Charged Particle Spectra Research Articles

Charged Particles Multiplicity and Scaling Violation of Fragmentation Functions in Electron-Positron Annihilation

By the use of data from the annihilation process of electron-positron in AMY detector at 60 GeV center of mass energy, charged particles multiplicity distribution is obtained and fitted with the KNO scaling. Then, momentum spectra of charged particles and momentum distribution with respect to the jet axis are obtained, and the results are compared to the different models of QCD; also, the distribution of fragmentation functions and scaling violations are studied. It is being expected that the scaling violations of the fragmentation functions of gluon jets are stronger than the quark ones. One of the reasons for such case is that splitting function of quarks is larger than splitting function of gluon.

Computer simulation of ion beam analysis of laterally inhomogeneous materials

The program STRUCTNRA for the simulation of ion beam analysis charged particle spectra from arbitrary two-dimensional distributions of materials is described. The code is validated by comparison to experimental backscattering data from a silicon grating on tantalum at different orientations and incident angles. Simulated spectra for several types of rough thin layers and a chessboard-like arrangement of materials as example for a multi-phase agglomerate material are presented. Ambiguities between back-scattering spectra from two-dimensional and one-dimensional sample structures are discussed.

Pseudorapidity and transverse-momentum distributions of charged particles in proton–proton collisions at [formula omitted

The pseudorapidity (η) and transverse-momentum (pT) distributions of charged particles produced in proton–proton collisions are measured at the centre-of-mass energy s=13 TeV. The pseudorapidity distribution in |η|<1.8 is reported for inelastic events and for events with at least one charged particle in |η|<1. The pseudorapidity density of charged particles produced in the pseudorapidity region |η|<0.5 is 5.31±0.18 and 6.46±0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15<pT<20 GeV/c and |η|<0.8 for events with at least one charged particle in |η|<1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators.

Degradation spectra of electrons in the ionosphere

Theory and numerical simulations of degradation spectra of electrons in gases are presented. Theory is based on the power spectra of degradation charged particles as the spectra with fluxes in energy space. Numerical calculations of the electron energy distribution function have been performed for ionospheric gas mixtures constituted of molecules N2, O2 and atom O under influence of high energy electron source with detailed elementary electron collision processes with molecules and atoms being taken into consideration. The energy expenses of electrons into ionization, dissociation and excitation of various levels have been obtained so that to determine the rates of electron collision processes. The dependence of the electron energy expenses into various inelastic electronic processes upon the energy of primary electron source has been revealed. The results are presented for the rates of numerous elementary processes of electron interaction with basic ionospheric components to be suitably determined.

Influence of the quark–gluon string fusion mechanism on long-range rapidity correlations and fluctuations

Multiparticle production in soft hadronic interactions can be successfully described in the framework of the color-string approach, which will probably be derived from the first principles of chromodynamics in the future. A fundamental property of this approach is the translation invariance of the rapidity spectrum of charged particles produced by one source at high energies. This symmetry results in the appearance of long-range rapidity correlations through event-by-event fluctuations of the number and/or type of strings. We describe the behavior of correlations between multiplicities (n–n) and between the transverse momentum and multiplicities (pt–n) of charged particles with the mechanism of forming sources of two types taken into account. We obtain an exact analytic expression for the (n–n)-correlation coefficient. Because no exact solution can be obtained for the (pt–n)-correlation coefficient, we propose an effective approximation that significantly simplifies numerical computations. We verify all these results by direct simulation using the Monte Carlo method. We also investigate how the fusion mechanism influences the behavior of strongly intensive variables characterizing the multiplicity fluctuations in two rapidity windows.

