Bulk Properties of the Medium Produced in Relativistic Heavy-Ion Collisions from the Beam Energy Scan Program

We present measurements of bulk properties of the matter produced in Au+Aucollisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, and 39 GeV using identifiedhadrons ($\pi^\pm$, $K^\pm$, $p$ and $\bar{p}$) from the STAR experiment in theBeam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC).Midrapidity ($|y|<$0.1) results for multiplicity densities $dN/dy$, averagetransverse momenta $\langle p_T \rangle$ and particle ratios are presented. Thechemical and kinetic freeze-out dynamics at these energies are discussed andpresented as a function of collision centrality and energy. These resultsconstitute the systematic measurements of bulk properties of matter formed inheavy-ion collisions over a broad range of energy (or baryon chemicalpotential) at RHIC.

Coherent diffractive photoproduction of $\rho^{0}$ mesons on gold nuclei at RHIC

The STAR Collaboration reports on the photoproduction of $\pi^+\pi^-$ pairsin gold-gold collisions at a center-of-mass energy of 200 GeV/nucleon-pair.These pion pairs are produced when a nearly-real photon emitted by one ionscatters from the other ion. We fit the $\pi^+\pi^-$ invariant mass spectrum with a combination of $\rho$and $\omega$ resonances and a direct $\pi^+\pi^-$ continuum. This is the firstobservation of the $\omega$ in ultra-peripheral collisions, and the firstmeasurement of $\rho-\omega$ interference at energies where photoproduction isdominated by Pomeron exchange. The $\omega$ amplitude is consistent with themeasured $\gamma p\rightarrow \omega p$ cross section, a classical Glaubercalculation and the $\omega\rightarrow\pi^+\pi^-$ branching ratio. The $\omega$phase angle is similar to that observed at much lower energies, showing thatthe $\rho-\omega$ phase difference does not depend significantly on photonenergy. The $\rho^0$ differential cross section $d\sigma/dt$ exhibits a cleardiffraction pattern, compatible with scattering from a gold nucleus, with 2minima visible. The positions of the diffractive minima agree better with thepredictions of a quantum Glauber calculation that does not include nuclearshadowing than with a calculation that does include shadowing.

Measurement of the cross section and longitudinal double-spin asymmetry for di-jet production in polarized $pp$ collisions at $\sqrt{s}$ = 200 GeV

We report the first measurement of the longitudinal double-spin asymmetry$A_{LL}$ for mid-rapidity di-jet production in polarized $pp$ collisions at acenter-of-mass energy of $\sqrt{s} = 200$ GeV. The di-jet cross section wasmeasured and is shown to be consistent with next-to-leading order (NLO)perturbative QCD predictions. $A_{LL}$ results are presented for two distincttopologies, defined by the jet pseudorapidities, and are compared topredictions from several recent NLO global analyses. The measured asymmetries,the first such correlation measurements, support those analyses that findpositive gluon polarization at the level of roughly 0.2 over the region ofBjorken-$x > 0.05$.

Evolution Of Massive Black Hole Binaries In Rotating Stellar Nuclei: Implications For Gravitational Wave Detection

We compute the isotropic gravitational wave (GW) background produced bybinary supermassive black holes (SBHs) in galactic nuclei. In our model,massive binaries evolve at early times via gravitational-slingshot interactionwith nearby stars, and at later times by the emission of GWs. Our expressionsfor the rate of binary hardening in the "stellar" regime are taken from therecent work of Vasiliev et al., who show that in the non-axisymmetric galaxiesexpected to form via mergers, stars are supplied to the center at high enoughrates to ensure binary coalescence on Gyr timescales. We also include, for thefirst time, the extra degrees of freedom associated with evolution of thebinary's orbital plane; in rotating nuclei, interaction with stars causes theorientation and the eccentricity of a massive binary to change in tandem,leading in some cases to very high eccentricities (e>0.9) before the binaryenters the GW-dominated regime. We argue that previous studies haveover-estimated the mean ratio of SBH mass to galaxy bulge mass by factors of 2- 3. In the frequency regime currently accessible to pulsar timing arrays(PTAs), our assumptions imply a factor 2 - 3 reduction in the characteristicstrain compared with the values computed in most recent studies, removing thetension that currently exists between model predictions and the non-detectionof GWs.

