Measurements of the 7 Be+n Big-Bang nucleosynthesis reactions at CRIB by the Trojan Horse method

Transcription

1 Measurements of the Be+n Big-Bang nucleosynthesis reactions at CRIB by the Trojan Horse method S. Hayakawa 1, K. Abe 1, O. Beliuskina 1, S. M. Cha 2, K. Y. Chae 2, S. Cherubini 3,4, P. Figuera 3,4, Z. Ge 5, M. Gulino 3,6, J. Hu, A. Inoue 8, N. Iwasa 9, D. Kahl 10, A. Kim 11, D. H. Kim 11, G. Kiss 5, S. Kubono 1,5,, M. La Cognata 3, M. La Commara 12,13, L. Lamia 4, M. Lattuada 3,4, E. J. Lee 2, J. Y. Moon 14, S. Palmerini 15,16, C. Parascandolo 13, S. Y. Park 11, D. Pierroutsakou 13, R. G. Pizzone 3,4, G. G. Rapisarda 3, S. Romano 3,4, H. Shimizu 1, C. Spitaleri 3,4, X. D. Tang, O. Trippella 15,16, A. Tumino 3,6, P. Vi 5, H. Yamaguchi 1, L. Yang 1, and N. T. Zhang 1 Center for Nuclear Study (CNS), University of Tokyo, 2 Sungkyunkwan University 3 INFN - Laboratori Nazionali del Sud, 4 University of Catania 5 RIKEN Nishina Center, 6 Kore University of Enna, Enna, Italy Institute of Modern Physics, Chinese Academy of Sciences 8 Research Center for Nuclear Physics (RCNP), Osaka University 9 Tohoku University, 10 University of Edinburgh, 11 Ewha Womans University 12 University of Naples Federico II, 13 INFN - Naples 14 High Energy Accelerator Research Organization (KEK) 15 INFN - Perugia, 16 University of Perugia + + and many others

2 Cosmological Li problem Be abundance at the end of BBN determines Li dominantly Nuclear Physics? Standard Big-Bang Nucleosynthesis model (BBN) Low-metallicity star obs. 10: Be(n,p) Li 14: Be(n,α) 4 He CMB obs. Iocco et al. Phys. Rep A. Coc et al. J. Cos. Astropart. Phys. 2014

3 Be(n,p) Li (Q = MeV) (Adahchour & Descouvemeont 2003) BBN energy ~ 100 MeV 8 Be R-matrix simulation è Main Be destruction process (>90%) è Sensitivity: logy Li / log σv Be = 0.1 If σv Be 2, Y Li 0.6 (Coc & Vangioni, 2010) è Direct measurement up to 13.5 kev, time-reversal reactions at higher energies. è R-matrix analysis: Adahchour & Descouvemont 2003 è One 2- close to the threshold, two 3 + resonances, one non-resonant broad 2 + è Accuracy: 1σ confidence level ~ 1% Be(n,p 0 ), Ada2003 Be(n,p 1 ) via 1 - if E cm = 300 kev, G n = 300 kev, G p1 = 300 kev Be(n,p 1 ) via 1 cm = 500 kev Enhancement by Be(n,p 1 ) via 1 -?

4 Be(n,α) 4 He (Q = MeV) BBN energy <10 >200 Barbagallo+ PRL11(2016)15201 Kawabata+ PRL118(201)05201 è Revised reaction rate from mirror reaction by Hou+ (2015) è Direct measurement up to 10 kev by Barbagallo+ at n_tof (2016) è Measured only α decays after γ-ray emission from 8 Be excited states è S-wave only 1/v law è Time-reversal reaction measurement down to 200 kev by Kawabata+ at RCNP (201) è Measured p-wave neutrons dominant at BBN energies

5 Trojan Horse Method for RI + n Trojan Horse method: e.g. Spitaleri+ Phys. of Atom. Nucl. 4(2011)125 Be(n,p) Li, Be(n,α) 4 He via 2 H( Be, Lip) 1 H, 2 H( Be,αα) 1 H E d-be > Coulomb barrier Accessible to low energy releasing deuteron binding energy Deuteron: low E bind., L p-n = 0 p p-n has maximum at 0 Useful also as virtual neutron target p s < 30 MeV/c E c.m. = E beam = 22.1 MeV

