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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
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

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 OSTI2012

Branching Ratio of the Electromagnetic Decay of the Σ + (1385)

The CLAS detector was used to obtain the first ever measurement of the electromagnetic decay of the Σ* + (1385) from the reaction γp → K 0 Σ* + (1385). A real photon beam with a maximum energy of 3.8 GeV was incident on a liquid-hydrogen target, resulting in the photoproduction of the kaon and Σ* hyperon. Kinematic fitting was used to separate the reaction channel from the background processes. The fitting algorithm exploited a new method to kinematically fit neutrons in the CLAS detector, leading to the partial width measurement of 250.0 ± 56.9(stat) -41.2 +34.3 (sys) keV. A U-spin symmetry test using the SU(3) flavor-multiplet representation yields predictions for the Σ* + (1385) → Σ + γ and Σ* 0 (1385) → Λγ partial widths that agree with the experimental measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Standard Model Prediction for Direct C P Violation in K → π π Decay

In this paper, we report the first lattice QCD calculation of the complex kaon decay amplitude A 0 with physical kinematics, using a 32 3 x 64 lattice volume and a single lattice spacing a, with 1/a = 1.3784(68) GeV. We find Re(A 0 ) = 4.66(1.00)(1.26) x 10 -7 GeV and Im(A 0 ) = -1.90(1.23)(1.08) x 10 -11 GeV, where the first error is statistical and the second systematic. The first value is in approximate agreement with the experimental result: Re(A 0 ) = 3.3201(18) x 10 -7 GeV, while the second can be used to compute the direct CP-violating ratio Re(ϵ'/ϵ) = 1.38(5.15)(4.59) x 10 -4 , which is 2.1σ below the experimental value 16.6(2.3) x 10 -4 . Finally, the real part of A 0 is CP conserving and serves as a test of our method while the result for Re(ϵ'/ϵ) provides a new test of the standard model theory of CP violation, one which can be made more accurate with increasing computer capability.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Symmetry and boundness of four-particle coulomb systems

The problem of boundness of a{sup +}b{sup +}c{sup -}d{sup -} four-particle Coulomb systems (quadrions) is studied versus the masses of the particles involved. Inequalities that make it possible to deduce that, if some reference quadrions form a bound state, the same is true for a large number of quadrions formed by particles having various masses were derived. A compendium of calculations for energies of reference systems that possess various symmetries [positronium molecules (e{sup +}e{sup +}e{sup -}e{sup -}) and quadrions of the a{sup +}b{sup +}b{sup -}b{sup -}, a{sup +}b{sup +}a{sup --}, and a{sup +}a{sup +}b{sup -}c{sup -} types] is given, and groups of bound asymmetric quadrions corresponding to them are determined. An inequality for kinetic energies of particles that makes it possible to find out, by using asymmetric reference systems, whether specific quadrions are bound is obtained. It is shown that the boundness of many quadrions is ensured by the boundness of respective three-particle systems. The entire body of the present results permits proving that, of the total number of 406 quadrions containing electrons, muons, pions, kaons, protons, deuterons, and tritons and their antiparticles, 227 quadrions are bound.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Evidence for the onset of deconfinement and quest for the critical point by NA49 at the CERN SPS

The NA49 results on hadron production obtained in PbPb collisions at SPS energies from 20 to 158 A GeV are shown and discussed as evidence for the onset of deconfinement. The primary measures are the pion yield, the kaon-to-pion ratio and the slope parameter of transverse mass distributions. The possible indication of the QCD critical point signatures was investigated in the event-by-event fluctuations of various observables such as the mean transverse momentum, particle multiplicity and azimuthal angle distributions as well as in the particle ratio fluctuations. The energy dependence of these observables was measured in central PbPb collisions in the full SPS energy range while for analysis of the system size dependence data from pp, CC, SiSi, and PbPb collisions at the top SPS energy were used.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Measurement of the e{sup +}e{sup −} → ηK{sup +}K{sup −} Cross Section by Means of the SND Detector

