Particle physics

  • Article
    | Open Access

    CPT violation could manifest itself in annihilating positronium events, but searching for this effect would require to know the spin of the annihilating system. Here, the authors do this using a positron-emission tomography scanner, finding no violation with a statistical precision of 10−4.

    • P. Moskal
    • , A. Gajos
    •  & W. Wiślicki
  • Article
    | Open Access

    Cherenkov detectors are used to detect high energy particles and their performance capabilities depend heavily on the material used. Here, the authors propose use of a Brewster-optics-based angular filter for a detector with increased sensitivity and particle identification capability.

    • Xiao Lin
    • , Hao Hu
    •  & Yu Luo
  • Article
    | Open Access

    Tensor network simulations of lattice gauge theories may overcome the limitations of the Monte Carlo approach, but results have been limited to 1+1 and 2+1 dimensions so far. Here, the authors report a tree-tensor-based numerical study of a 3+1d truncated U(1) lattice gauge theory with fermionic matter.

    • Giuseppe Magnifico
    • , Timo Felser
    •  & Simone Montangero
  • Article
    | Open Access

    Laser wakefield accelerators are compact sources of ultra-relativistic electrons which are highly sensitive to many control parameters. Here the authors present an automated machine learning based method for the efficient multi-dimensional optimization of these plasma-based particle accelerators.

    • R. J. Shalloo
    • , S. J. D. Dann
    •  & M. J. V. Streeter
  • Article
    | Open Access

    In order to detect relic neutrinos in the vicinity of the Earth, quantitative knowledge of the gravitational clustering effects on cosmic relic neutrinos in the Milky Way is necessary. Here, the authors develop a computational method capable of yielding neutrino density profiles for different neutrino masses and phase space distributions in a single simulation.

    • Jue Zhang
    •  & Xin Zhang
  • Article
    | Open Access

    Investigation of exotic electron–nucleon interactions with few-micrometers range requires micrometer-scale, highly-sensitive and well-isolated sensors. Here, the authors use an NV center to set limits on the monopole–dipole interaction between its electron spin and the nucleons of a half-ball lens.

    • Xing Rong
    • , Mengqi Wang
    •  & Jiangfeng Du
  • Article
    | Open Access

    It remains a challenge to find the structure and the distribution of the constituents of nucleons. Here the authors use a scattering method to get information about the gluons and quarks inside a proton and separate the contribution of Bethe-Heitler from the deeply virtual Compton scattering process.

    • M. Defurne
    • , A. Martí Jiménez-Argüello
    •  & P. Zhu
  • Article
    | Open Access

    Antihydrogen studies are important in testing the fundamental principles of physics but producing antihydrogen in large amounts is challenging. Here the authors demonstrate an efficient and high-precision method for trapping and stacking antihydrogen by using controlled plasma.

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

    The detection of Earth’s anti neutrino emission from potassium and the mantle remain elusive. Here the authors propose a method for measuring potassium and mantle geo-neutrinos by detecting their elastic scattering on electrons with direction-sensitive detectors.

    • Michael Leyton
    • , Stephen Dye
    •  & Jocelyn Monroe
  • Article
    | Open Access

    Wakefield accelerators are a cheaper and compact alternative to conventional particle accelerators for high-energy physics and coherent x-ray sources. Here, the authors demonstrate a field gradient in excess of a gigaelectron-volt-per-metre using a terahertz-frequency wakefield supported by a dielectric lined-waveguide.

    • B. D. O’Shea
    • , G. Andonian
    •  & J. B. Rosenzweig
  • Article
    | Open Access

    Plasma accelerators driven by particle beams are a promising technology, but the acceleration distance and energy gain are strongly limited by head erosion in a high-ionization-potential gas. Here the authors observe up to 130% energy boost in a self-focused electron beam, with limited head erosion.

    • S. Corde
    • , E. Adli
    •  & V. Yakimenko
  • Article
    | Open Access

    Plasma wakefield accelerators produce gradients that are orders of magnitude larger than in conventional particle accelerator, but beams tend to be disrupted by transverse forces. Here the authors create an extended hollow plasma channel, which accelerates positrons without generating transverse forces.

    • Spencer Gessner
    • , Erik Adli
    •  & Gerald Yocky
  • Article
    | Open Access

    The Positronium negative ion is formed by two electrons bound to a positron, and experimental investigations of its states and energy levels are difficult due to its short lifetime. Here, the authors report on laser spectroscopy of positronium using a source of efficiently produced ions.

    • Koji Michishio
    • , Tsuneto Kanai
    •  & Yasuyuki Nagashima
  • Article
    | Open Access

    Skyrmions are swirling topological magnetic textures that behave as if they were particles. Here, the authors present numerical simulations that describe the creation and destruction of these spin vortices in both chiral and dipolar magnets, and show what happens when skyrmions and antiskyrmions collide.

