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ATLAS Collaboration |
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Title  |
A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery |
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Journal Article |
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Year |
2022 |
Publication |
Nature |
Abbreviated Journal |
Nature |
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Volume |
607 |
Issue |
7917 |
Pages |
52-59 |
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Abstract |
The standard model of particle physics(1-4) describes the known fundamental particles and forces that make up our Universe, with the exception of gravity. One of the central features of the standard model is a field that permeates all of space and interacts with fundamental particles(5-9). The quantum excitation of this field, known as the Higgs field, manifests itself as the Higgs boson, the only fundamental particle with no spin. In 2012, a particle with properties consistent with the Higgs boson of the standard model was observed by the ATLAS and CMS experiments at the Large Hadron Collider at CERN10,11. Since then, more than 30 times as many Higgs bosons have been recorded by the ATLAS experiment, enabling much more precise measurements and new tests of the theory. Here, on the basis of this larger dataset, we combine an unprecedented number of production and decay processes of the Higgs boson to scrutinize its interactions with elementary particles. Interactions with gluons, photons, and W and Z bosons-the carriers of the strong, electromagnetic and weak forces-are studied in detail. Interactions with three third-generation matter particles (bottom (b) and top (t) quarks, and tau leptons (tau)) are well measured and indications of interactions with a second-generation particle (muons, mu) are emerging. These tests reveal that the Higgs boson discovered ten years ago is remarkably consistent with the predictions of the theory and provide stringent constraints on many models of new phenomena beyond the standard model. |
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0028-0836 |
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WOS:000820564200004 |
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no |
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yes |
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yes |
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IFIC @ pastor @ |
Serial |
5521 |
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Wilson, J.N. et al; Algora, A. |
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Title |
Angular momentum generation in nuclear fission |
Type |
Journal Article |
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Year |
2021 |
Publication |
Nature |
Abbreviated Journal |
Nature |
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Volume |
590 |
Issue |
7847 |
Pages |
566-570 |
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Abstract |
When a heavy atomic nucleus splits (fission), the resulting fragments are observed to emerge spinning(1); this phenomenon has been a mystery in nuclear physics for over 40 years(2,3). The internal generation of typically six or seven units of angular momentum in each fragment is particularly puzzling for systems that start with zero, or almost zero, spin. There are currently no experimental observations that enable decisive discrimination between the many competing theories for the mechanism that generates the angular momentum(4-12). Nevertheless, the consensus is that excitation of collective vibrational modes generates the intrinsic spin before the nucleus splits (pre-scission). Here we show that there is no significant correlation between the spins of the fragment partners, which leads us to conclude that angular momentum in fission is actually generated after the nucleus splits (post-scission). We present comprehensive data showing that the average spin is strongly mass-dependent, varying in saw-tooth distributions. We observe no notable dependence of fragment spin on the mass or charge of the partner nucleus, confirming the uncorrelated post-scission nature of the spin mechanism. To explain these observations, we propose that the collective motion of nucleons in the ruptured neck of the fissioning system generates two independent torques, analogous to the snapping of an elastic band. A parameterization based on occupation of angular momentum states according to statistical theory describes the full range of experimental data well. This insight into the role of spin in nuclear fission is not only important for the fundamental understanding and theoretical description of fission, but also has consequences for the gamma-ray heating problem in nuclear reactors(13,14), for the study of the structure of neutron-rich isotopes(15,16), and for the synthesis and stability of super-heavy elements(17,18). gamma-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. |
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[Wilson, J. N.; Thisse, D.; Lebois, M.; Jovancevic, N.; Adsley, P.; Babo, M.; Chakma, R.; Delafosse, C.; Haefner, G.; Hauschild, K.; Ibrahim, F.; Ljungvall, J.; Lopez-Martens, A.; Lozeva, R.; Matea, I; Nemer, J.; Popovitch, Y.; Qi, L.; Tocabens, G.; Verney, D.] Univ Paris Saclay, IJC Lab, CNRS, IN2P3, Orsay, France, Email: jonathan.wilson@ijclab.in2p3.fr |
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Nature Research |
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0028-0836 |
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Notes |
WOS:000621583600006 |
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no |
