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Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
L’esperimento
FINUDA
Stefano PianoINFN sez. Trieste
FINUDA Collaboration
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Bari University & INFN Bari
Brescia University & INFN Pavia
Pavia University & INFN Pavia
Torino University & INFN Torino
Trieste University & INFN Trieste
Torino Polytechnic & INFN Torino
L.N.F. / INFN Frascati
RIKEN
KEK
Seoul National University
Teheran Shahid Beheshty University
University of Victoria
JINRDubna
LNF -
INFNFrascati
DAΦNE
The FINUDA Collaboration
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FINUDA physics program-
Λ
HYPERNUCLEAR SPECTROSCOPY
essential tool
for testing :•
theoretical models
of Λ-N
potentials
•
single particle
nuclear model predictions •
bound
states with strangeness
-
Λ
HYPERNUCLEAR SPECTROSCOPY
essential tool
for testing :•
theoretical models
of Λ-N
potentials
•
single particle
nuclear model predictions •
bound
states with strangeness
-
HYPERNUCLEAR DECAYS•
study of baryon-baryon weak processes
in nuclear
matter: Λ →πN
and ΛN→NN
-
HYPERNUCLEAR DECAYS•
study of baryon-baryon weak processes
in nuclear
matter: Λ
→πN
and ΛN→NN
-
SEARCH FOR:•
Neutron-rich hypernuclei
•
Rare decays•
Sigma hypernuclei
•
Deeply bound kaonic nuclei•
K-
multi-nucleon absorption
-
SEARCH FOR:•
Neutron-rich hypernuclei
•
Rare decays•
Sigma hypernuclei
•
Deeply bound kaonic nuclei•
K-
multi-nucleon absorption
ON DIFFERENT NUCLEISIMULTANEOUSLY
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Hypernuclear
Physics at DAΦNE e+e-
collider
e+e-
Φ(1020) K+K-
~16 MeV
The K-
can be stopped in thin targets (~ 0.1
÷
0.3 g cm-2)
to produce hypernuclei
decay High resolution
spectroscopy
K-stop
+ + π-ΛZAZA
The Φ
decay is a source of:
• neutral and charged kaons
• collinear and tagged
• low energy (~16 MeV)
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FINUDA DetectorDetector capabilities:
Selective trigger based on fast scintillation detectors (TOFINO, TOFONE)
Clean K- vertex identification(ISIM P.ID.+
x,y,z
resolution
+
K+
tagging)π±, K, p, d, t … P.I.D. (dE/dx)High momentum resolution
(6‰ FWHM) (tracker resolution+ He bag + thin targets)
Neutron detection (TOFONE)Time-Of-Flight (TOFONE-
TOFINO)
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
(BR 49% -
Ekin
~ 16 MeV)
12 scintillators (TOFINO)8 silicon microstrips layer (ISIM)8 targets10 silicon microstrip layer (OSIM)
some hundreds
Φ/s
Φe+ e-
K-/+
K+/-
crossing angle: 12.5 mrad
Interaction Region
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FINUDA detectors performancess.c. solenoid: B = 1.0 T; field homogeneity within 2%
interaction/target region: K+/K-identification, hypernucleus production and detection
tracking devices: measurement of trajectories and momenta of charged particles (Δp/p 5‰)
external scintillator barrel: trigger and neutron detection
He chamber: minimization of particle multiple scattering
TOFout
:
σt
= 500 ps
FWHMefficiency ≥
10%;
ΔE = 8 MeV
Δp/p:
He atmosphere
= 5‰air
= 2%
VDET:
σz
= 30 μm;
ΔE = 25% FWHM (K)TOFin
:
σt
= 250 ps
LMDC:
σ(ρ, φ) = 150 μm;
σz
≤
1% wire length STB:
σ(ρ, φ) = 150 μm;
σz
500 μm
TOF
out
time resolutionTOFout
time resolution
VDET z resolutionVDET z resolution
PID in VDETPID in VDET
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
different targets in the same run➥
high degree of flexibility
simultaneous tracking of μ+
from the K+
decay ➥
energy and rate calibration
transparency ➥
“high”
resolution spectroscopyvery thin targets (0.1 ÷
0.3 g/cm2)
1
2 3
4
5
67
8
1 cm
coincidence measurement with large acceptancecomplete event ➥
decay mode study
4ΛHe → dd
FINUDA Key Features
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
2×6Li, 7Li, 3×12C, 27Al, 51V
Three
12C targets
for:•
calibration
data to
be
compared
with previous
measurements•
improvement
of the precision
of the measurement
on all
the hypernucleus observables
•
Other items of
physics
(deeply
bound kaonic states, multinucleon
K-absorption
) )
6Li6Li
7Li
51V 27Al
12C
12C 12C
Medium-heavy
targets:A-dependence
and feasibility
of higher
A studies
Light targets:
ideal for
weak
decay
studies.6
Λ
Li unstable
by
nucleon
emission, used
as doorway
for
light systems
5Λ
He, 4Λ
He, 4Λ
H.Light K--nucleus
systems
may
favour
the
formation
of
deeply
bound
kaonic states
The interaction-target region for the first data taking
•Average daily integrated luminosity ~ 2 pb-1
• Total integrated luminosity 257 pb-1
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
6Li 7Li
7Li
6Li
9Be
9Be
13C
D2
O
The interaction-target region for the second data taking
• 6Li e 7Liused
also
during
the first data taking;
•9Be: •hypernuclear
spectroscopy
with
high resolution
and high statistics• weak
decays
•D2
O:
important
comparison
with
“quasi” deuteron
in 6Li .
