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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Item Precision Higgs Physics at the CEPC(Institute of Physics Publishing, 2019-03-04) An, F.; Bai, Y.; Chen, C.; Chen, X.; Chen, Z.; Da Costa, J. G.; Cui, Z.; Jyotishmati, Susmmita; Lou, Xinchou; 0000-0003-0867-2189 (Lou, X); Jyotishmati, Susmmita; Lou, XinchouThe discovery of the Higgs boson with its mass around 125 GeV by the ATLAS and CMS Collaborations marked the beginning of a new era in high energy physics. The Higgs boson will be the subject of extensive studies of the ongoing LHC program. At the same time, lepton collider based Higgs factories have been proposed as a possible next step beyond the LHC, with its main goal to precisely measure the properties of the Higgs boson and probe potential new physics associated with the Higgs boson. The Circular Electron Positron Collider (CEPC) is one of such proposed Higgs factories. The CEPC is an e⁺e⁻ circular collider proposed by and to be hosted in China. Located in a tunnel of approximately 100 km in circumference, it will operate at a center-of-mass energy of 240 GeV as the Higgs factory. In this paper, we present the first estimates on the precision of the Higgs boson property measurements achievable at the CEPC and discuss implications of these measurements. © 2019 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.Item Reconstruction of Physics Objects at the Circular Electron Positron Collider with Arbor(Springer) Ruan, Manqi; Zhao, Hang; Li, Gang; Fu, Chengdong; Wang, Zhigang; Lou, Xinchou; Yu, Dan; Boudry, Vincent; Videau, Henri; Balagura, Vladislav; Brient, Jean-Claude; Lai, Peizhu; Kuo, Chia-Ming; Liu, Bo; An, Fenfen; Chen, Chunhui; Prell, Soeren; Li, Bo; Laketineh, Imad; Lou, XinchouAfter the Higgs discovery, precise measurements of the Higgs properties and the electroweak observables become vital for the experimental particle physics. A powerful Higgs/Z factory, the Circular Electron Positron Collider (CEPC) is proposed. The Particle Flow oriented detector design is proposed to the CEPC and a Particle Flow algorithm, Arbor is optimized accordingly. We summarize the physics object reconstruction performance of the Particle Flow oriented detector design with Arbor algorithm and conclude that this combination fulfills the physics requirement of CEPC.Item Measurement of the Spectral Function for the τ- →k-ksντ Decay(American Physical Society) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouThe decay τ⁻→ K⁻K_Sν_τ has been studied using 430×106e⁺e⁻ → τ⁺τ⁻ events produced at a center-of-mass energy around 10.6 GeV at the PEP-II collider and studied with the BABAR detector. The mass spectrum of the K⁻K_S system has been measured and the spectral function has been obtained. The measured branching fraction B(τ⁻ → K⁻K_Sν_τ)=(0.739±0.011(stat)±0.020(syst))×10⁻³ is found to be in agreement with earlier measurements.Item Monte Carlo Study of Particle Identification at the CEPC Using TPC dE/dx Information(Springer) An, F.; Prell, S.; Chen, C.; Cochran, J.; Lou, Xinchou; Ruan, M.; 0000-0003-0867-2189 (Lou, X); Lou, XinchouThe kaon identification is crucial for the flavor physics, and also benefits the flavor and charge reconstruction of the jets. We explore the particle identification capability for tracks with momenta ranging from 2- 20 GeV/c using the dE/dx measurements in the Time Projection Chamber at the future Circular Electron-Positron Collider. Based on Monte Carlo simulation, we anticipate that an average 3.2 σ (2.6 σ) K/π separation can be achieved based on dE/dx information for an optimistic (conservative) extrapolation of the simulated performance to the final system. Time-of-flight (TOF) information from the Electromagnetic Calorimeter can provide K/π separation around 1 GeV/c and reduce the K/p mis-identification rate. By combining the dE/dx and TOF information, we estimate that in the optimistic scenario a kaon selection in inclusive hadronic Z decays with both the average efficiency and purity approaching 95% can be achieved.Item Study of η(1475) and Χ(1835) in Radiative J/ψ Decays to γφ(Amer Physical Soc) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albayrak, O.; Albrecht, M.; Alekseev, M.; Ambrose, D. J.