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In this paper, we present an extension of MadGraph5_aMC@NLO which is able to evaluate tree-level QCD matrix-elements up to 2 → 6 (one more particle than before). To achieve this, we implemented Berends–Giele-like recursion, and re-implemented the way colour is computed such that we can now expand the colour matrix in powers of 1 / Nc and truncate this expansion to a chosen order. For high multipli
We present an overview of the options for diffraction implemented in the general-purpose event generator PYTHIA8. We review the existing model for low- and high-mass soft diffraction and present a new model for hard diffraction in pp and pp¯ collisions. Both models use the Pomeron approach pioneered by Ingelman and Schlein, factorising the single diffractive cross section into a Pomeron flux and a
We calculate the decay eta to3 pi at next-to-next-to-leading order or order p6 in Chiral Perturbation Theory. The corrections are somewhat larger than was indicated by dispersive estimates. We present numerical results for the Dalitz plot parameters, the ratio r of the neutral to charged decay and the total decay rate. In addition we derive an inequality between the slope parameters of
We describe predictions for top quark pair differential distributions at hadron colliders, by combining the next-to-next-to-leading order quantum chromodynamics calculations and next-to-leading order electroweak corrections with double resummation at the next-to-next-to-leading logarithmic accuracy of threshold logarithms and small-mass logarithms. To the best of our knowledge, this is the first s
We discuss the associated cc¯ and bb¯ quark pairs production in the double-parton scattering (DPS) process in ultraperipheral (UPCs) AA collisions. We derive an analogue of the inclusive DPS pocket formula and the photon-energy dependent effective cross section considering an overlap between the hard SPS scatterings. We provide numerical predictions for the DPS cross sections for the cc¯ bb¯ produ
First released in 2010, the RIVET library forms an important repository for analysis code, facilitating comparisons between measurements of the final state in particle collisions and theoretical calculations of those final states. We give an overview of RIVET’s current design and implementation, its uptake for analysis preservation and physics results, and summarise recent developments including p
We develop a program to perform a principal component analysis of flow fluctuations using simulations of nuclear collisions produced by the PYTHIA/Angantyr event generator. We consider both p+p and p+Pb collision events and study the leading and subleading modes of the second flow harmonic. The analysis is carried out using two different definitions of the flow matrix which differ in their sensiti
In this project we present a phenomenological study of signal to background interference effects in leptonic tridents produced in parton showers. The interference effects are introduced by linking matrix element corrections of a kinetically mixed dark photon model to the parton shower Dire. Using different dark photon masses and coupling strengths positron+proton collisions are simulated and diffe
Monte Carlo event generators are used by theoretical particle physicists to get a better understanding of the phenomena in particle physics. Given the improvements in precision and accuracy of event generators, using these tools can be very CPU intensive. A method of unweighting events using artificial neural networks is presented to improve the efficiency of event generation. An introduction to m
There are as many stories about being a doctoral student as there are doctoral students. Here, some of them share their stories. We also get to hear the supervisor's perspective. Sofia Åkerman, PhD student Sofia, what led you to choose to pursue a doctoral education? – When I had just graduated and was faced with choosing a career path, I was a single parent with two young children in preschool.
https://www.law.lu.se/research/doctoral-studies/being-doctoral-student - 2026-05-21
A new Monte Carlo method for computing thermodynamical properties of very large polyelectrolytes is presented. It is based on a renormalization group relating the original polymer to a smaller system, where, in addition to the naively rescaled forces, a corrective nearest-neighbor interaction originating from the short distance Coulomb cutoff is introduced. The method is derived for low T but is i
Unraveling functional and ancestral relationships between proteins as well as structure prediction procedures require powerful protein alignment methods. This paper describes the use of fuzzy alignments when matching protein structures. The method use mean-field annealing optimization of fuzzy alignment variables, based on a cost expressed in terms of distances between aligned atoms and of gaps. T
A lattice model for fibril formation on the basis of general peptide interactions is presented. Fibrils are well-structured protein aggregates and a key phenomenon in many diseases, among them Alzheimer. We study the model’s equilibrium and kinetic properties using Wang-Landau sampling and a Metropolis Monte Carlo algorithm with cluster moves. The peptides are shown to form ordered fibrilar aggreg
In the description of the production properties of gauge bosons (W±, Z0, γ*) at colliders, the lowest-order graph normally is not sufficient. The contributions of higher orders can be introduced either by an explicit order-by-order matrix-element calculation, by a resummation procedure or by a parton-shower algorithm. Each approach has its advantages and disadvantages. We here introduce a method t
In this first episode of the second season Nic and Rebecca invite Ori Fox to the podcast to discuss the newly launched JWST. Ori is an instrument scientist at the pace Telescope Science Institute (STSI) working on the Mid-Infrared Instrument (MIRI) which is one of four instruments on the James Webb Space Telescope. In this second season of the Meridian we are also bringing you some field reporting
We calculate the vector and scalar form factors of the pion to two loops in Chiral Perturbation Theory. We estimate the unknown O(p6) constants using resonance exchange. We make a careful comparison to the available data and determine two O(p4) constants rather precisely, and two O(p6) constants less precisely. We also use Chiral Perturbation Theory to two loops to extract in a model-independent m
Oscillator strengths for selected transitions of Sr II and Y III have been determined using ab initio multiconfiguration Hartree-Fock techniques. The importance of including an accurate treatment of the core-valence correlation is emphasized. The results are used to determine the abundances of Sr and Y in the chemically peculiar star chi Lupi from HST/GHRS Echelle spectra. Overabundances of 2.09 d
