Correlations in the hadron distributions produced in relativistic Au+Au collisions are studied in the discrete wavelet expansion method. The analysis is performed in the space of pseudorapidity (|eta| < 1) and azimuth (full 2 pi) in bins of transverse momentum (p_t) from 0.14 < p_t < 2.1 GeV/c. In peripheral Au+Au collisions a correlation structure ascribed to mini-jet fragmentation is observed. It evolves with collision centrality and p_t in a way not seen before which suggests strong dissipation of minijet fragmentation in the longitudinally-expanding medium.
Normalized dynamic texture for fineness scale m = 0
Normalized dynamic texture for fineness scale m = 1
Normalized dynamic texture for fineness scale m = 0
We present first measurements of the pseudorapidity and azimuth $(\eta,\phi)$ bin-size dependence of event-wise mean transverse momentum $<p_{t} >$ fluctuations for Au-Au collisions at $\sqrt{s_{NN}} = 200$ GeV. We invert that dependence to obtain $p_t$ autocorrelations on differences $(\eta_\Delta,\phi_\Delta)$ interpreted to represent velocity/temperature distributions on ($\eta,\phi$). The general form of the autocorrelations suggests that the basic correlation mechanism is parton fragmentation. The autocorrelations vary strongly with collision centrality, which suggests that fragmentation is strongly modified by a dissipative medium in the more central
Correlation amplitudes $B_{1}, B_{2}, B_{3}$ as well as positive-peak widths for pseudorapidity ($\sigma_{\eta_{1}}$) and azimuth ($\sigma_{\phi_{1}}$), plotted on mean participant path length $\nu$.
We present a measurement of the inclusive production of Upsilon mesons in U+U collisions at 193 GeV at mid-rapidity (|y| < 1). Previous studies in central Au+Au collisions at 200 GeV show a suppression of Upsilon(1S+2S+3S) production relative to expectations from the Upsilon yield in p+p collisions scaled by the number of binary nucleon-nucleon collisions (Ncoll), with an indication that the Upsilon(1S) state is also suppressed. The present measurement extends the number of participant nucleons in the collision (Npart) by 20% compared to Au+Au collisions, and allows us to study a system with higher energy density. We observe a suppression in both the Upsilon(1S+2S+3S) and Upsilon(1S) yields in central U+U data, which consolidates and extends the previously observed suppression trend in Au+Au collisions.
(Color online) $\Upsilon$(1S+2S+3S) (a) and $\Upsilon$(1S) (b) $R_{AA}$ vs. $N_{part}$ in $\sqrt{s_{NN}}$ = 193 GeV U+U collisions (solid circles), compared to 200 GeV RHIC Au+Au (solid squares [13] and hollow crosses [32]), and 2.76 TeV LHC Pb+Pb data (solid diamonds [33]). A 95% lower confidence bound is indicated for the 30-60% centrality U+U data (see text). Each point is plotted at the center of its bin. Centrality integrated (0-60%) U+U and Au+Au data are also shown as open circles and squares, respectively.
(Color online) $\Upsilon$(1S+2S+3S) (a) and $\Upsilon$(1S) (b) $R_{AA}$ vs. $N_{part}$ in $\sqrt{s_{NN}}$ = 193 GeV U+U collisions (solid circles), compared to 200 GeV RHIC Au+Au (solid squares [13] and hollow crosses [32]), and 2.76 TeV LHC Pb+Pb data (solid diamonds [33]). A 95% lower confidence bound is indicated for the 30-60% centrality U+U data (see text). Each point is plotted at the center of its bin. Centrality integrated (0-60%) U+U and Au+Au data are also shown as open circles and squares, respectively.
(Color online) $\Upsilon$(1S+2S+3S) (a) and $\Upsilon$(1S) (b) $R_{AA}$ vs. $N_{part}$ in $\sqrt{s_{NN}}$ = 193 GeV U+U collisions (solid circles), compared to different models [36–38], described in the text. The 95% lower confidence bound is indicated for the 30-60% centrality U+U data (see text). Each point is plotted at the center of its bin. Centrality integrated (0-60%) U+U and Au+Au data are also shown as open circles and squares, respectively.
We report results on rho(770)^0 -> pi+pi- production at midrapidity in p+p and peripheral Au+Au collisions at sqrt(s_NN) = 200 GeV. This is the first direct measurement of rho(770)^0 -> pi+pi- in heavy-ion collisions. The measured rho^0 peak in the invariant mass distribution is shifted by ~40 MeV/c^2 in minimum bias p+p interactions and ~70 MeV/c^2 in peripheral Au+Au collisions. The rho^0 mass shift is dependent on transverse momentum and multiplicity. The modification of the rho^0 meson mass, width, and shape due to phase space and dynamical effects are discussed.
The raw $\pi^{+} \pi^{-}$ invariant mass distributions after subtraction of the like-sign reference distribution for minimum bias p+p (top) and peripheral Au+Au (bottom) interactions.
The raw $\pi^{+} \pi^{-}$ invariant mass (solid line) and the like-sign reference distributions (open circles) for peripheral Au+Au collisions.
The $\rho^{0}$ mass as a function of $p_{T}$ for minimum bias $p$+$p$ (filled circles), high multiplicity $p$+$p$ (open triangles), and peripheral Au+Au (filled squares) collisions. The error bars indicate the systematic uncertainty. Statistical errors are negligible. The $\rho^{0}$ mass was obtained by fitting the data to the BW×PS functional form described in the text. The dashed lines represent the average of the $\rho^{0}$ mass measured in $e^{+} e^{−}$. The shaded areas indicate the ρ0 mass measured in $p$+$p$ collisions. The open triangles have been shifted downward on the abscissa by $50$ MeV/$c$ for clarity.
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