In-medium modification of hadrons
experiment overview(from cold matter to low energy HI
collisions)
P. Salabura
Jagiellonian University Kraków/GSI
hadron 2011
MotivationR. Rapp, J. Wambach, Adv. Nucl. Phys. 25 (2000) P. Muehlich et al. NPA 780(2006)
meson
• Many predictions for sizable modifications of meson spectral function A(m, p) in
cold and hot nuclear matter: broadening and „dropping mass” scenarios
A(m,p) QCD vacuum properties via QCD sum rules (B. Kaempfer talk)
• Experiments: +A, p+A, A+A mesons: ,, , , ’
cold matter, Spring8, CLAS @ JLAB, CBELSA/TAPS, : KEK E325 , ANKE, HADES
HI collisions: DLS, HADES, Helios, CERES, Na60, STAR, PHENIX, LHC..
mesonat rest
p = 0.3 GeV/c
„hot and dense matter”
„cold matter”
Experimental methods
Meson
Mass[MeV/c2]
[MeV/c2]
c [fm/c]
BR(Ve+e-) BR in hadrons
0 770 150 1.3 4.4x10-5 + - (~100%)
782 8.4 23.4 7.1x10-5 0 (8%)
1020 4.4 44.4 3.1x10-5 K+K- (50%)
Measure meson line shape in p()+A and A+A or/and Yield w.r.t NN case
p () + A
e-
e+
TF
NO FSI ! FSI !
tot
eemesoneeeeN
fireballeeeeN
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
!
Signal extraction :+A // e+e- (CLAS @JLAB) E (1.1-3.8) 0 (CBELSA/TAPS) E (1.2-2.2)
• strong contribution (in +N ~ 3 )
• Combinatorial background measured by
like sign method
• no contribution
• 0 FSI removed by cut on T >150 MeV
CBELSA/TAPS PRL 100 (2008) 192302 CLAS:PRL 99 (2007) 262302
Transparency from +ACLAS <p > =1.7 GeV/cCBELSA/TAPS <p > =1.1 GeV/c
p [ MeV/c]
CLAS <p >
P. Muehlich and U. Mosel, NPA773, 156 (2006).M. Kuskalov, E. Hernandez, and E. Oset, EPJ. A31, 245 (2007).
CBELSA/TAPS
• in-medium 210 MeV (in rest frame)
coll = v N N > (3-4 x) „free”N ! n>2
particle interaction - > low. density approx?
• larger TA seen in e+e- channel- / interferences?
CLAS: PRL 105 (2010) 0112301
upper limit
-line shape in analysis M. Thiel: Thursday session
CB/TAPS: Preliminary
• CB - Collisional broadenning consistent with TA
• shift : mass shift with density
m* = m0 (1.0 – 0.16* 0/ )
calculations: J.Weil GiBUU arXiv:1106.1344
• Line shape not sensitive to in-medium
width/ mass due to strong suppression of
in-medium decays
Yield ~ BW(m) * decay /tot 1/2
0
E : 900-1300 MeV close to threshold
Role of regeneration in TA : , ,’ CBELSA/TAPS
• absorption NOT affected by secondary reactions
• „Fast” are absorb similarly to , slow are enhanced by secondary production NN , NN(1535)
• weaker absorption of ’ (’ –N coupling) : ’ in-medium :25-30 MeV
M. Nanova: Tuesday session
0 AE (1.2-2.2)
Transparency from p +A
• p + A : in-medium ~ 33 -50 MeV @ <p > =1.1 GeV/c and 0:
+A (Spring-8, JLab) : in-medium ~ 23-100 MeV @ <p > 1.7 GeV/c
• 28 MeV from predictions (Valencia/Giessen) - kaon loop modification
ANKE : p @ 2.83 GeV
Phys. Lett. B 695, 74-77 (2011).
K+ K-
0 < < 8 0
0.6 <p < 1.6 GeV/c
lab
A. Polyanskiy : Tuesday session
Preliminary
e+e- pairs from p+A: HADES
• Large acceptance for pe+e- < 1GeV/c :
not measured by CLAS, KEK-E325
CLAS,KEK
M. Weber : Friday
N*/ ?
0 VM
Preliminary
cocktail : HADES + PYTHIA
Comparison to NN reaction
NNNNAApart
pNb
pA dpdNA
dpdNMpR
/*
/),(
/
• increase at low pe+e- for and
N*, / - secondary reactions:
NN NN , NN* NNe+e-
comparison with GiBUU (J.Weil)
• At high momenta :
() ~ () ~ 0 A0.69 0.2
0
,N*/
dp
d
dp
dN
reaction
1
Apart scaling : particle producton A AA/NN
part = N0
AA / N0NN
Apart from Glauber modelVM
PreliminaryM. Weber talk on Friday
/ regionCLAS PRL 99 (2007) 262302
p 1 GeV/c 217 MeV
• HADES: p + Nb : for pe+e- <0.8 GeV/c excess over pp: secondary from N(1520), (1700),…
Not seen in +A due to momentum cut?
• absorption compatible with CBTAPS(GiBuu) : in-medium 150 MeV
p>0.8 GeV/c
p<0.8 GeV/c
HADES
HADES
calculations: J. Weil GiBUU arXiv:1106.1344
p>0.8 GeV/c
p<0.8 GeV/c
Radiation from A+A @ SPSCERES @ SPS s=8.8 GeV Na60 @ SPS s=17.3 GeV
At SPS energies:
• excess due to pion annihilation +- l+ l-
• excess related to meson in-medium spectral function
•Na60: no change in line shape for and
PRL 96, 162302 (2006)
-meson in hot and dense matter Data : Na60 acceptance corrected : EPJC 59 (2009) 607
calculations: Hess/Rapp: NPA806(2008)339.
direct - N* / pion loop
Dalitz decays: em . Transition form factor?• - /N* couplings play big role in „rho” melting at SPS
Do these effects contribute to e+e- production at low energies?
„Baryonic loops ”
Baryonic sources at SIS18
C+CCa+Ca
TAPS -
HADES, DLS e+e-
„freez-out” meson cocktail
•Baryonic sources : (1232) ~10-20%, N(1535,..)- 1-2%, N–N bremsstr..
• Pair excess is NOT related to - scales as pions !
HADES @ SIS18 s=2.6 GeV arXiv:1103.0876
Isolating „true” excess
N e+e- +N-N bremsstr.
0 e+e-
subtracted
Baryonic sources from N N-”reference”
• Normalization to N0 takes care about Apart scaling
• excess of radiation in 0.12 < M < 0.55
„reference”
Apart = 38
PLB690(2010)118
Resonance „clock”
Apart = 38
SIS18: clock ?
HADES
Na60 data: EPJC 61 (2009) 711arXiv:1103.0876
SPS:„ clock „ : 6 generations in fireball
Apart :15 41 78 130 177
Helicity distributionse+
e-
* )cos1( 2
BA
d
dN 0
B=1
„excess”
: B= 1: B= 1
VM: M>0.6
B = 0(at SPS) • excess has polarization consistent with
0 VMexcess
/ from HADES
• SIS18 : deep sub-threshold production
• large / ratio , absorption and
enhanced production ?
SIS18 : ArKcl s=2.6 GeV arXiv:1103.0876
/e+e- from Na60
Na60: Eur.Phys.J. C 61 (2009) 711
e+e-
e+e-
• SPS: absoption at low pt , no effect for
• no changes in meson line shape
Na60: EPJC 64(2009)1In+In @ SPS s=17.3 GeV
meson line shape from HI
•no evidance for in-medium modifications
Na60: EPJC 64(2009)1In+In @ SPS s=17.3 GeV
Summary• Meson transparency in cold nuclear matter shows increased meson (, ,, ’ ) widths in-medium
>> free
• Estimates of meson absorption cross sections in nucleus indicate NV in-
medium > NV free : significant role of n (>2)- particle interactions ?
• determination of -meson shape in cold nuclear matter requires better understanding of /N* -
Ne+e- transitions and role of secondary processes - important for HI collisions !
• absorption observed in HI collisions (low pt ) , no effects found for
• e+e- excess in A+A collisions is related to recreation of short lived resonances : „resonance”
clock” : at SPS and baryonic resonances, ( ) at SIS18
• melting of the meson in hot and dense matter (SPS) is dominated by baryonic effects in
agreement with „hadronic” scenario
back-up
production in p+AANKE : p @ 2.83 GeV : differential cross sections
Preliminary
• not explained yield at low momentum :
secondary processes?
• at high momentum better agreement with models
for p > 1 GeV : in-medium
50 MeV
Effects of meson-baryon interactinos
=
• Background subtracted
Data described (both nuclei) assumming / mass modification m*=m0( 1 - .092/0)
• fit supports * consistent with the vacuum for /
/=0.7±0.2 /=0.9±0.2
• CB shape from mixed event but w.o absolute normalization (fit parameter)!
• Fit, excluding excess region, gives / <0.15 (Cu) and <0.32(C) with CL of 95% ! In contrast to other pp data /~1
2/dof =2.3
2/dof =1.8
p+A @ 12 GeV KEK-PS E325 M. Naruki Phys.Rev.Lett 96 (2006) 092301