Description
Conveners:
Marco Pappagallo (INFN and University of Bari)
Daniel Savoiu (Universität Hamburg)
Mikko Voutilainen (Helsinki University)
Marius Wiesemann (MPP)
Contact: eps23-conveners-t06 @desy.de
The elastic scattering of protons at 13 TeV is measured in the range of the protons??? transverse momenta allowing the access to the Coulomb-Nuclear-Interference region. The data were collected thanks to dedicated special LHC beta* = 2.5km optics. The total cross section as well as rho-parameter, the ratio of the real to imaginary part of the forward elastic scattering amplitude, are measured...
Exclusive and diffractive physics measurements are important for better understanding of the non-perturbative regime of QCD. Recent results from the CMS and TOTEM experiments using pp collisions at a center-of-mass energy of 13 TeV are presented in this talk.
We will gain unprecedented, high accuracy insights into internal structure of the atomic nucleus thanks to lepton-hadron collision studies in the coming years at the Electron-Ion-Collider (EIC) in the United States. A good control of radiative corrections is necessary for the EIC to be fully exploited and to extract valuable information from various measurements. However, there is a...
We evaluate the cross section for diffractive bremsstrahlung of a single photon in the $pp \to pp \gamma$ reaction at high energies and at forward photon rapidities. Several differential distributions, for instance, in ${\rm y}$, $k_{\perp}$ and $\omega$, the rapidity, the absolute value of the transverse momentum, and the energy of the photon, respectively, are presented. We compare the...
We discuss production of far-forward $D$ mesons/antimesons and neutrinos/antineutrinos from their semileptonic decays in proton-proton collisions at the LHC energies. We include the gluon-gluon fusion $gg \to c\bar{c}$, the intrinsic charm (IC) $gc \to gc$ as well as the recombination $gq \to Dc$ partonic mechanisms. The calculations are performed within the $k_T$-factorization approach and...
“The modeling of the soft radiation in MC approaches and the inclusion of the intrinsic kT effect in a consistent and “simple” way is one of the successes of the Parton Branching TMD approach. In this approach, a consistent treatment of the Parton Shower evolution and the TMD evolution is carried out by the PB-TMD initial state shower. In this talk, the azimuthal correlation, φ12, of high...
Multi-jet events at various kinematic regimes are subject of wide scaled studies in the LHC program and future colliders. Merging of TMDs, parton showers and matrix elements is a delicate matter that is sensitive to the process and observable of interest. We present studies of the merging scale in the TMD merging framework, using the Cascade3 Monte Carlo generator. The merging scale separates...
At leading order in positron-proton collisions, a lepton scatters off a quark through virtual photon exchange, producing a quark jet and scattered lepton in the final state. The total transverse momentum of the system is typically small, however deviations from zero can be attributed to perturbative initial and final state radiations in the form of soft gluon radiation when the transverse...
We present novel analyses on accessing the 3D gluon content of the proton via spin-dependent TMD gluon densities, calculated through the spectator-model approach. Our formalism embodies a fit-based spectator-mass modulation function, suited to catch longitudinal-momentum effects in a wide kinematic range. Particular attention is paid to the time-reversal even Boer-Mulders and the time-reversal...
We present a novel method of extraction of the Collins-Soper kernel directly from the comparison of differential cross-sections measured at different energies. Using this method, we analyze the simulated data from the CASCADE event generator and extract the Collins-Soper kernel predicted by the Parton Pranching method in the wide range of transverse distances. Using the method, we also solve a...
The Transverse Momentum Dependent (TMD) Parton Branching (PB) method is a Monte Carlo (MC) framework to obtain QCD high energy collider predictions grounded in ideas originating from the TMD factorization. It provides an evolution equation for the TMD parton distribution functions and allows to use those within TMD MC generators.
In this work, we analyze the structure of the TMD PB Sudakov...
The Parton-Branching method (PB) allows the determination of Transverse Momentum Dependent (TMD) parton densities, which cover the region from very small to $k_T$. In the very small $k_T$ region, the contribution from the intrinsic motion of partons (intrinsic $k_T$) plays a role, but also contributions of very soft gluons, which are resummed in the evolution equation. A detailed study shows...
QCD calculations for collider physics make use of perturbative solutions of renormalisation group equations (RGEs). RGE solutions can contribute significantly to systematic uncertainties of theoretical predictions for physical observables. We propose a method to express these systematic effects in terms of resummation scales, using techniques borrowed from soft-gluon resummation approaches. We...
The HERAPDF2.0 ensemble of parton distribution functions (PDFs) was introduced in 2015. The final stage is presented, a next-to-next-to-leading-order (NNLO) analysis of the HERA data on inclusive deep inelastic ep scattering together with jet data as published by the H1 and ZEUS collaborations. A perturbative QCD fit, simultaneously of αS(M2Z) and and the PDFs, was performed with the result...
