strangeness production at sis energies sqm 2007 international conference on strangeness in quark...
DESCRIPTION
In medium effects could be induced by a partial chiral symmetry restoration Decreasing part of quarks condensate Beam energy close or below the production threshold of strange particles High baryonic densities (2-3 ρ 0 ) reached during a relatively long time (~ 10 fm/c) The physics of strangeness at SIS (2 AGeV) SIS B. Friman et al., EJPA 3 (1998) 165 W. Weise, Prog. Theor. Phys. Suppl. 149 (2003) 1TRANSCRIPT
Strangeness Production at SIS Energies
SQM 2007International Conference on Strangeness in Quark Matter
Xavier [email protected]
• Introduction
• The FOPI Detector
• Strange resonances in medium
• Search of strange multi-baryonic states
• Conclusions / Outlook
Strangeness Production at SIS Energies
In medium effects could be induced by a partial chiral symmetry restoration
• Decreasing part of quarks condensate
• Beam energy close or below the production threshold of strange particles
• High baryonic densities (2-3 ρ0) reached during a relatively long time (~ 10 fm/c)
The physics of strangeness at SIS (2 AGeV)
SIS
B. Friman et al., EJPA 3 (1998) 165
W. Weise, Prog. Theor. Phys. Suppl. 149 (2003) 1
2ssu
2K
2K mOssuumm
21
fm
GeV49.2E
GeV58.1E
K
,K
• K+ and Y essentially produced via secondary reactions: Δ + N → K+,0 + Y + B
• K+,0 produced during the earlier stage of the collision (high densities) - repulsive potential (KN ~ 20-30 MeV from diff. v1) • Complex K- production mechanism - strangeness exchange reactions: π + Y ↔ K- + B - strong attractive potential (~ 70 MeV at ρ = ρ0)
- coupled in the medium with Σ(1385), Λ(1405) and Λ(1520)
Strangeness at SIS: Production mechanisms
M.F. M. Lutz et al., NPA 700 (2002) 309
C. Hartnack nucl-th/0507002
K- stopped in 12C
V.K. Magas, E. Oset nucl-th/0601013
• Akaishi and Yamazaki: K-N bound-state of -27 MeV prediction of the existence of K-pp state K-pp → p + Λ + 263 MeV B = 48 MeV, Γ = 60 MeV Measurement: FINUDA peak at 2.25 GeV and Γ = 67 MeV (Bmodel = 115 MeV)
• Weise and Doté: absorption KN→ πΛ, πΣ KNN→ ΛN, ΣN K-NN state of Γ = 100 MeV, B = 60 MeV
• Magas and Oset: final state interaction
• Therm. model: abondance of kaonic clusters ~ strange resonances yields at SIS
K-N potential: prediction of bound states
T. Yamazaki and Y. Akaishi nucl-exp/0609041
M. Agnello et al., PRL 94, (2005) 212303
K- stopped in 7Li
Search for KNN bound states in HIC at SIS energy
A. Andronic et al., NPA 765 (2006) 211
A. Doté and W.Weise hyp2006 nucl-th/0701050 N.V. Shevchenko et al., Phys. Rev. Lett. 98, 082301 (2007)
The FOPI Detector• FOPI - angular coverage close to 4π - identification of fragments (1 < Z < 12) - identification of p, d, t, 3He, 4He, , K
- reconstruction of resonances (, K0, , ,...)
• 2 high statistic experiments: study of strangeness production and propagation - Ni+Ni and Al+Al at 1.9 AGeV (108 Evt, 10 TBytes)
πp→Λ -
Production of Λ and K0 in Ni+Ni at 1.9 AGeV
• High Λ and K0 statistics (> 4·104 counts) and huge rapidity coverage - Λ/K0 produced at mid-rapidity - K+/K0 KaoS - FOPI data in agreement
- Λ colder than protons and emitted from different region
• No kinetic equilibrium between Λ and p
IQMD model: C. HartnackM. Merschmeyer, X. Lopez et al. (FOPI), submitted to PRC (2007), nucl-ex/0703036
MeV780μ
MeV70T4080b
64
Al+Al
Λ and K0 in Ni+Ni and Al+Al at 1.9 AGeV
Test of kinetic and chemical equilibrium • kinetic temperature - strange particles systematically colder than non-strange hadrons - radial flow in Ni+Ni, almost no expansion in Al+Al - same kinetical freeze-out temperature in Al+Al and Ni+Ni (~ 90 MeV)
• thermal model reproduce ratios with T ~ 70 MeV
- kinetical T ~ 90 MeV > chemical T ~ 70 MeV ??- limited number of particle species- need to extend the study to strange resonances production: , K(892), Σ(1385), ...
