Straw Tube Tracker Research Articles

New electronics for the HADES MDC drift chambers

The drift chambers of the HADES experiment at SIS-18 at GSI, Darmstadt/Germany, form the main tracking system of the spectrometer. Designed more than twenty years ago, the whole front-end electronics chain is being replaced with state-of-the-art electronics to cope with the increasing failure rate of the old electronics and with advanced requirements of the experiment, e.g. the trigger rate.The new analog signal processing is based on the PASTTREC ASIC, developed for the Straw Tube Tracker of the PANDA Experiment. The digitization of data happens in FPGA-based TDCs.The main challenges of the project are the strict spatial constraints given by the experiment setup to place the front-end boards and the noise sensitivity of the large area gas detectors. In addition, the power consumption needed to be kept low due to thermal constraints.

KinKal: A Kinematic Kalman filter Track Fitting Package for the Mu2e Experiment

Many current physics experiments require precision reconstruction of low-energy particles. One example is the Mu2e experiment, which requires reconstructing an isolated 105 MeV electron with better than 500 KeV/c momentum resolution. Mu2e uses a low-mass straw tube tracker, and a CsI crystal calorimeter, to reconstruct tracks. In this paper, we present the design and performance of a track reconstruction algorithm optimized for Mu2e’s unusual requirements. The algorithm is based on the KinKal [1] kinematic Kalman filter track fit package. KinKal supports multiple track parameterizations, including one optimized for looping tracks, such as Mu2e signal tracks, and others optimized for straight or slightly-curved tracks, such as the high-momentum (>1 GeV/c) cosmic ray muons used to calibrate and align the Mu2e detectors. All KinKal track parameterizations include the track origin time, to correctly model correlations arising from measurements that couple time and space, such as the straw drift time or the calorimeter cluster time. KinKal employs magnetic field inhomogeneity and material effect correction algorithms with 10−4 fractional precision. The Mu2e fit uses Artificial Neural Net functions to discriminate background hits from signal hits, and to resolve the straw tube hit left-right ambiguity, while iterating the extended Kalman filter. The efficiency, accuracy, and precision of the Mu2e track reconstruction, as tested on detailed simulations of Mu2e data, are presented.

Reconstructing charged-particle trajectories in the PANDA Straw Tube Tracker using the LOcal Track Finder (LOTF) algorithm

We present the LOcal Track Finder (lotf) algorithm, a method that performs charged-particle trajectory reconstruction using the Straw Tube Tracker, one of the central trackers of the antiProton ANnihilation at DArmstadt (PANDA) detector. The algorithm builds upon the neighboring relations of the tubes to connect individual hits and form track candidates. In addition, it uses a local fitting procedure to handle regions where several tracks overlap and utilizes a system of virtual nodes to reconstruct the z-information of the particle trajectories. We generated 30,000 events to assess the performance of our approach and compared its global track assignment efficiency with respect to two other track reconstruction methods. lotf has (1) an average of 85% of found tracks, (2) the largest number of Fully Pure tracks, (3) the lowest amount of incorrect reconstructions, and (4) is significantly faster than the other two approaches. Further, we compared the z-reconstruction performance with one of the two alternative methods and show that lotf improves the median z-error by a factor of 8.7. Finally, we tested our method using 3750 data sets composed of 4 events each, demonstrating that our approach handles cases in which events are mixed. The raw (without parallelization) average reconstruction rate is about 68,000 hits/s, which makes the present algorithm promising for online data selection and processing.

Production tests of front-end electronics for Straw Tube Trackers in HADES and PANDA experiments at FAIR

PASTTREC is an 8-channel readout Application-Specific Integrated Circuit (ASIC) designed for the Straw Tracking System (STS) in the HADES experiment and for the Straw Tube Tracker (STT) and the Forward Tracker (FT) detectors in the PANDA experiment, both at the FAIR facility. Since more than 5000 ASICs were produced for both experiments, efficient qualification tests are required. For this purpose, the multi-chip test setup and dedicated verification procedures were developed. In this paper, the measurement results for the first batch of 140 Front-End Boards (FEBs), each hosting two ASICs, are presented. Since a significant number (280) of PASTTREC chips were tested, obtained statistical distributions of key parameters are also reported. The estimated yield (97%) and the process-related spread of the chip parameters are discussed.

Design, assembly and operation of a Cosmic Ray Tagger based on scintillators and SiPMs

The Mu2e experiment at Fermilab aims to search for the SM forbidden μ−→e− conversion in Al muonic atoms. The signal signature consists of 104.96 MeV electrons, identified by a straw-tube tracker and a crystal calorimeter, made of two annular disks. In order to calibrate the calorimeter disks with minimum ionizing particles (MIP) before the installation, we have realized a Cosmic Ray Tagger (CRT) at Laboratori Nazionali di Frascati (LNF) of INFN. The CRT consists of two planes of eight 2.5×1.5×160 cm3 plastic scintillator (EJ-200) bars, coupled to SiPMs on both edges, so as to estimate longitudinal hit positions from time differences. 3D MIP tracking is achieved by reconstructing hit positions in the two planes, placed above and below the disks, and allows to calibrate the energy response, to align the time offsets, and to study the detector performances dependence along the crystals axis.

