CERN Prototype Materials

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Select Documents and Meetings

  • Current (2015)
    • Workup to the proposal
      • DocDB 10385: Brief review of Computing Requirements for the test
      • DocDB 10428: Draft proposal for the test and comments on the document
    • Proposal

Appendix I

An early example of the measurements program

Particle Type Momentum Range (GeV/c) Bin (MeV/c)
p 0.1-2.0 100
p 2.0-10.0 200
π± 0.1-2.0 100
π± 2.0-10.0 200
μ± 0.1-1.0 50
μ± 1.0-10.0 200
e± 0.1-2.0 100
e± 2.0-10.0 200
K+ 0.1-1.0 100
γ(π0) 0.1-2.0 100
γ(π0) 2.0-5.0 200

Appendix II

The detector characterization includes a few distinct areas, and the goals of measurements in each affect the desired statistics. A few items are presented below.

Energy Scale and Resolution

In terms of detector characterization, some of the important parameters include energy scale and resolution for both single tracks and showers - hadronic and EM. Let's consider them first (using comments from T.Junk):

  • Energy scale: for Gaussian distribution, uncertainty will be sigma/sqrt(n). Assuming resolution of 1%, and aiming for ±0.1% precision, only 100 events would be needed.
  • Hadronic showers: older calorimeters had resolution of 80%/sqrt(E). Since sampling fraction in LAr TPC is higher, we are likely to do better than this, but still conservatively assume O(10%)/sqrt. Qualitatively, we can follow arguments similar to the previous item. It follows then that O(103-104) events will be enough for the purposes of this measurement. Indeed, looking at typical test beam and calibration practices (per papers published), we see that 104 events is the typical statistics for a given incident beam momentum.

In summary, depending on case, this part of the measurement program can be accomplished with event sample of the size ~O(103-104), and in some cases less.

PID

Measuring the "fake" rate, i.e. particle mis-identification, is important for certain physics to be addressed by the experiment (cf. proton decay). If the probability of mis-PID is "p", then the statistical uncertainty can be expressed as sqrt(p*(1-p)/n). This can also be understood in terms of precise measurements of "tails" in certain distributions. If we are looking at probabilities of mis-identification of the order of 10-6, this translates into quite substantial statistics. At the time of writing, we need more guidance in this area, but in general it appears that in this case we would indeed be motivated to take as much data as practically feasible. This does mean that we will aim to take a few million events in each of a few momentum bins (TBD). Reading: Nucleon Decay Searches

Systematics

Let's assume we want to measure a signal with 5% precision and signal to background ratio is 1:10. To provide this scale of accuracy, we will need ~105 events in the momentum bin of interest.

Appendix III

DAQ references

Note: some of these links may be restricted to users associated with respective LHC experiments. This will be resolved at a later date (i.e. relevant and public information extracted, reduced and systematized).

Data Storage Links

General CERN Storage Info

  • In early 2000s, the CASTOR system was deployed at CERN which provides front-end to mass storage, in the form of both tape and disk pools. In early 2010s, the disk pools were largely migrated to EOS, a newer and high-performance system based on XRootD which has better functionality for managing large disk pools. CASTOR is still used for custodial data on tape.
  • Overview of LHC storage operations at CERN
  • CASTOR

EOS

bash-4.1$ more /afs/cern.ch/project/eos/installation/atlas/etc/setup.sh
# source me
alias eos="/afs/cern.ch/project/eos/installation/0.3.84-aquamarine/bin/eos.select"
alias eosumount="/afs/cern.ch/project/eos/installation/0.3.84-aquamarine/bin/eos.select -b fuse umount"
alias eosmount="/afs/cern.ch/project/eos/installation/0.3.84-aquamarine/bin/eos.select -b fuse mount"
alias eosforceumount="killall eosfsd 2>/dev/null; killall -9 eosfsd 2>/dev/null; fusermount -u "
  • Run EOS CLI ("eos")
    • Now you can use EOS CLI commands, e.g.: ls /eos/atlas/atlasdatadisk/rucio/data15_13TeV/ab/f4
    • FullEOS CLI list of commands:
access               Access Interface
archive              Archive Interface
attr                 Attribute Interface
backup               Backup Interface
clear                Clear the terminal
cd                   Change directory
chmod                Mode Interface
chown                Chown Interface
config               Configuration System
console              Run Error Console
cp                   Cp command
debug                Set debug level
dropbox              Drop box
exit                 Exit from EOS console
file                 File Handling
fileinfo             File Information
find                 Find files/directories
fs                   File System configuration
fsck                 File System Consistency Checking
fuse                 Fuse Mounting
group                Group configuration
help                 Display this text
io                   IO Interface
json                 Toggle JSON output flag for stdout
license              Display Software License
ls                   List a directory
map                  Path mapping interface
mkdir                Create a directory
motd                 Message of the day
node                 Node configuration
ns                   Namespace Interface
pwd                  Print working directory
quit                 Exit from EOS console
quota                Quota System configuration
reconnect            Forces a re-authentication of the shell
recycle              Recycle Bin Functionality
rmdir                Remove a directory
rm                   Remove a file
role                 Set the client role
rtlog                Get realtime log output from mgm & fst servers
silent               Toggle silent flag for stdout
space                Space configuration
stat                 Run 'stat' on a file or directory
test                 Run performance test
timing               Toggle timing flag for execution time measurement
transfer             Transfer Interface
version              Verbose client/server version
vid                  Virtual ID System Configuration
vst                  Virtual Storage Interface
whoami               Determine how we are mapped on server side
who                  Statistics about connected users
?                    Synonym for `help'
.q                   Exit from EOS console
  • Direct xrootd-based copy in Linux shell (example): xrdcp root://eosatlas//eos/atlas/atlasdatadisk/rucio/data15_13TeV/ab/01/NTUP_TRIGRATE.05805712._003841.pool.root.1 .

Misc

Data Management

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