Vector Mesons in the Nuclear Medium Volker Metag

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Vector Mesons in the Nuclear Medium Volker Metag II. Physikalisches Institut, Universität Gießen introduction

Vector Mesons in the Nuclear Medium Volker Metag II. Physikalisches Institut, Universität Gießen introduction medium modifications of vector-mesons: 1) -meson: CERES, KEK-PS 325 2) -meson: CB/TAPS@ELSA outlook: medium modification in the charm sector: D-mesons: PANDA@FAIR summary invited talk given at CHIRAL-05, RIKEN, Tokyo, Japan, 15. – 17. February 2005

Motivation Mass [Ge. V] Hadrons = excitations of the QCD vacuum QCD-vacuum: complicated structure

Motivation Mass [Ge. V] Hadrons = excitations of the QCD vacuum QCD-vacuum: complicated structure characterized by condensates In the nuclear medium: condensates are changed change of the hadronic excitation energy spectrum Þ widespread experimental activities to search for in-medium modifications of hadrons

theoretical predictions for mass changes of vector mesons in the nuclear medium T. Renk

theoretical predictions for mass changes of vector mesons in the nuclear medium T. Renk et al. , PRC 66 (2002) 014902 1. ) lowering of in-medium mass 2. ) broadening of resonance for B , T experimental approach: dilepton spectroscopy: , , f e+ereconstruction of invariant mass from 4 -momenta of decay products: essential advantage: no final state interaction

W. Schön et al. Act. Phys. Pol. B 27 (96) 2959 -p bound n

W. Schön et al. Act. Phys. Pol. B 27 (96) 2959 -p bound n at rest -mass in nuclei ne+e- “at rest”: | p | | p. F | exp: detect e+e- HADES M. Effenberger et al. PRC 60 (1999) 044614 expected signal: -A at p = 1. 3 Ge. V/c

 -mass in nuclei from photonuclear reactions J. G. Messchendorp et al. , Eur.

-mass in nuclei from photonuclear reactions J. G. Messchendorp et al. , Eur. Phys. J. A 11 (2001) 95 p 0 A + X 0 advantage: • 0 large branching ratio (8 %) • no -contribution ( 0 : 7 10 -4) disadvantage: • 0 -rescattering

expected mass distribution for p, Nb (including detector resolution and 2 0 background) after

expected mass distribution for p, Nb (including detector resolution and 2 0 background) after cut on 0 kinetic energy within 0. 6 < M 0 < 0. 8 :

The accelerator facility ELSA at Bonn ELSA = Elektron Strecher Anlage

The accelerator facility ELSA at Bonn ELSA = Elektron Strecher Anlage

The Crystal Barrel/ TAPS detector @ELSA tagging spectrometer: tagging range: 31% -94% of Ebeam

The Crystal Barrel/ TAPS detector @ELSA tagging spectrometer: tagging range: 31% -94% of Ebeam E = Ebeam - Ee CB: 1280 Cs. I modules TAPS: 540 Ba. F 2 modules

4 detector system CB/TAPS @ ELSA Crystal Barrel 1290 Cs. I side view TAPS

4 detector system CB/TAPS @ ELSA Crystal Barrel 1290 Cs. I side view TAPS 528 Ba. F 2 front view of TAPS F = 00 to 3600 = 300 to 1680 F = 00 to 3600 = 50 to 300

comparison of meson masses and lineshapes for LH 2 and nuclear targets 0 No

comparison of meson masses and lineshapes for LH 2 and nuclear targets 0 No change of mass and lineshape for longlived mesons ( 0, , ) decaying outside nuclei

inclusive 0 signal for LH 2 and Nb target D. Trnka (Giessen) after background

inclusive 0 signal for LH 2 and Nb target D. Trnka (Giessen) after background subtraction difference in line shape of signal for proton and nuclear target

contribution from in-medium decays in vacuum removed by subtracting mass distribution measured with LH

contribution from in-medium decays in vacuum removed by subtracting mass distribution measured with LH 2 target (64%) strength of in-medium decays concentrated around masses of 725 Me. V Þ mass drop by about 7% at estimated baryon density of about 0. 55 0 consistent with m = m 0 (1 - / 0); for = 0. 15

momentum dependence of signal mass modification only for p 0. 5 Ge. V/c first

momentum dependence of signal mass modification only for p 0. 5 Ge. V/c first indication for an in-medium modification of the meson mass !!

photoproduction of mesons off nuclei A A at E 1. 2 Ge. V (CB/TAPS@ELSA)

photoproduction of mesons off nuclei A A at E 1. 2 Ge. V (CB/TAPS@ELSA) in-medium mass distribution ( 0 ) exp: D. Trnka (Giessen) theo: P. Mühlich et al. , nucl-th/0310067 comparison to BUU calculation assuming m = m 0 (1 - / 0); for = 0. 16 first experimental indication for a dropping mass in the nuclear medium

CB/TAPS @ MAMI C TAPS forward wall 528 Ba. F 2 - modules -Beam

CB/TAPS @ MAMI C TAPS forward wall 528 Ba. F 2 - modules -Beam Crystal Ball 672 Na. I - modules

Charmed mesons in the medium @ PANDA in-medium spectral function of charmonia: consequence of

Charmed mesons in the medium @ PANDA in-medium spectral function of charmonia: consequence of dropping D-mass (cu) in the medium A. Hayashigaki, PLB 487 (2000) 96 Ye. S. Golubeva et al. , nucl-th/0212074 (3770)

FAIR Facility for Antiproton and Ion Research SIS 100 SIS 300 GSI as of

FAIR Facility for Antiproton and Ion Research SIS 100 SIS 300 GSI as of today CBM PP HESR Super-FRS Elec. Cooler Atom. Phys. CR+RESR NESR FLAIR PANDA

summary vector mesons: : first evidence for medium modifications from e+e- in ultra-relativistic nucleus-collisions

summary vector mesons: : first evidence for medium modifications from e+e- in ultra-relativistic nucleus-collisions (CERES/CERN); indications for medium modifications at normal nuclear matter density from e+e- in p. A collisions at 12 Ge. V (KEK); : • first evidence for medium-modifications at normal nuclear matter density from 0 by comparison of p( , ) and A( , ) (CB/TAPS @ ELSA); • -p n on bound protons, planned at HADES/GSI; mesons with charm: D: planned experiments at FAIR

conclusion Experiments so far are in accordance with theoretical scenarios for changes of hadron

conclusion Experiments so far are in accordance with theoretical scenarios for changes of hadron properties in the nuclear medium. Studying the in-medium behaviour of hadrons is a promising approach to learn more about the origin of their mass. We have come a little closer to understanding the mass of matter Thanks: CBELSA/TAPS collaboration (Bonn) A 2 -collaboration (Mainz) Giessen-team: in particular Johan Messchendorp, Susan Schadmand, David Trnka Giessen-Theory: W. Cassing, St. Leupold, U. Mosel, P. Mühlich