Search for Baryonium
and
FAIR Physics
S. Wycech, Warsaw
content
• old estimates
• contemporary signals - BES
J/Ψ  N N , γ
J/Ψ  6 π
=> X(1868)
=> X(1835)
antiprotonic atoms
radiochemical studies of
p
cold capture in nuclei
Relation to PANDA- FAIR/FLAIR
30 years of search
• baryonium = 2 q + 2q
▪ N – N quasi-bound states
?
!
p-pbar  γ + X
Adiels /LEAR (1990) no baryonium E < 1770 , Γ< 25 MeV
Experimental difficulties
No Pauli principle  many partial waves
Strong background from annihilation
MODERN-selective- SIGNAL
J/ψ  (p p ) , γ
BES collaboration,
CP : selects 3 possible partial waves
Swave
11 Swave
Potential model
Brian - Philips
N N  N N
G – parity transformation
Vπ  - Vπ
No Pauli exclusion - many allowed states
Strong attraction
- in many states
Annihilation at distances R < 1 fm
Potential in
11S
Bonn , Paris
Quasi-bound state in Paris potential model
E = 5 MeV , Γ ~ 50 MeV
B
No quasi-bound state in
Bonn potential model
Look below N
N threshold
Additional evidence needed
Antiprotonic atoms 
bound nucleons
Final state interactions in decay channels
J/ψ  (ππη’) , γ
BES experiment
Paris model understanding
Nature of X(1835)
11S
amplitude below threshold
Dedonder,Loiseau,S.W.Phys.Rev.C80
ATOMIC
EVIDENCE of
BARYONIUM
p N subthreshold energies
antiprotonic atoms
-40
•
P
•
D
•
T
He 4
-20
0
MeV
Absorptive parts of S-wave p N ampltiude
obtained from light atoms
Absorptive P-wave p N amplitude
from light atoms
Radiochemical measurements
of residual nuclei after p-bar absorption
Ratio
(p n )/ ( p p )
↓
Lower level ,
96 Zr
116 Cd
124 Sn
1.61(6)
2.60(35)
3.09(7)
in nuclei
↓
Upper level ,
1.91(6)
3.33(37)
3.43(25)
PS203
↓
cold capture
2.6(3)
5.6(5)
5.4(7)
Anomalies ( 4 cases)
========================================
106 Cd
1.65(80)
5.13(80)
0.5(1)
weakly bound proton ,
neutron
halo
proton halo ???
strongly bound neutron
P wave narrow quasi-bound state ?
SW,PhysReVC76,034316
A model for
J/ψ  (p p ) meson
And some applications
Final state emission model for
J/ψ  (p p ) meson
p
J/ p
p-bar
meson
One parameter – source radius .8 fm
(p p ) interactions in S waves
CP invariance, FSI interactions
Dedonder,Loiseau, SW
Good: relative rates , and spectra
π , ω, Φ
J/ψ  (p p ) meson
J/ψ  (p p )
J/ψ  (p p ) γ
FAILURE
1/3 of rate, no peaks
J/ψ  (n n ) γ (p p ) γ
J/ψ  (p p ) γ
DESTRUCTIVE INTERFERENCE –
IN MAGNETIC PHOTON EMISSION
γ emission before/during
hadronisation ?
J/ψ  J/ψ γ (p p ) γ
TWO PEAKS FROM FSI INTERACTIONS
BARYONIUM AND SHAPE RESONANCE
Applications
Further studies
Put J/ψ into nucleus-
p p 
J/ψ
J/ψ + meson
p pbar
Reasonable description :π, γ, ω,Φ
PANDA
Decays of J/ψ in nucleus
production with fast antiproton
 fast J/ψ leaves nucleus
p p  J/Ψ + π (or ω)
There is a special momentum :
J/Ψ goes backward in CM
Peripheral p nucleus collisions
• Invariant mass of pions to measure
Peaks at the end of heavy background
New clarifying experiments
Fine structure resolution in
deuterium, helium atoms
PAX – polarized beam proposal
p p
 (p p ) , γ
Peripheral collisions
Conclusions
consistent evidence of 11S broad
quasi-bound state
(the structure is less certain)
some evidence of
33P
quasi bound state
calculated narrow „ nuclear state in
Could be studied at FAIR
3He
Thanks
Appendix
More recent attempts
•
A. Abele , Crystal Barrel..Eur Phys Journ.C 17(2000) 583
p d annihilation into mesons
nB(1855)  3pi0+n
Gamma < 10 MeV could not be seen on 5*10^(-4)
level from n momentum distribution
• B.Bertini N.Phys B209 (1982) 269
p p -> pi- , X
no signal , X not excluded. ,
•
l.Adiels ..Phys. Lett 182
ppbar  gamma +X ,
no X Below 1770 MeV , Gamma < 25 Mev
Atomic level shifts
in light atoms , H,D,He
S waves
ΔE – i Г/2
~ | Ψ (0)|2 A
o
Ao - hadron-nucleus scattering length
Ψ - atomic wave function
P waves
ΔE – i Г /2 ~ | Ψ/r (0)|2 A
1
1
1
Absorbtive potential
model dependent
Antiprotonic atom data widths
and lower level shifts
Hydrogen
1s , 2p
CERN -PS- 207
fine structure
Deuteron
3He
, 4He
1s, 2p
2p, 3d
CERN -PS- 207
M.Schneider
Summary S-wave (p p ) state
Two experiments select
11S
J/ψ  (p p ) , γ
partial waves :
BES
J/ψ  (ππη’) , γ
BES X(1835)
Non-selective
p - atomic level widths
without fine structure
PS 209, PS 207
Nuclear regions studied in atoms
lower,
↓
ρ(r)
upper, cold capture to A-1 nuclei
↓
↓
Guidelines : Paris N-Nbar potential
model 2009
• But no bound state in 11S Juelich potential
Paris potential : M. Lacombe, B. Loiseau, S.W.
…C79(09)054001
decay modes
J/ψ  p p
J/ψ  n n
J/ψ  p pBAR
J/ψ  p pBAR
J/ψ  p pBAR
J/ψ  p p
J/ψS  p n
BAR
BAR
BAR
γ
ω
Φ
π0
π-
BAR
rate
2.17(7) 10-3
2.2(4) 10-3
3.8(1.0) 10-4
2.2(4) 10-3
4.5(1.5) 10-5
1.19(8) 10-3
2.00(10) 10-3
CP allowed p p
3S
3S
1 S 3P
1 S 3P
1 S 3P
3 S 1P
3S 1P
BAR
Currents, exchange currents
pn d γ
n
p
n
p
n
p
L= N* γ(∂–ieA) N
π, ρ exchange currents , subtract
pp  X γ exchange currents add up by G parity
Riska Phys Scr. 31(1985)
BAR
Electric photon
3S
 3P
e qε
Magnetic photon 3S  1S
μ Kxσ ε
large magnetic moments
exchange currents
strong enhancement in 1S
final state due to „ baryonium”
Potential
Scattering data
~4000 data + hydrogen p-bar atom
Low energy expansion for
scattering amplitudes
F
SCATTERING
= A + 3 kk’ A +…
o
1
A ( E = 0)
On a nucleus
i
In a p p sub-system
F
(p p )
(–B
BINDING
–E
RECOIL
)
negative energies
Nuclear regions studied in atoms
lower,
↓
ρ(r)
upper,
↓
Enhancement in 11S wave
BES experiment
reproduced by Paris and Juelich models