FINUDA : status of analysis and plans for next data taking

FINUDA: status of analysis and plans for next data taking

31st Meeting of the LNF

Scientific Committee

November 29, 2005

Monica Bertani , INFN Frascati

31st LNF SC , Nov 29, 2005 Monica Bertani INFN - LNF 2

Outline

Status of the analysis and plans for next data

taking (1fb1):

Deeply Bound Kaonic Nuclei

Hypernuclear physics

New targets choice

Hardware upgrades

Conclusions and prospects for next run


Deeply Bound Kaonic nuclei:

do they exist ?

+ K


Deeply bound kaonic nuclei

NO (shallow optical potential)small B & large Schaffner-Bielich et.al [N.P. A669 (2000)], Ramos et.al [N.P. A671 (2000) 481], Cieply et.al [N.P. A696 (2001) 173]

YES (deep optical potential)Akaishi-Yamazaki [PLB535(2002)70; PRC 65 (2002) 044005], Kaiser et.al, [NPA594 (1995) 325]

(S=-1) bound K-nucleus systemsDo they exist?

-

Crucially depends on shape of K-nucleus potential_

K-N potential, (1405),nuclear compressibility, chiral symmetry restoration, Kaon mass inside nuclear matter (strangeness condensation, neutron stars…), …

K-N potential, (1405),nuclear compressibility, chiral symmetry restoration, Kaon mass inside nuclear matter (strangeness condensation, neutron stars…), …

If found, they would provide fundamental data about


Theoretical predictions

Akaishi, Yamazaki,PRC 65(2002)044005

PLB 535(2002)70

•Large binding Energy •Narrow width•Favored decay channel: YN

K- + p

MeV -27K EMeV 04Γ

1 2 3r fm0

-50

-200

-300

-400

-500

nuclKU

MeV

(1405)+

+

+

H3

K ( ppnK-)

K- + 3He

MeV -108K EMeV 02Γ

1 2 3r fm0

-50

-200

-300

-400

-500

nuclKU

MeV

H3K

+

+

Akaishi and Yamazaki predict

deep K-nucleus optical potential

Deeply bound K-nucleus systems

_

_

MeV -48K E

-50

0

-200

-300

K- + ppnuclKU

MeV

1 2 r fm

+

+H

2

K ( ppK-)

, ...., ....

Experimentally visible

π Σ Ν Κ closed channelclosed channel

Λ(1405): doorway for the K-nucleus bound states?


Methods for deeply bound K-nuclear states serches

1) Missing mass spectroscopy–Measurement of the momentum of the monochromatic recoiling particle in a A(K-,N)X inclusive reactions–Search for the tri-baryon and generic many-body K- deeply bound states

•With stopped K-:_ •E471, @KEK-PS•FINUDA @ DAΦNE

•With in flight K-:•E930 @ BNL-AGS

2) Invariant mass spectroscopy•Based on the kaonic nuclear states feature of decaying into hyperons

–(K-pp) → Λ + p –(K-pn) → Λ + n –(K-ppn) → Λ + d , Λ + (pn) –(K-ppnn) → Λ + t–(K-pppn) → Λ + 3He

•Full reconstruction of decaying particles •The decay occurs at rest: angular correlation between the emitted particles

•Emitted in opposite directions

FINUDA @ DAΦNEFOPI @ GSI


Missing mass method exploited: SS0 0 statestate ? ?

Deeply-bound kaonic nuclei in FINUDA

preliminary !pSpnnK 0

•FINUDA first observation: Physical Review Letter 94, 212303 (2005)

• presenting here an update

•Back-to-back correlation of these decay modes are observed

•Some candidates of back-to-back -d pair are found

preliminary !

preliminary !

