Cosmology, Particle Physics and Phenomenology - CP3

ASTERICS is a test platform designed for the radiation testing of digital circuits.
It has been developed by the TIMA lab (Grenoble, France). The aim is to acquire the competence and develop further this tester.

The CMS silicon strip tracker is the largest device of its type ever built. There are 24244 single-sided micro-strip sensors covering an active area of 198m2.
While first data from collisions are coming in, the physics performances of the detector are being assessed and optimized.
Members of UCL are playing a major role in the understanding of the silicon strip tracker and in the finalization of all tools needed for its configuration, control, monitoring and calibration. We are sharing the convener-ship of the tracker detector performance group (DPG).

External collaborators: CMS tracker collaboration.

FROG is a generic framework dedicated to visualize events produced in particle collisions and detected by particle detectors.
It has been written in C++ and use OpenGL cross-platform libraries. It can be used to any particular physics experiment or detector design. The code is very light and very fast and can run on various Operating System. Moreover, FROG is self consistent and does not require installation of ROOT or Experiment software (e.g. CMSSW) libraries on user's computer.
It includes a lot of features based on an unique and powerful principle. Some of the functionalities are listed below :
3D and 2D visualization, graphical user interface, mouse interface, configuration files, production of pictures in various format, integration of personal objects.
One of the FROG application is to display events for one of the most complex physics experiment : the CMS experiment. But it works as well and even faster with smaller experiment like the Gastof detector.

Frog WebSite
CMS TWiki Page

The amount and distribution of the material composing a particle detector that measures the trajectories of charged particles must be known with high accuracy for two main reasons: 1) avoid any bias in the measurements of the momentum of charged particles and 2) provide an accurate Monte Carlo simulation of the detector.

A novel method for measuring the material of a generic tracking apparatus has been developed. The method exploits the multiple scattering experienced by charged particles while they sail through the detector. The method relies on the precise position measurement of the crossing points provided by the tracking detectors. The method is completely general and can be applied to any experiment equipped with detectors with good enough space resolution.

The material of the CMS Silicon Strip Tracker has been measured with this technique to a precision at the level of 10%.

NA62 will look for rare kaon decays at SPS accelerator at CERN. A total of about $10^{12}$ kaon decays will be produced in two years of data taking. Even though the topology of the events is relatively simple, and the amount of information per event small, the volume of data to be stored per year will be of the order of 1000 TB. Also, an amount of 500 TB/year is expected from simulation.

Profiting from the synergy inside CP3 in sharing computer resources our group is participating in the definition of the NA62 computing scheme. CP3 will be also one of the grid virtual organization of the experiment.

Two computers models are now under study. One with a centralized on line farm close to the experiment, in which raw data storage and level3 filters will be done at CERN, and different centres belonging to virtual organization will be used for reprocessing, simulation and analysis. The other model is based in a distribution of raw data to few computing centres outside CERN, where data storage will be assured as well as the tasks mentioned before. In both cases CP3 will contribute in a significative way. Tests and simulations of both concepts will be performed during 2010.

The scientific projects related to or directly integrated on the UCL computing cluster are the following: MadGraph/MadEvent, CMS-Tier2 and Cosmology.

External collaborators: INFN (Rome I), University of Birmingham.

The CMS detector at the LHC can be used to identify particles via the measurement of their ionization energy loss. The sub-detectors that are expected to provide useful information for this experimental technique are the silicon strip tracker, the pixel detectors and the electromagnetic calorimeter. Identification of low momentum hadrons, improvement of electron identification and detection of new exotic heavy stable charged particles can all benefit from this experimental method. Members of UCL have explored for the first time this technique and have developed the tools for calibrating and measuring the ionization energy loss with the silicon strip tracker. Particle identification with ionization energy loss was commissioned on cosmic rays and on first LHC collisions: it has proved to perform extremely well allowing protons, kaons, as well as light resonances decaying into kaons and protons to be cleanly identified. This technique has also allowed the first search for new heavy stable charged particles.
The pixel and electromagnetic calorimeter detectors are planned to be also used in order to further improve the current performance.

External collaborators: CMS collaboration.

Precise determination of the absolute luminosity is crucial for many measurements in CMS. The measurement of the exclusive two-photon production of muons pairs by CMS provides a powerful method to calibrate the integrated luminosity.

External collaborators: CMS forward physics analysis group, CMS luminosity group.

The detection of TeV muons is a fundamental ingredient of a number of key analyses (e.g. search for new high-mass di-muon resonances) to be performed by the CMS experiment at the LHC collider.

In the CMS experiment, the resolution on the measurement of the energy and direction of O(TeV) muons is dominated by the precision of the crossing point measurement performed by the muon chambers (including the alignment accuracy) and by the catastrophic energy losses in the material traversed by the muon.

A new algorithm for reconstructing high energy muons has been developed. The algorithm aims at improving both the purity of the measurements associated to the reconstructed muon track and at rejecting the measurements produced following a catastrophic energy loss, which would bias the muon measurement.

The algorithm has been proved to reduce significantly the non-Gaussian tails in the muon energy resolution, while leaving the width of the core distribution unchanged.

The World LHC Computing GRID (WLCG) is the worldwide distributed computing infrastructure controlled by software middleware that allows a seamless usage of shared storage and computing resources.

One PByte of data is expected to be produced every year by the CMS detector at the LHC collider. This data must be processed (iterative and refined calibration and analysis) by a large scientific community that is widely distributed geographically. Instead of concentrating all necessary computing resources in a single location, the LHC experiments have decided to set-up a network of computing centres distributed all over the world.

The overall WLCG computing resources needed by CMS alone in 2010 amount to about 25,000 CPUs, 25,000 TB of disk storage and 35,000 TB of tape storage. Working in the context of the WLCG translates into seamless access to shared computing and storage resources. End users do not need to know where their applications run. The choice is made by the underlying WLCG software on the basis of availability of resources, demands of the user application (CPU, input and output data,..) and privileges owned by the user.

Back in 2005 UCL proposed the WLCG Belgian Tier2 project that was endorsed by the 6 Belgian Universities involved in CMS. The Tier2 project consists of contributing to the set-up of the WLCG by building two computing centres, one at UCL and one at the IIHE (ULB/VUB).

The UCL site of the WLCG Belgian Tier2 is deployed in a dedicated room close to the cyclotron control room of the IRMP Institute and is currently a fully functional component of the WLCG.

The UCL Belgian Tier2 project also aims at integrating, bringing on the GRID and sharing resources with other scientific projects. The scientific projects related to or directly integrated on the UCL computing cluster are the following: MadGraph/MadEvent, NA62 and Cosmology.

External collaborators: CISM (UCL), Pascal Vanlaer (Belgium, ULB), Lyon computing centre, CERN computing centre.