We compute the NNLO massive corrections for diphoton production in quantum chromodynamics (QCD). This process is very important as a test of perturbative QCD and as a background process for the decay of a Higgs into two photons. We compute semi-analitically the master integrals via power series expansion, classifying Feynman diagrams in different topologies and finding the canonical basis for...
The production of jets and prompt isolated photons at hadron colliders provides stringent tests of perturbative QCD. The latest measurements by the ATLAS experiment, using proton-proton collision data at $\sqrt{s}$ =13 TeV, are presented. Prompt inclusive photon production is measured for two distinct photon isolation cones, R=0.2 and 0.4, as well as for their ratio. The measurement is...
Singular elements associated with the QCD factorization in the collinear limit are key ingredients for high-precision calculations in particle physics. They govern the collinear behaviour of scattering amplitudes, as well as the perturbative energy evolution of PDFs and FFs. In this talk, we explain the computation of multiple collinear and higher-order QCD splittings with massive partons. Our...
One of the main obstacles to the calculation of next-to-next-to-leading order (NNLO) corrections in QCD is the presence of infrared singularities. Together with Raoul Röntsch, Kirill Melnikov and other collaborators, I am developing a more general approach to the nested soft-collinear subtraction method to address this problem for the production of an arbitrary final state at hadron colliders....
A precise measurement of the luminosity is a crucial input for many ATLAS physics analyses, and represents
the leading uncertainty for W, Z and top cross-section measurements. The first ATLAS luminosity determination in Run-3 of the LHC, for the dataset recorded in 2022, at center-of-mass energy of 13.6TeV follows the procedure developed in Run-2 of the LHC. It is based on van der Meer scans...
The associated production of vector bosons V (W, Z or gamma) and jets originating from heavy-flavour (c or b) quarks is a dominant background for many SM and Higgs boson measurements and new physics searches beyond the SM. The study of events with a vector boson accompanied by heavy-flavour jets is crucial to test the theoretical predictions in perturbative QCD up to NNLO, and provides a key...
I will review the MSHT20 parton distribution functions and focus on our recent paper within the MSHT collaboration on the inclusion of theoretical uncertainties and higher order (N3LO) terms into the MSHT PDFs, producing the MSHT20aN3LO (approximate N3LO) set. This represents the first global analysis of parton distribution functions (PDFs) at approximate N3LO as well as simultaneously the...
The radiation pattern within high energy quark and gluon jets (jet substructure) is used extensively as a precision probe of the strong force as well as an environment for optimizing event generators for nearly all tasks in high energy particle and nuclear physics. While there has been major advances in studying jet substructure at hadron colliders, the precision achievable by collisions...
We investigate the impact of the recently released FNAL-E906 (SeaQuest) data concerning the ratio of proton-deuteron and proton-proton DY production cross-sections on the sea quark PDFs. We find that they have constraining power on the light-quark sea isospin asymmetry (dbar-ubar)(x) and on the (dbar/ubar)(x) ratio at large longitudinal momentum fraction x values, that they are particularly...
We present recent updates in the xFitter software framework for global fits of parton distribution functions (PDFs) in high-energy physics. Our focus is on investigating the sensitivity to Z boson couplings using the forward-backward asymmetry in Drell-Yan production. By utilizing an effective approach and simulated data, we assess the accuracy of these couplings, specifically considering the...
The production of dijet events containing at least two jets is among the largest cross sections at the LHC, with QCD predictions directly sensitive to the strong coupling constant. Dijet cross section measurements from ATLAS and CMS, at center-of-mass energies of 7, 8 and 13 TeV are exploited for the determination of the strong coupling constant, using state-of-the-art next-to-next-to-leading...
Measurements of individual electroweak bosons at hadron colliders provide stringent tests of perturbative QCD and improve the modelling of background to many BSM searches. We present the measurement of the production of W boson in association with D+ and D*+ mesons. This precision measurement provides information about the strange content of the proton and is compared to NLO theoretical...
The study of the associated production of vector bosons and jets constitutes an excellent ground field to test the state-of-art pQCD predictions, and to understand the EW aspects of their production. The newsr results on the differential cross sections of vector bosons produced in association with jets at 13 TeV center-of-mass energy will be presented. Differential distributions as function of...
Measurements of jet production in proton-proton collisions at the LHC are crucial for precise tests of QCD, improving the understanding of the proton structure and are important tools for searches for physics beyond the standard model. We present the most recent set of jet measurements performed using CMS data, from which measurements of the the strong coupling constant and PDF constraints are...
$J/\psi-$pair production at the LHC is currently the best tool available to probe gluon transverse momentum distributions (TMDs) which are very poorly known today. Data from LHCb at low transverse momentum are already available and more are expected soon from CMS and LHCb. Such data in the collider mode will allow one to probe the evolution of the unpolarised-gluon TMDs and to measure, for the...
