Publications

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The diagrammatic coaction and cuts of the double box

Einan Gardi, Aris Ioannou

SciPost Phys. Proc. 7, 012 (2022) · published 20 June 2022 | · pdf

The diagrammatic coaction encodes the analytic structure of Feynman integrals by mapping any given Feynman diagram into a tensor product of diagrams defined by contractions and cuts of the original diagram. Feynman integrals evaluate to generalized hypergeometric functions in dimensional regularization. Establishing the coaction on this type of functions has helped formulating and checking the diagrammatic coaction of certain two-loop integrals. In this talk we study its application on the fully massless double box diagram. We make use of differential equation techniques, which, together with the properties of homology and cohomology theory of the resulting hypergeometric functions, allow us to formulate the coaction on a range of cuts of the double box in closed form.
The 34th International Colloquium on Group Theoretical Methods in Physics

Rutwig Campoamor-Stursberg, Marc de Montigny, Michel Rausch de Traubenberg, Mauricio Valenzuela

SciPost Phys. Proc. 14, 001 (2023) · published 23 November 2023 | · pdf

Introduction to the proceedings of the 34th International Colloquium on Group Theoretical Methods in Physics.
Proton reconstruction with the Precision Proton Spectrometer (PPS) in Run 2 and the PPS at HL-LHC

Fabrizio Ferro

SciPost Phys. Proc. 8, 062 (2022) · published 12 July 2022 | · pdf

The Precision Proton Spectrometer (PPS) started operating in 2016 and has collected more than 110 fb$^{-1}$ of data over the course of the LHC Run 2, now fully available for physics analysis. This contribution covers the key features of the PPS alignment and optics calibration, which have been developed from scratch. The reconstructed proton distributions, the performance of the PPS simulation and finally the validation of the full reconstruction chain with physics data (dilepton events) are also illustrated.
Recent jet and jet substructure measurements at the LHC, and ML based tagging

Meena Meena

SciPost Phys. Proc. 10, 022 (2022) · published 10 August 2022 | · pdf

Recent jet and jet substructure measurements at the LHC, and of machine-learning-based tagging techniques are presented using proton-proton collision data collected by the ATLAS and CMS experiments at CERN's Large Hadron Collider. These measurements are crucial for precise tests of electroweak and pQCD calculations and searches for physics beyond the Standard Model. The measurements are compared with several Monte Carlo event generator predictions which provide valuable input to the tuning of perturbative and non-perturbative models and to constraining model parameters of advanced parton-shower Monte Carlo programs.
Measurement of splittings along a jet shower in $\sqrt{s} = 200$ GeV pp collisions at STAR

Raghav Kunnawalkam Elayavalli

SciPost Phys. Proc. 8, 059 (2022) · published 12 July 2022 | · pdf

Jets are algorithmic proxies of hard scattered partons, i.e. quarks and gluons, in high energy particle collisions. The STAR collaboration presents the first measurements of substructure observables at the first, second and third splits in the jet clustering tree via the iterative SoftDrop procedure. For each of these splits, we measure the fully corrected groomed shared momentum fraction (\zg) and groomed jet radius (\rg). We discuss the evolution of jet substructure in both the angular and momentum scales which allows for a self-similarity test of the DGLAP splitting function. We compare the fully corrected data to Monte Carlo models, providing stringent constraints on model parameters related to the parton shower and non-perturbative effects such as hadronization.
Mixed permutation symmetry quantum phase transitions of critical three-level atom models

Alberto Mayorgas, J. Guerrero, Manuel Calixto

SciPost Phys. Proc. 14, 036 (2023) · published 24 November 2023 | · pdf

We define the concept of Mixed Symmetry Quantum Phase Transition (MSQPT), considering each permutation symmetry sector $\mu$ of an identical particles system, as singularities in the properties of the lowest-energy state into each $\mu$ when shifting a Hamiltonian control parameter $\lambda$. A three-level Lipkin-Meshkov-Glick (LMG) model is chosen to typify our construction. Firstly, we analyze the finite number $N$ of particles case, proving the presence of MSQPT precursors. Then, in the thermodynamic limit $N\to∞$, we calculate the lowest-energy density inside each sector $\mu$, augmenting the control parameter space by $\mu$, and showing a phase diagram with four different quantum phases.
Investigation of the background in coherent $J/\psi$ production at the EIC

