K -

KK--

pp

n=25n=25

n=2n=2

n=1n=1

From kaonic atoms to

kaonic nuclei with DANE2

28-30 November 200531th LNF Scientific Committee

C. Curceanu and J. Zmeskal DEAR/SIDDHARTA Collaboration

Proposal of an international facility at DANE2

(pre)Letter of Intent

The case of deeply bound kaonic nuclear states

Proposal of an international facility at DANE2

September 2005

DEAR/SIDDHARTA Collaboration

Manifestation of interest from Institutions of:- Austria- Canada- France

- Germany- Hungary

- Italy- Japan

- Poland- Romania- Russia

- Sweden- USA- …

Letter o

f Inte

nt ->

Spring 2006

31th LNF Scientific Committee CC,JZ / Nov. 29, 2005

AntikaonicMatterAtDANE: anExperimentUnravelingSpectroscopy

AMADEUS


Contents1) Brief sketch of the scientific case of kaonic nuclear clusters

2) From kaonic atoms to K-–nuclear bound states

3) Current and future experiments => the unique features of DANE2

5) Features and identification of the setup and the experimental programme

6) First steps towards AMADEUS

7) Formation of an international collaboration

8) Conclusions 31th LNF Scientific Committee CC,JZ / Nov. 29, 2005

A new paradigm in strangeness nuclear physics, with important consequences in fundamental

physics, is represented by the recently observed

Deeply bound Kaonic Nuclear states

whose first experimental indications are being produced at

- KEK

and

- LNF - GSI- BNL

=> cold and dense nuclear system


KN interactionKN interaction• Until 1997: Confusing situation (part due to KH puzzle)

• 1997 KpX experiment at KEK Iwasaki et al. PRL(1997):

K-p atom shift: E1s “repulsive-type”,

• Indicating the K-p interaction is strongly attractive

2002 DEAR results -> PRL 94, 212302 (2005)

• Consistent with the view that(1405): 1s bound state of K-p• Scattering data (no data at low energy)• 2002: Akaishi-Yamazaki constructed “Nuclear

K bound states in light nuclei”Y. Akaishi & T. Yamazaki, Phys. Rev. C 65 (2002) 044005


Kaonic Nuclear Bound StatesKaonic Nuclear Bound States

• Believed (<2002) to be non-existing: > EB

• Akaishi-Yamazaki (2002) predicted: - K--p interaction so strong that it - might shrinks nuclei --> deeper bound states - deep enough that: the main decay channel KN--> closed - strongly (deeply) bound states

• EB > 100 MeV: narrow bound states (<10 MeV)


First experimental indications: E471 Experiment Results4He(K-

stopped, n) and 4He(K-stopped, p) missing mass spectra

(M. Iwasaki et al., nucl-ex/0310018 v2)

S0(3115): M = 3117 +3.8-2.0(sys)+/-0.9 (stat)< 21.6 MeV, B= -194 MeV with respect to K-+p+n+n rest mass Predicted NOT to exist! (B~20 MeV; ~100 MeV)

S+(3140): M = 3117 +3.8-2.0(sys)+/-2.3 (stat)< 21.6 MeV, B= -169 MeV with respect to K-+p+p+n rest massPredicted with B ~ 110 MeV

M. Iwasaki et al., NIM A 473 (2001) 286Y. Akaishi & T. Yamazaki, Phys. Rev. C 65 (2002) 044005


c ~ 4 -10 0

Explore cold and dense nuclear states

3He ---> 3HeK- shrinkage !! (AMD

methodDote et al. 2002)


Exploring dense nuclear states with K- bound states


- information concerning a modification of the kaon modification of the kaon mass and of the mass and of the KKN interaction in the nuclear mediumN interaction in the nuclear medium => interesting and important from the viewpoint of spontaneous and explicit symmetry breaking of spontaneous and explicit symmetry breaking of QCDQCD - information on a transition from the hadronic transition from the hadronic phase to a quark-gluon phasephase to a quark-gluon phase => changes of vacuum vacuum properties of QCD properties of QCD and and quark condensatequark condensate - kaonkaon condensation condensation in nuclear matter => implications on astrophysicsastrophysics: : neutron stars, strange neutron stars, strange starsstars

- nuclear dynamics under extreme conditionsnuclear dynamics under extreme conditions (nuclear compressibility, etc) could be investigated

Important impacts in fundamental physicsImportant impacts in fundamental physics


From low-energy KN interactions to

K-nuclear bound states “to what extent does our present knowledge of low-energy KN interactions support such expectations (the hypothesis ofnarrow K-nuclear states introduced by Akaishi and Yamazaki)?” (W. Weise, nucl-th/0507058)

1) the low-energy KN scattering data 2) the kaonic hydrogen shift of the ground state

3) the binding energy and decay width of (1405), asserted to be an I=0 quasi-bound state of KN.