In this talk, I will discuss the impact of one-loop QCD corrections[1] to the differential distributions of $J/\psi$ and $\Upsilon$ mesons produced in inclusive $\gamma \gamma$ collisions for the kinematical conditions of LEP and future high-energy $e^+e^-$ facilities. Firstly, I will focus on the pure QED processes $\gamma + \gamma \to Q\bar{Q}(^3S^{[1]}_1) +\gamma$, which only receive...
We calculate the total cross section and transverse momentum distributions for the production of the enigmatic $\chi_{c1}(3872)$ (or X(3872)) (see [1]) assuming different scenarios: $c \bar c$ state and $D^{0*} {\bar D}^0 + D^0 {\bar D}^{0*}$ molecule.
The derivative of the $c \bar c$ wave function needed in the first scenario is taken from a potential $c \bar c$ model calculations. Compared...
Recent CMS results on production of open heavy flavor hadrons and quarkonia in pp collisions are discussed. The measurements are performed with data collected in pp collisions at sqrt(s)=13 TeV between 2016 and 2018.
The study of quarkonium production in proton-proton collisions involves both the perturbative and non-perturbative regimes of QCD, providing an excellent probe for quantum chromodynamics. Its mechanism is widely studied but not yet fully understood. The associated production of quarkonia is not only useful to probe the quarkonium production puzzle, but also helpful to reveal the double parton...
Studying heavy-flavor mesons and baryons in hadronic collisions provides unique access to the properties of heavy-quark hadronisation in the presence of large partonic densities, where new mechanisms of hadron formation beyond in-vacuum fragmentation can emerge. It also tests calculations of perturbative QCD and explores the role of cold nuclear matter effects. Examining heavy-flavor...
The exclusive photoproduction reactions γp→J/ψ(1S)p and γp→ψ(2S)p have been studied at an ep centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 373 pb−1. The measurement has been made in the kinematic range 30 < W < 180 GeV, Q2 <1 GeV2, |t| <1 GeV2, where W is the photon--proton centre-of-mass energy, Q2 is the photon virtuality and t is the...
KLOE and KLOE-2 collected the largest dataset at an electron-positron collider operating at the $\phi$ resonance peak ($\sim$ 8 fb$^{-1}$),
corresponding to the production of about 24 billion of $\phi$ mesons, namely 8 billion pairs of neutral K mesons and 300 million $\eta$ mesons.
A wide hadron physics program, investigating rare meson decays, $\gamma\gamma$ interaction, and dark...
The first observation of hypertriton and antihypertriton at the LHCb experiment is reported. The used dataset consists of pp collisions at √s = 13 TeV, collected between 2016 and 2018, and corresponds to an integrated luminosity of L = 5.5/fb. The hypertriton candidates are reconstructed via the 2-body decay into helium-3 and a charged pion. The corresponding helium nuclei are identified with...
Quarkonium production in high-energy hadronic collisions is sensitive to both perturbative and non-perturbative aspects of quantum chromodynamics (QCD) calculations. Indeed, the production of the heavy-quark pair is described by perturbative QCD while the formation of the bound state is a non-perturbative process, treated in different ways by available theoretical models. Quarkonium...
The $p_T$-integrated cross section of inclusive hadro and photo-production of heavy quarkonia when computed up to NLO in Collinear Factorisation(CF) shows a perturbative instability at high hadronic or photon-hadron collision energies - the cross section could turn negative for reasonable factorisation/renormalisation scale-choices. We solve this problem by resummation of the subset of LLA...
The latest CMS results on spectroscopy and properties of beauty mesons and baryons are presented. The results are obtained with the data collected by the CMS experiment in proton-proton collisions at sqrt(s)=13 TeV.
The B->DDX and other related final states provides a bountiful arena for performing spectroscopy studies. This talk covers the latest results in this area from amplitude analyses and direct searches.
Measurements of neutral meson production with ALICE provide a precise determination of the production cross section over a wide range of transverse momentum across all collision systems available at the LHC. The measurements combine results from several reconstruction techniques, including the use of two different calorimeters and the reconstruction of conversion photons via their...
The quark model predicts exotic hadrons beyond the conventional quark-antiquark mesons and three quark baryons. Exotic candidates have since been observed in the early 2000's. Since then several exotic states have been discovered. LHCb has reported on tetraquark candidates such as the X(3872), the discovery of pentaquark resonances in 2015, and the first double charmed tetraquark. Many...
Belle II offers unique possibilities for the discovery and interpretation of exotic multiquark states to probe the fundamentals of QCD. This talk presents recent results on searches for the hidden bottom transition between $\Upsilon(10750)$ and $\chi_{bJ}$, and measurements of the energy dependence of the $e^+e^- \to B^{(*)} \bar B ^{(*)}$ cross section.
