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 Author "0000-0003-0867-2189 (Lou, X.)"
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Item Measurement of the Inclusive Jet Cross-Section in Proton-Proton Collisions at √s̅ = 7 TeV using 4.5 fb⁻¹ of Data with the ATLAS Detector(2015-02-24) Aad, G.; Abbott, B.; Abdallah, J.; Khalek, S. Abdel; Abdinov, O.; Aben, R.; Abi, B.; Abolins, M.; Izen, J. M.; Leyton, Michael; Lou, Xinchou; Meirose, Bernhard; Namasivayam, Harisankar; ATLAS Collaboration; 0000-0003-0867-2189 (Lou, X.); 250674117 (Izen, JM); 250674117 (Izen, JM); Izen, Joseph M.; Leyton, Michael; Meirose, Bernhard; Namasivayam, Harisankar; Reeves, KendallThe inclusive jet cross-section is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using a data set corresponding to an integrated luminosity of 4.5 fb⁻¹ collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-kT algorithm with radius parameter values of 0.4 and 0.6. The double-differential cross-sections are presented as a function of the jet transverse momentum and the jet rapidity, covering jet transverse momenta from 100 GeV to 2 TeV. Next-to-leading-order QCD calculations corrected for non-perturbative effects and electroweak effects, as well as Monte Carlo simulations with next-to-leading-order matrix elements interfaced to parton showering, are compared to the measured cross-sections. A quantitative comparison of the measured cross-sections to the QCD calcula tions using several sets of parton distribution functions is performed.Item Measurement of χ_{cJ} Decaying into η'K⁺K⁻(American Physical Society, 2014-04-11) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; An, F. F.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X.); Lou, XinchouUsing (106.41 ± 0.86) × 106 ψ(3686) events collected with the BESIII detector at BEPCII, we study for the first time the decay χcJ → η'K+K- (J = 1, 2), where η' → γρ0 and η' → ηπ+π-. A partial wave analysis in the covariant tensor amplitude formalism is performed for the decay χc1 → η'K+K-. Intermediate processes χc1 → η' f0 (980), χc1 → η' f0 (1710), χc1 → η' f2' (1525) and χc1 → K∗ 0 (1430)± K∓ (K∗ 0 (1430)± → η' K±) are observed with statistical significances larger than 5σ, and their branching fractions are measured.Item Observation of a Neutral Charmoniumlike State Z_c(4025)⁰ in e⁺e⁻ → (D*D̅*)⁰ π⁰(2015-10) 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, XinchouWe report a study of the process e⁺e⁻ → (D*D̅*)⁰ π⁰ using e⁺e⁻ collision data samples with integrated luminosities of 1092 pb⁻¹ at √s̅ = 4.23 GeV and 826 pb⁻¹ at √s̅ = 4.26 GeV collected with the BESIII detector at the BEPCII storage ring. We observe a new neutral structure near the (D*D̅*)⁰ mass threshold in the π⁰ recoil mass spectrum, which we denote as Z_c(4025)⁰. Assuming a Breit-Wigner line shape, its pole mass and pole width are determined to be (4025.5_{-4.7}^{+2.0) ± 3.1) MeV/c² and (23.0 ± 6.0 ± 1.0) MeV, respectively. The Born cross sections of e⁺e⁻→ Z_c(4025)⁰π⁰ → (D*D̅*)⁰ π⁰ are measured to be (61.6 ± 8.2 ± 9.0) pb at √s̅ = 4.23 GeV and (43.4 ± 8.0 ± 5.4) pb at √s̅ = 4.26 GeV. The first uncertainties are statistical and the second are systematic.Item Observation of a Neutral Structure Near the DD̅* Mass Threshold in e⁺e⁻ → (DD̅*)⁰π⁰ at √s= 4.226 and 4.257 GeV(Amer Physical Soc, 2015-11) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESII Collaboration; 0000-0003-0867-2189 (Lou, X.); Lou, XinchouA neutral structure in the DD̅* system around the DD̅* mass threshold is observed with a statistical significance greater than 10σ in the processes e⁺e⁻ → D⁺D*π° + c.c. and e⁺e⁻ →D°D̅*⁰ + c.c. At √s = 4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as Z_c(3885)⁰. Assuming the presence of a resonance, its pole mass and width are determined to be [3885.7_{-5.7}^{+4.3} (stat) ± 8.4(syst)] MeV/c² and [35_{-12}^{+11} (stat) ± 15(syst)] MeV, respectively. The Born cross sections are measured to be σ[e⁺e⁻ → Z_c(3885)°π°, Z_c(3885)° →DD̅*] = [77 ± 13(stat) ± 17(syst)] pb at 4.226 GeV and [47 ± 9(stat) ± 10(syst)] pb at 4.257 GeV. The ratio of decay rates B[Z_c(3885)° → D⁺D*⁻ + c.c.] / 𝓑ℬ[Z_c(3885)° → D°D̅*° + c.c.] is determined to be 0.96 ± 0.18(stat) ± 0.12(syst), consistent with no isospin violation in the process, Z_c(3885)° → DD̅*.Item Observation of e⁺e⁻ → π⁰π⁰h_c and a Neutral Charmoniumlike Structure Z_c(4020)°(American Physical Society, 2014-11-18) 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 collected with the BESIII detector operating at the Beijing Electron Positron Collider at center-of-mass energies of √s = 4.23, 4.26, and 4.36 GeV, we observe e⁺e⁻ → π⁰π⁰h_c for the first time. The Born cross sections are measured and found to be about half of those of e⁺e⁻ → π⁺π⁻h_c within less than 2σ In the π⁰h_c mass spectrum, a structure at 4.02 GeV/c² is found. It is most likely to be the neutral isospin partner of the Z_c(4020)^± observed in the process of e⁺e⁻ → π⁺π⁻h_c being found. A fit to the π°h_c invariant mass spectrum, with the width of the Z_c(4020)° fixed to that of its charged isospin partner and possible interferences with non- Z_c(4020)° amplitudes neglected, gives a mass of (4023.9 ± 2.2 ± 3.8) MeV/c² for the Z_c(4020)°, where the first error is statistical and the second systematic.Item Observation of Z_c (3900)⁰ in e⁺e⁻ → π⁰π⁰J/ψ(2015-09-11) 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 a data sample collected with the BESIII detector operating at the BEPCII storage ring, we observe a new neutral state Z_c (3900)⁰ with a significance of 10.4σ. The mass and width are measured to be 3894.8 ± 2.3 ± 3.2 MeV/c² and 29.6 ± 8.2 ± 8.2 MeV, respectively, where the first error is statistical and the second systematic. The Born cross section for e⁺e⁻ → π⁰π⁰J/ψ and the fraction of it attributable to π⁰Z_c(3900)⁰ → π⁰π⁰J/ψ in the range E_{c.m.} = 4.19-4.42 GeV are also determined. We interpret this state as the neutral partner of the four-quark candidate Z_c(3900)^±.Item Observation of η′ → ωe⁺e⁻(Amer Physical Soc, 2015-09-15) 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, XinchouBased on a sample of η′ mesons produced in the radiative decay J/ψ → γη′ in 1.31 x 10⁹ J/ψ events collected with the BESIII detector, the decay η′ → ωe⁺e⁻ is observed for the first time, with a statistical significance of 8σ. The branching fraction is measured to be ℬ(η′ → ωe⁺e⁻) = (1.97 ± 0.34(stat) ± 0.17(syst)) x 10⁻⁴, which is in agreement with theoretical predictions. The branching fraction of η′ → ωγ is also measured to be (2.55 ± 0.03(stat) ± 0.16(syst)) x 10⁻², which is the most precise measurement to date, and the relative branching fraction 𝓑(η′ → ωe⁺e⁻) / 𝓑(η′ → ωγ) is determined to be (7.71 ± 1.34(stat) ± 0.54(syst)) x 10⁻³.Item Search for Resonant Diboson Production in the ℓℓqq̅ Final State in pp Collisions at √s̅ = 8 TeV with the ATLAS Detector(Springer New York LLC, 2015-02-10) Aad, G.; Abbott, B.; Abdallah, J.; Abdel Khalek, S.; Abdinov, O.; Aben, R.; Abi, B.; Izen, Joseph M.; Leyton, Michael; Meirose, Bernhard; Namasivayam, Harisankar; Reeves, Kendall; Lou, Xinchou; ATLAS Collaboration; 0000-0003-0867-2189 (Lou, X.); 250674117 (Izen, JM); 250674117 (Izen, JM); Izen, Joseph M.; Leyton, Michael; Meirose, Bernhard; Namasivayam, Harisankar; Reeves, KendallThis paper reports on a search for narrow resonances in diboson production in the ℓℓqq̅ final state using pp collision data corresponding to an integrated luminosity of 20 fb⁻¹ collected at √s̅ = 8 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess of data events over the Standard Model expectation is observed. Upper limits at the 95% confidence level are set on the production cross section times branching ratio for Kaluza-Klein gravitons predicted by the Randall-Sundrum model and for Extended Gauge Model W' bosons. These results lead to the exclusion of mass values below 740 and 1590 GeV for the graviton and W' boson respectively.