Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e+e−→γISRX(3872)→γISRπ+π−J/ψ via the Initial State ...Radiation technique. The production of a resonance with quantum numbers JPC=1++ such as the X(3872) via single photon e+e− annihilation is forbidden, but is allowed by a next-to-leading order box diagram. We do not observe a significant signal of X(3872), and therefore give an upper limit for the electronic width times the branching fraction ΓeeX(3872)B(X(3872)→π+π−J/ψ)<0.13 eV at the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the ψ(3686) to be Γeeψ(3686)=2213±18stat±99sys eV.
The J/ψ meson has negative G parity so that, in the limit of isospin conservation, its decay into π+π− should be purely electromagnetic. However, the measured branching fraction B(J/ψ→π+π−) exceeds ...by more than 4.5 standard deviations the expectation computed according to BABAR data on the e+e−→π+π− cross section. The possibility that the two-gluon plus one-photon decay mechanism is not suppressed by G-parity conservation is discussed, even by considering other multipion decay channels. As also obtained by phenomenological computation, such a decay mechanism could be responsible for the observed discrepancy. Finally, we notice that the BESIII experiment, having the potential to perform an accurate measurement of the e+e−→π+π− cross section in the J/ψ mass energy region, can definitely prove or disprove this strong G-parity-violating mechanism by confirming or confuting the BABAR data.
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%.
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.
The residual strength in particular the compression strength after damages due to low velocity impact is one of the most critical issue for composite laminates. If the impact event induces relevant ...damages on composite components, a repair of the degraded parts is necessary. The aim of this work is to develop a repair criterion to be applied on the composite structures of the European launch vehicle VEGA. The criterion is based on a numerical procedure which was validated in a previous research work and which allows to predict the impact damage and the post impact residual strength as function of the impact energy, making possible to determine the energy threshold beyond which it is necessary to repair the component.
The BaBar RPC system Zallo, A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2000, Letnik:
456, Številka:
1-2
Journal Article
We report a measurement of the parameter yCP in D0–D¯0 oscillations performed by taking advantage of quantum coherence between pairs of D0D¯0 mesons produced in e+e− annihilations near threshold. In ...this work, doubly-tagged D0D¯0 events, where one D decays to a CP eigenstate and the other D decays in a semileptonic mode, are reconstructed using a data sample of 2.92 fb−1 collected with the BESIII detector at the center-of-mass energy of s=3.773 GeV. We obtain yCP=(−2.0±1.3±0.7)%, where the first uncertainty is statistical and the second is systematic. This result is compatible with the current world average.
The zero degree detector at BESIII Anelli, M.; Baldini Ferroli, R.; Bertani, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Letnik:
718
Journal Article
Recenzirano
Odprti dostop
A small-size calorimeter has been built in the Frascati National Laboratory of INFN for BESIII detector based on the BEPCII storage ring of the Institute of High Energy Physics in Beijing. It has ...been installed in one of the two small-theta angle regions of BEPCII to measure the energy of photons from Initial State Radiation events and is currently taking data together with BESIII. The detector is a sandwich of Pb and scintillating fibers, the same technique employed for the KLOE calorimeter at the DAΦNE accelerator, but the readout is actuated by way of bundles of clear plastic fibers. We describe here the fabrication, present results from tests with cosmic rays and at the Frascati Beam Test Facility, the installation in BESIII, and preliminary luminosity measurements.
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