Dilepton cocktail in p +A experiments

Dilepton cocktail in Dilepton cocktail in +A +A experimentsexperiments

EElenalena Bratkovskaya Bratkovskaya

12-13 February 2009 , Meeting of HADES experiments 12-13 February 2009 , Meeting of HADES experiments with pion beams, Orsay, Francewith pion beams, Orsay, France

‚‚History‘ ofHistory‘ of+ A reactions+ A reactions

W. SchönW. Schön, H. Bokemeyer, W. Koenig and V. Metag,, H. Bokemeyer, W. Koenig and V. Metag,

Act. Phys. Pol. B 27 (Act. Phys. Pol. B 27 (191996) 295996) 2959-pbound nat rest ne+e-“at rest”: Fpp

+ Pb, 1.3 GeV/c+ Pb, 1.3 GeV/c

Study ofStudy of in-medium effects such as in-medium effects such as dropping dropping mass mass withinwithin+ A reactions:+ A reactions:

=> Possibility for an experimental => Possibility for an experimental observation of the mass shift of observation of the mass shift of ::

decay decay ‚inside‘‚inside‘ Pb-nuclei Pb-nuclei

Medium effects in the production and decay of vector mesons in + A reactions+ A reactions

First dynamical calculations of in-medium effects in First dynamical calculations of in-medium effects in + A reactions:+ A reactions:W. CassingW. Cassing,, Y.S. Golubeva, Y.S. Golubeva, A.S. Iljinov, A.S. Iljinov, L.A. KondratyukL.A. Kondratyuk, Phys. Lett. B 396 (1997) 26, Phys. Lett. B 396 (1997) 26 Y.S. Golubeva, L.A. Kondratyuk, W. CassingY.S. Golubeva, L.A. Kondratyuk, W. Cassing,, Nucl. Nucl. Phys.Phys. AA 625625 (1997) (1997) 832832

Dropping massDropping mass of the vector mesons ( of the vector mesons (

Collisional broadeningCollisional broadening of the vector meson width of the vector meson width

Low momentum cutsLow momentum cuts for separation of the ‚inside‘ and ‚outside‘ components for separation of the ‚inside‘ and ‚outside‘ components

intranuclear cascade (INC) approachintranuclear cascade (INC) approach

Study of in-medium effects withStudy of in-medium effects with+ A reactions - BUU+ A reactions - BUU

Similar studies with BUU:Similar studies with BUU: T. Weidmann, E.B., W. Cassing, U. Mosel, PRC 59 (1999) 919T. Weidmann, E.B., W. Cassing, U. Mosel, PRC 59 (1999) 919

strong modification of dilepton spectra for in-medium scenarios strong modification of dilepton spectra for in-medium scenarios (dropping mass and collisional broadening)(dropping mass and collisional broadening)

gategate on low momenta on low momenta (q<0.3 GeV/c) increases the signal(q<0.3 GeV/c) increases the signal

+ N and + N and + A reactions - CBUU+ A reactions - CBUU

Similar studies with CBUU: Similar studies with CBUU: M. Effenberger, E.B., W. Cassing, U. Mosel, PRC 60 (1999) 044614M. Effenberger, E.B., W. Cassing, U. Mosel, PRC 60 (1999) 044614

--A at A at EE = 1.3 GeV = 1.3 GeV--NN at at EE = 1.3 GeV = 1.3 GeV

CBUU: CBUU: dominant meson production via baryonic resonances (Manley model)dominant meson production via baryonic resonances (Manley model)

different model for the production of vector mesons in elementary different model for the production of vector mesons in elementary N N and NN reactionsand NN reactions

due to Rdue to R

Study of in-medium effects withStudy of in-medium effects with+ A reactions - CBUU+ A reactions - CBUU

Similar studies with CBUU: Similar studies with CBUU: M. Effenberger, E.B., W. Cassing, U. Mosel, PRC 60 (1999) 044614M. Effenberger, E.B., W. Cassing, U. Mosel, PRC 60 (1999) 044614