Testing model energy spectra of charged particles produced in hadron interactions on the basis of atmospheric muons

An original method for calculating the spectrum of atmospheric muons with the aid of the CORSIKA 7.4 code package and numerical integration is proposed. The first step consists in calculating the energy distribution of muons for various fixed energies of primary-cosmic-ray particles and within several chosen hadron-interaction models included in the CORSIKA 7.4 code package. After that, the spectrum of atmospheric muons is calculated via integrating the resulting distribution densities with the chosen spectrum of primary-cosmic-ray particles. The atmospheric-muon fluxes that were calculated on the basis of the SIBYLL 2.1, QGSJET01, and QGSJET II-04 models exceed the predictions of the wellknown Gaisser approximation of this spectrum by a factor of 1.5 to 1.8 in the range of muon energies between about 103 and 104 GeV.Under the assumption that, in the region of extremely highmuon energies, a dominant contribution to the muon flux comes from one to two generations of charged π± and K ± mesons, the production rate calculated for these mesons is overestimated by a factor of 1.3 to 1.5. This conclusion is confirmed by the results of the LHCf and TOTEM experiments.

Parton-medium cross-section and average QGP viscosity in lead–lead collisions at the LHC

The recent experimental CMS and E-by-E ATLAS data on the elliptic anisotropy of particles in Pb–Pb collisions are used to extract parton medium cross-section and the quark–gluon plasma (QGP) viscosity-to-entropy ratio within the incomplete equilibration medium model. Our method assumes extrapolation of the measured pseudorapidity spectrum of charged particles to low-pT range. Then the rapidity distribution of both charged and neutral hadrons is restored. The extracted value of the parton-medium cross section is found to be It yields for the ratio of shear viscosity to entropy density in QGP phase. The last result is in a good agreement with the estimates obtained by calculations within the viscous hydrodynamics.

Free electron gas spectrum parameters of noble gases in dc electric field

Free electron gas is present in every gas, whether it is of atomic or molecular structure. Since the Maxwell spectrum type is the consequence of only thermal motion of constitutive gas particles; therefore, the presence of electric field leads to change the spectrum of charged particles due to their directed motion. However, it has been shown that in the case of occurrence only of elastic interactions between electrons and neutral gas particles (a condition that has been met in the case of weakly ionized noble gases of a relatively huge volume) the deviation of the gas spectrum of free electrons in the electric field from the Maxwell type is negligible. In such a case, the gas spectrum of free electrons is either of Maxwell type (if the frequency collision value is energy-independent) or of Druyvesteyn type (if the mean free electron path value is energy-independent). The Maxwell and Druyvesteyn distribution types are very similar. The only noticeable difference is that the tail of the Maxwell distribution decreases with the energy exponent to the first degree of energy, and the tail of Druyvesteyn distribution with the energy exponent to the second degree of energy. The aim of this paper is to determine whether the gas spectrum of free electrons in weakly ionized noble gases at small values of the product pd (pressure and inter-electrode distance) follows either the Maxwell's or Druyvesteyn's type, as well as to determine the dependence of spectrum parameters on the product pd. It has been established that better results are obtained on the assumption that the mean value of collision frequency is energy-independent.

Measurement of charged-particle spectra in Pb+Pb collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV with the ATLAS detector at the LHC

Charged-particle spectra obtained in 0.15 nb${}^{-1}$ of Pb+Pb interactions at $\sqrt{{s}_\mathsf{{NN}}}=2.76$TeV and 4.2 pb${}^{-1}$ of pp interactions at $\sqrt{s}=2.76$ TeV with the ATLAS detector at the LHC are presented in a wide transverse momentum ($0.5 < p_{\mathrm{T}} < 150$ GeV) and pseudorapidity ($|\eta|<2$) range. For Pb+Pb collisions, the spectra are presented as a function of collision centrality, which is determined by the response of the forward calorimeter located on both sides of the interaction point. The nuclear modification factors $R_{\mathrm{AA}}$ and $R_{\mathrm{CP}}$ are presented in detail as function of centrality, $p_{\mathrm{T}}$ and $\eta$. They show a distinct $p_{\mathrm{T}}$-dependence with a pronounced minimum at about 7 GeV. Above 60 GeV, $R_{\mathrm{AA}}$ is consistent with a plateau at a centrality-dependent value, within the uncertainties. The value is $0.55\pm0.01(stat.)\pm0.04(syst.)$ in the most central collisions. The $R_{\mathrm{AA}}$ distribution is consistent with flat $|\eta|$ dependence over the whole transverse momentum range in all centrality classes.

