Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “GeV”

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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Magnetic bubble chambers and sub-GeV dark matter direct detection

We propose a new application of single molecule magnet crystals: their use as “magnetic bubble chambers” for the direct detection of sub-GeV dark matter. The spins in these macroscopic crystals effectively act as independent nanoscale magnets. When antialigned with an external magnetic field they form metastable states with a relaxation time that can be very long at sufficiently low temperatures. The Zeeman energy stored in this system can be released through localized heating, caused for example by the scattering or absorption of dark matter, resulting in a spin avalanche (or “magnetic deflagration”) that amplifies the effects of the initial heat deposit, enabling detection. Much like the temperature and pressure in a conventional bubble chamber, the temperature and external magnetic field set the detection threshold for a single molecule magnet crystal. Here, we discuss this detector concept for dark matter detection and propose ways to ameliorate backgrounds. If successfully developed, this detector concept can search for hidden photon dark matter in the meV–eV mass range with sensitivities exceeding current bounds by several orders of magnitude.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Evidence for e + e - → γ η c ( 1 S ) at center-of-mass energies between 4.01 and 4.60 GeV

In this paper, we present first evidence for the process e + e - → γη c (1S) at six center-of-mass energies between 4.01 and 4.60 GeV using data collected by the BESIII experiment operating at BEPCII. We measure the Born cross section at each energy using a combination of twelve η c (1S) decay channels. We also combine all six energies under various assumptions for the energy-dependence of the cross section. Finally, if the process is assumed to proceed via the Y (4260), we measure a peak Born cross section σ peak (e + e - → γη c (1S)) = 2.11 ± 0.49(stat.) ± 0.36(syst.) pb with a statistical significance of 4.2σ.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Cross section and longitudinal single-spin asymmetry A L for forward W ± → μ ± ν production in polarized p + p collisions at s = 510 GeV

We have measured the cross section and single-spin asymmetries from forward W ± → μ ± ν production in longitudinally polarized $p+p$ collisions at $\sqrt{s}=510\text{ }\text{ }\mathrm{GeV}$ using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the $W$ bosons provides a natural flavor separation of the participating partons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Measurements of Higher Order Flow Harmonics in Au plus Au collisions at root s(NN)=200 Gev

Flow coefficients v{sub n} for n = 2, 3, 4, characterizing the anisotropic collective flow in Au+Au collisions at {radical}s{sub NN} = 200 GeV, are measured relative to event planes {Psi}{sub n}, determined at large rapidity. We report v{sub n} as a function of transverse momentum and collision centrality, and study the correlations among the event planes of different order n. The v{sub n} are well described by hydrodynamic models which employ a Glauber Monte Carlo initial state geometry with fluctuations, providing additional constraining power on the interplay between initial conditions and the effects of viscosity as the system evolves. This new constraint can serve to improve the precision of the extracted shear viscosity to entropy density ratio {eta}/s.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Beam-Target Double-Spin Asymmetry A LT in Charged Pion Production from Deep Inelastic Scattering on a Transversely Polarized He 3 Target at 1.4 < Q 2 < 2.7 GeV 2

We report the first measurement of the double-spin asymmetry A LT for charged pion electroproduction in semi-inclusive deep inelastic electron scattering on a transversely polarized 3 He target. The kinematics focused on the valence quark region, 0.16 < x < 0.35 with 1.4 < Q 2 < 2.7 GeV 2 . The corresponding neutron A LT asymmetries were extracted from the measured 3 He asymmetries and proton/ 3 He cross section ratios using the effective polarization approximation. These new data probe the transverse momentum dependent parton distribution function g 1T q and therefore provide access to quark spin-orbit correlations. Our results indicate a positive azimuthal asymmetry for π - production on 3 He and the neutron, while our π + asymmetries are consistent with zero.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Identified Hadron Compositions in p+p and Au+Au Collisions at High Transverse Momenta at √( s NN)=200 GeV

We report transverse momentum (pT≤15 GeV/c) spectra of π ± , K ± , p, p̄, K 0 S , and ρ⁰ at midrapidity in p+p and Au+Au collisions at √( s NN)=200 GeV. Perturbative QCD calculations are consistent with π ± spectra in p+p collisions but do not reproduce K and p(p̄) spectra. The observed decreasing antiparticle-to-particle ratios with increasing pT provide experimental evidence for varying quark and gluon jet contributions to high- pT hadron yields. The relative hadron abundances in Au+Au at pT ≳ 8 GeV/c are measured to be similar to the p+p results, despite the expected Casimir effect for parton energy loss.

Agakishiev, G.↗
DOE OSTI2013

Measurement of J/ψ Azimuthal Anisotropy in Au+Au Collisions at √s NN =200 GeV

The measurement of J/ψ azimuthal anisotropy is presented as a function of transverse momentum for different centralities in Au+Au collisions at √s NN>/sub>=200 GeV. The measured J/ψ elliptic flow is consistent with zero within errors for transverse momentum between 2 and 10 GeV/c. Our measurement suggests that J/ψ particles with relatively large transverse momenta are not dominantly produced by coalescence from thermalized charm quarks, when comparing to model calculations.

