• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 746
  • 504
  • 164
  • 164
  • 164
  • 164
  • 164
  • 162
  • 118
  • 57
  • 55
  • 6
  • 5
  • 5
  • 2
  • Tagged with
  • 2018
  • 2018
  • 1737
  • 835
  • 820
  • 552
  • 533
  • 220
  • 211
  • 195
  • 169
  • 168
  • 153
  • 125
  • 115
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

HIGHER-ORDER QUANTUM-CHROMODYNAMIC CORRECTIONS TO THE LONGITUDINAL COEFFICIENT FUNCTION IN DEEP-INELASTIC SCATTERING

Unknown Date (has links)
A calculation of the nonsinglet longitudinal coefficient function of deep-inelastic scattering through order-g('4) is presented, using the operator-product expansion and the renormalization group. Both ultraviolet and infrared divergences are regulated with dimensional regularization. The renormalization scheme dependence of the result is discussed along with its phenomenological application in the determination of R = (sigma)(,L)/(sigma)(,T). / Source: Dissertation Abstracts International, Volume: 43-09, Section: B, page: 2940. / Thesis (Ph.D.)--The Florida State University, 1982.
42

CASCADE RESONANCE PRODUCTION IN NEGATIVE KAON-PROTON INTERACTION AT 5 GEV

Unknown Date (has links)
The reaction K('-)p(--->)K('+)(,slow)X('-) was studied for (XI)* production using Brookhaven National Laboratory's Multi-Particle Spectrometer. The slow transverse K('+) was identified by two brass/scintillator detectors that detected the stopping K('+) and its subsequent decay. The reaction takes place via baryon exchange. The system in recoil to the K('+) has strangeness -2. The mass of the X('-) was determined as a missing mass for about 3400 events. Of the eleven previously reported (XI) states, two are well established, two are in need of clarification, and the rest need confirmation. In this experiment no new resonances were found, but six previously reported (XI) states were observed: (XI)(1320), (XI)(1530), (XI)(1820), (XI)(2020), (XI)(2220), and the (XI)(2350). Two body cross sections were measured for these states and they range from 1.25 to 7.25 (mu)b. Other previously reported states were not observed up to the 1 (mu)b level and they are: (XI)(1630), (XI)(1680), (XI)(1940), and the (XI)(2120). No conclusions were drawn on the (XI)(2500). / Source: Dissertation Abstracts International, Volume: 43-10, Section: B, page: 3276. / Thesis (Ph.D.)--The Florida State University, 1982.
43

Numerical simulations of quantum gravity on a Regge skeleton

Unknown Date (has links)
Quantum gravity suffers from the non-renormalizability and the unboundedness of the Einstein action. Non-perturbative methods may be crucial for an understanding. The lattice has become an important tool in probing the non-perturbative structure of field theories and could provide valuable hints in understanding quantum gravity as well. / Regge calculus has been used to make preliminary non-perturbative, numerical investigations of the theory. First simulations revealed the existence of an entropy dominated phase, where expectation values of physical quantities were stable. As a first step towards a more realistic theory, we couple a SU(2) field to gravity on the Regge skeleton to see whether the entropy dominated phase would allow the hadronic masses to be chosen arbitrarily small compared to the Planck mass and simultaneously allow the space to become flat on the hadronic scale. / We observe the existence of an entropy dominated phase in simulations on a 4$\sp3 \cdot 2$ lattice and study the phase diagram. The Polyakov loop is used as the order parameter and shows hysteresis, indicating a phase transition. However, to provide modest evidence for the scenario outlined above would require simulations on a larger system $(8\sp3 \cdot\ 4)$, currently outside the scope of our computing resources. / Source: Dissertation Abstracts International, Volume: 54-07, Section: B, page: 3676. / Major Professor: Bernd A. Berg. / Thesis (Ph.D.)--The Florida State University, 1993.
44

A next-to-leading-log Monte Carlo study of photon pairs and the search for the intermediate mass Higgs boson

Unknown Date (has links)
Symmetry breaking and the question of the origin of mass are the reasons the Superconducting Super Collider and the Large Hadron Collider are being built. The Standard Model of particle physics provides a solution to this problem by proposing the existence of a neutral scalar particle, the Higgs boson. This particle, via its interactions, gives mass to all of the particles in the Standard Model. The question of whether the Higgs boson can be detected at these machines depends critically on its final state decays. These decays in turn depend crucially on the mass of the Higgs boson, an unknown parameter of the theory. A lower bound of the Higgs mass has been set by experiment and a upper bound via theoretical arguments. Throughout much of the mass range Higgs decays via weak gauge bosons yield a clear signal. However, near the lower limit, the so-called intermediate mass region, the situation is less clear. In this region Higgs decays into photon pairs have been suggested as a viable signal. The significance of such a signal depends on other competing processes or backgrounds. This dissertation attempts to answer the question, "Can the Intermediate mass Higgs boson be detected via its electromagnetic decays?" To answer this question various Standard Model processes are calculated to the leading-log and next-to-leading-log level in a Monte Carlo environment. / Source: Dissertation Abstracts International, Volume: 54-03, Section: B, page: 1456. / Major Professor: Joseph F. Owens, III. / Thesis (Ph.D.)--The Florida State University, 1993.
45

