental groups.
The superiority of LEP with respect to
previous experiments is higher energy resulting in growth of the production
cross section for this reaction.
Looking for $\eta_c$ production process\\
\begin{equation}
e^{+}e^{-} \rightarrow e^+e^-\eta_c
\end{equation}
\\
we have analysed following exclusive final states:
\\
\begin{equation}
\eta_c \rightarrow K^{0}_{s} K \pi
\end{equation}
\\
\begin{equation}
\eta_c \rightarrow \pi^+ \pi^- \pi^+ \pi^-
\end{equation}
\\
\begin{equation}
\eta_c \rightarrow K^+ K^- K^+ K^-
\end{equation}
\\
\begin{equation}
\eta_c \rightarrow \rho^0 \rho^0
\end{equation}
\newpage
%\begin{center}
%\large\bf {Detector}
%\end{center}
\section{Detector}
A general description of the DELPHI detector can be found elsewhere
~\cite{detdel}. The main
features relevant to this analysis are a particle identification and trigger
quality. Due to relatively low momenta
of the decay products the identification method is mostly based on measurement of
ionization losses (dE/dx) in Time Projection Chamber, TPC. For higher particle
momentum which occurs when $\gamma \gamma$ system is strongly boosted forward/backward
one can
use both, (dE/dx) measurement and liquid Ring Imaging Cherenkov Detector which
assures an identification from 0.7 GeV to about 8 GeV. The particle momenta are
determined from track reconstruction and make use the Vertex Detector, Inner and
Outer Detectors and TPC. For tracks with polar angle smaller than $32^0$ and larger
than
$148^0$ the particles trajectories are determined by Forward Chambers. The
single track trigger
efficiency expressed in terms of transverse track momentum has an influence on,
overall efficiency of final states produced in $\gamma \gamma$ collisions where
hadrons have rather low
momenta. A brief description of a trigger system is presented in
~\cite{trig}.\\
\\
%\begin{center}
%\large\bf {General Data Selection}
%\end{center}
\section{General Data Selection}
Candidates for $\eta_c$ decay channels (2) - (5) were selected by requiring
the following selection criteria:
$\bullet$ No requirement has been made concerning scattered electron and
positron in the final state (no tag mode)
$\bullet$ There are exactly four charged tracks with zero total charge,
outcoming from
interaction region or two tracks originating from primary vertex and two tracks
originating from a secondary vertex. Fictitious tracks resulting from coilling low
momentum particle were not considered in the analysis since they are not
associated with
primary vertex
since their impact parameters measured with respect to the z axis are
greater
than
30 cm
$\bullet$ Only events with a total transverse momentum $({p_t}^2)$ of charged
tracks less than
1.5 $GeV^2$ are accepted\\
$\bullet$ The total detected energy of charged tracks is less than
9 GeV.\\
$\bullet$ There are no particles identified as electrons or muons - they were
removed using standard lepton identification algorithms \\
$\bullet$ The track length is longer than 30 cm \\
$\bullet$ Invariant mass of charged particles is smaller than 10 GeV \\
$\bullet$ Events with neutral tracks energy deposit in the
electromagnetic calorimeter greater than 5 GeV are rejected\\
Additional criteria which are specific for particular channel are discussed in next
section.\\
%\begin{center}
%\large\bf {Analysis}
%\end{center}
\section{Analysis}
In this paper a combined study of four decay channels of the $\eta_c$
resonance has been performed. In $\gamma \gamma$ events almost total available
energy and momentum is
carried
away by electron and positron which are scattered at very small angle. Therefore
the
total transverse momentum $({p_t}^2)$ distribution of the hadronic system is
peaked
as
shown in Fig.1. To suppress some background events which do not originate from
%$\gamma \gamma$ collision
the exclusive process (1)
, ${p_t}^2$ of hadrons is assumed to be smaller
than
0.01 $GeV^2$. \\
In order to calculate the detector efficiency, a Monte Carlo generation program
has been used, with the full kinematics of a system produced in $\gamma \gamma$
interactions. All kinematical variables
necessary for the description of the two-photon processes
were generated using algorithms taken from Vermaseren-Lepage
package ~\cite{Verm}. The matrix element factorized into flux of transverse
photons and
an amplitude describing both the two-photon $\eta_c$ production and its decay has been implemented. The resonance decay into
various modes was generated according to phase space, except for $\eta_c
\rightarrow \rho^0 \rho^0 \rightarrow \pi^+ \pi^- \pi^+ \pi^-$
, where production of an intermediate system of two vector mesons and their decay
into four pion system was generated according
to specific matrix element, ~\cite{mat}. \\
The trigger simulation has been applied to the generation level.