Adamczyk, L.↗
DOE OSTI2015

Measurement of long-range angular correlation and quadrupole anisotropy of pions and (anti)protons in central d + Au collisions at s N N = 200 GeV

In this study, we present azimuthal angular correlations between charged hadrons and energy deposited in calorimeter towers in central d+Au and aluminum bias p+p collisions at √s NN = 200 GeV. The charged hadron is measured at midrapidity lηl < 0.35, and the energy us measured at large rapidity (–3.7 < η < –3.1, Au-going direction). An enhanced near-side angular correlation across lΔηl > 2.75 is observed in d+Au collisions. Using the event plane method applied to the Au-going energy distribution, we extract the anisotropy strength v₂ for inclusive charged hadrons at midrapidity up to p T = 4.5 GeV/c. We also present the measurement of v₂ for identified π ± and (anti)protons in central d+Au collisions, and observe a mass-ordering pattern similar to that seen in heavy ion collisions. These results are compared with viscous hydrodynamic calculations and measurements from p+Pb at √s NN = 5.02 TeV. The magnitude of the mass-ordering in d+Au is found to be smaller than that in p+Pb collisions, which may indicate smaller radial flow in lower energy d+Au collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Precision measurement of the longitudinal double-spin asymmetry for inclusive jet production in polarized proton collisions at √s = 200 GeV

We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, A LL , in polarized pp collisions at center-of-mass energy √s = 200 GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. Lastly, the measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x > 0.05 .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Measurements of elliptic and triangular flow in high-multiplicity 3 He+Au collisions at √s NN =200 GeV

We present the first measurement of elliptic (v 2 ) and triangular (v 3 ) flow in high-multiplicity 3 He+Aucollisions at √s NN =200 GeV. Two-particle correlations, where the particles have a large separation in pseudorapidity, are compared in 3 He+Au and in p+p collisions and indicate that collective effects dominate the second and third Fourier components for the correlations observed in the 3 He+Ausystem. The collective behavior is quantified in terms of elliptic v 2 and triangular v 3 anisotropy coefficients measured with respect to their corresponding event planes. The v 2 values are comparable to those previously measured in d+Au collisions at the same nucleon-nucleon center-of-mass energy. Comparisons with various theoretical predictions are made, including to models where the hot spots created by the impact of the three 3 He nucleons on the Au nucleus expand hydrodynamically to generate the triangular flow. The agreement of these models with data may indicate the formation of low-viscosity quark-gluon plasma even in these small collision systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Centrality and Transverse Momentum Dependence of Elliptic Flow of Multistrange Hadrons and φ Meson in Au + Au Collisions at s N N = 200 GeV

In this paper, we present high precision measurements of elliptic flow near midrapidity (|y|<1.0) for multistrange hadrons and φ meson as a function of centrality and transverse momentum in Au+Au collisions at center of mass energy $\sqrt{sNN}$=200 GeV. We observe that the transverse momentum dependence of φ and Ωv 2 is similar to that of π and p, respectively, which may indicate that the heavier strange quark flows as strongly as the lighter up and down quarks. This observation constitutes a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy. Number of constituent quark scaling is found to hold within statistical uncertainty for both 0%-30% and 30%-80% collision centrality. Finally, there is an indication of the breakdown of previously observed mass ordering between φ and proton v 2 at low transverse momentum in the 0%-30% centrality range, possibly indicating late hadronic interactions affecting the proton v 2 .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Centrality-Dependent Modification of Jet-Production Rates in Deuteron-Gold Collisions at s N N = 200 GeV

We measured jet production rates in p+p and d+Au collisions at s N N = 200 GeV recorded in 2008 with the PHENIX detector at the Relativistic Heavy Ion Collider. Jets are reconstructed using the R=0.3 anti-k t algorithm from energy deposits in the electromagnetic calorimeter and charged tracks in multiwire proportional chambers, and the jet transverse momentum (p T ) spectra are corrected for the detector response. Spectra are reported for jets with 12 T <50 GeV/c, within a pseudorapidity acceptance of |η|<0.3. The nuclear-modification factor (R dAu ) values for 0%–100% d+Au events are found to be consistent with unity, constraining the role of initial state effects on jet production. Nonetheless, the centrality-selected R dAu values and central-to-peripheral ratios (R CP ) show large, p T -dependent deviations from unity, challenging the conventional models that relate hard-process rates and soft-particle production in collisions involving nuclei.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Charge-Dependent Directed Flow in Cu + Au Collisions at s N N = 200 GeV

Here we present the first measurement of charge-dependent directed flow in Cu + Au collisions at $\sqrt{s}$$_ {NN}$ = 200 GeV . The results are presented as a function of the particle transverse momentum and pseudorapidity for different centralities. A finite difference between the directed flow of positive and negative charged particles is observed that qualitatively agrees with the expectations from the effects of the initial strong electric field between two colliding ions with different nuclear charges. The measured difference in directed flow is much smaller than that obtained from the parton-hadron-string-dynamics model, which suggests that most of the electric charges, i.e., quarks and antiquarks, have not yet been created during the lifetime of the strong electric field, which is of the order of, or less than, 1fm / c .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Measurement of D 0 Azimuthal Anisotropy at Midrapidity in Au + Au Collisions at s N N = 200 GeV

