Axel Drees, University Stony Brook, February 10, 2003

Research Frontiers in Nuclear Physics

Central truths of nuclear physics

driving research for more than one century

We are dust (c. 1950)

We are nothing (c. 1900)

We don’t matter (c. 2000)

Axel Drees

Most of “us” is (nearly) empty space 99.9% of the mass of atoms is contained in the nucleus The nucleus is about 10-12 of the size of the atom Nuclear density 1014 times larger than density of water

ProtonProton

NeutronNeutronQuarksQuarksHeld togetherHeld togetherby gluonsby gluons(not shown)(not shown)

NucleusNucleus(“ion” when alone)(“ion” when alone)

AtomAtom

We are nothing !

birth of nuclear physics

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neutrons

pro

ton

s

50 100

5010

0

Nuclear Zoology and the Nuclear Chart Categorize properties of nuclei and present in nuclear chart

valley of s

tability

near Z

= NNo stable nuclei beyond 208 Pblimited range of nuclear force

Magic Z and N numbers with many stable nucleiIndication of shell structure

p n Coulomb repulsion of protonsFermi gas model

28

20

126

50

82

2

8

20

50

82

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Going to the Extremes of Nuclear Structure

The many body problem Nucleus is complex system of many strongly interacting particles Needs to be treated microscopically Remains one of the major theoretical challenges

Search for super heavy nuclei

Island of stability near next shell closer The ultimate test of shell models

Element 112 discovered at GSI“Ununbiium”

Nuclei with extreme angular momentum

Sensitive test of shell models Actively pursued by Prof. Fossan and Starosta at Stony Brook NSL and other facilities

184

114

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We are dust !Most elements create in stellar catastrophes long after big bang

~ 100 s after Big Bang

Nucleon Synthesisstrong force binds protons and neutrons bind into light nuclei He to Li

Elements up to Fe fussed in Stars Heavy elements created in super nova explosions

We are mostly stardust !

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Nuclei far from Stability Explore “Terra Incognita” to proton and neutron drip line

Important for creation of heavy elements in Supernovae Proton rich created with stable beams Neutron rich require radio active beams Neutron rich nuclei only created

with radioactive beams Interesting Atomic physics ongoing experiments in NSL

(Prof. Sprouse & Orozco)

Rare Isotope Accelerator

new $800M US project

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We don’t matter !

More accurately: We’re not matter

Nearly all the mass of each atom is concentrated in the nucleus:

Each nucleus consists of neutrons and protons

Each neutron and proton consists of 3 quarks

Each quark has the mass of 5-7 MeV/c2

~ 1% of a proton or neutron(!)

The rest of the mass of protons and neutrons (and hence our mass)

is “frozen energy” from the Big Bang

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~ 10 s after Big Bang

Hadron Synthesisstrong force binds quarks and gluons in massive objects: protons, neutrons mass ~ 1 GeV/c2

~ 100 s after Big Bang

Nucleon Synthesisstrong force binds protons and neutrons bind in nuclei

The Big Freeze

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Fundamental Puzzles of Hadrons Confinement

Quarks do not exist as free particles

Large hadron masses Free quark mass ~ 5-7 MeV Quarks become “fat” in hadrons constituent

mass ~ 330 MeV

Complex structure of hadrons Sea quarks and anti quarks Gluons

“spin crisis” Spin of protons not carried by quarks!

All addressed at RHIC

Go back in time to big bangFeasible in heavy ion collisions

Measurement with polarized proton beams at high energy

nuclear matter p, n

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“Travel” Back in Time QGP in Astrophysics

early universe after ~ 10 s possibly in neutron stars

Relativistic

Heavy

Ion

Collider at BNL

Quest of heavy ion collisions create QGP as transient state in heavy ion collisions verify existence of QGP Study properties of QGP study QCD confinement and how hadrons get their masses

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Detecting the QGP “matter box”

“ideal” experiment

Rutherford experiment atom discovery of nucleus

SLAC electron scattering e proton discovery of quarks

Experiments with QGP not quite that simple QGP created in nucleus-nucleus collisions can not be put in “box” Thousands of particles produced during collision

vacuum

QGP

penetrating beamabsorption or scattering pattern

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Au-Au Event in STAR summer 2001

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A Silly Analogy Suppose…

You lived in a frozen world where there’s only as ice and the ice is quantized in ice cubes Some weird physicists tell you there should be water and suggest to heat the ice by colliding two ice cubes So you form a “bunch” containing a billion ice cubes which you collide with another such bunch 10 million times per second which produces about 1000 IceCube-IceCube collisions per second which you observe from the vicinity of Mars

Change the length scale by about 10 trillion

You’re doing physics at RHIC!

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Relativistic Heavy Ion Collider

RHIC

STARPHENIX

PHOBOSBRAHMS

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11 nations 51 institutions

Stony Book:Prof. Averbeck, Drees, Jacak, Hemmick

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PHENIX at RHIC

2 central spectrometers

2 forward spectrometers

3 global detectors

West

EastSouth

North

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Central Magnet

East Carriage

West Carriage

Ring Imaging CerenkovDrift Chamber

PHENIX Central

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Space-time Evolution of Collisions

e

space

time

Hard Scattering

AuAu

Exp

ansi

on

Hadronization

Freeze-out

jet J/

QGPThermaliztion

ep K

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J/ Suppression in QGP

Hard scattering creates also heavy “charm” quark pairs cc Small fraction of charm pairs bind to J/

Perturbative Vacuum

cc

Color Screening

cc

Traveling through QGP

c and c are screened by “color” charges J/ states destroyed

In experiment measure J/

Suppression of J/ in Pb-Pb observed at CERN First data from RHIC, results coming soon

?

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Jets: New Penetrating Probe at RHIC

q

q

hadronsleadingparticle

leading particle

schematic view of jet production

hadrons

jets contribute ~30% of particle production at RHIC energies

hard to observe directly in A-A collisions indirect measurements through

high pT leading particles azimuthal correlation

q

q

hadrons

hadrons

leadingparticle

leadingparticle

jet production in quark matter

jet tomography of quark matter

q

q

hadronsleadingparticle

jet production in quark matter

in colored “quark matter” partons expected to lose significant energy via gluon bremsstrahlung suppression of high pT particles “jet quenching” suppression of angular correlation pT dependent modification of particle ratios

Positron Emission Tomography of the Brain

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RHICRHIC result on the suppression of high transverse momentum particles in high-energy gold-goldgold-gold collisions is featured on the cover of next week’s Physical Review LettersPhysical Review Letters (14 January 2002)and in the 12/21/01 Physics FocusPhysics Focus article on the web:http://focus.aps.org/v8/st34.htmlBrookhaven Science AssociatesU.S. Department of Energy

PHENIX

Axel Drees

New Au-Au data taken in 2001 Compare the yield per trigger for ~0 and ~

(Au+Au – flow) / p+p per trigger. Near angle ~ 1,

pT>4 GeV/c dominantly from jet. Back angle decrease with centrality

Disappearance of away side jet.

q

q

Near angleleadingparticle

Back angle

Now (2003) taking data with d-Au and p-p to complete picture

Axel Drees

Frontiers of Nuclear Physics

Extremes of Nuclear structure Super heavy elements High spin state nuclei

Radio active beams Nuclei far from stability

Hadron structure Spin structure of proton Confinement Hadron masses

Quark Gluon Plasma Study phase diagram of QCD

Nuclear Structure Lab future RIA

ongoing RHIC

Future upgrades e RHIC