Mini Bang at Big Accelerators

Prashant ShuklaInstitute of Physics

University of Heidelberg

Presentation at ISA, 30 January 2005, Heidelberg, Germany

Outline

● What is an Atom, Nucleus ? ● Nuclear Physics Experiment ?● A Particle Accelerator ?● A Nuclear Detector ?● Structure within nucleus ?● New state of matter- Quark Gluon Plasma ● History of the Universe● The Idea of the Big Bang● Big Bang in Lab● Large Hadron Collider (LHC) at CERN● The ALICE Experiment ● The TRD (Transition Radiation Detector)● Computer Simulations ● The studies done on the computer

An Atom

The smallest unit of any substance which decides ist The smallest unit of any substance which decides ist chemical propertieschemical properties

ee

ee

ee ee

Nucleus size ~ 10^(-14) meter

Atom ~ 10^(-10) meter

The Nucleus

All the mass of atom is inside nucleusAll the mass of atom is inside nucleus

Nuclear Physics Experiment

Energetic particles are used to see the nucleus and ist constituent which can not be seen by any optical microscope.

Alpha particle

Gold nucleusCharge = +79

Detector

Smaller the size you want to probe larger the energy of the probe particle

A Particle Accelerator

A charged particle when passes through a high voltage difference it gains energy or accelerated

Energy Gained

E = qV

+q

+V

An electron passes through 1 volt gains 1 eV of energy

1 MeV = 10^6 eV 1 TeV = 10^12 eV

Modern Particle Accelerator

TimeVoltage

A Multi-Accelerator ComplexThe Relativistic Heavy Ion Collider – RHIC

100 A GeV

1 A MeV

95 A MeV 10.8 A GeVPHENIX

Relativistic Heavy Ion Accelerators in the world

A Detector

+V

-V

Structure within nucleus

Ordinary matter is made of up and down quarks

Force between two quarks

Compare to gravitational force at Earth’s surface

Quarks exert 16300 Kg of force on each other!

quark quark

gluons

Introduction to Quark Gluon Plasma

Quarks are Freely moving inside proton but,  Forbidden to come outside

Hadrons Phase Transition QGP

Protonq q q

     Increase hadron Density --- Compressing

    Or increase K. E. of hadrons --- Heating

The unverse is supposed to have started from this soup

n p pin p pi p n pi p

q g qq g q q q q

History of the Universe

Weber

The Idea of the Big Bang

Weber

Three main ideas under the big bang model • The universe cools as it expands• In very early times, the universe was mostly

radiation• The hotter the universe, the more energetic photons

are available to make matter and anti-matter

The full story can be emerged if we produce conditions similar to BIG BANG:

Produce a temperature of 10^13 K

How to produce heat

Heavy Ion Collisions

Weber

PARTICLES!

, e+e-,

+ KpnDd,

J/Y,…

LHC at CERN

SPS 1986-2003 Pb upto 20 AGeVLHC 2007 upto 5.5 ATeV

The ALICE Experiment

ITSLow pt trackingVertexing

TPCTracking, dEdx

TRDElectron ID

TOFPID

HMPIDPID (RICH) @ high pt

PHOS,0 MUON

-pairs

PMD multiplicity

Y

X

Z

Expected dilepton invariant mass spectrum (Schematic)

Heavy Ion Collisions at LHC 5.5 TeV

The TRD (Transition Radiation Detector)

● 18 supermodules in phi sector

● 6 Radial layers● 5 Z longitudinal stack 540 chambers 750m2 active area 28m3 of gas

in total 1.18 million read out channels

|eta| < 0.9 45 <Theta <135

TRD Stack used in CERN test beam

AliRoot Simulations

dNch/d ~ 8000 (slice: 2o in

TPC

5000 PbPb events at 5.5 TeV/nucleon pair

ITS

PHOS

TRD

TOF

HMPID

Particle identification with TRD

● Transition Radiation photons are generated by charged particles crossing the border between two different di-electric media

● Elektron-/pion-discrimination: (p = 5 GeV/c): e- ~ 10000 pi ~ 36

Pi efficiency vs electron efficiency

Invariant Mass spectrum

e+e- invariant mass Signal/noise with pt-cut

Summary

● What is an Atom, Nucleus.● Nuclear Physics Experiment. Accelerator, Detector.● Structure within nucleus ?● New state of matter- Quark Gluon Plasma ● History of the Universe● Big Bang in Lab● LHC at CERN, ALICE Experiment ● Computer Simulations ● The studies done on the computer