Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

New directions in hypernuclear physics

Abstract

A hypernucleus, a subatomic bound system with at least one hyperon, is a great test ground to investigate nuclear forces and general baryonic interactions with up, down and strange quarks. Hypernuclei have been extensively studied for almost seven decades in reactions involving cosmic rays and with accelerator beams. In recent years, experimental studies of hypernuclei have entered a new stage using energetic collisions of heavy-ion beams. However, these investigations have revealed two puzzling results related to the lightest three-body hypernuclear system, the so-called hypertriton, and the unexpected existence of a bound state of two neutrons with a Λ hyperon. Solving these puzzles will not only impact our understanding of the fundamental baryonic interactions with strange quarks but also of the nature of the deep interior of neutron stars. In this Perspective, we discuss approaches to solving these puzzles, including experiments with heavy-ion beams and the analysis of nuclear emulsions using state-of-the-art technologies. We summarize ongoing projects and experiments at various facilities worldwide and outline future perspectives.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: The WASA-FRS hypernuclear experiment.
Fig. 2: Nuclear emulsion analysis.
Fig. 3: Upcoming hypernuclear experiments.

References

  1. 1.

    Weber, F. Strangeness in neutron stars. J. Phys. G Nucl. Part. Phys. 27, 465–474 (2001).

    ADS  Article  Google Scholar 

  2. 2.

    Weber, F., Ho, A., Negreiros, R. P. & Rosenfield, P. Strangeness in neutron stars. Int. J. Mod. Phys. D 16, 231–245 (2007).

    ADS  MATH  Article  Google Scholar 

  3. 3.

    Demorest, P. B., Pennucci, T., Ransom, S. M., Roberts, M. S. E. & Hessels, J. W. T. A two-solar-mass neutron star measured using Shapiro delay. Nature 467, 1081–1083 (2010).

    ADS  Article  Google Scholar 

  4. 4.

    Antoniadis, J. et al. A massive pulsar in a compact relativistic binary. Science 340, 1233232 (2013).

    Article  Google Scholar 

  5. 5.

    Barr, E. D. et al. A massive millisecond pulsar in an eccentric binary. Mon. Not. R. Astron. Soc. 465, 1711–1719 (2016).

    ADS  Article  Google Scholar 

  6. 6.

    Yamamoto, Y., Furumoto, T., Yasutake, N. & Rijken, T. A. Hyperon mixing and universal many-body repulsion in neutron stars. Phys. Rev. C 90, 045805 (2014).

    ADS  Article  Google Scholar 

  7. 7.

    Ekawa, H. et al. Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment. Prog. Theor. Exp. Phys. 2019, 021D02 (2019).

    Article  Google Scholar 

  8. 8.

    Hayakawa, S. H. et al. Observation of coulomb-assisted nuclear bound state of Ξ14N system. Phys. Rev. Lett. 126, 062501 (2021).

    ADS  Article  Google Scholar 

  9. 9.

    Takahashi, H. et al. Observation of a \({}_{\Lambda \Lambda }^{6}{\rm{He}}\) double hypernucleus. Phys. Rev. Lett. 87, 212502 (2001).

    ADS  Article  Google Scholar 

  10. 10.

    Nakazawa, K. & Takahashi, H. Experimental study of double-Λ hypernuclei with nuclear emulsion. Prog. Theor. Phys. Suppl. 185, 335–343 (2010).

    ADS  MATH  Article  Google Scholar 

  11. 11.

    Rappold, C. et al. Hypernuclear production cross section in the reaction of 6Li + 12C at 2 A GeV. Phys. Lett. B 747, 129–134 (2015).

    ADS  Article  Google Scholar 

  12. 12.

    The STAR Collaboration Observation of an antimatter hypernucleus. Science 328, 58–62 (2010).

    Article  Google Scholar 

  13. 13.

    Xu, Y. for the STAR Collaboration in Proceedings of the 12th International Conference on Hypernuclear and Strange Particle Physics (HYP2015) 021005 (2017).

  14. 14.

    Adamczyk, L. et al. Measurement of the \({\,}_{\Lambda }^{3}{\rm{H}}\) lifetime in Au+Au collisions at the BNL Relativistic Heavy Ion Collider. Phys. Rev. C 97, 054909 (2018).

    ADS  Article  Google Scholar 

  15. 15.

    Chen, J., Keane, D., Ma, Y.-G., Tang, A. & Xu, Z. Antinuclei in heavy-ion collisions. Phys. Rep. 760, 1–39 (2018).