An event was accepted according to some weight calculated on the basis of single track
efficiency. This efficiency has been parametrized as a function of the
transverse momentum $p_t$ of each particle and ranges
from 10 $\%$ at $p_t$= 0.1 GeV to about 95 $\%$ at $p_t$= 2 GeV
~\cite{grzel}.
Due to relatively
large mass of the $\eta_c$ resonant state, the trigger efficiency per event was
about 85 $\%$
for channels with pions and about 60 $\%$ for 4K final state. It
corresponds to single track efficiences, averaged over all available
momenta, 0.4 and 0.2 respectively. \\
The accepted generated events were passed then through a
detector simulation procedure which in case of the $K^{0}_{s} K \pi$ decay, simulated
also the
decay of the $K^{0}_{s}$ in the DELPHI detector. Event selection reconstruction
and analysis proceeded as for
real data leading to the efficiency estimates shown in Fig.2. \\
It has to be mentioned that particle identification was essential for all
analysed
channels and was based on the BBDXID DELPHI - package,
based on dE/dx energy losses
~\cite{ANT}.
\\
\\
%\hspace*{3cm}$\eta_c \rightarrow K^{0}_{s} K \pi$\\
\subsection{$\eta_c \rightarrow K^{0}_{s} K \pi$}
%\\++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%In $\gamma \gamma$ events almost total available energy and momentum is
%carried
%away by electron and positron which are scattered at very small angle. Therefore
%the
%total transverse momentum $({p_t}^2)$ distribution of the hadronic system is
%peaked as
%shown in Fig.1. To suppress some background events which do not originate from
%$\gamma \gamma$ collision, ${p_t}^2$ of hadrons is assumed to be smaller
%than
%0.01 $GeV^2$.
In case of $\eta_c \rightarrow K^{0}_{s} K \pi \rightarrow K \pi \pi \pi$
final state the $K^{0}_{s} \rightarrow {\pi}^+ {\pi}^-$ decay is identified taking
advantage of the relatively large $K^{0}_{s}$ decay length ( c$\tau$ =2.676 cm ).
Therefore, candidates for this decay mode had to have one secondary vertex which
have been reconstructed using an
algorithm which takes pair of oppositely charged tracks intersecting them and
determining a secondary vertex. Both momenta are recalculated with respect to the
new
interaction point and an invariant mass is computed. The resulting $K^{0}_{s}$
candidate
mass distribution is shown in Fig.3 where clear evidence of $K^{0}_{s}$
signal is seen.
There are still two particles which originate from primary interaction region.
One of them must be a candidate for charged kaon whereas second one has to be a pion.
The identification of charged kaon in full range of available momenta is not
always
possible since an identification of charged kaons with momenta below 300 MeV/c is
difficult.
We therefore consider both possibilities of kaon mass assignment and plot the
invariant mass distribution taking into account both
combinations.
Investigations of the Monte-Carlo simulated events based on
an assumption of a phase-space-like $\eta_c$ decay show that
both combinations provide invariant mass distributions
which are peaked at $\eta_c$ mass, resulting in double event counting.
The only difference between those distributions
is that correct entries form a narrower mass signal ($\sigma \sim$ 60 MeV ) as
compared to that
obtained for the uncorrect assignment ($\sigma \sim$ 100 MeV ), which
explains the relatively large observed width of the signal.
The $\eta_c$ invariant mass distributions for correct and uncorrect assignments
in simulated events are presented in Fig.4.
However one has to notice that the above consideration is model
dependent since one does not know the dynamics of the
$\eta_c \rightarrow K^{0}_{s} K \pi \rightarrow K \pi \pi \pi$ decay.\\
The invariant
mass distribution of $K \pi \pi \pi$ system for data obtained requiring only
a reconstructed secondary vertex, i.e. without requiring $K^{\pm}$ or
$K^{0}_{s}$
identification, is shown in Fig.5 where
incontestable signal of about 20 events is seen.