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yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4717 |
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Author |
T2K Collaboration (Abe, K. et al); Antonova, M.; Cervera-Villanueva, A.; Fernandez, P.; Izmaylov, A.; Novella, P. |
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Title |
Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations |
Type |
Journal Article |
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Year |
2020 |
Publication |
Nature |
Abbreviated Journal |
Nature |
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Volume |
580 |
Issue |
7803 |
Pages |
339-344 |
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Abstract |
The charge-conjugation and parity-reversal (CP) symmetry of fundamental particles is a symmetry between matter and antimatter. Violation of this CP symmetry was first observed in 1964(1), and CP violation in the weak interactions of quarks was soon established(2). Sakharov proposed(3) that CP violation is necessary to explain the observed imbalance of matter and antimatter abundance in the Universe. However, CP violation in quarks is too small to support this explanation. So far, CP violation has not been observed in non-quark elementary particle systems. It has been shown that CP violation in leptons could generate the matter-antimatter disparity through a process called leptogenesis(4). Leptonic mixing, which appears in the standard model's charged current interactions(5,6), provides a potential source of CP violation through a complex phase dCP, which is required by some theoretical models of leptogenesis(7-9). This CP violation can be measured in muon neutrino to electron neutrino oscillations and the corresponding antineutrino oscillations, which are experimentally accessible using accelerator-produced beams as established by the Tokai-to-Kamioka (T2K) and NOvA experiments(10,11). Until now, the value of dCP has not been substantially constrained by neutrino oscillation experiments. Here we report a measurement using long-baseline neutrino and antineutrino oscillations observed by the T2K experiment that shows a large increase in the neutrino oscillation probability, excluding values of dCP that result in a large increase in the observed antineutrino oscillation probability at three standard deviations (3 sigma). The 3 sigma confidence interval for delta(CP), which is cyclic and repeats every 2p, is [-3.41, -0.03] for the so-called normal mass ordering and [-2.54, -0.32] for the inverted mass ordering. Our results indicate CP violation in leptons and our method enables sensitive searches for matter-antimatter asymmetry in neutrino oscillations using accelerator-produced neutrino beams. Future measurements with larger datasets will test whether leptonic CP violation is larger than the CP violation in quarks. |
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[Berguno, D. Bravo; Ishii, T.; Labarga, L.] Univ Autonoma Madrid, Dept Theoret Phys, Madrid, Spain |
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Nature Publishing Group |
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English |
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0028-0836 |
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Notes |
WOS:000530151300023 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4388 |
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Author |
LHCb Collaboration (Aaij, R. et al); Martinez-Vidal, F.; Oyanguren, A.; Ruiz Valls, P.; Sanchez Mayordomo, C. |
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Title |
Determination of the quark coupling strength vertical bar V-ub vertical bar using baryonic decays |
Type |
Journal Article |
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Year |
2015 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
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Volume |
11 |
Issue |
9 |
Pages |
743-747 |
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Keywords |
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Abstract |
In the Standard Model of particle physics, the strength of the couplings of the b quark to the u and c quarks, vertical bar V-ub vertical bar and vertical bar V-ub vertical bar, are governed by the coupling of the quarks to the Higgs boson. Using data from the LHCb experiment at the Large Hadron Collider, the probability for the Lambda(0)(b) baryon to decay into the p mu(-)(nu) over bar (mu) final state relative to the Lambda(+)(c)mu(-)(nu) over bar (mu) final state is measured. Combined with theoretical calculations of the strong interaction and a previously measured value of vertical bar V-ub vertical bar, the first vertical bar V-ub vertical bar measurement to use a baryonic decay is performed. This measurement is consistent with previous determinations of vertical bar V-ub vertical bar using B meson decays to specific final states and confirms the existing incompatibility with those using an inclusive sample of final states. |
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Address |
[Bediaga, I.; De Miranda, J. M.; Ferreira Rodrigues, F.; Gomes, A.; Massafferri, A.; Rodrigues, B. Osorio; dos Reis, A. C.; Rodrigues, A. B.] Ctr Brasileiro Pesquisas Fis, Rio De Janeiro, Brazil, Email: u.egede@imperial.ac.uk |
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Nature Publishing Group |
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English |
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ISSN |
1745-2473 |
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Notes |
WOS:000360709200018 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
