• motivation (predicted medium effects in the charm sector)

Hadron modifications seen with electromagnetic probes

Hadron modifications seen with electromagnetic probes

Volker MetagII. Physikalisches Institut

Universität GiessenGermany

Observables in pp interactions and their relevance to QCDWorkshop at ECT*,Trento, Italy, July 3-7, 2006

• first observation of medium modifications of the meson: a.) mass shift b.) in-medium width in-medium spectral function s(,p)

B11ω

• first observation of an -nucleus bound state:

• summary and outlook

MotivationMotivation

widespread experimental activities to search for in-medium modifications of hadrons

Mas

s [G

eV]

• hadrons = excitations of the QCD vacuum

T.Hatsuda and S. Lee,PRC 46 (1992) R34

G.E.Brown and M. Rho,PRL 66 (1991) 2720

0

**

8.0qq

qq

mm

18.0;1mm

0

B

V

*V

• QCD-vacuum: complicated structure characterized by condensates

• in the nuclear medium: condensates are changed

change of the hadronic excitation energy spectrum

• in-medium mass shift (partial restoration of chiral symmetry, meson-baryon coupling)

possible in-medium modifications of hadronspossible in-medium modifications of hadrons

• in-medium broadening of hadron resonances (meson-baryon coupling, collisional broadening)

• hadron-nucleus bound states (meson-nucleus attractive potential)

model predictions for in-medium masses of mesonsmodel predictions for in-medium masses of mesons

K. Saito, K. Tushima, and A.W. ThomasPRC 55 (1997) 2637

Quark-meson coupling model (QMC)

decrease of -mass by 15%;decrease of D-mass by 3%at normal nuclear matter density

V. Bernard and U.-G. MeißnerNPA 489 (1988) 647

NJL-model

degeneracy of chiral partners

predictions in the charm sectorpredictions in the charm sector

consequences of a dropping D-meson mass

A. Hayashigaki, Phys. Lett. B 487 (2000) 96

QCD sum rules: mD - 50 MeV width of (3770) increases

2.7)MeV(23.6Γvac(3770)

on the other hand, Lee and Ko find:(S.H.Lee and C.M.Ko PRC67 (2003) 038202)

MeV38ΔmJ/ψ

MeV15140Δmψ(3770)

MeV30100Δmψ(2s)

from D-meson loops

(2s) may become instable to DD-decay

1.) lowering of in-medium mass 2.) broadening of resonance

for B

Model predictions for spectral functions of and mesonsModel predictions for spectral functions of and mesons

F. Klingl et al. NPA 610 (1997) 297 NPA 650 (1999) 299

- meson

00.25

0.5

0.75

10

0.2

0.40.6

0.811.20

0.5

1

1.5

2

00.25

0.5

0.75

1

m [GeV]q [GeV]

AT [GeV-2]

M. Post et al., nucl-th/0309085

-meson

-, -meson-nucleus potential-, -meson-nucleus potential

K. Saito, K. Tsushima, A.W. Thomas, hep-ph/0506314

: E(1s) = -39 MeV; = 29 MeV: E(1s) = -100 MeV; = 31 MeV

: E(1s) = -56 MeV; = 33 MeV: E(1s) = -118 MeV; = 33 MeV

predictions within the quark meson coupling model (QMC)

Predictions of nuclear bound quarkonium statesPredictions of nuclear bound quarkonium states

• S. Brodsky et al. , PRL 64 (1990) 1011

attractive cc – nucleon potential due to multi gluon exchange c binding energy to light nuclei of the order of 20 MeV

• Klingl et al., PRL 82 (1999) 3396

QCD sum rules: attractive mass shift of 5-10 MeV for J/ and c

• K. Saito et al., hep-ph/0506314

D- - nucleus bound states (superposition of Coulomb + strong interaction)

D- 208Pb (1s) bound by 24 MeV

• CLAS (Jlab): C. Tur et al., A , , +X

• HADES (GSI): planned experiment - p n on bound proton

essential advantage: no final state interactions !!