%One has to emphasise that due to
%identification efficiency a simultaneous requirements for kaon identification and
%visibility of secondary vertex with effective mass of $K^{0}_{s}$ results in
%significant
%reduction of the $\eta_c$ signal as could be seen on Fig. .
One might attempt to identify charged kaon simultaneously
applying a tight mass cut on the $K^{0}_{s}$
candidate. We have to stress however that while such cuts really improve
the signal/noise ratio, due to limited K
identification each such requirement reduces the signal by about a factor two
and their combination
provides $\eta_c$ signal
which is reduced by a factor of about four, see Fig.6. A similar effect is
observed for simulated data but only for charged kaon identification.\\
The fitted $\eta_c$ mass is shifted to larger masses by about 2 $\%$.
This effect is seen in all channels studied here and is
probably
caused by the worse reconstruction of low
momentum tracks than higher one.
%\hspace*{3cm}$\eta_c \rightarrow K^+ K^- K^+ K^-$ \\
\subsection{$\eta_c \rightarrow K^+ K^- K^+ K^-$}
%\\===============================================================================
In this decay channel , a requirement has been added that at least three
particles are identified kaons.
Only kaons with high identification probabilities,
corresponding to the so called "standard kaons", were considered for this
analysis.
The invariant mass of the system is presented in Fig.7.
%**********************************************************************
Scatter plot of the effective mass $K^+K^-$ combinations does not show a correlated
intermediate $\phi\phi$ state. \\
%*********************************************************************
Since the average particle c.m.
momentum is particularly low in this channel,
one could expect a strong effect on invariant mass
spectrum resulting from single track efficiency of trigger reproducing a fake signal
due to small efficiency at the threshold . This has been checked on $\eta_c
\rightarrow K^+ K^- K^+ K^-$
events which were generated according to $\gamma \gamma$ flux
(no resonance shape has been assumed). The generated $\gamma \gamma$ invariant mass
system has been decayed according to a phase-space matrix element .
These events were passed through
the trigger and detector simulations. No signal resulting from
the trigger activity on one side and the experimental cuts on the other
was observed in a region of the invariant masses corresponding to
the $\eta_c$ signal. The trigger efficiency
% has also been determined and
%, due to small momenta of charged kaons,
as referenced in section 4 turned out to be 60 $\%$.
\\
%\hspace*{3cm}$\eta_c \rightarrow {\pi^+}{\pi^-}{\pi^+}{\pi^-}$\\
\subsection{$\eta_c \rightarrow {\pi^+}{\pi^-}{\pi^+}{\pi^-}$}
%\\++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
The observation of $\eta_c \rightarrow {\pi^+}{\pi^-}{\pi^+}{\pi^-}$
decay mode reported by numerous
experimental groups seems to be controversial. This decay has been found by MARKIII
~\cite{MARKIII},TASSO ~\cite{TASSO}, L3 ~\cite{L3} (last two did not
distinguish between 4$\pi$ and $\rho^0 \rho^0$ decay channels)
whereas others did not confirm it, providing very often only an upper limit. The good
particle identification is very important since one can confuse the
${\pi^+}{\pi^-}{\pi^+}{\pi^-}$
final state
with a ${K^+} {\pi^-}{\pi^+}{\pi^-}$ decay.
In addition to the general selection and stringent cut on total
transverse momentum , the identification
%procedure based on BBDXID
%Delphi-package ~\cite{ANT}
has been used requiring that all particles are pions.
Only one, well
reconstructed primary vertex is required. The final selected sample consist of
$\sim$ 2000 events,and shows no enhancement around nominal mass of the
$\eta_c$
resonance independently if we include $\rho^0 \rho^0$ sample or not, see
Fig.8.
\\
%\hspace*{3cm}$\eta_c \rightarrow \rho^0 \rho^0 \rightarrow \pi^+ \pi^- \pi^+ \pi^-$
\subsection{$\eta_c \rightarrow \rho^0 \rho^0 \rightarrow \pi^+ \pi^- \pi^+
\pi^-$}
%\\+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A search for an $\eta_c$ resonant state in $\rho^0 \rho^0$ decay
mode was performed in a similar way as the above analysis of the four pion
final state.
The invariant masses for the two possible $\pi^+ \pi^-$ combinations have been
calculated and plotted in a scatter plot of
Fig.9, where distinct enhancement in the $\rho^0 \rho^0$ band is seen,
pointing out
a correlated production of these two vector mesons.
