Universal scaling dependence of QCD energy loss from data driven studies

In this paper we study the energy loss of jets in the QGP via the nuclear modification factor $R_{\textrm{AA}}$ for unidentified particles at high $p_{\textrm{T}}$ ($\gtrsim 10 \textrm{GeV}/c$) in and out of the reaction plane of the collision. We argue that at such a high $p_{\textrm{T}}$ there are no genuine flow effects and, assuming that the energy loss is only sensitive to initial characteristics such as the density and geometry, find that $R_{\textrm{AA}}$ depends linearly on the (RMS) length extracted from Glauber simulations. Furthermore we observe that for different centrality classes the density dependence of the energy loss enters as the square root of the charged particle multiplicity normalized to the initial overlap area. The energy loss extracted for RHIC and LHC data from the $R_{\textrm{AA}}$ is found to exhibit a universal behavior.Comment: 15 pages, 5 figures, version to be published in Phys. Rev.

String Formation Beyond Leading Colour

We present a new model for the hadronisation of multi-parton systems, in which colour correlations beyond leading $N_C$ are allowed to influence the formation of confining potentials (strings). The multiplet structure of $SU(3)$ is combined with a minimisation of the string potential energy, to decide between which partons strings should form, allowing also for "baryonic" configurations (e.g., two colours can combine coherently to form an anticolour). In $e^+e^-$collisions, modifications to the leading-colour picture are small, suppressed by both colour and kinematics factors. But in $pp$ collisions, multi-parton interactions increase the number of possible subleading connections, counteracting their naive $1/N_C^2$ suppression. Moreover, those that reduce the overall string lengths are kinematically favoured. The model, which we have implemented in the PYTHIA 8 generator, is capable of reaching agreement not only with the important \left(n_\mathrm{charged}) distribution but also with measured rates (and ratios) of kaons and hyperons, in both $ee$ and $pp$ collisions. Nonetheless, the shape of their $p_\perp$ spectra remains challenging to explain.Comment: 48 pages, 22 figure

Color reconnection and flow-like patterns in pp collisions

Increasingly, with the data collected at the LHC we are confronted with the possible existence of flow in pp collisions. In this work we show that PYTHIA 8 produces flow-like effects in events with multiple hard subcollisions due to color string formations between final partons from independent hard scatterings, the so called color reconnection. We present studies of different identified hadron observables in pp collisions at 7 TeV with the tune 4C. Studies have been done both for minimum bias and multiplicity intervals in events with and without color reconnection to isolate the flow-like effect.Comment: 4 pages, 4 figures. The first part of the manuscript was reorganized, some typos were corrected and references added. The final version should appear in PR

Further Evidence on Hedge Funds Performance.

In this analysis we identify dynamic hedge fund strategies quantitatively pursuing a Principal Component Analysis following Fung and Hsieh (1997). We extract five dominant hedge fund strategies each representing similar investment styles and analyse the performance of each strategy by employing a multi-factor model comprising both market indices and passive option strategies along the lines of Agerwal and Naik (2000). We find that the majority of the five homogenous strategies show superior performance. However, correcting for survivorship bias this superior performance disappears.Hedge funds; Investment in securities; Performance; Dynamic strategies; Hedge funds performance;