Structure Properties of Hypernuclei with Skyrme force based Energy
Search for neutron rich -hypernuclei with the FINUDA spectrometer
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Transcript of Search for neutron rich -hypernuclei with the FINUDA spectrometer
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Search for neutron rich Search for neutron rich -hypernuclei with the -hypernuclei with the FINUDA spectrometerFINUDA spectrometer
Barbara Dalena (Bari University and
INFN Bari, Italy) on behalf of the FINUDA Collaboration
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OutlineOutline
The scientific case: Neutron Rich -Hypernuclei
Production of NRH in FINUDAFINUDA
Upper Limits of the NRH production rate
results of the first FINUDAFINUDA data taking
Expected events for next FINUDAFINUDA run
2006/2007
Summary
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stable nucleineutron
rich nuclei proton rich
nuclei
N
1H 2H 3H
3He 4He 6He
6Li 7Li 8Li 9Li
7Be 9Be 10Be
11Li
11Be 12Be
8B 10B 11B 12B 13B 14B
8He
15B
14Be
Z
Neutron rich Neutron rich --hypernucleihypernucleiHypernuclei with a large neutron excess.
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N
1H 2H 3H
3He 4He 6He
6Li 7Li 8Li 9Li
7Be 9Be 10Be
11Li
11Be 12Be
8B 10B 11B 12B 13B 14B
8He
15B
14Be
Neutron rich Neutron rich --hypernucleihypernucleiHypernuclei with a large neutron excess.
Their existence has been theoretically predicted (L. Majling, NP A 585 (1995) 211c).
Z
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observed
N = Z
not observed
Finuda 1° run
1H 2H 3H
3He 4He 6He
6Li 7Li 8Li 9Li
7Be 9Be 10Be
11Li
11Be 12Be
8B 10B 11B 12B 13B 14B
8He
15B
14Be
N
S
-1
6Li
3H 4
H 5H 6
H 7H
4He 5
He 6He 7
He 8He 9
He
7Li 8
Li 9Li 10
Li
7Be 8
Be 9Be 10
Be 11Be
11Li 12
Li
12Be 13
Be
9B 10
B 11B 12
B 13B 14
B 15B
Neutron rich Neutron rich --hypernucleihypernucleiHypernuclei with a large neutron excess.
Their existence has been theoretically predicted (L. Majling, NP A 585 (1995) 211c). The Pauli principle does not apply to the inside the nucleus + extra binding energy ( “glue-like” role) a larger number of neutrons can be bound
Z
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MotivationsMotivations• Hypernuclear physics: N interactions at low densities,
the role of 3-body forces
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MotivationsMotivations• Hypernuclear physics: N interactions at low densities,
the role of 3-body forces• Neutron drip-line: response of neutron halo on
embedding of hyperon, hypernuclear species with unstable nuclear core
T. Yu. Tretyakova and D. E. Lanskoy, Nucl. Phys. A 691: 51c, 2001.
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MotivationsMotivations• Hypernuclear physics: N interactions at low densities,
the role of 3-body forces• Neutron drip-line: response of neutron halo on
embedding of hyperon, hypernuclear species with unstable nuclear core
T. 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.
Y. Yamamoto, S.Nishizaki and T. Taktsuka, Nucl. Phys. A 691: 432, 2001.
Y. Akaishi et al., Phys. Rev. Lett. 84: 3539,2000
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ΛπpK -
ΛKn
ΛπpK 0
ΛKp 0
ΛKp ee )(
;
;
;
;
ΛπpK 0 πnpπ0
ΣπpK ΛnpΣ
ΛKp 0 KK np0
-Kp ΛnpΣ
Calculated Production Rate of is 3 order of magnitude less than the measured one of ( 10-3) .
Production of Neutron Production of Neutron Rich Rich -hypernuclei-hypernuclei
T. Yu. Tretyakova and D.E. Lanskoy, Proc. Of Workshop “Recent progress in Strangeness nuclear physics”, H. Outa et al. eds., KEK (2003) 80.
