Search NASA⌕ Search

SEARCH · Search NASA

Results for “PSEUDOSCALARS”

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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Model-independent determination of the axial mass parameter in quasielastic neutrino-nucleon scattering

Quasielastic neutrino-nucleon scattering is a basic signal process for neutrino oscillation studies. At accelerator energies, the corresponding cross section is subject to significant uncertainty due to the poorly constrained axial-vector form factor of the nucleon. A model-independent description of the axial-vector form factor is presented. Data from the MiniBooNE experiment for quasielastic neutrino scattering on {sup 12}C are analyzed under the assumption of a definite nuclear model. The value of the axial mass parameter, m{sub A}=0.85{sub -0.07}{sup +0.22}{+-}0.09 GeV, is found to differ significantly from extractions based on traditional form factor models. Implications for future neutrino scattering and pion electroproduction measurements are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Revisit the radiative decays of J/{psi} and {psi}{sup '}{yields}{gamma}{eta}{sub c}({gamma}{eta}{sub c}{sup '})

With the new measurements of J/{psi} and {psi}{sup '}{yields}{gamma}{eta}{sub c}({gamma}{eta}{sub c}{sup '}) from the CLEO and BES-III collaboration, we reinvestigate the intermediate meson loop (IML) contributions to these radiative decays in association with the quark model M1 transitions in an effective Lagrangian approach. It shows that the ''unquenched'' effects due to the intermediate hadron loops can be better quantified by the new data for J/{psi}{yields}{gamma}{eta}{sub c}. Although the IML contributions are relatively small in J/{psi}{yields}{gamma}{eta}{sub c}, they play a crucial role in {psi}{sup '}{yields}{gamma}{eta}{sub c}({gamma}{eta}{sub c}{sup '}). A prediction for the IML contributions to {psi}(3770){yields}{gamma}{eta}{sub c}({gamma}{eta}{sub c}{sup '}) is made. Such unquenched effects allow us to reach a coherent description of those three radiative transitions, and gain some insights into the underlying dynamics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Dipion invariant mass distribution of the anomalous {Upsilon}(1S){pi}{sup +}{pi}{sup -} and {Upsilon}(2S){pi}{sup +}{pi}{sup -} production near the peak of {Upsilon}(10860)

Considering the defects of the previous work for estimating the anomalous production rates of e{sup +}e{sup -}{yields}{Upsilon}(1S){pi}{sup +}{pi}{sup -}, {Upsilon}(2S){pi}{sup +}{pi}{sup -} near the peak of the {Upsilon}(5S) resonance at {radical}(s)=10.87 GeV [K. F. Chen et al. (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008)], we suggest a new scenario where the contributions from the direct dipion transition and the final-state interactions interfere to result in not only the anomalously large production rates, but also line shapes of the differential widths consistent with experimental measurement when assuming the reactions are due to the dipion emission of {Upsilon}(5S). At the end, we raise a new puzzle that the predicted differential width d{Gamma}({Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -})/dcos{theta} has a discrepant trend from the data while other predictions are well in accord with the data. It should be further clarified by more accurate measurements carried by future experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

{pi}N transition distribution amplitudes: Their symmetries and constraints from chiral dynamics

Baryon to meson transition distribution amplitudes (TDAs) extend the concept of generalized parton distributions. Baryon to meson TDAs appear as building blocks in the collinear factorized description of amplitudes for a class of hard exclusive reactions, prominent examples of which being hard exclusive meson electroproduction off a nucleon in the backward region and baryon-antibaryon annihilation into a meson and a lepton pair. We study the general properties of these objects following the underlying symmetries of QCD. In particular, the Lorentz symmetry results in the polynomiality property of the Mellin moments in longitudinal momentum fractions. We present a detailed account of the isotopic and permutation symmetry properties of nucleon to pion ({pi}N) TDAs. This restricts the number of independent leading twist {pi}N TDAs to eight functions, providing description of all isotopic channels. Using chiral symmetry and the crossing relation between {pi}N TDAs and {pi}N generalized distribution amplitudes, we establish soft pion theorems for {pi}N TDAs, which determine the magnitude of {pi}N TDAs. Finally, we build a simple resonance exchange model for {pi}N TDAs considering N and {Delta}(1232) exchange contributions into the isospin-(1/2) and isospin-(3/2) {pi}N TDAs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Generalized quark transversity distribution of the pion in chiral quark models

