Recent Results from the SPS Christoph Blume Exploring the Phase Diagram of Strongly Interacting Matter Workshop in Stony Brook Nov. 17, 2004
Dec 21, 2015
Recent Results from the SPS
Christoph Blume Exploring the PhaseDiagram of StronglyInteracting MatterWorkshop in Stony BrookNov. 17, 2004
Christoph Blume Stony Brook Workshop, 17 November 2004 2
Heavy Ion Physics at the CERN SPSExploring the QCD Phase Diagram
SPS energy regime allows to explore an essential part of the phase diagram– If there is QGP seen at RHIC
the transition is likely to happen at SPS energies
– Ebeam = 20 - 158 AGeV (sNN = 6.3 - 17.3 GeV)
Is a phase transition reflected in hadronic observables?
Systematic studies required: Energy dependence
System size dependence
Cross over linefrom lattice QCD
Critical point
1st ordertransition
Lattice calculations:Fodor and KatzBielefeld-Swansea group
Christoph Blume Stony Brook Workshop, 17 November 2004 3
Heavy Ion Physics at the CERN SPS The NA49 Experiment
13m
Particle identification:
Pions, charged Kaons: dEdx in TPCs + TOF (mid-rapidity)
K0s, , , : Decay topology + invariant mass
: Invariant mass of identified Kaons
Christoph Blume Stony Brook Workshop, 17 November 2004 4
Heavy Ion Physics at the CERN SPSParticle Identification in NA49
dE/dx measured in TPCs– Large acceptance– Resolution 3-4%
Time-of-flight– Mid-rapidity– Resolution 60 ps
Example:Pb+Pb @ 40 AGeV
Christoph Blume Stony Brook Workshop, 17 November 2004 5
Heavy Ion Physics at the CERN SPSObservables
Try to characterize the “basic” features of heavy ion events with as few parameters as possible
Soft physics:– Particle production dominated by pt < 2 GeV/c
Systematic studies important– Vary control parameter like beam energy and system size
Focus of this talk: Energy Dependence + Central Collisions
AGS SPS RHIC
Christoph Blume Stony Brook Workshop, 17 November 2004 6
Heavy Ion Physics at the CERN SPSObservables
Rapidity Spectra– Longitudinal expansion
Particle Yields– Strangeness– Chemical freeze-out conditions
Transverse Mass Spectra– Transverse expansion ( EOS?)– Thermal freeze-out conditions
Fluctuations– Critical point of the phase diagram
Christoph Blume Stony Brook Workshop, 17 November 2004 7
Rapidity Spectra
Central Pb+Pb7% (20-80)5/10% (158)
Change of shape only for Others: ~ Gaussians
Christoph Blume Stony Brook Workshop, 17 November 2004 8
Rapidity SpectraPions
Single Gaussians!
ComparisonAGS, SPS, and RHIC
Central Pb+Pb/Au+Au
Christoph Blume Stony Brook Workshop, 17 November 2004 9
Rapidity DistributionsLandau Scenario in p+p
Prediction: dN/dy is Gaussian of a width = 2L given by: (simplified model)
pms
2ln2
L. D. Landau, Izv. Akad. Nauk. SSSR 17 (1953) 52P. Carruthers and M. Duong-Van, Phys. Ref. D8 (1973) 859
Pion production ~ Entropy Isentropic expansionDescription of the pion gas as a 3D relativistic fluid
Christoph Blume Stony Brook Workshop, 17 November 2004 10
Rapidity SpectraEnergy Dependence of Widths
Pion widths are closeto Landau prediction,but not perfectly
But: Perfect agreementto linear dependenceon ybeam
Christoph Blume Stony Brook Workshop, 17 November 2004 11
Rapidity SpectraEnergy Dependence of Widths
Linear dependenceon ybeam
Clear hierarchy forGaussian-like particles at SPS(p, , excluded):
> K+ > K-, >
Seems to break down at AGS
Christoph Blume Stony Brook Workshop, 17 November 2004 12
Rapidity SpectraMass Dependence of Widths
Approx. linear dependence on particle mass
Similar slope at all SPS energies
Thermal component of longitudinal flow
negatives
Christoph Blume Stony Brook Workshop, 17 November 2004 13
Rapidity SpectraDependence on Strangeness Content
Central Pb+Pb, 158 AGeV
Net protons: 3 valence quarks (uud )
Omegas: 3 produced quarks (sss )
Net s:1 valence (d ) + 2 produced quarks (ss )
Net s:2 valence (ud ) +1 produced quark (s )
Christoph Blume Stony Brook Workshop, 17 November 2004 14
Particle Yields
AGS NA49 BRAHMSCentral Au+Au, Pb+Pb
4 multiplicities only!
