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 "Astrophysics"
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Item Branching fraction of τ-→π-Ks0Ks0(π0)ν τ decays(American Physical Society, 2012-11-26) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present a study of τ -→π -KS0KS0(π0) ν τ and τ -→K -KS0KS0(π0) ν τ decays using a data set of 430 million tau lepton pairs, corresponding to an integrated luminosity of 468 fb(-1), collected with the BABAR detector at the PEP-II asymmetric energy e(+)e(-) storage rings. We measure branching fractions of (2.31 +/- 0.04 +/- 0.08) x 10(-4) and (1.60 +/- 0.20 +/- 0.22) x 10(-5) for the τ -→π -KS0KS0ν τ and τ -→π -KS0KS0π0ν τ decays, respectively. We find no evidence for τ -→K -KS0KS0ν τ and τ -→K -KS0KS0π0ν τ decays and place upper limits on the branching fractions of 6.3 x 10(-7) and 4.0 x 10(-7) at the 90% confidence level.Item Measurement of the Inclusive Isolated Prompt Photons Cross Section in pp Collisions at √s=7 TeV with the ATLAS Detector Using 4.6 fb⁻¹(American Physical Society, 2014-03-24) Aad, G.; Abajyan, T.; Abbott, B.; Abdallah, J.; Khalek, S. Abdel; Abdelalim, A. A.; Abdinov, O.; Wong, Wei-Cheng; Reeves, Kendall; Lou, Xinchou; Izen, Joseph M .; Namasivayam, Harisankar; ATLAS Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Izen, Joseph M.; Namasivayam, Harisankar; Reeves, Kendall; Lou, Xinchou; Wong, Wei-ChengA measurement of the cross section for the production of isolated prompt photons in pp collisions at a center-of-mass energy √s=7 TeV is presented. The results are based on an integrated luminosity of 4.6 fb⁻¹ collected with the ATLAS detector at the LHC. The cross section is measured as a function of photon pseudorapidity η^γ and transverse energy E_T^γ in the kinematic range 100 ≤ E_T^γ < 1000 GeV and in the regions |η^γ| < 1.37 and 1.52 ≤ |η^γ| < 2.37. The results are compared to leading-order parton-shower Monte Carlo models and next-to-leading-order perturbative QCD calculations. Next-to-leading-order perturbative QCD calculations agree well with the measured cross sections as a function of E_T^γ and η^γ.Item Measurement of the Proton Form Factor by Studying e⁺e⁻ → pp̅(Amer Physical Soc, 2015-06-09) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouUsing data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of e⁺e⁻ → pp̅ at 12 center-of-mass energies from 2232.4 to 3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal |G(E)| = |G(M)|. In addition, the ratio of electric to magnetic form factors, |G(E)/G(M)|, and |G(M)| are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at √s̅ = 2232.4 and 2400.0 MeV and a combined sample at √s̅ = 3050.0, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BABAR, improving the overall uncertainty by about 30%. |G(E)/G(M)| ratios are close to unity and consistent with BABAR results in the same q^2 region, which indicates the data are consistent with the assumption that |G(E)| = |G(M)| within uncertainties.Item Measurement of the Semileptonic Branching Fraction of the B_s Meson(American Physical Society, 2012-01-03) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Milanes, D. A.; Izen, Joseph M.; Lou, Xinchou; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We report a measurement of the inclusive semileptonic branching fraction of the B_s meson using data collected with the BABAR detector in the center-of-mass energy region above the Υ(4S) resonance. We use the inclusive yield of mesons and the yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B_s mesons relative to all B mesons as a function of center-of-mass energy. The inclusive semileptonic branching fraction of the B_s meson is determined to be ℬ(B_s → ℓνX) = 9.5_{-2.0}^{+2.5}(stat)_{-1.9}^{+1.1}(syst)%, where ℓ indicates the average of e and μ.Item Search for CP Violation in the Decay τ⁻ → π⁻ K_S⁰(0π⁰)ν_τ(American Physical Society, 2012-02-13) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Milanes, D. A.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We report a search for CP violation in the decay τ⁻ → π⁻ K_S⁰ (0π⁰)ν_τ using a data set of 437×106 τ-lepton pairs, corresponding to an integrated luminosity of 476 fb⁻¹, collected with the BABAR detector at the PEP-II asymmetric-energy e⁺e⁻ storage rings. The CP-violating decay-rate asymmetry is determined to be (-0.36 ± 0.23 ± 0.11)% approximately 2.8 standard deviations from the standard model prediction of (0.36 ± 0.01)%.Item Search for the Decay D⁰ → γγ and Measurement of the Branching Fraction for D⁰ → π⁰π⁰(American Physical Society, 2012-05-18) Lees, J. P.; Poireau, V.; Prencipe, E.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We search for the rare decay of the D⁰ meson to two photons, D⁰ → γγ, and present a measurement of the branching fraction for a D⁰ meson decaying to two neutral pions, B(D⁰ → π⁰π⁰). The data sample analyzed corresponds to an integrated luminosity of 470.5 fb⁻¹ collected by the BABAR detector at the PEP-II asymmetric-energy e⁺e⁻ collider at SLAC. We place an upper limit on the branching fraction, B(D⁰ → γγ) < 2.2 × 10⁻⁶ at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find B(D⁰→π⁰π⁰) = (8.4 ± 0.1 ± 0.4 ± 0.3) × 10⁻⁴.Item Search for the Z₁(4050)⁺ and Z₂(4250)⁺ States in B̅⁰→ χ_{c1}K⁻ π⁺ and B⁺ → χ_{c1}K_s⁰ π⁺(American Physical Society, 2012-03-16) Lees, J. P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Milanes, D. A.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We search for the Z₁(4050)⁺ and Z₂(4250)⁺ states, reported by the Belle Collaboration, decaying to χ_{c1}π⁺ in the decays B̅⁰ → χ_{c1}K⁻ π⁺ and B⁺ → χ_{c1}K_S⁰ π⁺ where χ_{c1} → J/ψγ. The data were collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e⁺e⁻ collider operating at center-of-mass energy 10.58 GeV, and correspond to an integrated luminosity of 429 fb⁻¹. In this analysis, we model the background-subtracted, efficiency-corrected χ_{c1}π⁺ mass distribution using the Kπ mass distribution and the corresponding normalized Kπ Legendre-polynomial moments, and then test the need for the inclusion of resonant structures in the description of the χ_{c1}π⁺ mass distribution. No evidence is found for the Z₁(4050)⁺ and Z₂(4250)⁺ resonances, and 90% confidence level upper limits on the branching fractions are reported for the corresponding B-meson decay modes.