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Search for axion-like particles using a variable baseline photon regeneration technique

Description: We report the first results of the GammeV experiment, a search for milli-eV mass particles with axion-like couplings to two photons. The search is performed using a 'light shining through a wall' technique where incident photons oscillate into new weakly interacting particles that are able to pass through the wall and subsequently regenerate back into detectable photons. The oscillation baseline of the apparatus is variable, thus allowing probes of different values of particle mass. We find no excess of events above background and are able to constrain the two-photon couplings of possible new scalar (pseudoscalar) particles to be less than 3.1 x 10 {sup -7} GeV {sup -1} (3.5 x 10{sup -7} GeV{sup -1}) in the limit of massless particles.
Date: October 1, 2007
Creator: Chou, A. S.; Wester, William Carl, III; Baumbaugh, A.; Gustafson, D.; Irizarry-Valle, Y.; Mazur, P. O. et al.
Partner: UNT Libraries Government Documents Department

Minimum entropy production of neutrino radiation in the steady state

Description: A thermodynamical minimum principle valid for photon radiation is shown to hold for arbitrary geometries. It is successfully extended to neutrinos, in the zero mass and chemical potential case, following a parallel development of photon and neutrino statistics. This minimum principle stems more from that of Planck than that of classical Onsager-Prigogine irreversible thermodynamics. Its extension from bosons to fermions suggests that it may have a still wider validity. 14 refs.
Date: August 1, 1997
Creator: Essex, C. & Kennedy, D.C.
Partner: UNT Libraries Government Documents Department

Realization of Center Symmetry in Two Adjoint Flavor Large-N Yang-Mills

Description: We report on the results of numerical simulations of SU(N) lattice Yang Mills with two flavors of (light) Wilson fermion in the adjoint representation. We analytically and numerically address the question of center symmetry realization on lattices with {Lambda} sites in each direction in the large-N limit. We show, by a weak coupling calculation that, for massless fermions, center symmetry realization is independent of {Lambda}, and is unbroken. Then, we extend our result by conducting simulations at non zero mass and finite gauge coupling. Our results indicate that center symmetry is intact for a range of fermion mass in the vicinity of the critical line on lattices of volume 2{sup 4}. This observation makes it possible to compute infinite volume physical observables using small volume simulations in the limit N {yields} {infinity}, with possible applications to the determination of the conformal window in gauge theories with adjoint fermions.
Date: August 26, 2010
Creator: Catterall, Simon; U., /Syracuse; Galvez, Richard; U., /Syracuse; Unsal, Mithat & /SLAC /Stanford U., Phys. Dept.
Partner: UNT Libraries Government Documents Department

Cherenkov Radiation from Jets in Heavy-ion Collisions

Description: The possibility of Cherenkov-like gluon bremsstrahlung in dense matter is studied. We point out that the occurrence of Cherenkov radiation in dense matter is sensitive to the presence of partonic bound states. This is illustrated by a calculation of the dispersion relation of a massless particle in a simple model in which it couples to two different massive resonance states. We further argue that detailed spectroscopy of jet correlations can directly probe the index of refraction of this matter, which in turn will provide information about the mass scale of these partonic bound states.
Date: July 26, 2005
Creator: Koch, Volker; Majumder, Abhijit & Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department

Absence of Rapid Proton Decay and Origin of Low-Energy Particlesand Yukawa Couplings

Description: In string theory, massless particles often originate from a symmetry breaking of a large gauge symmetry G to its subgroup H. The absence of dimension-4 proton decay in supersymmetric theories suggests that ({bar D},L) are different from {bar H}({bar 5}) in their origins. In this article, we consider a possibility that they come from different irreducible components in g/h. Requiring that all the Yukawa coupling constants of quarks and leptons be generated from the super Yang-Mills interactions of G, we found in the context of Georgi-Glashow H = SU(5) unification that the minimal choice of G is E{sub 7} and E{sub 8} is the only alternative. This idea is systematically implemented in Heterotic String, M theory and F theory, confirming the absence of dimension 4 proton decay operators. Not only H = SU(5) but also G constrain operators of effective field theories, providing non-trivial information.
Date: January 1, 2006
Creator: Tatar, Radu & Watari, Taizan
Partner: UNT Libraries Government Documents Department

