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\newcommand{\pim}	{\pi^{-}}
\newcommand{\piz}	{\pi^{o}}
\newcommand{\pip}	{\pi^{+}}
\newcommand{\mchi}	{\chi^{2}}
\newcommand{\pbarp}     {\overline{p}p}
\newcommand{\pbar}     {\overline{p}}
\newcommand{\dfunc}[4]	{d_{#2,#3}^{#1}(#4)}
\newcommand{\delfunc}[2] {\delta_{#1,#2}}
\newcommand{\Dfunc}[6]	{{\cal D}_{#2,#3}^{#1}(#4,#5,#6)}
\newcommand{\Dsfunc}[6]	{{\cal D}_{#2,#3}^{#1 *}(#4,#5,#6)}
\newcommand{\DfuncAB}[5]	{\cal{D}_{#2,#3}^{#1}(#4,#5)}
\newcommand{\kshort}	{K_{S}^{o}}
\newcommand{\lh}	{LH_{2}}
\newcommand{\ld}	{LD_{2}}

\begin{document}

%\title{Report on the July-August 1995 Crystal Barrel Run}
%\author{Curtis Meyer \and Rod McCrady \and Christian V\"{o}lker}
%\maketitle

\begin{titlepage}
 \begin{flushright}
  {\large CB Note \# 283}
 \end{flushright}

 \vspace{2.0in}

 \begin{center}
  {\huge Report on the July-August 1995 Crystal Barrel Run}
 \end{center}
 \begin{center}
  {\large Curtis Meyer \hspace{.5in} Rod McCrady \hspace{.5in}
          Christian V\"{o}lker}
 \end{center}
 \begin{center}
  {\large \today }
 \end{center}
\end{titlepage}

\section{General}
 This run was the first to use the new silicon vertex detector (SVTX) in
 triggering on $\kshort$'s in production data taking. The goals for data
 volume were: to collect 50k events in the $\kshort \kshort \piz$ Dalitz
 plot, and to study final states such as $\Lambda \kshort$,
 $\kshort \pi^{-} X$, $\kshort K^{-} X$, and
 $\kshort K^{\pm} \pi^{\mp} \pi$.

 The beam was shared with PS195 (principal user) and, at times, PS205.
 Additionally, LEAR delivered fast extracted beams to PS196 several
 times during the run.

 Data taking began on the morning of July 11 with the $\lh$ target
 in place. The change to the $\ld$ target began on the morning of
 August 9. $\ld$ data were collected from August 9 until August 17. Pedestal
 runs were made during each spill break, and minimum bias data
 were collected at the rate of 1 or 2 tapes per shift throughout
 the run.

\section{Statistics}
 The number of events per trigger
 is shown in the table below, and a description of each trigger follows.
 \begin{table}[h]
 \begin{tabular}{|l|r|}  \hline
  Trigger              & Events \\ \hline \hline
  kshort               & 4.691M \\
  2pr12ped             & 0.811M \\
  minimum bias         & 2.171M \\
  0 prong              & 1.500M \\
  4 prong              & 0.122M \\  \hline
 \end{tabular}
 \caption{Summary of statistics for the $\lh$ running}
 \end{table}

 \begin{table}[h]
 \begin{tabular}{|l|r|}  \hline
  Trigger              & Events \\ \hline \hline
  kshort               & 4.131M \\
  ksd13np              & 0.475M \\
  minimum bias         & 1.138M \\ \hline
 \end{tabular}
 \caption{Summary of statistics for the $\ld$ running}
 \end{table}
 The {\bf kshort} triggers evolved as we gained experience during the
 run. Most of these trigger files combined conditions for detecting one
 {\em or} two $\kshort$'s based on charged multiplicity changes between
 the SVTX and the JDC. As the run progressed, pileup rejection was added and
 the middle layers of the JDC were included in the JDC multiplicity count.
 The {\bf 1pr12ped} trigger was used in collecting collinear events for
 JDC alignment purposes, as well as for physics events in the
 $K_{L}\pi^{\pm}K^{\mp}$ channel.
 The {\bf minimum bias} events are for normalization and trigger performance
 studies; these were triggered on a $\overline{p}_{stop}$ condition.
 The {\bf 0 prong} events were triggered on no tracks in the JDC, and will
 be used for crystal calibration.
 The {\bf 4 prong} events were collected to allow study of the SVTX paddle
 alignment and of the $\kshort$ trigger performance.
 The {\bf ksd13np} trigger was for detecting events with one $\kshort$
 from the $\ld$ target.
 The {\bf ksh\_np} trigger was a mixed $\kshort$ trigger for $\ld$
 running, with 0 prong $\rightarrow \geq$2 prong,
 1 prong $\rightarrow \geq$3 prong,
 and 3 prong $\rightarrow \geq$5 prong conditions.
 Tables ~\ref{tbl:Trigs} and \ref{tbl:TrigSTSPar}
 list the trigger conditions for the various triggers.

