HADES experiment probing baryonic matter at SIS 18

HADES experiment probing baryonic matter at SIS 18 and future FAIR: Challenges and opportunities § Motivation § Detector § Highlights from SIS 18 and perspectives for SIS 100 Piotr Salabura Jagiellonian University, Kraków for the HADES collaboration

Two pilars of HADES physics programme Heavy ion physics: -in medium hadron properties - Nuclear matter at high density, T Proton-proton, pion-proton - Hadron properties in vacumm - Cross sections. .

Diagnostic of dense baryonic matter: (i) HI collisions at SIS 18/100 L. Mc. Lerran, R. D. Pisarski 2007 r. B / r 0 Evolution of average r. B ( tsystem) t >10 fm/c The case of Large B and moderate T : Composition of a hot p. DN gas (T) üinteresting region in phase diagram not probed means of rare penetrating probes: -> dielectrons, multistrange baryons (1321), ü Long live time, large baryon densities –> complementary to SPS and BES of RHIC • CBM detector • HADES : 2 -4 AGe. V – continuation of Physics Programme at SIS 18 1 -2 AGe. V by

e+e- from HI: melting of -role of baryons e+e- with subtracted coctail ->thermal radiation -> in-medium meson spectral function Data : Na 60 EPJC 59 (2009) 607 calculations: Hess/Rapp: NPA 806(2008)339. G consistent with “universal” medium effect : pion annihilation + in-medium spectral function G dropping mass scenario NOT supported G Baryons are driving force for observed melting of the meson – same conclusion for other exp RHIC/SPS !

Study of baryon resonance - meson interactions in proton and pion induced reactions • Dielectron decays of baryon resonances Ø R->Ne+e- never measured (BR ~10 -5 ) direct - N* / complementary to baryon excitation with real photon. role of meson? (validity of VDM) Ø Important for in-medium modification – verify the rho-baryon coupling mechanism at low energy! Resonance Dalitz decays (1405) • Kaon (K-, K+, K 0 ) – baryon interactions Ø K-N strongly interacting system- existence of K-N bound states –role of (1405) bound state? Ø K+, 0 weakly interacting with medium (no strong coupling to baryon resonances? ) – good messenger of in medium potential, EOS, SYM. . • Dedicated programme with p+p (A), π+p(A) ->precision spectroscopy in 2 -4 Ge. V ! K- KN-1

HADES at SIS 100 Side View ECAL for SIS 100 arx. Xiv: 1109. 55 FW START + v. Spectrometer with M/M - 2% at / and large pair accetance (~30%) v. Particle identification e/ /p/K– RICH (hadron blind), d. E/dx (MDC) and TOF, Pre-Shower-> to be replaced by lead glass (OPAL) ECAL with /E~ 5. 5%/ E new at SIS 100 : photons (18 -450) v Operates since 2002: Upgrade(2010): new DAQ 20 KHz Au+Au collisions , 50 k. Hz pp

HADES at SIS 100: phase space coverage for e+e- Ebeam = 1 Ge. V/u Ebeam = 8 Ge. V/u Ebeam = 11 Ge. V/u ■ overall acceptance for di-electron pairs Acc ≈ 35% ■Acc ≈ 20% ■ with nice mid-rapidity coverage ■shift towards backward rapidity (complementary to CBM detector) 7

PID capabilities at SIS 100 RPC K/ ~1. 2 Ge. V/c Au+Au @ 4 AGe. V To. F p/ ~1. 8 Ge. V/c K/ ~0. 8 Ge. V/c p/ ~1. 8 Ge. V/c Charged hadrons: Mass calculation from TOF measurements & d. E/dx from MDC Electrons – hadron blind RICH

Exp. challenge: tracking detector occupancies Au+Au @ 1. 23 Ge. V/u equivalent to Ni. Ni @ 8 AGe. V and factor 2 lower than Au+Au 4 AGe. V Cell size is factor of 2 larger tracking efficiency 9

HADES : expected performance at SIS 100 Proof of principle !: Au+Au @ 1. 2 AGe. V : track density equivalent to Ni+Ni @ 8 AGe. V 10

Particle rates in Ar+KCl @ 1. 75 and Au+Au @ 1. 25 AGe. V data: HADES: EPJA 47 (2011) 21 SHM: S. Wheaton, J. Cleymans, Comp. Phys. Comm. 180 (2009) 84 calculation with Thermus (SHM): strangeness: canonical ensamble with suppression induced via strangeness conservation volume (RC )works surprisingly well ( 2/n. d. f ) ~2. 3 except : • • • enhanced (2), (hidden strangeness) enhanced (~25) Tkin (mt spectra) > Tchem (? ) Ar. KCl

/K- and / ratio HADES: PRC 80(2009)025209 R / A+A >> R / in NN and πN reactions K+K e+e- w. r. t N-N threshold G meson plays important role in K- production at SIS 18 energies (increasing with decreasing energy!) • Statistical model describe rates with no suppression (i. e OZI rules)

Multistrange baryon production data: HADES PRL 103 (2009) 132310 Ar+KCl @ 1. 756 AGe. V 640 Me. V below NN threshold ! G at SIS 18 (1321) production significantly larger than transport model (Ur. QMD) and statistical model predictions SIS 100: Excitation function of , (pp, p. A, AA) (also ) not known below s. NN <7 Ge. V…

