94 Matching Results

Search Results

Advanced search parameters have been applied.

Flavor changing neutral currents and the third family

Description: We consider a Two Higgs Doublet Model with Flavor Changing Scalar Neutral Currents arising at the tree level. All the most important constraints are taken into account and the compatibility with the present Electroweak measurements is examined. The Flavor Changing couplings involving the third family are not constrained to be very small and this allows us to predict some interesting signals of new physics.
Date: September 16, 1996
Creator: Reina, L.
Partner: UNT Libraries Government Documents Department

Flavor and CP violations from sleptons at the Muon Collider

Description: Supersymmetric theories generally have new flavor and CP violation sources in the squark and slepton mass matrices. They will contribute to the lepton flavor violation processes, such as {mu}{yields}e{gamma}, which can be probed far below the current bound with an intense muon source at the front end of the muon collider. In addition, if sleptons can be produced at the muon collider, the flavor violation can occur at their production and decay, allowing us to probe the flavor mixing structure directly. Asymmetry between numbers of {mu}{sup +}e{sup -} and e{sup +}{mu}{sup -} events will be a sign for CP violation in supersymmetric flavor mixing.
Date: December 1, 1997
Creator: Cheng, H.-C.
Partner: UNT Libraries Government Documents Department

Questions of Identity

Description: As an introduction to {nu}Fact '99, the ICFA/ECFA Workshop on Neutrino Factories Based on Muon Storage Rings, I place the issues of neutrino properties and neutrino oscillations in the broader context of fermion flavor.
Date: August 25, 1999
Creator: Quigg, Chris
Partner: UNT Libraries Government Documents Department

Solving the SUSY CP problem with flavor breaking F-terms

Description: Supersymmetric flavor models for the radiative generation of fermion masses offer an alternative way to solve the SUSY-CP problem. We assume that the supersymmetric theory is flavor and CP conserving. CP violating phases are associated to the vacuum expectation values of flavor violating susy-breaking fields. As a consequence, phases appear at tree level only in the soft supersymmetry breaking matrices. Using a U(2) flavor model as an example we show that it is possible to generate radiatively the first and second generation of quark masses and mixings as well as the CKM CP phase. The one-loop supersymmetric contributions to EDMs are automatically zero since all the relevant parameters in the lagrangian are flavor conserving and as a consequence real. The size of the flavor and CP mixing in the susy breaking sector is mostly determined by the fermion mass ratios and CKM elements. We calculate the contributions to {epsilon}, {epsilon}' and to the CP asymmetries in the B decays to {psi}K{sub s}, {phi}K{sub s}, {eta}'K{sub s} and X{sub s}{gamma}. We analyze a case study with maximal predictivity in the fermion sector. For this worst case scenario the measurements of {Delta}m{sub K}, {Delta}m{sub B} and {epsilon} constrain the model requiring extremely heavy squark spectra.
Date: May 11, 2005
Creator: Diaz-Cruz, Lorenzo J. & Ferrandis, Javier
Partner: UNT Libraries Government Documents Department

Sea quark matrix elements and flavor singlet spectroscopy on the lattice

Description: I summarize the results of three recent lattice studies which use stochastic estimator techniques in order to investigate the flavor singlet dynamics in QCD. These include a measurement of the pion-nucleon {sigma}-term, the computation of the flavor singlet axial coupling constant of the nucleon and a determination of flavor singlet meson screening lengths in finite temperature QCD.
Date: December 31, 1996
Creator: Lagae, J.F.
Partner: UNT Libraries Government Documents Department

