Publications

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The study of hadron properties and structure in high energy multi-production processes

Shi-Yuan Li

SciPost Phys. Proc. 10, 039 (2022) · published 11 August 2022 | · pdf

In high energy scattering, the multi-production process is unique in its relevance to the total cross section and in its global properties, such as rapidity and other kinematic distributions. If there is a hard interaction, the jet rate and structure is a good arena for perturbative quantum chromodynamics. However, once any hadron is specified, its properties and structure must make sense, while the global and/or perturbative chromodynamic mechanism still can put important constraints. The relation of the hadron’s properties and structure with its production cross section, distribution etc. can be much more complex than its decay width. On the one hand there are many difficulties and challenges in the calculations, while on the other hand, the production process provides a unique way to study the details of properties and structure of the hadron, which is beyond the approach of its decay process. Here I review our works on such topics in recent years, mainly on the multi-quark state production in multi-production processes and the Bethe-Salpeter wave function in exclusive processes. For the former, I emphasize the unitarity of the hadronization process and relevant models, so that almost no multi-quark state is observed in multi-production processes. I also address how to calculate hadron molecule production in multi-production processes. The most recently observed T+cc is also stated with its relevance to colour and baryon number fluctuation of the preconfinement clusters. For the latter, I emphasize the Dirac structure of the hadron-quark coupling vertex.
Dark Sector searches with jets

Janik von Ahnen

SciPost Phys. Proc. 10, 029 (2022) · published 11 August 2022 | · pdf

The presence of a non-baryonic Dark Matter (DM) component in the Universe is inferred from the observation of its gravitational interaction. The ATLAS and CMS experiments located at the LHC have developed a broad search program for DM candidates, including resonance searches for the mediator and searches with large missing transverse momentum. Additionally, searches have been conducted in models where the Higgs Sector and the Dark Sector are connected leading for example to invisible Higgs boson decays. The results of recent searches on 13 TeV $pp$ data, their interplay and interpretation are presented.
Measurements of sub-jet fragmentation with ALICE

James Mulligan

SciPost Phys. Proc. 10, 020 (2022) · published 10 August 2022 | · pdf

High-energy jets offer rich opportunities to study quantum chromodynamics, from investigating the limits of perturbative calculability to constraining the emergent properties of the quark-gluon plasma (QGP). In these proceedings, we present new measurements of the fragmentation properties of jets. We report distributions of the sub-jet momentum fraction $z_r$ measured in pp and Pb-Pb collisions with ALICE at the Large Hadron Collider. These measurements serve as input to test the universality of jet fragmentation in the QGP, and offer a path to elucidate jet quenching effects in the large-$z$ region.
Study of $\text{D}^0$ meson interactions via femtoscopic correlations

Isabela Maietto Silvério, Sandra S. Padula, Gastão I. Krein

SciPost Phys. Proc. 10, 019 (2022) · published 10 August 2022 | · pdf

Femtoscopy is a powerful tool that can be used to investigate the space-time dimensions of the region from which the particles are emitted. When applied to high energy collisions this method is sensitive not only to quantum statistics, but also to final state interactions, such as strong interactions between hadrons and Coulomb interactions when considering charged particles. In particular, this procedure is used to investigate the sensitivity of the strong interaction to different source sizes for $\textrm{D}^{0}$ mesons correlations.
The importance of multiple scatterings in medium-induced gluon radiation

Carlota Andres, Fabio Dominguez, Marcos Gonzalez Martinez

SciPost Phys. Proc. 10, 016 (2022) · published 10 August 2022 | · pdf

In this work we disentangle the underlying physical picture of the in-medium gluon radiation process across its different energy regimes by comparing the recently obtained fully-resummed -- without any further approximations -- BDMPS-Z in-medium emission spectrum with the extensively used analytical approaches. We observe that in the high-energy regime the radiation process is dominated by a single hard scattering, while in the intermediate-energy region coherence effects among multiple scatterings are crucial. Finally, we prove that in the low-energy regime the dynamics is again controlled by a single scattering but where one must include a suppression factor accounting for the probability of not having any further scatterings.
Determination of $α_{S}$ beyond $NNLO$ using the event shape averages

