1. Shedding new Light on Kaon-Nucleon/Nuclei Interaction and its Astrophysical Implications with the AMADEUS experiment at DAFNE
Alessandro Scordo
HADRON 2015
18/09/2015

2. Before starting….
The aim of this talk is to let you into the wonderful possibilities of the DAFNE accelerator together with the AMADEUS exp.
No time for all the analysis details (and not so much astrophysics…)
All the presented MC simulations have been performed thanks to the very important collaboration of prof. Wycech (Warsaw)

3. The DANE accelerator e+ e- at 510 MeV ->  at-rest
resonance decays at 49.2 % in K+ K- back to back pair
Monochromatic beam of low momentum K- (pk = 127 MeV/c)
Currents of 2 A (e-) and 1 A (e+)
KLOE detector

4. What was done at DANE Past experiments
Low-energy
Kaon-nuclei
processes
Kaonic atoms
Hypernuclei
SIDDHARTA
FINUDA
FINUDA
AMADEUS
– step 0

5. What Next @ DANE Low-energy Kaonic atoms Kaon-Nuclei Hypernuclei
Hyperon-Nuclei
Kaonic atoms
Hypernuclei
SIDDHARTA-2
AMADEUS?
AMADEUS
Kaon mass

6. AMADEUS AMADEUS collaboration
116 scientists from 14 Countries and 34 Institutes
lnf.infn.it/esperimenti/siddharta
and
LNF-07/24(IR) Report on lnf.infn.it web-page (Library)
AMADEUS started in 2005 and
was presented and discussed in all the LNF Scientific Committees
Antikaon Matter At DANE: Experiments with Unraveling Spectroscopy
EU Fundings FP7 – I3HP2 and HP3:
Network WP9 – LEANNIS;
WP24 (SiPM JRA);
WP28 (GEM JRA) 6

7. The scientific goal of AMADEUS
1) K-N potential → how deep can an antikaon be bound in a nucleus?
- UKN strongly affects the position of the L(1405) state → we investigate it through (S-p)0 decay Y p CORRELATION
- if UKN is strongly attractive then possible K- multi-N bound states →
we investigate through (L/S-N) decay Y N CORRELATION
Y-N potential → extremely poor experimental information from scattering data
- UYN determines the strength of the final state YN (elastic & inelastic) → could be tested by Y N CORRELATION
K-N → L/S p cross section below 100 MeV/c (analysis still to be started)
Hypernuclei?

8. Essential impact on the case of NEUTRON STARS

9. Low-energy K- hadronic interactions studies with KLOE 2002-2005 data
MC simulations show that :
~ 0.1 of K- stopped in the DC gas (90% He, 10% C4H10)
~ 2% of K- stopped in the DC wall (750 mm c. f. , 150 mm Al foil).
Possibility to use KLOE materials as an active target
Advantage:
unprecedent resolution : p/p ~ 0.4 MeV/c
4-geometry with ~ 96% acceptance
Calorimeter optimized for  : m ~ 7 MeV/c2
Vertex position resolution ~ 1 mm (in DC)
Disadvantage:
Non dedicated target → different nuclei contamination → complex interpretation .. but → new features .. K- in flight absorption. K- K+

10. Pure Carbon target inside KLOE (2012)
AMADEUS step-0:
Pure Carbon target inside KLOE (2012)
Dedicated run in november/december 2012 with a Carbon target 4/6 mm thickness
Advantages:
gain in statistics
(~90 pb-1; analyzed 37 pb-1, x1.5 statistics)
K- absorptions occur in Carbon
at-rest.

11. PART 1 Y p CORRELATION resonant VS non-resonant production study

12. The 2 poles picture of (1405)
two poles: (z1 = – i ; z2 = – i ) MeV
mainly coupled to KN mainly coupled to  → line-shape depends on production mechanism
Line-shape also depends on the decay channel :
Pure I=0
(free from (1385) background)

13. The golden S0 p0 channel
L(1405) signal searched by K- interaction with a bound proton in Carbon
K- p → S0p0 detected via: (Lg)(gg)
Mass limit
on 12C at rest
data
2012 data
Only at rest events
(cut at mass limit)

14. The S+ p- channel DC gas DC wall
Total H
IF 4He
AR 4He
DC gas
DC wall
Total
IF H
IF 12C
AR 12C
Removing the H component is fundamental since it behaves like a high mass pole!!!