Christoph Blume Stony Brook Workshop, 17 November 2004 15
Particle YieldsStatistical Hadron Gas Model
Becattini et al., Phys. Ref. C69 (2004) 024905
Assumption of chemicalequilibrium at the freeze-out point
Particle production can be described with a few parameters: V, T, B, s
jsS
Christoph Blume Stony Brook Workshop, 17 November 2004 16
Particle YieldsPhase Diagram (II)
Chemical freeze-out pointsapproach phase boundaryat top SPS energies
Does the system cross the phase boundary ?And if yes, where ?
Christoph Blume Stony Brook Workshop, 17 November 2004 17
Particle YieldsEnergy Dependence
5.1
K+/+
K-/-
/
/
-/
-++/
Christoph Blume Stony Brook Workshop, 17 November 2004 18
Particle YieldsEnergy Dependence
5.1
UrQMDHSD
E.L. Bratkovskaya et al.,PRC 69 (2004), 054907
K+/+
K-/-
/
/
-/
-++/
Christoph Blume Stony Brook Workshop, 17 November 2004 19
Statistical hadron gasmodel: s = 1
P. Braun-Munzinger,J. Cleymans,H. Oeschler, and K. RedlichNucl. Phys. A697 (2002) 902
Particle YieldsEnergy Dependence
5.1
K+/+
K-/-
/
/
-/
-++/
Christoph Blume Stony Brook Workshop, 17 November 2004 20
Statistical hadron gasmodel: s free
F. Becattini,M. Gazdzicki,A. Keränen,J. Manninen,R. StockPRC 69 (2004), 024905
Particle YieldsEnergy Dependence
5.1
K+/+
K-/-
/
/
-/
-++/
Christoph Blume Stony Brook Workshop, 17 November 2004 21
Particle YieldsEnergy Dependence
5.1
K+/+
K-/-
/
/
-/
-++/
Christoph Blume Stony Brook Workshop, 17 November 2004 22
Particle YieldsComparison s- and s-Carriers
s-quark carriers: K-, K0 (1)
(incl. 0) 0,-, - (2)
± (3)
(1) K0 K+, K0 K- by isospin symmetry
(2) Taken from hadron gas fit by F. Becattini et al., if not measured.
(3) Empirical factor ( + ) / = 1.6 assumed.
s-quark carriers: K+, K0 (1)
(incl. 0) 0,+, + (2)
± (3)
Energy dependenceof strangeness productionchanges at 30 AGeV
Christoph Blume Stony Brook Workshop, 17 November 2004 23
Particle Yields(Anti-)Strangeness to Pion Ratio
Maximum in strangeness/pion ratio
Same for s and s quarks
Difficult to model Solid line: Statistical hadron gas model with s = 1 K. Redlich, priv. comm.
Predicted as signal for the onset of deconfinementM. Gazdzicki and M.I. Gorenstein, Acta Phys. Polon. B30 (1999), 2705
Christoph Blume Stony Brook Workshop, 17 November 2004 24
Transverse Mass Spectra
20 AGeV 30 AGeV
Central (7%) Pb+Pb
t
ttt
tt T
pI
T
mKm
dydmm
dN
1
01
tanh
sinhcosh
Schnedermann, Sollfrank, and Heinz,Phys. Rev. C46
Radial flow fit (“Blast Wave”)
Here: t independent of r
Christoph Blume Stony Brook Workshop, 17 November 2004 25
Transverse Mass Spectra
40 AGeV
80 AGeV
158 AGeV
Central Pb+Pb40+80 AGeV: 7%158 AGeV: 5%, 10%(), 23.5%()
Christoph Blume Stony Brook Workshop, 17 November 2004 26
Transverse Mass SpectraInverse Slope Parameters of Kaons
Step in energy dependence p+p compilation from:M. Kliemant, B. Lungwitz, and M. Gazdzicki, PRC 69 (2004) 044903Seems to be absent in p+p and models
How about other particle types?
Christoph Blume Stony Brook Workshop, 17 November 2004 27
Transverse Mass SpectraEnergy Dependence of mt-m0
Energy dependence of transverse activity seems to change around 30 AGeV.
General feature for pion, kaons and protons
Resonances or change of EOS?