Adam Kardos, Gábor Somogyi, Andrii Verbytskyi

SciPost Phys. Proc. 10, 014 (2022) · published 10 August 2022 | · pdf

In this proceedings we discuss a prescription to extract the QCD strong coupling constant at $N^{3}LO$ precision in perturbative QCD using a combination of ${\cal{O}}(\alpha_{S}^{3})$ calculations in pQCD and estimations of the ${\cal{O}}(\alpha_{S}^{4})$ corrections from the data. The method is applied to a set of event shape averages measured in experiments at the LEP, PETRA, PEP and TRISTAN colliders. In our analysis we account for hadronization effects with models from modern Monte Carlo event generators and analytic hadronization models. We conclude that the precision of the $\alpha_{S}$ extraction cannot be improved significantly only with pQCD predictions of higher orders, and further progress in these studies requires a significant advances in the studies and modeling of hadronization process.
Logarithmic corrections for jet production at the LHC

Emmet P. Byrne

SciPost Phys. Proc. 10, 010 (2022) · published 10 August 2022 | · pdf

Several important processes and analyses at the LHC are sensitive to higher-order perturbative corrections beyond what can currently be calculated at fixed order. One important class of logarithmic corrections are those which appear when the centre-of-mass energy of a QCD collision is much larger than the transverse momenta of the observed jets. We describe the High Energy Jets (HEJ) framework, which includes the dominant high-energy logarithms to provide all-order predictions for several LHC processes including Higgs, $W$, or $Z$ boson production in association with jets. We will summarise some recent developments, in particular the first matching of HEJ to a NLO calculation.
Transverse Momentum Dependent and collinear densities based on Parton Branching method

S. Taheri Monfared, H. Jung

SciPost Phys. Proc. 10, 008 (2022) · published 10 August 2022 | · pdf

We review the current status of collinear and Transverse Momentum Dependent densities based on the Parton Branching method. We investigate the performance of the PB-TMD evolution as well as PB-TMD parton shower with different configurations of the hard process in the four- and five-flavour schemes.
Light meson decays at BESIII

Xiao Lin Kang

SciPost Phys. Proc. 10, 007 (2022) · published 10 August 2022 | · pdf

The world’s largest sample of J/psi events accumulated at the BESIII detector offers a unique opportunity to investigate eta and eta' physics via two body J/psi radiative or hadronic decays. In recent years the BESIII experiment has made significant progresses in eta/eta' decays. A selection of recent highlights in light meson spectroscopy at BESIII are reviewed in this report, including the observation of eta'->pi+pi-mu+mu-, the study of eta'->pi+pi-e+e-, and search for CP-violation in this decay, search for the rare decays of eta'->4pi0 and eta'->gamma gamma eta, as well as the precision measurement of the branching fraction of eta' decays.
Fluctuations and Selection Bias in 5 and 13 TeV p-p Collisions: Where are the jets?

Thomas A. Trainor

SciPost Phys. Proc. 10, 003 (2022) · published 10 August 2022 | · pdf

The ALICE collaboration recently reported high-statistics $\bf p_t$ spectra from 5 TeV and 13 TeV p-p collisions with intent to determine the role of jets in high-multiplicity collisions. In the present study a two-component (soft + hard) model (TCM) of hadron production in p-p collisions is applied to ALICE $\bf p_t$ spectra. As in previous TCM studies of A-B collision systems jet and nonjet contributions to $\bf p_t$ spectra are accurately separated over the entire $\bf p_t$ acceptance. The statistical significance of data-model differences is established leading to insights concerning selection bias and spectrum model validity.

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