Azimuthal transverse single-spin asymmetries of inclusive jets and charged pions within jets from polarized-proton collisions at $\sqrt{s} = 500$ GeV

We report the first measurements of transverse single-spin asymmetries forinclusive jet and jet + $\pi^{\pm}$ production at midrapidity from transverselypolarized proton-proton collisions at $\sqrt{s} = 500$ GeV. The data werecollected in 2011 with the STAR detector sampled from 23 pb$^{-1}$ integratedluminosity with an average beam polarization of 53%. Asymmetries are reportedfor jets with transverse momenta $6 < p_{T, jet} < 55$ GeV/c and pseudorapidity$|\eta| < 1$. Presented are measurements of the inclusive-jet azimuthaltransverse single-spin asymmetry, sensitive to twist-3 initial-statequark-gluon correlators; the Collins asymmetry, sensitive to quark transversitycoupled to the polarized Collins fragmentation function; and the firstmeasurement of the "Collins-like" asymmetry, sensitive to linearly polarizedgluons. Within the present statistical precision, inclusive-jet andCollins-like asymmetries are small, with the latter allowing the firstexperimental constraints on gluon linear polarization in a polarized proton. Athigher values of jet transverse momenta, we observe the first non-zero Collinsasymmetries in polarized-proton collisions, with a statistical significance ofgreater than $5\sigma$. The results span a range of x similar to results fromSIDIS but at much higher $Q^{2}$. The Collins results enable tests ofuniversality and factorization-breaking in the transverse momentum-dependentformulation of perturbative quantum chromodynamics.

Probabilistic approach to nonlinear wave-particle resonant interaction

Measurement of $D^0$ azimuthal anisotropy at mid-rapidity in Au+Au collisions at \sNN = 200\,GeV

We report the first measurement of the elliptic anisotropy ($v_2$) of thecharm meson $D^0$ at mid-rapidity ($|y|$\,$<$\,1) in Au+Au collisions at \sNN =200\,GeV. The measurement was conducted by the STAR experiment at RHICutilizing a new high-resolution silicon tracker. The measured $D^0$ $v_2$ in0--80\% centrality Au+Au collisions can be described by a viscous hydrodynamiccalculation for transverse momentum ($p_{\rm T}$) less than 4\,GeV/$c$. The$D^0$ $v_2$ as a function of transverse kinetic energy ($m_{\rm T} - m_0$,where $m_{\rm T} = \sqrt{p_{\rm T}^2 + m_0^2}$) is consistent with that oflight mesons in 10--40\% centrality Au+Au collisions. These results suggestthat charm quarks have achieved local thermal equilibrium with the mediumcreated in such collisions. Several theoretical models, with thetemperature--dependent, dimensionless charm spatial diffusion coefficient($2{\pi}TD_s$) in the range of $\sim$2--12, are able to simultaneouslyreproduce our $D^0$ $v_2$ result and our previously published results for the$D^0$ nuclear modification factor.

Beam Energy Dependence of Jet-Quenching Effects in Au+Au Collisions at $\sqrt{s_{_{ \mathrm{NN}}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV

We report measurements of the nuclear modification factor, $R_{\mathrm{CP}}$, for charged hadrons as well as identified $\pi^{+(-)}$,$K^{+(-)}$, and $p(\overline{p})$ for Au+Au collision energies of $\sqrt{s_{_{\mathrm{NN}}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV. We observe aclear high-$p_{\mathrm{T}}$ net suppression in central collisions at 62.4 GeVfor charged hadrons which evolves smoothly to a large net enhancement at lowerenergies. This trend is driven by the evolution of the pion spectra, but isalso very similar for the kaon spectra. While the magnitude of the proton $R_{\mathrm{CP}}$ at high $p_{\mathrm{T}}$ does depend on collision energy, neitherthe proton nor the anti-proton $R_{ \mathrm{CP}}$ at high $p_{\mathrm{T}}$exhibit net suppression at any energy. A study of how the binary collisionscaled high-$p_{\mathrm{T}}$ yield evolves with centrality reveals anon-monotonic shape that is consistent with the idea that jet-quenching isincreasing faster than the combined phenomena that lead to enhancement.

