Search

A mechanism of baryogenesis and dark matter production via $B$-meson oscillations and decays has recently been proposed to explain the observed dark matter abundance and matter-antimatter asymmetry in the universe. This mechanism introduces a light dark sector particle ($\psi_D$) with a non-zero baryonic charge. We present a search for this new state in $B^+ \to \Lambda_c^+ \, \psi_D$ decays using data collected at the $\Upsilon(4S)$ resonance by the BABAR detector at SLAC, corresponding to an integrated luminosity of $431.0 \rm{~fb}^{-1}$. The search leverages the full reconstruction of the $B^-$ meson in $\Upsilon(4S) \to B^+B^-$ decays, accompanied by the reconstruction of a $\Lambda_c^+$, to infer the presence of $\psi_D$. No significant signal is observed, and limits on the $B^+ \to \Lambda_c^+ \, \psi_D$ branching fraction are set at the level of $1.6 \times 10^{-4}$ at 90% confidence level for $0.94 < m_{\psi_D} < 2.99$ GeV. These results set strong constraints on the parameter space allowed by $B$-meson baryogenesis., Comment: 7 pages, 5 figures, published version

A dedicated measurement of additional radiation in $e^+e^-\to\mu^+\mu^-\gamma$ and $e^+e^-\to\pi^+\pi^-\gamma$ 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 $e^+e^-\to\pi^+\pi^-(\gamma)$ 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., Comment: 9 pages, 8 figures and 1 table, v2 corresponds to the published version

We present a new technique, `Tau Polarimetry', for measuring the longitudinal beam polarization present in an $e^+e^-$ collider through the analysis of $e^+e^-\rightarrow\tau^+\tau^-$ events. By exploiting the sensitivity of $\tau$ decay kinematics to the longitudinal polarization of the beams, we demonstrate that the longitudinal polarization can be measured with a 3 per mil systematic uncertainty at the interaction point using a technique that is independent of spin and beam transport modeling. Using 424.2$\pm$1.8 fb$^{-1}$ of BABAR data at $\sqrt{s}=10.58$ GeV, the average longitudinal polarization of the PEP-II $e^+e^-$ collider has been measured to be $\langle P\rangle=0.0035 \pm 0.0024_{\textrm{stat}}\pm 0.0029_{\textrm{sys}}$. The systematic uncertainty studies are described in detail, which can serve as a guide for future applications of Tau Polarimetry. A proposed $e^-$ beam longitudinal polarization upgrade to the SuperKEKB $e^+e^-$ collider would benefit from this technique.

A new dark sector anti-baryon, denoted $\psi_{\text{D}}$, could be produced in decays of $B$ mesons. This letter presents a search for $B^{+} \rightarrow \psi_{\text{D}} + \text{p}$ (and the charge conjugate) decays in $e^{+}e^{-}$ annihilations at 10.58 GeV, using data collected in the ~\babar~ experiment. Data corresponding to an integrated luminosity of 398 fb$^{-1}$ are analyzed. No evidence for a signal is observed. Branching fraction upper limits in the range from $10^{-7} $ -- $ 10^{-5}$ are obtained at 90$\%$ confidence level for masses of 1.0 $< m_{\psi_{\text{D}}} < $ 4.3 GeV/c$^{2}$. The result is also reinterpreted to provide the first limits on a supersymmetric model with R-parity violation and a light neutralino., Comment: 5 pages, 6 figures

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 anti-baryon ($\psi_D$) with branching fractions accessible at $B$ factories. We present a search for $B \rightarrow \Lambda \psi_D$ 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 $\Lambda$ baryon in the remaining particles. No significant signal is observed, and bounds on the $B \rightarrow \Lambda \psi_D$ branching fraction are derived in the range $0.13 - 5.2\times 10^{-5}$ for $1.0 < m_{\psi_D} < 4.2$ GeV/$c^{2}$. These results set strong constraints on the parameter space allowed by the theory.

We study the processes $e^+e^-\to K^+K^-\pi^0\pi^0\pi^0\gamma$, $K^{0}_{S}K^{\pm}\pi^{\mp}\pi^0\pi^0\gamma$, and $K^{0}_{S}K^{\pm}\pi^{\mp}\pi^+\pi^-\gamma$ 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 1200, 2600, and 6000 events, respectively, are selected from a data sample corresponding to an integrated luminosity of 469\invfb. The invariant mass of the hadronic final state defines the effective \epem 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 $e^+e^-\to K^+K^-\pi^0\pi^0\pi^0$, $e^+e^-\to K^0_SK^{\pm}\pi^{\mp}\pi^0\pi^0$, and $e^+e^-\to K^0_SK^{\pm}\pi^{\mp}\pi^+\pi^-$ cross sections are performed. The contributions from the intermediate states that include $\eta$, $\phi$, $\rho$, $K^*(892)$, and other resonances 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., Comment: 17 pages, 15 figures

