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Mass hierarchies from anomalies: A peek behind the Planck curtain

Description: The masses of quarks and leptons suggest a strong hierarchical structure. We argue that their patterns can be reproduced through the introduction of a new Abelian symmetry. The data suggest that this symmetry is anomalous. We suggest that the cancellation of its anomalies occurs through the Green-Schwarz mechanism. An important check of this idea is that it links the Weinberg angle to a mass ration of the elementary fermions. The Green-Schwarz mechanism occurs naturally in many superstring compactifications, and produces a small parameter, which we use to determine the quark mass hierarchy. We show that hierarchy and mixings among the chiral fermions is a consequence of the Green-Schwarz mechanism. We present several models where this idea is realized. 16 refs., 2 tabs.
Date: May 1, 1996
Creator: Ramond, P.
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

Quasi-degenerate neutrinos from an abelian family symmetry

Description: The authors show that models with an abelian family symmetry which accounts for the observed hierarchies of masses and mixings in the quark sector may also accommodate quasi-degeneracies in the neutrino mass spectrum. Such approximate degeneracies are, in this context, associated with large mixing angles. The parameters of this class of models are constrained. The authors discuss their phenomenological implications for present and foreseen neutrino experiments.
Date: December 31, 1996
Creator: Binetruy, P.; Lavignac, S.; Petcov, S. & Ramond, P.
Partner: UNT Libraries Government Documents Department

{Delta}I = 4 bifurcation: Origins and criteria

Description: The new {gamma}-ray detector arrays have demonstrated that rotational sequences in certain superdeformed bands with angular momentum differing by two can split into two branches. This is commonly called {Delta}I = 4 bifurcation, and has attracted considerable interest in the nuclear structure community. An alternative approach for the {Delta}I = 4 bifurcation phenomenon has been presented without introducing either a Y{sub 44} deformation or an I{sup 4} term in the Hamiltonian explicitly. The optimal criteria for observing the phenomenon have been discussed as well.
Date: December 31, 1995
Creator: Zhang, J.Y.; Sun, Y. & Guidry, M.
Partner: UNT Libraries Government Documents Department

Lepton family number violation

Description: At present there is evidence from neutrino oscillation searches that the neutrinos are in fact massive particles and that they mix. If confirmed, this would imply that the conservation of LFN is not exact. Lepton family number violation (LFNV) has been searched for with impressive sensitivities in many processes involving charged leptons. The present experimental limits on some of them (those which the author shall consider here) are shown in Table 1. These stringent limits are not inconsistent with the neutrino oscillation results since, given the experimental bounds on the masses of the known neutrinos and the neutrino mass squared differences required by the oscillation results, the effects of LFNV from neutrino mixing would be too small to be seen elsewhere (see Section 2). The purpose of experiments searching for LFNV involving the charged leptons is to probe the existence of other sources of LFNV. Such sources are present in many extensions of the SM. In this lecture the author shall discuss some of the possibilities, focusing on processes that require muon beams. Other LFNV processes, such as the decays of the kaons and of the {tau}, provide complementary information. In the next Section he shall consider some sources of LFNV that do not require an extension of the gauge group of the SM (the added leptons or Higgs bosons may of course originate from models with extended gauge groups). In Section 3 he discusses LFNV in left-right symmetric models. In Section 4 he considers LFNV in supersymmetric models, first in R-parity conserving supersymmetric grand unified models, and then in the minimal supersymmetric standard model with R-parity violation. The last section is a brief summary of the author`s conclusions.
Date: March 1, 1999
Creator: Herczeg, P.
Partner: UNT Libraries Government Documents Department

Preliminary measurement of time-dependent B{sub d}{sup 0}-B{sub d}{sup 0} mixing using topology and charge selected semi-leptonic B decays