A Generalized Approach to Longitudinal Momentum Determination in Cylindrical Straw Tube Detectors

The upcoming PANDA experiment at FAIR will be among a new generation of particle physics experiments to employ a novel event filtering system realised purely in software, i.e. a software trigger. To educate its triggering decisions, online reconstruction algorithms need to offer outstanding performance in terms of efficiency and track quality. We present a method to reconstruct longitudinal track parameters in PANDA’s Straw Tube Tracker, which is general enough to be easily added to other track finding algorithms that focus on transversal reconstruction. For the pattern recognition part of this method, three approaches are employed and compared: a combinatorial path finding approach, a Hough transformation, and a recursive annealing fit. In a systematic comparison, the recursive annealing fit was found to outperform the other approaches in every category of quality parameters and reaches a reconstruction efficacy of 95% and higher. Due to its computational simplicity, the recursive annealing fit was also found to have faster execution times compared to the other algorithms.

Gigabit Ethernet Daisy Chain on FPGA for COMET Readout Electronics

The COMET experiment at J-PARC aims to search for the neutrinoless transition of a muon to an electron. We have developed the readout electronics board called ROESTI for the COMET straw tube tracker. We plan to install the ROESTI in the gas manifold of the detector. The number of vacuum feedthroughs needs to be reduced due to space constraints and cost limitations. In order to decrease the number of vacuum feedthroughs drastically, we developed a network processor with a daisy-chain function of Gigabit Ethernet for the FPGA on the ROESTI. We implemented two SiTCPs, which are hardware-based TCP processors for Gigabit Ethernet, in the network processor. We also added the data path controllers which handle the Ethernet frames and the event data. The network processor enables ROESTI to process the slow control over UDP/IP and to transfer event data over TCP/IP. By using the network processor, we measured the throughput, the stability, and the data loss rate for two to six ROESTIs. In any number of boards, the throughput of the event data transfer achieved the theoretical limit of TCP over the Gigabit Ethernet stably and ROESTI stably sent 100% of the data.

Track Finding for the PANDA Detector Based on Hough Transformations

The PANDA experiment at FAIR (Facility for Antiproton and Ion Research) in Darmstadt is currently under construction. In order to reduce the amount of data collected during operation, it is essential to find as many true tracks as possible and to be able to distinguish them from false tracks. Part of the preparation for the experiment is the development of a fast online track finder. This work presents an online track finding algorithm based on Hough transformations, which is comparable in quality and performance to the currently best offline track finder in PANDA. In contrast to most track finders the algorithm can handle the challenge of extended hits delivered by PANDA’s central Straw Tube Tracker and thus benefit from its precise spatial resolution. Furthermore, optimization methods are presented that improved the ghost ratio as well as the speed of the algorithm by 70 %. Due to further development potential in terms of track finding for secondary particles and speed optimization on GPUs, this algorithm promises to exceed the quality and speed of other track finders developed for PANDA.

Track Reconstruction with PANDA at FAIR

The future PANDA experiment at FAIR aims to investigate a wide range of physics processes in antiproton-proton collisions at rates of up to 20 MHz, while employing a purely software-based event filter. To educate the trigger decisions, a full event reconstruction has to be carried out in real time. This challenge is amplified when considering tracks from particles with long lifetimes and displaced decay vertices, which add to the complexity of the reconstruction algorithms. Here, we present modifications to a cellular automatonbased track finder taking detector time-stamps into account in addition to spatial information, as well as several pattern recognition methods for longitudinal track reconstrucion with PANDA’s Straw Tube Tracker.

Study of the performance of prototypes of straw tube tracker by measuring cosmic rays

Straw tube detector developed for the PANDA experiment in [1], will be used for tracking and identifcation of charged particles in the Forward Tracker (FT). The detector read-out will be incorporated in PANDA DAQ running in trigger-less mode by means of Synchronization Of Data Acquisition Network (SODAnet). SODAnet is the protocol used to synchronize individual detector subsystems by providing a common clock signal and timestamps. The reconstruction of events out of many fragments is done with the Burst Building Network. The first tests of such system have been performed with prototypes of FT and ElectroMagnetic Calorimeter modules (EMC) in [1] measuring cosmic rays. Those tests allow to evaluate the detectors as well as the synchronization and processing systems. The reconstruction of particle tracks has been developed and evaluated. The results on the track reconstruction, spatial resolution and energy loss via Time over Threshold (TOT) method is described together with the DAQ performance.