The transversity generalized parton distributions (tGPDs) of the pion, involving matrix elements of the tensor bilocal quark current, are analyzed in chiral quark models. We apply the nonlocal chiral models involving a momentum-dependent quark mass, as well as the local Nambu-Jona-Lasinio with the Pauli-Villars regularization to calculate the pion tGPDs, as well as related quantities following from restrained kinematics, evaluation of moments, or taking the Fourier-Bessel transforms to the impact-parameter space. The obtained distributions satisfy the formal requirements, such as proper support and polynomiality, following from Lorentz covariance. We carry out the leading-order QCD evolution from the low quark-model scale to higher lattice scales, applying the method of Kivel and Mankiewicz. We evaluate several lowest-order generalized transversity form factors, accessible from the recent lattice QCD calculations. These form factors, after evolution, agree properly with the lattice data, in support of the fact that the spontaneously broken chiral symmetry is the key element also in the evaluation of the transversity observables.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Charged bottomoniumlike states Z{sub b}(10610) and Z{sub b}(10650) and the {Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -} decay

Inspired by the newly observed two charged bottomoniumlike states, we consider the possible contribution from the intermediate Z{sub b}(10610) and Z{sub b}(10650) states to the {Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -} decay process, which naturally explains Belle's previous observation of the anomalous {Upsilon}(2S){pi}{sup +}{pi}{sup -} production near the peak of {Upsilon}(5S) at {radical}(s)=10.87 GeV [K. F. Chen et al. (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008)]. The resulting d{Gamma}({Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -})/dm{sub {pi}}{sup +}{sub {pi}}{sup -} and d{Gamma}({Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -})/dcos{theta} distributions agree with Belle's measurement after inclusion of these Z{sub b} states. This formalism also reproduces the Belle observation of the double-peak structure and its reflection in the {Upsilon}(2S){pi}{sup +} invariant mass spectrum of the {Upsilon}(5S){yields}{Upsilon}(2S){pi}{sup +}{pi}{sup -} decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Charged bottomoniumlike structures in the hidden-bottom dipion decays of {Upsilon}(11020)

Under the Initial Single Pion Emission mechanism, we study the hidden-bottom dipion decays of {Upsilon}(11020), i.e., {Upsilon}(11020){yields}{Upsilon}(nS){pi}{sup +}{pi}{sup -} (n=1, 2, 3) and {Upsilon}(11020){yields}h{sub b}(mP){pi}{sup +}{pi}{sup -} (m=1, 2). We predict explicit sharp peak structures close to the BB* and B*B* thresholds and their reflections in the {Upsilon}(1S){pi}{sup +}, {Upsilon}(2S){pi}{sup +} and h{sub b}(1P){pi}{sup +} invariant mass spectrum distributions. We suggest that a future experiment, i.e., Belle, BABAR, and forthcoming BelleII or Super-B, carry out the search for these novel phenomena, which can provide important tests to the Initial Single Emission mechanism existing in higher bottomonia.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Study of the pure annihilation B{sub c}{yields}A{sub 2}A{sub 3} decays

In this work, we calculate the CP-averaged branching ratios and the polarization fractions of the charmless hadronic B{sub c}{yields}A{sub 2}A{sub 3} decays within the framework of perturbative QCD (pQCD) approach, where A is either a light {sup 3}P{sub 1} or {sup 1}P{sub 1} axial-vector meson. These 32 decay modes can occur through the annihilation topology only. Based on the perturbative calculations and phenomenological analysis, we find the following results: (a) the branching ratios of the considered 32 B{sub c}{yields}A{sub 2}A{sub 3} decays are in the range of 10{sup -5} to 10{sup -8}; (b) B{sub c}{yields}a{sub 1}b{sub 1}, K{sub 1}{sup 0}K{sub 1}{sup +} and some other decays have sizable branching ratios and can be measured at the LHC experiments; (c) the branching ratios of B{sub c}{yields}A{sub 2}({sup 1}P{sub 1})A{sub 3}({sup 1}P{sub 1}) decays are generally much larger than those of B{sub c}{yields}A{sub 2}({sup 3}P{sub 1})A{sub 3}({sup 3}P{sub 1}) decays with a factor around (10{approx}100); (d) the branching ratios of B{sub c}{yields}K{sub 1}{sup 0}K{sub 1}{sup +} decays are sensitive to the value of {theta}{sub K}, which will be tested by the running LHC and forthcoming SuperB experiments; (e) the large longitudinal polarization contributions govern most considered decays and play the dominant role.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