--A at A at EEkinkin = 1.3 GeV = 1.3 GeV

……

strong influence of strong influence of baryonic resonancesbaryonic resonances (e.g. (e.g. N(1520)) on N(1520)) on -meson production-meson production

constructive interferenceconstructive interference

n e+e- p

Quantum interference of Quantum interference of 00 and and -mesons -mesons

in the in the N N e e++ee-- N reaction N reaction

MM. . SoyeurSoyeur,, M M.. F.M. Lutz F.M. Lutz;; B B.. Friman, nucl-th/0003013 Friman, nucl-th/0003013;; Nucl.Nucl. Phys.Phys. A713A713 (2003) (2003) 9797

distructive interferencedistructive interference

p e+e- n

RRN+N+(())

talk by talk by MM. . SoyeurSoyeur

based on coupled-channel approach for m+N scatteringbased on coupled-channel approach for m+N scattering

Baryon resonance dynamics inBaryon resonance dynamics in+ N+ NN+V (V=N+V (V=) ) reactions near thresholdreactions near threshold

B. KB. Käämpfer, A.I. Titov, B.L. Reznikmpfer, A.I. Titov, B.L. Reznik,, Nucl.Nucl. Phys.Phys. AA 721721 (2003) (2003) 583583

N(1520)N(1520)

distructive interferencedistructive interference

constructive interferenceconstructive interference

GeVGeV

=30=30oo

Invariant matrix elements squared as a function of Invariant matrix elements squared as a function of the energy (the energy (GeV, GeV, =30=30oo))

Summary - ISummary - I

What systems ( What systems ( +N or +N or +A)? - physics key issues+A)? - physics key issues

+A reactions: +A reactions:

• in-medium effects - a collisional broadening and in-medium effects - a collisional broadening and dropping mass of the vector mesons dropping mass of the vector mesons

•study of the mesonic and baryonic resonance dynamics study of the mesonic and baryonic resonance dynamics

+p(n) reactions: +p(n) reactions:

• control on different elementary channelscontrol on different elementary channels

• study of the baryon resonance dynamics study of the baryon resonance dynamics near thresholdnear threshold

• quantum interference of 0 and -mesons at low energies

possible ONLY forpossible ONLY for+p(n) reactions!+p(n) reactions!

impact onimpact on+A, A+A+A, A+A

‚‚History‘History‘ of dilepton cocktailsof dilepton cocktails

Gy. Wolf et al.,Gy. Wolf et al., Nucl.Nucl. Phys.Phys. AA517 (1990) 615517 (1990) 615

BUU: BUU:

• first calculation of dilepton production in first calculation of dilepton production in heavy-ion collisions within a transport modelheavy-ion collisions within a transport model

• implementation of the basic dilepton channelsimplementation of the basic dilepton channels

• time integration (‚shining‘) methodtime integration (‚shining‘) method

• discussion of in-medium effectsdiscussion of in-medium effects

E.B.,E.B., W. Cassing, W. Cassing, Nucl.Nucl. Phys.Phys. AA807 (2008) 214807 (2008) 214

HSD : HSD :

• … … + +

• off-shell transport dynamicsoff-shell transport dynamics

• dynamical treatment of resonances with broaddynamical treatment of resonances with broad spectral functionsspectral functions

• in-medium effects (dropping mass, collisional in-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]

Dilepton cocktail in HSDDilepton cocktail in HSD

•All particles decaying to dileptons are All particles decaying to dileptons are first produced in BB, mB or mm collisionsfirst 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 methodtime integration method..

N N

N

N

R

e+

*e-

=

e-

N N

N R

N

R

e+

*

electromagnetic electromagnetic decaysdecays

Zoom: Dilepton cocktail Zoom: Dilepton cocktail

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

heavy-ion collisionsheavy-ion collisions

p+p, p+A collisionsp+p, p+A collisions

+p, +p, +A collisions+A collisions

+ p+ p LowLowenergy energy pp reactions are reactions are dominated bydominated by resonance production and resonance production and decaydecay (important as secondary channels in (important as secondary channels in heavy-ion collisions!)heavy-ion collisions!)

pp

RR

NNRR

Zoom: Dilepton channels Zoom: Dilepton channels

production –production – can be can be controlled by exp. controlled by exp. data!data!