On the other hand, four pion candidates selected from an interval
of (2.8-3.2) GeV and corresponding to the $\eta_c$ signal are correlated
with an enriched $\rho^0\rho^0$ production.\\
In order to select the $\rho^0 \rho^0$ candidates we
required each $\pi^+ \pi^-$ invariant mass to be within 100 MeV of the nominal
$\rho^0$ mass.
For these events the invariant mass of the 4 $\pi$ system has been plotted
providing weak enhancement of about five events shown in Fig.10 .
To check the obtained
$\eta_c$ signal, events off the $\rho^0 \rho^0$ band have been analysed giving
no enhancement. Also combinations of two pions with wrong signs provided a
negative
result.
Relatively huge background, revealing known $\rho^0 \rho^0$ continuum
production, is
observed.
%Another cross check was performed on that sample of suppase $\eta_c$ events. If the
%effective mass of the final 4$\pi$ is within $\eta_c$ we plot effective mass of
%corresponding $\pi^+\pi^-$ combinations. Becouse we see $\rho^0$ signal on that plot
%we can conclude that observed $\eta_c$ is not comming from the background under
%$\rho^0$ what one could expect knowing results from the 4$\pi$ analysis.
The trigger efficiency does not play
a significant role due to relatively high momenta of the $\eta_c$ decay products,
reducing the overall efficiency shown in Fig.2 by only 15 $\%$. \\
%\begin{center}
%\large\bf {Results}
%\end{center}
\section{Results}
%+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Our estimation of the partial two-photon width is obtained using formulae
derived on the assumption that Breit-Wigner distribution can be approximated
by a delta function and does not depend on the total width of
the $\eta_c$ resonance ~\cite{PDG}.
For each channel a fit with a signal mass resolution resulting
from Monte-Carlo simulated events and an exponential or polynomial background has
been performed to obtain the number of observed signal
events.
All values obtained from fit to the $\eta_c$ mass are shifted by
about 60 MeV towards higher value. This shift is under investigation.
This number was an input to the formula quoted above. The systematic error
has been calculated taking into account different binning selections,
fit ranges and background parametrizations
and the large branching ratio uncertainties.\\
%********************************************************
\newpage
Final results for channels with corresponding branching ratios are
presented in \\
Table 1.For the $K^{0}_{s}K\pi$ channel, the result quoted is the
average of the results obtained with and without applying the tight
$K^{0}_{s}$ mass cut. \\
%\\
%For $\eta_c \rightarrow K^{0}_{s}K\pi$ channel where
%BR($\eta_c \rightarrow K^{0}_{s}K\pi$)=0.016
%is taken, one obtains \\
%\hspace*{3cm}$\Gamma_{\gamma\gamma}=17.4 \pm 3.8 (stat.) \pm 6.1
%(syst.)keV$ \\
For $\eta_c \rightarrow 4K $ combined value BR($\eta_c
\rightarrow 4K) \times \Gamma_{\gamma\gamma}$ has been determined
providing 0.94 $\pm$ 0.59 (stat.) $\pm$ 0.69 (syst.)keV .
%Our analysis for four charged kaon decay channel is supported by result
%of ARGUS Collaboration , published in ~\cite{ARGUS} \\
This analysis of the four charged kaons decay channel is in agreement,
within the large errors, with the result of ARGUS Collaboration ,
published in ~\cite{ARGUS}, wich gives 0.231 $\pm$ 0.090 (stat.) $\pm$
0.023 (syst.) keV .\\
%Large systematic error is caused by differences resulting from
%comparison of the efficiences for the 94 and 95 Monte-Carlo data sets.\\
%\\
%Finally assuming BR($\eta_c \rightarrow \rho^0\rho^0$)=0.85 the two photon
%radiative width
%for $\eta_c \rightarrow \rho^0\rho^0 \rightarrow 4\pi$ decay mode has been
%obtained, yielding\\
%\hspace*{3cm}$\Gamma_{\gamma\gamma}= 6.0 \pm 3.2 (stat.) \pm 2.5
%(syst.)keV $\\
%****************************************************************
%The results
%are summarized in Table 1, where, for each channel seperately,
%radiative width of the $\eta_c$ together with
%corresponding efficiences are presented.
