arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 271 records · Page 15Linked to original sources

arXiv2007

Improved Limits on the Lepton-Flavor Violating Decays tau- --> l-l+l-

A search for the neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using 376 fb^{-1} of data collected at an e^+e^- center-of-mass energy around 10.58 GeV with the BaBar detector at the PEP-II storage rings. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (4-8) x 10^{-8} at 90% confidence level.

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arXiv2007

Time-Dependent Analysis of the Decay B0 --> rho0 rho0

We study the decay B0 --> rho0 rho0 in a sample of about 427 million Upsilon(4S) --> BBbar decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find the branching fraction B = (0.84 +/- 0.29 +/- 0.17)*1e-6 and longitudinal polarization fraction of f_L = 0.70 +/- 0.14 +/- 0.05, where the first uncertainty is statistical, and the second is systematic. The evidence for the B0 --> rho0 rho0 signal has 3.6 sigma significance. We investigate the proper-time dependence of the longitudinal component in the decay and measure the CP-violating coefficients S^{00}_L = 0.5 +/- 0.9 +/- 0.2 and C^{00}_L = 0.4 +/- 0.9 +/- 0.2, corresponding to the sine and cosine terms in the time evolution of asymmetry. We study the implication of these results for penguin contributions in B --> rho rho decays and for the CKM unitarity angle alpha.

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arXiv2007

Measurement of the Time-Dependent CP Asymmetry in B0 --> D(*)0_CP h0 Decays

We report a measurement of the time-dependent CP-asymmetry parameters $\cal S$ and $\cal C$ in color-suppressed $B^0 \to D^{(*)0} h^0$ decays, where $h^0$ is a $π^0$, $η$, or $ω$ meson, and the $D^0$ decays to one of the CP eigenstates $K^+K^-$, $K_Sπ^0$, or $K_Sω$. The data sample consists of $383\times 10^{6}$ $Υ(4S)\to B\bar{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$-factory at SLAC. The results are ${\cal S}= -0.56 \pm 0.23 \pm 0.05$ and ${\cal C}= -0.23\pm 0.16\pm 0.04$, where the first error is statistical and the second is systematic.

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arXiv2007

A search for B+ --> tau+ nu with Hadronic B tags

We present a search for the decay B^+ --> tau^+ nu using $383 \times 10^{6}}$ BBbar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II B Factory. We select a sample of events with one completely reconstructed tag B in a hadronic decay mode ($B^- \to D^{(*)0} X^-$), and examine the rest of the event to search for a B^+ --> tau^+ nu decay. We identify the tau lepton in the following modes: tau^+ --> e^+ nu nu,tau^+ --> mu^+ nu nu, tau^+ --> pi^+ nu and tau^+ --> pi^+ pi^0 nu. We find a 2.2 sigma excess in data and measure a branching fraction of B(B+ --> tau^+ nu) = (1.8^{+0.9}_{-0.8}(stat.) \pm 0.4(bkg. syst.) \pm 0.2 (other syst.)) \times 10^{4}. We calculate the product of the B meson decay constant f_{B} and |V_{ub}| to be f_{B} |V_{ub}| = (10.1^{+2.3}_{-2.5}(stat.)^{+1.2}_{-1.5}(syst.))\times10^{-4} GeV

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arXiv2007

Time-dependent Dalitz Plot Analysis of B0 --> Ks pi+ pi-

We perform a time-dependent Dalitz plot analysis of $B^0 \to K^0_{\scriptscriptstyle S}π^+π^-$ in order to extract the ${CP}$ violation parameters of $f_0(980) K^0_{\scriptscriptstyle S}$ and $ρ^0(770) K^0_{\scriptscriptstyle S}$ and direct ${CP}$-asymmetries of $K^{*+}(892) π^-$. The results are obtained from a data sample of $(383\pm3)\times10^{6}$ $B \bar{B}$ decays, collected with the BaBar detector at the PEP2 asymmetric--energy $B$ factory at SLAC. The measured values of $2β_{\rm eff}$ in $B^0$ decays to $f_0(980)K^0_{\scriptscriptstyle S}$ and $ρ^0(770) K^0_{\scriptscriptstyle S}$ are $(89^{+22}_{-20} \pm 5 \pm 8)^\circ$ and $(37 ^{+19}_{-17} \pm 5 \pm 6)^\circ$, respectively, where the first quoted uncertainty is statistical, the second is systematic and the third is Dalitz plot signal model uncertainty. We measure the significance of $2β_{\rm eff}(f_0(980)K^0_{\scriptscriptstyle S})\neq 0$ to be $4.3 σ$. In decays to $K^*(892) π$ we find $A_{CP} = -0.18 \pm 0.10 \pm 0.03 \pm 0.03$. The measured phase difference between the decay amplitudes of $B^0 \to K^{*+}(892) π^-$ and $\bar{B}^0 \to K^{*-}(892) π^+$ is $(-164 \pm 24 \pm 12 \pm 15)^\circ$. All results are preliminary.

