The results of an amplitude analysis of the charmless three-body decay B+→π+π+π-, in which CP-violation effects are taken into account, are reported. The analysis is based on a data sample corresponding to an integrated luminosity of 3 fb-1 of pp collisions recorded with the LHCb detector. The most challenging aspect of the analysis is the description of the behavior of the π+π- S-wave contribution, which is achieved by using three complementary approaches based on the isobar model, the K-matrix formalism, and a quasi-model-independent procedure. Additional resonant contributions for all three methods are described using a common isobar model, and include the ρ(770)0, ω(782) and ρ(1450)0 resonances in the π+π- P-wave, the f2(1270) resonance in the π+π- D-wave, and the ρ3(1690)0 resonance in the π+π- F-wave. Significant CP-violation effects are observed in both S- and D-waves, as well as in the interference between the S- and P-waves. The results from all three approaches agree and provide new insight into the dynamics and the origin of CP-violation effects in B+→π+π+π- decays.

We report a new measurement of the exclusive e+e-→D(∗)±D∗ cross sections as a function of the center-of-mass energy from the D(∗)±D∗ threshold through s=6.0 GeV, using the initial-state radiation technique. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 951 fb-1. The accuracy of the cross section measurement is increased by a factor of 2 over the first Belle study. We perform the first angular analysis of the e+e-→D∗±D∗ process and decompose this exclusive cross section into three components corresponding to the D∗ helicities. © 2018 authors. Published by the American Physical Society.

The anomalous magnetic moment (AMM) for excited states of an electron in a constant magnetic field has been calculated within the framework of two-dimensional electrodynamics. The analytical results for the interaction energy of the anomalous magnetic moment with the external magnetic field are obtained in two limiting cases of nonrelativistic and relativistic energy values in a comparatively weak magnetic field. It is shown that the interaction energy of the spin with the external field does not contain infrared divergence and tends to zero as magnetic field decreases, while the electron’s AMM increases logarithmically.

The electron self-energy and anomalous magnetic moment in (2 + 1) QED with a Chern-Simons term are investigated at finite temperature and density in an external magnetic field. In the limiting case of a relatively weak magnetic field, the exact expression for the vacuum anomalous magnetic moment (AMM) has been found at zero temperature and density of the medium. The energy shift and AMM of an electron are analyzed as a function of the temperature and Chern-Simons parameter in the charge-symmetric case. We obtained the new asymptotic expression for the AMM in the high-temperature region. The electron AMM has been calculated also in the case of a completely degenerate magnetized electron gas.

This work reports the first observation of azimuthal asymmetries around the thrust axis in e+e- annihilation of pairs of back-to-back charged pions in one hemisphere, and π0 and η mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The π0 and η asymmetries rise with the relative momentum z of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function H1¥ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the η final states will provide additional information on the flavor structure of H1¥. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb-1 collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

It is well known that r-mode oscillations of rotating neutron stars may be unstable with respect to the gravitational wave emission. It is highly unlikely to observe a neutron star with the parameters within the instability window, a domain where this instability is not suppressed. But if one adopts the "minimal" (nucleonic) composition of the stellar interior, a lot of observed stars appear to be within the r-mode instability window. One of the possible solutions to this problem is to account for hyperons in the neutron-star core. The presence of hyperons allows for a set of powerful (lepton-free) nonequilibrium weak processes, which increase the bulk viscosity and thus suppress the r-mode instability. Existing calculations of the instability windows for hyperon neutron stars generally use reaction rates calculated for the Σ-Λ hyperonic composition via the contact W -boson-exchange interaction. In contrast, here we employ hyperonic equations of state where the Λ and Ξ- are the first hyperons to appear (the Σ-'s, if they are present, appear at much larger densities) and consider the meson-exchange channel, which is more effective for the lepton-free weak processes. We calculate the bulk viscosity for the nonpaired n p e μ Λ Ξ- matter using the meson-exchange weak interaction. A number of viscosity-generating nonequilibrium processes is considered (some of them for the first time in the neutron-star context). The calculated reaction rates and bulk viscosity are approximated by simple analytic formulas, easy to use in applications. Applying our results to calculation of the instability window, we argue that accounting for hyperons may be a viable solution to the r-mode problem.

