arXiv subjects

Pierre Van Mechelen

Publications and source records attributed to Pierre Van Mechelen.

11 recordsLinked to original sources

arXiv2024

Soft QCD Physics at the LHC: highlights and opportunities

The Large Hadron Collider (LHC) at CERN in Switzerland became operational in 2009 and has since then produced a plethora of results for proton-proton (pp) collisions. This short review covers results that relates to soft QCD focusing on non-diffractive physics at mid-rapidity. Most of the presented results comes from transverse momentum ($p_{\rm T}$) spectra and related/derived observables such as multiplicity, $\langle p_{\rm T} \rangle$ and ratios, but also the observed ``ridge'' and the questions of quark-gluon plasma in pp collisions will be discussed. The goal of the review is on one hand to introduce the topics and provide references for scientists joining the LHC program while at the same time highlighting what we consider the most interesting results and open questions to inspire novel measurements.

hep-ex↗

arXiv2023

Science4Peace in difficult times

The war on Ukraine has affected significantly scientific cooperation and communication in particle physics and also in many other fields of scientific, cultural and educational exchange. Immediately after the war in February 2022, many scientific institutions paused or banned scientific cooperation and exchange with Russian and Belorusian institutes and their scientists. Publications were out on hold or even banned, if Russian scientists were on the author list. The Science4Peace (S4P) Forum was created in March 2022 as a consequence of these restrictions, as a completely independent Forum for open communication among scientists, using independent ZOOM rooms and webpages. The basic ideas of the S4P Forum are fully in line with the policy of IUPAP of supporting and encouraging free scientific exchange. In the course of discussions on the consequences of the war on Ukraine, the S4P Forum organized a high-level panel discussion on "Sanctions in Science - One Year of Sanctions". The war on Ukraine has also increased enormously the risk of nuclear escalation. Together with 14 Nobel laureates and many Scientists, the S4P Forum launched an appeal to subscribe to the "no-first use" policy and urged the governments to subscribe to the Treaty of the Prohibition of Nuclear Weapons adopted by the United Nations. The S4P Forum fully supports the ideas and activities originating from the International Year of Basic Sciences for Sustainable Development (IYBSSD) to open and to keep open discussion channels at all levels, using Science as a common language.

physics.soc-ph↗

arXiv2017

Single inclusive jet production and the nuclear modification ratio at very forward rapidity in proton-lead collisions with $\sqrt{s_{NN}}$ = 5.02 TeV

We present calculations of single inclusive jet transverse momentum and energy spectra at forward rapidity ($5.2\!<\!y\!<\!6.6$) in proton-lead collisions with $\sqrt{s_{NN}}$ = 5.02 TeV. The predictions are obtained with the KaTie Monte Carlo event generator, which allows to calculate interactions within the High Energy Factorisation framework. The tree-level matrix element results are subsequently interfaced with the CASCADE Monte Carlo event generator to account for hadronisation. The effects of the saturation of the gluon density, leading to suppression of the cross section, are investigated.

hep-ph↗

arXiv2017

Single inclusive jet transverse momentum and energy spectra at very forward rapidity in proton-proton collisions with $\sqrt{s} = 7$ and 13 TeV

We present predictions of single inclusive jet transverse momentum, energy, and Feynman-$x$ spectra at forward rapidity ($5.2 < y < 6.6$) in proton-proton collisions with $\sqrt{s} = 7$ and 13 TeV. Calculations based on high-energy factorization and $k_T$-dependent parton densities are compared to simulations using the \pythia\ event generator. Effects from parton density evolution, parton shower dynamics, multi-parton interactions, and saturation of parton densities are investigated.

hep-ph↗

arXiv2012

Obtaining the CMS Ridge effect with Multiparton Interactions

We show that the "ridge" phenomenon in the two-particle angular correlation function, as observed by the CMS experiment, can be reproduced by implementing an impact parameter dependent azimuthal correlation of the scattering planes of individual partonic interactions. Such an approach is motivated by the observation that even for moderate impact parameters a substantial number of partonic interactions may be produced, while at the same time the protons are sufficiently far apart to create a preferential direction in azimuth. A re-tune of the Pythia6 Z2 tune based on underlying event and minimum bias distributions measured at the LHC shows that a better description of data can be obtained with this approach and that some tension existing between underlying event and minimum bias distributions can be removed. We show that, even though the CMS result on the angular correlation function itself is not used in the re-tune, we can predict the appearance of long-range, near-side angular correlations in proton-proton collisions.

hep-ph↗

arXiv2008

Experimental Results on Diffraction

Results on diffractive scattering observed at HERA and at the TEVATRON are reviewed. This includes the extraction of diffractive parton density functions and determination of the rapidity gap survival probability at HERA and the observation of central exclusive production of final states at the TEVATRON. Finally, preparations to observe diffractive signals at the LHC are discussed.

hep-ex↗

arXiv2003

Deep inelastic diffractive scattering at HERA

Recent high precision measurements of deep inelastic diffractive scattering at HERA are presented in an increased region of phase space. Current models for diffractive photon dissociation are compared to the data.

hep-ex↗

arXiv2003

Diffraction in ep collisions

Recent measurements of the diffractive deep-inelastic cross section are used to extract diffractive parton densities of the proton. These are subsequently applied in models to predict the production of jets and open charm in the final state. A rapidity gap suppression factor for dijet production in diffractive photoproduction relative to diffractive deep-inelastic scattering is obtained using a model-independent comparison.

hep-ex↗

arXiv2003

Jet production in ep collisions

Results obtained by the H1 and ZEUS Collaborations on jet production in photoproduction and deep-inelastic scattering are presented and compared to NLO QCD models.

hep-ex↗

arXiv2002

A Very Forward Proton Spectrometer for H1

A new, very forward, proton spectrometer with large acceptance will be installed in the proton beam line of the H1 experiment in 2003. The spectrometer, located 220 m downstream of the interaction point, is based on the Roman Pot technique and consists of two stations in the cold section of the proton beam line. A brief description of this new device and expected physics results are presented.

hep-ex↗

arXiv2000

Final States in Diffraction at HERA

Recent experimental results on diffractive high $E_T$ jet production and diffractive open charm production, obtained by the H1 and ZEUS experiments at HERA, are presented. Various theoretical models for diffractive hard scattering are discussed and confronted with the experimental data.

hep-ex↗