arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 37 records · Page 2Linked to original sources

arXiv2016

Measurement of the I=1/2 $K π$ $\mathcal{S}$-wave amplitude from Dalitz plot analyses of $η_c \to K \bar K π$ in two-photon interactions

We study the processes $γγ\to K^0_S K^{\pm}π^{\mp}$ and $γγ\to K^+ K^- π^0$ 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 $Υ(nS)$ ($n = 2,3,4$) resonances. We observe $η_c$ 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 $I=1/2$ $K π$ $\mathcal{S}$-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 $Γ=271 \pm 22 \pm 29 \ MeV$.

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arXiv2015

Search for CP violation In B0-B0bar mixing using partial reconstruction of B0bar -> D*+Xl-nubar and kaon tagging

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.

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arXiv2015

Study of the $e^+e^-\to K^+K^-$ reaction in the energy range from 2.6 to 8.0 GeV

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 $J/ψ$ and $ψ(2S)$ 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 $J/ψ$ and $ψ(2S)\to K^+K^-$ 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 $J/ψ$ meson and $\pm15\%$ for the $ψ(2S)$ meson.

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arXiv2015

Observation of $\overline{B} \to D^{(*)} π^+π^- \ell^-\overlineν$ decays in $e^+e^-$ collisions at the $Υ(4S)$ resonance

We report on measurements of the decays of $\overline{B}$ mesons into the semileptonic final states $\overline{B} \to D^{(*)} π^+π^- \ell^-\overlineν$, 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 $R^{(*)}_{π^+π^-} = \mathcal{B}(\overline{B} \to D^{(*)} π^+π^- \ell^- \overlineν)/\mathcal{B}(\overline{B} \to D^{(*)} \ell^-\overlineν)$ using events in which the second $B$ meson is fully reconstructed. We find $R_{π^+π^-} = 0.067 \pm 0.010 \pm 0.008$ and $R^*_{π^+π^-} = 0.019 \pm 0.005 \pm 0.004$, where the first uncertainty is statistical and the second is systematic. Based on these results, we estimate that $\overline{B} \to D^{(*)}ππ\ell^-\overlineν$ decays, where $π$ denotes both a $π^\pm$ and $π^0$ 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.

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arXiv2015

Dalitz plot analyses of $B^0 \to D^- D^0 K^+$ and $B^+ \to \overline{D}^0 D^0 K^+$ decays

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 $Γ(D^{*}_{s1}(2700)^+) = 127 {}^{+24}_{-19} \, \mathrm{MeV}$, 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 $Υ{(4S)}$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory.

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arXiv2015

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

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.

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arXiv2014

Study of B{+-,0} --> J/ψ K+ K- K{+-,0} and search for B0 --> J/ψ ϕ at BABAR

We study the rare B meson decays B{+-,0} --> J/ψ K^+ K^- K{+-,0}, B{+-,0} --> J/ψ ϕ K{+-,0}, and search for B0 --> J/ψ ϕ, 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/ψϕmass distribution in search of new charmonium-like states. In addition, we search for the decay B0 --> J/ψ ϕ, and find no evidence of a signal.

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arXiv2014

Search for new $π^0$-like particles produced in association with a $τ$-lepton pair

We report on a search in $e^+e^-$ annihilations for new $π^0$-like particles produced in association with a $τ$-lepton pair. These objects, with a similar mass and similar decay modes to $π^0$ 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.

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arXiv2014

Branching fraction measurement of B -> omega l nu decays

We present a measurement of the B -> omega l nu branching fraction based on a sample of 467 million BB pairs recorded by the BaBar detector at the SLAC PEP-2 e+e- collider. We observe 1125 +- 131 signal decays, corresponding to a branching fraction of BF(B -> omega l nu) = (1.21 +- 0.14 +- 0.08) x 10^{-4}, where the first error is statistical and the second is systematic. The dependence of the decay rate on q^2, the momentum transfer squared to the lepton system, is compared to QCD predictions of the form factors based on a quark model and light-cone sum rules.

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arXiv2014

Study of CP asymmetry in B0-B0bar mixing with inclusive dilepton events

We present a measurement of the asymmetry $A_{CP}$ between same-sign inclusive dilepton samples $\ell^+ \ell^+$ and $\ell^- \ell^-$ ($\ell= e, μ$) 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.

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arXiv2014

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 pi 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.

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arXiv2014

Search for a dark photon in e+e- collisions at BABAR

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.

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arXiv2014

Measurement of the B->Xsl+l- branching fraction and search for direct CP violation from a sum of exclusive final states

We present a measurement of the total branching fraction of the flavor-changing neutral-current process B->Xsl+l-, along with partial branching fractions in bins of dilepton and hadronic system (Xs) mass, using a sample of 471x10^6 Upsilon(4S)->BBbar events recorded with the BaBar detector at the PEP-II e+e- collider. B mesons are reconstructed by combining a dilepton pair, either e+e- or mu+mu-, with 10 different Xs final states containing exactly one charged or neutral kaon, two or fewer charged pions, and at most one pi0. Using a sum over these exclusive modes as the basis for extrapolation to the fully inclusive rate, we measure a lepton-flavor-averaged inclusive branching fraction BF(B->Xsl+l-) = (6.73 +0.70-0.64[stat] +0.34-0.25[exp syst] +/- 0.50[model syst])x10^-6 for m(l+l-)^2>0.1 GeV^2/c^4. Restricting our analysis exclusively to final states from which a decaying B meson's flavor can be inferred, we additionally report measurements of the direct CP asymmetry ACP in bins of dilepton mass; over the full dilepton mass range, we find ACP=0.04 +/- 0.11 +/- 0.01$ for a lepton-flavor-averaged sample.

