Hadron production at SIS energies: an update from HADES

Transcription

1 Hadron production at SIS energies: an update from HADES CPOD 2016 Wroclaw Manuel Lorenz for the HADES collaboration 1

2 Introduction Outline SIS 18 energy regime and HADES 0-20% most central 1.23 A GeV Kaon production Φ as source of K - and sequential kaon freeze-out Strangeness production: the complete picture Microscopic and macroscopic descriptions (and how they could come together) Virtual photon emission Teaser Net-Proton Fluctuations [MeV] T eff π K /K s p φ Λ Mass [MeV/c ] Summary and Conclusion

3 Heavy-ion collisions and QCD phase diagram Systematic probing of the phase diagram by varying kinetic beam energy K. Fukushima SIS 18 energy regime: beam energies of 1-2 AGeV for ions, highest µ B, baryon dominated rather long living system system

4 Heavy-ion collisions and QCD phase diagram Systematic probing of the phase diagram by varying kinetic beam energy Progress detector driven K. Fukushima SIS 18 energy regime: beam energies of 1-2 AGeV for ions, highest µ B, baryon dominated rather long living system system

5 Heavy-ion collisions and QCD phase diagram Systematic probing of the phase diagram by varying kinetic beam energy Progress detector driven K. Fukushima Hosan SIS 18 energy regime: beam energies of 1-2 AGeV for ions, highest µ B, baryon dominated rather long living system system HADES Fast detector: khz trigger rate Large Acceptance: Full azimuthal and polar angle coverage of Θ = 18 85

6 Heavy-ion collisions and QCD phase diagram Systematic probing of the phase diagram by varying kinetic beam energy Progress detector driven K. Fukushima Hosan SIS 18 energy regime: beam energies of 1-2 AGeV for ions, highest µ B, baryon dominated rather long living system system HADES Fast detector: khz trigger rate Large Acceptance: Full azimuthal and polar RPC angle coverage of Θ = 18 85

7 A GeV ( s=2.4 GeV): NN-threshold NN-threshold Complete strangeness production below free NN-threshold! World data from: C. Blume, C. Markert, arxiv: v2 [nucl-ex] 19 Aug 2011

8 Performance: mass spectrum # M/q Clear yield hierarchy: p, π, K +, K - Multiplicity 100,10,10-2,10-4 Fast and high resolution detectors 2.4x10 9 events analyzed # First observation at such low energy

9 Performance: mass spectrum # M/q Clear yield hierarchy: p, π, K +, K - Multiplicity 100,10,10-2,10-4 Fast and high resolution detectors 2.4x10 9 events analyzed # First observation at such low energy

10 Strangeness production at SIS 18 Difference in production thresholds for K +- due to quark content NN NK + Λ (E thr =1.58GeV ) NN NNK + K (E thr = 2.49GeV ) NN NNϕ (E thr = 2.59GeV )

11 KaoS data and interpretaion Förster et. al (KaoS) Similar A part dependence Different inverse slope parameters Conclusions:at that time - Production of K + /K - coupled Strangeness exchange dominant for K - Later freeze-out of K - compared to K +, due to coupling to baryons Strangeness production in HIC is very different from that in elementary interaction Phys.Rept. 510 (2012)

12 Kaon production: new HADES data K + K- K + T eff =105±4 MeV K - T eff =82±9 MeV HADES: highest quality data so far. As expected from previously gathered systematic: Inverse slope of K - lower than of K +

13 Kaon production: new HADES data K - / K + constant as a function of centrality

14 Kaon production: new HADES data K - / K + constant as a function of centrality K - / K + ratio follows energy dependence as observed by other experiments

15 Φ mesons as source of K - - φ/k HADES Au+Au HADES Ar+KCl FOPI Ni+Ni FOPI Al+Al E917 Au+Au Central NA49 Pb+Pb Central STAR Au+Au Central s NN [GeV] Enhanced Φ production at low beam energy è 30% of K - result from Φ decays! (and not from strangeness exchange) Multiplicities 10-4 of both particles

16 How does this effect the K - slope? High contribution from Φ feed down can explain lower inverse slope parameter of K - spectrum (T eff = 82 ± 9 MeV) in comparison to the one of K + (T eff = 105 ± 3 MeV) Measured rapidity distribution reproduced by cocktail àno indication for sequential K + K - freeze-out when feed-down corrected (Ockham s Razor)

