Dynamics Of Particle Production Research Articles

Intermittency analysis of charged particles generated in Xe-Xe~collisions at $\sqrt{s_{\rm{NN}}}$ = 5.44 TeV using the AMPT model

The multiplicity fluctuations are sensitive to QCD phase transition and to the presence of critical point in QCD phase diagram. At critical point a system undergoing phase transition is characterized by large fluctuations in the observables which is an important tool to understand the dynamics of particle production in heavy-ion interactions and phase changes. Multiplicity fluctuations of produced particles is an important observable to characterize the evolving system. Using scaling exponent obtained from the normalized factorial moments of the number of charged hadrons in the two dimensional (\eta,\phiη,ϕ) phase space, one can learn about the dynamics of system created in these collisions. Events generated using Xe-Xe collisions at $ = 5.44 $ TeV with string-melting (SM) version of the AMPT model are analyzed and the scaling exponent (\nu)(ν) for various p_TpT intervals is determined. It is observed that the calculated value of \nuν is larger than the universal value 1.304, as is obtained from Ginzburg-Landau theory for second order phase transition. Here we will also present the results of the dependence of the scaling exponent on the transverse momentum bin width.

Event topology and global observables in heavy-ion collisions at the Large Hadron Collider

Particle production and event topology are very strongly correlated in high-energy hadronic and nuclear collisions. Event topology is decided by the underlying particle production dynamics and medium effects. Transverse spherocity is an event shape observable, which has been used in pp and heavy-ion collisions to separate the events based on their geometrical shapes. It has the unique capability to distinguish between jetty and isotropic events. In this work, we have implemented transverse spherocity in Pb–Pb collisions at sqrt{s_text{NN}} = 5.02 TeV using A Multi-Phase Transport Model (AMPT). While awaiting for experimental explorations, we perform a feasibility study of transverse spherocity dependence of some of the global observables in heavy-ion collisions at the Large Hadron Collider energies. These global observables include the Bjorken energy density (varepsilon _text{Bj}), squared speed of sound (c_text{s}^2) in the medium and the kinetic freeze-out properties for different collision centralities. The present study reveals about the usefulness of event topology dependent measurements in heavy-ion collisions.

A unified formalism to study the pseudorapidity spectra in heavy-ion collision

The pseudorapidity distribution of charged hadron over a wide $\eta$ range gives us crucial information about the dynamics of particle production. Constraint on the detector acceptance, particularly at forward rapidities, demands a proper distribution function to extrapolate the pseudorapidity distribution to large $\eta$. In this work, we have proposed a phenomenological model based on Pearson statistical framework to study the pseudorapidity distribution. We have analyzed and fit data of charged hadrons produced in $Pb-Pb$ collision at $2.76$ TeV and $Xe-Xe$ collision at $5.44$ TeV using the proposed model.

Simulation of production of hollow silica particles in a plasma flow. Part 2. Hollow particle production dynamics

The paper presents the results of numerical simulation for the process of production of hollow microspheres during heating and melting of porous particles of silica (the precursor) by a flow of low-temperature plasma. This model takes into account the partial capturing of gas in the particle and offers the laws of evolution for the hollow microsphere diameter and the wall thickness for different precursors with the size D0 = (50–150) microns and porosity Pp = (0.2–0.6).

Study of Di-Muon Production Process in pp Collision in CMS Data from Symmetry Scaling Perspective

