We report the first lattice QCD calculation of the hadronic vacuum polarization (HVP) disconnected contribution to the muon anomalous magnetic moment at physical pion mass. The calculation uses a ...refined noise-reduction technique that enables the control of statistical uncertainties at the desired level with modest computational effort. Measurements were performed on the 48^{3}×96 physical-pion-mass lattice generated by the RBC and UKQCD Collaborations. We find the leading-order hadronic vacuum polarization a_{μ}^{HVP(LO)disc}=-9.6(3.3)(2.3)×10^{-10}, where the first error is statistical and the second systematic.
Multiple observational studies have demonstrated large ionospheric variations during the daytime associated with sudden stratospheric warming (SSW) events, but only limited evidence of ionospheric ...disturbances during the nighttime has been reported up to now. We focus on the American longitudinal sector with its extensive observational network of Global Navigation Satellite System receivers, four Digisondes located at low and middle latitudes, and the Arecibo and Millstone Hill incoherent scatter radars. The study focuses on a major SSW event of January 2013 to investigate large‐scale disturbances in the nighttime ionosphere. We report a deep decrease in total electron content that reaches a factor of 2–5 as compared to the background level and is observed between local midnight and local sunrise (6–12 UT). This decrease is observed for several consecutive days in the range of latitudes from ~55°S to ~45°N. It is accompanied by a strong downward plasma motion and a significant decrease in ion temperature, as observed by both Arecibo and Millstone Hill radars. These results demonstrate that SSW events cause changes in the nighttime ionosphere that are even larger than in the daytime ionosphere. We discuss variations in electric field and F‐region dynamics as possible drivers of this behavior and suggest that thermospheric winds play a much larger role than previously thought.
Plain Language Summary
Large‐scale meteorological disturbances like sudden stratospheric warmings are often used in research to illuminate a variety of mechanisms and processes that link different regions of the Earth's atmosphere across a wide range of altitudes and latitudes. Earlier studies have shown large and long‐lasting anomalies caused by sudden stratospheric warmings in the Earth's daytime ionosphere. In this study, we show that in addition to the daytime changes, large changes also occur at night. In particular, major warming of January 2013 carved a deep hole in the nighttime ionosphere that extended through half the globe and decreased electron density by a factor of 2 to 4. These results suggest that strong disturbances occurred in the upper atmospheric wind system in a wide region from middle latitudes in the Northern Hemisphere to middle latitudes in the Southern Hemisphere. These results improve our understanding of reasons for very large day‐to‐day variations in the ionosphere and move us a step closer to improvements in space weather forecasting.
Key Points
Impacts of sudden stratospheric warming on a nighttime ionosphere are studied
SSWs affect the nighttime electron density, decreasing it by a factor of 2‐4 in a large range of latitudes
These effects are likely to be related to changes in thermospheric zonal wind
A
bstract
We present results for the leading hadronic contribution to the muon anomalous magnetic moment due to strange quark-connected vacuum polarisation effects. Simulations were performed using ...RBC-UKQCD’s
N
f
= 2 + 1 domain wall fermion ensembles with physical light sea quark masses at two lattice spacings. We consider a large number of analysis scenarios in order to obtain solid estimates for residual systematic effects. Our final result in the continuum limit is
a
μ
(2)had,
s
= 53.1(9)(
− 3
+ 1
) × 10
− 10
.
A
bstract
We report on an exploratory study of domain wall fermions (DWF) as a lattice regularisation for heavy quarks. Within the framework of quenched QCD with the tree-level improved Symanzik ...gauge action we identify the DWF parameters which minimise discretisation effects. We find the corresponding effective 4
d
overlap operator to be exponentially local, independent of the quark mass. We determine a maximum bare heavy quark mass of
am
h
≈ 0
.
4, below which the approximate chiral symmetry and O(a)-improvement of DWF are sustained. This threshold appears to be largely independent of the lattice spacing. Based on these findings, we carried out a detailed scaling study for the heavy-strange meson dispersion relation and decay constant on four ensembles with lattice spacings in the range 2
.
