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LHC Experiment Help Pages

These pages document how to get started on the Grid if you are working on one of the 4 supported LHC experiments.

Step 1 - Get a Grid Certificate

To use the Grid you will need a digital certificate that authenticates you to the infrastructure. These can be obtained relatively easily from the UK Certification Authority, the process is fully outlined and can be started here (External Link).

Step 2 - Join a Virtual Organisation

Now the Grid knows who you are you need to be authorised to use its resources. Grid users are managed via the Virtual Organisation system where all users doing similar work, in similar disciplines or working on the same experiment are grouped together and have access rights (and restrictions) applied to them.

As a member of the ALICE, ATLAS, CMS or LHCb experiment you are entitled to be a member of the relevant Virtual Organisations. This gives you authorisation to use the resources allocated to the experiment.

The general method is the same for each of the experiments but there can be differences the following is the information presented by each experiment:

  • ALICE - AliEn documentation on the ALICE VO and Certificates
  • ATLAS - The section of the ATLAS workbook which details the first steps of getting on the Grid
  • CMS - The section of the CMS workbook which details the first steps of getting on the Grid
  • LHCb - The section of the LHCb workbook which details the first steps of getting on the Grid

Step 3 - Using The Grid

Each experiment uses different software and tools to access the Grid, the relevant documentation is below:

  • ALICE - AliEn documentation on using the ALICE software
  • ATLAS - The ATLAS workbook section on running a first Grid job
  • CMS - The CMS workbook section on running a first Grid job using CRAB
  • LHCb - GANGA help for the LHCb experiment
  • LHCb UK Computing help

Step 4 - Monitoring

Monitoring tools can be used to check the overall state of the Grid or particular sites, or to help track down problems if you have jobs failing. Various Grid monitoring and accounting tools are in development for different purposes, although so far they tend to be aimed at administrators rather than users.

Links to some of them can be found on the RAL Grid Operations Centre web site. If you have problems it's at least worth looking to see what the general state of the system is. Your VO may also have its own monitoring tools. The LCG ARDA project has developed a monitoring "dashboard" for each of the LHC experiments.

Specific Monitoring

General Monitoring

There is a Grid Service Monitoring Working Group who manage various monitoring tools information on them can be found here.

Step 5 - Trouble Shooting

Unfortunately it's unlikely that things will always work perfectly. Some things are covered in the documentation mentioned above, otherwise the links below may help:

Step 6 - User Guide

Currently the most comprehensive document for new Grid users is the gLite User Guide however it is orientated towards LCG. This is quite long, but it's worth knowing what it contains. The most up to date version can be found here:

http://edms.cern.ch/document/722398/

Step 7 - Reporting a problem

Experiment Specific

ATLAS Bugs are to be reported via the Savannah portal, http://savannah.cern.ch/projects/atlasukops/.

CMS Bugs are to be reported via the Savannah portal, http://savannah.cern.ch/support/?func=additem&group=cmssw.

LHCb Bugs are to be reported via the Savannah portal, https://savannah.cern.ch/support/?group=lhcb-comp-ops&func=additem.

General Grid Problems

To submit a ticket detailing an issue or problem you have had using the Grid use General Grid User Support, http://gus.fzk.de/pages/home.php

Step 8 - Training

Experiment Specific

General Grid Training

Grid Training is provided by NeSC. They provide courses both within the UK and across Europe as part of Enabling Grids for EsciencE's training activity, NA3.

The Rutherford Appleton Laboratory also provides more general IT/coding training aimed at the High Energy Physics community http://hepunx.rl.ac.uk/ukheptrain/

Last modified Fri 24 April 2009 . View page history