(Anti-)hypertriton lifetime and hyperon puzzle • Introduction • ALICE results • Future perspectives • Summary Jacek Otwinowski (IFJ PAN, Krakow) On behalf of the ALICE Collaboration Hypernuclei Hypernuclei are bound systems of nucleons and at least one hyperon (baryon with strange quark content) Hypernuclei measurements: • Properties of baryon-hyperon (N-Y) and hyperon-hyperon (Y-Y) strong and weak interactions in many-body systems • Direct tests of Pauli exclusion principle • Equation of State (EoS) of dense nuclear matter • Modification of hadron properties in dense nuclear matter • Phase transition from hadronic matter to quark-gluon plasma Theory of N-Y and Y-Y interactions using non-perturbative QCD: • Meson-exchange models (N-Y and Y-Y) • Chiral effective field theory (two and three body interactions) • Lattice QCD (recently big progress, almost physical quark masses) • Constraints from scattering experiments and astrophysical observations (e.g. pulsars, failed supernovea and gravitational waves) Resent reviews: I. Vidaña, Proc. R. Soc. A 474: 20180145, E. Botta et al. Nuovo Cimento 38 (2015) 387 11-06-2019 SQM2019 - Jacek Otwinowski 2 ~70 years of hypernuclear spectroscopy • Cosmic rays: photographic emulsions and ~ 1000 hypernuclei measured by now bubble chambers 700 • Discovery of hypernucleus (Pniewski & Proc. R. Soc. A 474: 20180145 Danysz 1952) 600 + + • Strangeness exchange reactions (AGS, CERN, n(π , K )Λ 500 [MeV/c] BNL, KEK and J-PARC): Λ + - A A - - p(γ, K )Λ • K + Z à �Z + � (K + n à � + �) 400 • Associate production reactions (BNL, KEK, GSI): + A A + + 300 • � + Z à �Z + K (�+ + n à � + K ) • Electroproduction of strangeness on protons 200 (JLAB, MAMI-C): - - A + A + Momentum Transferred to the n(K , π )Λ • e- + Z à e- + K + �(Z-1) (� + p à � + K ) 100 • Hypernuclei production using stable and 0 unstable ion beams (FAIR/GSI, HypHI): 0 500 1000 1500 2000 Incident Momentum [MeV/c] • 6Li + 12C at 2 AGeV • Hypernuclei production in heavy-ion collisions • Au+Au at √sNN = 200 GeV (BNL, STAR experiment) - first measurements of anti- nucleus (anti-hypertriton) in heavy-ion collisions, Science 328 (2010) 58 • Pb+Pb at √sNN = 2.76 and 5.02 TeV (CERN, ALICE experiment) 11-06-2019 SQM2019 - Jacek Otwinowski 3 Hypernuclei weak decays Proc. R. Soc. A 474: 20180145 3 238 U • � Γ Λ Free baryon decays Non-mesonic decay rate NM Total decay rate Γ • �à N + � 2.5 T 209 ΛBi • Hypernuclei decay via mesonic and free 2 Λ Γ / non-mesonic channels Γ 28 1.5 12 56 ΛSi Fe ΛC Λ 11 • In large hypernuclei mesonic decays 5 ΛB ΛHe Γ T Γ are strongly suppressed by the Pauli 1 1 Weak decay rate Γ principle (pN < Fermi momentum) NM • � N à N + N 0.5 Γ Γ • � N Nà N + N + N M 2 0 10 100 Total number of particles A+1 11-06-2019 SQM2019 - Jacek Otwinowski 4 Discovery of hypernucleus M. Danysz and J. Pniewski, Phil. Mag. 