Description: The time dependence of B{sub d}{sup 0}-B{sub d}{sup 0} mixing has been measured using a sample of 150,000 hadronic Z{sup 0} decays collected by the SLD experiment at the SLC between 1993 and 1995. The analysis identifies the semileptonic decays of B mesons with high (p, p{sub t}) leptons and reconstructs the B meson decay length and charge by vertexing the lepton with a partially reconstructed D meson. Vertex charge is used to enrich the selection of neutral over charged B mesons. This method results in a sample of 581 neutral decays with high charge purity. The B candidate is tagged at production with a combined tag that exploits the large polarized b forward-backward asymmetry in conjunction with the opposite hemisphere b jet charge. The final state is tagged by the sign of the high (p, p{sub t}) lepton. From their preliminary analysis the authors find a mass difference between the two B{sub d}{sup 0} mass eigenstates of, {Delta}m{sub d} = 0.452 {+-} 0.074(stat) {+-} 0.049(syst) ps{sup {minus}1}.
Date: July 1, 1996
Partner: UNT Libraries Government Documents Department

Group-Velocity-Matched Three Wave Mixing in Birefringent Crystals

Description: We show that the combination of pulse-front slant, k-vector tilt, and crystal birefringence often permits exact matching of both phase and group velocities in three wave mixing in birefringent crystals. This makes possible more efficient mixing of short light pulses, and it permits efficient mixing of chirped or broad bandwidth light. We analyze this process and present examples. Differences in the group velocities of the three interacting waves in a nonlinear crystal often limits the effective interaction length. For example, in mixing very short pulses, temporal walk off can stretch the pulses in time unless the crystal is very short. Efficient mixing with such short crystals requires high irradiances, but the irradiances are limited by higher order nonlinear effects such as intensity-dependent refractive index and two-photon absorption. Improved matching of the group velocities can alleviate this problem, allowing longer crystal and lower irradiances. Similarly, for high energy pulses, practical limits on crystal apertures mandate temporally stretching the pulses to reduce irradiances. For the resulting chirped pulses, temporal walk off restricts the chirp range unless the group velocities are well matched. In addition to perfectly matching the group velocities of all three waves, it is sometimes useful to match two velocities, such as the signal and idler in parametric amplification, permitting broadband parametric amplification, or to arrange the velocities of two inputs to bracket the generated sum frequency pulse, giving pulse compression under suitable circumstances.
Date: December 12, 2000
Partner: UNT Libraries Government Documents Department

Charm results on CP violation and mixing

Description: The most recent results on CP violation and mixing in the charm system are reviewed as a guide to the future. While no surprising results are reported so far, charm provides a unique window to physics beyond the Standard Model. The results reported here come from four sources, ALEPH at LEP, E791 and FOCUS/E831 at Fermilab, and CLEO II.V at CESR. Results beyond these sources may be expected as a byproduct of B-motivated experiments.
Date: March 14, 2000
Creator: Appel, J.A.
Partner: UNT Libraries Government Documents Department

B{sup +} {r_arrow} D{sup *+}{sub s}{gamma} and B{sup +} {r_arrow} -> D{sup *+}{gamma} as probes of V{sub ub}

Description: The decays B{sup +} {r_arrow} D{sup *+}{sub s}{gamma} and B{sup +} {r_arrow} D{sup *+}{gamma} can be used for an extraction of {vert_bar}V{sub ub}{vert_bar}. When the b and c quarks are nearly degenerate the rate for these modes can be determined in terms of other observed rates, namely B{anti B} mixing and D{sup *} {r_arrow} D{gamma} decay. To this end the authors introduce a novel application of heavy quark and flavor symmetries. Although somewhat unrealistic, this limit provides them with a first estimate of these rates.
Date: February 1, 1999
Creator: Grinstein, Benjamin & Lebed, Richard F.
Partner: UNT Libraries Government Documents Department