The Complete Four-Loop Four-Point Amplitude in N

Description: We present the complete four-loop four-point amplitude in N = 4 super-Yang-Mills theory, for a general gauge group and general D-dimensional covariant kinematics, and including all non-planar contributions. We use the method of maximal cuts - an efficient application of the unitarity method - to construct the result in terms of 50 four-loop integrals. We give graphical rules, valid in D-dimensions, for obtaining various non-planar contributions from previously-determined terms. We examine the ultraviolet behavior of the amplitude near D = 11/2. The non-planar terms are as well-behaved in the ultraviolet as the planar terms. However, in the color decomposition of the three- and four-loop amplitude for an SU(N{sub c}) gauge group, the coefficients of the double-trace terms are better behaved in the ultraviolet than are the single-trace terms. The results from this paper were an important step toward obtaining the corresponding amplitude in N = 8 supergravity, which confirmed the existence of cancellations beyond those needed for ultraviolet finiteness at four loops in four dimensions. Evaluation of the loop integrals near D = 4 would permit tests of recent conjectures and results concerning the infrared behavior of four-dimensional massless gauge theory.
Date: August 25, 2010
Creator: Bern, Z.; Carrasco, J.J.M.; /UCLA; Dixon, Lance J.; /CERN, /SLAC; Johansson, H. et al.
Partner: UNT Libraries Government Documents Department

Rapid cooling and structure of neutron stars

Description: This report discusses the following topics on neutron stars: direct URCA neutrino emission; thermal evolution models; analytic model for diffusion through the crust; and core superfluidity. (LSP).
Date: January 1, 1992
Creator: Van Riper, K.A. (Los Alamos National Lab., NM (United States)) & Lattimer, J.M. (State Univ. of New York, Stony Brook, NY (United States). Dept. of Earth and Space Sciences)
Partner: UNT Libraries Government Documents Department

Experiment to search for finite mass neutrinos at Los Alamos

Description: The strong current interest among physicists of the possibility of finite-mass neutrinos has resulted in several proposals at Los Alamos for experiments to detect nonzero neutrino masses. Three experiments now underway and three proposed experiments at LAMPF are discussed. 1 table.
Date: January 1, 1980
Creator: Bowles, T.
Partner: UNT Libraries Government Documents Department

NK Muon Beam

Description: The NK Muon Beam will be a modified version of the existing NT beam line. The decision to employ a modified version of the NT beam line was made based on considerations of cost and availability of the beam line. Preliminary studies considered use of other beam lines, e.g., the NW beam line, and even of moving the bubble chamber with its superconducting coils but were rejected for reasons such as cost, personnel limitations, and potential conflicts with other users.
Date: September 28, 1988
Creator: Koizumi, G.
Partner: UNT Libraries Government Documents Department

Neutrino oscillations in the early universe II

Description: We show that it is possible for neutrino oscillations to create a state of the universe in which the net lepton numbers are appreciable and different for each species at the time of nucleosynthesis. Under these conditions mixing induced by the oscillations can influence the abundances of the light elements.
Date: 1982
Creator: McKellar, B. H. J. & Granek, H.
Partner: UNT Libraries Government Documents Department

