Search for CP and CPT violation in positronium decay

Positronium, the electron-positron bound state, is described to a good approximation by pure QED. The states of positronium have definite values of C and P. Consequently, positronium is an attractive system for the investigation of possible violations of the discrete symmetries in the leptonic sector. We discuss signals for CP and CPT violation in the decay of spin-polarized orthopositronium and show where such correlations might arise in the context of the Standard-Model Extension.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 28-July 2, 201

Virtual annihilation contribution to orthopositronium decay rate

Order alpha^2 contribution to the orthopositronium decay rate due to one-photon virtual annihilation is found to be delta Gamma = (alpha/pi)^2 (pi^2 ln(alpha) - 0.8622(9))Gamma_LO.Comment: 2 pages, no figure

Composite Skyrme Model with Vector Mesons

We study the composite Skyrme model, proposed by Cheung and G\"{u}rsey, introducing vector mesons in a chiral Lagrangian. We calculate the static properties of baryons and compare with results obtained from models without vector mesons.Comment: LaTeX, 9 pages, 3 figures, to be published in Phys. Rev.

A search for massive neutral bosons in orthopositronium decay

We have searched for an exotic decay of orthopositronium into a single photon and a short-lived neutral boson in the hitherto unexplored mass region above 900 ${\rm keV}/{\it c}^{2}$, by noting that this decay is one of few remaining candidates which could explain the discrepancy of the orthopositronium decay-rate. A high-resolution measurement of the associated photon energy spectrum was carried out with a germanium detector to search for a sharp peak from this two-body decay. Our negative result provides the upper-limits of\mbox{ }$2.0 \times 10^{-4}$ on the branching ratio of such a decay in the mass region from 847 to 1013 ${\rm keV}/{\it c}^{2}$, and excludes the possibility of this decay mode explaining the discrepancy in the orthopositronium decay-rate.Comment: a LaTeX file (text 7 pages) and a uuencoded gz-compressed PostScript file (text 7 pages + figures 4 pages

THE MENTAL HEALTH OF MOTHERS AND FATHERS BEFORE AND AFTER COHABITATION AND MARITAL DISSOLUTION

Using data from years one and three of the Fragile Families and Child Well-being Study, changes in depressive and anxious symptoms are compared for mothers and fathers who: 1) dissolve a cohabitating union versus remain intact; 2) dissolve a marital union versus remain intact; and 3) dissolve a cohabiting as compared to a marital union. In order to take into account potential sources of third variable bias from selection factors that differentiate those who are in cohabitations from those who are in marriages, mothers and fathers were matched on several sociodemographic control variables that research has demonstrated to be related to union formation and mental health outcomes. Results indicated that fathers who dissolve cohabitating or marital unions have greater increases in depressive and anxious symptoms over time than those who remain in their unions. In contrast, mothers increased in depressive and anxious symptoms, regardless of the type or stability of the union. For both mothers and fathers, no differences were found in change in mental health by type of union dissolution. In this low income sample of parents, results suggest that the impact of cohabitation and marital dissolution on mental health are similar in magnitude.Depression, fragile families, marriage, cohabitation, income, mental health