Transcript Document
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)
~ 10 ms after
Big Bang
LHC
RHIC
Early Universe
Quark-Gluon
Plasma
Tc ~ 170 MeV
Temperature
SPS
AGS
Hadron gas
Nuclear
matter
Baryon density
Neutron Star
r
ec ~ 1 GeV/fm3
~ 5 - 10 nuclear
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
K+
Xp+
W+
s
d d
u
u u d u
d u
d u d
d d u
s s d u s
d
d
u d d d d
u
u s
u
u
d u u
d
s
s
u u
s u d d
d
s
s s u u
d
u
u s s d u s
u
d
u
s
s d
p-
p
L
Strange Particles
Strange particles are hadrons
containing at least one strange quark.
For example
K os (ds) kaon
Λ (uds) hyperon
V0 decay pattern
The starting particle disappears from
the interaction point and two
oppositely charged particles appear in
opposite directions
+π Ko
→
π
s
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
Bubble chambers
W– in 2-m CERN hydrogen bubble chamber
1973
30 เม.ย. – 1 พ.ค. 2555
Karel Šafařík: ParticleTracking
[email protected]
15
Bubble chambers
D* in BEBC hydrogen bubble chamber
1978
30 เม.ย. – 1 พ.ค. 2555
Karel Šafařík: ParticleTracking
[email protected]
16
Streamer chamber
p+m+e+ decay in streamer chamber
1984
30 เม.ย. – 1 พ.ค. 2555
Karel Šafařík: ParticleTracking
[email protected]
17
Streamer chamber
6.4 TeV Sulphur - Gold event (NA35)
1991
30 เม.ย. – 1 พ.ค. 2555
Karel Šafařík: ParticleTracking
[email protected]
18
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 Pho
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
Middleware
The gLite middleware is produced by
the EGEE project.
Computing model at ALICE
Computing
framework
Simulation
Reconstruction
Data
analysis
Main software
Root
Aliroot
Geant3
ROOT framework
33
AliRoot framework
• Modularity
• Re-usability
34
Event generators :
HIJING
DPMJET
PYTHIA
ALICE have developed
a generators base
class called
AliGenerator.
35
Detector response simulation
36
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.
2.
3.
4.
5.
6.
7.
8.
PWG-PP Detector Performance
PWG-CF Correlations Fluctuations Bulk
PWG-DQ Dileptons and Quarkonia
PWG-HF Heavy Flavour
PWG-GA photon and pion working group
PWG-LF Light Flavour Spectra
PWG-JE Jets
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 Cosmics
Ultra Peripheral Collisions
Cross section and Multiplicity
Diffraction
Cosmics
Acknowledgement
Suranaree University of Technology
Thailand Center of Excellence in
Physics (ThEP)
National Electronics and Computer
Technology Center