%
\clearpage
\begin{thebibliography}{99}
\bibitem{kwong} W.Kwong, J.L.Rosner and C.Quigg,
Ann. Rev. Nucl. Sci. 37 (1987) 325;
W.Kwong et al., Phys. Rev. D37 (1988) 3210;
\bibitem{rein} E.S.Ackleh and T.Barnes, Phys. Rev. D45 (1992) 232;
L.J.Reinders, H.Rubinstein and S.Yazaki, Phys. Rep. 127-1 (1985) 1;
\bibitem{PLUT} PLUTO Collab., Ch.Berger et al., Phys.Lett. B167 (1986) 120;
\bibitem{MARKIII} MARKIII Collab., R.M.Baltrusaitis et al., Phys.Rev. D33
(1986) 629;
\bibitem{R704} R704 Collab., C.Baglin et al., Phys.Lett. B187 (1987) 191;
\bibitem{TPC} TPC/2$\gamma$ Collab., H.Aihara et al., Phys. Rev. Lett.
60 (1988) 2355;
\bibitem{TASSO} TASSO Collab., W.Braunschweig et all.,Z.Phys. C41 (1989)
533;
\bibitem{CLEO} CLEO Collab., W.Y.Chen et al., Phys.Lett. B243 (1990) 169;
\bibitem{DM2} DM2 Collab., D.Bisello et al., NP B350 (1991) 1;
\bibitem{L3} L3 Collab., B.Adeva et al., Phys. Lett. B318 (1993) 578;
\bibitem{ARGUS} ARGUS Collab., H.Albrecht et al., Phys. Lett. B338 (1994)
390;
\bibitem{CLEO2} CLEO Collab., G.Crawford et al. CLEO CONF95-26 (1995);
\bibitem{detdel} DELPHI Collab., P.Abreu et al., Nucl. Instr. and Meth. A 378
(1996) 57-100;
\bibitem{trig} V.Bocci et al., Nucl.Instr. and Meth. A 362 (1995) 361;
\bibitem{ANT} P.Antilogus , DELPHI DST Analysis Libraries Writeup (1997) 1;
\bibitem{Verm} H.Krasemann and J.A.M.Vermaseren, Nucl.Phys. B184 (1981) 265;
J.A.M.Vermaseren, private communication;
\bibitem{mat} M.Poppe, Int. Journ. Modern Phys. A1 (1986) 545 \\ and private
communication;
\bibitem{grzel} K.Grzelak (DELPHI Warsaw )PhD thesis;
\bibitem{PDG} Particle Data Group : Review of Particle Physics.\\
R.M.Barnet et al., Phys. Rev. D54 (1996) 1;
\end{thebibliography}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez3.ps}}
\mbox{\epsfxsize 15cm\epsfbox{fin1.ps}}
\end{center}
\caption{ The hadronic system in the $p_{t}^{2}$ distribution
of events passing the general data selection }
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{sim94n.ps}}
\mbox{\epsfxsize 15cm\epsfbox{fin7.ps}}
\end{center}
\caption{ Efficiency for different channel - year 1994 - not
including trigger efficiency}
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez11.ps}}
\mbox{\epsfxsize 15cm\epsfbox{fin2.ps}}
\end{center}
\caption{ $V^0$ effective mass distribution }
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
\mbox{\epsfxsize 15cm\epsfbox{reszta3.ps}}
\end{center}
\caption{ Results of the analysis of the simulated data}
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez1001.ps}}
\mbox{\epsfxsize 15cm\epsfbox{fin3.ps}}
\end{center}
%\caption{ Effective mass distibutions ${p_t}^2 < .01$ }
\caption{ $K^{0}_{s}K\pi$ effective mass distributions }
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
\mbox{\epsfxsize 15cm\epsfbox{reszta2.ps}}
\end{center}
\caption{ Reduction of the signal and background for $K^{0}_{s}K\pi$ effective
mass distributions by identifying the $K^{0}_{s} , K^{\pm}$, and
both $K^{0}_{s} $ and $K^{\pm}$
}
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez1001.ps}}
\mbox{\epsfxsize 15cm\epsfbox{fin4.ps}}
\end{center}
%\caption{ Effective mass distibutions ${p_t}^2 < .01$ }
\caption{ $K^+K^-K^+K^-$ effective mass distributions }
