the experiment, learning the relevant techniques, setting up and troubleshooting principal types of detectors used in nuclear and particle physics experiments. Techniques for Nuclear and Particle Physics Experiments Digitally watermarked, DRM-free; Included format: PDF; ebooks can be used on all reading devices. The first € price and the £ and $ price are net prices, subject to local VAT. Prices indicated with * include VAT for books; the €(D) includes 7% for. Germany, the.
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Techniques for Nuclear and Particle. Physics Experiments. A How-to Approach. Second Revised Edition. With Figures, 40 Tables and Numerous Worked. Techniques for nuclear and particle physics experiments. 1. Particles (N^cit*j pbysics)-Techaique. 2. Particles (Nuclear physicsJ-Erpcrimcnu. 3. Nuclear physics-. I have been teaching courses on experimental techniques in nuclear and particle physics to master students in physics and in engineering for many years.
This division of efforts in particle physics is reflected in the names of categories on the arXiv , a preprint archive:  hep-th theory , hep-ph phenomenology , hep-ex experiments , hep-lat lattice gauge theory.
Practical applications[ edit ] In principle, all physics and practical applications developed therefrom can be derived from the study of fundamental particles. In practice, even if "particle physics" is taken to mean only "high-energy atom smashers", many technologies have been developed during these pioneering investigations that later find wide uses in society.
Particle accelerators are used to produce medical isotopes for research and treatment for example, isotopes used in PET imaging , or used directly in external beam radiotherapy. The development of superconductors has been pushed forward by their use in particle physics. Additional applications are found in medicine, national security, industry, computing, science, and workforce development, illustrating a long and growing list of beneficial practical applications with contributions from particle physics.
There are several powerful experimental reasons to expect new physics, including dark matter and neutrino mass.
There are also theoretical hints that this new physics should be found at accessible energy scales. Much of the effort to find this new physics are focused on new collider experiments. The Large Hadron Collider LHC was completed in to help continue the search for the Higgs boson , supersymmetric particles , and other new physics.
An intermediate goal is the construction of the International Linear Collider ILC , which will complement the LHC by allowing more precise measurements of the properties of newly found particles. In August , a decision for the technology of the ILC was taken but the site has still to be agreed upon.
In addition, there are important non-collider experiments that also attempt to find and understand physics beyond the Standard Model. One important non-collider effort is the determination of the neutrino masses, since these masses may arise from neutrinos mixing with very heavy particles. In addition, cosmological observations provide many useful constraints on the dark matter, although it may be impossible to determine the exact nature of the dark matter without the colliders.
Finally, lower bounds on the very long lifetime of the proton put constraints on Grand Unified Theories at energy scales much higher than collider experiments will be able to probe any time soon. In May , the Particle Physics Project Prioritization Panel released its report on particle physics funding priorities for the United States over the next decade. This report emphasized continued U. High energy physics compared to low energy physics[ edit ] The term high energy physics requires elaboration.
Intuitively, it might seem incorrect to associate "high energy" with the physics of very small, low mass objects, like subatomic particles. The outer detector layers deliberately use large amounts of material in order to materialize the neutral particles and to.
The outer layer of the calorimeter or an additional detection layer is frequently used to detect muons. As mentioned earlier, energetic muons are usually the only particles that can reach this outermost layer.
Inevitably as the layered levels of detection systems are built up, a detector will become large and correspondingly complex and expen- sive. A prime objective of detector development is, therefore' to keep detection systems as compact as possible and to combine detection roles whenever possible. Additional demands are imposed on detector systems associated with hadron colliders by the high ambient radiation levels at the detector and by the fact that events of interest may be separated only by short times from uninteresting background events.
Summarized below are the elements or layers constituting a typical modern detector system and some of the ongoing research and development aimed at maximizing present or future detector capabili- ties. Close-in Detection: Vertex Detectors A fraction of the particles emerging from a collision point decay in flight at distances as close as 0. Therefore use can be made of charged-particle detectors with high spatial resolution that are placed as close to the interaction point as possible.