A New Neutrino Oscillation

Description: Starting in the late 1960s, neutrino detectors began to see signs that neutrinos, now known to come in the flavors electron ({nu}{sub e}), muon ({nu}{sub {mu}}), and tau ({nu}{sub {tau}}), could transform from one flavor to another. The findings implied that neutrinos must have mass, since massless particles travel at the speed of light and their clocks, so to speak, don't tick, thus they cannot change. What has since been discovered is that neutrinos oscillate at two distinct scales, 500 km/GeV and 15,000 km/GeV, which are defined by the baseline (L) of the experiment (the distance the neutrino travels) divided by the neutrino energy (E). Neutrinos of one flavor can oscillate into neutrinos of another flavor at both L/E scales, but the amplitude of these oscillations is different for the two scales and depends on the initial and final flavor of the neutrinos. The neutrino states that propogate unchanged in time, the mass eigenstates {nu}1, {nu}2, {nu}3, are quantum mechanical mixtures of the electron, muon, and tau neutrino flavors, and the fraction of each flavor in a given mass eigenstate is controlled by three mixing angles and a complex phase. Two of these mixing angles are known with reasonable precision. An upper bound exists for the third angle, called {theta}{sub 13}, which controls the size of the muon neutrino to electron neutrino oscillation at an L/E of 500 km/GeV. The phase is completely unknown. The existence of this phase has important implications for the asymmetry between matter and antimatter we observe in the universe today. Experiments around the world have steadily assembled this picture of neutrino oscillation, but evidence of muon neutrino to electron neutrino oscillation at 500 km/GeV has remained elusive. Now, a paper from the T2K (Tokai to Kamioka) experiment in Japan, reports the first possible observation of ...
Date: July 1, 2011
Creator: Parke, Stephen J.
Partner: UNT Libraries Government Documents Department

Search for Higgs Bosons and Supersymmetric Particles in Tau Final States

Description: Elementary particle physics tries to find an answer to no minor question: What is our universe made of? To our current knowledge, the elementary constituents of matter are quarks and leptons, which interact via four elementary forces: electromagnetism, strong force, weak force and gravity. All forces, except gravity, can be described in one framework, the Standard Model of particle physics. The model's name reflects its exceptional success in describing all available experimental high energy physics data to high precision up to energies of about 100 GeV. An exception is given by the neutrino masses but even these can be integrated into the model. The Standard Model is based on the requirement of invariance of all physics processes under certain fundamental symmetry transformations. The consideration of these symmetries leads naturally to the correct description of the electromagnetic, weak and strong forces as the exchange of interaction particles, the gauge bosons. However, this formalism has the weakness that it only allows for massless particles. In order to obey the symmetries, a way to introduce the particle masses is given by the Higgs mechanism, which predicts the existence of the only particle of the Standard Model which has yet to be observed: the Higgs boson. In spite of the success of the Standard Model, it has to be considered as a low energy approximation of a more profound theory for various reasons. For example, the underlying theory is expected to allow for an integration of gravity into the framework and to provide a valid particle candidate for the dark matter in our universe. Furthermore, a solution has to be found to the problem that the Higgs boson as a fundamental scalar is sensitive to large radiative corrections driving its mass to the Planck scale of 10{sup 19} GeV. Several models have been proposed ...
Date: September 1, 2008
Creator: Torchiani, Ingo & U, /Freiburg
Partner: UNT Libraries Government Documents Department

Massive Degeneracy and Goldstone Bosons: A Challenge for the Light Cone

Description: Wherein it is argued that the light front formalism has problems dealing with Goldstone symmetries. It is further argued that the notion that in hadron condensates can explain Goldstone phenomena is false. This talk can be summarized as follows: (1) Exact symmetries can be realized in Wigner or Goldstone mode. (2) When a symmetry is realized in Wigner mode the states of the theory form degenerate irreducible representations of the symmetry group and the lowest energy state is unique. (3) When a symmetry is realized in Goldstone mode the lowest energy state of the theory is infinitely degenerate, the states of the theory do not form irreducible representations of the symmetry group and there are massless particles coupled by the conserved currents to any one of the possible ground states. (4) In finite volume the signal of a Goldstone realization of a symmetry is that the number of nearly degenerate states grows rapidly with increasing volume and the gap between these states shrinks exponentially with the volume. (5) The existence of a condensate such as the magnetization, for a ferromagnet, or the staggered magnetization for an anti-ferromagnet, signals a Goldstone symmetry. This is because this condensate transforms non-trivially under the symmetry transformations and so its existence implies the ground state isn't unique. (6) PCAC means that the pion, kaon and eta are would be Goldstone bosons of the theory where the quark masses are set to zero. This interpretation is overwhelmingly supported by experimental data. This means that these particles are really the wiggling of the order parameter or condensate. (7) Finally, in order for the Goldstone particle to exist there has to be something to wiggle every place where the particle can exist. This means that the condensate that is the order parameter for this Goldstone symmetry cannot be ...
Date: October 27, 2010
Creator: Weinstein, Marvin
Partner: UNT Libraries Government Documents Department

