[Show abstract][Hide abstract] ABSTRACT: The Higgs boson was postulated nearly five decades ago within the framework of the standard model of particle physics and
has been the subject of numerous searches at accelerators around the world. Its discovery would verify the existence of a
complex scalar field thought to give mass to three of the carriers of the electroweak force—the W+, W–, and Z0 bosons—as well as to the fundamental quarks and leptons. The CMS Collaboration has observed, with a statistical significance
of five standard deviations, a new particle produced in proton-proton collisions at the Large Hadron Collider at CERN. The
evidence is strongest in the diphoton and four-lepton (electrons and/or muons) final states, which provide the best mass resolution
in the CMS detector. The probability of the observed signal being due to a random fluctuation of the background is about 1
in 3 × 106. The new particle is a boson with spin not equal to 1 and has a mass of about 1.25 giga–electron volts. Although its measured
properties are, within the uncertainties of the present data, consistent with those expected of the Higgs boson, more data
are needed to elucidate the precise nature of the new particle.
[Show abstract][Hide abstract] ABSTRACT: We have been studying ways in which the light from several optical fibers that transmit light from scintillating tiles can be mixed and combined a single Silicon Photo Multiplier (SiPM). The purpose for mixing is to prevent a single high intensity fiber from saturating an area of the SiPM and thus causing an inaccurate reading of the overall light collected. In particular this is for use in detectors such as CMS HCAL1, 2 where light is transmitted from scintillating tiles in 940,.m fibers to a single photo-detector. If one tile has a large optical signal it can saturate an area of the SiPM and produce a signal lower than would be expected, resulting in an in-accurate energy measurement. The results of the test and the test setup will be described.
Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2012 IEEE; 01/2012
[Show abstract][Hide abstract] ABSTRACT: Scintillating, waveshifting, and waveguide fibers are used as particle detectors and light detection and transport elements in particle physics experiments. A study of light emission from such structures is being carried out for the Compact Muon Solenoid (CMS) experiment at CERN. For CMS, the fibers used are polystyrene core with a double-cladding and a diameter of 940 microns and lengths of up to several meters. Currently, the light produced and transported by such structures is detected by a conventional photo-detectors called hybrid photodiodes (HPD). The experiment is planning to replace the HPDs with a new photo-detectors known as a Silicon Photomultipliers (SiPM) with the possibility of each fiber having its own SiPM element for readout. Due to the thermal and electrical characteristics of SiPMs, and specifically their high thermal noise rate, it is best to keep the cross sectional area of the SiPM as small as possible. When light exits a fiber there is a distribution of the photons at various angles caused by: the differences in index of refraction of the core (n=1.59) and outer cladding (n=1.43) of the fiber; how and where in the fiber the initial light was created and the dominant transmission characteristics of the fiber/waveguide. This light distribution sets the size and placement of the SiPM devices. To study this, experimental measurements are being carried out using waveshifting and clear optical waveguide fibers that are used in CMS. Light is produced within such fiber core by exciting them through their cladding using UV light emitting diodes (LEDs). The LED light penetrates into the fiber and is waveshifted. On one end (called the readout end) is placed up against a fiber-optically-coupled CCD camera. The opposite end is either mirrored (with aluminum) or unmirrored and also read out using another CCD. Initial studies of attenuation and the profile of emergent light are discussed.
[Show abstract][Hide abstract] ABSTRACT: Preliminary results are presented of a study of organic liquid-based scintillators. The objectives of the study were to identify materials that have good spectral characteristics the match state of the art solid state photosensors such as SiPM devices, high quantum efficiency, rapid fluorescence decay and good handling and safety characteristics. Potential applications for such materials are in high radiation environments in forward-calorimetry in colliding beam experiments and for active instrumentation in large volume applications, such as underground experiments.
Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE; 01/2010
[Show abstract][Hide abstract] ABSTRACT: Fully functional imaging scintillating-glass fiber detectors have been fabricated by our group and operated successfully over many years. In this paper we present our initial efforts to produce coherent fiber-optic tracking detectors based upon organic plastic scintillating fiber materials. The goal is to create devices of relatively large volume that can be used in informal education settings and that likewise permit the imaging of trajectories of ionizing particles in real time as they pass through the material. To improve the rate of particle detection, coherent plates of sizeable volume (25 mm Ã 25 mm Ã 100 mm or more) are desirable.
Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE; 01/2009
[Show abstract][Hide abstract] ABSTRACT: The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 1034 cm−2 s−1 (1027 cm−2 s−1). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4π solid angle. Forward sampling calorimeters extend the pseudorapidity coverage to high values (|η| ≤ 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.
Journal of Instrumentation 08/2008; 3(08):S08004. DOI:10.1088/1748-0221/3/08/S08004 · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have developed an orientable cosmic ray telescope based on scintillating tile and waveshifting optical fiber technology for hands-on laboratory use and for interactive public displays. The device is sensitive to ionizing radiation and is composed of four individual scintillating tiles into which are embedded double-clad optical fibers doped with waveshifter dye. These fibers are coupled to photomultiplier tubes (PMT). The telescope is mounted on an adjustable (rotatable) structure to allow the measurement of the cosmic ray rate as a function of angle relative to the zenith. This motion is controlled by the user through a computer-controlled stepper motor. The readout system allows data to be collected and uploaded to the Web enhancing the interactive experience and for follow-up analysis.
[Show abstract][Hide abstract] ABSTRACT: CMS is a general purpose experiment, designed to study the physics of pp collisions at 14 TeV at the Large Hadron Collider ( LHC). It currently involves more than 2000 physicists from more than 150 institutes and 37 countries. The LHC will provide extraordinary opportunities for particle physics based on its unprecedented collision energy and luminosity when it begins operation in 2007. The principal aim of this report is to present the strategy of CMS to explore the rich physics programme offered by the LHC. This volume demonstrates the physics capability of the CMS experiment. The prime goals of CMS are to explore physics at the TeV scale and to study the mechanism of electroweak symmetry breaking - through the discovery of the Higgs particle or otherwise. To carry out this task, CMS must be prepared to search for new particles, such as the Higgs boson or supersymmetric partners of the Standard Model particles, from the start- up of the LHC since new physics at the TeV scale may manifest itself with modest data samples of the order of a few fb(-1) or less. The analysis tools that have been developed are applied to study in great detail and with all the methodology of performing an analysis on CMS data specific benchmark processes upon which to gauge the performance of CMS. These processes cover several Higgs boson decay channels, the production and decay of new particles such as Z' and supersymmetric particles, B-s production and processes in heavy ion collisions. The simulation of these benchmark processes includes subtle effects such as possible detector miscalibration and misalignment. Besides these benchmark processes, the physics reach of CMS is studied for a large number of signatures arising in the Standard Model and also in theories beyond the Standard Model for integrated luminosities ranging from 1 fb(-1) to 30 fb(-1). The Standard Model processes include QCD, B-physics, diffraction, detailed studies of the top quark properties, and electroweak physics topics such as the W and Z(0) boson properties. The production and decay of the Higgs particle is studied for many observable decays, and the precision with which the Higgs boson properties can be derived is determined. About ten different supersymmetry benchmark points are analysed using full simulation. The CMS discovery reach is evaluated in the SUSY parameter space covering a large variety of decay signatures. Furthermore, the discovery reach for a plethora of alternative models for new physics is explored, notably extra dimensions, new vector boson high mass states, little Higgs models, technicolour and others. Methods to discriminate between models have been investigated. This report is organized as follows. Chapter 1, the Introduction, describes the context of this document. Chapters 2-6 describe examples of full analyses, with photons, electrons, muons, jets, missing E-T, B-mesons and tau's, and for quarkonia in heavy ion collisions. Chapters 7-15 describe the physics reach for Standard Model processes, Higgs discovery and searches for new physics beyond the Standard Model.
Journal of Physics G Nuclear and Particle Physics 01/2007; 34:995. · 2.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The DO 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 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO. (c) 2006 Elsevier B.V. All rights reserved.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 09/2006; 565(2):463-537. DOI:10.1016/j.nima.2006.05.248 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Studies are presented of new blue-green to red emitting scintillator and waveshifter materials for tracking and calorimetry applications for the detection of ionizing radiation. Materials include plastic scintillators, liquid scintillators, and plastic scintillating and waveshifting fibers. Program goals are to develop faster and more efficient detection media for a variety of experimental applications
[Show abstract][Hide abstract] ABSTRACT: The D0 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 D0.