•13C:•hypernuclear
spectroscopy
with
high resolution
and high statistic•Comparison
with
12C from
the first data taking
2×6Li, 2×7Li, 13C, 2×9Be, D2
O
•Average daily integrated luminosity ~ 7 pb-1
• Total integrated luminosity 966 pb-1
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Hypernuclear
event
π−
μ+
μ+
Κ+
Κ−
π−
Φ
K−
+ A →
Λ
A + π−K−
+ A →
Λ
A + π−
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
12C (raw) excitation spectrum
0
100
200
300
400
500
600
700
0.18 0.2 0.24 0.26 0.28 0.3 0.320.22
Cou
nts/
1 M
eV/c
momentum (GeV/c)
K−
+ 12C →
12
Λ
C + π−K−
+ 12C →
12Λ
C + π−
Raw spectrum of
negative pions
coming out the 12C targets.
Hypernuclear peaks are visible
already without any background subtraction
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
the measurement of the π-
momentum is possible thanks to the FINUDA capabilities of tracking and resolution
How did we detect an hypernucleus?
by conserving energy and momentum
the “strangeness exchange”
reaction it is not
the only possible way in which a negative pion
can be present
in the interaction K-N final state
1
2
3
4
Detecting Hypernuclei
−π
+μ
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FINUDA vs. KEK-E369
H. Hotchi
et al., Phys. Rev. C 64 (2001) 044302 H. Hotchi
et al., Phys. Rev. C 64 (2001) 044302
ΔE ~ 1.5 MeV
FWHMΔE ~ 1.5 MeV
FWHM
12C(π+,K+)12C12C(π+,K+)12CC12Λ
ΔE ~ 1.3 MeV
FWHMΔE ~ 1.3 MeV
FWHM
12C(K-
,π-)12C12C(K-
,π-)12C−stopK C12
Λ
M.Agnello
et al., Phys. Lett. B 622 (2005) 35M.Agnello
et al., Phys. Lett. B 622 (2005) 35
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
simulation of the background -
by means of MC simulations -
we reproduced the BΛ
distribution of the pions
coming from the possible reactions
Background simulation
BΛ
distribution of the pions
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
anti-boost side boost side
1) we fit the experimental distribution with the sum of N gaussians (for the signal) and 4 histograms for the background (the mean and the sigma of the gaussians are free to move around the input values)2) we repeat the fit with a more sophisticated fit tool fixing also the mean values and the sigma of the gaussians [ROOT TFractionFitter]
Fitting the Data
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
the muons curves in a different way and do not cover all the “roads”
(possible source of systematics)
the MC tracks are “cleaner”
than the real ones,quality cuts act in a different way in real data and MC
(possible source of systematics)
road = a given combination of detectors (OSIM, inner Drift Chambers, outer Drift Chambers)
nΛ
=n. of hypernucleiNK-=n. of stoppped kaonscR = capture rate
(formation probability per stopped kaon)επ
= all other efficiencies (trigger, geometrical acceptance, reconstruction, cuts)
εD
= overall detector efficiency
Capture Rate
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FWHMFWHMfrom 1.65 to 1.95 from target to targetfrom 1.65 to 1.95 from target to target
BΛ
energy measurements-
absolute scale of the energy known at the level of 0.2 MeV-
possible systematic of the fit of 0.2-0.3 MeV -
global error of about 0.5 MeV
Hypernuclear
Spectroscopy: 7Li
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
capture Rate per stopped Kcapture Rate per stopped K
--
#1: 0.041 #1: 0.041 ±±
0.006 0.006 ±±
0.005 %0.005 %
#2: 0.058 #2: 0.058 ±±
0.008 0.008 ±±
0.006 %0.006 %
#3: 0.043 #3: 0.043 ±±
0.006 0.006 ±±
0.005 %0.005 %
#4: 0.052 #4: 0.052 ±±
0.007 0.007 ±±
0.006 %0.006 %
H. Tamura et al.
Nucl. Phys. A 754
(2005) 58c
excitation energies
are referred tothe ground state BΛ
= -5.58 ±
0.03 MeV[M. Juric et al. Nucl. Phys. B 52
(1973) 1]
Total in the bound region: 0.14 ±
0.02 ±
0.02 %
Hypernuclear
Spectroscopy: 7Li
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Hypernuclear
Spectroscopy: 9Be
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
H. Tamura et al.
Nucl. Phys. A 754
(2005) 58c
excitation energies
are referred to the ground stateBΛ
= -6.61 ±
0.04 MeV
[M. Juric et al. Nucl. Phys. B 52
(1973) 1]
