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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

The Jefferson Lab program: From 6 GeV operations to the 12 GeV upgrade

The Thomas Jefferson National Laboratory and the CEBAF accelerator operated for more than a decade, running a comprehensive scientific program that improved our understanding of the strong interaction. The facility is now moving toward an upgrade of the machine, from 6 to 12 GeV; a new experimental hall will be added and the equipment of the three existing halls will be enhanced. In this contribution some selected results from the rich physics program run at JLab, as well as the prospects for the near future, will be presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Luminosities and energies of e + e - collision data taken between $\sqrt{s}$=4.61 GeV and 4.95 GeV at BESIII*

From December 2019 to June 2021, the BESIII experiment collected approximately 5.85 fb -1 of data at center-of-mass energies between 4.61 and 4.95 GeV. This is the highest collision energy BEPCII has reached to date. The accumulated e + e - annihilation data samples are useful for studying charmonium(-like) states and charmed-hadron decays. By adopting a novel method of analyzing the production of $Λ^{+}_{c}$ $\overline{Λ}$ $^{-}_{c}$ pairs in e + e - annihilation, the center-of-mass energies are measured with a precision of ~0.6 MeV. Integrated luminosities are measured with a precision of better than 1% by analyzing the events of large-angle Bhabha scattering. These measurements provide important inputs to analyses based on these data samples.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Exclusive analysis of the gamma(pol.) n ---> K+ Sigma- reaction at E(gamma) = 0.8-GeV to 2.3-GeV

Strangeness channels are important in the experimental search for missing resonances. A recent experiment performed at Jefferson Lab (CLAS gl3 run period) used a liquid deuterium target with linearly and circularly polarized tagged photon beams covering energies from threshold to 2.5 GeV. It provides high-quality data (about 52 billion triggers) with good kinematic coverage and several experimental observables available for each reaction channel. We have analyzed a few percent of these data to measure strangeness photoproduction on the neutron, in particular, the yn --> K+ Sigma- reaction. The exclusive analysis of this reaction along with a very preliminary measurement of the photon beam asymmetry is presented.

Source record↗
DOE OSTI2026

Backward-Angle Electroproduction of η′ Mesons off Protons at W = 2.13 GeV and Q 2 = 0.46 (GeV/ c ) 2

The electroproduction of $\eta ^{\prime }$ mesons from a $\mathrm{^{1}H}$ target at $W=\mathrm{2.13~GeV}$, $Q^{2} = 0.46~\left( \mathrm{GeV/}c\right)^{2}$, and $\cos \theta ^{\mathrm{CM}}_{\gamma ^{*}\eta ^{\prime }} \approx -1$ has been experimentally measured. The differential cross section of virtual photoproduction has been obtained as $4.4 \pm 0.8 ~\left( \mathrm{stat.} \right) \pm 0.4 ~\left( \mathrm{sys.} \right)~ \mathrm{nb/sr}$ in the One-Photon-Exchange Approximation. This value is one-sixth of that of real photoproduction at backward angles. A comparison with newly developed isobar model calculations not only shows the validity of the theoretical framewark employed, but also imposes new constraints on coupling strength between the $\eta ^{\prime }p$ final state and nucleon resonances.

Nuclear Physics↗
DOE OSTI2015

Nucleon-gold collisions at 200A GeV using tagged d + Au interactions in the PHOBOS detector

Forward calorimetry in the PHOBOS detector has been used to study charged hadron production in d+Au, p+Au, and n+Au collisions at √s NN =200GeV. The forward proton calorimeter detectors are described and a procedure for determining collision centrality with these detectors is detailed. The deposition of energy by deuteron spectator nucleons in the forward calorimeters is used to identify p+Au and n+Au collisions in the data. A weighted combination of the yield of p+Au and n+Au is constructed to build a reference for Au+Au collisions that better matches the isospin composition of the gold nucleus. The p T and centrality dependence of the yield of this improved reference system is found to match that of d+Au. The shape of the charged-particle transverse momentum distribution is observed to extrapolate smoothly from p+p¯ to central d+Au as a function of the charged-particle pseudorapidity density. The asymmetry of positively and negatively charged hadron production in p+Au is compared to that of n+Au. No significant asymmetry is observed at midrapidity. In conclusion, these studies augment recent results from experiments at the CERN Large Hadron Collider and BNL Relativistic Heavy Ion Collider facilities to give a more complete description of particle production in p+A and d+A collisions, essential for the understanding the medium produced in high-energy nucleus-nucleus collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Measurement of e + e − → η J / ψ cross section from s = 3.808 GeV to 4.951 GeV

