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HADES experiments investigating in-
medium hadron properties
P. Salabura
Jagiellonian University
for the HADES collaboration
Study of hadron properties in dense and hot nuclear matter
Rear Probes:
dielectrons penetrating probes
emissivity and in medium hadron masses :
vector mesons (/e+e-) chiral sym.
strangeness production : , K , (1321)
EOS, K in-medium potentials, …
Strategy:
Reference measurements in N +N
and A+A at 1-2 AGeV (<2015) and
in future at SIS100 8-10 AGeV (FAIR)
Goal: to cover interesting and not fully covered region of baryonic matter at low T • „emissivity” of compressed matter • hadron properties in matter
e+ e- e+ e-
K+
e+ e-
K-
experiment: chemical freeze-out
RHIC BES Na61
CBMFair
HADES
HADES @ FAIR
L. McLerran, R.D. Pisarski 2007
Side View
START
FWFW
High Acceptance DiHigh Acceptance Di-E-Electron Spectrometerlectron Spectrometer
Beams from SIS18: protons, nuclei , pions
Spectrometer with high invariant mass resolution - 2% at /
Versatile detector for rear probes :
• dielectrons (e+,e-)
• strangeness: , K,0 , -
• Upgrade(2010): new DAQ (20 KHz, Tof-RPC (tof ~80 ps)
GeometryFull azimuth, polar angles 18 - 85 e+e- pair acceptance 0.35~ 80.000 channels, segmented solid or LH2 targets
1 m
RPC (from 2010)
HADES programme (so far) HADES programme (so far)
• pp reactions
(1.25, 2.2, 3.5 GeV)dp reactions (1.25 GeV)
• nucleus + nucleus
C+C, Ar+KClAu+Au (2012)
• p + nucleus (Nb @ 3.5 GeV)
• e+e- production in N+N – reference reactions for A+A
• single and double production (barion resonances in N+N)
• , , production- hadr.channels and rear e+e- decays
(new UL in PDG)
• (1405) , (1385) (new PDG entry)
• K0 production
• low mas e+e- „excess” : (DLS puzzle, emissivity,..) • kaon production : K0
s • Hyperon production; , , (1321)• production• -p, p-p, , correlations
• / mesons in cold nuclear matter• strangeness production K,
Low mass e+e- excess : „DLS puzzle”Low mass e+e- excess : „DLS puzzle”
DLS data: R.J. Porter et al.: PRL. 79 (1997) 1229
Calculation: E.L.Bratkovskaya et al. PLB445 (1999) 265
before HADES (< 2008) HADES data projected in DLS acceptance
HADES data: Agakishiev et al., PLB 663 (2008) 43
HADES fully confirms DLS results
• What about „excess” ? Is it true in-medium effect ? or not understood elementary process?
N+N reference (I): e+e- in p+pN+N reference (I): e+e- in p+p
Important source: pe+e- Dalitz decay
Time Like (q2 >0) (J=3/2) ->N (J=1/2) * transition:
22
2
2
2222
232, qqq
Δf G
mq
GGqm C
Δ
EM2
-
dq
)eNe(Δd
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)
G(q2 ) ? el. Transition Form Factors : extented baryon structure !
complemenary to (space like) N ( data: JLAB/Mainz/Bates)
HADES: PLB690 (2010)118
qqq
e-
e+
pion cloud
e+
e-
GM (q2) VMD
+
p
e+*
p
p
p
e+e-
pe+e-
N+N reference (II): e+e- in n+p N+N reference (II): e+e- in n+p
calculations: R. Shyam and U. Mosel Phys. Rev. C 82:062201, 2010 data: HADES
• production – fixed by COSY, WASA data
• bremsstrahlung pnpne+e- (non resonant), why it is so
much different from pp?
R. Shyam and U. Mosel Phys. Rev. C 82:062201, 2010
charge pion exchange & pion eFormFactor
~2
DLS
Large isospin effect at 1-2 AGeV!
p
n
n
p
+
for example:
e+e-
yie
ld r
atio
dp/
pp
CC compared to NN reference. CC compared to NN reference.