capture Ratecapture Rate#1: 0.022 #1: 0.022 ±±
0.006 0.006 ±±
0.002 %0.002 %
#2: 0.036 #2: 0.036 ±±
0.008 0.008 ±±
0.004 %0.004 %
#3: 0.027 #3: 0.027 ±±
0.006 0.006 ±±
0.003 %0.003 %
Total in the bound region: 0.058 ±
0.014 ±
0.006
Hypernuclear
Spectroscopy: 9Be
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Hypernuclear
Spectroscopy: 13C
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
excitation energies
are referred to the ground stateBΛ
= -11.22 ±
0.08 MeV[M. Juric et al.
Nucl. Phys. B 52
(1973) 1]
capture Ratecapture Rate#1: 0.006 #1: 0.006 ±±
0.001 0.001 ±±
0.001 %0.001 %
#2: 0.014 #2: 0.014 ±±
0.002 0.002 ±±
0.002 %0.002 %
#3: 0.018 #3: 0.018 ±±
0.002 0.002 ±±
0.002 %0.002 %
#4: 0.024 #4: 0.024 ±±
0.003 0.003 ±±
0.003 %0.003 %
#5: 0.035 #5: 0.035 ±±
0.005 0.005 ±±
0.004 %0.004 %
Total in the bound region: Total in the bound region: 0.062 0.062 ±±
0.0080.008
±±
0.008 %0.008 %
Hypernuclear
Spectroscopy: 13C
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Hypernuclear
Spectroscopy: 16O
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Total in the bound region: Total in the bound region: 0.027 0.027 ±±
0.0050.005
±±
0.003 %0.003 %
capture Ratecapture Rate#1: 0.006 #1: 0.006 ±±
0.002 0.002 ±±
0.001 %0.001 %
#2: 0.021 #2: 0.021 ±±
0.004 0.004 ±±
0.002 %0.002 %
Hypernuclear
Spectroscopy: 16O
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
bound region
binding energy of the ground state
ground state
Conclusions
The capture rate (formation probability),per stopped K-, has been measured in the same experiment
for different targets*
-
First measurements for
7Li,
9Be and 13C
*(27Al and 51V will also be added to the analysis
CAPTURE RATE (PER STOPPED KAON) VS A
NPA 835 (2010) 414
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
•
Mesonic
weak decay like Λ
free weak decay:–
Λ → pπ-
B.R. 63.9% (Гπ-
)–
Λ → nπ0
B.R. 35.8% (Гπ0
)
–
lifetime τΛ
free
= 263 ps–
nucleons emitted with a momentum q ~ 100MeV/c
–
The
mesonic
weak decay
is suppressed in
nuclear matter due to the
Pauli blocking
of the nucleon in the final state
The two main decay mechanism inside a hypernucleus
are
Mesonic Weak decay
Non Mesonic Weak Decay (NMWD)
Decay modes of
Λ
hypernuclei
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Non Mesonic
Weak Decay•
Λ
embedded in a nucleus
–
Λn → nn
(Гn
) “neutron-induced
decay”–
Λp → np
(Гp
) “proton-induced
decay”–
ΛNN → nNN
(Г2
) “two nucleons-induced
decay”
Total width decay ГT
=
ГM
+ ГNM
ГM
=
Гπ-
+ Гπ0
ГNM
=
Гn
+ Гp
+ Г2
mom
entu
m
270
MeV
/c
NΛ
N N
π
The non mesonic
decay
is the dominant decay channel for medium-heavy
nuclei
(A≥12)
(~ 415 MeV/c)
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Hypernuclear
decay study in FINUDAStrategy: coincidence measurement
p
π-
charged Non-Mesonic channel
K-
stop
+ AZ → AΛ
Z + π-
AΛ
Z →A-2(Z-1) + p + n
charged Mesonic channel
K-
stop
+ AZ → AΛ
Z + π-
AΛ
Z →A(Z+1) + π-
S-EX 260-280 MeV/c
MVD80-110 MeV/c
NMWD 170-600 MeV/c
π-
π-
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
12Λ
C
11Λ
B
kinetic energy (MeV)
Hypernuclear
decay study in FINUDA: strategy
MWD NMWD
NMWD
decay
π-
and p spectra
(Λqf
decay)/K-np background subtracted & acceptance
corrected
Inclusive production π-
spectra
K-np background corrected
π-p
p
12Λ
C
11Λ
B 11Λ
B
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
T. M
otob
a (P
rivat
e C
omm
unic
atio
n)
Mesonic weak decay spectra: 7Λ
Li•
Correspondence with the calculated strenght functions
T. Motoba et al, Progr. Theor. Phys. Suppl. 117 (1994) 477.
A. Gal, Nucl. Phys. A 828 (2009) 72.
•
Formation of different excited states of the daughter nucleus
•
Initial hypernucleus spinJπ
(7
Λ
Lig.s.
) = 1/2+ (Sasao, PLB 579 (2004) 258.)
•
Correspondence with the calculated strenght functions
T. Motoba et al, Progr. Theor. Phys. Suppl. 117 (1994) 477.
A. Gal, Nucl. Phys. A 828 (2009) 72.
•
Formation of different excited states of the daughter nucleus
• Initial hypernucleus spinJπ
(7Λ
Lig.s.
) = 1/2+ (Sasao, PLB 579 (2004) 258.)
7Be: 3/2-gs
& 1/2-
(429keV)
3-body decays
PLB 681
(2009)1
39
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
T. M
otob
a (P
rivate Com
mun
ication)
•
Correspondence with the calculated strenght functions
T. Motoba et al, Progr. Theor. Phys. Suppl. 117 (1994) 477.
A. Gal, Nucl. Phys. A 828 (2009) 72.
•
Initial hypernucleus spinJπ
(9
Λ
Beg.s.
) = 1/2+
O.Hashimoto NPA 639 (1998) 93c.
•
Correspondence with the calculated strenght functions
T. Motoba et al, Progr. Theor. Phys. Suppl. 117 (1994) 477.
A. Gal, Nucl. Phys. A 828 (2009) 72.
• Initial hypernucleus spinJπ
(9Λ
Beg.s.
) = 1/2+
O.Hashimoto NPA 639 (1998) 93c.
Mesonic weak decay spectra: 9Λ
Be
9B: 3/2-gs
& 1/2-(2.75 MeV)
FINUDA
ΔT ~ 4 MeV
FWHM @38 MeV
PLB 681
(2009)1
39
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
•
Correspondence with the calculated strenght functions
H. Bando et al, Pers. Meson Science (1992) p.571A. Gal, Nucl. Phys A 828 (2009) 72.
•
Two contributions of the 11C ground state 5/2-
and its 7/2-
excited state
• Initial hypernucleus spinJπ
(11Λ
Bg.s.