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 $\tau$ neutrino with a mixing strength of $|U_{\tau 4}|^{2}$, corresponding to the absolute square of the extended Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix element. Data from the \babar~ experiment, with a total integrated luminosity of $424~ \text{fb}^{-1}$, 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 $|U_{\tau 4}|^{2}$ at the 95$\%$ confidence level, depend on the HNL mass hypothesis and vary from $2.31 \times 10^{-2}$ to $5.04 \times 10^{-6}$ (with all uncertainties considered), across the mass range $100 < m_{4} < 1300 ~\text{MeV}/c^{2}$; the more stringent limits being placed at higher masses., Comment: 20 pages, 10 figures

Axion-like particles (ALPs) are predicted in many extensions of the Standard Model, and their masses can naturally be well below the electroweak scale. In the presence of couplings to electroweak bosons, these particles could be emitted in flavor-changing $B$ meson decays. We report herein a search for an ALP, $a$, in the reaction $B^\pm\rightarrow K^\pm a$, $a\rightarrow\gamma\gamma$ using data collected by the BABAR experiment at SLAC. No significant signal is observed, and 90% confidence level upper limits on the ALP coupling to electroweak bosons are derived as a function of ALP mass, improving current constraints by several orders of magnitude in the range $0.175\,\,\mathrm{GeV} < m_a < 4.78\,\,\mathrm{GeV}$., Comment: 11 pages, 8 figures, submitted to Phys. Rev. Lett

We study the processes $e^+e^-\to\pi^+\pi^-\pi^0\pi^0\pi^0\pi^0\gamma$ and $e^+e^-\to\pi^+\pi^-\pi^0\pi^0\pi^0\eta\gamma$ 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 $e^+e^-\to\pi^+\pi^-\pi^0\pi^0\pi^0\pi^0$ and the $e^+e^-\to\pi^+\pi^-\pi^0\pi^0\pi^0\eta$ 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., Comment: 20 pages, 27 figures

The process $e^+e^-\to \pi^+\pi^-\pi^0\gamma$ 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 $e^+e^-\to \pi^+\pi^-\pi^0$ 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 $e^+e^-\to \pi^+\pi^-\pi^0$ cross section from threshold to 2.0 GeV is $(45.86 \pm 0.14 \pm 0.58)\times 10^{-10}$. From the fit to the measured $3\pi$ mass spectrum we have determined the resonance parameters $\Gamma(\omega\to e^+e^-){\cal B}(\omega\to \pi^+\pi^-\pi^0)=(0.5698\pm0.0031\pm0.0082) \mbox{ keV}$, $\Gamma(\phi\to e^+e^-){\cal B}(\phi\to \pi^+\pi^-\pi^0)=(0.1841\pm0.0021\pm0.0080) \mbox{ keV}$, and ${\cal B}(\rho\to 3\pi)=(0.88\pm 0.23\pm 0.30)\times 10^{-4}$. The significance of the $\rho\to 3\pi$ signal is greater than $6\sigma$. For the $J/\psi$ resonance we have measured the product ${\Gamma(J/\psi\to e^+e^-){\cal B}(J/\psi\to 3\pi)}=(0.1248\pm0.0019\pm0.0026)\mbox{ keV}$., Comment: 35 pages, 28 figures, corrected cross section in Table IV

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 $\Upsilon (3S)\rightarrow e^{\pm}\mu^{\mp}$ in a sample of 118~million $\Upsilon (3S)$ 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 $\mathcal{B}(\Upsilon(3S)\rightarrow e^{\pm}\mu^{\mp})<3.6\times10^{-7}\mathrm{at~ 90\%~ CL}$. This result can be interpreted as a limit $\Lambda_{NP}/g^2_{NP} > 80~$TeV on the energy scale $\Lambda_{NP}$ divided by the coupling-squared $g^2_{NP}$ of relevant new physics.

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 $e^+e^- \rightarrow \gamma \Upsilon_D, \Upsilon_D \rightarrow A' A' A'$, where the dark photons subsequently decay into pairs of leptons or pions, using $514\text{ fb}^{-1}$ 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 $0.001 < m_{A'} < 3.16 \text{ GeV}$ and $0.05 < m_{\Upsilon_D} < 9.5 \text{ GeV}$., Comment: 10 pages, 22 figures, submitted to Phys. Rev. Lett

We study the processes $e^+e^-\to 2(\pi^+\pi^-)\pi^0\pi^0\pi^0\gamma$ and $2(\pi^+\pi^-)\pi^0\pi^0\eta\gamma$ 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 \epem 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 $e^+e^-\to 2(\pi^+\pi^-)\pi^0\pi^0\pi^0$ and the $e^+e^-\to2(\pi^+\pi^-)\pi^0\pi^0\eta$ cross sections are performed. The contributions from $\omega\pi^+\pi^-\pi^0\pi^0$, $\eta2(\pi^+\pi^-)$, 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., Comment: 22 pages, 31 pdf figures, submitted to PRD

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 ($\phi_L$) would be produced predominantly through radiation from a $\tau$ lepton. We report herein a search for $e^+e^- \to \tau^+\tau^- \phi_L$, $\phi_L \to \ell^+\ell^-$ ($\ell=e,\mu$) using data collected by the BABAR experiment at SLAC. No significant signal is observed, and we set limits on the $\phi_L$ coupling to leptons in the range 0.04 < m$_{\phi_L}$ < 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., Comment: 7 pages, 7 figures, published version

