\begin{slide}{}

{\Large IV. \underline{Backgrounds,Triggers, Rates}}
\begin{enumerate}
\item \underline{Typical Trigger Conditions}

Apparatus Immediately Below Main Ring\\
$\bar{p}$'s Accelerated 1 sec/2.5 sec\\
\vspace{.50in}
\begin{itemize}
\item Blinding Flashes of Background
\vspace{.50in}
\item Triggers Gated Off
\vspace{.50in}
\item MWPC High Voltage\\
Ramped Down 15\%
\end{itemize}
\vfill\eject

\underline{Typical Trigger Conditions (Continued)}\\
\begin{enumerate}
\item Scintillator within Telescope in Loose\\
Coincidence Dominated by\\
Upstream-p Beam-Gas Interactions
Generic Rate $\approx 4-10 \, kHz$
\item $p-\bar{p}$ Interaction Trigger Demands\\
at Least One Upstream Counter\\
in $\bar{p}$ Array Reporting (With $p-\bar{p}$ Collision
Timing) Together With Telescope Trigger:
\begin{itemize}
\item Generic Background Rate $\approx 5-20 \, Hz$
\item Mostly p-induced\\
Beam-Gas Interactions
\end{itemize}
\end{enumerate}
 
\vfill\eject

\item \underline{Trigger Performance}
\begin{enumerate}
\item Genuine $p-\bar{p}$ Collisions are seen;\\
Trigger Cross Section of 35-40 mb
\begin{itemize}
\item $\sigma_{p\bar{p}}= 50 \, mb$
\item Generic Rate $\approx 300 Hz$,\\
($\sim$ D0 Luminosity $=1 \times 10^{30} cm^{-2} sec^{-1}$)
\end{itemize}
\vspace{.50in}
\item Trigger Efficiency Much Higher\\
Than Estimated from\\
Detector Acceptance:\\
Most Triggers Initiated by\\
Showers from Beampipe, Floor, Etc.
\vfill\eject

\underline{Trigger Performance(Continued)}
\item Multiplicity Distributions in Upstream\\
$\bar{p}$ Scintillator Array Very Different for\\
Beam-Gas \& Beam-Beam Collisions:
\begin{itemize}
\item Very Low for p-Induced\\
Beam-Gas Collisions
\item Higher \& Broader for $p-\bar{p}$  Collisions
\item Background Level:\\
Monitored \& Updated\\
Every Min. During Runs
\end{itemize}
\end{enumerate}
\vfill\eject



\item  \underline{Luminosity Determination} 
\begin{enumerate}
\item Rely on D0 Luminosity Monitor\\
for Determination. $F(\beta^{*})$ is the D0\\
Bunch-Length Correction:
\begin{eqnarray*}
 Lum(C0)& = &{{\beta^{*}(D0)}\over {\beta^{*}(C0)}}F(\beta^{*})  \\
        & = &{{0.35m}\over {70}}\times 1.4   \\ 
        & = &{{1} \over {140}}            
\end{eqnarray*}
\item Correction for Bunch-to-Bunch\\
Intensity Fluctuations:\\
Required and Made
\item Run-to-Run Consistency within 10\%
\end{enumerate}
 
\vfill\eject 


\item \underline{Upstream Tags}\\
Purpose:\\
Study  Leading $\bar{p}$ or $\bar{n}$ Dependence\\
Calorimetry at 25 m:
\begin{itemize}
\item Lambertson Magnets Bend Secondary\\
($x_{F}=0.5 \pm 0.1$) $\bar{p}$'s into Calorimeter 
\item Leading $\bar{n}$'s ($\theta =0^{o}$)\\
into Other Calorimeter
\item Fraction of Events with Tags $\approx 15-20\%$
\item Purity of Sample $\longrightarrow 95\%$
\item Very Little Change in Tracking Data
\end{itemize}
\vfill\eject 

\underline{Upstream Tags (Continued)}\\
Scintillator at 60 m :
\begin{itemize}
\item Superconducting Dipoles Bend:\\
$\sim 800 \, GeV$ $\bar{p}$'s ($x_{F}=0.87 \pm 0.05$)\\
into Beam Pipe
\item Shower Products Seen in Scintillator
\item Fraction of Events with Tags\\
 $\sim 1\%-2 \%$
\item Purity of Sample $> 95\%$ in Late Runs
\item Strong Change in $\bar{p}$-Scintillator\\
Multiplicity Distribution
\item Some Change in Tracking Data
\end{itemize}

 

\end{enumerate}
\end{slide}{}