We present the results of the first Dalitz plot analysis of the decay D0→K-π+η. The analysis is performed on a data set corresponding to an integrated luminosity of 953 fb-1 collected by the Belle detector at the asymmetric-energy e+e- KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels K̄∗(892)0η, K-a0(980)+, K-a2(1320)+, K̄∗(1410)0η, K∗(1680)-π+ and K2∗(1980)-π+, together with Kπ and Kη S-wave components. The decays K∗(1680)-→K-η and K2∗(1980)-→K-η are observed for the first time. We measure ratio of the branching fractions, B(D0→K-π+η)B(D0→K-π+)=0.500±0.002(stat)±0.020(syst)±0.003(BPDG). Using the Dalitz fit result, the ratio B(K∗(1680)→Kη)B(K∗(1680)→Kπ) is measured to be 0.11±0.02(stat)-0.04+0.06(syst)±0.04(BPDG); this is much lower than the theoretical expectations (≈1) made under the assumption that K∗(1680) is a pure 13D1 state. The product branching fraction B(D0→[K2∗(1980)-→K-η]π+)=(2.2-1.9+1.7)×10-4 is determined. In addition, the πη′ contribution to the a0(980)± resonance shape is confirmed with 10.1σ statistical significance using the three-channel Flatté model. We also measure B(D0→K̄∗(892)0η)=(1.41-0.12+0.13)%. This is consistent with, and more precise than, the current world average (1.02±0.30)%, deviates with a significance of more than 3σ from the theoretical predictions of (0.51-0.92)%. © 2020 authors.

We study diffusion of charged particles in stationary stochastic magnetic field ${\bf B}$ with zero mean, $ \mean{\bf B} = 0 $. In the case when electric current is carried by electrons, the field is force-free, $\mathrm{curl} \,{\bf B} = \alpha{\bf B} $, where $\alpha({\bf r})$ is an arbitrary scalar function. In a small region where the function $\alpha $ and the field magnitude $|{\bf B}|$ are approximately constant, the equations of motion of charged particles are integrated and reduced to the equation of mathematical pendulum. The transition from trapped to untrapped particles is continuously traced. Averaging over the magnetic field spectrum gives the spatial diffusion coefficient $D$ of particles as a function of the Larmor radius $r_L$ in the large-scale magnetic fields ($B_{LS}$) and magnetic field correlation length $L_0$. The diffusion coefficient turns out to be proportional to the Larmor radius, $D\propto r_L $, for $r_L <L_0 / 2\pi $, and to the Larmor radius squared, $ D \propto r_L^2 $, for $ r_L> L_0 /2\pi $. We apply obtained results to the diffusion of cosmic rays in the Galaxy, which contains a large number of independent regions with parameters $L_0$ and $B_{LS}$ varying in wide range. We average over $B_{LS}$ with the Kolmogorov spectrum and over $L_0$ with the distribution function $f(L_0)\propto L_0^{- 1+ \sigma}$. For the practically flat spectrum $\sigma = 1/15$, we have $ D\propto r_m^{0.7}$, which is consistent with observations.

We study static spherically and hyperbolically symmetric solutions of the Einstein equations in the presence of a conformally coupled scalar field and compare them with those in the space filled with a minimally coupled scalar field. We then study the Kantowski-Sachs cosmological solutions, which are connected with the static solutions by the duality relations. The main ingredient of these relations is an exchange of roles between the radial and the temporal coordinates, combined with the exchange between the spherical and hyperbolical two-dimensional geometries. A brief discussion of questions such as the relation between the Jordan and the Einstein frames and the description of the singularity crossing is also presented.

