thomas k hemmick, stony brook university for the phenix collaboration

The PHENIX Experiment The PHENIX Experiment at RHIC:at RHIC:

Can We Rewind the Clock to Catch aCan We Rewind the Clock to Catch a

Glimpse Near the Beginning of Time?Glimpse Near the Beginning of Time?

Thomas K Hemmick, Stony Brook Universityfor the PHENIXPHENIX Collaboration

T.K. HemmickT.K. Hemmick

The Beginning of TimeThe Beginning of Time Time began with the Big Bang:Time began with the Big Bang:

All energy and matter of the universe was in a state All energy and matter of the universe was in a state of intense heat and compression.of intense heat and compression.

Since then the Universe has cooled Since then the Universe has cooled While cooling, the material of the universe While cooling, the material of the universe

underwent several phase changes.underwent several phase changes. 2.7 Kelvin is the temperature of most of the 2.7 Kelvin is the temperature of most of the

universe today.universe today. However, there exist a few “hot spots” where the However, there exist a few “hot spots” where the

expanding matter has collapsed back in upon itself.expanding matter has collapsed back in upon itself. What do we know and what can we learn from What do we know and what can we learn from

laboratory experiments about this past history?laboratory experiments about this past history?


Evolution of the UniverseEvolution of the Universe

Nucleosynthesis builds nuclei up to HeNuclear Force…Nuclear Physics

Universe too hot for electrons to bindE-M…Atomic (Plasma) Physics

E/M Plasma

Too hot for quarks to bind!!!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 HadronGas

SolidLiquid

Gas

Today’s Cold UniverseGravity…Newtonian/General Gravity…Newtonian/General

RelativityRelativity

Stars convert gravitational energy to temperature.

They “replay” and finish nucleosynthesis

~15,000,000 K in the center of our sun.

Collisions of “Large” nuclei convert beam energy to temperatures above 200 MeV or 1,500,000,000,000 K

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

“Large” as compared to mean-free path of produced particles.

Reheating Matter


RRelativistic elativistic HHeavy eavy IIon on CCollider (ollider (RHICRHIC))PPioneering ioneering HHigh igh EEnergy nergy NNuclear uclear IInteraction enteraction eXXperiment (periment (PHENIXPHENIX))

2 counter-circulating rings, 3.8 km circumference

Any nucleus on any other. Top energies (each beam):

100 GeV/nucleon Au-Au. 250 GeV polarizedpolarized p-p.

Maximal Set of Observables Photons, Electrons, Muons, ID-

hadrons Highly Selective Triggering

High Rate Capability. Rare Processes.


Nature is in ChargeNature is in Charge RHICRHIC provides the energy to reheat matter. provides the energy to reheat matter. PHENIXPHENIX observes the debris of the collision. observes the debris of the collision. Creation of a primordial medium is out of our Creation of a primordial medium is out of our

hands:hands: How and whether the collisions express the energy as How and whether the collisions express the energy as

new phases of matter cannot be controlled by us.new phases of matter cannot be controlled by us. The collisions are so fleeting (The collisions are so fleeting (t ~10t ~10-22-22 sec) the signals sec) the signals

from a single such collision travel only several nuclear from a single such collision travel only several nuclear diameters before the system breaks apart.diameters before the system breaks apart.

Nature must create both the medium and its Nature must create both the medium and its diagnostic signatures.diagnostic signatures.

We set the stage and fill the audience, We set the stage and fill the audience, Nature puts on the showNature puts on the show..


The Medium and the ProbeThe Medium and the Probe At RHIC energies different At RHIC energies different

mechanisms are mechanisms are responsible for different responsible for different regions of particle regions of particle production.production.

The rare process (Hard The rare process (Hard Scattering or “Jets”) is the Scattering or “Jets”) is the probe of whether the soft probe of whether the soft production products form a production products form a medium.medium.

Calibrated Probe Calibrated Probe ““The tail that wags the dog” The tail that wags the dog”

(M. Gyulassy)(M. Gyulassy)

p+p->0 + X

HardScatterin

g

Thermally-shaped Soft Production

hep-ex/0305013 S.S. Adler et al.

“Well Calibrated”


Fate of Hard Scattered Fate of Hard Scattered PartonsPartons

Hard scatterings in Hard scatterings in nucleon collisions nucleon collisions produce jets of particles.produce jets of particles.

In the presence of a In the presence of a color-deconfined color-deconfined medium, the partons medium, the partons strongly interact strongly interact (~GeV/fm) losing much (~GeV/fm) losing much of their energy.of their energy.

““Jet Quenching”Jet Quenching”

hadrons

q

q

hadrons leadingparticle

leading particle

schematic view of jet production

Once quenched, the jets could not re-appear since this would violate the

2nd Law of Thermodynamics


Particle Spectra EvolutionParticle Spectra Evolution

“Peripheral”

ParticlePhysics

“Central”

NuclearPhysics

K. Adcox et al, Phys Lett B561 (2003) 82-92


Nuclear Modification Factor: RNuclear Modification Factor: RAAAA

We define the nuclear We define the nuclear modification factor as:modification factor as:

RRAAAA is what we get divided by is what we get divided by what we expect.what we expect.

By definition, processes that By definition, processes that scale with the number of scale with the number of underlying nucleon-nucleon underlying nucleon-nucleon collisions (aka Ncollisions (aka Nbinarybinary) will ) will produce Rproduce RAAAA=1.=1.

ddpdNddpNd

NpR

T

NN

NNinel

binary

T

AA

evtTAA

2

21

)(

RAA is well below 1 for both charged hadrons and neutral pions.

