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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

The pp{yields}p{Lambda}K{sup +} and pp{yields}p{Sigma}{sup 0}K{sup +} reactions with chiral dynamics

We report on a theoretical study of the pp{yields}p{Lambda}K{sup +} and pp{yields}p{Sigma}{sup 0}K{sup +} reactions near threshold using a chiral dynamical approach. The production process is described by single-pion and single-kaon exchange. The final state interactions of nucleon-hyperon, K-hyperon, and K-nucleon systems are also taken into account. We show that our model leads to a fair description of the experimental data on the total cross section of the pp{yields}p{Lambda}K{sup +} and pp{yields}p{Sigma}{sup 0}K{sup +} reactions. We find that the experimental observed strong suppression of {Sigma}{sup 0} production compared to {Lambda} production at the same excess energy can be explained. However, ignorance of phases between some amplitudes does not allow one to properly account for the nucleon-hyperon final state interaction for the pp{yields}p{Sigma}{sup 0}K{sup +} reaction. We also demonstrate that the invariant mass distribution and the Dalitz plot provide direct information about the {Lambda} and {Sigma}{sup 0} production mechanisms and may be tested by experiments at COSY or HIRFL-CSR.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Generation of excited K bands in heavy nuclei

It is known that coupling an intrinsic excitation of integer spin and positive parity I{sup +} to a rotor having a degenerate set of states L{sup {pi}=}0{sup +},2{sup +},4{sup +},..., generates a series of K bands. A given value of I{sup +} gives rise to several bands labeled by K{sup +}=0{sup +},1{sup +},2{sup +},...,I{sup +}, that is, a total of (I+1) such bands, in the spectrum of the combined system. We discuss how a binary cluster model of an excited core orbited by a spinless cluster can approximate these conditions. A crucial point is that the radial wave functions of relative motion are very similar for low L, and their radial coupling integrals even more so, such that the wave functions play the model role of a common intrinsic state for the lowest excited states of the system. If the core has a 0{sup +} ground state and a low-lying 2{sup +} excited state, then lifting the degeneracy leads to a ground state K{sup +}=0{sup +} band and low-lying excited K{sup +}=0{sup +}, 1{sup +}, and 2{sup +} bands. Although these are all seen in light nuclei, the K{sup +}=1{sup +} band is conspicuous by its apparent absence in heavy nuclei, and we urge experimental groups to reexamine their data for signs of it.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Measurements of cross sections and charged pion spectra in proton-carbon interactions at 31 GeV/c

Interaction cross sections and charged pion spectra in p+C interactions at 31 GeV/c were measured with the large-acceptance NA61/SHINE spectrometer at the CERN SPS. These data are required to improve predictions of the neutrino flux for the T2K long-baseline neutrino oscillation experiment in Japan. A set of data collected during the first NA61/SHINE run in 2007 with an isotropic graphite target with a thickness of 4% of a nuclear interaction length was used for the analysis. The measured p+C inelastic and production cross sections are 257.2 {+-} 1.9 {+-} 8.9 and 229.3 {+-} 1.9 {+-} 9.0 mb, respectively. Inclusive production cross sections for negatively and positively charged pions are presented as functions of laboratory momentum in ten intervals of the laboratory polar angle covering the range from 0 up to 420 mrad. The spectra are compared with predictions of several hadron production models.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Initialization effect in heavy-ion collisions at intermediate energies

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model plus the Skyrme force parameters, the initialization effect is studied in heavy-ion collisions at intermediate energies. We find that there are moderate initialization effects in the following observables: free neutron to proton ratio (n/p), {pi}{sup -}/{pi}{sup +} ratio, and neutron to proton differential flow (F{sub n-p}{sup x}). Effects of initialization are larger for charged {pi}{sup -}/{pi}{sup +} ratios than for n/p ratios. And the effects of initialization are more evident in nuclear reactions at lower incident beam energies. We do not see large effects of initialization for light reaction systems or large asymmetric (neutron-richer) reaction systems. We also see relatively large effects of initialization on the neutron to proton differential flow at relatively lower incident beam energies or with large impact parameters. These results may be useful for the delicate studies of the equation of state of asymmetric nuclear matter.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Hadronic absorption cross sections of B{sub c}

