Search NASA⌕ Search

SEARCH · Search NASA

Results for “COMPOSITE MODELS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,639 records · Page 91
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Charm quark system at the physical point of 2+1 flavor lattice QCD

We investigate the charm quark system using the relativistic heavy quark action on 2+1 flavor PACS-CS configurations previously generated on 32{sup 3}x64 lattice. The dynamical up, down, and strange quark masses are set to the physical values by using the technique of reweighting to shift the quark-hopping parameters from the values employed in the configuration generation. At the physical point, the lattice spacing equals a{sup -1}=2.194(10) GeV and the spatial extent L=2.88(1) fm. The charm quark mass is determined by the spin-averaged mass of the 1S charmonium state, from which we obtain m{sub charm}{sup MS}({mu}=m{sub charm}{sup MS})=1.260(1)(6)(35) GeV, where the errors are due to our statistics, scale determination and renormalization factor. An additional systematic error from the heavy quark is of order {alpha}{sub s}{sup 2}f(m{sub Q}a)(a{Lambda}{sub QCD}), f(m{sub Q}a)(a{Lambda}{sub QCD}){sup 2}, which are estimated to be a percent level if the factor f(m{sub Q}a) analytic in m{sub Q}a is of order unity. Our results for the charmed and charmed-strange meson decay constants are f{sub D}=226(6)(1)(5) MeV, f{sub D{sub s}}=257(2)(1)(5) MeV, again up to the heavy quark errors of order {alpha}{sub s}{sup 2}f(m{sub Q}a)(a{Lambda}{sub QCD}), f(m{sub Q}a)(a{Lambda}{sub QCD}){sup 2}. Combined with the CLEO values for the leptonic decay widths, these values yield |V{sub cd}|=0.205(6)(1)(5)(9), |V{sub cs}|=1.00(1)(1)(3)(3), where the last error is because of the experimental uncertainty of the decay widths.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Dirac and Pauli form factors from lattice QCD

We present a comprehensive analysis of the electromagnetic form factors of the nucleon from a lattice simulation with two flavors of dynamical O(a)-improved Wilson fermions. A key feature of our calculation is that we make use of an extensive ensemble of lattice gauge field configurations with four different lattice spacings, multiple volumes, and pion masses down to m{sub {pi}{approx}1}80 MeV. We find that by employing Kelly-inspired parametrizations for the Q{sup 2} dependence of the form factors, we are able to obtain stable fits over our complete ensemble. Dirac and Pauli radii and the anomalous magnetic moments of the nucleon are extracted and results at light quark masses provide evidence for chiral nonanalytic behavior in these fundamental observables.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Gauge mediation to effective supersymmetry through U(1)s with a dynamical supersymmetry breaking, and string compactification

We investigate the possibility of U(1){sup '} mediation, leading to an effective SUSY where the first two family sfermions are above 100 TeV but the third family sfermions and the Higgs doublets are in the TeV region (or the light stop (t-tilde{sub l}) case). The U(1)' gaugino, Zprimino (Z'-ino), needs not to be at a TeV scale, but needs to be somewhat lighter than the messenger scale. We consider two cases, one the mediation is only through U(1){sup '} and the other through U(1)' and the electroweak hypercharge U(1){sub Y}. In the SUSY field theory framework, we calculate the superpartner mass spectra for these two cases. We also point out that the particle species needed for these mechanisms are already obtained from a Z{sub 12-I} orbifold compactification.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Back-to-back pair correlation of Majorana neutrinos with transit magnetic moments

The pair production of Majorana neutrinos with transit magnetic moments from the annihilation of charged particles in colliding experiments is discussed using the Pauli interaction, through which the neutral neutrinos with magnetic moments can be probed by the photon. The pair of neutrinos with different flavors are produced due to the transit magnetic moment coupling. We discuss the correlations of flavors in pairs produced back-to-back in the center of the mass frame, where the angular distribution peaks at {theta}={pi}/2 with respect to the beam direction. We demonstrate that the flavor mixing angle can be inferred by measuring the flavor correlation in pairs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

String or branelike solutions in four-dimensional Einstein gravity in the presence of a cosmological constant

We investigate string or branelike solutions for four-dimensional vacuum Einstein equations in the presence of a cosmological constant. For the case of negative cosmological constant, the Banados-Teitelboim-Zanelli black string is the only warped stringlike solution. The general solutions for nonwarped branelike configurations are found and they are characterized by the Arnowitt-Deser-Misner mass density and two tensions. Interestingly, the sum of these tensions is equal to the minus of the mass density. Other than the well-known black string and soliton spacetimes, all the static solutions possess naked singularities. The time-dependent solutions can be regarded as the anti-de Sitter extension of the well-known Kasner solutions. The speciality of those static regular solutions and the implication of singular solutions are also discussed in the context of cylindrical matter collapse. For the case of positive cosmological constant, the Kasner-de Sitter spacetime appears as time-dependent solutions and all static solutions are found to be naked singular.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Neutrino spectral split in core-collapse supernovae: A magnetic resonance phenomenon

