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Ph. Roloff

Publications and source records attributed to Ph. Roloff.

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Jet reconstruction at high-energy lepton colliders

In this paper we study the performance in $e^+e^-$ collisions of classical $e^+e^-$ jet reconstruction algorithms, longitudinally invariant algorithms and the recently-proposed Valencia algorithm. The study includes a comparison of perturbative and non-perturbative jet energy corrections and the response under realistic background conditions. Several algorithms are benchmarked with a detailed detector simulation at $\sqrt{s}= 3$~\tev. We find that the classical $e^+e^-$ algorithms, with or without beam jets, have the best response, but are inadequate in environments with non-negligible background. The Valencia algorithm and longitudinally invariant $k_t$ algorithms have a much more robust performance, with a slight advantage for the former.

hep-ex

Parton Radiation and Fragmentation from LHC to FCC-ee

This document collects the proceedings of the "Parton Radiation and Fragmentation from LHC to FCC-ee" workshop (http://indico.cern.ch/e/ee\_jets16) held at CERN in Nov. 2016. The writeup reviews the latest theoretical and experimental developments on parton radiation and parton-hadron fragmentation studies --including analyses of LEP, B-factories, and LHC data-- with a focus on the future perspectives reacheable in $e^+e^-$ measurements at the Future Circular Collider (FCC-ee), with multi-ab$^{-1}$ integrated luminosities yielding 10$^{12}$ and 10$^{8}$ jets from Z and W bosons decays as well as 10$^5$ gluon jets from Higgs boson decays. The main topics discussed are: (i) parton radiation and parton-to-hadron fragmentation functions (splitting functions at NNLO, small-$z$ NNLL resummations, global FF fits including Monte Carlo (MC) and neural-network analyses of the latest Belle/BaBar high-precision data, parton shower MC generators), (ii) jet properties (quark-gluon discrimination, $e^+e^-$ event shapes and multi-jet rates at NNLO+N$^{n}$LL, jet broadening and angularities, jet substructure at small-radius, jet charge determination, $e^+e^-$ jet reconstruction algorithms), (iii) heavy-quark jets (dead cone effect, charm-bottom separation, gluon-to-$b\bar{b}$ splitting), and (iv) non-perturbative QCD phenomena (colour reconnection, baryon and strangeness production, Bose-Einstein and Fermi-Dirac final-state correlations, colour string dynamics: spin effects, helix hadronization).

hep-ph

Top physics at high-energy lepton colliders

A summary is presented of the workshop "top physics at linear colliders" that was held at IFIC Valencia from the 30th of June to the 3rd July 2015. We present an up-to-date status report of studies into the potential for top quark physics of lepton colliders with an energy reach that exceeds the top quark pair production threshold, with a focus on the linear collider projects ILC and CLIC. This summary shows that such projects can offer very competitive determinations of top quark properties (mass, width) and its interactions with other Standard Model particles, in particular electroweak gauge bosons and the Higgs boson. In both areas the prospects exceed the LHC potential significantly - often by an order of magnitude.

hep-ex