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FINUDAFINUDA ((FIFIsica sica NUNUcleare at cleare at DADANENE)) DANE: Double Annular
e+- e- -factory for Nice
Experiments:Beam Energy 510 MeVL 5 1031cm-2s-1 - 250
’s s-1
KSKL
(34.1%)
(15.5%)
K+K-
(49.1%)
e+
e-
FINUDA
DEAR
KLOE
The decay of the is an intense source of:
• couples of neutral and charged kaons
• collinear and tagged• monochromatic and low energy
(16 MeV)
The decay of the is an intense source of:
• couples of neutral and charged kaons
• collinear and tagged• monochromatic and low energy
(16 MeV)
πZZK AΛ
Astop
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The FINUDA detectorThe FINUDA detector
Apparatus designed for a typical collider
experiment: Cylindrical geometry large solid angle (>
2 sr) multi-tracking
analysis
Detector capabilities: Selective trigger based on
fast scintilla- tion detectors (TOFINO, TOFONE)
Clean K- vertex identification (ISIM P.ID.+ x,y,z resolution + K+ tagging)
p, K, p, d, … P.ID. (OSIM dE/dx)
High momentum resolution (6‰ FWHM) (tracker resolution + He bag + thin targets)
Neutron detection (TOFONE) Time-Of-Flight (TOFONE-
TOFINO)
Simultaneous study of formation and decay of strange hadronic systems by full event
reconstruction
Mechanical support (clepsydra)
For: 2424 Straw Tubes (longitudinal +
stereo) 16 Low-Mass Drift Chambers 18 m-strip vertex detectors
(ISIM/OSIM) Inner scintillator barrel – 12 slabs
(TOFINO) 8 Targets
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Neutron Rich production inNeutron Rich production in FINUDAFINUDA
K-stop + 12C 12
Be + +
K-stop + 6Li 6
H + +
K-stop + 7Li 7
H + +
+ momentum is related to the binding energy (B) B
(MeV)p
(MeV/c)12Be 11.4 262
6H 4.1 252
7H 5.2 246
FINUDAFINUDA data taking 2003-2004:
Event selection:Reconstruction of a + with a momentum value in the hypernucleus bound region P.ID. made using dE/dx from OSIM and TOF from TOFINO & TOFONE
ΛπpK 0 πnpπ0
ΣπpK ΛnpΣ
;
;
ELEMENTARY
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Inclusive Inclusive spectraspectra
•K - + p + + - + + + n
(130 < p < 250 MeV/c)
•K - + pp + + n + + + n
(100 < p < 320 MeV/c)
Background:
Contaminations:
• + K+ decay (peak@235MeV/c)• p / decay
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Background reductionBackground reductionSimulated NRH production event (FINUDA vertex view)
K - + pp + + n + + + n
Simulated event of :
The reconstructed distance between the origin point of + and the K– stopping point it is broader (up to 8mm) for a + coming from + decay than for the signal (peaked at less than 1mm).
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Final spectra and U.L. Final spectra and U.L. evaluationevaluation
N
R
H
Rate / stopped K- (90% C.L. Upper Limit)
FINUDA PLB 640 (2006) pp.
145-149( 10-5)
Previous best publish
ed value
12Be
2.0± 0.4(stat) -
0.1+0.3(sys) 6.1
10-5
6H
2.5± 0.4(stat)–
0.1+0.4(sys) NEW
7H
4.5 ± 0.9(stat)–
0.1+0.4(sys) NEW
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Expected events for next Expected events for next runrun
HYPER-NUCLEU
S
TARGET
B
(MeV)
p
(MeV/c)
PRODUCTION RATE / k-
stop
EVS ROIU.L.
90% C.L.
6H 6Li 4.1 [1] 252 < 2.510-5
[3]430 6.5 10-6
7H 7Li 5.2 [2] 245 < 4.510-5
[3]460 6.9 10-6
9He 9Be 8.5 [2] 257 < 2. 310-4
[4] 600 6.7 10-6
13Be 13C 11.7 [2] 259 (?) 100 1.1 10-5
16C 16O
7.3(2+) [5]
264< 6.210-5
(0+)[4]
610-8 (2+) [5]
310-8 (0+) [5]
200 8.2 10-6
13.6(0+
)[2]271 190 8.5 10-6[1] Y. Akaishi et al., PRL 84 (2000)
3539 [2] L. Majling, NPA 585 (1995) 211c[3] M. Agnello et al. PLB 640 (2006) 145
[4] Kubota et al., NPA 602 (1996) 327[5] T. Yu. Tretyakova and D.E. Lanskoy, Proc. Of Workshop “Recent progress in Strangeness nuclear physics ”, H. Outa et al. eds., KEK (2003) 80.