NN, pN bremsstrahlung = NN, pN 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 N bremsstrahlung is needed!N bremsstrahlung is needed!

not for HADESnot for HADES

electromagnetic decays electromagnetic decays under control! under control!

NN and NN and N bremsstrahlung - SPAN bremsstrahlung - SPA

Soft-Photon-ApproximationSoft-Photon-Approximation (SPA): (SPA):

N N N N N N e N N e++ee- - (or(or N N N e N e++ee-- ))

-->e>e++ee--

Phase-space corrected Phase-space corrected soft-photon cross section:soft-photon cross section:

elast

N)NN(σ

1

qdMd

qM,s,dσ

qdMd

)qM,dP(s,

SPA implementation in HSD: SPA implementation in HSD: ee++ee- - production in production in elastic NN (elastic NN (N) N) collisionscollisions with probability: with probability:

elasticelastic

NN (NN (N)N)

‚‚quasi- elastic‘ quasi- elastic‘ N N -> N NN N -> N N N -> N -> N N

‚‚off-shell‘ correction factoroff-shell‘ correction factor

(as in Gy. Wolf et al.,(as in Gy. Wolf et al., NPANPA517 (1990) 615)517 (1990) 615)

Bremsstrahlung – a new view on an ‚old‘ storyBremsstrahlung – 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 0.510-4

10-3

10-2

10-1

100

101

0.0 0.1 0.2 0.3 0.4 0.510-4

10-3

10-2

10-1

100

101

Bremsstrahlung

SPA, in HSD'97 Schäfer et al.'94 Shyam&Mosel'03 Kaptari&Kämpfer'06

p+n, 1.04 GeV

d/d

M [

b/(

GeV

/c2 )]

Schäfer et al.'94 de Jong&Mosel'96 Shyam&Mosel'03 Kaptari&Kämpfer'06

M [GeV/c2]

p+p, 1.04 GeV

d/d

M [

b/(

GeV

/c2 )]

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

• pn pn bremstrahlung is bremstrahlung is largerlarger 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 zeronot zero; consistent ; consistent with the 1996 calculations from with the 1996 calculations from F.F. de Jong in a T-matrix approachde Jong in a T-matrix approach

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

• bremsstrahlungbremsstrahlung 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

100

101

102

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

100

101

102

Brems. NN Brems. N All

DLS Dalitz Dalitz Dalitz Dalitz

C+C, 1.04 A GeVin-medium effects: CB+DM

d/d

M [

b/(

GeV

c2 )]

M [GeV/c2]



C+C, 1.04 A GeVno medium effects

d/d

M [

b/(

GeV

c2 )]

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.010-3

10-2

10-1

100

101

102

103

104

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.010-3

10-2

10-1

100

101

102

103

104



Ca+Ca, 1.04 A GeVin-medium effects: CB+DM

d/d

M [

b/(

GeV

c2 )]

M [GeV/c2]



Ca+Ca, 1.04 A GeVno medium effects

d/d

M [

b/(

GeV

c2 )]

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

0.0 0.2 0.4 0.6 0.810-8

10-7

10-6

10-5

10-4

10-3

10-2

0.0 0.2 0.4 0.6 0.810-8

10-7

10-6

10-5

10-4

10-3

10-2

HADES

HSD: Dalitz Dalitz Dalitz Dalitz Brems. NN Brems. N All


1/N

dN

/dM

[1/

GeV

/c2 ]


M [GeV/c2]

HADES


1/N

dN

/dM

[1/

GeV

/c2 ]

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

• HADES data show exponentially decreasing mass spectra HADES data show exponentially decreasing mass spectra • Data are Data are better described by in-medium scenarios with collisional broadening better described by in-medium scenarios with collisional broadening • In-medium effects are more pronounced for In-medium effects are more pronounced for heavy systemsheavy systems such as Au+Au such as Au+Au

