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.

Angular distributions in the decay B -> K*l(+)l(-)

We use a sample of 384 million BBbar events collected with the Babar detector at the PEP-II e+e- collider to study angular distributions in the rare decays B -> K* l+l-, where l+l- is either e+e- or mu+mu-. For low dilepton invariant masses, m(l+l-)3.2$ GeV/c^2, we measure AFB=0.76 (+0.52,-0.32) +/- 0.07 FL=0.71 (+0.20,-0.22) +/- 0.04.We are grateful for the excellent luminosity and machine conditions provided by our PEP-II colleagues, and for the substantial dedicated effort from the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and kind hospitality. This work is supported by DOE and NSF (USA), NSERC (Canada), CEA and CNRS-IN2P3 (France), BMBF and DFG (Germany), INFN (Italy), FOM (The Netherlands), NFR (Norway), MES (Russia), MEC (Spain), and STFC (United Kingdom). Individuals have received support from the Marie Curie EIF (European Union) and the A. P. Sloan Foundation.Peer reviewe

Search for Lepton Flavor Violation in the Decay τ^{±}→μ^{±}γ

A search for the nonconservation of lepton flavor number in the decay τ±→μ±γ has been performed using 2.07×108 e+e-→τ+τ- events produced at a center-of-mass energy near 10.58 GeV with the BABAR detector at the PEP-II storage ring. We find no evidence for a signal and set an upper limit on the branching ratio of B(τ±→μ±γ)<6.8×10-8 at 90% confidence level

Measurements of Branching Fractions and Dalitz Distributions for B0\u2192D(*)\ub1K0\u3c0 13 Decays

We present measurements of the branching fractions for the three-body decays B0\u2192D(*) 13K0\u3c0\ub1 and their resonant submodes B0\u2192D(*) 13K*\ub1 using a sample of approximately 88 7106 BB\u305 pairs collected by the BABAR detector at the SLAC PEP-II asymmetric energy storage ring. We measure: B(B0\u2192D 13K0\u3c0\ub1)=(4.9\ub10.7stat\ub10.5syst) 710-4, B(B0\u2192D* 13K0\u3c0\ub1)=(3.0\ub10.7stat\ub10.3syst) 710-4, B(B0\u2192D 13K*\ub1)=(4.6\ub10.6stat\ub10.5syst) 710-4, B(B0\u2192D* 13K*\ub1)=(3.2\ub10.6stat\ub10.3syst) 710-4. From these measurements we determine the fractions of resonant events to be f(B0\u2192D 13K*\ub1)=0.63\ub10.08stat\ub10.04syst and f(B0\u2192D* 13K*\ub1)=0.72\ub10.14stat\ub10.05syst

Measurement of sin 2β with hadronic and previously unused muonic J/ψ decays

We report a measurement of the CP-violation parameter sin 2β with B0J/ψKS0 decays in which the J/ψ decays to hadrons or to muons that do not satisfy our standard identification criteria. With a sample of 88 million BB̄ events collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we reconstruct 100±17 such events, with J/ψ→π-π -π0 being the most prevalent, and measure sin2β=1.56± 0.42(stat)±0.21(syst). © 2004 The American Physical Society

Search for second-class currents in tau(-) -> omega pi(-)nu(tau)

We report an analysis of tau(-) decaying into omega pi(-)nu(tau) with omega -> pi(+)pi(-)pi(0) using a data sample containing nearly 320 x 10(6)tau pairs collected with the BABAR detector at the PEP-II B-Factory. We find no evidence for second-class currents, and we set an upper limit of 0.69% at 90% confidence level for the fraction of second-class currents in this decay mode

Search for B-meson decays to b(1 rho) and b(1)K

We present a search for decays of B mesons to final states with a b(1) meson and a rho or K*(d892) meson. The search is based on a data sample consisting of 465 million B (B) over bar pairs collected by the BABAR detector at the SLAC National Accelerator Laboratory. We do not observe any statistically significant signal. The upper limits we set on the branching fractions range from 1.4 to 8.0 x 10(-6) at the 90% confidence level, including systematic uncertainties

B meson decays to charmless meson pairs containing eta or eta' mesons

We present updated measurements of the branching fractions for B-0 meson decays to eta K-0, eta eta, eta phi, eta omega, eta K-'(0), eta(')eta('), eta(')phi, and eta(')omega, and branching fractions and CP-violating charge asymmetries for B+ decays to eta pi(+), eta K+, eta(')pi(+), and eta K-'(+). The data represent the full data set of 467x10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at the SLAC National Accelerator Laboratory. Besides large signals for the four charged B decay modes and for B-0 ->eta K-'(0), we find evidence for three B-0 decay modes at greater than 3.0 sigma significance. We find B(B-0 ->eta K-0)=(1.15(-0.38)(+0.43)+/- 0.09)x10(-6), B(B-0 ->eta omega)=(0.94(-0.30)(+0.35)+/- 0.09)x10(-6), and B(B-0 ->eta(')omega)=(1.01(-0.38)(+0.46)+/- 0.09)x10(-6), where the first (second) uncertainty is statistical (systematic). For the B+->eta K+ decay mode, we measure the charge asymmetry A(ch)(B+->eta K+)=-0.36 +/- 0.11 +/- 0.03