) = 5/2+ : experimental confirmation(Sato et al., PRC 71 (2005) 025203)
by different observable
Mesonic weak decay spectra: 11Λ
B
T. M
otob
a (P
rivate Com
mun
ication)
11C: 3/2-gs
& 7/2-
(~6.5 MeV)
PLB 681
(2009)1
39
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
•
Correspondence with the calculated strenght functions
T. Motoba et al, Nucl. Phys. A 489 (1988) 683.A. Gal, Nucl. Phys. A 828 (2009) 72.
• 15Λ
Ng.s spin not known. Jπ
(15Λ
Ng.s.
) = 3/2+
D.J.Millener, A.Gal, C.B.Dover Phys. Rev. C 31 (1985) 499. Spin ordering not obtained from γ-rays of 16
Λ
O M.Ukai et al. Phys. Rev.C 77 (2008) 054315.
• First experimental determination of Jπ
(15Λ
Ng.s.
) = 3/2+ from decay rate value (and spectrum shape)
Mesonic weak decay spectra: 15Λ
N
T. M
otob
a N
PA 489 (198
8) 683
.
15O: 1/2-gs
& sd
(~6 MeV)15O: 1/2-gs
& sd
(~6 MeV)
PLB 681
(2009)1
39
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present data
T. Motoba
PTPS 117 (1994) 477
previous data
A.Gal
NPA 828 (2009) 72
A
Mesonic decay ratio: Γπ−
/ ΓΛ
fit from measured values for A=4-12 hypernuclei
strong nuclear structure effects
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
12Λ
C
Acceptance
corrected
•
Spectrum of negative pions
for events in which a proton is detected in coincidence with a π-
•
Asking for the proton coincidence a clear peak emerges at
272 MeV/c
(ground state)
Non Mesonic weak decay spectra: the method
Proton energy spectrum from 12Λ
C p-induced NMWD before and after
the acceptance correction
339
events
Not acceptance
corrected
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NMWD p
Coincidence spectra: 12Λ
C, all targets
π-
normalization region
simulation + reconstruction + selection + normalization
Non Mesonic weak decay spectra: the methodbackground reaction: K-
np
Σ-
p
Σ-
n π-
coincidence
p
Data
subtraction
M. Agnello et al., NPA 804 (2008),151
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Ahigh
: spectrum area above μ1N + FSI 2N(>70 MeV) ~ 5% 2NtotG,Garbarino, A.Parreno
and A.Ramos, Phys.Rev.Lett. 91 (2003) 112501.Phys.Rev. C 69 (2004) 054603.
assumption
Alow
Ahigh
μ
from fit
NMWD p
gaussian
fitfree μ 12
Λ
C
FSI & ΛNN contribution evaluation: the method
Alow
: spectrum area below μ1N + 2N + FSI
W.Alberico
and G.Garbarino, Phys. Rev. 369 (2002) 1.assumption2N / NMWD independent on A
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N(Λp np)+Alow
+ Ahigh
Alow=
0.5 N(Λnp nnp) + NpFSI-lowN(Λp np) +
N(Λnp nnp) + NpFSI-low + Np
FSI-high
Alow
, Ahigh
proportional to A =
c’
+ A
d’Alow
+ Ahigh
Alow=
a’
+ A
b’a
+
A b
a=a’/c’= 0.65±0.14
b=b’/c’=0.009±0.013
d’/c’
< 10-3
Alow
Alow
+ Ahigh
= R(A)
FSI linear on A up to A=16
PLB 685 (2010) 247
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R(A) = 0.5 + Γ2
/Γp
1 + Γ2
/Γp
+ bA
Γ2
/Γp =R(A) -
bA
-
0.5
1 –
R(A) -
bAΓ2
/Γp
not dependent on A
Γ2
/Γp
: eight values weighted mean = 0.43±0.25
ΓNMWD
Γ2 =Γn
/Γp
+ 1 + Γ2
/Γp
Γ2
/Γp = 0.24 ±
0.10
Bhang et al., EPJ A33 (2007) 259.
from the linear fit
systematics: all p-shell
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
• p-induced NMWD proton spectra from 5Λ
He to 16Λ
O
• FSI & 2N: “model–independent”
analysis by the exploitation of a large systematics
•
first experimental indication of the relevant rôle
played by the two–nucleon induced mode in the NMWD of hypernuclei
• contribution as large as almost 27% 24% of all the non–mesonic weak decays
• very large contributions from 2N suggested by theoretical calculation (Γ2
/ΓNMWD
~ 0.19 -
0.29)
W.Alberico, A.De
Pace, G.Garbarino
and A.Ramos, Phys. Rev. C 61 (2000) 044314.
G. Garbarino, A.Parreno
and A.Ramos, Phys. Rev. C 69 (2004) 054603.
E. Bauer and G. Garbarino
, NPA 828 (2009) 29.
• Γ2
/ΓNMWD
experimental indications:
present value: 0.24±0.10 PLB 685 (2010) 247H. Bhang et al., EPJ A33 (2007), 259: ~ 0.4 12
Λ
CJ.D.Parker et al., PRC 76 (2007), 035501: ≤
0.24 (95% CL) 4Λ
He
NMWD, FSI & 2N: results
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
d
dμ+
6Li
Hypernuclear
rare
decay
⎪⎩
⎪⎨
⎧
++++
npdtpdd
Hyper-fragments
production
Hyper-fragments
production
p
d
= 570
MeV/cback to
back
topologypd
= 570
MeV/cback to
back
topology
⎪⎩
⎪⎨
⎧
++
++
+
Λ
Λ
Λ
ppHnpHe
pHe
4
4
5+→+ −− πLiK 6
4Λ H →e
Capture rate:10-5
– 10-4
per K-
stop
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Light hypernuclei
rare decays
in FINUDA•
large
angular
coverage
(~4π)
•
Excellent particle identification for charged hadrons
•
Good momentum resolution•
Capability to fully reconstruct the event topologies
–
Set of several targets allowing the production of different hypernuclei
and hypernuclear
fragments
•
4Λ
He
hyperfragments
production, from
all
targets–
4Λ
He
→ dd•
d momentum: 570 MeV/c
–
4Λ
He
→ pt•
p momentum: 508 MeV/c
•
5Λ
He hypernucleus formation–
From
6Li targets: K- 6Li →
5Λ
He
+ p + π
-
(π-
momentum: 275.15 MeV/c)–
From
7Li targets: K- 7Li → 5Λ
He
+ d + π
-
–
NM two-body
decay: 5Λ
He
→
dt•
d momentum: 597 MeV/c
dE/dx
p.id. TOF p.id.
p t
dd
p t
mips
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Neutron-rich hypernuclei Hypernuclei
with a large neutron excess
have been
theoretically predicted (L. Majling, NPA 585 (1995) 211c).
