We study the reaction e+e-→e+e -ηc, ηc→KSK±π" and obtain ηc mass and width values 2982.2±0.4±1.6MeV/c2 and 31.7±1.2±0.8MeV, respectively. We find Γ(ηc→γ γ)B(ηc→KK̄π)=0.374±0.009±0.031keV, and measure the γγ*→ηc transition form factor in the momentum transfer range from 2 to 50GeV2. The analysis is based on 469fb-1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV. © 2010 The American Physical Society.

We report measurements of the branching fractions of neutral and charged B meson decays to final states containing a K1(1270) or K1(1400) meson and a charged pion. The data, collected with the BABAR detector at the SLAC National Accelerator Laboratory, correspond to 454×106 BB̄ pairs produced in e+e- annihilation. We measure the branching fractions B(B0→K1(1270)+π-+K1(1400) +π -)=3.1-0.7+0.8×10-5 and B(B+→ K1(1270) 0π++K1(1400) 0π+)=2.9-1.7+2.9×10 -5 (<8.2×10-5 at 90% confidence level), where the errors are statistical and systematic combined. The B0 decay mode is observed with a significance of 7.5σ, while a significance of 3.2σ is obtained for the B+ decay mode. Based on these results, we estimate the weak phase α=(79±7±11)°from the time-dependent CP asymmetries in B0→a1(1260)±π decays. © 2010 The American Physical Society.

We measure the rate of D0-D̄0 mixing with the observable yCP=(τKπ/τKK)-1, where τKK and τKπ are, respectively, the mean lifetimes of CP-even D0→K+K- and CP-mixed D0→K-π+ decays, using a data sample of 384fb-1 collected by the BABAR detector at the SLAC PEP-II asymmetric-energy B Factory. From a sample of D0 and D̄0 decays where the initial flavor of the decaying meson is not determined, we obtain yCP=[1.12±0.26(stat)±0.22(syst)]%, which excludes the no-mixing hypothesis at 3.3σ, including both statistical and systematic uncertainties. This result is in good agreement with a previous BABAR measurement of yCP obtained from a sample of D*+→D0π+ events, where the D0 decays to K-π+, K+K-, and π+π-, which is disjoint with the untagged D0 events used here. Combining the two results taking into account statistical and systematic uncertainties, where the systematic uncertainties are assumed to be 100% correlated, we find yCP=[1.16±0.22(stat)±0. 18(syst)]%, which excludes the no-mixing hypothesis at 4.1σ. © 2009 The American Physical Society.

A precise measurement of the cross section of the process e(+)e(-) --> pi(+)pi(-)(gamma) from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using 232 fb(-1) of data collected with the BABAR detector at e(+)e(-) center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e(+)e(-) --> mu(+)mu(-)gamma(gamma). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the pipi cross section measured from threshold to 1.8 GeV is (514.1 +/- 2.2(stat) +/- 3.1(syst)) x 10(-10).

We present a measurement of the branching fractions of the 22 decay channels of the B0 and B+ mesons to D̄(*)D(*)K, where the D(*) and D̄(*) mesons are fully reconstructed. Summing the 10 neutral modes and the 12 charged modes, the branching fractions are found to be B(B0→D̄(*)D(*)K)=(3.68±0. 10±0.24)% and B(B+→D̄(*)D(*)K)=(4. 05±0.11±0.28)%, where the first uncertainties are statistical and the second systematic. The results are based on 429fb-1 of data containing 471×106BB̄ pairs collected at the Υ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. © 2011 American Physical Society.

We report a direct measurement of D0-D0 mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D(0) → K(S)(0) π+ π- and, for the first time, D0 → K(S)(0)K+ K- decays. The low-momentum pion π(s)(+) in the decay D*+ → D0 π(s)(+) identifies the flavor of the neutral D meson at its production. Using 468.5 fb(-1) of e+ e- colliding-beam data recorded near square root(s)=10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x = [1.6 ± 2.3(stat) ± 1.2(syst) ± 0.8(model)] × 10(-3), and y = [5.7 ± 2.0(stat) ± 1.3(syst) ± 0.7(model)] × 10(-3). These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing.

We present a study of the decays B0,+→J/ ψπ+π-π0K0,+, using 467×106 BB̄ pairs recorded with the BABAR detector. We present evidence for the decay mode X(3872)→J/ψω, with product branching fractions B(B+→X(3872)K+)×B(X(3872)→J/ ψω)=[0.6±0.2(stat)±0.1(syst)]×10-5, and B(B0→X(3872)K0)×B(X(3872)→J/ψω)=[0.6±0.3(stat) ±0.1(syst)]×10-5. A detailed study of the π+π-π0 mass distribution from X(3872) decay favors a negative-parity assignment. © 2010 The American Physical Society.

We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle γ through a Dalitz plot analysis of neutral D-meson decays to K(S)(0) π+ π- and K(S)(0) K+ K- produced in the processes B∓ → DK∓, B∓ D* K∓ with D* → Dπ(0), Dγ, and B∓ → DK*∓ with K*∓ → K(S)(0) π∓, using 468 million BB pairs collected by the BABAR detector at the PEP-II asymmetric-energy e+ e- collider at SLAC. We measure γ = (68 ± 14 ± 4 ± 3)° (modulo 180°), where the first error is statistical, the second is the experimental systematic uncertainty, and the third reflects the uncertainty in the description of the neutral D decay amplitudes. This result is inconsistent with γ = 0 (no direct CP violation) with a significance of 3.5 standard deviations.