The first such vertex detector for collider work was recently con- structed to operate with the Mark It detector at the PEP collider at the Stanford Linear Accelerator Center. Several such detectors are now being constructed or are operating at electron-positron and proton- antiproton colliders.
The principles of operation of these track detectors are described below. The chambers are typically only about 10 cm in radius, are fabricated with fine subdivisions to provide separation between adjoining tracks that might otherwise overlap, are aligned with great precision about 0. The second-generation vertex detectors now under development are based on modern silicon semiconductor technology.
This technology has already been used successfully on a small scale in experiments designed to measure decays of short-lived particles.
In these experiments the target is constructed of microstrips' and a detailed history of events occurring within these active targets can be recorded. Prelirrunary tests have been made and have established the feasibility of the proposed vertex detectors. Full-scale detectors should come into operation during the next 5 years. Three approaches are being tried: The handling, precision alignment, and electronic readout of such miniaturized devices present fascinating but soluble problems.
With reasonable confidence this second generation of detectors should pro- vide previsions an order of magnitude better than those currently obtainable.
Charged-Particle Tracking Chambers In a typical collider detector, beyond the vertex detector are charged-particle tracking chambers. These chambers serve to measure the directions and curvatures of the paths of the individual particles.
These paths are called tracks. The principle of operation of a multiwire drift chamber is shown in Figure 6.
The first such devices were coarse and measured only a few tracks. Modern devices are fine "rained in subdivision and may provide over a hundred measured points to a track.
The resulting image is almost of photographic quality and is reminiscent, even though produced at electronic speeds, of the superb track detection provided in bubble chambers. With some additional effort and with certain possible compromises these detectors can also be used to measure the ionization of the produced tracks. An elegant variant of this detection method is to remove the fine grid of wires and to drift the ionization with a collection electric field to the end caps, where the arrival positions of the ionization are measured and also the arrival times and the degree of ionization.
The arrival. In a drift chamber, slender wires are strung parallel to each other in a volume of gas. When a charged particle passes through the gas it leaves a track of ionized gas molecules and electrons.
Electrons are attracted by the electrical voltage on the wires, and when they reach the wire they send an electrical pulse down the wire.
Those pulses are collected and amplified electronically and recorded on magnetic tape. The position of the track is given roughly by knowing the wire that gave the signal. But a more accurate position is obtained knowing the time the electrons took to drift to the wire, hence the name drift chamber. This system. Charged-particle tracking detectors are often immersed in a magnetic field in order to make it possible, from measurements of the track curvatures, to determine the signs of the charges and the momenta of the particles.
Magnetic fields in the range of several kilogauss to several tens of kilogauss are used. The larger the field, the more the tracks curve, and the easier it is to measure the track momentum. To provide the highest possible magnetic fields, it is desirable to use superconducting coils to carry the required large currents.
Although a number of these coils have been constructed and successfully oper- ated, the technology of fabrication is demanding, and further research is desirable. Next in sequence beyond the tracking chamber there may be a detector layer that is used to identify the nature of the charged particles whether they are electrons protons, pions, kaons, or muons.
This region is still required to be nondestructive and thus to contain little material. A number of identification methods have been tested on small-scale devices and are under development for the next generation of detectors.
These include the following: This technique makes use of the property that particles produce light at an angle that depends on the velocity with which they are traveling through trans- parent matter.
This radiation can be focused to a ring image whose radius directly measures the particle velocity. Counters photoconvert this ultraviolet radiation into ionization, which is then detected with proportional-counting techniques.
This technique has been demon- strated successfully on a moderate scale but still requires considerable development to make it viable for large-scale detection. Calorimetric Detection and Energy Measurement The detection systems described so far do not serve to detect neutral particles, such as photons and neutrons, nor would they permit a precise measurement of the total energy in an event.