0.0 0.2 0.4 0.6 0.8 1.010-8

10-7

10-6

10-5

10-4

10-3

10-2

0.0 0.2 0.4 0.6 0.8 1.010-8

10-7

10-6

10-5

10-4

10-3

10-2

HADES



1/N

dN

/dM

[1/

GeV

/c2 ]


M [GeV/c2]

HADES


1/N

dN

/dM

[1/

GeV

/c2 ]

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

From A+A to N+N reactionsFrom A+A to N+N reactions

Does Does ΔΔ Dalitz and NN B Dalitz and NN Bremsstrahlungremsstrahlung explain explain the excess? the excess?

verification in NN collisions is neededverification in NN collisions is needed

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

• bremsstrahlungbremsstrahlung is one of the dominant contributions is one of the dominant contributions in p+d for 0.15 < M < 0.55 GeV at ~1-1.5 A GeV in p+d for 0.15 < M < 0.55 GeV at ~1-1.5 A GeV

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.510

-4

10-3

10-2

10-1

100

101

Dalitz

Dalitz Dalitz Dalitz Brems. NN Brems. N All

p+d, 1.04 GeV

d/d

M [

b/(

GeV

/c2 )]

Dalitz

Dalitz Dalitz Dalitz Brems. NN Brems. N All

p+d, 1.27 GeV

p+d, 1.61 GeV

d/d

M [

b/(

GeV

/c2 )]

0

p+d, 1.85 GeV

p+d, 2.09 GeV

d/d

M [

b/(

GeV

/c2 )]

M [GeV/c2]

p+d, 4.88 GeV

M [GeV/c2]

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

0.1 0.3 0.5 0.7 0.9 1.110

-4

10-3

10-2

10-1

100

101

Dalitz Dalitz Dalitz Dalitz Brems. pp All

p+p, 1.04 GeV

d/d

M [

b/(

GeV

/c2 )]


p+p, 1.27 GeV

p+p, 1.61 GeV

d/d

M [

b/(

GeV

/c2 )]

p+p, 1.85 GeV

p+p, 2.09 GeV

d/d

M [

b/(

GeV

/c2 )]

M [GeV/c2]

p+p, 4.88 GeV

M [GeV/c2]

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

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

•new (good quality) HADES data new (good quality) HADES data onon pp, pn pp, pn (pd) (pd) reactions provide an independant check for the reactions provide an independant check for the elementary channels involved in A+Aelementary channels involved in A+A

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

-Dalitz decay is the dominant channel (HSD consistent with -Dalitz decay is the dominant channel (HSD consistent with PLUTO)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) 214E.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/c2]

HSD


p+p, 1.25 GeV

1/N

dN

/dM

[(G

eV/c

2 )-1]

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

Dalitz Dalitz Dalitz Dalitz Brems. NN Brems. N All

M [GeV/c2]

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

"quasi-free" p+n 1.25 GeV

e+e->90

PLUTO

HSD predictions HSD predictions underestimate the HADES p+n (quasi-free) data at 1.25 GeV:underestimate the HADES p+n (quasi-free) data at 1.25 GeV:

1)1) 0.2<M<0.55 GeV: 0.2<M<0.55 GeV:

-Dalitz decay-Dalitz decay by a factor of ~10 is larger in PLUTO than in HSD since the c by a factor of ~10 is larger in PLUTO than in HSD since the channels hannels

d + p d + p ppspecspec + d + + d + (‘quasi-free’ (‘quasi-free’ -production --production - dominant at 1.25GeV!)dominant at 1.25GeV!) and and p p + n + n d + d + were NOT taken into account before! were NOT taken into account before!

Note: Note: these channels have these channels have NO impactNO impact for heavy-ion reactions and even for p+d results at for heavy-ion reactions and even for p+d results at higher energies!higher energies!

