XIII Workshop on HIC Wrocław, Jan 6, 2018 New results on strangeness production from the NA61/SHINE Maciej Lewicki mlewicki@ift.uni.wroc.pl University of Wrocław Institute of Theoretical Physics
NA61/SHINE on the Workshop Wojciech Brylinski : Charm physics in NA61/SHINE Dag Larsen : Upgrade of the NA61/SHINE facility beyond 2020 for an expanded physics programme
Section 1 Strangeness in Heavy Ion Collisions
Strangeness in HIC Most strangeness produced in the form of: The lightest (anti-)strange mesons ( M ≈ 0 . 5 GeV ): ◮ K + – ( u ¯ s ) ◮ K 0 – ( d ¯ s ) K 0 – (¯ ¯ ◮ K − – (¯ us ) ds ) ◮ The lightest (anti-)strange baryons ( M ≈ 1 . 1 GeV ): ◮ Λ – ( uds ) ◮ ¯ u ¯ Λ – (¯ d ¯ s ) Strangeness neutral mesons: ( M ≈ 1 . 0 GeV ): ◮ φ – ( s ¯ s ) Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 1 / 26
Main strangeness carriers in A+A collisions at high baryon density strangeness conservation ¯ = s s isospin isospin symmetry symmetry ≈ ≈ ¯ K + K 0 K − K 0 ≪ high baryon ≈ density high baryon density ≪ ¯ Λ Λ – sensitive to strangeness content only – sensitive to strangeness content and baryon density Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 2 / 26
Strange definitions Strangeness production: s – number of s - ¯ N s ¯ s pairs produced in a collision. The experimental ratio: E S = � Λ � + � K + ¯ K � ≈ 2 · N s ¯ s � π � � π � � π � ≈ 3 s ≈ � K + � + � K 0 � ≈ 2 · � K + � , � π + � + � π − � � � N s ¯ 2 � K + � N s ¯ � π � ≈ 2 s � π + � 3 � K + � E S ≈ 4 � π + � 3 It is convenient to study the ratio E S in this form, as the identification of charged hadrons is relatively easy. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 3 / 26
Section 2 Strangeness in Phase Transition
Strangeness in phase transition confined matter T C ≈ 150 MeV quark-gluon plasma − → K mesons (anti-)strange quarks Phase transition g K = 4 g s = 12 2 M ≈ 2 · 500 MeV 2 m ≈ 2 · 100 MeV Lightest strangeness carriers: relatively heavy kaons ( M > T C ) in the confined phase, relatively light strange quarks ( m � T C ) in QGP. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 4 / 26
Strangeness in Statistical Model of Early Stage � 3 / 2 e − M / T � MT ≈ gV � for heavy particles gV 1 2 π � n � = d 3 p e E / T ± 1 ( 2 π ) 3 ≈ gV 2 π 2 4 · 45 T 3 for light particles > non-strange < < N ss > / - T ∝ MT 3 / 2 � K � � s � � u + d + g � ∝ T 3 · e − M / T T 3 = const ( T ) � π � T 3 Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 5 / 26
Strangeness in Statistical Model of Early Stage Strange/non-strange Temperature dependence on collision energy in SMES : particle ratio: > T[MeV] 300 non-strange 250 QGP 200 < 150 < N ss > / - 100 0 5 10 15 20 25 s NN [GeV] s NN Crossing the phase transition leads to a decrease of the strange/non-strange particle ratio – the horn-like structure Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 6 / 26
Strangeness in Statistical Model of Early Stage Strange/non-strange Temperature dependence on collision energy in SMES : particle ratio: > T[MeV] 300 non-strange 250 QGP 200 < 150 < N ss > / - 100 0 5 10 15 20 25 s NN [GeV] s NN Crossing the phase transition leads to a decrease of the strange/non-strange particle ratio – the horn-like structure – Marek’s horn. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 6 / 26
Rafelski-Müller Dynamic Model strangeness production in confined matter strangeness production in QGP N + N → N + Y + K q 1 k 1 π + N → K + Y π + N → K + Y k 2 -q 2 π + Y → Ξ + K π + Y → Ξ + K π + Ξ → Ω + K π + Ξ → Ω + K q 1 k 1 k -q 2 2 1 fm/ c 100 fm/ c Rafelski, Müller, Phys. Rev. Lett. 48 (1982) 1066 Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 7 / 26
Rafelski-Müller Dynamic Model > non-strange QGP < < N ss > / - s NN Equilibrium value reached in QGP ← fast strangeness production. No enhancement in the transition region ← slow strangeness production in whole hadronic region. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 8 / 26
Section 3 Strangeness at N A 61/S HINE
N A 61/S HINE — facility MTPC-L T oF-L Vertex magnets T oF-F GAP VTPC-1 VTPC-2 T arget TPC FTPC-2/3 Beam PSD S4 S5 VD FTPC-1 V1 V1 p V0 x S1 S2 T oF-R CEDAR THC MTPC-R BPD-1 BPD-2 BPD-3 y z Beam detectors: TPCs: ToF: PSD: position electric charge E F – energy of tof projectile charge momentum spectators dE / dx mass reaction plane time Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 9 / 26