The cross sections of B{sub c} absorption by {pi} mesons are calculated using a hadronic Lagrangian based on the SU(5) flavor symmetry. Calculated cross sections are found to be in the ranges 2-7 mb and 0.2-2 mb for the processes B{sub c}{sup +}{pi}{yields}DB and B{sub c}{sup +}{pi}{yields}D*B*, respectively, when the monopole form factor is included. These results could be useful in calculating the production rate of B{sub c} mesons in relativistic heavy ion collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Suppression of high-p{sub T} hadrons in Pb+Pb collisions at energies available at the CERN Large Hadron Collider

The nuclear modification factor R{sub AA}(p{sub T}) for large transverse momentum pion spectra in Pb+Pb collisions at {radical}(s)=2.76 TeV is predicted within the next-to-leading order perturbative QCD parton model. The effect of jet quenching is incorporated through medium-modified fragmentation functions within the higher-twist approach. The jet transport parameter that controls medium modification is proportional to the initial parton density, and the coefficient is fixed by data on the suppression of large-p{sub T} hadron spectra obtained at the BNL Relativistic Heavy Ion Collider. Data on charged hadron multiplicity dN{sub ch}/d{eta}=1584{+-}80 in central Pb+Pb collisions from the ALICE experiment at the CERN Large Hadron Collider are used to constrain the initial parton density both for determining the jet transport parameter and the 3 + 1 dimensional (3 + 1D) ideal hydrodynamic evolution of the bulk matter that is employed for the calculation of R{sub PbPb}(p{sub T}) for neutral pions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

K*{sup 0} production in Cu + Cu and Au + Au collisions at {radical}(s{sub NN})=62.4 GeV and 200 GeV

We report on K*{sup 0} production at midrapidity in Au + Au and Cu + Cu collisions at {radical}(s{sub NN})=62.4 and 200 GeV collected by the Solenoid Tracker at the Relativistic Heavy Ion Collider detector. The K*{sup 0} is reconstructed via the hadronic decays K*{sup 0}{yields}K{sup +}{pi}{sup -} and K*{sup 0}{yields}K{sup -}{pi}{sup +}. Transverse momentum, p{sub T}, spectra are measured over a range of p{sub T} extending from 0.2 GeV/c up to 5 GeV/c. The center-of-mass energy and system size dependence of the rapidity density, dN/dy, and the average transverse momentum, <p{sub T}>, are presented. The measured N(K*{sup 0})/N(K) and N({phi})/N(K*{sup 0}) ratios favor the dominance of rescattering of decay daughters of K*{sup 0} over the hadronic regeneration for the K*{sup 0} production. In the intermediate p{sub T} region (2.0<p{sub T}<4.0 GeV/c), the elliptic flow parameter, v{sub 2}, and the nuclear modification factor, R{sub CP}, agree with the expectations from the quark coalescence model of particle production.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Determination of the {pi}{Sigma} scattering lengths from the weak decays of {Lambda}{sub c}

The scattering lengths of the {pi}{Sigma} systems are key quantities in understanding the structure of the {Lambda}(1405) resonance and the subthreshold extrapolation of the KN interaction. We demonstrate that the {pi}{Sigma} scattering lengths can be extracted from the threshold cusp phenomena in the weak {Lambda}{sub c}{yields}{pi}{pi}{Sigma} decays, analogously with Cabibbo's method for determination of the {pi}{pi} scattering length. We show that the substantial cusp effect should be observed in the spectrum, when the {pi}{Sigma} interaction in I=0 is strongly attractive to generate a near-threshold singularity, such as a bound state or a virtual state.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Extracting the photoproduction cross sections off the neutron, via the {gamma}n{yields}{pi}{sup -}p reaction, from deuteron data with final-state interaction effects

