arXiv subjects

The BABAR Collaboration

Publications and source records attributed to The BABAR Collaboration.

At least 217 records · Page 12Linked to original sources

arXiv2008

Measurement of $B \to X γ$ Decays and Determination of $|V_{td}/V_{ts}|$

Using a sample of 383 million $B\bar{B}$ events collected by the $BaBar$ experiment, we measure sums of seven exclusive final states $B\to X_{d(s)}γ$, where $X_d$($X_s$) is a non-strange (strange) charmless hadronic system in the mass range $0.6-1.8$ GeV$/c^2$. After correcting for unmeasured decay modes in this mass range, we obtain a branching fraction for $b \to d γ$ of $(7.2\pm 2.7(stat.)\pm 2.3(syst.))\times 10^{-6}$. Taking the ratio of $X_d$ to $X_s$ we find $Γ(b \to d γ)/Γ(b \to s γ) = 0.033 \pm 0.013 (stat.) \pm 0.009 (syst.),$ from which we determine $|V_{td}/V_{ts}|=0.177\pm 0.043$.

hep-ex↗

arXiv2008

Measurement of CP Asymmetries and Branching Fractions in B0 -> pi+ pi-, B0 -> K+ pi-, B0 -> pi0 pi0, B0 -> K0 pi0 and Isospin Analysis of B -> pi pi Decays

We present preliminary results of improved measurements of the CP-violating asymmetries and branching fractions in the decays B0 -> pi+ pi-, B0 -> K+ pi-, B0 -> pi0 pi0, and B0 -> K0 pi0. This update includes all data taken at the Y(4S) resonance by the BaBar experiment at the asymmetric PEP-II B-meson factory at SLAC, corresponding to 467 +- 5 million BBbar pairs. We find Spipi = -0.68 +- 0.10 +- 0.03, Cpipi = -0.25 +- 0.08 +- 0.02, AKpi = -0.107 +- 0.016 +0.006-0.004, Cpi0pi0 = -0.43 +- 0.26 +- 0.05, BF(B0 -> pi0 pi0) = (1.83 +- 0.21 +- 0.13) x 10^-6, BF(B0 -> K0 pi0) = (10.1 +- 0.6 +- 0.4) x 10^-6, where the first error is statistical and the second is systematic. We observe CP violation with a significance of 6.7 sigma in B0 -> pi+ pi- and 6.1 sigma in B0 -> K+ pi-. Constraints on the Unitarity Triangle angle alpha are determined from the isospin relation between all B -> pipi rates and asymmetries.

hep-ex↗

arXiv2008

Search for Second-Class Currents in tau- -> omega pi- nu_tau

We report on an analysis of $τ^-$ decaying into $ωπ^-ν_τ$ with $ω\toπ^+π^-π^0$ using data containing nearly 320 million tau pairs collected with the BABAR detector at the PEP-II asymmetric energy $B$-Factory. We find no evidence for second-class currents and set an upper limit at 0.69% at a 90% confidence level for the ratio of second- to first-class currents.

hep-ex↗

arXiv2008

Measurement of |V_cb| and the form-factor slope for Bbar -> D l^- nubar_l decays on the recoil of fully reconstructed B mesons

We present a measurement of the CKM matrix element |V_cb| and the form-factor slope rho^2 for Bbar -> D l^- nubar_l decays based on 417 fb-1 of data collected at the Upsilon(4S) resonance with the BaBar detector. The semileptonic decays are selected in BBar events in which the hadronic decay of the second B meson is fully reconstructed. From the measured differential decay rate of the signal decay we determine G(1) |V_cb|= (43.0 +/- 1.9 +/- 1.4) x 10^-3, rho^2 = 1.20 +/- 0.09 +/- 0.04, where G(1) is the hadronic form factor at the point of zero recoil. Using a lattice calculation for G(1) we extract |V_cb|= (39.8 +/- 1.8 +/- 1.3 +/- 0.9) x 10^-3, where the stated errors refer to the statistical, systematic, and form factor uncertainties. We also present a measurement of the exclusive branching fractions, BF(B^- -> D^0 l^- nubar_l) = (2.31 +/- 0.08 +/- 0.07)% and BF (B0bar -> D^+ l^- nubar_l)=(2.23 +/- 0.11 +/- 0.08)%.

