Studying hadron properties in baryonic matter with HADES „Nuclear matter at High densities”...
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Studying hadron properties in baryonic matter with HADES
„Nuclear matter at High densities” Hirschegg 18-25.01.2009
P. Salabura
Jagiellonian University/GSI for the HADES collaboration
23.01.2009 P.Salabura
Study of hadron properties in dense and hot nuclear matter
Dense matter Freeze-outA+A @ 1-2 AGeV
HADES case:
Probes:
dielectrons penetrating probes-direct access
to in medium hadron masses : vector mesons
(/e+e-)
strangeness production (, K , ) EOS(see
C.Sturm talk), K-N potentials
Strategy: Systematic spectroscopy in proton, pion and heavy ion induced reactions
TC~170 MeV
mB
HADES @ SIS
Nucleus te
mp
erat
ure
Quark Matter
Hadron Resonance Gas
DLS @ Bevelac
CERES, NA60 (SPS)
T
940 MeVbaryon chemical potential
thermal freeze out
chemical freeze out
KEK,JLAB, TAPS
PHENIX (RHIC)
CBM/FAIR
Goal: learn about properties of dense matter in collision zone• new forms of matter ? • properties of hadrons in matter
e+ e-e+ e-
1
Gross properties of the baryonic matter (from transport models)
23.01.2009 P.Salabura
freeze-out
Au+Au
1-2 AGeV : moderate densities but long system life time
Baryonic matter: • /N = 1-3, T< 80 MeV, ~12-14 fm/c
nucleons, baryonic resonances (~30%) 33 mesons(π0)~10% “resonance matter”
• abundances reach maximum at ~2-3B
• long lived sources π0/ decay outside fireball
• short lived resonances / (c1.3 fm/c) –absorption (NNN or NNπ)!
• dielectron emission over full history of coll….
„ALL – freeze-out”= in-medium
• Sub-threshold production of heavy mesons : Multi-step processes (K-) , Resonance decays ,N*N/
• for dielectrons x BR ~10-4 !
S.Vogel et al. (URQMD) arXiv:0710.4463v2
E.Bratkovskaya W. Cassing (HSD)
2
Pair excess in URHIC collisions
23.01.2009 P.Salabura
• D. Adamova, et al., subm. to PLB, nucl-ex/0611022
• large pair excess over yield from the “freeze-out”Main source (not for RHIC !) π+π-e+e-(+-)
in-medium spectral functions
What about baryon rich matter?(pion densities 5-6 lower as compared to SPS!)
sNN=17.4 GeV
submitted to Phys. Lett.B
arXiv: 0802.0050
3
23.01.2009 P.Salabura
Pair excess at low energies?
low mass (0.14<Mee< 0.6 GeV/c2) pair excess @ 1AGeV ("DLS" puzzle")
Calculation: E.L.Bratkovskaya et al.Phys. Lett. B445 (1999) 265
Calculation: Ernst et al.Phys. Rev. C58 (1998) 447
1 AGeV
Calculation: C. Fuchs et al. Phys. Rev. C68 (2003) 014904
DLS Data: R.J. Porter et al.: Phys.Rev.Lett. 79 (1997) 1229
Status before HADES era:
no explanation for pair excess in light and medium HI systems!
4
Side View
START
FW
5
High Acceptance Di-Electron Spectrometer
Beams from SIS18: pions, protons, nuclei
Spectrometer with high invariant mass resolution (2% at / mass) and powerful PID capabilities : p/π/K/e
Versatile detector for rear particle decays :
• dielectrons (e+,e-)
• strangeness: , K,0 ,
GeometryFull azimuth, polar angles 18 - 85 e+e- pair acceptance 0.35~ 80.000 channels, segmented solid or LH2 targets
1 m
23.01.2009 P.Salabura
6
Experimental campaigns
p+p
1.25 GeV (2006)
2.2 GeV (2002)
3.5 GeV (2007)
d+p
C+C
2.0 AGeV (2002)
1.0 AGeV (2004)
1.25 GeV (2007)Ar+KCl
1.75 GeV (2005)
p+Nb
3.5 GeV (2008)
p+p
„Anomalous” excess of e+e- pairsin 0.15 < Mee < 0.5 GeV/c2
NN-Bremsstrahlungand Dalitz decays
vector mesons / in-medium
p+p
Resonance (,N*) production Form-factors and studies of / Dalitz decays (helicity angles)
Strangeness: , K±,0, production in HI
23.01.2009 P.Salabura
N+N
N
()
re+
e-
e +e -
N
e+
e-
e+
e-
7
Cocktail A („background”) “long-lived sources at freeze-out” π0 → e+ e- , η → e+ e- Dalitz ω → e+e- (direct) , ω →e+e- π0 (dalitz)π0/ yield fixed by measurement(TAPS)
Cocktail B: Cocktail A + Δ + ρ = “short-lived” resonances Δ → e+ e- N (Dalitz decay) N(Δ) =3/2 N( π0) – fixed to „freeze-out” abund.
