First ฮณ-Ray Spectroscopy of an sd-shell Hypernucleus, ๐ฒ
19F
Seongbae Yang
for J-PARC E13 CollaborationDepartment of Physics
Korea University
-QNP2018-
November 14, 2018
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2
1. Introduction
Gamma-ray Spectroscopy of ฮ-Hypernuclei at J-PARC
โ There was a J-PARC beam time for ฮ19F in June 2015.
@PRL 120, 132505 (2018).
1. Introduction
3
ฮN Interaction and ฮ-Hypernucleus
โ ฮ-hypernucleus
Due to the short life time of ฮ, a scattering experiment is impossible for the ฮNinteraction. In this case, a spectroscopy of ฮ-hypernucleus is the most powerful tool.
โ ฮN interaction
It is the first step to understand the general baryon-baryon interaction.
N N
NN interaction
N ฮ
ฮN interaction
?
16O
p
19F
ฮ
ฮ19F
n
n
16O
p
n
Gamma-Ray Spectroscopy of ฮ Hypernuclei
โ Gamma-ray spectroscopy of ฮ-hypernuclei
4
J(โ 0)
J+1/2
J-1/2
ฮณ1
ฮณ2ฮณ3
โ By measuring energies of the ฮณ rays, the split energy spacing is precisely estimated and we can know a fine structure of the hypernucleus.
Aโ1Z
ฮ
ฮ
ฮAZCore Nucleus
ฮ Hypernucleus
1. Introduction
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โ Previous gamma-ray spectroscopy of ฮ hypernuclei
From 1998, several s- and p-shell hypernuclei were well studied through the method.
โ We continue this experiment at J-PARC.
@NPA 835, 3 (2010)
1. Introduction
Gamma-ray Spectroscopy of ๐ฒ๐๐๐
โ Precise level data for s- and p-shell hypernuclei have revealed strengths of the spin-dependent ฮ๐ interaction and the ฮ๐๐ interaction (ฮฮฃ coupling effect).
โ It is the first measurement of fine structure of an sd-shell hypernuclei, beyond s- and p-shell hypernuclei.
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2. Physics Motivation
s-shell (๐ ๐๐ ฮ)
p-shell (๐๐๐ ฮ)
They have าง๐(๐๐โ๐ ฮ) > าง๐(๐๐โ๐ ฮ) > าง๐(๐ ๐โ๐ ฮ)and different wave functions. Can we apply the ฮ๐ interaction to heavier hypernuclei?
sd-shell (๐๐๐ ฮ)
1.4 MeV
0.692 MeV
0.3 MeV ??
Experimental Setup for J-PARC E13
โ SKS & K1.8 Beamline Spectrometers
โ High resolution of missing mass
โ Large acceptance for (๐พโ, ๐โ)
โ good beam decay suppressor (SP0, SMF)
โ Hyperball-J
โ ~25 HPGe detectors - โE ~4.5 keV @ 1MeV
โ PWO counters - Fast background suppression
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Liquid. CF4
3. Experimental Setup
โ ฮ binding energy spectra of ฮ19F. We selected the ๐ตฮ range, โ21 < โ๐ตฮ < โ8
MeV, to observe gamma rays emitted from the ฮ19F low-lying states.
Results of J-PARC E13
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4. Results
9
4. Results
โ ฮณ-ray spectra with three ฮ binding energy conditions.
โ There are four gamma rays from low-lying states of ฮ19F.
background
background
signal
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4. Results
Two clear peaks
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4. Results
Compared to the theoretical calculation [A. Umeya and T. Motoba, NPA 954, (2016) 242]
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4. Results
Two more clear peaks at forward reaction angle
E1E1
E1E1
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4. Results
Energy difference (313 keV) between the two E1 transitions is consistent with the M1 transition.
