HESR…

Report
Antiproton Physics at GSI
• The GSI Future project
• The antiproton facility
• The physics program
- Charmonium spectroscopy
- Charmed hybrids and glueballs
- Interaction of charm particles with nuclei
- Strange baryons in nuclear fields
- Further options
• Detector concept
• Selected simulation results
• Conclusions
GSI Future Project: The Physics Case
• Research with Rare Isotope Beams
Nuclei Far From Stability
• Nucleus-Nucleus Collisions
Compressed Baryonic Matter
• Ion and Laser Induced Plasmas
High Energy Density in Matter
• From Fundamentals to Applications
QED, Strong Fields, Ion-Matter Interactions
• Research with Antiprotons
Hadron Spectroscopy and Hadronic Matter
Conceptual Design Report: http://www.gsi.de/GSI-Future/cdr/
What does 18.3 Tm mean?
Motion of particle in B-field: P = 0.3 B r Z (units=T,m,GeV/c)
p  0.3 18.3  Z
GeV / c
for a proton: Z  1
E  p  m  5.49 GeV 
K .E.  E  m  4.55 GeV
2
2
2
2
for 12 C 6
E 2  p 2  m 2  0.3 18.3  6   12 0.931
2
K .E.  E  m  34.78  12 0.931
 23.6GeV  1.97 AGeV
2
The GSI p Facility
p production similar to CERN,
HESR = High Energy Storage Ring
• Production rate 107/sec
• Pbeam
= 1.5 - 15 GeV/c
• Nstored
= 5x1010 p
High luminosity mode
• Lumin.
= 2x1032 cm-2s-1
• dp/p~10-4 (stochastic cooling)
High resolution mode
• dp/p~10-5 (el. cooling < 8 GeV/c)
• Lumin.
= 1031 cm-2s-1
Fundamental Aspects of QCD
QCD is confirmed to high accuracy
at small distances
At large distances, QCD is
characterized by:
• Confinement
• Chiral symmetry breaking
Challenge: can we develop a quantitative understanding of the
relevant degrees of freedom in strongly interacting systems?
Experimental approach: Charm physics opens a window in the
transition regime since mc is between the chiral and heavy
quark limits
Charmonium Spectroscopy
The charmonium system is the positronium of QCD.
It provides a unique window to study the interplay of
perturbative and non-perturbative effects.
Energy levels / widths
 details of QQ
interaction
Exclusive decays
 interplay of perturb.
and non-pert. effects
Comparison
+
ee
versus pp
e+e- interactions:
Only 1-- states are formed
Other states only by
secondary decays
(moderate mass resolution)
pp reactions:
All states directly formed
(very good mass resolution)
Severe limitations to existing experiments:
(no B-field, beamtime, beam momentum reproducibility,…)
Many open questions: h’c, states above DD threshold,…
Charmed Hybrids
Predictions for charmed hybrids (ccg)
Mass: lowest state 3.9-4.5 GeV/c2
Quantum numbers: many allowed
values, ground state JPC = 1-+ (exotic)
Width: could be narrow (~MeV) for
some states since DD suppressed
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/Yw,f,g
Search for Charmed Hybrids
Mixing with QQ states:
- Excluded for spin exotic hybrids
- Possible for non-exotic states, but less probable
than the light quark sector, since there are fewer
states with smaller width.
Example of state with exotic q.-n. (1-+)
pd  X(1-+)+p+p, X  hp [email protected]
Strength similar to qq states
Partial Wave Analysis as important tool
Expectations at HESR: 104 non-exotic q.-n. & 102 exotic /day
A signal in production but not in formation is interesting!
Charmed Hadrons in Nuclear
Matter
Investigating the properties of hadrons in matter is a
main research topic at GSI. Partial restoration of chiral
symmetry should take place in nuclear matter.
 Light quarks are sensitive to quark condensate
Evidence for mass changes of pions
r r
and kaons has been deduced previously:
p
- deeply bound pionic atoms
p±
p
- (anti)kaon yield and phase space
distribution
D mesons are the QCD analog of the
H atom. They allow chiral symmetry to
be studied on a single light quark
Open Charm in Nuclei
The expected signal for a
changing mass scenario would
be a strong enhancement of the
D meson cross section, and
relative D+ D- yields, in the
near/sub-threshold region.
This probes ground state
nuclear matter density and T~0
(complementary to heavy ion
collisions)
cc Production on Nuclei
A lowering of the DD mass
would allow charmonium
states to decay into this
channel, thus resulting in a
dramatic increase of width.
Thus one will study relative
changes to the yield and
width of the charmonium
states.
J/Y – Nucleon Absorbtion
The J/Y suppression observed
at SPS is believed to be
related the generation of the
QGP.
Such suppression can also be
generated by purely hadronic
interactions, so it is very
important to know the N-J/Y
cross section in nuclear
matter.
p + A  J/Y + (A-1)
Proton Form Factors at large
At high values of momentum
transfer |Q2| the system
should be describable by
perturbative QCD.
Due to dimensional scaling,
the FF should vary as Q4.
The time like FF remains
about a factor 2 above the
space like. These differences
should vanish in pQCD, thus
the asymptotic behavior has
not yet been reached at these
large values of |q2|.
(HESR up to s ~ 25 GeV2)
GM
p
q2>0
q2<0
2
Q

