Particle physics

  • Article |

    Electron scattering measurements are shown to reproduce only qualitatively state-of-the-art lepton–nucleus energy reconstruction models, indicating that improvements to these particle-interaction models are required to ensure the accuracy of future high-precision neutrino oscillation experiments.

    • M. Khachatryan
    • , A. Papadopoulou
    •  & S. Gardiner
  • Article
    | Open Access

    The successful laser cooling of trapped antihydrogen, the antimatter atom formed by an antiproton and a positron (anti-electron), is reported.

    • C. J. Baker
    • , W. Bertsche
    •  & J. S. Wurtele
  • Article |

    Quark–antiquark annihilation measurements provide a precise determination of the ratio of down and up antiquarks within protons as a function of momentum, which confirms the asymmetry between the abundance of down and up antiquarks.

    • J. Dove
    • , B. Kerns
    •  & Z. Ye
  • Article |

    A quantum enhanced search for dark matter that uses vacuum squeezing to overcome the quantum noise limit finds no evidence of dark matter axions in a well motivated mass range.

    • K. M. Backes
    • , D. A. Palken
    •  & H. Wang
  • Article
    | Open Access

    Correlations in momentum space between hadrons created by ultrarelativistic proton–proton collisions at the CERN Large Hadron Collider provide insights into the strong interaction, particularly the short-range dynamics of hyperons—baryons that contain strange quarks.

    • S. Acharya
    • , D. Adamová
    •  & N. Zurlo
  • Article |

    The T2K experiment constrains CP symmetry in neutrino oscillations, excluding 46% of possible values of the CP violating parameter at a significance of three standard deviations; this is an important milestone to test CP symmetry conservation in leptons and whether the Universe’s matter–antimatter imbalance originates from leptons.

    • K. Abe
    • , R. Akutsu
    •  & A. Zykova
  • Article |

    Precision measurements of the 1S–2P transition in antihydrogen that take into account the standard Zeeman and hyperfine effects confirm the predictions of quantum electrodynamics.

    • M. Ahmadi
    • , B. X. R. Alves
    •  & J. S. Wurtele
  • Article
    | Open Access

    Ionization cooling, a technique that delivers high-brightness muon beams for the study of phenomena at energy scales beyond those of the Large Hadron Collider, is demonstrated by the Muon Ionization Cooling Experiment.

    • M. Bogomilov
    • , R. Tsenov
    •  & C. Heidt
  • Article |

    A magnetic-spectrometer-free method for electron–proton scattering data reveals a proton charge radius 2.7 standard deviations smaller than the currently accepted value from electron–proton scattering, yet consistent with other recent experiments.

    • W. Xiong
    • , A. Gasparian
    •  & Z. W. Zhao
  • Article |

    In the charge-density-wave Weyl semimetal (TaSe4)2I, an axion is observed and identified as a sliding mode in the charge-density-wave phase characterized by anomalous magnetoelectric transport effects.

    • J. Gooth
    • , B. Bradlyn
    •  & C. Felser
  • Article |

    All components of the proton–proton nuclear fusion chain, in which hydrogen is converted into helium in the Sun, are described, with several implications for fundamental solar and particle physics.

    • M. Agostini
    • , K. Altenmüller
    •  & G. Zuzel
  • Review Article |

    By analysing particle production in high-energy nuclear collisions, the phase boundary of strongly interacting matter is located and the phase structure of quantum chromodynamics is elucidated, implying quark–hadron duality.

    • Anton Andronic
    • , Peter Braun-Munzinger
    •  & Johanna Stachel
  • Review Article |

    The application and development of machine-learning methods used in experiments at the frontiers of particle physics (such as the Large Hadron Collider) are reviewed, including recent advances based on deep learning.

    • Alexander Radovic
    • , Mike Williams
    •  & Taritree Wongjirad
  • Letter |

    Measurements of the quark pressure distribution in the proton reveal a strong repulsive pressure near the proton’s centre (stronger than the pressure in neutron stars) and a binding pressure at greater distances.

    • V. D. Burkert
    • , L. Elouadrhiri
    •  & F. X. Girod
  • Letter |

    Measurement of the asymmetry in the parity-violating scattering of polarized electrons on protons gives the weak charge of the proton as 0.0719 ± 0.0045, in agreement with the standard model.

    • D. Androić
    • , D. S. Armstrong
    •  & S. Zhamkochyan
  • Letter |

    Two singly charmed baryons can fuse into the recently discovered doubly charmed baryon and a neutron through an exothermic reaction analogous to the nuclear fusion between deuterium and tritium.

    • Marek Karliner
    •  & Jonathan L. Rosner
  • Review Article |

    The standard model of particle physics is incomplete, but experimental particle decays that occur through a ‘flavour-changing neutral current’ process, which show discrepancies to standard model predictions, may offer hints to the existence of new particles.

    • F. Archilli
    • , M.-O. Bettler
    •  & K. A. Petridis
  • Review Article |

    Recent measurements of B-meson decays in which tau leptons are produced might challenge the standard model assumption that interactions of leptons differ only because of their different masses.

    • Gregory Ciezarek
    • , Manuel Franco Sevilla
    •  & Yutaro Sato
  • Review Article |

    Advances in meson spectroscopy can enhance our understanding of how composite objects emerge from the fundamental underlying theory of interacting quarks and gluons, quantum chromodynamics.

    • Matthew R. Shepherd
    • , Jozef J. Dudek
    •  & Ryan E. Mitchell
  • Letter |

    A digital quantum simulation of a lattice gauge theory is performed on a quantum computer that consists of a few trapped-ion qubits; the model simulated is the Schwinger mechanism, which describes the creation of electron–positron pairs from vacuum.

    • Esteban A. Martinez
    • , Christine A. Muschik
    •  & Rainer Blatt
  • Letter |

    The interaction between antiprotons, produced by colliding high-energy gold ions, is shown to be attractive, and two important parameters of this interaction are measured, namely the scattering length and the effective range.

    • L. Adamczyk
    • , J. K. Adkins
    •  & M. Zyzak
  • Letter
    | Open Access

    The CPT theorem (the assumption that physical laws are invariant under simultaneous charge conjugation, parity transformation and time reversal) is central to the standard model of particle physics; here the charge-to-mass ratio of the antiproton is compared to that of the proton, with a precision of 69 parts per trillion, and the result supports the CPT theorem at the atto-electronvolt scale.

    • S. Ulmer
    • , C. Smorra
    •  & Y. Yamazaki
  • Letter
    | Open Access

    Combined analysis of proton-proton collision data from the Large Hadron Collider at CERN by the CMS and LHCb collaborations leads to the observation of the extremely rare decay of the strange B meson into muons; the result is compatible with the standard model of particle physics, and does not show any signs of new physics, such as supersymmetry.

    • V. Khachatryan
    • , A.M. Sirunyan
    •  & E. Pesen
  • Letter |

    An electronic analogue of a Michelson–Morley experiment, in which an electron wave packet bound inside a calcium ion is split into two parts and subsequently recombined, demonstrates that the relative change in orientation of the two parts that results from the Earth’s rotation reveals no anisotropy in the electron dispersion; this verification of Lorentz symmetry improves on the precision of previous tests by a factor of 100.

    • T. Pruttivarasin
    • , M. Ramm
    •  & H. Häffner