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arXiv2007

Evidence for $b \to d γ$ Transitions From a Sum of Exclusive Final States in the Hadronic Final State Mass Range $1.0 {GeV}/c^2< M(X_d)<1.8 {GeV}/c^2$

We present preliminary results of a search for $B\to X_dγ$ decays with a hadronic mass 1.0 GeV/$c^2<M(X_d)<$1.8 GeV/$c^2$. We consider seven final states with up to four charged pions and one neutral pion or $η$, which correspond to about 50% of the total $X_d$ fragmentation in this mass range. Based on a sample of 383 million $B\bar{B}$ events collected by the BaBar experiment at PEP-II, we measure a partial branching fraction $\sum\nolimits^{7}_{X_d=1}{{\ensuremath{\cal B}\xspace}}(B\to X_dγ)|_{(1.0{GeV}/c^2 <M(X_d)<1.8 {GeV}/c^2)}= (3.1\pm0.9 ^{+0.6}_{-0.5} \pm0.5)\cdot 10^{-6},$ where the uncertainties are statistical, systematic and model-dependent respectively.

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arXiv2007

Measurement of the Branching Fractions of Exclusive anti-B -> D/D/D() pi l- anti-nu_l Decays in Events Tagged by a Fully Reconstructed B Meson

We present a measurement of the branching fractions for anti-B -> D/D*/D(*) pi l^- anti-nu_l decays based on 341.1 fb-1 of data collected at the Upsilon(4S) resonance with the BaBar detector at the pep-II e^+e^- storage rings. Events are tagged by fully reconstructing one of the B mesons in a hadronic decay mode. We obtain BF (B^- -> D^0 l^- anti-nu_l) = (2.33 +/- 0.09(stat.) +/- 0.09(syst.))%, BF (B^- -> D^*0 l^- anti-nu_l) = (5.83 +/- 0.15(stat.) +/- 0.30(syst.))%, BF (B0bar -> D^+ l^- anti-nu_l) = (2.21 +/- 0.11(stat.) +/- 0.12(syst.))%, BF (B0bar -> D^*+ l^- anti-nu_l) = (5.49 +/- 0.16(stat.) +/- 0.25(syst.))%, BF (B^- -> D^+ pi^- l^- anti-nu_l) = (0.42 +/- 0.06(stat.) +/- 0.03(syst.))%, BF (B^- -> D^*+ pi^- l^- anti-nu_l) = (0.59 +/- 0.05(stat.) +/- 0.04(syst.))%, BF (B0bar -> D^0 pi^+ l^- anti-nu_l) = (0.43 +/- 0.08(stat.) +/- 0.03(syst.))% and BF (B0bar -> D^*0 pi^+ l^- anti-nu_l) = (0.48 +/- 0.08(stat.) +/- 0.04(syst.))%.

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arXiv2007

Measurement of the $B^0\to X_{u}^- \ell^+ {ν_\ell} $ decays near the kinematic endpoint of the lepton spectrum and search for violation of isospin symmetry

We present the first measurement of the $B^0\to X_{u}^- \ell^+ {ν_\ell} $ partial branching fraction in the end-point region of the lepton momentum spectrum, above the threshold for $B\to X_c\ell {ν_\ell}$ decays. The analysis is based on a sample of 383 million $Υ(4S)$ decays into $B{\bar B}$ pairs collected with the {\sc BaBar} detector at the PEP-II $e^+e^-$ storage rings. We select $B^0{\bar B}^0$ events by partially reconstructing one $\B$ meson via the ${\bar B}^0\to D^{*+} \ell^- \barν_\ell$ decays then select $B^0\to X_{u}^- \ell^+ {ν_\ell} $ decays identifying a second high momentum lepton. In the momentum interval ranging from 2.3 to 2.6 GeV/c we measure the partial branching fraction $Δ{\cal B}(B^0\to X_u\ellν)=(1.30\pm0.21_{stat}\pm0.07_{syst})\times 10^{-4}$ where the first error is statistical and the second is systematic. By comparing this measurement with the one obtained from untagged B decays we obtain $R^{+/0}=Δ{\cal B}(B^0\to X_u\ellν)/Δ{\cal B}(B^+\to X_u\ellν)= 1.18 \pm 0.35_{stat} \pm 0.17_{syst}$. Using this measurement we extract a limit on the contributions from processes breaking isospin symmetry in charmless semileptonic B decays.