    • Wataru Koshibae
    •  & Naoto Nagaosa
  • Article
    | Open Access

    The order parameter describing the spontaneous symmetry breaking which occurs when a system becomes a superfluid is analogous to the Higgs field in particle physics from which the Higgs boson arises. Here, the authors demonstrate the existence of a light Higgs boson in the B-phase of superfluid3He.

    • V. V. Zavjalov
    • , S. Autti
    •  & G. E. Volovik
  • Article
    | Open Access

    Brownian motion of biomolecules and colloidal particles near solid walls is expected to be rather different from that in bulk, but the details have been highly controversial. Here, Huang and Szlufarska show a general breakdown of traditional no-slip boundary conditions at short timescales that clarifies the controversy.

    • Kai Huang
    •  & Izabela Szlufarska
  • Article
    | Open Access

    Skyrmions—magnetic vortices with an additional twist—have only been observed in a small number of chiral magnets, all with specific non-centrosymmetric structure. Here, the authors suggest that skyrmions can be found in many frustrated magnets as long as they meet a specific set of criteria.

    • A. O. Leonov
    •  & M. Mostovoy
  • Article
    | Open Access

    Bloch oscillations consist of periodic spreading and relocalization of particle wave functions, but have been so far observed only in separable states. Here the authors observe them for two-photon N00N states in integrated photonic circuits, revealing transitions from particle bunching to anitbunching.

    • Maxime Lebugle
    • , Markus Gräfe
    •  & Alexander Szameit
  • Article
    | Open Access

    Various approaches based on the iterative search have failed in the deterministic creation of bandgaps in random networks. Here Yu et al. reveal a deterministic pathway to bandgaps in random-walk potentials by applying the notion of supersymmetry to the wave equation.

    • Sunkyu Yu
    • , Xianji Piao
    •  & Namkyoo Park
  • Article
    | Open Access

    Quantum simulation offers an unparalleled computational resource, but realizing it for fermionic systems is challenging due to their particle statistics. Here the authors report on the time evolutions of fermionic interactions implemented with digital techniques on a nine-qubit superconducting circuit.

    • R. Barends
    • , L. Lamata
    •  & John M. Martinis
  • Article
    | Open Access

    Magnetic skyrmions are circulating topologically-protected spin textures which can arise in chiral magnets and potentially be applied in information processing. Here, the authors demonstrate the appearance of skyrmions at and above room temperature in a β-Mn-type Co-Zn-Mn alloy.

    • Y. Tokunaga
    • , X. Z. Yu
    •  & Y. Tokura
  • Article
    | Open Access

    Rydberg atomic gases have proven a fertile playground for exploring exotic phases of condensed matter systems. Here, Li and Das Sarma study Rydberg-dressed atomic fermions in a 3D optical lattice and find a series of mixed topological density wave phases having no analogue in conventional materials.

    • Xiaopeng Li
    •  & S Das Sarma
  • Review Article
    | Open Access

    The observation of neutrino oscillations indicates that neutrinos have mass and that their flavours are quantum mechanical mixtures. Here, the authors review the past, present and future contributions of nuclear reactor-based neutrino oscillation experiments, their accomplishments and the remaining challenges.

    • P. Vogel
    • , L.J. Wen
    •  & C. Zhang
  • Article |

    A stable plasma state with a high ratio of plasma to magnetic pressures is likely to be a key requirement for any future magnetic fusion reactor. Here, the authors create such a plasma using a field reversed configuration and active plasma boundary control and demonstrate its stability.

    • H. Y. Guo
    • , M. W. Binderbauer
    •  & E. Trask
  • Article |

    Gamma-ray bursts are short-lived luminous explosions at cosmological distances caused by jets from the deaths of massive stars. Bustamante et al. study neutrino, gamma-ray and cosmic-ray production by internal shocks, and find that multi-messenger observations are crucial to understand the evolving outflows.

    • Mauricio Bustamante
    • , Philipp Baerwald
    •  & Walter Winter
  • Article
    | Open Access

    The Giant Pairing Vibration is a collective mode in an atomic nucleus caused by coherence between particle-particle excitations, which has so far eluded detection. Cappuzzello et al. present signatures for its existence via heavy-ion-induced two-neutron transfer reactions in carbon nuclei.

    • F. Cappuzzello
    • , D. Carbone
    •  & A. Vitturi
  • Article
    | Open Access

    Mass spectrometry (MS) involves ionization of analytes with spectra dependent upon the mass-to-charge ratio. Here, the authors demonstrate that MS based on nanoelectromechanical systems gives results that are independent of the charge state and allow the mass spectrum of neutral species to be obtained.

    • Eric Sage
    • , Ariel Brenac
    •  & Sébastien Hentz
  • Article |

    In chiral helimagnets, the Dzyaloshinskii–Moriya interaction is known to stabilize skyrmions, but the microscopic roots remain enigmatic. Here, Janson et al. apply a multi-scale approach to Cu2OSeO3and show that its skyrmions can be traced back to magnetic tetrahedra of a quantum nature.