We present a search for seven lepton-flavor-violating neutral charm decays of the type $D^{0}\rightarrow X^{0} e^{\pm} \mu^{\mp}$, where $X^{0}$ represents a $\pi^{0}$, $K^{0}_{\rm S}$, $\bar{K^{*0}}$, $\rho^{0}$, $\phi$, $\omega$, or $\eta$ meson. The analysis is based on $468$ fb$^{-1}$ of $e^+e^-$ annihilation data collected at or close to the $\Upsilon(4S)$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory. No significant signals are observed, and we establish 90\% confidence level upper limits on the branching fractions in the range $(5.0 - 22.5)\times 10^{-7}$. The limits are between one and two orders of magnitude more stringent than previous measurements., Comment: 12 pages, 2 figures, to be submitted to Physical Review D. arXiv admin note: text overlap with arXiv:1905.00608

Using the initial-state radiation method, the $e^+e^- \to K_S K_L$ 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 $e^+e^- \to K^+ K^-$, $e^+e^- \to \pi^+\pi^-$, $e^+e^- \to \pi^+\pi^-\eta$, and $e^+e^- \to \omega\pi\pi$ cross sections to investigate the nature of the resonance structure recently observed by the BESIII experiment in the $e^+e^- \to K^+ K^-$ cross section., Comment: 11 pages, 6 figures

We search for the rare flavor-changing neutral current process $B^- \to \Lambda {\overline p} \nu{\overline{\nu}}$ using data from the BABAR experiment. A total of 424 fb$^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy of the $\Upsilon$(4S) resonance is used in this study, corresponding to a sample of ${(471 \pm 3) \times 10^{6}}$ $B\overline{B}$ pairs. Signal $B^- \to \Lambda {\overline p} \nu{\overline{\nu}}$ candidates are identified by first fully reconstructing a $B^+$ decay in one of many possible exclusive decays to hadronic final states, then examining detector activity that is not associated with this reconstructed $B^+$ decay for evidence of a signal $B^- \to \Lambda {\overline p} \nu{\overline{\nu}}$ decay. The data yield is found to be consistent with the expected background contribution under a null signal hypothesis, resulting in an upper limit of ${{\cal B} (B^- \to \Lambda {\overline p} \nu{\overline{\nu}}) < 3.0\times 10^{-5}}$ at the $90\%$ confidence level., Comment: 10 pages, 7 figures

We report the observation of the rare charm decay $D^0\rightarrow K^-\pi^+e^+e^-$, based on $468$ fb$^{-1}$ of $e^+e^-$ annihilation data collected at or close to the center-of-mass energy of the $Y(4S)$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory. We find the branching fraction in the invariant mass range $0.675< m(e^+e^-) < 0.875 GeV/c^2$ of the electron-positron pair to be ${\cal B}(D^0\rightarrow K^-\pi^+e^+e^-) = (4.0\pm0.5\pm0.2\pm0.1) \times 10^{-6}$, where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty in the branching fraction of the decay $D^0\rightarrow K^-\pi^+\pi^+\pi^-$ used as a normalization mode. The significance of the observation corresponds to 9.7 standard deviations including systematic uncertainties. This result is consistent with the recently reported $D^0\rightarrow K^-\pi^+\mu^+\mu^-$ branching fraction, measured in the same invariant mass range, and with the value expected in the Standard Model. In a set of regions of $m(e^+e^-)$ where long-distance effects are potentially small, we determine a 90% confidence level upper limit on the branching fraction ${\cal B}(D^0\rightarrow K^-\pi^+e^+e^-) < 3.1 \times 10^{-6}$., Comment: 7 pages, 3 figures

We study the process $e^+e^-\to e^+e^- \eta'$ in the double-tag mode and measure for the first time the $\gamma^{\star}\gamma^{\star} \to \eta'$ transition form factor $F_{\eta'}(Q_1^2, Q_2^2)$ in the momentum-transfer range \mbox{2 $

The decay $\tau^{-}\to K^{-}K_S\nu_{\tau}$ has been studied using $430\times10^6$ $e^+e^-\to \tau^+\tau^-$ events produced at a center-of-mass energy around 10.6 GeV at the PEP-II collider and studied with the BABAR detector. The mass spectrum of the $K^{-}K_S$ system has been measured and the spectral function has been obtained. The measured branching fraction ${\cal B}(\tau^{-}\to K^{-}K_S\nu_{\tau}) = (0.739\pm 0.011(\rm stat.)\pm 0.020(\rm syst.))\times 10^{-3}$ is found to be in agreement with earlier measurements., Comment: 12 pages, 13 figures, submitted to Phys. Rev. D

A search is presented for the four-body decay $B^0\rightarrow p p \bar{p} \bar{p}$ in a sample of $471$ million $B\bar{B}$ pairs collected with the BaBar detector, operated at the SLAC PEP-II asymmetric-energy $e^+e^-$ collider. The center-of-mass energy is $10.58$ GeV. From a fit to the distribution of the energy-substituted mass $m_{\mathrm{ES}}$, the result $\mathcal{B}(B^0\rightarrow p p \bar{p} \bar{p})=(1.1 \pm 0.5 \pm 0.2) \times 10^{-7}$ is extracted, where the first uncertainty is statistical and the second is systematic. The significance of the signal is $2.9$ standard deviations. The upper limit on the branching fraction is determined to be $2.0 \times 10^{-7}$ at $90\%$ confidence level., Comment: 7 pages, 6 figures. To be submitted to Phys. Rev. D (Rapid Communications)

