123595435
Particle accelerators and the fundamental constants
As an instructive exercise in elementary quantum physics, we explore the relationship between the sizes of circular particle accelerators and the fundamental constants of nature.
116914560
Physicists make the most of antimatter.
117258763
A study of nucleon isobar production in proton-proton collisions
SummaryThe momentum spectra of protons scattered inelastically in proton-proton collisions were obtained in an external beam at NIMROD, using incident-proton momenta of 2.85, 4.55, 6.06 and 7.88 GeV/c, and various scattering angles in the range 22 to 144 mrad. The isobars of mass 1236, 1518 and 1688 MeV are clearly seen. There is evidence also in the spectra at small angles for the production of the 1410 MeV isobar at a mass of (1410±15) MeV and width (125±20) MeV. It is shown that the observed peak cannot be explained by the Deck effect. The differential cross-sections for the production of these isobars are presented in terms of the usual variabless andt, and are compared with absorption and Regge-pole model predictions. Fits to the data with various empirical functions of these variables are also investigated. The behaviour of the total cross-section for the 1236 MeV isobar is found to exhibit energy-dependence consistent with one-pion exchange, whereas the 1410 MeV and 1688 MeV isobar total cross-sections are found to be energy-independent. Also the total cross-section for the 1518 MeV isobar is found to exhibit energy-dependence in this energy range.RiassuntoSi sono ottenuti gli spettri delle quantità di moto dei protoni diffusi anelasticamente nelle collisioni protone-protone ottenute in un raggio esterno di NIMROD, usando quantità di moto del protone incidente di 2.85, 4.55, 6.06 e 7.88 GeV/c, e vari angoli di scattering da 22 a 144 mrad. Si vedono chiaramente gli isobari di massa 1236, 1518 e 1688 MeV. Si hanno anche prove negli spettri a piccoli angoli della produzione dell’isobaro da 1410 MeV di massa (1410±15) MeV e ampiezza (125±20) MeV. Si dimostra che il picco osservato non può essere spiegato con l’effetto Deck. Si presentano le sezioni d’urto differenziali per la produzione di questi isobari in funzioni delle usuali variabilis et, e si confrontano con le previsioni del modello dei poli di Regge e del modello di assorbimento. Si studiano anche le approssimazioni ai dati con varie funzioni empiriche di queste variabili. Si trova che il comportamento della sezione d’urto totale per l’isobaro da 1236 MeV presenta una dipendenza dall’energia che concorda con lo scambio di un pione, mentre le sezioni d’urto degli isobari da 1410 MeV e 1688 MeV risultano indipendenti dall’energia. Si trova che anche la sezione d’urto totale presenta una dipendenza dall’energia in questo intervallo di energie.РеэумеПолучаются импульсные спектры протонов, неупруго рассеянных в протон-протонных соударениях во внещнем пучке в HИMPOД, испольэуя импульсы падаюших протонов 2.85, 4.55, 6.06 и 7.88 ГЭB/c, и раэличные углы рассеяния в области от 22 до 144 миллирадиан. Четко видны иэобары с массами 1236, 1518 и 1688 MЭB. Также имеется подтверждение в спектрах при малых углах для рождения иэобары 1410 MЭB с массой (1410±15) MЭB и щириной (125±20) MЭB. Покаэывается, что наблюденный пик не может быть общяснен с помошью Эффекта Дека. Представлены дифференциальные поперечные сечения для рождения Этих иэобар в терминах обычных переменныхs иt, которые сравниваются с предскаэаниями моделей поглошения и полюсов Редже. Также исследуются подгонки для Этих данных с помошью раэличных Эмпирических функций Этих переменных. Найдено, что поведение полного поперечного сечения для иэобары 1236 MЭB обнаруживает Энергетическую эависимость, согласуюшуюся с одно-пионным обменом, в то зе время получено, что полные поперечные сечения иэобар 1410 MЭB и 1688 MЭB не эависят от Энергии. Также найдено, что полное поперечное сечение для иэобары 1518 MЭB обнаруживает эависимость от Энергии в Этой области Энергий.
120152123
Particle physics at the turn of the century
Aspects of particle physics are reviewed from an experimental viewpoint. The elementary constituents of the Universe are described, as are the fundamental forces through which they interact. Recent results are emphasized and there is some speculation about the future. No attempt has been made to give a complete bibliography, but a few references to recent reviews and original articles are given. A glossary of acronyms is included.
