Baryon Resonance production and em decays in proton

Baryon Resonance production and em. decays in proton and pion induced reaction with HADES ü Motivation: • vector meson( ) in HI physics • electromagnetic structure of baryons role of of baryon couplings, Vector Dominance Model ü Results from NN - exclusive channels ü preliminary results from run with pion • 2 pion Production from - p and p • e+e- P. Salabura M. Smoluchowski Institute of Physcis Jagiellonian University, Kraków Poland

Motivation Heavy ion physics: -in medium hadron Proton-proton, pion-proton properties - Vector Meson - Nuclear matter baryon couplings emissivity B, T - em trasnistion FF meson in nuclear matter: (1232) N-1 baryonic loops directly related to : Resonance Dalitz decay N* + +. . . N-1 R( , N*) dominant role of baryonic resonances for in-medium Self-Energy R more in talks of Joachim, Jochen, Ralf, . .

Electromagnetic structure of baryons Dalitz decays 33 (J=3/2) N (J=1/2) space-like e+e- NN(*) N* Ne+e- „pion cloud” e-N* „quark core” N I. G. Aznauryan and V. D. Burkert, Prog. Part. Nucl. Phys. 67, 1 (2012) R N * : em. Transition Form Factors for example for J=1/2 R (J 3/2) : (3) GM (q 2), GE (q 2) , GC (q 2) R (J=1/2) : (2) GM/E (q 2 ), GC (q 2 ) . . or covariant e. TFF „QED” M. I. Krivoruchenko, et. al Annals Phys. 296, 299 (2002)

Dalitz decays of Baryon resonance QED: point-like R- * vertex extended VDM 1: Coupling constants fixed from R->N dependence on spin, parity M. I. Krivoruchenko et al. Ann. Phys. 296, 299 (2002). M. Zetenyi et al. PRC 67, 044002 (2003). M. I. Krivoruchenko et al. Ann. Phys. 296, 299 (2002). el. Transition FF (Mee) extended VDM 2: Kroll, Zumino H. B. O’Connell, et al. Prog. Part. Nucl. Phys. 39, 201 (1997). M. Zetenyi, G. Wolf PRC 86(2012) 065209

Lepton angular distributions E. Speranza, B. Friman, M. Zetenyi Physics Letters B 764 (2017) 282– 288 A. Sarantsev to be published Spin density matrix Lepton emission angles for example * direction hadron decay to * QED: * decay to e+e- „Helicity frame” photon polarisation vectors transverse longitudinal transverse for example for Ne+e- at small q 2

e+e- sources at SIS 18 energies excitation function ! DLS/HADES data: isospin effects ! ° e+e- , Ne+e- (dp)/ (pp) e+e- M>M 0 ~2 1 2 3 4 5 E beam (Ge. V) DLS: PRC 57 (1998)1867 HADES PLB 715(2012)314, ar. Xiv: 1703. 08575 • Me+e- < 0. 15 Ge. V/c 2 dominated by 0 Dalitz • Me+e- > 0. 15 Ge. V/c 2 : Resonance ( , N*) Ne+e- , NN bremsstrahlung , e+e- , e+e- Strategy : combined analysis of hadronic and dielectron exclusive channels 6

exclusive (π+, π0) in pp@1. 25 Ge. V 13 PNPI + 2 HADES data sets Bonn-Ga PWA solutions FINAL STATES: P 33(1232) and P 11(1440) in πN state HADES coll: Eur. Phys. J. A 51 (2015) 137 red Δ(1232)P 33 blue N(1440)P 11

+/N(1440) { p 0 pe+e- } pp ppe+e- @ 1. 25 Ge. V 0 reconstruction - examples Inv. mass • q e+e- data after acceptance and 0 BR corrections HADES coll. ar. Xiv: 1703. 07840 accepted PRC(2017) production angle Helicity angle hadronic data PWA solutions for p. N • No adjustment of PWA solutions for e+e - data • Very good description of dielectron channel ECT 2017

+ { pe+e– } pp e+e-pp @ 1. 25 Ge. V HADES coll. ar. Xiv: 1703. 07840 accepted PRC(2017) GM(0)~3 , GE(0)~0 , GC(0)~0 G. Ramalho, M. T. Pena, et al Phys. Rev. D 93 014003 (2017), pion cloud Quark core more in Teresa talk ECT 2017

Angular distributions for Me+e- >M ( pe+e-) acceptance corrected Production in CM PWA solution for P 33 from hadronic channels + pe+e- : model based on PWA solution for P 33 and Dalitz decay (Ramahlo & Pena) electron in helicity frame d /dcos ~ 1 + B cos 2 ; B=1. 17 0. 34 + pe+e- : model assuming dominance of GM ; transverse photon polarization Consistent description by (1232) pe+e- BR ( pe+e-)= 4. 19 10 -5 0. 62 (sys) 0. 32(stat) First measurement ! ECT 2017

