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Abstract Control over the distribution of dopants in nanowires is essential for regulating their electronic properties, but perturbations in nanowire microstructure may affect doping. Conversely, dopants may be used to control nanowire microstructure including the generation of twinning superlattices (TSLs)—periodic arrays of twin planes. Here the spatial distribution of Be dopants in a GaAs nanowire with a TSL is investigated using atom probe tomography. Homogeneous dopant distributions in both the radial and axial directions are observed, indicating a decoupling of the dopant distribution from the nanowire microstructure. Although the dopant distribution is microscopically homogenous, radial distribution function analysis discovered that 1% of the Be atoms occur in substitutional-interstitial pairs. The pairing confirms theoretical predictions based on the low defect formation energy. These findings indicate that using dopants to engineer microstructure does not necessarily imply that the dopant distribution is non-uniform. 

We present the measurement of ${\pi }^{+}$-argon inelastic cross sections using the ProtoDUNE single-phase liquid argon time projection chamber in the incident ${\pi }^{+}$kinetic energy range of 500–800 MeV in multiple exclusive channels (absorption, charge exchange, and the remaining inelastic interactions). The results of this analysis are important inputs to simulations of liquid argon neutrino experiments such as the Deep Underground Neutrino Experiment and the Short Baseline Neutrino program at Fermi National Accelerator Laboratory. They will be employed to improve the modeling of final state interactions within neutrino event generators used by these experiments, as well as the modeling of ${\pi }^{+}$-argon secondary interactions within the liquid argon. This is the first measurement of ${\pi }^{+}$-argon absorption at this kinetic energy range as well as the first ever measurement of ${\pi }^{+}$-argon charge exchange. 

Abstract In a Quark-Gluon Plasma (QGP), the fundamental building blocks of matter, quarks and gluons, are under extreme conditions of temperature and density. A QGP could exist in the early stages of the Universe, and in various objects and events in the cosmos. The thermodynamic and hydrodynamic properties of the QGP are described by Quantum Chromodynamics (QCD) and can be studied in heavy-ion collisions. Despite being a key thermodynamic parameter, the QGP temperature is still poorly known. Thermal lepton pairs (e⁺e⁻andμ⁺μ⁻) are ideal penetrating probes of the true temperature of the emitting source, since their invariant-mass spectra suffer neither from strong final-state interactions nor from blue-shift effects due to rapid expansion. Here we measure the QGP temperature using thermale⁺e⁻production at the Relativistic Heavy Ion Collider (RHIC). The average temperature from the low-mass region (in-mediumρ⁰vector-meson dominant) is (2.01 ± 0.23) × 10¹²K, consistent with the chemical freeze-out temperature from statistical models and the phase transition temperature from Lattice QCD. The average temperature from the intermediate mass region (above theρ⁰mass, QGP dominant) is significantly higher at (3.25 ± 0.60) × 10¹²K. This work provides essential experimental thermodynamic measurements to map out the QCD phase diagram and understand the properties of matter under extreme conditions. 

The STAR experiment reports new, high-precision measurements of the transverse single-spin asymmetries for ${\pi }^{\pm }$within jets, namely the Collins asymmetries, from transversely polarized $p^{\uparrow }p$collisions at $\sqrt{s}=510\mathrm{GeV}$. The energy-scaled distribution of jet transverse momentum, $x_{\mathrm{T}}=2p_{\mathrm{T},\text{jet}}/\sqrt{s}$, shows a remarkable consistency for Collins asymmetries of ${\pi }^{\pm }$in jets between $\sqrt{s}=200\mathrm{GeV}$and 510 GeV. This indicates that the Collins asymmetries are nearly energy independent, with, at most, a very weak scale dependence in $p^{\uparrow }p$collisions. These results extend to high-momentum scales ( $Q^2\le 3400{\mathrm{GeV}}^2$) and enable unique tests of evolution and universality in the transverse-momentum-dependent formalism, thus providing important constraints for the Collins fragmentation functions.