SciPost: SciPost Physics Proceedings: issue detail

SciPost Physics Proceedings issue 10

50th International Symposium on Multiparticle Dynamics (ISMD2021)

Event dates: from 2021-07-12 to 2021-07-16.

The 50th edition of the ISMD conference series, postponed from summer 2020, bringing together physicists from across particle, nuclear, and astro-physics for talks and discussions on all aspects and consequences of the strong nuclear force and complex final states. ISMD is a "crossroads conference" between several different fields, with all talks in plenary session to encourage interaction, plus poster and pre-recorded talk sessions with short "flash talks". (see https://inspirehep.net/conferences/1812650 ).

(Guest) Fellows responsible for this Issue

Prof. Andy Buckley

Colouring the Higgs boson

Andy Buckley, Giuseppe Callea, Andrew J. Larkowski, Simone Marzani

SciPost Phys. Proc. 10, 001 (2022) · published 10 August 2022 | · pdf

The jet colour ring is a novel colour tagger observable designed to separate the decay of a colour-singlet into two jets from a two-jet background in a different colour configuration. Simulation studies in the case of the production of a boosted Higgs boson decaying in two b-quarks and an associate electroweak boson, showed notable discriminator powers when comparing the jet colour ring performances with other observables. These results are opening a wide scenario for further studies.
BFKL phenomenology: resummation of high-energy logs in inclusive processes

Francesco Giovanni Celiberto, Michael Fucilla, Dmitry Yu. Ivanov, Mohammed M. A. Mohammed, Alessandro Papa

SciPost Phys. Proc. 10, 002 (2022) · published 10 August 2022 | · pdf

We present recent phenomenological studies, tailored on kinematic configurations typical of current and forthcoming analyses at the LHC, for two novel probe channels of the BFKL resummation of energy logarithms. Particular attention is drawn to the behavior of distributions differential in azimuthal angle and rapidity, where significant high-energy effects are expected.
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.
Oscillations in Modified Combinants of Hadronic Multiplicity Distributions

P. Agarwal, H. W. Ang, Z. Ong, A. H. Chan, C. H. Oh

SciPost Phys. Proc. 10, 004 (2022) · published 10 August 2022 | · pdf

Oscillations in modified combinants ($C_j$s) have been of interest to multiparticle production mechanisms since the 1990s. Recently, there has been a discussion on how these oscillations can be reproduced by compounding a binomial distribution with a negative binomial distribution. In this work, we explore a stochastic branching model based on a simple interaction term $\lambda\overline{\psi}\phi\psi$ for partons and propose a hadronization scheme to arrive at the final multiplicity distribution. We study the effects that compounding our model with a binomial distribution has on $C_j$s and explore its physical implications. We find that there is a significant difference in the oscillations in $C_j$s between high energy $pp$ and $p\bar{p}$ scattering that our model can reproduce.
Probing hadronic interactions with measurements from the Pierre Auger Observatory

B. Andrada

SciPost Phys. Proc. 10, 005 (2022) · published 10 August 2022 | · pdf

The Pierre Auger Observatory is the largest facility in the world to study ultra-high-energy cosmic rays. It has a hybrid detection technique that combines the observation of the longitudinal development of extensive air showers and the measurement of their particles at the ground. This capability has opened the possibility to probe hadronic interactions taking place at energies well beyond those accessible by human-made accelerators. In this report, we present a selection of the latest results on hadronic interactions with measurements from the Pierre Auger Observatory. These data span over three decades in energy, showing the tension between data from the muon component of air showers and predictions based on the most updated hadronic interaction models.
Intermittency analysis in relativistic heavy-ion collisions

Zhiming Li, Jin Wu

SciPost Phys. Proc. 10, 006 (2022) · published 10 August 2022 | · pdf

Local density fluctuations near the QCD critical point can be probed by an intermittency analysis of power-law behavior on scaled factorial moments in relativistic heavy-ion collisions. We study the second-order scaled factorial moment in Au + Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7-200 GeV from the UrQMD model. Since the background subtraction and efficiency correction are two important aspects in this measurement, we propose a cumulative variable method to remove background contribution and a cell-by-cell method for efficiency correction in the intermittency analysis.
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.
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.
Phenomenological study on correlation between flow harmonics and mean transverse momentum in nuclear collisions

