Dilepton production and off- -shell shell Dilepton production and - - PowerPoint PPT Presentation

SLIDE 1

Dilepton production and off Dilepton production and off-

• shell

shell transport dynamics at SIS energies transport dynamics at SIS energies

E Elena lena Bratkovskaya Bratkovskaya

Institut für Theoretische Physik Institut für Theoretische Physik, Uni. Frankfurt , Uni. Frankfurt

12 August 2009, EMMI Workshop on ‘Virtual Bremsstrahlung 12 August 2009, EMMI Workshop on ‘Virtual Bremsstrahlung and HADES‘ and HADES‘

• Uni. Frankfurt
• Uni. Frankfurt

SLIDE 2

Applicability of t Applicability of transport approaches and viscous hydro ransport approaches and viscous hydro

The ratio of shear viscosity to entropy density The ratio of shear viscosity to entropy density η η/s /s defines the defines the applicability of applicability of many many-

• body approaches !

body approaches ! Recall: Recall: ideal hydro: ideal hydro: η η/s = 0 ! /s = 0 ! Validity of transport approaches (in 2PI approximation): Validity of transport approaches (in 2PI approximation): a) a) classically: classically: λ λ > d > d mean mean-

• free path

free path λ λ must be larger than the average distance d = must be larger than the average distance d = ρ ρ-

• 1/3

1/3 of

• f

the `degrees of freedom` (hadrons or partons) the `degrees of freedom` (hadrons or partons) for gluons for gluons (e.g. C. Greiner et al.) (e.g. C. Greiner et al.) : : λ λ > d = > d = ρ ρ-

• 1/3

1/3 =

= π π 2/3

2/3 /(16

/(161/3

1/3 T)

T) using using η η/s = 4/15 T /s = 4/15 T λ λ

• η

η/s > 0.22 /s > 0.22 b) b) quantum mechanics: quantum mechanics:

• < E/2

< E/2 width of quasi width of quasi-

• particles

particles must be less than about half the quasi must be less than about half the quasi-

• particle energy E = (p

particle energy E = (p2

2+M

+M2

2)

)1/2

1/2

(Juchem, Cassing, Greiner 2003) (Juchem, Cassing, Greiner 2003) : average energy <E> = (M : average energy <E> = (M2

2+(3T)

+(3T)2

2)

)1/2

1/2

• for M=0:

for M=0: η η/s > 0.18 /s > 0.18 ( (η η/s /s is even is even lower lower for M >2T as in PHSD!) for M >2T as in PHSD!)

PHSD:W. Cassing, E. B., PRC 78 (2008) 034919; arXiv:0907.5331 [ PHSD:W. Cassing, E. B., PRC 78 (2008) 034919; arXiv:0907.5331 [nucl nucl-

• th]

th]

SLIDE 3

What do we know about What do we know about η η/s /s? ?

• N. Demir, S.A. Bass : PRL 102 (09) 172302
• N. Demir, S.A. Bass : PRL 102 (09) 172302

hadron gas hadron gas − partons partons

• D. Teaney: nucl
• D. Teaney: nucl-
• th / 0905.2433

th / 0905.2433

In hadronic phase: In hadronic phase: η η/s > 0.5 /s > 0.5

• transport is valid!

transport is valid! i in partonic phase: n partonic phase: η η/s < 0.3 /s < 0.3

• D. Teaney:
• D. Teaney: dissipative

dissipative (viscous) hydro works for (viscous) hydro works for η η/s < 0.3 ! /s < 0.3 ! pQCD pQCD

UrQMD UrQMD

… What the experiment tells us about … What the experiment tells us about η η/s at RHIC? /s at RHIC?

SLIDE 4

PHENIX

η/ η/ η/ η/s=0.32 η/ η/ η/ η/s=0.16 η/ η/ η/ η/s=0.48

viscous hydro viscous hydro parton transport parton transport

Experimental situation in Au+Au at RHIC Experimental situation in Au+Au at RHIC

• The off

The off-

• shell transport

shell transport -

• with parton

with parton-

• hadron degrees of freedom

hadron degrees of freedom – – is is valid valid at least up to RHIC energies ! at least up to RHIC energies !

Data from R. Lacey: CBM Workshop, March 2009 Data from R. Lacey: CBM Workshop, March 2009

ideal hydro ideal hydro

η/ η/ η/ η/s=1/4π π π π

SLIDE 5

‚History‘ ‚History‘ of dilepton cocktails

• f dilepton cocktails
• Gy. Wolf et al.,
• Gy. Wolf et al., Nucl

Nucl. . Phys.