    ADS  MathSciNet  Article  Google Scholar 

  16. 16.

    Adam, J. et al. \({\,}_{\Lambda }^{3}{\rm{H}}\) and \({\,}_{\bar{\Lambda }}^{3}\bar{{\rm{H}}}\) production in Pb–Pb collisions at \(\sqrt{{s}_{{\rm{NN}}}}\) = 2.76 TeV. Phys. Lett. B 754, 360–372 (2016).

    ADS  Article  Google Scholar 

  17. 17.

    Acharya, S. et al. \({\,}_{\Lambda }^{3}{\rm{H}}\) and \({\,}_{\bar{\Lambda }}^{3}\bar{{\rm{H}}}\) lifetime measurement in Pb–Pb collisions at \(\sqrt{{s}_{{\rm{NN}}}}\) = 5.02 TeV via two-body decay. Phys. Lett. B 797, 134905 (2019).

    Article  Google Scholar 

  18. 18.

    Adam, J. et al. Measurement of the mass difference and the binding energy of the hypertriton and antihypertriton. Nat. Phys. 16, 409–412 (2020).

    Article  Google Scholar 

  19. 19.

    Rappold, C. et al. Search for evidence of \({\,}_{\Lambda }^{3}n\) by observing d + π and t + π final states in the reaction of 6Li+12C at 2A GeV. Phys. Rev. C 88, 041001 (2013).

    ADS  Article  Google Scholar 

  20. 20.

    Davis, D. H. 50 years of hypernuclear physics: I. The early experiments. Nucl. Phys. A 754, 3–13 (2005).

    ADS  Article  Google Scholar 

  21. 21.

    Bohm, G. et al. A determination of the binding-energy values of light hypernuclei. Nucl. Phys. B 4, 511–526 (1968).

    ADS  Article  Google Scholar 

  22. 22.

    JuriÄ, M. et al. A new determination of the binding-energy values of the light hypernuclei (A ≤ 15). Nucl. Phys. B 52, 1–30 (1973).

    ADS  Article  Google Scholar 

  23. 23.

    Prem, R. J. & Steinberg, P. H. Lifetimes of hypernuclei, ΛH3, ΛH4, ΛH5. Phys. Rev. 136, B1803–B1806 (1964).

    ADS  Article  Google Scholar 

  24. 24.

    Keyes, G. et al. New measurement of the ΛH3 lifetime. Phys. Rev. Lett. 20, 819–821 (1968).

    ADS  Article  Google Scholar 

  25. 25.

    Phillips, R. E. & Schneps, J. Lifetimes of light hyperfragments. II. Phys. Rev. 180, 1307–1318 (1969).

    ADS  Article  Google Scholar 

  26. 26.

    Bohm, G. et al. On the lifetime of the \({}_{\Lambda }^{3}{\rm{H}}\) hypernucleus. Nucl. Phys. B 16, 46–52 (1970).

    ADS  Article  Google Scholar 

  27. 27.

    Keyes, G. et al. Properties of ΛH3. Phys. Rev. D 1, 66–77 (1970).

    ADS  Article  Google Scholar 

  28. 28.

    Keyes, G., Sacton, J., Wickens, J. & Block, M. A measurement of the lifetime of the \({}_{\Lambda }^{3}{\rm{H}}\) hypernucleus. Nucl. Phys. B 67, 269–283 (1973).

    ADS  Article  Google Scholar 

  29. 29.

    Particle Data Group et al.Review of particle physics. Prog. Theor. Exp. Phys. 2020, 083C01 (2020).

    Article  Google Scholar 

  30. 30.

    Rappold, C. et al. Hypernuclear spectroscopy of products from 6Li projectiles on a carbon target at 2 AGeV. Nucl. Phys. A 913, 170–184 (2013).

    ADS  Article  Google Scholar 

  31. 31.

    Yu-Gang, M. (Anti)hypertriton lifetime puzzle. EPJ Web Conf. 117, 03003 (2016).

    Article  Google Scholar 

  32. 32.

    Perez-Obiol, A., Gazda, D., Friedman, E. & Gal, A. Revisiting the hypertriton lifetime puzzle. Phys. Lett. B 811, 135916 (2020).

    Article  Google Scholar 

  33. 33.

    Hildenbrand, F. & Hammer, H.-W. Lifetime of the hypertriton. Phys. Rev. C 102, 064002 (2020).

    ADS  Article  Google Scholar 

  34. 34.