FINUDA uses invariant- mass spectroscopy in light nuclei


First observations: the dibaryon . Evidences in FINUDA invariant mass method, 2004 data

X(K-pp)→Λp

-p p(Λ) ≈ 500 MeV/cp(p) ≈ 500 MeV/cp(-) ≈ 200 MeV/c


First application of Invariant mass spectroscopyFirst application of Invariant mass spectroscopy (K (K--stopstop, pp, pp--))

KK “pp”“pp” pp

p p pp inv. Mass.inv. Mass.

Phys. Rev. Lett. Phys. Rev. Lett. 9494 212303 (3 June 2005) 212303 (3 June 2005)

Step 1Step 1: selection of : selection of events; events; p angular correlationp angular correlation

First observation of KFirst observation of K--pp bound state in FINUDApp bound state in FINUDA

Step 2Step 2: inv. Mass of back-to-back : inv. Mass of back-to-back -p events-p events

threshold

M = (2255 ± 9) MeVYield ≈ 1%/stopped K-

6 light nuclear targets used: 6Li,7Li,12C6 light nuclear targets used: 6Li,7Li,12C


•703 entries703 entries

•3 & 4 hits tracks3 & 4 hits tracks

preliminary

6Li

•12C7Li

all

p-p- inv. mass (GeV/c inv. mass (GeV/c22))

threshold

Update on K-pp analysis: high+low resolution tracks

•New pattern recognition including 3-hit tracks in order to make up for 1 missing hit detector higher acceptance

• With same set of 6 light nuclear targets (6Li,7Li,12C) increase of statistics, possible to distinguish different nuclei

• Consistent result

203 entries203 entries

•4-hits tracks only4-hits tracks only

Phys. Rev. Lett. Phys. Rev. Lett. 9494 212303 (3 June 2005) 212303 (3 June 2005)

threshold


Search for the K-pn nn system in FINUDA

KK “pn”“pn” nn

p p nn inv. Mass.inv. Mass.

Invariant mass spectroscopyInvariant mass spectroscopy (K (K--stopstop, pn, pn--))

taggingtagging •back-to-back back-to-back n selectionn selection

TOO EARLY TO SAY SOMETHING TOO EARLY TO SAY SOMETHING

• not enough statistics (~100 events) not enough statistics (~100 events)

preliminary

threshold


Search for the K-pn pp system in FINUDA

KK “pn”“pn” pp

n n pp inv. Mass.inv. Mass.

Invariant mass spectroscopyInvariant mass spectroscopy (K (K--stopstop, pn, pn--))

- taggingtagging •back-to-back back-to-back - p selection- p selection

no cutsno cuts

pp>200MeV/c to reduce >200MeV/c to reduce

decay contaminationdecay contamination

•

TOO EARLY TO SAY SOMETHING - TOO EARLY TO SAY SOMETHING -

not enough statistics (~100 events)not enough statistics (~100 events)

preliminary

threshold


Search for the strange tribaryon K-ppn system in FINUDA (1)

KK “ppn”“ppn” d d

p p d d inv. Mass.inv. Mass.

Invariant mass spectroscopyInvariant mass spectroscopy (K (K--stopstop, dp, dp--) )

In the same set of light targets (6Li,7Li,C12)

deuteron selection by energy deposit at OSIM and Time of flight

invariant mass

&& d d must be back to back, high momentum

dd invariant mass in coincidence with


coincidence -,p,dde/dx selectionTOF selection

(p, d coincidence)

Search for the strange tribaryon K-ppn system in FINUDA (2)

-,p) inv mass-,p) inv mass

KK “ppn”“ppn” d d

p p

With dE/dx + TOF/track With dE/dx + TOF/track lenght : high S/N reduction, lenght : high S/N reduction, very low background leftvery low background left

•deuteron mass

dE/dxdE/dx + TOF

Very clean d and peaks !

invariant mass invariant mass

•d selection

dE/dxdE/dx + TOF


d) inv mass

Search for the strange K-ppn system in FINUDA (3) d invariant mass

Still poor statistics (57 evts), need more!Still poor statistics (57 evts), need more!