hep-ex↗

arXiv2008

Evidence for B semileptonic decays into the charmed baryon Lambda_c+

We present the first evidence for B semileptonic decays into the charmed baryon Lambda_c+ based on 420 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 measure the relative branching fraction BF(Bbar -> Lambda_c+ X l- nubar_l)/BF(Bbar -> Lambda_c+/Lambda_c- X) = (3.2 +/- 0.9_stat +/- 0.9_syst)%. The significance of the signal including the systematic uncertainty is 4.9 standard deviations.

hep-ex↗

arXiv2008

Measurement of branching fractions of B0 decays to K1(1270)+ pi- and K1(1400)+ pi-

We present a measurement of the branching fraction of neutral B meson decaying to final states containing a K_1 meson, i.e. K_1(1270) and K_1(1400), and a charged pion. The data, collected with the BaBar detector at the Stanford Linear Accelerator Center, represent 454 million BBbar pairs produced in e+e- annihilation. We measure the branching fraction BF(B0 -> K_1+ pi-) = (31.0 +- 2.7 +- 6.9) x 10^-6, where the first error quoted is statistical and the second is systematic. In the framework of the K-matrix formalism used to describe these decays, we also set limits on the ratio of the production constants for the K_1(1270)+ and K_1(1400)+ mesons in B0 decays.

hep-ex↗

arXiv2008

Measurement of D0-D0bar mixing from a time-dependent amplitude analysis of D0 -> K+ pi- pi0 decays

We present evidence of $D^0$-$\bar{D^0}$ mixing using a time-dependent amplitude analysis of the decay D0->K+pi-pi0 in a data sample of 384 fb^-1 collected with the BaBar detector at the PEP-II e+e- collider at SLAC. Assuming CP conservation, we measure the mixing parameters x'_{Kpipi0} = [2.61^{+0.57}_{-0.68} (stat.) +- 0.39 (syst.)]%, y'_{Kpipi0} = [-0.06 ^{+0.55}_{-0.64} (stat.) +- 0.34 (syst.)]%. The confidence level for the data to be consistent with the no-mixing hypothesis is 0.1%, including systematic uncertainties. This result is inconsistent with the no-mixing hypothesis with a significance of 3.2 standard deviations. We find no evidence of CP violation in mixing.

hep-ex↗

arXiv2008

Search for B+ --> mu+ nu_mu with inclusive reconstruction at BaBar

We search for the purely leptonic decay $B^{\pm} \to μ^{\pm} ν_μ$ in the full BaBar dataset, having an integrated luminosity of approximately 426 fb$^{-1}$. We adopt a fully inclusive approach, where the signal candidate is identified by the highest momentum lepton in the event and the companion $B$ is inclusively reconstructed without trying to identify its decay products. We set a preliminary upper limit on the branching fraction of $\BR(B^{\pm} \to μ^{\pm} ν_μ) < 1.3 \times 10^{-6}$ at the 90% confidence level, using a Bayesian approach.

hep-ex↗

arXiv2008

Evidence for charged B meson decays to a1(1260)+/- pi0 and a1(1260)0 pi+/-

We present measurements of the branching fractions for the decays B+/- --> a1(1260)+/- pi0 and B+/- --> a1(1260)0 pi+/- from a data sample of 232 * 10^6 BB pairs produced in e+e- annihilation through the Y(4S) resonance. We measure the branching fraction B(B+/- --> a1(1260)+/- pi0) * B(a1(1260)+/- --> pi- pi+ pi+/-) = (13.2 +/- 2.7 +/- 2.1) * 10^-6 with a significance of 4.2 sigma, and the branching fraction B(B+/- --> a1(1260)0 pi+/-) * B(a1(1260)0 --> pi- pi+ pi0) = (20.4 +/- 4.7 +/- 3.4) * 10^-6 with a significance of 3.8 sigma, where the first error quoted is statistical and the second is systematic.

hep-ex↗

arXiv2008

Study of B-meson decays to eta_c K^(), eta_c(2S) K^() and eta_c gamma K^(*)

We study two-body $B$-meson decays to a charmonium state ($η_c$, $η_c(2S)$ or $h_c$) and a $K^+$ or $K^{*0}(892)$ meson using a sample of $349 fb^{-1}$ of data collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We measure $BR(B^0\toη_c K^{*0})=(5.7\pm0.6 (stat)\pm0.9 (syst))\times 10^{-4}$, $BR(B^0\toη_c(2S) K^{*0})<3.9\times 10^{-4}$, $BR(B^+\to h_c K^+)\times BR(h_c\toη_cγ)<4.8\times 10^{-5}$ and $BR(B^0\to h_c K^{*0})\times BR(h_c\toη_cγ)<2.2\times 10^{-4}$ at the 90% C.L., and $BR(η_c(2S)\to K \bar{K} π)=(1.9\pm0.4 (stat) \pm1.1 (syst))%$. We also measure the mass and width of the $η_c$ meson to be $m(η_c)=(2985.8\pm 1.5(stat) \pm 3.1 (syst)) MeV/c^2$ and $Γ(η_c)=(36.3^{+3.7}_{-3.6} (stat) \pm 4.4 (syst)) MeV$.

