Bremsstrahlung*B. Kämpfer

Research Center Dresden-Rossendorf Technical University Dresden

* braking radiation, free-free radiation, * discovered by Nikola Tesla during high frequency research between 1888 and 1897* with L. P. Kaptari + Gy. Wolf & H.W. Barz

1. Hadron masses2. If we would have a theory3. Modelling, parametrizing, guessing

Hadrons = Excitations of QCD Ground State

QCD ground state (vacuum)n,T

Stark Zeeman

Dilute Gas Approx.

Hadron Masses (Facts)

hadron masses = strong interaction energy

non-perturbative regime: QCD condensates / chiral symmetry

Hadron Masses (Visions)

SU(3): numerically small

pot. importantWeise: enhancement via chiral gap hypothesis

Hadron Masses (Facts, contd)

QCD SR:

QCD lattice: Poles of propagators with V quantum numbers

HADES data: Agakishev et al. PRL `07BUU: Barz et al. `06/optim.

C(2AGeV) + C

T = 108 MeV

NA50

Gallmeisteret al. `01

T = 170 MeV

DLS Puzzle Solved by Bremsstrahlung?

Barz et al. Bratkovskaya, Cassing

M [GeV]

Aichelin 2008: differing #(NN) vs. sqrt(s) in different models

C(1 AGeV) + C

1997: bremsstrahlung ... contribution was found to be small2007: DLS puzzle... may be solved when incorporating a stronger bremsstr. contribution

C(1 AGeV) + C C(1 AGeV) + C

(known since 111 years)

If we had a Theory, e.g. QEDnaive (standard perturbative) QED

2. In medium (LPM effect): strong modifications by multiple scatterings + destruct. interference

1. Scattering problem in vacuum:

Gauge Invariance

3. No theory: modelling, parameterizing, guessingNo Brain –No Pain

Virtual Bremsstrahlung

SN

N

N

N

e+

e-

OBE approx.:

NN:

np:

Kroll-Ruderman

NNM

Effective Models at Work

confirmed by ANKE

confirmed by ANKE

ISI + FSI Jost function formalism (important at kinematical limit of e+ e- mass) Form Factors and Gauge Invariance

N N

M

check numerically gauge inv.

bremsstr. (N only)Deltatotal

constants „adjusted“ to Shyam-Mosel results:KK SM(4 pi) DLS

no new parameters

very different w/o contact term

Bremsstrahlung only

Contact term may be decisive: e.g. Compton scatt.1. QED

2. scalar QED

+

= 0 (Coulomb gauge)

contact

Contact Terms may be Large

VMD

danger:double counting

N only

w/ Delta

question: output = input?

Bethe-Salpeter amplitude with same OBE kernel:

x = 0.45

x = 0.50

x = 0.55

factorization works:

sub-thresholdproduction:

w/ VDM

HADES: data for pp and pn at the same energy are at our disposal

Spectator Distribution

1.25

1.90

3.50

pn/pp is not described

Conclusions

- Unambigious interpretation of HADES (e+e-) data is challenging- Careful tests of elementary channels in NN- Careful test of elementary channels in pA- Careful tests of elementary channels in AA- May be bremsstrahlung solves DLS puzzle- Identification of medium modifications of vector mesons is still an interesting perspective: M, pT, y spectra required- Isolating rho spectral function (as NA60)?

Vor etwa vierzig Jahren schrieb der Brite Peter Higgs (* 29. Mai 1929) an einen Studenten: "Ich habe etwas völlig Nutzloses entdeckt".

P. Higgs: „My Life as Boson“

BUU Transport Codepropagation of broad resonances

(Kadanoff-Baym Cassing-Juchem, Leupold)C(2 AGeV) + C

Elementary Cross SectionsBUU: resonsonance model no indep. cross sects. fit of many elemt. channels at once

Spectral Functions

Gauge Invariance

QCD Sum Rules

4-quark condensates(factorization fails:

Borel

QCD condensates

pert. term

Landau damp.

)

CB-TAPS constraints?

4-q cond. = order parameter of chiral symmetry?

BK, Pavlenko, Zschocke, EPJA ´03

The Case of phi Meson

fireball evolutionfor SIS18