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez1001.ps}}
\mbox{\epsfxsize 15cm\epsfbox{fin6.ps}}
\end{center}
%\caption{ Effective mass distibutions ${p_t}^2 < .01$ }
\caption{ $\pi^+\pi^-\pi^+\pi^-$ effective mass distributions, 4$\pi$
coming from $\rho^0 \rho^0$ channel
are not included in this plot }
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
\mbox{\epsfxsize 15cm\epsfbox{reszta6.ps}}
\end{center}
\caption{ Effective mass $\pi^+\pi^-$ first combination vs second}
\label{tracks1}
\end{figure}
\begin{figure}[h]
% \vspace{1cm}
\begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez1001.ps}}
\mbox{\epsfxsize 15cm\epsfbox{fin5.ps}}
\end{center}
%\caption{ Effective mass distibutions ${p_t}^2 < .01$ }
\caption{ $\rho^0 \rho^0$ effective mass distributions }
\label{tracks1}
\end{figure}
%\begin{figure}[h]
%% \vspace{1cm}
% \begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez12.ps}}
% \end{center}
%\caption{ $\rho^0$ mass distributions }
%\label{tracks1}
%\end{figure}
%\begin{figure}[h]
%% \vspace{1cm}
% \begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez13.ps}}
% \end{center}
%\caption{ $\rho^0 vs \rho^0$ mass distibutions }
%\label{tracks1}
%\end{figure}
%\begin{figure}[h]
%% \vspace{1cm}
% \begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{prez2.ps}}
% \end{center}
%\caption{ Additional mass distributions }
%\label{tracks1}
%\end{figure}
%\begin{figure}[h]
%% \vspace{1cm}
% \begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{sim95n.ps}}
% \end{center}
%\caption{ Efficiency for different channel - year 1995 }
%\label{tracks1}
%\end{figure}
%
%
%\begin{figure}[h]
%% \vspace{1cm}
% \begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{reszta1.ps}}
% \end{center}
%\caption{ Dod.1}
%\label{tracks1}
%\end{figure}
%\begin{figure}[h]
%% \vspace{1cm}
% \begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{reszta4.ps}}
% \end{center}
%\caption{ Dod.4}
%\label{tracks1}
%\end{figure}
%\begin{figure}[h]
% \vspace{1cm}
% \begin{center}
% \mbox{\epsfxsize 15cm\epsfbox{reszta5.ps}}
% \end{center}
%\caption{ Dod.5}
%\label{tracks1}
%\end{figure}
%\newpage
%\begin{table}
%\vspace{5cm}
%\centering
%\begin{tabular}{|l|l|l|l|l|l|r|} \hline
% & & & & & & \\
%Channel & $BR$ & $Eff.$ &\# Events & $\Gamma_{\gamma \gamma}$ & Stat. &
%Syst. \\
% & [\%] & [\%] & & [keV] & [keV] & [keV] \\
% & & & & & & \\ \hline
% & & & & & & \\
%$\eta_c\rightarrow K^{0}K\pi$ & 1.5 & & 20 & &
% & \\
% & & & & & & \\ \hline
% & & & & & & \\
%$\eta_c\rightarrow 4K$ & 2.1 & & 6.5 & & &
% \\
% & & & & & & \\ \hline
% & & & & & & \\
%$\eta_c\rightarrow \rho^{0}\rho^{0}$ & .85 & & 8.1 &
% & & \\
% & & & & & & \\ \hline
%\end{tabular}
\newpage
\begin{table}
\vspace{5cm}
\centering
\begin{tabular}{|l|l|l|l|l|l|r|} \hline
& & & & \\
Channel & $BR$ & $\Gamma_{\gamma \gamma}$ & Stat. &
Syst. \\
& & $ $ & error &
error \\
& [\%] & [keV] & [keV] & [keV] \\
& & & & \\ \hline
& & & & \\
$\eta_c\rightarrow K^{0}K\pi$ & 1.6 & 12.2 &
2.7 & 6.3 \\
& & & & \\ \hline
& & & & \\
$\eta_c\rightarrow \rho^{0}\rho^{0}$ & .85 &
6.0 & 3.0 & 2.5 \\
& & & & \\ \hline
\end{tabular}
\vspace{5cm}
\caption{ Final results }
\end{table}
\end{document}
\end{document}