Recent HADES resultsRecent HADES results

P. Salabura

M. Smoluchowski Institute of Physcis

Jagiellonian University

HADES 2010-2013 results HADES 2010-2013 results

• e+e- production in p+p, p+A @ 3.5 GeV

Vector meson and in (cold) nuclear matter Baryon Resonance decays

• e+e- production in HI collisions: status of Au+Au data

3

e+e-e+e- sources at SIS18 energies sources at SIS18 energies

• Me+e- < 0.15 GeV/c2 dominated by 0 Dalitz

• 0.15 < Me+e- < 0.55 GeV/c2 : Resonance (, N*)Ne+e- (Dalitz decays)

NN-bremmstrahlung, and e+e- decays ! • M > 0.55 GeV/c2 : Resonance (, N* ) Dalitz decays + /

° e+e-

e+e-

Ne+e-

e+e-

,

Understanding of Baryon Sources is essential for HADES physics

~2

Me+e->M

0

excitation function ! isospin effects Ebeam < 2 AGeV

DL

S: P

RC

57

(19

98

)18

67

1 2 3 4 5 Ebeam (GeV)

HA

DE

S P

RC

85

(20

12

) 05

40

05

Inclusive e+e- production inInclusive e+e- production in pp @ 2.2 and 3.5 GeV pp @ 2.2 and 3.5 GeV

• Unexplained yield excess above exp. cocktail below VM pole • At 3.5 GeV : 0 Dalitz decay fixed by data

and resonance (, N* ) not easy to isolate ! higher resonances? / fixed to some extent by exclusive pp data (hadronic channels) and clear peak

2.2 GeV 3. 5 GeVHADES PRC85 (2012) 054005 HADES EPJA 48 (2012) 64

e+e- pe+e- pT T distributions distributions

p+p @ 3.5 GeV

sensitive to / contributions !

p+p vs p+Nb @ 3.5 GeVp+p vs p+Nb @ 3.5 GeV

• large acceptance at small Me+e- and p (<1 GeV/c) ( first measurement at low p !)

• for slow e+e- : excess emerges above pp reference , peak less pronounced

pp data scaled by„Apart” scaling

„fast” pe+e->0.8 GeV/c „fast” pe+e-< 0.8 GeV/c

Nuclear modification factor

data: HADES PLB715 (2012) 304

Rapidity distributions pp vs pNb @ 3.5 GeVRapidity distributions pp vs pNb @ 3.5 GeV

p+Nb:clear shift towards target rapidity for M>M

e+e- excess in p+Nb : low pe+e- excess in p+Nb : low pe+e-e+e-

„excess over pp reference”„slow” (p<0.8 GeV/c) pairs

RpA (vs p) – increase at small momenta : largest for the „-region”

BUT NOT for peak absorption (observed also by CBTAPS and CLAS in (+A) ) !

clear excess in p+A below VM pole

- secondary reactions : +N (1720,..)(N* (1520),..) NNe+e- (see J. Weil talk)

or/and in medium modification ? first the p+p reference must be understood !

Rpa vs momentum

Me+e

00 / / production in p+Nb @ 3.5 GeV with production in p+Nb @ 3.5 GeV with conversion method conversion method

Total detection probability 10-6 -10-7 !

mT scaling of light mesons

Similar analysis for p+p in progress!

HADES (2013) arXiv:1305.3118

00// p pTT distribution/yields compared to distribution/yields compared to

transporttransport

EXP (4):

0

e+e- sources in pp @ 3.5 GeVe+e- sources in pp @ 3.5 GeV

E. Bratkovskaya et. al.: arXiv:1301.0786v1

J.Weil: EPJA48 (2012)111

• Many uncertainties: inclusive cross sections , , , / (fixed now by HADES) pe+e- transition (Dalitz decay); rates, em. Transition Form-Factors - spectral function !

Ne+e- Dalitz decay Ne+e- Dalitz decay

„point-like” N e- e +

• exact field theory calculation • 3 independent amplitudes: e.g. Electric, Magnetic and Coulomb

QED QCD

GM

Exp=3.00.05

(N)

Exp=0.660.06

Wolf, Nucl.Phys. A517 (1990) 615

GM=3.0 0.22

Ernst, Phys.Rev C 58, 447 (1998)

GM=3.0 1.03

Krivoruchenko Phys.Rev.D 65 (2001), 017502

GM(0)=3.0 0.65

Zetenyi and Wolf, Heavy Ion Phys. 17 (2003) 27.