All Tree-level Amplitudes in Massless QCD

Description: We derive compact analytical formulae for all tree-level color-ordered gauge theory amplitudes involving any number of external gluons and up to three massless quark-anti-quark pairs. A general formula is presented based on the combinatorics of paths along a rooted tree and associated determinants. Explicit expressions are displayed for the next-to-maximally helicity violating (NMHV) and next-to-next-to-maximally helicity violating (NNMHV) gauge theory amplitudes. Our results are obtained by projecting the previously-found expressions for the super-amplitudes of the maximally supersymmetric Yang-Mills theory (N = 4 SYM) onto the relevant components yielding all gluon-gluino tree amplitudes in N = 4 SYM. We show how these results carry over to the corresponding QCD amplitudes, including massless quarks of different flavors as well as a single electroweak vector boson. The public Mathematica package GGT is described, which encodes the results of this work and yields analytical formulae for all N = 4 SYM gluon-gluino trees. These in turn yield all QCD trees with up to four external arbitrary-flavored massless quark-anti-quark-pairs.
Date: October 25, 2010
Creator: Dixon, Lance J.; Henn, Johannes M.; Plefka, Jan & Schuster, Theodor
Partner: UNT Libraries Government Documents Department

Status of neutrino mass experiments

Description: In 1980 two experiments ignited a fertile field of research the determination of the neutrino masses. Subsequently, over 35 experiments using a variety of techniques have probed or are probing this question. Primarily I will discuss electron antineutrino (hereafter referred to as neutrino) mass experiments. However, let me begin in Section I to discuss astronomical and terrestrial observations which motivated these experiments. In Section II, I will quote limits from muon and tau mass determinations. These limits are more thoroughly discussed in other papers. I will continue by describing the four approaches used to measure the electron neutrino mass. In Section III, tritium beta decay mass determinations will be reviewed. This section includes a general summary of previous experimental results, and discussion of the major ongoing experiments. Section IV offers concluding remarks. 24 refs., 24 figs.
Date: December 1, 1985
Creator: Fackler, O.
Partner: UNT Libraries Government Documents Department

Calculation of dose-rate conversion factors for external exposure to photons and electrons

Description: Methods are presented for the calculation of dose-rate conversion factors for external exposure to photon and electron radiation from radioactive decay. A dose-rate conversion factor is defined as the dose-equivalent rate per unit radionuclide concentration. Exposure modes considered are immersion in contaminated air, immersion in contaminated water, and irradiation from a contaminated ground surface. For each radiation type and exposure mode, dose-rate conversion factors are derived for tissue-equivalent material at the body surface of an exposed individual. In addition, photon dose-rate conversion factors are estimated for 22 body organs. The calculations are based on the assumption that the exposure medium is infinite in extent and that the radionuclide concentration is uniform. The dose-rate conversion factors for immersion in contaminated air and water then follow from the requirement that all of the energy emitted in the radioactive decay is absorbed in the infinite medium. Dose-rate conversion factors for ground-surface exposure are calculated at a reference location above a smooth, infinite plane using the point-kernel integration method and known specific absorbed fractions for photons and electrons in air.
Date: January 1, 1978
Creator: Kocher, D.C.
Partner: UNT Libraries Government Documents Department

Limits on likesign dilepton production in nu/sub. mu. / interactions

Description: We have searched for the production of likesign dilepton events (nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + e/sup -/ + ...) in a wideband neutrino beam at FNAL using the 15' bubble chamber. We observe no signal above the background arising from conventional sources. We set 90% confidence level upper limits for the production rates of (nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + e/sup -/ + ...)/(nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + ...) less than or equal to 8 * 10/sup -5/ and (nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + e/sup -/ + ...)/(nu/sub ..mu../ + Ne ..-->.. ..mu../sup -/ + e/sup +/ + ...) less than or equal to 6 * 10/sup -2/.
Date: May 21, 1985
Creator: Baker, N.J.; Connolly, P.L.; Kahn, S.A.; Murtagh, M.J.; Palmer, R.B.; Samios, N.P. et al.
Partner: UNT Libraries Government Documents Department

