arXiv subjects

A. Hirsch

Publications and source records attributed to A. Hirsch.

41 records · Page 3Linked to original sources

arXiv2015

Long-range pseudorapidity dihadron correlations in $d$+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV

Dihadron angular correlations in $d$+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV are reported as a function of the measured zero-degree calorimeter neutral energy and the forward charged hadron multiplicity in the Au-beam direction. A finite correlated yield is observed at large relative pseudorapidity ($Δη$) on the near side (i.e. relative azimuth $Δϕ\sim0$). This correlated yield as a function of $Δη$ appears to scale with the dominant, primarily jet-related, away-side ($Δϕ\simπ$) yield. The Fourier coefficients of the $Δϕ$ correlation, $V_{n}=\langle\cos nΔϕ\rangle$, have a strong $Δη$ dependence. In addition, it is found that $V_{1}$ is approximately inversely proportional to the mid-rapidity event multiplicity, while $V_{2}$ is independent of it with similar magnitude in the forward ($d$-going) and backward (Au-going) directions.

nucl-ex↗

arXiv2011

Energy and system-size dependence of two- and four-particle $v_2$ measurements in heavy-ion collisions at RHIC and their implications on flow fluctuations and nonflow

We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants $v_2$ ($v_2\{2\}$ and $v_2\{4\}$) for Au+Au and Cu+Cu collisions at center of mass energies $\sqrt{s_{_{\mathrm{NN}}}} = 62.4$ and 200 GeV. The difference between $v_2\{2\}^2$ and $v_2\{4\}^2$ is related to $v_{2}$ fluctuations ($σ_{v_2}$) and nonflow $(δ_{2})$. We present an upper limit to $σ_{v_2}/v_{2}$. Following the assumption that eccentricity fluctuations $σ_ε$ dominate $v_2$ fluctuations $\frac{σ_{v_2}}{v_2} \approx \frac{σ_ε}ε$ we deduce the nonflow implied for several models of eccentricity fluctuations that would be required for consistency with $v_2\{2\}$ and $v_2\{4\}$. We also present results on the ratio of $v_2$ to eccentricity.

nucl-ex↗

arXiv2006

Magnetic fullerenes inside single-wall carbon nanotubes

C59N magnetic fullerenes were formed inside single-wall carbon nanotubes by vacuum annealing functionalized C59N molecules encapsulated inside the tubes. A hindered, anisotropic rotation of C59N was deduced from the temperature dependence of the electron spin resonance spectra near room temperature. Shortening of spin-lattice relaxation time, T_1, of C59N indicates a reversible charge transfer toward the host nanotubes above $\sim 350$ K. Bound C59N-C60 heterodimers are formed at lower temperatures when C60 is co-encapsulated with the functionalized C59N. In the 10-300 K range, T_1 of the heterodimer shows a relaxation dominated by the conduction electrons on the nanotubes.

cond-mat.str-el↗

arXiv2006

Encapsulating C59N azafullerene derivatives inside single-wall carbon nanotubes

Filling of single-wall carbon nanotubes with C59N azafullerene derivatives is reported from toluene solvent at ambient temperature. The filling is characterized by high resolution transmission electron microscopy and Raman spectroscopy. The filling efficiency is the same as for C60 fullerenes and the tube-azafullerene interaction is similar to the tube-C60 interaction. Vacuum annealing of the encapsulated azafullerene results in the growth of inner tubes, however no spectroscopic signature of nitrogen built in the inner walls is detected.

cond-mat.mtrl-sci↗

arXiv2000

Sideward Flow in Au + Au Collisions Between 2A GeV and 8A GeV

Using the large acceptance Time Projection Chamber of experiment E895 at Brookhaven, measurements of collective sideward flow in Au + Au collisions at beam energies of 2, 4, 6 and 8A GeV are presented in the form of in-plane transverse momentum and the first Fourier coefficient of azimuthal anisotropy v_1. These measurements indicate a smooth variation of sideward flow as a function of beam energy. The data are compared with four nuclear transport models which have an orientation towards this energy range. All four exhibit some qualitative trends similar to those found in the data, although none shows a consistent pattern of agreement within experimental uncertainties.

nucl-ex↗