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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,063 records · Page 59
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DOE OSTI2011

Resonant formation of {Lambda}(1405) by stopped-K{sup -} absorption in the deuteron

To solve the current debate on the position of the quasibound K{sup -}p state, namely, ''{Lambda}(1405) or {Lambda}*(1420),'' we propose to measure the T{sub 21}=T{sub {Sigma}{pi}<-K}-bar{sub N} {Sigma}{pi} invariant-mass spectrum in stopped-K{sup -} absorption in the deuteron, since the spectrum, reflecting the soft and hard deuteron momentum distribution, is expected to have a narrow quasifree component with an upper edge of M=1430 MeV/c{sup 2}, followed by a significant 'high-momentum' tail toward the lower mass region, where a resonant formation of {Lambda}(1405) of any mass and width in a wide range will be clearly revealed. We introduce a 'deviation' spectrum as defined by DEV = OBS (observed or calculated) / QF (nonresonant quasifree), in which the resonant component can be seen as an isolated peak free from the QF shape.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Hyperfine splitting and the Zeeman effect in holographic heavy-light mesons

We inspect the mass spectrum of heavy-light mesons in deformed N=2 super Yang-Mills theory using the AdS/CFT correspondence. We demonstrate how some of the degeneracies of the supersymmetric meson spectrum can be removed upon breaking the supersymmetry, thus leading to the emergence of a hyperfine structure. The explicit SUSY breaking scenarios we consider involve on the one hand, tilting one of the two fundamental D7-branes inside the internal R{sup 6} space, and on the other hand, applying an external magnetic field on the (untilted) branes. The latter scenario leads to the well-known Zeeman effect, which we inspect for both weak and strong magnetic fields.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Light and heavy mesons in a soft-wall holographic approach

We study the mass spectrum and decay constants of light and heavy mesons in a soft-wall holographic approach, using the correspondence of string theory in Anti-de Sitter space and conformal field theory in physical space-time.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Evidence for a conformal phase in SU(N) gauge theories

We discuss the existence of a conformal phase in SU(N) gauge theories in four dimensions. In this lattice study, we explore the model in the bare parameter space, varying the lattice coupling and bare mass. Simulations are carried out with three colors and 12 flavors of dynamical staggered fermions in the fundamental representation. The analysis of the chiral order parameter and the mass spectrum of the theory indicates the restoration of chiral symmetry at zero temperature and the presence of a Coulomb-like phase, depicting a scenario compatible with the existence of an infrared stable fixed point at nonzero coupling. Our analysis supports the conclusion that the onset of the conformal window for QCD-like theories is smaller than N{sub f}=12, before the loss of asymptotic freedom at 16 and 1/2 flavors. We discuss open questions and future directions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Higgs boson sector of the next-to-minimal supersymmetric standard model with CP violation

We perform a comprehensive study of the Higgs sector in the framework of the next-to-minimal supersymmetric standard model with CP-violating parameters in the superpotential and in the soft-supersymmetry-breaking sector. Since the CP is no longer a good symmetry, the two CP-odd and the three CP-even Higgs bosons of the next-to-minimal supersymmetric standard model in the CP-conserving limit will mix. We show explicitly how the mass spectrum and couplings to gauge bosons of the various Higgs bosons change when the CP-violating phases take on nonzero values. We include full one-loop and the logarithmically enhanced two-loop effects employing the renormalization-group (RG) improved approach. In addition, the LEP limits, the global minimum condition, and the positivity of the square of the Higgs-boson mass have been imposed. We demonstrate the effects on the Higgs-mass spectrum and the couplings to gauge bosons with and without the RG-improved corrections. Substantial modifications to the allowed parameter space happen because of the changes to the Higgs-boson spectrum and their couplings with the RG-improved corrections. Finally, we calculate the mass spectrum and couplings of the few selected scenarios and compare to the previous results in literature where possible; in particular, we illustrate a scenario motivated by electroweak baryogenesis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Type II seesaw dominance in SO(10)

Grand unified theories where the neutrino mass is given by type II seesaw have the potential to provide interesting connections between the neutrino and charged fermion sectors. We explore the possibility of having a dominant type II seesaw contribution in supersymmetric SO(10). We show that this can be achieved in the model where symmetry breaking is triggered by 54 and 45 dimensional representations, without the need for additional fields other than those already required to have a realistic charged fermion mass spectrum. Physical consequences, such as the implementation of the Bajc, Senjanovic, and Vissani mechanism, the possibility of the fields responsible for type II seesaw dominance being messengers of supersymmetry breaking, and the realization of baryo and leptogenesis in these theories, are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Confronting generalized hidden local symmetry chiral model with the ALEPH data on the decay {tau}{sup -{yields}{pi}+{pi}-{pi}-{nu}}{sub {tau}}

