Physicists working on the T2K experiment in Japan have reported the strongest hint so far that charge-conjugation × parity (CP) symmetry is violated by the weak interactions of leptons. Based on an analysis of nine years of neutrino-oscillation data, the T2K results indicate discrepancies between the way muon-neutrinos transform into electron-neutrinos and the way muon-antineutrinos transform into electron-antineutrinos, at 3σ confidence. Though models indicate that no value of δCP could explain the cosmological matter-antimatter asymmetry without new physics, the observation of leptonic CP violation would make models such as leptogenesis, which feature heavy Majorana partners for the Standard Model neutrinos, more plausible.
A search for direct production of the f1(1285) resonance in e+e− annihilation is performed with the SND detector at the VEPP-2000 e+e− collider. The analysis is based on data with an integrated luminosity of 15.1 pb−1 accumulated in the center-of-mass energy range 1.2–1.4 GeV. Two e+e− => f1(1285) candidate events are found at the peak of the resonance and zero events beyond the resonance. We consider this result as a first indication of the process e+e− => f1(1285). The measured branching fraction is consistent with the theoretical prediction.
Parameterization of the form factors of f1(1285) meson is proposed. This parameterization is consistent with the available experimental data on the cross sections of f1(1285) meson production in the processes e+e−→f1(1285) and e+e−→e+e−f1(1285), as well as on the widths of the decays f1(1285)→e+e−, f1(1285)→ρ0γ, f1(1285)→ρ0π+π−, and f1(1285)→2π+2π−. Our parameterization is also consistent with the predictions for the asymptotic behavior of these form factors.
The width of the f1(1285)→e+e− decay is calculated in the vector meson dominance model. The result depends on the relative phase between two coupling constants describing f1→ρ0γ decay. The width Γ(f1→e+e−) is estimated to be ≃0.07−0.19 eV. Direct f1 production in e+e− collisions is discussed, and the e+e−→f1→a0π→ηππ cross section is calculated. Charge asymmetry in the e+e−→ηπ+π− reaction due to interference between e+e−→f1 and e+e−→ηρ0 amplitudes is studied.
We study theoretically the decay τ−→ντP−A, with P− a π− or K− and A an axial-vector resonance b1(1235), h1(1170), h1(1380), a1(1260), f1(1285) or any of the two poles of the K1(1270). The process proceeds through a triangle mechanism where a vector meson pair is first produced from the weak current and then one of the vectors produces two pseudoscalars, one of which reinteracts with the other vector to produce the axial resonance. For the initial weak hadronic production we use a recent formalism to account for the hadronization after the initial quark-antiquark pair produced from the weak current, which explicitly filters G-parity states and obtain easy analytic formulas after working out the angular momentum algebra. The model also takes advantage of the chiral unitary theories to evaluate the vector-pseudoscalar amplitudes, where the axial-vector resonances were obtained as dynamically generated from the VP interaction. We make predictions for invariant mass distribution and branching ratios for the channels considered.
We provide a non-linear realisation of composite Higgs models in the context of the SU(4)/Sp(4) symmetry breaking pattern, where the effective Lagrangian of the spin-0 and spin-1 resonances is constructed via the CCWZ prescription using the Hidden Symmetry formalism. We investigate the EWPT constraints by accounting the effects from reduced Higgs couplings and integrating out heavy spin-1 resonances. This theory emerges from an underlying theory of gauge interactions with fermions, thus first principle lattice results predict the massive spectrum in composite Higgs models. This model can be used as a template for the phenomenology of composite Higgs models at the LHC and at future 100 TeV colliders, as well as for other application. In this work, we focus on the formalism for spin-1 resonances and their bounds from di-lepton and di-boson searches at the LHC.
New evidence supporting the existence of the hypothetic X17 particle (10.2019) (A.J.Krasznahorkay, M.Csatlos, L.Csige, J.Gulyas, M.Koszta, B.Szihalmi, J.Timar, D.S.Firak, A.Nagy, N.J.Sas, A.Krasznahorkay)
We observed electron-positron pairs from the electro-magnetically forbidden M0 transition depopulating the 21.01 MeV 0− state in 4He. A peak was observed in their e+e− angular correlations at 115∘ with 7.2σ significance, and could be described by assuming the creation and subsequent decay of a light particle with mass of mXc2=16.84±0.16(stat)±0.20(syst) MeV and ΓX= 3.9×10−5 eV. According to the mass, it is likely the same X17 particle, which we recently suggested [Phys. Rev. Lett. 116, 052501 (2016)] for describing the anomaly observed in 8Be.
