Particle Production Mechanisms Research Articles

Studying strangeness and baryon production mechanisms through angular correlations between charged Ξ baryons and identified hadrons in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV

The angular correlations between charged Ξ baryons and associated identified hadrons (pions, kaons, protons, Λ baryons, and Ξ baryons) are measured in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV with the ALICE detector to give insight into the particle production mechanisms and balancing of quantum numbers on the microscopic level. In particular, the distribution of strangeness is investigated in the correlations between the doubly-strange Ξ baryon and mesons and baryons that contain a single strange quark, K and Λ. As a reference, the results are compared to Ξπ and Ξp correlations, where the associated mesons and baryons do not contain a strange valence quark. These measurements are expected to be sensitive to whether strangeness is produced through string breaking or in a thermal production scenario. Furthermore, the multiplicity dependence of the correlation functions is measured to look for the turn-on of additional particle production mechanisms with event activity. The results are compared to predictions from the string-breaking model Pythia 8, including tunes with baryon junctions and rope hadronisation enabled, the cluster hadronisation model Herwig 7, and the core-corona model Epos-lhc. While some aspects of the experimental data are described quantitatively or qualitatively by the Monte Carlo models, no model can match all features of the data. These results provide stringent constraints on the strangeness and baryon number production mechanisms in pp collisions.

Study of transverse spherocity dependent identified particle spectra in a multi-phase transport model for O+O collisions at sNN = 7TeV

Large Hadron Collider at CERN has a plan to have Oxygen+Oxygen (O+O) collisions in the upcoming run. In this work, we use A Multi-Phase Transport Model (AMPT) to employ transverse spherocity in O+O collision at [Formula: see text][Formula: see text]TeV and obtain the transverse momentum spectra, integrated yield and mean transverse momentum for identified charged-particles i.e. pion, kaon and proton. We implement the spherocity analysis to separate and distinguish isotropic and jetty events and show that the particle production mechanism is different for both types of events. In addition, the mean transverse momentum for jetty events shows a completely different behavior from the isotropic one.

Mixed-species charge and baryon balance functions studies with PYTHIA

Mixed species charge and baryon balance functions are computed based on proton-proton (pp) collisions simulated with the PYTHIA8 model. Simulations are performed with selected values of the collision energy s and the Monash tune and the ropes and shoving modes of PYTHIA8 to explore whether such measurements provide useful new information and constraints on mechanisms of particle production in pp collisions. Charge balance functions are studied based on mixed pairs of pions, kaons, and protons, whereas baryon balance functions are computed for mixed low mass strange and nonstrange baryons. Both charge and baryon balance functions of mixed particle pairs feature shapes and amplitudes that sensitively depend on the particle considered owing largely to the particle production mechanisms implemented in PYTHIA. The evolution of balance functions integrals with the longitudinal width of the acceptance are presented and one finds that sums of such integrals for a given reference particle obey expected sum rules for both charge and baryon balance functions. Additionally, both types of balance functions are found to evolve in shape and amplitude with increasing collision energy s and the PYTHIA tunes considered. Published by the American Physical Society 2024

Study of negative binomial distribution in neutrino and anti-neutrino–nucleus interactions of CHORUS experiment

In this study, the charged particle multiplicity distribution produced in anti-neutrino and neutrino-nuclear emulsion interactions is studied in terms of negative binomial distribution in varying invariant mass of the hadronic system intervals for the first time. Many articles have shown that the negative binomial distribution is very useful in describing and interpreting the multiplicity of experimental data in the literature. For this reason, a similar study is conducted on neutrino and anti-neutrino interactions to better understand the particle production mechanism. Experimental data for the analysis are obtained from the CHORUS Collaboration paper on the production of charged particles in anti-neutrino and neutrino-nuclear emulsion interactions at high energy. For multiplicity distributions of both interactions, the invariant mass of the hadronic system intervals is defined as given in the CHORUS Collaboration article. Then the negative binomial fit is applied to the experimental data for each energy range. In terms of chi-square values for both interactions, a good agreement has been observed between the experimental data and their fit in each energy range. The results of applied fits are shown through figures and tables, presenting the obtained chi-square values, free parameters, and their energy dependence.