Probing new physics in rare charm processes

Description: The possibility of using the charm system to search for new physics is addressed. Phenomena such as D{sup 0} - {bar D}{sup 0} mixing and rare decays of charmed mesons are first examined in the Standard Model to test the present understanding and to serve as benchmarks for signals from new sources. The effects of new physics from various classes of non-standard dynamical models on D{sup 0} - {bar D}{sup 0} mixing are investigated.
Date: September 1, 1994
Creator: Hewett, J. L.
Partner: UNT Libraries Government Documents Department

Solar neutrinos with three flavor mixings

Description: The recent{sup 71}Ga solar neutrino observation is combined with the {sup 37}Cl and Kamiokande-II observations in an analysis for neutrino masses and mixings. The allowed parameter region is found for matter enhanced mixings among all three neutrino flavors. Distortions of the solar neutrino spectrum unique to three flavors are possible and may be observed in continuing and next generation experiments.
Date: December 31, 1992
Creator: Harley, D.; Pantaleone, J. & Kuo, T. K.
Partner: UNT Libraries Government Documents Department

Lepton flavor violation at LEP II and beyond

Description: At present, two fundamental mysteries in particle physics are the origins of electroweak symmetry breaking and the fermion mass matrices. The experimental discovery of superpartners would represent enormous progress in the understanding of electroweak symmetry breaking, but would it also allow progress on the flavor problem? To date, nearly all experimental studies of supersymmetry have ignored the possibility of flavor mixings in the sfermion sector. However, since all superpartners must be given masses, all supersymmetric theories necessarily allow for the possibility of new flavor mixings beyond the standard model. In addition, there are now many supersymmetric theories of flavor, which predict a wide variety of superpartner flavor mixings. In this study, the author examines the possibility of measuring these mixings at LEP II and the Next Linear Collider (NLC). Rare flavor changing processes, such as {mu} {yields} e{gamma}, {tau} {yields} {mu}{gamma}, {tau} {yields} e{gamma}, b {yields} s{gamma}, and neutral meson mixing, already provide important constraints on the sfermion flavor mixings through the virtual effects of superpartners. However, as will be seen below, once superpartners are discovered, it will be possible to probe these mixings much more powerfully by directly observing the change in flavor occurring at the superpartner production and decay vertices.
Date: July 1, 1996
Creator: Feng, J.L.
Partner: UNT Libraries Government Documents Department

Meson-meson scattering: K{anti K}-thresholds and f{sub 0}(980)-a{sub 0}(980) mixing

Description: The authors study the influence of mass splitting between the charged and neutral pions and kaons in the Juelich meson exchange model for {pi}{pi} and {pi}{eta} scattering. The calculations are performed in the particle basis, which permits the use of physical masses for the pseudoscalar mesons and a study of the distinct thresholds associated with the neutral and the charged kaons. Within this model the authors also investigate the isospin violation which arises from the mass splitting and an apparent violation of G-parity in {pi}{pi} scattering which stems from the coupling to the K{anti K} channel. Nonvanishing cross sections for {pi}{pi} {r_arrow} {pi}{sup 0}{eta} indicate a mixing of the f{sub 0}(980) and a{sub 0}(980) states.
Date: September 1, 1996
Creator: Krehl, O.; Rapp, R. & Speth, J.
Partner: UNT Libraries Government Documents Department

Explicit SO(10) supersymmetric grand unified model

Description: A complete set of Higgs and matter superfields is introduced with well-defined SO(10) properties and U(1) x Z{sub 2} x Z{sub 2} family charges from which the Higgs and Yukawa superpotentials are constructed. The Higgs fields solve the doublet-triplet splitting problem, while the structures of the four Dirac fermion mass matrices obtained involve just six effective Yukawa operators. The right-handed Majorana matrix arises from one Higgs field coupling to several pairs of superheavy conjugate neutrino singlets. In terms of 10 input parameters to the mass matrices, the model accurately yields the 20 masses and mixings of the lightest quarks and leptons, as well as the masses of the 3 heavy right-handed neutrinos. The bimaximal atmospheric and solar neutrino vacuum solutions are favored in this simplest version.
Date: June 23, 2000
Creator: Albright, Carl H. & Barr, S. M.
Partner: UNT Libraries Government Documents Department