The Mu2e Experiment

The Mu2e experiment at Fermilab will search for new phenomena by measuring the rate of muon to electron conversion in the field of a nucleus, μN → eN. Data collection will begin in 2021 and will continue for three years. The experiment will achieve a single-event sensitivity of 3 × 10−17 with < 0.5 background events. This equates to an experimental limit on the conversion rate of 8 × 10−17 at the 90%CL, which is a four-order-of-magnitude improvement over existing limits. A pulsed proton beam will be provided by the Fermilab booster, and a three-part solenoid will be used to produce, transport, and stop a muon beam on an Al target, whereafter the muons may interact and undergo conversion. The sensitivity requires that 1018 muons be stopped, which calls for the most intense muon beam ever made. The background requirement sets a strong constraint on the momentum resolution, which translates into stringent demands on detector performance. The major detectors consist of a precision, ultra low-mass straw-tube tracker, used for momentum reconstruction; a crystal calorimeter for enhanced PID; and an encasing multi-layer set of scintillation counters to veto false signals otherwise generated by cosmic muons.

Design and performance evaluation of front-end electronics for COMET straw tracker

Abstract The COMET experiment at J-PARC aims to search for the charged lepton flavor violating process of neutrinoless muon-to-electron conversion with an improvement of a sensitivity by a factor of 10000 to the current limit. We plan to use a straw tube tracker with high momentum resolution as an electron detector . To read out the signal from the tracker precisely, optimal front-end electronics is needed, and we have developed the readout electronics board called ROESTI, which contains all the front-end processes; preamplification, pulse shaping, discrimination, and digitization. All the functionalities are controlled by FPGA. Using the prototype, we have constructed the calibration method and evaluated the fundamental performance. In this paper, we report the details of the design and performance for the ROESTI prototype.

Performance of a prototype Straw Tube Tracker for the P̄ANDA experiment

The P̄ANDA experiment is one of the pillars of the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany. The P̄ANDA physics program is focused on answering fundamental questions related to Quantum Chromo Dynamics (QCD), using antiproton collisions on proton and nuclear targets. The central Straw Tube Tracker (STT) will be the main tracking detector which will reconstruct tracks induced by charged particles (with a transversal spatial resolution of ≃ 150 μm) and it will measure the specific energy-losses for particle identification (PID) with an energy resolution better than 10%. The PID information is especially needed to separate protons, kaons and pions in the momentum region below 1 GeV/c. Results obtained with a prototype STT using a proton and a deuteron beam in the momentum range from 0.5 to 3.0 GeV/c are shown and discussed.

Track propagation methods for the correlation of charged tracks with clusters in the calorimeter of the P̄ANDA experiment

To classify clusters of hits in the electromagnetic calorimeter (EMC) of P̄ANDA (antiProton ANnihilation at DArmstadt), one has to match these EMC clusters with tracks of charged particles reconstructed from hits in the tracking system. Therefore the tracks are propagated to the surface of the EMC and associated with EMC clusters which are nearby and below a cut parameter. In this work, we propose a helix propagator to extrapolate the track from the Straw Tube Tracker (STT) to the inner surface of the EMC instead of the GEANE propagator which is already embedded within the PandaRoot computational framework. The results for both propagation methods show a similar quality, with a 30% gain in CPU time when using the helix propagator. We use Monte-Carlo truth information to compare the particle ID of the EMC clusters with the ID of the extrapolated points, thus deciding upon the correctness of the matches. By varying the cut parameter as a function of transverse momentum and particle type, our simulations show that the purity can be increased by 3–5% compared to the default value which is a constant cut in the P̄ANDA simulation framework PandaRoot.

The Mu2e crystal calorimeter

The Mu2e Experiment at Fermilab will search for coherent, neutrino-less conversion of negative muons into electrons in the field of an Aluminum nucleus, μ− + Al → e− +Al. Data collection start is planned for the end of 2021. The dynamics of such charged lepton flavour violating (CLFV) process is well modelled by a two-body decay, resulting in a mono-energetic electron with an energy slightly below the muon rest mass. If no events are observed in three years of running, Mu2e will set an upper limit on the ratio between the conversion and the capture rates Rμe = μ− + A(Z,N) → e− + A(Z,N)/μ− + A(Z,N) → νμ− + A(Z−1,N) of ⩽ 6 × 10−17 (@ 90% C.L.). This will improve the current limit of four order of magnitudes with respect to the previous best experiment. Mu2e complements and extends the current search for μ → e γ decay at MEG as well as the direct searches for new physics at the LHC . The observation of such CLFV process could be clear evidence for New Physics beyond the Standard Model. Given its sensitivity, Mu2e will be able to probe New Physics at a scale inaccessible to direct searches at either present or planned high energy colliders. To search for the muon conversion process, a very intense pulsed beam of negative muons (∼ 1010 μ/sec) is stopped on an Aluminum target inside a very long solenoid where the detector is also located. The Mu2e detector is composed of a straw tube tracker and a CsI crystals electromagnetic calorimeter. An external veto for cosmic rays surrounds the detector solenoid. In 2016, Mu2e has passed the final approval stage from DOE and has started its construction phase. An overview of the physics motivations for Mu2e, the current status of the experiment and the required performances and design details of the calorimeter are presented.