The cross section for the process e{sup +}e{sup −} → ηK{sup +}K{sup −} wasmeasured at c.m. energies in the range between 1.56 and 2.00 GeV in an experiment with the SND detector at the VEPP-2000 e{sup +}e{sup −} collider. The invariant-mass distribution of kaon pairs is consistent with the hypothesis that the transition through the ηφ intermediate state makes a dominant contribution to the transition in question.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

COMPASS results on collins and sivers asymmetries for charged hadrons

The study of transverse spin and transverse momentum effects is an important part of the scientific program of COMPASS, a fixed target experiment at the CERN SPS taking data since 2002. The studies are carried on by measuring the hadrons produced in deep inelastic scattering (DIS) of 160 GeV/ c muons off different targets. Among the possible asymmetries in the hadron azimuthal distributions, particularly interesting are the Collins and Sivers asymmetries which the COMPASS Collaboration has measured using transversely polarised deuteron and proton targets. Here new results for charged pions and kaons obtained from the 2010 run with a transversely polarised proton target are presented for the first time.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

COMPASS results on transverse spin asymmetries in identified two-hadron production in SIDIS

COMPASS is a fixed target experiment at CERN where nucleon spin structure and hadron spectroscopy are investigated using a 160 GeV/c polarized μ{sup +} beam. An important part of its physics program are the measurements of single spin asymmetries (SSA) in semi-inclusive deep inelastic scattering (SIDIS) on transversely polarized targets. Data on a deuteron target ({sup 6}LiD) were taken in 2002–04. After taking the first data on a transversely polarized proton target (NH{sub 3}) in 2007, a full year of data taking followed in 2010 to increase precision. The SSA of identified hadron pairs consisting of charged pions and/or kaons from the 2010 data are shown for the first time and compared to model predictions and results from HERMES.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Flavor dependent azimuthal asymmetries in unpolarized semi-inclusive DIS at HERMES

The azimuthal cosϕ{sub h} and cos2ϕ{sub h} modulations of the distribution of hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of electrons and positrons off hydrogen and deuterium targets have been measured in the hermes experiment. For the first time these modulations were determined in a 4-Dimensional kinematic space for positively and negatively charged pions and kaons separately, as well as for unidentified hadrons. These azimuthal dependences are sensitive to the transverse motion and polarization of the quarks within the nucleon via, e.g., the Cahn, Boer-Mulders and Collins effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Charged hadron multiplicities at the HERMES experiment

The HERMES collaboration has measured charge-separated pion and kaon multiplicities in semi-inclusive deep inelastic scattering using a 27.6 GeV electron or positron beam scattering off a hydrogen or deuterium target. The results are presented as a function of the Bjorken variable x {sub B }, the negative squared four-momentum transfer Q {sup 2}, the hadron fractional energy z and it’s transverse momentum P {sub h ⊥}. These data will be very useful to understand the quark-fragmentation process in deep-inelastic hadron electro-production and will serve as crucial input in the understanding of spin asymmetries in polarized semi-inclusive deep-inelastic scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Mott-Anderson freeze-out and the strange matter “horn”

We discuss the √s-dependence of the K {sup +}/π{sup +} ratio in heavy-ion collisions (the “horn” effect) within a Mott-Anderson localization model for chemical freeze-out. The different response of pion and kaon radii to the hot and dense hadronic medium results in different freeze-out conditions. We demonstrate within a simple model that this circumstance enhances the “horn” effect relative to statistical models with universal chemical freeze-out.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