The Pauli principle
does not apply to the Λ
inside the nucleus + extra binding energy
(Λ
“glue-like”
role) ⇒
a larger number
of neutrons can be bound
with respect to ordinary nuclei.
•
Hypernuclear physics:ΛN interactions at low densities, the role of 3-body forces
•
Neutron drip-line:response of neutron halo on embedding of Λ
hyperon, hypernuclear species
with unstable nuclear coreT. Yu. Tretyakova
and D. E. Lanskoy, Nucl. Phys. A 691: 51c, 2001.
•
Astrophysics:Feedback with the astrophysics field: phenomena related to high-density nuclear matter
in neutron stars.
S. Balberg
and A. Gal, Nucl. Phys. A 625: 435, 1997.
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
1)
strangeness
+ double charge
exchangeK-
+ p → Λ + π0
→ π0
+ p → n
+ π+
π-
+ p → π0 + n→ π0
+ p → K+
+ Λ2)
strangeness
exchange with Λ-Σ
couplingK-
+ p → Σ-
+ π+
→ Σ-
+ p → Λ + nπ-
+ p → Σ-
+ K+
→ Σ-
+ p → Λ + n
Neutron-rich hypernuclei Two production mechanisms:
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Neutron-rich hypernucleiK-
+ 6Li 6ΛH + π+ (N/Z= 5) NEW
K-
+ 7Li 7ΛH + π+ (N/Z= 6) NEW
K-
+ 12C 12ΛBe + π+ (N/Z= 2)
K- + 6Li 6ΛH + π+ (N/Z= 5) NEW
K- + 7Li 7ΛH + π+ (N/Z= 6) NEW
K- + 12C 12ΛBe + π+ (N/Z= 2)
6.1·10-5/K-stop(2.0 ±0.4stat syst)·10-5/K-
stop12ΛBe
-(4.5 ±0.9stat syst)·10-5/K-stop
7ΛH
-(2.5 ±0.4stat syst)·10-5/K-stop
6ΛH
From litterature
FINUDA valueSystem
6.1·10-5/K-stop(2.0 ±0.4stat syst)·10-5/K-
stop12ΛBe
-(4.5 ±0.9stat syst)·10-5/K-stop
7ΛH
-(2.5 ±0.4stat syst)·10-5/K-stop
6ΛH
From litterature
FINUDA valueSystem
0.40.1
+
−
0.40.1
+
−
0.30.1
+
−
PLB 640 (2006)145
FINUDA value
90% C.L.
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Neutron-rich hypernucleiπ+ spectra (production) in coincidence with π-
(decay)Data Takin
g
2006-2007
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Investigation
of
hyperon-nucleon/nucleus
interaction
via production of hypernuclei:
-
A
success story in the Λ-sector
(several
Λ-hypernuclei
found, precious
info on Λ-N/A potential)-
A troubled
story in the Σ-sector:
(large
width
expected
from
ΣN → ΛN abs)
-Contradictory
claims:▪Σ-hyp. claimed
on 6Li, 9Be, 12C,16O, 4He
[1]
▪
No
evidence
on 6Li,9Be(K-,π); CH, Si, Ni, In, Bi
(π-,K+) [2]
4Σ+/0
He: presently
the only
well established
Σ-hypernucleus
[1] Bertini et
al, PLB136 (‘84),Yamazaki
et
al i PRL54(‘85),Paul et
al NPA479(‘88),…[2] Sawafta
et
al, NPA639 (1998);Bart et
al,PRL83 (1999); Hayano
et
al, PLB231 (1989), Noumi
et
al, PRL89 (2002); Saha
et
al.,PRC70 (2004)…
Experiments essentially based on A(K-,π) and A(π-,K+)
inclusive reactions.
Study of the K-stop
A→ΣπΑ'
Reaction at DAφNE
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
K+
K-n
π- μ+
π+ π+
π-μ+
FINUDA spectrometer Central region
TGTS: 2×6Li,
2×7Li, 13C, 2×9Be, D2
O
FINUDA studied the Σ
production via the (semi) exclusive
K-stop
A→ nπ+π−A’
reaction.