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arXiv2014

Search for the decay ${\overline B}^{0}\rightarrow{Λ_{\rm c}^{+}}{\overline p}{p}{\overline p}$

We report a search for the decay ${\overline B}^{0}\rightarrow{Λ_{\rm c}^{+}}{\overline p}{p}{\overline p}$. Using a data sample of $471 \times 10^6\: B{\overline B}$ pairs collected with the BABAR detector at the PEP-II storage ring at SLAC, we find no events and set an upper limit on the branching fraction ${\cal B}({\overline B}^{0}\rightarrow{Λ_{\rm c}^{+}}{\overline p}{p}{\overline p}) \times\frac{{\cal B}(Λ_{\rm c}^{+}\rightarrow p K^{-} π^{+})}{0.050} < 2.8\times10^{-6}$ at $90\,%$ C.L., where we have normalized ${\cal B}(Λ_{\rm c}^{+}\rightarrow p K^{-} π^{+})$ to the world average value.

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arXiv2014

Cross sections for the reactions $e^+ e^-\to K_S^0 K_L^0$, $K_S^0 K_L^0 π^+π^-$, $K_S^0 K_S^0 π^+π^-$, and $K_S^0 K_S^0 K^+K^-$ from events with initial-state radiation

We study the processes $e^+ e^-\to K_S^0 K_L^0 γ$, $K_S^0 K_L^0 π^+π^-γ$, $K_S^0 K_S^0 π^+π^-γ$, and $K_S^0 K_S^0 K^+K^-γ$, 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 $ϕ(1020)$ 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 $e^+ e^-\to K_S^0 K_L^0 π^+π^-$, $K_S^0 K_S^0 π^+π^-$, 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 $K_S^0 K_L^0 π^+π^-$, $K_S^0 K_S^0 π^+π^-$, and $K_S^0 K_S^0 K^+K^-$ final states.

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arXiv2014

Dalitz plot analysis of $η_c \to K^+ K^- η$ and $η_c \to K^+ K^- π^0$ in two-photon interactions

We study the processes $γγ\to K^+ K^- η$ and $γγ\to K^+ K^- π^0$ 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 $Υ(nS)$ ($n = 2,3,4$) resonances. We observe $η_c \to K^+ K^- η$ and $η_c \to K^+ K^- π^0$ decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the $K^*_0(1430) \to K η$ decay and measure its branching fraction relative to the $K π$ decay mode to be ${\cal R}(K^*_0(1430)) = \frac{{\cal B}(K^*_0(1430) \to K η)}{{\cal B}(K^*_0(1430) \to K π)} = 0.092 \pm 0.025^{+0.010}_{-0.025}$. The $η_c \to K^+ K^- η$ and $K^*_0(1430) \to K η$ results correspond to the first observations of these channels. The data also show evidence for $η_c(2S) \to K^+ K^- π^0$ and first evidence for $η_c(2S) \to K^+ K^- η$.

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arXiv2014

Evidence for the decay B0 --> omega omega and search for B0 --> omega phi

We describe searches for B meson decays to the charmless vector-vector final states omega omega and omega phi with 471 x 10^6 B Bbar pairs produced in e+ e- annihilation at sqrt(s) = 10.58 GeV using the BABAR detector at the PEP-II collider at the SLAC National Accelerator Laboratory. We measure the branching fraction B(B0 --> omega omega) = (1.2 +- 0.3 +0.3-0.2) x 10^-6, where the first uncertainty is statistical and the second is systematic, corresponding to a significance of 4.4 standard deviations. We also determine the upper limit B(B0 --> omega phi) < 0.7 x 10^-6 at 90% confidence level. These measurements provide the first evidence for the decay B0 --> omega omega, and an improvement of the upper limit for the decay B0 --> omega phi.

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arXiv2014

Evidence for the baryonic decay B0bar --> D0 Lambda Lambdabar

Evidence is presented for the baryonic $B$ meson decay $\bar{B}\rightarrow D^0 Λ\barΛ$ based on a data sample of $471 \times 10^6$ $B\bar{B}$ pairs collected with the {\it BABAR} detector at the PEP2 asymmetric $e^+e^-$ collider located at the SLAC National Accelerator Laboratory. The branching fraction is determined to be $\mathcal{B}(\bar{B}\rightarrow D^0 Λ\barΛ) = (9.8^{+2.9}_{-2.6} \pm 1.9)\times 10^{-6}$, corresponding to a significance of $3.4$ standard deviations including systematic uncertainties. A search for the related baryonic $B$ meson decay $\bar{B}\rightarrow D^0 Σ^0 \barΛ$ with $Σ^0\rightarrowΛγ$ is performed and an upper limit $\mathcal{B}(\bar{B}\rightarrow D^0 Σ^0 \barΛ + \bar{B}\rightarrow D^0 Λ\barΣ^0) < 3.1 \times 10^{-5}$ is determined at $90\%$ confidence level.

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