*In HSD:*In HSD: p+d = p + (p&n)-with Fermi motionp+d = p + (p&n)-with Fermi motion according to the Paris deuteron wave function according to the Paris deuteron wave function

10-3 10-2 10-1 10010-4

10-3

10-2

10-1

100

s1/2

th string

Parametrization: pn->X pp->X pn->d

Exp. data (exclusive):pn->pnpp->pppn->d

pN->X

[m

b]

s1/2-s0

1/2 [GeV]

Quasi-free pnQuasi-free pn (pd) @ 1.25 GeV: (pd) @ 1.25 GeV: -channel-channel

1)1) p + n p + n d + d +

2)2) d + p d + p ppspecspec + d + + d +

Add the following channels:Add the following channels:

Now HSD agreesNow HSD agreeswith PLUTO with PLUTO on the on the - Dalitz decay!- Dalitz decay!

10-3 10-2 10-1 10010-6

10-5

10-4

10-3

10-2

10-1

HADES: [email protected]

CELSIUS

pd->pd

[m

b]

s1/2-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

Dalitz Dalitz Dalitz Dalitz Brems. NN Brems. N All

M [GeV/c2]

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/N

dN

/dM

[(G

eV/c2 )-1

]

HSD

Dalitz Dalitz Dalitz Dalitz Brems. NN Brems. N All N(1520) Dalitz

M [GeV/c2]

HSD: preliminary !

HSD: preliminary !

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

1.01.0 1.3 1.51.5 1.8 2.02.0 2.3 2.52.5 2.8 3.03.010-4

10-3

10-2

10-1

100

101

102

Exp. data: N N

s1/2 [GeV]

N -> X

[m

b]

Free meson spectral function N->N(1520)->N non-resonant N->X

2 3 4 5 6 7 8 9 101010-4

10-3

10-2

10-1

100

101

Free meson spectral function NN->N(1520)->NN non-resonant NN->X

s1/2

th string

Exp. data:pp pp pp X

(s)

[m

b]

s1/2 [GeV]

pp X

2)2) M > 0.45 GeV:M > 0.45 GeV:

HSD HSD very(!) preliminaryvery(!) preliminary result for p+d @1.25 GeV result for p+d @1.25 GeV shows that the missing yield might be attributed to shows that the missing yield might be attributed to subthreshold subthreshold production via N(1520) production via N(1520) excitation and excitation and decay ?! decay ?!

Similar to our Similar to our NNPPA686A686 (2001) (2001) 568568

0.1 0.3 0.5 0.7 0.9 1.110-4

10-3

10-2

10-1

100

101

M [GeV/c2]

d/d

M [

b/(

GeV

/c2 )]

pn

all

0

p+d, 1.27 GeVDLS

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., NPA632NPA632 (1998) (1998) 109109

Summary IISummary II

Transport models give reliable Transport models give reliable resultsresults for A+A for A+A ONLYONLY with with reliable initial inputreliable 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. informationexperim. information

baryon-baryon p+p, p+A reactionsbaryon-baryon p+p, p+A reactions

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

meson-meson (for higher energies)meson-meson (for higher energies)

Warning:Warning: additional complication due to additional complication due to coherence effectscoherence effects in in p+d p+d reactions ! reactions !

Similar ‚problems‘ with Similar ‚problems‘ with +d reactions ?+d reactions ?

HSD: pHSD: prreliminary

eliminary

+ p reactions - HSD+ p reactions - HSD

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

1/N

dN

/dM

[G

eV-1]


+ p, 0.4 GeV

1/N

dN

/dM

[G

eV-1]

M [GeV/c2]

HSD: Dalitz Dalitz Dalitz Dalitz Brems. NN Brems. N All N(1520) Dalitz

+ p, 0.4 GeV with N(1520)

M [GeV/c2]

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

1/N

dN

/dM

[G

eV-1]


+ p, 0.8 GeV

1/N

dN

/dM

[G

eV-1]

M [GeV/c2]


+ p, 0.8 GeV with N(1520)

M [GeV/c2]

subthreshold subthreshold -meson -meson production viaproduction via N(1520) N(1520) excitation and decay!excitation and decay!

