Untersuchung der Systeme Ds+π+π−D_{s}^{+}\pi^{+}\pi^{-}, Ds+π−D_{s}^{+}\pi^{-} und Ds+π+D_{s}^{+}\pi^{+} in ccˉc\bar{c}-Fragmentationsereignissen

Elektron-Positron-Annihilationsereignisse bei einer Schwerpunktsenergie von 10,58 GeV, wie sie im Rahmen des Babar-Experiments am Stanford Linear Accelerator Center untersucht werden, stellen eine reichhaltige Quelle zur Erzeugung charmhaltiger Resonanzen dar. Die hervorragende Instrumentierung des Babar-Detektors bietet dabei gute experimentelle Möglichkeiten für das Studium solcher Resonanzen. In dieser Arbeit werden die Systeme Ds+pi+pi-, Ds+pi- und Ds+pi+ untersucht. Es wird der Zerfall der Resonanzen DsJ(2460)+ und Ds1(2536)+ in Ds+pi+pi- beobachtet. Ein Zerfall des Zustands DsJ*(2317)+ in Ds+pi+pi- sowie der hypothetische Zerfall möglicher Isospin-Partnerzustände des DsJ*(2317)+ in Ds+pi- und Ds+pi+ werden nicht beobachtet. Für die betrachteten Zerfallsmoden werden relative Verzweigungsverhältnisse bzw. deren obere Grenze bestimmt. Die angestellten Untersuchungen können zur Klärung der Natur der Resonanzen DsJ*(2317)+ und DsJ(2460)+ beitragen

Resonances in QCD

We report on the EMMI Rapid Reaction Task Force meeting ‘Resonances in QCD’, which took place at GSI October 12–14, 2015. A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions:• What is needed to understand the physics of resonances in QCD?• Where does QCD lead us to expect resonances with exotic quantum numbers?• What experimental efforts are required to arrive at a coherent picture?For light mesons and baryons only those with up, down and strange quark content were considered. For heavy–light and heavy–heavy meson systems, those with charm quarks were the focus.This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here

Hyperon signatures in the PANDA experiment at FAIR

We present a detailed simulation study of the signatures from the sequential decays of the triple-strange pbar p -> Ω+Ω- -> K+ΛbarK- Λ -> K+pbarπ+K-pπ- process in the PANDA central tracking system with focus on hit patterns and precise time measurement. We present a systematic approach for studying physics channels at the detector level and develop input criteria for tracking algorithms and trigger lines. Finally, we study the beam momentum dependence on the reconstruction efficiency for the PANDA detector

Measurement of singly Cabibbo-suppressed decays D0 → π0π0π0, π0π0η, π0ηη and ηηη

Using a data sample of e+e− collision data corresponding to an integrated luminosity of 2.93 fb−1 collected with the BESIII detector at a center-of-mass energy of s=3.773GeV, we search for the singly Cabibbo-suppressed decays D0→π0π0π0, π0π0η, π0ηη and ηηη using the double tag method. The absolute branching fractions are measured to be B(D0→π0π0π0)=(2.0±0.4±0.3)×10−4, B(D0→π0π0η)=(3.8±1.1±0.7)×10−4 and B(D0→π0ηη)=(7.3±1.6±1.5)×10−4 with the statistical significances of 4.8σ, 3.8σ and 5.5σ, respectively, where the first uncertainties are statistical and the second ones systematic. No significant signal of D0→ηηη is found, and the upper limit on its decay branching fraction is set to be B(D0→ηηη)<1.3×10−4 at the 90% confidence level

Study of J/ψ and ψ(3686) → Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0

We study the decays of J/ψ and ψ(3686) to the final states Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0 based on a single baryon tag method using data samples of (1310.6±7.0)×106 J/ψ and (447.9±2.9)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider. The decays to Σ(1385)0Σ¯(1385)0 are observed for the first time. The measured branching fractions of J/ψ and ψ(3686)→Ξ0Ξ¯0 are in good agreement with, and much more precise, than the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for J/ψ→Σ(1385)0Σ¯(1385)0, α=−0.64±0.03±0.10, is found to be negative, different to the other decay processes in this measurement. In addition, the "12\% rule" and isospin symmetry in the J/ψ and ψ(3686)→ΞΞ¯ and Σ(1385)Σ¯(1385) systems are tested

Measurements of the branching fractions for D+→KS0KS0K+, KS0KS0π+ and D0→KS0KS0, KS0KS0KS0

By analyzing 2.93 fb−1 of data taken at the ψ(3770) resonance peak with the BESIII detector, we measure the branching fractions for the hadronic decays D+ → K0S K0S K +, D+ → K0S K0Sπ+, D0 → K0S K0S and D0 → K0S K0S K0S . They are determined to be B(D+ → K0S K0S K +) = (2.54 ± 0.05stat. ± 0.12sys.) × 10−3, B(D+ → K0S K0Sπ+) = (2.70 ± 0.05stat. ± 0.12sys.) × 10−3, B(D0 → K0S K0S ) = (1.67 ± 0.11stat. ± 0.11sys.) × 10−4 and B(D0 → K0S K0S K0S ) = (7.21 ± 0.33stat. ± 0.44sys.) × 10−4, where the second one is measured for the first time and the others are measured with significantly improved precision over the previous measurements

Observation of the helicity-selection-rule suppressed decay of the χ_(c2) charmonium state

The decays of χc2→K+K−π0, KSK±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 χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 10 times larger than the upper limit of χc2→ρ(770)±π∓, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays

Study of the processes χcJ → Ξ−Ξ¯+ and Ξ0Ξ¯0

Using 448.1 × 106 ψ(3686) decays collected with the BESIII detector at the BEPCII e+e− storage rings, the branching fractions and angular distributions of the decays χcJ → Ξ−Ξ¯¯¯¯+ and Ξ0Ξ¯¯¯¯0 (J = 0, 1, 2) are measured based on a partial-reconstruction technique. The decays χc1 → Ξ0Ξ¯¯¯¯0 and χc2 → Ξ0Ξ¯¯¯¯0 are observed for the first time with statistical significances of 7σ and 15σ, respectively. The results of this analysis are in good agreement with previous measurements and have significantly improved precision