O n s t r a n g e n e s s i n N A 6 1 / S H I N E M a c i e j L e w - PowerPoint PPT Presentation

P h D S e m i n a r Wrocław, Feb 28 2018 O n s t r a n g e n e s s i n N A 6 1 / S H I N E M a c i e j L e w i c k i mlewicki@ift.uni.wroc.pl University of Wrocław Institute of Theoretical Physics

Section 1 Strangeness in Heavy Ion Collisions

Strangeness In particle physics: Strangeness ( S ) – property of particles, quantum number. Defined as: S = ( n s − n ¯ s ) , where n s and n ¯ s are the numbers of strange and anti-strange quarks. Strangeness is conserved in strong interactions. In heavy ion physics: produced strangeness means a number of pairs of strange and anti-strange particles, N s ¯ s Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Feb 28 2018 1 / 29

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 Feb 28 2018 2 / 29

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 Feb 28 2018 3 / 29

Strange definitions Wanted: strangeness / entropy Strangeness production: s � – number of s - ¯ � N s ¯ s pairs produced in a collision. s � = � Λ + ¯ Λ � + � K + ¯ 2 · � N s ¯ K � + � φ � + . . . multistrange hyperons Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Feb 28 2018 4 / 29

Strange definitions Wanted: strangeness / entropy Strangeness production: s � – number of s - ¯ � N s ¯ s pairs produced in a collision. s � = � Λ + ¯ Λ � + � K + ¯ 2 · � N s ¯ K � + � φ � + . . . multistrange hyperons s � ≈ � Λ � + � K + + K − + K 0 + ¯ 2 · � N s ¯ K 0 � Entropy production ∝ � π � The experimental ratio can be defined as: E S = � Λ � + � K + ¯ K � ≈ 2 · � N s ¯ s � � π � � π � Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Feb 28 2018 4 / 29

How to measure produced strangeness Decades ago... streamer chambers measured: ◮ charge ◮ momentum strange hadrons identified by reconstruction of their decays: ◮ Λ ◮ K 0 s � K 0 s � = 1 2 ( � K 0 � + � K 0 � ) s � = 2 � K 0 � + 2 � K 0 � ≈ � K 0 � + � K + � + � K − � + � K 0 � 4 � K 0 � Λ � + 4 � K 0 s � ≈ 2 � N ss � ≈ 2 � N ss � E s = � Λ � + 4 � K 0 s � � π � � π � Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Feb 28 2018 5 / 29

How to measure produced strangeness Nowadays: TPCs + ToF measured: ◮ momenta ◮ charges ◮ masses strange hadrons identified by mass measurement: ◮ K + ◮ K − � π � ≈ 3 s � ≈ � K + � + � K 0 � ≈ 2 · � K + � , � π + � + � π − � � � � N s ¯ 2 � K + � � N s ¯ s � ≈ 2 � π � � π + � 3 � K + � E S ≈ 4 � π + � 3 Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Feb 28 2018 6 / 29

Section 2 Strangeness and Phase Transition

Strangeness and 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 Feb 28 2018 7 / 29

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 Gaździcki, Gorenstein, Acta Phys.Polon. B30 (1999) 2705 Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Feb 28 2018 8 / 29

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 Feb 28 2018 9 / 29

Dynamical Approach by Rafelski-Müller 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 Feb 28 2018 10 / 29

Rafelski-Müller Dynamical Approach > non-strange QGP < < N ss > / - s NN Equilibrium value reached in QGP ← fast strangeness production. No enhancement in the confined phase ← slow strangeness production in whole hadronic region. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Feb 28 2018 11 / 29

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 Feb 28 2018 12 / 29

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 Feb 28 2018 13 / 29

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 Feb 28 2018 14 / 29

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 Feb 28 2018 15 / 29

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 Feb 28 2018 16 / 29

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 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 T was predicted to be sensitive to the phase transition between confined matter and QGP. Maciej Lewicki (UWr) Strangeness@N A 61/S HINE Feb 28 2018 17 / 29