17 Where do the Φ come from? - φ/k UrQMD predictions for Au+Au HADES Au+Au HADES Ar+KCl FOPI Ni+Ni FOPI Al+Al E917 Au+Au Central NA49 Pb+Pb Central STAR Au+Au Central UrQMD (tuned) Elementary p+p data N(1990), N(2080), N(2190), N(2220), N(2250) s NN [GeV] Tuned to match elementary data by increased branching ratios of N* (needed in the tails of the resonances, consistent with OZI rule) First transport model to explain Φ/K - J. Steinheimer, M. Bleicher J.Phys. G43 (2016) no.1,

18 Strangeness production: the complete picture - All strange particles are produced below elementary production threshold - Particle yields rise more than linear with centrality (M/A Part ~ A Partα ) - Similar trend for all strange particles àhierarchy in production threshold?! trange particles in this system - Within errors same trend as measured by KaoS and FOPI at higher energies (α K+ =1.34 ± 0.16, α K- = 1.22 ± 0.27, α Φ = 1.7 ± 0.5, α K = 1.20 ± 0.25, α Λ = 1.34 ± 0.16) - Sensitive to multi-particle interactions Comparison to transport models

19 Microscopic description of strangeness production Mult/<A Part > Data UrQMD HSD no pot IQMD no pot, α = 1.24 ± 0.11, α = 1.71 ± 0.04, α = 1.35 ± 0.02, α = 1.48 ± 0.03 Mult/<A Part > K 0 s Λ+Σ 0 Data, α = 1.37 ± 0.11 UrQMD, α = 1.68 ± 0.04 HSD no pot, α = 1.35 ± 0.02 IQMD no pot, α = 1.48 ± <A Part > <A Part > Model predictions: UrQMD 3.4, HSD 711n, IQMD c8, (full pot.= 40 MeV) HSD and IQMD reproduce rise with Apart à multi-particle interactions under control UrQMD overestimates the rise à due to production via resonances? General trend to overshoot data à uncertainty in overall yield Strangeness conservation: charged Σ s are missing à CBM Thanks to Y. Leifels, E. Bratkovskaya, C. Hartnack, J. Aichelin, J. Steinheimer and M. Bleicher

20 Microscopic description of strangeness production Mult/<A Part > Data, α = 1.24 ± 0.11 UrQMD, α = 1.71 ± 0.04 HSD no pot, α = 1.35 ± 0.02 IQMD no pot, α = 1.48 ± 0.03 HSD full pot, α = 1.32 ± 0.02 IQMD full pot, α = 1.39 ± 0.02 Mult/<A Part > K 0 s Λ+Σ 0 Data, α = 1.37 ± 0.11 UrQMD, α = 1.68 ± 0.04 HSD no pot, α = 1.35 ± 0.02 IQMD no pot, α = 1.48 ± 0.03 HSD full pot, α = 1.32 ± 0.02 IQMD full pot, α = 1.39 ± <A Part > <A Part > Model predictions: UrQMD 3.4, HSD 711n, IQMD c8, (full pot.= 40 MeV) HSD and IQMD reproduce rise with Apart à multi-particle interactions under control UrQMD overestimates the rise à due to production via resonances? General trend to overshoot data à uncertainty in overall yield Strangeness conservation: charged Σ s are missing à CBM Repulsive KN potential reduces the yield à compare shape of p t spectra Multiplicities 10-2 o f both particles Thanks to Y. Leifels, E. Bratkovskaya, C. Hartnack, J. Aichelin, J. Steinheimer and M. Bleicher

21 KN Potential revisited: comparison of the p t shape counts [a.u.] K 0 s 0.59 > y > 0.89 Normalization: MeV/c Data (0-10%) HSD no pot HSD full pot IQMD no pot IQMD full pot p t [MeV/c] KN-Potential affects mostly low p t à spectra normalized in high p t region Inclusion of potential: Same trend in HSD and IQMD, reduction of low p t à clear improvement of description (IQMD perfect)

22 KN Potential revisited: comparison of the p t shape counts [a.u.] K 0 s 0.59 > y > 0.89 Normalization: MeV/c Data (0-10%) HSD no pot HSD full pot IQMD no pot IQMD full pot UrQMD p t [MeV/c] KN-Potential affects mostly low p t à spectra normalized in high p t region Inclusion of potential: Same trend in HSD and IQMD, reduction of low p t à clear improvement of description (IQMD perfect) UrQMD: without any potential even lower yield at low p t à shape of spectra also modified by production via different baryonic resonances

