Antiprotons for Nuclear Structure Investigations

H. Lenske Institut für Theoretische Physik, U. Giessen

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

Antiprotons for Nuclear Structure Investigations @FAIR

Agenda:

Antiproton-N and Antiproton-Nucleus Antiproton-N and Antiproton-Nucleus InteractionsInteractions

Nuclear Radii from Absorption Cross SectionsNuclear Radii from Absorption Cross Sections Antiprotons and Neutron-SkinsAntiprotons and Neutron-Skins Screening Effects in Neutron-rich NucleiScreening Effects in Neutron-rich Nuclei Isospin Tagging by Pion ProductionIsospin Tagging by Pion Production Strangeness ProductionStrangeness Production OutlookOutlook

The antiproton-proton Interaction: LEAR Data

p p

p p

Antiproton-Nucleon Interactions

KK

p p

...

- 0

0

K K

n p

...

The History of the longterm relation…

…of antiprotons and nuclei:

• anti-protonic atoms and tails of nuclear densities

• antiproton-A elastic scattering

• annihilation and pion production

• G-parity transformation of scalar and vector self-energies deep potentials ~ -500 MeV

• dispersive self-energies from annihilation channels

• Annihilation and Quark Models

• Meson & Hadron Dynamics from pphh

Consequences of G-Parity in Nuclear Binding

Energy Deposition in a Nucleus

(Cascade-Calculations, Clover et al., PRC 26)

p p (at rest)

The antiproton-Nucleus Interaction

Antiproton+A scattering:

• Free Space pN T-Matrix

• Nuclear Structure: state-of-the-art HFB p and n Densities

• optical Potential in Impulse (t) Approximation

Antiproton+Nucleus Interactions:Elastic Scattering

pA Scattering: Optical Potential and Absorption Cross

Section From The Continuity

Equation:

3 ( )† ( )abs s s opt s2

2m 1tr d r r, k (U ) r, k

2s 1k

s2 (z,b)2abs s opt2

2m 1tr d bdz (U (r))e

2s 1k

Eikonal Approximation:

Antiproton Absorption on 58,78Ni: The Monopole Annihilation Kernel and the

Nuclear Density

( ) 2s

1 1ˆ(r, k) dr | (r, k) |

2s 1 4

Antiproton+A Absorption: Limiting Cases

Probing Nuclear Radii by Antiprotons

• scaling of abs ~ <r2>

• energy independent slope

• convergence of magnitude

• from proton to neutron skin

• increasing <r2>

• neutron skins up to 0.6 fm

• charge radii by e- scattering

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

Localization of the Annihilation Process

2

dP(b) (b)

bdb

bk ( 1)

Spatial Localization of Antiproton

Annihilation on a Nucleus:

Peripheral Process

Cascade Results by Clover et al., PRC 26

Absorption on Protons

b=4fm

Absorption on Neutrons

b=4fm

Shielding of Target Protons by the Neutron Skin

protons

neutrons

Tlab=700 MeV

Antiproton Annihilation on Ni-Isotopes: Scaling of abs

Antiproton+N Absorption: Isospin Symmetry

ppnp

ppnp

Antiproton+Nucleus Interactions: Isospin Symmetry

...)()()(

)()()(~)(

2

20

rrkt

rrktrU

pnF

pnFAp

Enhanced along isotopic chains!

p A(N,Z) C(N 1,Z) k

0p A(N,Z) B(N,Z 1) k n

Peripheral Antiproton Annihilation on a Nucleus:

Pion Production:

Differential Coherent Antiproton Annihilation on a Nucleus:

k kk

0

...

KK ...Np a hh

YY ...

... (N=n)

( )*3 3 ( )pN n nM (k ,k ) d r d r (k , r ) t (x) (r ) (k , r )

i(k r k r ) 2 (r , r )3 3pN n nM (k ,k ) ~ d r d r e t (x) (r )e

Differential Antiproton Annihilation on a Nucleus:

Eikonal Approximation:

Quantum Mechanical Amplitude:

LEAR-Data (PS185) on Strangeness Production

DDRH Flavour Dynamics: Single Particle Energies

DDRH Theory: Density Dependent NN and N Dirac-Brueckner Vertices

Nuclear Matter S

= 28 MeV

Phase Space Distribution for pbar+A -> anti-Y+B(Y)+pi^- Target: 40Ca

Lambda 300 200 100

Sigma^0 300 200 100

0100200300400500600700800k(anti-Y) [MeV/c] 100200300400500600700800

q(pi^-) [MeV/c]

050

100150200250300350

d^2P(k,q)/dE(k)dE(q)

Phase Space Distribution for pbar+A -> anti-Y+B(Y)+pi^- Target: 56Ca

Lambda 200 150 100 50

Sigma^0 200 150 100 50

0100200300400500600700800k(anti-Y) [MeV/c] 100200300400500600700800

q(pi^-) [MeV/c]

050

100150200250

d^2P(k,q)/dE(k)dE(q)

and Strangeness Production on Stable

and Exotic Nuclei

40Ca

56Ca

• Antiprotons as a Probe for Nuclear Structure

• Antipoton-neutron Interactions in Neutron-rich Nuclei

• Antiproton Absorption in Neutron Skin Matter:

• 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

Summary and Outlook

Antiproton Ion Collider (AIC) Collaboration @ FAIR

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