A search for the decay B+→K+ννˉB^+ \to K^+ \nu \bar{\nu}

We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ \nu \bar{\nu}$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of ${\mathcal B}(B^+ \to K^+ \nu \bar{\nu})<5.2 \times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of ${\mathcal B}(B^+ \to \pi^+ \nu \bar{\nu})<1.0 \times 10^{-4}$ using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let

High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe

We report on the realization of a high quality distributed Bragg reflector with both high and low refractive index layers lattice matched to ZnTe. Our structure is grown by molecular beam epitaxy and is based on binary compounds only. The high refractive index layer is made of ZnTe, while the low index material is made of a short period triple superlattice containing MgSe, MgTe, and ZnTe. The high refractive index step of Delta_n=0.5 in the structure results in a broad stopband and the reflectivity coefficient exceeding 99% for only 15 Bragg pairs.Comment: 4 pages, 3 figure

EuFe2_2As2_2 under high pressure: an antiferromagnetic bulk superconductor

We report the ac magnetic susceptibility $\chi_{ac}$ and resistivity $\rho$ measurements of EuFe$_2$As$_2$ under high pressure $P$. By observing nearly 100% superconducting shielding and zero resistivity at $P$ = 28 kbar, we establish that $P$-induced superconductivity occurs at $T_c \sim$~30 K in EuFe$_2$As$_2$. $\rho$ shows an anomalous nearly linear temperature dependence from room temperature down to $T_c$ at the same $P$. $\chi_{ac}$ indicates that an antiferromagnetic order of Eu$^{2+}$ moments with $T_N \sim$~20 K persists in the superconducting phase. The temperature dependence of the upper critical field is also determined.Comment: To appear in J. Phys. Soc. Jpn., Vol. 78 No.

Measurement of the electron energy spectrum and its moments in inclusive B -> Xe nu decays

We report a measurement of the inclusive electron energy spectrum for semileptonic decays of B mesons in a data sample of 52 million Y(4S)-->B(B) over bar decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We determine the branching fraction, first, second, and third moments of the spectrum for lower cutoffs on the electron energy between 0.6 and 1.5 GeV. We measure the partial branching fraction to be B(B-->Xenu,E-e>0.6 GeV)=[10.36+/-0.06(stat.)+/-0.23(sys.)]%

Improved measurement of CP asymmetries in B-0 ->(c(c)over-bar)K0((*)) decays

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227x10(6) Upsilon(4S)-> B (B) over bar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CPasymmetry, sin2 beta in the standard model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B-0 or (0) from its decay products. We measure sin2 beta=0.722 +/- 0.040(stat)+/- 0.023(syst) in agreement with the standard model expectation

Adjusting survival time estimates to account for treatment switching in randomised controlled trials – a simulation study

Abstract: Background Treatment switching commonly occurs in clinical trials of novel interventions, particularly in the advanced or metastatic cancer setting, which causes important problems for health technology assessment. It is unclear which methods to adjust for switching are most appropriate in realistic scenarios. Objectives: We aimed to assess statistical approaches for adjusting survival estimates in the presence of treatment switching in order to determine which methods are most appropriate in a range of realistic scenarios. Methods: We conducted a simulation study to assess the bias, mean squared error and coverage associated with alternative switching adjustment methods across a wide range of realistic scenarios. Results Simple methods such as censoring or excluding patients that switch always resulted in high levels of bias. More complex randomisation-based methods (e.g. Rank Preserving Structural Failure Time Models (RPSFTM)) were unbiased only when the treatment effect was not time-dependent. Observational-based methods: (e.g. inverse probability of censoring weights (IPCW)) coped better with time-dependent treatment effects but are heavily data reliant, are sensitive to model misspecification and often produced high levels of bias in our simulations, particularly when the proportion of patients that switched treatments was very high (approximately 90%). We introduce a novel “two stage” method, whereby a specific disease-related time-point is used to define a secondary baseline after which switching is permitted, allowing treatment effects to be estimated separately for patients that switch and patients randomised to the experimental group. We find that this method can perform well provided the treatment switching mechanism is amenable. Conclusions: Randomisation-based methods can accurately adjust for treatment switching when the treatment effect received by patients that switch is the same as that received by patients randomised to the experimental group. When this is not the case observational-based methods or simple twostage methods should be considered, although the IPCW is prone to substantial bias when the proportion of patients that switch is greater than approximately 90%. Simple methods such as censoring or excluding patients that switch should not be used

As low as is reasonably achievable (ALARA) studies relative to the NWTS program

The history of development of the as-low-as-is-reasonably achievable (ALARA) concept and ALARA criteria for radiation exposures as applied to both off-site (environmental) and on-site (occupational) exposures at nuclear power plants are reviewed. The current status of activities within the various federal agencies directed toward developing ALARA criteria for other areas of the nuclear fuel cycle is presented. Based on the historical development, the present activities, and on discussions with numerous people involved in this area, the future development of ALARA criteria and implications for the National Waste Terminal Storage (NWTS) Program is forecast. Environmental ALARA criteria which relate to minimizing radiation to the surrounding populaltion are discussed along with current occupational ALARA criteria and quidelines for risk-benefit assessments that are under development and recommendations to assure that evolving ALARA concepts are periodically brought up to date and that such concepts be made available to those subcontractors who have responsibility for design and operation of a repository. An annotated bibliography of some 83 sources giving information on ALARA criteria and its application is included. (JRD