Showing papers by "V. B. Golubev published in 2019"

Extraction of form Factors from a Four-Dimensional Angular Analysis of B →d∗-ν

Abstract: An angular analysis of the decay B[over ¯]→D^{*}l^{-}ν[over ¯]_{l}, l∈{e,μ}, is reported using the full e^{+}e^{-} collision data set collected by the BABAR experiment at the ϒ(4S) resonance. One B meson from the ϒ(4S)→BB[over ¯] decay is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the dilepton mass squared, q^{2}, and three angles. The first unbinned fit to the full four-dimensional decay rate in the standard model is performed in the so-called Boyd-Grinstein-Lebed approach, which employs a generic q^{2} parametrization of the underlying form factors based on crossing symmetry, analyticity, and QCD dispersion relations for the amplitudes. A fit using the more model-dependent Caprini-Lellouch-Neubert (CLN) approach is performed as well. Our form factor shapes show deviations from previous fits based on the CLN parametrization. The latest form factors also provide an updated prediction for the branching fraction ratio R(D^{*})≡B(B[over ¯]→D^{*}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]→D^{*}l^{-}ν[over ¯]_{l})=0.253±0.005. Finally, using the well-measured branching fraction for the B[over ¯]→D^{*}l^{-}ν[over ¯]_{l} decay, a value of |V_{cb}|=(38.36±0.90)×10^{-3} is obtained that is consistent with the current world average for exclusive B[over ¯]→D^{(*)}l^{-}ν[over ¯]_{l} decays and remains in tension with the determination from inclusive semileptonic B decays to final states with charm.

Measurement of the $e^+e^- \to \pi^+\pi^-\pi^0\eta$ cross section below $\sqrt{s}=2$ GeV

Abstract: The process $e^+e^- \to \pi^+\pi^-\pi^0\eta$ is studied in the center-of-mass energy region below 2 GeV with the SND detector at the VEPP-2000 $e^+e^-$ collider. The four intermediate states contribute to this process: $\omega\eta$, $\phi\eta$, $a_0(980)\rho$, and a structureless $\pi^+\pi^-\pi^0\eta$ state. We measure the total $e^+e^- \to \pi^+\pi^-\pi^0\eta$ cross section and the cross sections for its components: $\omega\eta$, $\phi\eta$, and a sum of $a_0(980)\rho$ and the structureless state. Our results are in agreement with previous measurements and have comparable or better accuracies.

Recent results from SND detector at VEPP-2000 collider

Abstract: Recent results on e + e − annihilation to hadrons from SND experiment at VEPP-2000 collider are presented. Corresponding data set is about 200 pb−1 of integrated luminosity collected at the energy region below 2 GeV. The processes e + e − → π+ π− , π0 γ, ωπ0 , π+ π− π0 , ηπ+ π− π0 , η , π+ π− 4π0 have been studied. Searches for e + e − annihilation to C -even resonances η and f 1(1285) were done.

Search for B-→ Λ p ν ν with the B a B ar experiment SEARCH for B-→ Λ p ν ν ... LEES J. P. et al.

Abstract: A search for the rare flavor-changing neutral current process B-→Λp¯νν¯ using data from the BABAR experiment has been performed. A total of 424 fb-1 of e+e- collision data collected at the center-of-mass energy of the ϒ(4S) resonance is used in this study, corresponding to a sample of (471±3)×106 BB¯ pairs. Signal B-→Λp¯νν¯ candidates are identified by first fully reconstructing a B+ decay in one of many possible exclusive decays to hadronic final states, then examining detector activity that is not associated with this reconstructed B+ decay for evidence of a signal B-→Λp¯νν¯ decay. The data yield is found to be consistent with the expected background contribution under a null signal hypothesis, resulting in an upper limit of B(B-→Λp¯νν¯)<3.0×10-5 at the 90% confidence level.

Study of the $e^+e^-$ annihilation into hadrons with the SND detector at the VEPP-2000 collider

Abstract: Recent results on study of exclusive processes of $e^+e^-$ annihilation into hadrons below 2 GeV obtained at the SND detector are presented. The analysis are based on data collected at the VEPP-2M and VEPP-2000 colliders. In particular, we present the measurements of the $e^+e^-\to\eta\pi^+\pi^-$, $e^+e^-\to\eta K^+K^-$, $e^+e^-\to K_SK_L\pi^0$ cross sections, and the preliminary results on study of the $e^+e^-\to\pi^+\pi^-$, $e^+e^-\to n\bar{n}$, $e^+e^-\to\pi^0\gamma$, and the upper limit for $\eta\to e^+e^-$ decay branching fraction