ρ → e+e- (direct)
Definition of „pair excess”
cocktail: thermal source PLUTO event generator I. Froehlich et al.,arXiv:0708.2382 Excess – pair yield above A
-> medium AND first chance coll.
23.01.2009 P.Salabura
23.01.2009 P.Salabura
Inclusive e+e- from C+C collisions A. Agakichiev Phys.Rev. Lett 98(2007) 052302 A. Agakichiev Phys. Lett. B 663 (2008) 43
NNN
2
10
NORMALIZATION: N± from the same data sample
(M
ee)
~9
% a
t Me
e~0
.8 G
eV
/c2
syst. error (27%)syst. error (21%)
8
23.01.2009 P.Salabura
Beam energy dependence of the excess
Y
Y
Y
YYF excexc
1
• enhancement scales like pions !
• Baryon resonance decays? N-N bremsstrahlung?
F(2.0) = 1.9 ± 0.2(stat) ± 0.3(sys) ± 0.3( sys)F(1.0) = 6.8 ± 0.6(stat) ± 1.3(sys) ± 2.0( sys)
TAPS collab.
Z.Phys. A 359 (1997) 65 Phys.Rev. C 56 (1997)
R2920
9
23.01.2009 P.Salabura
N-N Bremsstrahlung
E.L. Bratkovskaya and W. Cassing arXiv:0712.0635v1
NN ("quasielastic")-non resonant
• Strong + electromagnetic process (OBE models)
1
2
e+
e- + =
resonant -baryon resonances ()
1
2
+
collection of results from E.L Bratkovskaya & W. Cassing: Nucl.Phys A 807, 214 (2008).
• bremsstrahlung OBE calculations:
Kaptari & Kämpfer, NPA 764 (2006) 338:
K&K OBE calculation:
pn bremsstrahlung 4 larger
(simplified picture!)
10
23.01.2009 P.Salabura
Comparison with up-to-date HSD
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
C+C, 1.0 A GeVno medium effects
1/N
dN
/dM
[1
/GeV
/c2 ]
HSD: Dalitz Dalitz Dalitz Dalitz Brems. NN Brems. N All
M [GeV/c2]
HADES
C+C, 1.0 A GeVin-medium effects: CB+DM
1/N
dN
/dM
[1
/GeV
/c2 ]
M [GeV/c²]
HSD: E.L. Bratkovskaya and W. Cassing Nucl.Phys A 807, 214 (2008).
New treatment of Bremsstrahlung: L.P. Kaptari and B. Kämpfer, Nucl.Phys. A 764 (2006) 338
DLS Data: R.J. Porter et al. Phys.Rev.Lett. 79 (1997) 1229
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]
Brems. NN Brems. N All
DLS
Dalitz Dalitz Dalitz Dalitz
C+C, 1.04 A GeVno medium effects
d/d
M
[b/
(GeV
c2 )]
M [GeV/c²]Does Δ and Bremsstrahlung explain excess? verification in NN collisions is needed
11
Reference reaction: dielectrons from pp and “quasi-free” pn @ 1.25 AGeV
23.01.2009 P.Salabura
Model Calculations:a) NN-bremsstrahlung Kaptari & Kämpfer (K&K)
b) , yield constraint by data. Dalitz decay Krivoruchenko et al. Phys. Rev. D 65 (2001) 017502 + VMD form-factor (Q. Wan and F. Iachello, Int. J. Mod. Phys. A 20 (2005) 1846)
pn data are not described by calculations !
12
13
C+C @ 1 AGeV – pp & pn @ 1.25 GeV
• Dielectron spectrum from C+C given as superposition of NN collisions !
no indications for in-medium effects ! (at least for C+C)
• What about larger systems ?
spectra normalized to 0
yield in C+C and NN
Absolute scale:
• C+C @ 1 AGeV<M>/Apart = 0.056 ± 0.007
• N+N @ 1.25 (A)GeV
<MNN >/Apart 0.093
but for N+N @ 1.00 (A)GeV
<MNN >/Apart 0.06
23.01.2009 P.Salabura
Ar+Kcl @ 1.75 AGeV
15
centrality : <b>LVL1 = 3.5 fm Number of participating nucl. <Apart> 38.5 ±4
Thermal source model Transport (HSD) N =3/2 N
0 for propagation in matter accounted
estimate of at freeze-out (much larger yield) mT scaling NN bremsstrahlung : not important
at this energy
PRELIMINARY
E.L. Bratkovskaya and W. Cassing Nucl.Phys A 807, 214 (2008).
23.01.2009 P.Salabura
Excess vs beam energy and system size
15
• Excess scales with (Apart) , >1 (~2)
multistep processes?
NN->N, ->N, N->
Resonance radiation is the dominant source
of e+e- yield!