Electron microscopy methods in studies of archaeological objects

The usage of traditional and new material science methods for Cultural Heritage objects investigations resulted in a number of breakthroughs. The comprehensive composition and structural analysis plays highly important role in the scientific base for the development of the history, conservation and restoration of artifacts. One of the key methods used for these goals is the Electron Microscopy (EM) together with Microanalysis (MA). These methods provide relatively quick qualitative and quantitative data on the artifacts. The morphology of the samples in the range of 5 nm-500 μm is usually studied by Scanning EM (SEM) and energy dispersive X-ray spectroscopy (EDXS) [1]. Nowadays these methods are accompanied with focus ion beam (FIB), which enable to produce tiny cross sections and analyze not only the specimen surface but also the bulk. That technique is important for the study of coatings, thin films and multilayer systems, especially when the regular section cannot be prepared in the sake of preservation of the sample. Moreover, FIB together with SEM is used for 3D reconstruction of bulk samples. Recently, low voltage and environmental SEMs were used for the study of non conductive (like ceramic) and organic (wooden or parchment) in the “low vacuum” SEM specimen chamber. The crystal structure of the samples is analyzed by the means of the Transmission EM (TEM). A number of thoughtful studies of a number of cultural heritage objects have been conducted lately in the National Research Center “Kurchatov Institute“. These are inlayed metal alloys, ceramic and parchment found in different areas. In our presentation some of these studies like the ancient CrossEncolpion found near Chernizh-2 (Russia),which were initially dated to the 12th century. They are interesting not only as the historical and iconographic pieces, but as inlaid unknown alloys. The research helped to enlarge the scientific scope of knowledge on Mediaeval materials and manufacturing techniques, while the conservation efforts gave back the proper artistic value to the artifacts. The second is the Italian Terracotta "Madonna Friedrichstein" (XV AC). A study of the origin and manufacturing process (moulding, baking, touching up and painting) of these terracotta pieces has been made on the basis of the data obtained. Insight may then be gained into the technological knowledge and skill of ancient potters. The unique detailed results of these studies will be given in the present contribution. Authors are grateful to the Institute of Archaeology of the Russian Academy of Science, the Pushkin State Museum of Fine Arts, the State Historical Museum and the V.I. Vernadsky Crimean Federal University for providing of the artifacts. Janssens K, Van Grieken R (2004) (eds) Non-destructive microanalysis of cultural heritage materials XLII. Wilson and Wilson, Amsterdam

Comprehensive studies of cultural heritage objects in NRC Kurchatov Institute

Extensive use of natural science techniques for research of cultural heritage is one of the main world trends. It significantly expands the information about different artifacts, exploring their elemental and phase composition, degree of preservation, internal structure and so on. It is very effective for supporting of the traditional methods of extracting historical information from written and archaeological sources, which didn’t lost relevance, but largely exhausted their limits. It is also crucially important for the determination of the optimal methods for restoration, preservation, storage and demonstration of museum exhibits. In 2015 a laboratory of Natural Science Technology for Cultural Heritage (NSciTeCH Lab) was established at NRC Kurchatov Institute. Since the studies of museum artifacts with using a variety of synchrotron and neutron techniques as well as electron microscopy, chromatospectrometry, gen-analysis and etc. at NRC Kurchatov Institute were significantly strengthened and expanded. Currently we carry out a joint research in the field of historical material science with the State Historical Museum, Pushkin State Museum of Fine Arts, Institute of Archaeology RAS, V.I. Vernadsky Crimean Federal University and others. The range of objects under study is extremely wide: Egyptian mummies, Italian ceramics and marbles, organic decoration from bronze age wood artifacts, metal samples and tools from the different eras, etc. In this paper we present the results of the research of some artifacts, which were carried out at the Kurchatov Institute. The authors express profound gratitude to colleagues from State Historical Museum (N. Shishlina), Pushkin State Museum of Fine Arts (M. Loshak, V. Rastorguev), Institute of Archaeology RAS (E. Devlet, N. Makarov) for the objects provision and fruitful discussion of the results.