2388 |
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Author |
Cole, P.S.; Bertone, G.; Coogan, A.; Gaggero, D.; Karydas, T.; Kavanagh, B.J.; Spieksma, T.F.M.; Tomaselli, G.M. |
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Title |
Distinguishing environmental effects on binary black hole gravitational waveforms |
Type |
Journal Article |
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Year |
2023 |
Publication |
Nature Astronomy |
Abbreviated Journal |
Nat. Astron. |
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Volume |
7 |
Issue |
8 |
Pages |
943-950 |
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Keywords |
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Abstract |
A Bayesian approach to comparing the effects of accretion disks, dark matter or clouds of ultra-light bosons on gravitational waveforms from a black hole binary system concludes that detectors such as LISA can distinguish between these environments. Future gravitational wave interferometers such as the Laser Interferometer Space Antenna, Taiji, DECi-hertz Interferometer Gravitational wave Observatory and TianQin will enable precision studies of the environment surrounding black holes. These detectors will probe the millihertz frequency range, as yet unexplored by current gravitational wave detectors. Furthermore, sources will remain in band for durations of up to years, meaning that the inspiral phase of the gravitational wave signal, which can be affected by the environment, will be observable. In this paper, we study intermediate and extreme mass ratio binary black hole inspirals, and consider three possible environments surrounding the primary black hole: accretion disks, dark matter spikes and clouds of ultra-light scalar fields, also known as gravitational atoms. We present a Bayesian analysis of the detectability and measurability of these three environments. Focusing for concreteness on the case of a detection with LISA, we show that the characteristic imprint they leave on the gravitational waveform would allow us to identify the environment that generated the signal and to accurately reconstruct its model parameters. |
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Address |
[Cole, Philippa S.; Bertone, Gianfranco; Karydas, Theophanes; Spieksma, Thomas F. M.; Tomaselli, Giovanni Maria] Univ Amsterdam, Inst Theoret Phys Amsterdam, Gravitat Astroparticle Phys Amsterdam GRAPPA, Amsterdam, Netherlands, Email: p.s.cole@uva.nl |
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Nature Portfolio |
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English |
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Edition |
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ISSN |
2397-3366 |
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Notes |
WOS:001000769700001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5546 |
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Author |
Double Chooz collaboration (de Kerret, H. et al); Novella, P. |
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Title |
Double Chooz theta(13) measurement via total neutron capture detection |
Type |
Journal Article |
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Year |
2020 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
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Volume |
16 |
Issue |
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Pages |
558-564 |
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Abstract |
Neutrinos were assumed to be massless particles until the discovery of the neutrino oscillation process. This phenomenon indicates that the neutrinos have non-zero masses and the mass eigenstates (nu(1), nu(2), nu(3)) are mixtures of their flavour eigenstates (nu(e), nu(mu), nu(tau)). The oscillations between different flavour eigenstates are described by three mixing angles (theta(12), theta(23), theta(13)), two differences of the squared neutrino masses of the nu(2)/nu(1) and nu(3)/nu(1) pairs and a charge conjugation parity symmetry violating phase delta(CP). The Double Chooz experiment, located near the Chooz Electricite de France reactors, measures the oscillation parameter theta(13) using reactor neutrinos. Here, the Double Chooz collaboration reports the measurement of the mixing angle theta(13) with the new total neutron capture detection technique from the full data set, yielding sin(2)(2 theta(13)) = 0.105 +/- 0.014. This measurement exploits the multidetector configuration, the isoflux baseline and data recorded when the reactors were switched off. In addition to the neutrino mixing angle measurement, Double Chooz provides a precise measurement of the reactor neutrino flux, given by the mean cross-section per fission <sigma(f)& rang; = (5.71 +/- 0.06) x 10(-43) cm(2) per fission, and reports an empirical model of the distortion in the reactor neutrino spectrum. The Double Chooz collaboration reports the neutrino oscillation parameter theta(13) from a measurement of the disappearance of reactor anti-electron neutrinos with the total neutron capture technique. |
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Address |
[de Kerret, H.; Cabrera, A.; Dawson, J., V; Givaudan, A.; Gomez, H.; Hourlier, A.; Karakac, M.; Kryn, D.; Lasserres, T.; Obolensky, M.; Onillon, A.; Suekane, F.; Wagner, S.] Sorbonne Paris Cite Univ, Observ Paris, CEA IRFU, APC,CNRS IN2P3, Paris, France, Email: christian.buck@mpi-hd.mpg.de; |
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Nature Publishing Group |
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English |
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Series Issue |
