Search for a Dark Leptophilic Scalar in Collisions

Many scenarios of physics beyond the standard model predict the existence of new gauge singlets, which might be substantially lighter than the weak scale. The experimental constraints on additional scalars with masses in the MeV to GeV range could be significantly weakened if they interact predominantly with leptons rather than quarks. At an e+e- collider, such a leptophilic scalar (\u3c6L) would be produced predominantly through radiation from a \u3c4 lepton. We report herein a search for e+e-\u2192\u3c4+\u3c4-\u3c6L, \u3c6L\u2192\u2113+\u2113- (\u2113=e, \u3bc) using data collected by the BABAR experiment at SLAC. No significant signal is observed, and we set limits on the \u3c6L coupling to leptons in the range 0.04<7.0 GeV. These bounds significantly improve upon the current constraints, excluding almost entirely the parameter space favored by the observed discrepancy in the muon anomalous magnetic moment below 4 GeV at 90% confidence level

Measurement of the I=1/2 K pi S-wave amplitude from Dalitz plot analyses of eta(c) -> K(K)over-bar pi in two-photon interactions

We study the processes gamma gamma -> (KSK +/-)-K-0 pi(-/+) and gamma gamma -> K+K-pi(0) using a data sample of 519 fb(-1) recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e(+)e(-) collider at center-of-mass energies at and near the Upsilon(nS) (n = 2, 3, 4) resonances. We observe eta(c) decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the I = 1/2 K pi S-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of 1.5 GeV/c(2). In contrast, the amplitudes show very marked differences. The data require the presence of a new a(0)(1950) resonance with parameters m = 1931 +/- 14 +/- 22 MeV/c(2) and Gamma = 271 +/- 22 +/- 29 MeV

Measurements of the Absolute Branching Fractions of B-+/- -> K(+/-)Xc(c)over-bar

A study of the two-body decays B\ub1\u2192XccK\ub1, where Xcc refers to one charmonium state, is reported by the BABAR Collaboration using a data sample of 424 fb-1. The absolute determination of branching fractions for these decays are significantly improved compared to previous BABAR measurements. Evidence is found for the decay B+\u2192X(3872)K+ at the 3\u3c3 level. The absolute branching fraction B[B+\u2192X(3872)K+]=[2.1\ub10.6(stat)\ub10.3(syst)] 710-4 is measured for the first time. It follows that B[X(3872)\u2192J/\u3c8\u3c0+\u3c0-]=(4.1\ub11.3)%, supporting the hypothesis of a molecular component for this resonance

Measurement of initial-state-final-state radiation interference in the processes e+e- →μ+μ-γ and e+e- →π+π-γ

Charge asymmetry in the processes e+e-→μ+μ-γ and e+e-→π+π-γ is measured using 232 fb-1 of data collected with the BABAR detector at e+e- center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial- and final-state radiation (FSR). The asymmetry is determined as a function of the invariant mass of the final-state tracks from production threshold to a few GeV/c2. It is compared to the expectation from QED for e+e-→μ+μ-γ, and from theoretical models for e+e-→π+π-γ. A clear interference pattern is observed in e+e-→π+π-γ, particularly in the vicinity of the f2(1270) resonance. The inferred rate of lowest-order FSR production is consistent with the QED expectation for e+e-→μ+μ-γ, and is negligibly small for e+e-→π+π-γ. © 2015 American Physical Society

Collins asymmetries in inclusive charged KK and K pi pairs produced in e(+)e(-) annihilation

We present measurements of Collins asymmetries in the inclusive process e(+)e(-) -> h(1)h(2)X, h(1)h(2) = KK, K pi, pi pi, at the center-of-mass energy of 10.6 GeV, using a data sample of 468 fb(-1) collected by the BABAR experiment at the PEP-II B factory at SLAC National Accelerator Center. Considering hadrons in opposite thrust hemispheres of hadronic events, we observe clear azimuthal asymmetries in the ratio of unlike sign to like sign, and unlike sign to all charged h(1)h(2) pairs, which increase with hadron energies. The K pi asymmetries are similar to those measured for the pi pi pairs, whereas those measured for high-energy KK pairs are, in general, larger

Observation of (B)over-bar -> D-(*()) pi(+)pi(-)l(-)(nu)over-bar Decays in e(+)e(-) Collisions at the Upsilon(4S) Resonance

We report on measurements of the decays of B\uaf mesons into the semileptonic final states B\uaf\u2192D( 17)\u3c0+\u3c0-\u3bd\uaf, where D( 17) represents a D or D 17 meson and - is an electron or a muon. These measurements are based on 471 7106 BB\uaf pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R\u3c0+\u3c0-( 17)=B(B\uaf\u2192D( 17)\u3c0+\u3c0-\u3bd\uaf)/B(B\uaf\u2192D( 17)-\u3bd\uaf) using events in which the second B meson is fully reconstructed. We find R\u3c0+\u3c0-=0.067\ub10.010\ub10.008 and R\u3c0+\u3c0- 17=0.019\ub10.005\ub10.004, where the first uncertainty is statistical and the second is systematic. Based on these results and assuming isospin invariance, we estimate that B\uaf\u2192D( 17)\u3c0\u3c0-\u3bd\uaf decays, where \u3c0 denotes either a \u3c0\ub1 and \u3c00 meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions

SuperB: A High-Luminosity Asymmetric e+ e- Super Flavor Factory. Conceptual Design Report

The physics objectives of SuperB, an asymmetric electron-positron collider with a luminosity above 10^36/cm^2/s are described, together with the conceptual design of a novel low emittance design that achieves this performance with wallplug power comparable to that of the current B Factories, and an upgraded detector capable of doing the physics in the SuperB environment

Observation of the baryonic decay (B)over-bar(0) -> Lambda(+)(c)(p)over-barK(-)K(+)

We report the observation of the baryonic decay B\uaf0\u2192\u39bc+p\uafK-K+ using a data sample of 471 7106 BB\uaf pairs produced in e+e- annihilations at s=10.58GeV. This data sample was recorded with the BABAR detector at the PEP-II storage ring at SLAC. We find B(B\uaf0\u2192\u39bc+p\uafK-K+)=(2.5\ub10.4(stat)\ub10.2(syst)\ub10.6B(\u39bc+)) 710-5, where the uncertainties are statistical, systematic, and due to the uncertainty of the \u39bc+\u2192pK-\u3c0+ branching fraction, respectively. The result has a significance corresponding to 5.0 standard deviations, including all uncertainties. For the resonant decay B\uaf0\u2192\u39bc+p\uaf\u3c6, we determine the upper limit B(B\uaf0\u2192\u39bc+p\uaf\u3c6)<1.2 710-5 at 90% confidence level

Measurement of the branching fractions of the radiative leptonic tau decays tau -> e gamma v(v)over-bar and tau -> mu gamma v(v)over-bar at BABAR

We perform a measurement of the tau -> l gamma v (v) over bar (l = e, mu) branching fractions for a minimum photon energy of 10 MeV in the tau rest frame, using 431 fb(-1) of e(+) e(-) collisions collected at the center-of-mass energy of the Upsilon(4S) resonance with the BABAR detector at the PEP-II storage rings. We find B(tau -> mu gamma v (v) over bar = (3.69 +/- 0.03 +/- 0.10) x 10(-3) and B(tau -> e gamma v (v) over bar = (1.847 +/- 0.015 +/- 0.052) x 10(-2), where the first quoted error is statistical and the second is systematic. These results are substantially more precise than previous measurements