 An estimated 10,000 $\kshort \kshort \piz$ events were collected. The major
 factors contributing to the smaller than expected data collection rate were:
 the small $Si_{center}$ counter, the target bubble, high sensitivity to
 beam steering, JDC readout problems, triggering on ``garbage'' events, and
 downtime due to equipment failures. These factors are discussed in the
 following sections.

 \begin{table}[h]
 \begin{tabular}{|l|l|l|l|cccc|l|} \hline
  Trigger      & PWC  & FACE & SVTX & \multicolumn{4}{c|}{JDC layer mult} & Comment \\
               &      &      & mult & 9 & 10 & 19 & 20 & \\ \hline \hline
  ksh24        & 0/15 & 0/15 & 1/2  & - & -  & 4/f& 4/f&$2 \rightarrow \;\geq 4$ prong\\ \hline
  ksh\_02      & 0/0  & 0/15 & 0/0  & - &  - & 2/f& 2/f&$0 \rightarrow \;\geq 2$ prong\\ \hline
  ksh          &  -   & 0/15 & 0/0  & - & -  & 2/3& 2/3&$0 \rightarrow 2$ prong\\
               &      &      &      & - & -  & 4/f& 4/f&$0 \rightarrow \;\geq 4$ prong\\
                             \cline{4-8}
               &      &      & 1/2  & - & -  & 4/f& 4/f&$2 \rightarrow \;\geq 4$ prong\\ \hline
  ksh\_l       &  -   & 0/15 & 0/0  & - & -  & 2/3& 2/3& $Si_{L}$ \\
               &      &      &      & - & -  & 4/f& 4/f& $Si_{L}$ \\
                             \cline{4-8}
               &      &      & 1/2  & - & -  & 4/f& 4/f& $Si_{L}$ \\ \hline
  ksh\_l02     &  -   & 0/15 & 0/0  & - & -  & 2/3& 2/3& $Si_{L}$ \\
               &      &      &      & - & -  & 4/f& 4/f& $Si_{L}$ \\
                             \cline{4-8}
               &      &      & 1/2  & - & -  & 4/f& 4/f& \\ \hline
  ksh\_l02np   &  -   & 0/15 & 0/0  & - & -  & 2/3& 2/3& $Si_{L}$, pileup rej.\\
               &      &      &      & - & -  & 4/f& 4/f& $Si_{L}$, pileup rej.\\
                             \cline{4-8}
               &      &      & 1/2  & - & -  & 4/f& 4/f& pileup rej.\\ \hline
  ksh\_l02np19 &  -   & 0/15 & 0/0  & - & -  & 2/f& 2/3& $Si_{L}$, pileup rej.\\
               &      &      &      & - & -  & 4/f& 4/f& $Si_{L}$, pileup rej.\\
                             \cline{4-8}
               &      &      & 1/2  & - & -  & 4/f& 4/f& pileup rej.\\ \hline
  ksh\_l02npm3 &  -   & 0/15 & 0/0  & - & -  & 2/3& 2/f\,\dag& $Si_{L}$, pileup rej.\\
               &      &      &      &3/f& 3/f& 4/f& 4/f& $Si_{L}$, pileup rej.\\
                             \cline{4-8}
               &      &      & 1/2  &3/f& 3/f& 4/f& 4/f& pileup rej.\\ \hline
  ksh\_npm3    &  -   & 0/15 & 0/0  & - & -  & 2/3& 2/f\,\dag& pileup rej.\\
               &      &      &      &3/f& 3/f& 4/f& 4/f& pileup rej.\\
                             \cline{4-8}
               &      &      & 1/2  &3/f& 3/f& 4/f& 4/f& pileup rej.\\ \hline
  ksh02\_l     & 0/0  & 0/15 & 0/0  & - &  - & 2/f& 2/f& $Si_{L}$\\ \hline
  ksh24\_l     & 0/15 & 0/15 & 1/2  & - &  - & 4/f& 4/f& $Si_{L}$\\ \hline
  ksh\_l02npv14& 0/15 & 0/15 & 0/0  & - & -  & 2/3& 2/f& pileup rej.\\
               &      &      &      & - & -  & 4/f& 4/f& pileup rej.\\
                             \cline{4-8}
               &      &      & 1/2  & - & -  & 4/f& 4/f& pileup rej.\\ \hline
  0pr\_jdc     & 0/15 & 0/15 & 0/15 &0/0& 0/0& -  & -  & 0 prong \\ \hline
  minbias      & 0/15 & 0/15 &  -   & - &  - &  - &  - & minimum bias \\ \hline
  2pr12ped     & 0/15 & 1 2  & 0/15 & - &  - & 2/2& 2/2& 2 prong, 1 or 2 PEDs \\ \hline
  2pr13ped     & 0/15 & 1 3  & 0/15 & - &  - & 2/2& 2/2& 2 prong, 1 to 3 PEDs \\ \hline
  ksd13np      & ?    & 0/15 & 0/0  & - &  - & 3/f& 3/f& pileup rej.\\ \hline
  ksh\_np      &  -   & 0/15 & 0/0  & - &  - & 2/2& 2/2& pileup rej.\\
               &      &      &      & - &  - & 3/4& 3/4& pileup rej.\\
               &      &      &      & - &  - & 5/f& 5/f& pileup rej.\\
                             \cline{4-8}
               &      &      & 1/3  & - &  - & 3/4& 3/4& pileup rej.\\
               &      &      &      & - &  - & 5/f& 5/f& pileup rej.\\
                             \cline{4-8}
               &      &      & 2/3  & - &  - & 5/f& 5/f& pileup rej.\\ \hline
 \end{tabular}
 \caption{Trigger files. \hspace{.5in} \dag Changed to 2/3 before run 28843.}
 \label{tbl:Trigs}
 \end{table}


 \begin{table}[h]
 \begin{tabular}{|l|l|l|} \hline
  Trigger      & STS                 & Par       \\ \hline \hline
  ksh24        & bsvp1j1             & j4mxx4f   \\ \hline
  ksh\_02      & bsvp1j1             & j4xx2f    \\ \hline
  ksh          & bsvv1j1\_ksh        & ksh       \\ \hline
  ksh\_l       & bsvv1j1\_ksh\_l     & ksh       \\ \hline
  ksh\_l02     & bsvv1j1\_ksh\_l02   & ksh       \\ \hline
  ksh\_l02np   & bsvv1j1\_ksh\_l02np & ksh       \\ \hline
  ksh\_l02np19 & bsvv1j1\_ksh\_l02np & ksh\_19   \\ \hline
  ksh\_l02npm3 & bsvv1j1\_ksh\_l02np & ksh\_m3   \\ \hline
  ksh\_npm3    & bsvv1j1\_ksh\_np    & ksh\_m3   \\ \hline
  ksh02\_l     & bsvp1j1\_l          & j4xx2f    \\ \hline
  ksh24\_l     & bsvp1j1\_l          & j4mxx4f   \\ \hline
  ksh\_l02npv14& bsvv1j1\_ksh\_l02np & ksh\_v14  \\ \hline
  0pr\_jdc     & bsvj1               & j4m00xx   \\ \hline
  minbias      & bsv                 & ksh \dag  \\ \hline
  2pr12ped     & bsvj1f1             & j4mxx22   \\ \hline
  2pr13ped     & bsvj1f1             & j4mxx22   \\ \hline
  ksd13np      & bsvp1j1             & j4mxx3f   \\ \hline
  ksh\_np      & bsvv1j1\_ksd\_np    & ksd       \\ \hline
 \end{tabular}
 \caption{STS and Par files used for the various triggers.
          \newline \dag Changed to ksh\_m3 before run 29569.}
 \label{tbl:TrigSTSPar}
 \end{table}