hep-ex↗

arXiv2008

Measurement of the Mass Difference m(B0) - m(B+)

Using 230 million B Bbar events recorded with the BABAR detector at the e+ e- storage rings PEP-II, we reconstruct approximately 4100 B0 to J/psi K+ pi- and 9930 B+ to J/psi K+ decays with J/psi to mu+ mu- and e+ e-. From the measured B-momentum distributions in the e+ e- rest frame, we determine the mass difference m(B0) - m(B+) = (+0.33 +- 0.05 +- 0.03) MeV/c^2.

hep-ex↗

arXiv2008

Evidence for Direct CP Violation from Dalitz-plot analysis of B+/- -> K+/- pi+/- pi-/+

We report a Dalitz-plot analysis of the charmless hadronic decays of charged B mesons to the final state K+/- pi+/- pi-/+. Using a sample of 383.2 +/- 4.2 million BBbar pairs collected by the BaBar detector, we measure CP-averaged branching fractions and direct CP asymmetries for intermediate resonant and nonresonant contributions. We find evidence for direct CP violation in the decay B+ -> rho0(770) K+, with a CP violation parameter A_CP = (+44 +/- 10 +/- 4 +5,-13)%.

hep-ex↗

arXiv2008

Study of the decay Ds+ --> K+ K- e+ nu

Using 214 fb-1 of data recorded by the Babar detector at the PEPII electron-positron collider, we study the decay Ds+ --> K+ K- e+ nu. Except for a small S-wave contribution, the events with K+K- masses in the range 1.01-1.03 GeV/c2 correspond to phi mesons. For Ds+ --> phi e+ nu decays, we measure the relative normalization of the Lorentz invariant form factors at q2=0, rV=V(0)/A1(0)=1.849 +/- 0.060 +/- 0.095, r2=A2(0)/A1(0)=0.763 +/- 0.071 +/- 0.065 and the pol e mass of the axial-vector form factors mA=(2.28^{+0.23}_{-0.18}+/- 0.18) GeV/c2. Within the same K+K- mass range, we also measure the relative branching fraction B(Ds+ --> K + K- e+ nu)/B(Ds+ --> K+ K- pi+)=0.558 +/- 0.007 +/- 0.016, from which we obtain the total branching fraction B(Ds+ --> phi e+ nu) = (2.61 +/- 0.03 +/- 0.08 +/- 0.15)* 10^{-2}. By comparing this value with the predicted decay rate, we extract A1(0) = 0.607 +/- 0.011 +/- 0.019 +/- 0.018. The stated uncertainties are statistical, systematic, and from external inputs.

hep-ex↗

arXiv2008

Improved measurement of CP observables in B- --> D0_{CP} K- decays

We present a study of the decay B- -> D0_CP K- and its charge conjugate, where D0_CP is reconstructed in both a non-CP flavor eigenstate and in CP (CP-even and CP-odd) eigenstates, based on a sample of 382 million Y(4S) -> BBbar decays collected with the BABAR detector at the PEP-II e+e- storage ring. We measure the direct CP asymmetries A_CP\pm and the ratios of the branching fractions R_CP\pm: A_CP+ = 0.27\pm 0.09(stat)\pm 0.04(syst), A_CP- =-0.09\pm 0.09(stat)\pm 0.02(syst), R_CP+ = 1.06\pm 0.10(stat)\pm 0.05(syst), R_CP- = 1.03\pm 0.10(stat)\pm 0.05(syst). We also express the results in terms of the so called Cartesian coordinates x+, x-, and r^2: x+ = -0.09\pm 0.05(stat)\pm 0.02(syst)}, x- = 0.10\pm 0.05(stat)\pm 0.03(syst)}, r^2 = 0.05\pm 0.07(stat)\pm 0.03(syst)}. These results will help to better constrain the phase parameter $γ=\arg(-V_{ud}V_{ub}^*/V_{cd}V_{cb}^*)$ of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

