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Recent HADES results. P. Salabura M. Smoluchowski Institute of Physcis Jagiellonian University. 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

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Recent hades results

Recent 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


E e sources at sis18 energies
e+e-sourcesat SIS18 energies

excitation function !

isospin effects Ebeam < 2 AGeV

° e+e-

e+e- 

HADES PRC85 (2012) 054005

e+e-

DLS: PRC57 (1998)1867

, 

Ne+e-

1 2 3 4 5 Ebeam (GeV)



Me+e->M0

  • 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 + /

~2

Understanding of Baryon Sources is essential for HADES physics


Inclusive e e production in pp @ 2 2 and 3 5 gev
Inclusive e+e- productioninpp @ 2.2 and 3.5 GeV

3. 5 GeV

2.2 GeV

HADES EPJA48 (2012) 64

HADES PRC85 (2012) 054005

  • 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


E e p t distributions
e+e- pTdistributions

p+p @ 3.5 GeV

sensitive to / contributions !


P p vs p nb @ 3 5 gev
p+pvsp+Nb @ 3.5 GeV

data: HADES PLB715 (2012) 304

„fast” pe+e->0.8 GeV/c

„fast” pe+e-< 0.8 GeV/c

Nuclear modification factor

pp data scaled by

„Apart” scaling

  • 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


Rapidity distributions pp vs pnb @ 3 5 gev
RapiditydistributionsppvspNb @ 3.5 GeV

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


E e excess in p nb low p e e
e+e- excessinp+Nb : lowpe+e-

„slow” (p<0.8 GeV/c) pairs

„excess over pp reference”

Rpa vs momentum

Me+e

  • 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),..) NNe+e- (see J. Weil talk)

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


0 production in p nb @ 3 5 gev with conversion method
0 /  productioninp+Nb @ 3.5 GeVwithconversionmethod

HADES (2013) arXiv:1305.3118

mT scaling of light mesons

Total detection probability 10-6 -10-7 !

Similar analysis

for p+p in progress!


0 p t distribution yields compared to transport
0/ pTdistribution/yieldscompared to transport

EXP (4):

0


E e sources in pp @ 3 5 gev
e+e- sourcesinpp @ 3.5 GeV

J.Weil:

EPJA48 (2012)111

E. Bratkovskaya et. al.:

arXiv:1301.0786v1

  • 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-Dalitzdecay

QCD

QED

  • „point-like” N e- e +

  • exact field theory calculation

  • 3 independent amplitudes:

  • e.g. Electric, Magnetic and Coulomb

electromagnetic form factors

GM(q2),GE(q2),GC(q2)

spin flip

„pion cloud”

e+

I.G. Aznauryan andV.D. Burkert,

Prog. Part. Nucl. Phys.67 (2012)

q

„quark core”

q

q

e-

« Photon point » : q2=0

GM(0)=3, GE(0)=GC(0)~0

Jones and Scadron convention


N e e two component pion cloud quark core models
Ne+e- : twocomponent (pion cloud+quarkcore) models

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

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

cloud/core ~ 0.99/0.01

cloud/core ~ 0.44/0.56

M=1.8

QED

QED

M=1.5

M=1.23

Mee [GeV/c2]

  • pion cloud /core contribution affects strongly Q2 dependence of eTFF  VDM

  • T. Pena - higher resonances in work..


Higher resonances
Higherresonances..

QED: point-like R-* vertex

M. Zetenyi et al. PRC 67, 044002 (2003)

constraints from R->N

Resonance model

GiBUU, UrQMD, BUU,HSD ..

extended VDM:

M. I. Krivoruchenko et al.

Ann. Phys. 296, 299 (2002).

example:J. Weil EPJA 48(2012)111

„factorization”

eTFF (Mee)


Baryon resonaces in p p@3 5 gev
Baryonresonacesin [email protected] GeV

  • Goal: Study 3 connected exclusive channels:

  • pppp0and pppn+ to fix R (,N*) cross sections

  • Convert Rpe+e- and check in pp pp e+e-

  • 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)

BR(Rpe+e-) : „QED” point-like R-* vertex

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

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


One pion production
One pion production

A.Dybczak phd Kraków (2013)

pn+

  • Acceptance corrected spectra

  • ++ (1232) dominates !

  • excelent description of -line shape („Moniz” FF)

pp0

  • +(1232), N*(1440),N*(1520),..

P.Salabura


Exclusive production in pp @ 3 5 gev
exclusive / productioninpp @ 3.5 GeV

K.Teilab phd Frankfur (2011)

=

=

N* (1535) fixed from  Dalitz plot

N* (1535) ->p BR(42%)

N*(1535) = 1520.15 [mb]


Results for ppe+e- channel

„QED” : point like RN* vertex

  • 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 1232 etff
eVDM and (1232) eTFF

eTFF from

Iachello, Wan

saturates the yield- no place left for other resonances

  • large ambiguities related to the resonance selection


Comparison to other parametrizations
Comparison to otherparametrizations

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

comparison to S. Teis

Preliminary

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

Resonances with BR(N)


RNNe+e-

Resonance XS and RN BR from UrQMD

Resonance XS and RN BR from GiBUU

Preliminary



E e pairs from ar kcl @ 1 756
e+e- pairsfromAr+KCl @ 1.756

Cocktail with „freeze-out” comp.

 component subtracted

data PRC84(2001)014902

  • 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 !


