Performance studies for the trigger-less data acquisition of the PANDA experiment (phase-1)

Despite its successes, the Standard Model (SM) still contains certain gaps in the knowledge about the strong interactions. For example, a mass-generation mechanism (Higgs mechanism) is only responsible for 1% of the mass of proton, which is the first hadron discovered by physicists. The origin of the rest 99% is still not fully understood. According to Quantum Chromo Dynamics (QCD), the theory describing strong interactions within the SM, fundamental blocks of hadrons, quarks and gluons, are able to carry color charge and form color-neutral states. The latter can be a common matter (meson and baryon states) as well as an exotics (non-meson and non-baryon states). One of the possible ways to understand the dynamics of strong interactions is the investigation of conventional and exotic states in nuclear and particle physics experiments able to provide high-interaction rates sufficient for production of these states. AntiProton ANnihilations at DArmstadt (PANDA) at the Facility for Antiproton and Ion Research (FAIR) in Darmstadt is one such experiment. PANDA aims to explore a transition region between non-perturbative and perturbative regimes of QCD using antiproton-proton annihilations at high interaction rates. In this thesis, the performance of the trigger-less Data Acquisition (DAQ) system of the PANDA experiment is studied in terms of requirements for its starting phase (phase-1). Additionally, a possible data acquisition strategy was found for this phase. The results obtained from experimental measurements, as well as simulation studies, showed that trigger-less DAQ using the proposed strategy can fulfill the requirements of the PANDA experiment for phase-1

Measurement of the branching fraction of the singly Cabibbo-suppressed decay Λc+ → Λk+

We report a branching fraction measurement of the singly Cabibbo-suppressed decay Λc+→ΛK+ using a data sample collected with the BESIII detector at the BEPCII storage ring. The data span center-of-mass energies from 4.599 to 4.950 GeV and correspond to an integrated luminosity of 6.44 fb-1. The branching fraction of Λc+→ΛK+ relative to that of the Cabibbo-favored decay Λc+→Λπ+ is measured to be R=B(Λc+→ΛK+)B(Λc+→Λπ+)=(4.78±0.34±0.20)%. Combining with the world-average value of B(Λc+→Λπ+), we obtain B(Λc+→ΛK+)=(6.21±0.44±0.26±0.34)×10-4. Here the first uncertainties are statistical, the second systematic, and the third comes from the uncertainty of the Λc+→Λπ+ branching fraction. This result, which is more precise than previous measurements, does not agree with theoretical predictions, and suggests that nonfactorizable contributions have been underestimated in current models

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/

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/

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/

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

Search for a CP-odd light Higgs boson in J/ψ →γA⁰

Using J/ψ radiative decays from 9.0 billion J/ψ events collected by the BESIII detector, we search for di-muon decays of a CP-odd light Higgs boson (A0), predicted by many new physics models beyond the Standard Model, including the next-to-minimal supersymmetric Standard Model. No evidence for the CP-odd light Higgs production is found, and we set 90% confidence level upper limits on the product branching fraction B(J/ψ→γA0)×B(A0→μ+μ-) in the range of (1.2-778.0)×10-9 for 0.212≤mA0≤3.0 GeV/c2. The new measurement is a 6-7 times improvement over our previous measurement, and is also slightly better than the BABAR measurement in the low-mass region for tanβ=1