Pion beam experiment

Physics Motivation

(from HADES point of view)

EM emission from HIV.Koch @ RRTF’GSI

current-current correlator

-in medium: hadronic models

GeVm

mimM

77.0

)()(

VacuumVacuum::

one example:

W. Peters et.al. NPA 632(1998)109:

Nuclear matterNuclear matter: additional terms : additional terms

+

N-1

N(1520)

+ ...

(1232)

N-1

dominant role of baryons :dominant role of baryons :confirmed by Na60/ CERES resultsconfirmed by Na60/ CERES results

and Rapp/Wambach/Hess calc.and Rapp/Wambach/Hess calc.

2222 )]([)](Re[

)(2)(

MImMmM

MImMA

•Direct -N Interactions (‘Rhosobars’)

In medium vector meson properties and N scattering

..)4)( VN

N

V

VT

m

mVN

T forward scattering amplitude

)0(12),()(2

)(

VNCM

CMV

Vnp ImTsq

qMs

•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 TVN !

Which resonances are important for dielectrons ?

V. Koch: artist view of modeling of HI reactions

Resonance e+e- Decay Branch

Rp 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+pe+e-pp

eTFF-em. Transition Form Factorspp->ppe+e- @3.5 GeV

pppp0 @3.5 GeV

• Resonance (many!) contribution estimated from pp0 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 RN 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), NNe+e-

(i.e transport models) or/and in medium modification ?

first Rpe+e- decay process must be understood !

GiBUU

In medium Kaon properties

K+/K0 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-

N-1

K0s in Ar+KCl @ 1.756 GeV

data: PRC 82 (2010) 044907

IQMD : repulsive UKN 38 MeV

mK* = mK (1-*/B )

( negative for K0)

In medium K0 potential

K0s in p+Nb @ 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

KK00 production –sensitivity to production –sensitivity to potential 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 HADES

@1.2 GeV

KK-- / / production production

K- expectations for HADES

ANKEPhys. Lett. B 695, 74-77 (2011).

data on Transparency (p+A)

0 < < 8 0

0.6 <p < 1.6 GeV/c

*

absorption -> in medium width *

(model dependent – large ecceptrance! )

Expected count rates & target Expected count rates & target separations separations

K0 reconstruction

- +p experiment

(second beam block ~21 days)

• e+e- emission from baryon resonaces1 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 Meson and Resonanse production with pion beamsproduction with pion beams

Eth

resh

[GeV

]

Mx [GeV/c2]

/

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 Rn e+e- is /0 e+e-

N*,

1.21 1.52 1.68

s

There are also constraints from N reactions

: optical theorem

2 decay channels of resonances

Resonance excitation in 2 channel

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 - p2NM. Effenberger et al. PHYS. REV. C 60(1999) 044614 V. Shyklar: RRTF@GSI, Seillacbased on Maley and Saleski analysis of N

2014: B-G (A.Sarantsev) predictions for 2K-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 RRTF @ GSI)

e+e- production ampltidues in -p reactionsInteference effects are important below threshold!

S31 - S11 and D13 – D33

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 +n

e+e- production ampltidues in -p reactions

„Born terms”

N* resonance contribution

M. Zetenyi, G. Wolf PRC86 (2012) 065209 

+ extended VectorDominanceModel! k2 not m2 („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/c2 (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/c2 (full solid angle) 247 nb(~ 2.5 higher than in B-G)

Total component

Hyperon production

Hyperon production

D. Manley

large discrepancies in exp data around 1.7 GeV !

Cross sections

Angular distributions K0

Angular distributions K0

polarization

polarization

Angular distributions

• At low energy S11(1650) and P11(1710), P13(1720) are dominant resonances for Kbut 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”

Connection of K channel to „ puzzle”

Connection of K channel to „ puzzle”

Conclusion:

Summary of NK-M.DoeringHADES CM @ Saillac

count rate estimates

Estimates (e+e- M>140 MeV/c2)-TDR

p =1.1 GeV/c

Resonance model: constant eTFF (QED)from Zetenyi & Wolf

Estimates (2pion)- TDReff*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: 0.25 0.6 0.25

x2 x 4 x 2 counts

~96kE ~26kE ~20 kE

TDR @ p=1.7 GeV/c

440 kE 250 kE 220 kE

Reconstruction/day exclusive 48.000 1800 1400

Reconstruction semi exclusive(only K0) 13 000 10 000

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)

P13 (1720)P13 (1900)

non-resonat contributions

F15 (1685)

Isospin decompositon

A2I,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 CB @BNL exist for W=1.2:1.52 GeV

Coupled channel effects

Importance of CC effects !

Which resonances matters?

examples: resonance model

K()()

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

0.7

1.24*108