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SummarySummary
The search for hypernuclei with large neutron excess is a field of interest in modern nuclear physics
FINUDAFINUDA spectrometer can study NRH statesThe first FINUDAFINUDA data taking established the best
published U.L. 90% C.L. value for 12Be and for
the first time determined the same values for 6H and 7H.
FINUDAFINUDA run 2006/2007 will improve its published U.L. values of a factor 4. At the same time we will search for 9He, 13
Be and 16C.
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Back-up slidesBack-up slides
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Neutron rich Neutron rich --hypernucleihypernuclei
1953: Discovery of hypernuclei by M. Danysz e J. Pniewski (Philos. Mag. 44: 348, 1953) 1985: Evidence of production of 11Li e 11Be (Neutron Rich nuclei) Halo phenomena 1995: “ hypernuclei may be even better candidates to exhibit large values of N/Z and halo phenomena” L.Majling (Nucl. Phys. A 585: 211c,1995) 2005: “Production of the Neutron-Rich Hypernucleus 10Li in the ( - , K+ ) Double
Charge-Exchange Reaction” P.K. Saha et al. (Phys. Rev. Lett. 94: 052502, 2005)
40 events of 10Li
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Acceptance Acceptance
12C12C
6Li6Li
7Li7Li
Final spectra acceptance corrected
In the region 220-320 MeV/c acceptance is quite flat.
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Momentum resolution in Momentum resolution in our track selection our track selection
conditionsconditions+
stop + + n
p 0.9% FWHM @235 MeV/c 1 MeV/c [220-300 MeV/c]
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Distance SelectionDistance Selection
• The reconstructed distance between the origin point of + and the K– stopping point is peaked at less than 1 mm for a + coming from the signal (red line).
• Green line select 10% of background vs 50% of signal Noise to signal ratio improved of a factor 5.
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Rate /KRate /K--stop stop in the ROIin the ROI
N = number of + in the region of interest.
N = number of +.
= number of stopped kaons. D(+) D(+).
G(+)= , MC/RC.
G(+)= , MC/RC.
BR(K2) = 0.6343.
-
stopstop K,K
TG
TTG
μ2-
stop
stop
μ
πROI KBR
K
K
N
NR
G
G
D
D
ROI = 2p 2MeV/c
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S = signal, B = background : .
maximum fraction of NROI
that may be ascribed to NRH
at fixed C.L. (90%).
Upper Limit (U.L.)Upper Limit (U.L.)
ROIRxU.L.
ROIN
Sx
BSN ROI
BNS ROI
NROI
....0;..
!
..!..
LCLC
BμB
NROI
μN
NBLCdμB
eμ
LCdμN
eμ
C.L.
LC
ROI
NROI
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Background Background estimationestimation
2 /ndf = 145.7/95=1.5p0 = 0.0043410.000649p1 = 0.75250.0137
Fit range:0.190-0.250 0.256-0.320 GeV/c
2 /ndf = 107.8/92=1.2p0 = 0.0042070.000630p1 = 0.73380.0138p2 = 0.0803 0.0152 = 0.001092 0.000213Mean = 0.2355 0.0002
hypothesis 1
hypothesis 2
1) Different background shapes give good 2 [1.2 – 1.5] (due to big error), but different value of B and S = N-B Need to incorporate uncertainties in order to use Feldman & Cousins method.
2) Any evaluation of S = N-B gives values lower than the maximum not significant signal at 90% C.L. hypothe
sisNtot ROI
S=N-BR/K-
stop
(U.L.)
1 25 9.641.80.91
0-5
2 25 10.542.00.91
0-5
U.L. 25 112.00.41
0-5
6Li6Li