Rate of formation and additional constraints: 4) Kaonic helium transitions

The pillars of the existence of narrow K-nuclear states:


.

Future (expected) progress in the field:

1) Kaonic Hydrogen and kaonic deuterium (SIDDHARTA: 200 + 500 pb-1) -> to ~ eV => I=0 and I=1 KN scattering lengths

2) Low-energy scattering: A new facility at DANE2 to study K- nuclear clusters with a 4 detector, may include in its scientific program a K± scattering on nucleons/nuclei to build up a high quality set of data.

3) (1405) Precise KN measurements at threshold (SIDDHARTA) will substantially improve the knowledge of the sub-threshold KN dynamics and contribute to clarify the nature of (1405). More information can come from the measurement of two-body branching ratios in K- absorption at rest, which is precisely the kind of reactions to be studied in the new facility at DANE2. Specifically, one can investigate in-medium corrections to the branching ratios in K- absorption at rest and their effect

on the charged ± spectrum.


.

4) Kaonic Helium: SIDDHARTA (200 pb-1) - the rate + additional constraintsCrucial information about the formation of a specific deeply bound kaonic nuclear state (the K- 3He system) -> depends on the X ray transitions in the K- 4He atom.

There are three experiments which observed kaonic helium atomic transitions from 3d to 2p levels, giving an experimental average value for the width = 55 ± 34 eV. => the formation branching ratio turns out about 2%; right now -> E570 at KEK.

The theoretical widths are around = 2-4 eV. Analogous discrepancy between experiments and optical models calculations does exists for the shifts. This is what is dubbed “the kaonic helium puzzle”.

Preliminary Monte Carlo simulations, performed for the SIDDHARTA setup with a gaseous 4He target show that a measurement with a precision of eV can be performed at DANE with about 200 pb-1 of integrated luminosity. Similar estimations hold for the 3He case.

The capability to detect kaonic helium X-rays transitions might turn out extremely useful in implementing an X-ray trigger to reduce the background in the measurement of kaonic nuclear states by capture at rest on 4He in a new dedicated facility at DANE2.


Deeply Bound

Kaonic Nuclear States

Deeply Bound


KN low-energy scattering

Kaonic Hydrogen

and deuterium

(1405)


Production mechanisms of DBKNS: 1) Stopped K- reactions on light nuclei, with ejection of a

proton or a neutron as spectators

2) In-flight K- reactions: - Knock-out reactions (K-, N) where one nucleon is knocked out

in the formation stage; - (K-, π-) reactions in proton-rich systems to produce exotic

bound nuclear states on unbound systems.

3) Protons (3.5 – 4.5 GeV) on a deuteron target for the production of K–pp detected in a 4 detector.

4) The identification of clusters as residual fragments (“K fragments”) in heavy ion collisions via the invariant mass of their decay products.

Identification and study of DBKNS:- Formation -> missing mass

- Decay -> invariant mass -> Spectroscopy!


Current and future planned experiments

FINUDA at DANE

KEK: E549 E570

J-PARC (LOI06; LOI10)

GSI (FOPI)


Why DANE2 is a good place to study

kaonic nuclear clusters (1)

The future experiments in Japan (J-PARC) will produce kaonic nuclear states only with K--induced reactions in-flight (=1 2 GeV/c), either in (K-, N) or in (K-, -) processes.

The alternative approach, followed at GSI, is represented by proton-nucleus collisions at beam energies close to the strangeness production threshold and nucleus-nucleus collisions

It follows, that a dedicated facility at DANE2 can become THE scientific pole for studying kaonic nuclear states with K— induced reaction at rest.


Why DANE2 is a good place to study kaonic nuclear clusters (2)

The salient features of DANE2 are:

- Low-momentum (127 MeV/c) medium intensity charged kaons: 1200/s at L 1033 cm-2s-1;

- Low momentum spread (<0.1%);

- K pairs produced in a back-to-back topology;

- hadronic background intrinsically low – differently from an extracted beam.


How DANE2 characteristics can be exploited at best for the study of strongly bound kaonic nuclear states?

1) possibility to use either gaseous targets (as proven by DEAR) or thin targets (as proven by FINUDA).

2) Reduced neutron background generated by negative pion absorption (E47) exactly in the area of interest. The yield of these background neutrons depends on the equivalent g/cm2 of the target, namely on density and thickness, and on the materials put around the target itself.

