Observation of the suppressed Lambda 0 b rightarrow DpK - decay with D rightarrow K + pi - and measurement of its CP asymmetry
A study of baryon decays to the Dp\Km final state is presented based on a proton-proton collision data sample corresponding to an integrated luminosity of 9\invfb collected with the LHCb detector. Two decays are considered, \Lb→D\proton\Km with D→\Km\pip and D→\Kp\pim, where D represents a superposition of and states. The latter process is expected to be suppressed relative to the former, and is observed for the first time. The ratio of branching fractions of the two decays is measured, and the asymmetry of the suppressed mode, which is sensitive to the CKM angle γ, is also reported.
Nowadays High Energy Physics experiments can accumulate unprecedented statistics of heavy flavour decays that allows to apply new methods, based on the study of very rare phenomena, which used to be just desperate. In this paper we propose a new method to measure composition of K0-anti-K0, produced in a decay of heavy hadrons. This composition contains important information, in particular about weak and strong phases between amplitudes of the produced K0 and anti-K0. We consider possibility to measure these parameters with time dependent K0--> pi+ pi- analysis. Due to CP-violation in kaon mixing time-dependent decay rates of K0 and anti-K0 differ, and the initial amplitudes revealed in the CP-violating decay pattern. We perform phenomenological study of K0 decay evolution initially produced as a combination a |K0(t)> + b |anti-K0(t)>, where a and b, complex amplitudes, could also be dependent on decay time of heavy mother particle. In particular we consider cases of charmed hadrons decays: D+ --> K0 pi+, Ds --> K0 K, Lambda_c --> p K0 and with some assumptions D0 --> K0 pi0. This can be used to test the sum rule for charmed mesons and to obtain input for the full constraint of the two body amplitudes of D-mesons.
Dark photons are hypothetical massive vector particles that could mix with ordinary photons. The simplest theoretical model is fully characterised by only two parameters: the mass of the dark photon mγD and its mixing parameter with the photon, ε. The sensitivity of the SHiP detector is reviewed for dark photons in the mass range between 0.002 and 10 GeV. Different production mechanisms are simulated, with the dark photons decaying to pairs of visible fermions, including both leptons and quarks. Exclusion contours are presented and compared with those of past experiments. The SHiP detector is expected to have a unique sensitivity for mγDγD ranging between 0.8 and 3.3+0.2−0.5 0.5+0.2 GeV, and ε^2 ranging between 10^−11 and 10^−17
Dark matter is a well-established theoretical addition to the Standard Model supported by many observations in modern astrophysics and cosmology. In this context, the existence of weakly interacting massive particles represents an appealing solution to the observed thermal relic in the Universe. Indeed, a large experimental campaign is ongoing for the detection of such particles in the sub-GeV mass range. Adopting the benchmark scenario for light dark matter particles produced in the decay of a dark photon, with αD = 0.1 and mA′ = 3mχ, we study the potential of the SHiP experiment to detect such elusive particles through its Scattering and Neutrino detector (SND). In its 5-years run, corresponding to 2 · 1020 protons on target from the CERN SPS, we find that SHiP will improve the current limits in the mass range for the dark matter from about 1 MeV to 300 MeV. In particular, we show that SHiP will probe the thermal target for Majorana candidates in most of this mass window and even reach the Pseudo-Dirac thermal relic.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.