A variety of neutrino flavor conversion phenomena occur in core-collapse supernova, due to the large neutrino density close to the neutrinosphere, and the importance of the neutrino-neutrino interaction. Three different regimes have been identified so far, usually called the synchronization, the bipolar oscillations, and the spectral split. Using the formalism of polarization vectors, within two flavors, we focus on the spectral split phenomenon and we show for the first time that the physical mechanism underlying the neutrino spectral split is a magnetic resonance phenomenon. In particular, we show that the precession frequencies fulfill the magnetic resonance conditions. Our numerical calculations show that the neutrino energies and the location at which the resonance takes place in the supernova coincide well with the neutrino energies at which a spectral swap occurs. The corresponding adiabaticity parameters present spikes at the resonance location.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Some results on vector and tensor meson mixing in a generalized QCD-like theory

We present results for the mixing of quark flavor eigenstates to form low-lying vector and tensor meson mass eigenstates in a generalized QCD-like theory with l massless or light, degenerate quarks and one quark of substantial mass, m{sub Q}. We show that as m{sub Q}/{Lambda} gets large, where {Lambda} is the confinement scale, the angle governing this mixing approaches arctan(1/{radical}(l)). We give a generalization of the Gell-Mann Okubo mass relation for this theory. A comparison of the l=2 results with data on {omega}-{phi} and f{sub 2}(1275)-f{sub 2}{sup '}(1525) mixing is included.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Inclusive B-meson production at the LHC in the general-mass variable-flavor-number scheme

We calculate the next-to-leading-order cross section for the inclusive production of B mesons in pp collisions in the general-mass variable-flavor-number scheme, an approach that takes into account the finite mass of the b quarks. We use realistic evolved nonperturbative fragmentation functions obtained from fits to e{sup +}e{sup -} data and compare our results for the transverse-momentum and rapidity distributions at a center-of-mass energy of 7 TeV with recent data from the CMS Collaboration at the CERN LHC. We find good agreement, in particular, at large values of p{sub T}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

{rho} meson decay in 2+1 flavor lattice QCD

We perform a lattice QCD study of the {rho} meson decay from the N{sub f}=2+1 full QCD configurations generated with a renormalization group improved gauge action and a nonperturbatively O(a)-improved Wilson fermion action. The resonance parameters, the effective {rho}{yields}{pi}{pi} coupling constant and the resonance mass, are estimated from the P-wave scattering phase shift for the isospin I=1 two-pion system. The finite size formulas are employed to calculate the phase shift from the energy on the lattice. Our calculations are carried out at two quark masses, m{sub {pi}=}410 MeV (m{sub {pi}/}m{sub {rho}=}0.46) and m{sub {pi}=}300 MeV (m{sub {pi}/}m{sub {rho}=}0.35), on a 32{sup 3}x64 (La=2.9 fm) lattice at the lattice spacing a=0.091 fm. We compare our results at these two quark masses with those given in the previous works using N{sub f}=2 full QCD configurations and the experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Charmonium spectroscopy and mixing with light quark and open charm states from n{sub F}=2 lattice QCD

We study the charmonium spectrum including higher spin and gluonic excitations. We determine an upper limit on the mixing of the {eta}{sub c} ground state with light pseudoscalar flavor-singlet mesons and investigate the mixing of charmonia near open charm thresholds with pairs of (excited) D and D mesons. For charm and light valence quarks and n{sub F}=2 sea quarks, we employ the nonperturbatively improved Sheikholeslami-Wohlert (clover) action. Excited states are accessed using the variational technique, starting from a basis of suitably optimized operators. For some aspects of this study, the use of improved stochastic all-to-all propagators was essential.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Measurement of branching fractions for ψ ( 3686 ) → γ η ' , γ η , and γ π 0

In this paper, using a data sample of 448 x 10 6 ψ(3686) events collected with the BESIII detector operating at the BEPCII storage ring, the decays ψ(3686) → γη and ψ(3686) → γπ 0 are observed with a statistical significance of 7.3σ and 6.7σ, respectively. The branching fractions are measured to be β(ψ(3686) → γη) = (0.85 ± 0.18 ± 0.05) x 10 -6 and β(ψ(3686) → γπ 0 ) = (0.95 ± 0.16 ± 0.05) x 10 -6 . Finally, in addition, we measure the branching fraction of ψ(3686) → γη' to be β(ψ(3686) → γη') = (125.1 ± 2.2 ± 6.2) x 10 -6 , which represents an improvement of precision over previous results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Competing forces in five-dimensional fermion condensation

We study fermion condensation in the Randall-Sundrum background as a setting for composite Higgs models. We formalize the computation of the Coleman-Weinberg potential and present a simple, general formula. Using this tool, we study the competition of fermion multiplets with different boundary conditions, to find conditions for creating a little hierarchy with the Higgs field expectation value much smaller than the intrinsic Randall-Sundrum mass scale.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