6,767 research outputs found
Dependence of the leptonic decays of H^- on the neutrino mixing angles theta_{13} and theta_{23} in models with neutrinophilic charged scalars
In the Higgs Triplet Model and the neutrinophilic Two-Higgs-Doublet Model the
observed neutrinos obtain mass from a vacuum expectation value which is much
smaller than the vacuum expectation value of the Higgs boson in the Standard
Model. Both models contain a singly charged Higgs boson (H^-) whose Yukawa
coupling is directly related to the neutrino mass (i.e. a "neutrinophilic
charged Higgs"). The partial decay widths of H^- into a charged lepton and a
neutrino (H^- to l^- nu) depend identically on the neutrino masses and mixings
in the two models. We quantify the impact of the recent measurement of
sin^2(2theta_{13}), which plays a crucial role in determining the magnitude of
the branching ratio of H^- to e^- nu for the case of a normal neutrino mass
ordering if the lightest neutrino mass m_0 < 10^{-3} eV. We also discuss the
sizeable dependence of H^- to mu^- nu and H^- to tau^- nu on sin^2(theta_{23}),
which would enable information to be obtained on sin^2(theta_{23}) and the sign
of \Delta m^2_{31} if these decays are measured. Such information would help
neutrino oscillation experiments to determine the CP-violating phase \delta.Comment: 17 pages, 6 figure
Ground States for Diffusion Dominated Free Energies with Logarithmic Interaction
Replacing linear diffusion by a degenerate diffusion of porous medium type is
known to regularize the classical two-dimensional parabolic-elliptic
Keller-Segel model. The implications of nonlinear diffusion are that solutions
exist globally and are uniformly bounded in time. We analyse the stationary
case showing the existence of a unique, up to translation, global minimizer of
the associated free energy. Furthermore, we prove that this global minimizer is
a radially decreasing compactly supported continuous density function which is
smooth inside its support, and it is characterized as the unique compactly
supported stationary state of the evolution model. This unique profile is the
clear candidate to describe the long time asymptotics of the diffusion
dominated classical Keller-Segel model for general initial data.Comment: 30 pages, 2 figure
Probing Majorana Phases and Neutrino Mass Spectrum in the Higgs Triplet Model at the LHC
Doubly charged Higgs bosons (H^++) are a distinctive signature of the Higgs
Triplet Model of neutrino mass generation. If H^++ is relatively light
(m_{H^++} < 400GeV) it will be produced copiously at the LHC, which could
enable precise measurements of the branching ratios of the decay channels H^++
to l_i l_j. Such branching ratios are determined solely by the neutrino mass
matrix which allows the model to be tested at the LHC. We quantify the
dependence of the leptonic branching ratios on the absolute neutrino mass and
Majorana phases, and present the permitted values for the channels ee, emu and
mumu. It is shown that precise measurements of these three branching ratios are
sufficient to extract information on the neutrino mass spectrum and probe the
presence of CP violation from Majorana phases.Comment: 1+19 pages, 22 figures, typos corrected, references added, version to
appear in Phys. Rev.
Production of doubly charged scalars from the decay of singly charged scalars in the Higgs Triplet Model
The existence of doubly charged Higgs bosons (H^{\pm\pm}) is a distinctive
feature of the Higgs Triplet Model (HTM), in which neutrinos obtain tree-level
masses from the vacuum expectation value of a neutral scalar in a triplet
representation of SU(2)_L. We point out that a large branching ratio for the
decay of a singly charged Higgs boson to a doubly charged Higgs boson via
H^\pm\to H^{\pm\pm}W^* is possible in a sizeable parameter space of the HTM.
