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
