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Study of quark - gluon plasma production at the
ALICE detector, CERN
Chinorat Kobdaj
SPC 2012
11 May 2012
What is heavy ion physics? What is ALICE?
quark Found in proton and neutron Bound by strong force Mediated by exchanging gluons No free quark has been observed
(confinement)
quark-gluon plasma (qgp)
at very high temperatures and/or very high densities
Tc ≈ 170 MeV ≈ 2000 billion K (compare Sun core: 15 million K)
Tc ~ 170 MeV
r~ 5 - 10 nuclear
Quark-Gluon Plasma
Hadron gas
Nuclearmatter
Neutron Star
SPSAGS
Early Universe LHCRHIC
Baryon density
Tem
pera
ture
ec ~ 1 GeV/fm3
~ 10 ms after Big Bang
How to make qgp? By colliding two heavy
nuclei at a speed close to the speed of light
as the system expands and cools down it will undergo a phase transition from QGP to hadrons again, like at the beginning of the life of the Universe
QGP lifetime ~ a few fm/c
Where can we do it? at the CERN Large Hadron Collider
What is ALICE? ALICE (A Large Ion Collider Experiment) It has been designed to work with a large
number of particles obtained form collisions of lead nuclei at the extreme energies of the LHC.
How can we see the qgp? Strange quarks are not component of
the colliding nuclei. But we have observed some strange
quarks in the collision. This is called Strangeness enhancement.
Strange quarks or antiquarks observed have been created from the kinetic energy of colliding nuclei.
Therefore, we look at the strangeness enhancement as a signature for quark gluon plasma
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Strange Particles Strange particles are hadrons
containing at least one strange quark. For example
(d) kaonΛ (uds) hyperon
V0 decay pattern The starting particle disappears from
the interaction point and two oppositely charged particles appear in opposite directions
→ π+π-
Λ→ p + π-
Cascade decays Ξ- decays into π- and Λ Then the Λ then decays into π- and
proton Ξ-→π-Λ→ π- p + π-
30 เม.ย. – 1 พ.ค. 2555 Karel Šafařík: ParticleTracking [email protected] 15
Bubble chambers– in 2-m CERN hydrogen bubble chamber
1973
1630 เม.ย. – 1 พ.ค. 2555Karel Šafařík: ParticleTracking
Bubble chambers D* in BEBC hydrogen bubble chamber
1978
1730 เม.ย. – 1 พ.ค. 2555Karel Šafařík: ParticleTracking
Streamer chamber++e+ decay in streamer chamber
1984
1830 เม.ย. – 1 พ.ค. 2555Karel Šafařík: ParticleTracking
Streamer chamber6.4 TeV Sulphur - Gold event (NA35)
1991
Today there are so many tracks.2010
How can we do it? By the help of computer Simulation software Interface with the detectors
LHC Computing Grid The data stream from
the detectors provides approximately 300 GB/s
27 TB of raw data per day or 10–15 PB of data each year
These data is more than any single, current, system can handle
Scientists look at a computer screen at the control centre of the CERN in Geneva September 10, 2008. (Xinhua/Reuters Photo)
We need to find the system that
can handle massive amounts of data can process large computing jobs relatively inexpensive simple to use can access 24/7 easily upgraded
Why don’t we build a super Computers ?
very expensive very difficult to access obsolete quickly
http://gizmodo.com/298029/worlds-biggest-supercomputer-is-a-virus
Solution: using the Internet ?
A Computing Grid
GridPP masterclasstalk2009
What is middleware? Middleware is a computer software that
allows users to submit jobs to the Grid without knowing where the data is or where the jobs will run. The software can run the job where the data is, or move the data to where there is CPU power available.
How to set up LHC GRID site?
The basic LCG site consists of
UI User Interface CE Compute Element WN Worker Nodes SE Storage Element Site BDII Berkley
Database Information Index MON Monitor Accounting service
Operating system SLC5
Computing model at ALICE
Computing frameworkSimulationReconstructionData analysis
Main software Root Aliroot Geant3
ROOT framework
33
AliRoot framework
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• Modularity
• Re-usability
Event generators : HIJING DPMJET PYTHIA
ALICE have developed a generators base
class called AliGenerator.
35
Detector response simulation
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Simulation process : Event generation of final-state particles Particle transport Signal generation and detector response Digitization Fast simulation
37
Analysis tools Statistical tools Calculations of kinematics variables Geometrical calculations Global event characteristics Comparison between reconstructed
and simulated parameter Event mixing Analysis of the HLT data visualization
38
ALICE Physics Working Group
1. PWG-PP Detector Performance
2. PWG-CF Correlations Fluctuations Bulk
3. PWG-DQ Dileptons and Quarkonia
4. PWG-HF Heavy Flavour
5. PWG-GA photon and pion working group
6. PWG-LF Light Flavour Spectra
7. PWG-JE Jets
8. PWG-UD
1. PWG-PP Detector Performance Quality Assurance Calibration Event Characterization Particle Identification Event and Track Selections Tracking and Alignment Run Conditions
Embedding and mixing Monte Carlo
2. PWG-CF Correlations Fluctuations Bulk
Correlations Event-by-Event / Fluctuations Femtoscopy Flow
3. PWG-DQ Dileptons and Quarkonia Lmee Low Mass Dielectron Lmmumu Low Mass Mumu Jpsi2ee J/ψ to e+e- at mid-rapidity Jpsi2mumu J/ψ to Mumu Upsilon2mumu Upsilon to mumu
* 4. PWG-HF Heavy Flavour HFE Electrons from HF decays D2H Fully reconstructed charm hadron
decays HFM Muon from HF decays
5. PWG-GA photon and pion working group
Gamma and Neutral Pions
6. PWG-LF Light Flavour Spectra
GEO Global Event Observables Resonances Spectra Strangeness
7. PWG-JE Jets
8. PWG-UD Ultraperipheral, Diffractive, Cross
section and Multiplicity, and CosmicsUltra Peripheral CollisionsCross section and MultiplicityDiffraction Cosmics
Acknowledgement Suranaree University of Technology Thailand Center of Excellence in
Physics (ThEP) National Electronics and Computer
Technology Center
