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.

Measurement of interaction between antiprotons

This article has been updated

Abstract

One of the primary goals of nuclear physics is to understand the force between nucleons, which is a necessary step for understanding the structure of nuclei and how nuclei interact with each other. Rutherford discovered the atomic nucleus in 1911, and the large body of knowledge about the nuclear force that has since been acquired was derived from studies made on nucleons or nuclei. Although antinuclei up to antihelium-4 have been discovered1 and their masses measured, little is known directly about the nuclear force between antinucleons. Here, we study antiproton pair correlations among data collected by the STAR experiment2 at the Relativistic Heavy Ion Collider (RHIC)3, where gold ions are collided with a centre-of-mass energy of 200 gigaelectronvolts per nucleon pair. Antiprotons are abundantly produced in such collisions, thus making it feasible to study details of the antiproton–antiproton interaction. By applying a technique similar to Hanbury Brown and Twiss intensity interferometry4, we show that the force between two antiprotons is attractive. In addition, we report two key parameters that characterize the corresponding strong interaction: the scattering length and the effective range of the interaction. Our measured parameters are consistent within errors with the corresponding values for proton–proton interactions. Our results provide direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, and so are fundamental to understanding the structure of more-complex antinuclei and their properties.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: A schematic of the two-particle correlation process in a heavy-ion collision.
Figure 2: m2 versus nσz for negatively charged particles.
Figure 3: Correlation functions and their ratio.
Figure 4: d0 versus f0 for (anti)nucleon-(anti)nucleon interactions.

Change history

  • 18 November 2015

    In the Methods, the equation for the equal-time reduced Bethe-Salpeter amplitude (which can be approximated by the outer solution of the scattering problem) was corrected.

References

  1. 1

    STAR Collaboration. Observation of the antimatter helium-4 nucleus. Nature 473, 353–356 (2011); erratum 475, 412 (2011)

  2. 2

    STAR Collaboration. STAR detector overview. Nucl. Instrum. Methods Phys. Res. A 499, 624–632 (2003)

  3. 3

    Harrison, M., Ludlam, T. & Ozaki, S. RHIC project overview. Nucl. Instrum. Methods Phys. Res. A 499, 235–244 (2003)

    CAS  ADS  Article  Google Scholar 

  4. 4

    Hanbury Brown, R. & Twiss, R. Q. A new type of interferometer for use in radio astronomy. Phil. Mag. 45, 663–682 (1954)

    ADS  Article  Google Scholar 

  5. 5

    Yamazaki, T., Ishikawa, K., Kuramashi, Y. & Ukawa, A. Helium nuclei, deuteron, and dineutron in 2 + 1 flavor lattice QCD. Phys. Rev. D 86, 074514 (2012)

    ADS  Article  Google Scholar 

  6. 6

    Riotto, A. & Trodden, M. Recent progress in baryogenesis. Annu. Rev. Nucl. Part. Sci. 49, 35–75 (1999)

    CAS  ADS  Article  Google Scholar 

  7. 7

    Particle Data Group. Olive, K. A. et al. Review of particle physics. Chin. Phys. C 38, 090001, 96–106 (2014)

  8. 8

    Schellekens, M. et al. Hanbury Brown Twiss effect for ultracold quantum gases. Science 310, 648–651 (2005)

    CAS  ADS  Article  Google Scholar 

  9. 9

    Kiesel, H., Renz, A. & Hasselbach, F. Observation of Hanbury Brown–Twiss anticorrelations for free electrons. Nature 418, 392–394 (2002)

    CAS  ADS  Article  Google Scholar 

  10. 10

    Rom, T. et al. Free fermion antibunching in a degenerate atomic Fermi gas released from an optical lattice. Nature 444, 733–736 (2006)

    CAS  ADS  Article  Google Scholar 

  11. 11

    Goldhaber, G., Goldhaber, S., Lee, W. & Pais, A. Influence of Bose-Einstein statistics on the antiproton-proton annihilation process. Phys. Rev. 120, 300–312 (1960)

    CAS  ADS  MathSciNet  Article  Google Scholar 

  12. 12

    Kopylov, G. I. & Podgoretskiĭ, M. I. Interference of two-particle states in elementary-particle physics and astronomy. Sov. Phys. JETP 42, 211–214 (1975)

    ADS  Google Scholar 

  13. 13

    Podgoretskiĭ, M. I. Interference correlations of identical pions. Theory. Sov. J. Part. Nucl. 20, 266–282 (1989)

    Google Scholar 

  14. 14

    Gyulassy, M., Kauffmann, S. K. & Wilson, L. W. Pion interferometry of nuclear collisions. 1. Theory. Phys. Rev. C 20, 2267–2292 (1979)

    CAS  ADS  Article  Google Scholar 

  15. 15

    Boal, H. D., Gelbke, C.-K. & Jennings, B. K. Intensity interferometry in subatomic physics. Rev. Mod. Phys. 62, 553–602 (1990)

    CAS  ADS  Article  Google Scholar 

  16. 16

    Lednický, R. Correlation femtoscopy of multiparticle processes. Phys. Atom. Nucl . 67, 72–82 (2004)

    ADS  Article  Google Scholar 

  17. 17

    Lisa, M., Pratt, S., Soltz, R. & Wiedemann, U. Femtoscopy in relativistic heavy ion collisions: two decades of progress. Ann. Rev. Nucl. Part. Sci . 55, 357–402 (2005)

    CAS  ADS  Article  Google Scholar 

  18. 18

    Koonin, S. E. Proton pictures of high-energy nuclear collisions. Phys. Lett. B 70, 43–47 (1977)