Chunjian Zhang, Jiangyong Jia, Shengli Huang

SciPost Phys. Proc. 10, 009 (2022) · published 10 August 2022 | · pdf

To assess the properties of the quark-gluon plasma formed in nuclear collisions, the Pearson correlation coefficient between flow harmonics and mean transverse momentum, $\rho\left(v_{n}^{2},\left[p_{\mathrm{T}}\right]\right)$, reflecting the overlapped geometry of colliding atomic nuclei, is measured. $\rho\left(v_{2}^{2},\left[p_{\mathrm{T}}\right]\right)$ was found to be particularly sensitive to the quadrupole deformation of the nuclei. We study the influence of the nuclear quadrupole deformation on $\rho\left(v_{n}^{2},\left[p_{\mathrm{T}}\right]\right)$ in $\rm{Au+Au}$ and $\rm{U+U}$ collisions at RHIC energy using $\rm{AMPT}$ transport model, and show that the $\rho\left(v_{2}^{2},\left[p_{\mathrm{T}}\right]\right)$ is reduced by the prolate deformation $\beta_2$ and turns to change sign in ultra-central collisions (UCC).
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.
Lund jet plane for Higgs tagging

Charanjit K. Khosa

SciPost Phys. Proc. 10, 011 (2022) · published 10 August 2022 | · pdf

We study the boosted Higgs tagging using the Lund jet plane. The convolutional neural network is used for the Lund images data set to classify hadronically decaying Higgs from the QCD background. We consider $H\to b \bar{b}$ and $H \to gg$ decay for moderate and high Higgs transverse momentum and compare the performance with the cut based approach using the jet color ring observable. The approach using Lund plane images provides good tagging efficiency for all the cases.
The impact of ATLAS $V$+jet measurements on PDF fits

Eimear Conroy

SciPost Phys. Proc. 10, 012 (2022) · published 10 August 2022 | · pdf

The production of $W$/$Z$-bosons in association with jets is an important test of perturbative QCD predictions and also yields information about the parton distribution functions of the proton. We present fits to determine PDFs using inclusive $W$/$Z$-boson and $W$/$Z$+jets measurements from the ATLAS experiment at the LHC. The ATLAS measurements are used in combination with deep-inelastic scattering data from HERA. An improved determination of the sea-quark densities at high Bjorken-$x$ is seen, while confirming a strange-quark density similar in size to the up- and down-sea-quark densities in the range $x<0.02$ found by previous ATLAS analyses.
Quantized fragmentation of three-dimensional QCD string

S. Todorova-Nova

SciPost Phys. Proc. 10, 013 (2022) · published 10 August 2022 | · pdf

Recent developments of the model of quantized helical QCD string are presented, notably the baryon production. An overview of the experimental evidence is discussed as well as possible applications.
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.
Searches for new physics in collision events using a statistical technique for anomaly detection

S. V. Chekanov

SciPost Phys. Proc. 10, 015 (2022) · published 10 August 2022 | · pdf

This paper discusses a statistical anomaly-detection method for model-independent searches for new physics in collision events produced at the Large Hadron Collider (LHC). The method requires calculations of Z-scores for a large number of Lorenz-invariant variables to identify events that deviate from those expected for the Standard Model (SM).
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.
Cracking hadron and nuclear collisions open with ropes and string shoving in PYTHIA8

Smita Chakraborty

SciPost Phys. Proc. 10, 017 (2022) · published 10 August 2022 | · pdf

Enhancement in strangeness yields in heavy-ion collisions is regarded as one of the attributes of the Quark-Gluon Plasma (QGP) along with jet quenching and final-state collectivity. To reproduce these effects in the MC implementation of the Lund string model in \pythia, the inclusion of non-perturbative mechanisms like string shoving and rope hadronization is crucial. In this proceeding, we discuss our latest implementation of these mechanisms and the preliminary results for the strangeness enhancement in high-multiplicity p-p, p-Pb and Xe-Xe. We conclude with remarks on the ongoing development of the model.
Asymptotics of transverse momentum broadening in dense QCD media

Paul Caucal

SciPost Phys. Proc. 10, 018 (2022) · published 10 August 2022 | · pdf

We study the asymptotic behaviour of the transverse momentum broadening distribution of an energetic quark or gluon propagating through dense QCD matter, in the large system size $L$ limit, taking into account radiative corrections in the double logarithmic approximation. Thanks to a connection between the evolution of the jet quenching parameter $\hat{q}$ and the formation of traveling wave fronts in nonlinear physics, we obtain a formula for the $L$ dependence of the characteristic transverse momentum scale $Q_s$ of the distribution valid up to terms of order $1/\ln(L)$. We briefly discuss the physical implications of this formula for jet quenching and small-$x$ phenomenology.
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.
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.
Recent results on hyperon pair production and nucleon time-like form factors at BESIII

