The HADES Experiment at GSI: an Update Romain Holzmann, GSI - PowerPoint PPT Presentation

The HADES Experiment at GSI: an Update Romain Holzmann, GSI Helmholtzzentrum, for the HADES collaboration / RPC RPC 54 th International Winter Meeting on Nuclear Physics, Bormio 2016

The HADES detector High Acceptance DiElectron Spectrometer  large acceptance  2-3% mass resolution  hadron & lepton PID  RPC RPC  up to 20 kHz trigger rate General documentation at: http://www-hades.gsi.de 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 2

Technical layout of HADES 1 out of 6 HADES sectors hadron-blind RICH 4 planes of MDC Cryostat Forward Wall RICH not shown ! 3 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI

The RICH: excellent lepton ID γ > 18 p 0 Dalitz pair γ conversion pair g g e + p 0 e + Q ~ 15 0 Q ~ 1.5 0 e - e - 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 4

HADES operation at SIS18 2002 – 2009: light A+A, p+p, n+p, p+A 2011 – 2014: Au+Au, π -induced reactions 2018 – FAIR start: hight-statistics π +p & π +A, p+A and A+A Rate capabilities of HI expts at low & moderate c.m. energy  HADES is very competitive! (compiled by T. Galatyuk) 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 5

Physics we are after with HADES  Particle production in heavy-ion collisions (also p+A)  Properties of compressed nuclear matter; explore its phase diagram  dilepton emission  (multi)strangeness production  femtoscopy  see Thu afternoon talk by Oliver Arnold  global events characteristics (flow, flucs.)  systematic investigation dilepton & strangeness production in A+A, p+A and p+ A (at n/n 0  1-3) + event characterization  Hadron spectroscopy  Elementary production mechanisms  coupling of r and  to N* → needed to model p+A & A+A  isospin effects: s pn vs. s pp  strangeness production ( f , K, Σ , Λ , Ξ ) ω  systematic dilepton & hadron spectroscopy in pp, pn and p p (i.e. in vacuum) 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 6

The HADES Collaboration Cyprus: Italy: Russia: Department of Physics, University of Istituto Nazionale di Fisica Nucleare, INR, Moscow Cyprus Laboratori Nazionali del Sud JINR, Dubna ITEP, Moscow Czech Republic: Poland: Nuclear Physics Institute, Academy of Smoluchowski Institute of Physics, Spain: Sciences of Czech Republic Jagiellonian University of Cracow Departamento de Física de Partículas, University of Santiago de Compostela France: Portugal: Instituto de Física Corpuscular, IPN Orsay, CNRS/IN2P3, LIP-Laboratório de Instrumentação e Universidad de Valencia-CSIC Université Paris-Sud Física Experimental de Partículas Slovakia: Germany: Bratislava Univ. GSI, Darmstadt TU Darmstadt 18 institutions FZ Dresden-Rossendorf IKF, Goethe-Universität Frankfurt 120+ members II.PI, Justus Liebig Universität Giessen PD E12, Technische Universität München 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 7

Hadron masses in the medium 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 8

QCD: running coupling constant α s Strong interaction coupling strength Quarks are confined!  perturbative non-perturbative perturbative perturbative non-perturbative non-perturbative  4 c   + QCD: QCD: a S << 1 a S << 1 QCD: a S  1 f QCD: a S  1 s QCD: a S << << 1 QCD: a S  1 V ( r ) Kr 3 r Asymptotic freedom ~1 fm At low energy, the QCD lagrangian cannot be handled perturbatively, we have to  fall back on models (e.g. χ PTH)  solve on the lattice (LQCD)  explore symmetries of L QCD e.g. broken chiral symmetry 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 9

Setting the stage: non-perturbative QCD Arguments for in- medium modifications of hadrons are based on … … chiral symmetry restoration … hadronic many -body theories Chiral condensates Spectral functions <qq> vac ≠ 0 SF med ≠ SF vac hadronic medium QCD sum rules … relate condensates and spectral functions. Recent reviews of the field: Leupold, Metag & Mosel, Int. J. Mod. Phys. E19 (2010) Hayano & Hatsuda, Rev. Mod. Phys. 82 (2010) 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 10

