4,417,377 research outputs found
Majorana neutrinos and lepton-number-violating signals in top-quark and W-boson rare decays
We discuss rare lepton-number-violating top-quark and W-boson four-body
decays to final states containing a same-charge lepton pair, of the same or of
different flavors: t -> b W- li^+ lj^+ and W+ -> J J' li^+ lj^+, where i \ne j
or i=j and J J' stands for two light jets originating from a (u-bar d) or a
(c-bar s) pair. These \Delta L=2 decays are forbidden in the Standard Model and
may be mediated by exchanges of Majorana neutrinos. We adopt a model
independent approach for the Majorana neutrinos mixing pattern and calculate
the branching ratios (BR) for these decays. We find, for example, that for O(1)
mixings between heavy and light Majorana neutrinos (not likely but not ruled
out) and if at least one of the heavy Majorana neutrinos has a mass of ~100
GeV, then the BR's for these decays are: BR(t -> b li^+ lj^+ W-) ~ 10^{-4} and
BR(W+ -> li^+ lj^+ J J') ~ 10^{-7} if m_N ~ 100 GeV and BR(t -> b li^+ lj^+ J
J') ~ BR(W+ -> li^+ lj^+ J J') ~ 0.01 if m_N < 50 GeV. Taking into account the
present limits on the neutrino mixing parameters, we obtain more realistic
values for these BR's: BR(t -> b li^+ lj^+ W-) ~ 10^{-6} and BR(W+ -> li^+ lj^+
J J') ~ 10^{-10} for m_N ~ 100 GeV and BR(t -> b li^+ lj^+ J J') ~ BR(W+ ->
li^+ lj^+ J J') ~ 10^{-6} for m_N < 50 GeV.Comment: latex, 7 pages, 2 figures. V2 as published in PL
Long-term in situ observations on typhoon-triggered turbidity currents in the deep sea
This work is supported by the National Science Foundation of China (grants 91528304, 41576005, and 41530964). We thank J. Li, X. Lyu, P. Li, K. Duan, J. Ronan, Y. Wang, P. Ma, and Y. Li for cruise assistance; G. de Lange and J. Hinojosa for editing an early version of manuscript; and E. Pope and two anonymous reviewers for their reviews.Peer reviewedPublisher PD
Quantum dynamics of the Li+HF-->H+LiF reaction at ultralow temperatures
Quantum mechanical calculations are reported for the
Li+HF(v=0,1,j=0)-->H+LiF(v',j') bimolecular scattering process at low and
ultralow temperatures. Calculations have been performed for zero total angular
momentum using a recent high accuracy potential energy surface for the X 2A'
electronic ground state. For Li+HF(v=0,j=0), the reaction is dominated by
resonances due to the decay of metastable states of the Li...F-H van der Waals
complex. Assignment of these resonances has been carried out by calculating the
eigenenergies of the quasibound states. We also find that while chemical
reactivity is greatly enhanced by vibrational excitation the resonances get
mostly washed out in the reaction of vibrationally excited HF with Li atoms. In
addition, we find that at low energies, the reaction is significantly
suppressed due to the formation of rather deeply bound van der Waals complexes
and the less efficient tunneling of the relatively heavy fluorine atom.Comment: 24 pages, 8 figures, 1 table, submitted to J. Chem. Phy
Gamow shell model description of radiative capture reactions LiBe and LiLi
According to standard stellar evolution, lithium abundance is believed to be
a useful indicator of the stellar age. However, many evolved stars like red
giants show huge fluctuations around expected theoretical abundances that are
not yet fully understood. The better knowledge of nuclear reactions that
contribute to the creation and destruction of lithium can help to solve this
puzzle. In this work we apply the Gamow shell model (GSM) formulated in the
coupled-channel representation (GSM-CC) to investigate the mirror radiative
capture reactions LiBe and LiLi. The
cross-sections are calculated using a translationally invariant Hamiltonian
with the finite-range interaction which is adjusted to reproduce spectra,
binding energies and one-nucleon separation energies in Li, Be. All
relevant , , and transitions from the initial continuum states to
the final bound states and of Li and Be are
included. We demonstrate that the -wave radiative capture of proton
(neutron) to the first excited state of Be (Li) is
crucial and increases the total astrophysical -factor by about 40 \%.Comment: arXiv admin note: text overlap with arXiv:1502.0163
Dipole excited states in Li with complex scaling
The 1 excitations of the three--body halo nucleus Li are
investigated. We use adiabatic hyperspherical expansion and solve the Faddeev
equations in coordinate space. The method of complex scaling is used to compute
the resonance states. The Pauli forbidden states occupied by core neutrons are
excluded by constructing corresponding complex scaled phase equivalent two-body
potentials. We use a recently derived neutron--core interaction consistent with
known structure and reaction properties of Li and Li. The
computed dipole excited states with , , and
have energies ranging from 0.6 MeV to 1.0 MeV and widths between
0.15 MeV and 0.65 MeV. We investigate the dependence of the complex energies of
these states on the Li spectrum. The finite spin 3/2 of the core and the
resulting core-neutron spin-spin interaction are important. The connection with
Coulomb dissociation experiments is discussed and a need for better
measurements is pointed out.Comment: 28 pages, 6 figures, Nuclear Physics A, in pres
Piercing the Veil: William J. Brennan\u27s Account of Regents of the University of California v. Bakke
Porous nickel oxide films were deposited onto unheated indium tin oxide coated glass substrates by reactive dc magnetron sputtering. These films had a cubic NiO structure. Electrochromic properties were evaluated in 1 M potassium hydroxide (KOH) and in 1 M lithium perchlorate in propylene carbonate (Li-PC). Large optical modulation was obtained for similar to 500-nm-thick films both in KOH and in Li-PC (similar to 70% and similar to 50% at 550 nm, respectively). In KOH, tensile and compressive stresses, due to the expansion and contraction of the lattice, were found for films in their bleached and colored state, respectively. In Li-PC, compressive stress was seen both in colored and bleached films. Durability tests with voltage sweeps between -0.5 and 0.65 V vs Ag/AgCl in KOH showed good durability for 10,000 cycles, whereas voltage sweeps between 2.0 and 4.7 V vs Li/Li+ in Li-PC yielded significant degradation after 1000 cycles.EU GRINDOO
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