negatively charged
Christoph Blume Stony Brook Workshop, 17 November 2004 28
Transverse Mass SpectraBlast Wave Model
t
ttt
tt T
pI
T
mKm
dydmm
dN
1
01
tanh
sinhcosh
Basic blast wave model: Common freeze-out of all particle types Boost invariant longitudinal expansion Transverse expansion is modelled by a velocity profile “Standard” version:
Schnedermann, Sollfrank, and Heinz,Phys. Rev. C46
Extended version: Resonance contribution included
Baryonic resonances introduce dependence on B
Chemical freeze-out: Tch and B taken from freeze-out curve
Thermal freeze-out: System cools down, therefore assume: Conservation of entropy Conservation of effective particle numbers
U. Wiedemann and U. Heinz, Phys. Rev. C56 (1997) 3265B. Tomasik, nucl-th/0304079
Christoph Blume Stony Brook Workshop, 17 November 2004 29
Transverse Mass Spectra
E895: nucl-ex/0306033NA49: Phys. Rev. C66 (2002) 054902, nucl-ex/0403023PHENIX: Phys. Rev. C69 (2004) 024904, nucl-ex/0307022
Convave Resonances
Exponential Shoulder Radial flow
- K- p
Christoph Blume Stony Brook Workshop, 17 November 2004 30
Transverse Mass SpectraEnergy Dependence of Fit Parameter
Fit to -, K- and p
Box-shaped source profileand linear velocity profile
Fit range 0.1 < mt-m0 < 0.8 GeV
Energy dependence of Tf seems to change around 30 AGeVThermal and chemical freeze-out different? Single freeze-out model?
Continous increase of T
Tch
Christoph Blume Stony Brook Workshop, 17 November 2004 31
FluctuationsSearch for the Critical Point
Endpoint of the first orderphase transition line crossover on left side
Position quite uncertain
But recent lattice calculations by Fodor and Katz predictsposition at B = 360 MeV usingphysical quark masses
If the above it true and the phase boundary is really reached at 30 AGeV, it might be accessible at the SPS
Event-by-event fluctuations
Christoph Blume Stony Brook Workshop, 17 November 2004 32
20 GeVpreliminar
y
FluctuationsParticle Ratios
preliminary
160 GeVCompare to mixed eventreference Resolution
Finite number statistics
Extraction of dynamical fluctuations
2dynamic = 2
data - 2mix
= RMS/Mean * 100 [%]
Event-by-event fluctuationsof e.g. K/
NA49
NA49
Christoph Blume Stony Brook Workshop, 17 November 2004 33
FluctuationsEnergy Dependence of K/ Fluctuations
preliminary
Clear energy dependenceof K/ fluctuations observed Decrease with energy
Fluctuation from UrQMD independent of energy
Non-zero value due to energy and strangeness conservation
Data wider than mixed eventsreference
Promising, but no clear evidence for critical point yet
Christoph Blume Stony Brook Workshop, 17 November 2004 34
Summary
Systematic study of energy dependence (still ongoing)– Rapidity and transverse mass spectra– Particle Yields– Fluctuations
A variety of interesting features have been revealed:– Mass dependence of rapidity widths, seemingly
independent of beam energy at SPS– Clear change of the energy dependence of mt-spectra
at 30 AGeV Evidence for a change of EOS?
– Maximum in the strangeness to pion ratio at 30 AGeV Evidence for deconfinement?
Outlook: Search for critical point– No clear evidence yet
dedicated search with future projects (SPS, FAIR)
Christoph Blume Stony Brook Workshop, 17 November 2004 35
The NA49 Collaboration
C. Alt, T. Anticic, B. Baatar, D. Barna, J. Bartke, L. Betev, H. Bialkowska, A. Billmeier, C. Blume, B. Boimska, M. Botje, J. Bracinik, R. Bramm, R. Brun, P. Buncic, V. Cerny, P. Christakoglou, O. Chvala, J.G. Cramer, P. Csató, N. Darmenov, A. Dimitrov, P. Dinkelaker, V. Eckhardt, G. Farantatos, D. Flierl, Z. Fodor, P. Foka, P. Freund, V. Friese, J. Gál, M. Gazdzicki, G. Georgopoulos, E. Gladysz, K. Grebieszkow, S. Hegyi, C. Höhne, K. Kadija, A. Karev, M. Kliemant, S. Kniege, V.I. Kolesnikov, T. Kollegger, E. Kornas, R. Korus, M. Kowalski, I. Kraus, M. Kreps, M. van Leeuwen, P. Lévai, L. Litov, B. Lungwitz, M. Makariev, A.I. Malakhov, C. Markert, M. Mateev, B.W. Mayes, G.L. Melkumov, C. Meurer, A. Mischke, M. Mitrovski, J. Molnár, S. Mrowczynski, G. Pálla, A.D. Panagiotou, D. Panayotov, A. Petridis, M. Pikna, L. Pinsky, F. Pühlhofer, J.G. Reid, R. Renfordt, A. Richard, C. Roland, G. Roland, M. Rybczynski, A. Rybicki, A. Sandoval, H. Sann, N. Schmitz, P. Seyboth, F. Siklér, B. Sitar, E. Skrzypczak, G. Stefanek, R. Stock, H. Ströbele, T. Susa, I. Szentpétery, J. Sziklai, T.A. Trainor, D. Varga, M. Vassiliou, G.I. Veres, G. Vesztergombi, D. Vranic, A. Wetzler, Z. Wlodarczyk, I.K. Yoo, J. Zaranek, and J. Zimányi
Christoph Blume Stony Brook Workshop, 17 November 2004 37
Elliptic FlowEnergy Dependence
Mid-rapidity data,pt integrated
Change of energydependence of v2
between AGS and 40 AGeV
Christoph Blume Stony Brook Workshop, 17 November 2004 38
Rapidity SpectraRapidty Shift y
yP yT
y0
y y
y0
yP yT
y y y’Py’T
How does the rapidity shift y evolve with beam energy?