In this paper, we report the first measurement of the elliptic anisotropy (v2) of the charm meson D 0 at midrapidity (|y| < 1) in Au + Au collisions at $\sqrt{s}$$_ {NN}$ = 200 GeV. The measurement was conducted by the STAR experiment at RHIC utilizing a new high-resolution silicon tracker. The measured D 0 v 2 in 0%–80% centrality Au + Au collisions can be described by a viscous hydrodynamic calculation for a transverse momentum (p T ) of less than 4 GeV/c . The D 0 v 2 as a function of transverse kinetic energy (m T - m 0 , where m T = $\sqrt{p}$$2\atop{T}$ + m$2\atop{0}$) is consistent with that of light mesons in 10%–40% centrality Au + Au collisions. These results suggest that charm quarks have achieved local thermal equilibrium with the medium created in such collisions. In conclusion, several theoretical models, with the temperature-dependent, dimensionless charm spatial diffusion coefficient (2πTD s ) in the range of ~2–12 , are able to simultaneously reproduce our D 0 v 2 result and our previously published results for the D 0 nuclear modification factor.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Constraints on Sub-GeV Dark-Matter–Electron Scattering from the DarkSide-50 Experiment

Here, we present new constraints on sub-GeV dark matter particles scattering off electrons based on 6780.0 kg d of data collected with the DarkSide-50 dual-phase argon time projection chamber. This analysis uses electroluminescence signals due to ionized electrons extracted from the liquid argon target. The detector has a very high trigger probability for these signals, allowing for an analysis threshold of three extracted electrons, or approximately 0.05 keVee. We calculate the expected recoil spectra for dark matter-electron scattering in argon and, under the assumption of momentum-independent scattering, improve upon existing limits from XENON10 for dark-matter particles with masses between 30 and 100 MeV/c 2 .

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Pseudorapidity Dependence of Particle Production and Elliptic Flow in Asymmetric Nuclear Collisions of p + Al , p + Au , d + Au , and He 3 + Au at s N N = 200 GeV

Asymmetric nuclear collisions of p + Al , p + Au , d + Au , and He 3 + Au at s N N = 200 GeV rovide an excellent laboratory for understanding particle production, as well as exploring interactions among these particles after their initial creation in the collision. We present measurements of charged hadron production dN ch /dη in all such collision systems over a broad pseudorapidity range and as a function of collision multiplicity. A simple wounded quark model is remarkably successful at describing the full data set. We also measure the elliptic flow v 2 over a similarly broad pseudorapidity range. These measurements provide key constraints on models of particle emission and their translation into flow.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Results of a Search for Sub-GeV Dark Matter Using 2013 LUX Data

The scattering of dark matter (DM) particles with sub-GeV masses off nuclei is difficult to detect using liquid xenon-based DM search instruments because the energy transfer during nuclear recoils is smaller than the typical detector threshold. However, the tree-level DM-nucleus scattering diagram can be accompanied by simultaneous emission of a Bremsstrahlung photon or a so-called "Migdal" electron. These provide an electron recoil component to the experimental signature at higher energies than the corresponding nuclear recoil. The presence of this signature allows liquid xenon detectors to use both the scintillation and the ionization signals in the analysis where the nuclear recoil signal would not be otherwise visible. In this work, we report constraints on spin-independent DM-nucleon scattering for DM particles with masses of 0.4-5 GeV/c$^2$ using 1.4$\times10^4$ kg$\cdot$day of search exposure from the 2013 data from the Large Underground Xenon (LUX) experiment for four different classes of mediators. Finally, this analysis extends the reach of liquid xenon-based DM search instruments to lower DM masses than has been achieved previously.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Nuclear Dependence of the Transverse Single-Spin Asymmetry in the Production of Charged Hadrons at Forward Rapidity in Polarized p + p , p + Al , and p + Au Collisions at s N N = 200 GeV

We report on the nuclear dependence of transverse single-spin asymmetries (TSSAs) in the production of positively charged hadrons in polarized p ↑ + p , p ↑ + Al , and p ↑ + Au collisions at √ s N N = 200 GeV . The measurements have been performed at forward rapidity ( 1.4 < η < 2.4 ) over the range of transverse momentum ( 1.8 < p T < 7.0 G eV / c ) and Feynman x ( 0.1 < x F < 0.2 ). We observed positive asymmetries for positively charged hadrons in p ↑ + p collisions, and significantly reduced asymmetries in p ↑ + A collisions. These results reveal a nuclear dependence of TSSAs for charged-hadron production in a regime where perturbative techniques are applicable. These results provide new opportunities to use p ↑ + A collisions as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions and to use TSSAs as a new handle in studying small-system collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