GM(0)=3.0 0.65Jones and Scadron convention

22

2

2

2222

232, qqq

Δf G

mq

GGqm C

Δ

EM2

-

dq

)eNe(Δd

„quark core”

„pion cloud”

qqq spin flip

e-

e+

electromagnetic form factors GM(q2),GE(q2),GC(q2)

« Photon point » : q2=0 GM(0)=3, GE(0)=GC(0)~0

I.G. Aznauryan andV.D. Burkert, Prog. Part. Nucl. Phys.67 (2012)

N e+e- : two component (pion cloud+quark core) modelsN e+e- : two component (pion cloud+quark core) models

Iachello, Wan: implemented for HADES by I. Froehlich et. EPJA 45, 401 (2010)

• pion cloud /core contribution affects strongly Q2 dependence of eTFF VDMT. Pena - higher resonances in work..

M. Pena, G. Ramahlo PRD85 (2012) 113014

QEDQED

cloud/core ~ 0.99/0.01cloud/core ~ 0.44/0.56

M=1.23 M=1.5

M=1.8

22

2

2

2222

232, qqq

Δf G

mq

GGqm C

Δ

EM2

-

dq

)eNe(Δd

Mee [GeV/c2]

Higher resonances.. Higher resonances..

QED: point-like R-* vertex

M. Zetenyi et al. PRC 67, 044002 (2003)constraints from R->N

extended VDM:

M. I. Krivoruchenko et al. Ann. Phys. 296, 299 (2002).

Resonance model

GiBUU, UrQMD, BUU,HSD ..

„factorization”

example:J. Weil EPJA 48(2012)111

eTFF (Mee)

Baryon resonaces in p+p@3.5 GeVBaryon resonaces in p+p@3.5 GeV

• Resonance model: production amplitude is given by incoherent sum

of Resonance contributions, isospin relations

Starting point: S. Teis R parametrization (S. Teis et al., Z. Phys. A356, 421 (1997).) , take 4* resonances +

empirical angular distributions (strong forward-backward peaking))(

)(MR t

AM

dt

d

Goal: Study 3 connected exclusive channels:

• pppp0 and pppn+ to fix R (,N*) cross sections• Convert Rpe+e- and check in pp pp e+e-

BR(Rpe+e-) : „QED” point-like R-* vertexM. Zetenyi and Gy. Wolf., Heavy Ion Phys. 17 (2003) 27.

For the overlaping resonances only one resonance with largest BR(N) selected

One pion productionOne pion production

P.Salabura

• Acceptance corrected spectra

pn+

pp0

• ++ (1232) dominates !excelent description of -line shape („Moniz” FF)

• +(1232), N*(1440),N*(1520),..

A.Dybczak phd Kraków (2013)

exclusive exclusive // production in pp @ 3.5 GeV production in pp @ 3.5 GeV

=

=

K.Teilab phd Frankfur (2011)

N* (1535) fixed from Dalitz plot

N* (1535) ->p BR(42%)

N*(1535) = 1520.15 [mb]

„QED” : point like RN* vertex

Results for ppe+e- channel

• Significant contribution from higher (than ) mass resonances

• Addtional strength below VM pole needed – off shell meson coupling ! – extended interaction vertex • low mass resonances : (1232), N(1440), N(1520) ?

eVDM and eVDM and (1232) eTFF(1232) eTFF

• large ambiguities related to the resonance selection

eTFF fromIachello, Wan

saturates the yield- no place left for other resonances

Comparison to other parametrizationsComparison to other parametrizations

Preliminary

comparison to S. Teis

Resonances with BR(N)

J. Weil et al. EPJA 48(2012)111

comparison to UrQMD: S. Bass Prog.Part.Nucl.Phys. 41 (1998) 225-370

Resonance XS and RN BR from UrQMD

RNNe+e-Resonance XS and RN BR from GiBUU

Preliminary

e+e- from HI collisions

e+e- pairs from Ar+KCl @ 1.756e+e- pairs from Ar+KCl @ 1.756

Cocktail with „freeze-out” comp.