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Edition |
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ISSN |
1745-2473 |
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Notes |
WOS:000528019800001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4389 |
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Author |
Khachatryan, M. et al, Coloma, P. |
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Title |
Electron-beam energy reconstruction for neutrino oscillation measurements |
Type |
Journal Article |
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Year |
2021 |
Publication |
Nature |
Abbreviated Journal |
Nature |
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Volume |
599 |
Issue |
7886 |
Pages |
565-570 |
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Keywords |
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Abstract |
Neutrinos exist in one of three types or 'flavours'-electron, muon and tau neutrinos-and oscillate from one flavour to another when propagating through space. This phenomena is one of the few that cannot be described using the standard model of particle physics (reviewed in ref. (1)), and so its experimental study can provide new insight into the nature of our Universe (reviewed in ref. (2)). Neutrinos oscillate as a function of their propagation distance (L) divided by their energy (E). Therefore, experiments extract oscillation parameters by measuring their energy distribution at different locations. As accelerator-based oscillation experiments cannot directly measure E, the interpretation of these experiments relies heavily on phenomenological models of neutrino-nucleus interactions to infer E. Here we exploit the similarity of electron-nucleus and neutrino-nucleus interactions, and use electron scattering data with known beam energies to test energy reconstruction methods and interaction models. We find that even in simple interactions where no pions are detected, only a small fraction of events reconstruct to the correct incident energy. More importantly, widely used interaction models reproduce the reconstructed energy distribution only qualitatively and the quality of the reproduction varies strongly with beam energy. This shows both the need and the pathway to improve current models to meet the requirements of next-generation, high-precision experiments such as Hyper-Kamiokande (Japan)(3) and DUNE (USA)(4). 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. |
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Address |
[Khachatryan, M.; Hauenstein, F.; Weinstein, L. B.] Old Domin Univ, Norfolk, VA USA, Email: adishka@mit.edu |
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Nature Portfolio |
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English |
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0028-0836 |
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Notes |
WOS:000722366200013 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5073 |
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Author |
Otten, S.; Caron, S.; de Swart, W.; van Beekveld, M.; Hendriks, L.; van Leeuwen, C.; Podareanu, D.; Ruiz de Austri, R.; Verheyen, R. |
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Title |
Event generation and statistical sampling for physics with deep generative models and a density information buffer |
Type |
Journal Article |
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Year |
2021 |
Publication |
Nature Communications |
Abbreviated Journal |
Nat. Commun. |
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Volume |
12 |
Issue |
1 |
Pages |
2985 - 16pp |
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Keywords |
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Abstract |
Simulating nature and in particular processes in particle physics require expensive computations and sometimes would take much longer than scientists can afford. Here, we explore ways to a solution for this problem by investigating recent advances in generative modeling and present a study for the generation of events from a physical process with deep generative models. The simulation of physical processes requires not only the production of physical events, but to also ensure that these events occur with the correct frequencies. We investigate the feasibility of learning the event generation and the frequency of occurrence with several generative machine learning models to produce events like Monte Carlo generators. We study three processes: a simple two-body decay, the processes e(+)e(-)-> Z -> l(+)l(-) and pp -> tt<mml:mo><overbar></mml:mover> including the decay of the top quarks and a simulation of the detector response. By buffering density information of encoded Monte Carlo events given the encoder of a Variational Autoencoder we are able to construct a prior for the sampling of new events from the decoder that yields distributions that are in very good agreement with real Monte Carlo events and are generated several orders of magnitude faster. Applications of this work include generic density estimation and sampling, targeted event generation via a principal component analysis of encoded ground truth data, anomaly detection and more efficient importance sampling, e.g., for the phase space integration of matrix elements in quantum field theories. Here, the authors report buffered-density variational autoencoders for the generation of physical events. This method is computationally less expensive over other traditional methods and beyond accelerating the data generation process, it can help to steer the generation and to detect anomalies. |
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Address |