Particle identification — tof - dE / dx 120 120 ] ] 2 2 ) ) 2 1.4 Be+Be @40 A GeV/ c 2 1.4 Be+Be @40 A GeV/ c [(GeV/c [(GeV/c 1.2 1.2 100 100 2 p 2 p m 1 m 1 80 80 0.8 0.8 0.6 0.6 K - 60 60 + 0.4 0.4 K 0.2 + 0.2 π 40 40 + - e e π 0 0 20 20 -0.2 -0.2 -0.4 -0.4 0 0 0.8 1 1.2 1.4 1.6 1.8 0.8 1 1.2 1.4 1.6 1.8 dE/dx [a.u.] dE/dx [a.u.] Very good separation. Very efficient PID in mid-rapidity region. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 10 / 26
Particle identification — dE / dx Ar+Sc @30 A GeV/ c Ar+Sc @30 A GeV/ c pions 400 pions protons protons kaons kaons deuterons deuterons 1000 electrons electrons 300 sum sum ∈ ∈ p [12.59; 15.85) p [12.59; 15.85) ∈ ∈ p [0.20; 0.30) p [0.20; 0.30) T T 200 charge = 1 charge = -1 500 100 % 5 % 5 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 ∆ 1.7 σ 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 ∆ 1.7 σ / / 0 0 − − 5 5 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 dE/dx [a. b.] dE/dx [a. b.] Probability PID. Applicable in forward-rapidity region. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 11 / 26
Event selection The PSD is located most downstream on the beam line and measures the projectile spectator energy E F of the non-interacting nucleons of the beam nucleus. The energy measured by the PSD is used to select events classes corresponding to the collision "violence" ( ≈ centrality). Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 12 / 26
Section 4 Results on Strangeness
Results on strangeness production Results from NA61/SHINE on identified hadrons produced in strong and electromagnetic processes in primary interactions: Ar+Sc [CPOD 2017, arXiv:1712.02417] Be+Be [Nucl. Phys. A 967, 35 (2017)] p+p [Eur. Phys. J. C74 (2014) 2794, Eur. Phys. J. C77 (2017) 671] World data on Pb+Pb , Au+Au , C+C , Si+Si and p+p : NA49 [Phys.Rev. C77, 024903 (2008)], [Phys.Rev. C66 (2002) 054902], [Phys.Rev. C86 (2012) 054903] [Eur. Phys. J. C68 (2010) 1], [Eur. Phys. J. C45 (2006) 343] ALICE [Phys. Lett. B736 (2014) 196], [Eur. Phys. J. C71 (2011) 1655], [Phys. Rev. Lett. (2012) 109] STAR [Phys. Rev. C79 (2009) 034909], [Phys. Rev. C96 (2017) 044904] BRAHMS [Phys. Rev. C72 (2005) 014908] p+p world data [Z. Phys. C65 (1995) 215], [Phys. Rev. C69 (2004) 044903] Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 13 / 26
Results stand for primary particles produced in strong and electromagnetic processes. Corrections: Results are corrected for: ◮ biases in event selection ◮ secondary interactions ◮ reconstruction inefficiency ◮ detector geometrical acceptance. ◮ weak decays MC used for corrections: EPOS 1.99 model and GEANT3.2+N A 61/S HINE detector simulation. Uncertainties: There are two sources of statistical uncertainties in results: ◮ data uncertainties ◮ MC corrections uncertainties (insignificant). The systematic uncertainties comes from: ◮ limited precision of simulation and detector description. For nucleus-nucleus collisions, the event classes are defined by forward energy measured by PSD. Results for p+p collisions refer to all inelastic interactions. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 14 / 26
m T spectra and inverse slope parameter 3 3 10 10 ] ] -1 -1 + ≈ - ≈ ) K ( y 0) ) K ( y 0) 2 2 [(GeV/c [(GeV/c Pb+Pb Pb+Pb 2 2 10 10 75A GeV/c 75A GeV/c T N T N dydm A dydm A 10 6 10 6 n n 1 1 / S / S 2 2 d H d H I I N N E E p p r r e e T l T l 1 i m 1 i m 1 m 1 m i i n n a a r r y y -1 -1 10 10 Be+Be Be+Be -2 -2 10 10 p+p p+p -3 -3 10 10 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 m - m [GeV] m - m [GeV] + + T K T K m T spectra at mid-rapidity were fitted with an exponential function d 2 n � � 1 − m T dm T dy = A exp m T T which well describes K spectra for all beam momenta and all reactions The energy dependence of the inverse slope parameter was predicted to be sensitive to the phase transition between confined matter and QGP. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Jan 6, 2018 15 / 26
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