44 (1953) 348 • The first observation of an hypernucleus (or more precisely an hyperfragment) • Events recorded by a stack of photographic emulsions exposed to the cosmic radiation at about 26 km from the Earth surface in a balloon • Hypernuclear species were unambiguously identified by the kinematic analysis of the disintegration star • Photographic emulsion experiments provide extremely precise measurements of � binding energy B� in nuclei (reference as of today) 11-06-2019 SQM2019 - Jacek Otwinowski 5 Hyperon puzzle 450 2.5 Proc. R. Soc. A 474: 20180145 400 nucleons & leptons PSR J0348+0432 nucleons, hyperons & leptons 2 ) 350 -3 PSR J1614-2230 300 1.5 (solar mass units) 250 Hulse-Taylor PSR G 200 1 150 Pressure P (MeV fm 100 0.5 (a) 50 (b) 0 0 Gravitational mass M 0 200 400 600 800 1000 1200 0 0.5 1 1.5 -3 -3 Energy density ε (MeV fm ) Central baryon number density ρ (fm ) • Hyperons may appear in the inner core of neutron stars at densities of about 2−3ρ0 • Their presence in the neutron star interior leads to a softening of the EoS and consequently to a reduction of the maximum mass (current predictions 1.4-1.8 M⨀) • Astrophysical observations of pulsars rule out almost all currently proposed EoS with hyperons…? • Additional repulsion: Y-Y repulsive potential, hyperonic three-body forces (e.g. NNY, NYY, YYY), quark-gluon plasma below the hyperon threshold (hybrid neutron stars)…? 11-06-2019 SQM2019 - Jacek Otwinowski 6 (ANTI-)HYPERTRITON LIFETIME MEASUREMENT IN PB+PB COLLISIONS WITH ALICE 11-06-2019 SQM2019 - Jacek Otwinowski 7 A Large Ion Collider Experiment • Excellent particle identification capabilities over a wide pT range 0.1-20 GeV/c • Good momentum resolution ~1-5% for pT = 0.1-50 GeV/c Central barrel tracking and PID |η|< 0.9 Centrality V0A 2.8 < η < 5.1 V0C −3.7 < η < −1.7 MUON arm - 4.0 < η < -2.5 y x z 11-06-2019 SQM2019 - Jacek Otwinowski 8 ALICE at work since 2009 System Year √sNN (TeV) Lint Pb-Pb 2010-2011 2.76 ~75 μb-1 2015 5.02 ~250 μb-1 2018 5.02 ~0.9 nb-1 Xe-Xe 2017 5.44 ~0.3 μb-1 pp p-Pb 2013 5.02 ~15 nb-1 2016 5.02, 8.16 ~3 nb-1, ~25 nb-1 pp 2009-2013 0.9, 2.76, ~200 μb-1, ~100 μb-1, 7, 8 ~1.5 pb-1, ~2.5 pb-1 2015-2018 5.02, 13 ~1.3 pb-1 , ~59 pb-1 p-Pb • Energy and system dependence studies of particle production are possible • Large statistics of pp, p-Pb and Pb-Pb collisions at the same √sNN • Analysis of 2018 Pb-Pb data is not completed yet Pb-Pb 11-06-2019 SQM2019 - Jacek Otwinowski 9 ALICE case Enhanced hyperon production Similar amount of baryons and antibaryons 1.1 pp at s = 2.76 TeV Pb-Pb at sNN = 2.76 TeV, 0-80 % DPMJet prediction /B p/p: |y |<0.5, 0.45 < p < 1.05 GeV/c |y |<0.5, 0.45 < p < 1.05 GeV/c T T Pb-Pb at sNN = 2.76 TeV B Λ/Λ: |y |<0.8, 0.5 < p < 4.5 GeV/c |y |<0.6, 0.5 < p < 4.5 GeV/c + T p-Pb at s = 5.02 TeV 1.08 Ξ /Ξ-: |y |<0.8, 0.5 < pT < 4.5 GeV/c |y |<0.6, 0.5 < p < 5.5 GeV/c NN + T T Ω /Ω-: |y |<0.8, 1.0 < p < 5.5 GeV/c |y |<0.6, 1.0 < p < 4.5 GeV/c 1.06 T T p-Pb at sNN = 5.02 TeV, Min. Bias pp at s = 7 TeV p/p: -0.965 < y < 0.035, 0.45 < p < 1.05 GeV/c |y |<0.5, 0.45 < p < 1.05 GeV/c T T 1.04 Λ/Λ: -1.265 < y < 0.335, 0.5 < p < 10.5 GeV/c |y |<0.8, 0.5 < p < 10.5 GeV/c + T T Ξ /Ξ-: -1.265 < y < 0.335, 0.5 < p < 6.0 GeV/c |y |<0.8, 0.5 < p < 5.5 GeV/c + T T Ω /Ω-:-1.265 < y < 0.335, 1.0 < p < 5.5 GeV/c |y |<0.8, 1.0 < p < 5.5 GeV/c 1.02 T T 1 0.98 0.96 0.94 ALICE 0.92 preliminary + - + - ALI−PREL−72168 p/p Λ/Λ Ξ /Ξ Ω /Ω à ALICE is well suited for (anti-)hypernuclei measurements pp 7 TeV: Nature Physics 13 (2017) 535 p-Pb 5.02 TeV: Phys. Lett. B728 (2014) 25, Phys. Lett. B758 (2016) 389 11-06-2019 SQM2019 - Jacek Otwinowski 10 (Anti-)hypertriton 3 Hypertriton ( �H) is the lightest known hypernucleous (p, n, �), anti- �& hypertiton ( ) �&H • Mass ~ 2.992 GeV/c2 - D.H. Davis Nucl. Phys. A 754 (2006) 3 • Binding energy B� ~ 0.13 MeV (Bd = 2.2 MeV, Bt = 8.5 MeV, B3He = 7.7 MeV) • Unstable under weak decay (branching ratios are not well known; only few theoretical calculations available - H. Kamada et al. Phys. Rev. C 57 (1998) 1595) • Mesonic and non-mesonic decays • ALICE studied production of hypertriton in the charged mesonic decay channels • 2 body (B.R. ~ 25%) • 3 body (B.R. ~ 41%) • Only 2 body decay channel has been used for the lifetime measurements 11-06-2019 SQM2019 - Jacek Otwinowski 11 (radial (Antiflow) -)hypertriton signal extraction 3 3 - �H à He + � • Identify products of weak decay (3He, �-) • Specific energy loss in the TPC detector • For deuteron identification also TOF information • Apply topological cuts • Secondary decay vertex reconstruction • Reduction of combinatorial background • Reconstruct invariant mass 11-06-2019 SQM2019 - Jacek Otwinowski 12 (radial (Antiflow) -)hypertriton signal extraction ) 2 c 140 ALICE Performance, 28/11/2016 s = 5.02 TeV 120 NN Pb−Pb, 0−80% 100 |y| < 0.9 Counts / (2 MeV/ 80 60 ) 2 c 220 ALICE Performance 40 Data 200 − s Fit Pb Pb NN = 2.76 TeV (2011) 180 Background 20 0-10%, |y| < 0.5 160 0 Entries / (2 MeV/ 140 2.97 2.98 2.99 3 3.01 3.02 3.03 3.04 3.05 M( 3He, π-& 3He, π+) (GeV/c2) 120 ALI-PERF-114838 100 80 Corrections: 60 3 → π+ ΛH d + p + 40 • Detector acceptance and 20 reconstruction efficiency 0 2.96 2.97 2.98 2.99 3 3.01 3.02 3.03 3.04 3.05 • Absorption of (anti-)hypertiton 2 M + (GeV/c ) ALI-PERF-129924 d,p,π in detector material 11-06-2019 SQM2019 - Jacek Otwinowski 13 Hypernuclei yields vs thermal models in (radial flow) Pb-Pb at √sNN = 5.02 TeV • Production of (most) hadrons well described at freeze-out temperature Tch ~ 153 MeV • Light nuclei production Pb-Pb (0-10%) 5.02 TeV described by thermal models (binding energy << Tch)? • Other production processes e.g.