1.3 1.51.5 1.8 2.02.0 2.3 2.52.5 2.810-3

10-2

10-1

100

101 Tkin

[GeV] 0.8

0.60.4

N->N(1520)->N non-resonant N->X sum

s1/2

th string

N X Exp. data: N N N X

s1/2 [GeV]

(s

) [m

b]

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

1/N

dN

/dM

[G

eV-1]


+ p, 0.6 GeV

1/N

dN

/dM

[G

eV-1]

M [GeV/c2]


+ p, 0.6 GeV with N(1520)

M [GeV/c2]

HSD: p

HSD: prreliminary

eliminary

+ A reactions: study of the baryon resonance dynamics - HSD+ A reactions: study of the baryon resonance dynamics - HSD

0.0 0.2 0.4 0.6 0.8 1.010-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

0.0 0.2 0.4 0.6 0.8 1.010-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

1/N

dN

/dM

[G

eV-1]

1/N

dN

/dM

[G

eV-1]


+ Au, 0.4 GeVno medium effects

M [GeV/c2]

+ Au, 0.4 GeVno medium effects; with N(1520)


M [GeV/c2]

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

1/N

dN

/dM

[G

eV-1]

1/N

dN

/dM

[G

eV-1]



M [GeV/c2]



M [GeV/c2]

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

0.0 0.2 0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

10-3

10-2

10-1

100

1/N

dN

/dM

[G

eV-1]

1/N

dN

/dM

[G

eV-1]



M [GeV/c2]



M [GeV/c2]

Exp. signal:Exp. signal: strong excess strong excess of dilepton spectra at M>0.4 GeV due to theof dilepton spectra at M>0.4 GeV due to the subthreshold subthreshold -meson -meson production viaproduction via N(1520) N(1520) excitation and decay!excitation and decay!

Optimal energy: TOptimal energy: Tkin kin < 0.7 GeV< 0.7 GeV


eliminary

+ A reactions: study of the in-medium effects - HSD+ A reactions: study of the in-medium effects - HSD

0.0 0.2 0.4 0.6 0.8 1.010-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

0.0 0.2 0.4 0.6 0.8 1.010-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1


dN/d

M [

GeV

-1]

+ C, 1.4 GeVno medium effects

dN/d

M [

GeV

-1]

M [GeV/c2]

+ C, 1.4 GeVcollis. broadening + dropping mass


M [GeV/c2]

0.0 0.2 0.4 0.6 0.8 1.010-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

0.0 0.2 0.4 0.6 0.8 1.010-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1


dN/d

M [

GeV

-1]


dN/d

M [

GeV

-1]

M [GeV/c2]

+ Au, 1.4 GeVcollis. broadening + dropping mass


M [GeV/c2]

• in-medium scenario - in-medium scenario - a collisional broadening and dropping massa collisional broadening and dropping mass of of the vector mesons the vector mesons


eliminary

+ A reactions vs. medium effects - HSD+ A reactions vs. medium effects - HSD

0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

HSD: no medium effects coll. broad.+ dropp. mass

dN/d

M [

GeV

-1]

+ C, 1.4 GeV

dN/d

M [

GeV

-1]

M [GeV/c2]


+ Au, 1.4 GeV

M [GeV/c2]

• accounting of the in-medium accounting of the in-medium effects - a effects - a collisional broadening collisional broadening and dropping massand dropping mass of the vector of the vector mesons mesons – leads to – leads to changes of the final spectra:changes of the final spectra:

- reduction of the reduction of the peaks peaks

- enhancementenhancement of the dilepton of the dilepton yield for 0.4<M<0.7 GeVyield for 0.4<M<0.7 GeV

•effect is effect is strongerstronger for for heavy heavy nucleinuclei

HSD’09 HSD’09 similar to similar to W. CassingW. Cassing,, Y.S. Golubeva, Y.S. Golubeva, A.S. Iljinov, A.S. Iljinov, L.A. KondratyukL.A. Kondratyuk, Phys. Lett. B 396 (1997) 26, Phys. Lett. B 396 (1997) 26

+A vs. p+A reactions+A vs. p+A reactions

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.910-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

free spectral function

-Pb, 1.17 GeV p+Pb, 3.5 GeV

dN/d

M [

GeV

-1]

M [GeV/c2]