Study of the K-stop
A→ΣπΑ'
Reaction at DAφNE
μ+ ν K+
Φ K-
A
π-
n
π+ A’ Σ− Σ+
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Background reactions Inclusive vs. exclusive π-
spectra
K-
n→Λ π-
Λ→p π-
K-
p→Σ+ π-
K-
p→Σ-
π+
Σ-
→ n π-K-
(NN)→Σ-
NΣ-
→ n π-
K-
n→Σ0 π-
Sum
K-
n→Σ-
π0
Σ-
→ n π-
(K-stop
,nπ-
π+)
(K-stop
,π-
)
Σ
Bound region
π−
momenta
from 12C (K-stop
,π-) quasifree
reactions (simulated)
QF Σ
thresh
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Σ+
formation Σ-
decay
K-
p→Σ+ π-
π-
momenta
from K-stop
6Li nπ+π−X with FINUDA
K-
p→Σ-
π+
Σ-
→ n π-
main contributions
to π-
spectrum: Σ
production and decay
π−
momenta
from K-stop
6Li nπ+π−X
MeV/c
K-
n→Σ-
π0
π0 p nπ+
Σ-
→ n
π-Backgrounds also from2-step/complex reactions,
involving e.g.Σ
N → Λ N (conversion
reaction)π
N → π’ N (SCX)
and possible contaminations
…
K-
p→Σ-
π+
Σ-
p→ ΛnΛ → pπ-
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
min miss mass expectedM(X)=M(5He)
2σ
cut3σ
cut
unphysical region
S/B~0.7Σ−
signalS/B~1.0
nπ±
combinatorial + incoherent background
1.
Discard events with unphysical missing mass
(γ
contamination,rescattered
neutrons)
Σ+
signal
nπ-
invariant mass nπ+
invariant mass
Study of K- 6Li → nπ+π-
X : X : Σ±
identificationidentification
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
S/B~1.2 S/B~1.8
miss. mass cut
min miss mass expectedM(X)=M(5He)
2σ
cut3σ
cut
unphysical region
1.
Discard events with unphysical missing mass
(γ
contamination,rescattered
neutrons)
nπ-
invariant mass
Study of K- 6Li → nπ+π-
X : X : Σ±
identificationidentificationnπ+
invariant mass
Σ+
signalΣ−signal
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
S/B~1.2 S/B~1.8
Thr
Σ-
Σ-
decay
Thr
Σ+
Σ+
decayΣ+
formation Σ-
formation
Σ−
:remove
π-
from
Σ+
production Σ+
:remove
π+
from
Σ−
production
nπ-
invariant mass nπ+
invariant mass
Study of K- 6Li → nπ+π-
X : X : Σ±
identificationidentification
Σ+
signalΣ−signal
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
S/B~2.8S/B~1.9
Σ+
formationΣ-
decay
Mom π-
> Thr
Σ+
Σ-
formation Σ+
decay
Mom π
+> Thr
Σ-
Σ−
:remove
π-
from
Σ+
production Σ+
:remove
π+
from
Σ−
production
nπ-
invariant mass nπ+
invariant mass
Study of K- 6Li → nπ+π-
X : X : Σ±
identificationidentification
Σ+
signalΣ−signal
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Taglio 2
Cut on the other
pion
S/B~2.8S/B~1.9
Improve
S/B by
applying
further
quality
cuts
on track fitting
and vertex
selection
nπ-
invariant mass nπ+
invariant mass
Study of K- 6Li → nπ+π-
X : X : Σ±
identificationidentification
Σ+
signalΣ−signal
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Taglio 2S/B~2.9S/B~2.0
nπ-
invariant mass nπ+
invariant mass
Improve
S/B by
applying
further
quality
cuts
on track fitting
and vertex
selection
Study of K- 6Li → nπ+π-
X : X : Σ±
identificationidentification
Σ+
signalΣ−signal
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Taglio 2S/B~2.9S/B~2.0
Cut on Cos Θnπ
(Σ
momentum
below
~170MeV/c)Cos Θnπ
<-0.2
nπ-
invariant mass nπ+
invariant mass
Study of K- 6Li → nπ+π-
X : X : Σ±
identificationidentification
Σ+
signalΣ−signal
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
S/B~3.9S/B~2.8
Cut on Cos Θnπ
(Σ
momentum
below
~200MeV/c)Cos Θnπ
<-0.2
σ~3.4MeV/c2 σ~3.4MeV/c2
nπ-
invariant mass nπ+
invariant mass
Study of K- 6Li → nπ+π-
X : X : Σ±
identificationidentification
Σ+
signalΣ−signal
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
7Li: π-
momentum in coincidence with Σ+
Search
for
possible
bound
states
on 6Li,7Li,9Be, 13C, 16O Via K-
A→ nπ+π-
XX
reaction
6Li: π-
momentum in coincidence with Σ+
-BΣ+
~5.4 MeV
ΓΣ+
~ 3.4 MeV
Significance
Z2σ
~4Significance
Z2σ
<1
Exponential + gauss. fit
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Search
for
possible
bound
states
on 6Li,7Li,9Be, 13C, 16O Via K-
A→ nπ+π-
XX
reaction
-BΣ+
~7.6
MeV
ΓΣ+
~6.6 MeV
Significance
Z2σ
~5
-BΣ+
~ 4.7MeV ΓΣ+
~4MeV
9Be: π-
momentum in coincidence with Σ+ 13C: π-
momentum in coincidence with Σ+
Significance
Z2σ
~2
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Search
for
possible
bound
states
on 6Li,7Li,9Be, 13C, 16O Via K-
A→ nπ+π-
XX
reaction
-BΣ+
~8.3 MeV
ΓΣ+
~5 MeVSignificance
Z2σ
~3
16O: π-
momentum in coincidence with Σ+
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Search
for
possible
Σ-bound
states
on 6Li,7Li,9Be, 13C, 16O Via K-
A→ nπ+π-
XX
reaction
Significance
Z2σ
<1
6Li: π+
momentum in coincidence with Σ-
Significance
Z2σ
<1
7Li: π+
momentum in coincidence with Σ-
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Search
for
possible
Σ-bound
states
on 6Li,7Li,9Be, 13C, 16O Via K-
A→ nπ+π-
XX
reaction
Significance
Z2σ
<2 Significance
Z2σ
<2
9Be: π+
momentum in coincidence with Σ- 13C: π+
momentum in coincidence with Σ-
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Search
for
possible
Σ-bound
states
on 6Li,7Li,9Be, 13C, 16O Via K-
A→ nπ+π-
XX
reaction
Significance
Z2σ
<1
16O: π+
momentum in coincidence with Σ-
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
6Li data vs. 4He data6Li [1] DAFNE 4He[2] KEK
Yield (Σ−) No signal No signalYield (Σ+) ~2x10-3/K-
stop ~6x10-3/K-stop
[Σ+/Σ0]
B (Σ+) ~5.4 MeV 3.2 +0.4-1.4 MeV
Γ (Σ+) ~3.4 MeV 4.6 +2.1-1.8 MeV
[1] This work[2] Hayano
et al., PLB231(’89)
-6Li data appear consistent
to
4He data
[2]:
Binding
Energy, width
and Yield-isospin
dependence
similar
to
that
already
observed
on 4He (no
signals
of
Σ-
bound
states)
-Analysis is ongoing: refining data, further checks, better background description.
