DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Very preliminary results of Non Mesonic Weak Decays in

FINUDA

De Mori Francesca for the FINUDA Collaboration

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Outlook:

NMWD in hypernuclei NMWD in FINUDA Proton single nucleon spectra of various

targets Rare Decays of Conclusions and prospects

4He

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Non Mesonic Weak Decays

In nuclear medium :NNN

NNnNN (15%)

Dominant in medium-heavy hypernuclei(A12)

Unique opportunity to study the four-baryons weak interaction

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

2 6Li

1 7Li

3 12C

1 27Al

1 51V

5 cm

OSIM

ISIM

TOF

Target

Beam pipe

FINUDA allows in primis the measurement of emitted nucleon spectra from :

27Al12C

51V7Li

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Event selection of NMWD protons

Selected positive tracks from K- vertex with specific energy loss in the band of proton

Presence of pion track from K- vertex required with pion momentum corresponding to the production of the hypernucleus in the bound region

)()( NnpNp

ZZK AAstop

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

12C target 7Li target

51V target 27Al target

Preliminary not acceptance-corrected

-1.8<B<11.MeV -3.3<B<5.6

MeV

-1.2<B<16.8 MeV

-0.2<B<20.2 MeV

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Rare Decays of 4He

6 4K Li He n N

4He d d 4 3He p H

6Li is unstable

6 5K Li He N

6 4K Li H p N

Pd~570 MeV/c

Pt~510 MeV/c

exploiting 6Li target

Some three-four body decay channels

Possible 2-body decays of 4He with charged

particles

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Deuteron pair of rare decays selection (4

He d+d):

Looking for positive tracks from K- vertex

Looking for dE/dx over the proton band

Looking for a pair of tracks of this kind back to back with momentum greater than 400 MeV/c

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

PID (dE/dx in vertex silicon detectors)

Momentum(MeV/c)

dE/d

x(O

SIM

)

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Angle between pairs of tracks

P>400MeV/c

sel.deuterons

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

First observation of 4He d-d rare decayFirst observation of 4He d-d rare decay

ten deuteron pairs observed

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Evento fujoka 2

d

d

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

d

d

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

d

d

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Conclusions & prospects First very preliminary results of NMWD in FINUDA:

single proton spectra from all 5 different targets Clear evidence of rare non mesonic decay of 4

He never observed before

needed neutron identification: we are working on it needed improved backtracking: we are working on it needed better mass identification for back-tracking for

deuteron momenta better reconstruction:we are working on it

we are on the way to increase the number of good events

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

Contribute to the proton spectrum of the background reaction:

K (np) p

n

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

DAFNE04 Frascati, June 8 2004 De Mori Francesca ,Turin University and INFN

O.Hashimoto et al. Phys.Rev.Lett.88:042503,2002

KEK-PS E307