Wan Chang

SciPost Phys. Proc. 8, 053 (2022) · published 12 July 2022 | · pdf

Understanding fundamental properties of nucleons and nuclei are among the most important scientific goals of the next-generation machine, the Electron-Ion Collider (EIC). With the unprecedented versatility provided by the EIC, it will provide answers to many standing puzzles and open questions in modern nuclear physics. One of the golden measurements at the EIC is coherent vector meson production in electron-nucleus (eA) scattering in order to obtain the spatial gluon density distribution in heavy nuclei. This requires the experiment to overcome an overwhelmingly large background arising from the incoherent diffractive production, where the nucleus mostly breaks up into fragments of particles in the far-forward direction close to the hadron beam rapidity. In this talk, we systematically study the rejection of incoherent $J/\psi$ production by vetoing products from the nuclear breakup - protons, neutrons, and photons, which is modeled with the BeAGLE event generator and the most up-to-date EIC Far-forward Interaction Region design.
Transversity through Dihadron: a constrained fit

Aurore Courtoy

SciPost Phys. Proc. 8, 049 (2022) · published 12 July 2022 | · pdf

We present a study of the valence transversity PDF obtained through a constrained fit. The effects of the constraints on the uncertainties of the PDF are explored. We show that the resulting isovector tensor charge is largely undetermined and, hence, compatible with all lattice evaluations.
Measuring the light meson nuclear modification factor in p-Pb collisions over an unprecedented $p_{\text{T}}$ range with ALICE

Joshua König

SciPost Phys. Proc. 8, 048 (2022) · published 12 July 2022 | · pdf

Differential invariant cross sections of light neutral mesons in p-Pb collisions at $\sqrt{s_{\text{NN}}}$ = 8.16 TeV and in pp collisions at $\sqrt{s}$ = 8 TeV have been measured up to very high transverse momentum ($p_{\text{T}}$). By combining independent reconstruction techniques available in ALICE using the EMCal and PHOS calorimeters as well as the central barrel tracking detectors, the combined spectra cover almost two orders of magnitude in $p_{\rm T}$ for the $\pi^{0}$ meson. The nuclear modification factor $R_{\text{pPb}}$ has been measured for the $\pi^{0}$ and $\eta$ mesons and is found to be consistent with NLO pQCD, CGC and energy loss calculations. Comparisons to the $R_{\text{pPb}}$ of $\pi^{0}$ measured in $\sqrt{s_{\text{NN}}}$ = 5.02 TeV hint at a stronger suppression at low $p_{\rm T}$ with increasing collision energy.
Measurement of the transverse polarization of electrons emitted in neutron decay – nTRV experiment

K. Bodek, A. Kozela

SciPost Phys. Proc. 5, 015 (2021) · published 6 September 2021 | · pdf

This paper recalls the main achievements of the nTRV experiment which measured two components of the transverse polarization ($\sigma_{T_{1}}$, $\sigma_{T_{2}}$) of electrons emitted in the $\beta$-decay of polarized, free neutrons and deduced two correlation coefficients, $R$ and $N$, that are sensitive to physics beyond the Standard Model. The value of time-reversal odd coefficient $R$, 0.004$\pm$0.012$\pm$0.005, significantly improved limits on the relative strength of imaginary scalar coupling constant in the weak interaction. The value obtained for the time-reversal even correlation coefficient $N$, 0.067$\pm$0.011$\pm$0.004, agrees with the Standard Model expectation, providing an important sensitivity test of the electron polarimeter. One of the conclusions of this pioneering experiment was that the transverse electron polarization in the neutron $\beta$-decay is worth more systematic exploring by measurements of yet experimentally not attempted correlation coefficients such as $H$, $L$, $S$, $U$ and $V$. This article presents a brief outlook on that questions.

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