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Laurent Forthomme

Publications and source records attributed to Laurent Forthomme.

7 recordsLinked to original sources
arXiv2026

An electron-hadron collider at the high-luminosity LHC

We discuss a concept of a lower-energy version of the Large Hadron-electron Collider (LHeC), delivering electron-hadron collisions concurrently to the hadron-hadron collisions at the high-luminosity LHC at CERN. Assuming the use of a 20 GeV electron Energy Recovery Linac (ERL), we report the results on the optimised beam dynamics, accelerator technologies, and detector constraints required for such a "phase-one" LHeC. Finally, we also discuss the ERL configurations and the possibility of delivering electron-hadron collisions during the planned {Run5} of the LHC, which opens excellent research capabilities - the unique scientific potential of the proposed facility is outlined.

hep-ex↗
arXiv2021

CepGen -- A generic central exclusive processes event generator for hadron-hadron collisions

We present an event generator for the simulation of central exclusive processes in hadron-hadron reactions. Among others, it implements the two-photon production of lepton pairs previously introduced in LPAIR. As a proof of principle, we show that the two approaches are numerically consistent. The $k_{\rm T}$-factorized description of this process is also handled, along with the two-photon production of a quark, or a $W^\pm$ gauge boson pair. This toolbox may be used as a common framework for the definition of many other processes following this approach. Additionally, photoproduction and other photon induced processes are also considered, or being implemented.

hep-ph↗
arXiv2019

Rapidity gap survival factors caused by remnant fragmentation for $W^+ W^-$ pair production via $γ^*γ^* \to W^+ W^-$ subprocess with photon transverse momenta

We calculate the cross section for $p p \to W^{+} W^-$ in the recently developed $k_{\rm T}$-factorisation approach, including transverse momenta of the virtual photons. We focus on processes with single and double proton dissociation. First we discuss the gap survival on the parton level as due to the emission of extra jet. Both the role of valence and sea contributions is discussed. The hadronisation of proton remnants is performed with {PYTHIA 8} string fragmentation model, assuming a simple quark-diquark model for proton. Highly excited remnant systems hadronise producing particles that can be vetoed in the calorimeter. We calculate associated effective gap survival factors. The gap survival factors depend on the process, mass of the remnant system and collision energy. The rapidity gap survival factor due to remnant fragmentation for double dissociative (DD) collisions ($S_{R,DD}$) is smaller than that for single dissociative (SD) process ($S_{R,SD}$). We observe the approximate factorisation $S_{R,DD} \approx (S_{R,SD})^2$, however it is expected that this property will be violated by soft rescattering effects not accounted for in this letter.

hep-ph↗
arXiv2018

Production of $t\bar t$ pairs via $γγ$ fusion with photon transverse momenta and proton dissociation

We discuss the production of $t\bar t$ quark-antiquark pairs in proton-proton collisions via the $γγ$ fusion mechanism. We include topologies in which both protons stay intact or one or even both of them undergo dissociation. The calculations are performed within the $k_{\rm T}$-factorisation approach, including transverse momenta of intermediate photons. Photon fluxes associated to inelastic (dissociative) processes are calculated based on modern parameterisations of proton structure functions. We find an integrated cross section of about 2.36 fb at $\sqrt{s}=$ 13 TeV for all contributions. The cross section for the fully elastic process is the smallest. Inelastic contributions are significantly reduced when a veto on outgoing jets is imposed. We present several differential distributions in rapidity and transverse momenta of single $t$ or $\bar t$ quarks/antiquarks as well as distributions in invariant mass of both the $t\bar t$ and masses of dissociated systems. A few two-dimensional distributions are presented in addition.

hep-ph↗
arXiv2017

Test of Ultra Fast Silicon Detectors for Picosecond Time Measurements with a New Multipurpose Read-Out Board

Ultra Fast Silicon Detectors (UFSD) are sensors optimized for timing measurements employing a thin multiplication layer to increase the output signal. A multipurpose read-out board hosting a low-cost, low-power fast amplifier was designed at the University of Kansas and tested at the European Organization for Nuclear Research (CERN) using a 180 GeV pion beam. The amplifier has been designed to read out a wide range of detectors and it was optimized in this test for the UFSD output signal. In this paper we report the results of the experimental tests using 50 $\rm{μm}$ thick UFSD with a sensitive area of 1.4 $\rm{mm^2}$. A timing precision below 30 ps was achieved.

physics.ins-det↗
arXiv2014

Central $μ^{+}μ^{-}$ production via photon-photon fusion in proton-proton collisions with proton dissociation

We present a formalism which uses fluxes of equivalent photons including transverse momenta of the intermediate photons. The formalism reminds the familiar $k_t$-factorization approach used, e.g., to study the two-photon production of $c\bar{c}$ or $b\bar{b}$ pairs. The results of the new method are compared with those obtained using the code LPAIR, and a good agreement is obtained. The inclusion of the photon transverse momenta is necessary in studies of correlation observables. We present distributions for the dimuon invariant mass, transverse momentum of the muon pair and relative azimuthal angle between muons separately for elastic-elastic, elastic-inelastic, inelastic-elastic and inelastic-inelastic mechanisms. For typical experimental cuts all mechanisms give similar contributions. The results are shown for different sets of cuts relevant for the LHC experiments. The cross sections in different regions of phase space depend on $F_2$ structure function in different regions of $x$ and $Q^2$. A comment on $F_2$ is made.

hep-ph↗
arXiv2013

Exclusive processes in proton-proton collisions with the CMS experiment at the LHC

We present the recent measurements of exclusive processes performed in the CMS experiment at the LHC using data collected at a centre of mass energy of 7 TeV. These measurements include the double-pomeron production of photon pairs, the two-photon production of leptons pairs, and the previously undetected two-photon production of W boson pairs. While in case of the two first processes that enables to set limits on production cross-section, in the later case it provides also stringent limits on the anomalous quartic gauge couplings.

hep-ex↗