We study the process $e^+e^- \to \pi^+\pi^-\eta \gamma$, where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BaBar data sample with an integrated luminosity of 469~fb$^{-1}$. Using the $\pi^+\pi^-\eta$ invariant mass spectrum we measure the $e^+e^- \to \pi^+\pi^-\eta$ cross section in the $e^+e^-$ center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson Dominance model with four $\rho$-like states. We observe $49\pm9$ events of the $J/\psi$ decay to $\pi^+\pi^-\eta$, and measure the product $\Gamma_{J/\Psi \to e^+e^-} \text{B}_{J/\Psi \to \pi^+\pi^-\eta} = 2.34 \pm 0.43_{\text{stat}} \pm 0.16_{\text{syst}}$~eV., Comment: 17 pages, 21 postscript figues, submitted to Phys. Rev. D

The process $e^+e^- \to \pi^+\pi^-2\pi^0\gamma$ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using $454.3 \rm{fb}^{-1}$ of data collected around a center-of-mass energy of $\sqrt{s} = 10.58 \rm{GeV}$ by the BaBar experiment at SLAC, approximately 150000 signal events are obtained. The corresponding non-radiative cross section is measured with a relative uncertainty of $3.6\%$ in the energy region around $1.5 \rm{GeV}$, surpassing all existing measurements in precision. Using this new result, the channel's contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as $(g_\mu^{\pi^+\pi^-2\pi^0}-2)/2 = (17.9 \pm 0.1_\mathrm{stat} \pm 0.6_\mathrm{syst}) \times 10^{-10}$ in the energy range $0.85\rm{GeV} < E_\mathrm{CM} < 1.8\rm{GeV}$. In the same energy range, the impact on the running of the fine structure constant at the $Z^0$-pole is determined as $\Delta\alpha^{\pi^+\pi^-2\pi^0}(M^2_\mathrm{Z}) = (4.44 \pm 0.02_\mathrm{stat} \pm 0.14_\mathrm{syst}) \times 10^{-4}$. Furthermore, intermediate resonances are studied and especially the cross section of the process $e^+e^- \to \omega\pi^0 \to \pi^+\pi^-2\pi^0$ is measured., Comment: Version accepted by PRD. 19 pages, 21 figures

We measure the mass difference, $\Delta m_+$, between the $D^{*}(2010)^+$ and the $D^+$ using the decay chain $D^{*}(2010)^+\to D^+ \pi^0$ with $D^+\to K^-\pi^+\pi^+$. The data were recorded with the BABAR detector at center-of-mass energies at and near the $\Upsilon(4S)$ resonance, and correspond to an integrated luminosity of approximately 468 ${\rm fb}^{-1}$. We measure $\Delta m_+ = \left(140\,601.0 \pm 6.8[{\rm stat}] \pm 12.9[{\rm syst}]\right)$ keV. We combine this result with a previous BABAR measurement of $\Delta m_0\equiv m(D^{*}(2010)^+) - m (D^0)$ to obtain $\Delta m_D = m(D^+) - m(D^0) = \left(4\,824.9 \pm 6.8[{\rm stat}] \pm 12.9[{\rm syst}]\right)$ keV. These results are compatible with and approximately five times more precise than the Particle Data Group averages., Comment: 7 pages, 3 figures, submitted to Physical Review Letters

The processes $e^+e^-\to K^0_{\scriptscriptstyle S}K^\pm\pi^{\mp}\pi^0$ and $e^+e^-\to K^0_{\scriptscriptstyle S}K^\pm\pi^{\mp}\eta$ are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb$^{-1}$ data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from $K^{*0}(K\pi)^0$, $K^{*}(892)^\pm(K\pi)^\mp$ and $K^0_{\scriptscriptstyle S}K^\pm\rho^{\mp}$ are studied. The $J/\psi$ is observed in all of these channels, and corresponding branching fractions are measured., Comment: 19 pages, 38 figures

We study the processes $e^+ e^- \to \ \gamma_{\rm ISR} J/\psi$ where $J/\psi \to \pi^+ \pi^- \pi^0$, $J/\psi \to K^+ K^- \pi^0$, and $J/\psi \to K^0_S K^{\pm} \pi^{\mp}$ 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 measure the ratio of branching fractions $R_1 = \frac{B(J/\psi \ \to \ K^+ K^- \pi^0)}{B(J/\psi \ \to \ \pi^+ \pi^- \pi^0)}$ and $R_2 = \frac{B(J/\psi \ \to \ K^0_S K^{\pm} \pi^{\mp})}{B(J/\psi \ \to \ \pi^+ \pi^- \pi^0)}$. We perform Dalitz-plot analyses of the three $J/\psi$ decay modes and measure fractions for resonances contributing to the decays. We also analyze the $J/\psi \to \pi^+ \pi^- \pi^0$ decay using the Veneziano model. We observe structures compatible with the presence of $\rho(1450)$ in all the three $J/\psi$ decay modes and measure the relative branching fraction: $R(\rho(1450)) = \frac{B(\rho(1450) \ \to \ K^+ K^-)}{B(\rho(1450) \ \to \ \pi^+ \pi^-)} = 0.307 \pm 0.084 ({\rm stat}) \pm 0.082 ({\rm sys})$., Comment: 22 pages, 17 postscript figures, to be published in Phys. Rev. D

