arXiv subjects

Katerina Lipka

Publications and source records attributed to Katerina Lipka.

15 recordsLinked to original sources

arXiv2026

Simultaneous extraction of top quark mass, strong coupling, effective mixing angle, and proton PDFs using inclusive DIS and proton-proton collision data

We present the first simultaneous determination of the proton parton distribution functions (PDFs) together with the strong coupling, the top quark pole mass, and the effective weak mixing angle. The analysis is performed at next-to-next-to-leading order in QCD using the xFitter framework, based on inclusive deep-inelastic scattering measurements at HERA and precise measurements of jet, electroweak boson, and top quark-antiquark pair production in proton-proton collisions at the LHC. Non-relativistic QCD effects in top quark-antiquark pair production are considered at next-to-leading order, and combined with next-to-leading logarithmic soft-gluon resummation. Simultaneously with PDFs and Standard Model (SM) parameters, relevant top quark SM effective-field-theory (SMEFT) operators are constrained. The precision of the obtained SM parameters is competitive with the state-of-the art individual extractions and accounts for the correlations among those parameters and PDFs. This work paves the way for future global interpretation of the LHC data in terms of QCD, SM and SMEFT.

hep-ph↗

arXiv2025

Running of the top quark mass at NNLO in QCD

The running of the top quark mass ($m_\mathrm{t}$) is probed at the next-to-next-to-leading order in quantum chromodynamics for the first time. The result is obtained by comparing calculations in the modified minimal subtraction ($\mathrm{\overline{MS}}$) renormalisation scheme to the CMS result on differential measurement of the top quark-antiquark ($\mathrm{t\bar{t}}$) production cross section at $\sqrt{s} = 13~\mathrm{TeV}$. The scale dependence of $m_\mathrm{t}$ is extracted as a function of the invariant mass of the $\mathrm{t\bar{t}}$ system, up to an energy scale of about $0.5~\mathrm{TeV}$. The observed running is found to be in good agreement with the three-loop solution of the renormalisation group equations of quantum chromodynamics.

hep-ph↗

arXiv2024

A framework for simultaneous fit of QCD and BSM parameters with xFitter

An extension of the xFitter open-source program for QCD analyses is presented, allowing for a polynomial parameterization of the dependence of physical observables on theoretical parameters. This extension enables simultaneous determination of parton distribution functions (PDFs) and new physics parameters within the framework of the Standard Model Effective Field Theory (SMEFT). The functionalities of the code are illustrated in a sensitivity study, where a simultaneous determination of the PDFs, top quark mass and the couplings of selected dimension-6 SMEFT operators is addressed using projections for measurements of top quark-antiquark pair production at the High-Luminosity LHC. The importance of considering all the correlations of the parton distributions, top quark mass and the EFT parameters in a simultaneous QCD+SMEFT analysis is demonstrated. This work serves as a new platform for simultaneous extraction of the PDFs and the SM/SMEFT parameters based on xFitter.

hep-ph↗

arXiv2024

Probing the weak mixing angle at high energies at the LHC and HL-LHC

Measurements of neutral current Drell-Yan production at large invariant dilepton masses can be used to test the energy scale dependence (running) of the electroweak mixing angle. In this work, we make use of a novel implementation of the full next-to-leading order electroweak radiative corrections to the Drell-Yan process using the $\overline{\mathrm{MS}}$ renormalization scheme for the electroweak mixing angle. The potential of future analyses using proton-proton collisions at $\sqrt{s}=13.6~\mathrm{TeV}$ in the Run 3 and High-Luminosity phases of the LHC is explored. In this way, the Standard Model predictions for the $\overline{\mathrm{MS}}$ running at $\mathrm{TeV}$ scales can be probed.

hep-ph↗

arXiv2023

Investigation of the scale dependence in the MSR and $\overline{\textrm{MS}}$ top quark mass schemes for the $\mathrm{t}\overline{\mathrm{t}}$ invariant mass differential cross section using LHC data

