Pion beam experiment Physics Motivation (from HADES point of view)

EM emission from HI RRTF’GSI current-current correlator

 -in medium: hadronic models    Vacuum:   one example: W. Peters et.al. NPA 632(1998)109: Nuclear matter: additional terms +  N-1N-1 N(1520) +...  (1232)  N -1  dominant role of baryons : confirmed by Na60/ CERES results and Rapp/Wambach/Hess calc.

Direct  -N Interactions (‘Rhosobars’) In medium vector meson properties and  N scattering forward scattering amplitude low density theorem Optical and detailed balance theorem B.Friman N.PhysA610(1996) R. Rapp and J.Wambach In medium properties are related to elementary T VN !

Which resonances are important for dielectrons ? V. Koch: artist view of modeling of HI reactions

Resonance e+e- Decay Branch R  p  exp data

Which resonances matters at SIS18-100? GiBUU – J. Weil p+p at 3.5 GeV  -dominance , N(1520) , N(1520), +..

How resonances radiate dielectrons?: p+p  e+e-pp eTFF-em. Transition Form Factors GeV pp  pp  GeV Resonance (many!) contribution estimated from pp  0 and pn  + channels Most important for dielectron production are:  (1232) N*(1520), N*(1720),  (1910) Resonances (R) with Mass up to 2 GeV included calculations with point-like RN  * (QED) does not describe data eTFF(Me + e-) dependence very important -> Vector Meson contribution is visible! eTFF

What are Resonanse-N  BR? GiBUU:  (1232) (19%) N*(1520) (38%) N*(1720) (22%),  (1620)(15%),  (1905)(6%), model1: HADES N * (1520) resonance cross section (x 6 GiBUU !) BUT BR for all resonances from BG New PWA results indicate lower R  N  couplings !

p+Nb „excess over pp reference”„slow” (p<0.8 GeV/c) pairs  clear excess in p+A below VM pole & absorption of  (observed also in  +A exp) secondary reactions :  +N  N * (1520),N*(1720),  (1620),  (1905),  N  Ne+e- (i.e transport models) or/and in medium  modification ? first R  pe+e- decay process must be understood ! GiBUU

In medium Kaon properties K+/K 0 considered as good quasiparticle (no strong resonance couplins)-small absorption K - : spectral function due to coupling to  (1405) (similar effects as for  ) - strong absorption  (1405) K-K- K-K- N -1

K 0 s in GeV data: PRC 82 (2010) IQMD : repulsive U KN  38 MeV m K * = m K (1-  *  /  B ) (  negative for K 0 ) In medium K 0 potential K 0 s in 3.5 GeV GiBUU : Chiral (Scalar+Vector) potential no potential with potential

 +A experiment (first beam time) measurement of kaon (K +, K - ) absorption in cold nuclear matter –> kaon potential  meson large counting rates for HADES – possibility to obtain important physics output within 2-3 days of beam on target

K 0 production –sensitivity to potential higher beam energy prefered because of possibility to study K - and  production FOPI: PRL102(2009)183591, ANKE : EPJA22(2006) 301 previous data from: expectations for GeV

K - /  production K - expectations for HADES ANKE Phys. Lett. B 695, (2011). data on  Transparency (p+A) 0 <   < <p  < 1.6 GeV/c ** absorption -> in medium width  *  (model dependent – large ecceptrance! )

Expected count rates & target separations K 0 reconstruction

 - +p experiment (second beam block ~21 days) e+e- emission from baryon resonaces 1 or 2 energy points ;  s=1.48 GeV,  s=1.7 GeV + minimal energy scan around (2-3) points (  40 MeV) for 2  final states to constrain  (  2  ) production K ,  K  production at  s=1.7 GeV

Meson and Resonanse production with pion beams E thresh [GeV] M x [GeV/c 2 ]   //  pp->ppX  - p->Xn Meson production thresholds direct resonance excitation: second, third res. region p>0.5 GeV/c weak contribution from  (1232)  (1232)->Ne+e- small main background for  -p  R  n e+e- is  /  0  e+e-  N*,  ss