Higher mass resonances pp@3. 5 Ge. V n p π+ Resonance model: Z. Teis et al. , Z. Phys. A 356 (1997) 421 J. Weil et al. (Gi. BUU) Eur. Phys. J. A 48 (2012) 111 HADES : EPJA 50(2014) 42 Many overlapping R=( , N*) resonances p p π0 p 1 p 2 angular parametrisation as a function of t for all resonances t- channel dominance

p+p ppe+e- @ 3. 5 Ge. V HADES coll. EPJA 50(2014) 82 „QED” cocktail : • several contributing resonances : N*(1520), N*(1720), (1620), (1905), . . G Excess above „QED” cocktail. Seems to originate from N*(1520) region ECT 2017

Comparison to models with strict VDM Resonance model + strict VDM with dominance G better description achieved by „HADES resonance decomposition” (more N*(1520) ) AND lower (!) BR for N decay (B-G upper limits) • HADES resonance decomposition + BR from Gi. BUU (PDG) overestimate data by factor 2 Contr. to e+e- 38% 15% 22% 7% Resonace -> N Branching Ratios

pion beam in HADES 2014 Polyethylen (CH 2)n and C • Reaction N+Be 8 -10* 1010 N 2 ions/spill (4 s) • secondary - with I ~ 2 -3 105/s p = 654. 1, 683. 5, 738. 9 , 791 Me. V/c ( s 1. 46 -1. 55 Ge. V) • PE (CH 2 )n and C targets • Pion momentum p/p =2. 2% ( ), ~50% acceptance of pion beam line • in beam tracking system: (X 1, X 2/Y 1/Y 2) for pion mometum determination : p/p =0. 1% • Investigated channels: n + - / p - 0 / ne+e- : off-shell coupling of to resonance

Separation of channels elastic p - (normalization) PE C p 791 n + 791 938, 8 Me. V ( = 1. 7%) 939, 4 Me. V ( = 1. 0%) beam tracker p - 0 791 PE C, C e. b. e p 132, 8 133, 2 beam tracker SAID ECT 2017

A. Saranstev B-G PWA CB-ELSA, MAMI Included in fit

Invariant masses PRELIMINARY n + - 683, 5 Me. V/c n + - acceptance corrected N, , N p 0 - N,

Angular distributions n + - n + - 683, 5 Me. V/c acceptance corrected p 0 - Conference

Total cross sections PRELIMINARY -p + - n PWA solutions & HADES cross sections n - total 3/2 - (D 13+. . ) 1/2 - (S 11+. . ) 3/2+ (P 33+. . Total cross section: = 1. 3 mb (PWA solutions) BR D 13 (1520) N ~ 12 2 % ECT 2017

Exclusive -p e+e- n PRELIMINARY QED 103 from PWA Very strong contribution from (along strict VMD) More details in talk of Federico on Wednesday

e+e- production from microscopic models M. Lutz et al. . Resonance contribution N*/ + Interference Kaempfer , A Titov , R. Reznik Nucl. Phys. A 721(2003)583 M. Zetenyi, G. Wolf PRC 86(2012) 065209 (S + P –wave -N) Very large differences in e+e- yield up to factor 10 ! b/Ge. V M. F. M. Lutz , B. Frimann, M. Soyuer. Nuclear Physics A 713 (2003) 97– 118 (S-wave -N) 10 -3 M. Zetenyi et al. . Predictions ! d /d. M [ b/Ge. V] effects (important / threshold!) 10 -4 10 -5

Outlook [mb] Beam Eenergy Scan N 2 N : Bon/Gatchina PWA N(1440, 1710) + (1910) N(1535) + (1620) N(1720) + (1600) N(1520) + (1700) N(1675) + (1925) N(1680) + (1905) 3`d 4`d 2`d GSI - momentum range 0. 65 -2. 5 s Ge. V/c s : 1. 46 : 2. 3 Ge. V Range of BES HADES: 2 N, N (calorimter), K , VM, … ECT 2017

Summary • Strong coupling of meson to baryon resonances supported by NN and N dielectron data • VMD inspired models of et. FF are in agreement with pe+e- data • Pion reactions offers cleanest way to measure resonance-vector meson couplings but extraction of et. FF is demanding (high statisics, multi-differantial analysis ) needs development of method which reduces model dependence. Combined PWA of hadronic and e+e- channels ? Extraction of spin density matrix elements (first results- see Federico , Andrey, Miklos talks)?

The HADES collaboration Ø Cracow (Univ. ), Poland Ø Darmstadt (GSI), Germany Ø Dresden (FZD), Germany Ø Dubna (JINR), Russia Ø Frankfurt (Univ. ), Germany SIS Ø LIP, Portugal Ø Giessen (Univ. ), Germany Ø München (TUM), Germany Ø Moscow (ITEP, RAS), Russia Ø Nicosia (Univ. ), Cyprus Ø Orsay (IPN), France Ø Rez (CAS, GSI NPI), Czech Rep. Ø Sant. de Compostela (Univ. ), Spain and with particular thanks to A. Sarantsev 23. 01. 2009 P. Salabura 24

