6,152 research outputs found
The Higgs mechanism for undergraduate students
The Higgs mechanism gives mass to particles as a result of the interaction between massless particles and a scalar
field. In this version it is reformulated in a purely classical form, using a simple formalism suitable for undergraduate
students. The need for the Higgs field is justified with arguments following from a review of the concept of energy
and from special relativity.
While most of the popularisations of the Higgs mechanism relies on analogies with friction, the proposed explanation
appears to be at the same time formally coherent and simple enough to be proposed to undergraduate students,
the prerequisites being just the knowledge of the energy density of electric and magnetic fields
Avalanche photodiodes for the CMS electromagnetic calorimeter
Avalanche Photodiodes (APDs) will be used as photodetectors for the CMS crystal barrel calorimeter, made of lead tungstate (PWO) scintillating crystals. After two years of strong R&D effort a significant progress was achieved, in collaboration with manufacturers, in the relevant properties of the device for LHC applications. Quantum efficiency, noise contributions and radiation resistance measurements of APDs are presented
Performance of the PADME calorimeter prototype at the DANE BTF
The PADME experiment at the DANE Beam-Test Facility (BTF) aims at
searching for invisible decays of the dark photon by measuring the final state
missing mass in the process , with undetected. The
measurement requires the determination of the 4-momentum of the recoil photon,
performed using a homogeneous, highly segmented BGO crystals calorimeter. We
report the results of the test of a 55 crystals prototype performed
with an electron beam at the BTF in July 2016
From Design to Production Control Through the Integration of Engineering Data Management and Workflow Management Systems
At a time when many companies are under pressure to reduce "times-to-market"
the management of product information from the early stages of design through
assembly to manufacture and production has become increasingly important.
Similarly in the construction of high energy physics devices the collection of
(often evolving) engineering data is central to the subsequent physics
analysis. Traditionally in industry design engineers have employed Engineering
Data Management Systems (also called Product Data Management Systems) to
coordinate and control access to documented versions of product designs.
However, these systems provide control only at the collaborative design level
and are seldom used beyond design. Workflow management systems, on the other
hand, are employed in industry to coordinate and support the more complex and
repeatable work processes of the production environment. Commercial workflow
products cannot support the highly dynamic activities found both in the design
stages of product development and in rapidly evolving workflow definitions. The
integration of Product Data Management with Workflow Management can provide
support for product development from initial CAD/CAM collaborative design
through to the support and optimisation of production workflow activities. This
paper investigates this integration and proposes a philosophy for the support
of product data throughout the full development and production lifecycle and
demonstrates its usefulness in the construction of CMS detectors.Comment: 18 pages, 13 figure
Characterization and Performance of PADME's Cherenkov-Based Small-Angle Calorimeter
The PADME experiment, at the Laboratori Nazionali di Frascati (LNF), in
Italy, will search for invisible decays of the hypothetical dark photon via the
process , where the escapes detection. The
dark photon mass range sensitivity in a first phase will be 1 to 24 MeV. We
report here on measurement and simulation studies of the performance of the
Small-Angle Calorimeter, a component of PADME's detector dedicated to rejecting
2- and 3-gamma backgrounds. The crucial requirement is a timing resolution of
less than 200 ps, which is satisfied by the choice of PbF crystals and the
newly released Hamamatsu R13478UV photomultiplier tubes (PMTs). We find a
timing resolution of 81 ps (with double-peak separation resolution of 1.8 ns)
and a single-crystal energy resolution of 5.7%/ with light yield of
2.07 photo-electrons per MeV, using 100 to 400 MeV electrons at the Beam Test
Facility of LNF. We also propose the investigation of a two-PMT solution
coupled to a single PbF crystal for higher-energy applications, which has
potentially attractive features.Comment: 12 pages, 19 figures. v2: added section on radiation damage studie
Response of microchannel plates in ionization mode to single particles and electromagnetic showers
Hundreds of concurrent collisions per bunch crossing are expected at future
hadron colliders. Precision timing calorimetry has been advocated as a way to
mitigate the pileup effects and, thanks to their excellent time resolution,
microchannel plates (MCPs) are good candidate detectors for this goal. We
report on the response of MCPs, used as secondary emission detectors, to single
relativistic particles and to electromagnetic showers. Several prototypes, with
different geometries and characteristics, were exposed to particle beams at the
INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency
are measured for single particles and as a function of the multiplicity of
particles. Efficiencies between 50% and 90% to single relativistic particles
are reached, and up to 100% in presence of a large number of particles. Time
resolutions between 20ps and 30ps are obtained.Comment: 20 pages, 9 figures. Paper submitted to NIM
Performance of a Tungsten-Cerium Fluoride Sampling Calorimeter in High-Energy Electron Beam Tests
A prototype for a sampling calorimeter made out of cerium fluoride crystals
interleaved with tungsten plates, and read out by wavelength-shifting fibres,
has been exposed to beams of electrons with energies between 20 and 150 GeV,
produced by the CERN Super Proton Synchrotron accelerator complex. The
performance of the prototype is presented and compared to that of a Geant4
simulation of the apparatus. Particular emphasis is given to the response
uniformity across the channel front face, and to the prototype's energy
resolution.Comment: 6 pages, 6 figures, Submitted to NIM
Response of microchannel plates to single particles and to electromagnetic showers
We report on the response of microchannel plates (MCPs) to single
relativistic particles and to electromagnetic showers. Particle detection by
means of secondary emission of electrons at the MCP surface has long been
proposed and is used extensively in ion time-of-flight mass spectrometers. What
has not been investigated in depth is their use to detect the ionizing
component of showers. The time resolution of MCPs exceeds anything that has
been previously used in calorimeters and, if exploited effectively, could aid
in the event reconstruction at high luminosity colliders. Several prototypes of
photodetectors with the amplification stage based on MCPs were exposed to
cosmic rays and to 491 MeV electrons at the INFN-LNF Beam-Test Facility. The
time resolution and the efficiency of the MCPs are measured as a function of
the particle multiplicity, and the results used to model the response to
high-energy showers.Comment: Paper submitted to NIM
Detector Construction Management and Quality Control: Establishing and Using a CRISTAL System
The CRISTAL (Cooperating Repositories and an Information System for Tracking
Assembly Lifecycles) project is delivering a software system to facilitate the
management of the engineering data collected at each stage of production of
CMS. CRISTAL captures all the physical characteristics of CMS components as
each sub-detector is tested and assembled. These data are retained for later
use in areas such as detector slow control, calibration and maintenance.
CRISTAL must, therefore, support different views onto its data dependent on the
role of the user. These data viewpoints are investigated in this paper. In the
recent past two CMS Notes have been written about CRISTAL. The first note, CMS
1996/003, detailed the requirements for CRISTAL, its relationship to other CMS
software, its objectives and reviewed the technology on which it would be
based. CMS 1997/104 explained some important design concepts on which CRISTAL
is and showed how CRISTAL integrated the domains of product data man- agement
and workflow management. This note explains, through the use of diagrams, how
CRISTAL can be established for detector production and used as the information
source for analyses, such as calibration and slow controls, carried out by
physicists. The reader should consult the earlier CMS Notes and conference
papers for technical detail on CRISTAL - this note concentrates on issues
surrounding the practical use of the CRISTAL software.Comment: 16 pages, 14 figure
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