23 Macroscopic description of hadron production Particle production from a homogeneous source: Grand canonical ensemble - (T, µ= µ B µ s µ Q, V and sometimes γ s, usually µ s and µ Q are constrained) 0-20% most central Strangeness canonical ensemble - (T, µ= µ B µ Q, R c, R) - Strangeness canonically suppressed at low temperatures, not enough to explain data additional parameter - R C < R v ) Fits at low beam energies based on limited number of particle species (ratios) Additional input: Hadron spectrum and BR to final states ϕ meson (hidden strangeness, not suppressed by R C but strongly by γ S )

24 Macroscopic description of hadron production Particle production from a homogeneous source: Grand canonical ensemble - (T, µ= µ B µ s µ Q, V and sometimes γ s, usually µ s and µ Q are constrained) Strangeness canonical ensemble - (T, µ= µ B µ Q, R c, R) - Strangeness canonically suppressed at low temperatures, not enough to explain data additional parameter - R C < R v ) Fits at low beam energies based on limited number of particle species (ratios) yield Exp/THERMUS THERMUS V2.3: S. Wheaton, J.Cleymans Comput.Phys.Commun.180:84-106, % most central Apart p - π η Λ Data, s NN =2.4 GeV T=68±2MeV, µ =883MeV±25, b R C =2.1±0.3fm, R =5.8±0.9fm V 2 Χ /ndof=2.3 + K 0 Ks - K φ Additional input: Hadron spectrum and BR to final states ϕ meson (hidden strangeness, not suppressed by R C but strongly by γ S ) Hadron yields described by 4 parameters (T, µ B, R, R c ) Rather large values for T and µ B γ s instead of R c delivers similar results but misses the ϕ yield

25 Kinetic vs. chemical freeze-out [MeV] T eff % most central T kin extracted from Siemens-Rassmusen fit to p spectra - π K /K s p φ Λ Mass [MeV/c ] T and µ b higher than expected from parameterization and universal freezeout line (E/B=1GeV) Freeze-out points: A. Andronic, P. Braun-Munzinger and J. Stachel, Nucl. Phys. A 772, 167 (2006). J. Cleymans, H. Oeschler, K. Redlich and S. Wheaton, Phys. Rev. C 73, (2006). Parameterization: Cleymans, Oeschler et al, Phys.Rev.C73:034905, (2006). Distortion of spectra by e.g. resonance decays or potentials, caveats! T kin T chem (no conflict as previously reported) Light nuclei important for further constraints

26 And how the two might come together.. UrQMD yields fitted with SHM (Thermus and Florence) Very good χ 2 /dof after 6 fm/c Similar results as using a coarse grained method (used for virtual photon emission) à Apparent equilibrium driven by (baryon) resonance decays Along the same line also p+nb data from HADES are well described using a similar THERMUS fit as for Ar+KCl and Au+Au data arxiv.org/abs/ accepted by EPJA J. Steinheimer, M. Lorenz, F. Becattini, R. Stock, M. Bleicher arxiv.org/abs/ , accepted by PRC

27 Virtual photon emission in A+A collisions Excess radiation Ar+KCl HADES ArKCl data: Phys.Rev.C 84 (2011) CG FRA: Phys. Rev. C 92, (2015) CG GSI-Texas: Eur.Phys.J. A52 (2016) no.5, 131 HSD HSD: E. Bratkovskaya et al., Phys.Rev. C87 (2013)

28 Virtual photon emission in A+A collisions Excess radiation Ar+KCl HADES ArKCl data: Phys.Rev.C 84 (2011) Au+Au 1.23 A GeV CG FRA: Phys. Rev. C 92, (2015) CG GSI-Texas: Eur.Phys.J. A52 (2016) no.5, 131 HSD HSD: E. Bratkovskaya et al., Phys.Rev. C87 (2013) Experimentally defined hadronic cocktail: π 0 à charged pions or conversion method η à conversion method φ à K + K - channel ω à Statistical hadronization model Inmedium ρ: CG GSI-Texas