{phi} meson production in pp annihilation at rest

Apparent channel-dependent violations of the Okubo-Zwieg-Iizuka (OZI) rule in nucleon-antinucleon annihilation reactions in the presence of an intrinsic strangeness component in the nucleon are discussed. Admixture of ss quark pairs in the nucleon wave function enables the direct coupling to the {phi}-meson in the annihilation channel without violating the OZI rule. Three forms are considered in this work for the strangeness content of the proton wave function, namely, the uud cluster with a ss sea-quark component, kaon-hyperon clusters based on a simple chiral quark model, and the pentaquark picture uudss. Nonrelativistic quark model calculations reveal that the strangeness magnetic moment {mu}{sub s} and the strangeness contribution to the proton spin {sigma}{sub s} from the first two models are consistent with recent experimental data, where {mu}{sub s} and {sigma}{sub s} are negative. For the third model, the uuds subsystem with the configurations [31]{sub FS}[211]{sub F}[22]{sub S} and [31]{sub FS}[31]{sub F}[22]{sub S} leads to negative values of {mu}{sub s} and {sigma}{sub s}. With effective quark line diagrams incorporating the {sup 3}P{sub 0} model, we give estimates for the branching ratios of the annihilation reactions at rest pp{yields}{phi}X (X={pi}{sup 0}, {eta}, {rho}{sup 0}, {omega}). Results for the branching ratios of {phi}X production from atomic pp s-wave states are for the first and third model found to be strongly channel dependent, in good agreement with measured rates.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Long-distance contribution to {Delta}{Gamma}{sub s} of the B{sub s}-B{sub s} system

We estimate the long-distance contribution to the width difference of the B{sub s}-B{sub s} system, based mainly on two-body D{sub s}{sup (*)}D{sub s}{sup (*)} modes and three-body D{sub s}{sup (*)}D{sup (*)}K{sup (*)} modes (and their CP conjugates). Some higher cs resonances are also considered. The contribution to {Delta}{Gamma}{sub s}/{Gamma}{sub s} by two-body modes is (10.2{+-}3.0)%, slightly smaller than the short-distance result of (13.3{+-}3.2)%. The contribution to {Delta}{Gamma}{sub s}/{Gamma}{sub s} by D{sub s0}*(2317), D{sub s1}(2460), and D{sub s1}(2536) resonances is negligible. For the three-body D{sub s}{sup (*)}D{sup (*)}K{sup (*)} modes, we adopt the factorization formalism and model the form factors with off-shell D{sub s}{sup (*)} poles, the D{sub sJ}(2700) resonance, and nonresonant contributions. These three-body modes can arise through current-produced or transition diagrams, but only SU(3)-related D{sub u,d}{sup (*)}D{sup (*)}K modes from the current diagram have been measured so far. The pole model results for D{sub u,d}*D{sup (*)}K agree well with the data, while D{sub u,d}D{sup (*)}K rates agree with the data only within a factor of 2 to 3. All measured D{sub u,d}{sup (*)}D{sup (*)}K rates can be reproduced by including nonresonant contributions. The total {Delta}{Gamma}{sub s}/{Gamma}{sub s} obtained is (16.7{+-}8.5)%, which agrees with the short-distance result within uncertainties. For illustration, we also demonstrate the effect of D{sub sJ}(2700) in modes with D{sup (*)}K{sup *}. In all scenarios, the total {Delta}{Gamma}{sub s}/{Gamma}{sub s} remain consistent with the short-distance result. Our results indicate that (a) the operator product expansion in the short-distance picture is a valid assumption, (b) approximating the B{sub s}{yields}D{sub s}{sup (*)}D{sub s}{sup (*)} decays to saturate {Delta}{Gamma}{sub s} has a large correction, (c) the effect of three-body modes cannot be neglected, and (d) in addition to the D{sub s} and D{sub s}* poles, the D{sub sJ}(2700) resonance also plays an important role in three-body modes. Future experiments are necessary to improve the estimation of {Delta}{Gamma}{sub s} from the long-distance point of view.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Matrix elements of the electromagnetic operator between kaon and pion states

