Hadron spectroscopy, the study of states bound by the strong interaction, has received renewed interest in recent years, motivated by the discovery of states that to not conform to the usual classification of mesons (q qbar) or baryons (qqq). This opens up a new field of spectroscopy for these unconventional states. In this talk I will give a short overview of the field and present several...
Studying the spectroscopy of hadrons from lattice QCD, much like in experiment, involves determining hadronic scattering amplitudes and investigating enhancements due to resonances. Lattice QCD offers a method for first-principles computation of hadronic scattering amplitudes and thus enables resonance properties to be determined directly from the fundamental theory. I will present several...
Based on a sample of 448 million psi(2S) events and a scan data sample above 3.7 GeV with an integrated luminosity of 22/fb, charmonium spectroscopy and decays are studied. In the talk the latest results will be presented. The production of psi2(3823) via e+e- -> pi+ pi- psi2(3823) is measured, the most precise measurement of the mass of psi2(3823) is achieved, and the new decay modes of...
Jet substructure is a powerful tool to probe the perturbative regime of jet evolution in proton-proton and heavy-ion collisions. Over the past few years, a wide variety of substructure observables have been proposed in order to understand specific aspects of jet dynamics in a quark-gluon plasma (QGP).
In this talk, based on [1,2], we will explore the ability of such an observable, called...
Jets in relativistic heavy-ion collisions interact with the quark-gluon plasma (QGP), leading to effects such as a suppression of jet yields and modification of internal jet structure that are used to measure the properties of the QGP. The dependence of jet suppression on the cone size ($R$) and jet $p_{\rm T}$ is a useful observable to disentangle competing energy loss mechanisms with a high...
The LHCb experiment at the LHC is suited for studying how hadrons are formed from scattered quarks and gluons, in energetic proton-proton collisions. The hadronization and fragmentation processes can be studied via measurements such as those involving jet substructure. Equipped with a forward spectrometer, the LHCb experiment achieves an excellent transverse momentum for charged tracks, that...
Quenching features of mullti-partonic cascades in expanding
media are important in understanding the complex phenomena of jet
quenching. We present results for the inclusive jet $R_{AA}$ by
including phenomenologically driven combinations of quark and gluon
fractions inside a jet. In addition, we have also studied the effect of
the nPDF as well as vacuum like emissions on the
jet...
This talk presents a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive-charged particle yields in 13 TeV pp collisions. Measurements are made differentially for Upsilon momentum and for different Upsilon states. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV pp...
The Multiplicity fluctuations are sensitive to QCD phase transition and to the presence of of critical point in QCD phase diagram. At critical point a system undergoing phase transition is characterized by large fluctuations in the observables. Fluctuation study is thus one of the important techniques to explore phases of the QCD matter and to search for the critical end point of ...
Relativistic heavy-ion beams at the LHC are accompanied by a large flux of equivalent photons. New measurements of exclusive dilepton production (electron, muon, and tau pairs) are discussed. We present the photon-induced production of tau pairs and constraints on the tau lepton's anomalous magnetic dipole moment. In addition, measurements of photon-induced electron and muon pair production...
Multiparton interactions in proton-proton collisions have long been a topic of great interest. A new look at them has begun to emerge from work being done to understand the dynamics of ‘small systems’, a topic that is taking center stage in the physics of relativistic heavy-ion interactions. Numerous studies conducted at the LHC and lower energies reveal that proton-proton collisions at high...
We revisit the picture of jets propagating in the quark-gluon plasma. In addition to vacuum radiation, related to the high initial virtuality of a jet, jet particles scatter on the medium constituents resulting in induced emissions. Analytical approaches to resumming these interactions have traditionally dealt separately with multiple, soft [1,2], or rare, hard scatterings [3,4]. A full...
The MSHT20 PDFs represented a significant step forward in terms of the accuracy and precision of the resulting PDFs, and followed substantial progress on the experimental, methodological and theoretical fronts. I will review the MSHT20 PDFs before detailing several of the subsequent studies we have undertaken within the MSHT collaboration, both completed and ongoing work. This will range from...