THERM. MOD.: .A. Andronic et al., NPA 772 (2006) 167
Tm
T reff 23
232 20
K(892)
Strange resonances production • Measurement of , K(892) and Σ(1385) in Al+Al at 1.9 AGeV
S = 185± 17S/B = 1.9MEAN = 1020 MeV/c2
σ = 4 ± 2 MeV/c2
Σ(1385)
(1020)
• First sub-threshold measurements - K(892) (< 800 MeV) - Σ(1385) (< 400 MeV) 1-2 counts/105 events !
X. Lopez et al. (FOPI), submitted to PRL (2007)
short life time resonances should probe finite density
K+ + K- K*0 K+ + - Σ*± + ±
Γ (MeV) 4.3 50.7 39.4c (fm) 46 4 5
Eth (GeV) 2.6 2.75 2.33
preliminary
Strange resonances and thermal model
6 independent ratios with 5 strange particles: p, π-, K0, (Λ+Σ0), , K*0(892) and Σ*±(1385) in Al+Al at 1.9 AGeV
- canonical ensemble (γs = 1)
- adding resonances increase T - the is not describe at all - chemical T ε [70;80] MeV < kinetical T (90 MeV)
Taking into account strangeness production at SIS leads for Tch ~ [70-80] MeV Difficult to get a clear picture from thesemodel assumptionsNeed to include γs in the model (fit the ) ?Measurement with an heavier system ?
preliminary
A. Andronic, private communication
Strange resonances and transport model
Σ*±(1385) and K*0(892) in Al+Al at 1.9 AGeVwith UrQMD model (M. Bleicher, S. Vogel) - no in medium effect (cascade mode) - production time t ~ 7-8 fm - reconstruction at t ~ 12-15 fm - dominant production channel:
70% K+π→K* σ ~ 20 mb
30% N*(∆)+B →K*
76% Λ+π→Σ* σ ~ 37 mb
12% Σ+π→Σ*
12% N*(∆)+B →Σ*
Al+Al s½ = 2.7 GeV Data UrQMD
P(Σ*±)/P(Λ+Σ0)0.125 ± 0.026 (stat.) ± 0.033 (syst.)
0.177
P(K*0/K0)0.032 ± 0.003 (stat.) ± 0.012 (syst.) 0.1
Σ* K*
preliminary
Yield of K*(892) over-estimated → measurements allow to fix limits on Kπ & Λπ fusion cross section within this model
Strange resonances and Chiral theory
• Σ*±(1385) and the Chiral Unitary theory (E. Oset)
Σ(1385)→Λπ(Σπ) at ρ = ρ0
Γ = -2Im[Σ]Σ(1385) = 76 MeV
Mean mass: attractive potential ≈ - 45 MeV
Σ(1385) Al+Al
• Σ*±(1385) measurement in Al+Al s½ = 2.7 GeV - no broadening observed (PDG values with errors) - relevance to have a measurement of Σ(1385) from heavier systems
Murat M. Kaskulov, E. Oset, PRC 73 (2006) 045213
Need to include spectral function in transport codes
KNN clusters: search for Λp correlations
• Excess observed in Ni+Ni and Al+Al with significance ~ 5
• Interpretation unclear - final state interaction - ΣN interaction (2.13 GeV/c2) - bound state (H-dibaryons) - partial inv. mass of heavier state (e.g. 4
ΛHe)
• Excess located to target rapidity region → cold protons
S-BSignal BKG
Target cm Proj.