\section{Components}
 \subsection{Beam Counters}
  Ken's Chamber (KC) was in place. The silicon counters consisted of a
  300 $\mu$m thick by 5mm diameter center counter placed 5mm upstream of the
  target entrance window, and a 300 $\mu$m thick by 8mm diameter four quadrant
  counter placed 22mm upstream of the center counter. The following $\pbar$
  stop condition was used:
%  \begin{displaymath}
%   \overline{p}_{stop} = 
%   KC \cdot Si_{center} \cdot \sum_{i=1}^{4} Si_{i} \cdot \overline {Si_{high}}
%  \end{displaymath}
  \begin{displaymath}
   \overline{p}_{stop} = (Si_{center}^{low} \wedge \overline{High}) \wedge
    (\sum_{i=1}^{4}{\rm OR}(Si_{i}^{low} \wedge \overline{High}))
    \; \; {\rm where} \; \;
    High = \sum_{i=1}^{4}Si_{i}^{high} \vee Si_{center}^{high}
  \end{displaymath}
  The pileup flag was provided by KC.

  The gas delivery system for KC had problems near the end of the $\lh$
  running. This problem seemed similar to the gas problems in the JDC
  described below. The problem was quickly repaired, and did not affect
  the data quality.

  The ratio of $Si_{center}\wedge\sum_{i=1}^{4}Si_{i} : KC$ constituted
  the criterion by which beam steering quality was monitored. These scalers
  were viewed on a CRT in the control room. A ratio of less than 20\% was
  considered grounds for resteering; 25\% was typical and 30\% was the best
  achievable ratio.

 \subsection{Silicon Vertex Detector}
  The SVTX was used extensively in the triggers, and performed
  well without much attention. The SVTX readout system, v3xtal,
  did hangup once due to a drifting pedestal.
  One Viking was not operational.
  Signal timing and setting of thresholds were issues for about the first
  half of the run.

  See the report by P. Kammel concerning the
  performance of the SVTX in this run for details.

 \subsection{JDC}
  The JDC performed reliably. The frequent high voltage trips which had
  been experienced during previous runs did not occur. One problem
  with the the JDC in this run was the operation of the gas delivery system.
  The isobutane and $CO_{2}$ flow rates dropped suddenly and quickly in
  two separate incidents. On both occasions, the problem was noticed soon
  after it began, due to the shift crews having done the checklist {\em
  and checked the results.} The gas system had worked reliably for several
  years up to this point. Presumably due to the hot weather, there was a
  problem with the JDC cooling system; this was fixed early in the run.

  One clock cable for the FADC's was replaced to fix ``double ringing''
  condition. The problem was noticed early in the run by people looking
  at the data offline.

  A water leak in one of the FADC rack cooling systems occurred before
  the run. This was noticed quickly and repaired, preventing damage to
  the electronics.

 \subsection{Target}
  The standard liquid hydrogen target was used. There were two additional
  heat loads on the target for this run: the proximity of the central silicon
  beam counter, and the new SVTX. It was obvious that there was a bubble
  at the top of the target from the z vertex distributions for $\pbar$'s
  entering the target via the various quadrants of the entrance counters:
  for events where the $\pbar$ entered the target via $Si_{UL}$ or
  $Si_{UR}$, a large fraction of the z vertices were downstream of the
  target. The problem was ameliorated by increasing the pressure of the
  hydrogen in the target, but evidence for a small bubble persisted
  throughout the $\lh$ run. Approximately 1\% to 4\% of the beam was
  passing through the bubble.

 \subsection{Crystals}
  Four crystals consistently showed up as defective in the lightpulser data
  analysis. Two of these could possibly be attributed to loose connectors
  on the crystal ch\^{a}peaux.