37 Years with the light scalar mesons. The learned lessons

Attention is paid to the production mechanisms of light scalars that reveal their nature. We reveal the chiral shielding of the σ(600) meson. We show that the kaon loop mechanism of the ϕ radiative decays, ratified by experiment, is four-quark transition and points to the four-quark nature of light scalars. We show also that the light scalars are produced in the two photon collisions via four-quark transitions in contrast to the classic P wave tensor qq̅ mesons that are produced via two-quark transitions γγ → qq̅. We study the mechanism of production of the light scalar mesons in the D{sup +}{sub s }→ π{sup +}π{sup −} e {sup +}ν decays: D{sup +}{sub s }→ ss̅e {sup +}ν → [σ(600) + f {sub 0}(980)]e {sup +}ν → π{sup +}π{sup −} e {sup +}ν, and compare it with the mechanism of production of the light pseudoscalar mesons in the D{sup +}{sub s }→ (η/η′)e {sup +}ν decays: D{sup +}{sub s }→ ss̅e {sup +}ν → (η/η′)e {sup +}ν. As a result we find support to four-quark nature of light scalars. In the end, we outline the future research program.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Cross sections of hadronic reactions e{sup +} e{sup −} → K{sup +} K{sup −} nπ (n =1,2,3) measured with the CMD3 detector at the VEPP-2000 electron-positron collider

We analyze the data on e{sup +} e{sup −} collisions at c.m.s. energies between 0.32 and 2 GeV collected in 2011–2013 with the CMD3 detector operating at the VEPP-3 e{sup +} e{sup −} collider of the Budker Institute of Nuclear Physics. The data correspond to an integrated luminosity of nearly 60 pb{sup -1}. Preliminary results e{sup +} e{sup −} → K{sup +} K{sup −} nπ (n = 1, 2, 3) on the reactions with two charged kaons in the final state are presented, and the procedure for estimating the integrated luminosity for each energy setting is described.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Coherent production of the K{sup +}π{sup 0} system by K{sup +} mesons on copper nuclei in the OKA detector

In a sample of ∼5 × 10{sup 9} positive kaon collisions with copper nuclei, the events of coherent production of K{sup +}π{sup 0} pairs are selected, the contributions of the Coulomb and strong production mechanisms are discriminated, and the corresponding cross sections are determined. The phase shift difference between the Coulomb and strong amplitudes is obtained.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Experimental study of the $ \gamma p \rightarrow K^{0}\Sigma^{+}$, $ \gamma n \rightarrow K^{0} \Lambda$, and $ \gamma n \rightarrow K^{0} \Sigma^{0}$ reactions at the Mainz Microtron

This work measured dσ/dΩ for neutral kaon photoproduction reactions from threshold up to a c.m. energy of 1855MeV, focussing specifically on the $ \gamma p \rightarrow K^{0}\Sigma^{+}$, $ \gamma n \rightarrow K^{0} \Lambda$, and $ \gamma n \rightarrow K^{0} \Sigma^{0}$ reactions. Our results for $ \gamma n \rightarrow K^{0} \Sigma^{0}$ are the first-ever measurements for that reaction. These data will provide insight into the properties of N* resonances and, in particular, will lead to an improved knowledge about those states that couple only weakly to the πN channel. Integrated cross sections were extracted by fitting the differential cross sections for each reaction as a series of Legendre polynomials and our results are compared with prior experimental results and theoretical predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Study of High-multiplicity 3-prong and 5-prong $\tau$ Decays at $B\small{A}$$B\small{AR}$

We present measurements of the branching fractions of 3-prong and 5-prong $\tau$ decay modes using a sample of 430 million $\tau$ lepton pairs, corresponding to an integrated luminosity of 468 fb -1 , collected with the $B\small{A}$$B\small{AR}$ detector at the PEP-II asymmetric energy $e^+e^-$ storage rings. The$\tau^- \to (3\pi)^- \eta'(958)\nu_\tau, \tau^- \to (3\pi)^- \omega\nu_\tau$ and $\tau^- \to \pi^-f_1(1285)\nu_\tau$ branching fractions are presented as well as a new limit on the branching fraction of the isospin-forbidden, second-class current $\tau^- \to \pi^-\eta'(958)\nu_\tau$ decay. We find no evidence for charged kaons in these decay modes and place the first upper limits on their branching fractions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