arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 55 records · Page 3Linked to original sources

arXiv2013

Improved Limits on $B^{0}$ decays to invisible $(+γ)$ final states

We establish improved upper limits on branching fractions for B0 decays to final States 10 where the decay products are purely invisible (i.e., no observable final state particles) and for final states where the only visible product is a photon. Within the Standard Model, these decays have branching fractions that are below the current experimental sensitivity, but various models of physics beyond the Standard Model predict significant contributions for these channels. Using 471 million BB pairs collected at the Y(4S) resonance by the BABAR experiment at the PEP-II e+e- storage ring at the SLAC National Accelerator Laboratory, we establish upper limits at the 90% confidence level of 2.4x10^-5 for the branching fraction of B0-->Invisible and 1.7x10^-5 for the branching fraction of B0-->Invisible+gamma

hep-ex↗

arXiv2013

Search for lepton-number violating B+ -> X- l+ l'+ decays

We report on a search for eleven lepton-number violating processes B+ -> X- l+ l'+ with X- = K-, pi-, rho-, K*- or D- and l+/l'+ = e+ or mu+, using a sample of 471+/-3 million BBbar events collected with the BaBar detector at the PEP-II e+e- collider at the SLAC National Accelerator Laboratory. We find no evidence for any of these modes and place 90% confidence level upper limits on their branching fractions in the range $(1.5-26)\times 10^{-7}$.

hep-ex↗

arXiv2013

Production of charged pions, kaons and protons in e+e- annihilations into hadrons at sqrt{s} = 10.54 GeV

Inclusive production cross sections of $π^\pm$, $K^\pm$ and $p\bar{p}$ per hadronic $e^+e^-$ annihilation event in $e^+e^-$ are measured at a center-of-mass energy of 10.54 GeV, using a relatively small sample of very high quality data from the BaBar experiment at the PEP-II $B$-factory at the SLAC National Accelerator Laboratory. The drift chamber and Cherenkov detector provide clean samples of identified $π^\pm$, $K^\pm$ and $p\bar{p}$ over a wide range of momenta. Since the center-of-mass energy is below the threshold to produce a $B\bar{B}$ pair, with $B$ a bottom-quark meson, these data represent a pure $e^+e^- \rightarrow q\bar{q}$ sample with four quark flavors, and are used to test QCD predictions and hadronization models. Combined with measurements at other energies, in particular at the $Z^0$ resonance, they also provide precise constraints on the scaling properties of the hadronization process over a wide energy range.

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arXiv2013

The BABAR Detector: Upgrades, Operation and Performance

The BABAR detector operated successfully at the PEP-II asymmetric e+e- collider at the SLAC National Accelerator Laboratory from 1999 to 2008. This report covers upgrades, operation, and performance of the collider and the detector systems, as well as the trigger, online and offline computing, and aspects of event reconstruction since the beginning of data taking.

physics.ins-det↗

arXiv2013

Measurement of the B+ --> omega l+ nu branching fraction with semileptonically tagged B mesons

We report a measurement of the branching fraction of the exclusive charmless semileptonic decay B+ --> omega l+ nu, where l is either an electron or a muon. We use samples of B+ mesons tagged by a reconstructed charmed semileptonic decay of the other B meson in the event. The measurement is based on a dataset of 426.1 fb-1 of e+e- collisions at a center-of-mass energy of 10.58 GeV recorded with the BABAR detector at the PEP-II asymmetric-energy e+e- storage rings. We measure a branching fraction of BF(B+ --> omega l+ nu) = (1.35 +/- 0.21 +/- 0.11) x 10(-4), where the uncertainties are statistical and systematic, respectively. We also present measurements of the partial branching fractions in three bins of q2, the invariant-mass squared of the lepton-neutrino system, and we compare them to theoretical predictions of the form factors.

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arXiv2013

Measurement of the e+e- --> p anti-p cross section in the energy range from 3.0 to 6.5 GeV

The e+ e- --> p anti-p cross section and the proton magnetic form factor have been measured in the center-of-mass energy range from 3.0 to 6.5 GeV using the initial-state-radiation technique with an undetected photon. This is the first measurement of the form factor at energies higher than 4.5 GeV. The analysis is based on 469 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II collider at e+e- center-of-mass energies near 10.6 GeV. The branching fractions for the decays J/psi --> p anti-p and psi(2S) --> p anti-p have also been measured.

hep-ex↗

arXiv2013

Measurement of the Mass of the D0 Meson

We report a measurement of the D0 meson mass using the decay chain D*(2010)+ -> D0 pi+ with D0 -> K- K- K+ pi+. The data were recorded with the BaBar detector at center-of-mass energies at and near the Y(4S) resonance, and correspond to an integrated luminosity of approximately 477 1/fb. We obtain m(D0) = (1864.841 +- 0.048 +- 0.063) MeV, where the quoted errors are statistical and systematic, respectively. The uncertainty of this measurement is half that of the best previous measurement.

hep-ex↗

arXiv2013

Search for a light Higgs boson decaying to two gluons or ss-bar in the radiative decays of Y(1S)

We search for the decay Y(1S) -> gamma A0, A0 -> gg or ss-bar, where A0 is the pseudoscalar light Higgs boson predicted by the next-to-minimal supersymmetric standard model. We use a sample of (17.6 +- 0.3)x 10^6 Y(1S) mesons produced in the BaBar experiment via e+e- -> Y(2S) -> pi+pi-Y(1S). We see no significant signal and set 90%-confidence-level upper limits on the product branching fraction B(Y(1S) -> gamma A0) x B(A0 -> gg or ss-bar) ranging from 10^-6 to 10^-2 for A0 masses in the range 0.5 to 9.0GeV/c^2.

hep-ex↗

arXiv2013

Search for B --> K(*) nu nubar and invisible quarkonium decays

We search for the flavor-changing neutral-current decays B->K(*)nu nubar, and the invisible decays J/psi->nu nubar and psi(2S)->nu nubar via B->K(*)J/psi and B->K(*)psi(2S) respectively, using a data sample of 471 x10^6 BB pairs collected by the BaBar experiment. We fully reconstruct the hadronic decay of one of the B mesons in the Upsilon(4S)->BB decay, and search for the B->K(*)nu nubar decay in the rest of the event. We observe no significant excess of signal decays over background and report branching fraction upper limits of BR(B+->K+nu nubar)<3.7 x10^-5, BR(B0->K0nu nubar)< 8.1 x10^-5, BR(B+->K*+nu nubar)<11.6 x10^-5, BR(B0->K*0nu nubar)<9.3 x10^-5, and combined upper limits of BR(B->Knu nubar)<3.2 x10^-5 and BR(B->K*nu nubar)<7.9 x10^-5, all at the 90% confidence level. For the invisible quarkonium decays, we report branching fraction upper limits of BR(J/psi->nu nubar)<3.9 x10^-3 and BR(psi(2S)->nu nubar)<15.5 x10^-3 at the 90% confidence level. Using the improved kinematic resolution achieved from hadronic reconstruction, we also provide partial branching fraction limits for the B->K(*)nu nubar decays over the full kinematic spectrum.

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arXiv2013

Study of the $K^+ K^-$ invariant-mass dependence of CP asymmetry in $B^+ \rightarrow K^+ K^- K^+$ decays

As a followup to the latest BABAR amplitude analysis of the decay $B^+ \rightarrow K^+ K^- K^+$, we investigate the $K^+ K^-$ invariant-mass dependence of the CP asymmetry and compare it to that obtained by the LHCb collaboration. The results are based on a data sample of approximately $470 \times 10^6 B\bar{B}$ decays, collected with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at the SLAC National Accelerator Laboratory.

hep-ex↗

arXiv2013

Time-Integrated Luminosity Recorded by the BABAR Detector at the PEP-II e+e- Collider

We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the Upsilon(4S), Upsilon(3S) and Upsilon(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e- --> e+e- and (for the Upsilon(4S) only) e+e- --> mu+mu- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross sections of e+e- --> e+e- and e+e- --> mu+mu-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross sections. For data collected on the Upsilon(3S) and Upsilon(2S) resonances, an additional uncertainty arises due to Upsilon --> e+e-X background. For data collected off the Upsilon resonances, we estimate an additional uncertainty due to time-dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the Upsilon(4S), 0.58% (0.72%) for the Upsilon(3S), and 0.68% (0.88%) for the Upsilon(2S).

hep-ex↗

arXiv2013

Observation of direct CP violation in the measurement of the Cabibbo-Kobayashi-Maskawa angle gamma with B+- --> D()K()+- decays

We report the determination of the Cabibbo-Kobayashi-Maskawa CP-violating angle gamma through the combination of various measurements involving B^{+-} --> D K^{+-}, B^{+-} --> D^{*} K^{+-}, and B^{+-} --> D K^{*+-} decays performed by the BaBar experiment at the PEP-II e^{+}e^{-} collider at SLAC National Accelerator Laboratory. Using up to 474 million B\bar{B} pairs, we obtain gamma = (69 ^{+17}_{-16})^\circ (modulo 180^\circ). The total uncertainty is dominated by the statistical component, with the experimental and amplitude-model systematic uncertainties amounting to +-4^\circ. The corresponding two-standard-deviation region is 41^\circ < gamma < 102^\circ. This result is inconsistent with gamma = 0 with a significance of 5.9 standard deviations.

hep-ex↗

arXiv2013

A Search for the Rare Decays B --> pi l+l- and B0 --> eta l+l-

We present the results of a search for the rare flavor-changing neutral-current decays B --> pi l+l- (pi=pi+/-, pi0 and l = e,mu) and B0 --> eta l+l- using a sample of e+e- --> Y(4S) BB decays decays corresponding to 428 fb^-1 of integrated luminosity collected by the BABAR detector. No significant signal is observed, and we set an upper limit on the isospin and lepton-flavor averaged branching fraction of BF(B --> pi l+l-) < 7.0 x 10^-8 and a lepton-flavor averaged upper limit of BF(B0 --> eta l+l-) < 9.2 x 10^-8, both at the 90% confidence level. We also report 90% confidence level branching fraction upper limits for the individual modes B+ --> pi+ e+e-, B0 --> pi0 e+e-, B+ --> pi+ mu+mu-, B0 --> pi0 mu+mu-, B0 --> eta e+e-, and B0 --> eta mu+mu-.

hep-ex↗

arXiv2013

Measurement of an Excess of B -> D(*) Tau Nu Decays and Implications for Charged Higgs Bosons

Based on the full BaBar data sample, we report improved measurements of the ratios R(D(*)) = B(B -> D(*) Tau Nu)/B(B -> D(*) l Nu), where l is either e or mu. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D) = 0.440 +- 0.058 +- 0.042 and R(D*) = 0.332 +- 0.024 +- 0.018, which exceed the Standard Model expectations by 2.0 sigma and 2.7 sigma, respectively. Taken together, our results disagree with these expectations at the 3.4 sigma level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model. Kinematic distributions presented here exclude large portions of the more general type III two-Higgs-doublet model, but there are solutions within this model compatible with the results.

hep-ex↗

arXiv2013

Measurement of CP Asymmetries and Branching Fractions in Charmless Two-Body B-Meson Decays to Pions and Kaons

We present improved measurements of CP-violation parameters in the decays $B^0 \to π^+ π^-$, $B^0 \to K^+ π^-$, and $B^0 \to π^0 π^0$, and of the branching fractions for $B^0 \to π^0 π^0$ and $B^0 \to K^0 π^0$. The results are obtained with the full data set collected at the $Υ(4S)$ resonance by the BABAR experiment at the PEP-II asymmetric-energy $B$ factory at the SLAC National Accelerator Laboratory, corresponding to $467 \pm 5$ million $B\bar B$ pairs. We find the CP-violation parameter values and branching fractions $ S_{π^+π^-} = -0.68 \pm 0.10 \pm 0.03, C_{π^+π^-} = -0.25 \pm 0.08 \pm 0.02, A_{K^-π^+} = -0.107 \pm 0.016 ^{+0.006}_{-0.004}, C_{π^0π^0} = -0.43 \pm 0.26 \pm 0.05, Br(B^0 \to π^0 π^0) = (1.83 \pm 0.21 \pm 0.13) \times 10^{-6}, Br(B^0 \to K^0 π^0) = (10.1 \pm 0.6 \pm 0.4) \times 10^{-6},$ where in each case, the first uncertainties are statistical and the second are systematic. We observe CP violation with a significance of 6.7 standard deviations for $B^0 \toπ^+π^-$ and 6.1 standard deviations for $B^0 \to K^+ π^-$, including systematic uncertainties. Constraints on the Unitarity Triangle angle $α$ are determined from the isospin relations among the $B \to ππ$ rates and asymmetries. Considering only the solution preferred by the Standard Model, we find $α$ to be in the range $[71^\circ,109^\circ]$ at the 68% confidence level.

hep-ex↗

arXiv2013

Search for CP violation in the Decays $D^{\pm} \to K^0_{\scriptscriptstyle S} K^\pm$, $D_s^{\pm} \to K^0_{\scriptscriptstyle S} K^\pm$, and $D_s^{\pm}\to K^0_{\scriptscriptstyle S} π^\pm$

We report a search for CP violation in the decay modes $D^{\pm} \to K^0_{\scriptscriptstyle S} K^\pm$, $D_s^{\pm} \to K^0_{\scriptscriptstyle S} K^\pm$, and $D_s^{\pm}\to K^0_{\scriptscriptstyle S} π^\pm$ using a data set corresponding to an integrated luminosity of $469\,{\,fb}^{-1}$ collected with the {\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the PEP-II asymmetric energy $e^+e^-$ storage rings. The decay rate CP asymmetries, $A_{CP}$, are determined to be $(+0.13 \pm 0.36 \stat \pm 0.25 \syst)%$, $(-0.05 \pm 0.23 \stat \pm 0.24 \syst)%$, and $(+0.6 \pm 2.0 \stat \pm 0.3 \syst)%$, respectively. These measurements are consistent with zero, and also with the standard model prediction ($(-0.332 \pm 0.006)%$ for the $D^{\pm} \to K^0_{\scriptscriptstyle S} K^\pm$ and $D_s^{\pm} \to K^0_{\scriptscriptstyle S} K^\pm$ modes, and $(+0.332 \pm 0.006)%$ for the $D_s^{\pm}\to K^0_{\scriptscriptstyle S} π^\pm$ mode). They are the most precise determinations to date.

hep-ex↗

arXiv2013

Study of e+e- --> p anti-p via initial-state radiation at BABAR

The process e+e- --> p anti-p gamma is studied using 469 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II collider, at an e+e- center-of-mass energy of 10.6 GeV. From the analysis of the p anti-p invariant mass spectrum, the energy dependence of the cross section for e+e- --> p anti-p is measured from threshold to 4.5 GeV. The energy dependence of the ratio of electric and magnetic form factors, |G_E/G_M|, and the asymmetry in the proton angular distribution are measured for p anti-p masses below 3 GeV. We also measure the branching fractions for the decays J/psi --> p anti-p and psi(2S) --> p anti p.

hep-ex↗

arXiv2013

Observation of Time Reversal Violation in the B0 Meson System

Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time reversal violation. The decays of entangled neutral B mesons into definite flavor states ($B^0$ or $\bar{B}^0$), and $J/ψK_S^0$ or $c\bar{c} K_S^0$ final states (referred to as $B_+$ or $B_-$), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, $\bar{B}^0 \rightarrow B_-$ and $B_- \rightarrow \bar{B}^0$, as a function of the time difference between the two B decays. Using 468 million $B\bar{B}$ pairs produced in $Υ(4S)$ decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding $ΔS_T^+ = -1.37 \pm 0.14 (stat.) \pm 0.06 (syst.)$ and $ΔS_T^- = 1.17 \pm 0.18 (stat.) \pm 0.11 (syst.)$. These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.

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