Alessio Mangoni

SciPost Phys. Proc. 10, 021 (2022) · published 10 August 2022 | · pdf

The BESIII experiment, based on the BEPCII collider at IHEP in Beijing, China, is capable of measuring nucleon form factors with unprecedented precision. We report recent results achieved by the BESIII collaboration concerning the nucleon time-like form factors and the hyperon pair production. More in detail we outline the results obtained by the study of the process $e^+e^- \to p \overline p$, using both the scan-energy and initial-state radiation techniques, those of the process $e^+e^- \to n \overline n$, and the study of the $\Sigma$ polarization regarding the process $e^+e^- \to J/\psi \to \Sigma^+\overline \Sigma{}^-$.
Recent jet and jet substructure measurements at the LHC, and ML based tagging

Meena Meena

SciPost Phys. Proc. 10, 022 (2022) · published 10 August 2022 | · pdf

Recent jet and jet substructure measurements at the LHC, and of machine-learning-based tagging techniques are presented using proton-proton collision data collected by the ATLAS and CMS experiments at CERN's Large Hadron Collider. These measurements are crucial for precise tests of electroweak and pQCD calculations and searches for physics beyond the Standard Model. The measurements are compared with several Monte Carlo event generator predictions which provide valuable input to the tuning of perturbative and non-perturbative models and to constraining model parameters of advanced parton-shower Monte Carlo programs.
Comparison of $pp$ and $p \bar{p}$ differential elastic cross sections and observation of the exchange of a Colorless $C$-odd gluonic compound

C. Royon

SciPost Phys. Proc. 10, 023 (2022) · published 11 August 2022 | · pdf

We describe the discovery of the colorless $C$-odd gluonic compound, the odderon, by the D0 and TOTEM Collaborations by comparing elastic differential cross sections measured in $pp$ and $p \bar{p}$ interactions at high energies.
Intermittency Analysis of Toy Monte Carlo Events

Sheetal Sharma, Ramni Gupta

SciPost Phys. Proc. 10, 024 (2022) · published 11 August 2022 | · pdf

Event-by-event intermittency analysis of Toy Monte Carlo events is performed in the scenario of high multiplicity events as is the case at recent colliders RHIC and LHC for AA collisions. A power law behaviour of Normalized Factorial Moments (NFM), $F_{q}$ as function of number of bins ($M$) known as intermittency, is a signature of self-similar fluctuations. Dependence of NFM on the detector efficiencies and on the presence of fluctuations have been studied. Results presented here provide a baseline to the experimental results and clarity on the application of efficiency corrections to the experimental data.
The QCD Equation of State in Small Systems

W. A. Horowitz, Alexander Rothkopf

SciPost Phys. Proc. 10, 025 (2022) · published 11 August 2022 | · pdf

We present first results on finite system size corrections to the equation of state, trace anomaly, and speed of sound for two model systems: 1) free, massless scalar theory and 2) quenched QCD with periodic boundary conditions (PBC). We further present work-in-progress results for quenched QCD with Dirichlet boundary conditions.
Application of Lorentzian CFT Principal Series Representation to Near Forward Scattering

Pulkit Agarwal, Richard C. Brower, Timothy G. Raben, Chung-I Tan

SciPost Phys. Proc. 10, 026 (2022) · published 11 August 2022 | · pdf

We present a discussion on recent progress in high energy diffraction from the perspective of AdS/CFT, through which a unified treatment for both perturbative and nonperturbative Pomeron emerges. By working with Unitary Irreducible Representation of Conformal group, a frame is provided in extending AdS/CFT to both forward and nearforward scattering. We present an analysis involving an exact solution to conformal blocks in Minkowski CFT and discuss possible applications. Phenomenological applications can range from forward scattering to DIS/DVCS/TMD at LHC energies and beyond.
The Giant Radio Array for Neutrino Detection (GRAND) Project

Bruno Lazarotto Lago

SciPost Phys. Proc. 10, 027 (2022) · published 11 August 2022 | · pdf

GRAND is designed to detect ultra-high-energy cosmic particles -- specially neutrinos, cosmic rays and gamma rays using radio antennas. With $\sim$20 mountainous sites around the world it will cover a total area of 200,000 km$^{2}$. The planned sensitivity of 10$^{-10}$ GeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ above $5\times10^{17}$ eV will likely ensure the detection of cosmogenic neutrinos predicted by most common scenarios enabling neutrino astronomy. Furthermore, PeV--EeV neutrinos can test particle interactions at energies above those achieved in accelerators. The pathfinder stage GRANDProto300 is planned to start taking data in 2021. We present the current overall status of the project with emphasis on the neutrino physics.
Multi-differential studies to explore strangeness enhancement in pp with ALICE at the LHC

