\documentclass{article}
\usepackage{graphicx}

\begin{document}

%\begin{frontmatter}
\title{Performance of MRPC telescopes of the EEE Project}

\author{EEE Collaboration}
\maketitle
%%%%\author[1,11]{D. De Gruttola}
%%%%%\cortext[email]{\it{email address}: daniele.de.gruttola@cern.ch}
%%%%%\ead{daniele.de.gruttola@cern.ch}
%%%%\author[1,2]{M. Abbrescia}
%%%%\author[1,3]{C. Avanzini}
%%%%\author[1,3]{L. Baldini}
%%%%\author[1,4]{R. Baldini Ferroli}
%%%%\author[1,3]{G. Batignani}
%%%%\author[4]{G. Bencivenni}
%%%%\author[1,5]{E. Bossini}
%%%%\author[1,6]{E. Bressan}
%%%%\author[7]{A. Chiavassa}
%%%%\author[1,8]{C. Cical\`o}
%%%%\author[1,6]{L. Cifarelli}
%%%%\author[9]{E. Coccia}
%%%%\author[1,10]{A. Corvaglia}
%%%%\author[1,11]{S. De Pasquale}
%%%%\author[12]{A. Di Giovanni}
%%%%\author[12]{M. D$\textquoteright$Incecco}
%%%%\author[4]{M. Dreucci}
%%%%\author[4]{F.L. Fabbri}
%%%%\author[13]{E. Fattibene}
%%%%\author[13]{A. Ferraro}
%%%%\author[14,15]{R. Forster}
%%%%\author[16]{V. Frolov}
%%%%\author[1,7]{P. Galeotti}
%%%%\author[1,6]{M. Garbini}
%%%%\author[17]{G. Gemme}
%%%%\author[1,7]{I. Gnesi}
%%%%\author[1,17]{S. Grazzi}
%%%%\author[12]{C. Gustavino}
%%%%\author[1,6,15]{D. Hatzifotiadou}
%%%%\author[1,18]{P. La Rocca}
%%%%\author[7]{A. Maggiora}
%%%%\author[13]{G. Maron}
%%%%\author[13]{B. Martelli}
%%%%\author[19]{M. N. Mazziotta}
%%%%\author[1,4,9]{S. Miozzi}
%%%%\author[1,13]{F. Noferini}
%%%%\author[9,20]{F. Nozzoli}
%%%%\author[1,10]{M. Panareo}
%%%%\author[1,10]{M. P. Panetta}
%%%%\author[1,5]{R. Paoletti}
%%%%\author[1,17]{L. Perasso}
%%%%\author[1,3]{F. Pilo}
%%%%\author[1,7]{G. Piragino}
%%%%\author[1,18]{F. Riggi}
%%%%\author[1]{G.C. Righini}
%%%%\author[14,15]{A. R. Rodriguez}
%%%%\author[1,6]{G. Sartorelli}
%%%%\author[6]{E. Scapparone}
%%%%\author[1,21]{M. Schioppa}
%%%%\author[1,3]{A. Scribano}
%%%%\author[6]{M. Selvi}
%%%%\author[7]{S. Serci}
%%%%\author[8]{E. Siddi}
%%%%\author[17]{S. Squarcia}
%%%%\author[17]{M. Taiuti}
%%%%\author[3]{G. Terreni}
%%%%\author[13]{M. C. Vistoli}
%%%%\author[12]{L. Votano}
%%%%\author[6,15]{M.C.S. Williams}
%%%%\author[13]{G. Zani}
%%%%\author[1,6,15]{A. Zichichi}
%%%%\author[1,15]{R. Zouyevski}