The incoherent pion photoproduction reaction {gamma}d {yields} {pi}{sup -}pp is considered theoretically in a wide energy region E{sub th}{<=}E{sub {gamma}}{<=}2700 MeV. The model applied contains the impulse approximation as well as the NN and {pi}N final-state-interaction (FSI) amplitudes. The aim of the paper is to study a reliable way for getting the information on elementary {gamma}n {yields} {pi}{sup -}p reaction cross sections beyond the impulse approximation for {gamma}d {yields} {pi}{sup -}pp. For the elementary {gamma}N {yields} {pi}N, N N {yields} N N, and {pi}N {yields} {pi}N amplitudes, the results of The George Washington University (GW) Data Analysis Center (DAC) are used. There are no additional theoretical constraints. The calculated cross sections d{sigma} /d{Omega}({gamma}d {yields} {pi}{sup -}pp) are compared with existing data. The procedure used to extract information on the differential cross section d{sigma} /d{Omega}({gamma}n {yields} {pi}{sup -}p) on the neutron from the deuteron data using the FSI correction factor R is discussed. The calculations for R versus {pi}{sup -}p center-of-mass (CM) angle {theta}{sub 1} of the outgoing pion are performed at different photon-beam energies with kinematic cuts for a ''quasifree'' process {gamma}n {yields} {pi}{sup -}p. The results show a sizable FSI effect R{ne}1 from the S-wave part of pp-FSI at small angles close to {theta}{sub 1}{approx}0: this region narrows as the photon energy increases. At larger angles, the effect is small (|R - 1|<<1) and agrees with estimations of FSI in the Glauber approach.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Dense stellar matter with strange quark matter driven by kaon condensation

The core of neutron-star matter is supposed to be at a much higher density than the normal nuclear-matter density, for which various possibilities have been suggested, such as, for example, meson or hyperon condensation and/or deconfined quark or color-superconducting matter. In this work, we explore the implication on hadron physics of a dense compact object that has three ''phases'': nuclear matter at the outer layer, kaon condensed nuclear matter in the middle, and strange quark matter at the core. Using a drastically simplified but not unreasonable model, we develop the scenario where the different phases are smoothly connected with the kaon condensed matter playing a role of a ''doorway'' to a quark core, the equation of state of which with parameters restricted within the range allowed by nature could be made compatible with the mass vs radius constraint given by the 1.97-solar-mass object PSR J1614-2230 recently observed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

First observation of radiative B⁰ → ΦK⁰γ decays and measurements of their time-dependent CP violation

We report the first observation of the radiative decay B⁰→ ΦK⁰γ using a data sample of 772 × 10⁶ BB¯ pairs collected at the (4S) resonance with the Belle detector at the KEKB asymmetric-energy e⁺e⁻ collider. We observe a signal of 37 ± 8 events with a significance of 5.4 standard deviations including systematic uncertainties. The measured branching fraction is B(B⁰→ ΦK⁰γ) = (2.74±0.60±0.32)×10⁻⁶, where the uncertainties are statistical and systematic, respectively. We also report the first measurements of time-dependent CP-violation parameters: S ΦK⁰ S γ = +0.74 ⁺0.72 –1.05 (stat) +0.10 –0.24 (syst) and A ΦK⁰ S γ = +0.35 ± 0.58(stat) +0.23 –0.10 (syst). Furthermore, we measure B(B⁺ → ΦK⁺γ) = (2.48 ± 0.30 ± 0.24) × 10⁻⁶, ACP = –0.03 ± 0.11 ± 0.08 and find that the signal is concentrated in the M ΦK mass region near threshold.