Studies of the strong and electroweak interactions at the Z{sub 0} pole

Description: This thesis presents studies of the strong and electroweak forces, two of the fundamental interactions that govern the behavior of matter at high energies. The authors have used the hadronic decays of Z{sup 0} bosons produced with the unique experimental apparatus of the e{sup +}e{sup {minus}} Linear Collider at the Stanford Linear Accelerator Center (SLAC) and the SLAC Large Detector (SLD) for these measurements. Employing the precision tracking capabilities of the SLD, they isolated samples of Z{sup 0} events containing primarily the decays of the Z{sup 0} to a chosen quark type. With an inclusive selection technique, they have tested the flavor independence of the strong coupling, {alpha}{sub s} by measuring the rates of multi-jet production in isolated samples of light (uds), c, and b quark events. They find: {alpha}{sub s}{sup uds}/{alpha}{sub s}{sup all} 0.987 {+-} 0.027(stat) {+-} 0.022(syst) {+-} 0.022(theory), {alpha}{sub s}{sup c}/{alpha}{sub s}{sup all} = 1.012 {+-} 0.104(stat) {+-} 0.102(syst) {+-} 0.096(theory), {alpha}{sub s}{sup b}/{alpha}{sub s}{sup all} = 1.026 {+-} 0.041(stat) {+-} 0.030(theory), which implies that the strong interaction is independent of quark flavor within the present experimental sensitivity. They have also measured the extent of parity-violation in the Z{sup 0} c{bar c} coupling, given by the parameter A{sub c}{sup 0}, using a sample of fully and partially reconstructed D* and D{sup +} meson decays and the longitudinal polarization of the SLC electron beam. This sample of charm quark events was derived with selection techniques based on their kinematic properties and decay topologies. They find A{sub c}{sup 0} = 0.73 {+-} 0.22(stat) {+-} 0.10(syst). This value is consistent with that expected in the electroweak standard model of particle interactions.
Date: March 1, 1995
Creator: Hildreth, M.D.
Partner: UNT Libraries Government Documents Department

Scalar mass relations and flavor violations in supersymmetric theories

Description: Supersymmetry provides the most promising solution to the gauge hierarchy problem. For supersymmetry to stablize the hierarchy, it must be broken at the weak scale. The combination of weak scale supersymmetry and grand unification leads to a successful prediction of the weak mixing angle to within 1{percent} accuracy. If supersymmetry is a symmetry of nature, the mass spectrum and the flavor mixing pattern of the scalar superpartners of all the quarks and leptons will provide important information about a more fundamental theory at higher energies. We studied the scalar mass relations which follow from the assumption that at high energies there is a grand unified theory which leads to a significant prediction of the weak mixing angle; these will serve as important tests of grand unified theories. Two intragenerational mass relations for each of the light generations are derived. A third relation is also found which relates the Higgs masses and the masses of all three generation scalars. In a realistic supersymmetric grand unified theory, nontrivial flavor mixings are expected to exist at all gaugino vertices. This could lead to important contributions to the neutron electric dipole moment, the decay mode p {r_arrow} K{sup 0}{mu}{sup +}, weak scale radiative corrections to the up-type quark masses, and lepton flavor violating signals such as {mu} {r_arrow} e{gamma}. These also provide important probes of physics at high energy scales. Supersymmetric theories involving a spontaneously broken flavor symmetry can provide a solution to the supersymmetric flavor-changing problem and an understanding of the fermion masses and mixings. We studied the possibilities and the general conditions under which some fermion masses and mixings can be obtained radiatively. We also constructed theories of flavor in which the first generation fermion masses arise from radiative corrections while flavor-changing constraints are satisfied. 69 refs., 19 figs., 9 tabs.
Date: May 9, 1996
Creator: Cheng, Hsin-Chia
Partner: UNT Libraries Government Documents Department

Family universal anomalous U(1) in realistic superstring derived models

Description: An important issue in supersymmetry phenomenology is the suppression of squarks contributions to Flavor Changing Neutral Currents (FCNC). Recently it was noted that in some free fermionic three generation models the anomalous U(1) is family universal. It was further shown that if the D-term of the U(1){sub A} is the dominant source of supersymmetry breaking, the squark masses are indeed approximately degenerate. In this paper the author discusses the properties of the superstring models that give rise to the flavor universal anomalous U(1). The root cause for the universal U(1){sub A} is the cyclic permutation symmetry, the characteristic property of the Z{sub 2} X Z{sub 2} orbifold compactification, realized in the free fermionic models by the NAHE set of boundary condition basis vectors. The properties of the three generation models that preserve this cyclic permutation symmetry in the flavor charges are discussed. The cyclic permutation symmetry of the Z{sub 2} x Z{sub 2} orbifold compactification is proposed to be the characteristic property, of phenomenological interest, that distinguishes it from other classes of superstring compactifications.
Date: January 1, 1998
Creator: Faraggi, A.E.
Partner: UNT Libraries Government Documents Department