  {\bf Which crystals?}

 \subsection{FERA}
  The FERA crystal readout was problematic, particularly at the beginning
  of the run. Many problems were associated with poor connections on the
  ECL busses and on the CAMAC backplanes. There were several instances of bad
  FERA modules, some of which were the well known ``test point'' problem.
  A water leak in the rack cooling system had occurred before the run,
  and the experts strongly suspect this as a source of the FERA problems
  during this run.

  The diagnosis of FERA problems was complicated by an apparent problem
  with COLA\@. C. Pinder suggested that this could be the result of
  misalignment of the computer memory shared by the many analysis programs
  on the VAX.

 \subsection{2282}
  The 2282 crystal readout worked fine throughout the run.

 \subsection{FACE}
  After thourough checkout by S. Spanier, the FACE was deemed to be in fine
  working order. The FACE was used effectively in the 2pr12ped trigger.

 \subsection{Magnet}
  The magnet itself seemed to work well, but the power supply, which had
  worked fine for many years, failed on July 20th. The failure was
  attributed to a bad thyristor, and was corrected by CERN staff that
  afternoon.
  
  On the especially warm days, the cooling water temperature was quite
  high, nearly causing a shutdown of the experiment at times. Since this
  water also cools the PS195 magnet, which was also operating,
  the total load on the cooling system was quite heavy.

 \subsection{DAQ}
  Some problems occurred in the JDC readout system, most
  notably j1xtal and j2xtal timeouts.
  The trigger conditions in use tended to enrich the sample of
  ``garbage events,'' consisting mostly of
  splash-back from the crystals and $\pbar$ - nucleus annihilations
  from upstream and downstream of the target. The j1xtal and j2xtal timeout
  problems seemed to be correlated with these events, but the exact
  nature of the problem is still obscure. The problems were tended to
  by B. Barnett as they occurred.
  The JDC pedestal calculation was streamlined to reduce downtime
  between runs.
  Improvements to the event builder were also made during the run
  as necessary.

  A note in the log book indicated that the multiplicity for the SVTX
  was added to the RTRG bank, beginning with run 27898. See the log book
  for details.

  For the most part, one tape drive was used with the stacker in place.
  The only difficulties as a result of this arose when the drive needed
  cleaning and when a tape was needed for analysis immediately after
  being written.

 \subsection{Beam Delivery}
  We ran in parasitic mode, as PS195 was the principal user during this period.
  Additionally, PS205 was taking part of the beam. Problems relating to the
  three way splitting of the beam arose, mostly when the splitting was being
  changed or after long shutdowns. Also present was the persistent
  problem of steering when PS195 changed the polarity of their spectrometer
  magnet (every 4 to 8 hours).
  
  A vacuum leak occurred in the LEAR ring itself on July 21st. It took four
  days to fix this problem and to bring LEAR back into operation. Additional
  time was lost due to the fact that the electron cooling changed during the
  repair process and had to be tested and tuned for a few days after
  operation of LEAR resumed.
  
  There was a problem with the steering of the beam drifting during spills.
  This might have been caused by a temperature related instability in a
  bending magnet. LEAR staff put a field probe in the magnet so that the field
  itself could be monitored directly.

  Several times during the run, LEAR operators reported to
  us that a sextupole magnet in LEAR had failed. These resulted in lost beam
  time.

  Power supply problems in the PS and injection system, as well as a problem
  with the septum, also occurred.

 \section{Recommendations}
  \begin{itemize}
   \item Check gas systems for the JDC and KC.
   \item Check rack cooling systems before the run and when performing
         a checklist.
   \item Fix COLA.
   \item Change $Si$ beam counters to: reduce the heat load on the target,
         and increase the triggered incoming $\pbar$ rate.
   \item Fix the target bubble by: changing the $Si$ beam counters, and reducing
         heat losses.
   \item Fix j1xtal and j2xtal timeouts by: software changes, and improving
         trigger conditions and hardware.
   \item Investigate why our beam needs such frequent steering and how
         the steering could be done more quickly.
  \end{itemize}
\end{document}
