2,843 research outputs found
Search full text options here 2 of 4 KMT-2021-BLG-0912Lb: a microlensing super Earth around a K-type star
Aims. The light curve of the microlensing event KMT-2021-BLG-0912 exhibits a very short anomaly relative to a single-lens single-source form. We investigate the light curve for the purpose of identifying the origin of the anomaly.
Methods. We model the light curve under various interpretations. From this, we find four solutions, in which three solutions are found under the assumption that the lens is composed of two masses (2L1S models), and the other solution is found under the assumption that the source is comprised of binary stars (1L2S model). The 1L2S model is ruled out based on the contradiction that the faint source companion is bigger than its primary, and one of the 2L1S solutions is excluded from the combination of the poorer fit, blending constraint, and lower overall probability, leaving two surviving solutions with the planet/host mass ratios of q similar to 2.8 x 10(-5) and similar to 1.1 x 10(-5). A subtle central deviation supports the possibility of a tertiary lens component, either a binary companion to the host with a very large or small separation, or a second planet lying near the Einstein ring, but it is difficult to claim a secure detection due to the marginal improvement of the fit, lack of consistency among different data sets, and difficulty in uniquely specifying the nature of the tertiary component.
Results. With the observables of the event, it is estimated that the masses of the planet and host are similar to(6.9 M-circle plus, 0.75 M-circle dot) according to one solution and similar to(2.8 M-circle plus, 0.80 M-circle dot) according to the other, indicating that the planet is a super Earth around a K-type star, regardless of the solution. The fact that 16 (including the one reported in this work) out of 19 microlensing planets with M less than or similar to 10 M-circle plus were detected during the last 6 yr nicely demonstrates the importance of high-cadence global surveys in detecting very low-mass planets
The Galactic Magnetic Field's Effect in Star-Forming Region
We investigate the effect of the Milky Way's magnetic field in star forming
regions using archived 350 micron polarization data on 52 Galactic star
formation regions from the Hertz polarimeter module. The polarization angles
and percentages for individual telescope beams were combined in order to
produce a large-scale average for each source and for complexes of sources. In
more than 80% of the sources, we find a meaningful mean magnetic field
direction, implying the existence of an ordered magnetic field component at the
scale of these sources. The average polarization angles were analyzed with
respect to the Galactic coordinates in order to test for correlations between
polarization percentage, polarization angle, intensity, and Galactic location.
No correlation was found, which suggests that the magnetic field in dense
molecular clouds is decoupled from the large-scale Galactic magnetic field.
Finally, we show that the magnetic field directions in the complexes are
consistent with a random distribution on the sky
TeV Symmetry and the Little Hierarchy Problem
Constraints from precision electroweak measurements reveal no evidence for
new physics up to 5 - 7 TeV, whereas naturalness requires new particles at
around 1 TeV to address the stability of the electroweak scale. We show that
this "little hierarchy problem" can be cured by introducing a symmetry for new
particles at the TeV scale. As an example, we construct a little Higgs model
with this new symmetry, dubbed T-parity, which naturally solves the little
hierarchy problem and, at the same time, stabilize the electroweak scale up to
10 TeV. The model has many important phenomenological consequences, including
consistency with the precision data without any fine-tuning, a stable
weakly-interacting particle as the dark matter candidate, as well as collider
signals completely different from existing little Higgs models, but rather
similar to the supersymmetric theories with conserved R-parity.Comment: 15 pages, 1 figure; v.2: typos corrected and various minor
modifications/expansions on the presentations. now 16 pages and 1 figure.
version to appear on JHE
Missing Momentum Reconstruction and Spin Measurements at Hadron Colliders
We study methods for reconstructing the momenta of invisible particles in
cascade decay chains at hadron colliders. We focus on scenarios, such as SUSY
and UED, in which new physics particles are pair produced. Their subsequent
decays lead to two decay chains ending with neutral stable particles escaping
detection. Assuming that the masses of the decaying particles are already
measured, we obtain the momenta by imposing the mass-shell constraints. Using
this information, we develop techniques of determining spins of particles in
theories beyond the standard model. Unlike the methods relying on Lorentz
invariant variables, this method can be used to determine the spin of the
particle which initiates the decay chain. We present two complementary ways of
applying our method by using more inclusive variables relying on kinematic
information from one decay chain, as well as constructing correlation variables
based on the kinematics of both decay chains in the same event.Comment: Version to appear in JHE
GABAergic Neuron-Specific Loss of Ube3a Causes Angelman Syndrome-Like EEG Abnormalities and Enhances Seizure Susceptibility
Loss of maternal UBE3A causes Angelman syndrome (AS), a neurodevelopmental disorder associated with severe epilepsy. We previously implicated GABAergic deficits onto layer (L) 2/3 pyramidal neurons in the pathogenesis of neocortical hyperexcitability, and perhaps epilepsy, in AS model mice. Here we investigate consequences of selective Ube3a loss from either GABAergic or glutamatergic neurons, focusing on the development of hyperexcitability within L2/3 neocortex and in broader circuit and behavioral contexts. We find that GABAergic Ube3a loss causes AS-like increases in neocortical EEG delta power, enhances seizure susceptibility, and leads to presynaptic accumulation of clathrin-coated vesicles (CCVs) – all without decreasing GABAergic inhibition onto L2/3 pyramidal neurons. Conversely, glutamatergic Ube3a loss fails to yield EEG abnormalities, seizures, or associated CCV phenotypes, despite impairing tonic inhibition onto L2/3 pyramidal neurons. These results substantiate GABAergic Ube3a loss as the principal cause of circuit hyperexcitability in AS mice, lending insight into ictogenic mechanisms in AS
Structure of the first representative of Pfam family PF04016 (DUF364) reveals enolase and Rossmann-like folds that combine to form a unique active site with a possible role in heavy-metal chelation.
The crystal structure of Dhaf4260 from Desulfitobacterium hafniense DCB-2 was determined by single-wavelength anomalous diffraction (SAD) to a resolution of 2.01 Å using the semi-automated high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the NIGMS Protein Structure Initiative (PSI). This protein structure is the first representative of the PF04016 (DUF364) Pfam family and reveals a novel combination of two well known domains (an enolase N-terminal-like fold followed by a Rossmann-like domain). Structural and bioinformatic analyses reveal partial similarities to Rossmann-like methyltransferases, with residues from the enolase-like fold combining to form a unique active site that is likely to be involved in the condensation or hydrolysis of molecules implicated in the synthesis of flavins, pterins or other siderophores. The genome context of Dhaf4260 and homologs additionally supports a role in heavy-metal chelation
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