![Page 1: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/1.jpg)
What is SO special about strangeness in heavy ion
collisions ?
Rene Bellwied Wayne State University
7th International Conference on Strangeness in Quark Matter
North Beach, March 12-17, 2003
![Page 2: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/2.jpg)
A connection to cosmology
• Essential: Witten’s ‘Cosmic Separation of phases’ (Phys.Rev.D 30 (1984) 272) and his idea of strange quark matter.
• The impact on cosmology might be far reaching and definitely affected the search for strangeness enhancement in general and strange quark matter in particular (see Jack Sandweiss talk).
• Strange Quark Matter is still considered a possibility for stable or metastable matter in the universe.
![Page 3: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/3.jpg)
Two recent examples in astrophysicsFundamental paper on ‘How to identify a strange star’ by Jes Madsen, PRL 81 (1998) 3311Recent measurements by Drake et al. and Helfand et al. in 2002 with the Chandra X-ray telescope (see Markus Thoma’s talk)
These two NASA Chandra X-ray Observatory images show two stars - one too small, one too cold - that reveal cracks in our understanding of the structure of matter. (AFP)
RXJ18563C58
![Page 4: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/4.jpg)
Did quark matter strike the earth ?Two anomalous seismic events occurred in 1993, and were measured independently by 9 monitoring stations.
Strange quark matter should pass through the earth at 400 km/s (40 times the speed of seismic waves), i.e. search for seismic events not connected with traditional seismic disturbances e.g. earth quakes. (Herrin et al., SMU, 2002)
![Page 5: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/5.jpg)
What can we do in the laboratory ?
The idea of strange quark matter did not only initiate strangelet searches (see Jack’s talk) but led also to potential signatures for the QGP phase transition.
Increasing strangeness enhancement as a signal for QGP and strangeness equilibration as a signal for thermalization of the particle emitting source were for years at the forefront of our research.
![Page 6: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/6.jpg)
Re-invent strangeness as a QGP signature
• 2000’s: parton quenching (strange particles as leading jet particles), timescales (strange resonances), fluctuations (strange particles e-by-e), partonic flow (radial and elliptic flow of strange particles)
• 1990’s: Strangeness enhancement (multistrange antibaryons as function of system size and beam energy)
• Early 80’s: Strangeness enhancement (K/ and later anti-baryon/baryon as function of beam energy (Rafelski, Mueller, Koch et al.)
• Late 80’s: Strangeness equilibration (strangeness production in thermal models as signal for phase equilibration and collective flow)
![Page 7: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/7.jpg)
History of strangeness enhancement• K/ – the benchmark for abundant strangeness production:
K/
K+/
[GeV]
![Page 8: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/8.jpg)
The impact of baryon density• K-/ – is a simple function of baryon density
STAR preliminary
STAR preliminary
see talk by M.Velkovsky
![Page 9: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/9.jpg)
NA49: volume effects (saturation ?)• Compare:
different system sizes at common incident energy
• Search for better scaling variable than Npart
• Good measure: mean collision density in space and time
(UrQMD simulation)
See talks by Ingrid Kraus & Jean Cleymans
![Page 10: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/10.jpg)
Wroblewski factor evolution
Wroblewski factor dependent on T and B
dominated by Kaons
Lines of constant S
<E>/<N> = 1 GeV
I. Increase instrange/non-strangeparticle ratiosII. Maximum isreached
III. Ratios decrease(Strange baryonsaffected more stronglythan strange mesons)
Peaks at 30 A GeV in AA collisions due to strong B dependence
mesons
baryons
hidden strangeness mesons
PBM et al., hep-ph/0106066
total
![Page 11: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/11.jpg)
Experimental
4 yieldsmid-rapidity yields
![Page 12: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/12.jpg)
New machines to explore the high density regime
new European ‘can-do-all’ facilitysee talk by H.Gutbrod
A new European heavy-ion and anti-proton machine
A complementary high energyhadron facility in Japan (JHF)
![Page 13: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/13.jpg)
Strangeness enhancement in B/B ratios
• Baryon over antibaryon production can be a QGP signature as long as the baryochemical potential is high (Rafelski & Koch, Z.Phys. 1988)
• With diminishing baryochemical potential (increasing transparency) the ratios approach unity with or without QGP, and thus only probe the net baryon density at RHIC.
