Search for rare quark-annihilation decays, B --> Ds(*) Phi

We report on searches for B- --> Ds- Phi and B- --> Ds*- Phi. In the context of the Standard Model, these decays are expected to be highly suppressed since they proceed through annihilation of the b and u-bar quarks in the B- meson. Our results are based on 234 million Upsilon(4S) --> B Bbar decays collected with the BABAR detector at SLAC. We find no evidence for these decays, and we set Bayesian 90% confidence level upper limits on the branching fractions BF(B- --> Ds- Phi) Ds*- Phi)<1.2x10^(-5). These results are consistent with Standard Model expectations.Comment: 8 pages, 3 postscript figues, submitted to Phys. Rev. D (Rapid Communications

A Precision Measurement of the Lambda_c Baryon Mass

The $\Lambda_c^+$ baryon mass is measured using $\Lambda_c^+\to\Lambda K^0_S K^+$ and $\Lambda_c^+\to\Sigma^0 K^0_S K^+$ decays reconstructed in 232 fb$^{-1}$ of data collected with the BaBar detector at the PEP-II asymmetric-energy $e^+e^-$ storage ring. The $\Lambda_c^+$ mass is measured to be $2286.46\pm0.14\mathrm{MeV}/c^2$. The dominant systematic uncertainties arise from the amount of material in the tracking volume and from the magnetic field strength.Comment: 14 pages, 8 postscript figures, submitted to Phys. Rev.

Observation of the Decay B=> J/psi eta K and Search for X(3872)=> J/psi eta

We report the observation of the $B$ meson decay $B^\pm\to J/\psi \eta K^\pm$ and evidence for the decay $B^0\to J/\psi \eta K^0_S$, using {90} million $BBbar$ events collected at the \ensuremath{\Upsilon{(4S)}}\xspace resonance with the $BaBar$ detector at the PEP-II $e^+ e^-$ asymmetric-energy storage ring. We obtain branching fractions of $\cal{B}$$(B^\pm\to J/\psi \eta K^{\pm}$)=$(10.8\pm 2.3(\rm{stat.})\pm 2.4(\rm{syst.}))\times 10^{-5}$ and $\cal{B}$$(B^0\to J/\psi\eta K_{\rm{S}}^{0}$)=$(8.4\pm 2.6(\rm{stat.})\pm 2.7(\rm{syst.}))\times 10^{-5}$. We search for the new narrow mass state, the X(3872), recently reported by the Belle Collaboration, in the decay B^\pm\to X(3872)K^\pm, X(3872)\to \jpsi \eta and determine an upper limit of $\cal{B}$(B^\pm \to X(3872) K^\pm \to \jpsi \eta K^\pm) $<7.7\times 10^{-6}$ at 90% C.L.Comment: 7 pages and two figures, submitted to Phys. Rev. Lett

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Measurement of branching fractions and resonance contributions for B-0 ->(D)over-bar(0)K(+)pi(-) and search for B-0 ->(DK+)-K-0 pi(-) decays

Using 226x10(6) Upsilon(4S)-> B (B) over bar events collected with the BABAR detector at the PEP-II e(+)e(-) storage ring at the Stanford Linear Accelerator Center, we measure the branching fraction for B-0->(D) over bar (0)K(+)pi(-), excluding B-0-> D*-K+, to be B(B-0->(0)K(+)pi(-))=(88 +/- 15 +/- 9)x10(-6). We observe B-0->(D) over bar K-0(*)(892)(0) and B-0-> D-2(*)(2460)K--(+) contributions. The ratio of branching fractions B(B-0-> D*-K+)/B(B-0-> D(*-)pi(+))=(7.76 +/- 0.34 +/- 0.29)% is measured separately. The branching fraction for the suppressed mode B-0-> D(0)K(+)pi(-) is B(B-0-> D(0)K(+)pi(-))< 19x10(-6) at the 90% confidence level

Measurements of branching fractions and dalitz distributions for B-0 ->(DK0)-K-(*)+/-pi(-/+) decays

We present measurments of the branching fractions for the three-body decays B-0 -> D((*) -/+)K(0)pi(+/-) and their resonant submodes B0 -> D(*)K-/+*(+/-) usinga sample of approximately 88 x 10(6) B (B) over bar pairs collected by the BABER detector at the SLAC PEP-II assymetric energy storage ring. We measure: B(B-0-> D(-/+)K(0)pi(+/-)) = (4.9 +/- 0.7(stat) +/- 0.5(syst)) x 10(-4), B(B-0 -> D*(-/+)K(0)pi(+/-)) = (3.0 +/- 0.7(stat) +/- 0.3(syst)) x 10(-4), B(B-0 -> D-/+K*(+/-)) = (4.6 +/- 0.6(stat) +/- 0.5(syst)) x 10(-4), B(B-0 -> D*K-/+*(+/-) = (3.2 +/- 0.6(stat) +/- 0.3(syst)) x 10(-4). From these measurements we determine the fractions of resonant events to be f(B0 -> D+/-K*(-/+)) = 0.63 +/- 0.08(stat) +/- 0.04(syst) and f(B-0 -> D*K-/+*(+/-)) = 0.72 +/- 0.14(stat) +/- 0.05(syst)

Search for strange-pentaquark production in e(+)e(-) annihilation at root s=10.58 GeV

We search for strange-pentaquark states that have been previously reported by other experiments-the Theta(1540)(+), Xi(5)(1860)(--), and Xi(5)(1860)(0)-in 123 fb(-1) of data recorded with the BABAR detector at the PEP-II e(+)e(-) storage ring. We find no evidence for these states and set 95% confidence level upper limits on the number of Theta(1540)(+) and Xi(5)(1860)(--) pentaquarks produced per e(+)e(-) annihilation into q (q) over bar and per Upsilon(4S) decay. For q (q) over bar events the Theta(1540)(+) [Xi(5)(1860)(--)] limit is about 8 [4] times lower than the rates measured for ordinary baryons of similar mass

Measurements of the branching fraction and CP-violation asymmetries in B-0 -> f(0)(980)K-S(0)

We present measurements of the branching fraction and CP-violating asymmetries in the decay B-0-->f(0)(980)K-S(0). The results are obtained from a data sample of 123x10(6) Y(4S)-->B (B) over bar decays. From a time-dependent maximum likelihood fit, we measure the branching fraction B(B-0-->f(0)(980)(-->pi(+)pi(-))K-0)=(6.0+/-0.9+/-0.6+/-1.2)x10(-6), the mixing-induced CP violation parameter S=-1.62(-0.51)(+0.56)+/-0.09+/-0.04, and the direct CP violation parameter C=0.27+/-0.36+/-0.10+/-0.07, where the first errors are statistical, the second systematic, and the third due to model uncertainties. We measure the f(0)(980) mass and width to be m(f0)(980)=(980.6+/-4.1+/-0.5+/-4.0) MeV/c(2) and Gamma(f0)(980)=(43(-9)(+12)+/-3+/-9) MeV/c(2), respectively

Search for lepton-flavor violation in the decay tau(-)-> l(-)l(+)l-

A search for the lepton-flavor-violating decay of the tau into three charged leptons has been performed using 91.5 fb(-1) of data collected at an e(+)e(-)center-of-mass energy around 10.58 GeV with the BABAR detector at the SLAC storage ring PEP-II. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1-3)x10(-7) at 90% confidence level