An extensive knowledge of the dynamics of the process of pp collision serves as input to exhaustive theoretical models of strong interaction. This knowledge is also a baseline for a system to decipher the dynamics of AA collisions at relativistic and ultrarelativistic energies. Recent availability of di-muon data has triggered a spate of interests in revisiting strong interaction process, the study of which in detail is extremely important for enhancement of our understanding of not only the theory of strong interaction but also possible physics scenarios beyond the standard model. Apart from conventional approaches to the study of the dynamics of particle production in high-energy collision the present authors proposed a new approach with successful application in context of symmetry scaling in AA collision data from (ALICE-Collaboration, 2014) in the work (Bhaduri, S. et al., 2019) and pp collision data at 8TeV from (CMS-collaboration, 2017) in the work (Bhaduri, S. et al., 2019) and also in other numerous works with different collision data. This different approach essentially analyses fluctuation pattern from the perspective of symmetry scaling or degree of self-similarity involved in the process. This was done with the help of multifractal scaling analysis and also multifractal cross-correlation analysis using the single variable of pseudorapidity values of di-muon data taken out from the primary dataset of RunA(2011) and RunB(2012) of the pp collision at 7 TeV and 8 TeV, respectively, from (CMS-collaboration, 2016, 2017). High degree of persistent long-range cross-correlations (MF-DXA) exist between pseudorapidity-value and its corresponding azimuthal-value for different rapidity ranges. The different values of scaling exponents (across rapidity ranges and energies) signify that there may be multiple processes other than those conjectured, involved in the underlying dynamics of the production process of oppositely charged di-muons resulting in different kinds of scaling. Otherwise, the scaling exponents at different degrees would have remained the same across the rapidity ranges and also for different energies.

Compelling Evidence of Oscillatory Behaviour of Hadronic Multiplicities in the Shifted Gompertz Distribution

Study of charged particle multiplicity distribution in high-energy interactions of particles helps in revealing the dynamics of particle production and the underlying statistical patterns, by which these distributions follow. Several distributions derived from statistics have been employed to understand its behaviour. In one of our earlier papers, we introduced the shifted Gompertz distribution to investigate this variable and showed that the multiplicity distributions in a variety of processes at different energies can be very well described by this distribution. The fact that the shifted Gompertz distribution, which has been extensively used in diffusion theory, social networking and forecasting, has been used for the first time in high-energy physics collisions remains interesting. In this paper, we investigate the phenomenon of oscillatory behaviour of the counting statistics observed in the high-energy experimental data, resulting from different types of recurrence relations defining the probability distributions. We search for such oscillations in the multiplicity distributions well described by the shifted Gompertz distribution and look for retrieval of additional valuable information from these distributions.

Fractal Structure of Hadrons: Experimental and Theoretical Signatures

One important ingredient in the study of cosmological evolution is the equation of state of the primordial matter formed in the first stages of the Universe. It is believed that the first matter produced was of hadronic nature, probably the quark–gluon plasma which has been studied in high-energy collisions. There are several experimental indications of self-similarity in hadronic systems—in particular in multiparticle production at high energies. Theoretically, this property was associated with the dynamics of particle production, but it is also possible to relate self-similarity to the hadron structure—in particular to a fractal structure of this system. In doing so, it is found that the thermodynamics of hadron systems at equilibrium must present specific properties that are indeed supported by data. In particular, the well-known self-consistence principle proposed by Hagedorn 50 years ago is shown to be valid, and can correctly describe experimental distributions, mass spectrum of observed particles, and other properties of the hadronic matter. In the present work, a review of the theoretical developments related to the thermodynamical properties of hadronic matter and its applications in other fields is presented.

Rapidity-dependent jet energy loss in small systems with finite-size effects and running coupling

Longitudinal dynamics of particle production and rapidity-dependent jet energy loss are investigated in small and asymmetric colliding systems. We utilize an improved version of martini in which two improvements are implemented to calculate the effect of the strongly coupled QGP droplet on jet energy loss. We show that those realistic prescriptions improve the results of nuclear modification factor calculations. We also observe visible energy loss of jets in a thermal background of high-multiplicity p-Pb collisions, and a clear correlation between the energy loss and elliptic flow coefficients for energetic particles. We conclude that systematic measurements of jet quenching in central collisions of small systems can support the formation of the QGP droplet.