hep-ex↗

arXiv2008

Observation of e+e- --> rho+rho- near sqrt(s)=10.58 GeV

We report the first observation of $e^+e^- \to ρ^+ρ^-$, in a data sample of 379 $fb^{-1}$ collected with the BABAR detector at the {PEP-II} $e^+e^-$ storage ring at center-of-mass energies near $\sqrt{s} = 10.58 GeV. We measure a cross section of $σ({e^+e^-\} \to ρ^+ ρ^-) = {19.5 \pm 1.6(stat) \pm 3.2(syst) fb}$. Assuming production through single-photon annihilation, there are three independent helicity amplitudes. We measure the ratios of their squared moduli to be $|{F}_{00}|^2 : |{F}_{10}|^2 : |{F}_{11}|^2 = 0.51 \pm 0.14(stat) \pm 0.07(syst) : 0.10 \pm 0.04(stat) \pm 0.01(syst) : 0.04 \pm 0.03(stat) \pm 0.01(syst)$. The $|{F}_{00}|^2$ result is inconsistent with the prediction of 1.0 made by QCD models with a significance of 3.1 standard deviations including systematic uncertainties.

hep-ex↗

arXiv2008

The $e^+ e^-\to K^+ K^- π^+π^-$, $K^+ K^- π^0π^0$ and $K^+ K^- K^+ K^-$ Cross Sections Measured with Initial-State Radiation

We study the processes $e^+ e^-\to K^+ K^- π^+π^-γ$, $K^+K^-π^0π^0γ$ and $K^+ K^- K^+ K^-γ$, where the photon is radiated from the initial state. About 34600, 4400 and 2300 fully reconstructed events, respectively, are selected from 232 \invfb of \babar data. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy, so that the $K^+ K^- π^+π^-γ$ data can be compared with direct measurements of the $e^+ e^-\to K^+K^- \pipi$ reaction; no direct measurements exist for the $e^+ e^-\to K^+ K^- π^0π^0$ or $\epem\to K^+ K^- K^+ K^-$ reactions. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from $e^+ e^-\toϕ(1020) f_{0}(980)$ and study its structure near threshold. In the charmonium region, we observe the $J/ψ$ in all three final states and several intermediate states, as well as the $ψ(2S)$ in some modes, and measure the corresponding branching fractions. We see no signal for the Y(4260) and obtain an upper limit of $\BR_{Y(4260)\toϕπ^+π^-}\cdotΓ^{Y}_{ee}<0.4 \ev$ at 90% C.L.

hep-ex↗

arXiv2008

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

Using 226 million BBbar events recorded on the Upsilon(4S) resonance with the BABAR detector at the SLAC e+e- PEPII storage rings, we reconstruct B- -> D*0 e- nubar decays using the decay chain D*0 -> D0 pi0 and D0 -> K pi. From the dependence of their differential rate on w, the dot product of the four-velocities of B and D*0, and using the form factor description by Caprini et al. with the parameters F(1) and rho_A1^2, we obtain the results rho_A1^2 = 1.16 +- 0.06 +- 0.08, F(1)|V_cb| = (35.9 +- 0.6 +- 1.4) 10^-3, and BF(B- -> D*0 e- nubar) = (5.56 +- 0.08 +- 0.41)%.

hep-ex↗

arXiv2008

Measurements of the Branching Fractions of B0 --> K^0K+K-, B0 --> K^0pi+K-, B0 --> K0K+pi-, and B0 --> K0pi+pi-

Branching fraction and asymmetry measurements of charmless $B^0\to K^{*0}h^+_1h^-_2$ ($h_{1,2}$ = $K$, $π$) decays are presented, using a data sample of 383 million $Υ(4S) \to$ $B\bar{B$} decays collected with the BaBar detector at the PEP-II asymmetric-energy $B$-meson factory at SLAC. The results are: ${\cal B}$($B^0 \to K^{*0}K^+ K^-)$ = (27.5 $\pm$ 1.3 $\pm$ 2.2) $\times$ 10$^{-6}$, ${\cal B}$($B^0$ $\to$ $K^{*0}π^+ K^-$) = (4.6 $\pm$ 1.1 $\pm$ 0.8) $\times$ 10$^{-6}$ and ${\cal B}$($B^0$ $\to$ $K^{*0}π^+π^-$) = (54.5 $\pm$ 2.9 $\pm$ 4.3) $\times$ 10$^{-6}$. The first errors quoted are statistical and the second are systematic. An upper limit is set for ${\cal B}$($B^0$ $\to$ $K^{*0}K^+ π^-$) $<$ 2.2 $\times$ 10$^{-6}$ at 90% confidence level. We also present measurements of CP-violating asymmetries for the observed decays.

hep-ex↗