Design of the forward straw tube tracker for the PANDA experiment

The design of the Forward Tracker for the Forward Spectrometer of the PANDA experiment is described. The tracker consists of 6 tracking stations, each comprising 4 planar double layers of straw tube detectors, and has a total material budget of only 2% X0. The straws are made self-supporting by a 1 bar over-pressure of the working gas mixture (Ar/CO2). This allows to use lightweight and compact rectangular support frames for the double layers and to split the frames into pairs of C-shaped half-frames for an easier installation on the beam line.

Components Qualification for a Possible use in the Mu2e Calorimeter Waveform Digitizer

The Mu2e experiment at Fermilab searches for the charged flavor violating conversion of a muon into an electron in the Coulomb field of a nucleus. The detector consists of a straw tube tracker and a CSI crystal electromagnetic calorimeter, both housed in a superconducting solenoid. Both the front-end and the digital electronics, located inside the cryostat, will be operated in vacuum under a 1 T magnetic field, having to sustain the high flux of neutrons and ionizing particles coming from the muons stopping target. These harsh experimental conditions make the design of the calorimeter waveform digitizer quite challenging. All the selected commercial devices must be tested individually and qualified for radiation hardness and operation in high magnetic field. At the moment the expected particles flux and spectra at the digitizers location are not completely simulated and we are using initial rough estimates to select the components for the first prototype. We are gaining experience in the qualification procedures using the selected components but the choice will be frozen only when dose and neutron flux simulations will be completed. The experimental results of the first qualification campaign are presented.

The calorimeter of the Mu2e experiment at Fermilab

The Mu2e experiment at Fermilab looks for Charged Lepton Flavor Violation (CLFV) improving by 4 orders of magnitude the current experimental sensitivity for the muon to electron conversion in a muonic atom. A positive signal could not be explained in the framework of the current Standard Model of particle interactions and therefore would be a clear indication of new physics. In 3 years of data taking, Mu2e is expected to observe less than one background event mimicking the electron coming from muon conversion. Achieving such a level of background suppression requires a deep knowledge of the experimental apparatus: a straw tube tracker, measuring the electron momentum and time, a cosmic ray veto system rejecting most of cosmic ray background and a pure CsI crystal calorimeter, that will measure time of flight, energy and impact position of the converted electron. The calorimeter has to operate in a harsh radiation environment, in a 10−4 Torr vacuum and inside a 1 T magnetic field. The results of the first qualification tests of the calorimeter components are reported together with the energy and time performances expected from the simulation and measured in beam tests of a small scale prototype.

Reconstructing Hyperons with the ANDA Detector at FAIR

Hyperon production and the study of their properties is an important part of the physics programme of the future ANDA experiment at FAIR. Antihyperon-hyperon pairs will be produced in antiproton-proton collisions through the annihilation of at least one light antiquark-quark (u, d) pair and the creation of a corresponding number of antiquark-quark s pairs. By measuring the decay products of the hyperons, spin observables such as the polarisation can be measured.Many hyperons have a long life-time which gives rise to final state particles originating from displaced vertices. A pattern recognition algorithm using information from the ANDA Straw Tube Tracker is extended to reconstruct not only the transversal, but also the longitudinal components of charged tracks. A Hough transform and a path finding method as tools to extract the longitudinal components are being developed.

FPGA Online Tracking Algorithm for the PANDA Straw Tube Tracker

A novel FPGA based online tracking algorithm for helix track reconstruction in a solenoidal field, developed for the PANDA spectrometer, is described. Employing the Straw Tube Tracker detector with 4636 straw tubes, the algorithm includes a complex track finder, and a track fitter. Implemented in VHDL, the algorithm is tested on a Xilinx Virtex-4 FX60 FPGA chip with different types of events, at different event rates. A processing time of 7 $\mu$s per event for an average of 6 charged tracks is obtained. The momentum resolution is about 3\% (4\%) for $p_t$ ($p_z$) at 1 GeV/c. Comparing to the algorithm running on a CPU chip (single core Intel Xeon E5520 at 2.26 GHz), an improvement of 3 orders of magnitude in processing time is obtained. The algorithm can handle severe overlapping of events which are typical for interaction rates above 10 MHz.