C
 s 
s 2 ln 2  2 
 
Strange Baryons in Nuclear Fields
Hypernuclei open a 3rd dimension (strangeness) in the
nuclear chart
• New Era:
K+K
Trigger
p
_
X
3 GeV/c
X-
high resolution g-spectroscopy
• Double-hypernuclei:
very little data
• Baryon-baryon interactions:
-N only short ranged (no 1p
exchange due to isospin)
- impossible in scattering
reactions
secondary target
X-(dss) p(uud)  (uds)
Experiments with Open Charm
HESR will produce about 2.5x109 DD/year (~1% reconstr.)
• Leptonic decays: structure of D mesons
(G/Gtot Dn ~ 104)
• D0/D0 mixing:
should be small <108
• CP: direct is dominant
Need about 108 decays
Direct CP in hyperon decays (self analyzing decay)
Production of charmed baryons:
excitation function, differential cross sections,
spin observables
Inverted DVCS
„Deeply Virtual Compton Scattering“ (DVCS) allows the
„Skewed Parton Distributions“ to be measured using the
Handbag-Diagram
 Dynamics of quarks and gluons in hadrons
Measurements of the inverted process less stringent
requirements on the detector resolution.
(however the connection of DVCS to the SPDs needs to be
theoretically analyzed in this kinematic region)
General Purpose Detector
Detector requests:
• nearly 4p solid angle
• high rate capability
• good PID (g,e,,p,K,p)
• efficient trigger (e,,K,D,)
pp  Y‘
Y‘ +J/Y+-
pp (s=3.6 GeV)ff4K
Detector
Target
• A fiber/wire target will be needed for D physics,
• A pellet target is conceived:
1016 atoms/cm2 20-40 m
• Open point: heating of the beam
1 mm
Central Tracking Detectors
• Micro Vertex Detector: (Si) 5 layers
• Straw-Tubes: 15 skewed double-layers
• Mini-Drift-Chambers
GEANT4 simulation
for HESR:
PID with DIRC
([email protected])
GEANT4 simulation
for HESR:
PbWO4 Calorimeter
Length = 17 X0
APD readout (in field)
pp  J/Y h   gg
e/p-Separation
Muon Detector
Performance of Full Spectrometer
Probability to measure the reaction:
pp  J / Y h
J/Y  ee

s  4.4 GeV

J/Y  
Neutral Vertex Finder
Reaction: pp2K0s
|D0|>0.4 mm or |Z0|>0.5 mm for each track
Kinematic refit (constraint=common vertex)
3-Momentum conservation
p+
K0S
pp+ p-
p-
Summary
• HESR will deliver cooled antiprotons up to 15 GeV/c
• The physics program
- Charmonium spectroscopy
- Hybrids and glueballs
- Interaction of charm particles with nuclei
- Strange baryons in nuclear fields
- Further options
• Detector concept
• Selected simulation results
Working group: T. Barnes, D. Bettoni, R. Calabrese, M. Düren, S. Ganzhur,
Hartmann, V. Hejny, H. Koch, U. Lynen, V. Metag, H. Orth, S. Paul, K. Peters,
Pochodzalla, J. Ritman, L. Schmitt, C. Schwarz, K. Seth, W. Weise, U. Wiedner
O.
J.
Glueballs
Predictions for Glueballs:
Masses:
1.5-5.0 GeV/c2
Quantum numbers:
several spin exotics, e.g. 2-Widths:
>100 MeV/c2
Mixing with qq and QQ:
excluded for exotics
mixing with QQ small
Production cross section:
comparable to qq systems (b)
HESR Detector
•
• Pellet-Target: 1016 Atoms/cm2 20-40 m
• MicroVertexDetektor: (Si) 5 layers
•
• Straw-Tubes: 15 skewed double layers
•
• RICH: DIRC and Aerogel (Proximityfocussing) •
•Straw-Tubes + Mini-Drift-Chambers
PbWO4-calorimeter 17X0
2T-Solenoid & 2Tm-Dipole
Muon filter
EM- & H-cal. near 0°

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