Measurement of additional radiation in the initial-state-radiation processes e+e- →μ+μ-γ and e+e- →π+π-γ at BABAR

A dedicated measurement of additional radiation in e+e-→μ+μ-γ and e+e-→π+π-γ initial-state-radiation events is presented using the full BABAR data sample. For the first time results are presented at next-to- and next-to-next-to-leading order, with one and two additional photons, respectively, for radiation from the initial and final states. Comparison with predictions from phokhara and afkqed Monte Carlo generators is performed, revealing discrepancies in the one-photon rates and angular distributions for the former. This disagreement has a negligible effect on the BABAR measurement of the e+e-→π+π-(γ) cross section, but could affect other measurements significantly. This study sheds a new light on the longstanding discrepancy in this channel that affects the theoretical prediction of hadronic vacuum polarization contributions to the muon magnetic moment anomaly

Search for B mesogenesis at BaBar

A new mechanism has been proposed to simultaneously explain the presence of dark matter and the matter-antimatter asymmetry in the Universe. This scenario predicts exotic B -meson decays into a baryon and a dark-sector antibaryon (ψ D ) with branching fractions accessible at B factories. We present a search for B→ΛψD decays using data collected by the BABAR experiment at SLAC. This reaction is identified by fully reconstructing the accompanying B meson and requiring the presence of a single Λ baryon in the remaining particles. No significant signal is observed, and bounds on the B → Λ ψ D branching fraction are derived in the range 0.13 – 5.2 × 10 − 5 for 1.0 < m ψ D < 4.2 GeV / c 2. These results set strong constraints on the parameter space allowed by the theory

Search for heavy neutral leptons using tau lepton decays at <i>BaBaR</i>

This article presents a model-independent search for an additional, mostly sterile, heavy neutral lepton (HNL), that is capable of mixing with the Standard Model τ neutrino with a mixing strength of |Uτ4|2, corresponding to the absolute square of the extended Pontecorvo-Maki-Nakagawa-Sakata matrix element. Data from the BABAR experiment, with a total integrated luminosity of 424 fb-1, are analyzed using a kinematic approach that makes no assumptions on the model behind the origins of the HNL, its lifetime or decay modes. No significant signal is found. Upper limits on |Uτ4|2 at the 95% confidence level, depend on the HNL mass hypothesis and vary from 2.31×10-2 to 5.04×10-6 (with all uncertainties considered), across the mass range 100<m4<1300 MeV/c2; the more stringent limits being placed at higher masses

Study of the reactions e plus e- ? K+K-,r0,r0,r0, e+ e-?K0SK?,r?,r0,r0, and e plus e-? K0SK?,r?,r+,r- at center-of-mass energies from threshold to 4.5 GeV using initial-state radiation

We study the processes e+e-→K+K-π0π0π0γ, KS0K±π?π0π0γ, and KS0K±π?π+π-γ in which an energetic photon is radiated from the initial state. The data were collected with the BABAR detector at the SLAC National Accelerator Laboratory. About 1200, 2600, and 6000 events, respectively, are selected from a data sample corresponding to an integrated luminosity of 469 fb-1. The invariant mass of the hadronic final state defines the effective e+e- center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From the mass spectra, the first ever measurements of the e+e-→K+K-π0π0π0, e+e-→KS0K±π?π0π0, and e+e-→KS0K±π?π+π- cross sections are performed. The contributions from the intermediate states that include η, φ, ρ, K∗(892), and other resonances are presented. We observe the J/ψ and ψ(2S) in most of these final states and measure the corresponding branching fractions, many of them for the first time

Search for Rare or Forbidden Decays of the D^{0} Meson.

We present a search for nine lepton-number-violating and three lepton-flavor-violating neutral charm decays of the type D^{0}→h^{'-}h^{-}ℓ^{'+}ℓ^{+} and D^{0}→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

Study of the process e+e- →π+π-π0 using initial state radiation with BABAR

The process e+e-→π+π-π0γ is studied at a center-of-mass energy near the D(4S) resonance using a data sample of 469 fb-1 collected with the BABAR detector at the PEP-II collider. We have performed a precise measurement of the e+e-→π+π-π0 cross section in the center-of-mass energy range from 0.62 to 3.5 GeV. In the energy regions of the ω and φ resonances, the cross section is measured with a systematic uncertainty of 1.3%. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured e+e-→π+π-π0 cross section from threshold to 2.0 GeV is (45.86±0.14±0.58)×10-10. From the fit to the measured 3π mass spectrum we have determined the resonance parameters Γ(ω→e+e-)B(ω→π+π-π0)=(0.5698±0.0031±0.0082) keV, Γ(φ→e+e-)B(φ→π+π-π0)=(0.1841±0.0021±0.0080) keV, and B(ρ→3π)=(0.88±0.23±0.30)×10-4. The significance of the ρ→3π signal is greater than 6σ. For the J/ψ resonance we have measured the product Γ(J/ψ→e+e-)B(J/ψ→3π)=(0.1248±0.0019±0.0026) keV

Precision Measurement of the Ratio B(γ(3S) → τ+τ-)/B(γ(3S) → μ+μ-)

We report on a precision measurement of the ratio R_{τμ}^{ϒ(3S)}=B(ϒ(3S)→τ^{+}τ^{-})/B(ϒ(3S)→μ^{+}μ^{-}) using data collected with the BABAR detector at the SLAC PEP-II e^{+}e^{-} collider. The measurement is based on a 28  fb^{-1} data sample collected at a center-of-mass energy of 10.355&nbsp;GeV corresponding to a sample of 122 million ϒ(3S) mesons. The ratio is measured to be R_{τμ}^{ϒ(3S)}=0.966±0.008_{stat}±0.014_{syst} and is in agreement with the standard model prediction of 0.9948 within 2 standard deviations. The uncertainty in R_{τμ}^{ϒ(3S)} is almost an order of magnitude smaller than the only previous measurement

Resonances in e+e- annihilation near 2.2 GeV RESONANCES in E+E- ANNIHILATION NEAR 2.2 GEV LEES J. P. et al.

Using the initial-state radiation method, the e+e-→KSKL cross section from 1.98 to 2.54 GeV is measured in a data sample of 469 fb-1 collected with the BABAR detector. The results are used in conjunction with previous BABAR results for the e+e-→K+K-, e+e-→π+π-, e+e-→π+π-η, and e+e-→ωππ cross sections to investigate the nature of the resonance structure recently observed by the BESIII experiment in the e+e-→K+K- cross section

Measurements of the Absolute Branching Fractions of B^{±}→K^{±}X_{cc[over ¯]}.

A study of the two-body decays B^{±}→X_{cc[over ¯]}K^{±}, where X_{cc[over ¯]} 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