0-5
.
7 GeV. We observe very mild
a
2
scaling towards the continuum limit. Our findings establish a sound basis for heavy DWF in dynamical simulations of lattice QCD with relevance to Standard Model phenomenology.
The behavior of the Earth’s middle atmosphere and ionosphere is governed by multiple processes resulting not only from downward energy transfer from the Sun and magnetosphere but also upward energy ...transfer from terrestrial weather. Understanding the relative importance of mechanisms beyond solar and geomagnetic activity is essential for progress in multi-day predictions of the Earth’s atmosphere-ionosphere system. The recent development of research infrastructure, particularly in Antarctica, allows the observation of new ionospheric features. Here we show for the first time that large disturbances observed in the Arctic winter polar stratosphere (20–50 km above ground and at 60–90°N) during a sudden stratospheric warming event are communicated across the globe and cause large disturbances in the summertime ionospheric plasma over Antarctica (60–90°S). Ionospheric anomalies reach ∼100% of the background level and are observed for multiple days. We suggest several possible terrestrial mechanisms that could contribute to the formation of upper atmospheric and ionospheric anomalies in the southern hemisphere.
We review the status of the determination of |V_{us}| from both flavor-breaking finite-energy sum rules based on inclusive non-strange and strange hadronic tau decay data and the recent lattice-based ...analysis of inclusive strange hadronic tau decay data. In particular, we update the results from these analysis frameworks taking into account recent improvements to a number of strange branching fractions reported by HFLAV at CKM2018 and this meeting. We find that inclusive tau decay data yields results for |V_{us}| compatible within errors with the expectations of three-family unitarity.
The purpose of this study was to compare bone marrow aspirate concentrate (BMAC) with cancellous allograft to iliac crest bone graft (ICBG) in the treatment of long bone nonunions.
Retrospective ...cohort study.
A single level I trauma center.
26 patients with long bone diaphyseal or metaphyseal nonunions with defects >2 mm and treated with open repair and BMAC, compared to 25 patients with long bone diaphyseal or metaphyseal nonunions with defects >2 mm and treated with open repair and ICBG.
Open repair of long bone nonunion using either autologous ICBG or BMAC with cancellous allograft.
Nonunion healing, radiographically measured by the modified Radiographic Union Score for Tibia (mRUST) score. Secondary outcomes included risk factors associated with failed repair.
The union rates for the BMAC and ICBG cohorts were 75% and 78%, respectively (
.8). Infection was the only risk factor of statistical significance for failure.
In this study, we found no significant difference in union rate for long bone nonunions treated with ICBG or BMAC with allograft. BMAC and allograft led to 75% successful healing in this series. Given the heterogeneity of the control group and loss to follow-up, further prospective investigation should be conducted to more rigorously compare BMAC to ICBG for nonunion treatment.
III, retrospective cohort.
JHEP 1604 (2016) 063 We present results for the leading hadronic contribution to the muon
anomalous magnetic moment due to strange quark-connected vacuum polarisation
effects. Simulations were ...performed using RBC--UKQCD's $N_f=2+1$ domain wall
fermion ensembles with physical light sea quark masses at two lattice spacings.
We consider a large number of analysis scenarios in order to obtain solid
estimates for residual systematic effects. Our final result in the continuum
limit is $a_\mu^{(2)\,{\rm
had},\,s}=53.1(9)\left(^{+1}_{-3}\right)\times10^{-10}$.
We report the first lattice QCD calculation of the hadronic vacuum polarization disconnected contribution to the muon anomalous magnetic moment at physical pion mass. The calculation uses a refined ...noise-reduction technique which enabled the control of statistical uncertainties at the desired level with modest computational effort. Measurements were performed on the \(48^3 \times 96\) physical-pion-mass lattice generated by the RBC and UKQCD collaborations. We find \(a_\mu^{\rm HVP~(LO)~DISC} = -9.6(3.3)(2.3)\times 10^{-10}\), where the first error is statistical and the second systematic.
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