物理与天体物理最新文献

In this talk recent new results from CMS on the search for New Physics effects in heavy flavor decays are presented. Particularly, lepton flavor unification violation was searched for by measuring (R(K)) and (R(J/psi)) ratios. Also, lepton flavor violating decay (taurightarrow 3mu) was searched for and upper limit on its branching fraction was extracted. The discussed results were obtained with the RUN II data of pp collisions at (sqrt{s}=13) TeV.

The (K^{+}topi^{0}mu^{+}nugamma) ((K_{mu 3gamma})) decay is measured with OKA detector at the RF-separated 17.7 GeV/c momentum kaon beam from the U-70 synchrotron. The data obtained corresponds to the value of (2.62times 10^{10}) ‘‘live’’ kaons passing to the decay volume. About 1000 (K_{mu 3gamma}) events are extracted. The ratio of (textrm{Br}(K_{mu 3gamma})/textrm{Br}(K_{mu 3})) is measured. The T-odd correlation ({xi}_{pimugamma}), which is the mixed product of the momenta of (mu^{+},pi^{0}), and (gamma) in the kaon rest frame, is measured. The asymmetry of the distribution in (xi) is characterized by the ratio (A_{xi}=(N_{+}-N_{-})/(N_{+}+N_{-})), where (N_{+}) ((N_{-})) is the number of events with positive (negative) (xi). The values of (A_{xi}) is obtained. Our results are preliminary, with systematic errors being estimated.

Spectroscopy of the fully heavy tetraquarks with open charm and/or bottom is studied within the relativistic quark model, based on the quasipotential approach and QCD. A special emphasize is given to the asymmetric in flavor compositions. A tetraquark is considered as a bound state of a diquark and an antidiquark which are treated as a spatially extended colored objects and interact as a whole. Relativistic effects are consistently taken into account. It is found, that a significant mixing between the asymmetric in flavor states of tetraquarks occurs for the same total momentum-parity ((J^{P})), but different full spins of the tetraquark ((S)) within the same excitation. We confront the calculated masses of such tetraquarks with the fall-apart decay thresholds into a pair of heavy mesons. Such comparison allows us to select states that could be observed as narrow resonances.

Joint analysis of the results of the Neutrino-4 experiment and the data of the GALLEX, SAGE and BEST experiments confirms the parameters of neutrino oscillations declared by the Neutrino-4 experiment ((Delta m_{14}^{2}=7.3text{ eV}^{2}) and (sin^{2}2theta_{14}approx 0.36)) and increases the confidence level to (5.8sigma). Such a sterile neutrino thermalizes in cosmic plasma, contributes 5(%) to the energy density of the Universe, and can explain (15{-}20%) of dark matter. It is discussed that the extension of the neutrino model by introducing two more heavy sterile neutrinos in accordance with the number of types of active neutrinos but with very small mixing angles to avoid thermalization will make it possible to explain the large-scale structure of the Universe and bring the contribution of sterile neutrinos to the dark matter of the Universe to the level of 27(%). This approach to the problem of dark matter means that dark matter can be explained in terms of an extended Standard Model with right-handed neutrinos.

Recent CMS results on conventional spectroscopy and production of heavy flavour in (pp) collisions at (sqrt{s}=13) TeV states are reported. The observations and properties of new excited beauty baryons are discussed, as well as precision measurements of cross section ratios.