We present fits to determine parton distribution functions (PDFs) using a diverse set of measurements from the ATLAS experiment at the LHC, including inclusive W and Z boson production, ttbar production, W+jets and Z+jets production, inclusive jet production and direct photon production. These ATLAS measurements are used in combination with deep-inelastic scattering data from HERA. Particular...
The interpretation of measurements from high energy collisions at experiments like the Large Hadron Collider (LHC) relies heavily on the performance of full event generators, specifically their accuracy and speed in simulating complex multi-particle final states. With the rapid and continuous improvement in quantum computers, these devices present an exciting opportunity for high energy...
The elastic scattering of protons at 13 TeV is measured in the range of 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 and...
The factorization hypothesis states that the production cross-section of heavy-flavor hadrons can be calculated as the convolution of three independent terms: the parton distribution function of the colliding hadrons, the production cross sections of the heavy-quarks in the hard partonic process, and finally the fragmentation functions of the heavy-flavor quarks into the given heavy-flavor...
Mass ordering is expected for energy loss of quarks traversing the quark gluon plasma (QGP). Gluon bremsstrahlung is the dominant mechanism for light quark energy loss; however, both radiative and collisional energy loss must be considered for heavy quarks. At low transverse momentum these mechanisms have significant quark mass dependence. Therefore, separated charm and beauty measurements are...
Cross-section measurements for a Z boson produced in association with high-transverse-momentum jets (pT > 100 GeV) and decaying into a charged-lepton pair are presented. The measurements are performed using proton-proton collisions at sort(s) = 13 TeV corresponding to an integrated luminosity of 139 fb^-1 collected by the ATLAS experiment at the LHC. Measurements of angular correlations...
We compute for the first time the finite size corrections to NLO $2\rightarrow2$ scattering in $\phi^4$ theory on a $\mathbb{R}^{1,(3-n)}\times \text{T}^n$ spacetime. In order to do so we developed multiple novel techniques, including denominator regularization, a generalization of a formula by Ramanujan using the sum of squares function, and an analytic continuation of the generalized Epstein...
The interpretation of measurements from high energy collisions at experiments like the Large Hadron Collider (LHC) relies heavily on the performance of full event generators, specifically their accuracy and speed in simulating complex multi-particle final states. With the rapid and continuous improvement in quantum computers, these devices present an exciting opportunity for high energy...
Time-Like Compton Scattering (TCS) is a hard, exclusive process, involving the elastic scattering of a real photon from a nucleon, and the production of a virtual photon that decays to a heavy lepton pair in the final state. Studies of TCS observables are used to broaden our understanding of Generalised Parton Distributions (GPD’s) which can offer insights into the internal structure of the...
The Multiplicity fluctuations are sensitive to QCD phase transition and to the presence of of critical point in QCD phase diagram. At critical point a system undergoing phase transition is characterized by large fluctuations in the observables. Fluctuation study is thus one of the important techniques to explore phases of the QCD matter and to search for the critical end point of ...
Measurements of jet production and jet properties in pp collisions provide a test of perturbative quantum chromodynamics (pQCD) and form a baseline for similar measurements in heavy ion (A–A) collisions. Recent studies of high-multiplicity final states of small collision systems exhibit signatures of collective effects that could be associated with hot and dense, color-deconfined QCD matter,...
We consider the experimental data on yields of protons, strange Λ’s, and multistrange baryons (Ξ, Ω), and antibaryons production on nuclear targets, and the experimental ratios of multistrange to strange antibaryon production, at the energy region from SPS up to LHC, and compare them to the results of the Quark-Gluon String Model calculations. In the case of heavy nucleus collisions, the...
