Based on e+e− annihilation data samples collected with the BESIII detector at the BEPCII collider at 13 center-of-mass energies from 4.008 to 4.600 GeV, measurements of the Born cross section of ...e+e−→pp¯π0 are performed. No significant resonant structure is observed in the measured energy dependence of the cross section. The upper limit on the Born cross section of e+e−→Y(4260)→pp¯π0 at the 90% C.L. is determined to be 0.01 pb. The upper limit on the ratio of the branching fractions B(Y(4260)→pp¯π0)B(Y(4260)→π+π−J/ψ) at the 90% C.L. is determined to be 0.02%.
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)×106J/ψ and (447.9±2.9)×106ψ(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) to 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 decays of J/ψ and ψ(3686) to ΞΞ¯ and Σ(1385)Σ¯(1385) are tested.
The lineshapes and peak position of Doppler corrected
γ
-ray
spectra from in-beam experiments at relativistic energies are investigated with respect to the intrinsic energy resolution of the employed ...detectors, the particles’ velocities, and the photons’ emission angle uncertainties at the moment of
γ
-ray
emission. The uncertainties in velocity and photon emission angle are dependent on the lifetime of the excited state. The impact of these two observables on the lineshape and energy resolution are studied for the RISING
γ
-spectrometer
by means of simulations and experimental results from a two-step fragmentation experiment at
≈
200
MeV
/
u
. Potential use of the distinct lineshape for lifetime determination is demonstrated for measured
γ
-ray
transitions.
Hypernuclear production cross sections have been deduced for the first time with induced reaction of heavy ion beam on fixed target and by means of the invariant mass method by the HypHI ...Collaboration exploiting the reaction of 6Li + 12C at 2A GeV or sNN=2.70 GeV. A production cross section of 3.9±1.4 μb for 3ΛH and of 3.1±1.0 μb for 4ΛH respectively in the projectile rapidity region was inferred as well as the total production cross section of the Λ hyperon was measured and found to be equal to 1.7±0.8 mb. A global fit based on a Bayesian approach was performed in order to include and propagate statistical and systematic uncertainties. Production ratios of 3ΛH/4ΛH, 3ΛH/Λ and 4ΛH/Λ were included in the inference procedure. The strangeness population factors S3 and S4 of 3ΛH and 4ΛH respectively were extracted. In addition, the multiplicities of the Λ hyperon, 3ΛH, and 4ΛH together with the rapidity and transversal momentum density distributions of the observed hypernuclei were extracted and reported.
By analyzing a data set of 2.92 fb−1 of e+e− collision data taken at s=3.773 GeV and 106.41×106ψ(3686) decays taken at s=3.686 GeV with the BESIII detector at the BEPCII collider, we measure the ...branching fraction and the partial decay width for ψ(3770)→γχc0 to be B(ψ(3770)→γχc0)=(6.88±0.28±0.67)×10−3 and Γψ(3770)→γχc0=(187±8±19) keV, respectively. These are the most precise measurements to date.
A novel experiment, aiming at demonstrating the feasibility of hypernuclear spectroscopy with heavy ion beams, was conducted. Using the invariant mass method, the spectroscopy of hypernuclear ...products of 6Li projectiles on a carbon target at 2A GeV was performed. Signals of the Λ-hyperon and HΛ3 and HΛ4 hypernuclei were observed for final states of p+π−, He3+π− and He4+π−, respectively, with significance values of 6.7, 4.7 and 4.9σ. By analyzing the proper decay time from secondary vertex distribution with the unbinned maximum likelihood fitting method, their lifetime values were deduced to be 262−43+56±45 ps for Λ, 183−32+42±37 ps for HΛ3, and 140−33+48±35 ps for HΛ4.
The P̄ANDA detection system at FAIR, Germany, is designed to study antiproton-proton annihilations, in order to investigate, among others, the realm of charm-meson states and glueballs, which has ...still much to reveal. The yet unknown properties of this field are to be unraveled through studying QCD phenomena in the non-perturbative regime. The multipurpose P̄ANDA detector will be capable of tracking, calorimetry, and particle identification, and is planned to run at high luminosities providing average reaction rates up to 2 · 10
7
interactions/s. The envisaged physics program requires measurements of photons and charged particles with excellent energy, position, and time resolutions. The electromagnetic calorimeter (EMC) will serve as one of the basic components of the detector setup and comprises cooled lead-tungstate (PbWO
4
) crystals. This paper presents the mechanical design of the Forward End-cap calorimeter and analyzes the response of the Forward End-cap calorimeter in conjunction with the full EMC and the complete P̄ANDA detector. The simulation studies are focused on the performance of the planned EMC with respect to the energy and spatial resolution of the reconstructed photons. Results of the Monte Carlo simulations, excluding very low-energy photons, have been validated by data obtained from a prototype calorimeter and shown to fulfil the requirements imposed by the P̄ANDA physics program.
The PANDA detection system at FAIR, Germany, is designed to study antiproton-proton annihilations, in order to investigate among others the realm of charm-meson states and glueballs, which has still ...much to reveal. The yet unknown properties of this field are to be unraveled through studying QCD phenomena in the non-perturbative regime. The multipurpose PANDA detector will be capable of tracking, calorimetry, and particle identification, and is foreseen to run at high luminosities providing average reaction rates up to 20 Million interactions/s. The envisaged physics program requires measurements of photons and charged particles with excellent energy, position, and time resolutions. The electromagnetic calorimeter (EMC) will serve as one of the basic components of the detector setup and comprises cooled Lead-Tungstate (PbWO4) crystals. This paper presents the mechanical design of the Forward End-cap calorimeter and analyses the response of this detector component in conjunction with the full EMC and the complete PANDA detector. The simulation studies are focused on the performance of the planned EMC with respect to the energy and spatial resolution of the reconstructed photons. Results of the Monte Carlo simulations, excluding very low-energy photons, have been validated by data obtained from a prototype calorimeter and shown to fulfil the requirements imposed by the PANDA physics program.
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