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.

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

The BaBar detector: Upgrades, operation and performance

Contains fulltext : 121729.pdf (preprint version ) (Open Access

Study of e(+)e(-)->Lambda(Lambda)over-bar, Lambda(Sigma)over-bar(0), Sigma(0)(Sigma)over-bar(0) using initial state radiation with BABAR

We study the e(+)e(-)->Lambda(Lambda) over bar gamma, Lambda(Sigma) over bar (0)gamma, Sigma(0)(Sigma) over bar (0)gamma processes using 230 fb(-1) of integrated luminosity collected by the BABAR detector at e(+)e(-) center-of-mass energy of 10.58 GeV. From the analysis of the baryon-antibaryon mass spectra the cross sections for e(+)e(-)->Lambda(Lambda) over bar, Lambda(Sigma) over bar (0), Sigma(0)(Sigma) over bar>(0) are measured in the dibaryon mass range from threshold up to 3 GeV/c(2). The ratio of electric and magnetic form factors, |G(E)/G(M)|, is measured for e(+)e(-)->Lambda(Lambda) over bar, and limits on the relative phase between Lambda form factors are obtained. We also measure the J/psi ->Lambda(Lambda) over bar, Sigma(0)(Sigma) over bar (0), and psi(2S)->Lambda(Lambda) over bar branching fractions

Observation of the decay B+-> K+K-pi(+)

We report the observation of charmless hadronic decays of charged B mesons to the final state K+K-pi(+). Using a data sample of 347.5 fb(-1) collected at the Upsilon(4S) resonance with the BABAR detector, we observe 429 +/- 43 signal events with a significance of 9.6 sigma. We measure the inclusive branching fraction B(B+-> K+K-pi(+))=[5.0 +/- 0.5(stat)+/- 0.5(syst)]x10(-6). Inspection of the Dalitz plot of signal candidates shows a broad structure peaking near 1.5 GeV/c(2) in the K+K- invariant mass distribution. We find the direct CP asymmetry to be consistent with zero

Branching fraction and CP-violation charge asymmetry measurements for B-meson decays to ηK±, ηπ±, η′K, η′π±, ωK, and ωπ±

We present measurements of the branching fractions for B-0-meson decays to eta'K-0 and omega K-0, and of the branching fractions and CP-violation charge asymmetries for B+-meson decays to eta pi(+), eta K+, eta'pi(+), eta'K+, omega pi(+), and omega K+. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 383x10(6) B (B) over bar pairs produced in e(+)e(-) annihilation. The measurements agree with previous results; we find no evidence for direct CP violation

Production and decay of Ωc0

We present an analysis of inclusive Omega(0)(c) baryon production and decays in 230.5 fb(-1) of data recorded with the BABAR detector. Omega(0)(c) baryons are reconstructed in four final states (Omega(-)pi(+), Omega(-)pi(+)pi(0), Omega(-)pi(+)pi(+)pi(-), Xi K--(-)pi(+)pi(+)) and the corresponding ratios of branching fractions are measured. We also measure the momentum spectrum in the e(+)e(-) center-of-mass frame. From the spectrum, we observe Omega(0)(c) production from B decays and in c (c) over bar events, and extract the two rates of production