3) The back-to-back topology which characterizes K- production, can be used to trigger on (K-, K+)-pairs, so selecting K- induced events.

4) Another trigger system might be implemented by taking advantage of the X rays emitted in the decay of the kaonic atom, created in the initial stage of the process.


Features of the experimental setup

The complete study of the characteristic features of the kaonic bound nuclear systems requires knowledge of: binding energy, level width and partial widths, angular momenta, isospin, sizes, densities, etc.

This can be done by simultaneously observing the production stage of the K--clusters via missing mass spectroscopy, and their decay products since their momentum correlations contain information on the internal structure of the exotic system.

It is therefore necessary to use a 4π dedicated detector capable of detecting all particles created in both the formation and decay of the K-clusters.


Features of the experimental setupFormation process:

Exotic nuclear states in light nuclei produced with (K-, N) reactions at rest will be observed by the energy distribution of the ejected protons and neutrons via the missing mass spectra of the (K-, p) and (K-, n) reactions.

The setup should be capable to measure:

- Outgoing protons up to 600 MeV/c- Outgoing neutrons up to 600 MeV/c

in a 4π acceptance detector, with good efficiency and resolution.

K- + 4He -> n + (K-ppn); n ~ 510 MeV/c

K- + 4He -> p + (K-pnn); p ~ 550 MeV/c


K- + 4He -> n + (K-ppn)

n-

d

pn 0pn -pp

p- (~64%)

n0 (~36%)

p-

n0 n0

p-

n(~500 MeV/c)2pn-

n(~500 MeV/c)2p;n;;-

1p;2n;0;

n(~500 MeV/c)2p;n;-

1p;2n;0

n(~500 MeV/c)p;d;-

n;d;0

Features of the exp. setup: the decay process


Monte Carlo simulation:

P() GeV/c

P(p) GeV/c

P() GeV/c

P(n) GeV/c

n(~500 MeV/c)+npppn-

-> p -; n < 600 MeV/c; - < 300 MeV/c


Features of the experimental setupDecay process

The exotic states are expected to predominantly decay into final states containing and hyperons and protons, neutrons, deuterons or larger systems of nucleons. The most important feature of a detector is therefore the reconstruction capability for and hyperons from the invariant mass of their decay into nucleon + and/or .

This implies good particle identification for these particles and their decay products.


Features of the experimental setupDecay process

From this data, frame-invariant Dalitz plots can be constructed, which are expected to reflect the size and density of the initial exotic state. Special attention must be paid to two-body correlations in a Dalitz plane, which may lead to a fake effect in an invariant mass spectrum + p, which might be confused with the genuine mass of an exotic strange dibarion K-pp + p if all the three particles are not detected.


Density distribution of K nuclear clusters

JZ / Nov. 29, 2005

by observing the momentum correlation in their 3-body decay products (P. Kienle, Y. Akaishi, T. Yamazaki to be published in Phys. Lett. B)

K-ppn + p + n


The detector satisfying all these features =>

The KLOE detectorPerformance of the KLOE 4 detector:-fully checked and exploited in the numerous measurements done already by KLOE;-studies of processes with BR of < 10-3 (10-6)-acceptance 96%-DC: p/p ~ 0.4% -Spatial resolution of vertices in DC: 3 mm-dE/dx capacity for particle ID implemented-ECAL dE/E ~ 5.7%/E1/2 t= (54/E1/2 + 50) ps-Ks->+- at 0.8 MeV/c2

0 mass resolution to 2-3 % (reconstruction)-Resol. for n of 500 MeV/c ~ 3%……


AMADEUS Experimental programme

Measurements to be performed:

The most fundamental system which we plan to study are the kaonic dibaryon states of ppK- and npK-, which are favorable produced using a 3He gas target in 3He(K-, n/p) reactions.

Their masses including their total width will be determined by neutron and proton energy measurements respectively. Exclusive measurements of their decays allow to extract further information:size/density, angular momentum, ...

A similar programme is planned for kaonic 3-baryon states, populated in reactions using a 4He gas target.

Furthermore we plan to extend these studies systematically over a broad range of nuclear targets starting by Li, B and Be.



