We search for evidence of a light scalar boson in the radiative decays of the Υ (2S) and Υ (3S) resonances: Υ (2S, 3S) → γA 0 , A 0 → µ + µ − . Such a particle appears in extensions of the Standard Model, where a light CP -odd Higgs boson naturally couples strongly to b-quarks. We find no evidence for such processes in the mass range 0.212 ≤ m A 0 ≤ 9.3 GeV in the samples of 99 × 10 6 Υ (2S) and 122 × 10 6 Υ (3S) decays collected by the BABAR detector at the PEP-II B-factory and set stringent upper limits on the effective coupling of the b quark to the A 0 . We also limit the dimuon branching fraction of the η b meson: B(η b → µ + µ − ) < 0.9% at 90% confidence level.

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element |V(cb)| and the form-factor slope rho2 in B --> Dl- nu(l) decays based on 460x10(6) BB events recorded at the Upsilon(4S) resonance with the BABAR detector. B --> Dl- nu(l) decays are selected in events in which a hadronic decay of the second B meson is fully reconstructed. We measure B(B- --> D0 l- nu(l))/B(B- --> Xl- nu(l)) = (0.255+/-0.009+/-0.009) and B(B0 --> D+ l- nu(l))/B(B0 --> Xl- nu(l)) = (0.230+/-0.011+/-0.011), along with the differential decay distribution in B --> Dl- nu(l) decays. We then determine G(1)|V(cb)| = (42.3+/-1.9+/-1.4)x10(-3) and rho2 = 1.20+/-0.09+/-0.04, where G(1) is the hadronic form factor at the point of zero recoil.

arXiv:1804.07130v3 [hep-ph] 15 Jul 2019 Higgs boson are very different among the SM, two-Higgs doublet models (2HDM), and MSSM. One of the probes of Higgs self-coupling is Higgs-boson-pair production at the LHC [4][5][6]. There have been a large number of works in literature on Higgs-pair production in the SM [7], in model-independent formalism [8], in models beyond the SM [9], and in SUSY [10]. The predictions for various models are largely different such that the production rates can give valuable information on the self-coupling λ 3H . In the SM, Higgs-pair production receives contributions from both the triangle and box diagrams, which interfere with each other. It is only the triangle diagram that involves the Higgs self-trilinear coupling λ 3H , yet the top-Yukawa coupling appears in both triangle and box diagrams. Therefore, we have to disentangle the triangle diagram from the box diagram in order to probe the Higgs trilinear coupling. In Ref.[11], we pointed out that the triangle diagram, with s-channel Higgs propagator, is more important at low invariant-mass region than the box diagram. Thus, the Higgs-boson pair from the triangle diagram tends to have lower invariant mass, and therefore the opening angle in the decay products of each Higgs boson tends to be larger than that from the box diagram. Indeed, the opening angle separations ∆R γγ and ∆R bb between the decay products of the Higgs-boson pair are very useful variables to disentangle the two sources. However, in Ref. [11] we only assumed some level of signal uncertainties to evaluate the sensitivity to the parameter space of self-coupling λ 3H and the top-Yukawa coupling g S t , without calculating all the other SM backgrounds, e.g., jet-fake backgrounds, single Higgs associated backgrounds, and non-resonant backgrounds.In this work, we perform the most up-to-date comprehensive signal-background analysis for Higgs-pair production through gluon fusion and the HH → bbγγ decay channel. For other production and decay channels and some combined analyses, see Refs. [12]. We simulate the signal and all background processes using simulation tools as sophisticated as what experimentalists use. The signal subprocess is gg → HH → bbγγ with various values for λ 3H . The background includes tt, ttγ, single Higgs associated backgrounds (e.g. ZH, ttH, bbH, ggH followed by H → γγ), and non-resonant or jet-fake backgrounds (e.g. bbγγ, bbjγ, bbjj, jjγγ, etc). We found a set of useful selection cuts to reduce the backgrounds. We express the sensitivity that can be achieved in terms of significance. We find that even for the most promising channel HH → bbγγ at the HL-LHC, the significance is still not high enough to establish the Higgs self-coupling at the SM value, though the self-coupling can be constrained to the range 0 < λ 3H < 7.1 at 95% confidence level (CL) with an integrated luminosity of 3000 fb −1 . Taking account of the uncertainties associated with the top-Yukawa coupling and the estimation of backgrounds, we have found that the 95% CL region broadens i...

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We study the reactions e + e − → e + e − η (′) in the single-tag mode and measure the γγ * → η (′) transition form factors in the momentum-transfer range from 4 to 40 GeV 2 . The analysis is based on 469 fb −1 of integrated luminosity collected at PEP-II with the BABAR detector at e + e − centerof-mass energies near 10.6 GeV.

Semileptonic B decays to DXℓν (ℓ = e or µ) are selected by reconstructing D 0 ℓ and D + ℓ combinations from a sample of 230 million Υ (4S) → BB decays recorded with the BABAR detector at the PEP-II e + e − collider at SLAC. A global fit to these samples in a 3-dimensional space of kinematic variables is used to determine the branching fractions B(B − → D 0 ℓν) = (2.34 ± 0.03 ± 0.13)% and B(B − → D * 0 ℓν) = (5.40 ± 0.02 ± 0.21)% where the errors are statistical and systematic, respectively. The fit also determines form factor parameters in a HQET-based parameterization, resulting in ρ 2 D = 1.20 ± 0.04 ± 0.07 for B → Dℓν and ρ 2 D * = 1.22 ± 0.02 ± 0.07 for B → D * ℓν. These values are used to obtain the product of the CKM matrix element |V cb | times the form factor at the zero 4 recoil point for both B → Dℓν decays, G(1)|V cb | = (43.1 ± 0.8 ± 2.3) × 10 −3 , and for B → D * ℓν decays, F(1)|V cb | = (35.9 ± 0.2 ± 1.2) × 10 −3 .

Higgs-boson pair production is well known being capable to probe the trilinear self-coupling of the Higgs boson, which is one of the important ingredients of the Higgs sector itself. Pair production then depends on the top-quark Yukawa coupling g S,P t , Higgs trilinear coupling λ 3H , and a possible dim-5 contact-type ttHH coupling g S,P tt , which may appear in some higher representations of the Higgs sector. We take into account the possibility that the top-Yukawa and the ttHH couplings involved can be CP violating. We calculate the cross sections and the interference terms as coefficients of the square or the 4th power of each coupling (g S,P t , λ 3H , g S,P tt ) at various stages of cuts, such that the desired cross section under various cuts can be obtained by simply inputing the couplings. We employ the HH → γγbb decay mode of the Higgs-boson pair to investigate the possibility of disentangle the triangle diagram from the box digram so as to have a clean probe of the trilinear coupling at the LHC. We found that the angular separation between the b andb and that between the two photons is useful. We obtain the sensitivity reach of each pair of couplings at the 14 TeV LHC and the future 100 TeV pp machine. Finally, we also comment on using the bbτ + τ − decay mode in appendix.

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