123687310
Antiproton--proton annihilation into charged pion and kaon pairs
Events of the type anti pp $Yields$ K$sup -$K$sup +$, $pi$$sup - $$pi$$sup +$ were studied at 0.79 to 2.43 GeV/c. Differential cross sections and Legendre coefficient ratios are shown. Resonances found as a result of model fitting showing spin--parity assignment versus mass squared are also shown. (JFP)
123678522
Options for machines and experiments in the future
The highest energy particle accelerators in operation and under construction are described briefly, together with a selection of detectors. Extrapolations of existing techniques both for accelerators and for detectors appear to be adequate for the next upward step in energy, but beyond this new techniques will probably have to be developed. Some predictions are given.
3138911
Accurate measurement of the time delay in the response of the LIGO gravitational wave detectors
We present a method to precisely calibrate the time delay in a long baseline gravitational-wave interferometer. An accurate time stamp is crucial for data analysis of gravitational wave detectors, especially when performing coincidence and correlation analyses between multiple detectors. Our method uses an intensity-modulated radiation pressure force to actuate on the mirrors. The time delay is measured by comparing the phase of the signal at the actuation point with the phase of the recorded signal within the calibrated data stream used for gravitational wave searches. Because the signal-injection path is independent of the interferometer's control system, which is used for the standard calibration, this method can be an independent verification of the timing error in the system. A measurement performed with the 4 km interferometer at the LIGO Hanford Observatory shows a 1 µs relative accuracy when averaging over 50 min. Our understanding of the systematic time delay in the detector response has reached the level of 10 µs.
14925786
Benefits of artificially generated gravity gradients for interferometric gravitational-wave detectors
We present an approach to experimentally evaluate gravity gradient noise, a potentially limiting noise source in advanced interferometric gravitational-wave detectors. In addition, the method can be used to provide sub-percent calibration in phase and amplitude. Knowledge of calibration to such certainties shall enhance the scientific output of the instruments in the case of an eventual detection of gravitational waves. The method relies on a rotating symmetrical two-body mass, a dynamic gravity field generator (DFG). The placement of the DFG in the proximity of one of the interferometer's suspended test masses generates a change in the local gravitational field detectable with current interferometric gravitational-wave detectors.
117574348
Excluding Source Models with Multiple Astrophysical Observations
We describe a general method to observationally exclude a theoretical model for gravitational wave (GW) emission from a transient astrophysical source (event) by using a null detection from a network of GW detectors. In the case of multiple astrophysical events with no GW detection, statements about individual events can be combined to increase the exclusion confidence. We frame and demonstrate the method using a population of hypothetical core collapse supernovae.
26319866
Accurate calibration of test mass displacement in the LIGO interferometers
We describe three fundamentally different methods we have applied to calibrate the test mass displacement actuators to search for systematic errors in the calibration of the LIGO gravitational-wave detectors. The actuation frequencies tested range from 90 Hz to 1 kHz and the actuation amplitudes range from 10−6 m to 10−18 m. For each of the four test mass actuators measured, the weighted mean coefficient over all frequencies for each technique deviates from the average actuation coefficient for all three techniques by less than 4%. This result indicates that systematic errors in the calibration of the responses of the LIGO detectors to differential length variations are within the stated uncertainties.
36815013
Prospects of gravitational wave data mining and exploration via evolutionary computing
Techniques of evolutionary computing have proven useful for a diverse array of fields in science and engineering. Because of the expected low signal to noise ratio of LIGO data and incomplete knowledge of gravitational waveforms, evolutionary computing is an excellent candidate for LIGO data analysis studies. Using the evolutionary computing methods of genetic algorithms and genetic programming, we have developed, as a proof of principle, search algorithms that are effective at finding sine-gaussian signals hidden in noise while maintaining a small false alarm rate. Because we used realistic LIGO noise as a training ground, the algorithms we have evolved should be well suited to detecting signals in actual LIGO data, as well as in simulated noise. These algorithms have continuously improved during the five days of their evolution and are expected to improve further the more they are evolved. The top performing algorithms from generation 100 and 199 were benchmarked using gaussian white noise to illustrate their performance and the improvement over 100 generations.