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.

Dalitz plot analysis of the decay B±→K±K±K∓

We analyze the three-body charmless decay B-+/-->(KKK -/+)-K-+/--K-+/- using a sample of 226.0 +/- 2.5 million B (B) over bar pairs collected by the BABAR detector. We measure the total branching fraction and CP asymmetry to be B=(35.2 +/- 0.9 +/- 1.6)x10(-6) and A(CP)=(-1.7 +/- 2.6 +/- 1.5)%. We fit the Dalitz plot distribution using an isobar model and measure the magnitudes and phases of the decay coefficients. We find no evidence of CP violation for the individual components of the isobar model. The decay dynamics is dominated by the K+K- S-wave, for which we perform a partial-wave analysis in the region m(K+K-)< 2 GeV/c(2). Significant production of the f(0)(980) resonance, and of a spin zero state near 1.55 GeV/c(2) are required in the isobar model description of the data. The partial-wave analysis supports this observation.This work is supported by DOE and NSF (USA), NSERC (Canada), IHEP (China), CEA and CNRS-IN2P3 (France), BMBF and DFG (Germany), INFN (Italy), FOM (The Netherlands), NFR (Norway), MIST (Russia), and PPARC (United Kingdom). Individuals have received support from CONACyT (Mexico), Marie Curie EIF (European Union), the A. P. Sloan Foundation, the Research Corporation, and the Alexander von Humboldt Foundation

Search for the decay B+-> K+ v(v)over-bar

Contains fulltext : 128764.pdf (publisher's version ) (Open Access

Branching Fractions and C

04 BABARWe measure the branching fractions and CP asymmetries in the decays B0 --&gt; K+K-K0S and B+ --&gt; K+K0S K0S using a sample of approximately 122 million BBbar pairs collected by the BaBar detector. From a time-dependent analysis of the K+ K- K0S sample that excludes phi K0S, the values of the CP-violation parameters are S = -0.56 +/- 0.25 +/- 0.04 and C = -0.10 +/- 0.19 +/- 0.10, where the first uncertainty is statistical, the second is systematic. We confirm that the final state is nearly purely CP-even. Using this result and setting C=0, we extract the Standard Model parameter sin2beta = 0.57 +/- 0.26 +/- 0.04 +0.17/-0 where the last error is due to uncertainty on the CP content. We present the first measurement of the CP-violating charge asymmetry ACP(B+ --&gt; K+K0S K0S) = -0.04 +/- 0.11 +/- 0.02, with a 90% confidence-level interval of [-0.23, 0.15]. The branching fractions are BF(B0 --&gt; K+K-K0) = (23.8 +/- 2.0 +/- 1.6) x 10^{-6} and BF(B+ --&gt; K+K0S K0S) = (10.7 +/- 1.2 +/- 1.0) x 10^{-6}