Pattern recognition for the HADES RICH detector

The strangeness production ratios [bar wedge]/∧ and [bar wedge]/K0S are measured by the LHCb detector from 0.3 nb-1 of proton-proton collisions delivered by the Large Hadron Collider (LHC) at CERN with centre-of-mass energy √s = 0.9TeV and 1.8 nb-1 at √s = 7TeV. Both ratios are presented as a function of transverse momentum, pT, and rapidity, y, in the ranges 0.15 < pT < 2.50 GeV/c and 2.0 < y < 4.5. The ratios measured at the two energies are in good agreement in an overlapping region of rapidity loss, Δ y = ybeam - y, and are consistent with previous measurements. A review of the Standard Model is presented with emphasis on the diffculties in its application for predictions of physics at the LHC. Phenomenological models are introduced as the current state of the art for such predictions. Accurate models are required as an essential benchmark for future discoveries of physics beyond the Standard Model. LHCb's results represent a powerful test for these models in the soft QCD regime for processes including hadronisation. The ratio [bar wedge]/∧, measuring the transport of baryon number from the collision into the detector, is smaller in data than predicted, particularly at high rapidity. The ratio [bar wedge]/K0 S, measuring the baryon-to-meson suppression in strange quark hadronisation, is significantly larger than expected. The LHCb experiment is introduced, with particular focus on its Ring Imaging Cherenkov (RICH) detectors. The development and successful implementation of a method to align those RICH detectors is presented, using proton-proton collision data from the early running period of the Large Hadron Collider, which began in November 2009. The performance of the RICH detectors is investigated with preliminary analysis of the Cherenkov photon yield. The RICH mirror positions are monitored using an automated software control system, which has been running successfully since October 2008.

This thesis consists of two independent parts; development of Cherenkov Ring Imaging Detector (CRID) system and analysis of high-statistics data of strange meson reactions from the LASS spectrometer. Part 1: The CRID system is devoted to charged particle identification in the SLAC Large Detector (SLD) to study e[sup +]e[sup [minus]] collisions at [radical]s = m[sub Z[sup 0]]. By measuring the angles of emission of the Cherenkov photons inside liquid and gaseous radiators, [pi]/K/p separation will be achieved up to [approximately]30 GeV/c. The signals from CRID are read in three coordinates, one of which is measured by charge-division technique. To obtain a [approximately]1% spatial resolution in the charge-division, low-noise CRID preamplifier prototypes were developed and tested resulting in <1000 electrons noise for an average photoelectron signal with 2 [times] 10[sup 5] gain. To help ensure the long-term stability of CRID operation at high efficiency, a comprehensive monitoring and control system was developed. Part 2: Results from the partial wave analysis of strange meson final states in the reactions K[sup [minus]]p [yields] K[sup [minus]][omega]p and K[sup [minus]]p [yields] [bar K][sup 0][phi]n are presented. The analyses are based on data from a 4.1 event/nb exposure of the LASS spectrometer in K[sup [minus]]p interactions at 11 GeV/c. The data sample of K[sup [minus]][omega]p final state contains [approximately]10[sup 5] events. From the partial wave analysis, resonance structures of J[sup P] = 2[sup [minus]], 3[sup [minus]] and 2[sup +] amplitudes are observed in the K[omega] system. The analysis of 2[sup [minus]] amplitudes provides an evidence for two strange meson states in the mass region around 1.75 GeV/c[sup 2]. The appropriate branching fractions are calculated and compared with the SU(3) predictions. The partial wave analysis of [bar K][sup 0][phi] system favors J[sup P] = 1[sup [minus]] and 2[sup +] states in the 1.9--2.0 GeV/c[sup 2] region.

Real-time track-less Cherenkov ring fitting trigger system based on Graphics Processing Units

The present article describes the ring imaging Cherenkov (RICH) detectors of the LHCb experiment. The two RICH detectors of LHCb contain three radiators, carefully designed to provide particle identification of B meson decays in the relevant momentum range of the experiment. A status of the design of the RICH system will be presented with the expected overall performance.

The DELPHI collaboration has designed and implemented a Cherenkov Ring Imaging Detector (RICH) which surrounds the interaction region of DELPHI at the LEP e+e− storage ring. The Barrel part of the RICH detector, which covers the 40°–140° polar angle, is fully operational since October 1991.The RICH detector measures the emission angle of Cherenkov light photons emitted by charged particles crossing first a 1 cm×22 m2 liquid radiator (C6F14) and next a 40 cm×32 m2 gas radiator (C5F12). The light is detected by a 5 cm×27 m2 photon converter which acts as a Time Projection Chamber. The conversion volume is filled with ethane‐methane mixture, with the addition of a small amount of vapor of a photosensitive substance (TMAE) that acts as the photon converter. It identifies charged particles with a momenta between 0.7 and 20 GeV.The analysis of the performance of the RICH is given using the Z0 events collected since October 1991. This performance is close to the values of the original design.

The LHCb experiment is designed for precision measurements of CP violation and rare decays of beauty and charm hadrons. A key component enabling these studies is the Ring Imaging Cherenkov (RICH) system, which provides robust particle identification (PID) over a wide momentum range. With the start of Run 3 and the transition to a software-based trigger at 40 MHz, the RICH detectors have undergone a major upgrade to meet the new data-taking and performance demands. This contribution presents the design, implementation, and commissioning of the upgraded RICH system. Key features include the replacement of the Hybrid Photon Detectors with new multi-anode photomultiplier tubes (MaPMT), the development of custom readout electronics capable of handling the increased data rate, and the re-optimization of the optical layout to maintain PID performance despite a reduced material budget. Performance metrics such as PID efficiency and stability under high occupancy conditions will be presented, demonstrating that the upgraded RICH system is fully equipped to support the LHCb physics program throughout Run 3.

The CLAS12 Ring Imaging Cherenkov detector

In this paper two different approaches to provide information from events by high energy physics experiments are shown. Usually the representations produced in such experiments are spot-composed and the classical algorithms to be needed for data analysis are time consuming. For this reason the possibility to speed up pattern recognition tasks by soft computing approach with parallel algorithms has been investigated. The first scheme shown in the following is a two-layer neural network with forward connections, the second one consists of an evolutionary algorithm with elitistic strategy and mutation and cross-over adaptive probability. Test results of these approaches have been carried out analysing a set of images produced by an optical ring imaging Cherenkov (RICH) detector at CERN.

Aerogel and its applications to RICH detectors

Micro-Pattern Gas Detectors (MPGDs) have become an important component in high-energy physics experiments due to their good spatial and time resolution. This paper presents the design and testing of a 512-channel front-end electronics (FEE) prototype based on a 32-channel custom application-specific integrated circuit (ASIC) to read the Ring Imaging Cherenkov (RICH) detector. The test results show a gain non-uniformity of below 5% and a charge resolution of better than 0.24 fC, meeting the design requirements. The time resolution is around 1 ns root mean square (RMS). The readout electronics have also been validated with the prototype RICH detector, in the Super Tau-Charm Facility (STCF), and clear hit images can be measured with the ^55Fe radiation source.

The LHCb experiment has been successfully taking data at the Large Hadron Collider (LHC) at CERN since the end of 2009. One of its key detector components is the Ring-Imaging Cherenkov (RICH) system. It provides charged particle identification over a wide momentum range, from 2 to 100 GeV/c. It consists of two RICH detectors that cover between them the full angular acceptance of the experiment, 15–300 mrad with respect to the beam axis. The LHCb RICH system has been performing extremely well and is providing the LHCb experiment with a robust, reliable and precise particle identification system for all hadronic processes. Particle identification performance is presented, as measured using data from the LHC. A few important physics channels, where PID is critical for the correct evaluation of high energy processes will be shown. At present, LHCb is preparing for three years of intense data taking, before entering a proposed upgrade, which should push it further in the possible realm of new physics and should improve statistical relevance of flavour physics quantities. The main option for the RICH system upgrade will be described.

directly (forward tracks) or after two mirror reflections (large angle tracks). Extensive tests have been performed on Hamamatsu H8500 and novel flat multi-anode photomultipliers under development and on various types of silicon photomultipliers. A large scale prototype based on 28 H8500 MA-PMTs has been realized and tested with few GeV/c hadron beams at the T9 test-beam facility of CERN. In addition a small prototype was used to study the response of customized SiPM matrices within a temperature interval ranging from 25 down to –25 °C. The preliminary results of the individual photon detector tests and of the prototype performance at the test-beams are here reported.

The characterization of the single photon response of the Hamamatsu R7600 multi-anode photomultiplier tube (MaPMT) is presented, in view of a possible application in Ring Imaging Cherenkov (RICH) detectors and high rate single photon counting applications in general. For most of the measurements the main source of single photons was a commercial blue LED biased with a small current of a few nA. The spectra obtained with this source match those obtained with Cherenkov light from a PbF2 crystal illuminated with a 22Na gamma source, confirming that the test signals are single photons. Dark current and cross-talk were measured at the single photoelectron level. The single photon response of the PMT was also studied as a function of the bias ratio between dynodes. The sensitivity to magnetic field up to 30 G and the effectiveness of three magnetic shields with different geometries were evaluated. Gain loss due to aging was also studied up to 2000 hours of operation at high counting rate.

Ring imaging Cherenkov detector

The High Acceptance Di-Electron Spectrometer (HADES) at the GSI Helmholtzzentrum für Schwerionenforschung investigates dilepton and strangeness production in elementary and heavy-ion collisions. In April - May 2012 HADES recorded 7 billion Au+Au events at a beam energy of 1.23 GeV/u with the highest multiplicities measured so far. The track reconstruction and particle identification in the high track density environment are challenging. The most important detector component for lepton identification is the Ring Imaging Cherenkov detector. Its main purpose is the separation of electrons and positrons from large background of charged hadrons produced in heavy-ion collisions. In order to improve lepton identification this backtracking algorithm was developed. In this contribution we will show the results of the algorithm compared to the currently applied method for e+/-identification. Efficiency and purity of a reconstructed e+/- sample will be discussed as well.