• Phys. A

A517 (1990) 615 517 (1990) 615 BUU: BUU:

• first calculation of dilepton production in

first calculation of dilepton production in heavy heavy-

• ion collisions within a transport model

ion collisions within a transport model

• implementation of the basic dilepton channels

implementation of the basic dilepton channels

• time integration (‚shining‘) method

time integration (‚shining‘) method

• discussion of in

discussion of in-

• medium effects

medium effects E.B., E.B., W. Cassing,

• W. Cassing, Nucl

Nucl. . Phys.

• Phys. A

A807 (2008) 214 807 (2008) 214 HSD : HSD :

• … +

… +

• off
• ff-
• shell transport dynamics

shell transport dynamics

• dynamical treatment of resonances with broad

dynamical treatment of resonances with broad spectral functions spectral functions

• in

in-

• medium effects (dropping mass, collisional

medium effects (dropping mass, collisional broadening) broadening) [Similar to : C.M. Ko et al., NPA 512 (1990) 772] [Similar to : C.M. Ko et al., NPA 512 (1990) 772]

SLIDE 6

Dilepton cocktail in HSD Dilepton cocktail in HSD

• All particles decaying to dileptons are

All particles decaying to dileptons are first produced in BB, mB or mm collisions first produced in BB, mB or mm collisions

• ‚Factorization‘ of diagrams

‚Factorization‘ of diagrams in the in the transport approach: transport approach:

• The dilepton spectra are calculated

The dilepton spectra are calculated perturbatively perturbatively with the with the time integration method time integration method. .

N N N N R e+ γ γ γ γ* e-

=

e- N N N R N R e+ γ γ γ γ*

electromagnetic decays electromagnetic decays

SLIDE 7

Zoom: Dilepton channels Zoom: Dilepton channels

π,η,∆,ω,ρ,φ,... π,η,∆,ω,ρ,φ,... π,η,∆,ω,ρ,φ,... π,η,∆,ω,ρ,φ,... π,η,∆,ω,ρ,φ,... π,η,∆,ω,ρ,φ,... π,η,∆,ω,ρ,φ,... π,η,∆,ω,ρ,φ,... production production – – can be controlled by N+N and can be controlled by N+N and π π π π π π π π+N exp. data +N exp. data

NN, NN, π π π π π π π πN bremsstrahlung N bremsstrahlung = ‚background‘ radiation = ‚background‘ radiation -

• hard to control by

hard to control by

• exp. data!
• exp. data!
• reliable theoretical model for NN and

reliable theoretical model for NN and π π π π π π π πN bremsstrahlung is needed! N bremsstrahlung is needed!

not for HADES not for HADES electromagnetic decays electromagnetic decays

• under control!

under control!

SLIDE 8

NN and NN and π π π π π π π πN bremsstrahlung N bremsstrahlung -

• SPA

SPA

Soft Soft-

• Photon

Photon-

• Approximation

Approximation (SPA): (SPA): N N N N − − − − − − − −> > > > > > > > N N e N N e+

+e

e-

• (or

(or π π π π π π π π N N − − − − − − − −>π >π >π >π >π >π >π >π N e N e+

+e

e-

• )

) γ γ γ γ γ γ γ γ∗

∗ ∗ ∗ ∗ ∗ ∗ ∗-

• >e

>e+

+e

e-

• Phase

Phase-

• space corrected

space corrected soft soft-

• photon cross section:

photon cross section:

( ( ( ( ) ) ) )

elast N) NN(

σ 1 q dMd q M, s, dσ q dMd ) q M, dP(s,

π π π π

⋅ ⋅ ⋅ ⋅ = = = =

• SPA implementation in HSD:

SPA implementation in HSD: e e+

+e

e-

• production in

production in elastic NN ( elastic NN (π π π π π π π πN) N) collisions collisions with probability: with probability:

elastic elastic NN ( NN (π π π π π π π πN) N)

‚quasi ‚quasi-

• elastic‘

elastic‘ N N N N -

• > N N

> N N π π π π π π π π N N -

• >

> π π π π π π π π N N

‚off ‚off-

• shell‘ correction factor

shell‘ correction factor

(π) (π) (π) (π) (π) (π) (π) (π) (π) (π) (π) (π) (π) (π) (π) (π)

(as in Gy. Wolf et al., (as in Gy. Wolf et al., NPA NPA517 (1990) 615) 517 (1990) 615)

SLIDE 9

Bremsstrahlung Bremsstrahlung – – a new view on an ‚old‘ story a new view on an ‚old‘ story

2007 ‚DLS puzzle‘ : 2007 ‚DLS puzzle‘ : Experimentally: HADES = DLS ! Experimentally: HADES = DLS ! Theory: Theory: the DLS puzzle is solved by accounting for a larger pn the DLS puzzle is solved by accounting for a larger pn bremsstrahlung ! bremsstrahlung !

