motivation (predicted medium effects in the charm sector)

1. Hadron modifications seen with electromagnetic probes Volker Metag II. Physikalisches Institut Universität Giessen Germany in-medium spectral function s(,p) • first observation of an -nucleus bound state: Observables in pp interactions and their relevance to QCD Workshop at ECT*,Trento, Italy, July 3-7, 2006 • motivation (predicted medium effects in the charm sector) • first observation of medium modifications of the  meson: • a.) mass shift • b.) in-medium width • summary and outlook

2. hadrons = excitations of the QCD vacuum Mass [GeV] G.E.Brown and M. Rho, PRL 66 (1991) 2720 T.Hatsuda and S. Lee, PRC 46 (1992) R34 Motivation • QCD-vacuum: complicated structure • characterized by condensates • in the nuclear medium: • condensates are changed • change of the hadronic excitation energy spectrum • widespread experimental activities to search for in-medium modifications of hadrons

3. possible in-medium modifications of hadrons • in-medium mass shift • (partial restoration of chiral symmetry, meson-baryon coupling) • in-medium broadening of hadron resonances • (meson-baryon coupling, collisional broadening) • hadron-nucleus bound states • (meson-nucleus attractive potential)

4. V. Bernard and U.-G. Meißner NPA 489 (1988) 647 NJL-model K. Saito, K. Tushima, and A.W. Thomas PRC 55 (1997) 2637 Quark-meson coupling model (QMC) decrease of  -mass by  15%; decrease of D-mass by 3% at normal nuclear matter density degeneracy of chiral partners model predictions for in-medium masses of mesons

5. A. Hayashigaki, Phys. Lett. B 487 (2000) 96 QCD sum rules: mD - 50 MeV  width of (3770) increases • (2s) may become instable to DD-decay on the other hand, Lee and Ko find: (S.H.Lee and C.M.Ko PRC67 (2003) 038202) from D-meson loops predictions in the charm sector consequences of a dropping D-meson mass

6. - meson -meson F. Klingl et al. NPA 610 (1997) 297 NPA 650 (1999) 299 M. Post et al., nucl-th/0309085 AT [GeV-2] 1.) lowering of in-medium mass 2.) broadening of resonance for rB m [GeV] q [GeV] Model predictions for spectral functions of r and w mesons

7. -, -meson-nucleus potential K. Saito, K. Tsushima, A.W. Thomas, hep-ph/0506314 predictions within the quark meson coupling model (QMC) : E(1s) = -39 MeV; = 29 MeV : E(1s) = -100 MeV; = 31 MeV : E(1s) = -56 MeV; = 33 MeV : E(1s) = -118 MeV; = 33 MeV

8. Predictions 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

9. reconstruction of invariant mass from 4-momenta of decay products: p (12 GeV) A ,  +X • KEK-E325: M. Naruki et al., PRL 96 (2006) 092301: no broadening in the medium!! -meson: • NA60: R. Arnaldi et al., PRL 96 (2006) 162302: In + In (158 AGeV) -spectral function shows strong broadening but no shift in mass experimental approach: dilepton spectroscopy: r, w, f e+e- essential advantage: no final state interactions !! • CLAS (Jlab): C. Tur et al., A , ,  +X • HADES (GSI): planned experiment - p   n on bound proton

10. J.G.Messchendorp et al., Eur. Phys. J. A 11 (2001) 95 gA   + X p g p0g g M. Effenberger et al.  w p0 g g fraction of -decays in the medium (  0.1 0) :  35% -mass in nuclei from photonuclear reactions advantage: • p0g large branching ratio (8 %) • no -contribution (  0 : 7  10-4) disadvantage: • p0-rescattering

11. Expected  in-medium signal rescattering of pions in nuclei predominantly proceeds through (1232) excitation: scattered pions have Ekin150 MeV no distortion by pion rescattering expected in mass range of interest

12. 4 p detector system CB/TAPS @ ELSA Crystal Barrel 1290 CsI TAPS 528 BaF2 front view of TAPS side view E= 900-2200 MeV • = 00 to 3600  = 300 to 1680 • = 00 to 3600  = 50 to 300

13. comparison of meson masses and lineshapes for LH2 and nuclear targets 0   No change of mass and lineshape for longlived mesons (0, , ) decaying outside nuclei

14. after background subtraction mNb = 763 MeV;   0.110consistent with m =m0 (1 -  /0) for  = 0.13 inclusive 0 signal for LH2 and Nb target D. Trnka et al., PRL 94 (2005)192303 difference in line shape of  signal for proton and nuclear target

15. D. Trnka, PhD thesis, Univ. Giessen 2006 vacuum contribution in-medium contribution decomposition of  signal into in-medium and vacuum decay contributions Nb: in-medium: 45% C: in-medium: 40% 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)

