PANDA: An Experiment To
Investigate Hadron Structure
Using Antiproton Beams
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Overview of the GSI Upgrade
Overview of the PANDA Physics Program
Exotic Hadrons in the Charm Mass Region
HESR: High Energy Storage Ring
The PANDA Detector
James Ritman Univ. Giessen
The GSI Future Project
• Nuclear Structure:
paths of nucleo-synthesis
• Heavy Ion Physics:
hot and dense nuclear matter
• Ion and laser induced Plasma:
very high energy densities
• Atomic physics:
QED, strong EM fields, Ion-Matter interactions
• Physics with Antiprotons
properties of the strong force
Project approved Feb 2003
James Ritman Univ. Giessen
What Do We Want To Know?
• Why don‘t we observe isolated quarks?
Q-Q potential in the charmonioum system
• Why are hadrons so much heavier than their
constituents?
p-A interactions
• Are there other forms of hadrons?
e.g. Hybrids qqg or Glueballs gg
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Why Don’t We See Isolated
Quarks?
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Charmonium – the Positronium of QCD
• Charmonium
• Positronium
Mass [MeV]
Binding energy
[meV]
4100
y (4040)
P 2(~ 3940)
Ionisationsenergie
0
3 1S 0
-1000
1
2 S0
3 3S 1
3
2 S1
33D 2
33D 1
33D 2
3900
~ 600 meV
3700
3 1D 2
23P2
23P1
23P0
2 1P1
3
y  (3770)
P 0(~ 3800)
3
y  (3686)
D2
3
DDThreshold
hc(3525)
3500
D2
1
D1
3
h c(3590)
10-4 eV
-3000
D 3 (~ 3800)
3
P 1(~ 3880)
3
c 2(3556)
c 1(3510)
c 0(3415)
-5000
11S 0
-7000
1 3S 1
3300
8·10-4 eV
e+
0.1 nm
e-
3100
y (3097)
hc(2980)
2900
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C
1 fm
C
Charmonium Spectroscopy
_
Probe large separations with highly excited qq states
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Open Questions
• h`c(3590)
• confirm hc
• Little is known about states
above DD
• Partial width mostly unknown
• Precision spectroscopy
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Why Antiprotons?
• e+e- annihilation via
virtual photon: only
states with Jpc = 1-• In pp annihilation all
mesons can be formed
• Resolution of the mass
and width is only limited
by the beam momentum
resolution
Resonance
cross
section
Measured
rate
Beam
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CM Energy
High Resolution
• Crystal Ball: typical
resolution ~ 10 MeV
• Fermilab: 240 keV
 p/p < 10-4 needed
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Why Are Hadrons So Heavy?
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Hadron Masses
Protons = (uud) ?
2Mu + Md ~ 15 MeV/c2
Mp
= 938 MeV/c2
no low mass hadrons
(except p, K, h)
spontaneously broken
chiral symmetry
(P.Kienle)
Spontaneous Breaking of
Chiral Symmetry
Although the QCD Lagrangian is symmetric, the
ground state need not be. (e.g. Fe below TCurie )
Example:
Quark Condensate
The QCD vacuum is not empty
qq  0
Hadron masses are generated by the strong
interaction with <qq> (also with gluon condensate)
The density of the quark condensate will change as
a function of temperature and density in nuclei.
This should lead to modifications of the hadron’s
spectral properties.
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Hadrons in the Nuclear Medium
Reduction of <qq>
Spectral functions
<qq>
S.Klimt et al., Nucl. Phys. A515, 429 (1990).
W.Peters et al., Nucl. Phys. A632, 109 (1998).