There are also constraints from  N reactions : optical theorem

2  decay channels of resonances

Resonance excitation in 2  channel ss N(1440,1710) +  (1910) N(1535) +  (1620) N(1720) +  (1600) N(1520) +  (1700) N(1680) +  (1905) N(1675) +  (1925)  s =1.5 dominance of D13(1520)  s =1.7 dominance of F15(1680), D33(1700), P13(1720) expectations for dielectrons: 2014: B-G (A.Sarantsev) K-matrix approach constraints from  N,  N

Predictions for  - p  2  N M. Effenberger et al. PHYS. REV. C 60(1999) V. Shyklar: Seillac based on Maley and Saleski analysis of  N 2014: B-G (A.Sarantsev) predictions for 2  K-matrix approach -constraints from  N,  N controversial results: „old” Manley and new B-G results direct measurement of 2pion and e+e- channels are mandatory! (also conclusion from GSI)

e+e- production ampltidues in  - p reactions Inteference effects are important below  threshold! S 31 - S 11 and D 13 – D 33 M.F.M. Lutz, B. Friman, M. Sayuer. Nuclear Physics A 713 (2003) 97–118 Kaempfer, A Titov, R.Reznik Nucl. Phys. A721(2003)583 are interference effects important? measure e+e- mass and angular distributions M.F.M. Lutz, B. Friman, M. Sayuer NPA 713 (2003) 97–118 π - p π +nπ +n

e+e- production ampltidues in  - p reactions „Born terms” N* resonance contribution M. Zetenyi, G. Wolf PRC86 (2012) extended VectorDominanceModel ! k 2 not m 2 („clasical VDM”)  *(k)

e+e- production ampltidues in  - p reactions  s=1.9 GeV

Predictions from GiBUU  - p : J.Weil’2014 E  = 540 MeV (p=0.66 GeV/c) Integrated cross section for M>0.28 GeV/c 2 (full solid angle) 484 nb (~ 8 higher than in B-G model) Total  component E  = 900 MeV (p=1.03 GeV/c) Integrated cross section for M>0.28 GeV/c 2 (full solid angle) 247 nb (~ 2.5 higher than in B-G) Total  component

Hyperon production

D. Manley large discrepancies in exp data around 1.7 GeV !

Cross sections

Angular distributions K 0 

 polarization

Angular distributions

At low energy S11(1650) and P11(1710), P13(1720) are dominant resonances for K  but still controversy about amplitudes from various PWA B.t.w S11(1650) is the one which couples strongly to  in Lutz/Souyer model and P13(1720) to  ! at higher energy essentially no exp information available

Connection of K  channel to „  puzzle”

Conclusion:

Summary of  N  K  -M.Doering HADES Saillac

count rate estimates

Estimates (e+e- M>140 MeV/c 2 )-TDR p =1.1 GeV/c Resonance model: constant eTFF (QED)from Zetenyi & Wolf

Estimates (2pion)- TDR eff*acc(2pion)~ 0.17 CS ~5 mb(  -  0 ) 6-11 mb (  +  - )

Remark: At  s ~1.7 GeV (p~1.05 GeV/c (maximum of cs) we have foll. numbers: Cs: x2 x 4 x 2 counts ~96kE ~26kE ~20 kE p=1.7 GeV/c 440 kE 250 kE 220 kE Reconstruction/day exclusive Reconstruction semi exclusive(only K 0 )

additional information

No conclusion about  -N * coupling - polarization experiment needed

 coupling to resonances:  +p data: CBTAPS (total and differential cross sections, polarization) fit: PWA B-G (p.com. A.Sarantsev) P 13 (1720) P 13 (1900) non-resonat contributions F 15 (1685)

Isospin decompositon A 2I,I, I –isopin of input channel, I ’ -isospin 2pions (or e+e system) 4 amplitudes -> 6 constants (modules and phases) are needed ! – we cannot obtained it from future HADES data only. Instead we have to use other data (  N and  N) to constrain possible solutions For example Precise data from exist for W=1.2:1.52 GeV

Coupled channel effects

Importance of CC effects !

Which resonances matters?

examples:resonance model

K()K() ()()

remark: at 1.7 GeV/c we would have less pions/spill (see prev.slide) *10 8