- -like np. / pp Normalized to same 0 HADES coll, ar. Xiv: 1703. 08575 EPJA(2017)to be published pp ppe+ vs pn pne+e- - et. FF Dalitz Strong off – shell contribution in n-p collisions (absent in p-p) - FSI emission from pion exchange line - pion e. FF Clement & Bashkanov EPJA 50 (2014) 107 R. Shyam and U. Mosel Phys. Rev. C 82: 062201, 2010 - et. FF ECT’ 2017

Angular distributions for Me+e- >M ( pe+e-) acceptance corrected helicity frame OBE calculations „ -like” E. L. Bratkovskaya, at. al Phys. Lett. B 348, 325 (1995). „ ” B pe+e- model: Dalitz decay with d /dcos ~ 1 + cos 2 e+e- model: isotropic d /dcos ~ 1 + B cos 2 ; fit B=1. 52 0. 58 d /dcos ~ 1 + B cos 2 ; fit with B= -0. 4 0. 2. For + - e+e- expected B= -1 ! Change of photon polarization with * mass P. Salabura ECT 2017

Lepton angular distributions (helicity fame) M>400 Me. V 0<cos <0. 5 cos <0 ij cos >0. 5 11 1 -1 10 cos

p+p @ 1. 25 Ge. V – P 33 (1232), P 11 N(1440) resonance production • below pp production threshold Partial Wave Analysis Final: S 2 L 2 J 2 p p Initial : SLJ Final: S’L’ • • • Coherent sum of partial waves Energy dependent solutions: many experimental sets treated together by max. Loglikehood method event by event Detector acceptances taken into account PWA applied to hadronic – NN channel in collaboration with Bonn-Gatchina group maximum log-likelihood event-by-event initial NN system transition amplitude A. V. Anisovich et al. Eur. Phys. J. A 34 (2007) 129 system of two final particles two-final particle system and spectator final state amplitude (resonant, non resonant) 28

Partial Wave Analysis (Bonn/Gatchina ) A. Saranstev et al. . • An excellent tool widely used in hadron spectroscopy ( N, pp reactions) • Based on K-Matrix approach (coupled channels): allows to fit several reactions channels at the same time with strong unitarity constraints • Take into account specific detector acceptances and efficiencies (data are analysed together with phase space Monte Carlo passed through detector response) • Fit is done on event by event basis with maximum likehood method (correlation in multidimensional space following are taken into account!) At present ~0. 34 mln data points taken in global fit with 2 /DOF= 1. 6 In HADES we use Energy dependent extraction of amplitudes: several energy points are analysed together with different final states. Resonance properties (masses, widths are not subject to fit) Already several channels analysed and published (pp pk , pp pn +, pp 0 )

+ { p 0 pe+e- } –dielectron spectra 0 Dalitz e+e- mass (in HADES acceptance) electron angle in helicity frame (in HADES acceptance) Conference

Vector Meson Dominance in work for mesons. . example: decay KLOE 2 0 e+e- VMD • very important for hadronic corrections in muon g-2. .

production in pion and photon -induced react. R 1 has well defined J, P for example for pion-nucleon S-wave JP = 1/2– L 2 I, 2 J = S 11 or S 31 Reaction amplitude A: Pion induced reactions: P-wave JP = 1/2+ or 3/2 + P 11 , P 13 or P 31 , P 33 Photon induced reactions: -helicity ampl In both same K matrix accounts for hadronic part : resonances with masses M , coupling to channels g(i, j), phase space for decay and background terms fij

Angular distributions 683, 5 Me. V/c n + - p 0 - n + - acceptance corrected p 0 - ECT 2017

Separation into initial states (waves) p 0 0 p I, JP D 13(1520)+. . P 11(1440)+. . F 15(1680)+. . [ b] [mb] -p 0 0 n Data Bonn Data Cristal Ball s [Ge. V] In 1. 45 -1. 55 Ge. V in 2 pion production only few resonances matters D 13(1520), P 11(1440)

Separation into final states: , N (I=0), N* p 0 0 p [mb] N N(1440) N(1520) [ b] -p 0 0 n N N(1440) N(1520) s [Ge. V] • Dominat channels in 2 0 are and N (2 0 in I=0) • does not contribute because it is I=1, hence does not decay to 2 0

e+e- inclusive inv. mass vs model EXP - PE @ 690 Me. V/c PLUTO coctail based on known PRELIMINARY SIM Nbeam =Nel /( el * d) (target dens) ( P + 0. 5 C )(M) [mb] NPE e+e- = Nbeam( P + 0. 5 C) d 0 2 0 Dalitz e+e. D 13(1520) ne+e- (QED) (with = tot N N ) (from PWA) e+e! BR(M)~ „strict VMD” (1/M 3 ) ne+e- (QED)

Real photon production -p n • data from -p n and n -p (related via detailed balance) analysed together • Separation into resonances: @ s ~1. 5 Ge. V : dominance of D 13 and S 11 • D 13 in fair agreement with the cross section extracted from pion analysis and BR(N ) • For point-like particle Ne+e- N * (=1/137) • but details of d /dm depends on spin and parity of the resonance M. Zetenyi et al. PRC 67, 044002 (2003). 3/2 - N(1520) 3/2+ !!