Hadron Production in the Nuclear
Medium
Mass of particles may change in dense matter
K  (su ) : ms mu  40
D  (cd ) : mc md  200  Quark atom
u
d
d
D+
_
c d
attractive
_
D-
c d
repulsive
u
d
d
u
d
d
u
d
d
u
d
d
u
d
d
Advantages of p-A Reactions
Compared to A-A
Much lower momentum for heavy produced
particles (2 GeV for “free”)
(Effects are smaller at high momentum)
Open charm mass region (H atom of QCD) @HESR
(single light quark)
Well defined nuclear environment (T and r)
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Strange Baryons in Nuclear Fields
Hypernuclei open a 3rd dimension (strangeness) in the
nuclear chart
• Double-hypernuclei:
K+K
Trigger
very little data
p
_
• Baryon-baryon interactions:
X
3 GeV/c
L-N only short ranged (no 1p
Xexchange due to isospin)
LL impossible in scattering
reactions
secondary target
X-(dss) p(uud)  L(uds)
Exotic Hadrons
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Glueballs
Self interaction between gluons
g
g
g
 Construction of color-neutral
hadrons with gluons possible
RG
BG
GR
RB
GR
exotic glueballs don‘t mix with
mesons (qq)
0--, 0+-, 1-+, 2+-, 3-+,...
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C. Morningstar PRD60, 034509 (1999)
Charm Hybrids ccg
Prediction in QCD:
Collective gluon excitation
(Gluons contribute to quantum
numbers)
R
BR
B
Ground state:
JPC = 1-+ (spin exotic)
distance between quarks
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Mixing With Mesonic States
2
O+-  DD,D*D*,DsDs
(CP-Inv.)
(QQg)  (Qq)L=0+(Qq)L=0
Selection Rule)
(Dynamic
1
Exotic light qq
DD suppressed for some states
10
1-- 1-+
Exotic cc
Width: could be narrow (5-50 MeV) since
If DD forbidden, then the preferred decay is
(ccg)  (cc) + X
10
-2
, e.g. 1-+  J/Yw,f,g
0
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2000
4000 2
MeV/c
Partial Wave Analysis
Partial wave analysis as
important tool
Example of 1-+ (CB@LEAR)
pd  X(1-+)+p+p, X  h p
Strength ~ qq States !
Signal in production but not in
formation is interesting !
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The Experimental Facility
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HESR
HESR: High Energy Storage
Ring
Beam Momentum
1.5 - 15 GeV/c
High Intensity Mode:
Luminosity
2x1032 cm-2s-1 (2x107Hz)
dp/p (st. cooling) ~10-4
High Resolution Mode:
Luminosity
2x1031 cm-2s-1
dp/p (e- cooling) ~10-5
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Target
• A fiber/wire target will be needed for D physics,
• A pellet target is conceived:
1016 atoms/cm2 for D=20-40 mm
1 mm
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Micro Vertexing
7.2 mio. barrel pixels
50 x 300 μm
2 mio. forward pixels
100 x 150 μm
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Central Tracking Detectors
• MVD: (Si) 5 layers
• Straw-Tubes: 15 skewed double-layers
• Mini-Drift-Chambers
example event: pp  f f  4K
Tracking Resolution
Single track resolution
Invariant mass resolution
J/y  mm
Example reaction:
pp  J/y  F
(s = 4.4 GeV/c2)
F  K+K-
s(J/y) = 35 MeV/c2
s(F)
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= 3.8 MeV/c2
PID with DIRC
(DIRC@BaBar)
GEANT4 simulation
for HESR:
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Electromagnetic Calorimeter
Detector material
PbWO4
Photo sensors
Avalanche Photo Diodes
Crystal size
 35 x 35 x 150 mm3 (i.e. 1.5 x 1.5 RM2 x 17 X0)
Energy resolution
1.54 % / E[GeV] + 0.3 %
Time resolution
s  130 ps (N.B. with PMT!)
Total number of crystals
7150
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Staged Construction
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Summary
• GSI will explore the intensity frontier
• High luminosity cooled p-bar from 1-15
GeV/c
• Wide physics program including
• Charmonium spectroscopy
• pbar-A reactions
• Search for glueballs and charm hybrids
• Panda collaboration forming
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List of participating
institutions
(incomplete)
40 Institutes (32 Locations)
from 9 Countries:
Austria - Germany – Italy –
Netherlands – Poland – Russia –
Sweden – U.K. – U.S.
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Physics with stopped antiprotons 18-19 September 2003 at GSI
James Ritman Univ. Giessen