We study the processes $e^+ e^-\to K^0_S K^0_L\pi^0\gamma$, $K^0_S K^0_L\eta\gamma$, and $K^0_S K^0_L\pi^0\pi^0\gamma$, where the photon is radiated from the initial state, providing cross section measurements for the hadronic final states over a continuum of center-of-mass energies. The results are based on 469~$fb^{-1}$ of data collected at or near the $\Upsilon(4S)$~ resonance with the BaBar detector at SLAC. We present the first measurements of the $e^+ e^-\to K^0_S K^0_L\pi^0$, $K^0_S K^0_L\eta$, and $K^0_S K^0_L\pi^0\pi^0$ cross sections up to a center-of-mass energy of 4~GeV, and study their intermediate resonance structures. We observe $J/\psi$ decays to all of these final states for the first time, present measurements of their $J/\psi$ branching fractions, and search for $\psi(2S)$ decays., Comment: 18 pages, 27 postscript figures

Based on the full BaBar data sample of 466.5 million BBbar pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B -> Xu e nu decays from the CKM-favored B -> Xc e nu decays, and from various other backgrounds, and determine the total semileptonic branching fraction BR(B -> X e nu) = (10.34 +- 0.04_stat +- 0.26_syst)%, averaged over B+- and B0 mesons. We determine the spectrum and branching fraction for charmless B -> Xu e nu decays and extract the CKM element |Vub|, by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1GeV/c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element |Vub| are presented, with the lower limit on the electron momentum varied from 0.8GeV/c to the kinematic endpoint. We determine |Vub| using each of these different calculations and find, |Vub| = (3.794 +- 0.107_exp +0.292-0.219_SF +0.078-0.068_theory)*10^{-3} (De Fazio and Neubert), (4.563 +- 0.126_exp +0.230-0.208_SF +0.162-0.163_theory)*10^{-3} (Bosh, Lange, Neubert, and Paz), (3.959 +- 0.104_exp +0.164-0.154_SF +0.042-0.079_theory)*10^{-3} (Gambino, Giordano, Ossola, and Uraltsev), (3.848 +- 0.108_exp +0.084-0.070_theory)*10^{-3} (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations., Comment: 27 pages, 42 postscript figures, Published in Phys. Rev. D95, 072001 (2017)

Using a sample of (470.9 +- 2.8) x 10^6 BB-bar pairs, we measure the decay branching fraction B(B^0 -> D^*- pi^+ pi^- pi^+) = (7.26 +- 0.11 +- 0.31) x 10^-3, where the first uncertainty is statistical and the second is systematic. Our measurement will be helpful in studies of lepton universality by measuring B(B^0 -> D^*- tau^+ nu_tau) using tau^+ -> pi^+ pi^- pi^+ nu-bar_tau decays, normalized to B(B^0 -> D^*- pi^+ pi^- pi^+., Comment: 7 pages, 3 postscript figures, submitted to PRD-RC

Many models of physics beyond the Standard Model predict the existence of new Abelian forces with new gauge bosons mediating interactions between "dark sectors" and the Standard Model. We report a search for a dark boson Z' coupling only to the second and third generations of leptons in the reaction e+e- -> mu+mu- Z', Z' -> mu+mu- using 514 fb-1 of data collected by the BABAR experiment. No significant signal is observed for Z' masses in the range 0.212 - 10 GeV. Limits on the coupling parameter g' as low as 7x10^-4 are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments., Comment: 6 pages, 5 figures, submitted to Phys. Rev. D (Rapid Communications)

We search for the rare flavor-changing neutral current process $B^{+}\rightarrow K^{+}\tau^{+}\tau^{-}$ using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the $\Upsilon{(4S)}$ resonance, corresponds to a total integrated luminosity of 424 fb$^{-1}$ and to 471 million $B\overline{B}$ pairs. We reconstruct one $B$ meson, produced in the $\Upsilon{(4S)}\rightarrow B^{+} B^{-}$ decay, in one of many hadronic decay modes and search for activity compatible with a $B^{+}\rightarrow K^{+} \tau^{+}\tau^{-}$ decay in the rest of the event. Each $\tau$ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The measured branching fraction is ($1.31^{+0.66}_{-0.61}$( stat.)$^{+0.35}_{-0.25}$( sys.)$) \times 10^{-3}$ with an upper limit, at the 90\% confidence level, of $\mathcal{B}(B^{+}\rightarrow K^{+}\tau^{+}\tau^{-})$$< 2.25\times 10^{-3}$., Comment: 7 pages, 1 pdf figure and 2 postscipt figures