%%%%\address[1]{Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi, Roma, Italy}
%%%%\address[2]{INFN and Dipartimento di Fisica, Universit\`a di Bari, Bari, Italy}
%%%%\address[3]{INFN and Dipartimento di Fisica, Universit\`a di Pisa, Pisa, Italy}
%%%%\address[4]{INFN, Laboratori Nazionali di Frascati, Frascati (RM), Italy}
%%%%\address[5]{INFN Gruppo Collegato di Siena and Dipartimento di Fisica, Università di Siena, Siena, Italy}
%%%%\address[6]{INFN and Dipartimento di Fisica, Universit\`a di Bologna, Bologna, Italy}
%%%%\address[7]{INFN and Dipartimento di Fisica, Universit\`a di Torino, Torino, Italy}
%%%%\address[8]{INFN and Dipartimento di Fisica, Universit\`a di Cagliari, Cagliari, Italy}
%%%%\address[9]{INFN and Dipartimento di Fisica, Universit\`a di Roma Tor Vergata, Roma, Italy}
%%%%\address[10]{INFN and Dipartimento di Matematica e Fisica, Universit\`a del Salento, Lecce, Italy}
%%%%\address[11]{INFN and Dipartimento di Fisica, Universit\`a di Salerno, Salerno, Italy}
%%%%\address[12]{INFN, Laboratori Nazionali del Gran Sasso, Assergi (AQ), Italy}
%%%%\address[13]{INFN-CNAF, Bologna, Italy}
%%%%\address[14]{ICSC World Laboratory, Erice, Italy}
%%%%\address[15]{CERN, Geneva, Switzerland}
%%%%\address[16]{JINR Joint Institute for Nuclear Research, Dubna, Russia}
%%%%\address[17]{INFN and Dipartimento di Fisica, Universit\`a di Genova, Genova, Italy}
%%%%\address[18]{INFN and Dipartimento di Fisica e Astronomia, Universit\`a di Catania, Catania, Italy}
%%%%\address[19]{INFN, sezione di Bari, Bari, Italy}
%%%%\address[20]{ASI Science Data Center, Roma, Italy}
%%%%\address[21]{Dipartimento di Fisica, Unversità della Calabria, Cosenza, Italy}

\begin{abstract}
%% Text of abstract

The muon telescopes of the Extreme Energy Events (EEE) Project \cite{eee} are based on
Multigap Resistive Plate Chamber (MRPC) technology. 
The EEE array is composed, so far, of 47 telescopes, each made of
three MRPC planes, spanning more than 10 degrees in latitude and 11
in longitude, organized in clusters and single telescope stations 
distributed all over the Italian territory and installed in High Schools.
The study of Extensive Air Showers (EAS) requires excellent
performance in terms of time and spatial resolution, efficiency and tracking capability.
The data from two recent coordinated data taking periods have been
used to measure these quantities and the results are described,
together with a comparison with results from beam test performed in
2006 at CERN.

\end{abstract}

%%%%\begin{keyword}
%% keywords here, in the form: keyword \sep keyword
%\keywords{cosmic rays; Multigap Resistive Plate Chambers; Extensive
%Air Showers}
%%%%cosmic rays \sep Multigap Resistive Plate Chambers \sep Extensive Air
%%%%Showers \sep time resolution \sep spatial resolution
%% MSC codes here, in the form: \MSC code \sep code
%% or \MSC[2008] code \sep code (2000 is the default)

%%%%\end{keyword}

%\end{frontmatter}

%%
%% Start line numbering here if you want
%%
% \linenumbers

%% main text
%\section{}
\section{Introduction}
%\label{}

The Extreme Energy Events (EEE) Project is a Centro Fermi - CERN -
INFN - MIUR Collaboration Project, for the study of extremely
high-energy cosmic rays, with the further goal to introduce students 
to particle and astroparticle Physics.
The array of cosmic muon telecopes, exploiting the MRPC technology and 
covering about 10$^{6}$ km$^{2}$ across the Italian territory, has
been built and successfully operated in the last years.
More than 20 billion tracks have been collected by the XXX telescopes
of the array, during three coordinated data taking starting from 2014
and currently ongoing.
The activity of the project is focused on the study of local
properties of the cosmic-ray flux (among them the Forbush decrease), 
the detection of EAS by looking at the coincidences between telescopes 
located in the same town and, possibly, the search for long-distance correlations between far
telescopes.
Anisotropies in the muon distribution looking at the Sub-TeV sky and the
muon decay by measuring the upgoing electrons coming from the
interaction of the muons with the floor under the telescopes are other
examples of recent results obtained thank to the excellent performance 
of the MRPC customised for the EEE project.


