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.

D. A. Sanders, E. M. Aitala, S. Amato, J. C. Anjos, J. A. Appel, D. Ashery, S. Banerjee, I. Bediaga, G. Blaylock, S. B. Bracker, P. R. Burchat, R. A. Burnstein, T. Carter, H. S. Carvalho, N. K. Copty, L. M. Cremaldi, C. Darling, K. Denisenko, S. Devmal, A. Fernandez, G. F. Fox, P. Gagnon, C. Gobel, K. Gounder, A. M. Halling, G. Herrera, G. Hurvits, C. James, P. A. Kasper, S. Kwan, D. C. Langs, J. Leslie, B. Lundberg, J. Magnin, S. MayTal-Beck, B. Meadows, J. R. T. de Mello Neto, D. Mihalcea, R. H. Milburn, J. M. de Miranda, A. Napier, A. Nguyen, A. B. d’Oliveira, K. O’Shaughnessy, K. C. Peng, L. P. Perera, M. V. Purohit, B. Quinn, S. Radeztsky, A. Rafatian, N. W. Reay, J. J. Reidy, A. C. dos Reis, H. A. Rubin, A. K. S. Santha, A. F. S. Santoro, A. J. Schwartz, M. Sheaff, 17 R. A. Sidwell, A. J. Slaughter, M. D. Sokoloff, J. Solano, N. R. Stanton, R. J. Stefanski, K. Stenson, D. J. Summers, S. Takach, K. Thorne, A. K. Tripathi, S. Watanabe, R. Weiss-Babai, J. Wiener, N. Witchey, E. Wolin, S. M. Yang, D. Yi, S. Yoshida, R. Zaliznyak, and C. Zhang

A model-independent partial-wave analysis of the S-wave component of the Kπ system from decays of D+ mesons to the three-body K−π+π+ final state is described. Data come from the Fermilab E791 experiment. Amplitude measurements are made independently for ranges of K−π+ invariant mass, and results are obtained below 825 MeV/c2, where previous measurements exist only in two mass bins. This method of parametrizing a three-body decay amplitude represents a new approach to analyzing such decays. Though no model is required for the S-wave, a parametrization of the relatively well-known reference P- and D-waves, optimized to describe the data used, is required. In this paper, a Breit-Wigner model is adopted to describe the resonances in these waves. The observed phase variation for the S-, P-, and D-waves do not match existing measurements of I=12 K−π+ scattering in the invariant mass range in which scattering is predominantly elastic. If the data are mostly I=12, this observation indicates that the Watson theorem, which requires these phases to have the same dependence on invariant mass, may not apply to these decays without allowing for some interaction with the other pion. The production rate of K−π+ from these decays, if assumed to be predominantly I=12, is also found to have a significant dependence on invariant mass in the region above 1.25 GeV/c2. These measurements can provide a relatively model-free basis for future attempts to determine which strange scalar amplitudes contribute to the decays.2 MoreReceived 27 July 2005Corrected 24 August 2006DOI:https://doi.org/10.1103/PhysRevD.73.032004©2006 American Physical Society

A model-independent partial-wave analysis of the S-wave component of the K pi system from decays of D+ mesons to the three-body K-pi(+)pi(+) final state is described. Data come from the Fermilab E791 experiment. Amplitude measurements are made independently for ranges of K-pi(+) invariant mass, and results are obtained below 825 MeV/c(2), where previous measurements exist only in two mass bins. This method of parametrizing a three-body decay amplitude represents a new approach to analyzing such decays. Though no model is required for the S-wave, a parametrization of the relatively well-known reference P- and D-waves, optimized to describe the data used, is required. In this paper, a Breit-Wigner model is adopted to describe the resonances in these waves. The observed phase variation for the S-, P-, and D-waves do not match existing measurements of I=1/2 K-pi(+) scattering in the invariant mass range in which scattering is predominantly elastic. If the data are mostly I=1/2, this observation indicates that the Watson theorem, which requires these phases to have the same dependence on invariant mass, may not apply to these decays without allowing for some interaction with the other pion. The production rate of K-pi(+) from these decays, if assumed to be predominantly I=1/2, is also found to have a significant dependence on invariant mass in the region above 1.25 GeV/c(2). These measurements can provide a relatively model-free basis for future attempts to determine which strange scalar amplitudes contribute to the decays.

A model-independent partial-wave analysis of the \swave component of the $K\pi$ system from decays of $D^{+}$ mesons to the three-body $\Km\pip\pip$ final state is described. Data come from the Fermilab E791 experiment. Amplitude measurements are made independently for ranges of $\Km\pip$ invariant mass, and results are obtained below 825 \MeVcc, where previous measurements exist only in two mass bins. This method of parametrizing a three-body decay amplitude represents a new approach to analysing such decays. Though no model is required for the \swave, a parametrization of the relatively well-known reference \pdash and \dwave s, optimized to describe the data used, is required. In this paper, a Breit-Wigner model is adopted to describe the resonances in these waves. The observed phase variation for the \sdash, \pdash and \dwave s do not match existing measurements of $I=\half$ $\Km\pip$ scattering in the invariant mass range in which scattering is predominantly elastic. If the data are mostly $I=\half$, this observation indicates that the Watson theorem, which requires these phases to have the same dependence on invariant mass, may not apply to these decays without allowing for some interaction with the other pion. The production rate of $\Km\pip$ from these decays, if assumed to be predominantly $I=\half$, is also found to have a significant dependence on invariant mass in the region above 1.25 \GeVcc. These measurements can provide a relatively model-free basis for future attempts to determine which strange scalar amplitudes contribute to the decays.

D. A. Sanders, E. M. Aitala, S. Amato, J. C. Anjos, J. A. Appel, D. Ashery, S. Banerjee, I. Bediaga, G. Blaylock, S. B. Bracker, P. R. Burchat, R. A. Burnstein, T. Carter, H. S. Carvalho, N. K. Copty, L. M. Cremaldi, C. Darling, K. Denisenko, S. Devmal, A. Fernandez, G. F. Fox, P. Gagnon, C. Gobel, K. Gounder, A. M. Halling, G. Herrera, G. Hurvits, C. James, P. A. Kasper, S. Kwan, D. C. Langs, J. Leslie, B. Lundberg, J. Magnin, S. MayTal-Beck, B. Meadows, J. R. T. de Mello Neto, D. Mihalcea, R. H. Milburn, J. M. de Miranda, A. Napier, A. Nguyen, A. B. d’Oliveira, K. O’Shaughnessy, K. C. Peng, L. P. Perera, M. V. Purohit, B. Quinn, S. Radeztsky, A. Rafatian, N. W. Reay, J. J. Reidy, A. C. dos Reis, H. A. Rubin, A. K. S. Santha, A. F. S. Santoro, A. J. Schwartz, M. Sheaff, 17 R. A. Sidwell, A. J. Slaughter, M. D. Sokoloff, J. Solano, N. R. Stanton, R. J. Stefanski, K. Stenson, D. J. Summers, S. Takach, K. Thorne, A. K. Tripathi, S. Watanabe, R. Weiss-Babai, J. Wiener, N. Witchey, E. Wolin, S. M. Yang, D. Yi, S. Yoshida, R. Zaliznyak, and C. Zhang

We search for direct CP violation in charmless hadronic B decays observed in a sample of about 22.7 million B (B) over bar pairs collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e(+)e(-) collider. We measure the following charge asymmetries: A(CP)(B+/- --> eta'K+/-) = -0.11 +/- 0.11 +/- 0.02, A(CP)(B+/- --> omegapi+/-) = -0.01 +/- (0.29)(0.31) +/- 0.03, A(CP)(B+/- -->phiK+/-)= -00.5 +/-0.20+/-0.03, A(CP)(B+/- --> phiK*=/-)= -0.43 (+0.36)(-0.30) +/-0.06, and A(CP)((B) over bar (0) --> phi(K) over bar*(0)) = 0.00 +/- 0.27 +/- 0.03.

We study the Dalitz plot of the decay D(+)-->K(-)pi(+)pi(+) with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known Kpi resonances and a uniform nonresonant term, we do not obtain an acceptable fit. If we allow the mass and width of the K(*)(0)(1430) to float, we obtain values consistent with those from PDG but the chi(2) per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797+/-19+/-43 MeV/c(2) and width 410+/-43+/-87 MeV/c(2). The mass and width of the K(*)(0)(1430) become 1459+/-7+/-5 MeV/c(2) and 175+/-12+/-12 MeV/c(2), respectively. Our results provide new information on the scalar sector in hadron spectroscopy.

We have studied the B+/--->J/psipi(+/-) and B+/--->J/psiK(+/-) decays using a 20.7 fb(-1) data set collected with the BABAR detector. We observe a signal of 51+/-10 B+/--->J/psipi(+/-) events and determine the ratio B(B+/--->J/psipi(+/-))/B(B+/--->J/psiK(+/-)) to be [3.91+/-0.78(stat)+/-0.19(syst)]%. The CP-violating charge asymmetries for the B+/--->J/psipi(+/-) and B+/--->J/psiK(+/-) decays are determined to be A(pi)=0.01+/-0.22(stat)+/-0.01(syst) and A(K)=0.003+/-0.030(stat)+/-0.004(syst).

We report a measurement of the branching fraction of the decay B0-->D(*+)D(*-) and of the CP-odd component of its final state using the BABAR detector. With data corresponding to an integrated luminosity of 20.4 fb (-1) collected at the Upsilon(4S) resonance during 1999-2000, we have reconstructed 38 candidate signal events in the mode B0-->D(*+)D(*-) with an estimated background of 6.2+/-0.5 events. From these events, we determine the branching fraction to be B(B0-->D(*+)D(*-))=[8.3+/-1.6(stat)+/-1.2(syst)]x10(-4). The measured CP-odd fraction of the final state is 0.22+/-0.18(stat)+/-0.03(syst).

We present a measurement of time-dependent CP-violating asymmetries in neutral B meson decays collected with the BABAR detector at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider at the Stanford Linear Accelerator Center. The data sample consists of 29.7 ${\mathrm{fb}}^{\mathrm{\ensuremath{-}}1}$ recorded at the $\ensuremath{\Upsilon}(4S)$ resonance and 3.9 ${\mathrm{fb}}^{\mathrm{\ensuremath{-}}1}$ off resonance. One of the neutral B mesons, which are produced in pairs at the $\ensuremath{\Upsilon}(4S),$ is fully reconstructed in the CP decay modes $J/\ensuremath{\psi}{K}_{S}^{0},$ $\ensuremath{\psi}{(2S)K}_{S}^{0},$ ${\ensuremath{\chi}}_{c1}{K}_{S}^{0},$ $J/\ensuremath{\psi}{K}^{*0}$ ${(K}^{*0}\ensuremath{\rightarrow}{K}_{S}^{0}{\ensuremath{\pi}}^{0})$ and $J/\ensuremath{\psi}{K}_{L}^{0},$ or in flavor-eigenstate modes involving ${D}^{(*)}\ensuremath{\pi}/\ensuremath{\rho}{/a}_{1}$ and $J/\ensuremath{\psi}{K}^{*0}$ ${(K}^{*0}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}).$ The flavor of the other neutral B meson is tagged at the time of its decay, mainly with the charge of identified leptons and kaons. A neural network tagging algorithm is used to recover events without a clear lepton or kaon tag. The proper time elapsed between the decays is determined by measuring the distance between the decay vertices. Wrong-tag probabilities, the time-difference resolution function, and the ${B}^{0}\ensuremath{-}{B}^{0}$ oscillation frequency $\ensuremath{\Delta}{m}_{d}$ are measured with a sample of about 6350 fully-reconstructed ${B}^{0}$ decays in hadronic flavor-eigenstate modes. A maximum-likelihood fit to this flavor eigenstate sample finds $\ensuremath{\Delta}{m}_{d}=0.516\ifmmode\pm\else\textpm\fi{}0.016(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.010(\mathrm{syst}){\mathrm{ps}}^{\ensuremath{-}1}.$ The value of the asymmetry amplitude $\mathrm{sin}2\ensuremath{\beta}$ is determined from a simultaneous maximum-likelihood fit to the time-difference distribution of the flavor-eigenstate sample and about 642 tagged ${B}^{0}$ decays in the CP-eigenstate modes. We find $\mathrm{sin}2\ensuremath{\beta}=0.59\ifmmode\pm\else\textpm\fi{}0.14(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.05(\mathrm{syst}),$ demonstrating that CP violation exists in the neutral B meson system. We also determine the value of the CP violation parameter $|\ensuremath{\lambda}|=0.93\ifmmode\pm\else\textpm\fi{}0.09(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{syst}),$ which is consistent with the expectation of $|\ensuremath{\lambda}|=1$ for no direct CP violation.