Using the eight time dependences for the decays Upsilon(4S)-> B0 B0bar -> fj fk with the dacay into a flavor-specific state fj = ell+- X before or after the decay into a CP eigenstate fk = c cbar KS,KL, as measured by the BABAR experiment, we determine the three CPT-sensitive parameters Re(z) and Im(z) in B0-B0bar mixing and |Abar/A| in B0 -> c cbar K0 decays. We find Im(z) = 0.010 +- 0.030 +- 0.013, Re(z) = -0.065 +- 0.028 +- 0.014, and |Abar/A| = 0.999 +- 0.023 +- 0.017, in agreement with CPT symmetry., Comment: 7 pages, no figures

We measure the $D^0 - {\bar{D}}^0$ mixing parameters using a time-dependent amplitude analysis of the decay $D^0\to\pi^+\pi^-\pi^0$. The data were recorded with the BABAR detector at center-of-mass energies at and near the $\Upsilon(4S)$ resonance, and correspond to an integrated luminosity of approximately 468.1 ${\rm fb}^{-1}$. The neutral $D$ meson candidates are selected from $D^{*}(2010)^+\to D^0 \pi_s^+$ decays where the flavor at the production is identified by the charge of the low momentum pion, $\pi_s^+$. The measured mixing parameters are $x = (1.5\pm1.2\pm0.6) \%$ and $y = (0.2\pm0.9\pm0.5) \%$, where the quoted uncertainties are statistical and systematic, respectively., Comment: 11 pages, 2 figures, to be published in Phys. Rev. D

We study the processes $\gamma \gamma \to K^0_S K^{\pm}\pi^{\mp}$ and $\gamma \gamma \to K^+ K^- \pi^0$ 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 $I=1/2$ $K \pi$ $\mathcal{S}$-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behaviour 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 $m=1931 \pm 14 \pm 22 \ MeV/c^2$ and $\Gamma=271 \pm 22 \pm 29 \ MeV$., Comment: 20 pages, 14 postscript figures, Submitted to Phys. Rev. D

We study the lepton forward-backward asymmetry AFB and the longitudinal K* polarization FL, as well as an observable P2 derived from them, in the rare decays B->K*l+l-, where l+l- is either e+e- or mu+mu-, using the full sample of 471 million BBbar events collected at the Upsilon(4S) resonance with the Babar detector at the PEP-II e+e- collider. We separately fit and report results for the B+->K*+l+l- and B0->K*0l+l- final states, as well as their combination B->K*l+l-, in five disjoint dilepton mass-squared bins. An angular analysis of B+->K*+l+l- decays is presented here for the first time., Comment: 19 pages, 9 figures, submitted to PRD

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. D

We report on measurements of the decays of $\overline{B}$ mesons into the semileptonic final states $\overline{B} \to D^{(*)} \pi^+\pi^- \ell^-\overline{\nu}$, where $D^{(*)}$ represents a $D$ or $D^*$ meson and $\ell^-$ is an electron or a muon. These measurements are based on $471\times 10^6$ $B\overline{B}$ pairs recorded with the $BABAR$ detector at the SLAC asymmetric $B$ Factory PEP-II. We determine the branching fraction ratios $R^{(*)}_{\pi^+\pi^-} = \mathcal{B}(\overline{B} \to D^{(*)} \pi^+\pi^- \ell^- \overline{\nu})/\mathcal{B}(\overline{B} \to D^{(*)} \ell^-\overline{\nu})$ using events in which the second $B$ meson is fully reconstructed. We find $R_{\pi^+\pi^-} = 0.067 \pm 0.010 \pm 0.008$ and $R^*_{\pi^+\pi^-} = 0.019 \pm 0.005 \pm 0.004$, where the first uncertainty is statistical and the second is systematic. Based on these results, we estimate that $\overline{B} \to D^{(*)}\pi\pi\ell^-\overline{\nu}$ decays, where $\pi$ denotes both a $\pi^\pm$ and $\pi^0$ 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., Comment: 8 pages, 2 figures, submitted to PRL

The $e^+e^-\to K^+K^-$ cross section and charged-kaon electromagnetic form factor are measured in the $e^+e^-$ center-of-mass energy range ($E$) from 2.6 to 8.0 GeV using the initial-state radiation technique with an undetected photon. The study is performed using 469 fb$^{-1}$ of data collected with the BABAR detector at the PEP-II $e^+e^-$ collider at center-of-mass energies near 10.6 GeV. The form factor is found to decrease with energy faster than $1/E^2$, and approaches the asymptotic QCD prediction. Production of the $K^+K^-$ final state through the $J/\psi$ and $\psi(2S)$ intermediate states is observed. The results for the kaon form factor are used together with data from other experiments to perform a model-independent determination of the relative phases between single-photon and strong amplitudes in $J/\psi$ and $\psi(2S)\to K^+K^-$ decays. The values of the branching fractions measured in the reaction $e^+e^- \to K^+K^-$ are shifted relative to their true values due to interference between resonant and nonresonant amplitudes. The values of these shifts are determined to be about $\pm5\%$ for the $J/\psi$ meson and $\pm15\%$ for the $\psi(2S)$ meson., Comment: 18 pages, 19 postscript figures

