James Ritman Univ. Giessen PANDA: An Experiment To Investigate Hadron Structure Using Antiproton...
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Transcript of James Ritman Univ. Giessen PANDA: An Experiment To Investigate Hadron Structure Using Antiproton...
James Ritman Univ. Giessen
PANDA: An Experiment To Investigate Hadron Structure
Using Antiproton Beams
• 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
• Heavy Ion Physics: hot and dense nuclear matter
• Nuclear Structure: paths of nucleo-synthesis
• 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
• Are there other forms of hadrons?e.g. Hybrids qqg or Glueballs gg
• Why are hadrons so much heavier than their constituents?
p-A interactions
James Ritman Univ. Giessen
Why Don’t We See Isolated Quarks?
James Ritman Univ. Giessen
Charmonium – the Positronium of QCD
3D2
2900
3100
3300
3500
3700
3900
4100
c(3590)
c(2980)
hc(3525)
(3097)
(3686)
(3770)
(4040)
0(3415)
1(3510) 2(3556)
3D1
3D3
1D2
3P2(~ 3940)
3P1(~ 3880)
3P0(~ 3800)
(~ 3800)
1 fm
C C
~ 600 meV -1000
-3000
-5000
-700011S
0
13S1
21S0 23S
121P
1 23P2
23P1
23P0
031S
0 31D
2 33D2
33D1
33D2
Ionisationsenergie33S
1
e+ e-0.1 nm
Binding energy [meV]
Mass [MeV]
DDThreshold
8·10-4 eV
10-4 eV
• Positronium • Charmonium
James Ritman Univ. Giessen
Probe large separations with highly excited qq states_
Charmonium Spectroscopy
James Ritman Univ. Giessen
Open Questions `
c(3590)
• Partial width mostly unknown• Precision spectroscopy
• confirm hc
• Little is known about states above DD
James Ritman Univ. Giessen
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
Measured rate
Beam
Resonance cross
section
CM Energy
James Ritman Univ. Giessen
High Resolution
• Crystal Ball: typical resolution ~ 10 MeV
• Fermilab: 240 keV
p/p < 10-4 needed
James Ritman Univ. Giessen
Why Are Hadrons So Heavy?
Hadron Masses
Protons = (uud) ?2Mu + Md ~ 15 MeV/c2
Mp = 938 MeV/c2
(P.Kienle)
no low mass hadrons (except , K, )
spontaneously broken chiral symmetry
Spontaneous Breaking of Chiral Symmetry
Although the QCD Lagrangian is symmetric, the ground state need not be. (e.g. Fe below TCurie )
Example:
James Ritman Univ. Giessen
Quark Condensate
The QCD vacuum is not empty 0qq
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.
Hadrons in the Nuclear Medium
Spectral functions
W.Peters et al., Nucl. Phys. A632, 109 (1998).S.Klimt et al., Nucl. Phys. A515, 429 (1990).
<qq>
Reduction of <qq>
Hadron Production in the Nuclear Medium
c d_
d du
c_ d
repulsive
attractive
D-
D+d du
d du
d du
d du
d du
Quark atom
Mass of particles may change in dense matter( ) : 40
( ) : 200
s u
c d
K su m m
D cd m m
James Ritman Univ. Giessen
Advantages of p-A Reactions Compared to A-A
Much lower momentum for heavy producedparticles (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 )
Strange Baryons in Nuclear FieldsHypernuclei open a 3rd dimension (strangeness) in the nuclear chart
-
3 GeV/c
K+KTrigger
_
secondary target
p
• Double-hypernuclei: very little data
• Baryon-baryon interactions: -N only short ranged (no 1 exchange due to isospin) impossible in scattering reactions
-(dss) p(uud) (uds) (uds)
James Ritman Univ. Giessen
Exotic Hadrons
James Ritman Univ. Giessen
Glueballs
gg
g
RG
GR
BGGRRB
C. Morningstar PRD60, 034509 (1999)Self interaction between gluons
Construction of color-neutral hadrons with gluons possible
exotic glueballs don‘t mix with mesons (qq)
0--, 0+-, 1-+, 2+-, 3-+,...
James Ritman Univ. Giessen
RBRB
Prediction in QCD:
Collective gluon excitation
(Gluons contribute to quantum numbers)
Ground state: JPC = 1-+ (spin exotic)
Charm Hybrids ccg
distance between quarks
James Ritman Univ. Giessen
Mixing With Mesonic States
Width: could be narrow (5-50 MeV) since
DD suppressed for some states
O+- DD,D*D*,DsDs (CP-Inv.)
(QQg) (Qq)L=0+(Qq)L=0 (Dynamic Selection Rule)
If DD forbidden, then the preferred decay is
(ccg) (cc) + X , e.g. 1-+ J/
Ex
oti
c lig
ht
Ex
oti
c cc
1 - - 1 - +
0 2 0 0 0 4 0 0 0M e V / c2
10 - 2
1
1 0 2
James Ritman Univ. Giessen
Partial Wave Analysis
Partial wave analysis as important tool
Example of 1-+ (CB@LEAR)pd X(1-+)++p, X
Strength ~ qq States !
Signal in production but not in formation is interesting !
James Ritman Univ. Giessen
The Experimental Facility
HESR
James Ritman Univ. Giessen
HESR: High Energy Storage Ring
Beam Momentum 1.5 - 15 GeV/c
High Intensity Mode:Luminosity 2x1032 cm-2s-1 (2x107Hz)p/p (st. cooling) ~10-4
High Resolution Mode:Luminosity 2x1031 cm-2s-1 p/p (e- cooling) ~10-5
James Ritman Univ. Giessen
James Ritman Univ. Giessen
Target• A fiber/wire target will be needed for D physics,• A pellet target is conceived:
1016 atoms/cm2 for D=20-40m
1 mm
James Ritman Univ. Giessen
Micro Vertexing
7.2 mio. barrel pixels50 x 300 μm
2 mio. forward pixels100 x 150 μm
Central Tracking Detectors
example event: pp 4K
• MVD: (Si) 5 layers• Straw-Tubes: 15 skewed double-layers• Mini-Drift-Chambers
James Ritman Univ. Giessen
Tracking Resolution
J/ K+K- (J) = 35 MeV/c2
() = 3.8 MeV/c2
Example reaction: pp J/ (s = 4.4 GeV/c2)
Single track resolution
Invariant mass resolution
James Ritman Univ. Giessen
PID with DIRC
(DIRC@BaBar)
GEANT4 simulationfor HESR:
James Ritman Univ. Giessen
Electromagnetic CalorimeterDetector 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 130 ps (N.B. with PMT!)
Total number of crystals 7150
James Ritman Univ. Giessen
Staged Construction
James Ritman Univ. Giessen
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
James Ritman Univ. Giessen
List of participatinginstitutions(incomplete)
40 Institutes (32 Locations) from 9 Countries:Austria - Germany – Italy – Netherlands – Poland – Russia – Sweden – U.K. – U.S.
James Ritman Univ. Giessen
Physics with stopped antiprotons 18-19 September 2003 at GSI