[Show abstract][Hide abstract] ABSTRACT: New scintillators and waveshifter materials are under development for use in detecting charged particles in tracking applications and for detecting showering particles in calorimetric applications. Goals have been to identify and produce fast and efficient dye materials that fluoresce in the middle of the visible spectrum where polystyrene and polyvinyl toluene have good optical transparency, to replace existing materials currently in use in the field of particle physics. As a result of this study, several fluorescent dyes have been identified with fast and efficient emission, that fluorescence in the green (lambda ~ 490-520 nm). These are candidate materials for new scintillators and waveshifters.
[Show abstract][Hide abstract] ABSTRACT: New waveshifter and scintillator materials are under development for use in detecting charged particles in tracking applications and for detecting showering particles in calorimetric applications. Goals have been to identify and produce fast and efficient dye materials that fluoresce in the middle of the visible spectrum where polystyrene and polyvinyltoluene have good optical transparency, to replace existing materials currently in use in the field of particle physics. As a result of this study, several fluorescent dyes have been identified with fast and efficient emission, that fluorescence in the green (λ ∼ 490-520 nm), and from these a number waveshifter and scintillator materials have been fabricated.
[Show abstract][Hide abstract] ABSTRACT: The CMS Hadron Calorimeter (HCAL) will use optical decoder units (ODU) as a link between scintillating plastic tiles, arranged in megatile layers around the HCAL, and multi-channel hybrid photodiodes. Photons are produced in the scintillating tiles as sub-atomic particles pass through and deposit energy. Y-11 waveshifting fiber and cables of clear optical fiber serve as connecting transmission lines from scintillating tiles to the ODU. The ODU reorganizes light signals from layer geometry to tower geometry for particle energy measurement. The hybrid photodiode (HPD) converts the light signals to electrical signals that are amplified and digitized for the data acquisition system. This paper provides aspects of the production of optical decoder units.
[Show abstract][Hide abstract] ABSTRACT: A method is necessary to cool the electronics contained in the
readout boxes for the CMS HCAL. The electronics to pre-amplify and
digitize signals from the optical detectors will generate a large amount
of heat that must be removed from the CMS HCAL system. To accomplish
this a thermal management system has been designed that uses metallic
extrusions, liquid coolant, and thermal foam to transfer the heat from
the electronics to the exterior cooling system. Because the electronics
are difficult to access throughout the life of the experiment, the
temperature must be kept low to extend life expectancy. In order to test
the concepts before the final design is implemented a thermal test
station was built. Several methods to are under study to determine the
best method of making the thermal routing from source of the heat to the
liquid for heat removal. The test bed for this evaluation and methods to
monitor the electronics temperature in situ are discussed
[Show abstract][Hide abstract] ABSTRACT: The CMS experiment is a complex instrument to study particle
physics at the energy frontier. An important detector subsystem within
CMS is the hadron calorimeter or HCAL, consisting of four subsystems
that cover the kinematic region |η|<5. This paper provides
details of the electro-optical interfaces for the central barrel
subsystem that operates in a region of high magnetic field and converts
scintillation signals from megatile sampling layers to lower geometry
for energy measurement
[Show abstract][Hide abstract] ABSTRACT: We have developed a hand-held, particle tracking detector based on
scintillating-glass, fiber-optic plate technology for applications in
classroom teaching. The active element is sensitive to ionizing
radiation and is a coherent fiber-optic plate consisting of 10<sup>6
</sup> individual clad fiber waveguides that contain Terbium (3+) oxide
in a silicate glass host. Scintillation light in the individual fiber
elements is transferred via total internal reflection to a multi-stage
image intensifier that senses and amplifies the light signal while
maintaining the spatial coherence of the input optical image. The output
screen of the image intensifier can be viewed directly by eye under
low-level room light conditions or via video imaging with a CCD camera.
The system is ideal for hands-on laboratory use and for public lecture
[Show abstract][Hide abstract] ABSTRACT: Experimental applications requiring fast timing and/or high
efficiency position and energy measurements typically use scintillation
materials. Scintillators utilized for triggering, tracking, and
calorimetry in colliding beam detectors are vulnerable to the high
radiation fields associated with such experiments. We have begun an
investigation of several fluorescent dyes which might lead to fast,
efficient, and radiation resistant scintillators. Preliminary results of
spectral analysis and efficiency are presented