Publications

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ATLAS results on charmonium production

Vato Kartvelishvili

SciPost Phys. Proc. 8, 014 (2022) · published 11 July 2022 | · pdf

An overview is given of the results on charmonium production obtained by the ATLAS collaboration at the LHC. Recent preliminary measurements covering prompt and non-prompt production of $J/\psi$ and $\psi(2S)$ states in the range of high transverse momenta from 60 to 360~GeV are highlighted.
Recent results from heavy ion collisions at LHCb

Óscar Boente García

SciPost Phys. Proc. 8, 007 (2022) · published 11 July 2022 | · pdf

LHCb is a fully instrumented spectrometer covering the forward rapidity region at the LHC, which provides unique access to the small Bjorken-x region inside the nucleus. In this contribution, a selection of recent results from the LHCb heavy-ion program are presented, including a measurement of charged hadron production in proton-proton (pp) and proton-lead (pPb) collisions, chic2/chic1 production in pPb collisions, and coherent J/psi production in peripheral and ultra-peripheral PbPb collisions. Comparisons with calculations and effects from the nuclear PDFs and dense QCD medium are discussed.
Measuring single-top-associated Higgs production at the HL-LHC

Henning Bahl

SciPost Phys. Proc. 8, 010 (2022) · published 11 July 2022 | · pdf

Precision measurements of top-associated Higgs production are an important ingredient to unravel the $\mathcal{CP}$ nature of the Higgs boson. In this work, we constraint the $\mathcal{CP}$ nature of the top-Yukawa coupling taking into account all relevant inclusive and differential Higgs boson measurements. Based upon this fit, we show that it is crucial to disentangle single- and di-top-associated Higgs production for tightening indirect constraints on a $\mathcal{CP}$-odd top-Yukawa coupling in the future. In this context, we propose an analysis strategy for measuring $tH$ production at the HL-LHC without relying on assumptions about the Higgs $\mathcal{CP}$ character.
Longitudinal Z-boson polarization and the Higgs boson production cross-section

Simone Amoroso

SciPost Phys. Proc. 8, 016 (2022) · published 11 July 2022 | · pdf

Lepton pairs are produced copiously in high-energy hadron collisions via electroweak gauge boson exchange, and are one of the most precisely measured final states in proton- proton collisions at the Large Hadron Collider (LHC). We propose that measurements of lepton angular distributions can be used to improve the accuracy of theoretical predic- tions for Higgs boson production cross sections at the LHC. To this end, we exploit the sensitivity of the lepton angular coefficient associated with the longitudinal Z-boson polarization to the parton density function (PDF) for gluons resolved from the incoming protons, in order to constrain the Higgs boson cross section from gluon fusion processes. By a detailed numerical analysis using the open-source platform xFitter, we find that high-statistics determinations of the longitudinally polarized angular coefficient at the LHC Run III and high-luminosity HL-LHC improve the PDF systematics of the Higgs boson cross section predictions by 50 % over a broad range of Higgs boson rapidities.
Hard color-singlet exchange in dijet events in proton-proton collisions at $\sqrt{s} = 13$ TeV

Cristian Baldenegro Barrera

SciPost Phys. Proc. 8, 015 (2022) · published 11 July 2022 | · pdf

We present a measurement of events with two jets separated by a pseudorapidity gap (jet-gap-jet). The signature is expected from hard color-singlet exchange. The jets are reconstructed with the CMS detector. The highest $p_\text{T}$ jets have $p_\text{T}^\text{jet1,2} > 40$ GeV, with $1.4 < |\eta^\text{jet1,2}| < 4.7$ and $\eta^\text{jet1} \eta^\text{jet2} < 0$. We measure the fraction of color-singlet exchange dijet events, $f_\text{CSE}$, and compare it to previous measurements and to predictions. We also study jet-gap-jet events where the colliding protons remain intact and are detected with the Roman pots of TOTEM. A larger fraction $f_\text{CSE}$ is found in the latter subsample.
Transverse Single Spin Asymmetries of Heavy Flavor Electrons and Charged Pions in 200 GeV $p+p^{\uparrow}$ Collisions at Midrapidity

