Susan Gardner

GALACTOSEISMOLOGY: DISCOVERY OF VERTICAL WAVES IN THE GALACTIC DISK

We present evidence for a Galactic North-South asymmetry in the number density and bulk velocity of solar neighborhood stars. The number density profile, which is derived from main-sequence stars in the Sloan Digital Sky Survey, shows a (North–South)/(North+South) deficit at |z| 400 pc and an excess at |z| ~ 800 pc. The bulk velocity profile, which is derived from the Sloan Extension for Galactic Understanding and Exploration, shows a gradual trend across the Galactic midplane as well as smaller-scale features. We speculate that the North-South asymmetry, which has the appearance of a wavelike perturbation, is intrinsic to the disk. We explore the physics of this phenomenon through an analysis of the linearized Boltzmann and Poisson equations and through one-dimensional simulations. The perturbation may be excited by the passage of a satellite galaxy or dark matter subhalo through the Galactic disk, in which case we are witnessing a recent disk-heating event.

Beta decays and non-standard interactions in the LHC era

Abstract We consider the role of precision measurements of beta decays and light meson semi-leptonic decays in probing physics beyond the Standard Model in the LHC era. We describe all low-energy charged-current processes within and beyond the Standard Model using an effective field theory framework. We first discuss the theoretical hadronic input which in these precision tests plays a crucial role in setting the baseline for new physics searches. We then review the current and upcoming constraints on the various non-standard operators from the study of decay rates, spectra, and correlations in a broad array of light-quark systems. We finally discuss the interplay with LHC searches, both within models and in an effective theory approach. Our discussion illustrates the independent yet complementary nature of precision beta decay measurements as probes of new physics, showing them to be of continuing importance throughout the LHC era.

Rescattering and chiral dynamics in B ! decay

We examine the role of B 0 ( ¯ B 0 ) ! �� 0 ! � + � − � 0 decay in the Dalitz plot analysis of B 0 ( ¯ B 0 ) ! �� ! � + � − � 0 decays, employed to extract the CKM parameter �. The �� channel is significant because it can break the relationship between the penguin contributions in B ! � 0 � 0 , B ! � + � − , and B ! � − � + decays consequent to an assumption of isospin symmetry. Its presence thus mimics the effect of isospin violation. The �� 0 state is of definite CP, however; we demonstrate that the B ! �� analysis can be generalized to

THE STELLAR NUMBER DENSITY DISTRIBUTION IN THE LOCAL SOLAR NEIGHBORHOOD IS NORTH-SOUTH ASYMMETRIC

We study the number density distribution of a sample of K and M dwarf stars, matched north and south of the Galactic plane within a distance of 2 kpc from the Sun, using observations from the Ninth Data Release of the Sloan Digital Sky Survey. We determine distances using the photometric parallax method, and in this context systematic effects exist which could potentially impact the determination of the number density profile with height from the Galactic plane—and ultimately affect a number density north-south asymmetry. They include: (1) the calibration of the various photometric parallax relations, (2) the ability to separate dwarfs from giants in our sample, (3) the role of stellar population differences such as age and metallicity, (4) the ability to determine the offset of the Sun from the Galactic plane, and (5) the correction for reddening from dust in the Galactic plane, though our stars are at high Galactic latitudes. We find the various analyzed systematic effects to have a negligible impact on our observed asymmetry, and using a new and larger sample of stars we confirm and refine the earlier discovery of Widrow et al. of a significant Galactic north-south asymmetry in the stellar number density distribution.

Sharpening low-energy, standard-model tests via correlation coefficients in neutron beta decay.

The correlation coefficients a, A, and B in neutron beta decay are proportional to the ratio of the axial-vector-to-vector weak coupling constants, gA/gV, to leading recoil order. With the advent of the next generation of neutron-decay experiments, the recoil-order corrections to these expressions become experimentally accessible, admitting a plurality of standard model (SM) tests. The measurement of both a and A, e.g., allows one to test the conserved-vector-current (CVC) hypothesis and to search for second-class currents (SCC) independently. The anticipated precision of these measurements suggests that the bounds on CVC violation and SCC from studies of nuclear beta decay can be qualitatively bettered.

Particle physics models for the 17 MeV anomaly in beryllium nuclear decays

The

Evidence for the absence of gluon orbital angular momentum in the nucleon

6.8\ensuremath{\sigma}

Comment on “New Limits on Intrinsic Charm in the Nucleon from Global Analysis of Parton Distributions”

anomaly in excited

Additional isospin-breaking effects in ϵ′/ϵ

^{8}\mathrm{Be}

Discrete Symmetries on the Light Front and a General Relation connecting Nucleon Electric Dipole and Anomalous Magnetic Moments

nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in