Sahoo, Himansu B.↗
DOE OSTI2011

Observation of the Baryonic B decay B0bar to Lambda_c^+ anti-Lambda K-

The authors report the observation of the baryonic B decay {bar B}{sup 0} {yields} {Lambda}{sub c}{sup +} {bar {Lambda}}K{sup -} with a significance larger than 7 standard deviations based on 471 x 10{sup 6} B{bar B} pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. They measure the branching fraction for the decay {bar B}{sup 0} {yields} {Lambda}{sub c}{sup +} {bar {Lambda}}K{sup -} to be (3.8 {+-} 0.8{sub stat} {+-} 0.2{sub sys} {+-} 1.0 {sub {Lambda}{sub c}{sup +}}) x 10{sup -5}. The uncertainties are statistical, systematic, and due to the uncertainty in the {Lambda}{sub c}{sup +} branching fraction. They find that the {Lambda}{sub c}{sup +} K{sup -} invariant mass distribution shows an enhancement above 3.5 GeV/c{sup 2}.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Search for charmonium and charmoniumlike states in Υ ( 2 S ) radiative decays

Using a sample of 158 x 10⁶ Υ(2S) events collected with the Belle detector, charmonium and charmoniumlike states with even charge parity are searched for in Υ(2S) radiative decays. No significant Xcl or nc signal is observed, and the following upper limits at 90% confidence level (C. L.) are obtained: Β(Υ(2S)→YXco)<1.0×10 - ⁴, Β(Υ(2S)→yxc1)<3.6×10 - ⁶, Β(Υ(2S)→yxc2)<1.5 x 10 - ⁵, and Β(Υ(2S)→ync)<2.7×10 - ⁵. No significant signal of any charmoniumlike state is observed, and we obtain the limits Β(Υ(2S)→yX(3872)) x Β(X(3872)→π⁺π⁻J/ψ)<0.8×10-6, Β(Υ(2S)→γX(3872))× Β(X(3872)→ π⁺π⁻π⁰Jlψ)<2.4 x 10⁻⁶, Β(Υ(2S)→γX(3915))× Β(X(3915)→ωJ/ψ)<2.8×10⁻⁶, Β(Υ(2S)→γY(4140)) x Β(Y(4140)→$\phi$J/ψ))<1.2 x 10 - ⁶, and Β(Υ(2S)→yX(4350))× Β(X(4350)→$\phi$J/ψ))<1.3×10⁻⁶ at 90% C. L.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Sterile neutrino decay explanation of LSND and MiniBooNE anomalies

We examine a recently proposed explanation of the liquid scintillator neutrino detector and MiniBooNE anomalies, given in terms of a sterile neutrino N of the mass 40MeV < or approx. m{sub N} < or approx. 80MeV mixed with {nu}{sub {mu}} at the strength 10{sup -3} < or approx. |U{sub {mu}N}|{sup 2} < or approx. 10{sup -2} and which dominantly decays into a light neutrino and photon: N{yields}{nu}{gamma}. We check compatibility of this scenario with the existing experimental data on radiative {tau}-lepton and K-meson decays. We find that neither of these data are able to totally rule out the above indicated region of m{sub N}-|U{sub {mu}N}|{sup 2}. However, we show that the current experimental data on K{yields}{mu}{nu}{gamma} decay exclude a significant part of this region. We propose experimental cuts on this decay allowing to improve its sensitivity to the region in question. We also show that measurements of K{yields}{mu}{nu}ee decay have good prospects for testing the decaying sterile neutrino scenario.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Observation of B - →$\bar{p}$ΛD 0 at Belle

We study B- meson decays to $\bar{p}$ΛD (*)0 final states using a sample of 657×10 6 B$\bar{B}$ events collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. The observed branching fraction for B - →$\bar{p}$ΛD 0 is (1.43$+0.28\atop{-0.25}$±0.18)×10 -5 with a significance of 8.1 standard deviations, where the uncertainties are statistical and systematic, respectively. Most of the signal events have the $\bar{p}$ Λ mass peaking near threshold. No significant signal is observed for $\bar{p}$ΛD (*)0 and the corresponding upper limit on the branching fraction is 4.8×10 -5 at the 90% confidence level.

43 PARTICLE ACCELERATORS↗