What do we study
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Too hot for quarks to bind!!! Standard Model (N/P) Physics. Too hot for nuclei to bind Nuclear/Particle (N/P) Physics. Hadron Gas. Nucleosynthesis builds nuclei up to He Nuclear Force…Nuclear Physics. E/M Plasma. Universe too hot for electrons to bind E-M…Atomic (Plasma) Physics.

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What do we study

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What do we study

Too hot for quarks to bind!!!

Standard Model (N/P) Physics

Too hot for nuclei to bind

Nuclear/Particle (N/P) Physics

HadronGas

Nucleosynthesis builds nuclei up to He

Nuclear Force…Nuclear Physics

E/M Plasma

Universe too hot for electrons to bind

E-M…Atomic (Plasma) Physics

SolidLiquidGas

Today’s Cold Universe

Gravity…Newtonian/General Relativity

What do we study

Quark-GluonPlasma??


Structure of matter in the universe

Wood

Iron

Universe

Structure of matter in the Universe

Huge scale

Gravitational

Current building block

Leptons: electron, muon, etc

scale ~ 10-10 m

Electromagnetic

scale ~ 10-15 m

Strong


What do we study

Particles

hadrons

Leptons

Force carriers

d

meson

baryon

Gluons

Glue the quark together

pion

u


Quarks are confined inside particles

Quarks are Confined inside Particles

  • Electromagnetic Interaction

  • Force (r) ~ 1/r2

  • Two charges can be broken apart and set free

  • Strong Interaction (QCD)

  • Strong interaction is mediated by gluons

  • Both gluons and quarks has “color” charge.

  • V(r) = -k1/r + k2r, k2 1 GeV / fm, constant force.

As two quarks are pulling away, energy increase. Color string fragment into new pairs of quark. Single quarks are confined inside particles. When energy is high enough, it forms a jet.


How to liberate quarks and gluons

Bayon

(pressure)

pressure

How to Liberate Quarks and Gluons

Increase Temperature and/or Pressure

Water molecule is liberated with high T and P

  • 1,500,000,000,000 K

    • ~100,000 times higher temperature than the center of our sun.

Librated Quarks and Gluons


One way to increase temperature or pressure

One Way to Increase Temperature or Pressure

Small “Bang”

Heavy alien object hits the heavy earth

Tremendous kinetic energy converted into tremendous heat and pressure.


One nuclear physicist way to increase temperature or pressure

One (Nuclear Physicist’) Way to Increase Temperature or Pressure

Mini “Bang”

Heavy (Au) Nuclei hits the heavy (Au) Nuclei

Tremendous kinetic energy converted into tremendous heat


One real nuclear physicist way to increase temperature or pressure

One (Real Nuclear Physicist’) Way to Increase Temperature or Pressure

Mini “Bang”

Heavy Nuclei hits the heavy Nuclei

Tremendous kinetic energy converted into tremendous heat


What do we study

Different Stage after the Collision

  • Right before the collision.

  • Instantly (< 1 fm/c) after the collision. Highest energy density (15GeV/fm3).

  • After ~1fm, system thermalized, i.e. thermal equilibrium. Temperature is the same everywhere.

System continue the expension and cool down.

Quarks and gluons start to fragment into hadrons. The particle ratio kept on changing due to the chemical reactions. At the point of Chemical Freezout, the chemical reaction ceased

Hadron continue to interact with each other elastically. Hadron is not changed but the momentum distribution does. At Kinetic freezout, the elastic interaction between hadrons stop. Hadron spree out and detected by the experiment


What do we study

What are the probes.

  • soft hadron: Pions, kions, protons, etc

    • coming from the fragmentation process after chemical freezout.

    • To study their behavior (cross section, correlation, suppression, etc) can leads to the estimation of the QGP properties, e.g. temperature, pressure, energy density.

  • Penetrating probes: direct photons, jet, heavy flavor, etc

    • Coming from the QGP, i.e. before the chemical freezout. Directly bring the information of the QGP properties.


What do we study

What are Detected

particle tracks

Detector in Rphi plane

beam

beam

  • collision vertex

  • particle momentum (px, py, pz) right after the collsion through bending curvature in the magnet field.

  • particle energy (photon, no bending in the magnet field).

  • particle species identification through, e.g. energy loss (dE/dx) and particle speed (time of flight), cerenkov radiation, etc.


What do we study

How an experiment take data


What do we study

Take what is necessary: trigger

  • One can take all the collision events with enough resources.

  • Not every collision is interesting.

