| dc.description.abstract | The ALICE ("A Large Ion Collider Experiment")-experiment at the LHC ("Large
Hadron Collider") at CERN is an experiment with the prime aim being investigating interaction forces of particles at extreme temperature and energy density. [12] The ALICE experiment
consists of several detectors, with the HMPID ("High Momentum IDenfification") being
the detector able to identify particles with the highest momentum. [87]
The HMPID has seven chambers; in each chamber, there are three radiator vessels and six
HV ("High-Voltage") sectors. [32, p. 38][39]
Motivation
This thesis documents the migration of code for calibration of the HMPID from the old
framework (AliRoot), to the new, O2 ("Offline Online Processing").
The calibration procedure calculates the radiators’ refractive index in the HMPID and the
Charge threshold for each sector. The refractive index of the HMPID-radiators will, together
with the Cherenkov angle, yield the velocities of particles transversing ALICE. Together with
energy measurements obtained by Calorimeters at the ALICE experiment, this enables the
identification of particles through the particle’s mass. The charge threshold sets the threshold
for which digits in spatial proximity will be included in clusters.
Prior Work
The calibration procedure has been done for the HMPID for the old framework in [19].
Moreover, the calibration procedure has been done for other ALICE detectors in the
O2-framework, the calibration for the TOF-detector can be found in [83].
Frameworks
Before starting Run 3, the ALICE experiment moved away from the previous framework,
AliRoot - which was used in Run 1 and 2 - towards O2 ("Online Offline processing").
The new computing framework was developed to meet the computing resources needed in
run 3, where interaction rates are expected to increase 100-fold. Data flow to the O2 system
is ensured by the DCS ("Detector Control System") interface. [51]. Data in Run 3 for
ALICE is processed through the CCDB ("Condition and Calibration Data Base"). [86]
Project Outcome
The calibration will result in CCDB-objects, stored in the DCS of the O2 system. The
project is finalized and will - subject to review and modifications - be part of the official
ALICE-O2 project [17]. At the time of delivering the thesis, a code review was received
pointing out some minor bugs related to the storing of objects in the central server of the
CCDB; the process of writing and retrieving objects from the CCDB , however, work on a
local installation. The calibration procedure in the project will be used for both Monte Carlo
simulations and for measured values in Run 3. | |