Mass generated by breaking QCD chiral symmetry Model calculations, e.g. Lattice QCD, PDG 2010 adjusted to exp. hadron spectrum Current quark masses Aoki et al., PRD 79 (2009) … Constituent quark mass: M quark = M weak + M strong spontaneous Higgs χ sym. breaking mechanism → <qq> ≠ 0 Zhu et al., PLB 647 (2007) 366  99% of the observed large hadron masses are dynamically generated! 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 11

Evolution of the universe & mass generation Two steps in mass generation: Big Bang 1. Electro-weak transition (Higgs mechanism) 1. ► weak mass 1 millionth 2. = current mass 10 12 o K of a second ~100 GeV (1 μ s) 10 9 o K 2. Chiral transition 3 minutes ~100 MeV (hadronization) 300.000 ► strong mass 3.000 o K years 1 billion 20 o K We observe the years constituent mass: 15 billion 3 o K years M = M w + M s T time 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 12

Evolution of the universe Rafelski 2005 hadronization ρ ≈ few times ρ 0 T ≈ 100 MeV Such conditions can be realized in heavy-ion collisions t reac ≈ 10 -23 s << 10 -6 s ! 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 13

In-medium masses: a cornucopia of models Effective Lagrangian model Quark-Meson Coupling model Klingl et al. NPA 650 (1999) 299 Nambu Jona-Lasinio model and for f in PLB 431 (1998) 254 Saito et al. PRC55 (1997) 2637 Bernard & Meißner NPA 489 (1988) 647 r ω … and quite a few more ! Coupled-channels approach Chiral power counting model Lacour, Oller & Meißner J Phys G37 (2010) 125002 M. Lutz et al. NPA 706 (2002) 431 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 14

Vector meson spectral function in HMBT r in baryonic medium modified by r in vacuum coupling to resonance-hole states Hadronic Many-Body Theory: Rapp & Wambach Adv Nucl Phys 25 (2000) 1 for p>0 in medium in vacuum Leupold, Mosel, Post et al. NPA 741 (2004) 81; NPA 780 (2006) 187 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 15

QCD sum rules connect both worlds However , is not an observable !! q q ► QCD sum rules provide a link between hadronic observables and condensates: Hatsuda & Lee, PRC 46 (1992) R34; Leupold & Mosel, PRC 58 (1998) 2939         2 Q R s 1 1 1   + + +   2 s s ds 1  m q q G    + higher order terms p p p p q 2 2 2   4 +   24 16 Q 24 2 s Q      2 1 s s   R s ~ F hadronic spectral function:     p 2  +  2 2 s M s s r ► Chiral condensate is related to integral over hadronic spectral functions only  spectral function are constrained, but not fully determined  Models ls are still ll needed d for specifi cific c predict ction ons s of hadron on properties erties !! 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 16

Experimental access to in-medium effects 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 17

e + e - spectroscopy of hadronic matter π 0 , , r, , f , Δ , N *... A + A Modus operandi: 1. produce hadron p + A 2. let decay into leptons e + 3. detect products 4. reconstruct inv mass e - π + A Pair invariant mass: 𝑞 1 + 𝑞 2 2 M 𝑓𝑓 = 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 18

Dileptons from nucleus-nucleus collisions (in few GeV/u regime) collision lasts in total <100 fm/c Au+Au collision: dense phase ≈15 fm/c time e + e - e + e - e + e - Freeze – out Hot and dense phase First-chance NN collisions multistep production decays of (long-lived) states: p 0 , ,  of resonances and mesons π o , γ  N N R R p π o , η N R g * N N g * e - N N p N e + e+ , r, f Observed dilepton yields are integrated over full duration ! e- g * 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 20

Electron/positron identification in HADES MDC hit finder & RICH pattern hit/track matching Pre-Shower condition e - + + velocity vs. momentum Data e + Monte Carlo e - e - e + Momentum * charge [MeV/C] 54 th International Winter Meeting on Nuclear Physics, Bormio 2016 R. Holzmann, GSI 21