221 ppm

reconstruction of invariant mass from 4-momenta of decay products:

experimental approach: dilepton spectroscopy: , , e+e-experimental approach: dilepton spectroscopy: , , e+e-

• KEK-E325: M. Naruki et al., PRL 96 (2006) 092301:

;092.01mm0

0

no broadening in the medium!!-meson:

p (12 GeV) A , +X

• NA60: R. Arnaldi et al., PRL 96 (2006) 162302: In + In (158 AGeV)

-spectral function shows strong broadening but no shift in mass

-mass in nuclei from photonuclear reactions-mass in nuclei from photonuclear reactions

disadvantage:

• 0-rescattering

advantage:

• 0 large branching ratio (8 %)

• no -contribution ( 0 : 7 10-4)

J.G.Messchendorp et al., Eur. Phys. J. A 11 (2001) 95

p

A + X

0

2ppm

fraction of -decays in the medium( 0.1 0) : 35%

M. Effenberger et al.

rescattering of pions in nucleipredominantly proceeds through (1232) excitation:scattered pions have Ekin150 MeV

Expected in-medium signalExpected in-medium signal

no distortion by pion rescattering expected in mass range of interest

detector system CB/TAPS @ ELSAdetector system CB/TAPS @ ELSA

front view of TAPS

= 00 to 3600

= 50 to 300

side view

Crystal Barrel 1290 CsI

= 00 to 3600 = 300 to 1680

E=900-2200 MeV

TAPS 528 BaF2

comparison of meson masses and lineshapesfor LH2 and nuclear targets

comparison of meson masses and lineshapesfor LH2 and nuclear targets

No change of mass and lineshape for longlived mesons (0, , ) decaying outside nuclei

0

inclusive 0 signal for LH2 and Nb targetinclusive 0 signal for LH2 and Nb target

difference in line shape of signal for proton and nuclear target

D. Trnka et al., PRL 94 (2005)192303

after background subtraction

m = m0 (1 - /0) for = 0.13mNb = 763 MeV; 0.110 consistent

with

decomposition of signal into in-medium and vacuum decay contributions

decomposition of signal into in-medium and vacuum decay contributions

lineshape of vacuum contribution taken from LH2 experiment

shape of in-medium contribution taken from BUU simulation (P. Mühlich and U. Mosel, NPA (2006)), assuming m = m0(1 - 0.16 /0)

Nb: in-medium: 45% C: in-medium: 40%

c/MeV400p c/MeV400p

vacuum contributionin-medium contribution

D. Trnka, PhD thesis,Univ. Giessen 2006

access to in-medium widthaccess to in-medium width

in-medium width proportional to absorption: vabs

normalization to C!!E= 1,5 GeV

P. Mühlich and U. MoselNPA (2006)

74 MeV

37 MeV

= 19 MeV

M. Kaskulov and E. Osetpriv. communication

= 34 MeV

94 MeV

transparency ratio:XN

XAA A

T

access to in-medium widthaccess to in-medium width

in-medium width proportional to absorption: vabs

transparency ratio:XN

XAA A

T

normalization to C!!

E=1.5 GeV

37 MeV

74 MeV

= 19 MeV

= 34 MeV

94 MeV

Comparison to data taken at E = 1.45-1.55 GeV (D.Trnka et al.(preliminary))

dependence of width on momentumdependence of width on momentum

P. Mühlich , private communication

MeV 40 0)p,Γ(ρ ω0

750MeV/cpω

MeV100MeV/c)750p,Γ(ρ ω0

taking the momentum dependenceof the width into account,both analyses agree:

MeV100MeV/c)750p,Γ(ρ ω0

• gets broadened in the medium by a factor 10!!

• transparency ratio measurement also possible for charmed mesons in the nuclear medium inel (p) (p); (J/-suppression in AA collisions)

• experimental problem: luminosity L A-2/3 (for Au factor 30 !!)

p - loss due to single Coulomb scattering Z2

momentum dependence of signal (Nb-target)momentum dependence of signal (Nb-target)

mass modification only for p 0.5 GeV/c

determination of momentum dependence of - nucleus potential requires finer momentum bins improved 2nd. generation experiment