![Page 14: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/14.jpg)
New RHIC data of baryon ratios
• The ratios for pp and AA at 130 and 200 GeV are almost indistinguishable. The baryochemical potentials drop from SPS to RHIC by almost an order of magnitude to ~50 MeV at 130 GeV and ~20 MeV at 200 GeV.
STAR p+p 200 GeV
STAR preliminary BRAHMS, PRL
nucl-ex/0207006
See talk by J.H.Lee
![Page 15: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/15.jpg)
Strangeness enhancement in yields
• Enhancement factors up to 20 (!) comparing pp to AA for . Still very large centrality dependence for . See talks by C.Meurer, M.Mitrovski, L.Sandor
STAR Preliminaryequilibration volume ?
Tounsi et al.
![Page 16: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/16.jpg)
Is strangeness still enhanced at RHIC ?
NA49 preliminary
• Anti-strange baryon production is a measure of enhancement, whereas strange baryon production at RHIC is strongly affected by vanishing net baryon density
![Page 17: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/17.jpg)
Strangeness thermalization: Do yields (ratios) agree with the statistical
model picture ?
![Page 18: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/18.jpg)
Are thermal models boring ?
Good success with thermal models in e+e-, pp, and AA collisions.Thermal models generally maketell us nothing about QGP, but (e.g. PBM et al., nucl-th/0112051):
Elementary particle collisions: canonical description, i.e. local quantum number conservation (e.g.strangeness) over small volume.Heavy ion collisions: grand-canonical description, i.e. percolation of strangeness over large volumes, most likely in deconfined phase if chemical freeze-out is close to phase boundary.
![Page 19: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/19.jpg)
Do we understand strangeness production ?
• Chemical (and thermal) equilibrium models describe the data, so do non-equilibrium models ! Is equilibrium an applicable concept ? (see QM round table discussion)
• Even if we assume thermal equilibrium, do we understand production on a microscopic (partonic) level ? Not really.
![Page 20: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/20.jpg)
Radial flow and thermalization ?
see Javier Castillo’s talk
STAR preliminary
STAR preliminary
![Page 21: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/21.jpg)
Common parametrization of flow ?
• Do particles with smaller interaction cross section decouple earlier and still show transverse flow ?
• Blast wave parametrization fits for NA49 & STAR
,
,K,P,
NA49 – PbPb 158 A GeV
STAR preliminary
![Page 22: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/22.jpg)
Particle identified elliptic flow
• v2 measurements: , k, p, flow, do and flow ?
see talk by Paul Sorensen
STAR preliminary
![Page 23: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/23.jpg)
RHIC Particle Spectra at 200 GeV
BRAHMS: 10% centralPHOBOS: 10%PHENIX: 5%STAR: 5%
see PHOBOS talk by Gabor Veres
![Page 24: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/24.jpg)
Strangeness pushing the boundaries of particle identification
One sees the mass dependence of the transverse expansion, which is well described by thermal and hydrodynamics models
preliminary preliminary
![Page 25: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/25.jpg)
Strange jet-like particles• R(AA) & v2 measurements in Au-Au (see talks by Hui Long, Paul Sorensen and Julia Velkovska)
Effects due to:initial state (gluon saturation)or final state (partonic energy loss, quark coalescence, hadronic/partonic flow) ?
Is there a mass dependenceor a flavor dependence ?
Note: show no suppressionout to 3 GeV/c (similar to PHENIXprotons and D-mesons)
![Page 26: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/26.jpg)
Interplay between soft and hard processes (Vitev et al., QM 2002)
+bar/K0s
preliminary
see talks by B.Norman and H.Long
![Page 27: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/27.jpg)
Strange resonances in medium
Short life time [fm/c] K* < *< (1520) < 4 < 6 < 13 < 40
Red: before chemical freeze outBlue: after chemical freeze out
Medium effects on resonance and their decay products before (inelastic) and after chemical freeze out (elastic).
