Low energy reaction K−p→ΛηK^-p\rightarrow\Lambda\eta and the negative parity Λ\Lambda resonances

The reaction $K^-p\rightarrow\Lambda\eta$ at low energies is studied with a chiral quark model approach. Good descriptions of the existing experimental data are obtained. It is found that $\Lambda(1670)$ dominates the reaction around threshold. Furthermore, $u$- and $t$-channel backgrounds play crucial roles in this reaction as well. The contributions from the $D$-wave state $\Lambda(1690)$ are negligibly small for its tiny coupling to $\eta\Lambda$. To understand the strong coupling properties of the low-lying negative parity $\Lambda$ resonances extracted from the $\bar{K}N$ scattering, we further study their strong decays. It is found that these resonances are most likely mixed states between different configurations. Considering these low-lying negative parity $\Lambda$ resonances as mixed three-quark states, we can reasonably understand both their strong decay properties from Particle Data Group and their strong coupling properties extracted from the $\bar{K}N$ scattering. As a byproduct, we also predict the strong decay properties of the missing $D$-wave state $|\Lambda\frac{3}{2}^-\ >_3$ with a mass of $\sim1.8$ GeV. We suggest our experimental colleagues search it in the $\Sigma(1385)\pi$ and $\Sigma\pi$ channels.Comment: 11 pages and 4 figure

Antiferromagnetic phase of the gapless semiconductor V3Al

Discovering new antiferromagnetic compounds is at the forefront of developing future spintronic devices without fringing magnetic fields. The antiferromagnetic gapless semiconducting D03 phase of V3Al was successfully synthesized via arc-melting and annealing. The antiferromagnetic properties were established through synchrotron measurements of the atom-specific magnetic moments, where the magnetic dichroism reveals large and oppositely-oriented moments on individual V atoms. Density functional theory calculations confirmed the stability of a type G antiferromagnetism involving only two-third of the V atoms, while the remaining V atoms are nonmagnetic. Magnetization, x-ray diffraction and transport measurements also support the antiferromagnetism. This archetypal gapless semiconductor may be considered as a cornerstone for future spintronic devices containing antiferromagnetic elements.Comment: Accepted to Physics Review B on 02/23/1

Selection into Mixed Marriages: Evidence from North Carolina, 1894-1906

Using a novel dataset from agricultural censuses and geological sources, I examine the selec- tion into mixed marriages between whites and Cherokee Indians in North Carolina during the late nineteenth century. I find that the well-documented wealth advantage of Cherokee Indian households containing white husbands is driven mostly by positive selection. Thus, once family fixed effects are controlled for, the observed intermarriage premium is completely eliminated. (JEL D03, N31, O12.

Meson assisted dibaryons

We discuss a new type of L=0 positive-parity dibaryons, pion-B-B', where the dominant binding mechanism is provided by resonating p-wave pion-baryon interactions. Recent calculations of such pion assisted dibaryons are reviewed with special emphasis placed on the non-strange I(JP)=1(2+) N-Delta dibaryon D_{12}(2150) studied recently at JLab, and on the 0(3+) Delta-Delta dibaryon D_{03}(2380) discovered recently by the WASA-at-COSY Collaboration. We review recent searches by the HADES Collaboration at GSI and by the E15 and E27 Experiments at J-PARC for a strangeness S=-1 I(JP)=1/2(0-) K-pp dibaryon and perhaps also for a strange I(JP)=3/2(2+) N-Sigma(1385) pion assisted dibaryon Y_{3/2(2+)}(2270). Charm C=+1 dibaryons, predicted with these same I(JP) values, are also briefly reviewed.Comment: Presented at the Jagiellonian Symposium on Fundamental and Applied Subatomic Physics, Cracow, June 2015; matches published versio

Evidence for Merger Remnants in Early-Type Host Galaxies of Low-Redshift QSOs

We present results from a pilot HST ACS deep imaging study in broad-band V of five low-redshift QSO host galaxies classified in the literature as ellipticals. The aim of our study is to determine whether these early-type hosts formed at high redshift and have since evolved passively, or whether they have undergone relatively recent mergers that may be related to the triggering of the nuclear activity. We perform two-dimensional modeling of the light distributions to analyze the host galaxies' morphology. We find that, while each host galaxy is reasonably well fitted by a de Vaucouleurs profile, the majority of them (4/5) reveal significant fine structure such as shells and tidal tails. These structures contribute between ~5% and 10% to the total V-band luminosity of each host galaxy within a region of r ~ 3 r_eff and are indicative of merger events that occurred between a few hundred Myr and a Gyr ago. These timescales are comparable to starburst ages in the QSO hosts previously inferred from Keck spectroscopy. Our results thus support a consistent scenario in which most of the QSO host galaxies suffered mergers with accompanying starbursts that likely also triggered the QSO activity in some way, but we are also left with considerable uncertainty on physical mechanisms that might have delayed this triggering for several hundred Myr after the merger.Comment: 22 pages, 4 figures. Accepted for publication in the Astrophysical Journa