By observing momentum correlation in the three-body decay channel, such as

pppK- +p+p or ppnK- +p+n,

one will get information, using the correlation pattern in the Dalitz plane, of the size, density and the angular momentum of the involved kaonic cluster.

all decay products have to be identified their 4-momenta have to be determined


The scientific programme of the nuclear cluster facility will be discussed in dedicated meetings and in the dedicated Workshop:

“Exotic hadronic atoms, deeply bound nuclear states and antihydrogen: present results and future”

to be held at ECT* (Trento), on June 19-24, 2006

Organizers: Catalina Curceanu (Petrascu) – LNF – INFN, Frascati (Italy) coordinator Eberhard Widmann , Stefan Meyer Institut für subatomare Physik - Austrian Academy of Sciences, Vienna (Austria) Akaki Rusetsky, Univ. Bonn, Germany


First actions towards

AMADEUS


First actions towards AMADEUS

KLOE calorimeter efficiency for neutrons

a) Monte Carlo simple GEANT simulation => to be continued => eV/c > 20% (~30%)

b) KLOE+SIDDHARTA tests on KLOE calorimeter prototype(long and short modules) on neutron beam:

- n_TOF at CERN

- BTF at LNF (?)



- at n_TOF at CERN – if available in 2006

Neutrons from 1 eV to 150 MeV energy- possibility to collimate the beam- 10 –100 MeV ~106n/pulse- dE/E (100 MeV) ~ 2%

Prepare request to Research Board



- at BTF (LNF)

Neutrons from photoproduction (-> 800 MeV electrons)- Feasibility study (working group)



AMADEUS integration in KLOE: first drawing

to be continued with:

- setup integration: gaseous and solid targets

- Physics Scientific program


Search for anti-kaon clusters with KLOE


KLOE – EMC

KLOE –Drift Chamber

Possible setupfor AMADEUSwithin KLOE:

Cryogenic targetInner trackerKaon trigger

Preliminary design: AMADEUS setup at KLOE

• a first draft of the interaction region

DEAR beam pipeInner tracker

Kaon trigger

Cryogenic target cell

K+

K-


Preliminary extrapolations

AMADEUS on KLOE setup confronted with KEK E471


E471 Experiment Results4He(K-


M. Iwasaki et al., nucl-ex/0310018 v2

0S

0SB


E471 features

The results were obtained for a total number of about 2 x 108 stopped negative kaons inside the liquid helium target. - acceptance for detection of charged particles: 34%;- detection efficiency for neutron: 36%;- solid angle for the neutron/proton detector: 8%.

With these conditions, the number of events in the missing mass spectra of the two reactions, are:

- about 450 events in the (K-, p) reaction for the S0 (3115) neutral tribaryon, with a signal/background ratio about 1/10;

- about 120 events in the (K-, n) reaction for the S+ (3140) charged tribaryon, with a signal/background ration about 1/10;

The formation ratios for the considered reactions turned out to be of the order of ~ 10-3.


Extrapolation from KEK to DANE2

- more than 70% of kaons generated by –decay can be stopped, with an optimized degrader, inside a gaseous helium target.

For a yearly integrated luminosity of about 10 fb-1, the total numbers of kaons generated in about 2 months (same time interval as at KEK) will be ~ 2 x 109 and ~ 1.4 x 109 will stop inside the target.

For a dedicated 4 detector we assume the following figures of merit:- acceptance for the detection of charged particles: 90%;- detection efficiency for neutrons detector: 30%;- solid angle for the neutron/proton detector: 90%.

Expected events in the case of a 4He target:

- about 45000 in the (K-, p) reaction for the neutral tribaryon K-pnn

- about 12000 in the (K-, n) reaction for the charged tribaryon K-ppn



Pre-experiment: PROPOSAL to KLOE

The DC of KLOE seen as an active target (4He) where=> some K- stop => DBKNS

DC

K-

p

K-pnn


First actions towards AMADEUS Pre-experiment: PROPOSAL to KLOE

A preliminary Monte Carlo simulation shows that with 2 fb-1 one might have due to K- stopped in the He gas of the DC:> 1500 events of

-> the BEST measurement in the world

> 500 events of

AMADEUS group -> willing to help KLOE in data analysis

K- + 4He -> n + (K-ppn); n ~ 510 MeV/c

K- + 4He -> p + (K-pnn); p ~ 550 MeV/c


Even more:

K-ppn ° + p + n

p + -

energy [MeV]

d

- p

K-ppn ° + d

p + -

4He + K- K-ppn + n

n

n

p

p

-

-


Formation of an international collaboration

The Proposal is presented by physicists of the international collaboration DEAR/SIDDHARTA, which are working on DANE since 1996 and where they will be still engaged for the next three years.

To the DEAR/SIDDHARTA collaboration belong 11 institutions from 8 different countries. The interest raised in the international community by kaonic atoms physics at DANE involved, since the beginning, also scientists from outside Europe, like Japan, USA and Canada, which actively participated and are participating to the experiments at DANE.