Using data samples with an integrated luminosity of 22.42 fb − 1 collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the e + e − → η J / ψ process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with ψ ( 4040 ) , two additional resonances, and a nonresonant component are performed. The mass and width of the first additional state are ( 4219.7 ± 2.5 ± 4.5 ) MeV / c 2 and ( 80.7 ± 4.4 ± 1.4 ) MeV , respectively, consistent with the ψ ( 4230 ) . For the second state, the mass and width are ( 4386 ± 13 ± 17 ) MeV / c 2 and ( 177 ± 32 ± 13 ) MeV , respectively, consistent with the ψ ( 4360 ) . The first uncertainties are statistical, and the second ones are systematic. The statistical significance of ψ ( 4040 ) is 8.0 σ and those for ψ ( 4230 ) and ψ ( 4360 ) are more than 10.0 σ . Published by the American Physical Society 2024

Ablikim, M.↗
DOE OSTI2011

Suppression of Back-to-Back Pairs at Forward Rapidity in d + Au Collisions sqrt(s_NN)=200 GeV

Back-to-back hadron pair yields in d+Au and p+p collisions at {radical}s{sub NN} = 200 GeV were measured with the PHENIX detector at the Relativistic Heavy Ion Collider. Rapidity separated hadron pairs were detected with the trigger hadron at pseudorapidity |{eta}| < 0.35 and the associated hadron at forward rapidity (deuteron direction, 3.0 < {eta} < 3.8). Pairs were also detected with both hadrons measured at forward rapidity; in this case, the yield of back-to-back hadron pairs in d+Au collisions with small impact parameters is observed to be suppressed by a factor of 10 relative to p+p collisions. The kinematics of these pairs is expected to probe partons in the Au nucleus with a low fraction x of the nucleon momenta, where the gluon densities rise sharply. The observed suppression as a function of nuclear thickness, p{sub T}, and {eta} points to cold nuclear matter effects arising at high parton densities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Observation of D 0 meson nuclear modifications in Au + Au collisions at s NN = 200 GeV

We report the first measurement of charmed-hadron (D 0 ) production via the hadronic decay channel (D 0 → K - + π + ) in Au + Au collisions at √ s NN = 200 GeV with the STAR experiment. The charm production cross section per nucleon-nucleon collision at midrapidity scales with the number of binary collisions, N bin , from p + p to central Au + Au collisions. The D 0 meson yields in central Au + Au collisions are strongly suppressed compared to those in p + p scaled by N bin , for transverse momenta p T > 3 GeV/c, demonstrating significant energy loss of charm quarks in the hot and dense medium. Here, an enhancement at intermediate p T is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of electron neutrino quasielastic and quasielasticlike scattering on hydrocarbon at $\langle E_{\nu} \rangle $ = 3.6 GeV

The first direct measurement of electron neutrino quasielastic and quasielasticlike scattering on hydrocarbon in the few-GeV region of incident neutrino energy has been carried out using the MINERvA detector in the NuMI beam at Fermilab. The flux-integrated differential cross sections in the electron production angle, electron energy, and Q 2 are presented. The ratio of the quasielastic, flux-integrated differential cross section in Q 2 for ν e with that of similarly selected ν μ -induced events from the same exposure is used to probe assumptions that underpin conventional treatments of charged-current νe interactions used by long-baseline neutrino oscillation experiments. Furthermore, the data are found to be consistent with lepton universality and are well described by the predictions of the neutrino event generator GENIE.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for direct pair production of a chargino and a neutralino decaying to the 125 GeV Higgs boson in √s = 8 TeV pp collisions with the ATLAS detector

A search is presented for the direct pair production of a chargino and a neutralino pp→ χ~± 1 χ ~0 2 , where the chargino decays to the lightest neutralino and the W boson, χ ~± 1 →χ ~0 1 (W ± → ℓ ± ν), while the neutralino decays to the lightest neutralino and the 125 GeV Higgs boson, χ ~0 2 →χ ~0 1 (h → bb/γγ/ℓ ± νqq). The final states considered for the search have large missing transverse momentum, an isolated electron or muon, and one of the following: either two jets identified as originating from bottom quarks, or two photons, or a second electron or muon with the same electric charge. The analysis is based on 20.3 fb -1 of √s=8 TeV proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with the Standard Model expectations; limits are set in the context of a simplified super-symmetric model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurements of $$\pi ^\pm $$ π ± , K $$^\pm $$ ± , p and $${\bar{\text {p}}}$$ p ¯ spectra in proton-proton interactions at 20, 31, 40, 80 and 158 $$\text{ GeV }/c$$ GeV / c with the NA61/SHINE spectrometer at the CERN SPS: The NA61/SHINE Collaboration

Measurements of inclusive spectra and mean multiplicities of $\pi^\pm$, K$^\pm$, p and $\bar{\textrm{p}}$ produced in inelastic p+p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 GeV/c ($\sqrt{s} = $ 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively) were performed at the CERN Super Proton Synchrotron using the large acceptance NA61/SHINE hadron spectrometer. Spectra are presented as function of rapidity and transverse momentum and are compared to predictions of current models. The measurements serve as the baseline in the NA61/SHINE study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