Dillon Fitzgerald

SciPost Phys. Proc. 8, 012 (2022) · published 11 July 2022 | · pdf

Transverse single spin asymmetries of particles produced in $p+p^{\uparrow}$ collisions provide insight on the partonic spin and momentum structure of hadrons; heavy flavor electrons provide access to initial state spin-momentum correlations of gluons in the proton, while charged pions provide access to initial and final state transverse spin effects. Charged particles are measured at midrapidity at PHENIX using the silicon vertex detector and central arm spectrometer, made of an electromagnetic calorimeter, a ring-imaging Cherenkov detector, and drift and pad chambers. Recent results for both electron and charged pion measurements from the 2015 running period will be presented.
Transverse Single-Spin Asymmetries of Midrapidity Direct Photons and Neutral Mesons at PHENIX

Nicole Lewis

SciPost Phys. Proc. 8, 009 (2022) · published 11 July 2022 | · pdf

Results are presented for the transverse single-spin asymmetries of direct photons, neutral pions, and eta mesons for $|\eta|<0.35$ from $p^\uparrow + p$ collisions with $\sqrt{s} = 200$ GeV at PHENIX. As hadrons, $\pi^0$ and $\eta$ mesons are sensitive to both initial- and final-state effects and at midrapidity probe the dynamics of gluons along with a mix of quark flavors. Because direct photon production does not include hadronization, the direct photon TSSA is only sensitive to initial-state effects and at midrapidity provides a clean probe of the gluon dynamics in transversely polarized protons. All three of these results will help constrain the collinear twist-3 trigluon correlation function as well as the gluon Sivers function, improving our knowledge of spin-dependent gluon dynamics in QCD.
Ultraperipheral collisions and low-x physics

Tuomas Lappi

SciPost Phys. Proc. 8, 003 (2022) · published 11 July 2022 | · pdf

Ultraperipheral collisions at the LHC and RHIC offer the highest currently available energy for photon-nucleon and photon-nucleus collisions. Thus they are a valuable tool for studying the gluonic structure of hadrons and nuclei at small x. We discuss recent theoretical work towards understanding such exclusive processes at NLO accuracy in QCD perturbation theory. These theoretical advances are also immediately relevant for understanding the physics of deep inelastic scattering at small x. We also discuss experimental results in ultraperipheral collisions, most prominently for exclusive vector meson production.
Physics motivation and detector upgrades for the new era of the ATLAS experiment

Jason Nielsen

SciPost Phys. Proc. 8, 126 (2022) · published 13 July 2022 | · pdf

The ATLAS experiment at CERN’s Large Hadron Collider (LHC) will be upgraded in two stages to prepare first for the Run 3 data-taking campaign, during which the integrated luminosity will roughly double, and then for the High-Luminosity LHC program with an ultimate integrated luminosity of up to 4 ab-1. These upgrades and high-statistics datasets will allow ATLAS to perform searches and precision measurements to constrain the Standard Model in yet-unexplored phase spaces and in the Higgs sector. This contribution summarizes the ATLAS detector upgrades and selected physics prospects for Run 3 and the HL-LHC.
Resummation of the Sivers asymmetry in heavy flavor dijet production at the Electron-Ion Collider

Zhong-Bo Kang, Jared Reiten, Ding Yu Shao, John Terry

SciPost Phys. Proc. 8, 175 (2022) · published 14 July 2022 | · pdf

We review our transverse momentum dependent factorization and resummation formalism for heavy flavor dijet production at the EIC. In this formalism, we have calculated the heavy flavor mass corrections in the collinear-soft and jet functions, and in the resummed expression for the cross section. By establishing this formalism, we then study the effects of the mass corrections by providing predictions at the EIC for the massive case and for the case where the mass is neglected. We find that the heavy flavor mass effects can give sizable corrections to the predicted asymmetry.

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