NN and C+C normalized to the individual N(0 )
C+C data (1 and 2 AGeV !) reproduced (within 20%) by superposition of NN interactions
(reference) – 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
Vector mesons in medium- motivationVector mesons in medium- motivation
p - beams
SIS 18
SIS 200T [MeV] 300
LHC
RHIC
SPS
G.E. Brown / M. Rho: Scaling of masses with -condensate (PRL 1989, 1991)
T. Hatsuda / S. Lee: QCD sum rules PRC46(1992)R34
uqqqqmm **
how it begun..
second graph is related to elementary process:
hadronic many body interactions- spectral functions..
- meson at 2 x N
S. L
eupo
ld e
t al.
NP
A 7
41 (
2004
) 81
, NP
A 7
80 (
2006
) 18
7
Dalitz decay
prefered by data
Data : Na60 EPJC 59 (2009) 607calculations: Hess/Rapp: NPA806(2008)339.
Vector mesons in cold matter- experimentsVector mesons in cold matter- experiments
217 MeV
CLAS PRL 99 (2007) 262302 direct : meson line shape
• no mass shift• broadenning
• mass shift m*/m0 =1 – 0.09N/ 0
KEK-E325 PRL 96 (2006) 092301
CLAS: PRL 105 (2010) 0112301CBTAPS: PRL 100 (2008) 192302
absorption
VXN
VXAA AT
indirect: transparency
tot
eemesoneeeeN
large absorption
* tot, 210 MeV !
meson (SPRING8, ANKE)
* ~ 33 - 50 MeV
* N v VN
+A1.1-3.3 GeV
p+Cu 12 GeV
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 !)
• p+p cockail : based on known sources fixed to data 0 // / , with constant eTFF
underestimeted e+e- yield below VM pole missing component? -> higher resonances (, N*)
pp data scaled by„Apart” scaling
„fast” pe+e->0.8 GeV/c „fast” pe+e-< 0.8 GeV/c
Nuclear modification factor
data: arXiv:1205.1918 submitted to PRL
Fixing resonance contribution : exclusive Fixing resonance contribution : exclusive channels in p+p @ 3.5 GeVchannels in p+p @ 3.5 GeV
pn+ pp0
ppe+ e-
Preliminary
…many differential distribution studied for pp0 , pn+, pp, pp
RNe+e- constant eTFFM. Zetenyi et. al. Heavy Ion Phys. 17 (2003) 27
no off shell coupling to VM assumed lower limit for e+e- emission
/ from data (hadronic dec.)
missing yield related to low mass resonances and off shell VM !
e+e- excess in p+Nb e+e- excess in p+Nb
„excess over pp reference”„slow” (p<0.8 GeV/c) pairs
clear excess in p+A below VM pole
- secondary reactions : +N (1720,..)(N* (1520),..) NNe+e- ?
el. TFF important ! constraint from ppe+e- …… work in progress
- in medium modification ? answer only after understanding of the p+p reference
RpA (vs p) – increase at small momenta : largest for the „-region” BUT NOT for peak
strong absorption consistent with CBTAPS (+A) results!
Rpa vs momentum
Me+e
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
Excess yield scales with system size ~ Apart1.4 multistep processes?
component subtracted
data PRC84(2001)014902
15
Transport model Transport model results results for Ar+KCl for Ar+KCl
Transport models: not consistent picture
don’t describe (yet) pn data „excess” region dominated by but
different predictions ! Me+e->0.60 dominates complicated
vacumm structure !
Are in-medium effects needed? Not clear yet… systematic studies needed new Au +Au data are essential!
E.L. Bratkovskaya, W. Cassing, NPA 807 (2008) 214
GiBUU: J. Weil at al., arXiv:1106.1344v1
and and // ratio in Ar + KCl ratio in Ar + KCl
meson plays important role (~18%) in K-
production at SIS18 energies
• Statistical model describe rates with no
suppression (i.e OZI rules) !
R/ A+A : enhanced production and absorption?
K+K- e+e-
R/ A+A >> R/ in NN and πN reactions
w.r.t N-N threshold
Double strange Double strange -- (1321) in Ar+KCl (1321) in Ar+KCl
P.Salabura
640 MeV below NN threshold !
data: PRL 103 (2009) 132310
data: EPJA 47 (2011) 21 SHM: S. Wheaton, J. Cleymans, Comp. Phys. Comm. 180 (2009) 84
production significantly larger then transport model (UrQMD) and statistical model predictions
Note that also is enhanced and is not suppressed at all all have ss(bar) content !