6 Trojan Horse Method for RI + n Assuming Quasi-free mechanism is dominant, one can use (PW)IA: d p n Virtual Decay Ä n p Be Li Virtual reaction = d Be n p p Li 3-body Reaction KF Φ (P s ) 2 Confirm momentum distribution then use Monte Carlo simulation dσ HOES dω 2-body cross section of interest d 3 σ dω p dω Li de cm Measured at high energy Normalization needed σ OES σ HOES Penetrability

7 Collaboration with BELICOS project è BELICOS project: Beryllium and Lithium in the Cosmos è Be+d THM experiment for Be(n,α) 4 He (L. Lamia, C. Spitaleri, Catania M. Mazzocco, Padova) è Done at EXOTIC, INFN-LNL è BELICOS: better statistics, only Be(n,α) CRIB: better resolution, both Be(n,p) and Be(n,α) è See L. Lamia s talk (14:30, Thr., Indirect methods 1 )

8 Be beam production at CRIB CRIB: CNS Radioactive-Isotope Beam separator (in-flight technique), managed by Center for Nuclear Study, Univ. of Tokyo, located at RIBF, RIKEN. H 2 cryogenic Torr Li@ 4.6 MeV/u, 440 pna AVF Be MeV/u, pps

9 Experimental setup PPAC a Be beam: ± 0.1 MeV on target PPAC b CD 2 target α Li p α ΔE-E position sensitive silicon telescopes 56 CD 2 : 64 μg/cm 2 ΔE beam ~ 150 kev Hamamatsu Chargedivision PSD: position resolution ~ 0.5 mm Au CD 2 CH 2 Total angular resolution 0.5 ΔE cm ~ 60 kev

10 Particle identification ΔE + E (MeV) ΔE + E (MeV) Selected Li Be Li ΔE (MeV) in 20 μm Si Selected μm ΔE (MeV) in 300 μm Si

11 Q-value spectra of the 3-body channels Be(d, Lip)p Be(d,2α)p 1 st ex. g.s. g.s. Known value: Q(g.s.) = MeV Q(1st) = Mev Reaction Q-value (MeV) Threshold (MeV) p+2α Li+2p Be+n+p He+p+ 3 He Q 3body = E 1 + E 2 + E 3 E beam Known value: Q(g.s.) = MeV ΔQ 3body ~ (ΔE ΔE ΔE 3 2 +ΔE beam 2 ) ~ 200 kev expected with 64 μg/cm 2 CD 2

12 Kinematics check Be(d, Lip)p Be(d,2α)p Energy correlation Angular correlation Monte Carlo simulation and experimental data are in a good agreement. The simulation does not include uncertainties yet The data is broader.

13 Energy, angle vs. spectator s momentum Be(d, Lip)p Simulation Exp. data Energy cut Angle cut Energy cut Evidence that Energy & angle cut quasi-free contribution Hulthén function is dominant. in momentum space THM is valid! for p-n intercluster motion Y exp /Y sim = d 3 σ/(dω p dω Li de cm ) / KF Φ(p s ) 2 at a fixed E c.m. and θ c.m..

14 Energy, angle vs. spectator s momentum Be(d,2α)p Energy cut Angle cut Energy & angle cut Energy cut

15 HOES cross sections for p s < 40 MeV/c dσ(e)/dω HOES (arb. unit) dσ(e)/dω HOES (arb. unit) Be(n,p) Yeild 3-body / KF Φ (P s ) 2 dσ HOES dω Be(n,α) Adahchour & Descouvemont (2003) Kawabata et al. (201)

16 Summary è Measured Be(n,p) Li and Be(n,α) 4 He by THM è Evidence of quasi-free reaction mechanism: validity of THM è Excitation functions: roughly consistent with the previous data è Able to approach the BBN energies ~ 100 kev è Be(n,p 1 ) Li* contribution is not clear: better Q-value resolution? è Upper limit of p 1 contribution from p 0 spectrum?