Stefano Piano, FINUDA Collaboration – da ne 2004 - Frascati, 7 th – 11 th June 2004 Examining...

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Examining bounds stateswith FINUDA

FINUDA COLLABORATIONStefano Piano

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004-Hypernuclei

Present knowledge:Only one -hyp. bound state found: 4

He ()Pratically no data in heavier systems

Possible explanations :a) [A] B: previous expt.’s were

unable to detect Bb) NN previous expt.’s were

unable to discriminate S/Nc) no B bound system nothing to be seen !

FINUDA can detect the formation and decay of -hypernuclei in the (K-

stop, )

reaction due to its tracking capabilities

A -hyp. forms when a substitutes a N into a nucleus (S=-1)

R.S. Hayano et al., Phys. Lett. B 231 (1989) 355T. Nagae et al., Phys. Rev. Lett. 80 (1998) 1605

4He

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

How to “dig-out” -hypernuclei with FINUDA

K-stop + A B +

prompt + N + N

pBC

nCC

C

pBC

C

nBeBe

Be

CK

prompt

prompt

prompt

stop

1012

1012

12

1012

12

1012

12

12

0

0

0

-hyp simulated eventReaction steps

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Silicon Vertex Detector PID

Inner microstrip layer Outer microstrip layer

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

+prompt x -

+prompt x p

+prompt x - x p

+prompt in coincidence with daughter particles

+

+prompt

+prompt x -

p

K-stopped + 12C 12

-Be + +prompt

+ p + n p + -

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

K-stopped + 12C 12

-Be + +prompt

+ p + n p + -

… due to 12-Be ???

due to proton contamination

predicted ~ 4-7 MeV(*)

(*) E.Oset et al, Phys. Rep. 188(1990)79

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

M[ p-] = 1114 MeV/c2

Topology of a -hyp event for 12C

-

+prompt

p

K- vertex:• + 176 MeV/c• p 500 MeV/c• - 158 MeV/c

K- + 12C 12-Be + +

prompt

12-Be 12Be + + n

- + p

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

-

+prompt

p

Topology of a -hyp event for 12C

-+

prompt

p

vertex

12-Be vertex

Front viewSide view

Central region

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

K-stopped + 12C 12

-Be + +prompt

+ p + n p + -

[ - p] invariant mass distribution; (+, -, p) coincidence

Invariant mass, MeV/c2

Ent

ries

/ 4

MeV

/c2

needs to be improved !!!

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

-

+prompt

p

+

Topology of a -hyp event for 6Li

+ +prompt

-

p

vertex

Central region front view

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

-+p

Topology of a -hyp event for 51V

-

+prompt

p

vertex 49-Sc vertex

Central region side view

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Summary• FINUDA/DANE a unique facility for -hyp studies• Initial analysis yields positive expectations for bound B

beyond A=4• Improve data analysis:

– Better pattern recognition increases a statistics: x3– Better definition of improves (conversion reaction)

invariant mass – Further improve to pPID

• Strategy for future analysis: – tune-up analysis for the “reference nucleus” 12C– go for 6,7Li, 27Al and 51V– have a glance at 0/+-hyps– get theorists involved

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

A first glance at 6Li

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

-

+

p

+

K- vertex:• + 151 MeV/c• p 271 MeV/c• - 127 MeV/c

K+ vertex:• + 236 MeV/c

(p + -) Inv. Mass = 1116 MeV/c2

K- + 6Li (5He+-) + +

(5He+-) 3H + + n +n

Topology of a -hyp event for 6Li

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

-

+

p

+

K-

K+

+ +

-

p

Topology of a -hyp event for 6Li

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

-

+

p

+

K-

K+

++

-

p

Topology of a -hyp event for 6Li

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

27Al target: typical event

-

+

p

K- vertex:• + 149 MeV/c• p 156 MeV/c• - 142 MeV/c

(p + -) Inv. Mass = 1117 MeV/c2

K- + 27Al (26Mg+-) + +

(26Mg+-)25Na + + n

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

27Al target: typical event

-

+

p

K+

K-

-p

+

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

51V target: typical event

-+p

K- vertex:• + 163 MeV/c• p 248 MeV/c• - 124 MeV/c

(p + -) Inv. Mass = 1110 MeV/c2

K- + 51V (50Ti+-) + +

(50Ti+-) 49Sc + + n

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

51V target: typical event

-

+

p

K+

K-

- p

+

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Sigma Hypernuclei in FINUDA

Kstopped + A B +

prompt + N + N

pBC

nCC

C

pBC

C

nBeBe

Be

CK

prompt

prompt

prompt

stopped

1012

1012

12

1012

12

1012

12

12

0

0

0

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Monte Carlo simulations of -hypernuclei

pBC

nCC

C

pBC

C

nBeBe

Be

CK

prompt

prompt

prompt

stop

1012

1012

12

1012

12

1012

12

12

0

0

0

binding energies and width are taken from: E.Oset et al., Phys. Rept. 188 (1990) 79

bound nucleons have Fermi mom. mom. distr. prob. dens. funct.final state particles tested for Paulikinematics of f.s.p. feeds GEANT3 (geom., en. loss, trajectories)

E.Oset, A.Ramos, I.Vidana, private communication

2p

1s

tot

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Kstop + 12C

p

nBeBe

Be prompt

1012

12

2p

1s

tot

2p

1s

tot

2p

1s

tot

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Monte Carlo simulations of background reactions: -spectra

K- n -

p -

K- p+ -

K- p- +

- n -

K- (NN)- N - n -

K- n0 -

TOT

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Monte Carlo simulations of background reactions: -spectra

+,0-hyp region

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

Monte Carlo simulations of background reactions: -spectra

--hyp region

K- p- + K- p+ -

+ n +

K- (NN)+ N + n +

TOT

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

- Hypernuclei at 1.1 T

• trigger: +

17% of K+K-

• tagging with:

– +prompt, -, p

– two vertices– : invariant mass

Starting-line

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

- Hypernuclei at 0.6 T

• trigger: +prompt

56% of 12-Be

• improved tagging

• better track and vertex fitting

Finishing-line

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004- Hypernuclei in FINUDA at 0.6 T

vertex region

Stefano Piano, FINUDA Collaboration – dane 2004 - Frascati, 7th – 11th June 2004

+/o Hypernuclei in FINUDA

• trigger: -prompt

• tagging with:– -

prompt, -, p– two vertices– : invariant mass

• background: o & quasi-free reactions