Comparing Tsallis and Boltzmann temperatures from relativistic heavy ion collider and large hadron collider heavy-ion data

The transverse momentum spectra of charged particles produced in Au + Au collisions at the relativistic heavy ion collider and in Pb + Pb collisions at the large hadron collider with different centrality intervals are described by the multisource thermal model which is based on different statistic distributions for a singular source. Each source in the present work is described by the Tsallis distribution and the Boltzmann distribution, respectively. Then, the interacting system is described by the (two-component) Tsallis distribution and the (two-component) Boltzmann distribution, respectively. The results calculated by the two distributions are in agreement with the experimental data of the Solenoidal Tracker At Relativistic heavy ion collider, Pioneering High Energy Nuclear Interaction eXperiment, and A Large Ion Collider Experiment Collaborations. The effective temperature parameters extracted from the two distributions on the descriptions of heavy-ion data at the relativistic heavy ion collider and large hadron collider are obtained to show a linear correlation.

Pulse-shape analysis for gamma background rejection in thermal neutron radiation using CVD diamond detectors

A novel technique for the rejection of gamma background from charged-particle spectra was demonstrated using a CVD diamond detector with a 6Li neutron converter installed at a thermal neutron beamline of the TRIGA research reactor at the Atominstitut (Vienna University of Technology). Spectra of the alpha particles and tritons of 6Li(n,T)4He thermal neutron capture reaction were separated from the gamma background by a new algorithm based on pulse-shape analysis. The thermal neutron capture in 6Li is already used for neutron flux monitoring, but the ability to remove gamma background allows using a CVD diamond detector for thermal neutron counting. The pulse-shape analysis can equally be applied to all cases where the charged products of an interaction are absorbed in the diamond and to other background particles that fully traverse the detector.

Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at [Formula: see text][Formula: see text

Transverse momentum spectra of charged particles are measured by the CMS experiment at the CERN LHC in pPb collisions at sqrt{s_{_mathrm {NN}}} =5.02 ,text {TeV}, in the range 0.4 < p_{mathrm {T}} < 120 {,text {GeV/}c} and pseudorapidity |eta _textsc {cm} | < 1.8 in the proton–nucleon center-of-mass frame. For p_{mathrm {T}} <10 {,text {GeV/}c}, the charged-particle production is asymmetric about eta _textsc {cm} = 0, with smaller yield observed in the direction of the proton beam, qualitatively consistent with expectations from shadowing in nuclear parton distribution functions (nPDF). A pp reference spectrum at sqrt{s}=5.02 ,text {TeV} is obtained by interpolation from previous measurements at higher and lower center-of-mass energies. The p_{mathrm {T}} distribution measured in pPb collisions shows an enhancement of charged particles with p_{mathrm {T}} >20 {,text {GeV/}c} compared to expectations from the pp reference. The enhancement is larger than predicted by perturbative quantum chromodynamics calculations that include antishadowing modifications of nPDFs.

The landscape of M-theory compactifications on seven-manifolds with G2 holonomy

We study the physics of globally consistent four-dimensional $\mathcal{N}=1$ supersymmetric M-theory compactifications on $G_2$ manifolds constructed via twisted connected sum; there are now perhaps fifty million examples of these manifolds. We study a rich example that exhibits $U(1)^3$ gauge symmetry and a spectrum of massive charged particles that includes a trifundamental. Applying recent mathematical results to this example, we compute membrane instanton corrections to the superpotential and spacetime topology change in a compact model; the latter include both the (non-isolated) $G_2$ flop and conifold transitions. The conifold transition spontaneously breaks the gauge symmetry to $U(1)^2$, and associated field theoretic computations of particle charges make correct predictions for the topology of the deformed $G_2$ manifold. We discuss physical aspects of the abelian $G_2$ landscape broadly, including aspects of Higgs and Coulomb branches, membrane instanton corrections, and some general aspects of topology change.