    • heavy flavor, photon are very rare.

trigger

target

  • soft hadron production ……………………………..…………… Minimum-bias trigger

  • Direct photons ………………………………………..…………… photon trigger

  • High pT particles (belong to jet). ………………………………….. High pt trigger

  • J/psi, D meson production. ………………….…………………… J/psi, D meson trigger

  • ………………………..


What do we study

What is needed for the result to be publishable

  • The result, in principle, need to be independent of a specific experiment.

  • An experiment is specific in it:

  • detector acceptance (Accp):

    • N (accepted by the detector)/N (produced from the collision).

  • Detector efficiency (Eff).

    • HV trip, construction flaw. The efficiency < 100%

  • Experiment trigger efficiency (Trg_eff).

    • Trigger always biased,

      • e.g. photon trigger: only accept events with hits above a certain energy.

accp

pT

y

x

Trg_eff

pT


What do we study

Example of Publishable Results.

  • cross section (σ):a Lorentz invariant measure of the probability of interactions. It has dimension of area (unit cm2 or barn )

    • σ x L = N(events), where L is the luminosity, i.e. the intensity of the beams


How to study qgp

How to Study QGP

p+p

  • Nuclei is made of protons and neutrons: p+p collision is a natural reference (note: QGP may have already been produced by p+p collisions: ask Rolf and Brijesh)

  • Behavior Quarks and gluons in a static nuclei is different from that in proton.

    • Cold nuclear effect, or initial state nuclear effect, i.e. before collisions

    • p(d)+Au can quantify this effect.

  • New matter is produced after the collisions ( hot or final state effect).

d+Au

Au+Au

time


What do we study

Study QGP in different Centrality

Most Central events (highest multiplicity), e.g. top 5% central, i.e. 5% of the events with largest multiplicity

Mid Central events

Most Peripheral events

From most central to most peripheral event, the collision is more like a p+p collisions.

One can also collision smaller size of nuclear, e.g. Cu+Cu, Si+Si, instead of Au+Au to gain more luminosity.

Centrality can be quantified by the number of collisions (N_coll) and number of participants (N_part) through the glauber model calculation with

N_coll: 8 N_part: 6


What do we study

Ways to Reveal the QGP properties---RAA

RAA ( or RdA)

No medium effect

  • nuclear modification factor (RAA):


What do we study

Au + Au Experiment (200GeV)

d + Au Control Experiment (200GeV)

Final Data

Preliminary Data

Cronin enhancement: parton pT smearing from random kick before collisions (i.e. initial state effect)

Energy loss: parton loss lots of energy (dE/dx = ???GeV/fm) through bremsstrahlung when pass through the new state of matter (final state effect)


What do we study

trigger

Adler et al., PRL90:082302 (2003), STAR

away-side

near-side

Ways to Reveal the QGP properties---Jet correlation

Calculate angle between two jet particles

Energy dissipated when parton pass through opaque medium. How?


What do we study

1 < pT (assoc) < 2.5 GeV/c

Thanks Andy


Ways to reveal the qgp properties particle ratio

Ways to Reveal the QGP properties---particle ratio

  • abundances in hadrochemical equilibrium

Particle ratio is determined by Temperature and chemical potential

>= critical temperature


Ways to reveal the qgp properties flow

Ways to Reveal the QGP properties---flow

V1: directed flow

V2: elliptic flow

Higher order


A movie of glass bead show liquid behavior

A Movie of Glass Bead Show Liquid Behavior

http://www-news.uchicago.edu/releases/07/071106.liquids.shtml


What do we study

Decreasing the number of glass beads in the cross section of the jet changes the behavior of the granular stream after hitting the target from liquid-like pattern to one that looks like fireworks. This latter pattern is more characteristic of how individual particles would behave after hitting a wall.


A movie of glass bead show liquid behavior1

A Movie of Glass Bead Show Liquid Behavior

http://www-news.uchicago.edu/releases/07/071106.liquids.shtml


More materials

More Materials

  • RHIC white paper: for physics understanding

    • J. Adams et al., Nucl. Phys. A 757, 102 (2005); K. Adcox et al., Nucl. Phys. A 757, 184 (2005) ; I. Arsene et al., Nucl. Phys. A 757, 1 (2005); B. B. Back et al., Nucl. Phys. A 757, 28 (2005).

  • CERN detector and analysis brief book: For nice explanation of jargon in this field.

    • http://physics.web.cern.ch/Physics/DataAnalysis/BriefBook/

    • http://physics.web.cern.ch/Physics/ParticleDetector/BriefBook/


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