daniel cebra - physics 295 seminar 29-jan-02 the ucd nuclear physics group daniel cebra goal of this...

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


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


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


What Do We Do?What Do We Do?


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.


BasicsBasics

Hadrons =Made of quarks

Baryon = 3 qmeson = q q

p = uudn = udd+ = udK+ = us


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.


Nuclear Matter Phase DiagramNuclear Matter Phase Diagram

Baryon Density

Tem

per

atu

re


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


The STAR Experiment - PlansThe STAR Experiment - Plans


STAR - Under ConstructionSTAR - Under Construction


The Detector Now...The Detector Now...


The FIRST The FIRST Event!Event!


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


STAR - peripheral event - sideSTAR - peripheral event - side• Determines

the z location of the vertex

• emission angles of the tracks.

• Demonstrate true 3D tracking


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


STAR Event -- Side ViewSTAR Event -- Side View


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


SpectraSpectra

• Temperatures are measured in the range expected for a QGP transition

• Suggestive result, but further analysis is needed


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


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


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


dd/dN vs N/dN vs N

Comparison to cascade models demonstrates to collective behavior of nuclear systems

Used to determine centrality of collisions


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


dN/ddN/dHigher multiplicity than comparable p+p collisions indicates collective nature.

Impressive agreement between the exps

STARPHENIX

BRAHMS


Source Source RadiiRadii

• The expected expansion of the outward radius is not seen.

• Transition may be at lower energy or more subtle.

PHENIX


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


Hydrodynamic Flow - ResultsHydrodynamic Flow - ResultsThe RQMD cascade can not account for the observed flow. Collective behavior is demonstrated.


Hydrodynamic Flow - ResultsHydrodynamic Flow - Results

Hydrodynamic model

V2

Centrality

midrapidity : |h| < 1.0

SPS

AGS

Preliminary

RQMD


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


Compact Muon SolenoidCompact Muon Solenoid


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


Intramural Sports!Intramural Sports!

• Basketball Basketball • SoccerSoccer• SoftballSoftball• Other sports?Other sports?

daniel cebra - physics 295 seminar 29-jan-02 the ucd nuclear physics group daniel cebra goal of this...

Documents

properties of nuclear

phase of matter

nuclear physics groupand

d trackingstar event

rhic summer

tpcs accpectancestar

nucleusnucleus collisions

postdoc lbnl mike heffner