Strange clusters could probe the cold and dense baryonic matter
FINUDA
FOPI upgrade and scheduled experiments
• Heavy ion program (2007-2009) - Ni+Ni and Ni+Pb at 1.9 AGeV
- Ru+Ru at 1.69 AGeV
• Elementary processes (2007-2009) - π beam on p and Pb at 1.7 GeV/c - p beam on p/d at 3 AGeV
• FOPI ToF Upgrade: MMRPC - size: 6 m2 (150 MMRPC)
- channels: 4800
- t < 100 ps and < 0.5 cm
- PiD π±, K± up to p = 1 GeV/c
resonances productionK- flowsearch for strange clusters
K- and productionsearch for strange clusters
Conclusion / Outlook
Strangeness physic at SIS energies with new probes from the medium !
- sub-threshold measurement of K(892), Σ(1385) resonances
- K- potential and the production are not understood - strange multi-baryonic states could probe the cold and dense medium
- measurements of resonances from heavier system are already scheduled (2007-2009)
SQM 2007International Conference on Strangeness in Quark Matter
Xavier Lopez, [email protected]
The FOPI CollaborationBudapest (Hungary)Bucharest (Romany)
Clermont-Ferrand (France)Darmstadt (Germany)Dresden (Germany)
Heidelberg (Germany)Lanzhou (China)Moscow (Russia)
Munich (Germany)Seoul (South Korea)
Split (Croatia) Strasbourg (France)
Vienna (Austria)Warsaw (Poland)Zagreb (Croatia)
THE END
Conclusion / Outlook
• Measurement of resonances in Ni+Pb s½ = 2.7 GeV - highest beam kinetic energy / projectile mass
- enhancement of the number of nucleons in the target
- best compromise between s½ and ρ - better acceptance/ PiD of kaons
K-, , K(892), Σ(1385),...
K clusters: Λp and Λd corr.
chiral predictions (e.g. Σ(1385), ,...)
higher statistics of K(892) and
• Strangeness physic at SIS energies with new probes from the medium ! - sub-threshold measurement of K(892), Σ(1385) resonances - K- potential and the production are not understood
- strange multi-baryonic states could probe the cold and dense medium - measurement of resonances from heavier system
with gamma s
Directed flow of K+
P. Crochet et al., PLB 486 (2000) 6
Ru+Ru 1.69 AGeV
Study of integrated sideward flow of K+ :• absence of K+ flow doesn't due to columbian repulsion (K0)• co-production of K+ and Λ but different propagations
Study of differential sideward flow of K+ :• anti-flow at low pt and flow at high pt
• good agreement with the version of model which take into account a repulsive K-N potential (~ 20 MeV)
Evidence of in medium effects on K+ propagation
J.L.Ritman et al., ZPA 352 (1995) 355
• Consistent results between FOPI and KAOS• Sign of V2 for K+ and K- show in-medium effect• The trend of V2 for K+ and K- is different compared to the models
Elliptic flow of Kaons
A. Mishra et al. PRC 70(2004) 044904
in plane
out of plane
Y-J. Kim, to be submitted to PRL
KAOS data: F. Uhlig et al. PRL 95(2005) 0123101
K+
K-
Ni+Ni at 1.93 AGeV
Rapidity distribution of K-/K+ ratio:• enhancement of the ratio at mid-rapidity• version of the model which take into account an attractive (repulsive) potentials for K-(K+) reproduce the data
K-/K+ ratio function of the number of participant:• constant for a light system (Ni)• decrease for heavy system (Au)
Ambiguity for the evidence of in medium effect on K- productionStrangeness exchange reaction could be the reason: +Y ↔ K-+B
K-/K+ ratio
K. Wisniewki et al., EPJA 9 (2000) 515 A. Förster et al., PRL 91 (2003) 152301
1.5 AGeV
Strangeness exchange reactions
A. Förster et al., nu/ex 0701014
• Transport model predict a later time production of K- with respect to K+
→ different emission time caused by +Y ↔ K-+B (Y=Λ, Σ)• Centrality and system size dependence similar for both K+ and K-
Experimental results and models predictions confirm that strangeness exchange reactions are the dominant process for K- production→ Need to extend the study of production and propagation of strangeness to other particles species: K0, Λ, Σ(1385), ...
