The design and principle of operation of a Linnik-scheme-based interference microscope with a low-coherent radiation source and a reference mirror in the form of a monoatomic silicon layer are ...described. The microscope is designed to measure the heights of the surface profiles of reflecting objects by the phase-shifting method and provides a measurement error of up to 0.6 Å. The results of experiments on measuring the heights of monoatomic silicon layers to determine the sensitivity and on balls of silicon dioxide to assess the temporal stability of measurements are presented.
We report the first measurement of rapidity-odd directed flow (v1) for D0 and D0¯ mesons at midrapidity (|y|<0.8) in Au+Au collisions at sNN=200 GeV using the STAR detector at the Relativistic Heavy ...Ion Collider. In 10–80% Au+Au collisions, the slope of the v1 rapidity dependence (dv1/dy), averaged over D0 and D0¯ mesons, is −0.080±0.017(stat)±0.016(syst) for transverse momentum pT above 1.5 GeV/c. The absolute value of D0 meson dv1/dy is about 25 times larger than that for charged kaons, with 3.4σ significance. These data give a unique insight into the initial tilt of the produced matter, and offer constraints on the geometric and transport parameters of the hot QCD medium created in relativistic heavy-ion collisions.
We report on the first measurement of the charmed baryon Λc± production at midrapidity (|y|<1) in Au+Au collisions at sNN=200 GeV collected by the STAR experiment at the Relativistic Heavy Ion ...Collider. The Λc/D0 denoting (Λc++Λc−)/(D0+D¯0) yield ratio is measured to be 1.08±0.16 (stat)±0.26 (sys) in the 0%–20% most central Au+Au collisions for the transverse momentum (pT) range 3<pT<6 GeV/c. This is significantly larger than the pythia model calculations for p+p collisions. The measured Λc/D0 ratio, as a function of pT and collision centrality, is comparable to the baryon-to-meson ratios for light and strange hadrons in Au+Au collisions. Model calculations including coalescence hadronization for charmed baryon and meson formation reproduce the features of our measured Λc/D0 ratio.
Here, we report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at $ \sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR ...experiment at RHIC. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter B2 are discussed. We find that the values of B2 for antideuterons are systematically lower than those for deuterons, indicating that the correlation volume of antibaryons is larger than that of baryons at $ \sqrt{s_{NN}}$ from 19.6 to 39 GeV. In addition, values of B2 are found to vary with collision energy and show a broad minimum around $ \sqrt{s_{NN}}$ = 20 to 40 GeV, which might imply a change of the equation of state of the medium in these collisions.
A local tomography by differential interface contrast (DIC) projections is proposed for optical studies of the internal structure of transparent objects. The advantage of local tomography is that it ...allows quickly calculating the desired distribution in the point or area of interest without a complete reconstruction of the entire cross section. To obtain quantitative DIC-projections, a tomographic microscope with a transverse shear interferometer is developed, in which the method of phase steps for phase recovery is implemented. A procedure is proposed for normalizing projection data on geometric moments from DIC-projections. It is theoretically shown and confirmed by computer simulation that the total image from the DIC-projections is proportional to the Hilbert transform from the original function describing the object, and the application of the inverse Hilbert transform to this image leads to the restoration of the tomogram of the object. The results of reconstructing a tomogram of a ball made of silicon dioxide by its experimental DIC-projections are presented. Comparison of the simulation results with the experimental results showed their close agreement.
We report a new measurement of D0-meson production at mid-rapidity (| y | < 1) in Au + Au collisions at $\sqrt{s}$$_ {NN}$ = 200 GeV utilizing the heavy flavor tracker, a high resolution silicon ...detector at the STAR experiment. Invariant yields of D0 mesons with transverse momentum pT ≲ 9 GeV / c are reported in various centrality bins (0–10%, 10–20%, 20–40%, 40–60%, and 60–80%). Blast-wave thermal models are used to fit the D0-meson pT spectra to study D0 hadron kinetic freeze-out properties. The average radial flow velocity extracted from the fit is considerably smaller than that of light hadrons (π, K, and p), but comparable to that of hadrons containing multiple strange quarks (Φ, Ξ -) , indicating that D0 mesons kinetically decouple from the system earlier than light hadrons. The calculated D0 nuclear modification factors reaffirm that charm quarks suffer a large amount of energy loss in the medium, similar to those of light quarks for pT > 4 GeV/c in central 0–10% Au + Au collisions. At low pT, the nuclear modification factors show a characteristic structure qualitatively consistent with the expectation from model predictions that charm quarks gain sizable collective motion during the medium evolution. The improved measurements are expected to offer new constraints to model calculations and help gain further insights into the hot and dense medium created in these collisions.
We present the spectral analysis method of measuring phase shift from interferograms based on the differences between them. Limitations of the method are explained and ways of increasing its accuracy ...are clarified. We examine the effect of the phase shift value and additive noise on the measurement error.
We present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at s=500 GeV by the STAR experiment at RHIC. The ...measured observable is sensitive to the Sivers function, one of the transverse-momentum-dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. These data provide the first experimental investigation of the nonuniversality of the Sivers function, fundamental to our understanding of QCD.
The 2nd generation composite HTS tapes samples based on the GdBCO (123) compound were irradiated in a pulsed electron accelerator (Terek-2 facility, IOF RAS) through a tantalum target to determine ...the thermal and shock loads effect at the tantalum-HTS boundary on the HTS tapes superconducting characteristics. Scanning Hall magnetometry was used to characterize the HTS samples after the electron irradiation exposure. The thermal modes and shock load in a composite superconductor under the irradiation influence are estimated depending on the magnitude of energy contribution to the target. At a silver surface temperature equal to the melting temperature, the critical current value drops by 87% of the initial value. At lower energy, a weaker critical current decrease was observed. The temperature effects and shock waves roles under the irradiation is discussed.
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