The neutral pions fall below the charged hadrons since they do not contain contributions from protons and kaons.

nucl-ex/0304022 S.S. Adler et al.

Au+Au->0+X


d+Au Control Experimentd+Au Control Experiment

Collisions of small with large nuclei were always foreseen as necessary to Collisions of small with large nuclei were always foreseen as necessary to quantify quantify coldcold nuclear matter effects. nuclear matter effects.

Recent theoretical work on the “Color Glass Condensate” model provides Recent theoretical work on the “Color Glass Condensate” model provides alternative explanation of data:alternative explanation of data:

Jets are not quenched, but are a priori made in fewer numbers.Jets are not quenched, but are a priori made in fewer numbers. Color Glass Condensate hep-ph/0212316; Kharzeev, Levin, Nardi, Gribov, Ryshkin, Mueller,

Qiu, McLerran, Venugopalan, Balitsky, Kovchegov, Kovner, Iancu Small + Large distinguishes Small + Large distinguishes allall initial and final state effects. initial and final state effects.

Nucleus- nucleuscollision

Proton/deuteron nucleuscollision


d+Au Spectrad+Au Spectra

Final spectra for charged hadrons and identified pions.Final spectra for charged hadrons and identified pions. Data span 7 orders of magnitude.Data span 7 orders of magnitude.


RRAAAA vs. R vs. RdA dA for Identified for Identified 00

d+Au

Au+Au

Initial State Effects Only

Initial + Final State Effects

d-Au results rule out CGC as the explanation for Jet d-Au results rule out CGC as the explanation for Jet Suppression at Central Rapidity and high pSuppression at Central Rapidity and high pTT


Charged Hadron ResultsCharged Hadron Results Striking difference of Striking difference of

d+Au and Au+Au results.d+Au and Au+Au results. Charged Hadrons higher Charged Hadrons higher

than neutral pions.than neutral pions.

Cronin Effect:

Multiple Collisions broaden high PT

spectrum


Centrality DependenceCentrality Dependence

Dramatically different and opposite centrality Dramatically different and opposite centrality evolution of Au+Au experiment from d+Au control.evolution of Au+Au experiment from d+Au control.

Jet Suppression is clearly a final state effect. Jet Suppression is clearly a final state effect.

“PHENIX Preliminary” results, consistent with PHOBOS data in submitted paper

Au + Au Experiment d + Au Control Experiment

Preliminary DataFinal Data


The “Away-Side” JetThe “Away-Side” Jet

Jets produced on the periphery of the Jets produced on the periphery of the collision zone coming out should collision zone coming out should survive.survive.

However, their partner jet will However, their partner jet will necessarily be pointed into the necessarily be pointed into the collision zone and be absorbed.collision zone and be absorbed.

60-90%60-90%

PHENIX Preliminary

Escaping Jet“Near Side”

Lost Jet“Far Side”

d+Aud+Au Au+AuAu+Au

NearNear Far Far

Min BiasMin Bias 0-10%0-10%

PHENIX Preliminary

Peripheral Au+Au similar to d+AuPeripheral Au+Au similar to d+Au Central Au+Au shows distinct Central Au+Au shows distinct

reduction in far side correlation.reduction in far side correlation. Away-side Jet is missing in Au+AuAway-side Jet is missing in Au+Au

“PHENIX Preliminary” results, consistent with STAR data in submitted paper


What’s NextWhat’s Next

We must investigate other probes that look deeply into the We must investigate other probes that look deeply into the medium to characterize it.medium to characterize it.

Same paradigm, Same paradigm, The Rare Processes Probe the MediumThe Rare Processes Probe the Medium:: Heavy Quark StatesHeavy Quark States

• Dissolution of J/Dissolution of J/ & & ’, the bound states of charm-anticharm quarks ’, the bound states of charm-anticharm quarks probes quark deconfinement.probes quark deconfinement.

Electromagnetic Probes (no strong interaction)Electromagnetic Probes (no strong interaction)• Lack of strong interaction allows them to penetrate the black medium Lack of strong interaction allows them to penetrate the black medium

and see through the hadronic veil and see through the hadronic veil • Direct Photons, eDirect Photons, e++ee--, , ++--

PHENIX plans to make these measurements in the next PHENIX plans to make these measurements in the next Au+Au run.Au+Au run.


SummarySummary We have seen via Au+Au Jet Quenching and the d+Au We have seen via Au+Au Jet Quenching and the d+Au

control experiment that a medium with strong final state control experiment that a medium with strong final state effects is formed in Au+Au collisions at RHIC.effects is formed in Au+Au collisions at RHIC.

Our announcement today is that we indeed have the Our announcement today is that we indeed have the opportunity to learn about the conditions of our universe opportunity to learn about the conditions of our universe soon after the Big Bang.soon after the Big Bang.

We have set the stage and Nature has granted us a show. We have set the stage and Nature has granted us a show. We will measure the properties of the medium and will We will measure the properties of the medium and will learn whether or not the quarks are confined.learn whether or not the quarks are confined.

It would be presumptuous without having measured the It would be presumptuous without having measured the additional medium probes to now label the medium in additional medium probes to now label the medium in accordance with our preconceptions as being the Quark-accordance with our preconceptions as being the Quark-Gluon Plasma.Gluon Plasma.

Nature has been known to include surprise endings, the Nature has been known to include surprise endings, the observation and understanding of which represent the real observation and understanding of which represent the real progress in science. progress in science.

thomas k hemmick, stony brook university for the phenix collaboration

Documents

au aup0

gevnucleon auau

hemmickthe medium

primordial medium

expanding matter

cold nuclear matter

colordeconfined medium

nuclear diameters