α=1.25±0.12α=1.22±0.27
α=1.26±0.06α=1.34±0.16
α=1.0±0.05α=0.96±0.05
αpartA~M
N+Δ→K++Λ+pπ+Λ→K-+N
Summary and perspectives
Adams et al., PRC 71 J(2005) 064902
FOPI Al+Al PRE
LIM
INA
RY
?
RHIC DATA: STAR Collaboration, PRL 97 (2006) 132301
THERM. MOD.: .A. Andronic, NPA 772 (2006) 167
URQMD MOD.: M. Bleicher, NPA 715 (2003) 85
X. Lopez et al., to be submitted to PRL
K(892) with K+π- in Al+Al @ 1.9 AGeV
K* K*
BW FIT
Adams et al., PRC 71 J(2005) 064902
fo
2t
2Kπ
2t
2Kπ
Kπ
23
2K
2π
22K
2π
20
2K
2π
22K
2π
2Kπ
4Kπ
400
220
220
2Kπ
0Kπ
FIT
TPM
expPM
MPS
M4M)MM(MM4M)MM(M
MMΓ
Γ
ΓM)M(MΓMM
BW
PSBWF
FFIT
Effect of PS function: colder temperature ↔ high Inv. Mass
• Mean Value of Pt = 422 MeV
• "Freeze out temperature": Tfo = 65 MeV
Final parameters (mass, Γ) in agreement with PDG
Measurement of K(892) with FOPI
• First sub-threshold measurement of K(892) at SIS energy
• Mean and width in agreement with PDG
• Time production ~7 fm/c
• Dominant channel in UrQMD K+π→K*
• Thermal(transport) models under(over)-predicts the K(892)/K0 yields ratio
• A temperature of 70 MeV does not reproduce ratio with resonances
K*0 K++π- (2/3)
K0+π0 (1/3))s(d
cτ = 4 fm Eth=2.75 GeV
PDG: Mass = 896 MeV
Γ = 50 MeV
K++ π-
Al+Al 1.9 AGeV
DATA Therm. (T=70 MeV)
UrQMD
P(K*0/K0) 0.0383±0.0105 0.0225 0.1
PRELIMINARY
Σ(1385) in transport model UrQMD (M. Bleicher-S. Vogel)
• Ratio at production time (~10 fm/c)
P(Σ*-+Σ*+)/P(Λ+Σ0) = 0.195
• Ratio with reconstructable Σ* (>200 fm/c)
P(Σ*-+Σ*+)/P(Λ+Σ0) = 0.177
~8% πΣ* lost in inelastic rescattering
• Σ* creation processes
76% Λ+π→Σ* σ ~ 37 mb
12% Σ+π→Σ*
12% N*(∆)+B →Σ*
• Single yields are in agreement with the data
• Similar rapidity distributions for Σ and Λ
Data σgeo ≤315 mb:
P(Σ*-+Σ*+)/(Λ+Σ0)=0.125±0.026(stat.)±0.033(syst)
K(892) in transport model UrQMD (M. Bleicher-S. Vogel)
• Ratio at production time (~10 fm)
P(K*0)/P(K++K0) = 0.0803
• Ratio with reconstructable K*0 (>200 fm and in K++π-)
P(K*0)/P(K++K0) = 0.077
~4% πK* lost in inelastic rescattering
• K* creation processes
Data σgeo ≤315 mb preliminary:
P(K*0)/(K++K0)=0.021±0.005(stat.)±(syst.→P. Velten)
70% K+π→K* (σ under calculation)
30% N*(∆)+B →K*
Kaonic Cluster predictions
Clusters of anti-kaons : K- bind with nucleus with strong interaction
• Hypothesis of discrete states of this objects
• High binding energy (~100 MeV)
• New state of the matter
• Densities could reach 10 times the normal nuclear density
Y. Akaishi et al., PRC 65 (2002)044005 T. Yamazaki et al., PLB (2002) 53570 A. Doté et al., PRC 70 (2004) 044313
V.K. Magas et al., nucl-th/0601013E. Oset et al., nucl-th/0509048BUT theoretical controversies !