Dilepton emission point of Dilepton emission point of projection of the dN/db/dz distribution, b=(x projection of the dN/db/dz distribution, b=(x22+y+y22))1/21/2

•p+A and p+A and +A reactions probe the +A reactions probe the nuclear matter at (max.) nuclear matter at (max.) normal normal nuclear densitynuclear density

•vector mesons are produced vector mesons are produced dominantly at the surface and travel dominantly at the surface and travel through the nuclei through the nuclei medium effectsmedium effects

• about ½ of about ½ of ‘s decay ‚outside‘, i.e. ‘s decay ‚outside‘, i.e. in the vacuum in the vacuum experimental experimental separation of separation of in- and out- componentsin- and out- components by implementing low momentum cuts by implementing low momentum cuts ( (as suggested in as suggested in W. CassingW. Cassing,, Y.S. Golubeva, Y.S. Golubeva, A.S. Iljinov, A.S. Iljinov, L.A. KondratyukL.A. Kondratyuk, Phys. Lett. B 396 , Phys. Lett. B 396 (1997) 26(1997) 26 ))

-10 -8 -6 -4 -2 0 2 4 6 8 100

2

4

6

8

10

12

14

z [fm]z [fm]

p+Pb, 2.5 GeV

b [f

m]

-10 -8 -6 -4 -2 0 2 4 6 8 100

2

4

6

8

10

12

14

p+Pb, 3.5 GeV

b [f

m]

-10 -8 -6 -4 -2 0 2 4 6 8 100

2

4

6

8

10

12

14

+Pb, 2.5 GeV

-10 -8 -6 -4 -2 0 2 4 6 8 100

2

4

6

8

10

12

14

+Pb, 1.17 GeV

+A vs. p+A reactions : in-medium effects+A vs. p+A reactions : in-medium effects

0.0 0.2 0.4 0.6 0.8 1.010-1

100

101

102

103

104

105

0.4 0.5 0.6 0.7 0.8 0.9

101

102

p+Nb, 3.5 GeVcollis. broadening + dropp. mass


d/d

M [

b G

eV-1]

d/d

M [

b G

eV-1]

M [GeV/c2]

HSD: free coll. broad. coll. broad. + dropp. mass

p+Nb, 3.5 GeV

M [GeV/c2]

p+Ap+A and and +A+A reactions: in-medium effects – comparable reactions: in-medium effects – comparable

p+Ap+A reactions: probe dominantly baryon+baryon dynamics reactions: probe dominantly baryon+baryon dynamics

+A+A reactions: probe dominantly meson+baryon dynamics reactions: probe dominantly meson+baryon dynamics

0.4 0.6 0.8 1.010-7

10-6

10-5

10-4

0.4 0.6 0.8 1.010-7

10-6

10-5

10-4


dN/d

M [

GeV

-1]

+ C, 1.4 GeV

dN/d

M [

GeV

-1]

M [GeV/c2]


+ Au, 1.4 GeV

M [GeV/c2]

A+AA+A

reactionsreactions

SummarySummary

What systems ( What systems ( +N or +N or +A)? - physics key issues+A)? - physics key issues

+A reactions: +A reactions:

• in-medium effects - collisional broadening and dropping in-medium effects - collisional broadening and dropping mass of the vector mesons mass of the vector mesons

•study of the mesonic and baryonic resonance dynamics study of the mesonic and baryonic resonance dynamics

+p(n) reactions: +p(n) reactions:

• control on different elementary channelscontrol on different elementary channels

• study of the baryon resonance dynamics study of the baryon resonance dynamics near thresholdnear threshold

• quantum interference of 0 and -mesons at low energies

possible ONLY forpossible ONLY for+p(n) reactions!+p(n) reactions!

impact onimpact on+A, A+A+A, A+A

ThanksThanks to to

HADES collegues: HADES collegues:

Beatrice, Yvonne, Gosia, Romain, Beatrice, Yvonne, Gosia, Romain, Piotr, Joachim, Tatyana, Volker …Piotr, Joachim, Tatyana, Volker …

+ + WolfgangWolfgang

Documents

Dilepton cocktail in p +A experiments