0.0 0.1 0.2 0.3 0.4 0.5 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.0 0.1 0.2 0.3 0.4 0.5 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

Bremsstrahlung SPA, in HSD'97 Schäfer et al.'94 Shyam&Mosel'03 Kaptari&Kämpfer'06 p+n, 1.04 GeV dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

Schäfer et al.'94 de Jong&Mosel'96 Shyam&Mosel'03 Kaptari&Kämpfer'06 M [GeV/c

2]

p+p, 1.04 GeV dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

New OBE New OBE-

• model

model (Kaptari&Kämpfer, NPA 764 (2006) 338): (Kaptari&Kämpfer, NPA 764 (2006) 338):

• pn

pn bremstrahlung is bremstrahlung is larger larger by a factor of by a factor of 4 4 than it has been than it has been calculated before (and used in transport calculations before calculated before (and used in transport calculations before)! )!

• pp

pp bremstrahlung is smaller than pn, however, bremstrahlung is smaller than pn, however, not zero not zero; consistent ; consistent with the 1996 calculations from with the 1996 calculations from F.

• F. de Jong in a T

de Jong in a T-

• matrix approach

matrix approach

SLIDE 10

HSD: Dileptons from A+A at 1 A GeV HSD: Dileptons from A+A at 1 A GeV -

• DLS

DLS

• bremsstrahlung

bremsstrahlung and and ∆ ∆ ∆ ∆ ∆ ∆ ∆ ∆-

• Dalitz are the dominant contributions

Dalitz are the dominant contributions in A+A for 0.15 < M < 0.55 GeV at 1 A GeV ! in A+A for 0.15 < M < 0.55 GeV at 1 A GeV !

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

• 3

10

• 2

10

• 1

10 10

1

10

2

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

• 3

10

• 2

10

• 1

10 10

1

10

2

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All DLS π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

C+C, 1.04 A GeV in-medium effects: CB+DM dσ σ σ σ/dM [µ µ µ µb/(GeV c

2)]

M [GeV/c

2]

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All DLS π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

C+C, 1.04 A GeV no medium effects dσ σ σ σ/dM [µ µ µ µb/(GeV c

2)]

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 10

• 3

10

• 2

10

• 1

10 10

1

10

2

10

3

10

4

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 10

• 3

10

• 2

10

• 1

10 10

1

10

2

10

3

10

4

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All DLS π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

Ca+Ca, 1.04 A GeV in-medium effects: CB+DM dσ σ σ σ/dM [µ µ µ µb/(GeV c

2)]

M [GeV/c

2]

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All DLS π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

Ca+Ca, 1.04 A GeV no medium effects dσ σ σ σ/dM [µ µ µ µb/(GeV c

2)]

E.B., Cassing, NPA807 (2008) 214 E.B., Cassing, NPA807 (2008) 214

SLIDE 11

0.0 0.2 0.4 0.6 0.8 10

• 8

10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

0.0 0.2 0.4 0.6 0.8 10

• 8

10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

HADES

HSD: π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All

C+C, 1.0 A GeV no medium effects 1/Nπ

π π π

0 dN/dM [1/GeV /c

2]

HSD: π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All

M [GeV/c

2]

HADES

C+C, 1.0 A GeV in-medium effects: CB+DM 1/Nπ

π π π

0 dN/dM [1/GeV /c

2]

HSD: Dileptons from C+C at 1 and 2 A GeV HSD: Dileptons from C+C at 1 and 2 A GeV -

• HADES

HADES

• HADES data show exponentially decreasing mass spectra

HADES data show exponentially decreasing mass spectra

• Data are

Data are better described by in better described by in-

• medium scenarios with collisional broadening

medium scenarios with collisional broadening

• In

In-

• medium effects are more pronounced for

medium effects are more pronounced for heavy systems heavy systems such as Au+Au such as Au+Au

0.0 0.2 0.4 0.6 0.8 1.0 10

• 8

10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

0.0 0.2 0.4 0.6 0.8 1.0 10

• 8

10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

HADES

HSD: π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All

C+C, 2.0 A GeV no medium effects 1/Nπ

π π π 0 dN/dM [1/GeV /c

2]