We describe in detail a previously published measurement of CP violation induced by B0-anti B0 oscillations, based on an integrated luminosity of 425.7 fb-1 collected by the BABAR experiment at the PEPII collider. We apply a novel technique to a sample of about 6 million B0bar -> D*+ l- nubar decays selected with partial reconstruction of the D*+ meson. The charged lepton identifies the flavor of one B meson at its decay time, the flavor of the other B is determined by kaon tagging. We determine a CP violating asymmetry ACP = (0.0006 +- 0.0017 + 0.0038 - 0.0032). This measurement is consistent and competitive with those obtained at the B factories with dilepton events., Comment: 15 pages, 5 figure, submitted to Phys. Rev. D

A search is presented for the decay Y(1S) -> gamma A0, A0 -> cc-bar, where A0 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 Y(2S) resonance. A sample of Y(1S) mesons is selected via the decay Y(2S) -> pi+pi-Y(1S). The A0 -> cc-bar decay is identified through the reconstruction of hadronic D0, D+, and D*(2010)+ meson decays. No significant signal is observed. The measured 90% confidence-level upper limits on the product branching fraction B(Y(1S) -> gamma A0) x B(A0 -> cc-bar) range from 7.4 x 10^-5 to 2.4 x 10^-3 for A0 masses from 4.00 to 8.95 GeV/c^2 and 9.10 to 9.25 GeV/c^2, where the region between 8.95 and 9.10 GeV/c^2 is excluded because of background from Y(2S) -> gamma chi_bJ(1P), chi_bJ(1P) -> gamma Y(1S) decays., Comment: 8 pages, 8 postscript figures, submitted to PRD-RC

We perform a measurement of the tau -> l gamma nu anti-nu (l = e, mu) branching fractions for a minimum photon energy of 10 MeV in the tau rest frame, using 431fb^-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 nu anti-nu ) = (3.69pm0.03pm0.10)x10^-3, and B(tau -> e gamma nu anti-nu ) = (1.847pm0.015pm0.052)x10^-2, where the first quoted error is statistical, and the second is systematic. These results are substantially more precise than previous measurements., Comment: 7 pages, 9 figures

We present Dalitz plot analyses for the decays of $B$ mesons to $D^- D^0 K^+$ and $\overline{D}^0 D^0 K^+$. We report the observation of the $D^{*}_{s1}(2700)^+$ resonance in these two channels and obtain measurements of the mass $M(D^{*}_{s1}(2700)^+) = 2699 {}^{+14}_{-7} \, \mathrm{MeV}/c^2$ and of the width $\Gamma(D^{*}_{s1}(2700)^+) = 127 {}^{+24}_{-19} \, \mathrm{MeV}$, including statistical and systematic uncertainties. In addition, we observe an enhancement in the $D^0K^+$ invariant mass around 2350--2500 MeV/$c^2$ in both decays $B^0 \to D^- D^0 K^+$ and $B^+ \to \overline{D}^0 D^0 K^+$, which we are not able to interpret. The results are based on $429~\mathrm{fb}^{-1}$ of data containing $471\times10^6\, B\overline{B}$ pairs collected at the $\Upsilon{(4S)}$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory., Comment: 15 pages, 4 figures, published version

We present a measurement of the asymmetry $A_{CP}$ between same-sign inclusive dilepton samples $\ell^+ \ell^+$ and $\ell^- \ell^-$ ($\ell= e, \mu$) from semileptonic B decays in Y(4S) --> BBbar events, using the complete data set recorded by the BABAR experiment near the Y(4S) resonance, corresponding to 471 million BBbar pairs. The asymmetry A_{CP} allows comparison between the mixing probabilities P(B0bar --> B0) and P(B0 --> B0bar), and therefore probes CP and T violation. The result, $A_{CP} = (-3.9 \pm 3.5 (stat) \pm 1.9 (syst)) \times 10^{-3}$, is consistent with the Standard Model expectation., Comment: 7 pages, 3 figures, submitted to Phys. Rev. Lett

We report on a search in $e^+e^-$ annihilations for new $\pi^0$-like particles produced in association with a $\tau$-lepton pair. These objects, with a similar mass and similar decay modes to $\pi^0$ mesons, could provide an explanation for the non-asymptotic behavior of the pion-photon transition form factor observed by the Babar Collaboration. No significant signal is observed, and limits on the production cross section at the level of 73 fb or 370 fb, depending on the model parameters, are determined at 90% confidence level. These upper limits lie below the cross section values needed to explain the Babar form factor data., Comment: 8 pages, 6 figures, submitted to Phys. Rev. D

We report the observation of the baryonic decay $\bar{B}^0 \to \Lambda^+_c \bar{p} K^- K^+$ using a data sample of $471 \times 10^6$ $B\bar{B}$ pairs produced in $e^+e^-$ annihilations at $\sqrt{s}=10.58 \mathrm{\,GeV}$. This data sample was recorded with the $BABAR$ detector at the PEP-II storage ring at SLAC. We find ${\cal B}\left(\bar{B}^0 \to \Lambda^+_c \bar{p} K^- K^+ \right) = \left(2.5 \pm 0.4_{(\text{stat})} \pm 0.2_{(\text{syst})}\pm 0.6_{{\cal B}\left(\Lambda^+_c\right)} \right) \times 10^{-5}$, where the uncertainties are statistical, systematic, and due to the uncertainty of the $\Lambda^+_c \to p K^- \pi^+$ branching fraction, respectively. The result has a significance corresponding to 5.0 standard deviations, including all uncertainties. For the resonant decay $\bar{B}^0 \to \Lambda^+_c \bar{p} \phi$, we determine the upper limit ${\cal B}\left(\bar{B}^0 \to \Lambda^+_c \bar{p} \phi \right) <1.2 \times 10^{-5}$ at $90\%$ confidence level.

