A Fit to the Available <i>e</i>⁺<i>e</i>⁻ → <inline-formula><math display="inline"><semantics><mrow><msubsup><mi mathvariant="sans-serif">Λ</mi><mi>c</mi><mo>+</mo></msubsup><msubsup><mover accent="true"><mi mathvariant="sans-serif">Λ</mi><mo>¯</mo></mover><mi>c</mi><mo>−</mo></msubsup></mrow></semantics></math></inline-formula> Cross Section Data Nearby Production Threshold by Means of a Strong Correction to the Coulomb Enhancement Factor

There are two available sets of data on the e+e−→Λc+Λ¯c− cross section at energies close to the production threshold, collected by the Belle and by the BESIII Collaborations. The measurement of the former, performed by means of the initial state radiation technique, is compatible with the presence of a resonance, called ψ(4660), observed also in other final states. On the contrary, the latter is measured an almost flat and hence non-resonant cross section in the energy region just above the production threshold, but the data stop before the possible rise in the cross section for the resonant production. We propose an effective model to describe the behavior of the data near this threshold, which is based on a Coulomb-like enhancement factor due to the strong interaction among the final state particles. In the framework of this model, it is possible to describe both datasets

Operation of the CGEM Detector

A ten years extension of the data taking of BESIII experiment, recently approved, motivated an upgrade program both for the leptonic collider BEPCII and for some of the sub-detectors of the spectrometer. BESIII is a multipurpose spectrometer optimized for physics in the charm-τ energy region. In particular, the current inner drift chamber is suffering from aging and the proposal is to replace it with a detector based on Cylindrical Gas Electron Multiplier (CGEM) technology to improve both the secondary vertex reconstruction and the radiation tolerance. The CGEM Inner Tracker will be composed of three coaxial layers of cylindrical triple GEMs, operating in an Ar + iC4H10 (90:10) gas mixture with field and gain optimized to maximize the spatial resolution. The new detector is readout with innovative TIGER electronics produced in 110 nm CMOS technology. A cosmic telescope instrumented with two out of three layers is in operation in Beijing since January 2020, remotely controlled by Italian groups due to the pandemic situation. A dedicated readout chain was developed for data acquisition. In this paper, the general status of the project will be presented with a particular focus on the preliminary results from the cosmic data taking and future plans

Test beam results of a Cylindrical GEM detector for the BESIII experiment

Gas detector are very light instrument used in high energy physics to measure the particle properties: position and momentum. Through high electric field is possible to use the Gas Electron Multiplier (GEM) technology to detect the charged particles and to exploit their properties to construct a large area detector, such as the new IT for BESIII. The state of the art in the GEM production allows to create very large area GEM foils (up to 50x100 $\mathrm{cm}^2$) and thanks to the small thickness of these foils is it possible to shape it to the desired form: a Cylindrical Gas Electron Multiplier (CGEM) is then proposed. The innovative construction technique based on Rohacell, a PMI foam, will give solidity to cathode and anode with a very low impact on material budget. The entire detector is sustained by Permaglass rings glued at the edges. These rings are used to assembly the CGEM, together with a dedicated Vertical Insertion System and moreover they host the On-Detector electronic. The anode has been improved w.r.t. the state of the art through a jagged readout that minimize the inter-strip capacitance. The mechanical challenge of this detector requires a precision of the entire geometry within few hundreds of microns in the whole area. In this contribution an overview of the construction technique, the validation of this technique through the realization of a CGEM, and its first tests will be presented. These activities are performed within the framework of the BESIIICGEM Project (645664), funded by the European Commission in the action H2020-RISE-MSCA-2014.Gas detector are very light instrument used in high energy physics to measure the particle properties: position and momentum.Through high electric field is possible to use the Gas Electron Multiplier (GEM) technology to detect the charged particles and to exploit their properties to construct a large area detector, such as the new IT for BESIII. The state of the art in the GEM production allows to create very large area GEM foils (up to 50x100 $\mathrm{cm}^2$) and thanks to the small thickness of these foils is it possible to shape it to the desired form: a Cylindrical Gas Electron Multiplier (CGEM) is then proposed.The innovative construction technique based on Rohacell, a PMI foam, will give solidity to cathode and anode with a very low impact on material budget. The entire detector is sustained by Permaglass rings glued at the edges. These rings are used to assembly the CGEM, together with a dedicated Vertical Insertion System and moreover they host the On-Detector electronic. The anode has been improved w.r.t. the state of the art through a jagged readout that minimize the inter-strip capacitance.The mechanical challenge of this detector requires a precision of the entire geometry within few hundreds of microns in the whole area.In this contribution an overview of the construction technique, the validation of this technique through the realization of a CGEM, and its first tests will be presented.These activities are performed within the framework of the BESIIICGEM Project (645664), funded by the European Commission in the action H2020-RISE-MSCA-2014