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