Upload
glyn
View
36
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Research Frontiers in Nuclear Physics. Central truths of nuclear physics driving research for more than one century. We are nothing(c. 1900). We are dust(c. 1950). We don’t matter (c. 2000). Atom. Nucleus. (“ion” when alone). Proton. Neutron. Quarks. Held together. by gluons. - PowerPoint PPT Presentation
Citation preview
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
Axel Drees
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
Axel Drees
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
Axel Drees
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 !
Axel Drees
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
Axel Drees
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
Axel Drees
~ 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
Axel Drees
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
Axel Drees
“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
Axel Drees
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
Axel Drees
Au-Au Event in STAR summer 2001
Axel Drees
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!
Axel Drees
Relativistic Heavy Ion Collider
RHIC
STARPHENIX
PHOBOSBRAHMS
Axel Drees
11 nations 51 institutions
Stony Book:Prof. Averbeck, Drees, Jacak, Hemmick
Axel Drees
PHENIX at RHIC
2 central spectrometers
2 forward spectrometers
3 global detectors
West
EastSouth
North
Axel Drees
Central Magnet
East Carriage
West Carriage
Ring Imaging CerenkovDrift Chamber
PHENIX Central
Axel Drees
Space-time Evolution of Collisions
e
space
time
Hard Scattering
AuAu
Exp
ansi
on
Hadronization
Freeze-out
jet J/
QGPThermaliztion
ep K
Axel Drees
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
?
Axel Drees
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
Axel Drees
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