STUDY OF n-n CORRELATIONS IN d + 2 H → p + p + n + n REACTION

1. The 2nd International Conference on Particle Physics and AstrophysicsICPPA - 2016 October10 – 14, 2016, Moscow STUDY OF n-n CORRELATIONS IN d + 2H → p + p + n + nREACTION E.Konobeevski1, A.Kasparov1, V.Lebedev2, M.Mordovskoy1, A.Spassky2, S.Zuyev1 1Institute for Nuclear Research, Russian Academy of Sciences 2Skobeltsyn Institute of Nuclear Physics, Moscow State University

2. NN-Interaction pp and np Interaction A huge amount of data on pp and np interactions has been accumulated. Careful analysis of these data led to constructing NN interaction potentials describing vast majority of experimental data. nn Interaction The situation around neutron–neutron interaction is more ambiguous. Because of the absence of neutron target, data on this interaction are obtained primarily from reactions with two neutrons in the final state. But in many cases, there are serious discrepancies between available experimental data and the results of the current precise calculations on the basis of Faddeev equations. 2

3. Unresolved Problems in Nd-breakup nn-quasifree scattering nd- and pd-breakup in SS-configuration Experimental CS for nn-QFS exceed theoretical estimates by about 18%. At the same time, the theory describes well the CS obtained for np QFS Experimental CS for pd- and nd- breakup differ greatly while the theoretical CS are almost identical and do not agree with the experimental data The analysis performed by several authors showed that theoretical results remain quite stable using different standard NN-potentials and introducing modern three-nucleon forces 3

4. Modification of 1S0 nn force H. Witala & W. Gloeckle suggested Vnn(1S0) = λ×VCDBonn(1S0) nn QFS @ 25MeV • H. Witala &W. Gloeckle, Phys. Rev. C83, 034004 (2011) =1.08 No arguments for this modification X.C.Ruan et al., Phys. Rev. C 75, 057001 (2007) 4

5. Dibaryon Model (Kukulin et al) Strong discrepancies observed in Nd-breakup can be explained by a significant strengthening of nn- and pp-correlations of attractive character in the third nucleon field. • dd → D + D → n+n+p+p • Nd or t (3He) • New mechanism arising in the Dibaryon Model: New force –meson exchange between the nucleon and dibaryon Our plans: study of nd→p+nn, nt →d+nn and dd→pp+nn We present a study of d+2H→(pp)+(nn) reaction, in which nn-correlated pair can be produced dynamically in the intermediate state. Thus, measured nn-correlation, in particular energy of nn quasi-bound singlet state, may be different from those inherent for the free NN-systems.

6. Simulation of d+ 2H→ 2ns + 2psReaction; Ed=15 MeV Output parameters:Θp1=Θp2=27°; Θn=36°(red areas) Corresponding energies: E(2p)~6 MeV; E(2n)~4 MeV

7. Simulation of d+ 2H→n +n + p + pReaction: Ed=15 MeV, p1=27º, p2=27º, n1=36º Enn Spectrum En1 vs En2 For democratic breakup two neutrons can have a relative energy in the range 0 - 1.8 MeV

8. Democratic breakup Democratic breakup Simulation of d+ 2H→n +n + p + pReaction: En1 vs En2 En Spectrum Enn= 120 keV, nn = 50 keV Enn= 120 keV, nn = 50 keV This structure in spectrum is due to the fact that to reach detector, installed at angle of emitting nn-system in two-body reaction, may only breakup particles emitted in c.m. system in forward or in backward direction 8

9. Simulation of d+ 2H→n +n + p + pReaction: Different Energies of Singlet State Enn= 50keV, nn = 30 keV Enn= 200keV, nn = 100 keV Enn= 120keV, nn = 70 keV The distance between peaks depends on the state energy (excess mass of quasibound two-nucleon system over the sum of masses of its constituents) 9

10. Simulation of d+ 2H→n +n + p + pReaction: Different Widths of Singlet State; Enn=120 keV nn = 110 keV nn = 70 keV nn = 20 keV The shape of time spectra is sensitive to values of the state energy and width, that will allow us to determine these quantities from a comparison of experimental data and simulation results One can see that the change of the state width affects mainly on degradation of "valley" between the peaks and on a slight shift of the peak with larger time to the middle of distribution. 10