Implications of energy and momentum conservation for particle emission in A+A collisions at energies available at the CERN Super Proton Synchrotron

We construct a simple model of heavy ion collisions, local in the impact parameter plane, and appropriate for the SPS energy range. This model can be regarded as a new realization of the "fire-streak" approach, originally applied to studies of lower energy nucleus-nucleus reactions. Starting from local energy and momentum conservation, we nicely describe the broadening of the pion rapidity distribution when going from central to peripheral Pb+Pb collisions at $\sqrt{s_{NN}}$=17.3 GeV. The results of our calculations are compared with SPS experimental data. We discuss the resulting implications on the role of energy and momentum conservation for the dynamics of particle production in heavy ion collisions. A specific space-time picture emerges, where the longitudinal evolution of the system strongly depends on the position in the impact parameter (${b_x}$, ${b_y}$) plane. This picture is consistent with our earlier findings on the longitudinal evolution of the system as deduced from electromagnetic effects on charged pion directed flow, and can provide an explanation for specific low-$p_T$ phenomena seen in the fragmentation region of Pb+Pb collisions.

A New Two-Component Model for Hadron Production in Heavy-Ion Collisions

Using the experimental data from the ALICE program on the centrality dependence of the transverse momentum (pT) spectra in Pb+Pb collisions at sNN=2.76 TeV, we show that the double-Tsallis distribution and the generalized Fokker-Planck (FP) solution cannot describe the spectra of pions, kaons, and protons from central to peripheral collisions in the entire pT region, simultaneously. Hence, a new two-component distribution, which is a hydrodynamic extension of the generalized FP solution accounting for the collective motion effect in heavy-ion collisions, is proposed in order to reproduce all the identified particle spectra. Our results suggest that the particle production dynamics may be different for different particles, especially at very low pT region.

Nuclear dynamics induced by antiprotons

Reaction dynamics in collisions of antiprotons on nuclei is investigated within the Lanzhou quantum molecular dynamics model. The reaction channels of elastic scattering, annihilation, charge exchange and inelastic collisions of antiprotons on nucleons have been included in the model. Dynamics on particle production, in particular pions, kaons, antikaons and hyperons, is investigated in collisions of p on12 C,20Ne,40 Ca and181Ta from low to high incident momenta. It is found that the annihilations of p on nucleons are of importance to the dynamics of particle production in phase space. Hyperons are mainly produced via meson induced reactions on nucleons and strangeness exchange collisions, which lead to delayed emission in antiproton-nucleus collisions.

Study of Charmonia Production vs. Charged Track Multiplicity in p + p Collisions at PHENIX

Charmonia production is a unique probe to explore the dynamics of particle production in hot and cold nuclear matter. Traditionally, charmonia suppression has been studied in heavy-ion collisions to quantify various nuclear effects. Since the “long-range, nearside angular correlation in p + p collisions” discovered at the LHC, collective QCD phenomena in smaller systems have been a hot research topic. A recent PHENIX d + Au results also show intriguing hints that the comover effect may play an important role along with other competing effects. At PHENIX the newly upgraded silicon detector FVTX provides improved dimuon mass resolution at forward rapidity as well as the capability of measuring charged track multiplicity directly. In these proceedings, we present the latest result on ψ(2S) production in d+Au collisions at midrapidity, the first ψ(2S) measurement at forward rapidity at RHIC and the expected precision for the charmonia production vs. charged track multiplicity in p + p collisions at PHENIX.

PHENIX results on heavy quarks at low x

It is becoming increasingly clear that initial state effects inherent to collisions of nuclei play an important role in the interpretation of data from heavy ion collisions at RHIC and the LHC. Such effects are more apparent in kinematic regions where the gluon density is expected to be significantly modified in the nucleus. The PHENIX experiment has studied these effects through the production of heavy quarks at backwards, middle, and forward rapidity, where partonic interactions in the nucleus and changes in the gluon structure function influence heavy quark production in different ways. Comparisons between these different rapidities in d+Au collisions offer us a window into the dynamics of particle production and transport in the nucleus. In these proceedings, new PHENIX results on heavy quark production at low x values are discussed, in the context of A+A data from RHIC and the LHC.

