1,220 research outputs found
Search for Light New Physics at B Factories
No full textMany extensions of the Standard Model include the possibility of light new particles, such as light Higgs bosons or dark matter candidates. These scenarios can be probed using the large datasets collected by B factories, complementing measurements performed at the LHC. This paper summarizes recent searches for light new physics conducted by the BABAR and Belle experiments
Search for B^+→ℓ^+ν_ℓ recoiling against B^-→D^0ℓ^-ν̅ X
No full textWe present a search for the decay B^+→ℓ^+ν_ℓ(ℓ=τ, μ, or e) in (458.9±5.1)×10^6 BB̅ pairs recorded with the BABAR detector at the PEP-II B-factory. We search for these B decays in a sample of B^+B^- events where one B-meson is reconstructed as B^-→D^0ℓ^-ν̅ X. Using the method of Feldman and Cousins, we obtain B(B^+→τ^+ν_τ)=(1.7±0.8±0.2)×10^(-4), which excludes zero at 2.3σ. We interpret the central value in the context of the standard model and find the B meson decay constant to be f_B^2=(62±31)×10^3 MeV^2. We find no evidence for B^+→e^+ν_e and B^+→μ^+ν_μ and set upper limits at the 90% C.L. B(B^+→e^+ν_e)<0.8×10^(-5) and B(B^+→μ^+ν_μ)<1.1×10^(-5)
Evidence of B+→τ+ν decays with hadronic B tags
No full textWe present a search for the decay B+→τ+ν using 467.8×10^6 BB̅ pairs collected at the Υ(4S) resonance with the BABAR detector at the SLAC PEP-II B-Factory. We select a sample of events with one completely reconstructed B- in the hadronic decay mode (B-→D(*)0X- and B-→J/ψX-). We examine the rest of the event to search for a B+→τ+ν decay. We identify the τ+ lepton in the following modes: τ+→e+νν̅ , τ+→μ+νν̅ , τ+→π+ν̅ and τ+→ρ+ν̅ . We find an excess of events with respect to the expected background, which excludes the null signal hypothesis at the level of 3.8σ (including systematic uncertainties) and corresponds to a branching fraction value of B(B+→τ+ν)=(1.83_(-0.49)^(+0.53)(stat)±0.24(syst))×10^(-4)
Dalitz plot analyses of B-0 -> (D-DK+)-K-0 and B+-> (D)over-bar(-)D(0)K(+) decays
No full text© 2015, APS Journal
Study of the baryonic B decay B^- → Σ_c^(++)pπ^-π^-
No full textWe report the measurement of the baryonic B decay B^-→Σ_c^(++)p π^-π^-. Using a data sample of 467×10^6 BB pairs collected with the BABAR detector at the PEP-II storage ring at SLAC, the measured branching fraction is (2.98±0.16_((stat))±0.15_((syst))±0.77_((Λc)))×10^(-4), where the last error is due to the uncertainty in B(Λ_c^+→pK^-π^+). The data suggest the existence of resonant subchannels B^-→Λ_c(2595)^+p π^- and, possibly, B^-→Σ_c^(++)Δ^(--)π^-. We see unexplained structures in m(Σ_c^(++)π^-π^-) at 3.25 GeV/c^2, 3.8 GeV/c^2, and 4.2 GeV/c^2
Two-photon physics with L3 at LEP
No full textThe knowledge of two-photon processes increased during the last years thanks to the large sample of e/sup +/e/sup -/ to e/sup +/e/sup -/ hadrons, events collected by L3 at LEP. Inclusive single hadron production such as pi /sup 0/, pi /sup +or-/, K/sub s//sup 0/, K/sup +or-/ and inclusive charm and bottom production are compared to NLO QCD predictions. Nonperturbative QCD phenomena are also investigated through the study of exclusive baryon pair production. (11 refs)
Exclusive production of hadron pairs in two-photon interactions
No full textThe knowledge of two-photon processes increased during the last years thanks to the large sample of \mbox{e}^+\mbox{e}^{-} \rightarrow \mbox{e}^+\mbox{e}^{-} \; hadrons events collected at LEP. Non perturbative QCD phenomena are investigated through the study of exclusive meson and baryon pair production. The cross sections are measured as a function of the γ
γ center-of-mass energy, W
γ
γ
, and the center-of-mass production angle of the hadron, θ
*. Exclusive ρ
0
ρ
0 and ρ
+
ρ
– production for quasi-real photons are investigated through a spin-parity-helicity analysis. Exclusive ρ
0
ρ
0 production is also studied as a function of the photon virtuality Q
2 and compared to recent QCD predictions.
PACS: 13.66Bc Hadron production in \mbox{e}^+\mbox{e}^- interaction
Measurement of B (B → X_sγ), the B → X_sγ photon energy spectrum, and the direct CP asymmetry in B → X_(s+d)γ decays
No full textThe photon spectrum in B → X_sγ decay, where X_s is any strange hadronic state, is studied using a data sample of (382.8±4.2) × 10^6 e^+e^- → Υ(4S) → BB events collected by the BABAR experiment at the PEP-II collider. The spectrum is used to measure the branching fraction B(B → X_sγ)=(3.21±0.15±0.29±0.08) × 10^(-4) and the first, second, and third moments ⟨E_γ⟩=2.267±0.019±0.032±0.003 GeV, ⟨(E_γ-⟨E_γ⟩)^2⟩=0.0484±0.0053±0.0077±0.0005 GeV^2, and ⟨(E_γ-⟨E_γ⟩)^3⟩=-0.0048±0.0011±0.0011±0.0004 GeV^3, for the range E_γ > 1.8 GeV, where E_γ is the photon energy in the B-meson rest frame. Results are also presented for narrower E_γ ranges. In addition, the direct CP asymmetry A_(CP)(B → X_(s+d)γ) is measured to be 0.057±0.063. The spectrum itself is also unfolded to the B-meson rest frame; that is the frame in which theoretical predictions for its shape are made
- …