\section{MRPC for the EEE telescopes}
\label{eee_mrpc}

TEXT

\subsection{Set-up}
\label{setup}

MODIFICARE
Three MRPC chambers (160 $\times$ 80 cm$^{2}$ active area), each of them with six gas gaps
obtained by a sandwich of glass plates, are assembled in a telescope,
shown in Fig. \ref{telescope}.
The gap between the glass plates is obtained by means of 300 $\mu$m
spacers (common fishing line). Fig. \ref{mrpc} shows the layout of the MRPC used in EEE: the pick-up
electrodes, the glass plates and the avalanches generated in the gaps are visible.
The induced signal on the external electrodes is the sum over all the
gaps. 
A gas consisting of a 98\%/2\% mixture of Freon
(C$_{2}$F$_{4}$H$_{2}$) and SF$_{6}$, with a continuous flow of 40 cc/minute, is used at atmospheric pressure. 
The high voltage to the chambers is provided by a set of DC/DC
converters, able to provide a voltage up to $\pm$10 kV. 
A chamber is equipped with two readout planes (anode and cathode)
each with 24 copper strips and can provide 
two-dimensional information when a cosmic muon crosses the chamber:
one coordinate is given by the hit strip, while the second 
is obtained by the time comparison of the arrival signals at the opposite ends in each
strip. 
The strips are read out by front-end (FEA) cards, which
incorporate an ultrafast and low power ASIC amplifier/discriminator 
specifically designed for MRPC operation \cite{asic}. 
%In Fig. \ref{fea_chamber} a FEA (left) and a schematic upper view of
%a chamber (right) are shown.
In Fig. \ref{fea_chamber} a schematic top view of a chamber is shown.

%
\begin{figure}[!htb]
\centerline{
\includegraphics[width=1.\columnwidth]{telescope.png}
}
\caption{One EEE telescope composed of three MRPC chambers.}
\label{telescope}
\end{figure}
%

%
\begin{figure}[!htb]
\centerline{
\includegraphics[width=1.2\columnwidth]{mrpc.png}
}
\caption{Layout of a Multigap Resistive Plate Chamber used in the EEE telescopes.}
\label{mrpc}
\end{figure}
%

The trigger logic foresees a six-fold coincidence of the OR signals of the FEA cards
(corresponding to a triple coincidence of the chambers), whose signals
are combined in a VME module.
Two TDC modules (64 and 128 channels each) are used to get the signal
trasmitted by twisted pairs Amphenol cables from the front-end; the TDC bin is 100 ps.
A GPS unit, providing a time stamp associated to each measured event,
is used for the time synchronization between far telescopes; its
precision is of the order of 40 ns.
Data acquisition, monitoring and control are managed by a software based on LabVIEW.

%
\begin{figure}[htb][!htb]
\centerline{
%\includegraphics[width=0.5\columnwidth]{fea.pdf}
\includegraphics[width=1.1\columnwidth]{chamberUpperView.png}
}
%\caption{three ultrafast and low power amplifier/discriminator ASICs are visible on a FEA (left); upper sketch of a MRPC chamber, showing the 24 copper
%strips, the 2 FEAs at the edges of the chamber and the 2 DC/DC
%converters providing the HV (right)}
\caption{upper sketch of a MRPC chamber, showing the 24 copper strips,
  the 2 FEAs at the edges of the chamber and the 2 DC/DC converters
  providing the HV (top left and bottom right in red).}
\label{fea_chamber}
\end{figure}
%


%
%
%

\subsection{Track reconstruction}
\label{track_reco}

MODIFICARE

For track reconstruction, a preliminary evaluation of the hit
multiplicity is first carried out, selecting only those hits whose 
timing information (from TDC) is compatible with a point
whose coordinates are included in the strip geometry; good hits are
then associated to clusters. 
In most cases the cluster size is equal to 1, since only a single strip is involved; however, for tracks which produce a signal in two or
three close strips, a cluster is built, whose centre is the average
position of the fired strip. A simple tracking procedure is then applied to
the set of reconstructed clusters, using two consecutive
bi-dimensional fits (xz plane followed by yz), which provides the orientation of each incoming muon. Additional
track quality checks are also applied, to consider only those tracks which have a correct time of flight between the
top and bottom chambers, a correspondingly correct track length and
the lowest $\chi^{2}$ among all the possible combinations. These
cuts help to keep the amount of spurious coincidences below 0.1\%. Both single-track and two-tracks events
(which are present in a few percent of the cases) are reconstructed whenever possible.
The detection efficiency depends on the applied voltage. At the operating voltage of 18 kV, the measured MRPC efficiency is typically 95\%.
Efficiency curves have been measured for each telescope at the moment of installation, and are replicated from time to time, also to involve high-school teams in advanced experimental activities. In Fig. \ref{performance1} the dependence of the efficiency from the applied HV is shown for
one of the EEE chambers \cite{eff} .