โ Low-lying energy scheme of ฮ19F
โ We clearly observed four ฮณ rays from low-lying states of ฮ19F and successfully
assigned them to their gamma transitions. 14
4. Results
โ Effective ฮN interaction from Nijmegen SC97 models
*by A. Motoba and T. Umeya
419 ร 0.6 NSC97f + 245 ร 0.4 NSC97e = 315 keV ?
*Similar to the case of s- and p-shell hypernuclei
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5. Discussion
TheoreticalCalculation
(Experiment) NSC97f NSC97e
ฮ๐ธ(3/2+, 1/2+)[keV]
315.5 ยฑ0.4โ0.2+0.3 419* 245*
0.692 MeV
โ 704 keV
1.25 MeV*
โ 1.24 MeV*ฮ4He andฮ
4H(1+, 0+; 1.25 MeV in average)
โ Phenomenological calculation
*by D. J. Millener
โ The energy spacing, 3/2+ โ 1/2+, is well represented by the spin-dependent interactions obtained from s- and p-shell hypernuclei. It indicates that the present theoretical frameworks work quite successfully in describing structure of not only light s-and p-shell hypernuclei but also a heavier one beyond p-shell hypernuclei.โ ฮฮฃ coupling effect is negligibly small in the sd-shell hypernuclei?
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5. Discussion
TheoreticalCalculation
(Experiment)ฮN spin-dependent interaction at p-shell
hypernuclei
ฮ๐ธ(3/2+, 1/2+)[keV]
315.5 ยฑ0.4โ0.2+0.3 305*
6. Summary
Summary
โ Gamma-ray spectroscopy of ฮ19F J-PARC E13 was successfully
performed in June, 2015.
โ We clearly observed four ฮณ rays from low-lying states of
ฮ19F and successfully assigned them to their gammatransitions.โ The energy spacing between the ground state doublet isdetermined to be 316 keV. It is well represented by the spin-dependent ฮN Interaction in p-shell hypernuclei.โ The experiment will be continued at the new constructedbeam line (K1.1 beam line), and next targets are ฮ
4H and ฮ7Li.
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*Backup Slides
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Gamma-ray Spectroscopy of ๐ฒ๐๐๐ (J-PARC E13 1st Phase)
โ It is the first ฮณ-ray spectroscopy for sd-shell hypernuclei.
โ Energy spacing between ground state doublet (1/2+, 3/2+)
โ Radial dependency of the ฮN spin-spin interaction?
โ ฮN spin-dependent interaction with different wave-function?
low-lying energy levels of ฮ19F
*A. Umeya and T. Motoba, NPA 116, 122501 (2016) 19
Spin-spin interaction16O
n
pฮ
+
ฮ
* Backup Slides
ฮ4H ฮ
7Li ฮ19F
Four-bodyCluster model
Wave-function ๐๐ต๐๐ฆ ๐๐ต๐๐ฆ (๐๐ )๐ต๐๐ฆ
N, RMS
radius [fm]2.5 (0๐ )
3.0 (0๐1/2)
2.9 (0๐3/2)
3.4 (1๐ 1/2)
3.5 (0๐1/2)
3.3 (0๐5/2)
ฮ, RMS radius [fm] 3.5 (0๐ ) 2.6 (0๐ ) 2.3 (0๐ )
โ๐ธ๐ฅ(ground
state doublet)
1.1 MeV0.695 MeV
(ฮ๐๐๐ฮ=0.43 MeV) ?20
nn
pฮ+ 4He
n
pฮ+ 16O
n
pฮ+
@by Millener, private communication
@by Millener, private communication
* Backup Slides
ฮณ-ray Detector (Hyperball-J)
โ 19F(๐พโ, ๐โ) ฮ
19F โ, ฮ19F โ โ ๐พ + ฮ
19F
โ Hyperball-J
โ 25 HPGe detectors - โE ~4.5 keV @ 1MeV
โ PWO counters - Fast background suppression
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@NPA, 835, 3 (2012)
*a view of K1.8 experimental hall
Mechanical cooling systemCrystal temp. ~70 K
* Backup Slides