Search for Darkonium in e+e- Collisions

Collider searches for dark sectors, new particles interacting only feebly with ordinary matter, have largely focused on identifying signatures of new mediators, leaving much of dark sector structures unexplored. In particular, the existence of dark matter bound states (darkonia) remains to be investigated. This possibility could arise in a simple model in which a dark photon (A0 ) is light enough to generate an attractive force between dark fermions. We report herein a search for a JPC ¼ 1−− darkonium state, the ϒD, produced in the reaction eþe− → γϒD, ϒD → A0 A0 A0 , where the dark photons subsequently decay into pairs of leptons or pions, using 514 fb−1 of data collected with the BABAR detector. No significant signal is observed, and we set bounds on the γ − A0 kinetic mixing as a function of the dark sector coupling constant for 0.001 < mA0 < 3.16 GeV and 0.05 < mϒD < 9.5 GeV.publishedVersio

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 Υ(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

Study of the process e+e−→π+π−π0e^+e^-\to \pi^+\pi^-\pi^0 using initial state radiation with BABAR

International audienceThe process e+e-→π+π-π0γ is studied at a center-of-mass energy near the ϒ(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

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&lt;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

Study of the reactions e + e − → π + π − π0π0π0π0 and π + π − π0π0π0η at center-of-mass energies from threshold to 4.5 GeV using initial-state radiation

We study the processes e+e−→π+π−π0π0π0π0γ and π+π−π0π0π0ηγ 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 7300 and 870 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−→π+π−π0π0π0π0 and the e+e−→π+π−π0π0π0η cross sections are performed. The contributions from ωπ0π0π0, ηπ+π−π0, ωη, and other intermediate states 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

Study of the reactions e + e − → 2ðπ + π − Þπ0π0π0 and 2ðπ + π − Þπ0π0η at center-of-mass energies from threshold to 4.5 GeV using initial-state radiation

We study the processes e+e−→2(π+π−)π0π0π0γ and 2(π+π−)π0π0ηγ in which an energetic photon is radiated from the initial state. The data were collected with the BABAR detector at SLAC. About 14 000 and 4700 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−→2(π+π−)π0π0π0 and the e+e−→2(π+π−)π0π0η cross sections are performed. The contributions from ωπ+π−π0π0, η2(π+π−), and other intermediate states 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

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