Bibliografie tematiche / Neutron lifetime discrepancy

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Letteratura scientifica selezionata sul tema "Neutron lifetime discrepancy"

Autore: Grafiati

Pubblicato: 7 dicembre 2024

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Articoli di riviste sul tema "Neutron lifetime discrepancy"

Wietfeldt, F. "Measurements of the Neutron Lifetime". Atoms 6, n. 4 (10 dicembre 2018): 70. http://dx.doi.org/10.3390/atoms6040070.

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Abstract (sommario):

Free neutron decay is a fundamental process in particle and nuclear physics. It is the prototype for nuclear beta decay and other semileptonic weak particle decays. Neutron decay played a key role in the formation of light elements in the early universe. The precise value of the neutron mean lifetime, about 15 min, has been the subject of many experiments over the past 70 years. The two main experimental methods, the beam method and the ultracold neutron storage method, give average values of the neutron lifetime that currently differ by 8.7 s (4 standard deviations), a serious discrepancy. The physics of neutron decay, implications of the neutron lifetime, previous and recent experimental measurements, and prospects for the future are reviewed.

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Wietfeldt, Fred E. "The Neutron Lifetime Discrepancy and Its Implications for Cosmology and Dark Matter". Symmetry 16, n. 8 (26 luglio 2024): 956. http://dx.doi.org/10.3390/sym16080956.

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Abstract (sommario):

Free neutron decay is the prototype for nuclear beta decay and other semileptonic weak particle decays. It provides important insights into the symmetries of the weak nuclear force. Neutron decay is important for understanding the formation and abundance of light elements in the early universe. The two main experimental approaches for measuring the neutron lifetime, the beam method and the ultracold neutron storage method, have produced results that currently differ by 9.8 ± 2.0 s. While this discrepancy probably has an experimental origin, a more exciting prospect is that it may be explained by new physics, with possible connections to dark matter. The experimental status of the neutron lifetime is briefly reviewed, with an emphasis on its implications for cosmology, astrophysics, and dark matter.

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Beck, D. H. "Neutron decay, dark matter and neutron stars". EPJ Web of Conferences 219 (2019): 05006. http://dx.doi.org/10.1051/epjconf/201921905006.

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Following up on a suggestion that decay to a dark matter fermion might explain the 4σ discrepancy in the neutron lifetime, we consider the implications of such a fermion on neutron star structure. We find that including it reduces the maximum neutron star mass to well below the observed masses. In order to recover stars with the observed masses, the (repulsive) self-interactions of the dark fermion would have to be stronger than those of the nucleon-nucleon interaction.

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Fornal, Bartosz. "Neutron Dark Decay". Universe 9, n. 10 (16 ottobre 2023): 449. http://dx.doi.org/10.3390/universe9100449.

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Abstract (sommario):

There exists a puzzling disagreement between the results for the neutron lifetime obtained in experiments using the beam technique versus those relying on the bottle method. A possible explanation of this discrepancy postulates the existence of a beyond-Standard-Model decay channel of the neutron involving new particles in the final state, some of which can be dark matter candidates. We review the current theoretical status of this proposal and discuss the particle physics models accommodating such a dark decay. We then elaborate on the efforts undertaken to test this hypothesis, summarizing the prospects for probing neutron dark decay channels in future experiments.

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Fornal, Bartosz, e Benjamín Grinstein. "Neutron’s dark secret". Modern Physics Letters A 35, n. 31 (21 agosto 2020): 2030019. http://dx.doi.org/10.1142/s0217732320300190.

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Abstract (sommario):

The existing discrepancy between neutron lifetime measurements in bottle and beam experiments has been interpreted as a sign of the neutron decaying to dark particles. We summarize the current status of this proposal, including a discussion of particle physics models involving such a portal between the Standard Model and a baryonic dark sector. We also review further theoretical developments around this idea and elaborate on the prospects for verifying the neutron dark decay hypothesis in current and upcoming experiments.

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Fornal, Bartosz, e Benjamín Grinstein. "Dark side of the neutron?" EPJ Web of Conferences 219 (2019): 05005. http://dx.doi.org/10.1051/epjconf/201921905005.

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Abstract (sommario):

We discuss our recently proposed interpretation of the discrepancy between the bottle and beam neutron lifetime experiments as a sign of a dark sector. The difference between the outcomes of the two types of measurements is explained by the existence of a neutron dark decay channel with a branching fraction 1%. Phenomenologically consistent particle physics models for the neutron dark decay can be constructed and they involve a strongly self-interacting dark sector. We elaborate on the theoretical developments around this idea and describe the efforts undertaken to verify it experimentally.

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Sun, X., E. Adamek, B. Allgeier, M. Blatnik, T. J. Bowles, L. J. Broussard, M. A. P. Brown et al. "Search for neutron dark decay: n → χ + e+e−". EPJ Web of Conferences 219 (2019): 05008. http://dx.doi.org/10.1051/epjconf/201921905008.

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Abstract (sommario):

In January, 2018, Fornal and Grinstein proposed that a previously unobserved neutron decay branch to a dark matter particle (χ) could account for the discrepancy in the neutron lifetime observed in two different types of experiments. One of the possible final states discussed includes a single χ along with an e+e− pair. We use data from the UCNA (Ultracold Neutron Asymmetry) experiment to set limits on this decay channel. Coincident electron-like events are detected with ∼ 4π acceptance using a pair of detectors that observe a volume of stored Ultracold Neutrons (UCNs). We use the timing information of coincidence events to select candidate dark sector particle decays by applying a timing calibration and selecting events within a physically-forbidden timing region for conventional n → p + e- + ν̅e decays. The summed kinetic energy (Ee+e−) from such events is reconstructed and used to set limits, as a function of the χ mass, on the branching fraction for this decay channel.