    Hiyama, E. et al. Three-body structure of the nnΛ system with ΛN–ΣN coupling. Phys. Rev. C 89, 061302 (2014).

    ADS  Article  Google Scholar 

  35. 35.

    Gal, A. & Garcilazo, H. Is there a bound \({}_{\Lambda }^{3}{\rm{n}}\)? Phys. Lett. B 736, 93–97 (2014).

    ADS  Article  Google Scholar 

  36. 36.

    Garcilazo, H. & Valcarce, A. Nonexistence of a Λnn bound state. Phys. Rev. C 89, 057001 (2014).

    ADS  Article  Google Scholar 

  37. 37.

    Schafer, M. et al. The continuum spectrum of hypernuclear trios. Phys. Lett. B 808, 135614 (2020).

    Article  Google Scholar 

  38. 38.

    Ando, S.-I., Raha, U. & Oh, Y. Investigation of the nnΛ bound state in pionless effective theory. Phys. Rev. C 92, 024325 (2015).

    ADS  Article  Google Scholar 

  39. 39.

    Hildenbrand, F. & Hammer, H.-W. Three-body hypernuclei in pionless effective field theory. Phys. Rev. C 100, 034002 (2019).

    ADS  Article  Google Scholar 

  40. 40.

    Afnan, I. R. & Gibson, B. F. Resonances in the Λnn system. Phys. Rev. C 92, 054608 (2015).

    ADS  Article  Google Scholar 

  41. 41.

    Tang, L. et al. Determining the unknown Λ-n interaction by investigating the Λnn Resonance. Approved proposal E12-17-003 by PAC at Jefferson Lab. https://www.jlab.org/exp_prog/proposals/17/PR12-17-003.pdf (2017).

  42. 42.

    Bleser, S. et al. Has the neutral double hypernucleus \({}_{\Lambda \Lambda }^{4}{\rm{n}}\) been observed? Phys. Lett. B 790, 502–508 (2019).

    ADS  Article  Google Scholar 

  43. 43.

    Le, H., Haidenbauer, J., Meiner, U.-G. & Nogga, A. Implications of an increased λ-separation energy of the hypertriton. Phys. Lett. B 801, 135189 (2020).

    Article  Google Scholar 

  44. 44.

    Haidenbauer, J., Meißner, U.-G. & Nogga, A. Hyperon–nucleon interaction within chiral effective field theory revisited. Eur. Phys. J. A 56, 91 (2020).

    ADS  Article  Google Scholar 

  45. 45.

    Geissel, H. et al. The GSI projectile fragment separator (FRS): a versatile magnetic system for relativistic heavy ions. Nucl. Instrum. Methods Phys. Res. B 70, 286–297 (1992).

    ADS  Article  Google Scholar 

  46. 46.

    Bargholtz, C. et al. The WASA detector facility at CELSIUS. Nucl. Instrum. Methods Phys. Res. A 594, 339–350 (2008).

    ADS  Article  Google Scholar 

  47. 47.

    Saito, T. R. et al. Studies of the d+π signal and lifetime of the \({}_{\Lambda }^{3}{\rm{H}}\) and \({}_{\Lambda }^{4}{\rm{H}}\) hypernuclei by new spectroscopy techniques with FRS. Approved proposal S447 by GSI G-PAC (2017).

  48. 48.

    Outa, H. et al. Mesonic and non-mesonic decay widths of \({}_{\Lambda }^{4}{\rm{H}}\) and \({}_{\Lambda }^{4}{\rm{He}}\). Nucl. Phys. A 639, 251c–260c (1998).

    ADS  Article  Google Scholar 

  49. 49.

    Facility for Antiproton and Ion Research in Europe (FAIR). https://fair-center.eu.

  50. 50.

    High Intensity Heavy-ion Accelerator Facility (HIAF). http://hiaf.impcas.ac.cn/hiaf_en/public/c/news.html.

  51. 51.

    Imai, K., Nakazawa, K. & Tamura, H. J-PARC E07 experiment: Systematic study of double strangeness system with an emulsion-counter hybrid method. Proposal for Nuclear and Particle Physics Experiments at J-PARC (2006). http://j-parc.jp/researcher/Hadron/en/pac_0606/pdf/p07-Nakazawa.pdf.

  52. 52.

    Aoki, S. et al. Nuclear capture at rest of Ξ hyperons. Nucl. Phys. A 828, 191–232 (2009).

    ADS  Article  Google Scholar 

  53. 53.