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arXiv2007

Measurement of The Time-Dependent CP Asymmetry in B0 --> K*0 gamma Decays

We present a preliminary measurement of the time-dependent CP asymmetry in B0 --> K*0 (K_S0 pi0) gamma decays based on 431 x 10^6 Upsilon(4S) --> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy e+e- collider at SLAC. In a sample containing 316 +/- 22 signal events we measure S_{K* gamma} = -0.08 +/- 0.31 +/- 0.05 and C_{K* gamma} = -0.15 +/- 0.17 +/- 0.03. The uncertainties are statistical and systematic, respectively.

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arXiv2007

Measurement of branching fraction and CP asymmetries in B->D0(cp)K decays

We present a preliminary study of $B^- \to D^0_{CP} π^-$ and $B^- \to D^0_{CP} K^-$ decays, with the $D^0_{CP}$ reconstructed in the CP-odd eigenstates $K_s π^0$, $K_s ω$, in the CP-even eigenstates $K^+ K^-$, $π^+ π^-$, and in the (non-CP) flavor eigenstate $K^\mp π^\pm$. Using a sample of about 382 million Y(4S) decays into BBbar pairs, collected with the BABAR detector operating at the PEP-II asymmetric-energy B Factory at SLAC, we measure the ratios of the branching fractions R_CP+- and the direct CP asymmetries A_CP+-. The results are: R_CP- = 0.81 \pm 0.10 (stat) \pm 0.05 (syst) R_CP+ = 1.07 \pm 0.10 (stat) \pm 0.04 (syst) A_CP- = -0.19 \pm 0.12 (stat) \pm 0.02 (syst) A_CP+ = 0.35 \pm 0.09 (stat) \pm 0.05 (syst)

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arXiv2007

Measurement of cos2beta in B0->D(*)h0 Decays with a Time-Dependent Dalitz Plot Analysis of D->KSpi+pi-

We study the time-dependent Dalitz plot of D->KSpi+pi- in B0->D(*)h0 decays, where h0 is a pi0, eta, eta', or omega meson and D*->Dpi0 using a data sample of 383 X 10^6 Upsilon(4S)->BBbar decays collected with the BABAR detector. We determine cos2beta = 0.42+-0.49+-0.09+-0.13, sin2beta = 0.29+-0.34+-0.03+-0.05, and |lambda| = 1.01+-0.08+-0.02, where the first error is statistical, the second is the experimental systematic uncertainty, and the third, where given, is the Dalitz model uncertainty. Assuming the world average value for sin2beta and |lambda|=1, cos2beta>0 is preferred over cos2beta<0 at 86% confidence level.

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arXiv2007

Search for the rare charmless hadronic decay B+ -> a0+ pi0

We present a search for B decays to a charged scalar meson a0+ and a pi0 where the a0+ decays to an eta meson and a pi+. The analysis was performed on a data sample consisting of 383x10-6 BBbar pairs collected with the Babar detector at the PEP-II asymmetric-energy B Factory at SLAC. We find no significant signal and set an upper limit on the product branching fraction BF[(B+ -> a0+ pi0) x (a0+ -> eta pi+)] of 1.4x10-6 at the 90% confidence level.

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arXiv2007

Production and Decay of Omega_c^0

We present an analysis of inclusive Omega_c^0 baryon production and decays in 230.5 fb^-1 of data recorded with the BABAR detector at the PEP-II asymmetric-energy e+ e- collider at the Stanford Linear Accelerator Center. Omega_c^0 baryons are reconstructed in four final states (Omega- pi+, Omega- pi+ pi0, Omega- pi+ pi+ pi-, Xi- K- pi+ pi+) and the ratios of branching fractions for these final states are measured. We also measure the momentum spectrum of the Omega_c^0 baryons in the e+ e- center-of-mass frame. From the spectrum, we observe Omega_c^0 production from B decays and in ccbar events, and extract the two rates of production.

