- \section{Detector and simulation}
- \label{sec:Detector}
-
-
-
-
- The \lhcb detector~\cite{Alves:2008zz,LHCb-DP-2014-002} is a single-arm forward
- spectrometer covering the \mbox{pseudorapidity} range $2<\eta <5$,
- designed for the study of particles containing \bquark or \cquark
- quarks. The detector includes a high-precision tracking system
- consisting of a silicon-strip vertex detector surrounding the $pp$
- interaction region~\cite{LHCb-DP-2014-001}\verb!*!, a large-area silicon-strip detector located
- upstream of a dipole magnet with a bending power of about
- $4{\mathrm{\,Tm}}$, and three stations of silicon-strip detectors and straw
- drift tubes~\cite{LHCb-DP-2013-003}\verb!*! placed downstream of the magnet.
- The tracking system provides a measurement of momentum, \ptot, of charged particles with
- a relative uncertainty that varies from 0.5\% at low momentum to 1.0\% at 200\gevc.
- The minimum distance of a track to a primary vertex (PV), the impact parameter (IP),
- is measured with a resolution of $(15+29/\pt)\mum$,
- where \pt is the component of the momentum transverse to the beam, in\,\gevc.
- Different types of charged hadrons are distinguished using information
- from two ring-imaging Cherenkov detectors~\cite{LHCb-DP-2012-003}\verb!*!.
- Photons, electrons and hadrons are identified by a calorimeter system consisting of
- scintillating-pad and preshower detectors, an electromagnetic
- calorimeter and a hadronic calorimeter. Muons are identified by a
- system composed of alternating layers of iron and multiwire
- proportional chambers~\cite{LHCb-DP-2012-002}\verb!*!.
- The online event selection is performed by a trigger~\cite{LHCb-DP-2012-004}\verb!*!,
- which consists of a hardware stage, based on information from the calorimeter and muon
- systems, followed by a software stage, which applies a full event
- reconstruction.
-
- A more detailed description of the 'full event reconstruction' could be:
- \begin{itemize}
- \item
- The trigger~\cite{LHCb-DP-2012-004}\verb!*! consists of a
- hardware stage, based on information from the calorimeter and muon
- systems, followed by a software stage, in which all charged particles
- with $\pt>500\,(300)\mev$ are reconstructed for 2011\,(2012) data.
- For triggers that require neutral particles,
- energy deposits in the electromagnetic calorimeter are
- analysed to reconstruct \piz and $\gamma$ candidates.
- \end{itemize}
-
- The trigger description has to be specific for the analysis in
- question. In general, you should not attempt to describe the full
- trigger system. Below are a few variations that inspiration can be
- taken from. First from a hadronic analysis, and second from an
- analysis with muons in the final state. In case you have to look
- up specifics of a certain trigger, a detailed description of the trigger
- conditions for Run 1 is available in Ref.~\cite{LHCb-PUB-2014-046}.
- {\bf Never cite this note in a PAPER or CONF-note.}
-
-
- \begin{itemize}
- \item At the hardware trigger stage, events are required to have a muon with high \pt or a
- hadron, photon or electron with high transverse energy in the calorimeters. For hadrons,
- the transverse energy threshold is 3.5\gev.
- The software trigger requires a two-, three- or four-track
- secondary vertex with a significant displacement from any primary
- $pp$ interaction vertex. At least one charged particle
- must have a transverse momentum $\pt > 1.6\gevc$ and be
- inconsistent with originating from a PV.
- A multivariate algorithm~\cite{BBDT} is used for
- the identification of secondary vertices consistent with the decay
- of a \bquark hadron.
- %\item The software trigger requires a two-, three- or four-track
- % secondary vertex with a large sum of the transverse momentum, \pt, of
- % the tracks and a significant displacement from the primary $pp$
- % interaction vertices~(PVs). At least one track should have $\pt >
- % 1.7\gevc$ and \chisqip with respect to any
- % primary interaction greater than 16, where \chisqip is defined as the
- % difference in \chisq of a given PV reconstructed with and
- % without the considered track.\footnote{If this sentence is used to define \chisqip
- % for a composite particle instead of for a single track, replace ``track'' by ``particle'' or ``candidate''}
- % A multivariate algorithm~\cite{BBDT} is used for
- % the identification of secondary vertices consistent with the decay
- % of a \bquark hadron.
- \item The $\decay{\Bd}{\Kstarz\mumu}$ signal candidates are first required
- to pass the hardware trigger, which selects events containing at least
- one muon with transverse momentum $\pt>1.48\gevc$ in the 7\tev data or
- $\pt>1.76\gevc$ in the 8\tev data. In the subsequent software
- trigger, at least one of the final-state particles is required to
- have $\pt>1.7\gevc$ in the 7\tev data or $\pt>1.6\gevc$ in the 8\tev
- data, unless the particle is identified as a muon in which case
- $\pt>1.0\gevc$ is required. The final-state particles that
- satisfy these transverse momentum criteria are also required
- to have an impact parameter larger than $100\mum$ with respect
- to all PVs in the event. Finally, the tracks of two or more of
- the final-state particles are required to form a vertex that is
- significantly displaced from the PVs."
-
- % Candidate events are first required to pass the hardware trigger,
- % which selects muons with a transverse momentum $\pt>1.48\gevc$
- % in the 7\tev data or $\pt>1.76\gevc$ in the 8\tev data.
- % In the subsequent software trigger, at least
- % one of the final-state particles is required to have both
- % $\pt>0.8\gevc$ and impact parameter larger than $100\mum$ with respect to all
- % of the primary $pp$ interaction vertices~(PVs) in the
- % event. Finally, the tracks of two or more of the final-state
- % particles are required to form a vertex that is significantly
- % displaced from the PVs.
- \end{itemize}
-
-