12,489 research outputs found
Reconsidering the One Leptoquark solution: flavor anomalies and neutrino mass
We reconsider a model introducing a scalar leptoquark to explain recent deviations from the standard model in
semileptonic decays. The leptoquark can accommodate the persistent tension
in the decays as long as its mass is
lower than approximately , and we show that a sizeable Yukawa
coupling to the right-chiral tau lepton is necessary for an acceptable
explanation. Agreement with the measured rates is mildly compromised for parameter choices addressing the
tensions in , where the model can significantly reduce the
discrepancies in angular observables, branching ratios and the
lepton-flavor-universality observables and . The leptoquark can
also reconcile the predicted and measured value of the anomalous magnetic
moment of the muon and appears naturally in models of radiative neutrino mass
derived from lepton-number violating effective operators. As a representative
example, we incorporate the particle into an existing two-loop neutrino mass
scenario derived from a dimension-nine operator. In this specific model, the
structure of the neutrino mass matrix provides enough freedom to explain the
small masses of the neutrinos in the region of parameter space dictated by
agreement with the anomalies in , but
not the transition. This is achieved without excessive fine-tuning in
the parameters important for neutrino mass.Comment: 43 pages, 17 figures, 3 tables; corrected fit contours in fig. 1
Reconciliation of the Surface Brightness Fluctuations and Type Ia Supernovae Distance Scales
We present Hubble Space Telescope measurements of surface brightness
fluctuations (SBF) distances to early-type galaxies that have hosted Type Ia
supernovae (SNIa). The agreement in the relative SBF and SNIa multicolor light
curve shape and delta-m_15 distances is excellent. There is no systematic scale
error with distance, and previous work has shown that SBF and SNIa give
consistent ties to the Hubble flow. However, we confirm a systematic offset of
about 0.25 mag in the distance zero points of the two methods, and we trace
this offset to their respective Cepheid calibrations. SBF has in the past been
calibrated with Cepheid distances from the H_0 Key Project team, while SNIa
have been calibrated with Cepheid distances from the team composed of Sandage,
Saha, and collaborators. When the two methods are calibrated in a consistent
way, their distances are in superb agreement. Until the conflict over the
``long'' and ``short'' extragalactic Cepheid distances among many galaxies is
resolved, we cannot definitively constrain the Hubble constant to better than
about 10%, even leaving aside the additional uncertainty in the distance to the
Large Magellanic Cloud, common to both Cepheid scales. However, recent
theoretical SBF predictions from stellar population models favor the Key
Project Cepheid scale, while the theoretical SNIa calibration lies between the
long and short scales. In addition, while the current SBF distance to M31/M32
is in good agreement with the RR Lyrae and red giant branch distances,
calibrating SBF with the longer Cepheid scale would introduce a 0.3 mag offset
with respect to the RR Lyrae scale.Comment: 13 pages, 3 PostScript figures, LaTeX with AASTeX 5.02 and natbib.sty
v7.0 (included). Accepted for publication in The Astrophysical Journa
Underwater radiated noise levels of a research icebreaker in the central Arctic Ocean
U.S. Coast Guard Cutter Healy\u27s underwater radiated noise signature was characterized in the central Arctic Ocean during different types of ice-breaking operations. Propulsion modes included transit in variable ice cover, breaking heavy ice with backing-and-ramming maneuvers, and dynamic positioning with the bow thruster in operation. Compared to open-water transit, Healy\u27s noise signature increased approximately 10 dB between 20 Hz and 2 kHz when breaking ice. The highest noise levels resulted while the ship was engaged in backing-and-ramming maneuvers, owing to cavitation when operating the propellers astern or in opposing directions. In frequency bands centered near 10, 50, and 100 Hz, source levels reached 190–200 dB re: 1 μPa at 1 m (full octave band) during ice-breaking operations
BOSS Ultracool Dwarfs I: Colors and Magnetic Activity of M and L dwarfs
We present the colors and activity of ultracool (M7-L8) dwarfs from the Tenth
Data Release of the Sloan Digital Sky Survey (SDSS). We combine previous
samples of SDSS M and L dwarfs with new data obtained from the Baryon
Oscillation Sky Survey (BOSS) to produce the BOSS Ultracool Dwarf (BUD) sample
of 11820 M7-L8 dwarfs. By combining SDSS data with photometry from the Two
Micron All Sky Survey and the Wide-Field Infrared Sky Explorer mission, we
present ultracool dwarf colors from to as a function of spectral
type, and extend the SDSS-2MASS-WISE color locus to include ultracool dwarfs.
The , , and colors provide the best indication of spectral type
for M7-L3 dwarfs. We also examine ultracool dwarf chromospheric activity
through the presence and strength of H emission. The fraction of active
dwarfs rises through the M spectral sequence until it reaches 90% at
spectral type L0. The fraction of active dwarfs then declines to 50% at
spectral type L5; no H emission is observed in the late-L dwarfs in the
BUD sample. The fraction of active L0-L5 dwarfs is much higher than previously
observed. The strength of activity declines with spectral type from M7 through
L3, after which the data do not show a clear trend. Using one-dimensional
chromosphere models, we explore the range of filling factors and chromospheric
temperature structures that are consistent with H observations of M0-L7
dwarfs. M dwarf chromospheres have a similar, smoothly varying range of
temperature and surface coverage while L dwarf chromospheres are cooler and
have smaller filling factors.Comment: 24 pages and 13 figures, submitted to AJ. A short video describing
these results can be found at https://www.youtube.com/watch?v=wwX5WkuJCU
Policies for the Treatment of Alcohol and Drug Use Disorders: A Research Agenda for 2010-2015
Provides an agenda for policy research on drug and alcohol addiction treatment, including integrating screening and short-term interventions into primary care and other settings, services in specialty treatment centers, and ongoing support services
Conflicts of Interest Among Existing Clients: The Civil Litigator\u27s Obligations and Options
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