PRELIMINARY
• Apart dependence need more studies :
Au+Au @ 1 AGeV vs C+C @ 1AGeV (2010)
Ni+Ni @ 1.93 AGeV – dilepton mass
dependence
inclusive meson production (TAPS data)(min. bias)
e+e- pair excessHADES DLS
ArkCl <Apart> = 19 vs. CC <Apart> = 6
23.01.2009 P.Salabura
23.01.2009 P.Salabura
Vector mesons in medium
16
Vector mesons in medium
23.01.2009 P.Salabura
Na60: R. Arnaldi et al., PRL 96 (2006) 162302
calculations: H. van Heesand R. Rapp, PRL 99 (2006) 102301, R. Rapp, J. WambachEPJA 6 (1999) 415
CERES D. Adamova et al. nucl-ex/0611022
• SPS energies: broadening due to interactions with hadronic medium (baryons are more important !)
• What is the situation at lower energies?
• No unique evidence for in medium modifications from p+A or +A reactions (CLAS/KEK/CBTAPS)
17
Vector mesons / at SIS
p+p at 3.5 GeV
PRELIMINARY
h
Dr
2005
40Ar+ 38KCl 1.75 AGeVp+ 92Nb 3.5 GeV
w
20072008“on-line spectrum!”
• Data are available! • No quick answer to the question on in-medium / spectral function ! • Only comprehensive analysis (in progress) of the pp/p+A/and A+A can give full
picture
resonance contribution?
What is K-N potential ?
23.01.2009 P.Salabura
• K+ potential seems to be slightly repulsive-> confirmed also by K0 pt distributions)• Precise data on K- /K0 flow can be provided byFOPI , HADES (2009,2010)
18
K- Production at SIS energies
NNNNKNNKNN
K- Production in HI reactions
Similar scaling of K+ and K- Mesons as a function of Apart
correlated production via strangeness-exchange
or Strangeness Exchange? belived to be dominant (KAOS data)
NK
NKNN
non-resonant resonant (->K+K- )
• important to clarify for prediction of in-medium effects on K± production ( rates, flow phenomena)
NNNKNKN
sub-threshold in NN (Ethreshold 2.6 GeV) !
secondary reactions (in-medium)
B.Kampfer et. al Phys. G: Nucl. Part. Phys. 28 (2002) 2133–2136, 2035-2040
23.01.2009 19P.Salabura
K+ K- , differential production rates
23.01.2009 P.Salabura
• for the first time measured in the same (large) acceptance
• /K- =0.340.13 ~17% K- comes from !… but there is also non-resonant part!
MeV884)( yTB
M =1017,8 ± 0.9 MeV/c2
= 6.2 MeV/c2
20
K-/ ratio
23.01.2009 P.Salabura
Statistical model K. Redlich, H. Oeschler-priv.comm
• For NN at threshold /K- = 1.02±0.1 ANKE coll. PHYS. REV. C 77, 015204 (2008)
• /K- in Ar+KCl is ~ 3 smaller -> more K- thanks to medium (i.e strangeness exchange)
• …but reactions of the type NN->NN and NN->NNK+K- (non-resonat) is important,too !
• Agreement with Kaon systematics
21
23.01.2009 P.Salabura 22
Outlook: future exp.Upgrade RPC, DAQ, MDC1, EM Calorimeter (for SIS100)2008/9/10
Hades goes to FAIR ( 8 AGeV)> 2013 (SIS100)
2011
p + N, p + A resonance (, N*) radiative decays, strangeness
2010
Ni + Ni @ Au+Au dielectrons (/), strangeness (K-K+)2009-2011
SIS18
increase of Mul(/) by 2 orders of magnitue !!
CBM
HADES
23.01.2009 P.Salabura
Outlook and summary:Radiation from nuclear matter at 1-2 AGeV :• at low energy ( 1 AGeV) first chance NN colisions are important source of pairs
(pn- bremsstrahlung? strong isospin effect pp vs pn!)• small systems (i.e C+C) can be described by superposition of NN collisions• for larger systems (i.e Ar+KCl) and larger energies strong contribution from „resonance
matter”” () visible with non-linear Apart dependence
• In medium masses• strong (broadenning) modification of meson spectral function at SPS energies• vector mesons observed for a first time at SIS/Bevalac energy regime• / region measured with good precision – possibility to search for in-medium
modifications of v.m. spectral functions• K- in medium mass accessible only via indirect observables (flow,rates)- reaction
mechanism must be known accurately (strangeness exchange)
• Outlook >2009 - HI collisions (Au+Au/Ni+Ni) at SIS18 and pion physics
>2012 - HADES at FAIR
Conference
23.01.2009 P.Salabura 26
The Collaboration
GSI
SIS
Catania (INFN - LNS), Italy
Cracow (Univ.), Poland
Darmstadt (GSI), Germany
Dresden (FZD), Germany
Dubna (JINR), Russia
Frankfurt (Univ.), Germany
Giessen (Univ.), Germany
Milano (INFN, Univ.), Italy
München (TUM), Germany
Moscow (ITEP,MEPhI,RAS), Russia
Nicosia (Univ.), Cyprus
Orsay (IPN), France
Rez (CAS, NPI), Czech Rep.
Sant. de Compostela (Univ.), Spain
Valencia (Univ.), Spain
Coimbra (Univ.), LIP, Portugal
23.01.2009 P.Salabura
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