Summary and conclusions
NPA 835 (2010) 398
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Akaishi & Yamazaki: What a Deeply Bound Kaon Nuclear State is
•
Nuclear bound states formed by a single (double) K-
and few nucleons, S = -1•
Deeply bound due to the strength of the KN strongly attractive interaction, I = 0
–
Simplest case: (KN) bound state: Λ(1405)•
The presence of Λ(1405) prevents a reliable perturbative
treatment
•
More composite states: can be interpreted as molecules formed by
Λ(1405)+xN–
covalent bonding K--nucleons, much stronger than the nuclear force–
The Λ(1405) should persist as such in a nuclear system
High nuclear density in a low temperature system !!!
ρ0 = 0.14 fm-3
Akaishi & Yamazaki (PLB535(2002), 70; PRC65(2002)…)
ρ0 = 1.39 fm-3
¯¯
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Experimental approaches to DBKS•
Missing mass spectroscopy–
Measurement of the momentum of monochromatic recoiling particlesin the A(K-,N)X reaction
•
KEK-PS E471 (K-stop
)•
AGS E930 (K-in-flight
)•
FINUDA (K-stop
)•
KEK-PS E549 (K-stop
)
•
Invariant mass spectroscopy–
Based on the kaonic nuclear state decaying into YN pairs
•
(K-pp) → Λ + p•
(K-ppn) → Λ + d•
(K-ppnn) → Λ + t •
Typically: –
pΛ,p
~ 500 MeV/c–
pΛ,π
< 200 MeV/c–
p decay p
~ 500 MeV/c
–
Full event reconstruction desirable (necessary)–
Angular correlation between the emitted pairs necessary (desirable)
•
FOPI (heavy ion collisions) •
FINUDA (K-stop
)•
OBELIX (p He)•
KEK-PS E549 (K-stop
)
(d,t)
¯
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Inclusive proton spectra (FINUDA)
No mono-energetic emission of N and YOnly on 6Li FINUDA
observes a bump (FINUDA Coll., NPA 775 (2006), 35)
:
two
nucleon
absorption
reaction
on quasi-deuteron: K-”d”→ Σ-+p
[6Li = α
+ d]
6Li 7Li
9Be 13C 16O
4HeE471
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Inclusive proton spectra (FINUDA)
No mono-energetic emission of N and YOnly on 6Li FINUDA
observes a bump (FINUDA Coll., NPA 775 (2006), 35)
:
two
nucleon
absorption
reaction
on quasi-deuteron: K-”d”→ Σ-+p
[6Li = α
+ d]
6Li 7Li
9Be 13C 16O
4HeE549
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Experimental approaches to DBKS•
Missing mass spectroscopy–
Measurement of the momentum of monochromatic recoiling particlesin the A(K-,N)X reaction
•
KEK-PS E471 (K-stop
)•
AGS E930 (K-in-flight
)•
FINUDA (K-stop
)•
KEK-PS E549 (K-stop
)
•
Invariant mass spectroscopy–
Based on the kaonic nuclear state decaying into YN pairs
•
(K-pp) → Λ + p•
(K-ppn) → Λ + d•
(K-ppnn) → Λ + t •
Typically: –
pΛ,p
~ 500 MeV/c–
pΛ,π
< 200 MeV/c–
p decay p
~ 500 MeV/c
–
Full event reconstruction desirable (necessary)–
Angular correlation between the emitted pairs necessary (desirable)
•
FOPI (heavy ion collisions) •
FINUDA (K-stop
)•
OBELIX (p He)•
KEK-PS E549 (K-stop
)
(d,t)
¯
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Λ
identification with FINUDAFINUDA FRONTAL VIEW
VERTEX REGION
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
2NA: K- pp identification with
FINUDAΛp Invariant Mass to measure K-pp:
1.
Data taking 2003-2004:–
200 pb-1
2.
reconstruction of Λ’s–
pΛ
>
300 MeV/c–
6 MeV
FWHM
3.