Nb

LH2

D. Trnka et al., PRL 94 (2005)192303

The population of meson-nucleus bound states in recoil-free kinematics

The population of meson-nucleus bound states in recoil-free kinematics

forward going nucleon takes over photon momentum

magic incident energies : E 930 MeV : E 2750 MeV

(ELSA)

quasifree

-mesic states

T. Nagahiro et al. N. Phys. A 761 (2005) 92

quasifree

E. Marco and W. Weise, PLB 502 (2001) 59

attractive potential

signature for - mesic states

repulsivepotential

no intensity for negative energies

5°

15°

740 MeV/c

240 MeV/c

p

E = 2750 MeV

correlation between momentum and proton angle

simulation

E = 1.5 –2.5 GeV

background

bound states expected for p < 140

|p| < 500 MeV/c for p < 140

candidates

comparison of data on LH2 and Ccomparison of data on LH2 and C

large proton angles180 < p< 280

• for large proton angles: similar background distributions for C and LH2 data

C

LH2

small proton angles70 < p< 140

LH2

• for small proton angles: difference between C and LH2 data for negative energies

Cquasi-free

D. Trnka, PhD thesis,Univ. Giessen 2006

carbon data after background subtraction

70 < p< 140

quasifree

Evidence for Evidence for B11ω

first evidence for the existenceof an -nucleus bound state:

here: B11ω

sr

nb550

d

d

theo

E.Marco and W.WeisePLB 502 (2001) 59

theoretical prediction mesic states

sr

b4.1

d

d

exp

population of charmed meson bound states??population of charmed meson bound states??

No chance for populating a state bound with 20 MeV!!!

labinEtotηc

labinpcη

p 4He c3H (S. Brodsky et al., PRL 64 (1990) 1011)

c bound by 20 MeV; exp. signature -decay (branching 4•10-4)

in the laboratory: minimum c momentum: 2.1 GeV/c;

c = 0.59; Ekin(c) = 400 MeV

minimum incident p-kinetic energy: 1.54 GeV

in the laboratory: minimum J/(1s) momentum: 4.4 GeV/c; J/ = 0.82; Ekin(J/) = 2.28 GeV

no chance of forming a J/- nucleus bound state!!

labinEtotJ/ψ labinpJ/ψ

kinematics for pp (2s) J/(1s) + 2 at threshold: Ekin(p) = 5.37 GeV

(allowing for phase space of 3 GeV)

Summary and outlookSummary and outlook

major step forward towards understanding the origin of hadron masses

• first information on in-medium width: 0ω ρρatMeV100Γ

• first evidence for mesic 11B

• An in-medium dropping of the meson mass has been observed

consistent with

00 14.01mm

difficult to transfer techniques and approaches to the charm sector !!

second generation experiments with improved statistics are needed and in preparation

CBELSA/TAPS collaborationCBELSA/TAPS collaboration

EEB

0

Decay of a bound -mesic state: 3HeDecay of a bound -mesic state: 3He

excitation function: rise in cross section near threshold:-mesic 3He state ? (N-final state interaction?)

3He

E [MeV]structure in excitation function for 0 p back-to-back emission

0p+X

3He

S11

3He*

p

2H

He3

p – decay of He3

p S11

3He 3He* 2H

He3

E [MeV]E [MeV] E

[MeV]structure in excitation function of 0p back-to-back emission near -threshold: B(3He)= ( 5.5 5) MeV; = (39 21) MeV

2fi

i

ffi T̂

s

16

2p

20p

0

0

0

0p0p022

0

,00

,pimmm

AmT̂

Flatte fit to TAPS dataFlatte fit to TAPS data

finer energy binning

2 poles: m-i/2 = (1487.7-i4.8) MeV; (1483.9-i8.9) MeV

M. Pfeiffer et al., PRL 94 (2005)

Prediction of mesic states in QMC and QHD modelsPrediction of mesic states in QMC and QHD modelsK. Saito, K. Tsushima, A.W. Thomas, hep-ph/0506314

Search for mesic states in heavier nucleiSearch for mesic states in heavier nuclei

C. Garcia-Recio et al., PLB 550 (2002) 47unitarized chiral model

preferably only 1s-state24Mg: B=12.6 MeV; =33 MeV

experiment at COSY (ENSTAR/Big-Karl): Roy et al. : p 12C 3He + 10B; p 6Li 3He + 4Heexperiment at GSI: Hayano et al., EPJ A6 (1999) 105; 7Li(d,3He)6He; Td = 3.6GeV

Prediction of mesic statesPrediction of mesic states

E. Marco and W. Weise, PLB 502 (2001) 59

A. Hayashigaki, PLB487 (2000) 96

Ye.S.Golubeva et al.,nucl-th/0212074

(3770)