Au au may 2012
Au+Au May’2012

  • New RPC detector (180 << 450 )

  • New DAQ and read-out – 10 kHz data taking rate


Strangeness reconstruction
Strangenessreconstruction


Lepton id and purity
Lepton ID and purity

Single lepton purity

PID: Multi-Variante Analysis

Vertex reconstruction

electrons

hadrons


Summary
Summary

  • 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-, pp0 , pn+ show that off-shell -R coupling in R-> pe+e- isvery 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


The hades collaboration

SIS

The HADES collaboration

13 Institutions

Technical Proposal accepted 1995

First experiments 2001

  • 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

  • GSI

    P.Salabura


    Study of hadron properties in dense baryonic matter
    Study of hadron properties in dense baryonic matter

    • 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

    L. McLerran, R.D. Pisarski 2007

    • 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

    RHIC, BES

    Na61

    experiment: chemical freeze-out

    VDM

    CBM

    Fair

    Begun et. al. arXiv:1208.410

    HADES


    Resonance properties urqmd
    ResonancepropertiesUrQMD

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

    P.Salabura


    Baryon resonance structure

    N

    R

    g*

    e+

    r, w,

    e-

    Baryonresonancestructure

    Time-Like el.Transition Form Factors : Dalitz decays

    Space-Like el.Transition Form Factors

    n

    -

    e-

    R

    q2 <0

    p

    *

    e+

    *

    R

    p

    q2 > 0

    e-

    e-

    0

    e--

    p

    Vector Dominance Model

    studied at JLab/CLAS/MAMI,..

    pion electroproduction

    Dalitz Decays: poorly known !

     directly related to :

    e+e-NNe+e-

    Dalitz decays ,

    e-pe-N 

    Time Like domain : q2 >0

    Space Like domain

    q2 <0

    0

    q2


    E e from c c collisions and nn
    e+e- fromC+Ccollisions and NN

     contribution subtracted

    cocktail: „long lived sources”-freeze out

    data: HADES PLB690 (2010)118

    baryons

    PRL98(2007) 052302

    ratio CC/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


    Excess scaling with a part e beam
    ExcessscalingwithApart/Ebeam

    C+C

    Ca+Ca

    TAPS -

    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

    pspec

    pt

    Quasi freep+nreactionwithdeutron

    d

    spectator model

    X

    p

    n

    • average pn distance ~ 3 fm

    • total cross section reduced by ~8%

    • (p shadowing + meson absorption)

    Ek=1.25 AGeV

    momentum in deuteron rest frame


    Quasi free pn reactions in d p collisions

    pspec

    pt

    Quasi-free pn reactionsind+pcollisions

    spectator model

    d

    X=, , ..

    p

    n

    spectator on-shell

    CELSIUS: PRC58(1998)2667

    Ed=0.76 GeV

    Ep=1.35 GeV

    COSY-TOF EPJA29(2006) 353


    Spectator model at work q 100 mev
    Spectator model atwork (Q<100 MeV)

    p+d -> ps pn 

    d+p -> ps pp-

    p+d -> ps d

    COSY11, SATURNE, CELSIUS P. Moskal, nucl–ex/0110001 and

    P. Moskal PRC79(2009) 015208

    COSY-TOF EPJ. A 29, (2006) 353

    ANKE PRL 97 (2006)142301

    pspectator momentum

    MC

    ( NN pot)

    • overall good agreement with spec. model

    p+d -> ns pp


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

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

    ppe+e-

    npe+e-

    • excess in np reaction visible also in exclusive channels (note: no  contribution! )

    • missing mass spectra reproduced by simulation

    ppppe+e-

    npnpe+e-

    Me+e- >M0

    Me+e- >M0


    Inclusive e e n p qf vs pp
    Inclusive e+e- (n+p)QFvspp

    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

    pion eTFF :

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

    p

    p

    n

    p

    e+

    π0

    ρ

    π+

    ρ

    e+

    e-

    e-

    π0

    π-

    p

    p

    n

    p


    E e in p p @ 1 25 gev
    e+e- inp+p @ 1.25 GeV

    inclusive

    Mainsource: pe+e- Dalitz decay

     production not possible – belowthreshold

    GM (q2) VMD

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

    Calculations: Vector Meson Dominance Krivoruchenko et al. PRD 65 (2001) 017502

    G. Ramalho and T. Pena arxiv: 1205.2575v1 (2012)

    F. Dohrmann et al., Eur. Phys. J. A 45, 401 (2010)

    HADES: PLB690 (2010)118

    p

    p

    • 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..

    p

    p

    D+

    *

    e+


    Emissivity of baryonic matter
    Emissivity” of baryonicmatter

    Dense matter : 3*B ~ 0.5/fm3

    30% baryon resonances 33

    pions (T~ 80 MeV)

    e+

    Vacumm

    e-

    RNe+e-

    pion cloud

    e+

    e+

    e+

    q

    q

    q

    q

    q

    q

    q

    q

    q

    e+

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    q

    -

    e-

    e-

    e-

    e-

    qq

    -

    qq

    How does the radiation from overlaping baryons looks like?


    Transparency ratio in cold matter

    in-medium width

    Transparencyratioin „coldmatter”

    • „disapearance of meson in nuclear matter”

    Glauber Picture;

    CabreraNPA733(2004)130

    Production AbsorptionFSI of decay products

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

    • normalization to C to

    • reduce nuclear effects

    absent for e+e-


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