HSD: π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All

M [GeV/c

2]

HADES

C+C, 2.0 A GeV in-medium effects: CB+DM 1/Nπ

π π π 0 dN/dM [1/GeV /c

2]

E.B., Cassing, NPA807 (2008) 214 E.B., Cassing, NPA807 (2008) 214

SLIDE 12

0.0 0.2 0.4 0.6 0.8 1.0 10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

HSD: free s.f. in-medium s.f.: CB+DM

M [GeV/c

2]

Ar+KCl, 1.75 A GeV

1/N

π π π π

0 dN/dM [1/GeV /c

2]

HSD: Dileptons from Ar+KCl at 1.75 A GeV HSD: Dileptons from Ar+KCl at 1.75 A GeV -

• HADES

HADES

• preliminary

preliminary HADES data show a peak structure at M~0.78 GeV

HADES data show a peak structure at M~0.78 GeV

• HSD overestimates yield

HSD overestimates yield at M~0.5 at M~0.5-

• 0.8 GeV for the in

0.8 GeV for the in-

• medium as well as for free

medium as well as for free scenarios scenarios

• no medium effects observed ?!

no medium effects observed ?! NO !!! NO !!!

⇒ ⇒ Indication that the

Indication that the ρ ρ ρ ρ ρ ρ ρ ρ-

• meson production cross section from NN closer to

meson production cross section from NN closer to threshold is overestimated in HSD threshold is overestimated in HSD

• In

In-

• medium effects are more pronounced for heavy systems such as Ar+

medium effects are more pronounced for heavy systems such as Ar+KCl KCl

• The peak at M~0.78 GeV relates to

The peak at M~0.78 GeV relates to ω/ρ ω/ρ ω/ρ ω/ρ ω/ρ ω/ρ ω/ρ ω/ρ mesons decaying in vacuum mesons decaying in vacuum HSD by HSD by Filip Krizek Filip Krizek

SLIDE 13

From A+A to N+N reactions and backward From A+A to N+N reactions and backward

• Does

Does Dalitz and NN B Dalitz and NN Bremsstrahlung remsstrahlung explain the excess? explain the excess?

• Control on vector meson production cross

Control on vector meson production cross sections at threshold! sections at threshold! → → → → → → → → verification in NN collisions is needed verification in NN collisions is needed

SLIDE 14

HSD: Dileptons from p+p and p+d HSD: Dileptons from p+p and p+d -

• DLS

DLS

• bremsstrahlung

bremsstrahlung is one of the dominant contributions is one of the dominant contributions in p+d for 0.15 < M < 0.55 GeV at ~1 in p+d for 0.15 < M < 0.55 GeV at ~1-

• 1.5 A GeV

1.5 A GeV

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

π

π π π

0 Dalitz

η

η η η Dalitz

ω

ω ω ω Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All

p+d, 1.04 GeV

dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

π

π π π

0 Dalitz

η

η η η Dalitz

ω

ω ω ω Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All

p+d, 1.27 GeV p+d, 1.61 GeV

dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

π π π π

p+d, 1.85 GeV p+d, 2.09 GeV

dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

M [GeV/c

2]

p+d, 4.88 GeV

M [GeV/c

2]

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. pp

All

p+p, 1.04 GeV

dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. pp

All

p+p, 1.27 GeV p+p, 1.61 GeV

dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

p+p, 1.85 GeV p+p, 2.09 GeV

dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

M [GeV/c

2]

p+p, 4.88 GeV

M [GeV/c

2]

SLIDE 15

pp, pn (pd) reactions pp, pn (pd) reactions

• DLS data

DLS data (low statistics and mass resolution) do (low statistics and mass resolution) do not allow for definite conclusions not allow for definite conclusions

• new (good quality) HADES data

new (good quality) HADES data on

• n pp, pn

pp, pn (pd) (pd) reactions for different energies provide an reactions for different energies provide an independant check for the elementary channels independant check for the elementary channels involved in A+A involved in A+A

SLIDE 16

pp @ 1.25GeV : pp @ 1.25GeV : new HADES data new HADES data

• ∆

∆ ∆ ∆ ∆ ∆ ∆ ∆-

• Dalitz decay is the dominant channel (HSD consistent with PLUTO)

Dalitz decay is the dominant channel (HSD consistent with PLUTO)

• HSD predictions:

HSD predictions: good description of new HADES data for p+p! good description of new HADES data for p+p! PLUTO