The final layers of a collider detector therefore comprise thick, highly instrumented blocks of material calorimeters in which electromagnetic and hadronic particles cascade and convert their energy into ionization. These final instrumented blocks are placed at large radii, away from the point at which the beams interact, to leave sufficient space in which to insert the nondestructive low-density systems. The large radii of these blocks, coupled with the requirement of substantial thicknesses, result in calorimeters that are massive objects.
Maximum precision is obtained when the calorimeters are constructed of materials, such as sodium iodide, in which the total. However, such active calorimeters for collider detectors would with present technology, be prohibitively expensive.
It is still very desirable to construct at least the electromag- netic calorimeter out of active material.
Some of the materials under development, or in use, for electromagnetic calorimetry are heavy glasses, bismuth germanate crystals, and barium fluoride crystals. These systems are still costly, and their use at present is only made possible by leaving less space for the low-density systems in order to minimize the material requirements.
Further developments in the production of comparatively low-cost materials for use in electromag- netic calorimeters would be useful. Even with substantial advances, however, most electromagnetic calorimeters and all hadronic calorimeters are likely to continue to rely on the introduction of many active sampling layers interspersed throughout the large passive calorimeter block in order to measure the ionization produced. Another design goal that is important but hard to realize is a finely divided calorimeter that is able to provide precise locations of the deposited energy.
This requirement follows from the fact that the particles emitted from events in high-energy colliders are tightly bunched into jets. This fine division or segmentation typically may require the recording of information from many hundreds or thousands of electronic channels reading out the information from the individual cells.
Since we cannot do justice here to the range and variety of these detectors, we will only give several examples. The examples can be brief because the components of these detectors are in general just the same elements that we have been describing. The major exception is the bubble chamber, which is discussed at the end of this section. Small or Simple Fixed-Target Experiments Fixed-target experiments can sometimes be carried out with small or simple particle-detection equipment.
This is often the case when the physicist is studying a simple reaction of elementary particles or studying one particular property of a particle.
Two examples are given. The neutral pion decays to two photons a, and A,. The apparatus is relatively small and primarily uses two electromagnetic calorimeters. Figure 6. The detector is of moderately large size but simple construction; its function is to detect neutrinos and to distinguish between muon neutrinos and electron neutrinos. It is intended primarily for studying the production of charmed particles. A photon beam produced by the primary proton beam strikes a liquid hydrogen target.
Recoiling protons are identified by the recoil detector. The spectrometer has magnetic analysis to measure charged-particle momenta; Cerenkov counters to identify pions.
This sequence of analysis steps is the same as that used in most collider detectors, but the target is not surrounded by all the components of the detector as it is in a collider detector. A nuclear emulsion is a thick photographic emulsion that when developed shows the paths of charged particles that have passed through it. This detector was used at Fermilab to measure the lifetimes of charmed mesons.
The emulsion gave precise pictures of how the mesons decayed close to their production point. Bubble Chamber The bubble chamber, invented in the s, was for many years the workhorse of elementary-particle physics experiments.
A bubble chamber uses a superheated liquid, such as liquid hydrogen, neon, or Freon. Charged particles passing through this liquid leave tracks of tiny bubbles, which are photographed. The bubble chamber has gradually been replaced in most experimental applications by electronic detec- tors. The latter are more versatile, often give more information about the products of the collision, and usually provide that information in a form that can be directly used in computers.
Nevertheless, the large volume and precise track information provided by bubble chambers. Used to measure the lifetime of charmed particles, the emulsions give a precise location for where the charmed particle decayed. Chief among these are the study of neutrino interactions and the study of particles with short lifetimes.
Recent improvements in bubble-chamber technology include high repetition rates, precise track measurements, and holographic photography. In recent years, apart from the sheer increase in scale of these experiments, data reduction has evolved to become more integrated with and intrinsic to an experiment's operation.
A particular example is Monte Carlo computer simulation, which has become an important means of experimental calibration.
New detector capabilities have made this evolution both possible and necessary. Very precise time resolution billionths of a second. In turn, these fast detectors can supply information in a form that can be. Advanced systems for the reduction of high-energy data have unified the traditionally separate functions of trigger decision making, data logging. The trigger is critical to the success of many experiments because collisions may occur at a rate exceeding per second.