Mixing-induced CP asymmetries in radiative B decays in and beyond the Standard Model

Description: In the Standard Model (SM) the photon in radiative {anti B}{sup 0} and {anti B}{sub s} decays is predominantly left-handed. Thus, mixing induced CP asymmetries in b {r_arrow} s{gamma} and b {r_arrow} d{gamma} are suppressed by m{sub s}/m{sub b} and m{sub d}/m{sub b}, respectively, and are very small. In many extensions of the SM, such as the left-right symmetric model (LRSM), SU(2)xU(1) models with exotic fermions and SUSY, the amplitude of right-handed photons grows proportional to the virtual heavy fermion mass, which can lead to large asymmetries. As an example, in the LRSM, asymmetries larger than 50% are possible even when radiative decay rate measurements agree with SM predictions.
Date: April 1, 1997
Creator: Gronau, M.; Atwood, D. & Soni, A.
Partner: UNT Libraries Government Documents Department

CP violation and rare decays

Description: After a brief essay on the current state of particle physics and possible approaches to the opportunities that have presented themselves, the author summarizes the contributions to the Third Workshop on Physics and Detectors for DA{Phi}NE that deal with CP Violation and Rare Decays.
Date: January 24, 2000
Creator: Quigg, C.
Partner: UNT Libraries Government Documents Department

Light U(1) gauge boson coupled to baryon number

Description: The authors discuss the phenomenology of a light U(1) gauge boson, {gamma}{sub B}, that couples only to baryon number. Gauging baryon number at high energies can prevent dangerous baryon-number violating operators that may be generated by Planck scale physics. However, they assume at low energies that the new U(1) gauge symmetry is spontaneously broken and that the {gamma}{sub B} mass m{sub B} is smaller than m{sub z}. They show for m{sub {Upsilon}} < m{sub B} < m{sub z} that the {gamma}B coupling {alpha}{sub B} can be as large as {approximately} 0.1 without conflicting with the current experimental constraints. The authors argue that {alpha}{sub B} {approximately} 0.1 is large enough to produce visible collider signatures and that evidence for the {gamma}{sub B} could be hidden in existing LEP data. They show that there are realistic models in which mixing between the {gamma}{sub B} and the electroweak gauge bosons occurs only as a radiative effect and does not lead to conflict with precision electroweak measurements. Such mixing may nevertheless provide a leptonic signal for models of this type at an upgraded Tevatron.
Date: June 1, 1995
Creator: Carone, C.D. & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

B{sub s} mixing via {psi}K*

Description: The decay mode B{sub s} {yields} {psi}K* is suggested as a very good way to measure the B{sub s} mixing parameter x{sub s}. These decays can be gathered using a {psi} {yields} {ell}{sup +}{ell}{sup {minus}} trigger. This final state has a well resolved four track decay vertex, useful for good time resolution and background rejection.
Date: August 1, 1995
Creator: McBride, P. & Stone, S.
Partner: UNT Libraries Government Documents Department

Applications of flavor symmetry to the phenomenology of elementary particles

Description: Some applications of flavor symmetry are examined. Approximate flavor symmetries and their consequences in the MSSM (Minimal Supersymmetric Standard Model) are considered, and found to give natural values for the possible B- and L-violating couplings that are empirically acceptable, except for the case of proton decay. The coupling constants of SU(3) are calculated and used to parameterize the decays of the D mesons in broken flavor SU(3). The resulting couplings are used to estimate the long-distance contributions to D-meson mixing.
Date: May 1, 1995
Creator: Kaeding, T. A.
Partner: UNT Libraries Government Documents Department

Experimental particle physics at the University of Pittsburgh. Progress report, November 1, 1995--October 31, 1996