Lepton flavor violation

Description: The connection of rare decays to supersymmetric grand unification is highlighted, and a review of the status of rare decay experiments is given. Plans for future investigations of processes that violate lepton flavor are discussed. A new result from the MEGA experiment, a search for {mu}{sup +} {yields} e{sup +} {gamma}, is reported to be B.R. < 3.8 x 10{sup -11} with 90% confidence.
Date: October 1, 1997
Creator: Cooper, M.D. Brooks, M. & Hogan, G.E.
Partner: UNT Libraries Government Documents Department

Rapidity Gap Results from Tevatron

Description: Results of rapidity gap physics in the CDF and DO Collaborations are presented. In particular, hard diffraction (diffractive dijet and heavy flavor quark production, dijet production in Double Pomeron Exchange) and color-singlet exchange are described.
Date: April 8, 1999
Creator: Terashi, K.
Partner: UNT Libraries Government Documents Department

Signals from flavor changing scalar currents at the future colliders

Description: We present a general phenomenological analysis of a class of Two Higgs Doublet Models with Flavor Changing Neutral Currents arising at the tree level. The existing constraints mainly affect the couplings of the first two generations of quarks, leaving the possibility for non negligible Flavor Changing couplings of the top quark open. The next generation of lepton and hadron colliders will offer the right environment to study the physics of the top quark and to unravel the presence of new physics beyond the Standard Model. In this context we discuss some interesting signals from Flavor Changing Scalar Neutral Currents.
Date: November 22, 1996
Creator: Atwood, D.; Reina, L. & Soni, A.
Partner: UNT Libraries Government Documents Department

Flavor tagging nd CP-violation measurements at the Tevatron

Description: The CDF collaboration has adapted several heavy flavor tagging techniques and employed them in analyses of time-dependent flavor asymmetries using data from the Tevatron Run I. The tagging algorithms were calibrated using low-P{sub t} inclusive lepton and dilepton trigger data samples. The tagging techniques were applied to a sample of {approximately} 400 B{sub d}{sup 0}/{anti B}{sub d}{sup 0} {r_arrow} J/{psi}K{sub s}{sup 0} decays and were used to measure the CP violation parameter, sin(2{beta}). Prospects for future improved measurements of the CP violation parameters at the Tevatron are briefly discussed.
Date: April 28, 1999
Creator: Tkaczyk, S.
Partner: UNT Libraries Government Documents Department

A hexagonal theory of flavor

Description: The authors construct a supersymmetric theory of flavor based on the discrete gauge group (D{sub 6}){sup 2}, where D{sub 6} describes the symmetry of a regular hexagon under proper rotations in three dimensions. The representation structure of the group allows one to distinguish the third from the lighter two generations of matter fields, so that in the symmetry limit only the top quark Yukawa coupling is allowed and scalar superpartners of the first two generations are degenerate. Light fermion Yukawa couplings arise from a sequential breaking of the flavor symmetry, and supersymmetric flavor-changing processes remain adequately suppressed. They contrast the model with others based on non-Abelian discrete gauge symmetries described in the literature, and discuss the challenges in constructing more minimal flavor models based on this approach.
Date: May 1, 1999
Creator: Carone, C.D. & Lebed, R.F.
Partner: UNT Libraries Government Documents Department

The Top...is it There? A Survey of the CDF and D0 Experiments

Description: This paper describes: (1) features that the top quark must have if it exists, and how those features are inferred from various experiments; (2) how top quarks may be produced; (3) what must be accomplished to directly establish that the top quark has been produced in an experiment. Relevant features of the CDF and D0 detectors are described, as are methods useful in a top-quark search for identifying and detecting various kinds of particles. The author reviews data found by both CDF and D0, and discusses differences between the detectors and the data found with each. 57 figures.
Date: December 1, 1994
Creator: Tollestrup, A.V.
Partner: UNT Libraries Government Documents Department