The computation of the single-differential top quark-antiquark pair ($\mathrm{t}\overline{\mathrm{t}}$) production cross section at NLO in the fixed-order expansion is examined consistently using the MSR and $\overline{\textrm{MS}}$ short-distance top quark mass schemes. A thorough investigation of the dependence of different regions of the $\mathrm{t}\overline{\mathrm{t}}$ invariant mass spectrum on the renormalization scales $R$ and $μ_m$ of the MSR mass $m_\mathrm{t}^{\textrm{MSR}}(R)$ and $\overline{\textrm{MS}}$ mass $\overline{m}_\mathrm{t}(μ_m)$, respectively, is carried out. We demonstrate that a scale choice of $R\sim 80$~GeV is important for the stability of the cross-section predictions for the low $\mathrm{t}\overline{\mathrm{t}}$ invariant mass range, which is important for a reliable extraction of the top quark mass. Furthermore, a choice of semi-dynamical renormalization and factorization scales is preferred. These findings are expected to remain valid once non-relativistic quasi-bound state effects are included in the low invariant mass region.

hep-ph↗

arXiv2022

Single-differential top quark pair production cross sections with running mass schemes at NLO

Single-differential cross section predictions for top quark pair production are presented at next-to-leading order, using running top quark mass renormalization schemes. The evolution of the mass of the top quark is performed in the MSR scheme $m_{\mathrm{t}}^{\textrm{MSR}}(μ)$ for renormalization scales $μ$ below the $\overline{\textrm{MS}}$ top quark mass $\overline{m}_{\mathrm{t}}(\overline{m}_{\mathrm{t}})$, and in the $\overline{\textrm{MS}}$ scheme $\overline{m}_{\mathrm{t}}(μ)$ for scales above. In particular, the implementation of a mass renormalization scale independent of the strong coupling renormalization scale and factorization scale in quantum chromodynamics allows investigating independent dynamical scale variations. Furthermore, the first theoretically consistent extraction of the top quark MSR mass from experimental data is presented.

hep-ph↗

arXiv2018

Threshold and jet radius joint resummation for single-inclusive jet production

The QCD predictions for single-inclusive jet production are computed with joint resummation of threshold and jet radius logarithms. The results are compared to those based on fixed order perturbation theory up to next-to-next-to-leading order and to data by the CMS collaboration measured in proton-proton collisions at the LHC at $\sqrt{S}=8$ TeV. The joint resummation results are in remarkable agreement with the data.

hep-ph↗

arXiv2016

Calibration of the Top-Quark Monte-Carlo Mass

We present a method to establish experimentally the relation between the top-quark mass $m_t^{MC}$ as implemented in Monte-Carlo generators and the Lagrangian mass parameter $m_t$ in a theoretically well-defined renormalization scheme. We propose a simultaneous fit of $m_t^{MC}$ and an observable sensitive to $m_t$, which does not rely on any prior assumptions about the relation between $m_t$ and $m_t^{MC}$. The measured observable is independent of $m_t^{MC}$ and can be used subsequently for a determination of $m_t$. The analysis strategy is illustrated with examples for the extraction of $m_t$ from inclusive and differential cross sections for hadro-production of top-quarks.

hep-ph↗

arXiv2015

The PDF4LHC report on PDFs and LHC data: Results from Run I and preparation for Run II

The accurate determination of the Parton Distribution Functions (PDFs) of the proton is an essential ingredient of the Large Hadron Collider (LHC) program. PDF uncertainties impact a wide range of processes, from Higgs boson characterisation and precision Standard Model measurements to New Physics searches. A major recent development in modern PDF analyses has been to exploit the wealth of new information contained in precision measurements from the LHC Run I, as well as progress in tools and methods to include these data in PDF fits. In this report we summarise the information that PDF-sensitive measurements at the LHC have provided so far, and review the prospects for further constraining PDFs with data from the recently started Run II. This document aims to provide useful input to the LHC collaborations to prioritise their PDF-sensitive measurements at Run II, as well as a comprehensive reference for the PDF-fitting collaborations.