selection cuts:selection cuts:

106<mass<1126 MeV/c2 Cos(d) < - 0.8

-,p) inv. mass

•6Li,7Li,12C targets

•Cos(d)

threshold

all

6Li

7Li

12C

•comparison with previous observations:comparison with previous observations:•(next slide)(next slide) GSI-FOPI

KEK-PS E471

d inv. massd inv. mass

•dE/dx + TOF •dE/dx + TOF


KEK-E471 & FOPI-GSI experimental indications of the strange tribaryon K-ppn

GSI-FOPI inv. mass methodpreliminary, HPC2005

Ni+Ni @ 1.93AGeV: ΛΛ+d+d(Kppn)(Kppn) B=149MeV,M = (3159 M = (3159 ±± 20)MeV 20)MeV~(100± 50) MeV± 50) MeVPOOR SIGNAL/NOISE RATIOPOOR SIGNAL/NOISE RATIO

4He(K-stop,n) K-ppn [ S+(3140)]

T=0, B =169 MeV

M = (3140.5 +3.0-0.8 ±2.3) MeV

Γ < 21.6 MeV , Main decay NN

KEK-PS E471 miss. mass methodIwasaki et al, nucl-ex/0310018, Suzuki et al, Phys. Lett. B597 (2004) 263

•((ΛΛ+d)+d) inv. mass (GeV) inv. mass (GeV)

3 3.2 3.4 3.6 3.8 3 3 3.2 3.4 3.6 3.83 3.2 3.4 3.6 3.8 3 3 3.2 3.4 3.6 3.8


KEK-E471 experimental indications of the strange tribaryon K-pnn

4He(K-stop,p) K-pnn : Signal observed in the semi-inclusive proton momentum

spectrum ~ 510 Mev/c, in coincidence with a fast -, identified with the strange

tribaryon S0(3115) : T=1, B =194 MeV , M = (3117.7 +3.8-2.0 ±0.9) MeV,

Γ < 21.6 MeV (95%C.L.) , Main decay : NN, d

proton momentum (MeV/c)proton momentum (MeV/c)

KEK-PS E471 miss. mass method Iwasaki et al, nucl-ex/0310018, Suzuki et al, Phys. Lett. B597 (2004) 263


Tribaryon (K-pnn) search with the missing mass technique in FINUDA (1)

inclusive proton momentum spectrumnot acceptance corrected

FINUDA looks for S0 signal:in the inclusive proton spectrum weobserve a clear peak around 510 MeV

only in Li6, not in other targets.6Li behaves like a cluster of

4He-d:Is it the same signal found by KEK-E471 due to the strange tribaryon S0(3115) on a “quasi-4He” substructure of 6Li ?

K-stop+4He (K-pnn)+p

the proton momentum should exhibit a peak at about 500MeV/cMissing mass spectroscopy method

???510MeV/c

PRELIMINARY

PRELIMINARY

Contributions from hyperfragment

non-mesonic decays (i.e. 5Hep+n+t)



Selected with p > 260 MeV/c:Clear peak structure!

momentum

•Study of semi-inclusive proton/pion spectra on 6Li (not acceptance corrected) :

•strong correlation of the 500 MeV/c protons with high momentum -

In the assumption: K-

stop+4He (K-pnn)+p

Do the proton come from S0 formation and the pion from the its decay ? K-pnn –d

– n -

NO ! p (NO ! p (-) < 280 MeV/c !

WARNING ON MISSING

MASS METHOD !!!!PRELIMINARY

•p momentum

•p momentump momentum

-

mo

men

tum

- m

om

entu

m



If we observe a proton from S0

formation and a pion from its decay:

K-stop + 4He S0 (3115) + p

S0 (3115) –NN we expect no strong angular correlationbetween proton and pion

INSTEAD: BACKWARD CORRELATION INSTEAD: BACKWARD CORRELATION

OBSERVED BETWEEN PROTON AND OBSERVED BETWEEN PROTON AND

PION!PION!