\section{Performance}
\label{setup}

A sample of XXX tracks collected during the Run 2 (?) was used to
measure the time and spatial resolution of the MRPCs. In particular
the events collected in TORI-03, PISA-01 and SAVO-02 (to be confirmed)
were chosen for this analysis. The main feature of the selected
telescopes is the common clock distribution to the 2 TDC boards,
provided by xxxx; the obtained results are compared with data from
CAGL-01, where the TDCs receive different clocksignals, as the most of
the EEE telescopes.
An R\&D activity for a new trigger card (ref to be added?) providing a common clock
distribution to the TDCs, is ongoing and all the EEE telescopes will
be equipped with this card in the next......(?).
In the next paragraphs the strategy to measure time and spatial
resolution will be described and the results presented.
The last paragraph of this section will show the results on the
efficiency measurement.
The track selection is done by requiring $\chi^{2}$ $< $10 and
taking into account only events without clusters (MODIFICARE).

\subsection{Time resolution}

The study of the time resolution $\sigma_{t}$ has been performed 
by looking at the time information on the upper and lower chambers and 
comparing the expected time on the middle chamber with the measured value.
The simple formula to get this time difference is:

$\Delta T_{hit}$ = ($T_{top}$  + $T_{bot}$)/2 - $T_{mid}$


%
\begin{figure}[htb!]
\centerline{
\includegraphics[width=1.\columnwidth]{time_res.png}
}
\caption{$\Delta T$ distribution of one of th e EEE telescope, showing
  the gaussian fit and the time resoultion $\sigma_{t}$ = 210 ps.}
\label{t_res}
\end{figure}
%



Fig. \ref{t_res} shows the $\Delta T_{hit}$ distribution of TORI-03;
the ditribution is fitted with a gaussian function and gives as a
result $\sigma_{\Delta T}$ = 242.77ps.
According to this result, the final result on the time resolution is $\sigma_{t}$ = 210 ps.

\subsection{Spatial resolution}
The spatial resolution of a EEE MRPC chamber is related both to the readout strip layout and to the hit position and energy deposit. As already defined in \ref{setup}, each EEE MRPC chamber is equipped by 24 cupper strips, 2.5 cm width equally spaced by 0.7 cm, thus a total pitch of 3.2 cm. In case of particles travelling through the space between two strips, or in case of large energy deposit, a signal ({\it hit}) can be induced on 2 or more adiacent strips, thus giving rise to a {\it cluster}. In case a single strip collects a signal of an ionizing particle, the {\it hit} and the {\it cluster} definition does not differ (see \ref{track_reco}).\\
The {\it cluster} position along the strip coordinate, as well as the {\it hit}, are related to the signal propagation speed through the strips and are affected by its fluctuations, as well as by the jitter of the read-out electronics and TDC resolution. In case of a cluster the uncertainty on the position is driven by the 1.5 ns time cut defining the {\it hits} contributing to the same cluster w.r.t. uncorrelated {\it hits} (see fig. \ref{figClusTimCut}), which is in any case comparable the single-{\it hit} uncertainty.\\   
The cluster position across the strips is therefore the cluster center of gravity and the related uncertainty is pitch/$\sqrt{12N}$, where N is the number of strips involved. In case of a single {\it} position and uncertainty across the strips will be the center of the strip and the pitch/$\sqrt{12}$, respectively.\\
%
\begin{figure}[!htb]
\centerline{
\includegraphics[width=1.\columnwidth]{figClusTimCut.pdf}
}
\caption{$\Delta T$ distribution for {\it hits} from adiacent strip (left) and for non-adiacent strips (right)}
\label{figClusTimCut}
\end{figure}
%
The cluster parameters and the resolution are also obviously correlated to the use of slewing corrections. Finally the measurement of a telescope chamber resolution is also affected by the general alignment of the three planes composing a station.\\
A general approach to the evaluation of the telescope spatial resolution has to rely on the relative measurement of the chambers composing the station. Therefore the resolution of the chamber has been taken to be the standard deviation of the distribution of differences between the {\it cluster/hit} position as measured by the middle chamber and as expected on the same plane by linearly interlacing corresponding clusters on top and bottom chambers.
$$\Delta x(y)_{mid} = \big[x(y)_{top}  + x(y)_{bot}\big]/2 - x(y)_{mid}$$
In order to correctly address the resolution of the chambers we'll refer to $\sigma_x$ when addressing the coordinate along the direction of the strips, while to $\sigma_y$ when addressing the coordinate across the strips.

