Lou, Xinchou
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/2305
Dr. Lou’s research interests focus on elementary particle physics experiments at electron-position colliders, high performance cluster computing, and application of data mining techniques to other fields of research. He is currently searching for new elementary particles, measuring charmonium production with the BABAR detector located at the Stanford Linear Accelerator Center.
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Browsing Lou, Xinchou by Subject "Asymmetry"
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Item Measurement of Collins Asymmetries in Inclusive Production of Charged Pion Pairs in e⁺e⁻ Annihilation at BaBar(American Physical Society, 2014-09-09) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present measurements of Collins asymmetries in the inclusive process e⁺e⁻ → ππX, where π stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb⁻¹ collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis.Item Measurements of Direct CP Asymmetries in B→X_sγ Decays using Sum of Exclusive Decays(Amer Physical Soc, 2014-11-05) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We measure the direct CP violation asymmetry, A_{CP}, in B→X_s and the isospin difference of the asymmetry, ΔA_{CP}, using 429 fb⁻¹ of data collected at ϒ(4S) resonance with the BABAR detector at the PEP- II asymmetric-energy e⁺e⁻ storage rings operating at the SLAC National Accelerator Laboratory. B mesons are reconstructed from ten charged B final states and six neutral B final states. We find A_{CP} = +(1.7 ± 1.9 ± 1.0)%, which is in agreement with the Standard Model prediction and provides an improvement on the world average. Moreover, we report the first measurement of the difference between A_{CP} for charged and neutral decay modes, ΔA_{CP} = +(5.0 ± 3.9 ± 1.5)%. Using the value of ΔA(CP), we also provide 68% and 90% confidence intervals on the imaginary part of the ratio of the Wilson coefficients corresponding to the chromomagnetic dipole and the electromagnetic dipole transitions.Item Search for CP Violation in B⁰- B̅⁰ Mixing Using Partial Reconstruction of B⁰ → D*‾ Xℓ⁺ νℓ and a Kaon Tag(American Physical Society, 2013-09-03) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Lou, Xinchou; Izen, Joseph M.; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present results of a search for CP violation in B⁰- B̅⁰ mixing with the BABAR detector. We select a sample of B⁰ → D*‾ Xℓ⁺ν decays with a partial reconstruction method and use kaon tagging to assess the flavor of the other B meson in the event. We determine the CP violating asymmetry A_{CP} ≡ [N(B⁰B⁰) - N(B̅⁰B̅⁰)]/N(B⁰B⁰) + N(B̅⁰B̅⁰)] = (0.06 ± 0.17_{-0.32} ^{+0.38})%, corresponding to Δ_{CP} = 1 - |q/p| = (0.29 ± 0.84_{-1.61}^{+1.88}) x 10⁻³.