Partial-wave analysis of the radiative decay of J/psi into p pbar

The Standard Model describes the smallest building blocks of our universe, so-called quarks and leptons, and the forces that act on them. The building blocks can bundle into larger and heavier particles. These composite particles are called hadrons. One of the best-known hadrons is the proton. The Higgs boson, which was first detected in 2012, explains how the smallest building blocks get their mass. However, the Higgs mechanism only explains 1% of the mass of the proton. The other 99% arises from internal strong forces that are not yet well-understood. To better understand the 99%, it is important to study the production of hadrons in different processes, and to obtain information from as many different decay reactions as possible. Hadrons of the charmonia group, such as J/psi and the ground state eta_c, are highly suitable particles for this, and result in a relatively easy-to-interpret spectrum of narrow peaks that do not overlap. In this thesis the radiative decay of J/psi into a proton (p) and antiproton (pbar) is studied. The aim of this study was to gain a better understanding of the full spectrum of the proton-antiproton invariant mass, and especially to gain more insight into the poorly-understood properties of the intermediate resonance eta_c. In this study, a special multidimensional analysis, a so-called partial-wave analysis, was applied for the first time to the radiative decay from J/psi to eta_c. This study is based on data taken by the Beijing Spectrometer (BES) III, which has collected world's largest dataset of J/psi reactions

Search for the semileptonic decays Ds+ →k1 (1270)0e+νe and Ds+ →b1 (1235)0e+νe

By analyzing 7.33  fb−1 of e+e− collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we search for the semileptonic decays D+s→K1(1270)0e+νe and D+s→b1(1235)0e+νe for the first time. No significant signals are observed for either decay mode. The upper limits on the (product) branching fractions are determined to be B[D+s→K1(1270)0e+νe]&lt;4.1×10−4 and B[D+s→b1(1235)0e+νe]⋅B[b1(1235)0→ωπ0]&lt;6.4×10−4 at 90% confidence level.<br/

Search for the semileptonic decays Ds+ →k1 (1270)0e+νe and Ds+ →b1 (1235)0e+νe

By analyzing 7.33  fb−1 of e+e− collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we search for the semileptonic decays D+s→K1(1270)0e+νe and D+s→b1(1235)0e+νe for the first time. No significant signals are observed for either decay mode. The upper limits on the (product) branching fractions are determined to be B[D+s→K1(1270)0e+νe]&lt;4.1×10−4 and B[D+s→b1(1235)0e+νe]⋅B[b1(1235)0→ωπ0]&lt;6.4×10−4 at 90% confidence level.<br/

Search for the semileptonic decays Ds+ →k1 (1270)0e+νe and Ds+ →b1 (1235)0e+νe

By analyzing 7.33  fb−1 of e+e− collision data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we search for the semileptonic decays D+s→K1(1270)0e+νe and D+s→b1(1235)0e+νe for the first time. No significant signals are observed for either decay mode. The upper limits on the (product) branching fractions are determined to be B[D+s→K1(1270)0e+νe]&lt;4.1×10−4 and B[D+s→b1(1235)0e+νe]⋅B[b1(1235)0→ωπ0]&lt;6.4×10−4 at 90% confidence level.<br/

Improved measurement of the branching fraction of Ds+ →μ+νμ

Using e+e- collision data with an integrated luminosity of 7.33 fb-1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector operating at the BEPCII collider, the branching fraction of the leptonic decay Ds+→μ+νμ is measured to be (0.5294±0.0108stat±0.0085syst)%. Based on this, the product of the Ds+ decay constant fDs+ and the magnitude of the c→s quark mixing matrix element |Vcs| is determined to be fDs+|Vcs|=241.8±2.5stat±2.2syst MeV. Using the value of |Vcs| given by the global standard model fit, fDs+ is found to be 248.4±2.5stat±2.2syst MeV. Alternatively, using the value of fDs+ from a recent lattice quantum chromodynamics calculation, |Vcs| is determined to be 0.968±0.010stat±0.009syst. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.<br/

Improved measurement of the branching fraction of Ds+ →μ+νμ

Using e+e- collision data with an integrated luminosity of 7.33 fb-1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector operating at the BEPCII collider, the branching fraction of the leptonic decay Ds+→μ+νμ is measured to be (0.5294±0.0108stat±0.0085syst)%. Based on this, the product of the Ds+ decay constant fDs+ and the magnitude of the c→s quark mixing matrix element |Vcs| is determined to be fDs+|Vcs|=241.8±2.5stat±2.2syst MeV. Using the value of |Vcs| given by the global standard model fit, fDs+ is found to be 248.4±2.5stat±2.2syst MeV. Alternatively, using the value of fDs+ from a recent lattice quantum chromodynamics calculation, |Vcs| is determined to be 0.968±0.010stat±0.009syst. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.<br/

Improved measurement of the branching fraction of Ds+ →μ+νμ

Using e+e- collision data with an integrated luminosity of 7.33 fb-1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector operating at the BEPCII collider, the branching fraction of the leptonic decay Ds+→μ+νμ is measured to be (0.5294±0.0108stat±0.0085syst)%. Based on this, the product of the Ds+ decay constant fDs+ and the magnitude of the c→s quark mixing matrix element |Vcs| is determined to be fDs+|Vcs|=241.8±2.5stat±2.2syst MeV. Using the value of |Vcs| given by the global standard model fit, fDs+ is found to be 248.4±2.5stat±2.2syst MeV. Alternatively, using the value of fDs+ from a recent lattice quantum chromodynamics calculation, |Vcs| is determined to be 0.968±0.010stat±0.009syst. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.<br/

Study of ψ (3686) → Λ Λ ¯ ω

Based on a data sample of (448.1±2.9)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider, the branching fraction of ψ(3686)→ΛΛ¯ω is measured to be (3.30±0.34(stat)±0.29(syst))×10-5 for the first time. In addition, the Λω (or Λ¯ω) invariant mass spectra is studied and the potential presence of excited Λ states has been investigated