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouThe decay J/ψ → γγφ is studied using a sample of 1.31 x 10⁹ J/ψ events collected with the BESIII detector. Two structures around 1475 MeV/c² and 1835 MeV/c² are observed in the γφ invariant mass spectrum for the first time. With a fit on the γφ invariant mass, which takes into account the interference between the two structures, and a simple analysis of the angular distribution, the structure around 1475 MeV/c² is found to favor an assignment as the η(1475) and the mass and width for the structure around 1835 MeV/c² are consistent with the X(1835). The statistical significances of the two structures are 13.5σ and 6.3σ, respectively. The results indicate that both η(1475) and X(1835) contain a sizeable ss̅ component.Item Study of the Process e⁺e⁻ → π⁺π⁻η Using Initial State Radiation(Amer Physical Soc) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe study the process e⁺e⁻ → π⁺π⁻ηγ, where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BABAR data sample with an integrated luminosity of 469 fb⁻¹. Using the π⁺π⁻η invariant mass spectrum, we measure the e⁺e⁻ → π⁺π⁻η cross section in the e⁺e⁻ center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson dominance model with four ρ-like states. We observe 49 ± 9 events of the J/ψ decay to π⁺π⁻η and measure the product Γ_{J/ψ → e⁺e⁻}ℬ_{J/ψ → π⁺π⁻η) = 2.34 ± 0.43(stat) ± 0.16(syst) eV.Item Study of Υ(1s) Radiative Decays to γπ⁺π⁻ and γK⁺K⁻(Amer Physical Soc) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Giannuzzi, F.; Palano, A.; Eigen, G.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe study the Υ(1S) radiative decays to γπ⁺π⁻ and γK⁺K⁻ using data recorded with the BABAR detector operating at the SLAC PEP-11 asymmetric-energy e⁺e⁻ collider at center-of-mass energies at the Υ(2S) and Υ(3S) resonances. The Υ(1S) resonance is reconstructed from the decay Υ(nS) → π⁺π⁻ Υ(1S), n =2, 3. Branching fraction measurements and spin-parity analyses of Υ(1S) radiative decays are reported for the I = 0 S-wave and ∫₂ (1270) resonances in the π⁺π⁻ mass spectrum, the ∫′₂ (1525) and ∫₀ (1500) in the K⁺K⁻ mass spectrum, and the ∫₃(1710) in both.Item Precision Study of η′ → γπ⁺π⁻ Decay Dynamics(American Physical Society, 2018-11-05) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouUsing a low background data sample of 9.7×10⁵ J/ψ→γη′, η′→γπ⁺π⁻ events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the BESIII detector at BEPCII, the decay dynamics of η′→γπ⁺π⁻ are studied with both model-dependent and model-independent approaches. The contributions of ω and the ρ(770)-ω interference are observed for the first time in the decays η′→γπ⁺π⁻ in both approaches. Additionally, a contribution from the box anomaly or the ρ(1450) resonance is required in the model-dependent approach, while the process specific part of the decay amplitude is determined in the model-independent approach.Item Improved Measurements of Two-Photon Widths of The χ(cJ) States and Helicity Analysis For χ(c2) → γγ(Amer Physical Soc, 2018-10-01) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albrecht, M.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouBased on 448.1 x 10⁶ ψ(3686) events collected with the BESIII detector, the decays ψ(3686) → γ χ(cJ), χ(cJ) → γγ(J = 0, 1, 2) are studied. The decay branching fractions of χ(c0,2) → γγ are measured to be ℬ(χ(c0) → γγ) = (1.93 ± 0.08 ± 0.05 ± 0.05) x 10⁻⁴ and ℬ(χ(c2) → γγ) = (3.10 ± 0.09 ± 0.07 ± 0.11) x 10⁻⁴ which correspond to two-photon decay widths of Γ(γγ)(χ(c0)) = 2.03 ± 0.08 ± 0.06 ± 0.13 keV and Γ(γγ)(χ(c2)) = 0.60 ± 0.02 ± 0.01 ± 0.04 keV with a ratio of R = Γ(γγ)(χ(c2))/Γ(γγ)(χ(c0)) = 0.295 ± 0.014 ± 0.007 ± 0.027, where the uncertainties are statistical, systematic and associated with the uncertainties of