Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Charmed Hadrons in Matter

• Introduction

• Medium Effects in the light quark sector

• Expectations for the charm quark sector

• J/ψ-N interaction

• Requirements for the Experiment

• Conceptual Design

• Conclusions

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Introduction

Origin of Hadron Masses ?

Chiral Symmetry in QCD is spontaneously broken

Mass Modifications due to

• Chiral Dynamics

• Partial Restoration of C.S. in Hadronic Environment

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Deeply bound Pionic States

• 206Pb(d,3He)Pion-Nucleus Potential from binding energy and width

isospinasymmetric matter, ρ ρ0

m(π-) increased by 25 MeV

A. G

illitz

er, H

irsch

egg

‘01

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Production of Open Strangeness

• Excitation functionfor K+/K- productionin H.I. Reactions

• Different from elementary reaction:enhanced σ(K-)

• K- mass loweredby 100 MeV (ρρ0) F. L

aue,

EP

J A

9 39

7

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Expectations for charmed Mesons

• J/ψ, ηc: -5 to -10 MeV• D-Mesons

“Hydrogen of QCD”

- mass lowering- 50 MeV mass split

Charm quark mass: 1.3-1.5 GeV

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Consequences for Observables

A. S

ibirt

sev

EP

J A

6 35

1

• DD production will be enhanced below threshold

• D-mesons decay semi-leptonic (10-20% BR)

• Cross sections 1 nb near threshold

• D,D,Ds,Ds,J/ψ,ψ’

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Consequences for Observables II

Threshold lowered by 100 MeV “new” decay channels open (ψ’,χc2) width increases

ψ(3770) broadening(lepton pair detection)

A. H

ayas

higa

ki P

LB48

7 96

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

J/ψ-N Absorption Cross Section

• In URHIC: suppression of J/ψ observed

? Hadronic Interactions?• 3-4 mb from γN

6-7 mb from pA, AA Antiproton annihilation on

nuclei

• also for J/ψ, ψ’, χJ

on various nuclear targets

K.K

. Set

h, H

irsch

egg

‘01

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Dissociation of Charmonium

• p + d D- + Λc+

• cc interacts with residual neutron

• Studying energy dependence

p + d J/ψ + + n: measuring σ(J/ψ-N)elastic down to lower relative momenta

• J/ψ -meson scattering cross section

A. S

ibirt

sev

NP

A68

0 27

4c

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Requirements for the Experiment

• Production of charmed mesonsσ(DD) 1 nb 100 d-1 @ L = 2·1031 cm-2s-1

high luminosity

• c(D±) = 315 µm, c(DS) = 149 µm well-defined interaction point good vertex resolution ( 100 µm )

• D’s decay semileptonic (10 – 20 % B.R.)decay kinematics: high pt, large opening angles momentum determination, PID

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Microvertex Tracking

Silicon Pixel Detector, 200 µm wafers (0.25% X0)

7.2 MPixels50·300 µm²

2 MPixels100·150 µm²

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Microvertex Tracking II

Does the concept meet the requirements?

σ(D0) = 50 µm

σ(Z0) = 85 µm

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Momentum determination, PID

• Straw Tubes for trackingσxy = 150µm, σz = 1mm

• Drift chambers• Separation of π/K

(DIRČ)

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Lepton identification

• Electromagnetic calorimeter (PbWO4)

96% coverage of the

solid angle• Muon hodoscope

(plastic scintillators)

Workshop on Experiments with Antiprotons at the HESR – April 2002, GSI

Conclusions

• GSI has a successful history in studying medium effects in the light quark sector

• Extending the program to the charm quark sector promises exciting perspectives

• The proposed program requires a versatile detector in terms of resolution, PID, rate capability and triggering