Superallowed Fermi beta decay and Coulomb mixing in nuclei

Superallowed $0^+ \to 0^+$ nuclear beta decay provides a direct measure of the weak vector coupling constant, \GV. We survey current world data on the nine accurately determined transitions of this type, which range from the decay of $^{10}$C to that of $^{54}$Co, and demonstrate that the results confirm conservation of the weak vector current (CVC) but differ at the 98% confidence level from the unitarity condition for the Cabibbo-Kobayashi-Maskawa (CKM) matrix. We examine the reliability of the small calculated corrections that have been applied to the data, and conclude that there are no evident defects although the Coulomb correction, $\delta_C$, depends sensitively on nuclear structure and thus needs to be constrained independently. The potential importance of a result in disagreement with unitarity, clearly indicates the need for further work to confirm or deny the discrepancy. We examine the options and recommend priorities for new experiments and improved calculations. Some of the required experiments depend upon the availability of intense radioactive beams. Others are possible with existing facilities.Comment: 12 pages, LaTeX with aipproc2.sty (included) and epsf.sty; Invited talk at Nuclear Structure 98, Gatlinburg, Tennessee, Aug. 199

Nonlocality, Asymmetry, and Distinguishing Bipartite States

Entanglement is an useful resource because some global operations cannot be locally implemented using classical communication. We prove a number of results about what is and is not locally possible. We focus on orthogonal states, which can always be globally distinguished. We establish the necessary and sufficient conditions for a general set of 2x2 quantum states to be locally distinguishable, and for a general set of 2xn quantum states to be distinguished given an initial measurement of the qubit. These results reveal a fundamental asymmetry to nonlocality, which is the origin of ``nonlocality without entanglement'', and we present a very simple proof of this phenomenon.Comment: 5 pages, 1 figure. Improved in line with referees comments, references added, typo corrected. To appear in Phys. Rev. Let

New limit on fundamental weak-interaction parameters from superallowed beta decay

A new critical survey of all world data on superallowed beta decays provides demanding tests of, and tight constraints on, the weak interaction. In confirmation of the conserved vector current (CVC) hypothesis, the vector coupling coupling constant is demonstrated to be constant to better than 3 parts in 10^4, and any induced scalar current is limited to fs \leq 0.0013 in electron rest-mass units. The possible existence of a fundamental scalar current is similarly limited to |Cs/Cv| \leq 0.0013. The superallowed data also determine the CKM matrix element to be Vud = 0.9738(4). With PDG values for Vus and Vub, the top-row test of CKM unitarity yields Vud^2 + Vus^2 + Vub^2 = 0.9966(14); although, if a recent result on Ke3 decay is used exclusively to obtain Vus, this sum becomes 0.9999(16). Limits on possible right-hand currents are given.Comment: 4 pages, one postscript fil

Who makes better use of technology for learning in D&T? Schools or university?

University teacher training departments have many functions in their role as Schools for Initial Teacher Education (ITE), these include accrediting qualified teacher status, teaching subject knowledge and pedagogy, and influencing change in a school subject's content and pedagogy. This paper discusses this latter area. It can be easy for teacher training in universities to become ivory towers, modelling new ideas for curriculum delivery and content in a 'bubble' away from the real world of the school classroom. A centre of design and technology (D&T) education at an English university has undertaken research-led developments in the use of web 2.0 technologies and technology enhanced learning (TEL), modelling how they can be used in the classroom. The research examined in this paper is the next stage of the centre's curriculum development to ensure the relevance of the university curriculum content and practices. Anecdotal evidence suggests that the use of TEL in secondary schools is inconsistent and sporadic with D&T teachers using TEL, with minimal awareness of research available, which could inform their practice. This impacts on the centre's trainee teachers as they begin teaching in schools during their final year of the course, with a possible unrealistic expectation of how TEL is used in schools, based on their university experiences

CURRENTS AND THEIR COUPLINGS IN THE WEAK SECTOR OF THE STANDARD MODEL

Beta-decay and muon-capture experiments in nuclei are reviewed. The conserved vector current hypothesis is confirmed through the observed constancy of the vector coupling constant determined from the superallowed Fermi transitions and from the measurement of the weak-magnetism term in mirror Gamow-Teller transitions. The axial-vector and pseudoscalar coupling constants in the nucleon are determined from neutron decay and muon capture on the proton respectively. In finite nuclei, evidence for these coupling constants being reduced relative to their free-nucleon values is discussed. Meson-exchange currents are shown to be an important correction to the time-like part of the axial current as evident in first-forbidden beta decays. Tests of the Standard Model are discussed, as well as extensions beyond it involving right-hand currents and scalar interactions.Comment: 67 pages, plain LaTex, uses worldsci.sty, two figures embedded in manuscript as tex statements. A chapter for a book entitled 'The Nucleus as a Laboratory for Studying Symmetries and Fundamental Interactions', eds. E.M. Henley and W.C. Haxto