    • Oleg Janson
    • , Ioannis Rousochatzakis
    •  & Helge Rosner
  • Review Article |

    Neutrinos are ghost-like particles that interact only very weakly with other particles. As ongoing experiments to measure their properties improve, Ohlsson and Zhou review neutrino mass models and the renormalization group running of neutrino parameters that aim to understand the origin of neutrino mass.

    • Tommy Ohlsson
    •  & Shun Zhou
  • Article |

    Electrons moving in strongly curved paths emit radiation that is used in free-electron laser designs. Here, the authors demonstrate the inverse force principle, where a laser light field is used in a compact experimental design to accelerate electrons to produce high-quality electron beams.

    • J. Duris
    • , P. Musumeci
    •  & V. Yakimenko
  • Article |

    Magnetic reconnection is believed to play a key role in the acceleration and heating of particles in astrophysical plasmas but the details are unclear. Yamada et al. study reconnection in a laboratory plasma, enabling them to determine the exact mechanisms of energy flow from magnetic field to particles.

    • Masaaki Yamada
    • , Jongsoo Yoo
    •  & Clayton E. Myers
  • Article |

    Topological excitations in insulating magnets have recently attracted great interest from a fundamental and applied perspective. Here, Pereiro et al.report on the conditions to generate, stabilize and control skyrmions, even at room temperature, in a kagome magnet.

    • Manuel Pereiro
    • , Dmitry Yudin
    •  & Anders Bergman
  • Article
    | Open Access

    Measuring forces on antimatter is vital to testing our understanding of fundamental physics. Towards this aim, Aghion et al.present a method to measure the deflection of antiprotons based on an atom optical tool, the moiré deflectometer, which could be extended to future antihydrogen gravity measurements.

    • S. Aghion
    • , O. Ahlén
    •  & J. Zmeskal
  • Article |

    High-energy particle colliders are important for finding new particles, but huge volumes of data must be searched through to locate them. Here, the authors show the use of deep-learning methods on benchmark data sets as an approach to improving such new particle searches.

    • P. Baldi
    • , P. Sadowski
    •  & D. Whiteson
  • Article
    | Open Access

    Fundamental theories do not predict a difference between the properties of matter and antimatter, but experimental tests of this are still in their infancy. To this end, this study analyses the effects of electric fields on antihydrogen atoms in the ALPHA trap to place a bound on the charge of antihydrogen.

    • C. Amole
    • , M. D. Ashkezari
    •  & A. E. Charman
  • Article |

    Although synchrotron facilities routinely operate in a multi-bunch regime for maximum average brilliance, studies relying on time-of-flight schemes require single-bunch operation. Here, Holldack et al.isolate and apply single bunch X-ray pulses from multibunch radiation using pulse picking by resonant excitation.

    • K. Holldack
    • , R. Ovsyannikov
    •  & A. Föhlisch
  • Article |

    In contrast to real atoms, Bose–Einstein condensation of quasi-particles does not require low temperature, but is obtained via external pumping. Here, the authors show an unexpected transitional dynamics of a Bose–Einstein condensate of magnons due to a nonlinear evaporative supercooling mechanism.

    • Alexander A. Serga
    • , Vasil S. Tiberkevich
    •  & Burkard Hillebrands
  • Article |

    The coupling of particles with physical waves is a generic phenomenon observed in various systems, but its differentiation from quantum effect is still unclear. Perrard et al.address this issue using a bouncing liquid drop confined in a magnetic potential well, where quantized motions are obtained.

    • Stéphane Perrard
    • , Matthieu Labousse
    •  & Yves Couder
  • Article
    | Open Access

    Comparing hydrogen and antihydrogen—its antimatter counterpart—provides important tests of fundamental symmetries in the Standard Model. Kuroda et al. present a source of antihydrogen atoms that may provide high-precision in-flight measurements of their ground-state hyperfine splitting.

    • N. Kuroda
    • , S. Ulmer
    •  & Y. Yamazaki
  • Article |

    Current-induced motion of skyrmions is attracting attention due to its low critical current density, however, its microscopic mechanisms have not been elucidated yet. Using numerical simulations, the authors demonstrate a universal current-velocity relation of skyrmion motion, independent of disorder or nonadiabatic effects.

    • Junichi Iwasaki
    • , Masahito Mochizuki
    •  & Naoto Nagaosa
  • Article |

    For the ultrasensitive detection of magnetic fields either atomic transitions or superconducting circuits are used. Bal et al. combine such approaches and demonstrate a superconducting device functioning as an artificial atom for magnetic field detection with high sensitivity and spatial resolution.

    • M. Bal
    • , C. Deng
    •  & A. Lupascu