29 Virtual photon emission in A+A collisions Excess radiation Ar+KCl Au+Au 1.23 A GeV HADES ArKCl data: Phys.Rev.C 84 (2011) CG FRA: Phys. Rev. C 92, (2015) CG GSI-Texas: Eur.Phys.J. A52 (2016) no.5, 131 HSD HSD: E. Bratkovskaya et al., Phys.Rev. C87 (2013) More information: Experiment: Szymon Harabasz Fr. 16:30 Theory: Florian Seck Th. 14:00 Stephan Endres Th. 14:30 Experimentally defined hadronic cocktail: π 0 à charged pions or conversion method η à conversion method φ à K + K - channel ω à Statistical hadronization model Inmedium ρ: CG GSI-Texas

30 Net-proton number fluctuations at HADES Phase space bit y p t GeV/c Correct the moments Bzdak & Koch, PRC 86 (2012); Xiaofeng Luo, arxiv: (2014) Bzdak, Holzmann, Koch arxiv: Calculate moments Mean measured Variance measured Skewness measured Kurtosis measured Skew*Sig measured Correct moments efficiency correction Mean true Variance true Skewness true Kurtosis true Skew*Sig true Kurt*Sig 2 measured Kurt*Sig 2 true àunfolding G. D Agostino, Nucl. Instr. Meth. A 362 (1995) 487. J. Albert et al. (MAGIC), Nucl. Instr. Meth. A 583 (2007) 494. S. Schmitt, J. Instr. 7 (2012) T y = A x y: measured histogram x: true histogram A: response matrix Matrix inversion

31 Performance study based on UrQMD Corrected moments vs Unfolding Applied to real data à First results ready for SQM in Berkeley next month

32 Summary Strangeness exchange dominant for K - Later freeze-out of K - compared to K + Strangeness production in HIC is very different from that in elementary interaction No indication for sequential K + K - freeze-out when correcting for ϕ feeddown (Ockham s Razor) UrQMD describes ϕ/k - ratio when tuned to match elementary data - φ/k HADES Au+Au HADES Ar+KCl FOPI Ni+Ni FOPI Al+Al E917 Au+Au Central NA49 Pb+Pb Central STAR Au+Au Central [GeV] s NN

33 Summary Strangeness exchange dominant for K - Later freeze-out of K - compared to K + Strangeness production in HIC is very different from that in elementary interaction No indication for sequential K + K - freeze-out when correcting for ϕ feeddown (Ockham s Razor) UrQMD describes ϕ/k - ratio when tuned to match elementary data Similar rise of all particle yields containing strangeness although clear hierarchy in production thresholds - φ/k HADES Au+Au HADES Ar+KCl FOPI Ni+Ni FOPI Al+Al E917 Au+Au Central NA49 Pb+Pb Central STAR Au+Au Central [GeV] s NN K 0,+ and Λ yields and spectra well predicted by HSD and IQMD including repulsive KN potential SHM describes data with 4 parameters (T, µ B, R, R c ) rather high values for T, µ B counts [a.u.] > y > 0.89 Normalization: MeV/c Data (0-10%) HSD no pot HSD full pot IQMD no pot IQMD full pot UrQMD p [MeV/c] t

34 Summary Strangeness exchange dominant for K - Later freeze-out of K - compared to K + Strangeness production in HIC is very different from that in elementary interaction No indication for sequential K + K - freeze-out when correcting for ϕ feeddown (Ockham s Razor) UrQMD describes ϕ/k - ratio when tuned to match elementary data Similar rise of all particle yields containing strangeness although clear hierarchy in production thresholds - φ/k HADES Au+Au HADES Ar+KCl FOPI Ni+Ni FOPI Al+Al E917 Au+Au Central NA49 Pb+Pb Central STAR Au+Au Central [GeV] s NN K 0,+ and Λ yields and spectra well predicted by HSD and IQMD including repulsive KN potential SHM describes data with 4 parameters (T, µ B, R, R c ) rather high values for T, µ B Virtual photon emission at low s described with similar approach as used for higher energies, modifications baryon driven (more on Thursday and Friday) counts [a.u.] > y > 0.89 Normalization: MeV/c Data (0-10%) HSD no pot HSD full pot IQMD no pot IQMD full pot UrQMD p [MeV/c] t

