Antiprotons as Probes for Nuclear Structure
Investigations of Exotic Nuclei
H. Lenske
Institut für Theoretische Physik, U. Giessen
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Neutron Skins in Exotic Nuclei
Antiproton-Nucleus Interactions
Elastic Scattering
Nuclear Radii from Absorption Cross Sections
Screening of Protons in Neutron-rich Nuclei
Outlook
Neutron Skins in Ni and
Sn Isotopes
Neutron Skins and PDR
Strength in Sn Isotopes
a4=32MeV
a4=26MeV
F. Hofmann et al., PRC64 (2001); N. Tsoneva.
H.L., PLB586 (2004) and PRC (2007)
Measuring Neutron Skins on Isotopic Chains (Ni,Sn…):
p + A Absorption@FAIR: the AIC Proposal
P. Kienle, NMB 214 (2004)
and AIC@FAIR Proposal
H.L., P. Kienle, Phys.Lett.
B647 (2007) 82-87
Antiproton-Nucleon Annihilation
The antiproton-Nucleon Interaction
 
  t pN 
 t pN
1
3
The antiproton-Nucleus Interaction
Antiproton+A scattering:
• Free Space pN T-Matrix
• Nuclear Structure Input: HFB p and n Densities
• optical Potential in Impulse or t Approximation
Antiproton+Nucleus Interactions:Elastic Scattering
pA Scattering:
Optical Potential and Absorption Cross Section
From The Continuity Equation:
 
2m
 
1
abs  
trs  d3rs()† r, k (Uopt (r))s( ) r, k
2 2s  1
k
Eikonal Approximation:
2m
1
abs  
trs  d 2bdz(Uopt (r))e2s (z,b)
2 2s  1
k
Antiproton Absorption on 58,78Ni: The Monopole
Annihilation Kernel and the Nuclear Density
(r, k) 
1 1
drˆ |  s(  ) (r, k) |2

2s  1 4
Probing Nuclear Radii by Antiprotons
• increasing <r2>
• from proton to neutron skin
• neutron skins up to 0.6 fm
• charge radii by e- scattering
• scaling of abs ~ <r2>
• energy independent slope
• convergence of magnitude
Measuring Neutron Skins on Isotopic Chains (Ni,Sn…):
p + A Absorption on protons and neutrons
H.L., P. Kienle, Phys.Lett. B647 (2007) 82-87
Antiproton Annihilation on Ni-Isotopes: Scaling of abs
Q1: Antiproton+N Absorption: Isospin Symmetry

 pn   pp
 pn   pp
Q2: Peripheral Antiproton Annihilation on a Nucleus:
p  A(N, Z)  B(N, Z  1)  k
p  A(N, Z)  A(N  1, Z)  k  
Differential Antiproton Annihilation on a Nucleus:
(n)
M
 ( )  t pN (x) p n (rn )  ( )
k 2 
(n) 2  k
0
 M
  dnp
a k(q)
 ~ pN
bkn q   
nk 
n

Summary and Outlook
• Microscopic Approach to Antiproton-Nucleus Interactions
• Antiprotons as a Probe for Nuclear Skins
• Screening of the Core Protons in neutron-rich Nuclei
• Exclusive Processes: Studies of A  A-1 Reactions
• Multi-Pion and YY Production
• Antiproton In-Medium Interactions:
• Test of G-parity for antiproton-N interactions,
• Study of dispersive self-energies
Together with: Nadia Tsoneva, Urnaa Badarch, P. Kienle
Antiproton Ion Collider (AIC) Collaboration @ FAIR