11. Experimental: Setup for Study d+2H→p+p+n+n Reaction @ Ed=15 MeV Conditions: 15 MeV deuteron beam of U120 cyclotron of SINP MSU CD2-target p- and n-detectors are set at angles of 2p and 2n emitting both protons are detected in one E-E telescope n-detector at 83° was used for timing calibration in dd→3He+n reaction

12. Experimental E-E Plot and Simulated Plot for Two-Proton Events Selecting events on p+p region and determining the neutron time of flight for these events we obtained neutron timing spectrum 12

13. vs Simulated Experimental: Neutron Time-of-flight Spectrum events ns 13

14. 2-Fitting on nn for Different Enn 14

15. Dependence of 2on Einn. 2-Fitting over Enn To determine Enn the dependence of minimum value on Еnn was fitted by a quadratic polynomial. The minimum value of 2 determines the most probable value of the quasibound state energy. Error in determining Enn is given as The minimum value of the polynomial is achieved at Enn = 76 keV, Enn = ± 6 keV 15

16. Summary and Conclusions

17. Thank you!

18. Experimental Spectrum vs Simulated 18

19. Analysis: Fitting Procedure

20. Simulation of d+ 2H→n +n + p + pReaction: Democratic vs Quasibound state Enn= 120 keV, nn = 50 keV Democratic breakup Simulated time-of-flight spectra of neutrons: 1 – for events of democratic breakup, 2 – for events with Enn= 120 keV, nn = 50 keV. Neutron time-of-flight base 0.79 м. 20

27. Space Star (SS) Anomaly nd exp. Erlangen & TUNL （●）（○） EN=13 MeV Space Star (c.m. system) (1996) (1989) ~30% nd calc. pd exp. Koeln （1991） 90° Space Star equilateral triangle J.STRATE et al., Nucl. Phys. A501 (1989) 51H.R.Setzeet al., Physics Letters B388 (1996) 229 G.RAUPRICH et al., Nucl.Phys. A535 (1991) 313 • In Star configuration, outgoing 3 nucleons have the same energy and form an equilateral triangle. • In Space Star (SS), the star plane is perpendicular to the beam axis in c.m. system. 27 31 August 2009 19th International IUPAP Conference on Few-Body Problems in Physics SS Anomaly was first found in 1989 in nd breakup reaction at 13 MeV.

28. p n n n p p p p 2n 2He 3H 3He p n n n p p The Search for NN-Correlations in 3N-Systems In 3H proton causes a correlation of two neutrons leading to an appearance of quasibound 1S0 dineutron state In 3He neutron causes a correlation of two protons leading to an appearance of quasibound 1S0 diproton state Removal of proton from3Hand/or neutron from 3Heprovide conditions advantageous forNN-correlations to search 28

29. Space Star (SS) Anomaly in pd breakup pdcalc. by Deltuvaet al. (2005) nd exp. Erlangen & TUNL （●）（○） EN=13 MeV nd calc. EN=13 MeV (1996) (1989) ~30% ~15% nd calc. pd exp. Koeln（□）& KUTL（■） pd exp. Koeln （1991） (2002) Space Star A.Deltuva et al., PRC72,054004 (2005) J.STRATE et al., Nucl. Phys. A501 (1989) 51H.R.Setze et al., Physics Letters B388 (1996) 229 G.RAUPRICH et al., Nucl.Phys. A535 (1991) 313 • At pd SS, exp. cross section is smaller than pd calc. • At nd SS, exp. cross section is larger than nd calc. 29 • pd calc. were made by Deltuva et al. and by Ishikawa.

30. Our Preliminary Results of d+D→2He+2n Neutron TOF Spectrum @ TOF Base 1 m N Experiment: 2He=27°; n=36° Simulation: Enn = 80 keV N Experiment: 2He=27°; n=36° Tn Spectrum Tn Spectrum t, ns t, ns

31. The Search for NN-Correlations Результаты кинематического моделирования реакции d + 2H→ 2ns + 2ps − двумерные диаграммы 2n-2p(a) и E2n-E2p(б), где 2n и 2p – углы вылета, а E2n и E2p – энергии двухнейтронной и двухпротонной систем. Красные области соответствуют вылету системы 2ps под углом 27° ± 1.5° 31

32. nd-breakup configurations and unresolved problems 32