An analytical expression is obtained for the anomalous magnetic moment of an electron in a constant magnetic field in topologically massive two-dimensional electrodynamics. In the limiting case of a relatively weak magnetic field, asymptotic formulas are found, which specify the dependence of the anomalous magnetic moment on the Chern-Simons parameter and dynamic parameter of synchrotron radiation. The conditions are identified for the applicability of the computations of the anomalous magnetic moment of an electron, which have previously been made based on the calculation of the vertex function in two-dimensional electrodynamics with the Chern-Simons term.

We report the measurement of e+e-→Ds+Ds2∗(2573)-+c.c. via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb-1 collected with the Belle detector at the γ(4S) and nearby. We find evidence for an enhancement with a 3.4σ significance in the invariant mass of Ds+Ds2∗(2573)-+c.c. The measured mass and width are (4619.8-8.0+8.9(stat.)±2.3(syst.)) MeV/c2 and (47.0-14.8+31.3(stat.)±4.6(syst.)) MeV, respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmoniumlike state at 4626 MeV/c2 recently reported by Belle in e+e-→Ds+Ds1(2536)-+c.c. The product of the e+e-→Ds+Ds2∗(2573)-+c.c. cross section and the branching fraction of Ds2∗(2573)-→D¯0K- is measured from Ds+Ds2∗(2573)- threshold to 5.6 GeV. © 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

A search for the decays B+→hcK+ and B0→hcKS0 is performed. Evidence for the decay B+→hcK+ is found; its significance is 4.8σ. No evidence is found for B0→hcKS0. The branching fraction for B+→hcK+ is measured to be (3.7-0.9+1.0 -0.8+0.8)×10-5; the upper limit for the B0→hcKS0 branching fraction is 1.4×10-5 at 90% C.L. In addition, a study of the ppπ+π- invariant mass distribution in the channel B+→(ppπ+π-)K+ results in the first observation of the decay ηc(2S)→ppπ+π- with 12.1σ significance. The analysis is based on the 711 fb-1 data sample collected by the Belle detector at the asymmetric-energy e+e- collider KEKB at the (4S) resonance. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the «https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.

A search for the associated production of the Higgs boson with a top quark pair (t¯tH) is reported. The search is performed in multilepton final states using a data set corresponding to an integrated luminosity of 36.1 fb−1 of proton-proton collision data recorded by the ATLAS experiment at a center-of-mass energy √s=13 TeV at the Large Hadron Collider. Higgs boson decays to WW∗, ττ, and ZZ∗ are targeted. Seven final states, categorized by the number and flavor of charged-lepton candidates, are examined for the presence of the Standard Model Higgs boson with a mass of 125 GeV and a pair of top quarks. An excess of events over the expected background from Standard Model processes is found with an observed significance of 4.1 standard deviations, compared to an expectation of 2.8 standard deviations. The best fit for the t¯tH production cross section is σ(t¯tH)=790+230−210 fb, in agreement with the Standard Model prediction of 507+35−50 fb. The combination of this result with other t¯tH searches from the ATLAS experiment using the Higgs boson decay modes to b¯b, γγ and ZZ∗→4ℓ, has an observed significance of 4.2 standard deviations, compared to an expectation of 3.8 standard deviations. This provides evidence for the t¯tH production mode.

We report a search for the charmless baryonic decay B0→ppπ0 with a data sample corresponding to an integrated luminosity of 711 fb-1 containing (772±10)×106 BB pairs. The data were collected by the Belle experiment running on the (4S) resonance at the KEKB e+e- collider. We measure a branching fraction B(B0→ppπ0)=(5.0±1.8±0.6)×10-7, where the first uncertainty is statistical and the second is systematic. The signal has a significance of 3.1 standard deviations and constitutes the first evidence for this decay mode. We also search for the intermediate two-body decays B0→Δ+p and B0→Δ-p, and set an upper limit on the branching fraction, B(B0→Δ+p)+B(B0→Δ-p)<1.6×10-6 at 90% confidence level. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the »https://creativecommons.org/licenses/by/4.0/» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

