| 1 |
\newpage
|
| 2 |
aaa\\
|
| 3 |
|
| 4 |
\newpage
|
| 5 |
bbb\\
|
| 6 |
|
| 7 |
\newpage
|
| 8 |
ccc\\
|
| 9 |
\newpage
|
| 10 |
ddd\\
|
| 11 |
|
| 12 |
\newpage
|
| 13 |
\newpage
|
| 14 |
|
| 15 |
|
| 16 |
|
| 17 |
|
| 18 |
\section{Triggering on Single Charged Particle}
|
| 19 |
|
| 20 |
For the purpose of Hcal calibration, a dedicated trigger path has been
|
| 21 |
designed in order to record a high rate of single charge particle
|
| 22 |
(mainly pions). Using these data, Hcal will be able to obtained an
|
| 23 |
intercalibration of the cells as well as an energy scale. The momentum
|
| 24 |
of such particle will be equalized using appropriate weight to the sum
|
| 25 |
of the energy deposited in Ecal and Hcal. It is clear that such events
|
| 26 |
can also be used in order to have a clean sample of charged pions. The
|
| 27 |
study of the energy deposition respectively in Ecal and Hcal can then
|
| 28 |
be compared to the simulation in order to tune it.
|
| 29 |
|
| 30 |
|
| 31 |
\subsection{Specificity of the Trigger}
|
| 32 |
In order to perform a sensible calibration, Hcal detector needs a
|
| 33 |
important amount of events. Single charge particle will be mainly
|
| 34 |
produced within multijet production and such production is highly
|
| 35 |
prescale at the trigger level.
|
| 36 |
|
| 37 |
The trigger path has been modified in order to keep the bandwidth low:
|
| 38 |
even if the rate of such events is high, the information kept is
|
| 39 |
minimal. These kind of triggers are named AlCaRaw as their purpose is
|
| 40 |
the calibration of the detector. The selection of the event is strong
|
| 41 |
and the content of it is simply the minimal need request by Hcal
|
| 42 |
calibration.
|
| 43 |
|
| 44 |
\subsection{Selection of the Events}
|
| 45 |
The High Level Trigger path is seeded using an OR of L1 single jets
|
| 46 |
and L1 single tau jet. The corresponding level 1 rate for a
|
| 47 |
instantaneous luminosity of $2\times 10^{30}$ or $2\times 10^{31}$ is
|
| 48 |
of the order of 4.5 kHz.
|
| 49 |
|
| 50 |
The selection is based on a L1TauJet object with a matching within a
|
| 51 |
cone of 0.5 to a pixel track with a $p_T > 20$GeV. In a cone of 0.5
|
| 52 |
around this object also no pixel track with $p_T > 2$GeV should be
|
| 53 |
found.
|
| 54 |
|
| 55 |
Once such candidate is found, the FED collections to be written out is
|
| 56 |
reduced. Only tracker FEDs around the nominal tracks are recorded as
|
| 57 |
well as for the Ecal while most of the FEDs of Hcal are written. This
|
| 58 |
gives the possibility to access to all timing information needed to
|
| 59 |
perform Hcal calibration.
|
| 60 |
|
| 61 |
The total rate of such events is expected to be around 20Hz which
|
| 62 |
should give a bandwidth occupation of around 2MB/s.
|
| 63 |
|
| 64 |
Such events require tracker measurement, so they will cover at maximum
|
| 65 |
the calibration up to $|\eta| \leq 2.4$.
|
