BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., Oyanguren, A., & Villanueva-Perez, P. (2015). Search for a light Higgs resonance in radiative decays of the Upsilon(1S) with a charm tag. Phys. Rev. D, 91(7), 071102–9pp.
Abstract: A search is presented for the decay Upsilon(1S) -> gamma A(0), A(0) -> c (c) over barc, where A(0) is a candidate for the CP-odd Higgs boson of the next-to-minimal supersymmetric standard model. The search is based on data collected with the BABAR detector at the Upsilon(2S) resonance. A sample of Upsilon(1S) mesons is selected via the decay Upsilon(2S) -> pi(+)pi(-)Upsilon(1S) . The A(0) -> c (c) over bar decay is identified through the reconstruction of hadronic D-0, D+,and D-0 (2010)(+) meson decays. No significant signal is observed. The measured 90% confidence-level upper limits on the product branching fraction beta(Upsilon(1S) -> gamma A(0)) x beta(A(0) -> (c) over barc range from 7.4 x 10(-5) to 2.4 x 10(-3) for A(0) masses from 4.00 to 8.95 GeV/c(2) and 9.10 to 9.25 GeV/c(2), where the region between 8.95 and 9.10 GeV/c(2) is excluded because of background from Upsilon(2S) -> gamma chi(bJ)(1P), chi(bJ)(1P) -> gamma Upsilon(1S) decays.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2015). Study of the e(+)e(-) -> K+K- reaction in the energy range from 2.6 to 8.0 GeV. Phys. Rev. D, 92(7), 072008–16pp.
Abstract: The e(+)e(-) -> K+K- cross section and charged-kaon electromagnetic form factor are measured in the e(+)e(-) center-of-mass energy range (E) from 2.6 to 8.0 GeV using the initial-state radiation technique with an undetected photon. The study is performed using 469 fb(-1) of data collected with the BABAR detector at the PEP-II2 e(+)e(-) collider at center-of-mass energies near 10.6 GeV. The form factor is found to decrease with energy faster than 1/E-2 and approaches the asymptotic QCD prediction. Production of the K+K- final state through the J/psi and psi(2S) intermediate states is observed. The results for the kaon form factor are used together with data from other experiments to perform a model-independent determination of the relative phases between electromagnetic (single-photon) and strong amplitudes in J/psi and psi(2S). K+K- decays. The values of the branching fractions measured in the reaction e(+)e(-) -> K+K- are shifted relative to their true values due to interference between resonant and nonresonant amplitudes. The values of these shifts are determined to be about +/- 5% for the J/psi meson and +/- 15% for the psi(2S) meson.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2015). Measurement of initial-state-final-state radiation interference in the processes e(+)e(-) -> mu(+)mu(-)gamma and e(+)e(-) -> pi(+)pi(-)gamma. Phys. Rev. D, 92(7), 072015–29pp.
Abstract: Charge asymmetry in the processes e(+)e(-) -> mu(+)mu(-)gamma and e(+)e(-) -> pi(+)pi(-)gamma is measured using 232 fb(-1) of data collected with the BABAR detector at e(+)e(-) center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial-and final-state radiation (FSR). The asymmetry is determined as a function of the invariant mass of the final-state tracks from production threshold to a few GeV/c(2). It is compared to the expectation from QED for e(+)e(-) -> mu(+)mu(-)gamma, and from theoretical models for e(+)e(-) -> pi(+)pi(-)gamma. A clear interference pattern is observed in e(+)e(-) -> pi(+)pi(-)gamma, particularly in the vicinity of the f(2)(1270) resonance. The inferred rate of lowest-order FSR production is consistent with the QED expectation for e(+)e(-) -> mu(+)mu(-)gamma, and is negligibly small for e(+)e(-) -> pi(+)pi(-)gamma.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2015). Collins asymmetries in inclusive charged KK and K pi pairs produced in e(+)e(-) annihilation. Phys. Rev. D, 92(11), 111101–8pp.
Abstract: We present measurements of Collins asymmetries in the inclusive process e(+)e(-) -> h(1)h(2)X, h(1)h(2) = KK, K pi, pi pi, at the center-of-mass energy of 10.6 GeV, using a data sample of 468 fb(-1) collected by the BABAR experiment at the PEP-II B factory at SLAC National Accelerator Center. Considering hadrons in opposite thrust hemispheres of hadronic events, we observe clear azimuthal asymmetries in the ratio of unlike sign to like sign, and unlike sign to all charged h(1)h(2) pairs, which increase with hadron energies. The K pi asymmetries are similar to those measured for the pi pi pairs, whereas those measured for high-energy KK pairs are, in general, larger.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2016). Measurement of the I=1/2 K pi S-wave amplitude from Dalitz plot analyses of eta(c) -> K(K)over-bar pi in two-photon interactions. Phys. Rev. D, 93(1), 012005–16pp.
Abstract: We study the processes gamma gamma -> (KSK +/-)-K-0 pi(-/+) and gamma gamma -> K+K-pi(0) using a data sample of 519 fb(-1) recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e(+)e(-) collider at center-of-mass energies at and near the Upsilon(nS) (n = 2, 3, 4) resonances. We observe eta(c) decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the I = 1/2 K pi S-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of 1.5 GeV/c(2). In contrast, the amplitudes show very marked differences. The data require the presence of a new a(0)(1950) resonance with parameters m = 1931 +/- 14 +/- 22 MeV/c(2) and Gamma = 271 +/- 22 +/- 29 MeV.
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