Description: This report covers the progress on two different tasks, Task A and Task B. Task A focuses on rare and semi-rare decays of {phi} and of the short-lived kaon with emphasis on those aspects needed in preparation for the proposed {Phi}-Factory measurements of CPT violation and {epsilon}{prime}/{epsilon} from the CP-violating decays of the K{sub L}K{sub S} final state. The second aspect of the kaon decay work is participation in the so-called rare kaon decay experiments, E865, at BNL. The major goals of Task B, Fermilab program, are as follows: (1) participation in the analysis of the E706 data taken during the 1990--1991 fixed target run at Fermilab and (2) the continuation of the work with the CDF collaboration particularly the SVX II upgrade. The E706 part of the program involves the completion of publications reporting the results of the 1990--91 data run. The analysis of these data is now mature and physics results are emerging. The CDF program involves a dedicated effort to the design of a silicon vertex detector upgrade, SVX II, to be accomplished by the time Fermilab run II collider run (1999). In addition they are participating in the 1993--1995 collide run Ib and actively analyzing the data from both runs Ia and Ib.
Date: May 1, 1996
Creator: Boudreau, J.F.; Engels, E. Jr.; Shepard, P.F. & Thompson, J.A.
Partner: UNT Libraries Government Documents Department

Heavy flavour physics from top to bottom

Description: We review the status of heavy flavour physics at the Fermilab Tevatron collider by summarizing recent top quark and B physics results from CDF and D0. In particular we discuss the measurement of the top quark mass and top production cross section as well as B meson lifetimes and time dependent B{bar B} mixing results. An outlook of perspectives for top and B physics in Run II starting in 1999 is also given. 38 refs., 23 figs., 8 tabs.
Date: January 1, 1997
Creator: Paulini, M. & Collaborations, CDF and D0
Partner: UNT Libraries Government Documents Department

Lattice gauge theory on a massively parallel computing facility. Final report

Description: This grant provided access to the massively parallel computing facilities at Oak Ridge National Laboratory for the study of lattice gauge theory. The major project was a calculation of the weak decay constants of pseudoscalar mesons with one light and one heavy quark. A number of these constants have not yet been measured, so the calculations constituted a set of predictions which will be tested by future experiments. More importantly, f{sub B} and f{sub B{sub s}}, the decay constants of the B and B{sub s} mesons, are crucial inputs for extracting information regarding the CKM matrix element V{sub td} from experimental measurements of B-{anti B} mixing, and future measurements of B{sub s}-{anti B}{sub s} mixing planned for the B-factory currently under construction at the Stanford Linear Accelerator Center. V{sub td} is one of the least well determined parameters of the Standard Model of High Energy Physics. It does not appear likely that F{sub B} and f{sub B{sub s}} will be measured experimentally in the near future, so lattice calculations such as this will play a crucial role in extracting information about the Standard Model from the B-factory experiments. The author has carried out the most accurate calculations of the heavy-light decay constants to date within the quenched approximation, that is ignoring the effects of sea quarks. Furthermore, his was the only group to have estimated the errors in the decay constants associated with the quenched approximation.
Date: August 7, 1998
Creator: Sugar, R.
Partner: UNT Libraries Government Documents Department

b{bar b} production correlations, b{bar b} mixing and {epsilon}{sub B} at CDF

Description: We present preliminary measurements of b{bar b} production correlations, the average B{bar B} mixing, and a limit on the CP violating parameter {epsilon}{sub b} using dimuon events from the dual semileptonic decay of b{bar b}. Data used in this analysis was taken during the 1992--1993 CDF run of the Fermilab Tevatron collider with an integrated luminosity of 17.4 {plus_minus} 0.6 pb{sup {minus}1}. The results on b{bar b} production correlations are compared to predictions of next-to-leading order QCD.
Date: July 1, 1995
Creator: Abe, F.
Partner: UNT Libraries Government Documents Department