16. normalization to C!! E= 1,5 GeV transparency ratio: = 19 MeV = 34 MeV 37 MeV 94 MeV 74 MeV M. Kaskulov and E. Oset priv. communication P. Mühlich and U. Mosel NPA (2006) access to in-medium  width in-medium  width proportional to  absorption:   vabs

17. transparency ratio: = 19 MeV = 34 MeV 37 MeV 94 MeV 74 MeV access to in-medium  width in-medium  width proportional to  absorption:   vabs normalization to C!! E=1.5 GeV Comparison to data taken at E = 1.45-1.55 GeV (D.Trnka et al.(preliminary))

18. P. Mühlich , private communication taking the momentum dependence of the  width into account,both analyses agree: • experimental problem: luminosity L  A-2/3 (for Au factor 30 !!) • p - loss due to single Coulomb scattering  Z2 dependence of  width on  momentum •  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)

19. Nb LH2 momentum dependence of  signal (Nb-target) D. Trnka et al., PRL 94 (2005)192303 • mass modification only for p 0.5 GeV/c determination of momentum dependence of  - nucleus potential requires finer momentum bins  improved 2nd. generation experiment

20. 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)

21. E. Marco and W. Weise, PLB 502 (2001) 59 quasifree quasifree -mesic states T. Nagahiro et al. N. Phys. A 761 (2005) 92 attractive potential repulsive potential no intensity for negativeenergies signature for -mesic states

22. E = 2750 MeV simulation E = 1.5 –2.5 GeV p 5° 15° candidates background 740 MeV/c  |p| < 500 MeV/c for p < 140 240 MeV/c bound states expected forp < 140 correlation between  momentum and proton angle

23. D. Trnka, PhD thesis, Univ. Giessen 2006 small proton angles 70 < p< 140 large proton angles 180 < p< 280 quasi- free C C LH2 LH2 • for small proton angles: difference between C and LH2 data for negative energies • for large proton angles: similar background distributions for C and LH2 data comparison of data on LH2 and C

24. Evidence for carbon data after background subtraction quasifree 70 < p< 140  mesic states theoretical prediction E.Marco and W.Weise PLB 502 (2001) 59 firstevidence for the existence of an -nucleus bound state: here:

25. p 4He  c3H (S. Brodsky et al., PRL 64 (1990) 1011) c bound by  20 MeV; exp. signature -decay (branching 4•10-4) minimum incident p-kinetic energy: 1.54 GeV in the laboratory: minimum c momentum: 2.1 GeV/c;  c = 0.59; Ekin(c) = 400 MeV population of charmed meson bound states??  No chance for populating a state bound with 20 MeV!!!

26. kinematics for pp  (2s)  J/(1s) + 2 at threshold: Ekin(p) = 5.37 GeV (allowing for phase space of 3 GeV) in the laboratory: minimum J/(1s) momentum: 4.4 GeV/c;  J/ = 0.82; Ekin(J/) = 2.28 GeV no chance of forminga J/- nucleus bound state!!

27. An in-medium dropping of the  meson mass has been observed • consistent with • first information on in-medium  width: Summary and outlook • major step forward towards understanding the origin • of hadron masses • first evidence for mesic 11B  second generation experiments with improved statistics are needed and in preparation  difficult to transfer techniques and approaches to the charm sector !!

28. CBELSA/TAPS collaboration

29. Decay of a bound -mesic state: 3He   3He h G 0 E EB 0p+X excitation function: rise in cross section near threshold: -mesic 3He state ? (N-final state interaction?) p S11 p g 3He 3He* 2H E [MeV] structure in excitation function for 0 p back-to-back emission

30. pp – decay of p h p S11 g 3He 3He* 2H E [MeV] E [MeV] E [MeV] structure in excitation function of p0p back-to-back emission near h-threshold: B(3He)= ( 5.5  5) MeV; = (39  21) MeV 

31. Flatte fit to TAPS data M. Pfeiffer et al., PRL 94 (2005) finer energy binning 2 poles: m-i/2 = (1487.7-i4.8) MeV; (1483.9-i8.9) MeV

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

33. Search for  mesic states in heavier nuclei C. Garcia-Recio et al., PLB 550 (2002) 47 unitarized chiral model preferably only 1s-state 24Mg: B=12.6 MeV; =33 MeV experiment at COSY (ENSTAR/Big-Karl): Roy et al. : p 12C  3He + 10B; p 6Li  3He + 4He experiment at GSI: Hayano et al., EPJ A6 (1999) 105; 7Li(d,3He)6He; Td = 3.6GeV

34. Prediction of  mesic states E. Marco and W. Weise, PLB 502 (2001) 59

35. Ye.S.Golubeva et al., nucl-th/0212074  (3770) A. Hayashigaki, PLB487 (2000) 96