In the ATLAS detector, electrons and positrons, collectively referred to as electrons, leave characteristic signatures which allow them to be reconstructed and identified. The poster will present measurements of electron reconstruction and identification in Jpsi->ee and Z->ee events using Run2 data collected at centre-of-mass energy of 13 TeV in p-p collisions. The poster will also show the...
Mass ordering is expected for energy loss of quarks traversing the quark gluon plasma (QGP). Gluon bremsstrahlung is the dominant mechanism for light quark energy loss; however, both radiative and collisional energy loss must be considered for heavy quarks. At low transverse momentum these mechanisms have significant quark mass dependence. Therefore, separated charm and beauty measurements are...
The factorization hypothesis states that the production cross-section of heavy-flavor hadrons can be calculated as the convolution of three independent terms: the parton distribution function of the colliding hadrons, the production cross sections of the heavy-quarks in the hard partonic process, and finally the fragmentation functions of the heavy-flavor quarks into the given heavy-flavor...
This talk presents a new measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states with the inclusive-charged particle yields in 13 TeV pp collisions. Measurements are made differentially for Upsilon momentum and for different Upsilon states. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV pp...
The elastic scattering of protons at 13 TeV is measured in the range of 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 and...
The production of jets and prompt isolated photons at hadron colliders provides stringent tests of perturbative QCD. We present the latest measurements using proton-proton collision data collected by the ATLAS experiment at sqrt(s)=13 TeV. 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...
The search for the QCD critical point (CP), and the study of quark-hadron phase transition (and vice-versa), at finite baryon density and high temperature, is the main task in contemporary relativistic heavy-ion collision experiments. Fluctuation analysis with global and local measures is the basic tool to achieve this goal. Local density fluctuations are directly related to the critical...
At BESIII, the lineshapes of e+e- ->phi eta', phi eta, KK, omega pi0, eta pipi, omega pipi are measured from 2.0 to 3.08 GeV, where resonant structures are observed in these processes. Multiple lineshapes of intermediate state are obtained by a partial wave analysis of e+e- ->K+ K- pi0 pi0, K+K- pi0 and the structures observed provide essential input to understand the nature of phi2170. ...
Cross-section measurements for a Z boson produced in association with high-transverse-momentum jets (pT > 100 GeV) and decaying into a charged-lepton pair are presented. The measurements are performed using proton-proton collisions at sort(s) = 13 TeV corresponding to an integrated luminosity of 139 fb^-1 collected by the ATLAS experiment at the LHC. Measurements of angular correlations...
Correlations between charged particles provide important insight about hadronization process. The analysis of the momentum difference between charged hadrons in pp, p-lead, and lead-lead collisions of various energies is performed in order to study the dynamics of hadron formation. The spectra of correlated hadron chains are explored and compared to the predictions based on the quantized...
Spatial distributions of produced charged particles characterise the system formed in heavy-ion collisions. To learn about the mechanism of particle production and the phase space changes from quarks to hadrons, one of the basic tools is to study fluctuations in particle production. Local charged particle density fluctuations in the phase space are expected to scale with universal scaling...
Hadronic resonaces production provide insight into the properties of the hadronic phase. Studying the dependence of the yield of resonances on transverse spherocity and multiplicity allows us to understand the resonance production mechanism with event topology and system size, respectively.In this contribution,we present hadronic resonances production as a function of transverse spherocity...
Recent results on diffractive measurements will be presented.
Invited by the Forward and Diffractive Physics
session convener
We describe the gain on sensitivities to quartic $\gamma \gamma \gamma \gamma$, $\gamma \gamma WW$ and $\gamma \gamma \gamma Z$ anomalous couplings and to the search for Axion-Like Particles by two or three orders of magnitude with respect to standard methods at the LHC by tagging intact protons in the final state, and matching the information from the intact protons and the $WW$, $ZZ$,...
The Electron Ion Collider (EIC) to be built by JLab and BNL will be unique in colliding polarized electrons off polarized protons and light nuclei, providing the spin degrees of freedom essential to pursue its physics program to study spin structure, multi-dimensional tomographic images of protons and nuclei, and collective effects of gluons in nuclei. The unprecedented luminosity of the EIC,...