We study the rare B meson decays B{+-,0} --> J/\psi\ K^+ K^- K{+-,0}, B{+-,0} --> J/\psi\ \phi\ K{+-,0}, and search for B0 --> J/\psi\ \phi, using 469 million BBbar events collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II e+e- asymmetric-energy collider. We present new measurements of branching fractions and a study of the J/\psi\phi mass distribution in search of new charmonium-like states. In addition, we search for the decay B0 --> J/\psi\ \phi, and find no evidence of a signal., Comment: 13 pages, 25 figures, accepted as Phys. Rev. D article

Dark sectors charged under a new Abelian force have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon (A'), connecting the dark sector to the Standard Model. We present a search for a dark photon in the reaction e+e- -> gamma A', A'-> e+e-, mu+mu- using 514 fb-1 of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the mixing strength between the photon and dark photon at the level of 10^-4 - 10^-3 for dark photon masses in the range 0.02 - 10.2 GeV. We further constrain the range of the parameter space favored by interpretations of the discrepancy between the calculated and measured anomalous magnetic moment of the muon., Comment: 7 pages, 7 figures, to appear in PRL, published version

We measure the direct CP violation asymmetry, A_CP, in B to X_s gamma and the isospin difference of the asymmetry, Delta A_CP, using 429 fb^-1 of data collected at Upsilon(4S) resonance with the BaBar detector at the PEP-II asymmetric-energy e+e- storage rings operating at the SLAC National Accelerator Laboratory. B mesons are reconstructed from 10 charged B final states and 6 neutral B final states. We find A_CP = +(1.7 +- 1.9 +- 1.0)%, which is in agreement with the Standard Model prediction and provides an improvement on the world average. Moreover, we report the first measurement of the difference between A_CP for charged and neutral decay modes, Delta A_CP = +(5.0 +- 3.9 +- 1.5)%. Using the value of Delta A_CP, we also provide 68% and 90% confidence intervals on the imaginary part of the ratio of the Wilson coefficients corresponding to the chromo-magnetic dipole and the electromagnetic dipole transitions., Comment: 14 pages, 4 figures Submitted to Phys. Rev. D

We study the processes $e^+ e^-\to K_S^0 K_L^0 \gamma$, $K_S^0 K_L^0 \pi^+\pi^-\gamma$, $K_S^0 K_S^0 \pi^+\pi^-\gamma$, and $K_S^0 K_S^0 K^+K^-\gamma$, where the photon is radiated from the initial state, providing cross section measurements for the hadronic states over a continuum of center-of-mass energies. The results are based on 469 fb$^{-1}$ of data collected with the BaBar detector at SLAC. We observe the $\phi(1020)$ resonance in the $K_S^0 K_L^0$ final state and measure the product of its electronic width and branching fraction with about 3% uncertainty. We present a measurement of the $e^+ e^-\to K_S^0 K_L^0 $ cross section in the energy range from 1.06 to 2.2 GeV and observe the production of a resonance at 1.67 GeV. We present the first measurements of the $e^+ e^-\to K_S^0 K_L^0 \pi^+\pi^-$, $K_S^0 K_S^0 \pi^+\pi^-$, and $K_S^0 K_S^0 K^+K^-$ cross sections, and study the intermediate resonance structures. We obtain the first observations of \jpsi decay to the $K_S^0 K_L^0 \pi^+\pi^-$, $K_S^0 K_S^0 \pi^+\pi^-$, and $K_S^0 K_S^0 K^+K^-$ final states., Comment: 28 pages, 42 figures

We study the processes $\gamma \gamma \to K^+ K^- \eta$ and $\gamma \gamma \to K^+ K^- \pi^0$ 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 $\eta_c \to K^+ K^- \eta$ and $\eta_c \to K^+ K^- \pi^0$ decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the $K^*_0(1430) \to K \eta$ decay and measure its branching fraction relative to the $K \pi$ decay mode to be ${\cal R}(K^*_0(1430)) = \frac{{\cal B}(K^*_0(1430) \to K \eta)}{{\cal B}(K^*_0(1430) \to K \pi)} = 0.092 \pm 0.025^{+0.010}_{-0.025}$. The $\eta_c \to K^+ K^- \eta$ and $K^*_0(1430) \to K \eta$ results correspond to the first observations of these channels. The data also show evidence for $\eta_c(2S) \to K^+ K^- \pi^0$ and first evidence for $\eta_c(2S) \to K^+ K^- \eta$., Comment: 19 pages, 13 postscript figures, submitted to Phys. Rev. D