Correcting correlation function measurements

Correlation functions measured as a function of $\ensuremath{\Delta}\ensuremath{\eta},\ensuremath{\Delta}\ensuremath{\phi}$ have emerged as a powerful tool to study the dynamics of particle production in nuclear collisions at high energy. They are however subject, like any other observables, to instrumental effects which must be properly accounted for to extract meaningful physics results. We compare the merits of several techniques used towards measurement of these correlation functions in nuclear collisions. We discuss and distinguish the effects of finite acceptance, and detection efficiency that may vary with collision parameters such as the position of the event in the detector and the instantaneous luminosity of the beam. We focus in particular on instrumental effects which break the factorization of the particle pair detection efficiency, and describe a technique to recover the robustness of correlation observables. We finally introduce a multidimensional weight method to correct for efficiencies that vary simultaneously with particle pseudo rapidity, azimuthal angle, transverse momentum, and the collision vertex position. The method can be generalized to account for any number of ``event variables'' that may break the factorability of the pair efficiency.

Constituent Quark Scaling of Strangeness Enhancement in Heavy-Ion Collisions

In the framework of a nuclear overlap model, we estimate the number of nucleons and quark participants in proton-proton, proton-nucleus, and nucleus-nucleus collisions. We observe the number of nucleon- (NN-part-) normalized enhancement of multistrange particles, which shows a monotonic increase with centrality and turns out to be a centrality-independent scaling behavior when normalized to number of constituent quarks participating in the collision (Nq-part). In addition, we observe that theNq-part-normalized enhancement, when further normalized to the strangeness content, shows a strangeness-independent scaling behavior. This holds good at top RHIC energy. However, the corresponding SPS data show a weakNq-part-scaling. Moreover, the strangeness scaling seems to be violated at top SPS energy. This scaling at RHIC indicates that the partonic degrees of freedom play an important role in the production of multistrange particles. Top SPS energy, in view of the above observations, shows a coexistence of hadronic and partonic phases. Therefore we give a comparison of data with HIJING, AMPT, and UrQMD models to understand the particle production dynamics at different energies.

Parton Cascades, Small x, Multiple Interactions, and Saturation

In this paper I discuss the dynamics of particle production in high energy reactions. It includes parton cascades and hadronization in e(+)e(-)-annihilation, small x evolution including the Double Leading Log approximation and the BFKL equation, saturation at high densities and the BK equation, and finally the Lund Dipole Cascade model for high energy collisions, which is implemented in the DIPSY MC.

Direct hadron production in hadronic collisions

The scaling behavior of the invariant production cross section is a powerful tool in order to probe the dynamics of particle production. Here, we investigate the scaling properties of large- p ⊥ hadron, jet and prompt photon production in hadronic collisions by comparing systematically world data to NLO QCD predictions. In the hadron sector a significant discrepancy is reported, while prompt photon and jet production data prove in agreement with leadingtwist expectations. We interpret these results as coming from a non-negligible contribution of higher-twist processes, in which the hadron is produced directly in the hard subprocess. Predictions at RHIC are successfully compared to PHENIX preliminary measurements and LHC predictions are given.

Dynamics of particle production by strong electric fields in non-Abelian plasmas

We develop methods for computing the dynamics of fermion pair production by strong color electric fields using the semi-classical Boltzmann-Vlasov equation. We present numerical results for a model with SU(2) symmetry in (1+1) dimension.

Recent results from BRAHMS in the context of longitudinal dynamics at RHIC

The BRAHMS Collaboration has measured identified charged hadron production as a function of rapidity for Au+Au and Cu+Cu collisions at energies of and 62.4 GeV at RHIC. Selected recent results are presented with emphasis on longitudinal dynamics of particle production. The rapidity dependence of particle production imposes stringent additional constraints on theoretical models describing dynamics of hadronic/partonic matter created by high-energy heavy-ion collisions.

Probing Longitudinal Dynamics at RHIC

Particle production of charged hadrons in Au+Au collisions at \(\sqrt {s_{NN} } = 200\) GeV bas been studied as a function of rapidity by the BRAHMS Collaboration at RHIC. Selected recent results are presented with emphasis on longitudinal dynamics of particle production. The rapidity dependence of particle production imposes more stringent constraints on theoretical models describing dynamics of nuclear matter created by high-energy heavy ion collisions.