In order to select those interactions that are of particular interest in an experiment. The trigger is a fast electronic decision made to record the data from a particular event on the basis of the signals received from the detector. The triggering decision itself may be based on detector input that no single computer could process fast enough. Fortunately, the repetitive nature of these calculations can be adapted to the use of fast but relatively primitive processors working in parallel.
These are the first steps in what traditionally would have been termed off-line analysis. Without the results of these and other computations' the operation of advanced detectors cannot be monitored or controlled. Even the logging of data onto tape may use many levels of the data-acquisition system. One experiment in one year can accumulate data amounting to 10 million such reports. Because of the enormous software devel- opment required programs for real-time and off-line event analysis increasingly must share common subroutines and other features.
The distinction between real-time and off-line analysis is further blurred by the scale of processing power that must be dedicated -to a single experiment, in notable cases reaching a level comparable with that of a mayor computer. The trend toward large-solid-angle general-purpose detectors at the colliding-beam facilities has been noted. As the collider energy rises, the events become more complex, and the amount of computer time required to analyze these events becomes large.
For example, a Z" decay into hadrons has an average of about 20 charged particles and " neutral particles, and the off-line analysis time for such events in the detectors proposed for the SLC or LEP is of the order of seconds of central processor unit CPU time for moderate-size computers. Millions of such events per year may need to be processed. As another example, it has been estimated that a dedicated capacity equivalent to tens of moderate-size computers will be required to process the inter- esting events from the 2-TeV proton-antiproton collider at Fermilab.
These requests for computer power are marginally met by current commercially available computers. The supercomputers tend to be machines optimized for vector or array calculations typically encoun- tered in solving large sets of partial differential equations, such as in weather prediction. These machines are not well suited to the large input-output 10 requirements of higb-energy physics nor to the large address-space requirements of the detector analysis codes.
Some manufacturers have addressed the 10 problems and have reasonable CPU power but are relatively weak in modern software tools and in the system architecture to support them.
These are important issues in high-energy physics, where the data production codes are being constantly improved. Tools that improve the efficiency of the physicist are clearly valuable. Finally, the manufacturers of superminicomputers who have advanced the soft- ware state of the art do not produce machines of sufficient CPU power to analyze the data from a modern collider detector.
The present situation is sufficiently serious to motivate noncommer- cial attempts to provide adequate computing power.
Most of these attempts are based on the relatively large fraction of CPU to 10 activity that characterizes detector event analysis, so that many relatively simple. Related projects involve even more specialized processors designed for lattice gauge theory calculations or accelerator ray tracing. It is, of course, possible that commercial developments will prove adequate in the next few generations of machines, but the present situation is murky. Computing represents a significant expense at the national laboratories and universities in terms of actual hardware, support personnel, and physicist involvement.
Even with the rapid decline in the unit costs of computing crudely a reduction by a factor of 2 every 3 years ' the overall costs of computing increase. Thus computers of both large and medium size are now necessary parts of almost all elementary-particle physics experiments.
Not only are they needed to reduce and study the data, but they are also used to monitor and control the experimental apparatus.
The extensive use of computers has stimulated advances in some types of computer tech-. This is because physicists have been willing to work with computers that were still in an early stage of production, interacting closely with the computer manufacturers. In this section we sketch some of the ways in which elementary particles are studied without using accelerators.
Atomic, Optical, Electronic, and Cryogenic Experiments Elementary-particle physicists are concerned with precise measure- ments of the properties of the more stable particles, such as electrons, positrons, muons, protons, and neutrons. For example, the electric charge of the proton is the same magnitude as the electric charge of the electron according to the most precise measurements that can be made.
This is one of the reasons why we believe that there is a connection between the leptons the electron is a lepton and the quarks the proton is composed of quarks.
Such precise measurements are carried out using the methods of atomic, optical, electronic, or cryogenic physics. These include measurements of the electron g-factor, of the positronium Lamb shift, and of parity violation in atomic systems.