Characterizing nuclear modification effects in high-energy O-O collisions at energies available at the CERN Large Hadron Collider: A transport model perspective

The present work focuses on oxygen-oxygen (O-O) collisions, which are planned at the CERN Large Hadron Collider. Oxygen, being a doubly magic number nucleus, has some very unique features. This study attempts to probe the exotic state of QCD matter in O-O collisions. Additionally, the role of different nuclear density profiles in governing the final-state dynamics in ultrarelativistic nuclear collisions is also explored. Using a multiphase transport model, we obtain the nuclear modification factor (RAA) for all charged hadrons and identified particles for O-O collisions at sNN = 7 TeV. Furthermore, we investigate the behavior of RAA as a function of transverse momentum (pT) for three centralities (most central, mid-central, and peripheral) considering both α-cluster and Woods-Saxon nuclear density profiles. We also extend this work to study the rapidity dependence of RAA for all charged hadrons. To better understand our findings of O-O collisions, the results are confronted with the available data of RAA for Pb-Pb collisions. The present study sheds light on particle production mechanisms, emphasizing factors influencing particle yield from precollision to postcollision stages in the context of O-O collisions. Published by the American Physical Society 2024

Numerical Simulation Study on the Mechanism of Plasma Dissociation of Carbon Dioxide in Atmospheric Pressure Packed-Bed Reactors

This article presents a comprehensive study on the streamer propagation and electric field distribution within a two-dimensional fluid model of a packed bed reactor (PBR) filled with carbon dioxide, utilizing the PASSKEy simulation platform. The research delves into the spatiotemporal evolution of electron density, electric fields and key plasma species in the discharge process. The model simulates a PBR with layered dielectric spheres, indicates that the inner sides of the first and second layers of dielectric spheres are not the primary regions for reactions such as CO<sub>2</sub> dissociation; instead, the main regions are along the streamer propagation path and the outer side of the first layer of dielectric spheres. The study by examining the propagation of streamers in the presence of an electric field, highlighting the influence of anode voltage rise and dielectric polarization on local electric field enhancement. This enhancement leads to increased electron density and temperature, facilitating streamer propagation and the formation of filamentary microdischarges and surface ionization waves. The article provides a detailed analysis of the local electric field evolution at specific points within the PBR. The research further investigates the spatiotemporal dynamics of spatial and surface charges, revealing that negative charges concentrate within the streamer and on the dielectric surface, with densities significantly higher than positive charges. The positive charges' distribution is closely related to the streamer's path, and over time, they come to dominate the charge distribution in the discharge space. The study also explores the surface charge deposition on the dielectric spheres, discusses the evolution trends of the distribution. Additionally, the article discusses the temporal and spatial evolution of key plasma species, including ions and radicals, and their contribution to the overall discharge characteristics. The production mechanisms of carbon monoxide particles, carbon dioxide ions, and oxygen ions are analyzed, with a focus on their spatial distribution and correlation with electron density. The study concludes with an examination of the energy deposition within the PBR, integrating the spatial energy deposition of electrons and major positive ions. The results indicate a total energy deposition value of approximately 1.428 mJ/m, with carbon dioxide ions accounting for 8.8% of this value.

