g rays from giant resonances of 12 C and 16 O Makoto Sakuda for C01 - - PowerPoint PPT Presentation

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g rays from giant resonances of 12 C and 16 O Makoto Sakuda for C01 - - PowerPoint PPT Presentation

Jan 06, 2024 347 likes •609 views

Study of Gd(n, g ) reaction and g rays from giant resonances of 12 C and 16 O Makoto Sakuda for C01 Efforts (Okayama) @ Revealing the History of the Universe with Underground Particle and Nuclear Research 2019, Tohoku, 2019.03.09 Outline:

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SLIDE 1

Study of Gd(n,g) reaction and g rays from giant resonances of 12C and 16O

Makoto Sakuda for C01 Efforts (Okayama)

@ “Revealing the History of the Universe with Underground Particle and Nuclear Research 2019”, Tohoku, 2019.03.09

Outline:

  • 1. g-ray spectrum of Gd(n,g) and ANNRI-Gd

model for SK-Gd project

  • 2. g rays from giant resonances of 12C and 16O
  • 3. Evaluation of O,C(n,n’g) events for SN neutrinos (10kpc)
  • 4. Summary
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SLIDE 2

Giant Resonances (GR)

and g rays from resonances 158,156Gd, 12C and 16O.

160Gd resonance seen

in photo-absorption=Photon Strength Function f(Eg) (PSF).

  • We study 157Gd(n,g)158Gd and g rays

from 158Gd.

12C and 16O GR

in (p,p’) reaction

160Gd

(~158Gd)

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SLIDE 3
  • 1. Study of g rays from 157,155,natGd(n,g) reaction and

MC (ANNRI-Gd) Model for SK-Gd project

 We performed a series of measurements of Gd(n,g) reactions using high intensity pulsed neutron beam and ANNRI Germanium spectrometer.

  • 1. g-ray spectrum from thermal neutron capture on 157Gd,
  • K. Hagiwara, T. Yano, T. Tanaka, M.S. Reen, P.K. Das, S. Lorenz, I. Ou, T. Sudo, Y.

Yamada, T. Mori, T. Kayano, R. Dhir, Y. Koshio, M. Sakuda, A. Kimura, S. Nakamura,

  • N. Iwamoto, H. Harada, M. Wurm, W. Focillon, M. Gonin, A. Ali and G. Collazuol

(ANNRI-Gd), PTEP 2019, 023D01 (29pages).

  • 2. g-ray spectrum from 155, natGd(n,g),

A.Ali et al. (ANNRI-Gd), PoS (ICHEP2018) 120 (4 pages), in preparation for PTEP.

  • 3. 2g angular correlations in 155, 157Gd(n,g) reaction

b-version of MC (ANNRI-Gd) model is already being used in SK-Gd, XENONnT and NEOS (IBS, Korea).

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SLIDE 4
  • 1. Feature of g-ray spectrum from 157,155Gd(n,g)
  • ~4g rays/event (Etot=8MeV)-

 Probability Distribution from ExEa= Ex –Eg

 Fermi Golden Rule: Probability=|Amptilude|2*(Number of States)  Eg

3 favors Large Eg , f(Eg) favors Large Eg , But r(Ea) favors Very Small Eg.

2- Ex Ea x r(Ea)

0+

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SLIDE 5

1-1) 157,155Gd(n,g) Eg spectrum (Data) and MC(ANNRI-Gd model), Tested for multiplicity=1,2,3,4.

157Gd(n,g) Eg (single) spectrum 155Gd(n,g) Eg spectrum

157Gd(n,g) Multiplicity=2,3,4 Eg spectrum

 Data and MC in reasonable agreement.

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SLIDE 6

1-2) g-g angular correlation W(z) in 157,155Gd(n,g) (p6

 The definition of angular correlation W(z) for z=cosq=[-1,1].

 Select 2 g-ray dataset (E1 and E2) and make z distribution.

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SLIDE 7

1-2) Angular correlation W(z) of 2 g rays in cascade (JAJBJC), z=cosq

(skip-7)

 For the angular momentum (j,m) of g1 in z-direction, only

L=0 and m=+1 and -1 are allowed. Thus, the weight p(M)

  • n M of (J,M) for g2 is restricted. Then, W(z) is not uniform.