hep-ph↗

arXiv2015

Impact of heavy-flavour production cross sections measured by the LHCb experiment on parton distribution functions at low x

The impact of recent measurements of heavy-flavour production in deep inelastic $ep$ scattering and in $pp$ collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions $x$ of the proton momentum, down to $x \sim 5 \times 10^{-6}$. This kinematic range is currently not covered by other experimental data in perturbative QCD fits.

hep-ph↗

arXiv2015

Top-quark pair production at hadron colliders: differential cross section and phenomenological applications with DiffTop

The results of phenomenological studies of top-quark pair production in proton-proton collisions are presented. Differential cross sections are calculated in perturbative QCD at approximate next-to-next-to-leading order ${\cal O}(α_s^4)$ by using methods of threshold resummation beyond the leading logarithmic accuracy. Predictions for the single-particle inclusive kinematics are presented for transverse momentum and rapidity distributions of final-state top quarks. Uncertainties related to the description of proton structure, top-quark mass and strong coupling constant are investigated in detail. The results are compared to the recent measurements by the ATLAS and CMS collaborations at the LHC at the center of mass energy of 7 TeV. The calculation presented here is implemented in the computer code \textsc{Difftop} and can be applied to the general case of heavy-quark pair production at hadron-hadron colliders. For the first time, a fit of parton distribution functions at NNLO is performed by using the differential cross sections of top-quark pair production together with other data sets. The impact of the top-pair production on the precision of the gluon distribution at high scales is illustrated.

hep-ph↗

arXiv2014

Differential cross sections for top pair production at the LHC

We present results of phenomenological studies for top-quark pair production at the LHC at the center of mass energy $\sqrt{S} = 7$ TeV. The transverse momentum and rapidity distributions for final-state top quarks are calculated in perturbative QCD at approximate next-to-next-to-leading order ${\cal O}(α_s^4)$ by using methods of threshold resummation beyond the leading logarithmic accuracy. The theoretical predictions are obtained by using the computer code \textsc{DiffTop} and are compared to recent measurements by the ATLAS and CMS collaborations. \textsc{Difftop} can be employed in the general case of heavy-quark pair production at hadron-hadron colliders and provides a basis for applications in QCD analyses for parton distribution functions determination.

hep-ph↗

arXiv2013

Top-quark production at the LHC: differential cross section and phenomenological applications

We discuss top-quark pair production at hadron colliders and review available calculations of differential top-pair production cross section in perturbative QCD at approximate next-to-next-to-leading order (NNLO) within the threshold resummation formalism. These calculations are implemented into an open source program under development. We present phenomenological studies at the LHC that include transverse momentum and rapidity distribution of the top quarks at a center-of-mass energy of 7 TeV. Preliminary results obtained with this program are in very good agreement with the recent LHC measurements.

hep-ph↗

arXiv2012

Determination of the top quark mass from the $t\bar t$ cross section measured by CMS at $\sqrt{s} = 7$ TeV

Higher-order QCD predictions are used to extract the top quark mass, both in the pole and in the $\bar{\mathrm{MS}}$ scheme, from the top quark pair production cross section measured in the dilepton final state. The analysed dataset corresponds to an integrated luminosity of 1.14 fb$^{-1}$ collected by the CMS experiment in 2011 in proton-proton collisions at $\sqrt{s} = 7$ TeV.

hep-ex↗

arXiv2010

Heavy Flavours in DIS and Hadron Colliders: Working Group Summary

The recent theory developments and latest experimental results on heavy-flavour production in Deep Inelastic Scattering and at hadron colliders are summarized. Models of heavy quarkonia production, non-perturbative corrections to fragmentation, theory of heavy-hadron production in heavy-ion collisions, and interpretation of new exotic hadrons are discussed. Progress in event generators development is reported. Most recent experimental results from HERA and e+e- colliders as well as from proton-(anti)proton and heavy ion experiments are presented and the role of charm and beauty quarks in the analyses of the proton structure is stressed.

hep-ph↗