Insight into the light-flavour particle production mechanism from studies of the transverse spherocity dependence in pp collisions at √s =13 TeV with ALICE at the LHC

The Large Hadron Collider (LHC) Run 1 and Run 2 data revealed heavy-ion-like features such as enhanced strangeness production and long-range azimuthal correlation in high-multiplicity pp collisions paving the way to rethink particle production in small collision systems. Event shape observables like transverse spherocity are sensitive to isotropic and jet-like topologies, which are useful tools to distinguish the pp collisions dominated by soft or hard physics. The interplay between multiplicity and transverse spherocity on light-flavour particle production can be understood by comparing the results obtained by selecting multiplicity and/or transverse spherocity. This contribution presents recent results on light-flavour particle production (π, K, p, ф, K*0, K0s, Λ, ξ) at midrapidity obtained by the ALICE experiment in pp collisions at √s = 13 TeV as a function of event multiplicities and transverse spherocity. The results are even obtained by going to the most extreme selections such as the highest 0–1% in multiplicity and the highest 0–10% in transverse sphe rocity. The results include the transverse momentum spectra, yields, 〈pT〉 and their ratios. These measurements will be compared with the Monte Carlo (MC) predictions obtained from models such as PYTHIA8, EPOS and Herwig7.

Exploring the hadron gas phase of relativistic heavy-ion collisions at the LHC

The lifetimes of hadronic resonances are comparable to the one of the hadron gas phase created in the late stages of high-energy nuclear collisions. Therefore, a significant fraction of resonances decay inside a high-density medium and their decay daughters rescatter with nearby hadrons destroying their initial kinematic correlations. The competing effect of resonance regeneration via pseudo-elastic interactions of hadrons interplays between the rescattering effect, modifying the measured yields and transverse-momentum spectra of hadronic resonances. These effects are studied by measuring the production yield ratio of resonances to the corresponding long-lived particle as a function of the hadronic lifetime, i.e. charged-particle multiplicity. In addition, measurements of the differential yields of resonances with different masses, quark content, and quantum numbers help in understanding particle production mechanisms, strangeness production, and parton energy loss. This article reports recent ALICE measurements on resonances and the use of the experimental input in a partial chemical equilibrium-based thermal model to constrain the kinetic freezeout temperature. This is a novel procedure that is independent of assumptions on the flow velocity profile and the freeze-out hypersurface.

Evolution of midrapidity average transverse momentum of pions, kaons, protons and antiprotons in Au+Au collisions in (snn)1∕2= 7–39-GeV energy range from the beam energy scan program

The [Formula: see text] dependencies of the experimental average transverse momentum, [Formula: see text], of the charged pions, charged kaons, protons and antiprotons produced at midrapidity ([Formula: see text]) in [Formula: see text] collisions from the Beam Energy Scan (BES) program at the RHIC (Relativistic Heavy Ion Collider), measured by STAR Collaboration in the [Formula: see text]–39-GeV energy range, have been described quite well with the power-law model function. We have obtained [Formula: see text] inequality at all BES energies, indicating the clear mass ordering (dependence) of the power parameter [Formula: see text]. On the whole, the exponent parameter [Formula: see text] for the charged kaons as well as (anti)protons decreases noticeably with increasing [Formula: see text] collision energy from [Formula: see text][Formula: see text]GeV to [Formula: see text][Formula: see text]GeV. Drastic change observed in the energy ([Formula: see text]) dependence of the parameter [Formula: see text] for the charged kaons at [Formula: see text][Formula: see text]GeV could possibly indicate a significant change in the mechanism(s) of the charged kaon production in [Formula: see text] collisions at around [Formula: see text][Formula: see text]GeV. Significant change in the [Formula: see text] dependence of the parameter [Formula: see text] for the charged pions observed at around [Formula: see text][Formula: see text]GeV is consistent with a possible change in the mechanism(s) of the particle production in [Formula: see text] collisions at around [Formula: see text][Formula: see text]GeV, reported earlier by STAR Collaboration. Significant gaps between [Formula: see text] (protons) and [Formula: see text] (antiprotons) as well as between ([Formula: see text]) and [Formula: see text] have been seen in the region [Formula: see text]–20[Formula: see text]GeV. These gaps diminish and practically disappear with [Formula: see text] and [Formula: see text] (protons) [Formula: see text] (antiprotons) in the region [Formula: see text][Formula: see text]GeV. Altogether, the findings, regarding collision energy dependencies of the parameter [Formula: see text] for the studied particle species, could indicate the probable phase transition of a nuclear matter to the mixed phase of QGP and hadrons taking place in [Formula: see text] collisions at around [Formula: see text][Formula: see text]GeV. The differences found between parameter [Formula: see text] versus [Formula: see text] dependencies of the particles and antiparticles have been connected with the ratios of antiparticle and particle yields and differences in the mechanisms of production of particles and antiparticles. It is deduced that the exponent parameter [Formula: see text] should be sensitive to the degree of particle (system) thermalization and particle production mechanisms, and its drastic change could be related to the change in the mechanisms of particle production or/and phase transitions in the nuclear/hadronic matter.

