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| Open AccessResonant X-ray excitation of the nuclear clock isomer 45Sc
Resonant X-ray excitation of the 45Sc nuclear isomeric state was achieved by irradiation of a Sc-metal foil with 12.4-keV photon pulses from a state-of-the-art X-ray free-electron laser, allowing a high-precision determination of the transition energy.
- Yuri Shvyd’ko
- , Ralf Röhlsberger
- & Tomasz Kolodziej
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Article
| Open AccessFirst observation of 28O
Observation of 28O and 27O through their decay into 24O and four and three neutrons, respectively, is reported, with the 28O nucleus being of particular interest owing to proton and neutron magic numbers and its extremely asymmetric neutron-to-proton ratio.
- Y. Kondo
- , N. L. Achouri
- & S. Yoshida
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Observation of the radiative decay of the 229Th nuclear clock isomer
The authors report on the radiative decay of a low-energy isomer in thorium-229 (229mTh), which has consequences for the design of a future nuclear clock and eases the search for direct laser excitation of the atomic nucleus.
- Sandro Kraemer
- , Janni Moens
- & Ulrich Wahl
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Determining the gluonic gravitational form factors of the proton
The gluonic gravitational form factor of the proton was determined using various models, and these analyses showed that the mass radius of the proton was smaller than the electric charge radius.
- B. Duran
- , Z.-E. Meziani
- & Z. Zhao
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Article
| Open AccessMeasurement of the axial vector form factor from antineutrino–proton scattering
The authors measure the nucleon axial vector form factor, which encodes information on the distribution of the nucleon weak charge, through antineutrino–proton scattering.
- T. Cai
- , M. L. Moore
- & L. Zazueta
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Pattern of global spin alignment of ϕ and K*0 mesons in heavy-ion collisions
At the Relativistic Heavy Ion Collider, observations of two meson species produced by heavy-ion collisions, ϕ and K*0, show surprising patterns of global spin alignment, being unexpectedly large and consistent with zero, respectively.
- M. S. Abdallah
- , B. E. Aboona
- & M. Zyzak
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STEREO neutrino spectrum of 235U fission rejects sterile neutrino hypothesis
Accurate measurements of the antineutrino energy spectrum of 235U fission by the STEREO detector reject the sterile neutrino hypothesis and point to biases in the nuclear data to explain the discrepancies with the prediction.
- H. Almazán
- , L. Bernard
- & M. Vialat
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Measured proton electromagnetic structure deviates from theoretical predictions
Measurements of the proton’s electromagnetic structure show enhancement of its electric generalized polarizability compared with theoretical expectations, confirming the presence of a new dynamical mechanism not accounted for by current theories.
- R. Li
- , N. Sparveris
- & J. Zhou
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Revealing the short-range structure of the mirror nuclei 3H and 3He
A comparison of electron scattering from the mirror nuclei hydrogen-3 and helium-3 reveals that proton–proton pairs have a much larger contribution to short-range correlations in helium-3 than in heavier nuclei, implying an unexpected nuclear structure.
- S. Li
- , R. Cruz-Torres
- & X. Zheng
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Nuclear moments of indium isotopes reveal abrupt change at magic number 82
Precision laser spectroscopy measurements of neutron-rich indium isotopes were performed to investigate the validity and identify limitations of theoretical descriptions of nuclei based on simple single-particle approaches.
- A. R. Vernon
- , R. F. Garcia Ruiz
- & D. T. Yordanov
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Article
| Open AccessObservation of a correlated free four-neutron system
Experiment based on knocking out an alpha particle from a high-energy helium isotope shows a resonance-like structure that is consistent with a quasi-bound tetraneutron state existing for a very short time.
- M. Duer
- , T. Aumann
- & M. V. Zhukov
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| Open AccessDirect measurement of the 3He+ magnetic moments
Measuring the hyperfine structure of a single helium-3 ion in a Penning trap enables direct measurement of the nuclear magnetic moment of helium-3 and provides the high accuracy needed for NMR-based magnetometry.
- A. Schneider
- , B. Sikora
- & K. Blaum
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Article
| Open AccessConstraining neutron-star matter with microscopic and macroscopic collisions
The physics of dense matter extracted from neutron star collision data is demonstrated to be consistent with information obtained from heavy-ion collisions, and analyses incorporating both data sources as well as information from nuclear theory provide new constraints for neutron star matter.
- Sabrina Huth
- , Peter T. H. Pang
- & Chris Van Den Broeck
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Article
| Open AccessProbing CP symmetry and weak phases with entangled double-strange baryons
Using spin-entangled baryon–antibaryon pairs, the BESIII Collaboration reports on high-precision measurements of potential charge conjugation and parity (CP)-symmetry-violating effects in hadrons.