    Ahn, J. K. et al. Double-Λ hypernuclei observed in a hybrid emulsion experiment. Phys. Rev. C 88, 014003 (2013).

    ADS  Article  Google Scholar 

  54. 54.

    LeCun, Y., Bengio, Y. & Hinton, G. Deep learning. Nature 521, 436–444 (2015).

    ADS  Article  Google Scholar 

  55. 55.

    He, K., Zhang, X., Ren, S. & Sun, J. Deep residual learning for image recognition. Preprint at arXiv http://arxiv.org/abs/1512.03385 (2015).

  56. 56.

    Yoshida, J. et al. CNN-based event classification of alpha-decay events in nuclear emulsion. Nucl. Instrum. Methods Phys. Res. A 989, 164930 (2021).

    Article  Google Scholar 

  57. 57.

    Goodfellow, I. J. et al. Generative adversarial networks. Preprint at arXiv https://arxiv.org/abs/1406.2661 (2014).

  58. 58.

    Wang, T. et al. High-resolution image synthesis and semantic manipulation with conditional GANs. Preprint at arXiv http://arxiv.org/abs/1711.11585 (2017).

  59. 59.

    He, K., Gkioxari, G., Dollár, P. & Girshick, R. B. Mask R-CNN. Preprint at arXiv https://arxiv.org/abs/1703.06870 (2017).

  60. 60.

    Barkas, W. H. Nuclear Research Emulsions. Pure & Applied Physics Series 15-1 (Academic, 1963).

  61. 61.

    Danysz, M. et al. The identification of a double hyperfragment. Nucl. Phys. 49, 121–132 (1963).

    Article  Google Scholar 

  62. 62.

    Dalitz, R. H. et al. The identified ΛΛ-hypernuclei and the predicted H-particle. Proc. R. Soc. Lond. A Math. Phys. Sci. 426, 1–17 (1989).

    ADS  Google Scholar 

  63. 63.

    Aoki, S. et al. Direct observation of sequential weak decay of a double hypernucleus. Prog. Theor. Phys. 85, 1287–1298 (1991).

    ADS  Article  Google Scholar 

  64. 64.

    Nakazawa, K. et al. The first evidence of a deeply bound state of Xi14N system. Prog. Theor. Exp. Phys. 2015, 033D02 (2015).

    ADS  Article  Google Scholar 

  65. 65.

    Ichikawa, A. et al. Production of twin Λ-hypernuclei from Ξ hyperon capture at rest. Phys. Lett. B 500, 37–46 (2001).

    ADS  Article  Google Scholar 

  66. 66.

    Yoshimoto, M. et al. First observation of a nuclear s-state of a Ξ hypernucleus, \({}_{\Xi }^{15}{\rm{C}}\). Prog. Theor. Exp. Phys. 2021, 073D02 (2021).

  67. 67.

    Yoshida, J., Nakazawa, K. & Umehara, K. New methods and technologies for double-lambda hypernucleus search in nuclear emulsion in J-PARC E07. https://doi.org/10.7566/JPSCP.1.013070 (2014).

  68. 68.

    Yoshida, J. et al. A new scanning system for alpha decay events as calibration sources for range-energy relation in nuclear emulsion. Nucl. Instrum. Methods Phys. Res. A 847, 86–92 (2017).

    ADS  Article  Google Scholar 

  69. 69.

    Yamamoto, T. O. et al. Observation of spin-dependent charge symmetry breaking in ΛN interaction: gamma-ray spectroscopy of \({}_{\Lambda }^{4}{\rm{He}}\). Phys. Rev. Lett. 115, 222501 (2015).

    ADS  Article  Google Scholar 

  70. 70.

    Superconducting fragment separator (Super-FRS). https://fair-center.eu/en/for-users/experiments/nustar/super-frs.html.

  71. 71.

    Rappold, C. & López-Fidalgo, J. Examination of experimental conditions for the production of proton-rich and neutron-rich hypernuclei. Phys. Rev. C 94, 044616 (2016).

    ADS  Article  Google Scholar 

  72. 72.

    Saito, T. R., Ekawa, H. & Nakagawa, M. Novel method for producing very-neutron-rich hypernuclei via charge-exchange reactions with heavy ion projectiles. Eur. Phys. J. A 57, 159 (2021).

    ADS  Article  Google Scholar 

  73. 73.

    Bass, S. et al. Microscopic models for ultrarelativistic heavy ion collisions. Prog. Part. Nucl. Phys. 41, 255–369 (1998).