B Flavour Tagging with Artificial Neural Networks for the CDF II Experiment

Description: One of the central questions arising from human curiosity has always been what matter is ultimately made of, with the idea of some kind of elementary building-block dating back to the ancient greek philosophers. Scientific activities of multiple generations have contributed to the current best knowledge about this question, the Standard Model of particle physics. According to it, the world around us is composed of a small number of stable elementary particles: Electrons and two different kinds of quarks, called up and down quarks. Quarks are never observed as free particles, but only as bound states of a quark-antiquark pair (mesons) or of three quarks (baryons), summarized as hadrons. Protons and Neutrons, the constituents forming the nuclei of all chemical elements, are baryons made of up and down quarks. The electron and the electron neutrino - a nearly massless particle without electric charge - belong to a group called leptons. These two quarks and two leptons represent the first generation of elementary particles. There are two other generations of particles, which seem to have similar properties as the first generation except for higher masses, so there are six quarks and six leptons altogether. They were around in large amounts shortly after the beginning of the universe, but today they are only produced in high energetic particle collisions. Properties of particles are described by quantum numbers, for example charge or spin. For every type of particle, a corresponding antiparticle exists with the sign of all charges swapped, but similar properties otherwise. The Standard Model is a very successful theory, describing the properties of all known particles and the interactions between them. Many of its aspects have been tested in various experiments at very high precision. Although none of these experimental tests has shown a significant deviation from the corresponding Standard Model ...
Date: January 1, 2010
Creator: Schmidt, Andreas
Partner: UNT Libraries Government Documents Department

Microdosimetric measurements for photons in a water phantom

Description: Microdosimetric event distributions were determined in air at three primary photon energies (60, 660 and 1250 keV) and at depths of 2, 5, and 10 cm in a water phantom (30 x 30 x 30cm) from measurements of charge produced in a walled Rossi-type proportional counter. For 660 and 1250 keV photon energies free air sources of /sup 137/Cs and /sup 60/Co, respectively, were used at the Brookhaven National Laboratory (BNL) calibration facility and for 60 keV a 300 mCi /sup 241/Am source was used. Event size spectra were taken at simulated site diameters of 0.5, 1, and 2 ..mu..m. The frequency mean (anti Y/sub F/) and dose mean (anti Y/sub D/) of lineal energy density were determined from these measurements. Our results without a phantom indicate reasonably good agreement for anti Y/sub F/ and anti Y/sub D/ with measurements reported in the literature for walled proportional counters. Ratios anti Y/sub F/(water)/anti Y/sub F/(air) and anti Y/sub D/(water)/anti Y/sub D/(air) were determined for each site diameter and depth in the phantom. For 60 keV photons the maximum increase in these ratios was approximately 8 percent for a site diameter of 2 microns at 10 cm depth in the phantom. For 660 keV photons the maximum increase in these ratios was 24 percent whereas for 1250 keV photons this maximum increase was approximately 15 percent. However, for 60 keV photons only about 8 percent increase was observed; this small increase is consistent with the fact that about half of the scattered photons are removed by photoelectric processes. Since anti Y/sub D/ in the phantom increased only by about 24 percent large changes in biological effectiveness are not expected as a function of depth in typical biological systems.
Date: January 1, 1980
Creator: Varma, M N; Baum, J W; Kliauga, P & Bond, V P
Partner: UNT Libraries Government Documents Department

Neutrino mixing and oscillation in a grand unified field theory SO(10)

Description: The investigation shows that it is very difficult to achieve neutrino mixing of other than the V/sub ..mu../-..nu../sub tau/ type in any minimal SO(10) model in which neutrino masses are generated by the Gell-Mann-Ramond-Slansky mechanism, because of the severe constraints placed on the mass matrix by quark phenomenology.
Date: January 1, 1980
Creator: Tanaka, K.
Partner: UNT Libraries Government Documents Department