6,241 research outputs found
Type-I Seesaw as the Common Origin of Neutrino Mass, Baryon Asymmetry, and the Electroweak Scale
The type-I seesaw represents one of the most popular extensions of the
Standard Model. Previous studies of this model have mostly focused on its
ability to explain neutrino oscillations as well as on the generation of the
baryon asymmetry via leptogenesis. Recently, it has been pointed out that the
type-I seesaw can also account for the origin of the electroweak scale due to
heavy-neutrino threshold corrections to the Higgs potential. In this paper, we
show for the first time that all of these features of the type-I seesaw are
compatible with each other. Integrating out a set of heavy Majorana neutrinos
results in small masses for the Standard Model neutrinos; baryogenesis is
accomplished by resonant leptogenesis; and the Higgs mass is entirely induced
by heavy-neutrino one-loop diagrams, provided that the tree-level Higgs
potential satisfies scale-invariant boundary conditions in the ultraviolet. The
viable parameter space is characterized by a heavy-neutrino mass scale roughly
in the range GeV and a mass splitting among the nearly
degenerate heavy-neutrino states up to a few TeV. Our findings have interesting
implications for high-energy flavor models and low-energy neutrino observables.
We conclude that the type-I seesaw sector might be the root cause behind the
masses and cosmological abundances of all known particles. This statement might
even extend to dark matter in the presence of a keV-scale sterile neutrino.Comment: 41 pages, 5 figures, matches version published in PR
Collisions of Deformed Nuclei and Superheavy-Element Production
A detailed understanding of complete fusion cross sections in heavy-ion
collisions requires a consideration of the effects of the deformation of the
projectile and target. Our aim here is to show that deformation and orientation
of the colliding nuclei have a very significant effect on the fusion-barrier
height and on the compactness of the touching configuration. To facilitate
discussions of fusion configurations of deformed nuclei, we develop a
classification scheme and introduce a notation convention for these
configurations. We discuss particular deformations and orientations that lead
to compact touching configurations and to fusion-barrier heights that
correspond to fairly low excitation energies of the compound systems. Such
configurations should be the most favorable for producing superheavy elements.
We analyse a few projectile-target combinations whose deformations allow
favorable entrance-channel configurations and whose proton and neutron numbers
lead to compound systems in a part of the superheavy region where alpha
half-lives are calculated to be observable, that is, longer than 1 microsecond.Comment: 15 pages. LaTeX with iopconf.sty style file. Presented at 2nd
RIKEN/INFN Joint Symposium, Wako-shi, Saitama, Japan, May 22-26, 1995. To be
published in symposium proceedings by World Scientific, Singapore. Seven
figures not included here. PostScript version with figures available at
http://t2.lanl.gov/pub/publications/publications.html or at
ftp://t2.lanl.gov/pub/publications/riken9
Neutrino mean free path and in-medium nuclear interaction
Neutrinos produced during the collapse of a massive star are trapped in a
nuclear medium (the proto-neutron star). Typically, neutrino energies (10-100
MeV) are of the order of nuclear giant resonances energies. Hence, neutrino
propagation is modified by the possibility of coherent scattering on nucleons.
We have compared the predictions of different nuclear interaction models. It
turns out that their main discrepancies are related to the density dependence
of the k-effective mass as well as to the onset of instabilities as density
increases. This last point had led us to a systematic study of instabilities of
infinite matter with effective Skyrme-type interactions. We have shown that for
such interactions there is always a critical density, above which the system
becomes unstable.Comment: 4 pages, 4 figures, Proceedings of the 17th Divisional Conference on
Nuclear Physics in Astrophysics (NPDC17), 30th September - 4th October 2002,
ATOMKI, Debrecen, Hungary, to appear in Nuclear Physics
The Peculiar Type Ic Supernova 1997ef: Another Hypernova
SN 1997ef has been recognized as a peculiar supernova from its light curve
and spectral properties. The object was classified as a Type Ic supernova (SN
Ic) because its spectra are dominated by broad absorption lines of oxygen and
iron, lacking any clear signs of hydrogen or helium line features. The light
curve is very different from that of previously known SNe Ic, showing a very
broad peak and a slow tail. The strikingly broad line features in the spectra
of SN 1997ef, which were also seen in the hypernova SN 1998bw, suggest the
interesting possibility that SN 1997ef may also be a hypernova. The light curve
and spectra of SN 1997ef were modeled first with a standard SN~Ic model
assuming an ordinary kinetic energy of explosion erg. The
explosion of a CO star of mass gives a
reasonably good fit to the light curve but clearly fails to reproduce the broad
spectral features. Then, models with larger masses and energies were explored.
Both the light curve and the spectra of SN 1997ef are much better reproduced by
a C+O star model with 8 \e{51} erg and .
Therefore, we conclude that SN 1997ef is very likely a hypernova on the basis
of its kinetic energy of explosion. Finally, implications for the deviation
from spherical symmetry are discussed in an effort to improve the light curve
and spectral fits.Comment: "To appear in the Astrophysical Journal, Vol.534 (2000)
Coffee inventory through orbital imagery
There are no author-identified significant results in this report
Single-photon emitting diode in silicon carbide
Electrically driven single-photon emitting devices have immediate
applications in quantum cryptography, quantum computation and single-photon
metrology. Mature device fabrication protocols and the recent observations of
single defect systems with quantum functionalities make silicon carbide (SiC)
an ideal material to build such devices. Here, we demonstrate the fabrication
of bright single photon emitting diodes. The electrically driven emitters
display fully polarized output, superior photon statistics (with a count rate
of 300 kHz), and stability in both continuous and pulsed modes, all at room
temperature. The atomic origin of the single photon source is proposed. These
results provide a foundation for the large scale integration of single photon
sources into a broad range of applications, such as quantum cryptography or
linear optics quantum computing.Comment: Main: 10 pages, 6 figures. Supplementary Information: 6 pages, 6
figure
Health considerations for transgender women and remaining unknowns : a narrative review
Transgender (trans) women (TW) were assigned male at birth but have a female gender identity or gender expression. The literature on management and health outcomes of TW has grown recently with more publication of research. This has coincided with increasing awareness of gender diversity as communities around the world identify and address health disparities among trans people. In this narrative review, we aim to comprehensively summarize health considerations for TW and identify TW-related research areas that will provide answers to remaining unknowns surrounding TW's health. We cover up-to-date information on: (1) feminizing gender-affirming hormone therapy (GAHT); (2) benefits associated with GAHT, particularly quality of life, mental health, breast development and bone health; (3) potential risks associated with GAHT, including cardiovascular disease and infertility; and (4) other health considerations like HIV/AIDS, breast cancer, other tumours, voice therapy, dermatology, the brain and cognition, and aging. Although equally deserving of mention, feminizing gender-affirming surgery, paediatric and adolescent populations, and gender nonbinary individuals are beyond the scope of this review. While much of the data we discuss come from Europe, the creation of a United States transgender cohort has already contributed important retrospective data that are also summarized here. Much remains to be determined regarding health considerations for TW. Patients and providers will benefit from larger and longer prospective studies involving TW, particularly regarding the effects of aging, race and ethnicity, type of hormonal treatment (e.g. different oestrogens, anti-androgens) and routes of administration (e.g. oral, parenteral, transdermal) on all the topics we address
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