..to be continued with Ag+Ag
Kaons in nuclear matterKaons in nuclear matter
G.E Brown et.al NPA 567 (1994) 937, T. Waas, e al. PLB 379 (1996) 34J. Schaffner-Bielich, et al.. NPA 625 (1997),..
indirect measurements :
K+/K0 considered as good quasiparticle
at SIS K+ 5 fm (weak absorption)
repulsion from spectator matter :flow out of plane (KAOS data PRL.95 (2005)
012301,FOPI-> Y. Leifels talks this afternoon ) reduced yield at low pt (p): ( FOPI, ANKE data
PRL102(2009)183591)
Acta Phys. Hung. A22 2005 21
(1405)
K- K-
N-1
K- in medium: more complicated spectral function
(1405) physics : entry to K- in mediumproperties , kaonic clusters ppK- .., kaonic atoms,..
KK00s s in medium potential and in medium potential and (1405) (1405)
K0s in Ar+KCl @ 1.756 GeV
data: PRC 82 (2010) 044907
IQMD : repulsive UKN 38 MeV
(1405) –bound K- N system?
(1405) pole
• pole shift? intereference with non. res ? importnat bench mark for theory
Preliminary
• new data will come from p+A • ..and Au+Au (+ flow measurement)
Au+Au run (finished 3 weeks ago) at 1.23 AGeVAu+Au run (finished 3 weeks ago) at 1.23 AGeV
• Thank to essential HADES upgrade (DAQ,MDC,RPC_TOF)
Ready for campaigns at FAIR SIS100!
on line PID
vertex reconstruction
SSummary:ummary: Low mass pair production in light systems (C+C) explained by known 0 cross sections
and baryonic sources fixed from the NN reference reactions:
pn- bremsstrahlung + Dalitz are the essential e+ e- sources explaining „DLS” puzzle
OBE models come closer to pp/pn data : further studies are on-going
for larger systems , Ar+KCl, evidence for onset of pair excess over NN reference :
radiation from „resonance (, N*) matter”: New Au+Au data are of key importance !
in-medium effects on (A+A and p+A) are not clear yet :
determination of -meson shape in N-N collisions (vacumm) is far from trivial and requires
better understanding of /N* - couplings el.Transition Form Factors , work is in progress
absorption of and enhanced production in nuclear matter can be explain large R /
new K0S data support repulsive KN in-medium potential ; (1405) is crucial for antykaon
properties in nuclear matter
Large production yields (above SHM predictions) of double strange (1321)
Outlook:Outlook:
2012-2013 - HI collisions (Au+Au/Ag+Ag) at SIS18 with upgraded HADES continuation of
dielectrons + strangeness programme (also K+,K- , e+e-, flow measurements)
> in discussion: pion beams : el.TFF of baryon resonances, pion, strangeness production
> 2016 - HADES at FAIR (SIS100) - zero day experiment- part of CBM physics programme
HADES
CBM
stay tuned: lot of new interesting results are expected !
23.01.2009 P.Salabura 23
The CollaborationThe Collaboration
GSIGSI
SISSIS
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
Gross properties of the baryonic Gross properties of the baryonic matter matter
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 (, N*) matter”
• Sub-threshold production of (, , K- K+, ) :
• confined to high density zone
• Multi-step processes ~ Apart >1
S.Vogel et al. (URQMD) arXiv:0710.4463v2
Rapp & Wambach Adv. Nucl. Phys. 25 (2000)
N+N->N , +NN +N +
ex: production
SIS
AGSSPS
K+
K-
/
P/ e+e- 10-6 !
Upcoming experiments : Au+Au and Upcoming experiments : Au+Au and Ag+Ag (2010-2012) Ag+Ag (2010-2012)
simulation: 4 weeks of beam (no in-medium effects included)
½(pp+pn)
• maximum excess (intermdediate mass)
• High statistics differential studies of excess
centrality, dN/dmt , angular distributions
counts
• Ag+Ag : maximal density VM (/)
production rate at SIS18
• High stat. spectroscopy of VM region
• Strangeness programme
Resonance reconstruction Resonance reconstruction strangenessstrangeness
->+-
Ar + KCl @ 1.75 AGeV: excellent rec. capabilities
->p+-
K0s ->+ + -
->K+ + K-
GeV/c2
first observation at SIS