25th MCnet meeting 2023 @ CERN

24 Apr 2023, 09:00 → 27 Apr 2023, 17:05 Europe/Zurich

CERN

Zoom link

Monday 24 April

Collaboration Board meeting

Convener: Leif Lönnblad (Lund University (SE))

Tuesday 25 April

Student and Postdoc talks

Conveners: Peter Meinzinger, Pratixan Sarmah

1 Introduction

2 Novel approach to measure quark/gluon jets at the LHC

In this talk, we present a new proposal on how to measure quark/gluon jet properties at the Large Hadron Collider (LHC). Our measurement strategy takes advantage of the fact that the LHC has collected data at different energies and focuses on measuring jet angularities. By studying these angularities, we aim to enrich statistically the given data sample by quark or gluon jets based on derived quark and gluon angularities.

The measurement of quark/gluon jet properties is important in understanding the underlying physics of high-energy collisions. The proposed measurement strategy has the potential to improve the separation ability of the background of these measurements and provide a deeper understanding of the properties of quark/gluon jets.

We will discuss the details of the measurement strategy, including the theoretical basis for jet angularities and the experimental techniques for measuring them. We will also present preliminary results from our phenomenological analysis of samples generated by Herwing and Pythia event generators using this approach.

Overall, our proposed measurement strategy provides a promising new avenue for studying quark/gluon jet properties at the LHC, and has the potential to deepen our understanding of the fundamental building blocks of matter.

Speaker: Petr Baron (Palacky University (CZ))

3 Lepton-hadron collisions in MadGraph5_aMC@NLO

In the coming years, the Electron-Ion-Collider (EIC) in the United States will enable researchers to study lepton-hadron collisions with unprecedented precision. To consolidate figures of merit of a variety of measurements at the EIC, it is essential to include radiative corrections in simulations of electron-proton and electron-nucleus collisions. For the time being, there do not exist any automated simulation tools for such reactions, including even only next-to-leading order (NLO) radiative corrections.
In this talk, I will present our recent progress in the implementation of photoproduction, where the photon is either coming from an electron or from a proton in an ultra-peripheral collision at the LHC. We perform the calculations at NLO in the fixed-order mode within MadGraph5_aMC@NLO, a framework for (N)LO computation, intensively used at the LHC.

Speaker: Manna Laboni

MCNET_meeting2023_final_n.pdf

4 The new Alaric Parton Shower in Sherpa

I will present the logarithmically accurate parton shower Alaric. The algorithm is implemented in the Sherpa framework, and I show its NLL accuracy in final state evolution both numerically as well as by analytical agruments. I will also present phenomenological results compared to observables measured at LEP.

Speaker: Daniel Reichelt (Durham University, IPPP)

MCNetMeeting_2023.pdf

5 Photon splitting corrections to soft-photon resummation

In this talk I present an algorithm to add photon-splitting corrections
to the Yennie-Frautschi-Suura-style soft-photon resummation available in
the Sherpa Monte-Carlo event generator.
Then, I introduce different lepton dressing strategies which incorporate
further leptons and hadrons in addition to the customary photons,
and discuss their sensitivity to dressing parameters such as the
cone size. Results are presented for the academic case of on-shell Z decay as well
as Drell-Yan lepton production at a proton-proton collider.

Speaker: Lois Flower

MCnet_Talk_CERN_2023.pdf

Wednesday 26 April

Student and Postdoc talks: Student and Postoc talks

Conveners: Peter Meinzinger, Pratixan Sarmah

6 Rivet, YODA and Contur: recent updates and ongoing developments

Speaker: Yoran Yeh (University College London (UK))

2023_04_26_mcnet_yyeh.pdf

7 Develpment of novel, portable Matrix Element + Phase Space methods

For more than a decade the current generation of fully automated,
matrix element generators has provided hard scattering events with
excellent flexibility and good efficiency. However, as recent studies
have shown, they are a major bottleneck in the established Monte Carlo
event generator toolchains. With the advent of the HL-LHC and ever
rising precision requirements, future developments will need to focus
on computational performance, especially at intermediate to large jet
multiplicities. We present a novel family of fast matrix
element algorithms that are amenable for GPU acceleration, making use
of modern, minimal color decompositions. Moreover, we discuss the
performance achieved for standard candle processes such as V+jets and
ttbar+jets production.

Speaker: Max Knobbe (University of Göttingen)

knobbe_mcnet_2023.pdf

8 Jets and multiparton interactions in photon and proton collisions

We present a study using a Rivet - including a new routine for low pT jet data - of the pythia 8 modelling of photoproduction (HERA), photon-photon (LEP) and proton-(antiproton) (LHC, Tevatron) jet measurements. We look the influence of the underlying event model, and its energy dependence.

Speaker: Juan Jose Castella

CERN_presentation.pdf

9 Unweighting multijet event generation using factorisation-aware neural networks

The generation of unit-weight events for complex scattering processes presents a severe challenge to modern Monte Carlo event generators. Even when using sophisticated phase-space sampling techniques adapted to the underlying transition matrix elements, the efficiency for generating unit-weight events from weighted samples can become a limiting factor in practical applications. Here we present the combination of a two-staged unweighting procedure with a factorisation-aware matrix element emulator using neural networks which we make accessible in the Sherpa event generation framework. The algorithm can significantly accelerate the unweighting process, while it still guarantees unbiased sampling from the correct target distribution. We apply, validate and benchmark the approach for partonic channels contributing at the tree-level to the high-multiplicity LHC production processes $Z+4,5$ jets and $t\bar{t}+3,4$ jets, where we find speed-up factors between 16 and 350.

Speaker: Timo Janssen

slides.pdf

10 Dinner

Da Ettore

Thursday 27 April

Collaboration meeting

Convener: Leif Lönnblad (Lund University (SE))

11 Discussion on MCnet in relation to LPCC

12 Discussion on future MCnet activities

10:00 Coffee

Student and Postdoc talks

13 KrkNLO Matching

Speaker: James Whitehead

Whitehead.pdf

14 Students and Postdoc Committee

MCnet S&P.pdf

Collaboration meeting: AOB

MCnet open meeting: CPU performance

Convener: Leif Lönnblad (Lund University (SE))

15 Introduction

Speaker: Leif Lönnblad (Lund University (SE))

16 Experiment view on generators

Speakers: Dominic Hirschbuehl (Bergische Universitaet Wuppertal (DE)), Saptaparna Bhattacharya (Northwestern University (US))

ATLAS_MCNet.pdf

CMS_MCNet.pdf

17 Response from Generator authors

SherpaPerformanceImprovements.pdf

18 Discussions

15:30 Coffee

19 Presentation of the MCnet (new) collaboration

Speaker: Leif Lönnblad (Lund University (SE))

NewMCnetCERN23.pdf

20 More discussions?