Rescattering vs. Regeneration ?
see talks by:L. GaudichetH. ZhangJ. MaP. FachiniD. Jouan
![Page 28: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/28.jpg)
Resonances come into their own• Resonances tells us about production, rescattering, and
regeneration & medium modifications• Resonances tell us about timescales (together with
balance functions & HBT measurements)
Giorgio Torrieri and Johann RafelskiPhys.Lett.B509:239-245, 2001
STAR preliminary
![Page 29: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/29.jpg)
-measurements at SPS & RHIC• The is interesting in terms of thermal radial flow and in terms of
medium modifications.
• NA50 / NA 49 difference due to different decay channels (i.e. medium modifications) ? PHENIX will do precision measurement in the K+K- and the e+e--channels
see J.Ma’s talk
![Page 30: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/30.jpg)
Some puzzles along the way
Large ratio at AGS (and SPS) still not understood
1.0
2.0
3.0
4.0
/ p
AGS:measured by E864/E878confirmed by E917SPS:measured by NA49RHIC:measured by STAR
![Page 31: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/31.jpg)
Sub-threshold Kaon production (KaOS)
see Andreas Foerster, Laura Tolos & Christoph Hartnack talks
![Page 32: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/32.jpg)
Recent non-RHIC measurement production in Au-Au collisions at 6 A GeV (E895@AGS)
see Paul Chung’s talk
![Page 33: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/33.jpg)
Future measurement of interest • Hyperon polarization in AA: is measured (E896 @ AGS) and in
agreement with pp and pA data, but pp and pA data from FNAL show intriguing differences between and their antiparticles
![Page 34: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/34.jpg)
What did we learn in pp ?
STAR p+p 200 GeV
STAR preliminary
see talks by: A. Billmeier, R. Witt & posters by: M.Heinz and J.Adams
STAR preliminarySTAR preliminary
![Page 35: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/35.jpg)
What is to come in pA ?use particle identifiedstrange particle spectrafrom the RHIC dA run:
a.) as reference forstrangeness enhancement& production mechanisms
b.) as reference for high pt phenomena: (Cronin, jet quenching, quark coalescence)
P.B. Straub et al., PRL 68 (1992)FNAL experiments measuring R (W / Be) for identified particles at s of 27.4 and 51.3 GeV.
![Page 36: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/36.jpg)
Main topics for the ‘new’strangeness
• Can we prove that we have buildup of transverse and elliptic flow in the partonic phase by measuring multistrange baryon elliptic, transverse, and directed flow ?
• Can we show that high pt particle suppression (measured through R(AA), v2, and back-to-back jets) is due to final state effects (e.g. quenching in the QGP) and that these effects are flavor and/or mass dependent by measuring K+,K-,K0, -bar, -bar R(AA) functions ?
• Can we determine timescales for all phases of the collision and quantify medium modifications by precisely measuring the generation, rescattering, and regeneration of strange resonances ?
• We need pp and pA reactions for reference
![Page 37: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/37.jpg)
We have come a long way !
4th SQM 98, Padova,RHIC summary talk:
Yes !?!
Well, maybe ….
Let’s just waitand see !
Yeah !
Heck, YEAH !!
![Page 38: What is SO special about strangeness in heavy ion collisions ?](https://reader035.vdocument.in/reader035/viewer/2022062314/56813c53550346895da5d535/html5/thumbnails/38.jpg)
Strangeness is alive & well
• The systematic studies of strangeness production have entered a very sophisticated stage (volume effects, timescales, medium effects)
• We have a program that is relevant at high energies (RHIC,LHC) and high densities (new facilities in Europe and Japan).
• Old ‘smoking guns’ (e.g. strangeness enhancement) get replaced by new ‘smoking guns’ (e.g. strangeness quenching and flow).
There will be plenty more SQM’s to make Jan’s day !!