K-+d→π-+Λ+p
at rest
T.H. Tan, PRL 23 (1969) 395
K- +d reaction: the search for dibaryonsvia Λp correlations (1963-1985)
C. Pigot el al., NPB 249 (1985) 172
R.J. Oakes, PR 131 (1963) 2239 R.L. Jaffe, PRL 38 (1977) 195
K-+d→π-+X+ 1.06GeV/c
K-+d→π-+X+ 0.92GeV/c
Prediction of strange partner of the deuteron {10} (1963) and octet of dibaryons (1977): both cases assume H1+(Λp)
Experiments show an excess at 2.13 GeV/c2. The major source of background proposed is ΣN interactions, H1+ not yet discovered.
First excess measured in Λp inv.
mass at 2.13 GeV (Γ=17 MeV)
K- stopped in 12C
M. Agnello et al., PRL 94, (2005) 212303
V.K. Magas, E. Oset nucl-th/0601013
T. Yamazaki and Y. Akaishi nucl-exp/0609041
E. Oset et al., attributes the structure to final state interaction (FSI) → no peak in pp reac.
K- stopped on 4He, 7Li, 12C (2005-2006)
T. Yamazaki et al. Prediction of K- bound state to explain Finuda results (KeK)
Excess in Λp inv. mass [2.2;2.3]GeV/c2
(Γ=67 MeV)
Controversies start on Λ(1405) description
K- stopped in 7Li
A. Andronic et al., NPA 765 (2006) 211
SIS
Σ*
Search for kaonic clusters in heavy ions collisions
Thermal model predicts a high production yield of anti-kaonic clusters in heavy ions collisions at SIS energies
MeV219
MeV217
MeV219
MeV208
MeV263
3
HepppnK
tppnnK
pppppK
dppnK
pppK
Decay channels of clusters of anti-kaons accessible with FOPI
• Excess found at 2.13 GeV/c2 - limit of the significance - final state interaction (ΣN), dibaryons H1+(2130) ? - flat distribution in [2.2;2.4] GeV/c2 → no evidence of the FINUDA structure
• Structure present also in Al+Al collisions in the same mass region
• Excess distributed around the spectator region: need cold matter to form Λp clusters ? FINUDA
Ni+Ni 1.93 AGeV
Λp
Kaonic clusters in heavy ions collisions
A. Andronic et al., NPA 765 (2006) 211
Thermal model predicts a high production yield of anti-kaonic clusters in heavy ions collisions at SIS energies
MeV219
MeV217
MeV219
MeV208
MeV263
3
HepppnK
tppnnK
pppppK
dppnK
pppK
Decay channels of clusters of anti-kaons accessible with FOPI :
Excess found on Λd analysis, but cluster mass range unknownNeed to test analyses on ΛX correlation already measured → Σ*(1385)• Resonances measured in heavy ions collisions (RHIC, S. Salur et al., J.Phys. G31 (2005) S179 )• Thermal model predicts similar Σ* and clusters yields at SIS energy (P(Σ*/Λ)~10-2)
SIS
PRELIMIN
ARY
Ni+Ni, 1.93 AGeV
Excess distribution around the spectator region: need cold
matter to form Λp clusters ?
Where is located the excessin phase space ?
Λp in Ni+Ni:
y0<-0.35ally0>-0.35
y0=ycm -1
S-BSignal
BKG
Target cm Proj.
Enhancement of the signal by selecting rapidity far off the mid-rapidity (y0=0)
• K- N interaction is dominated by sub-threshold resonances ()
KN potential and states
K* with K+ (Al+Al @ 1.9 AGeV) DATA
K+K*
NEVT=290853550
NK+=411941±641
NK*=5792±950
Al+Al Ni+Ni
Raw yields: ~ 2 times more Λ (due to N events) in Al and S/B better (factor 2.6) for the same set of cuts
Λ selected for Σ* analysis in Al & Ni data
10<TMUL<33 25<TMUL<58