1 / 35

motivation (predicted medium effects in the charm sector)

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

eamon
Télécharger la présentation

motivation (predicted medium effects in the charm sector)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related