ℬ(ψ(3686) → γχ(c2)) and the total widths Γχ(c0,2), respectively. For the forbidden decay of χ(c1) → γγ, no signal is observed, and an upper limit on the two-photon width is obtained to be Γ(γγ)(χ(c1)) < 5.3 eV at the 90% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay χ(c2) → γγ is also measured to be f(0/2) = Γ(γγ)(λ=0) (χ(c2)) / Γ(γγ)(λ=2) (χ(c2) = (0.0 ± 0.6 ± 1.2) x 10(-2), where the uncertainties are statistical and systematic, respectively.Item Measurements of the Branching Fractions for the Semileptonic Decays D(s)⁺ → φe⁺ν(e), φμ⁺ν(μ), ημ⁺ν(μ) and η′μ⁺ν(μ)(Amer Physical Soc, 2018-10-01) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albrecht, M.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, XinchouBy analyzing 482 pb⁻¹ of e⁺e⁻ collision data collected at the center-of-mass energy √s = 4.009 GeV with the BESIII detector, we measure the branching fractions for the semi-leptonic decays D(s)⁺ → φe⁺ν(e), φμ⁺ν(μ), ημ⁺ν(μ) and η′μ⁺ν(μ) to be ℬ(D(s)⁺ → φe⁺ν(e)) = (2.26 ± 0.45 ± 0.09)%, ℬ(D(s)⁺ → φμ⁺ν(μ)) = (1.94 ± 0.53 ± 0.09)%, ℬ(D(s)⁺ → ημ⁺ν(μ)) = (2.42 ± 0.46 ± 011)% and ℬ(D(s)⁺ → η′μ⁺ν(μ)) = (1.06 ± 0.54 ± 0.07)%, where the first and second uncertainties are statistical and systematic, respectively. The branching fractions for the three semi-muonic decays D(s)⁺ → φμ⁺ν(μ), ημ⁺ν(μ) and η′μ⁺ν(μ) are determined for the first time and that of D(s)⁺ → φe⁺ν(e) is consistent with the world average value within uncertainties.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 Observation of the Helicity-Selection-Rule Suppressed Decay of the χ(c2) Charmonium State(Amer Physical Soc, 2018-10-01) 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, XinchouThe decays of χ(c2) → K⁺K⁻ π⁰, K(S)K(±)π(∓), and π⁺π⁻π⁰ are studied with the ψ(3686) data samples collected with the Beijing Spectrometer ( BESIII). For the first time, the branching fractions of χ(c2) → K*K̅, χ(c2) → a₂(±)(1320)π(∓)/a₂⁰(1320)π⁰, and χ(c2) → ρ(770)(±)π(∓) are measured. Here, K*K̅ denotes both K*(±)K(∓) and its isospin-conjugated process K*⁰K̅⁰ + c.c., and K* denotes the resonances K*(892), K₂*(1430), and K₃*(1780). The observations indicate a strong violation of the helicity selection rule in χ(c2) decays into vector and pseudoscalar meson pairs. The measured branching fractions of χ(c2) → K*(892)K̅ are more than ten times larger than the upper limit of χ(c2) → ρ(770)(±)π(∓), which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.Item Measurement of Cross Sections of the Interactions e⁺e⁻ → φφω and e⁺e⁻ → φφφ at Center-Of-Mass Energies from 4.008 to 4.600 GeV(Elsevier Science B.V., 2018-10-01) 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 data samples collected with the BESIII detector at the BEPCII collider at six center-of-mass energies between 4.008 and 4.600 GeV, we observe the processes e⁺e⁻ → φφω and e⁺e⁻ → φφφ. The Born cross sections are measured and the ratio of the cross sections σ(e⁺e⁻ → φφω)/σ(e⁺e⁻ → φφφ) is estimated to be 1.75 ± 0.22 ± 0.19 averaged over six energy points, where the first uncertainty is statistical and the second is systematic. The results represent first measurements of these interactions.Item Measurement of the e⁺e⁻ → K_s⁰ K^± π^∓ π⁰ and K_s⁰ K^± π^∓η Cross Sections Using Initial-State Radiation(American Physical Society, 2017-05-30) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBaR Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouThe processes e⁺e⁻ → K_s⁰ K^± π^∓ π⁰ and e⁺e⁻ → K_s⁰ K^± π^∓η are studied over a continuum of energies from threshold to 4 GeV with the initial-state photon radiation method. Using 454 fb⁻¹ of data collected with the BABAR detector at the SLAC PEP-II storage ring, the first measurements of the cross sections for these processes are obtained. The intermediate resonance structures from K*⁰ (Kπ)⁰, K*(892)^±(Kπ)^∓, and K_s⁰ K^± ρ^∓ are studied. The J/ψ is observed in all of these channels, and corresponding branching fractions are measured.Item Evidence for CP Violation in B⁺ → K*(892)⁺π⁰ from a Dalitz