=>“hard core” of an international collaboration does already exist.


Formation of an international collaboration

Other considerations support the strong appealing of the new initiative and consequently a potentially large interested community: The DANE2 with AMADEUS would represent the only facility in the world where K—induced reactions at rest are studied. Moreover, after the GSI merging into FAIR, Frascati would be the only laboratory in Europe to go along this line of research.

The fact to become the European counterpart with respect to the Japanese programmes at J-PARC reinforces the plan to apply to the Seventh Framework Programme of EU to obtain a substantial economical support both for developments of detectors and for the upgrading of the actual machine.


Dec. 21-22, 2005Workshop on “Antikaon Mediated Bound Systems – Doorway to Kaon Condensation in Neutron Stars”

The scientific case of the study of deeply bound kaonic nuclear states deals with one of the most important, yet unsolved, problems in hadron physics: how the hadron masses and hadron interaction change in the nuclear medium and what is the structure of cold dense hadronic matter.

After the shutdown of KEK in December 2005, two facilities will be active in the field: J-PARC in Japan, and GSI (FOPI) in Europe. The first one will produce kaonic nuclear clusters with K--induced reactions in flight. GSI will follow, before being absorbed in the new complex of facilities FAIR, an alternative approach, represented by nucleus-nucleus and proton-nucleon collisions.

DANE2 can become the world-scientific pole to study the K-

induced processes at rest, which were indicated as the more direct way to investigate the clusters in nuclear matter.


Conclusions (1)

Conclusions (2)As far as the experimental setup is concerned, the 4 KLOE detector, implemented for AMADEUS program, operated in DAFNE2, satisfies the requirements to study the characteristic features of the K-nuclear clusters, which must consists both in observing the production stage of a K-nuclear clusters and detecting the decay products.

First steps towards the realization:

-Monte Carlo intensive simulations-Measurement (KLOE+SIDDHARTA) of KLOE calorimeter for n-efficiency-Feasibility of AMADEUS in KLOE-Possibility to participate to KLOE2 – new parts

Spring 2006 -> Letter of Intent


Deeply Bound


KN low-energy scattering

Kaonic Hydrogen

and deuterium

(1405)

From kaonic atoms to kaonic-nucleiContinuity and innovation


First experimental indications: E471 Experiment Results4He(K-


(M. Iwasaki et al., nucl-ex/0310018 v2)

S0(3115): M = 3117 +3.8-2.0(sys)+/-0.9 (stat)< 21.6 MeV,

B= -194 MeV with respect to K-+p+n+n rest mass Predicted NOT to exist! (B~20 MeV; ~100 MeV)

0S

0SB

S+(3140): M = 3117 +3.8-2.0(sys)+/-2.3 (stat)< 21.6 MeV,

B= -169 MeV with respect to K-+p+p+n rest massPredicted with B ~ 110 MeV

M. Iwasaki et al., NIM A 473 (2001) 286Y. Akaishi & T. Yamazaki, Phys. Rev. C 65 (2002) 044005


Monte Carlo simulation: phase space

P() GeV/c

P(p) GeV/c

P() GeV/c

P(p) GeV/c

n(~500 MeV/c)+ppppn-

- -> n -; n < 500 MeV/c; - < 300 MeV/c



Is based on precision spectroscopy studies of light kaonic nuclei, as function of their baryon number A and isospin T.

In addition, heavier nuclear targets will be studied.

The first objective is to determine the quantum numbers (spin, parity, isospin) of all states, including excited ones, and their energies.

A precise measurement of the energies of a T=1 multiplet would give its Coulomb energy difference (about 4 MeV) and thus information on the size of kaonic nuclei. The challenge of this programme is to reach the necessary accuracy in the determination of the mass differences of the multiplet.



The study of the spin-orbit interaction of the strange tribaryon system [(NNN)K], by measuring the spin-orbit splitting (0p1/2 – 0p3/2) which is predicted to be as large as

60 MeV (for small size kaonic nuclei).

Important information on the structure of kaonic clusters is contained in their total and partial decay widths.Until now, only on upper limit of = 21 MeV is known for a kaonic tribaryon state and no information on partial decay channels is available.

For an accurate measurement of the total width of kaonic nuclei an energy resolution of ~MeV or better is required.


As far as the signal/background ratio (S/B) is concerned, the neutrons produced by low-energy negative pion absorption, will be strongly reduced at DANE2, as previously shown.

Moreover, the implementation of a (K+, K-)-pair trigger and of an X-rays trigger from kaonic atoms decay, should improve S/B by more than a factor 2.


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