From the production mechanism q'qbar\to W^* \to H^{\pm\pm}H^\mp the above decay
mode would give rise to pair production of H^{\pm\pm}, with a cross section
which can be comparable to that of the standard pair-production mechanism
qqbar\to \gamma^*,Z^* \to H^{++}H^{--}. We suggest that the presence of a
sizeable branching ratio for H^\pm\to H^{\pm\pm}W^* could significantly enhance
the detection prospects of H^{\pm\pm} in the four-lepton channel. Moreover, the
decays H^0\to H^\pm W^* and A^0\to H^\pm W^* from production of the neutral
triplet scalars H^0 and A^0 would also provide an additional source of H^\pm,
which can subsequently decay to H^{\pm\pm}.Comment: 13 pages, 3 figures, two figures added in v2, to appear in Physical
Review
Magnetic anisotropy and geometrical frustration in the Ising spin-chain system Sr5Rh4O12
A structural and thermodynamic study of the newly synthesized single crystal
Sr5Rh4O12 is reported. Sr5Rh4O12 consists of a triangular lattice of spin
chains running along the c-axis. It is antiferromagnetically ordered below 23 K
with the intrachain and interchain coupling being ferromagnetic (FM) and
antiferromagnetic (AFM), respectively. There is strong evidence for an Ising
character in the interaction and geometrical frustration that causes incomplete
long-range AFM order. The isothermal magnetization exhibits two step-like
transitions leading to a ferrimagnetic state at 2.4 T and a FM state at 4.8 T,
respectively. Sr5Rh4O12 is a unique frustrated spin-chain system ever found in
4d and 5d based materials without a presence of an incomplete 3d-electron
shell.Comment: 15 pages, 4 figure
Systematic limits on sin^2{2theta_{13}} in neutrino oscillation experiments with multi-reactors
Sensitivities to sin^2{2theta_{13}} without statistical errors (``systematic
limit'') are investigated in neutrino oscillation experiments with multiple
reactors. Using an analytical approach, we show that the systematic limit on
sin^2{2theta_{13}} is dominated by the uncorrelated systematic error sigma_u of
the detector. Even in an experiment with multi-detectors and multi-reactors, it
turns out that most of the systematic errors including the one due to the
nature of multiple sources is canceled as in the case with a single reactor
plus two detectors, if the near detectors are placed suitably. The case of the
KASKA plan (7 reactors and 3 detectors) is investigated in detail, and it is
explicitly shown that it does not suffer from the extra uncertainty due to
multiple reactors.Comment: 26 pages, 10 eps-files, revtex
Quantum Monte Carlo method using phase-free random walks with Slater determinants
We develop a quantum Monte Carlo method for many fermions that allows the use
of any one-particle basis. It projects out the ground state by random walks in
the space of Slater determinants. An approximate approach is formulated to
control the phase problem with a trial wave function . Using
plane-wave basis and non-local pseudopotentials, we apply the method to Si
atom, dimer, and 2, 16, 54 atom (216 electrons) bulk supercells. Single Slater
determinant wave functions from density functional theory calculations were
used as with no additional optimization. The calculated binding
energy of Si2 and cohesive energy of bulk Si are in excellent agreement with
experiments and are comparable to the best existing theoretical results.Comment: 5 pages, Latex, with 1 fi
Quantum Monte Carlo study of confined fermions in one-dimensional optical lattices
Using quantum Monte Carlo (QMC) simulations we study the ground-state
properties of the one-dimensional fermionic Hubbard model in traps with an
underlying lattice. Since due to the confining potential the density is space
dependent, Mott-insulating domains always coexist with metallic regions, such
that global quantities are not appropriate to describe the system. We define a
local compressibility that characterizes the Mott-insulating regions and
analyze other local quantities. It is shown that the momentum distribution
function, a quantity that is commonly considered in experiments, fails in
giving a clear signal of the Mott-insulator transition. Furthermore, we analyze
a mean-field approach to these systems and compare it with the numerically
exact QMC results. Finally, we determine a generic form for the phase diagram
that allows us to predict the phases to be observed in the experiments.Comment: RevTex file, 13 pages, 19 figures, published versio
Large spin-orbit splitting and weakly-anisotropic superconductivity revealed with single-crystalline noncentrosymmetric CaIrSi3
We report normal and superconducting properties of the Rashba-type
noncentrosymmetric com- pound CaIrSi3, using single crystalline samples with
nearly 100% superconducting volume fraction. The electronic density of states
revealed by the hard x-ray photoemission spectroscopy can be well explained by
the relativistic first-principle band calculation. This indicates that strong
spin-orbit interaction indeed affects the electronic states of this compound.
The obtained H - T phase diagram exhibits only approximately 10% anisotropy,
indicating that the superconducting properties are almost three dimensional.
Nevertheless, strongly anisotropic vortex pinning is observed.Comment: 8 pages, 6 figures, 1 table, accepted for publication in Phys. Rev.
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