Determines the energy available in the produced fireball
Baryon number distributions at
lower energies: higher energies:
Christoph Blume Stony Brook Workshop, 17 November 2004 39
Rapidity SpectraEnergy Dependence of y
BRAHMS, I.G. Bearden et al.PRL 93 (2004), 102301
py BB
partp
p
dydy
dNy
Ny
yyy
0
)(2
Seems to increase linearly at AGS and SPS:
y /ybeam 0.27
Rapidity shift:
But: Weaker increaseto RHIC energies!
dyydy
dNmE BBy
y yT
p
p
cosh)(
Energy loss E :
RHIC (sNN = 200 GeV): E/Nucleon = 73 ± 6 GeV
Christoph Blume Stony Brook Workshop, 17 November 2004 40
Rapidity Spectra Energy Dependence of Net-Protons
BRAHMS, I.G. Bearden et al.PRL 93 (2004), 102301
The shape of the distributionschanges dramatically with energy
AGS: baryonic system RHIC: mesonic system Large implications in the hadronic sector
Christoph Blume Stony Brook Workshop, 17 November 2004 41
Particle YieldsEnergy Dependence
Central Pb+Pb/Au+Au
Mid-rapidity ratios
Christoph Blume Stony Brook Workshop, 17 November 2004 42
Transverse Mass SpectraThe Omega
Evidence for earlyfreeze-out of the Omega from blast wave fits?
Blast Wave Model
VelocityProfile
Tf (MeV) t
A constant 125 0.5 from fits shown before
(*) M.I. Gorenstein, K. A. Bugaev and M. Gazdzicki, PRL. 88 (2002), 132301.
Fit to K, p, , 0.590linearB1
Fit to J/ and ’ (*)0.2170linearB2
NA49 publication:C. Alt et al., nucl-ex/0409004
Christoph Blume Stony Brook Workshop, 17 November 2004 43
Transverse Mass SpectraInverse Slope Parameters of Kaons
Hydro calculation
M. Gazdzicki, M.I. Gorenstein, F. Grassi, Y. Hama, T. Kodama, and O. Socolowski Jr.,Braz. J. Phys. 34 (2004), 322, hep-ph/0309192
Assuming 1st orderphase transition
Initial conditions from NeXus
Pure Landau initial conditions do not allow for simultaneousdescription of all observables (y-, mt-spectra, yields)
Christoph Blume Stony Brook Workshop, 17 November 2004 44
Transverse Mass SpectraInverse Slope Parameters of Kaons
Model comparisons
M. Bleicher, SQM04
Additional resonances?UrQMD 2.1
Initial QGP pressure?
Christoph Blume Stony Brook Workshop, 17 November 2004 45
Elliptic FlowEnergy Dependence
30 AGeVData shows saturation of scaled v2
High mass resonances like in UrQMD 2.1 can not explainv2 above 40 AGeV
Strong hint for initial QGP pressure from30 AGeV on !M. Bleicher, SQM04
Christoph Blume Stony Brook Workshop, 17 November 2004 46
FluctuationsEnergy Dependence of p/ Fluctuations
Clear energy dependenceof p/ fluctuations observed Increase with energy
preliminary
Similar trend seen in UrQMD Resonance contribution changes with beam energy
Data narrower than reference Can be caused by resonances
Christoph Blume Stony Brook Workshop, 17 November 2004 47
Rapidity SpectraKaons
Single Gaussian worksreasonably well for K-
Does not really work for K+ at lower SPS energies
Use RMS
Christoph Blume Stony Brook Workshop, 17 November 2004 48
Heavy Ion Physics at the CERN SPS NA49 Strangeness measurements
Energy K+ K- - + - +
158 AGeV pub. pub. pub. pub. pub. pub. pub. pub. sub. sub.
80 AGeV pub. pub. pub. prel. pub. pub.
40 AGeV pub. pub. pub. prel. pub. pub. prel. sub. sub.
30 AGeV prel. prel. prel. prel. prel. prel.
20 AGeV prel. prel. prel. prel. prel. prel.
: Phys. Lett. B491 (2000) 59: Phys. Rev. Lett. 93 (2004) 022302: Phys. Lett. B538 (2002) 275: nucl-ex/0409004K, : Phys. Rev. C66 (2002) 054902
Minimum Bias Pb+Pb andC+C, Si+Si at 40 and 158 AGeV
Central Pb+Pb: