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The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 343 records · Page 19Linked to original sources

arXiv2006

Updated Measurement of the CKM Angle alpha Using B0->rho+rho- Decays

We present results from an analysis of B0->rho+rho- using 316fb^-1 of Y(4S) -> B0B0bar decays observed with the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure the B0->rho+rho- branching fraction, longitudinal polarization fraction fL, and the CP-violating parameters S_LONG and C_LONG: B(B0->rho+rho-) = (23.5 +/- 2.2 [stat] +/- 4.1 [syst]) * 10^-6, fL = 0.977 +/- 0.024 [stat] +0.015/-0.013 [syst] S_LONG = -0.19 +/- 0.21 [stat] +0.05/-0.07 [syst] C_LONG = -0.07 +/- 0.15 [stat] +/- 0.06 [syst] Using an isospin analysis of B->rhorho decays we determine the angle alpha of the unitarity triangle. One of the two solutions, alpha = [74, 117] degrees at 68% CL, is compatible with the standard model. All results presented here are preliminary.

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arXiv2006

Search for Charmonium States Decaying to J/psi gamma gamma Using Initial-State Radiation Events

We study the processes e+e- -> (J/psi gamma gamma) gamma and e+e- -> (J/psi pi- pi+) gamma where the hard photon radiated from an initial e+e- collision with center-of-mass (CM) energy near 10.58 GeV is detected. In the final state J/psi gamma gamma we consider J/psi pi0, J/psi eta, chi_{c1} gamma, and chi_{c2} gamma candidates. The invariant mass of the hadronic final state defines the effective e+e- CM energy in each event, so these data can be compared with direct e+e- measurements. We report 90% CL upper limits for the integrated cross section times branching fractions of the J/psi gamma gamma channels in the Y(4260) mass region.

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arXiv2006

Measurement of branching fractions and charge asymmetries in B decays to an eta meson and a K* meson

We present measurements of branching fractions and charge asymmetries for the decays etaK*, where K* indicates a spin 0, 1, or 2 Kpi system. The data sample corresponds to 344x10^6 BBbar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We measure the branching fractions (in units of 10^-6): BR(B0->etaK*0)=16.5\pm1.1\pm0.8, BR(B+->etaK*+)=18.9\pm1.8\pm1.3, BR(B0->eta(Kpi)_0*0)=11.0\pm1.6\pm1.5, BR(B+->eta(Kpi)_0*+)=18.2\pm2.6\pm 2.6, BR(B0->etaK_2*0(1430))=9.6\pm1.8\pm1.1, and BR(B+->etaK_2*+(1430))=9.1\pm2.7\pm 1.4. We also determine the charge asymmetries for all decay modes.

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arXiv2006

Measurement of the CKM angle gamma in B ->D(*)0K decays with a Dalitz analysis of D0->KS pi- pi+

We present a measurement of the Cabibbo-Kobayashi-Maskawa CP-violating phase gamma with a Dalitz analysis of neutral D-meson decays to the K^0_s pi^- pi^+ final state from B^+/- -> D^{(*)}K^+/- decays, using a sample of 347 million B\bar{B} events collected by the BaBar detector. We measure gamma = (92 +/- 41 +/- 11 +/- 12)deg, where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the Dalitz model uncertainty. For the ratios r_B^{(*)} between the magnitudes of amplitudes A(B- -> D^{(*)0}K-) and A(B- ->\bar{D}^{(*)0} K-) we obtain the one-standard deviation intervals [0,0.14] and [0.02,0.20], respectively. All results presented here are preliminary.

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arXiv2006

Measurement of Time-dependent CP Asymmetries in B0 -> K0S K0S K0S Decay

We present an updated measurement of the time-dependent CP-violating asymmetry in B0->K0S K0S K0S decays based on 347 million Upsilon(4S)->B Bbar decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We obtain the CP asymmetries S_f = -0.66 +/- 0.26 +/- 0.08 and C_f = -0.14 +/- 0.22 +/- 0.05, where the first uncertainties are statistical and the second systematic.

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arXiv2006

A search for the decays $B^+\to e^+ ν_e$ and $B^+\to μ^+ ν_μ$ using hadronic-tag reconstruction

We report on a search for the rare decay modes $B^+\to e^+ ν_e$ and $B^+\to μ^+ ν_μ$ with data collected from the BaBar detector at the PEP-II $e^+e^-$ storage ring. This search utilizes a new technique in which we fully reconstruct the accompanying $B^-$ in $Υ(4S)\righarrow B^+ B^-$ events, and look for a mono-energetic lepton in the $B^+$ rest frame. No signal candidates are observed in either of the channels, consistent with the expected background, in a data sample of approximately 229 million $B\bar{B}$ pairs. The branching-fraction upper limits are set at $\mathcal{B}(B^+\to e^+ν_{e})<7.9 \times 10^{-6}$ and $\mathcal{B}(B^+\toμ^+ν_μ)<6.2 \times 10^{-6}$ at the 90% confidence level.

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arXiv2006

Measurement of CP-Violating Asymmetries in the B0->K+K-K0 Dalitz Plot

We present a preliminary measurement of CP-violation parameters in the decay B0 -> K+K-K0, using approximately 347 million BBbar events collected by the BABAR detector at SLAC. Reconstructing the neutral kaon as KS -> pi+pi-, KS -> pi0pi0, or KL, we analyze the Dalitz plot distribution and measure fractions to intermediate states. We extract CP parameters from the asymmetries in amplitudes and phases between B0 and B0bar decays across the Dalitz plot. For decays to phiK0, we find beta_eff=0.06 +/- 0.16 +/- 0.05, Acp=-0.18 +/- 0.20 +/- 0.10, where the first uncertainty is statistical and the second one is systematic. For decays to f0K0, we find beta_eff=0.18 +/- 0.19 +/- 0.04, Acp=0.45 +/- 0.28 +/- 0.10. Combining all KKK0 events and taking account of the different CP eigenvalues of the individual Dalitz plot components, we find beta_eff = 0.361 +/- 0.079 +/- 0.037, Acp = -0.034 +/- 0.079 +/- 0.025. The trigonometric reflection at pi/2 - beta_eff is disfavored at 4.6 sigma. We also study angular distributions in B0 -> K+K-KS and B+ -> phi K+ decays and measure the direct CP asymmetry in B+ -> phi K+ decays, Acp = 0.046 +/- 0.046 +/- 0.017.

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arXiv2006

Measurement of the Ratio ${\cal B}\xspace(\B^+ \to X e ν)$ / ${\cal B}\xspace(\B^0 \to X e ν)

We report measurements of the inclusive electron momentum spectra in decays of charged and neutral B mesons, and of the ratio of semileptonic branching fractions ${\cal B}\xspace(\B^+ \to X e ν)$ and ${\cal B}\xspace(\B^0 \to X e ν)$. These were performed on a sample of 231 million $B\kern 0.18em\bar{\kern -0.18em B}{}\xspace$ events recorded with the \mbox{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the $Υ{(4S)}\xspace$ resonance. Events are selected by fully reconstructing a hadronic decay of one $B$ meson and identifying an electron among the decay products of the recoiling $\Bbar$ meson. We obtain ${\cal B}\xspace(\Bu \to X e ν)$/${\cal B}\xspace(\Bz \to X e ν)$ = $1.084 \pm 0.041_{\mathrm{(stat)}}\xspace\pm 0.025_{\mathrm{(syst)}}\xspace$.

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arXiv2006

Time-dependent CP-violation parameters in B0->eta' K0 decay

We present measurements of time-dependent CP-violation asymmetries for the decays B0 to eta'K0. The data sample corresponds to 347 million BBbar pairs produced by e+e- annihilation at the Upsilon(4S) resonance in the PEP-II collider, and collected with the BaBar detector. The preliminary results are S = 0.55+/-0.11+/-0.002, and C = -0.15+/-0.07+/-0.03, where the first error quoted is statistical, the second systematic.

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arXiv2006

Measurements of CP-Violating Asymmetries in B Decays to omegaKs

We present preliminary measurements of CP-violating asymmetries for the decay omega K0S. The data sample corresponds to 347 million BBbar pairs produced by e+e- annihilation at the Upsilon(4S) resonance. For the decay omega K0S, we measure the time-dependent CP-violation parameters S = 0.62+0.25-0.30+/-0.002, and C = -0.43+0.25-0.23+/-0.03, where the first uncertainty is statistical and the second systematic.

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arXiv2006

Search for CPT and Lorentz Violation in B0-B0bar Oscillations with Inclusive Dilepton Events

We report preliminary results of a search for CPT and Lorentz violation in B0-B0bar oscillations using an inclusive dilepton sample collected by the BABAR experiment at the PEP-II B Factory. Using a sample of 232 million BBbar pairs, we search for time-dependent variations in the complex CPT parameter z = z0 + z1*cos(Omega*t^ + phi) where Omega is the Earth's sidereal frequency and t^ is sidereal time. We measure Im(z0) = (-14.1 +- 7.3(stat) +- 2.4(syst)) x 10E-3, DeltaGamma*Re(z0) = (-7.2 +- 4.1(stat) +- 2.1(syst)) x 10E-3 ps-1, Im(z1) = (-24.0 +- 10.7(stat) +- 5.9(syst)) x 10E-3, and DeltaGamma*Re(z1) = (-18.8 +- 5.5(stat) +- 4.0(syst)) x 10E-3 ps-1, where DeltaGamma is the difference between the decay rates of the neutral B mass eigenstates. The statistical correlation between the measurements of Im(z0) and DeltaGamma*Re(z0) is 76%; between Im(z1) and DeltaGamma*Re(z1) it is 79%. These results are used to evaluate expressions involving coefficients for Lorentz and CPT violation in the general Lorentz-violating standard-model extension. In a complementary approach, we examine the spectral power of periodic variations in z over a wide range of frequencies and find no significant signal.

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arXiv2006

Measurement of cos(2beta) in B0 -> D(*)0 h0 decays with a time-dependent Dalitz plot analysis of D0 -> Ks pi+ pi-

We report a preliminary measurement of $\cos2β$ in $B^0\to D^{(*)0}h^0$ decays with a time-dependent Dalitz plot analysis of $D^0\to K_Sπ^+π^-$, where $h^0$ is a light neutral meson such as $π^0$, $η$, $η'$ or $ω$. The strong phase variation on the Dalitz plot allows the access to the angle $β$ with only a two-fold ambiguity ($β+π$). Using $311\times 10^{6}$ $B\bar{B}$ pairs collected at the Babar detector, we obtain $\cos2β= 0.54 \pm 0.54 \pm 0.08 \pm 0.18$, $\sin2β= 0.45 \pm 0.36 \pm 0.05 \pm 0.07$, and $|λ| = 0.975^{+0.093}_{-0.085} \pm 0.012 \pm 0.002 $, where the first errors are statistical, the second are experimental systematic uncertainties, and the third are the signal Dalitz model uncertainties. This measurement favors the solution of $β= 22^\circ$ over $68^\circ$ at an 87% confidence level.

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arXiv2006

Improved Measurement of CP Asymmetries in $\Bz \to (\ccbar) K^{(*)0}$ Decays

We present an updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays to several CP eigenstates containing a charmonium meson. The measurements use a data sample of (347.5 +/- 3.8) x 10^{6} $\FourS \to B\Bbar$ decays collected with the babar detector at the PEP-II B factory between 1999 and 2006. We determine sin2beta = 0.710 +/- 0.034(stat) +/- 0.019(syst) and |λ| = 0.932 +/- 0.026(stat) +/- 0.017(syst). Both of these results are preliminary.