A search for IceCube events in the direction of ANITA neutrino candidates (01.2020)
During the first three flights of the Antarctic Impulsive Transient Antenna (ANITA) experiment, the collaboration detected several neutrino candidates. Here, we test the hypothesis that these events are astrophysical in origin, possibly caused by a point source in the reconstructed direction. We compare these limits to ANITA's sensitivity in the same direction and show that an astrophysical explanation of these anomalous events under standard model assumptions is severely constrained regardless of source spectrum or time profile.
Heavy sterile neutrinos with masses Script O(100) MeV mixing with active neutrinos can be produced in the core of a collapsing supernova (SN). Moreover, we show that in the viable parameter space the decay of such "heavy" sterile neutrinos in the SN envelope would lead to a very energetic flux of daughter active neutrinos.
Heat transfer in solids is typically conducted through either electrons or atomic vibrations known as phonons. In a vacuum, heat has long been thought to be transferred by radiation but not by phonons because of the lack of a medium. Here we experimentally demonstrate heat transfer induced by quantum fluctuations between two objects separated by a vacuum gap.
The LHCb collaboration has announced the discovery of a new pentaquark particle. The particle, named Pc(4312)+, decays to a proton and a J/ψ particle (composed of a charm quark and an anticharm quark). This latest observation has a statistical significance of 7.3 sigma, passing the threshold of 5 sigma traditionally required to claim a discovery of a new particle.
EUROPEAN STRATEGY ENTERS NEXT PHASE (02.10.2019)
Physicists in Europe have published a 250-page “briefing book” to help map out the next major paths in fundamental exploration. Compiled by an expert physics-preparatory group set up by the CERN Council, the document is the result of an intense effort to capture the status and
prospects for experiment, theory, accelerators, computing and other vital machinery of high-energy physics.
Light-by-light scattering is a very rare phenomenon in which two photons – particles of light – interact, producing another pair of photons. This process was among the earliest predictions of quantum electrodynamics (QED), the quantum theory of electromagnetism, and is forbidden by classical physics theories (such as Maxwell’s theory of electrodynamics).
THERMONUCLEAR FUSION REACTORS
Article about the new thermonuclear fusion reactor developed by the MIT, fueled by 3 types of ions.
Experiences on the Alcator C-Mod tokamak.
See also, in English: https://www.psfc.mit.edu/research/topics/alcator-c-mod-tokamak
US private company Tri Alpha Energy promised to set up the first ever commercial thermonuclear fusion reactor by 2027, investing for this some $ 500 mln.
See also, in English: https://trialphaenergy.com/ ;
PHYSICISTS DISCOVER HIDDEN ASPECTS OF ELECTRODYNAMICS (11.04.2017) (pdf)
Maxwell's theory displays a remarkable feature: it remains unaltered under the interchange of the electric and magnetic fields, when charges and currents are not present. This symmetry is called the electric-magnetic duality.
However, while electric charges exist, magnetic charges have never been observed in nature. If magnetic charges do not exist, the symmetry also cannot exist. This mystery has motivated physicists to search for magnetic charges, or magnetic monopoles.
However, no one has been successful. Agullo and his colleagues may have discovered why.
EPFL scientists have been able to measure the ultrashort time delay in electron photoemission without using a clock. The discovery has important implications for fundamental research and cutting-edge technology.
STILL NO VIOLATION OF LORENTZ SYMMETRY, DESPITE STRONGEST TEST YET (2016) (pdf)
The team of physicists from the Paris Observatory and the University of California, Los Angeles, analyzed 44 years of data from lunar laser ranging (LLR) observations.
In order to analyze the LLR data in the context of Lorentz symmetry, the researchers first developed a "lunar ephemeris," which is a model that accounts for dozens of factors to compute the estimated position, velocity, and orientation of the Moon with respect to the Earth at any given time. The framework for this ephemeris comes from a theory called the standard-model extension (SME), which combines general relativity and the Standard Model of particle physics, and allows for the possibility of Lorentz symmetry breaking.
The researchers' analysis shows that no evidence that LLR depends on the velocity or the direction of its reference frame, indicating no Lorentz symmetry breaking.
Scientists have confirmed the existence of a new kind of matter: "Time crystals".
Two independent groups of scientists claim that they really managed to create in the laboratory "time crystals" ("space-time crystals") — strange crystals, the atomic structure of which is repeated not only in space but also in time, which means that they are constantly transformed without energy costs.
ANNOTATION ABOUT THE ARTICLE "PHYSICSTS CREATED THE FIRST-EVER TIME CRYSTALS" (pdf, in Russian)
OBSERVATION OF DISCREATE TIME - CRYSTALLINE ORDER IN A DISORDERED DIPOLAR MANY - BODY (pdf)