Implementation of ACTS for STCF track reconstruction

With an electron-positron collider operating at center-of-mass-energy 2-7 GeV and a peak luminosity above $0.5\times10^{35} cm^{-2} s^{-1}$, the STCF physics program will provide an unique platform for in-depth studies of hadron structure and non-perturbative strong interaction as well as probing new physics beyond the Standard Model in the $\tau$-Charm sector, succeeding the present Beijing Electron-Positron Collider. To fulfill the physics targets and further maximize the physics potential at STCF, the STCF tracking software should have capability to reconstruct charged particles with high efficiency and excellent momentum resolution, especially for the charged particles with low transverse momentum down to 50 MeV. A Common Tracking Software (ACTS) providing a set of detector-independent tracking algorithms is adopted for reconstructing charged tracks with the information of two sub-detectors, a $\mu$RWELL-based inner tracker and a drift chamber, at STCF. This is the first demonstration of ACTS for a drift chamber. The implementation details and performance of track reconstruction are presented.Comment: 14 pages, 7 figure

Probing highly collimated photon-jets with deep learning

Many extensions of the standard model (SM) predict the existence of axion-like particles and/or dark Higgs in the sub-GeV scale. Two new sub-GeV particles, a scalar and a pseudoscalar, produced through the Higgs boson exotic decays, are investigated. The decay signatures of these two new particles with highly collimated photons in the final states are discriminated from the ones of SM backgrounds using the Convolutional Neural Networks and Boosted Decision Trees techniques. The sensitivities of searching for such new physics signatures at the Large Hadron Collider are obtained

Performance of Track Reconstruction at STCF Using ACTS

The STCF physics program will provide an unique platform for studies of hadron physics, strong interactions and searches for new physics beyond the Standard Model in the τ-charm region. To deliver those physics programs, the charged particles at STCF are required to be reconstructed with high efficiency and excellent momentum resolution. In particular, charged particles with transverse momentum down to 50 MeV are required to be reconstructed. The tracking performance at STCF is studied using A Common Tracking Software (ACTS) based on the information of the STCF tracking system, a µRWELL-based inner tracker and a drift chamber. We demonstrated the first application of ACTS for a drift chamber. The implementation and tracking performance are presented

Offline Data Processing Software for the Super Tau Charm Facility

The Super Tau Charm Facility (STCF) proposed in China is a newgeneration electron–positron collider with center-of-mass energies covering 2-7 GeV and a peak luminosity of 0.5 1035 cm−2 s−1. The offline software of STCF (OSCAR) is developed to support the offline data processing, including detector simulation, reconstruction, calibration as well as physics analysis. To meet STCF’s specific requirements, OSCAR is designed and developed based on the SNiPER framework, a lightweight common software for HEP experiments. Besides the commonly used software such as Geant4 and ROOT, several state-ofthe-art software packages and tools in the HEP community are incorporated as well, such as the Detector Description Toolkit (DD4hep), the plain-old-data I/O (podio) and Intel Thread Building Blocks (TBB) etc. This paper will present the overall design as well as some implementation details of OSCAR, including the event data management, paralleled data processing based on SNiPER and TBB as well as the geometry management system based on DD4hep. Currently, OSCAR is fully functioning to facilitate the conceptual design of the STCF detector and the study of its physics potential

Simulation study of BESIII with stitched CMOS pixel detector using ACTS

Reconstruction of tracks of charged particles with high precision is very crucial for HEP experiments to achieve their physics goals. As the tracking detector of BESIII experiment, the BESIII drift chamber has suffered from aging effects resulting in degraded tracking performance after operation for about 15 years. To preserve and enhance the tracking performance of BESIII, one of the proposals is to add one layer of thin CMOS pixel sensor in cylindrical shape based on the state-of-the-art stitching technology, between the beam pipe and the drift chamber. The improvement of tracking performance of BESIII with such an additional pixel detector compared to that with only the existing drift chamber is studied using the modern common tracking software ACTS, which provides a set of detector-agnostic and highly performant tracking algorithms that have demonstrated promising performance for a few high energy physics and nuclear physics experiments

Modelling of friction stir welding of DH36 steel

A 3-D computational fluid dynamics (CFD) model was developed to simulate the friction stir welding of 6-mm plates of DH36 steel in an Eulerian steady-state framework. The viscosity of steel plate was represented as a non- Newtonian fluid using a flow stress function. The PCBN-WRe hybrid tool was modelled in a fully sticking condition with the cooling system effectively represented as a negative heat flux. The model predicted the temperature distribution in the stirred zone (SZ) for six welding speeds including low, intermediate and high welding speeds. The results showed higher asymmetry in temperature for high welding speeds. Thermocouple data for the high welding speed sample showed good agreement with the CFD model result. The CFD model results were also validated and compared against previous work carried out on the same steel grade. The CFD model also predicted defects such as wormholes and voids which occurred mainly on the advancing side and are originated due to the local pressure distribution between the advancing and retreating sides. These defects were found to be mainly coming from the lack in material flow which resulted from a stagnant zone formation especially at high tra- verse speeds. Shear stress on the tool surface was found to in- crease with increasing tool traverse speed. To produce a “sound” weld, the model showed that the welding speed should remain between 100 and 350 mm/min. Moreover, to prevent local melt- ing, the maximum tool’s rotational speed should not exceed 550 RPM

The Layout and Performance of the Phase-II upgrade of the tracking detector of the ATLAS experiment

HL-LHC will deliver about 3000 fb-1 of integrated luminosity in over 10 year. This will present an extremely challenging environment to the ATLAS experiment, well beyond that for which it was designed. In ATLAS Phase II upgrade, the Inner Detector will be replace by a new all-silicon Inner Tracker to maintain tracking performance in this high-occupancy environment and to cope with the increase of approximately a factor of ten in the integrated radiation dose. The ITk Detector layout is designed to meet the requirement for identifying charged particles with high efficiency and measuring their properties with high precision in the denser environment. The Layout and performance of the ITk is presented

A non-linear Kalman filter for track parameters estimation in high energy physics

The Kalman Filter is a widely used approach for the linear quadratic estimation of dynamical systems and is frequently employed within nuclear and particle physics experiments for the reconstruction of charged particle trajectories, known as tracks. Implementations of this formalism often make assumptions on the linearity of the underlying dynamic system and the Gaussian nature of the process noise and measurement model, which are violated in a number of track reconstruction applications. This paper introduces an implementation of a Non-Linear Kalman Filter (NLKF) within the ACTS track reconstruction toolkit. The NLKF addresses the issue of non-linearity by using a set of representative sample points during the projection of the track state to the measurement. In a typical use case, the NLKF outperforms the so-called Extended Kalman Filter in the accuracy and precision of the track parameter estimates obtained, with an increase in CPU time below a factor of two. It is therefore a promising approach for use in applications where precise estimation of track parameters is a key concern