Preshower Detector Research Articles

Application of fuzzy-based pattern recognition techniques for cluster finding in a preshower detector in high energy heavy ion experiments

We apply the Fuzzy c-mean clustering algorithm for the data set consisting of hits in a highly granular preshower detector in the case of collision of heavy nuclei at high energy. A set of validity indexes are examined for optimum clustering performances suitable for the particular data set. The performance is also studied for different densities of hit pattern. Using information from one of the validity indexes giving good performance, FCM clustering is also studied for fixed set of parameters. The results compare well with those obtained using iterative optimization.

Time alignment and calibration of the LHCb calorimeter

The calorimeter system of the LHCb experiment consists of a scintillator layer (SPD), a preshower detector (PS), an electromagnetic calorimeter (ECAL) and a hadronic calorimeter (HCAL), and allows to trigger on hadron, electron and photon candidates. The time synchronization of the four sub-detectors studied with cosmic rays, LHC beam injection tests and LHC proton proton collisions is presented. Energy calibration methods for each subsystem are discussed as well.

The CMS Preshower construction and commissioning

The main physics goal of the CMS Preshower detector is to provide good γ – π 0 separation in the endcap regions. The Preshower detector, comprising nearly 4300 silicon strip sensors, was assembled and commissioned in 2008 before being installed in CMS in Spring 2009. The detector check-out shows 99.9% of channels operational with good noise performance.

Performance of CMS ECAL Preshower in 2007 test beam

The Preshower detector is part of the CMS Electromagnetic Calorimeter, located in the endcap regions, in front of the lead tungstate crystals. It consists of two orthogonal planes of silicon strip sensors interleaved with two planes of lead absorbers. A combined beam test of close-to-final prototypes of the Hadron calorimeter, the crystal calorimeter and the Preshower detector was performed in the summer of 2007. Calibrations were made using electron and pion data. Good signal/noise performance was obtained in both gains of measurements

The electromagnetic calorimeter of cms, summary and status

The construction of the lead tungstate crystal calorimeter for the CMS experiment at the Large Hadron Collider (LHC) is close to completion. The barrel part of the calorimeter composed of 61200 crystals is installed and operated inside CMS. Only 102 readout channels are problematic including the 21 entirely dead, corresponding to 0.17 % and 0.034 %, respectively. All 14648 end-cap crystals are mounted. The electronics installation and commissioning of one end-cap has finished and the second will be finished in few weeks. The construction of the pre-shower detectors installed in front of the end-caps is well advanced.The many challenges of the design and construction imposed by a 4 Tesla magnetic field, radiation levels ranging from 100 krad up to several Mrad and a bunch crossing rate of 40 MHz were mastered by a huge effort in developing and testing appropriate crystals, photo-detectors and readout electronics carried out over the past ∼ 15 years.Test beam results demonstrate that the energy resolution obtained is better than 0.5 % at high energies. All readout channels in the barrel are inter-calibrated to better than 2% using cosmic muons.

Preshower detector for π +π − hadronic atom studies

A preshower (PSh) detector has been prepared, tested and used at the CERN-DIRAC experiment [B. Adeva, et al., DIRAC proposal, CERN/SPSLC 95-1, SPSLC/P 284, 1995]. The aim of this experiment was to test some nonperturbative QCD predictions [J. Gasser, H. Leutwyler, Phys. Lett. B 125 (1983) 325; J. Gasser, H. Leutwyler, Ann. Phys. 158 (1984) 142; J. Gasser, H. Leutwyler, Nucl. Phys. B 250 (1985) 465; J. Bijnens, G. Colangelo, G. Ecker, J. Gasser, M.E. Sainio, Phys. Lett. B 374 (1996) 210] by measuring pionium (π +π − hadronic atom) lifetime. In this context the PSh detector, together with the Cherenkov detector, pursued to reject the background electron pairs in the region 1–4 GeV where the pion pairs from atom breakup were present. The technique used for pion/electron separation was to probe the electron shower development in the early formation stage in Pb converter. We have studied the dependence of the amplitude spectra on particle momentum and converter and scintillator thickness. The estimated electron rejection efficiency was better than 85% with a pion loss less than 5% for a preshower detector with Pb converter thickness w Pb =2.5 cm and scintillator slab w Sc =1 cm. The PSh track efficiency within the DIRAC setup has been measured with a global efficiency per arm better than 99%, slab efficiency per arm better than 96% and corresponding pair events efficiency per arm ∼99% and per slab ∼93%.

