The Amadeus project at Dafne
The AMADEUS project at DAΦNE  
Catalina. Curceanu 
LNF – INFN, Via. E. Fermi 40, 00044 Frascati (Roma), Italy 
On behalf on the AMADEUS Collaboration 
1. The AMADEUS scientific case 
The change of the hadron masses and hadron interactions  in  the  nuclear 
medium  and  the  structure  of  cold  dense  hadronic  matter  are  hot  topics 
of  hadron  physics  today. These important, yet unsolved, problems will be 
the  research  field  of  AMADEUS  [1] (Antikaonic  Matter  At  DAFNE:  
Experiments  with  Unraveling Spectroscopy).  
AMADEUS will search for antikaon-mediated deeply bound nuclear 
states,  which  could  represent,  indeed, the ideal conditions  for  investigating 
the  way  in  which  the  spontaneous  and  explicit  chiral  symmetry  breaking 
pattern  of  low-energy  QCD  occur  in  the  nuclear  environment.  
In a few-body nuclear system the isospin I=0 K N interaction plays an 
important role: it can favor the existence of discrete nuclear bound states of 
K in nuclei, while contracting the nucleus, thus producing a cold dense 
nuclear system, named “deeply bound kaonic nucleus” or “kaonic nuclear 
cluster”. 
Many important impacts then follow: 
- such compact exotic nuclear systems might get formed with binding 
energies so large (~100 MeV) that their widths turn out rather narrow, since 
the Σπ decay channel is energetically closed and, additionally, the Λπ 
channel is forbidden by isospin selection rule; 
- high-density cold nuclear matter might be formed around K⎯, which could 
provide information concerning a modification of the kaon mass and of the 
K N interaction in the nuclear medium; 
- empirical information could be obtained on whether kaon condensation can 
occur in nuclear matter, with implications in astrophysics: neutron stars, 
strange stars. 
- nuclear dynamics under extreme conditions (nuclear compressibility, etc) 
could be investigated. 
The  hypothesis  of  the possible existence of deeply  bound  kaonic 
 nuclear  states  was  already  formulated  in  1986  by  Wycech  [2] but  is 
 only  a  few  years  old  in  the  structured  form  of  a  phenomenological 
 model  formulated  by  Akaishi  and  Yamazaki  [3]. The existence or not of 
such deeply bound systems is presently matter of vivid discussions among 
theoreticians and experimentalists. 
First experimental indications have been produced at KEK [4-6], LNF 
[7], GSI [8] and BNL [9]. Lately, the experimental situation became more 
complicated, since one of the two systems seen at KEK by E471, the 
S0(3115), was not re-seen in E570 with a larger statistics, as preliminary 
presented at the IX International Conference on Hypernuclear and Strange 
Particle Physics, Mainz 10-14 October 2006. In the same time, the 
interpretation of the experimental results is matter of lively discussion, as 
resulting from the talks given at the previously mentioned Workshop. 
The new proposal, AMADEUS at DAΦNE, has the goal to perform, for 
the first time, a systematic and complete spectroscopic study of deeply 
bound kaonic nuclei, both in formation and in the decay processes.  
 Moreover, AMADEUS aims to perform other types of measurements as: 
elastic and inelastic kaon interactions on various nuclei, obtaining important 
information for a better understanding of the undergoing processes. 
2.   AMADEUS at DAΦNE 
The φ-factory DAΦNE   at LNF is a double-ring e+e- collider, designed to 
operate at the center of mass energy of the φ-meson, whose decay delivers 
almost monochromatic K+K- pairs with a momentum of 127 MeV/c. A peak 
luminosity in excess of 1x10 32 cm-2 s-1 is presently obtained in the FINUDA 
run. Such a source of kaons is intrinsically clean, a situation unattainable with 
a hadron machine, which normally has an intense pion background. The 
planned upgrade of DAΦNE will reach a peak luminosity in excess of 10 33 
cm-2 s-1 [10],  which,  of  course,  makes  it  an  ideal  machine to  study 
stopped  K- induced  reactions  to  search  for  deeply  bound antikaon nuclear 
clusters.   
This new facility will deliver an integrated luminosity of about 10 fb-1 per 
year and equipped with a dedicated 4π detector KLOE [11] complemented 
with the AMADEUS apparatus   will become the top level scientific center to 
study kaonic nuclei using K- induced processes at rest, as proposed in the 
original work of Akaishi and Yamazaki  [3]. This represents a complementary 
approach to other experimental studies, planned at GSI with the FOPI detector 
and at J-PARC, E15 experiment, to be seen as part of a global strategy 
to attack these important open problems of low-energy QCD.  
In Figure 1 the location of AMADEUS setup within KLOE detector is 
shown. 
Figure 1: The AMADEUS setup within KLOE. 