This does NOT look like a signal from This does NOT look like a signal from S0 .

proton peak region: (p(p)=505-515MeV/c)+p(pi-) >260MeV/c


Tribaryon (K-pnn) search with the missing mass technique in FINUDA(4 ): objection to the interpretation of S0 production

from an 4He cluster

• Is the peak, observed in 6Li by FINUDA and in 4He by KEK-E471, simply due to the scattering on a quasi-deuteron ?

• KK- - + d + d - - + p ?+ p ?• Proton momentum: 515 MeV/c - momentum from - decay: 200-300 MeV/c• Quite significant formation branching ratio expected• Indications for a sizeable d-cluster presence from old exp. of pi- capture on 4He

•WARNING: a peak in missing mass methods can be misleading ! WARNING: a peak in missing mass methods can be misleading !

•FINUDA will exploit both missing mass and invariant mass FINUDA will exploit both missing mass and invariant mass techniques and will give an answer with next data taking using also techniques and will give an answer with next data taking using also a Da D22O target O target


Deeply Bound Kaonic Nuclear states: yield estimation for next run [1fb-1]

2004 run 2006 run (1fb-1)

6 Targets

(6Li, 7Li, 12C)

8 Targets

(6Li, 7Li, 9Be,D2O,13C)

200 4000

100 1600

100 1600

60 1200


Hypernuclear spectroscopy and Non Mesonic Weak

Decays:

status of the analysis and prospects for next run


Hypernuclear spectroscopy: Hypernuclear spectroscopy: 1212CC [published][published]

Result on 12C (KEK E369)

Resolution 1.45 MeV FWHM Production reaction: (+,K+)

First FINUDA result on 12C :

Resolution 1.29 MeV FWHMProduction reaction: (K-

stop, p-)

PR C64(2001)044302PR C64(2001)044302

Phys. L

ett. B

622(2

005)35

12,K C 12,K C

•FINUDA has achieved better resolution than previous experiments FINUDA has achieved better resolution than previous experiments

FINUDA RESULTSFINUDA RESULTSFINUDA RESULTSFINUDA RESULTS CK stop12,

CK stop12,

Capture Rates for Capture Rates for 1212LLC in FINUDA:C in FINUDA:

#1 ground state: ~ (1.01 #1 ground state: ~ (1.01 0.11)x10 0.11)x10-3-3/K/K-stop #6 excited state: ~ (2.04 #6 excited state: ~ (2.04 0.17 )x10 0.17 )x10-3-3/K/K-

stop


Integrated Capture Rates

0

0,001

0,002

0,003

0,004

0,005

0,006

0,007

0 10 20 30 40 50 60

Mass Number A

Cap

ture

Rat

e/st

oppe

d K

-

Preliminary!Preliminary!

Hypernuclear capture rate/KHypernuclear capture rate/K--stopstop (integrated over the bound (integrated over the bound

region) as a function of the mass number. region) as a function of the mass number.

5151VV2727AlAl

1212CC

77LiLi

FINUDA hypernuclear results: summary


Li 7 : - momentum and proton energy spectra

momentummomentum

•proton energyproton energy

FINUDAFINUDA Proton Proton spectra in the spectra in the hypernucleus bound hypernucleus bound region in region in coincidencecoincidence with a with a -- from hypernucleus from hypernucleus formation.formation.

Pion momentum Pion momentum from 7Li formation. from 7Li formation.

Evidence of ground Evidence of ground state and first low state and first low lying statelying state

Np=90Np=90


C12 - momentum spectra

To increase statistics,no selection To increase statistics,no selection quality cuts on quality cuts on -, bw+fw tracks, -, bw+fw tracks, •b<0.3 cm to reduce bck from in flight b<0.3 cm to reduce bck from in flight - decays- decays

momentum (MeV/c)momentum (MeV/c)

Pion momentum from Pion momentum from 1212CC

• formationformation

Pion momentum from Pion momentum from 1212CC

formation in coincidence withformation in coincidence with

proton from decay proton from decay 1212C : C :

ss and p and p clearly show up clearly show up

with better S/N.with better S/N.