We compute the matrix elements of the electromagnetic operator sF{sub {mu}{nu}}{sigma}{sup {mu}{nu}}d between kaon and pion states, using lattice QCD with maximally twisted-mass fermions and two flavors of dynamical quarks (N{sub f}=2). The operator is renormalized nonperturbatively in the RI'/MOM scheme and our simulations cover pion masses as light as 270 MeV and three values of the lattice spacing from {approx_equal}0.07 up to {approx_equal}0.1 fm. At the physical point our result for the corresponding tensor form factor at zero-momentum transfer is f{sub T}{sup K{pi}}(0)=0.417(14{sub stat})(5{sub syst}), where the systematic error does not include the effect of quenching the strange and charm quarks. Our result differs significantly from the old quenched result f{sub T}{sup K{pi}}(0)=0.78(6) obtained by the SPQ{sub cd}R Collaboration with pion masses above 500 MeV. We investigate the source of this difference and conclude that it is mainly related to the chiral extrapolation. We also study the tensor charge of the pion and obtain the value f{sub T}{sup {pi}{pi}}(0)=0.195(8{sub stat})(6{sub syst}) in good agreement with, but more accurate than the result f{sub T}{sup {pi}{pi}}(0)=0.216(34) obtained by the QCDSF Collaboration using higher pion masses.

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

Hyperon forward spin polarizabilty {gamma}{sub 0}

We present the results of a systematic leading-order calculation of hyperon Compton scattering and extract the forward spin polarizability--{gamma}{sub 0}--of hyperons within the framework of SU(3) heavy baryon chiral perturbation theory (HBChPT). The results obtained for {gamma}{sub 0} in the case of nucleons agree with that of the known results of SU(2) HBChPT when kaon loops are not considered.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Extremely high energy neutrinos from cosmic strings

Superstring theory and other supersymmetric theories predict the existence of relatively light, weakly interacting scalar particles, called moduli, with a universal form of coupling to matter. Such particles can be emitted from cusps of cosmic strings, where extremely large Lorentz factors are achieved momentarily. Highly boosted modulus bursts emanating from cusps subsequently decay into gluons; they generate parton cascades which in turn produce large numbers of pions and then neutrinos. Because of very large Lorentz factors, extremely high energy neutrinos, up to the Planck scale and above, are produced. For some model parameters, the predicted flux of neutrinos with energies > or approx. 10{sup 21} eV is observable by JEM-EUSO and by the future large radio detectors LOFAR and SKA.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Cosmogenic gamma rays and the composition of cosmic rays

We discuss the prospects of detecting the sources of ultrahigh energy (UHE) cosmic ray (CR) nuclei via their emission of cosmogenic {gamma} rays in the GeV to TeV energy range. These {gamma} rays result from electromagnetic cascades initiated by high energy photons, electrons, and positrons that are emitted by CRs during their propagation in the cosmic radiation background and are independent of the simultaneous emission of {gamma} rays in the vicinity of the source. The corresponding production power by UHE CR nuclei (with mass number A and charge Z) is dominated by pion photo production ({proportional_to}A) and Bethe-Heitler pair production ({proportional_to}Z{sup 2}). We show that the cosmogenic {gamma}-ray signal from a single steady UHE CR source is typically more robust with respect to variations of the source composition and injection spectrum than the accompanying signal of cosmogenic neutrinos. We study the diffuse emission from the sum of extragalactic CR sources as well as the point-source emission of the closest sources.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