[Otten, Sydney; Caron, Sascha; de Swart, Wieske; van Beekveld, Melissa; Hendriks, Luc; Verheyen, Rob] Radboud Univ Nijmegen, Inst Math Astro & Particle Phys IMAPP, Nijmegen, Netherlands, Email: Sydney.Otten@ru.nl |
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Nature Research |
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English |
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ISSN |
2041-1723 |
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Notes |
WOS:000658761600003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4862 |
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Author |
Cederwall, B. et al; Algora, A.; Gadea, A. |
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Title |
Evidence for a spin-aligned neutron-proton paired phase from the level structure of Pd-92 |
Type |
Journal Article |
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Year |
2011 |
Publication |
Nature |
Abbreviated Journal |
Nature |
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Volume |
469 |
Issue |
7328 |
Pages |
68-71 |
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Keywords |
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Abstract |
Shell structure and magic numbers in atomic nuclei were generally explained by pioneering work(1) that introduced a strong spin-orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron-proton pairing(2-6), in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus Pd-92. Gamma rays emitted following the Ni-58(Ar-36,2n)Pd-92 fusion-evaporation reaction were identified using a combination of state-of-the-art high-resolution c-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron-proton coupling scheme, different from the previous prediction(2-6). We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling(7,8)) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron-proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis. |
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Address |
[Cederwall, B.; Moradi, F. Ghazi; Back, T.; Johnson, A.; Blomqvist, J.; Andgren, K.; Lagergren, K.; Liotta, R.; Qi, C.; Hadinia, B.; Khaplanov, A.; Persson, A.; Sandzelius, M.] Royal Inst Technol, Dept Phys, SE-10691 Stockholm, Sweden, Email: cederwall@nuclear.kth.se |
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Nature Publishing Group |
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English |
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0028-0836 |
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Conference |
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Notes |
ISI:000285921600032 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
588 |
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| Permanent link to this record |
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Author |
ATLAS Collaboration (Aaboud, M. et al); Alvarez Piqueras, D.; Barranco Navarro, L.; Cabrera Urban, S.; Castillo Gimenez, V.; Cerda Alberich, L.; Costa, M.J.; Fernandez Martinez, P.; Ferrer, A.; Fiorini, L.; Fuster, J.; Garcia, C.; Garcia Navarro, J.E.; Gonzalez de la Hoz, S.; Higon-Rodriguez, E.; Jimenez Pena, J.; Lacasta, C.; Mamuzic, J.; Marti-Garcia, S.; Melini, D.; Mitsou, V.A.; Pedraza Lopez, S.; Rodriguez Rodriguez, D.; Romero Adam, E.; Salt, J.; Sanchez Martinez, V.; Soldevila, U.; Sanchez, J.; Valero, A.; Valls Ferrer, J.A.; Vos, M. |
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Title |
Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC |
Type |
Journal Article |
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Year |
2017 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
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Volume |
13 |
Issue |
9 |
Pages |
852-858 |
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Keywords |
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Abstract |
Light-by-light scattering (gamma gamma -> gamma gamma) is a quantum-mechanical process that is forbidden in the classical theory of electrodynamics. This reaction is accessible at the Large Hadron Collider thanks to the large electromagnetic field strengths generated by ultra-relativistic colliding lead ions. Using 480 μb(-1) of lead-lead collision data recorded at a centre-of-mass energy per nucleon pair of 5.02 TeV by the ATLAS detector, here we report evidence for light-by-light scattering. A total of 13 candidate events were observed with an expected background of 2.6 +/- 0.7 events. After background subtraction and analysis corrections, the fiducial cross-section of the process Pb + Pb (gamma gamma) -> Pb-(center dot) + Pb-(center dot) gamma gamma, for photon transverse energy E-T > 3 GeV, photon absolute pseudorapidity vertical bar eta vertical bar < 2.4, diphoton invariant mass greater than 6 GeV, diphoton transverse momentum lower than 2 GeV and diphoton acoplanarity below 0.01, is measured to be 70 +/- 24 (stat.) +/- 17 (syst.) nb, which is in agreement with the standard model predictions. |
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Address |
[Jackson, P.; Lee, L.; Petridis, A.; White, M. J.] Univ Adelaide, Dept Phys, Adelaide, SA, Australia |
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Corporate Author |
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Thesis |
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Publisher |
Nature Publishing Group |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1745-2473 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000409235100017 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
3287 |
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| Permanent link to this record |