C12 proton & neutron energy spectra

• C12 C12 protonproton energy (MeV) energy (MeV)

•

Counts

/ 1

0 M

eV

) C

ounts

/ 1

0 M

eV

)

• C12 C12 neutronneutron energy (MeV) energy (MeV)

FINUDAFINUDA Proton Proton and and neutronneutron spectra in spectra in coincidencecoincidence with a with a -- from hypernucleus from hypernucleus formation in the hypernucleus bound region formation in the hypernucleus bound region (s (s + p + p )) . .

KEK-PS E462/E508KEK-PS E462/E508 [Okada et al, [Okada et al, PLB597(2004)249]PLB597(2004)249]

neutron (filled circle) and proton (open circle)neutron (filled circle) and proton (open circle)


Non Mesonic Weak decays: yield estimation for next data taking [1fb-1]

Target Np

( coinc.)

Nn

( coinc.)

Nnp/Nnn

( coinc.)

6Li (2T) 1200 800 120/80

7Li (2T) 1200 800 120/80

9Be (2T) 800 600 80/60

13C (1T) 300 200 no

16O(1T) 300 200 no


New set of targets for next data taking

New set of targets: 2x 6Li, 2x 7Li, 2x 9Be, 13C, D2OExpected results with ~ 1 fb-1

All the targets can be used for deeply bound kaonic states searches, (K-pp,K-pn) and A dependence can be studied.

FINUDA can give an answer to many open questions

6Li,9Be are d, n clusters useful to investigate the strange tri-baryion systems9Be: high resolution and high statistics hypernuclear spectroscopy and weak decays (never done before)

D2O = (free d + Oxygen), to be compared with behavior of quasi “d” in 6LiO: high resolution and high statistics hypernuclear spectroscopy and weak decays of 16O (poorly studied)

7Li :the best known hypernucleus concerning spectroscopy, weak decays never measured

13C: high resolution and high statistics hypernuclear spectroscopy, comparison with 12C , poorly known only with (K+,pi+).


New targets simulation [ with 1fb-1]

expected hypernuclear expected hypernuclear

momentum spectra frommomentum spectra from

next set of new targets:next set of new targets:

Be9Be9, , C13C13, , O16O16assuming 0.4% FWHM assuming 0.4% FWHM momentum resolutionmomentum resolution

Be9Be9

13C13C

16O16O


HARDWARE UPGRADES


New TOFINO in Frascati PMTs case

TOFINOinner side

•New Tofino detector built at KEK by New Tofino detector built at KEK by

Japanese collaborators:Japanese collaborators:•Use of Hamamatsu photomultipliers•1.8 mm thickness vs 2.3 mm

• is in Frascati, is in Frascati,

Astra lab.Astra lab.

The use of PM’s allows toThe use of PM’s allows toreduce the thickness of the scintillator reduce the thickness of the scintillator slabs (less energy loss) and to suitably slabs (less energy loss) and to suitably modify the assembly geometrymodify the assembly geometry


New TOFINO in Frascati


New TOFINO in Frascati


CONCLUSIONS

FINUDA in the first 3-month run has demonstrated its capability of performing world-class hypernuclear spectroscopy, and has explored a new field in the search for deeply bound kaonic nuclear states.

FINUDA in the next run with 1fb-1 will use nuclear targets that will proof or disproof the existence of such states.

The deeply bound kaonic nuclear states are still largely unexplored: the existence of such states is not experimentally established at the moment and there are different theoretical predictions.

Simultaneously, FINUDA will continue the experimental hypernuclear physics program mainly focused on NMWD.

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