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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2010

Heavy quark potentials derived from lattice QCD

We compute the heavy quark potentials including relativistic corrections by using lattice QCD simulations within the quenched approximation. These results are important nonperturbative inputs of an effective field theory called potential nonrelativistic QCD, which serves for the systematic study of heavy quarkonia. Utilizing the multilevel algorithm and the transfer matrix theory, we determine the potentials at the distances ranged from 0.25 to 1.2 fm. We observe long-range nonperturbative contributions to the potentials as well as a reasonable scaling behavior with respect to the change of lattice spacing.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Monotops at the LHC

We explore scenarios where top quarks may be produced singly in association with missing energy, a very distinctive signature, which, in analogy with monojets, we dub monotops. We find that monotops can be produced in a variety of modes, typically characterized by baryon number-violating or flavorchanging neutral interactions. We build a simplified model that encompasses all the possible (tree-level) production mechanisms and study the LHC sensitiveness to a few representative scenarios by considering fully hadronic top decays. We find that constraints on such exotic models can already be set with 1 fb{sup -1} of integrated luminosity collected at {radical}(s)=7 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Effects of dynamical masses of gluons and quarks on hadronic B decays

We study hadronic annihilation decays of B mesons within the perturbative QCD at collinear approximation. The regulation of endpoint divergences is performed with the help of an infrared finite gluon propagator characterized by a non-perturbative dynamical gluon mass. The divergences at twist-3 are regulated by a dynamical quark mass. Our results fit quite well the existent data of B{sup 0}{yields}D{sub s}{sup -}K{sup +} and B{sup 0}{yields}D{sub s}{sup -*}K{sup +} for the expected range of dynamical gluon masses. We also make predictions for the rare decays B{sup 0}{yields}K{sup -}K{sup +}, B{sub s}{sup 0}{yields}{pi}{sup -}{pi}{sup +}, {pi}{sup 0}{pi}{sup 0}, B{sup +}{yields}D{sub s}{sup (*)+}K-bar{sup 0}, B{sup 0}{yields}D{sub s}{sup {+-}(*)}K{sup {+-}} and B{sub s}{sup 0}{yields}D{sup {+-}(*)}{pi}{sup {+-}}, D{sup 0}{pi}{sup 0}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Studies of charmed hadronic B decays with the early LHCb data and prospects for {gamma} measurements

We present the first studies of decays of the type B{yields}DX, where D represents a charmed meson (D{sup 0}, D{sup (*)+}, or D{sub s}) from the LHCb experiment at CERN. Our studies use data accumulated during the 2010 run of the LHC. This work represents the first steps on a programme towards a precision measurement of the angle {gamma} of the CKM Unitarity Triangle. The prospects for this {gamma} measurement will be reviewed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Charmless hadronic B decays into a tensor meson