At BESIII, the R value is measured with a total of 14 data points with the corresponding c.m. energy going from 2.2324 to 3.6710 GeV.
The statistical uncertainty of the measured R is less than 0.6%. Two different simulation models, the LUARLW and a new Hybrid generated, are used and give consistent detection efficiencies and initial-state-radiation corrections. An accuracy of better than 2.6%...
Time-Like Compton Scattering (TCS) is a hard, exclusive process, involving the elastic scattering of a real photon from a nucleon, and the production of a virtual photon that decays to a heavy lepton pair in the final state. Studies of TCS observables are used to broaden our understanding of Generalised Parton Distributions (GPD’s) which can offer insights into the internal structure of the...
Measurements of jet production and jet properties in pp collisions provide a test of perturbative quantum chromodynamics (pQCD) and form a baseline for similar measurements in heavy ion (A–A) collisions. Recent studies of high-multiplicity final states of small collision systems exhibit signatures of collective effects that could be associated with hot and dense, color-deconfined QCD matter,...
The search for the QCD critical point (CP), and the study of quark-hadron phase transition (and vice-versa), at finite baryon density and high temperature, is the main task in contemporary relativistic heavy-ion collision experiments. Fluctuation analysis with global and local measures is the basic tool to achieve this goal. Local density fluctuations are directly related to the critical...
The Belle II experiment at the SuperKEKB energy-asymmetric e+e− collider is a substantial upgrade of the B factory facility at the Japanese KEK laboratory. The design luminosity of the machine is 6×1035 cm−2s−1 and the Belle II experiment aims to ultimately record 50 ab−1 of data, a factor of 50 more than its predecessor. With this data set, Belle II will be able to measure the...
Less explored from both the theoretical and the experimental sides are the B-meson semileptonic transitions to the lowest lying excited charmed mesons. An accurate knowledge of the form factors of these transitions is important to understand the problem of filling the gap between the inclusive $B \to X_c \ell \bar\nu_\ell $ width and the sum of the exclusive semileptonic widths. These...
The charmoniumlike state ψ(4230)1 is now widely considered as predominantly a D1 ̄D hadronic molecule. The heavy quark spin symmetry (HQSS) thus implies the possible emergence of its heavy quark spin partners with molecular configuration as D1 ̄D∗ and D∗ 2 ̄D∗ below these charmed mesons’ thresholds. Similar heavy quark spin patterns are already identified for instance for recently observed...
Colour evolution and parton branching at the amplitude level have become important theoretical frameworks to improve parton showers, and are algorithms in their own right to complement shower development by resummation algorithms capable of including interference effects and subleading-N contributions at an unprecedented level. I will cover recent development in the field, with a focus on soft...
As classic WIMP-based signatures for dark matter at the LHC have found no compelling evidence, several phenomenological studies have raised the possibility of accessing a strongly-interacting dark sector through new collider-event topologies. If dark mesons exist, their evolution and hadronization procedure are currently little constrained. They could decay promptly and result in QCD-like jet...
invited by Jets and QCD at high scales session conveners
Experiments measure hadrons, but pQCD calculations deal with quarks and gluons. While there are several prescriptions for relating the two, the actual process of hadronization is not well understood. I will discuss different descriptions of the hadron formation process, and what we can learn from jet substructure measurements about hadronization. Insights from current LHC data and future...
Recent results on jet-based anomaly detection at the LHC
The strong interaction of quarks and gluons is governed by quantum chromodynamics (QCD). The QCD Lagrangian contains a theta-term that describes the topological feature of the gluon field of the vacuum. Interactions with this term will change the relative numbers of left- and right-handed quarks and antiquarks. This chirality imbalance will yield an electric current along a strong magnetic...