We study the Dalitz plot of the decay D+ --> K- pi(+) pi(+) with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known Kpi resonances and a uniform nonresonant term, we do not obtain an acceptable fit If we allow the mass and width of the K-0*(1430) to float, we obtain values consistent with those from PDG but the chi(2) per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797 +/- 19 +/- 43 MeV/c(2) and width 410 +/- 43 +/- 87 MeV/c(2). The mass and width of the K-0*(1430) become 1459 +/- 7 +/- 5 MeV/c(2) and 175 +/- 12 +/- 12 MeV/c(2), respectively. Our results provide new information on the scalar sector in hadron spectroscopy.

We measure the branching fractions of the y(2S) meson to the leptonic final states e+e- and m+m- relative to that for y(2S) -> J/yp+p-. The method uses y(2S) mesons produced in the decay of B mesons at the U(4S) resonance in a data sample collected with the BABAR detector at the Stanford Linear Accelerator Center. Using previous measurements for the y(2S) -> J/yp+p- branching fraction, we det. the e+e- and m+m- branching fractions to be 0.0078+-0.0009+-0.0008 and 0.0067+-0.0008+-0.0007, resp. [on SciFinder (R)]

The B(0) lifetime was measured with a sample of 23 million BB pairs collected by the BABAR detector at the PEP-II e(+)e(-) storage ring during 1999 and 2000. Events from the semileptonic decay B(0)-->D(*-)l(+)nu(l) have been selected with a partial reconstruction method in which only the charged lepton and the slow pi from the D*--->D(0)pi(-) decay are reconstructed. The result is tau(B(0)) = 1.529+/-0.012(stat)+/-0.029(syst) ps.

New measurements of Ds+ and Ds*+ meson production rates from B decays and from qqbar continuum events near the Y(4S) resonance are presented. Using 20.8 fb-1 of data on the Y(4S) resonance and 2.6 fb-1 off resonance, we find the inclusive branching fractions BR(B --> Ds+ X) = (10.93+/-0.19+/-0.58+/-2.73)% and BR(B --> Ds*+ X) = (7.9+/-0.8+/-0.7+/-2.0)%, where the first error is statistical, the second is systematic, and the third is due to the Ds+ --> phi pi+ branching fraction uncertainty. The branching fractions SumBR(B --> Ds(*)+ Dbar(*)) = (5.07+/-0.14+/-0.30+/-1.27)% and SumBR(B --> Ds*+ Dbar(*)) = (4.1+/-0.2+/-0.4+/-1.0)% are determined from the Ds(*)+ momentum spectra.

We present a measurement of the time-dependent CP-violating asymmetries in neutral B decays to the π+π−CP eigenstate, and an updated measurement of the charge asymmetry in B0→K+π− decays. In a sample of 33 million Υ(4S)→B¯B decays collected with the BABAR detector at the SLAC PEP-II asymmetric B factory, we find 65+12−11 π+π− and 217±18 K+π− candidates and measure the asymmetry parameters Sππ=0.03+0.53−0.56±0.11, Cππ=−0.25+0.45−0.47±0.14, and AKπ=−0.07±0.08±0.02, where the first error is statistical and the second is systematic.Received 25 October 2001DOI:https://doi.org/10.1103/PhysRevD.65.051502©2002 American Physical Society