Two-body charmless hadronic B decays involving a tensor meson in the final state are studied within the framework of QCD factorization (QCDF). Because of the G-parity of the tensor meson, both the chiral-even and chiral-odd two-parton light-cone distribution amplitudes of the tensor meson are antisymmetric under the interchange of momentum fractions of the quark and antiquark in the SU(3) limit. Our main results are: (i) In the naieve factorization approach, the decays such as B{sup -}{yields}K{sub 2}*{sup 0}{pi}{sup -} and B{sup 0}{yields}K{sub 2}*{sup -}{pi}{sup +} with a tensor meson emitted are prohibited because a tensor meson cannot be created from the local V-A or tensor current. Nevertheless, the decays receive nonfactorizable contributions in QCDF from vertex, penguin and hard spectator corrections. The experimental observation of B{sup -}{yields}K{sub 2}*{sup 0}{pi}{sup -} indicates the importance of nonfactorizable effects. (ii) For penguin-dominated B{yields}TP and TV decays, the predicted rates in naieve factorization are usually too small by 1 to 2 orders of magnitude. In QCDF, they are enhanced by power corrections from penguin annihilation and nonfactorizable contributions. (iii) The dominant penguin contributions to B{yields}K{sub 2}*{eta}{sup (')} arise from the processes: (a) b{yields}sss{yields}s{eta}{sub s} and (b) b{yields}sqq{yields}qK{sub 2}* with {eta}{sub q}=(uu+dd)/{radical}(2) and {eta}{sub s}=ss. The interference, constructive for K{sub 2}*{eta}{sup '} and destructive for K{sub 2}*{eta}, explains why {Gamma}(B{yields}K{sub 2}*{eta}{sup '})>>{Gamma}(B{yields}K{sub 2}*{eta}). (iv) We use the measured rates of B{yields}K{sub 2}*({omega},{phi}) to extract the penguin-annihilation parameters {rho}{sub A}{sup TV} and {rho}{sub A}{sup VT} and the observed longitudinal polarization fractions f{sub L}(K{sub 2}*{omega}) and f{sub L}(K{sub 2}*{phi}) to fix the phases {phi}{sub A}{sup VT} and {phi}{sub A}{sup TV}. (v) The experimental observation that f{sub T}/f{sub L}<<1 for B{yields}K{sub 2}*(1430){phi}, whereas f{sub T}/f{sub L}{approx}1 for B{yields}K{sub 2}*(1430){omega} with f{sub T} being the transverse polarization fraction, can be accommodated in QCDF, but it cannot be dynamically explained at first place. For penguin-dominated B{yields}TV decays, we find f{sub L}(K{sub 2}*{rho}){approx}f{sub L}(K{sub 2}*{omega}){approx}0.65, whereas f{sub L}(K*f{sub 2}){approx}0.93. It will be of great interest to measure f{sub L} for these modes to test QCDF. Theoretically, transverse polarization is expected to be small in tree-dominated B{yields}TV decays except for the a{sub 2}{sup -}{rho}{sup 0}, a{sub 2}{sup -}{rho}{sup +}, K{sub 2}*{sup 0}K*{sup -} and K{sub 2}*{sup 0}K*{sup 0} modes. (vi) For tree-dominated decays, their rates are usually very small except for the a{sub 2}{sup 0}({pi}{sup -},{rho}{sup -}), a{sub 2}{sup +}({pi}{sup -},{rho}{sup -}) and f{sub 2}({pi}{sup -},{rho}{sup -}) modes with branching fractions of order 10{sup -6} or even larger.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Studying the decay mode of the J/{psi} into a vector meson and a tensor resonance

The decay mode of the J/{psi} into a vector meson and a tensor resonance is presented. The tensor resonances are considered as dynamically generated states from the vector meson-vector meson interaction provided by the hidden gauge formalism upon unitarization in coupled channels. The couplings of the resonances to the pairs of vector-vector building blocks were evaluated in a previous work. Four ratios of partial decay widths are evaluated using one parameter and compared with experimental data including BES collaboration. The theoretical results are compatible with present experimental data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Bethe-Salpeter equation for doubly heavy baryons in the covariant instantaneous approximation

In the heavy quark limit, a doubly heavy baryon is regarded as composed of a heavy diquark and a light quark. We establish the Bethe-Salpeter equations for the heavy diquarks and the doubly heavy baryons, respectively, to leading order in a 1/m{sub Q} expansion. The Bethe-Salpeter equations are solved numerically under the covariant instantaneous approximation with the kernels containing scalar confinement and one-gluon-exchange terms. The masses for the heavy diquarks and the doubly heavy baryons are obtained, and the nonleptonic decay widths for the doubly heavy baryons emitting a pseudoscalar meson are calculated within the model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Bulk viscosity of spin-one color superconducting strange quark matter

The bulk viscosity in spin-one color superconducting strange quark matter is calculated by taking into account the interplay between the nonleptonic and semileptonic week processes. In agreement with previous studies, it is found that the inclusion of the semileptonic processes may result in non-negligible corrections to the bulk viscosity in a narrow window of temperatures. The effect is generally more pronounced for pulsars with longer periods. Compared to the normal phase, however, this effect due to the semileptonic processes is less pronounced in spin-one color superconductors. Assuming that the critical temperature of the phase transition is much larger than 40 keV, the main effect of spin-one color superconductivity in a wide range of temperatures is an overall increase of the bulk viscosity with respect to the normal phase. The corresponding enhancement factor reaches up to about 9 in the polar and A phases, about 25 in the planar phase, and about 29 in the color-spin-locked (CSL) phase. This factor is determined by the suppression of the nonleptonic rate in color superconducting matter and, therefore, may be even larger if all quark quasiparticles happen to be gapped.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Charmonium dissociation in matter: perspectives from CERN to JLab