35 Summary Strangeness exchange dominant for K - Later freeze-out of K - compared to K + Strangeness production in HIC is very different from that in elementary interaction No indication for sequential K + K - freeze-out when correcting for ϕ feeddown (Ockham s Razor) UrQMD describes ϕ/k - ratio when tuned to match elementary data Similar rise of all particle yields containing strangeness although clear hierarchy in production thresholds - φ/k HADES Au+Au HADES Ar+KCl FOPI Ni+Ni FOPI Al+Al E917 Au+Au Central NA49 Pb+Pb Central STAR Au+Au Central [GeV] s NN K 0,+ and Λ yields and spectra well predicted by HSD and IQMD including repulsive KN potential SHM describes data with 4 parameters (T, µ B, R, R c ) rather high values for T, µ B Virtual photon emission at low s described with similar approach as used for higher energies, modifications baryon driven (more on Thursday and Friday) Outlook: First attemp of extracting fluctuations of net-proton distribution from data at low s, results will be presented on SQM in Berkeley Light nuclei, HBT, iterative resonance reconstruction, v1,v2 More experiments at SIS18 to come 2018 counts [a.u.] > y > 0.89 Normalization: MeV/c Data (0-10%) HSD no pot HSD full pot IQMD no pot IQMD full pot UrQMD p [MeV/c] t

36 The HADES collaboration Thank you for your attention!

37 Back up

38

39 Au+Au data vs T and µ B parameterized yield Data, s NN =2.4 GeV T=59MeV fixed, µ =788MeV fixed, b R C =3.5±0.1fm, R =10.8±0.2fm V 2 Χ /ndof=9.3 Exp/THERMUS % most central Apart p - π η Λ + K 0 Ks - K Cleymans, Oeschler et al, Phys.Rev.C73:034905,2006 φ THERMUS V2.3: S. Wheaton, J.Cleymans: Comput.Phys.Commun.180:84-106,2009

40 Constraining the resonance contributions Iterative procedure Georgy Kornakov 40

41 Ξ - with tuned UrQMD / constraining the resonances J. Steinheimer and M. Bleicher, arxiv: Inclusive measurements in p+p Resonance contributions to final state can be constraint by e.g. angular distributions p+p -> K 0 +Λ+p+π + Increased hyperon-hyperon cross sections not sufficient to explain Ξ - /Λ ratio Increased N* branching ratios can explain it. Resonances! Not included in Thermus! Phys. Rev. C 90, (2014)

42 Eur. Phys. J., A 47(21) Phys.Rev.Lett. 103,

43 3.5 GeV Very similar fit for p+nb as for Ar+KCl! arxiv.org/abs/ Strong excess of the Ξ - already present in cold nuclear matter Statistical model gives similar results for p+a and light A +A collisions! THERMUS V3.0: 43 S. Wheaton, J.Cleymans: Comput.Phys.Commun.180:84-106,2009

44 Ξ - production in 3.5 GeV Phys.Rev.Lett. 114 (2015) 21, THERMUS GiBUU UrQMDv3.4 Subthreshold Ξ - production in p+nb collisions at E beam = 3.5 GeV s- s th =-70MeV Parameterization: f(x)=c(1-(d/x) G ) H Excess already present in cold nuclear matter! Reference

45 Φ production (in lighter systems) Enhanced Φ production at low beam energy First indication from FOPI (first hints from FOPI data) Feed-down of Φ can explain different slope parameters of K + and K - Statistical model Ar+KCl See also new data from FOPI in: Phys.Rev. C91 (2015) 5, Can we understand the yields, with fewer assumptions also in larger system? (Ockham s razor)

46 Hadrons in GeV Eur. Phys. J., A 47(21) Phys.Rev.Lett. 103, Ξ - Probability P ss to produce a strange quark pair 0.05 à P Ξ- 0.1 P ss 2 Strangeness production not independent?

47 Ar+KCl: vector mesons ω-meson: subthreshold + electromagnetic decay channel: 50 million events for one ω! Φ/ω ratio: suppressed in elementary reactions due to OZI rule φ K + K -, multiplicity: (2.6 ± 0.7) 10-4 ω e + e -, multiplicity: (6.7 ± 2.8) 10-3 >> R φ/ω in NN and πn reactions! Impact of other channels besides NN and πn? (e.g. ρn, ρδ, ) Effect of the medium? G. Agakishiev et al. [HADES Collaboration]. Dielectron production in Ar+KCl collisions at 1.76A GeV. Phys. Rev., C84(014902), [arxiv: [nucl-ex]]. 2011