Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma

Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma is measured using 232 fb-1 of data collected with the BABAR detector at 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. The asymmetry is determined as afunction 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- --> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order FSR production is consistent with the QED expectation for e+ e- --> mu+ mu- gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.

First Observation of CP Violation in B0->D(*)CP h0 Decays by a Combined Time-Dependent Analysis of BaBar and Belle Data

We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0 decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the neutral D meson is reconstructed in the CP eigenstates K+ K-, K0S pi0 or K0S omega. The measurement is performed combining the final data samples collected at the Y(4S) resonance by the BaBar and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06 (syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results correspond to the first observation of CP violation in B0->D(*)CP h0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.Comment: 9 pages, 2 figures, submitted to Physical Review Letter

Search for a light Higgs resonance in radiative decays of the ϒ(1S) with a charm tag

A search is presented for the decay ϒ(1S)→γA[superscript 0], A[superscript 0] → c[bar over c], where A[superscript 0] is a candidate for the CP-odd Higgs boson of the next-to-minimal supersymmetric standard model. The search is based on data collected with the BABAR detector at the ϒ(2S) resonance. A sample of ϒ(1S) mesons is selected via the decay ϒ(2S) → π[superscript +]π[superscript -]ϒ(1S). The A[superscript 0] → c[bar over c] decay is identified through the reconstruction of hadronic D[superscript 0], D[superscript +], and D[superscript *](2010)[superscript +] meson decays. No significant signal is observed. The measured 90% confidence-level upper limits on the product branching fraction B(ϒ(1S) → γA[superscript 0]) × B(A[superscript 0] → c[bar over c]) range from 7.4 × 10[superscript -5] to 2.4 × 10[superscript -3] for A[superscript 0] masses from 4.00 to 8.95  GeV/c[superscript 2] and 9.10 to 9.25  GeV/c[superscript 2], where the region between 8.95 and 9.10  GeV/c[superscript 2] is excluded because of background from ϒ(2S) → γχ[subscript bJ](1P), χ[subscript bJ](1P) → γϒ(1S) decays.United States. Dept. of EnergyNational Science Foundation (U.S.)United States-Israel Binational Science FoundationAlfred P. Sloan Foundatio

Light meson spectroscopy from Dalitz plot analyses ηc decays to η0K + K − , η0π + π − , and ηπ + π − produced in two-photon interactions

We study the processes γγ → ηc → η0KþK−, η0πþπ−, and ηπþπ− 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 Υ(nS) (n = 2, 3, 4) resonances. This is the first observation of the decay ηc → η0KþK− and we measure the branching fraction Γðηc → η0KþK−Þ=ðΓðηc → η0πþπ−Þ 1⁄4 0.644 0.039stat 0.032sys. Significant interference is observed between γγ → ηc → ηπþπ− and the nonresonant two-photon process γγ → ηπþπ−. A Dalitz plot analysis is performed of ηc decays to η0KþK−, η0πþπ−, and ηπþπ−. Combined with our previous analysis of ηc → KK ̄ π, we measure the K 0ð1430Þ parameters and the ratio between its η0K and πK couplings. The decay ηc → η0πþπ− is dominated by the f0ð2100Þ resonance, also observed in J=ψ radiative decays. A new a0(1700)→ ηπ resonance is observed in the ηc → ηπþπ− channel. We also compare ηc decays to η and η0 final states in association with scalar mesons as they relate to the identification of the scalar glueball

Search for rare or forbidden decays of the D0 meson

We present a search for nine lepton-number-violating and three lepton-flavor-violating neutral charm decays of the type D0→h'−h−ℓ'+ℓ+ and D0→h'−h+ℓ'±ℓ∓, where h and h′ represent a K or π meson and ℓ and ℓ′ an electron or muon. The analysis is based on 468 fb−1 of e+e− annihilation data collected at or close to the Υ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the twelve modes, and we establish 90% confidence level upper limits on the branching fractions in the range (1.0–30.6)×10−7. The limits are between 1 and 3 orders of magnitude more stringent than previous measurements.publishedVersio

Measurements of the absolute branching fractions of B± →k±Xc c

A study of the two-body decays B±→Xc¯cK±, where Xc¯c 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+→X(3872)K+ at the 3σ level. The absolute branching fraction B[B+→X(3872)K+]=[2.1±0.6(stat)±0.3(syst)]×10−4 is measured for the first time. It follows that B[X(3872)→J/ψπ+π−]=(4.1±1.3)%, supporting the hypothesis of a molecular component for this resonance.publishedVersio

Measurement of Collins asymmetries in inclusive production of charged pion pairs in e(+)e(-) annihilation at BABAR

We present measurements of Collins asymmetries in the inclusive process e(+)e(-) -> pi pi X, where p stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb(-1) collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis