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Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
The UCD The UCD Nuclear Physics Nuclear Physics
Group Group
Daniel CebraDaniel Cebra
Goal of this talk - to introduce the nuclear physics groupand explain what we do and why it is interesting
PS… Check out our web page at http://nuclear.ucdavis.edu
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Meet the GroupMeet the Group
• FACULTY:• Jim Draper (emeritus)• Paul Brady (emeritus)• Daniel Cebra• Ramona Vogt• Daniel Ferenc
• STAFF:• Juan Romero• Tom Gutierrez
• GRAD STUDENTS:• Mike Anderson (2002)• Ian Johnson (2002)• Steve Oliver (2004)• Roppon Picha (2005)
• UNDERGRADS:• Mark Allen• Trieu Mai• Daniel Clayton• Stephen Baumgarten
Come visit us on the fifth floor - WEST end
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Recent GraduatesRecent Graduates
• Jenn Klay (2001) Postdoc LBNL• Mike Heffner (2000) Postdoc LLNL• Tom Gutierrez (2000) Postdoc UCD• Bill Caskey (1999) Z-World, Davis CA• Lynn Wood (1998) Z-World, Davis CA• Jerry Chance (1997) Postdoc LBNL• Doug Mayo (1997) Staff Scientist LANL• Jason Dunn (1997) Professor - Idaho Christian• Isaac Huang (1997) FunMail.com• Jack Osbourn (1995) Professor - Sac State• Jessica Kintner (1995) Professor - St. Mary’s
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
What Do We Do?What Do We Do?
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Abstract of Research GoalsAbstract of Research Goals
The study of collisions between relativistic nuclei will ultimately allow the determination of the properties of nuclear matter over a wide range of temperatures and densities. Without the possibility of direct studies of nuclear matter in bulk (as in neutron stars, supernovae, or the Big Bang), one resorts to the challenging studies of finite and transient systems as provided by nucleus-nucleus collisions. Our experiments search for signatures of the Quark Gluon Plasma (QGP), a phase of matter which dominated the early stages of the Big Bang.
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
BasicsBasics
Hadrons =Made of quarks
Baryon = 3 qmeson = q q
p = uudn = udd+ = udK+ = us
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Goals of Relativistic Heavy IonsGoals of Relativistic Heavy Ions• To study the
properties of nuclear matter.
• Specifically to study the Quark-gluon plasma
• Allows a better understanding of the earliest phase of the universe.
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Nuclear Matter Phase DiagramNuclear Matter Phase Diagram
Baryon Density
Tem
per
atu
re
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
The Start of RHIC - Summer 00The Start of RHIC - Summer 00
Daniel Cebra - Physics 295 Seminar 129-Jan-0229-Jan-02
Brief History of the RHIC ProjectBrief History of the RHIC Project• 1947 BNL founded
• 1952 Cosmotron
• 1960 AGS
• 1970 Tandem
• 1979 ISABELLE
• 1983 CBA canceled
• 1983 RHIC proposed
• 1991 RHIC approved
• 1992 STAR approved
• 1999 First Beams
• 2000 First collisions
• 2001 Full Energy
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
The STAR Experiment - PlansThe STAR Experiment - Plans
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
STAR - Under ConstructionSTAR - Under Construction
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
The Detector Now...The Detector Now...
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
The FIRST The FIRST Event!Event!
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
STAR - peripheral event - FrontSTAR - peripheral event - Front• Tracks emerge from
common vertex point
• Grazing collisions produce few tracks
• Magnetic field bends trajectories into helices - allows measure of momentum
• Particle ID through gas dE/dx
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
STAR - peripheral event - sideSTAR - peripheral event - side• Determines
the z location of the vertex
• emission angles of the tracks.
• Demonstrate true 3D tracking
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
STAR Event - Front ViewSTAR Event - Front View
Central events have much higher multiplicity of tracks. Up to 2000 charged particles in the TPC’s accpectance
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
STAR Event -- Side ViewSTAR Event -- Side View
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
STAR Calibration and AnalysisSTAR Calibration and Analysis• Spatial
resolution 700• Tracking - better
then 90% efficiency
• dE/dx resolution = 8%
• momentum resolution better than 1%
K p
e
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
SpectraSpectra
• Temperatures are measured in the range expected for a QGP transition
• Suggestive result, but further analysis is needed
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
How we “see” StrangenessHow we “see” Strangeness
• See Strange Hadrons– kaon (u or d and s)
– lambda (uds)
– Omega (sss)
– etc...
• Distinguishing Decay Topologies – V0
– kink
V0
vertex
kink
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Centrality: Centrality: Participants vs. SpectatorsParticipants vs. Spectators
“Spectators”
Zero-degreeCalorimeter
“Spectators”
Many things scale with Npart:• Transverse Energy• Particle Multiplicity• Particle Spectra
“Participants”
Only ZDCs measure Npart
specpart NAN
The collision geometry (i.e. the impact parameter) determines the number of nucleons that participate in the collision
Produced Particles
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
ZZeroeroDDegreeegreeCCaloalo as centrality device as centrality device• Only shared detector
– Rates: luminosity via well-known reference process
– Timing: substantial background rejection
– Pulse height: measures centrality
• Directly confirms monotonic relationship between participants with multiplicity
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
dd/dN vs N/dN vs N
Comparison to cascade models demonstrates to collective behavior of nuclear systems
Used to determine centrality of collisions
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Shapes of dNShapes of dNchch/d/d for different N for different Npartpart
dNch
/d
(dN
ch/d
)/(
½N
pa
rt)
dNch
/d
Data
HIJING
HIJING
(dN
ch/d
)/(
½N
pa
rt)
354
216
102
Mean Npart% 0-3
15-20
35-40
Data
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
dN/ddN/dHigher multiplicity than comparable p+p collisions indicates collective nature.
Impressive agreement between the exps
STARPHENIX
BRAHMS
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Source Source RadiiRadii
• The expected expansion of the outward radius is not seen.
• Transition may be at lower energy or more subtle.
PHENIX
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Hydrodynamic Flow - DefinedHydrodynamic Flow - Defined• Radial flow
– Not seen in angular distributions
– Use HBT, spectra (T = To + m<2>
• Directed flow– Forward rapidities
– Not measured yet PHOBOS/STAR
– Interesting predictions for phase transition…
• Elliptic flow– Early time push,
hydrodynamic evolution
– Strongest at y=0
y2 x2 y2 x2
2cos2 v
x
y
p
patan
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Hydrodynamic Flow - ResultsHydrodynamic Flow - ResultsThe RQMD cascade can not account for the observed flow. Collective behavior is demonstrated.
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Hydrodynamic Flow - ResultsHydrodynamic Flow - Results
Hydrodynamic model
V2
Centrality
midrapidity : |h| < 1.0
SPS
AGS
Preliminary
RQMD
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
ConclusionsConclusions
• ‘00 and ‘01 Heavy-ion running was successful - physics results already. But the QGP question is not yet resolved.
• ‘02 polarized proton+proton running.
• Detectors Continue to improve (5-10 years).
• Future: eRHIC
• Future: LHC
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Compact Muon SolenoidCompact Muon Solenoid
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
APS - join NowAPS - join Now
• All active physicists should join APS
• Students memberships a very reasonable
• Go to meetings, give talks!
• California Section - next meeting will be in Davis
Daniel Cebra - Physics 295 Seminar29-Jan-0229-Jan-02
Intramural Sports!Intramural Sports!
• Basketball Basketball • SoccerSoccer• SoftballSoftball• Other sports?Other sports?