Λ
and p angular correlation–
Events with a Λ-p coincidence: ~ 5%
–
Light targets only (3x
12C, 2x 6Li, 1x 7Li)
–
Λ
p should be oppositely emitted, apart from FSI
1
2
cosθYN
< -0.8
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Λp invariant mass in FINUDA•
High resolution tracks only
•
A bump is observed–
Two nucleon absorption
•
K-
+ (pp) → Λp peak expected at 2.34 GeV
•
K-
+ (pp) → Σ0p → Λγ p 74 MeV
lower distribution, and
broadened–
Kaon nuclear bound state formation
•
K-
(pp) → X → Λp→ Σ0p → Λγ p
B = 115+6-5 (stat)+3
-4 (sys)
MeVΓ= 67+14
-11
(stat)+2-3 (sys)
MeV
fit region
FINUDA Coll., PRL 94(2005)212303
Acc
epta
nce
corr
ectio
n
M =
(2255 ±
9) MeV/c2
mK
+2mp
~ 20
0 ev
ents
in th
e pu
blis
hed
pape
r
SEMISEMI--EXCLUSIVE ANALYSISEXCLUSIVE ANALYSIS
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FINUDA: 6Li(K-stop
,Λp)X
2006-2007 Data Taking• 8x statistics on: 6Li (7Li, 9Be)-
Improved tracking efficiency
-
Extended range of the reconstructed momentum-
Improved selections (missing mass)
-
Statistics large enough to study single tgt
spectra
not a
ccep
tanc
e co
rrect
ed
not a
ccep
tanc
e co
rrect
ed
not a
ccep
tanc
e co
rrect
ed
unphysical region
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FINUDA: 6Li(K-stop
,Λp)X
FINUDA Coll., PRL 94(2005)212303
New inv mass spectra compatible with published one
New data Old dataSame cuts applied
A=6Li,7Li,12CA=6Li
not a
ccep
tanc
e co
rrect
ed
not a
ccep
tanc
e co
rrect
ed
not a
ccep
tanc
e co
rrect
edno
t acc
epta
nce
corre
cted
unphysical region
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
3NA: FINUDA study of 6Li(K-stop
,Λd)X•
Λd invariant mass to measure K-
ppn
absorption
•
Use of 6Li target: low background
•
6Li is
a well
known
[α+d] cluster–
Bump
observed
at MΛd
= 3251 MeV,
ΓΛd
=37 MeV–
25 events
in the peak,
statistical
significance 3.9σ
–
Yield: (4.4±1.4)x10-3/K-stop FI
NU
DA
Col
l., P
LB 6
54 (2
007)
80
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FINUDA: study of A(K-,Λt)X
(A=6Li,7Li,9Be) (I)
•
K-
A → Λ t X•
A = 6Li,7Li,9Be
•
FINUDA thresholds:–
Λ
140 MeV/c
–
t 430 MeV/c
•
Λ
signal background free•
Λ, t pairs emitted back-to-back
•
High momenta
for Λ, t
FIN
UD
A C
oll.,
PLB
669
(200
8) 2
29
Only one measurement exists so far, from bubble chamber: 3 events by kin fit40 events observed in FINUDACapture rate: ~1x10-3/K-
Direct measurement of K-
absorption on 4He
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
FINUDA: study of A(K-,Λt)X
(A=6Li,7Li,9Be) (II)•
Many body K-
absorption role–
Simulations of different phase space reactions with cos(ΘΛt
)<-0.9 (filtered through apparatus acceptance)
–
Λ
and t momentum distribution compatible with:
a)
Four nucleon absorption with (Λt) or (Σt)
emissionb)
Four nucleon absorption with (Λt)N
emissionc)
NOT with (Λt)π: too small Λ
momentumd)
2-step pickup reaction (suppressed?)
K-
A → Σ0
t A’Σ0
→ Λ γ
a) b)
d)e)
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
DBKS and K-(multiN) conclusions•
[K-pp] → Λp:
–
MΛp
signal on different targets–
CosΘΛp ~ 1–
FSI alone cannot explain at the same time
MΛp
and CosΘΛp–
Needed a realistic model: K-
dynamics (bound state) + proton pairs momenta–
What is the role of short-range correlated proton pairs ?(R. Subedi
et al., Science 320(2008)1476)–
The models should explain most the observables !•
[K-ppn] → Λd:
–
CosΘΛd ~ 1–
Identified the QF-3NA–
Identified other two final states (analysis in progress)–
K-
is absorbed on quasi “α” (6Li = α
+ d)–
The role of Σ0
seems negligible•
[K-ppnn] → Λt:
–
CosΘΛt ~ 1–
Direct measurement of K-
absorption on 4He–
Capture rate: ~1x10-3/K-
•
Near Future: –
acceptance correction and final analysis of Λp
(and Λd)•
bump position and width with A from 6 to 16 –
neutron on coincidence with Λ, Λp and Λd•
participant (energy carrier) and spectator•
role of K-
α
absorption on Λp and Λd spectra
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Summary•
1993 FINUDA experiment proposal (preprint LNF-93/021, 11 May 1993)
•
2003-04 FINUDA 1st data taking (200 pb-1 integrated luminosity)•
2006-07 FINUDA 2nd data taking (968 pb-1integrated luminosity)
•
2008 FINUDA 3rd data taking proposed in 2009 (for 1 fb-1 integr. lum. )
•
The proposed 3rd data taking could not find room in the LNF planning:“…
The FINUDA collaboration was placed in stand-by, until the
uncertainties on the roll-in of KLOE (entailing the switch of the IR) could be removed. It now appears clear that the roll-in of KLOE in late 2009 will take place, which suppresses the time window that FINUDA could have used. …”37th MEETING OF THE LNF SCIENTIFIC COMMITTEE (December 1 -2, 2008)
•
As a consequence, at beginning of 2009, decision was taken to de- commission the experiment
Giornata di Seminari - INFN sez. Trieste - 05/07/2010 - S.Piano - L’esperimento FINUDA
Conclusions
•
The FINUDA main task (the simultaneous study of spectroscopy and decay of hypernuclei
in a broad range of
A) has been achieved, with the ability of the apparatus to measure also MWD and rare decays into d-d
and p-t
of light
hypernuclei, not foreseen in the proposal.
•
FINUDA capability to reconstruct secondary verteces, short tracks and light ions allowed the study of the interaction of stopped K-
on multi-nucleons aggregates and the Σ±
hypernuclei
production.
•
Some other items, as the search of neutron rich hypenuclei, and the decay of hypernuclei
into two neutrons, cannot be
fully pursued because of the lack of statistics.