The heavy top quark and supersymmetry

Description: Three aspects of supersymmetric theories are discussed: electroweak symmetry breaking, the issues of flavor, and gauge unification. The heavy top quark plays an important, sometimes dominant, role in each case. Additional symmetries lead to extensions of the standard model which can provide an understanding for many of the outstanding problems of particle physics. A broken supersymmetric extension of spacetime allows electroweak symmetry breaking to follow from the dynamics of the heavy top quark; an extension of isospin provides a constrained framework for understanding the pattern of quark and lepton masses; and a grand unified extension of the standard model gauge group provides an elegant understanding of the gauge quantum numbers of the components of a generation. Experimental signatures for each of these additional symmetries are discussed.
Date: May 8, 1996
Creator: Hall, L.J.
Partner: UNT Libraries Government Documents Department

A Test of the Flavor Independence of Strong Interactions in e+e- Annihilation at the Z0 Pole

Description: This thesis presents a comparison of the strong coupling of the gluons to light (q<sub>l</sub> = u + d + s), c, and b quarks, determined from multijet rates in flavor-tagged samples of approximately 150,000 hadronic Z<sup>0</sup> decays recorded with the SLC Large Detector at the SLAC Linear Collider between 1993 and 1995. Flavor separation among primary q<sub>l</sub> {anti q<sub>l</sub>} , c{anti c} and b {anti b} final states was made on the basis of the reconstructed mass of long-lived heavy-hadron decay vertices, yielding tags with high purity and low bias against {>=} 3-jet final states. The data obtained imply no flavor dependence within our sensitivity.
Date: September 3, 1999
Creator: Muller, David
Partner: UNT Libraries Government Documents Department

On the model discriminating power of mu to e conversion in nuclei

Description: Lepton Flavor Violating (LFV) charged lepton decays provide a highly sensitive probe of physics beyond the Standard Model (SM), due to the un-observably small branching fractions ({approx}10{sup -50}) predicted for these modes in the SM (minimally extended to include massive neutrinos). Searches for SM forbidden muon processes, such as {mu} {yields} e{gamma}, {mu} {yields} e{bar e}e, and {mu} {yields} e conversion in nuclei, have provided so far the strongest constraints on LFV new physics. This statement can be characterized in a model-independent way as a lower bound on the scale associated to a set of dimension six effective operators parameterizing new physics beyond the SM. It is a well known fact that while the decay {mu} {yields} e{gamma} is only sensitive to a transition magnetic dipole operator, both {mu} {yields} e{bar e}e and {mu} {yields} e conversion in nuclei are sensitive to transition charge radii operators as well as purely contact four-fermion interactions induced by physics beyond the SM. In other words, different LFV decays have different sensitivities to underlying LFV mechanisms (effective operators). This leads naturally to ask the question whether one could infer the relative strength of these different operators in a completely phenomenological and model-independent way. This would allow one to discriminate among different underlying models of LFV and thus would provide valuable input for model building. In Ref. [1] it was pointed out that in principle, by combining the rates of {mu} {yields} e{gamma} and {mu} {yields} e conversion on different target nuclei, one could discriminate underlying models. In this work we go back to this issue with the aim to: quantify the theoretical uncertainty induced by the hadronization process; and quantify the experimental precision required to realistically infer useful information on the underlying LFV mechanisms. We organize our discussion as follows: in Section 2 we ...
Date: January 1, 2009
Creator: Cirigliano, Vincenzo; Kitano, Ryuichiro; Okada, Yashuiro & Tuzon, Paulo
Partner: UNT Libraries Government Documents Department

A modal approach to modeling spatially distributed vibration energy dissipation.

Description: The nonlinear behavior of mechanical joints is a confounding element in modeling the dynamic response of structures. Though there has been some progress in recent years in modeling individual joints, modeling the full structure with myriad frictional interfaces has remained an obstinate challenge. A strategy is suggested for structural dynamics modeling that can account for the combined effect of interface friction distributed spatially about the structure. This approach accommodates the following observations: (1) At small to modest amplitudes, the nonlinearity of jointed structures is manifest primarily in the energy dissipation - visible as vibration damping; (2) Correspondingly, measured vibration modes do not change significantly with amplitude; and (3) Significant coupling among the modes does not appear to result at modest amplitudes. The mathematical approach presented here postulates the preservation of linear modes and invests all the nonlinearity in the evolution of the modal coordinates. The constitutive form selected is one that works well in modeling spatially discrete joints. When compared against a mathematical truth model, the distributed dissipation approximation performs well.
Date: August 1, 2010
Creator: Segalman, Daniel Joseph
Partner: UNT Libraries Government Documents Department