The inherent characteristic of parton energy losses, both radiative and collisional, in QGP is the evident flavor dependence. Experimentally observed suppression mass ordering, as well as comprehensively studied dead-cone effect in radiative energy loss, encouraged us to address the mass hierarchy in heavy flavor suppression more thoroughly.
With this goal in mind, we employ the recently...
We present a method of merging the exclusive LO-matched high energy resummation of High Energy Jets (HEJ) with the parton shower of Pythia which preserves the accuracy of the LO cross sections and the logarithmic accuracy of both resummation schemes across all of phase space. Predictions produced with this merging prescription are presented with comparisons to data from previous experimental...
The LHCb detector at the LHC offers unique coverage of forward rapidities for studies of Central Exclusive Production (CEP) and soft QCD. CEP measurements allow the investigation of the nature of pomerons, and provide constraints on low-x gluon phenomenology, probing potential saturation effects. Moreover LHCb can test phenomenological models of soft QCD processes, by measuring the production...
The RAA of pions in small system collisions like p/d/He+Au at high pT show suppression in central collisions and enhancement in peripheral collisions. Although the suppression can be understood by probable formation of Quark Gluon Plasma (QGP) in central collision, there is no known physics mechanism to understand the observed enhancement.
As direct photons are transparent to the QGP and...
Invited by Jets and QCD at high scales session convener"
Recent results from the proton-proton collision data taken by the ATLAS experiment on exotic resonances will be presented. A search for $J/\psi\ p$ resonances in $\Lambda_b \to J/\psi\ p K$ decays with large $pK$ invariant masses will be reported. Studies of $Z_c$ states in $B$-meson decays with the Run 2 data at 13 TeV will also be discussed. Searches for exotic resonances in 4 muon final...
CP violation, as one of the key ingredients necessary to explain the dominance of matter over antimatter in our Universe, has been very well established experimentally in heavy-flavour decays. Nevertheless, the CKM mechanism within the Standard Model predicts an interdependence between several CP-violating observables governed by unitarity, which motivates their continued study. We discuss...
Cosmic rays that enter the Earth's atmosphere interact with air nuclei, initiating a cascade - an air shower. The secondary particles that reach the ground can be measured with large detector arrays. Understanding the air-shower development is crucial for the interpretation of cosmic-ray observables and strongly depends on our knowledge of high-energy hadron production. During the air-shower...
The CORSIKA 8 project is a collaborative effort aiming to develop a versatile C++ framework for the simulation of extensive air showers, intended to eventually succeed the long-standing FORTRAN version. I present an overview of its current capabilities, focusing on aspects concerning the hadronic and muonic shower components. In particular, I demonstrate the “cascade history” feature and its...
In the sub-TeV regime, the most widely used hadronic interaction models disagree significantly in their predictions of particle spectra from cosmic ray induced air showers. We investigate the nature and impact of model uncertainties, focussing on air shower primaries with energies around the transition between high and low energy hadronic interaction models, where the dissimilarities are...
An enhanced production of strange over non-strange hadrons (strangeness enhancement) was one of the first experimental signatures of the formation of quark-gluon plasma (QGP). The ALICE experiment at the LHC observed such an enhancement in strangeness production in heavy ion collisions at $\sqrt{s_{NN}}$ = 2.76 TeV, contributing to the evidence that a QGP had been formed at LHC...
A brief overview of properties of the model of quantized fragmentation of a helical QCD string followed by the discussion of the evolution of average transverse momentum in hadronic events, as function of leading particle pT and particle multiplicity. Reference to experimental data is included.
Continuum reduction can be used to study mesons in the limit of large number of colors with no finite volume effects. We will describe some technical details that are relevant for such a numerical project and present results on the quark parton distribution functions of the pion in this limit.
Studies of properties such as the azimuthal modulations of hadrons produced in the target fragmentation region serve as a test of our complete understanding of the different production mechanisms in SIDIS and provide additional information on QCD dynamics that are not accessible with hadron production in the current fragmentation region. We present the first multidimensional studies of beam...