The generalized hidden local symmetry (GHLS) model is the chiral model of pseudoscalar, vector, and axial vector mesons and their interactions. It contains also the couplings of strongly interacting particles with electroweak gauge bosons. Here, GHLS model is confronted with the ALEPH data on the decay {tau}{sup -{yields}{pi}-{pi}-{pi}+{nu}}{sub {tau}}. It is shown that the invariant mass spectrum of final pions in this decay calculated in GHLS framework with the single a{sub 1}(1260) resonance disagrees with the experimental data at any reasonable number of free GHLS parameters. Two modifications of GHLS model based on inclusion of two additional heavier axial vector mesons are studied. One of them, which gives a good description of the ALEPH data with all the parameters kept free, is shown to result in very large {Gamma}{sub a{sub 1}{sup {+-}}{sub {yields}{pi}}{sup {+-}}{sub {gamma}}}partial width. The other scheme with the GHLS parameters fixed in a way that the universality is preserved and the observed central value of {Gamma}{sub a{sub 1}{sup {+-}}{sub {yields}{pi}}{sup {+-}}{sub {gamma}}}is reached, which results in a good description of the three pion spectrum in {tau}{sup -{yields}{pi}+{pi}-{pi}-{nu}}{sub {tau}}decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Phenomenological implications of supersymmetric family nonuniversal U(1){sup '} models

We construct a class of anomaly-free supersymmetric U(1){sup '} models that are characterized by family nonuniversal U(1){sup '} charges motivated from E{sub 6} embeddings. The family nonuniversality arises from an interchange of the standard roles of the two SU(5) 5{sup *} representations within the 27 of E{sub 6} for the third generation. We analyze U(1){sup '} and electroweak symmetry breaking and present the particle mass spectrum. The models, which include additional Higgs multiplets and exotic quarks at the TeV scale, result in specific patterns of flavor-changing neutral currents in the b{yields}s transitions that can accommodate the presently observed deviations in this sector from the standard model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Minimal supersymmetric SU(5) and gauge coupling unification at three loops

We consider the relations between the gauge couplings at the electroweak scale and the high scale where unification of the three gauge couplings is expected. Threshold corrections are incorporated both at the supersymmetric and at the grand unified scale and, where available, three-loop running and two-loop decoupling are employed. We study the impact of the current experimental uncertainties of the coupling constants and the supersymmetric mass spectrum on the prediction of the superheavy masses within the so-called minimal supersymmetric SU(5). As a main result of the three-loop analysis we confirm that minimal supersymmetric SU(5) cannot be ruled out by the current experimental data on proton decay rates.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Bulk antisymmetric tensor fields coupled to a dilaton in a Randall-Sundrum model

A string-inspired three-form-dilaton-gravity model is studied in a Randall-Sundrum brane world scenario. As expected, the rank-3 antisymmetric field is exponentially suppressed. For each mass level, the mass spectrum is bigger than the one for the Kalb-Ramond field. The coupling between the dilaton and the massless Kaluza-Klein mode of the three-form is calculated, and the coupling constant of the cubic interactions is obtained numerically. This coupling are of the order of Tev{sup -1}; therefore, there exists a possibility to find some signal of it at Tev scale.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Measurement of the WW+WZ production cross section using a matrix element technique in lepton+jets events

We present a measurement of the WW+WZ production cross section observed in a final state consisting of an identified electron or muon, two jets, and missing transverse energy. The measurement is carried out in a data sample corresponding to up to 4.6 fb{sup -1} of integrated luminosity at {radical}(s)=1.96 TeV collected by the CDF II detector. Matrix element calculations are used to separate the diboson signal from the large backgrounds. The WW+WZ cross section is measured to be 17.4{+-}3.3 pb in agreement with standard model predictions. A fit to the dijet invariant mass spectrum yields a compatible cross section measurement.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Form invariance and symmetry in the neutrino mass matrix