Plot Analysis of B⁺ → K_s⁰π⁺π⁰ Decays(American Physical Society, 2017-10-02) 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); Izen, Joseph M.; Lou, XinchouWe report a Dalitz plot analysis of charmless hadronic decays of charged B mesons to the final state K_s⁰ π⁺π⁰ using the full BABAR data set of 470.9 ± 2.8 million BB̅ events collected at the Υ(4S) resonance. We measure the overall branching fraction and CP asymmetry to be Β(B⁺ → K⁰ π⁺π⁰) = (31.8 ± 1.8 ± 2.1_{-0.0}^{+6.0}) x 10⁻⁶ and A_{CP}(B⁺ → K⁰ π⁺π⁰) = 0.07 ± 0.05 ± 0.03_{-0.03}^{+0.02}, where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for B⁺ → K⁰ π⁺π⁰. We find first evidence of a CP asymmetry in B⁺ → K*(892)⁺π⁰ decays: A_{CP}(B⁺ → K*(892)⁺π⁰) = -0.52 ± 0.14 ± 0.04_{-0.02}^{+0.04}. The significance of this asymmetry, including systematic and model uncertainties, is 3.4 standard deviations. We also measure the branching fractions and CP asymmetries for three other intermediate decay modes.Item Search for B⁺→ K⁺τ⁺τ⁻ at the Babar Experiment(American Physical Society, 2018-08-24) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe search for the rare flavor-changing neutral current process B⁺→ K⁺τ⁺τ⁻ using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the Υ(4S) resonance, corresponds to a total integrated luminosity of 424 fb⁻¹ and to 471 x 10⁶ BB̅ pairs. We reconstruct one B meson, produced in the Υ(4S) → B⁺B⁻ decay, in one of many hadronic decay modes and search for activity compatible with a B⁺→ K⁺τ⁺τ⁻ decay in the rest of the event. Each τ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The resulting upper limit, at the 90% confidence level, is 𝓑(B⁺→ K⁺τ⁺τ⁻) < 2.25 x 10⁻³.Item Measurement of the D*(2010)⁺ –D⁺ Mass Difference(American Physical Society, 2018-08-24) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe measure the mass difference, Δm₊, between the D*(2010)⁺ and the D⁺ using the decay chain D*(2010)⁺ → D⁺π⁰ with D⁺ → K⁻π⁺π⁺. The data were recorded with the BABAR detector at center-of-mass energies at and near the Υ(4S) resonance, and correspond to an integrated luminosity of approximately 468 fb⁻¹. We measure Δm₊ = (140 601.0 ± 6.8 [stat] ± 12.9 [syst]) keV. We combine this result with a previous BABAR measurement of Δm₀ ≡ m(D*(2010)⁺) - m(D⁰) to obtain Δm_D = m(D⁺) - m(D⁰) = (4824.9 ± 6.8 [stat] ± 12.9 [syst]) keV. These results are compatible with and approximately five times more precise than the Particle Data Group averages.Item Search for Invisible Decays of a Dark Photon Produced in e⁺e⁻ Collisions at Babar(American Physical Society, 2017-09) Lees, J. P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D. N.; Izen, Joseph M.; Lou, Xinchou; BaBar Collaboration; 0000-0003-0867-2189 (Lou, X); 250674117 (Izen, JM); Izen, Joseph M.; Lou, XinchouWe search for single-photon events in 53 fb⁻¹ of e⁺e⁻ collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A' through the process e⁺e⁻ → γA'; A' → invisible. Such particles, referred to as "dark photons," are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A' to e⁺e⁻ in the mass range m_{A'} ≤ 8 GeV. In particular, our limits exclude the values of the A' coupling suggested by the dark-photon interpretation of the muon (g - 2)_μ anomaly, as well as a broad range of parameters for the dark-sector models.Item Measurement of the Absolute Branching Fraction for Λ_c⁺ → Λμ⁺ν_μ(2018-06-01) 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, XinchouWe report the first measurement of the absolute branching fraction for Λ_c⁺ → Λμ⁺ν_μ. This measurement is based on a sample of e⁺e⁻ annihilation data produced at a center-of-mass energy √s̅ = 4.6 GeV, collected with the BESIII detector at the BEPCII storage rings. The sample corresponds to an integrated luminosity of 567 pb⁻¹. The branching fraction is determined to be ℬ(Λ_c⁺ → Λμ⁺ν_μ) = (3.49 ± 0.46(stat) ± 0.27(syst))%. In addition, we calculate the ratio ℬ(Λ_c⁺ → Λμ⁺ν_μ) / ℬ(Λ_c⁺ → Λe⁺ν_e) to be 0.96 ± 0.16(stat) ± 0.04(syst).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.