- M. Ablikim
- , M. N. Achasov
- & J. H. Zou
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Article
| Open AccessDirect observation of the dead-cone effect in quantum chromodynamics
The direct measurement of the QCD dead cone in charm quark fragmentation is reported, using iterative declustering of jets tagged with a fully reconstructed charmed hadron.
- S. Acharya
- , D. Adamova
- & N. Zurlo
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| Open AccessSearch for Majorana neutrinos exploiting millikelvin cryogenics with CUORE
The CUORE experiment finds no evidence for neutrinoless double beta decay after operating a large cryogenic TeO2 calorimeter stably for several years in an extreme low-radiation environment at a temperature of 10 millikelvin.
- D. Q. Adams
- , C. Alduino
- & S. Zucchelli
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Electron-beam energy reconstruction for neutrino oscillation measurements
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
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Matters Arising |
Possible overestimation of isomer depletion due to contamination
- Song Guo
- , Yongde Fang
- & C. M. Petrache
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Matters Arising |
Reply to: Possible overestimation of isomer depletion due to contamination
- C. J. Chiara
- , J. J. Carroll
- & A. B. Hayes
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Article |
The asymmetry of antimatter in the proton
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
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Angular momentum generation in nuclear fission
γ-ray spectroscopy experiments on the origin of spin in the products of nuclear fission of spin-zero nuclei suggest that the fission fragments acquire their spin after scission, rather than before.
- J. N. Wilson
- , D. Thisse
- & S. Ziliani
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Article
| Open AccessCoherent X-ray−optical control of nuclear excitons
Suitably shaped X-ray pulses are used to coherently steer the quantum dynamics of atoms’ nuclei rather than their electrons, with few-zeptosecond temporal stability of the phase control.
- Kilian P. Heeg
- , Andreas Kaldun
- & Jörg Evers
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Article
| Open AccessMeasuring the α-particle charge radius with muonic helium-4 ions
The 2S–2P transitions in muonic helium-4 ions are measured using laser spectroscopy and used to obtain an α-particle charge-radius value five times more precise than that from electron scattering.
- Julian J. Krauth
- , Karsten Schuhmann
- & Franz Kottmann
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Article
| Open AccessUnveiling the strong interaction among hadrons at the LHC
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
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The impact of nuclear shape on the emergence of the neutron dripline
A mechanistic explanation for the origin of the neutron dripline shows that nuclei accommodate the addition of neutrons by becoming increasingly ellipsoidal, up to a maximum number of neutrons, reconciling theory and experiments.
- Naofumi Tsunoda
- , Takaharu Otsuka
- & Hideki Ueno
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Penning trap mass measurements of the deuteron and the HD+ molecular ion
Penning trap mass spectrometry is used to measure the masses of the deuteron and the HD+ ion with unprecedented precision, reducing the uncertainty of the proton mass reference value.
- Sascha Rau
- , Fabian Heiße
- & Klaus Blaum
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Impact of ionizing radiation on superconducting qubit coherence
Ionizing radiation from environmental radioactivity and cosmic rays increases the density of broken Cooper pairs in superconducting qubits, reducing their coherence times, but can be partially mitigated by lead shielding.
- Antti P. Vepsäläinen
- , Amir H. Karamlou
- & William D. Oliver
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Article
| Open AccessSpectroscopy of short-lived radioactive molecules
Measurements of low-energy electronic states of radium monofluoride validate predictions of the use of this short-lived radioactive molecule in exploring fundamental physics and provide evidence of its suitability for laser cooling.
- R. F. Garcia Ruiz
- , R. Berger
- & X. F. Yang
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Mirror-symmetry violation in bound nuclear ground states
Observations of the decay of 73Sr, when compared to its mirror nucleus 73Br, indicate that the spin assignment of their ground states differ, demonstrating mirror-symmetry violation.
- D. E. M. Hoff
- , A. M. Rogers
- & S. Waniganeththi
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Probing the core of the strong nuclear interaction
High-energy electron scattering that can isolate pairs of nucleons in high-momentum configurations reveals a transition to spin-independent scalar forces at small separation distances, supporting the use of point-like nucleon models to describe dense nuclear systems.
- A. Schmidt
- , J. R. Pybus
- & X. Zheng
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Article
| Open AccessDemonstration of cooling by the Muon Ionization Cooling Experiment
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
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A small proton charge radius from an electron–proton scattering experiment
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
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Letter |
X-ray pumping of the 229Th nuclear clock isomer
Excitation to the second excited state of 229Th is used to populate the metastable state 229mTh, enabling accurate determination of the isomer’s energy, half-life and excitation linewidth.