We combine model-independent reconstructions of the expansion history from the latest Pantheon supernovae distance modulus compilation and measurements from baryon acoustic oscillation to test some important aspects of the concordance model of cosmology namely the Friedmann-Lemaître-Robertson-Walker (FLRW) metric and flatness of spatial curvature. We then use the reconstructed expansion histories to fit growth measurement from redshift-space distortion and obtain constraints on (Ωm, γ, σ8) in a model independent manner. Our results show consistency with a spatially flat FLRW Universe with general relativity to govern the perturbation in the structure formation and the cosmological constant as dark energy. However, we can also see some hints of tension among different observations within the context of the concordance model related to high redshift observations (z>1) of the expansion history. This supports earlier findings of [G.-B. Zhao, Nat. Astron. 1, 627 (2017), V. Sahni, A. Shafieloo, and A. A. Starobinsky, Astrophys. J. 793, L40 (2014)] and highlights the importance of precise measurement of expansion history and growth of structure at high redshifts.

In [Gusakov et al. Phys. Rev. D 96, 103012 (2017), 10.1103/PhysRevD.96.103012], we proposed a self-consistent method to study the quasistationary evolution of the magnetic field in neutron-star cores. Here, we apply it to calculate the instantaneous particle velocities and other parameters of interest, which are fixed by specifying the magnetic field configuration. Interestingly, we found that the magnetic field can lead to generation of a macroscopic fluid motion with the velocity significantly exceeding the diffusion particle velocities. This result calls into question the standard view on the magnetic field evolution in neutron stars and suggests a new, shorter time scale for such evolution.

The Ξc0 baryon is unstable and usually decays into charmless final states by the c→sud¯ transition. It can, however, also disintegrate into a π- meson and a Λc+ baryon via s quark decay or via cs→dc weak scattering. The interplay between the latter two processes governs the size of the branching fraction B(Ξc0→π-Λc+), first measured here to be (0.55±0.02±0.18)%, where the first uncertainty is statistical and second systematic. This result is compatible with the larger of the theoretical predictions that connect models of hyperon decays using partially conserved axial currents and SU(3) symmetry with those involving the heavy-quark expansion and heavy-quark symmetry. In addition, the branching fraction of the normalization channel, B(Ξc+→pK-π+)=(1.135±0.002±0.387)% is measured.

We present the first measurements of the absolute branching fractions of Ξ+*c* decays into Ξ−*π*+*π*+ and *p**K*−*π*+ final states. Our analysis is based on a data set of (772±11)×106 *B**B*¯ pairs collected at the Υ(4*S*) resonance with the Belle detector at the KEKB *e*+*e*− collider. We measure the absolute branching fraction of *B*¯0→Λ¯−*c*Ξ+*c* with the Ξ+*c* recoiling against Λ¯−*c* in *B*¯0 decays resulting in B(*B*¯0→Λ¯−*c*Ξ+*c*)=[1.16±0.42(stat.)±0.15(syst.)]×10−3 . We then measure the product branching fractions B(*B*¯0→Λ¯−*c*Ξ+*c*)B(Ξ+*c*→Ξ−*π*+*π*+) and B(*B*¯0→Λ¯−*c*Ξ+*c*)B(Ξ+*c*→*p**K*−*π*+) . Dividing these product branching fractions by *B*¯0→Λ¯−*c*Ξ+*c* yields: B(Ξ+*c*→Ξ−*π*+*π*+)=[2.86±1.21(stat.)±0.38(syst.)]% and B(Ξ+*c*→*p**K*−*π*+)=[0.45±0.21(stat.)±0.07(syst.)]% . Our result for B(Ξ+*c*→Ξ−*π*+*π*+) can be combined with Ξ+*c* branching fractions measured relative to Ξ+*c*→Ξ−*π*+*π*+ to set the absolute scale for many Ξ+*c* branching fractions.