Francesca Ercolessi

SciPost Phys. Proc. 10, 028 (2022) · published 11 August 2022 | · pdf

The study of energy and multiplicity dependence of strange hadron production in proton-proton collisions provides a powerful tool to understand similarities and differences between small and large collision systems. In order to better understand the origin of strangeness enhancement in pp new multi-differential analyses have been performed. The first separates the contribution of soft and hard processes, such as jets, to strange hadron production through two-particle correlation techniques. The second exploits the concept of the effective energy available for particle production in the event, which is estimated by an anti-correlation with the energy deposited in ALICE's Zero Degree Calorimeters. The results indicate that strangeness production emerges from the growth of the underlying event and confirm it is related to the final state multiplicity.
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 charm production in pp collisions with ALICE

Tiantian Cheng

SciPost Phys. Proc. 10, 030 (2022) · published 11 August 2022 | · pdf

The production of charm-hadrons at midrapidity in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV was recently measured by the ALICE Collaboration. The results show that the baryon-to-meson yield ratios differ from predictions where the hadronisation has been tuned to measurements obtained in $\rm e^{+}e^{-}$ and ep collisions for different charm-baryon species. These observations suggest that the charm fragmentation fractions are not universal and that the baryon-to-meson ratio depends on the collision systems. The results are compared to the predictions from Monte Carlo event generators and theoretical calculations.
Flow decorrelation in heavy-ion collisions at $\sqrt{s_{_{\rm NN}}}$=27 and 200 GeV with 3D event-by-event viscous hydrodynamics

Jakub Cimerman, Iurii Karpenko, Boris Tomasik, Barbara Antonina Trzeciak

SciPost Phys. Proc. 10, 031 (2022) · published 11 August 2022 | · pdf

We present the first calculation of longitudinal decorrelation of anisotropic flow at RHIC Beam Energy Scan (BES) energies using event-by-event viscous hydrodynamic model (vHLLE), with two different initial states (GLISSANDO2 and UrQMD) and hadronic cascade. We investigate the origin of the observed decorrelation by checking separately flow angle and flow magnitude decorrelation and by calculating decorrelation in the initial state eccentricity.
Intermittency in pp collisions at $\sqrt{s}=$ 0.9, 7 and 8 TeV from the CMS collaboration

Z. Ong, P. Agarwal, H. W. Ang, A. H. Chan, C. H. Oh

SciPost Phys. Proc. 10, 032 (2022) · published 11 August 2022 | · pdf

The intermittency-type fluctuations as outlined by Bialas and Peschanski in the 1980s is analysed in $pp$ collisions at $\sqrt{s}=$ 0.9, 7 and 8 TeV from the CMS collaboration at CERN. Our preliminary analysis shows that the intermittency exponents in the bin-averaged scaled factorial moments decrease in magnitude with increasing collision energy at the TeV scale, which suggests that the cascading nature of multiparticle production described by the $\alpha$-model is weakening. We outline possible areas planned for future studies.
Measurements of heavy-flavor production as a function of multiplicity with ALICE at the LHC

Yoshini Bailung

SciPost Phys. Proc. 10, 033 (2022) · published 11 August 2022 | · pdf

In this contribution, the production of heavy-flavor hadrons as a function of multiplicity, via the study of the D-meson and heavy-flavor hadron decay leptons self-normalized yields in pp collisions at the center of mass energy $\sqrt{s} = 13$ TeV is discussed. Comparisons are made with similar measurements of J/$\psi$ at $\sqrt{s} = 13$ TeV and various model calculations. The $\mathrm{\Lambda_{c}^{+}/D^{0}}$ and $\mathrm{D^{+}_{s}/D^{0}}$ yield ratios in different multiplicity intervals in pp collisions at $\sqrt{s} = 13$ TeV are also reported. In addition, the ALICE measurement of $\mathrm{\Lambda_{c}^{+}}$ production in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV down to transverse momentum ($p_{\rm T}$) = 0 GeV/$c$ is presented. Finally, the nuclear modification factor is shown for open charm hadrons at $\sqrt{s} = 5.02$ TeV in p-Pb collisions. Finally, measurements of the elliptic flow of heavy-flavor hadron decay leptons in p-Pb systems are presented, which hint towards a possible collective behaviour in high multiplicity p-Pb collisions.
Collective dynamics of heavy ion collisions in ATLAS

