18429197
Solar Neutrinos and Lepton Mixing
With latest experimental data the solar neutrino problem enters new phase when crucial aspects of the problem can be formulated in an essentially (solar) model independent way. Original neutrino fluxes can be considered as free parameters to be found from the solar neutrino experiments. Resonance flavour conversion gives the best fit of all experimental results. Already existing data allow one to constraint both the neutrino parameters and the original neutrino fluxes. The reconciliation of the solution of the solar neutrino problem with other neutrino mass hints (atmospheric neutrino problem, hot dark matter etc.) may require the existence of new very light singlet fermion. Supersymmetry can provide a framework within which the desired properties of such a light fermion follow naturally. The existence of the fermion can be related to axion physics, mechanism of $\mu$-term generation etc..
18492548
Pontecorvo's original oscillations revisited
Abstract We show that a left-handed neutrino ν L can oscillate into its CPT -conjugate state ν R with maximal amplitude, in direct analogy with K 0 − K 0 oscillations. Peculiarities of such oscillations under different conditions are studied.
119540272
Self-induced spectral splits in supernova neutrino fluxes
In the dense-neutrino region above the neutrino sphere of a supernova (r < or approx. 400 km), neutrino-neutrino refraction causes collective flavor transformations. They can lead to 'spectral splits' where an energy E{sub split} splits the transformed spectrum sharply into parts of almost pure but different flavors. Unless there is an ordinary MSW resonance in the dense-neutrino region, E{sub split} is determined by flavor-lepton number conservation alone. Spectral splits are created by an adiabatic transition between regions of large and small neutrino density. We solve the equations of motion in the adiabatic limit explicitly and provide analytic expressions for a generic example.
31519375
Multiple spectral splits of supernova neutrinos.
Collective oscillations of supernova neutrinos swap the spectra f(nu(e))(E) and f(nu[over ](e))(E) with those of another flavor in certain energy intervals bounded by sharp spectral splits. This phenomenon is far more general than previously appreciated: typically one finds one or more swaps and accompanying splits in the nu and nu[over ] channels for both inverted and normal neutrino mass hierarchies. Depending on an instability condition, swaps develop around spectral crossings (energies where f(nu(e))=f(nu(x)), f(nu[over ](e))=f(nu[over ](x)) as well as E-->infinity where all fluxes vanish), and the widths of swaps are determined by the spectra and fluxes. Washout by multiangle decoherence varies across the spectrum and splits can survive as sharp spectral features.
59164737
Recent developments in neutrino phenomenology
The first phase of studies of the neutrino mass and mixing is essentially over. The outcome is the discovery of non-zero neutrino mass and determination of the dominant structure of the lepton mixing matrix. In some sense this phase was very simple, and nature was very collaborative with us: Two main effects - the vacuum oscillations and the adiabatic conversion in matter (the MSW-effect) - provide complete interpretation of the experimental results. Furthermore, with the present accuracy of measurements the $3\nu-$mixing analysis is essentially reduced to the $2\nu$ consideration. I will present a concise and comprehensive description of this first phase. The topics include: (i) the concept of neutrino mixing in vacuum and matter; (ii) physics of the oscillations and adiabatic conversion; (iii) the experimental evidences of the flavor transformations and determination of the oscillation parameters. Some implications of the obtained results are discussed. Comments are given on the next phase of the field that will be much more involved.
115887973
Solar neutrinos: Theoretical aspects
119111785
Applications of FIESTA
Sector decomposition in its practical aspect is a constructive method used to evaluate Feynman integrals numerically. We present a new program performing the sector decomposition and integrating the expression afterwards. The program can be also used in order to expand Feynman integrals automatically in limits of momenta and masses with the use of sector decompositions and Mellin--Barnes representations. The program is parallelizable on modern multicore computers and even on multiple computers. Also we demonstrate some new numerical results for four-loop massless propagator master integrals.
18167542
Fermionic Decays of Scalar Leptoquarks and Scalar Gluons in the Minimal Four-Color Symmetry Model
Fermionic and weak decays of the scalar leptoquarks S = S1(+), S1(−), and Sm and the scalar gluons F = F1 and F2 predicted by the minimal model involving four-color symmetry and the Higgs mechanism of quark-and lepton-mass splitting are considered. The widths and the branching ratios are calculated for these decays, and the results are analyzed versus the couplings and masses of decaying particles. It is shown that, at relatively small mass splittings Δm within scalar doublets (Δm mW, the weak decays S → S′W and F → F’W compete with the above fermionic decays. In the case of mS < mt, the processes S1(+) → clj+, S1(−) → vi\(\tilde b\), Sm → blj+, and Sm → c\(\tilde \nu \)j, whose total branching ratios are Br(S1(+) → cl+) ≈ Br(S1(−) → v\(\tilde b\)) ≈ 1, Br(Sm → bl+) ≈ 0.9, and Br(Sm → c\(\tilde \nu \)) ≈ 0.1, appear to be dominant decays of scalar leptoquarks. Searches for these decays at LHC and the Tevatron are of interest.
122714200
Limits on the scalar-leptoquark and scalar-gluon masses from the parameters S, T, and U in the minimal model based on four-color symmetry
The contributions to the parameters S, T, and U of radiative corrections from the doublets of scalar leptoquarks and scalar gluons are analyzed within the minimal model based on four-color symmetry of the Pati-Salam type. It is shown that current experimental data on the parameters S, T, and U admit the existence of relatively light scalar leptoquarks and scalar gluons (of mass lower than 1 TeV), the best fit to experimental data being attained at mass values not greater than 400 GeV. In particular, the existence of scalar leptoquarks of mass below 300 GeV is found to be compatible with data on the parameters S, T, and U at χ2 < 3.1 (3.2) for mH = 115 (300) GeV as against χSM2 = 3.5 (5.0) in the Standard Model. The mass of the lightest scalar gluon is then predicted to be less than 850 (720) GeV. It is emphasized that the aforementioned doublets of scalar leptoquarks and scalar gluons can play a significant role in processes involving a t quark at LHC.
15966773
Fermionic contributions to the three-loop static potential
Abstract We consider the three-loop corrections to the static potential which are induced by a closed fermion loop. For the reduction of the occurring integrals a combination of the Grobner and Laporta algorithm has been used and the evaluation of the master integrals has been performed with the help of the Mellin–Barnes technique. The fermionic three-loop corrections amount to 2% of the tree-level result for top quarks, 8% for bottom quarks and 27% for the charm quark system.
120951273
Parameters S, T, and U of radiative corrections and masses of scalar leptoquarks in the minimal model featuring four-color symmetry
The contributions to the parameters S, T, and U of radiative corrections are discussed within the minimal model featuring four-color symmetry of the Pati-Salam type. A numerical analysis of these contributions is given for the Higgs mechanism of mass generation for scalar leptoquarks and the simplest version of scalar-leptoquark mixing. It is shown that up-to-date experimental data on S, T, and U are compatible with the existence of relatively light scalar leptoquarks (of masses about 1 TeV or below), still lighter scalar leptoquarks (of masses below 1 TeV) improving the agreement of theoretical results with experimental data on S, T, and U.