Higgs mass triviality bounds on F(4) lattices

Unknown Date (has links)
In order to accurately describe the cutoff dependence of the Higgs mass triviality bound, the $\varphi\sp4$ theory is formulated on an $F\sb4$ lattice which preserves Lorentz invariance to a higher degree than the commonly used hypercubic lattice. / We solve this model non-perturbatively by evaluating the linked cluster expansion through 12th order following the approach of Luscher and Weisz. The results are continued across the transition line into the broken phase by integrating the perturbative renormalization group equations. In the Goldstone phase, the renormalized coupling never exceeds 2/3 of the tree level unitarity bound when $\Lambda$/$m\sb{R}\ge 2$. Our results confirm recent Monte Carlo data and we obtain as an upper bound for the Higgs mass $m\sb{R}$/$f\sb\pi=2.45(7)$ at $\Lambda$/$m\sb{R}=2$. / Attempting to produce a heavier Higgs on the lattice, additional four-derivative terms are introduced in the naive action which serve to parameterize the leading order cutoff effects. Using a cluster reflection algorithm of the Swendsen-Wang-Wolff type, we simulate this action on an $F\sb4$ lattice in a region where the region where the effects of the new terms are expected to be maximal. As an upper bound we now obtain $M\sb\sigma$/$f\sb\pi\approx 2.8$, an increase of about 20% compared to the simplest non-linear action. Despite triviality, the scalar sector may thus not be weakly interacting. / Source: Dissertation Abstracts International, Volume: 53-11, Section: B, page: 5775. / Major Professors: Urs M. Heller; Dennis W. Duke. / Thesis (Ph.D.)--The Florida State University, 1992.
46

THE PRODUCTION OF ETA AND OMEGA MESONS IN POSITIVE PION-PROTON INTERACTIONS AT 16 GEV

Unknown Date (has links)
Two and four prong (pi)('+)p interactions at 16 GeV/c were used to study the reactions: (pi)('+)p (--->) p(pi)('+)(pi)('+)(pi)('-)(eta), (pi)('+)p (--->) p(pi)('+)(eta) and (pi)('+)p (--->) p(pi)('+)(omega). The data were taken by the SLAC 1 meter hybrid bubble chamber facility augmented with a lead glass wall assembly for forward going neutral energy detection. The wall was used to trigger the bubble chamber for neutral energy greater than 3 GeV. / The detection of the (eta) and (pi)('0) signals is shown in the neutral missing mass of the 2 and 4 prongs. A strong (DELTA)('++) signal is seen in both 2 and 4 prong topologies. The invariant mass for the (eta)(pi)('+),(eta)(pi)('-),(eta)(pi)('+)(pi)('-),(pi)('+)(pi)('-)(pi)('0) and (omega)(pi)('+) are given but no new high mass resonances were found. / The cross section for (pi)('+)p (--->) (pi)('+)(pi)('+)(pi)('-)p(eta), (eta) (--->) neutrals production was calculated to be 72 (+OR-) 20 (mu)b, while for the (pi)('+)p (--->) (pi)('+)p(eta), (eta) (--->) neutrals it was 31 (+OR-) 8 (mu)b. The cross section for the production of the (pi)('+)p (--->) (pi)('+)p(omega) was 45 (+OR-) 8 (mu)b and (pi)('+)p (--->) (DELTA)('++)(omega) was found to be 16 (+OR-) 2 (mu)b. / Signals were observed and cross sections calculated for the following mesonic resonances: (delta)('(+OR-))(980) (--->) (eta)(pi)('(+OR-)):(sigma) (.) BR = 13 (+OR-) 5 (mu)b, (eta)' (--->) (eta)(pi)('+)(pi)('-):(sigma) (.) BR = 8 (+OR-) 3 (mu)b and B('+)(1235) (--->) (omega)(pi)('+):(sigma) = 11 (+OR-) 2 (mu)b. Cross sections for resonances opposite (DELTA)('++) were found: (eta)'(980):(sigma) = 6 (+OR-) 1.8 (mu)b and D('0)(1285):(sigma) = 4 (+OR-) 1 (mu)b. / Source: Dissertation Abstracts International, Volume: 45-01, Section: B, page: 0235. / Thesis (Ph.D.)--The Florida State University, 1984.
47

