Stefano Piano, FINUDA Collaboration – da ne 2004 - Frascati, 7 th – 11 th June 2004 Examining bounds states with FINUDA FINUDA COLLABORATION Stefano Piano

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


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



Silicon Vertex Detector PID

Inner microstrip layer Outer microstrip layer


+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 + -


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


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


-

+prompt

p

Topology of a -hyp event for 12C

-+

prompt

p

vertex

12-Be vertex

Front viewSide view

Central region


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 !!!


-

+prompt

p

+

Topology of a -hyp event for 6Li

+ +prompt

-

p

vertex

Central region front view


-+p

Topology of a -hyp event for 51V

-

+prompt

p

vertex 49-Sc vertex

Central region side view


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


A first glance at 6Li


-

+

p

+


K+ vertex:• + 236 MeV/c

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

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

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



-

+

p

+

K-

K+

+ +

-

p



-

+

p

+

K-

K+

++

-

p



27Al target: typical event

-

+

p


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

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

(26Mg+-)25Na + + n


27Al target: typical event

-

+

p

K+

K-

-p

+


51V target: typical event

-+p


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

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

(50Ti+-) 49Sc + + n


51V target: typical event

-

+

p

K+

K-

- p

+


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


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


Kstop + 12C

p

nBeBe

Be prompt

1012

12

2p

1s

tot

2p

1s

tot

2p

1s

tot


Monte Carlo simulations of background reactions: -spectra

K- n -

p -

K- p+ -

K- p- +

- n -

K- (NN)- N - n -

K- n0 -

TOT



+,0-hyp region



--hyp region

K- p- + K- p+ -

+ n +

K- (NN)+ N + n +

TOT


- Hypernuclei at 1.1 T

• trigger: +

17% of K+K-

• tagging with:

– +prompt, -, p

– two vertices– : invariant mass

Starting-line


- 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


+/o Hypernuclei in FINUDA

• trigger: -prompt

• tagging with:– -

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

• background: o & quasi-free reactions

Documents

Stefano Piano, FINUDA Collaboration – da ne 2004 - Frascati, 7 th – 11 th June 2004 Examining bounds states with FINUDA FINUDA COLLABORATION Stefano Piano