 BUT, If p(M)=1 for all M,

W(z)=uniform, because

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SLIDE 8

Angular correlation of 2g rays for

157Gd(n,g) (specially chosen) cascades

 We observe the expected angular

correlations for 2-2+0+ and 2-2+2+ cascade transitions.

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SLIDE 9

No angular correlations of 2 g rays from continuum (bulk) of 157,155Gd(n,g)

 We observe no correlations for bulk of 2g rays from continuum.

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SLIDE 10
  • 2. RCNP E398 12C,16O(p,p’g)
  • Study of g emission rate Rg(Ex) from Giant Resonance-

(10)

12C and 16O are being used as a target material in large scale

neutrino experiments, since they are abundant (cheap).

[Nulcear Physics] No systematic measurements of g rays from giant resonance region (Ex=16-35MeV).

(1) Hadronic decay (2) Electromagnetic decay

[Supernova Detection] Neutral-Current g production cross sections n-12C/16O may be significant, next to dominant inverse b-decay cross section.

12C 11B

Ex 𝛿

(1) (2) 𝛿0

p

11B*

Sp →

C C* p’ p

+ +

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SLIDE 11

2-1) E398 Experiment at RCNP(Osaka)

  • Magnetic Spectrometer (Ex) and NaI array (E) –

25cm 25cm

  • Excitation energy Ex=Ep-Ep’
  • ∆Ex = 100-200 keV
  • 𝜄scat = 0o(covers 0o~3o)

Focal plane detectors

NaI Array

Target

392 MeV

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SLIDE 12

(Ep=392MeV) Grand Raiden Spectrometer Target Focal Plane (Ep’)

RCNP Magnetic Spectrometer “Grand Raiden”

  • Ex = 392MeV - Ep’ , DEx=100keV -

12

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SLIDE 13

g ray detector(NaI)

→γ線が検出器内でのエネルギー損失を最終的に電気信号に変え測定

13

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SLIDE 14

Analysis Method: Ex and E (NaI)

For each event, we measure: (1) Ex (Excitation energy) (2) E (g-ray energy deposited in NaI detectors)

1

Ex= E B.G.

Sp

1 .

20. 30. 40.

0 10.0 20.0 30.0 40.0

E (MeV) Ex (MeV)

E=11 MeV Ex=16 MeV

  • Ex > 16 MeV:Giant resonance
  • Region 1 : Hadronic Decays
  • Region 2 : Electromagnetic

Decays

Region 2 Region 1 10.

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SLIDE 15

[Region 1] g rays from hadronic decays (16)

 g-rays are emitted from the excited states of 11B and 11C after hadronic decay. As Ex increases, Rg increases. For Ex>27MeV, GR cross section becomes small and Rg decreases.

p n

1

E (MeV)

2.0 4.0 6.0 8.0 10.0 2.0 4.0 6.0 8.0 10.0

Sp~11MeV=max Eg

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SLIDE 16

g-ray emission rate Rγ(Ex) from hadronic decay

  • Rg~45% (12C) and 60% (16O) at max. -

Data（---) are lower by 20-30% than the simple transmission calculations using optical potential（---）.

12C 16O

0.2 0.4 0.6 0.8 16 18 20 22 24 26 28 30 32

Ex (MeV) 𝛿-ray emission probability (R𝛿)

QE Contribution

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SLIDE 17

(Region 2): Search for Electromagnetic decays

  • Make Ex-E plot -

1

Ex= E B.G.

Sp

1 .

20. 30. 40.

0 10.0 20.0 30.0 40.0

E (MeV) Ex (MeV)

E=11 MeV Ex=16 MeV

  • Ex > 16 MeV:Giant resonance
  • Region 1 : Hadronic Decays
  • Region 2 : Electromagnetic

Decays

Region 2 Region 1 10.

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SLIDE 18

We are beginning to observe the high energy g rays (E=11-33MeV) from direct electromagnetic decay at Rγ0=(0.37± 0.04± 0.04)%. To establish the result, we must work on the systematic errors.

[Region 2] g rays from Direct Electromagnetic Decay

(p19

40000

  • 30000
  • 20000
  • 10000
  • 10000

20000

50 100 150 200 250 300 350 400 True Events MC prediction(Scaled)

Ex-E𝛿(keV)

Events/2 MeV

16<Ex<33 MeV E𝜹>11 MeV 0.0 0.1 0.2 0.3 0.4 0.5 0.6 16 18 20 22 24 26 28 30 32

x 10-2

Ex (MeV)

R𝜹𝒑(Ex)

18 0.