The J/{Psi}-meson dissociation in nuclear matter remains one of the most surprising problems in physics. In 2000 the NA50 Collaboration at CERN reported anomalous results on J/{Psi} absorption that was considered as evidence of Quark-Gluon Plasma formation. On the other hand, there may be other mechanisms which produce an increase in J/{Psi} absorption in a hot dense medium due to the modification of the charm mesons. Our detailed calculations were one of the first indications that the CERN data can indeed be well explained by a mechanism different from QGP formation. For further clarification we proposed to study the modification of charm in nuclei through antiproton annihilation, which is now part of the PANDA project at FAIR GSI. The experiment on charmonium dissociation in nuclei is under discussion at JLab as part of its 12 GeV upgrade.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Hadronic spectra in AdS/QCD correspondence

We present an holographical soft wall model which is able to reproduce Regge spectra for hadrons with an arbitrary number of constituents. The model includes the anomalous dimension of operators that create hadrons, together with a dilaton, whose form is suggested by Einstein's equations and the AdS metric.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Nonleptonic two-body decays of charmed mesons

Nonleptonic decays of charmed mesons into two pseudoscalar mesons or one pseudoscalar meson and one vector meson are studied on the basis of a generalized factorization method considering the resonance effects in the pole model for the annihilation contributions. Large strong phases between different topological diagrams are considered in this work, simply taking the phase in the coefficients a{sub i}. We find that the annihilation-type contributions calculated in the pole model are large in both of the PP and PV modes, which make our numerical results agree with the experimental data better than those previous calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Charm form factors in hadronic interactions

We calculate the form factors and the coupling constants in vertices with charm mesons, such as {rho}D*D*, in the framework of QCD sum rules. We first discuss the applications of these form factors in heavy ion collisions and in B decays. We then present an introduction to the method of QCD sum rules and describe how to work with the three-point function. We give special attention to the procedure employed to extrapolate results obtained in the deep euclidean region to the poles of the particles, located in the time-like region. Finally we present a table of ready-to-use parametrizations of all the form factors, which are relevant for the processes mentioned in the introduction. We also give the coupling constants.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Tests of factorization and SU(3) relations in B decays into heavy-light final states

Using data from the B factories and the Tevatron, we perform tests of how well nonleptonic B decays of the kind B{yields}D{sub (s)}{sup (*)}P, where P is a pion or kaon, are described within the factorization framework. We find that factorization works well--as is theoretically expected--for color-allowed, tree-diagram-like topologies. Moreover, also exchange topologies, which have a nonfactorizable character, do not show any anomalous behavior. We discuss also isospin triangles between the B{yields}D{sup (*)}{pi} decay amplitudes, and determine the corresponding amplitudes in the complex plane, which show a significant enhancement of the color-suppressed tree contribution with respect to the factorization picture. Using data for B{yields}D{sup (*)}K decays, we determine SU(3)-breaking effects and cannot resolve any nonfactorizable SU(3)-breaking corrections larger than {approx}5%. In view of these results, we point out that a comparison between the B{sub d}{sup 0}{yields}D{sup +}{pi}{sup -} and B{sub s}{sup 0}{yields}D{sub s}{sup +}{pi}{sup -} decays offers an interesting new determination of f{sub d}/f{sub s}. Using CDF data, we obtain the most precise value of this ratio at CDF, and discuss the prospects for a corresponding measurement at LHCb.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Transition nucleon resonance electrocouplings from CLAS data on {pi}{sup +}{pi}{sup -}p electroproduction off protons

Electrocouplings of excited proton states with masses less than 1.8 GeV were determined for the first time from the CLAS data on {pi}{sup +}{pi}{sup -}p electroproduction at photon virtualities Q{sup 2}<1.5 GeV{sup 2}. Electrocouplings were obtained from a combined fit of all available observables within the framework of a phenomenological reaction model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