For  the  integration  of  the  AMADEUS  setup  within  KLOE a solution 
which is presently under  study  is  to  use  a  toroidal  target  placed  around 
the  beam  pipe  and surrounding  the  interaction  region. The  beam  pipe can 
be a  thin-walled  aluminum  pipe  with  carbon  fiber  reinforcement. A 
degrader which  might  be  an  “active” one, i.e. a  scintillator  (or scintillating 
fiber) detector  is  placed  around  the  pipe  just  in  front  of  the  target. This 
detector  is  essential,  delivering  an  optimal  trigger  condition  by  making 
use  of  the  back-to-back  topology  of  the  kaons  generated  from  the  φ-
decay. The AMADEUS  collaboration  considers  as  well  the implementation 
 of  an  inner  tracker, to  get  more  information  about  the  formation  region 
(for  better  background  suppression) of  the  deeply  bound  states. Since  the 
 KLOE  collaboration  envisages  the  use  of  an  inner  vertex  detector  this 
 might  open  the  way  to  a  unique  inner  vertex  detector  to  be  used  by 
 both  groups. The possible setup is shown in Figure 2. 
two TPC sections 
with triple GEM and  
x-y readout on both sides 
kaon trigger made of 
2+3 scintillating fibers 
layers, 
inside a vacuum chamber
half-toroidal  
cryogenic 
target cell 
vacuum  
chamber 
thin-walled 
beam pipe 
Figure 2: A possible layout of AMADEUS within KLOE 
 3.  AMADEUS scientific program 
The  AMADEUS  first phase program  foresees  the  investigation  of  the 
 most basic  antikaon - mediated  clusters, namely:  
- kaonic  dibaryon  states  ppK- and   pnK-, produced  via 
3He (stopped K, n/p) reactions;   
- kaonic  3-baryon  states  ppnK- and   pnnK-, produced  via   4He 
(stopped  K-, n/p) reactions. 
The  first goal of AMADEUS  is  to  clearly  settle  the  question  about 
the  existence  of  antikaon-mediated  bound  nuclear  clusters. To this aim a 
systematic and complete campaign of spectroscopic studies on light and 
medium nuclei looking for nuclear clusters both in formation and in decay 
will be performed 
 The  program  is  based  on  the  following  objectives:  
(i) To  perform  precision  measurements in order  to  determine  the 
quantum  numbers (spin, parity, isospin) of  all  states, including  excited 
ones, in  addition  to  their  binding  energies  and  decay  widths. Masses  of 
kaonic  clusters  are  obtained  by  missing  mass  analysis, measuring  proton 
and  neutron  distributions  from  the  formation  process. In  KLOE  the 
proton  spectra  can  be  obtained  with   1 -2  MeV  precision. For  the neutron 
 spectra  the  achieved  precision  is  of  the  order  of  2-4  MeV.  
 (ii) As  all  the  states  of  kaonic  nuclei  are  quasi -stationary, important 
information  on  their  structure  is  contained  in  their  total  and  partial 
decay  widths. Until  now, the  experimental  values  on  the  total  decay 
width  are  under  discussion  and  no  information  on  partial  decay  channels 
is  available. Total  decay  widths, accessible  via  the  formation  process, can 
be  resolved  in  AMADEUS  at  the  1 -3  MeV  level  for  proton  
spectra, and  at  a  few  MeV, still  under  study, for  neutron  spectra. The 
partial  decay  widths  may  be  resolved  at  the  level  from  2  to  10  MeV 
depending  on  the  decay  channel.  
(iii) Detailed  structure  information  can  be  extracted  from  a  Dalitz 
analysis  of  three-body  decays  of  kaonic  nuclei, as  was  pointed  out 
recently  by  Kienle, Akaishi  and  Yamazaki  [6].  
Acknowledgements 
We gratefully acknowledge the very good cooperation with the DAΦNE 
and KLOE teams.  
Part of this work was supported by  “Transnational access to Research 
Infrastructure”, TARI – LNF activity within the HadronPhysics I3 project, 
Contract No. RII3-CT-2004-506078. 
References 
[1] AMADEUS LOI, www.lnf.infn.it (Nuclear Physics – SIDDHARTA)  
[2] S. Wycech, Nucl. Phys. A450  (1986) 399c.  
[3] Y. Akaishi and T. Yamazaki, Phys. Rev. C 65 (2002) 044005. 
[4] T. Suzuki et al., Phys. Lett. B 597 (2004) 263. 
[5] M. Iwasaki et al., arXiv: nucl-ex/0310018. 
[6] M. Iwasaki (KEK PS-E471 Collaboration), Proceedings EXA05, 
Editors A. Hirtl, J. Marton, E. Widmann, J. Zmeskal, Austrian Academy 
of Science Press, Vienna 2005, p.191. 
[7] M. Agnello et al., Phys. Rev. Lett. 94 (2005) 212303. 
[8] N. Hermann (FOPI Collaboration), Proceedings EXA05, Editors A. 
Hirtl, J. Marton, E. Widmann, J. Zmeskal, Austrian Academy of Science 
Press, Vienna 2005, p.61.  
[9] T. Kishimoto et al., Nucl. Phys. A 754 (2005) 383c. 
[10] http://www.lnf.infn.it/acceleratori/dafne/NOTEDAFNE/G/G-68.pdf
[11] KLOE: A General Purpose Detector for DAFNE, The KLOE 
Collaboration, LNF-92/019 (IR). 
[12] P. Kienle, Y. Akaishi and T. Yamazaki, Phys. Lett. B 632 (2006) 187. 
http://www.lnf.infn.it/acceleratori/dafne/NOTEDAFNE/G/G-68.pdf
	On behalf on the AMADEUS Collaboration
	Figure 2: A possible layout of AMADEUS within KLOE
	Acknowledgements
	We gratefully acknowledge the very good cooperation with the DANE and KLOE teams. 
	Part of this work was supported by  “Transnational access to Research Infrastructure”, TARI – LNF activity within the HadronPhysics I3 project, Contract No. RII3-CT-2004-506078.
