Online Estimation of Particle Track Parameters based on Neural Networks for the Belle II Trigger System

The Belle II particle accelerator experiment is experiencing substantial background from outside of the interaction point. To avoid taking data representing this background, track parameters are estimated within the pipelined and dead time-free level 1 trigger system of the experiment and used to suppress such events. The estimation of a particle track\u27s origin with respect to the z-Axis, which is along the beamline, is performed by the neural z-Vertex trigger. This system is estimating the origin or z-Vertex using a trained multilayer perceptron, leveraging the advantages of training to current circumstances of operation. In order fulfil the requirements set by the overall trigger system it has to provide the estimation within an overall latency of 5 us while matching a refresh rate of up to 31.75 for new track estimations. The focus of this contribution is this system\u27 current status. For this both implementation and integration into the level 1 trigger will be presented, supported by first data taken during operation as well as figures of merit such as latency and resource consumption. In addition its upgrade plan for the near future will be presented. The center of these is a Hough based track finding approach that uses Bayes theorem for training the weighting of track candidates. Characteristics of this system\u27s current prototypical implementation on FPGAs as well as present plants towards integration for future operation will be presented

The Event Timing Finder for the Central Drift Chamber Level-1 Trigger at the Belle II experiment

The level-1 trigger system of the Belle II experiment is designed to select physics events of interest with almost 100% efficiency for hadronic events. In terms of event timing decision, the level-1 trigger is required to have an accuracy of less than 10 ns. The Central Drift Chamber (CDC) level-1 trigger provides the event timing information as one of the level-1 timing sources. We developed the new algorithm to measure the event timing with an accuracy of about 10 ns based on the CDC hit timing. Two-dimensional charged track reconstruction by Hough transformation was utilized to reduce high background hits. We used a new-developed general-purpose FPGA board (Universal Trigger board 4) for this module for the first time. We report the performance of the new algorithm using e$^+$e$^−$ collision data collected in 2020

The high-rate data challenge: computing for the CBM experiment

The Compressed Baryonic Matter experiment (CBM) is a next-generation heavy-ion experiment to be operated at the FAIR facility, currently under construction in Darmstadt, Germany. A key feature of CBM is very high interaction rate, exceeding those of contemporary nuclear collision experiments by several orders of magnitude. Such interaction rates forbid a conventional, hardware-triggered readout; instead, experiment data will be freely streaming from self-triggered front-end electronics. In order to reduce the huge raw data volume to a recordable rate, data will be selected exclusively on CPU, which necessitates partial event reconstruction in real-time. Consequently, the traditional segregation of online and offline software vanishes; an integrated on- and offline data processing concept is called for. In this paper, we will report on concepts and developments for computing for CBM as well as on the status of preparations for its first physics run

A precision device needs precise simulation: Software description of the CBM Silicon Tracking System

Precise modelling of detectors in simulations is the key to the understanding of their performance, which, in turn, is a prerequisite for the proper design choice and, later, for the achievement of valid physics results. In this report, we describe the implementation of the Silicon Tracking System (STS), the main tracking device of the CBM experiment, in the CBM software environment. The STS makes uses of double-sided silicon micro-strip sensors with double metal layers. We present a description of transport and detector response simulation, including all relevant physical effects like charge creation and drift, charge collection, cross-talk and digitization. Of particular importance and novelty is the description of the time behavior of the detector, since its readout will not be externally triggered but continuous. We also cover some aspects of local reconstruction, which in the CBM case has to be performed in real-time and thus requires high-speed algorithms

Performance for proton anisotropic flow measurement of the CBM experiment at FAIR

The Compressed Baryonic Matter experiment (CBM) performance for proton anisotropic flow measurements is studied with Monte-Carlo simulations using collisions of gold ions at lab momentum of 12A GeV/c employing DCM-QGSM-SMM heavy-ion event generator. Realistic procedures are used for centrality estimation with the number of registered tracks and particle identification with information from Time-Of-Flight detector. Variation of directed flow estimates depending on various combinations of PSD modules is used to evaluate possible systematic biases due to collision symmetry plane estimation

Using multiplicity of produced particles for centrality determination in heavy-ion collisions with the CBM experiment

The evolution of matter created in a heavy-ion collision depends on its initial geometry. Experimentally collision geometry is characterized with centrality. Procedure of centrality determination for the Compressed Baryonic Matter (CBM) experiment at FAIR is presented. Relation between parameters of the collision geometry (such as impact parameter magnitude) and centrality classes is extracted using multiplicity of produced charged particles. The latter is connected to the collision geometry parameters using Monte-Carlo Glauber approach

The very forward hadron calorimeter PSD for the future CBM@FAIR experiment

The Projectile Spectator Detector (PSD) of the CBM experiment at the future FAIR facility is a compensating lead-scintillator calorimeter designed to measure the energy distribution of the forward going projectile nucleons and nuclei fragments (reaction spectators) produced close to the beam rapidity. The detector performance for the centrality and reaction plane determination is re- viewed based on Monte-Carlo simulations of gold-gold collisions by means of four different heavy-ion event generators. The PSD energy resolution and the linearity of the response measured at CERN PS for the PSD supermodule consisting of 9 modules are presented. Predictions of the calorimeter radiation conditions at CBM and response measurement of one PSD module equipped with neutron irradiated MPPCs used for the light read out are discussed