Background Signal

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SLIDE 19

0.4 0.8 1.2 1.6 2

1 2

0.0 0.1 0.2 0.3 0.4 0.5 0.6 16 18 20 22 24 26 28 30 32

Interpretation of Direct EM decay (12C and 208Pb) in terms of E1 transition

19

J𝜌 = 1- J𝜌 = 0+ E1

12C (g.s.) 12C*

x 10-2

Ex (MeV)

𝛿-ray emission probability (R𝛿0)

𝐹𝛿0 = Energy of emitted γ-ray Eγ Calculation using (g,total) (Shape only)

𝑆𝛿0 ∝ Γ

𝛿0 ∝ 𝐹𝛿0 3 𝐶 𝐹1

x 10-2 Comparison with 208Pb

12C 208Pb

Data(Averaged) Calculations (normalized with carbon) 𝛿-ray emission probability (R𝛿0)

 Only one result on direct EM decay of a heavy nucleus 208Pb is reported.

Beene et al., Phys.Rev C 41, 920(1990).

12C rate is 5 times smaller, due to the

small B(E1) = coupling of the photon to the giant resonance for 12C w.r.t.

208Pb.

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SLIDE 20
  • 3. Estimation of O,C(n,n’g) events for SN (10kpc)

(20)

 SN n flux dF/dEn: we use MB/FD or Nakazato Flux

 MB/FD T=3MeV (ne), 5 MeV (ne) and T=8MeV (nm,nt).  Nakazato flux (Nakazato,Suzuki et al., ApJS.205,2(2013)).

 Cross sections ds(En)/dEx: we use 12C [T.Yoshida et al.,

ApJ686,448(2008)] and 16O[T.Suzuki et al. PRC98,034613(2018)]. Shell Model calculation.

 The g-ray emission rate Rg(Ex) : we use our own data.

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SLIDE 21

For NC events MB and FD, T = 8 MeV For CC events MB and FD, T = 5 MeV

SN rate evaluation: 12C and 16O targets

Expected number of neutrino events from a core-collapse supernova at 10 kpc to be detected at JUNO (20 kton). [Very preliminary]

Expected number of neutrino events from a core-collapse supernova at 10 kpc to be detected at Super-K (32.8kton). [Very preliminary]

Charged-current scattering off 16O nucleus as a detection channel for supernova neutrinos, K.Nakazato, T.Suzuki, MS, PTEP 2018,123E02.

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SLIDE 22

Summary (23)

Measurement of g-ray spectrum from 157, 155, natGd(n,g) and ANNRI-Gd Model

157Gd(n,g) data and model: PTEP2019,023D01.

155,natGd(n,g) and 2g correlation, papers in preparation.

 Download Web Page in preparation.

Measurement of g emission probabability Rg(Ex)=σp,p′γ/σp,p′ from Giant Resonance in 12C,16O(p,p’g) reaction

We measure Rγ(Ex) = σp,p′γ/σp,p′ for the first time for 12C for Ex = 16-32 MeV for the hadronic decay mode. Rγ(Ex) starts from zero at Ex = 16 MeV and increases to Rγ(Ex)= 47.9 ± 0.5 ± 3.5% at Ex =27 MeV and then decreases. The paper for 12C(p,p’g) was submitted for publication.

We are beginning to observe the high energy g rays (E=16-33MeV) from electromagnetic decay with Rγ(Ex)=(0.37± 0.04± 0.04)%. To establish the result, we must work on the systematic errors.

We have similar result on 16O.

We use dF/dEn(Nakazato et al.)+ds/dE(T.Suzuki)＋ Rg(Ex) (our hadronic decay rate) to evaluate NC g production rate from SN neutrinos. (Ongoing)

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SLIDE 23

Future

We hope to extend E398 experiment by replacing a NaI array by Clover (Ge) Array (on-going at RCNP), and obtain a comprehensive understanding of both the hadronic and electromagnetic decay of

12C and 16O giant resonances.

We can evaluate the NC g production rate for SN neutrinos very precisely.

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SLIDE 24