OBSERVATION OF DOUBLE PHI MESON PRODUCTION IN 400 GEV/C PROTON-NUCLEON INTERACTIONS

Unknown Date (has links)
The production of pairs of (phi) mesons has been observed in 400 GeV/c proton-nucleon interactions at the Fermilab Multiparticle Spectrometer in the inclusive reaction p N (--->) (phi)(phi) + X, where each (phi) decays to a K+K-pair. / A fast (200ns), high-level trigger processor was used on-line to selectively trigger on events containing two pairs of oppositely charged kaons having low invariant masses. The experimental apparatus and trigger processor are described. / From a sample of 120,000 reconstructed events having at least 2 K+ and 2 K- tracks in the momentum range 5.8 (LESSTHEQ) p (LESSTHEQ) 23.0 GeV/c, the K+K-K+K-, (phi)K+K- and (phi)(phi) invariant mass spectra are presented. A total of 1503 events are identified as being consistent with (phi)(phi) production. / After background subtraction and acceptance corrections, the total cross sections per nucleon for (phi)(phi) and (phi)K+K- production at 400 GeV/c are found to be (sigma)(,T)(pN(--->)(phi)(phi)+X) = 0.87 (+OR-) 0.27 (mu)b and (sigma)(,T)(pN(--->)(phi)K+K-+X) = 23.6 (+OR-) 2.7 (mu)b. An upper limit on the cross section times branching ratio for (eta)(,c) production at 400 GeV/c is established to be (sigma)(,T)(pN(--->)(eta)(,c)+X)(.)BR((eta)(,c)(--->)(phi)(phi)) (LESSTHEQ) 30 nb. / Source: Dissertation Abstracts International, Volume: 46-01, Section: B, page: 0204. / Thesis (Ph.D.)--The Florida State University, 1984.
48

D(1285) AND E(1420) MESON PRODUCTION IN ANTIPROTON-PROTON ---> (POSITIVE KAON, KAON(SHORT-LIVED), NEGATIVE PION)X AT 6.6 GEV/C (SPECTROSCOPY)

Unknown Date (has links)
We have observed the D(1285) and E(1420) mesons in the interaction pp (--->) (K('+)K(,s)(pi)('-))X with a p beam at 6.6 GeV/c. The data were taken at the Brookhaven National Laboratory Multiparticle Spectrometer facility in the spring of 1983. We have 420 D events and 620 E events in a sample of 11,686 total events. We have fitted the K('+)K(,s)(pi)('-) mass spectrum, corrected for acceptance, with two Breit-Wigner functions and background. We have performed a Dalitz plot/Zemach analysis using intermediate decay modes (delta)(pi) and K('*)K and spin-parity/G-parity J('PG) 0('-+), 0('--), 1('++), 1('+-), 1('-+), 1('--). We find the D to have mass (1.277 (+OR-) .002) GeV and width (32 (+OR-) 8) MeV and to be consistent with J('PG) = 1('++), decay mode (delta)(pi). We find the E to have mass (1.424 (+OR-) .003) GeV and width (60 (+OR-) 10) MeV, with J('PG) = 1('++) and decay mode predominantly (delta)(pi), with some K('*)K present. We find a large non-resonant 1('++) K('*)K background in the E region. The results of the E analysis compare well with those from the (pi)('-)p (--->) (K('+)K(,s)(pi)('-))n experiment performed at the same facility by the same collaboration. / Source: Dissertation Abstracts International, Volume: 46-09, Section: B, page: 3096. / Thesis (Ph.D.)--The Florida State University, 1985.
49

ON THE UNIQUENESS OF INTERACTIONS INVOLVING HIGHER SPIN PARTICLES

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 32-09, Section: B, page: 5370. / Thesis (Ph.D.)--The Florida State University, 1971.
50

CONSTITUENT QUARK PAIR PRODUCTION IN A POTENTIAL MODEL OF MESONS (CHARMONIUM, UPSILONIUM)

Unknown Date (has links)
The coupling of primitive qq meson states to four-quark qq qq states is investigated. The basic mechanism is the production of a massive quark-antiquark pair. The Feynman diagram for this process is considered and, with suitable approximations, this diagram yields a coupling operator. The heavy meson systems cc and bb are treated in some detail. Energy shifts for the first three J('P) = 1('-) states in charmonium are found to be in the range 50-80 MeV. The calculated width of the state (psi)'' is 14 MeV. The decay (psi)'(--->)(psi)(eta) is treated as a two-stage process of pair production followed by quark exchange and a width of 1.6 keV is obtained. An attempt is made to study the lighter meson systems ss and nn. Using a coupling operator similar to that used for the heavy mesons, the widths of the (phi) and (rho) mesons are determined to within an order of magnitude. / Source: Dissertation Abstracts International, Volume: 45-09, Section: B, page: 2963. / Thesis (Ph.D.)--The Florida State University, 1984.

Page generated in 0.1055 seconds