arXiv subjects

Anthony R. Timmins

Publications and source records attributed to Anthony R. Timmins.

6 recordsLinked to original sources

arXiv2013

Event by event di-hadron correlations in Pb-Pb 2.76 TeV collisions from the ALICE experiment

The large multiplicities at the LHC may permit flow harmonics to be determined on an event by event basis in Pb-Pb collisions. We extract these harmonics from event by event di-hadron correlations. Within a fine centrality bin, we find the correlation function varies substantially on an event by event basis, indicating large fluctuations in the initial conditions for a given impact parameter. Such large fluctuations lead to some events being highly triangular or highly elliptical, where the angular correlation function is completely dominated by the respective second and third Fourier harmonics. We will show unfolded $v_{2}$ distributions for various centralities, and implications for our understanding of the initial conditions.

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arXiv2011

Untriggered di-hadron correlations in Pb-Pb collisions at $\sqrt{s_{NN}} =$ 2.76 TeV from ALICE

We present measurements of untriggered di-hadron correlations as a function of centrality in Pb-Pb \sNN collisions, for charged hadrons with $p_{T} > 0.15$ GeV$/c$. These measurements provide a map of the bulk correlation structures in heavy-ion collisions. Contributions to these structures may come from jets, initial density fluctuations, elliptic flow, resonances, and/or momentum conservation. We decompose the measured correlation functions via a multi-parameter fit in order to extract the nearside Gaussian, the longer range $Δη$ correlation often referred to as the soft ridge. The effect of including higher harmonics ($v_{3}$ and $v_{4}$) in this procedure will be discussed. We investigate how the nearside Gaussian scales with the number of binary collisions. Finally, we show the charge dependence of the nearside Gaussian.

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arXiv2010

Strangeness production in jets from p+p \sqrt{s} = 200 GeV collisions

Measurements of strangeness production in jets help illuminate the QCD mechanisms in fragmentation. Furthermore, they provide a crucial baseline for heavy-ion studies where modifications in jet chemistry have recently been predicted. We present new results on strange particle production in jets from p+p \sqrt{s} = 200 GeV collisions measured by the STAR experiment. The momentum distributions of the Λ, \barΛ and K0Short particles are obtained using various jet finding algorithms, and then compared to various models. Strange particle ratios in jets are obtained and compared to values obtained from the inclusive spectra. Finally, we show jets tagged with leading strange baryons and mesons, in order to investigate whether gluon or quark jets can be isolated in this way.

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arXiv2009

The Modification of high-$p_{T}$ hadro-chemistry in Au+Au collisions relative to p+p

We present high transverse momentum, $p_{T}$, pion ($π$), proton ($p$), kaon ($K$), and rho ($ρ$) spectra measured with the STAR experiment from p+p and Au+Au collisions with \sNN{200}. We find the $K/π$ ratio to be enhanced in Au+Au \sNN{200} collisions relative to p+p \sNN{200} collisions at $p_{T} > 5$ GeV/c. The enhancement persists until $p_{T} \sim 12$ GeV/c for central Au+Au 200 GeV collisions. We also show the nuclear modification factor, $R_{AA}$, measured at the same center of mass energy, and find $R_{AA}(K)$ and $R_{AA}(p)$ to be higher than $R_{AA}(π)$ at $p_T > 5$ GeV/c. Implications for medium induced modifications of jet chemistry is discussed.

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arXiv2008

Strange Particle Production at RHIC

We report STAR measurements of mid-rapidity yields for the $Λ$, $\barΛ$, $K^{0}_{S}$, $Ξ^{-}$, $\barΞ^{+}$, $Ω^{-}$, and $\barΩ^{+}$ particles in Cu+Cu and Au+Au $\sqrt{s_{NN}} = 200$ GeV collisions. We show that at a given number of participating nucleons, bulk strangeness production is higher in Cu+Cu collisions compared to Au+Au collisions at the same center of mass energy, counter to predictions from the Canonical formalism. We compare both the Cu+Cu and Au+Au yields to AMPT and EPOS predictions, and find they reproduce key qualitative aspects of the data. Finally, we investigate other scaling parameters and find bulk strangeness production for both the measured data and theoretical predictions, scales better with the number participants that undergo more than one collision.

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arXiv2007

The Centrality Dependence of Strange Baryon and Meson Production in Cu+Cu and Au+Au sqrt(s_NN) = 200 GeV collisions

Transverse momentum spectra of Lambda and K0Short particles are presented for Cu+Cu sqrt(s_NN) = 200 GeV collisions observed at STAR, and compared to Au+Au measurements at the same energy. For both systems, a number of observables are shown to increase at mid-rapidity (|y| < 0.5) with increasing centrality. These are the integrated Lambda and K0Short yields, the integrated Lambda and K0Short yields per participating nucleon, and mid-pT (1 GeV/c -> 4.5 GeV/c) Lambda/KK0Short ratios. The RCP ratio is found to be higher for the Lambda yields at mid-pT compared to the K0Short yields for both the Cu+Cu and Au+Au data. In contrast, when similar numbers of participating nucleons are considered for the Cu+Cu and Au+Au data, an indication of increased bulk strangeness production and a higher mid-pT (1 -> 4.5 GeV/c) Lambda/K0Short ratio are found, for Cu+Cu.

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