Tue·Sep 13, 2011Tuesday·September 13, 2011

1. 01*

   Cold nuclear matter physics at forward rapidities from d+Au collisions in PHENIX

   Mickey Chiu (for the PHENIX Collaboration)🇺🇸

   We present measurements by the PHENIX experiment at RHIC of di-hadron pair production in \dAu collisions where the particles in the pair are varied across a wide range of pseudorapidity, out to $\eta =3.8$. With di-hadrons, varying the $p_T$ and rapidity of the particles in the di-hadron pair allows studying any effects as a function of partonic $x$ in the nucleus. These di-hadron measurements might probe down to parton momentum fractions x $\sim$ $10^{-3}$ in the gold nucleus, where the interesting possibility of observing gluon saturation effects at RHIC is the greatest. Our measurements show that the correlated yield of back-to-back pairs in \dAu collisions is suppressed by up to an order of magnitude relative to \pp collisions, and increases with greater nuclear path thickness and with a selection for lower x in the Au nucleus.

   nucl-exJ.Phys.G(2011)·2 citations
2. 02*

   High $p_T$ inclusive hadron and photon spectra in pp and PbPb collisions

   Sevil Salur for CMS Collaboration🇺🇸

   In this article, we report the inclusive charged hadron and isolated photon spectra at $\sqrt{s_{NN}}=2.76$ TeV PbPb collisions measured with the CMS detector at LHC. Charged particle momentum spectra are compared to a constructed reference measurement of proton-proton collisions at $\sqrt{s}=2.76$ TeV by using a combination of $x_T$ scaling and direct interpolation at fixed $p_T$. Photon results are compared to next to leading order calculations at the same center of mass energy. Nuclear modification factors ($R_{AA}$) are calculated to study the properties of the medium. While a large suppression is observed in the charged particle $R_{AA}$ at high transverse momentum, isolated photons show no modifications, revealing that PbPb collisions at $\sqrt{s_{NN}}=2.76$ TeV produce a strongly interacting colored medium.

   nucl-exAIP Conf.Proc.(2012)·0 citations
3. 03*

   Harmonic decomposition of two-particle angular correlations in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV

   ALICE Collaboration

   Angular correlations between unidentified charged trigger ($t$) and associated ($a$) particles are measured by the ALICE experiment in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV for transverse momenta $0.25<p_T^{t,a}<15$ GeV/$c$, where $p_T^t>p_T^a$. The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval $|\eta |<1.0$. Distributions in relative azimuth $\Delta \varphi \equiv {\varphi }^t-{\varphi }^a$ are analyzed for $|\Delta \eta |\equiv |{\eta }^t-{\eta }^a|>0.8$, and are referred to as "long-range correlations". Fourier components $V_{n\Delta }\equiv ⟨\cos (n\Delta \varphi )⟩$ are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy $V_{n\Delta }(p_T^t,p_T^a)$ is fully described in terms of single-particle anisotropies $v_n(p_T)$ as $V_{n\Delta }(p_T^t,p_T^a)=v_n(p_T^t)v_n(p_T^a)$. This expectation is tested for $1\le n\le 5$ by applying a global fit of all $V_{n\Delta }(p_T^t,p_T^a)$ to obtain the best values $v_n\{GF\}(p_T)$. It is found that for $2\le n\le 5$, the fit agrees well with data up to $p_T^a\sim 3$-4 GeV/$c$, with a trend of increasing deviation as $p_T^t$ and $p_T^a$ are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full $0.25<p_T<15$ GeV/$c$ range using a single $v_n(p_T)$ curve; such a description is however approximately possible for $2\le n\le 5$ when $p_T^a<4$ GeV/$c$. For the $n=1$ harmonic, however, a single $v_1(p_T$ curve is not obtained even within the reduced range $p_T^a<4$ GeV/$c$.

   nucl-exPLB(2012)·376 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.