    ADS  Article  Google Scholar 

  74. 74.

    Bleicher, M. et al. Relativistic hadron-hadron collisions in the ultra-relativistic quantum molecular dynamics model. J. Phys. G Nucl. Part. Phys. 25, 1859–1896 (1999).

    ADS  Article  Google Scholar 

  75. 75.

    Yang, J. et al. High intensity heavy ion accelerator facility (hiaf) in China. Nucl. Instrum. Methods Phys. Res. B 317, 263–265 (2013).

    ADS  Article  Google Scholar 

  76. 76.

    Kalantar-Nayestanaki, N. & Bruce, A. NUSTAR: NUclear STructure Astrophysics and Reactions at FAIR. Nucl. Phys. News 28, 5–11 (2018).

    Article  Google Scholar 

  77. 77.

    Danysz, M. & Pniewski, J. Delayed disintegration of a heavy nuclear fragment: I. Phil. Mag. 44, 348–350 (1953).

    Article  Google Scholar 

  78. 78.

    Hashimoto, O. & Tamura, H. Spectroscopy of Λ hypernuclei. Prog. Part. Nucl. Phys. 57, 564–653 (2006).

    ADS  Article  Google Scholar 

  79. 79.

    Saito, T. R. et al. Hypernuclei with stable heavy ion beam and RI-beam induced reactions at GSI (HypHI). Letter of intent submitted to GSI G-PAC (2005).

  80. 80.

    Saito, T. R. et al. Phase 0 experiment of the HypHI project: Hypernuclear spectroscopy of \({}_{\Lambda }^{3}{\rm{H}}\), \({}_{\Lambda }^{4}{\rm{H}}\) and \({}_{\Lambda }^{5}{\rm{He}}\)He with a 6Li beam at 2 A GeV on a 12C target. Proposal approved by GSI G-PAC (2006).

Download references

Acknowledgements

Discussions presented for the WASA-FRS experiment here are based on the experiment S447, which is currently scheduled in 2022 at the FRS at the GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany) in the context of FAIR Phase 0. The authors thank the accelerator departments at GSI and IMP, the FRS department at GSI and the Experiment Electronics department at GSI for the technical support. The authors thank the J-PARC E07 collaboration for providing us with the nuclear emulsion data. The authors thank Luise Doersching-Steitz of GSI, Rita Krause of GSI, Yukiko Kurakata of RIKEN, Daniela Press of GSI, Miao Yang of IMP and Xiaohua Yuan of IMP for supporting the projects, including the administrative works. The authors also thank Risa Kobayashi of RIKEN and Yoko Tsuchii of Gifu University for their technical support in mining hypertriton events in the E07 nuclear emulsions. K.N., J.Y. and M.Y. acknowledge support by JSPS KAKENHI grant numbers JP23224006, JP16H02180, JP20H00155 and JP20J00682, and MEXT KAKENHI grant numbers JP24105002 (Grant-in-Aid for Scientific Research on Innovative Areas 2404), JP18H05403 and JP19H05147 (Grant-in-Aid for Scientific Research on Innovative Areas 6005). S.E. and C.R. are supported by the grant 2019-T1/TIC-13194 of the program ‘Atracción de Talento Investigador’ of the Community of Madrid.

Author information

Affiliations

Authors

Contributions

All authors contributed to the manuscript. T.R.S., V.D., H.E., S.E., N.K.-N., A.K., M.K., E.L., S.M., A.M., M.N., C.R., N.S., C.S., M.T., Y.K.T., J.Y. and H.W. contributed to the WASA-FRS experiment at GSI and will contribute to future hypernuclear projects at FAIR. T.R.S., W.D., H.E., A.K., E.L., A.M., M.N., K.N., C.R., N.S., M.T., Y.K.T., J.Y., M.Y. and H.W. contributed to the development of the method to analyse the nuclear emulsion with machine learning. T.R.S., H.E., Y.H., E.L., Y.M., M.N., C.R., H.W. and X.Z. are working on the hypernuclear project at HIAF.

Corresponding author

Correspondence to Takehiko R. Saito.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information

Nature Reviews Physics thanks Yu-Gang Ma, Stefano Trogolo, Ed Hungerford and the other, anonymous, reviewer for their contribution to the peer review of this work.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Saito, T.R., Dou, W., Drozd, V. et al. New directions in hypernuclear physics. Nat Rev Phys (2021). https://doi.org/10.1038/s42254-021-00371-w

Download citation

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing