Browsing by Author "Lou, Xinchou"
Now showing 1 - 20 of 249
- Results Per Page
- Sort Options
Item Amplitude Analysis and Measurement of the Time-Dependent CP Asymmetry of B⁰→K_S⁰K_S⁰K_S⁰ Decays(American Physical Society, 2012-03-27) 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 present the first results on the Dalitz-plot structure and improved measurements of the time-dependent CP-violation parameters of the process B⁰→K_S⁰K_S⁰K_S⁰ obtained using 468×10⁶ BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The Dalitz-plot structure is probed by a time-integrated amplitude analysis that does not distinguish between B⁰ and B̅⁰ decays. We measure the total inclusive branching fraction ℬ(B⁰→K_S⁰K_S⁰K_S⁰)=(6.19 ± 0.48 ± 0.15 ± 0.12)×10⁻⁶, where the first uncertainty is statistical, the second is systematic, and the third represents the Dalitz-plot signal model dependence. We also observe evidence for the intermediate resonant states ʄ₀(980), ʄ₀(1710), and ʄ₂(2010). Their respective product branching fractions are measured to be (2.70_{-1.19}^{+1.25} ± 0.36 ± 1.17)×10⁻⁶, (0.50_{-0.24}^{+0.46 ± 0.04 ± 0.10)×10⁻⁶, and (0.54_{-0.20}^{+0.21} ± 0.03 ± 0.52)×10⁻⁶. Additionally, we determine the mixing-induced CP-violation parameters to be S = -0.94_{-0.21}^{+0.24 ± 0.06 and C = -0.17 ± 0.18 ± 0.04, where the first uncertainty is statistical and the second is systematic. These values are in agreement with the standard model expectation. For the first time, we report evidence of CP violation in B⁰→K_S⁰K_S⁰K_S⁰ decays; CP conservation is excluded at 3.8 standard deviations including systematic uncertainties.Item Amplitude Analysis of the Decays η′ → π⁺π⁻π⁰ and η′ → π⁰π⁰π⁰(American Physical Society, 2017-01-06) 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 1.31 x 10⁹ J/ψ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays η′ → π⁺π⁻π⁰ and η′ → π⁰π⁰π⁰ is performed. A significant P-wave contribution from η′ → ρ^{±} π^{∓} is observed for the first time in η′ → π⁺π⁻π⁰. The branching fraction is determined to be ℬ(η′ → ρ^{±} π^{∓}) = (7.44 ± 0.60 ± 1.26 ± 1.84) x 10⁻⁴, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant S-wave component, there is a significant σ meson component. The branching fractions of the combined S-wave components are determined to be ℬ(η′ → π⁺π⁻π⁰)s = (37.63 ± 0.77 ± 2.22 ± 4.48) x 10⁻⁴ and ℬ(η′ → π⁰π⁰π⁰) = (35.22 ± 0.82 ± 2.54) x 10⁻⁴, respectively. The latter one is consistent with previous BESIII measurements.Item Amplitude Analysis of the χ_{c1} → ηπ⁺π⁻ Decays(2018-05-24) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouUsing 448.0 x 10⁶ ψ(3686) events collected with the BESIII detector, an amplitude analysis is performed for ψ(3686)→γχ_{c1}, χ_{c1} → ηπ⁺π⁻ decays. The most dominant two-body structure observed is α₀(980)^± π^∓; α₀(980)^±→ηπ^±. The α₀(980) line shape is modeled using a dispersion relation, and a significant nonzero α₀(980) coupling to the η′π channel is measured. We observe χ_{c1} → α₂(1700)π production for the first time, with a significance larger than 17σ. The production of mesons with exotic quantum numbers, J^{PC} = 1⁻⁺, is investigated, and upper limits for the branching fractions χ_{c1}→π₁(1400)^±π^∓, χ_{c1} → π₁(1600)^±π^∓, and χ_{c1} → π₁(2015)^±π^∓, with subsequent π₁(X)^± → ηπ^± decay, are determined.Item Antideuteron Production in ϒ(nS) Decays and in e⁺e⁻→qq̅ at √s ≈ 10.58 GeV(American Physical Society, 2014-06-24) 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 measurements of the inclusive production of antideuterons in e+e- annihilation into hadrons at ≈ 10.58 GeV center-of-mass energy and in ϒ(1S,2S,3S) decays. The results are obtained using data collected by the BABAR detector at the PEP-II electron-positron collider. Assuming a fireball spectral shape for the emitted antideuteron momentum, we find ℬ(ϒ(1S) → d̅X) = (2. 81 ± 0.49 (stat) _{-0.24}^{+0.20} (syst)) x 10⁻⁵ ℬ(ϒ(2S) → d̅X) = (2. 64 ± 0.11 (stat) _{-0.21}^{+0.26} (syst)) x 10⁻⁵, B(ϒ(3S) → d̅X) = (2. 33 ± 0.15 (stat) _{-0.28}^{+0.31} (syst)) x 10⁻⁵, and σ(e⁺e⁻ → d̅X) = (9.63 ± 0.41 (stat) _{-1.01}^{+1.17} (syst) fb.Item ATLAS Measurements of the Properties of Jets for Boosted Particle Searches(American Physical Society, 2012-10-15) Ahsan, Mahsana; Izen, Joseph M.; Lou, Xinchou; Reeves, Kendall; Wong, Wei-Cheng; ATLAS Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Ahsan, Mahsana; Izen, Joseph M.; Lou, Xinchou; Reeves, Kendall; Wong, Wei-Cheng; ATLAS CollaborationMeasurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of √s=7 TeV. The data correspond to an integrated luminosity of 35 pb⁻¹ and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-k_t algorithm with distance parameters R=0.6 and 1.0, with transverse momentum p_T > 300 GeV and pseudorapidity |η| < 2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions.Item Bottomonium Spectroscopy and Radiative Transitions Involving the χ_{bJ} (1p, 2p) States at BaBar(American Physical Society, 2014-12-24) 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 use (121 ± 1) million ϒ(3S) and (98 ± 1) million ϒ(2S) mesons recorded by the BABAR detector at the PEP-II e⁺e⁻ collider at SLAC to perform a study of radiative transitions involving the χ_{bJ}(1P, 2P) states in exclusive decays with μ⁺μ⁻γγ final states. We reconstruct twelve channels in four cascades using two complementary methods. In the first we identify both signal photon candidates in the electromagnetic calorimeter (EMC), employ a calorimeter timing-based technique to reduce backgrounds, and determine branching-ratio products and fine mass splittings. These results include the best observational significance yet for the χ_{b0}(2P) → γϒ(2S) and χ_{b0}(1P) → γϒ(1S) transitions. In the second method, we identify one photon candidate in the EMC and one which has converted into an e⁺e⁻ pair due to interaction with detector material, and we measure absolute product branching fractions. This method is particularly useful for measuring ϒ(3S) → γχ_{b1,2}(1P) decays. Additionally, we provide the most up-to-date derived branching fractions, matrix elements and mass splittings for χ_b transitions in the bottomonium system. Using a new technique, we also measure the two lowest-order spin-dependent coefficients in the nonrelativistic QCD Hamiltonian.Item Branching Fraction and Form-Factor Shape Measurements of Exclusive Charmless Semileptonic B Decays, and Determination of |V_{ub}|(American Physical Society, 2012-11-05) Lees, J. P.; Poireau, V.; Tisserand, V.; Tico, J. Garra; Grauges, E.; Palano, A.; Eigen, G.; 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 report the results of a study of the exclusive charmless semileptonic decays, B0→π -+ν, B+ → π0⁺ν, B +→ω +ν, B +→η +ν, and B +→η ′+ν (=e or μ) undertaken with approximately 462×106 BB̄ pairs collected at the Υ(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q2, the square of the momentum transferred to the lepton-neutrino pair, for B0→π - +ν, B +→π0 +ν, B +→ω +ν, and B +→η +ν. From these distributions, we extract the form-factor shapes f +(q2) and the total branching fractions B(B0→π -+ν)=(1.45±0.04 stat±0.06 syst)×10 -4 (combined π - and π0 decay channels assuming isospin symmetry), B(B +→ω +ν)=(1.19±0.16 stat±0.09 syst)×10 -4 and B(B +→η +ν)=(0.38±0.05 stat±0.05 syst)×10 -4. We also measure B(B +→η ′+ν)=(0.24±0. 08 stat±0.03 syst)×10 -4. We obtain values for the magnitude of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V ub| by direct comparison with three different QCD calculations in restricted q2 ranges of B→π +ν decays. From a simultaneous fit to the experimental data over the full q2 range and the FNAL/MILC lattice QCD predictions, we obtain |V ub|=(3.25±0.31)×10 -3, where the error is the combined experimental and theoretical uncertainty. © 2012 American Physical Society.Item Branching Fraction Measurements of ψ(3686) → γχ_{cj}(2018-05-24) Ablikim, M.; Achasov, M. N.; Albrecht, M.; Ahmed, S.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouUsing a sample of 106 million ψ(3686) decays, the branching fractions of ψ(3686) → γχ_{c0}, ψ(3686) → γχ_{c1}, and ψ(3686) → γχ_{c2} are measured with improved precision to be (9.389 ± 0.014 ± 0.332) %, (9.905 ± 0.011 ± 0.353) %, and (9.621 ± 0.013 ± 0.272) %, respectively, where the first uncertainties are statistical and the second ones are systematic. The product branching fractions of ψ(3686) → γχ_{c1}, χ_{c1} → γJ/ψ and ψ(3686) → γχ_{c2}, χ_{c2} → γJ/ψ and the branching fractions of χ_{c1} → γJ/ψ and χ_{c2} → γJ/ψ are also presented.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 Centrality and Rapidity Dependence of Inclusive Jet Production in √{S_{NN}} = 5.02 TeV Proton-Lead Collisions with the ATLAS Detector(Elsevier B.V., 2015-07-17) Abbott, B.; Abdallah, J.; Abdel Khalek, S.; Abdinov, O.; Aben, R.; Abi, B.; Abolins, M.; Izen, Joseph M.; Leyton, Michael; Lou, Xinchou; Namasivayam, Harisankar; Reeves, Kendall; ATLAS Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Izen, Joseph M.; Leyton, Michael; Namasivayam, Harisankar; Reeves, Kendall; Lou, XinchouMeasurements of the centrality and rapidity dependence of inclusive jet production in the √s̅̅ {̅N̅N̅}=5.02 TeV proton–lead (p+Pb) collisions and the jet cross-section in √s̅=2.76 TeV proton–proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb⁻¹ and 4.0 pb⁻¹, respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The p+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval −4.9 < η < −3.2 in the direction of the lead beam. Results are presented for the double-differential per-collision yields as a function of jet rapidity and transverse momentum (p_T) for minimum-bias and centrality-selected p+Pb collisions, and are compared to the jet rate from the geometric expectation. The total jet yield in minimum-bias events is slightly enhanced above the expectation in a p_T-dependent manner but is consistent with the expectation within uncertainties. The ratios of jet spectra from different centrality selections show a strong modification of jet production at all p_T at forward rapidities and for large p_t at mid-rapidity, which manifests as a suppression of the jet yield in central events and an enhancement in peripheral events. These effects imply that the factorisation between hard and soft processes is violated at an unexpected level in proton–nucleus collisions. Furthermore, the modifications at forward rapidities are found to be a function of the total jet energy only, implying that the violations may have a simple dependence on the hard parton–parton kinematics.Item Collins Asymmetries in Inclusive Charged KK and Kπ Pairs Produced in e⁺e⁻ Annihilation(American Physical Society, 2015-12-22) 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 present measurements of Collins asymmetries in the inclusive process e⁺e⁻ → h₁h₂Χ, h₁h₂ = KK, Kπ, ππ 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 h₁h₂ pairs, which increase with hadron energies. The Kπ asymmetries are similar to those measured for the ππ pairs, whereas those measured for high-energy KK pairs are, in general, larger.Item Comprehensive Measurements of T-Channel Single Top-Quark Production Cross Sections at √s = 7 TeV with the ATLAS Detector(American Physical Society, 2014-12-11) Aad, G.; Abbott, B.; Abdallah, J.; Abdel Khalek, S.; Abdinov, O.; Aben, R.; Abi, B.; Izen, Joseph M.; Leyton, Michael; Lou, Xinchou; Namasivayam, Harisankar; Reeves, Kendall; ATLAS Collaboration; 250674117 (Izen, JM); 250674117 (Izen, JM); Izen, Joseph M.; Leyton, Michael; Namasivayam, Harisankar; Reeves, Kendall; Lou, XinchouThis article presents measurements of the t-channel single top-quark (t) and top-antiquark (t̅) total production cross sections σ(tq) and σ(t̅q), their ratio R_t= σ(tq) / σ(tq), and a measurement of the inclusive production cross section σ(tq+t̅q) in proton-proton collisions at √s = 7 TeV at the LHC. Differential cross sections for the tq and t̅q processes are measured as a function of the transverse momentum and the absolute value of the rapidity of t and t̅, respectively. The analyzed data set was recorded with the ATLAS detector and corresponds to an integrated luminosity of 4.59 fb⁻¹. Selected events contain one charged lepton, large missing transverse momentum, and two or three jets. The cross sections are measured by performing a binned maximum-likelihood fit to the output distributions of neural networks. The resulting measurements are σ(tq) = 46 ± 1(stat) ± 6(syst) pb, σ(t̅q )= 23 ± 1(stat) ± 3(syst) pb, R_t = 2.04 ± 0.13(stat) ± 0.12(syst), and σ(tq+t̅q) = 68 ± 2(stat) ± 8(syst) pb, consistent with the Standard Model expectation. The uncertainty on the measured cross sections is dominated by systematic uncertainties, while the uncertainty on R_t is mainly statistical. Using the ratio of σ(tq+t̅q) to its theoretical prediction, and assuming that the top-quark-related CKM matrix elements obey the relation |V_{tb} ≫ |V_{ts}|,|V_td|, we determine |V_{tb}| = 1.02 ± 0.07.Item Cross Sections for the Reactions e⁺e⁻ → K⁺ K⁻ π⁺π⁻, K⁺ K⁻ π⁰π⁰, and K⁺ K⁻K⁺ K⁻ Measured Using Initial-State Radiation Events(Amer Physical Soc, 2012-07-26) Lees, J. P.; Poireau, V.; Prencipe, E.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 56366505900 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We study the processes e⁺e⁻ → K⁺ K⁻ π⁺π⁻γ, K⁺ K⁻ π⁰π⁰γ, and K⁺ K⁻ K⁺ K⁻ γ, where the photon is radiated from the initial state. About 84000, 8000, and 4200 fully reconstructed events, respectively, are selected from 454 fb⁻¹ of BABAR data. The invariant mass of the hadronic final state defines the e⁺e⁻ center-of-mass energy, so that the K⁺ K⁻ π⁺π⁻γ data can be compared with direct measurements of the e⁺e⁻ → K⁺ K⁻ π⁺π⁻ reaction. No direct measurements exist for the e⁺e⁻→ K ⁺K ⁻ π⁰π⁰ or e⁺e⁻ → K⁺ K⁻K⁺ K⁻ - reactions, and we present an update of our previous result based on a data sample that is twice as large. Studying the structure of these events, we find contributions from a number of intermediate states and extract their cross sections. In particular, we perform a more detailed study of the e⁺e⁻ → φ(1020)ππγ reaction and confirm the presence of the Y(2175) resonance in the φ(1020)f⁰(980) and K⁺ K⁻ f⁰ (980) modes. In the charmonium region, we observe the J/ψ in all three final states and in several intermediate states, as well as the ψ(2S) in some modes, and measure the corresponding products of branching fraction and electron width.Item Cross sections for the reactions e⁺e⁻→ K_s^0 K_L^0, K_s^0 K_L^0 π⁺π⁻, K_s^0 K_s^0 π⁺π⁻, K_s^0 K_s^0 K⁺ K⁻ from events with initial-state radiation(American Physical Society, 2014-05-06) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; 56366505900 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We study the processes e⁺e⁻ → K_s^0 K_L^0γ, K_s^0 K_L^0π⁺π⁻γ, K_s^0 K_s^0 π⁺ π⁻ γ, K_s^0 K_s^0 K⁺ K⁻ γ, where the photon is radiated from the initial state. providing cross section measurements for the hadronic states over a continuum of center-of-mass energies. The results are based on 469 fb−1 of data collected with the BABAR detector at SLAC. We observe the ϕ(1020) resonance in the K_s^0 K_L^0 final state and measure the product of its electronic width and branching fraction with about 3% uncertainty. We present a measurement of the e⁺e⁻ → K_s^0 K_L^0 cross section in the energy range from 1.06 to 2.2 GeV and observe the production of a resonance at 1.67 GeV. We present the first measurements of the e⁺e⁻ → K_s^0 K_L^0 π⁺π⁻ and K_s^0 K_s^0 K⁺ K⁻ cross sections and study the intermediate resonance structures. We obtain the first observations of J/ψ decay to the K_s^0 K_L^0 π⁺π⁻, K_s^0 K_s^0 π⁺π⁻, and K_s^0 K_s^0 K⁺ K⁻ final states.Item Cyclopamine Tartrate, An Inhibitor of Hedgehog Signaling, Strongly Interferes with Mitochondrial Function and Suppresses Aerobic Respiration in Lung Cancer Cells(American Physical Society, 2016-03-29) del Amo Sanchez. P.; Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe measure the time-dependent CP asymmetry in the radiative-penguin decay B0→KS0π-π+γ, using a sample of 471×106 (4S)→BB-events recorded with the BABAR detector at the PEP-II e+e- storage ring at SLAC. Using events with mKππ<1.8 GeV/c2, we measure the branching fractions of B+→K+π-π+γ and B0→K0π-π+γ, the branching fractions of the kaonic resonances decaying to K+π-π+, as well as the overall branching fractions of the B+→ρ0K+γ, B+→K∗0π+γ and S-wave B+→(Kπ)0∗0π+γ components. For events from the ρ mass band, we measure the CP-violating parameters SKS0π+π-γ=0.14±0.25±0.03 and CKS0π+π-γ=-0.39±0.20-0.02+0.03, where the first uncertainties are statistical and the second are systematic. We extract from this measurement the time-dependent CP asymmetry related to the CP eigenstate ρ0KS0 and obtain SKS0ργ=-0.18±0.32-0.05+0.06, which provides information on the photon polarization in the underlying b→sγ transition.Item Dalitz Plot Analyses of B⁰ → D⁻D⁰K⁺ and B⁺ → D̅⁰D⁰K⁺ Decays(American Physical Society, 2015-03-02) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 56366505900 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We present Dalitz plot analyses for the decays of B mesons to D⁻D⁰K⁺ and D̅⁰D⁰K⁺. We report the observation of the D*{s1} (2700)⁺ resonance in these two channels and obtain measurements of the mass M(D*{s1} (2700)⁺) = 2699{₋₇}⁺¹⁴ MeV/c² and of the width Γ(D*{s1} (2700)⁺) = 127{₋₁₉}⁺²⁴ MeV, including statistical and systematic uncertainties. In addition, we observe an enhancement in the D⁰K⁺ invariant mass around 2350-2500 MeV/c² in both decays B⁰ → D⁻D⁰K⁺ and B⁺ → D̅⁰D⁰K⁺, which we are not able to interpret. The results are based on 429 fb⁻¹ of data containing 471 x10⁶ BB̅ pairs collected at the ϒ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory.Item Dalitz Plot Analysis of η_c → K⁺K⁻η and η_c → K⁺K⁻π⁰ in Two-Photon Interactions(American Physical Society, 2014-06-16) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Stugu, B.; Izen, Joseph M.; Lou, Xinchou; 56366505900 (Lou, X); 250674117 (Izen, JM); 250674117 (Izen, JM); Lou, Xinchou; Izen, Joseph M.We study the processes γγ→K⁺K⁻η and γγ→K⁺K⁻π⁰ 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 Υ(nS) (n = 2, 3, 4) resonances. We observe η_c → K⁺K⁻π⁰ and η_c → K⁺K⁻η decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the K₀*(1430) → K η decay and measure its branching fraction relative to the K π decay mode to be R(K₀*(1430)) = ℬ(K₀*(1430) → K η) / ℬ(K₀*(1430) → K π) = 0.092 ± 0.025_(-0.025)^(+0.010). The η_c → K⁺K⁻η and K₀*(1430) → Kη results correspond to the first observations of these channels. The data also show evidence for η_c(2S) → K⁺K⁻π⁰ and first evidence for η_c(2S) → K⁺K⁻η.Item Dark Photon Search in the Mass Range between 1.5 and 3.4 GeV/c²(Elsevier Science B.V., 2018-10-01) 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 set of 2.93 fb⁻¹ taken at a center-of-mass energy √s = 3.773 GeV with the BESIII detector at the BEPCII collider, we perform a search for an extra U(1) gauge boson, also denoted as a dark photon. We examine the initial state radiation reactions e⁺e⁻ → e⁺e⁻γ(ISR) and e⁺e⁻ → μ⁺μ⁻γ(ISR) for this search, where the dark photon would appear as an enhancement in the invariant mass distribution of the leptonic pairs. We observe no obvious enhancement in the mass range between 1.5 and 3.4 GeV/c² and set a 90% confidence level upper limit on the mixing strength of the dark photon and the Standard Model photon. We obtain a competitive limit in the tested mass range.Item Determination of the Spin and Parity of the Z_c (3900)(American Physical Society, 2017) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; 0000-0003-0867-2189 (Lou, X); Lou, XinchouThe spin and parity of the Z_{c}(3900)^{±} state are determined to be J^{P} =1⁺ with a statistical significance larger than 7σ over other quantum numbers in a partial wave analysis of the process e⁺e⁻ → π⁺π⁻J/ψ. We use a data sample of 1.92 fb⁻¹ accumulated at √s̅=4.23 and 4.26 GeV with the BESIII experiment. When parametrizing the Z_{c}(3900)^{±} with a Flatté-like formula, we determine its pole mass M_{pole} = (3881.2 ± 4.2_{stat} ± 52.7_{syst}) MeV/c² and pole width Γ_{pole} = (51.8 ± 4.6_{stat} ± 36.0_{syst}) MeV. We also measure cross sections for the process e⁺e⁻→ Z_{c}(3900)^{±}π⁻ + c.c.→ J/ψπ⁺π⁻ and determine an upper limit at the 90% confidence level for the process e⁺e⁻→ Z_{c}(4020)^{±}π⁻ + c.c.→J/ψπ⁺π⁻Item Development of Transformations of Pyridotriazoles and Photoinduced Palladium Hydride-enabled Reactions(December 2023) Zhang, Ziyan; Gevorgyan, Vladimir; Lou, Xinchou; Smaldone, Ronald A.; Gassensmith, Jeremiah J.; Romiti, FilippoThe thesis describes the development of denitrogenative transformations of pyridotriazoles and photoinduced palladium hydride-enabled reactions. A general and efficient method for arylation, X–H insertions, and cyclopropanation reactions of pyridotriazoles was developed. This protocol proceeded via pyridyl carbene intermediates, under mild, transition metal-free, and light-induced conditions. Furthermore, a Co-catalyzed transannulation reaction of pyridotriazoles with isothiocyanates and xanthate esters was developed. This method features the conversion of pyridotriazoles into two N-fused heterocycles, such as imino-thiazolopyridines and oxo- thiazolopyridine derivatives, via one-step Co(II)-catalyzed transannulation reaction proceeding though a radical mechanism. Next, three protocols enabled by visible light and palladium hydride were developed. A variety of substrates, such as diazo compounds, N-tosylhydrazones, strained molecules, acrylic acids, acrylic amides, and Baylis-Hillman adducts were found to produce hybrid palladium alkyl radical intermediates under photoinduced and palladium hydride-catalyzed conditions. These alkyl radical species subsequently participated in diverse transformations, including Heck reaction, hydroalkenylation and cascade annulation reactions.