Status of the D0 fiber tracker and preshower detectors

In this report we focus on the performance of the D0 central fiber tracker and preshower detectors during the high luminosity p p ¯ collisions at s = 1.96 GeV delivered by the Tevatron collider at Fermilab (Run IIb). Both fiber tracker and preshower detectors utilize a similar readout system based on high quantum efficiency solid state photo-detectors capable of converting light into electrical signals. We also give a brief description of the D0 detector and the central track trigger, and conclude with a summary on the central tracker performance.

Silicon detector technology development in India for the participation in international experiments

A specific research and development program has been carried out by BARC in India to develop the technology for large area silicon strip detectors for application in nuclear and high energy physics experiments. These strip detectors will be used as pre-shower detector in the CMS experiment at LHC, CERN for π0/λ rejection. The fabrication technology to produce silicon strip detectors with very good uniformity over a large area of ∼40 cm2, low leakage currents of the order of 10 nA/cm2 per strip and high breakdown voltage of >500 V has been developed by BARC. The production of detectors is already under way to deliver 1000 detector modules for the CMS and 90% production is completed. In this paper, research and development work carried out to develop the detector fabrication technology is briefly described. The performance of the silicon strip detectors produced in India is presented. The present status of the detector technology is discussed.

Tester Board for testing mass-produced SMB modules for CMS Preshower

We have developed a Tester Board to test the electrical characteristics of theSystem Motherboard (SMB) for the CMS Preshower detector at CERN. The board is designedto test input resistances, output resistances, connections, interconnections and possible short-circuits of a module having up to 640 connector pins. The Tester Board is general-purpose innature: it could be used to test any electronic module or cable by using dedicated cable sets. Themodule can detect a variety of problems not detected by either functional tests or the "flyingprobes" technique. The design, algorithms and results of using the Tester Board during massproduction of CMS Preshower SMBs are presented.

CMS Preshower in situ absolute calibration with physics events

This paper describes the in situ absolute calibration of the Preshower (ES) detector of CMS. Energy deposited in the lead of the Preshower is measured by silicon sensors, allowing a re-scaling of the energy measured by the endcap crystals. Measurement of the energy deposited in the lead absorbers to 5% accuracy is required over a very large dynamic range (1–400 MIPs equivalent); a maximum accuracy of 1% on the measurement of the charge deposited in the silicon will be sufficient. Radiation damage to the sensors (decrease in charge collection efficiency by up to 17% over 10 years) and the electronics (decrease in gain by up to 2% over 10 years) will need to be assessed by periodic in situ calibrations. A precise in situ absolute calibration using particle signals from physics events is examined. It is shown that sufficient calibration accuracy can be obtained by using muon or pion events, and that the time required for the calibration is of the order of a few days at initial LHC luminosity and at least a factor of two less for nominal LHC luminosity.

The Electromagnetic Calorimeter of CMS

The electromagnetic calorimeter of CMS at the Large Hadron Collider (LHC) has been designed to measure the energy of electrons and photons with high resolution over a wide energy range. The detector consists of 61200 PBWO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystals for the barrel and 14648 crystals for the endcaps, with a pseudo-rapidity coverage of |eta|les3.0. Preshower detectors are located in front of each endcap. The calorimeter has a pseudo-projective geometry. Great care has been taken in its design to minimize the effects of gaps and cracks in order to ensure the required energy resolution. The detector will operate in a magnetic field of 4 Tesla, and with a bunch crossing rate of 40 MHz. This requires fast and radiation hard crystals, photo-detectors and read-out electronics. An overview of the design, and the status of the construction, will be presented with special consideration given to the challenging goals

The upgraded DØ detector

The DØ experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DØ.

An efficient hardware design for rejecting common mode in a group of adjacent channels of silicon microstrip sensors used in high energy physics experiments

Algorithms have been studied using Monte Carlo techniques and implemented in a fast Xilinx Virtex II pro field programmable gate array (FPGA), in order to calculate and remove, after pedestal subtraction, the common mode of a group of adjacent channels. The implementation of the algorithms has been optimized both for speed and minimal FPGA resources, so as to be used in multi-channel applications. The aim of this work is to define the optimum algorithm for common mode calculation to be implemented for common mode rejection in the CMS Preshower detector.

Detection of muons at 150 GeV/ c with a CMS Preshower prototype

The analysis of 150 GeV/ c muon data collected during a test of a CMS Preshower prototype is presented. The test took place in 2004 in the H4 beam at CERN. The muon signal extraction is possible after pedestal subtraction and common mode correction. The results of a Geant-4-based simulation, developed for the Preshower prototype test, are also presented. The results of the simulation are found to be in excellent agreement with the data. It is also demonstrated that by combining the results of the data analysis and simulation an absolute calibration of the CMS Preshower detector system can be performed.

A scintillator tile-fiber preshower detector for the CDF central calorimeter

The front face of the CDF central calorimeter is being equipped with a new Preshower detector, based on scintillator tiles read out by WLS fibers, in order to cope with the luminosity increase provided by the Main Injector during the Tevatron's Run II data taking. A light yield of about 40 pe/MIP at the tile exit was obtained, exceeding the design requirements.

A new scintillator tile/fiber preshower detector for the CDF central calorimeter

A detector designed to measure early particle showers has been installed in front of the central CDF calorimeter at the Tevatron. This new preshower detector is based on scintillator tiles coupled to wavelength-shifting fibers read out by multi-anode photomultipliers and has a total of 3,072 readout channels. The replacement of the old gas detector was required due to an expected increase in instantaneous luminosity of the Tevatron collider in the next few years. Calorimeter coverage, jet energy resolution, and electron and photon identification are among the expected improvements. The final detector design, together with the R$&$D studies that led to the choice of scintillator and fiber, mechanical assembly, and quality control are presented. The detector was installed in the fall 2004 Tevatron shutdown and started collecting colliding beam data by the end of the same year. First measurements indicate a light yield of 12 photoelectrons/MIP, a more than two-fold increase over the design goals.

Role of guard rings in improving the performance of silicon detectors

BARC has developed large-area silicon detectors in collaboration with BEL to be used in the pre-shower detector of the CMS experiment at CERN. The use of floating guard rings (FGR) in improving breakdown voltage and reducing leakage current of silicon detectors is well-known. In the present work, it has been demonstrated that FGRs can also be used to improve the spectroscopic response of silicon detectors. The results have been confirmed by carrying outα-particle (≈5 MeV) andγ-ray (60 keV) spectroscopies with the FGR floating or biased and the underlying physics aspect behind the change in spectra is explained. Although reduction in leakage current after biasing one of the guard rings has been reported earlier, the role of a guard ring in improving the spectroscopic response is reported for the first time. Results of TCAD simulations for silicon detectors with the guard ring under different biasing conditions have been presented. Low yield in producing large-area silicon detectors makes them very costly. However, with one of the FGRs biased even a detector having large surface leakage current can be used to give the same response as a very good detector. This makes the use of large-area silicon detectors very economical as the yield would be very high (>90%).

Development and large-scale production of ceramic PCBs for the preshower detector of the CMS experiment

Fabrication of printed circuit boards (PCBs) in high-radiation areas requires new technologies. The CMS detector in the CERN Large Hadron Collider will have portions in high-radiation environment. The preshower detector in front of the endcap electromagnetic calorimeter is such an area. During the past several years, the emphasis has been put on the research and development of individual components of the preshower detector. Several prototypes of PCBs were manufactured on ceramic substrates. The final prototype was a high-quality product with the ceramic board meeting all specifications, including the adherence of metallic pastes, the resistivity of the metallic lines and the precision of the laser cutting. The Yerevan Physics Institute in collaboration with the MARS Factory, Rubin L. Tech. JSC and Yerevan Telecommunication Research Institute made 4.500 units of the ceramics PCBs and are now being incorporated in the preshower detector. This article describes in detail the R&D for the technology of thick film printing on a ceramic substrate with different pastes and the precise cutting of ceramic plates by a laser.

The central track trigger of the DO experiment

The general purpose DO collider detector, located at Fermi National Accelerator Laboratory, is operated in the high luminosity (L=2/spl times/10/sup 32/ cm/sup -2//spl middot/s/sup -1/) and high-collision-rate environment (396 ns between beam crossings) of the upgraded Tevatron proton anti-proton accelerator. DO uses a three-tiered trigger system to select events for offline storage and analysis. This paper describes the architecture and performance of the DO central track trigger (CTT) system based on the new central fiber tracker, central preshower and forward preshower detectors, with emphasis on the interface to and integration with the second tier L2 Trigger system.

First results from the central tracking trigger of the DO experiment

An overview of the DO Central Track Trigger (CTT) for the Tevatron Run 2 program is presented. This newly commissioned system uses information from the DO Central Fiber Tracker and Preshower Detectors to generate trigger information for the first level of the three-tiered DO Trigger. The system delivers tracking detector trigger decisions every 132 ns, based on input data flowing at a rate of 475 Gbit per second. Initial results indicate excellent performance of the CTT. First studies of efficiency and trigger performance of the CTT are presented.