Profs. Vicki Greene, Charles F. Maguire, and Julia Velkovska The Little Big Bang Profs. Vicki Greene, Charles F. Maguire, and Julia Velkovska Physics 300: October 10, 2006

Relativistic Heavy Ion Physics Relativistic – kinetic energy is close to (or greater than) the rest mass energy E=mc2. Heavy – any nucleus; in practice from silicon to gold. Ion – must remove electrons from atom in order to accelerate electromagnetically. October 10, 2006 Physics 300

The Structure of the Atom October 10, 2006 Physics 300

The Strong Force – One of four fundamental forces Gravity: Electricity: The strong nuclear force between the quarks increases as the separation increases – this is very different from gravitational or electric forces which get weaker very fast as you get away from the mass or charge October 10, 2006 Physics 300

Quark-Gluon Plasma If quark-gluon plasma is formed in a RHIC collision, it will last less than 0.00000000000000000000001 seconds. (10-23 s) October 10, 2006 Physics 300

A Familiar Phase Transition October 10, 2006 Physics 300

Evolution of the Universe Too hot for quarks to bind!!! Standard Model (N/P) Physics Quark- Gluon Plasma?? Too hot for nuclei to bind Nuclear/Particle (N/P) Physics Hadron Gas Nucleosynthesis builds nuclei up to He Nuclear Force…Nuclear Physics Universe too hot for electrons to bind E-M…Atomic (Plasma) Physics E/M Plasma Solid Liquid Gas Today’s Cold Universe Gravity…Newtonian/General Relativity October 10, 2006 Physics 300

A Relativistic Heavy Ion Collision October 10, 2006 Physics 300

RHIC - The Relativistic Heavy Ion Collider October 10, 2006 Physics 300

Relativistic Heavy Ion Collider RHIC's two concentric rings are made up of 1,740 superconducting magnets. RHIC is powered by over 1,600 miles of superconducting niobium titanium wire, wrapped around the RHIC magnets. October 10, 2006 Physics 300

Interesting RHIC Facts In 20 years of running, RHIC will use less than one gram of gold (which costs about $30 today) RHIC uses enough helium to fill all the balloons in the Macy's Thanksgiving Day Parades for the next 100 years. To get the helium chilled down, RHIC's refrigerators draw 15 megawatts of electrical power. (One megawatt is enough to power 1,000 homes.) RHIC's two large experiments, STAR and PHENIX, are bigger than houses. PHENIX weighs 3,000 tons and STAR weights 1,200 tons. RHIC costs about $99 million per year to operate October 10, 2006 Physics 300

The PHENIX Detector October 10, 2006 Physics 300

The PHENIX Detector October 10, 2006 Physics 300

PHENIX Central Arms East Carriage Central Magnet West Carriage Ring Imaging Cerenkov Drift Chamber Beam-Beam Counter Central Magnet West Carriage October 10, 2006 Physics 300

Pad Chambers from Vanderbilt October 10, 2006 Physics 300

Au+Au Collision at Center-of-Mass Energy of 200•A GeV October 10, 2006 Physics 300

A collision between two gold nuclei in the PHENIX experiment (200 GeV per nucleon) October 10, 2006 Physics 300

Temperature The temperature inside a RHIC collision can exceed 1,000,000,000,000 degrees above absolute zero (that’s one trillion degrees Kelvin) This is ten thousand times the temperature at the center of our sun. October 10, 2006 Physics 300

How to pick the most head-on collisions October 10, 2006 Physics 300

How to tell if we have a plasma hadrons q leading particle leading particle schematic view of jet production Hard scatterings in nucleon collisions produce jets of particles. In the presence of a quark-gluon plasma, the jets lose much of their energy. “Jet Quenching” Once quenched, the jets could not re-appear since this would violate the 2nd Law of Thermodynamics October 10, 2006 Physics 300

Particle Identification using Time Of Flight Time of Flight array <120ps resolution Tracking system used for momentum reconstruction Resulting spectrum shows Both charge signs e/p/K/p Good signal/background!! October 10, 2006 Physics 300

Have we done it? October 10, 2006 Physics 300

RAA vs. RdA for Identified p0 Initial State Effects Only d+Au Initial + Final State Effects Au+Au d-Au results rule out initial state effects as the explanation for Jet Suppression at high pt October 10, 2006 Physics 300

Φ→K+K- RAA for Au-Au 200 GeV/c D. Pal (VU) Φ RAA looks like the π rather than the proton, consistent with recombination models October 10, 2006 Physics 300

Flow: A collective effect Elliptic flow = v2 = 2nd Fourier coefficient of momentum anisotropy dn/d ~ 1 + 2 v2(pT) cos (2 ) + ... Initial spatial anisotropy is converted into momentum anisotropy. Efficiency of the conversion depends on the properties of the medium  x y z October 10, 2006 Physics 300

Why does large flow imply early thermalization? Look at the converse: for a free-streaming system, spatial anisotropy and thus v2 do not develop PHENIX Huovinen et al V2 Pt GeV/c What is RG? From detailed hydrodynamics: therm ~ 0.6 -1.0 fm/c ~15-25 GeV/fm3 cold matter 0.16 GeV/fm3 Teany et al, Huovinen et al October 10, 2006 Physics 300

Put the results together The matter is dense The matter is strongly coupled We look forward to working with the theory community to extract the properties of the matter > 15 GeV/fm3 dNg/dy > 1100 Can we determine the properties of the matter? Tave = 300 - 400 MeV (?) Vs = ? e(dielec) = ? PHENIX preliminary The matter modifies jets The matter may melt but regenerate J/y’s The matter is hot October 10, 2006 Physics 300

Summary: Probing partonic state of dense matter RHIC has produced a strongly interacting, partonic state of dense matter We now have started probing the properties of the matter The energy loss mechanism and initial parton density from jet suppression and flow data of light and heavy quarks e >15 GeV/fm3 and dNg/dy > 1100 the initial state temperature from thermal radiation T0ave = 300-400 MeV? These high densities and temperatures are unprecedented We look forward to working with new graduate students to relate the wealth of experimental observables to the properties of matter. October 10, 2006 Physics 300

October 10, 2006 Physics 300

Probing Partonic State of Matter The matter is dense The matter is strongly coupled We look forward to working with the theory community to extract the properties of the matter PHENIX preliminary The matter modifies jets The matter may melt but regenerate J/y’s The matter is hot October 10, 2006 Physics 300

Does This Mean We Have found the Quark-Gluon Plasma? Almost certainly, and at least we have definitely found something extremely interesting. Theorists may find another explanation for these results, there may be another state of matter but this seems highly unlikely at this juncture We need to make more measurements in order to know what we have. Good scientists are careful people. Watch for another announcement in a few weeks These are exciting times for nuclear physics! October 10, 2006 Physics 300