13535076
X-ray emission from betatron motion in a plasma wiggler.
The successful utilization of an ion channel in a plasma to wiggle a 28.5-GeV electron beam to obtain broadband x-ray radiation is reported. The ion channel is induced by the electron bunch as it propagates through an underdense 1.4-meter-long lithium plasma. The quadratic density dependence of the spontaneously emitted betatron x-ray radiation and the divergence angle of approximately (1-3)x10(-4) radian of the forward-emitted x-rays as a consequence of betatron motion in the ion channel are in good agreement with theory. The absolute photon yield and the peak spectral brightness at 14.2-keV photon energy are estimated.
5366774
Observation of spontaneous emitted X-ray betatron radiation in beam-plasma interactions
An experiment is being carried out at the Stanford Linear Accelerator Center (SLAC) to see if an ion channel can wiggle a beam of ultra-relativistic electrons to produce X-ray radiation. The goal is to create an intense source of undulator radiation using a plasma wiggler in the 1-10 keV range and also to determine the suitability of such an electrostatic wiggler to create a coherent beam of X-rays via the ion channel laser mechanisml. Here we give some of the scaling laws for the power and frequency distribution of the spontaneous emission from sending an electron beam through such an ion channel. Some initial experimental observations are also presented.
118333622
Nonequilibrium Phenomena in Quantum Field Theory: From Linear Response to Dynamical Renormalization Group
This thesis is devoted to studying aspects of real-time nonequilibrium dynamics in quantum field theory by implementing an initial value formulation of quantum field theory. The main focus is on the linear relaxation of mean fields and quantum kinetics in nonequilibrium multiparticle quantum systems with potential applications to ultrarelativistic heavy ion collisions, cosmological phase transitions and condensed matter systems. We first study the damping of fermion mean fields in a fermion-scalar plasma with a view towards understanding baryon transport phenomena during electroweak baryogenesis. Secondly, we apply and extend the renormalization group method to study nonequilibrium dynamics with the goals of constructing a quantum kinetic description that goes beyond usual Boltzmann kinetics and understanding anomalous relaxation associated with infrared phenomena. The final part of this thesis presents a real-time kinetic analysis of direct photon production from a quark-gluon plasma created in ultrarelativistic heavy ion collisions. We show that the direct photon yield is significantly enhanced by the lowest order energy-nonconserving processes originated in the transient lifetime of the quark-gluon plasma.
11384397
Direct photon cross section with conversions at CDF
We present a measurement of the isolated direct photon cross section in pp collisions at {radical}(s)=1.8 TeV and |{eta}|<0.9 using data collected between 1994 and 1995 by the Collider Detector at Fermilab (CDF). The measurement is based on events where the photon converts into an electron-positron pair in the material of the inner detector, resulting in a two track event signature. To remove {pi}{sup 0}{yields}{gamma}{gamma} and {eta}{yields}{gamma}{gamma} events from the data we use a new background subtraction technique which takes advantage of the tracking information available in a photon conversion event. We find that the shape of the cross section as a function of photon p{sub T} is poorly described by next-to-leading-order QCD predictions, but agrees with previous CDF measurements.
119228618
New primordial-magnetic-field limit from the latest LIGO S5 data
Since the energy momentum tensor of a magnetic field always contains a spin-2 component in its anisotropic stress, stochastic primordial magnetic field (PMF) in the early universe must generate stochastic gravitational-wave (GW) background. This process will greatly affect the relic gravitational wave (RGW), which is one of the major scientific goals of the laser interferometer GW detections. Recently, the fifth science (S5) run of laser interferometer gravitational-wave observatory (LIGO) gave a latest upper limit Omega(GW) < 6.9 x 10(-6) on the RGW background. Utilizing this upper limit, we derive new PMF limits: for a scale of galactic cluster lambda = 1 Mpc, the amplitude of PMF, that produced by the electroweak phase transition, has to be weaker than B(lambda) <= 4 x 10(-7) G; for a scale of supercluster lambda = 100 Mpc, the amplitude of PMF has to be weaker than B(lambda) <= 9 x 10(-11) G. In this manner, GW observation has potential to make interesting contributions to the study of primordial magnetic field.
122950163
The performance of the CDF luminosity monitor
Abstract We describe the initial performance of the detector used for the luminosity measurement in the CDF experiment in Run II at the Tevatron. The detector consists of low-mass gaseous Cherenkov counters with high light yield (∼100 photoelectrons) and monitors the process of inelastic p p scattering. It allows for several methods of precise luminosity measurements at peak instantaneous luminosities of 2×10 32 cm −2 s −1 , corresponding to an average of six p p interactions per bunch crossing.
121984352
The BES detector
Abstract The Beijing Spectrometer (BES) is a general purpose solenoidal detector at the Beijing Electron Positron Collider (BEPC). It is designed to study exclusive final states in e + e − annihilations at the center of mass energy from 3.0 to 5.6 GeV. This requires large solid angle coverage combined with good charged particle momentum resolution, good particle identification and high photon detection efficiency at low energies. In this paper we describe the construction and the performance of BES detector.