    ADS  Article  Google Scholar 

  19. 19

    Lednický, R. & Lyuboshitz, V. L. Influence of final-state interaction on correlations of two particles with nearly equal momenta. Sov. J. Nucl. Phys . 35, 770–788 (1982)

    Google Scholar 

  20. 20

    Lednický, R. Notes on correlation femtoscopy. Phys. Atom. Nucl . 71, 1572–1578 (2008)

    Article  Google Scholar 

  21. 21

    STAR Collaboration. Proton-Λ correlations in central Au+Au collisions at . Phys. Rev. C 74, 064906 (2006)

  22. 22

    STAR Collaboration. Λ-Λ correlation function in Au+Au collisions at . Phys. Rev. Lett. 114, 022301 (2015)

  23. 23

    Anderson, M. et al. The STAR time projection chamber: a unique tool for studying high multiplicity events at RHIC. Nucl. Instrum. Methods Phys. Res. A 499, 659–678 (2003)

    CAS  ADS  Article  Google Scholar 

  24. 24

    STAR Collaboration. Multigap RPCs in the STAR experiment at RHIC. Nucl. Instrum. Methods Phys. Res. A 661, S110–S113 (2012)

  25. 25

    Kisiel, A., Zbroszczyk, H. & Szymański, M. Extracting baryon-antibaryon strong-interaction potentials from femtoscopic correlation functions. Phys. Rev. C 89, 054916 (2014)

    Google Scholar 

  26. 26

    Chojnacki, M., Kisiel, A., Florkowski, W. & Broniowski, W. THERMINATOR 2: THERMal heavy IoN generATOR 2. Comput. Phys. Commun. 183, 746–773 (2012)

    CAS  ADS  Article  Google Scholar 

  27. 27

    Pochodzalla, J. et al. Two-particle correlations at small relative momenta for 40Ar-induced reactions on 197Au at E/A = 60 MeV. Phys. Rev. C 35, 1695–1719 (1987)

    CAS  ADS  Article  Google Scholar 

  28. 28

    ALICE Collaboration. One-dimensional pion, kaon, and proton femtoscopy in Pb-Pb collisions at . Preprint at http://arxiv.org/abs/1506.07884 (2015)

  29. 29

    Mathelitsch, L. & VerWest, B. J. Effective range parameters in nucleon-nucleon scattering. Phys. Rev. C 29, 739–746 (1984)

    CAS  ADS  Article  Google Scholar 

  30. 30

    Šlaus, I., Akaishi, Y. & Tanaka, H. Neutron-neutron effective range parameters. Phys. Rep. 173, 257–300 (1989)

    ADS  Article  Google Scholar 

  31. 31

    Lednický, R. Femtoscopic correlations in multiparticle production and beta-decay. Braz. J. Phys. 37, 939–946 (2007)

    ADS  Article  Google Scholar 

  32. 32

    Lednický, R. Finite-size effect on two-particle production in continuous and discrete spectrum. Phys. Part. Nucl. 40, 307–352 (2009)

    Article  Google Scholar 

  33. 33

    Erazmus, B. et al. Influence of the emitting nucleus on the light-particle correlation function. Nucl. Phys. A 583, 395–400 (1995)

    ADS  Article  Google Scholar 

  34. 34

    Gmitro, M., Kvasil, J., Lednický, R. & Lyuboshitz, V. L. On the sensitivity of nucleon-nucleon correlations to the form of short-range potential. Czech. J. Phys. B 36, 1281–1287 (1986)

    ADS  Article  Google Scholar 

  35. 35

    Landau, L. D. & Lifshitz, E. M. Kvantovaya Mekhanika: Nerelyativistskaya Teoriya 3rd edn 585–685 (Nauka, 1974); Landau, L. D. & Lifshitz, E. M. Quantum Mechanics: Non-relativistic theory 3rd edn (Pergamon, 2013) [transl.].

  36. 36

    Bodmer, A. R. & Usmani, Q. N. Coulomb effects and charge symmetry breaking for the A = 4 hypernuclei. Phys. Rev. C 31, 1400–1411 (1985)

    CAS  ADS  Article  Google Scholar 

  37. 37

    Heller, L. Interaction of two nucleons at low energies. Rev. Mod. Phys. 39, 584–590 (1967)

    CAS  ADS  Article  Google Scholar 

  38. 38

    Bergervoet, J. R., van Campen, P. C., van der Sanden, W. A. & de Swart, J. J. Phase shift analysis of 0–30 MeV pp scattering data. Phys. Rev. C 38, 15–50 (1988)

    CAS  ADS  Article  Google Scholar 

Download references

Acknowledgements

We thank the RHIC Operations Group and RCF at BNL, the NERSC Center at LBNL, the KISTI Center in Korea, and the Open Science Grid consortium for providing resources and support. This work was supported in part by the Office of Nuclear Physics within the US DOE Office of Science, the US NSF, the Ministry of Education and Science of the Russian Federation, NSFC, the MoST of China (973 Programme No. 2014CB845400), CAS, MoST and MoE of China, the Korean Research Foundation, GA and MSMT of the Czech Republic, FIAS of Germany, DAE, DST and UGC of India, the National Science Centre of Poland, National Research Foundation, the Ministry of Science, Education and Sports of the Republic of Croatia, and RosAtom of Russia.

Author information

Affiliations

Consortia

Contributions

All authors contributed equally.

Ethics declarations

Competing interests

The author declare no competing financial interests.

Extended data figures and tables

Extended Data Table 1 The decomposition of systematic errors

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

The STAR Collaboration. Measurement of interaction between antiprotons. Nature 527, 345–348 (2015). https://doi.org/10.1038/nature15724

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

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