117635066
LOW-MOMENTUM ANTIPROTON PRODUCTION AT THE CERN PROTON SYNCHROTRON.
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.
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.
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.
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)
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.
44041464
Inferring core-collapse supernova physics with gravitational waves
Stellar collapse and the subsequent development of a core-collapse supernova explosion emit bursts of gravitational waves (GWs) that might be detected by the advanced generation of laser interferometer gravitational-wave observatories such as Advanced LIGO, Advanced Virgo, and LCGT. GW bursts from core-collapse supernovae encode information on the intricate multidimensional dynamics at work at the core of a dying massive star and may provide direct evidence for the yet uncertain mechanism driving supernovae in massive stars. Recent multidimensional simulations of core-collapse supernovae exploding via the neutrino, magnetorotational, and acoustic explosion mechanisms have predicted GW signals which have distinct structure in both the time and frequency domains. Motivated by this, we describe a promising method for determining the most likely explosion mechanism underlying a hypothetical GW signal, based on principal component analysis and Bayesian model selection. Using simulated Advanced LIGO noise and assuming a single detector and linear waveform polarization for simplicity, we demonstrate that our method can distinguish magnetorotational explosions throughout the Milky Way (D≲10  kpc) and explosions driven by the neutrino and acoustic mechanisms to D≲2  kpc. Furthermore, we show that we can differentiate between models for rotating accretion-induced collapse of massive white dwarfs and models of rotating iron core collapse with high reliability out to several kpc.
118446989
Stacking gravitational wave signals from soft gamma repeater bursts
Soft gamma repeaters (SGRs) have unique properties that make them intriguing targets for gravitational wave (GW) searches. They are nearby, their burst emission mechanism may involve neutron star crust fractures and excitation of quasinormal modes, and they burst repeatedly and sometimes spectacularly. A recent LIGO search for transient GW from these sources placed upper limits on a set of almost 200 individual SGR bursts. These limits were within the theoretically predicted range of some models. We present a new search strategy which builds upon the method used there by “stacking” potential GW signals from multiple SGR bursts. We assume that variation in the time difference between burst electromagnetic emission and burst GW emission is small relative to the GW signal duration, and we time-align GW excess power time-frequency tilings containing individual burst triggers to their corresponding electromagnetic emissions. Using Monte Carlo simulations, we confirm that gains in GW energy sensitivity of N^(1/2) are possible, where N is the number of stacked SGR bursts. Estimated sensitivities for a mock search for gravitational waves from the 2006 March 29 storm from SGR 1900+14 are also presented, for two GW emission models, “fluence-weighted” and “flat” (unweighted).
14181827
Search method for unmodeled transient gravitational waves associated with SGR flares
We describe a method for searching for transient gravitational waves associated with soft gamma-ray repeater (SGR) flares or other burst-like events using data collected by interferometric gravitational wave detectors. The method can be used to analyze data from either a single detector or from two detectors coherently. The excess power-type algorithm creates event sets from conditioned detector data which may be compared to signal simulations of known strength based on plausible waveform classes. Estimated search sensitivities obtained by performing two-detector searches on the simulated data are presented. In the case of 22 ms duration white noise bursts in the 100–200 Hz band injected into simulated noise, we find a characteristic strain sensitivity h90%rss = 3.0 × 10−22 .
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.