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arXiv2006

Search for D0--anti-D0 mixing in the decays D0 --> K+ pi- pi+ pi-

We present a search for D0--anti-D0 mixing in the decays D0 --> K+ pi- pi+ pi- using 230.4 fb-1 of data collected with the BaBar detector at the PEP-II e+ e- collider at SLAC. Assuming CP conservation, we measure the time-integrated mixing rate R_M = (0.019 +0.016/-0.015(stat.) +/- 0.002(syst.))%, and R_M < 0.048% at the 95% confidence level. Using a frequentist method, we estimate that the data are consistent with no mixing at the 4.3% confidence level. We present results both with and without the assumption of CP conservation. By combining the value of R_M from this analysis with that obtained from an analysis of the decays D0 --> K+ pi- pi0, we find R_M = (0.020 +0.011/-0.010)%, where the uncertainty is statistical only. We determine the upper limit R_M < 0.042% at the 95% confidence level, and we find the combined data are consistent with the no-mixing hypothesis at the 2.1% confidence level.

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arXiv2006

A measurement of CP-violation parameters in B0B0bar mixing using partially reconstructed D*- l+ nu_l events at BaBar

CP violation in B0B0bar mixing is characterized by the value of the parameter |q/p| being different from 1, and the Standard Model predicts this difference to be smaller than 10^{-3}. We present a measurement of this parameter using a partial reconstruction of one of the B mesons in the semileptonic channel D*- l+ nu_l, where only the hard lepton and the soft pion from the D*- --> D0bar pi- decay are reconstructed. The flavor of the other B is determined by means of lepton tagging. The determination of |q/p| is then performed with a fit to the proper time difference of the two B decays. We use a luminosity of 200.8 fb^-1, collected at the Y(4S) resonance by the BaBar detector at the PEP-II asymmetrical-energy e+e- collider, in the period 1999-2004. We obtain the preliminary result: |q/p| - 1 = (6.5 +/- 3.4(stat.) +/- 2.0(syst.)) x 10^{-3}

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arXiv2006

Measurement of the CP-violating Asymmetries in B0 -> KS pi0 and of the Branching Fraction of B0 -> K0 pi0

We present a measurement of the time-dependent CP-violating asymmetries in B0 -> K0S pi0 decays based on 348 million Y(4S) -> BBbar events collected by the BABAR experiment at the PEP-II asymmetric-energy B Factory at SLAC. We measure the direct CP-violating asymmetry C_{K0S pi0} = 0.20 +/- 0.16 +/- 0.03 and the CP-violating asymmetry in the interference between mixing and decay S_{K0S pi0} = 0.33 +/- 0.26 +/- 0.04 where the first error is statistical and the second systematic. On the same sample, we measure the decay branching fraction, obtaining B(B0 -> K0S pi0)= (10.5 +/- 0.7 +/- 0.5) 10^{-6}. All results presented here are preliminary.

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arXiv2006

Evidence for the B0->rho0rho0 Decay and Implications for the CKM Angle alpha

We search for the decays B0->rho0rho0, B0->rho0f0, and B0->f0f0 in a sample of about 348 million Upsilon(4S)->BBbar decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find evidence for B0->rho0rho0 with 3.0 sigma significance and measure the branching fraction B = (1.16 +0.37-0.36 +-0.27) 10^{-6} and longitudinal polarization fraction f_L = 0.86 +0.11-0.13 +-0.05. As a consequence, the uncertainty on the CKM unitarity angle alpha due to penguin contributions in B->rhorho decays is estimated to be 18 degrees at 1 sigma level. We also set upper limits on the B0->rho0f0 and B0->f0f0 decay rates. All results are preliminary.

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arXiv2006

Measurements of branching fraction, polarization, and charge asymmetry of B+ --> rho+ rho0 and a search for B+ --> rho+ f0(980)

We measure the branching fraction, polarization and CP asymmetry of B+ -> rho+rho0 decays and search for the decay B+ -> rho+f_0(980) based on a data sample of 231.8 million Y(4S)->BB decays collected with the BaBar detector at the SLAC PEP-II asymmetric-energy B factory. In B+ -> rho+rho0 decays we measure B=(16.8+-2.2+-2.3)x10-6, f_L=0.905+-0.042+0.023-0.027, and A_CP=-0.12+-0.13+-0.10, and find an upper limit on the branching fraction of B+ -> rho+f_0(980)(->pi+pi-) of 1.9x10-6 at 90% Confidence Level.

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