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Zhang, Liang, Bin Zhang, Cong Liu e Yixue Chen. "Evaluation of PWR pressure vessel fast neutron fluence benchmarks from NUREG/CR-6115 with ares transport code". Nuclear Technology and Radiation Protection 32, n. 3 (2017): 204–10. http://dx.doi.org/10.2298/ntrp1703204z.

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An accurate evaluation of PWR pressure vessel fast neutron fluence is essential to ensure pressure vessel integrity over the design lifetime. The discrete ordinates method is one of the main methods to treat such problems. In this paper, evaluations have been performed for three PWR benchmarks described in NUREG/CR-6115 using ARES transport code. The calculated results were compared to the reference values and a satisfactory agreement was obtained. In addition, the effects of SN numeric and source distribution modeling for pressure vessel fast neutron fluence calculation are investigated. Based on the fine enough grids adopted, the different spatial and angular discretization introduces derivations less than 3 %, and fix-up for negative scattering source causes no noticeable effects when calculating pressure vessel fast neutron fluence. However, the discrepancy of assembly-wise and pin-wise source modeling for peripheral assemblies reaches ~20 %, which indicates that pin-wise modeling for peripheral assemblies is essential. These results provide guidelines for pressure vessel fast neutron fluence calculation and demonstrate that the ARES transport code is capable of performing neutron transport calculations for evaluating PWR pressure vessel fast neutron fluence.

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Kunst, Ernst Karl. "On the common relativistic origin of the neutron lifetime discrepancy, the slight superluminality of neutrinos at Fermilab, and several astrophysical problems". Physics Essays 31, n. 2 (7 giugno 2018): 219–24. http://dx.doi.org/10.4006/0836-1398-31.2.219.

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Pols, Onno R., e Jasinta D. M. Dewi. "Helium-star Mass Loss and Its Implications for Black Hole Formation and Supernova Progenitors". Publications of the Astronomical Society of Australia 19, n. 2 (2002): 233–37. http://dx.doi.org/10.1071/as01121.

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AbstractRecently the observationally derived stellar-wind mass-loss rates for Wolf-Rayet stars, or massive naked helium stars, have been revised downwards by a substantial amount. We present evolutionary calculations of helium stars incorporating such revised mass-loss rates, as well as mass transfer to a close compact binary companion. Our models reach final masses well in excess of 10 M⊙, consistent with the observed masses of black holes in X-ray binaries. This resolves the discrepancy found with previously assumed high mass-loss rates between the final masses of stars which spend most of their helium-burning lifetime as Wolf-Rayet stars (˜3 M⊙) and the minimum observed black hole masses (6 M⊙). Our calculations also suggest that there are two distinct classes of progenitors for Type Ic supernovae: one with very large initial masses (35 M⊙), which are still massive when they explode and leave black hole remnants, and one with moderate initial masses (˜12–20 M⊙) undergoing binary interaction, which end up with small pre-explosion masses and leave neutron star remnants.

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Più fonti

Tesi sul tema "Neutron lifetime discrepancy"

Le, joubioux Marius. "Search fοr a neutrοn dark decay in 6Ηe". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMC223.

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L’écart entre les expériences dites du faisceau et de la bouteille mesurant la durée de vie du neutron libre pourrait être expliqué en considérant une nouvelle voie de désintégration du neutron en matière noire. Une telle décroissance pourrait être mis en lumière dans une sélection de noyaux radioactifs dans lesquels certains neutrons sont très faiblement liés au reste de la structure nucléaire. Dans le cas du noyau borroméen 6He, une décroissance en matière noire d’un des deux neutrons du halo produirait nécessairement les particules suivantes : 4He + n +x. Observer une émission de neutron corrélée à la décroissance de l’hélium 6 fournirait ainsi une signature claire et unique de création de matière noire. Unfaisceau intense 6He+ produit au Grand Accélérateur National d’Ions Lourds (GANIL)couplé au détecteur de neutron TETRA a permis d’établir une limite supérieure à l’existence de cette décroissance en matière noire dans l’hélium 6 à Brx <4:0 x 1010 >avec un degré de confiance de 95%. Cette limite expérimentale a également été traduite en une contrainte de l’ordre de Op105q pour la probabilité de décroissance en matière noire du neutron libre
Neutron dark decays have been suggested as a solution to the discrepancy between bottleand beam experiments, providing a dark matter candidate that can be searched for inhalo nuclei. The free neutron in the final state following the decay of 6He into 4He + n +x provides an exceptionally clean detection signature when combined with a high-efficiencyneutron detector. Using a high-intensity 6He beam at the Grand Accélérateur Nationald’Ions Lourds (GANIL), a search for a coincident neutron signal resulted in an upper limiton a dark decay branching ratio of Brx <4:0 x 1010 > with a 95% confidence level. Usingthe dark neutron decay model proposed originally by Fornal and Grinstein, we translatethis into an upper bound on a dark neutron branching ratio of Op105q, improving overglobal constraints by one to several orders of magnitude depending on m

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Atti di convegni sul tema "Neutron lifetime discrepancy"

Morris, Christopher. "Experimental search for an excited neutron state as an explanation of the beam-bottle neutron lifetime discrepancy." In Annual Meeting of the American Physical Society (APS) - Division of Nuclear Physics (DNP) ; 2024-10-07 - 2024-10-07. US DOE, 2024. http://dx.doi.org/10.2172/2460466.

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