Highlights of B physics at CDF

Description: The CDF experiment at the Fermilab Tevatron collider has produced many B physics results. Recent measurements on B meson masses, B lifetimes, B branching ratios, limits on rare B decays, and B flavour tagging studies are reviewed.
Date: August 1, 1995
Creator: Paulini, M.
Partner: UNT Libraries Government Documents Department

Manifestations of the axial anomaly in finite temperature QCD

Description: We compute the flavor singlet meson correlators and screening masses in quenched and N{sub {ital f}} = 2 QCD at N{sub {ital t}} = 8. The consequences of our results for the realization of the U{sub A}(1) symmetry at finite T are discussed and an interpretation of our measurements in terms of the behavior of the low lying fermionic modes is proposed.
Date: October 1, 1996
Creator: Kogut, J.B.; Lagaee, J.-F. & Sinclair, D.K.
Partner: UNT Libraries Government Documents Department

Rare decays experimental summary and prospects

Description: I review the status and future prospects of searches for forbidden and highly kaon suppressed decays. This workshop comes as we are poised at the threshold of a new generation of rare K decay experiments. There are new experiments running or about to run at KEK, BNL, FNAL, and CERN. In another year or so these will be joined by the KLOE experiment at DA{Phi}NE. The good news is that it`s a very exciting time. The bad news, at least for a reviewer, is that there aren`t too many new results. Thus I`ll be giving a little more attention than usual to what the experimenters expect to do. My discussion of rare K decays covers processes that are forbidden in the Standard Model, those that highly suppressed and to a smaller extent, those that are merely discouraged.
Date: December 31, 1996
Creator: Littenberg, L.
Partner: UNT Libraries Government Documents Department

The spin and flavor content of intrinsic sea quarks

Description: The intrinsic quark-antiquark pairs generated by the minimal energy nonperturbative meson-baryon fluctuations in the nucleon sea provide a consistent framework for understanding a number of empirical anomalies observed in the deep inelastic quark-parton structure of nucleons: the flavor asymmetry of the nucleon sea implied by the violation of Gottfried sum rule, the proton spin problem implied by the violation of the Ellis-Jaffe sum rule, and the outstanding conflict between two different determinations of the strange quark sea in the nucleon.
Date: July 1, 1997
Creator: Bo-Qiang Ma & Brodsky, S.J.
Partner: UNT Libraries Government Documents Department

(S{sub 3}){sup 3} theories of flavor

Description: The author presents a supersymmetric theory of flavor based on the discrete flavor group (S{sub 3}){sup 3}. The model can account for the masses and mixing angles of the standard model, while maintaining sufficient sfermion degeneracy to evade the supersymmetric flavor problem. The author demonstrates that the model has a viable phenomenology and makes one very striking prediction: the nucleon decays predominantly to Kl where l is a first generation lepton. He shows that the modes n {yields} K{sup 0}{bar {nu}}{sub e}, p {yields} K{sup +}{bar {nu}}{sub e}, and p {yields} K{sup 0}e{sup +} occur at comparable rates, and could well be discovered simultaneously at the SuperKamiokande experiment.
Date: July 1, 1996
Creator: Carone, C.D.
Partner: UNT Libraries Government Documents Department

Measuring the {anti u}/{anti d} asymmetry in the proton sea: Fermilab E866

Description: Experiment E866, conducted at the Fermi National Accelerator Laboratory, is a high statistics experiment to measure {anti u}(x)/{anti d}(x) in the proton over a wide range of x. A review of the current evidence for {anti u}(x) {ne} {anti d}(x) in the proton is given and is followed by a short description of the spectrometer and the experimental procedures used in E866. Preliminary results are shown for the ratio of the Drell-Yan cross sections {sigma}{sup pd}/2{sigma}{sup pp}. The preliminary results confirm the conclusions of both the NMC and NA51 collaborations that there is an {anti u}/{anti d}(x) asymmetry in the proton sea.
Date: July 1, 1998
Creator: Hawker, E.A.; Awes, T.; Brown, C. & Collaboration, E866
Partner: UNT Libraries Government Documents Department