E.L.B. &W. Cassing, NPA 807 (2008) 214 E.L.B. &W. Cassing, NPA 807 (2008) 214

0.0 0.2 0.4 0.6 0.8 10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

M [GeV/c

2]

HSD π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. pp

All

p+p, 1.25 GeV 1/Nπ

π π π

0 dN/dM [(GeV/c

2)

• 1]

SLIDE 17

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 10

• 8

10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

HADES preliminary

p+n(d), 1.25 GeV

HSD π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All

M [GeV/c

2]

Quasi Quasi-

• free pn

free pn (pd) reaction: HADES data @ 1.25 GeV (pd) reaction: HADES data @ 1.25 GeV

"quasi-free" p+n 1.25 GeV θ θ θ θe+e->90

PLUTO ∆ ∆ ∆ ∆ η η η η

HSD predictions HSD predictions underestimate the HADES p+n (quasi underestimate the HADES p+n (quasi-

• free) data at 1.25 GeV:

free) data at 1.25 GeV: 1) 1) 0.2<M<0.55 GeV: 0.2<M<0.55 GeV: η η η η η η η η-

• Dalitz decay

Dalitz decay is by a factor of ~10 is larger in PLUTO than in HSD since the is by a factor of ~10 is larger in PLUTO than in HSD since the channels channels d + p d + p → → → → → → → →p pspec

spec + d

+ d + + η η η η η η η η ( (‘ ‘quasi quasi-

• free

free’ ’ η η η η η η η η-

• production

production -

• dominant at 1.25GeV!)

dominant at 1.25GeV!) and and p + n p + n → → → → → → → →d d + + η η η η η η η η were NOT taken into account before! were NOT taken into account before! Note: Note: these channels have these channels have NO impact NO impact for heavy for heavy-

• ion reactions and even for p+d results

ion reactions and even for p+d results at higher energies! at higher energies!

*In HSD: *In HSD: p+d = p + (p&n) p+d = p + (p&n)-

• with

with Fermi Fermi motion motion according to the Paris deuteron wave function according to the Paris deuteron wave function

η η η η

SLIDE 18

10

• 3

10

• 2

10

• 1

10 10

• 4

10

• 3

10

• 2

10

• 1

10

s

1/2 th string

Parametrization: pn->η

η η ηX

pp->η

η η ηX

pn->η

η η ηd

• Exp. data (exclusive):

pn->η

η η ηpn

pp->η

η η ηpp

pn->η

η η ηd

pN->η

η η ηX

σ σ σ σ [mb] s

1/2-s0 1/2 [GeV]

Quasi Quasi-

• free pn

free pn (pd) @ 1.25 GeV: (pd) @ 1.25 GeV: η η η η η η η η-

• channel

channel

1) 1) p + n p + n → → → → → → → →d d + + η η η η η η η η 2) 2) d + p d + p → → → → → → → →p pspec

spec + d

+ d + + η η η η η η η η Add the following channels: Add the following channels: Now HSD agrees Now HSD agrees with PLUTO with PLUTO

• n the
• n the η

η η η η η η η-

• Dalitz decay!

Dalitz decay!

10

• 3

10

• 2

10

• 1

10 10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

10

• 1

HADES: pd@1.25GeV

CELSIUS

pd->pdη

η η η

σ σ σ σ [mb] s

1/2-s0(pd) 1/2 [GeV]

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 10

• 8

10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

HADES preliminary

p+n(d), 1.25 GeV

HSD π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All

M [GeV/c

2]

η η η η

SLIDE 19

2 3 4 5 6 7 8 9 10 10 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

Free ρ

ρ ρ ρ meson spectral function

NN->N(1520)->NNρ

ρ ρ ρ

non-resonant NN->ρ

ρ ρ ρX

s

1/2 th string

• Exp. data:

pp−>

−> −> −> ρ ρ ρ ρpp

pp−>

−> −> −> ρ ρ ρ ρX

σ σ σ σ (s) [mb]

s

1/2 [GeV]

pp −>

−> −> −> ρ ρ ρ ρ X

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 10

• 8

10

• 7

10

• 6

10

• 5

10

• 4

10

• 3

10

• 2

HADES preliminary

p+n(d), 1.25 GeV 1/Nπ

π π π

0 dN/dM [(GeV/c

2)

• 1]

HSD π

π π π

0 Dalitz

η

η η η Dalitz

∆

∆ ∆ ∆ Dalitz

ω

ω ω ω Dalitz

ω

ω ω ω

ρ

ρ ρ ρ

• Brems. NN
• Brems. π

π π πN

All N(1520) Dalitz

M [GeV/c

2]

HSD: preliminary ! HSD: preliminary !