A review on anisotropic flow in heavy-ion collisions

We present a review of published experimental measurements on anisotropic flow in heavy-ion collisions. Flow coefficients [Formula: see text] are presented for charged and identified hadrons at various beam energies ranging from [Formula: see text][Formula: see text]GeV to 200[Formula: see text]GeV at the Relativistic Heavy Ion Collider (RHIC) and [Formula: see text][Formula: see text]GeV at the Large Hadron Collider (LHC). We present [Formula: see text] and its slope [Formula: see text] and discuss possible first-order Quantum chromodynamics (QCD) phase transition. [Formula: see text] of particles containing heavy quarks (Charm quarks) is also discussed to illustrate the effect of the magnetic field produced in relativistic heavy-ion collisions. We also present flow harmonics ([Formula: see text], [Formula: see text] and [Formula: see text]) for inclusive charged and identified hadrons. We compare the charged particle [Formula: see text] coefficients with hydrodynamics to study and constrain initial conditions in the transport models. The results of identified particle [Formula: see text] from ideal and viscous hydrodynamics are discussed to understand the dynamics and mechanism of particle production in high-energy nuclear collisions.

Measurement of R 2(Δη, Δφ) and P 2(Δη, Δφ) correlation functions in pp collisions at TeV with ALICE

In high-energy collisions, the mechanism of particle production, diffusivity, and conservation of charge and momentum are all revealed by the two-particle normalised cumulants of particle number correlations (R 2) and transverse momentum, p T, correlations (P 2), which are measured as a function of relative pseudorapidity and relative azimuthal angle difference (Δη, Δφ). We measure these observables in pp collisions at TeV with transverse momentum (p T) range of 0.2 - 2.0 GeV/c, to complement the recent ALICE measurements in Pb–Pb collisions and for a better understanding of the jet contribution and nature of collectivity in small systems. The observed correlations on the near- and away-side are qualitatively similar, but differ quantitatively. Additionally, it is shown that the near-side peak of P 2 is much narrower than the near-side peak of R 2 for both charge-independent (CI) and charge-dependent (CD) combinations, similar to the recently published ALICE results in p—Pb and Pb—Pb collisions. These results not only establish a baseline for heavy-ion collisions but also help one to better understand signals that are compatible with the existence of collective effects in small systems because they are sensitive to the interplay between the underlying event and mini-jets in pp collisions.

STUDYING THE RESONANCE PRODUCTION CROSS-SECTION OF THE HEAVY VECTORS WITHIN HEAVY VECTOR TRIPLET MODEL

In the context of TeV-scale extensions of the Standard Model both the experimental data and the construction of phenomenological models for the new heavy bosons searches are used by us. Heavy particles are predicted by the Simplified Model to describe only the on-shell resonance, have to be compared with LHC data. Bosons V’ created and decay according to the process pp->V’->Vh (V=W, Z) have certain properties that can be modeled within the Heavy Vector Triplet model using the Madgraph computer program. We have calculated the production cross sections of heavy particles using the experimental constraints in the parameter space (cH, cF) imposed on the benchmark scenario. The nature of the functional dependence of the cross section on the mass of the new boson, as well as the mechanism for the heavy particle production is studied with variation of the model parameters.

Novel Mode of nanoLuciferase Packaging in SARS-CoV-2 Virions and VLPs Provides Versatile Reporters for Virus Production.

