BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2021). Light meson spectroscopy from Dalitz plot analyses of eta(c) decays to eta ' K+K-, eta 'pi(+)pi(-), and eta pi(+)pi(-) produced in two-photon interactions. Phys. Rev. D, 104(7), 072002–23pp.
Abstract: We study the processes gamma gamma -> eta(c )-> eta'K+K-, eta'pi(+)pi(-), and eta pi(+)pi(-) 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. This is the first observation of the decay eta(c)-> eta'K+K- and we measure the branching fraction Gamma (eta(c) -> eta' K+K- )/(Gamma(eta(c) -> eta'pi(+)pi(-)) = 0.644 +/- 0.039(stat) +/- 0.032(sys). Significant interference is observed between gamma gamma ->eta(c)->eta pi(+)pi(-) and the nonresonant two-photon process gamma gamma -> eta pi(+)pi(-). A Dalitz plot analysis is performed of eta(c) decays to eta'K+K-, eta'pi(+)pi(-) and eta pi(+)pi(-). Combined with our previous analysis of eta(c) -> K (K) over bar pi, we measure the K-0*(1430) parameters and the ratio between its eta'K and pi K couplings. The decay eta(c) -> eta'pi(+)pi(-) is dominated by the f(0)(2100) resonance, also observed in J/psi radiative decays. A new a(0) (1700) -> eta pi resonance is observed in the eta(c) -> eta pi(+)pi(-) channel. We also compare eta(c) decays to eta and eta' final states in association with scalar mesons as they relate to the identification of the scalar glueball.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2022). Search for Darkonium in e(+) e(-) Collisions. Phys. Rev. Lett., 128(2), 021802–7pp.
Abstract: 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 (A') is light enough to generate an attractive force between dark fermions. We report herein a search for a J(PC) = 1(--) darkonium state, the Upsilon(D), produced in the reaction e(+) e(-) -> gamma Upsilon(D), Upsilon(D) -> A'A'A', 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 gamma – A' kinetic mixing as a function of the dark sector coupling constant for 0.001 < m(A)' < 3.16 GeV and 0.05 < m(Upsilon D) < 9.5 GeV.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2021). Study of the reactions e(+)e(-)-> pi(+) pi(-) pi(0)pi(0)pi(0)pi(0) and pi(+) pi(-) pi(0)pi(0)pi(0)eta at center-of-mass energies from threshold to 4.5 GeV using initial-state radiation. Phys. Rev. D, 104(11), 112004–19pp.
Abstract: We study the processes e(+)e(-) -> pi+ pi-pi(0)pi(0)pi(0)pi(0)gamma and pi(+) pi(-) pi(0)pi(0)pi eta gamma 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(-) -> pi(+)pi(-) pi(0)pi(0)pi(0)pi(0) and the e(+)e(-) -> pi(+)pi(-) pi(0)pi(0)pi(0)eta cross sections are performed. The contributions from omega pi(0)pi(0)pi(0), eta pi(+)pi(-)pi(0), omega eta, and other intermediate states are presented. We observe the J=psi and psi(2S) in most of these final states and measure the corresponding branching fractions, many of them for the first time.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2021). Study of the process e(+) e(-) -> pi(+)pi (-) pi(0) using initial state radiation with BABAR. Phys. Rev. D, 104(11), 112003–31pp.
Abstract: The process e(+)e(-) -> pi(+) pi(-) pi(0)gamma is studied at a center-of-mass energy near the Upsilon(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(-) -> pi(+) pi(-) pi(0) cross section in the center-of-mass energy range from 0.62 to 3.5 GeV. In the energy regions of the omega and phi 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(-) -> pi(+) pi(-) pi(0) cross section from threshold to 2.0 GeV is (45.86 +/- 0.14 +/- 0.58) x 10(-10). From the fit to the measured 3 pi mass spectrum we have determined the resonance parameters Gamma(omega -> e(+)e(-)) B(omega -> pi(+) pi- pi(0)) = (0.5698 +/- 0.0031 +/- 0.0082) keV, Gamma(phi -> e(+)e(-)) B(phi -> pi(+) pi(-)pi(0)) = (0.1841 +/- 0.0021 +/- 0.0080) keV, and B(rho -> 3 pi) = (0.88 +/- 0.23 +/- 0.30) x 10(-4). The significance of the rho -> 3 pi signal is greater than 6 sigma. For the J/psi resonance we have measured the product Gamma(J/psi -> e(+) e(-)) B (J/psi -> 3 pi) = (0.1248 +/- 0.0019 +/- 0.0026) keV.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2022). Search for Lepton Flavor Violation in Upsilon(3S) -> e(+/-)mu(-/+). Phys. Rev. Lett., 128(9), 091804–7pp.
Abstract: We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state. We look for the LFV decay Upsilon(3S) -> e(+/-) mu(-/+) in a sample of 118 million gamma(3S) mesons from 27 fb(-1) of data collected with the BABAR detector at the SLAC PEP-II e(+) e(-) collider operating with a 10.36 GeV center-of-mass energy. No evidence for a signal is found, and we set a limit on the branching fraction B[Upsilon(3S) -> e(+/-) mu(-/+)] < 3.6 x 10(-7) at 90% C. L. This result can be interpreted as a limit Lambda(NP)/g(NP)(2) > 80 TeV on the energy scale Lambda(NT) divided by the coupling-squared g(NP)(2) of relevant new physics (NP).
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