The spectroscopy of charmonium-like states together with the spectroscopy of charmed and strange baryons is discussed. It is a good testing tool for the theories of strong interactions, including: QCD in both the perturbative and non-perturbative regimes, LQCD, potential models and phenomenological models [1, 2, 3]. An understanding of the baryon spectrum is one of the primary goals of...
Collisions of small systems show signatures suggestive of collective flow associated with QGP formation in heavy-ion collisions. Jet quenching is also a consequence of QGP formation, but no significant evidence of it in small systems has been found to date. Measuring or constraining the magnitude of jet quenching in small systems is essential to determine the limits of QGP formation. The ALICE...
In recent years, evidence of collective effects has been observed in small collision systems at the LHC; however, its precise origin remains unknown.
In this presentation, we will discuss new measurements of anisotropic flow observables (flow harmonic coefficients, flow vector correlation and decorrelation, nonlinear flow response) in pp and p--Pb collisions with ALICE. The highlights...
Femtoscopy is a technique used to measure the space--time dimensions of hot and dense matter created in high-energy collisions via particles with low relative momentum correlating due to quantum statistics effects and/or final-state interactions. It allows investigating the dynamics of the medium emitting correlating particles and to explore the hadronic interaction among the produced...
This study presents measurements of dijet and neutral pion production in high-energy nuclear
collisions using the LHCb detector. The measurements provide essential insights into the parton
distribution functions, nuclear structure, and particle production dynamics within the
framework of Quantum Chromodynamics (QCD). The nuclear modification factors for neutral
pions produced in...
Fragmentation Functions (FF) are universal non-perturbative objects that model hadronization in some general kind of processes. They are mainly extracted from experimental data, hence constraining the parameters of the corresponding fits is crucial for achieving reliable results. As expected, the production of lighter hadrons is favoured w.r.t. heavy ones, thus we would like to exploit the...
We discuss the preliminary results of the new global nCTEQ23 nuclear PDF analysis, combining a number of our previous analyses into one consistent framework with updates to the underlying theoretical treatment as well as the addition of new available data. In particular, the nCTEQ23 global release will be the first nCTEQ release containing neutrino DIS scattering data in a consistent manner...
A first measurement of the 1-jettiness event shape observable in neutral-current deep-inelastic electron-proton scattering is presented. The 1-jettiness observable $\tau_{1b}$ is defined such that it is equivalent to the thrust observable defined in the Breit frame. The data were taken in the years 2003 to 2007 with the H1 detector at the HERA ep collider at a center-of-mass energy of 319 GeV...
The Future Circular Collider (FCC) is a post-LHC project aiming at direct and indirect searches for physics beyond the SM in a new 91-km tunnel at CERN. In addition, the FCC-ee offers unique possibilities for high-precision studies of the strong interaction in the clean environment provided by e$^+$e$^-$ collisions, thanks to its broad span of center-of-mass energies, ranging from the Z pole...
The Large Hadron-electron Collider and the Future Circular Collider in electron-hadron mode [1] will make possible the study of DIS in the TeV regime providing electron-proton (nucleus) collisions with per nucleon instantaneous luminosities around $10^{34}$ ($10^{33}$) cm$^{−2}$s$^{−1}$. In this talk we review the opportunities that these proposals offer for the determination of the partonic...
The measurement of exclusive $e^+e^-$ to hadrons processes is a significant part of the physics program of $BABAR$ experiment, aimed to improve the calculation of the hadronic contribution to the muon g−2 and to study the intermediate dynamics of the processes. We present the most recent studies performed on the full data set of about 470 $\text{fb}^{-1}$ collected at the PEP-II $e^+e^-$...
We present FMNLO, a framework to combine general-purpose Monte Carlo generators and fragmentation functions (FFs). It is based on a hybrid scheme of phase-space slicing method and local subtraction method, and is accurate to next-to-leading order (NLO) in QCD. The new framework has been interfaced to MG5_aMC@NLO and made publicly available in this work. We demonstrate its unique ability by...
Fragmentation functions are one of the key components of the factorisation theorem used to calculate heavy-flavour hadron production cross-sections. Due to their non-perturbative nature, fragmentation functions are typically constrained in the clean environments of $\mathrm{e^{+}e^{-}}$ and $\mathrm{e^{-}p}$ collisions.
Recent measurements of charm-hadron spectra and of the ratios of...
Properties of partonic fragmentation in QCD depend on parton flavours in $1\rightarrow2$ splitting processes in parton showers due to the different Casimir factors of quarks and gluons, and to the different masses of light- and heavy-flavour quarks. Heavy-flavour jets provide a unique experimental tool to probe these flavour dependencies, particularly at low and intermediate transverse momenta...