SARS-CoV-2 is a positive-strand RNA virus in the Coronaviridae family that is responsible for morbidity and mortality worldwide. To better understand the molecular pathways leading to SARS-CoV-2 virus assembly, we examined a virus-like particle (VLP) system co-expressing all structural proteins together with an mRNA reporter encoding nanoLuciferase (herein nLuc). Surprisingly, the 19 kDa nLuc protein itself was encapsidated into VLPs, providing a better reporter than nLuc mRNA itself. Strikingly, infecting nLuc-expressing cells with the SARS-CoV-2, NL63 or OC43 coronaviruses yielded virions containing packaged nLuc that served to report viral production. In contrast, infection with the flaviviruses, dengue or Zika, did not lead to nLuc packaging and secretion. A panel of reporter protein variants revealed that the packaging is size-limited and requires cytoplasmic expression, indicating that the large virion of coronaviruses can encaspidate a small cytoplasmic reporter protein. Our findings open the way for powerful new approaches to measure coronavirus particle production, egress and viral entry mechanisms.

A high-resolution pixel silicon Vertex Detector for open charm measurements with the NA61/SHINE spectrometer at the CERN SPS

The study of open charm meson production provides an efficient tool for the investigation of the properties of hot and dense matter formed in nucleus–nucleus collisions. The interpretation of the existing di-muon data from the CERN SPS suffers from a lack of knowledge on the mechanism and properties of the open charm particle production. Due to this, the heavy-ion programme of the NA61/SHINE experiment at the CERN SPS has been extended by precise measurements of charm hadrons with short lifetimes. A new Vertex Detector for measurements of the rare processes of open charm production in nucleus–nucleus collisions was designed to meet the challenges of track registration and high resolution in primary and secondary vertex reconstruction. A small-acceptance version of the vertex detector was installed in 2016 and tested with Pb + Pb collisions at 150A,text{ GeV }!/!c. It was also operating during the physics data taking on Xe + La and Pb + Pb collisions at 150A,text{ GeV }!/!c conducted in 2017 and 2018. This paper presents the detector design and construction, data calibration, event reconstruction, and analysis procedure.

Two-particle transverse momentum correlations in pp and p -Pb collisions at energies available at the CERN Large Hadron Collider

Two-particle transverse momentum differential correlators, recently measured in Pb--Pb collisions at energies available at the CERN Large Hadron Collider (LHC), provide an additional tool to gain insights into particle production mechanisms and infer transport properties, such as the ratio of shear viscosity to entropy density, of the medium created in Pb-Pb collisions. The longitudinal long-range correlations and the large azimuthal anisotropy measured at low transverse momenta in small collision systems, namely pp and p-Pb, at LHC energies resemble manifestations of collective behaviour. This suggests that locally equilibrated matter may be produced in these small collision systems, similar to what is observed in Pb-Pb collisions. In this work, the same two-particle transverse momentum differential correlators are exploited in pp and p-Pb collisions at $\sqrt{s} = 7$ TeV and $\sqrt{s_{\rm NN}} = 5.02$ TeV, respectively, to seek evidence for viscous effects. Specifically, the strength and shape of the correlators are studied as a function of the produced particle multiplicity to identify evidence for longitudinal broadening that might reveal the presence of viscous effects in these smaller systems. The measured correlators and their evolution from pp and p--Pb to Pb--Pb collisions are additionally compared to predictions from Monte Carlo event generators, and the potential presence of viscous effects is discussed.

Modeling Hadronic Gamma-Ray Emissions from Solar Flares and Prospects for Detecting Nonthermal Signatures from Protostars

We investigate gamma-ray emission in the impulsive phase of solar flares and the detectability of nonthermal signatures from protostellar flares. Energetic solar flares emit high-energy gamma rays of GeV energies, but their production mechanism and emission site are still unknown. Young stellar objects, including protostars, also exhibit luminous X-ray flares, but the triggering mechanism of the flaring activity is still unclear owing to the strong obscuration. Nonthermal signatures in millimeter/submillimeter and gamma-ray bands are useful to probe protostellar flares owing to their strong penetration power. We develop a nonthermal emission model of the impulsive phase of solar flares, where cosmic-ray protons accelerated at the termination shock produce high-energy gamma rays via hadronuclear interaction with the evaporation plasma. This model can reproduce gamma-ray data in the impulsive phase of a solar flare. We apply our model to protostellar flares and show that the Cherenkov Telescope Array will be able to detect gamma rays of TeV energies if particle acceleration in protostellar flares is efficient. Nonthermal electrons accelerated together with protons can emit strong millimeter and submillimeter signals via synchrotron radiation, whose power is consistent with the energetic millimeter/submillimeter transients observed from young stars. Future gamma-ray and millimeter/submillimeter observations from protostars, coordinated with a hard X-ray observation, will unravel the nonthermal particle production and triggering mechanism of protostellar flares.

On Particle Production Mechanism in High-Energy Nucleus–Nucleus Collisions

On Particle Production Mechanism in High-Energy Nucleus–Nucleus Collisions

Exploring the hadronic phase of relativistic heavy-ion collisions with resonances in ALICE

Hadronic resonances, having short lifetimes, are useful for studying the hadrongas phase that characterizes the late-stage evolution of high-energy nuclear collisions. Indeed, regeneration and rescattering processes occurring in the hadron gas modify the measured yields of hadronic resonances and can be studied by measuring resonance yields as a function of system size and comparing them to model predictions with and without hadronic interactions. Measurements of the differential yields of resonances with different lifetime, mass, quark content, and quantum numbers help in understanding particle production mechanisms, the lifetime of the hadronic phase, strangeness production, parton energy loss, rapidity yield asymmetry, and collective effects. With its excellent tracking and particle identification capabilities, the ALICE experiment measured a comprehensive set of mesonic and baryonic resonances. We present recent results on resonance production in pp, p–Pb, Xe–Xe and Pb–Pb collisions at various center-of-mass energies, highlighting new results of K*±, Λ(1520), and Σ*±(1385). The results are also compared to lower energy measurements and model calculations.

Evaluation of gradient boosting and deep learning algorithms in dimuon production

Usage of artificial intelligence (AI) and gradient boosting based machine learning (ML) algorithms in various fields has been favored to advance the human performances due to their accomplishments in real-world issues requiring intensive computation. For this reason, these methods have been started to be applied in physics fields such as material science, particle, and nuclear physics. Dimuons are muon (µ−) and anti-muon (µ+) pairs produced at the different stages of the medium created in high-energy collisions which can be used to understand the formation of the universe. Since they do not interact strongly, they can be utilized to scrutinize properties of the formed medium such as the thermal radiation and production mechanism of various particles. The success of AI and gradient boosting based ML methods suggested their adaptations in particle analysis. In this study, LightGBM, a gradient boosting framework, and Deep Neural Networks (DNNs) performances were examined for the determination of dimuon mass spectrum in proton-proton collisions at the LHC which can be an example for other spectrum studies. From the comparison of the models it is revealed that DNNs performed 99.993% success to determine dimuon invariant mass spectrum with 99.989% sensitivity and 99.989% precision. The results demonsrate the power of nonlinearity property of DNNs to find spectrum in physics studies.

Rivet and the analysis preservation in heavy-ion collisions experiments

The comparison of experimental data and theoretical predictions is important for our understanding of the mechanisms for interactions and particle production in hadron collisions, both at the Large Hadron Collider and at the Relativistic Heavy-Ion Collider experiments. Several tools were ideated to help with that. Rivet (Robust Independent Validation of Experiment and Theory) is a framework that facilitates the comparison between measurements from high-energy physics experiments and Monte Carlo event generators able to produce outputs using the HepMC package. Rivet contains a repository with analysis algorithms developed by experiments, providing analysis documentation and preservation. The recent developments for the implementation of centrality and multiplicity classes in Rivet are presented in this contribution.