Helena Santos

SciPost Phys. Proc. 10, 034 (2022) · published 11 August 2022 | · pdf

The latest measurements of collective behaviour in a variety of collision systems with the ATLAS detector at the LHC, including pp collisions at 13 TeV, Xe+Xe collisions at 5.44 TeV, and Pb+Pb collisions at 5.02 TeV, are presented. They include vn-[pT] correlations, which carry important information about the initial-state geometry of the quark-gluon plasma and can shed light on any quadrupole deformation in the Xe nucleus, and measurements of flow decorrelations differential in rapidity, which probe the longitudinal structure of the colliding system. These measurements furthermore provide stringent tests of the theoretical understanding of the initial state in heavy ion collisions.
First indication on self-similarity of strangeness production in Au+Au collisions at RHIC: Search for signature of phase transition in nuclear matter

M. V. Tokarev, I. Zborovsky

SciPost Phys. Proc. 10, 035 (2022) · published 11 August 2022 | · pdf

New results of analysis of $K^0_S-$meson spectra measured over a wide range of energy $\sqrt {s_{NN}}=7.7-200$ GeV and centrality in $Au+Au$ collisions by the STAR Collaboration at RHIC using the $z$-scaling approach are presented. Indication on self-similarity of fractal structure of nuclei and fragmentation processes with $K^0_S$ probe is demonstrated. The energy loss as a function of the collision energy, centrality and transverse momentum of the inclusive strange meson is estimated.
Hadron structure from basis light-front quantization

Chandan Mondal, Jiangshan Lan, Kaiyu Fu, Siqi Xu, Zhi Hu, Xingbo Zhao, James P. Vary

SciPost Phys. Proc. 10, 036 (2022) · published 11 August 2022 | · pdf

We present our recent progress in applying basis light-front quantization approach to investigate the structure of the light mesons and the nucleon.
Hadron Production in terms of Green's Functions in Non-Equilibrium Matter

A. V. Koshelkin

SciPost Phys. Proc. 10, 037 (2022) · published 11 August 2022 | · pdf

Following the quark-hadron duality concept, we show that the number of hadrons generated in the deconfinement matter is entirely determined by the exact non-equilibrium Green's functions of partons in the medium and the vertex function governing the probability of the confinement-deconfinement phase transition. In such an approach, compactifying the standard (3+1) chromodynamics into $ QCD_{xy} + QCD_{zt}$, the rate of the hadrons produced in particle collisions is derived in the explicit form provided that the hadronization is the first order phase transition. The pion production is found to be in good agreement to the experimental results on the pion yield in pp collisions.
Measurements of $\phi$ meson and $\Xi^-$ hyperon production in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV from STAR experiment

Yingjie Zhou

SciPost Phys. Proc. 10, 038 (2022) · published 11 August 2022 | · pdf

In this proceedings, we present our first measurements of $\phi$ meson and $\Xi^-$ hyperon production in Au+Au collisions at $\sqrt{s_{NN}}$ = 3 GeV. Various models including thermal and transport model calculations are compared to data, these results imply that the matter produced in the 3 GeV Au+Au collisions is considerably different from that at higher energies.
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.
Light Nuclei Production in Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV from the STAR experiment

Hui Liu

SciPost Phys. Proc. 10, 040 (2022) · published 11 August 2022 | · pdf

Light nuclei production is expected to be sensitive to baryon density fluctuations and can be used to probe the signatures of QCD critical point and/or a first-order phase transition in heavy-ion collisions. In this proceedings, we present the spectra and yields of protons ($p$) and light nuclei ($d$, $t$, $^{3}\mathrm{He}$, $^{4}\mathrm{He}$) in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 3 GeV by the STAR experiment. Finally, it is found that the kinetic freeze-out dynamics (temperature $T_{kin}$ $vs.$ average radial flow velocity $\langle\beta_{T}\rangle$) at 3 GeV extracted with the blast-wave model deviate from the trends at high energies ($\sqrt{s_{\mathrm{NN}}}$ = 7.7 - 200 GeV), indicating a different medium equation of state.
Measurement of Intermittency for Charged Particles in Au + Au Collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7-200 GeV from STAR

Jin Wu

SciPost Phys. Proc. 10, 041 (2022) · published 11 August 2022 | · pdf

Local density fluctuations near the QCD critical point can be probed by intermittency analysis of scaled factorial moments in relativistic heavy-ion collisions. We report the first measurement of intermittency for charged particles in Au + Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7-200 GeV from the STAR experiment at RHIC. We observe scaling behaviors in central Au + Au collisions, with the extracted scaling exponent decreasing from mid-central to the most central Au + Au collisions. Furthermore, the scaling exponent exhibits a non-monotonic energy dependence with a minimum around $\sqrt{s_\mathrm{NN}}$ = 20-30 GeV in central Au + Au collisions.