- Takahiko Masuda
- , Akihiro Yoshimi
- & Koji Yoshimura
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Energy of the 229Th nuclear clock transition
The transition energy of the first excited state of 229Th to the ground state is determined through the measurement of internal conversion electrons to correspond to a wavelength of 149.7 ± 3.1 nanometres.
- Benedict Seiferle
- , Lars von der Wense
- & Peter G. Thirolf
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Perspective |
Revisiting the cold case of cold fusion
Three years of investigation by a multi-disciplinary team into claims of ‘cold fusion’ found no evidence that the phenomenon exists, but identified a parameter space potentially worthy of further exploration.
- Curtis P. Berlinguette
- , Yet-Ming Chiang
- & Matthew D. Trevithick
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78Ni revealed as a doubly magic stronghold against nuclear deformation
A spectroscopic study of 78Ni confirms its doubly magic nature and reveals it as a stronghold beyond which the magic numbers 28 and 50 break down because of competing deformation.
- R. Taniuchi
- , C. Santamaria
- & Z. Y. Xu
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Letter |
Observation of two-neutrino double electron capture in 124Xe with XENON1T
Two-neutrino double electron capture is observed experimentally in 124Xe with the XENON1T detector, yielding a half-life of 1.8 × 1022 years.
- E. Aprile
- , J. Aalbers
- & J. P. Zopounidis
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Letter |
Modified structure of protons and neutrons in correlated pairs
Simultaneous high-precision measurements of the EMC effect and short-range correlated abundances for several nuclei reveal a universal modification of the structure of nucleons in short-range correlated neutron–proton pairs.
- B. Schmookler
- , M. Duer
- & X. Zheng
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Letter |
The surprisingly large neutron capture cross-section of 88Zr
The thermal neutron capture cross-section of 88Zr is measured to be 861,000 ± 69,000 barns, the second-largest neutron capture cross-section ever measured.
- Jennifer A. Shusterman
- , Nicholas D. Scielzo
- & Anton P. Tonchev
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Letter |
Impact of pear-shaped fission fragments on mass-asymmetric fission in actinides
Quantum many-body calculations of superfluid fission dynamics reveal that heavy fragments from asymmetric fission of actinides are associated with considerable octupole (pear-shaped) deformation acquired on the way to fission.
- Guillaume Scamps
- & Cédric Simenel
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Letter |
Probing high-momentum protons and neutrons in neutron-rich nuclei
Electron-scattering experiments reveal that the fraction of high-momentum protons in medium-to-heavy nuclei increases considerably with neutron excess, whereas that of high-momentum neutrons decreases slightly, in contrast to shell-model predictions.
- M. Duer
- , O. Hen
- & Z. W. Zhao
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Letter |
A per-cent-level determination of the nucleon axial coupling from quantum chromodynamics
Lattice quantum chromodynamics and a method inspired by the Feynman–Hellmann theorem are used to make a theoretical determination of the nucleon axial coupling with a precision of one per cent, giving the value 1.271 ± 0.013.
- C. C. Chang
- , A. N. Nicholson
- & A. Walker-Loud
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Letter |
An increase in the 12C + 12C fusion rate from resonances at astrophysical energies
The rate of carbon burning—12C + 12C fusion—in stars is boosted by resonant behaviour at astrophysical energies.
- A. Tumino
- , C. Spitaleri
- & L. Trache
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Letter |
Precision measurement of the weak charge of the proton
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
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Letter |
Isomer depletion as experimental evidence of nuclear excitation by electron capture
Experimental evidence is presented for isomer depletion through nuclear excitation by electron capture in molybdenum-93 nuclei.
- C. J. Chiara
- , J. J. Carroll
- & S. A. Karamian
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Letter |
Photonuclear reactions triggered by lightning discharge
Ground-based observations during a thunderstorm provide conclusive evidence of positrons being produced after lightning, confirming that lightning can trigger photonuclear reactions.
- Teruaki Enoto
- , Yuuki Wada
- & Harufumi Tsuchiya
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Letter |
Global Λ hyperon polarization in nuclear collisions
The measurement of an alignment between the angular momentum of a non-central collision between heavy ions and the spin of emitted particles reveals that the fluid produced in the collision is extremely vortical.
- L. Adamczyk
- , J. K. Adkins
- & M. Zyzak
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Background-free search for neutrinoless double-β decay of 76Ge with GERDA
If neutrinos are their own antiparticles, neutrinoless double-β decay of 76Ge should occur; a new lower-limit half-life of 5 × 1025 years for this process has now been determined under background-free conditions.
- M. Agostini
- , M. Allardt
- & G. Zuzel