15. non-resonant / resonant absorption ratio: - at rest ~ 2.3
The Non-Resonant L p- channel
Preliminary
non-resonant / resonant
absorption ratio:
- at rest ~ 2.3
- in flight ~ 4.1
c2/ (ndf – np) = 1.5
non-resonant / resonant
absorption ratio:
- at rest ~ 2.3
- in flight ~ 4.1
c2/ (ndf – np) = 1.5
counts/(10MeV/c)
Counts/(0.04)
+++ Data
----- Global fit
cosqp (MeV/c)
pp (MeV/c)
Absorptions in 12C
(from Carbon wall data)
Σ/Λ nuclear conversion
K-N→Σ π
counts/(3MeV/c2)
ΣN→ΛN
Non-Resonant
(in-flight)
(at-rest)
Resonant S*
(in-flight)
(at-rest)
mp (MeV/c)

16. PART 2 Single & multi – nucleon K- absorption kaonic nuclear clusters investigation through Lp,t / S0p correlation

17. Λp correlation study Preliminary without 3NA Fit 3D (PΛ, Pp, θΛp)
K-N → Σπ Σp/Λp conversion in 4He
K-H → Σπ Σp/Λp conversion in 12C
- No fragmentation (higher mass)
- Residual fragmented (lower mass)
K-NN → Λπp (higher mass)
K-NN → Σπp (lower mass)
K-NN → Σp Σp/Λp conversion in 4He
K-NN → Λp (higher mass)
K-NN → Σ0p (lower mass)
Uncorrelated background
Preliminary without 3NA
+++ Data
---- Global fit
MΛp (MeV/c2)

18. We need to fix the yield of
Λp correlation study
Fit 3D (PΛ, Pp, θΛp)
with 3NA
We need to fix the yield of
2NA/3NA absorption!!!
never measured before

19. Λt correlation studies in 4He
150 events in gas of the DC (He + C4H10 )
red line -
back to back events
(cosΘΛt ) < -0.95
4NA process :
- highest part of invariant mass
- back-to-back topology
Clear back-to-back enhancement of Λt events

20. Λt correlation studies in 4He: preliminary mass and angle simulataneous fit
data
Highest statistics ever in the Λt channel
--- carbon data from DC wall
--- 4NA K- 4He → Λt in flight MC
--- 4NA K- 4He → Λt at rest MC
--- 4NA K- 4He → Σ0t , Σ0 → Λγ MC
BR(K-4He(4NA) → Λt) < 1.1 x 10-4 /Kstop
σ(100 MeV/c) (K-4He(4NA)→Λt) =
(0.41 ± 0.13 (stat ) (sys)) mb
paper in preparation

21. S0p correlation study Final fit
2NA-QF clearly separated
From other processes
From the contributions to the fit, the yields are extracted for K- stop

22. Absorption results
...is there room for the signal of a ppK- bound state?
Repeat the fit with the inclusion of a simulated bound state in a grid with different values for the Binding Energy and Width:
B.E. : MeV/c2 (15 MeV/c2 steps)
Width: MeV/c2 (20 MeV/c2 steps)

23. S0p correlation study Significance: 1 s Fit with ppK- Best solution:
(best c2 and higher yield)
- B.E. = 45 MeV/c2
- Width = 30 MeV/c2
Significance:
1 s

24. PART 3 Exploring the possibility to study Hypernuclei

25. L hypernuclei with K- at rest on Carbon
Pion momentum (MeV/c):
NMWD:
Proton momentum (MeV/c): (273550) MeV/c
Looking for a monochromatic pion and a proton in coincidence

26. π- momentum
273 MeV/c (corresponding to the ground state, with B =10.8 MeV)

27. Conclusions
The DAFNE accelerator, together with the AMADEUS experiment, represents a unique possibility to perform complete studies in the low-energy strangeness sector
SIDDHARTA & AMADEUS experiments already obtained excellent results
SIDDHARTA could take new data in 2017
AMADEUS is still not an approved experiment, it is using old existing KLOE data, yet…..
1) Already shown impressive capabilities to investigate several processes
2) Many channels have been studied and papers are in preparation
3) Even more channels still have to be opened….there’s room for everyone!
The final goal is to have the possibility to have a DEDICATED experiment in order to really investigate the KN, YN, L(1405), hypernuclei physics with no contaminations
If you are interested in such a possibility….join the cause! We are looking for other institutes/universities/groups to become members of the AMADEUS collaboration