first ->e+e- observation at SIS18 energies

first evidence for „true” excess above NN and light CC systems

Excess yield scales with system size ~ Apart1.4 multistep processes?

let’s see Au+Au !

component subtracted

data PRC84(2001)014902

Au+Au May’2012Au+Au May’2012

• New RPC detector (180 << 450 )• New DAQ and read-out – 10 kHz data taking rate

Strangeness reconstruction Strangeness reconstruction

Lepton ID and purityLepton ID and purity

Conference

Single lepton purity

Vertex reconstructionPID: Multi-Variante Analysiselectrons

hadrons

SummarySummary

Precise e+e- data collected for pp/pNb @ 3.5 GeV

evidences for interesting physics („excess” below VM pole) Intepretation is challanging !

- pp reference net (yet) well understood

exclusive ppe+e-, pp0 , pn+ show that off-shell -R coupling in R-> pe+e- is very important

- inclusive production is possible with conversion technique !

IT IS IMPORTANT REFERENCE system for HADES at FAIR

HADES made succefull Au+Au @1.23 GeV campaign• single track and resonance (hadron) reconstruction shows great data

quality• e+e- spectra are very close to be produced

23.01.2009 P.Salabura 28

GSIGSI

SISSIS

The HADES collaborationThe HADES collaboration

Cracow (Univ.), Poland

Darmstadt (GSI), Germany

Dresden (FZD), Germany

Dubna (JINR), Russia

Frankfurt (Univ.), Germany

Giessen (Univ.), Germany

München (TUM), Germany

Moscow (ITEP,RAS),

Russia

Nicosia (Univ.), Cyprus

Orsay (IPN), France

Rez (CAS, NPI), Czech Rep.

Sant. de Compostela (Univ.), Spain

LIP, Portugal

13 InstitutionsTechnical Proposal accepted 1995First experiments 2001

Study of hadron properties in dense baryonic matter

Probes:

dielectrons :

sensitive probe of extended baryon structure

-medium modifications ?

meson in medium properies

Multistrange baryons: -(1321),

Strategy:

Systematic measurements

in p +p, p+A and A+A at 2- 8 AGeV

experiment: chemical freeze-outRHIC, BES Na61

CBMFair

HADES

L. McLerran, R.D. Pisarski 2007 • The case of Large B and moderate T :

interesting region in phase diagramme with a large

discovery potential

not probed experimentally by means of rare

penetrating probes

VDMBe

gu

n e

t. al. a

rXiv:1

20

8.4

10

Resonance properties UrQMDResonance properties UrQMD

23.01.2009 P.Salabura Conference

S. Bass Prog.Part.Nucl.Phys. 41 (1998) 225-370

Baryon resonance structureBaryon resonance structure

pe-

e-e-

*

0

R

p

Space-Like el.Transition Form Factors

q2 <0

studied at JLab/CLAS/MAMI,..

Time-Like el.Transition Form Factors : Dalitz decays

e+

n

e--

*

-

p

R

q2 > 0 e+

e-

RN

e-pe-N

Space Like domainq2 <0

Time Like domain : q2 >0

e+e- NNe+e-

0 q2

Dalitz Decays: poorly known !pion electroproduction

Dalitz decays ,

directly related to :

Vector Dominance Model

e+e- from C+C collisions and NNe+e- from C+C collisions and NN

NN=1/2(np+pp) –reference- and C+C normalized to the individual N(0 )=1/2(N(+) + N(-))

e+e- subtracted („long lived” source) - cross section known from other exp.( TAPS)

C+C data (1 and 2 AGeV !) reproduced (within 20%) by NN reference up to 0.45 GeV/c2 –

no room (within error bars) for in-medium effects

data: H

AD

ES

PLB

690 (2010)118

contribution subtracted

PR

L98

(20

07

) 05

23

02ra

tio

CC

/NN

cocktail: „long lived sources”-freeze out

baryons

Excess scaling with AExcess scaling with Apartpart/E/Ebeambeam

C+CCa+CaTAPS -

HADES, DLS e+e-

• Baryonic sources : (1232) ~10-20%, N(1535,..)- 1-2%, N–N bremsstr..