\subsubsection{Resolution along strip coordinate}

\subsubsection{Resolution across strip coordinate}

\subsection{Efficiency}

TEXT

\subsection{Comparison with beam-test results}

A series of beam test measurements on the EEE MRPCs was 
performed at CERN \cite{beamTest} in 2006, providing a value 
of $\sigma$ of about 70 ps for the time resolution and 0.7 cm 
for the spatial resolution along the readout strips direction.
TEXT

\section{Conclusions}

TEXT


%% The Appendices part is started with the command \appendix;
%% appendix sections are then done as normal sections
%% \appendix

%% \section{}
%% \label{}

%% References
%%
%% Following citation commands can be used in the body text:
%% Usage of \cite is as follows:
%%   \cite{key}         ==>>  [#]
%%   \cite[chap. 2]{key} ==>> [#, chap. 2]
%%

%% References with BibTeX database:
\nocite{*}
%\bibliographystyle{elsarticle-num}

%\section{References}

\begin{thebibliography}{00}

\bibitem{eee} A. Zichichi, Progetto “La Scienza nelle Scuole” — EEE: Extreme Energy Events, Societ\`a Italiana di Fisica (Bologna), 3 May 2004; 2nd edition, 1 April 2005; 3rd edition, 20 April 2012. See also: http://www.centrofermi.it/EEE
\bibitem{beamTest} M.Abbrescia et al., Nuclear Instruments and Methods in Phys.Research A593(2008)263

%\bibitem{tof1} ALICE Collaboration, Addendum to TOF Technical Design Report, CERN/LHCC, 2002-016
%\bibitem{tof2} A. Akindinov et al., Nucl. Instrum. Methods Phys. Res. A 661, S98 (2012)
%\bibitem{asic} F.Anghinolfi et al., Nuclear Instruments and Methods in Phys.Research A533(2004)183
%\bibitem{eff} Abbrescia, M. et al. Nucl.Instrum.Meth. A593 (2008) 263-268 
%\bibitem{MC_coincidences} M.Abbrescia et al., Eur. Phys. J. Plus 129 (2014) 166
%\bibitem{coinc1} M.Abbrescia et al., First detection of extensive air showers with the EEE experiment, Nuovo Cim. B125(2010) 243.
%\bibitem{coinc2} M.Abbrescia et al., A multigap resistive plate chamber array for the Extreme Energy Events project, JINST 9 (2014) 10, C10024.
%\bibitem{coincidences} M.Abbrescia et al., Eur. Phys. J. Plus (2013) 128: 148
%\bibitem{forbushDec1} Oulu Neutron Monitor, http://cosmicrays.oulu.fi
%\bibitem{forbushDec2} M.Abbrescia et al., Eur. Phys. J. Plus (2011) 126: 61
%\bibitem{forbushDec3} M.Abbrescia et al., Eur. Phys. J. Plus (2013) 128: 62
%\bibitem{subTev1} R. Abbasi et al., Astrophys. J. 718, L194 (2010)
%\bibitem{subTev2} G. Guillian et al., Phys.Rev.D 75, 063002 (2007)
%\bibitem{subTev3} M. Amenomori et al., Science 314, 439 (2006)
%\bibitem{subTev4} A.A. Abdo et al., Astrophys. J. 698, 2121 (2009)
%\bibitem{anisotropies} M.Abbrescia et al., Eur.Phys.J.Plus 130 (2015) 187

\end{thebibliography}

%\bibliography{martin}

%% Authors are advised to use a BibTeX database file for their reference list.
%% The provided style file elsarticle-num.bst formats references in the required Procedia style

%% For references without a BibTeX database:

% \begin{thebibliography}{00}

%% \bibitem must have the following form:
%%   \bibitem{key}...
%%

% \bibitem{}

% \end{thebibliography}

\end{document}

%%
%% End of file `nuphbp-template.tex'. 

 