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arXiv2007

Search for the rare decay B to pi l+ l-

We have performed a search for the flavor-changing neutral-current decays B --> pi l+l-, where l+l- is either e+e- or mu+mu-, using a sample of 230 million Y(4S)-->BBbar decays collected with the BABAR detector. We observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be BF(B --> pi l+ l-) < 9.1 x 10^{-8} at 90% confidence level. We also search for the lepton-flavor--violating decays B --> pi e mu and measure an upper limit on the isospin-averaged branching fraction of BF(B --> pi e mu) < 9.2 x 10^{-8} at 90% confidence level.

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arXiv2007

Search for b--> u transitions in B- -> [K+pi-pi0]_D K-

We search for decays of a B meson into a neutral D meson and a kaon, with the D meson decaying into K+pi-pi0. This final state can be reached through the b --> c transition B- -> D0K- followed by the doubly Cabibbo-suppressed D0 --> K+pi-pi0, or the b --> u transition B- --> D0bar K- followed by the Cabibbo-favored D0bar --> K+ pi-pi 0. The interference of these two amplitudes is sensitive to the angle gamma of the unitarity triangle. We present preliminary results based on 226 10^{6} e+e- --> Y(4s) --> BBbar events collected with the BABAR detector at SLAC. We find no significant evidence for these decays and we set a limit R_ADS =(BR(B- -->[K+pi-pi0]_D K-)+ BR(B+ --> [K-pi+pi0]_D K+))/(BR(B- -->[K-p i+pi0]_D K-)+ BR(B+ --> [K+pi-pi0]_D K+))<0.039 at 95% confidence level, which we translate with a Bayesian approach into r_B = |A(B- --> D0bar K-)|/|A(B- --> D0bar K-)| < 0.185 at 95% confidence level.

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arXiv2007

A study of B-meson decays to eta_c K* and eta_c gamma K(*)

We present preliminary results of a study of the two-body B-meson decays to a charmonium state (ccbar) and a K+ or K*0(892) meson using a sample of about 349 fb-1 of data collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. Here ccbar indicates either the eta_c state, reconstructed in the K_S K+- pi-+ and K+K-pi0 decay channels, or the h_c state, reconstructed in its decay to eta_c gamma. We measure BR(B0 -> eta_c K*0)=(6.1+-0.8_stat +- 1.1_syst) * 10-4, BR(B+ -> h_c K+) * BR(h_c -> eta_c gamma)<5.2 * 10-5 and BR(B0 -> h_c K*0) * BR(h_c -> eta_c gamma)<2.41 * 10^-4, at the 90% C.L.

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arXiv2007

Measurement of the tau- --> K- pi0 nu_tau Branching Fraction

A measurement of the tau- --> K- pi0 nu_tau branching fraction has been made using 230.2 fb-1 of data recorded by the BABAR detector at the PEP-II e+ e- collider, located at the Stanford Linear Accelerator Center (SLAC), at a center of mass energy sqrt{s} close to 10.58 GeV. We measure BF(tau- --> K- pi0 nu_tau) = (0.416 +/- 0.003 (stat) +/- 0.018 (syst)) %.

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arXiv2007

Measurement of the Decay B- --> D*0 e- nubar

Using 226 million $B\bar{B}$ events recorded on the $Υ(4S)$ resonance with the BABAR detector at the SLAC $e^+e^-$ storage rings PEPII, we reconstruct $B^-\to D^{*0} e^-\barν_e$ decays using the decay chain $D^{*0}\to{}D^0{}π^0$ and $D^{0}\to{}K^-π^+$. From the dependence of their differential rate on $w$, the product of the four-velocities of $B^-${} and $D^{*0}$, and using the description of the form factor $F(w)$ by Caprini et al., we obtain the preliminary results $ρ^2_{A_1} = 1.15\pm 0.06 \pm 0.08$, $F(1)\cdot|V_{cb}| = (36.3\pm 0.6 \pm 1.4)\cdot 10^{-3}$, and ${\cal B}(B^-\to D^{*0} e^-\barν_e) = (5.71\pm 0.08\pm 0.41)%$. The first errors are statistical and the second ones are systematic. \\

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