Quasi Quasi-

• free pn

free pn (pd) @ 1.25 GeV: (pd) @ 1.25 GeV: N(1520) ?! N(1520) ?!

1.0 1.0 1.3 1.5 1.5 1.8 2.0 2.0 2.3 2.5 2.5 2.8 3.0 3.0 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

10

2

• Exp. data:

π

π π πN−> −> −> −> ρ ρ ρ ρN

s

1/2 [GeV]

π

π π πN -> ρ ρ ρ ρX

σ σ σ σ [mb]

Free ρ

ρ ρ ρ meson spectral function

π

π π πN->N(1520)->ρ ρ ρ ρN

non-resonant π

π π πN->ρ ρ ρ ρX

2) 2) M > 0.45 GeV:

M > 0.45 GeV: HSD HSD very(!) preliminary very(!) preliminary result for p+d @1.25 GeV result for p+d @1.25 GeV shows that the missing yield might be only shows that the missing yield might be only PARTLY (!) PARTLY (!) attributed to attributed to subthreshold subthreshold ρ ρ ρ ρ ρ ρ ρ ρ− − − − − − − −production via N(1520) production via N(1520) excitation and decay excitation and decay Similar to our Similar to our N NP PA686 A686 (2001) (2001) 568 568

0.1 0.3 0.5 0.7 0.9 1.1 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

M [GeV/c

2]

dσ σ σ σ/dM [µ µ µ µb/(GeV/c

2)]

pn

η η η η

ρ ρ ρ ρ

all

∆ ∆ ∆ ∆ π π π π

p+d, 1.27 GeV DLS

N(1520) N(1520) N(1520) N(1520)

Model for N(1520): Model for N(1520): according to according to Peters et al., Peters et al., NPA632 NPA632 (1998) (1998) 109 109

SLIDE 20

Summary I Summary I

Warnings: Warnings:

• isospin dependence of cross sections is important, too!

isospin dependence of cross sections is important, too!

• additional complication due to

additional complication due to coherence effects coherence effects in in p+d p+d reactions ! reactions ! Similar ‚problems‘ with Similar ‚problems‘ with π π π π π π π π+d reactions ! +d reactions ! Transport models give reliable Transport models give reliable results results for A+A for A+A ONLY ONLY with with reliable initial input reliable initial input, i.e. if the elementary reactions are under control , i.e. if the elementary reactions are under control => => REQUESTS: REQUESTS: cross sections for elementary channels: cross sections for elementary channels: experim. information

• experim. information

baryon baryon-

• baryon p+p, p+A reacti

baryon p+p, p+A reactions

• ns

meson meson-

• baryon

baryon π π π π π π π π+p, +p, π π π π π π π π+A reactions +A reactions meson meson-

• meson (for higher energies)

meson (for higher energies)

SLIDE 21

Summary II: Summary II: physics key issues physics key issues

Α+Α, Α+Α, Α+Α, Α+Α, Α+Α, Α+Α, Α+Α, Α+Α, p p+Α, π +Α, π +Α, π +Α, π +Α, π +Α, π +Α, π +Α, π+A reactions: +A reactions:

• in

in-

• medium effects

medium effects -

• collisional broadening and dropping

collisional broadening and dropping mass of the vector mesons mass of the vector mesons (ρ,ω,φ) (ρ,ω,φ) (ρ,ω,φ) (ρ,ω,φ) (ρ,ω,φ) (ρ,ω,φ) (ρ,ω,φ) (ρ,ω,φ)

• study of the mesonic and baryonic

study of the mesonic and baryonic resonance dynamics resonance dynamics p+p(n), p+p(n), π π π π π π π π+p(n) reactions: +p(n) reactions:

• control on different elementary channels

control on different elementary channels

• study of the b

study of the baryon resonance dynamics aryon resonance dynamics near threshold near threshold

• quantum interference of ρ

ρ ρ ρ0 and ω ω ω ω-mesons at low energies (?)

impact on impact on A+A A+A

SLIDE 22

Thanks Thanks to

to

HADES collegues: HADES collegues: Yvonne, Gosia, Romain, Piotr, Yvonne, Gosia, Romain, Piotr, Joachim, Tatyana, Volker, Beatrice, Joachim, Tatyana, Volker, Beatrice, Filip, … Filip, …

+ + Wolfgang

Wolfgang