K 0 s in medium potential , K-N bound states? (1405) K 0 s in Ar+KCl @ 1. 756 Ge. V (1405) –bound K- N system? data: PRC 82 (2010) 044907 IQMD : repulsive UKN 38 Me. V • data from p+p @ 3. 5 Ge. V • +data from p+A @3. 5 Ge. V • . . and Au+Au (+ flow measurement) • + new results from πA reactions (2104) ! (1405) pole • pole shift? intereference with non. res ? Need for PWA (more data. . )

e+e- excess @ 1 -2 AGe. V contribution subtracted • Excess above reference NN and Mee > 150 Me. V/c 2 increases from ~0 (light systems) to ~3 (Ar. Kcl) and ~8 -10 in Au-Au. Precise measurement of NN (np. and pp) reference was an essential input ! • Excess yield scales with system size ~ Apart 1. 4 multistep processes? • Rapid increase of relative yield reflects the number of ‘s/ N*’s regenerated in fireball with life time ~10 fm/c

e+e- reference measurements for SIS 100 Vacuum: pp->ppe+e- 3. 5 Ge. V Cold matter: p+ Nb @ 3. 5 Ge. V ? • Vector mesons visible in mass spectra • Clear excess in cold matter below the VM pole: in medium modification or an effect of secondary pion reactions? important constraint πN data (2014 ) ! HOT & Dense matter Au + Au @ 3. 5 Ge. V ? Answer at SIS 100

Dielectron decays of baryon resonances: from exclusive pion and e+e- channels pp@ 3. 5 Ge. V pp (p + ) n pp (n + ) p („BUU’s”) („Ur. QMD”) N(1440) N(1520) N(1680) Point-like coupling Intermediate N*(1520), N*(1720), . . BR?

SIS 100: Dalitz dacays of Hyperons pp p. K+ Y p. K+ e+e- At SIS 100 we have unique opportunity to investigate electromagnetic decays (transition form factors) of non and strange baryons ! • beam energy scan to control resenance excitation (Partial Wave analysis)

pion beams at SIS 18 For physics discussed in this talk: • single pion, + - production : coupling of to baryon resonances our knowledge (PDG) on BR(R->N ) 1. 3 < s <2 is based on 240 000 events (differential; distributions not avialable) needed for PWA and coupled channel calculations • e+e- never measured from pion induced reactions Resonance Dalitz decays R Ne+e- • strangeness production of nucleus : K , K 0 , • Secondary beams (C+Be, N+Be, . . ) - beams with I ~ 106/s • p (0. 7 -2 Ge. V/c) : Access to second/third resonance region 2. 0> s>1. 6 Ge. V • Pion momentum p/p =4% : in beam tracking system: (X 1, X 2 -Y 3) for pion mometnum determination : p/p =0. 1%

Pion-nucleus – on line spectra from 2 weeks ago Mesons – π+ π- decay • bayons – pπ- decays measurement combined with machine developments for SIS 100 • (1/3 below space chargé limit of SIS 18) K+K-

Summary • SIS 100 opens new opportunities : larger beam energy, larger density compressed baryonic matter not studied before by means of penetrating probes • Proton-proton collisions at SIS 100 : an experimental access to baryon and hyperons em. Dalitz decays , kaon-nucleon interactions, provides mandatory reference (cross sections) for AA programme at SIS 100 • Pion beams at FAIR? • Results from SIS 18 strongly motivate continuation of HADES physics programme at SIS 100 • HADES detector is in big part ready for new campaigns

Search for U(1)’ -boson „dark photon” • candidate for dark matter: coupling to SM via kinematic mixing with strength 2 = ’/ • can appear in any el. decay via coupling to photon in M <1 Ge. V/c 2 • could explain (g-2)muon discrepency (~2. 6 ) between data and theory , anomaluous e+/eratio (E>10 Ge. V) observed from Universe, … Use large sample of e+e- collected by HADES on 0 ( ) e+e- and Ne+e- (Dalitz decays) /

Upper limits from HADES New A 1 results G Also PDG Entry 2012 : BR( ->e+e-) < (2. 5)x 10 -6 with 90% CL

SIS 100 energy regime: terra incognita Inclusive cross sections of mesons cascades, are to large extent unknown. .

Models for Dalitz decays QED: point-like R- * vertex M. Zetenyi et al. PRC 67, 044002 (2003). extended VDM: M. I. Krivoruchenko et al. Ann. Phys. 296, 299 (2002). el. Transition Form. Factor (Mee) Resonance model Gi. BUU, Ur. QMD, BUU, . . J. Weil EPJA (2012) „factorization” based on BR from PDG (large error bars ! )

Ecal for HADES electron ID: Ni+Ni @ 8 AGe. V reconstruction C+C @ 8 AGe. V = 6% S/B = 2% Ni+Ni @ 8 AGe. V = 6% S/B = 0. 4%

-meson in hot and dense matter Meson spectral function : Data : Na 60 acceptance corrected : EPJC 59 (2009) 607 calculations: Hess/Rapp: NPA 806(2008)339. pion loop direct - N* / „Baryonic loops ” • - /N* couplings play big role in „rho” melting observed at SPS and RHIC -> connection to Baryon Resonance Dalitz decays HADES can provide essential precision data ! Resonance Dalitz decays !