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NA64 Collaboration(Andreev, Y. M. et al), & Molina Bueno, L. (2022). Search for a New B-L Z' Gauge Boson with the NA64 Experiment at CERN. Phys. Rev. Lett., 129, 161801–6pp.
Abstract: A search for a new Z′ gauge boson associated with (un)broken B−L symmetry in the keV–GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22×10^11 electrons on target collected during 2016–2021 runs, no signal events were found. This allows us to derive new constraints on the Z′−e coupling strength, which, for the mass range 0.3≲ mZ′≲ 100 MeV, are more stringent compared to those obtained from the neutrino-electron scattering data.
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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Measurement of the Ratio sigma(t(t)over-bar)/sigma(Z/gamma*-> ll) and Precise Extraction of the t(t)over-bar Cross Section. Phys. Rev. Lett., 105(1), 012001–7pp.
Abstract: We report a measurement of the ratio of the t (t) over bar to Z/gamma* production cross sections in root s = 1.96 TeV p (p) over bar collisions using data corresponding to an integrated luminosity of up to 4.6 fb(-1), collected by the CDF II detector. The t (t) over bar cross section ratio is measured using two complementary methods, a b-jet tagging measurement and a topological approach. By multiplying the ratios by the well-known theoretical Z/gamma* -> ll cross section predicted by the standard model, the extracted t (t) over bar cross sections are effectively insensitive to the uncertainty on luminosity. A best linear unbiased estimate is used to combine both measurements with the result sigma(t (t) over bar) = 7.70 +/- 0.52 pb, for a top-quark mass of 172.5 GeV/c(2).
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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Search for Supersymmetry with Gauge-Mediated Breaking in Diphoton Events with Missing Transverse Energy at CDF II. Phys. Rev. Lett., 104(1), 011801–8pp.
Abstract: We present the results of a search for supersymmetry with gauge-mediated breaking and (chi) over tilde (1)(0) -> gamma(G) over tilde in the gamma gamma + missing transverse energy final state. In 2.6 +/- 0.2 fb(-1) of p (p) over bar collisions at root s 1.96 TeV recorded by the CDF II detector we observe no candidate events, consistent with a standard model background expectation of 1.4 +/- 0.4 events. We set limits on the cross section at the 95% C.L. and place the world's best limit of 149 GeV/c(2) on the (chi) over tilde (1)(0) mass at tau((chi) over tilde 01) << 1 ns. We also exclude regions in the (chi) over tilde (1)(0) mass-lifetime plane for tau((chi) over tilde 01) less than or similar to 2 ns.
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BABAR Collaboration(Aubert, B. et al), Azzolini, V., Lopez-March, N., Martinez-Vidal, F., Milanes, D. A., & Oyanguren, A. (2010). Measurement of vertical bar V-cb vertical bar and the Form-Factor Slope in (B)over-bar -> Dl(-) (nu)over-bar(l) Decays in Events Tagged by a Fully Reconstructed B Meson. Phys. Rev. Lett., 104(1), 011802–7pp.
Abstract: We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element vertical bar V-cb vertical bar and the form-factor slope rho(2) in (B) over bar -> Dl(-) (nu) over bar (l) decays based on 460 X 10(6) B (B) over bar events recorded at the Gamma(4S) resonance with the BABAR detector. (B) over bar -> Dl(-) (nu) over bar (l) decays are selected in events in which a hadronic decay of the second B meson is fully reconstructed. We measure B(B- -> D(0)l(-) (nu) over bar (l))/B(B- -> Xl(-) (nu) over bar (l)) = (0.255 +/- 0.009 +/- 0.009) and B((B) over bar (0) -> D(+)l(-) (nu) over bar (l))/B((B) over bar (0) -> Xl(-) (nu) over bar (l)) = (0.230 +/- 0.011 +/- 0.011), along with the differential decay distribution in (B) over bar -> Dl(-) (nu) over bar (l) decays. We then determine G(1)vertical bar V-cb vertical bar = 42.3 +/- 1.9 +/- 1.4) X 10(-3) and rho(2) = 1.20 +/- 0.09 +/- 0.04, where G(1) is the hadronic form factor at the point of zero recoil.
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ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Ferrer, A., et al. (2012). Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of the W -> lv and Z -> ll Cross Sections. Phys. Rev. Lett., 109(1), 012001–17pp.
Abstract: A QCD analysis is reported of ATLAS data on inclusive W-+/- and Z boson production in pp collisions at the LHC, jointly with ep deep-inelastic scattering data from HERA. The ATLAS data exhibit sensitivity to the light quark sea composition and magnitude at Bjorken x similar to 0:01. Specifically, the data support the hypothesis of a symmetric composition of the light quark sea at low x. The ratio of the strange-to-down sea quark distributions is determined to be 1:00(-0:28)(+0.25) at absolute four-momentum transfer squared Q(2) = 1: 9 GeV2 and x = 0: 023.
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