excitation function similar in shape to pions

Quasi free p+n reaction with deutron Quasi free p+n reaction with deutron

• average pn distance ~ 3 fm• total cross section reduced by ~8%(p shadowing + meson absorption)

pspec

pt

dd

nn

Xp

spectator model

Ek=1.25 AGeV

momentum in deuteron rest frame

Quasi-free pn reactions in d+p collisions Quasi-free pn reactions in d+p collisions

pspec

pt

dd

nn

p

X=, , .. spectator model

spectator on-shell

CO

SY

-TO

F E

PJA

29

(20

06

) 3

53

CELSIUS: PRC58(1998)2667

Ep=1.35 GeVEd=0.76 GeV

Spectator model at work (Q<100 MeV)Spectator model at work (Q<100 MeV)

COSY-TOF EPJ. A 29, (2006) 353COSY11, SATURNE, CELSIUS P. Moskal, nucl–ex/0110001 andP. Moskal PRC79(2009) 015208

d+p -> ps pp-

p+d -> ns pp

p+d -> ps d

ANKE PRL 97 (2006) 142301

pspectator momentum

MC( NN pot)

p+d -> ps pn

• overall good agreement with spec. model

exclusive channel: np.exclusive channel: np.npe+e- npe+e-

ppe+e-npe+e-

Exclusive (e+e-) - one proton e+e- in HADES

Me+e- >M0 Me+e- >M0

npnpe+e- ppppe+e-

• excess in np reaction visible also in

exclusive channels (note: no contribution! )

• missing mass spectra reproduced by

simulation

Inclusive e+e- (n+p)Inclusive e+e- (n+p)QFQF vs pp vs pp

calculations: R. Shyam and U. Mosel Phys. Rev. C 82:062201, 2010 data: HADES PLB690 (2010)118 • excess np. over pp !

R. Shyam and U. Mosel Phys. Rev. C 82:062201, 2010

due to eFF of charged pion

charge pion exchange & pion eFormFactor

p n

π+

π-

ρ e+

e-

n p

p p

pp

π0

π0

ρ e+

e-

pion eTFF : W. Weise, G. Brown, M. Rho NPA 474(1986)669

e+e- in p+p @ 1.25 GeVe+e- in p+p @ 1.25 GeV

Main source: pe+e- Dalitz decay production not possible – below threshold

Time Like (q2 >0) (J=3/2) ->N (J=1/2) * transition:

Calculations: Vector Meson Dominance Krivoruchenko et al. PRD 65 (2001) 017502G. Ramalho and T. Pena arxiv: 1205.2575v1 (2012)F. Dohrmann et al., Eur. Phys. J. A 45, 401 (2010)

• 0 , fixed by 1 pion exclusive production : HADES EPJA48(2012) 74

BR (Ne+e-) 4*10-5 agrees with model predictions.

G(q2 ) dependence not very essential at this low energy..

HADES: PLB690 (2010)118

GM (q2) VMD

+

p

e+*

p

p

p

inclusive

„„Emissivity” of baryonic matterEmissivity” of baryonic matter

qqq pion cloud

e+

e-e-

e+

Vacumm

qqq

e-

e+

qqq

e-

e+

Dense matter : 3*B ~ 0.5/fm3

30% baryon resonances 33

pions (T~ 80 MeV)

qq- q

qq

qqq

qqq

qqq

qq-

qqq

RNe+e-

e+

e-

How does the radiation from overlaping baryons looks like?

qqq

Transparency ratio in „cold matter”Transparency ratio in „cold matter”• „disapearance of meson in nuclear matter”

)'()))(,(Im1

exp()( '

0

3 rrPrqdlqd

drrdd

medium

NA

in-medium width

VXN

VXAA AT

Production Absorption FSI of decay products

ISI (not for ), Pauli-blocking, Fermi-motion, secondary processes, shadowing ….

normalization to C to reduce nuclear effects

)(Im)(

qqcoll

absent for e+e-

Glauber Picture;CabreraNPA733(2004)130

||'

q

qlrr