We present the general form of the unitary matrices keeping invariant the Majorana neutrino mass matrix of specific texture suitable for explaining oscillation data. In the case of the tri-bimaximal pattern with two degenerate masses, we give a specific realization of the underlying U(1) symmetry which can be uplifted to a symmetry in a complete theory including charged leptons. For this, we present a model with three light SM-like Higgs doublets and one heavy Higgs triplet and find that one can accommodate the hierarchy of the charged-lepton masses. The lepton mass spectrum can also be achieved in another model extending the SM with three SM-singlet scalars transforming nontrivially under the flavor symmetry. We discuss how such a model has room for generating enough baryon asymmetry through leptogenesis in the framework of type-I and -II seesaw mechanisms.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Baryon magnetic moments in alternate 1/N{sub c} expansions

Recent work shows not only the necessity of a 1/N{sub c} expansion to explain the observed mass spectrum of the lightest baryons, but also that at least two distinct large N{sub c} expansions, in which quarks transform under either the color-fundamental or the two-index antisymmetric representation of SU(N{sub c}), work comparably well. Here we show that the baryon magnetic moments do not support this ambivalence; they strongly prefer the color-fundamental 1/N{sub c} expansion, providing experimental evidence that nature decisively distinguishes among 1/N{sub c} expansions for this observable.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Lower bounds on the smallest lepton mixing angle

We give minimal values for the smallest lepton mixing parameter |U{sub e3}|, applying 2-loop renormalization group equations in an effective theory approach. This is relevant in scenarios that predict an inverted neutrino mass spectrum with the smallest mass and |U{sub e3}| being zero at tree level, a situation known to be preserved at 1-loop order. At 2-loop, |U{sub e3}| is generated at a level of 10{sup -12}-10{sup -14}. Such small values are of interest in supernova physics. Corresponding limits for the normal mass ordering are several orders of magnitude larger. Our results show that |U{sub e3}| can in general be expected to be nonzero.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Neutrino masses and mixing from S{sub 4} flavor twisting

We discuss a neutrino mass model based on the S{sub 4} discrete symmetry where the symmetry breaking is triggered by the boundary conditions of the bulk right-handed neutrino in the fifth spacial dimension. The three generations of the left-handed lepton doublets and the right-handed neutrinos are assigned to be the triplets of S{sub 4}. The magnitudes of the lepton mixing angles, especially the reactor angle, are related to the neutrino mass patterns, and the model will be tested in future neutrino experiments, e.g., an early discovery of the reactor angle favors the normal hierarchy. For the inverted hierarchy, the lepton mixing is predicted to be almost the tribimaximal mixing. The size of the extra dimension has a connection to the possible mass spectrum; a small (large) volume corresponds to the normal (inverted) mass hierarchy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Minimal flipped SO(10) x U(1) supersymmetric Higgs model

We investigate the conditions on the Higgs sector that allow supersymmetric SO(10) grand unified theories to break spontaneously to the standard electroweak model at the renormalizable level. If one considers Higgs representations of dimension up to the adjoint, a supersymmetric standard model vacuum requires, in most cases, the presence of nonrenormalizable operators. The active role of Planck-induced nonrenormalizable operators in the breaking of the gauge symmetry introduces a hierarchy in the mass spectrum at the grand unified theory scale that may be an issue for gauge unification and proton decay. We show that the minimal Higgs scenario that allows for a renormalizable breaking to the standard model is obtained by considering flipped SO(10) x U(1) with one adjoint (45{sub H}) and two pairs of 16{sub H}+16{sub H} Higgs representations. We consider a nonanomalous matter content and discuss the embedding of the model in an E{sub 6} grand unified scenario just above the flipped SO(10) scale.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Quarks in supersymmetry with gauge coupling unification

I investigate the phenomenology of supersymmetric models with extra vectorlike supermultiplets that couple to the standard model gauge fields and transform as the fundamental representation of a new confining non-Abelian gauge interaction. If perturbative gauge coupling unification is to be maintained, the new group can be SU(2), SU(3), or SO(3). The impact on the sparticle mass spectrum is explored, with particular attention to the gaugino mass dominated limit in which the supersymmetric flavor problem is naturally solved. The new confinement length scale is astronomical for SO(3), so the new particles are essentially free. For the SU(2) and SU(3) cases, the new vectorlike fermions are quirks; pair production at colliders yields quirk-antiquirk states bound by stable flux tubes that are microscopic but long compared to the new confinement scale. I study the reach of the Tevatron and LHC for the optimistic case that in a significant fraction of events the quirk-antiquirk bound state will lose most of its energy before annihilating as quirkonium.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