SIMLA: Simulating particle dynamics in intense laser and other electromagnetic fields via classical and quantum electrodynamics

We present the Fortran program SIMLA, which is designed for the study of charged particle dynamics in laser and other background fields. The dynamics can be determined classically via the Lorentz force and Landau–Lifshitz equations or, alternatively, via the simulation of photon emission events determined by strong-field quantum-electrodynamics amplitudes and implemented using Monte-Carlo routines. Multiple background fields can be included in the simulation and, where applicable, the propagation direction, field type (plane wave, focussed paraxial, constant crossed, or constant magnetic), and time envelope of each can be independently specified. Program summaryProgram title: SIMLACatalogue identifier: AEWD_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEWD_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 4536No. of bytes in distributed program, including test data, etc.: 38351Distribution format: tar.gzProgramming language: Fortran.Computer: Home and office-spec desktop and laptop machines, networked or stand alone.Operating system: Linux, Mac OS, Windows, with Fortran compiler. Matlab required to exploit full post-processing features.RAM: Varies greatly depending on calculation to be performed.Supplementary material: A SIMLA manual with tutorial type examples is available.Classification: 15.Nature of problem: Calculation of dynamics and emission spectra of charged particles in multiple (intense) laser and other background fields, including effects of classical and quantum radiation reaction.Solution method: Solution of the Landau–Lifshitz equation (or simply Lorentz equation for weak fields), or alternatively, via the simulation of photon emission events determined by strong-field quantum-electrodynamics amplitudes and implemented using Monte-Carlo type routines.Restrictions: As a single particle code, the parameters are restricted to a regime in which pair production does not occur. The program will abort with an explicit error message if such a parameter regime does occur in a given simulation.Additional comments: Classical spectra calculated separately in independent Matlab program ‘spectrum.m’. Manual included with tutorial style examplesRunning time: Varies greatly depending on calculation requested, from seconds to hours.

$\beta $-delayed $\gamma $-proton Decay in $^{56}$Zn: Analysis of the Charged-particle Spectrum

A study of the β decay of the proton-rich Tz = –2 nucleus ⁵⁶Zn has been reported in a recent publication. A rare and exotic decay mode, β-de-layed γ-proton decay, has been observed there for the first time in the fp shell. Here, we expand on some of the details of the data analysis, focusing on the charged particle spectrum.

Study of angular momentum hindrance in heavy ion fusion reactions

The systematic study of the properties of hot nuclei by detecting the emitted charged particles and neutrons in coincidence with residual nuclei provides very critical information about its nuclear level density. These emitted particles capable to explain the behavior of the nucleus at various stages of the de-excitation cascade process. So, we have studied, a set of four compound nuclei, which were populated by mass-symmetric and mass-asymmetric channels, leading to the same compound nuclei, namely 80 Sr* , 79 Se* , 76 Kr* and 58 Ni* at same excitation energies, respectively and found that the experimental neutron and charged particle spectra for symmetric channel show deviations at higher energies in comparison to the statistical model calculations.

Measurements of charged particle spectra and nuclear modification factor in p+Pb collisions with the ATLAS detector

The ATLAS detector at the LHC obtained the sample of p+Pb data at $\sqrt{s_{NN}}={}$5.02TeV with integrated luminosity of 25nb${}^{-1}$, which can be compared to the pp data obtained by interpolating pp measurements at $\sqrt{s}={}$2.76TeV and 7TeV. Due to the excellent capabilities of the ATLAS detector, and its stable operation in heavy ion as well as proton-proton physics runs, the data allow measurements of the nuclear modification factor, ratio of heavy ion charged particle spectra divided by pp reference, in different centrality classes over a wide range of rapidity. The charged particle nuclear modification factor is found to vary significantly as a function of transverse momentum with a stronger dependence in more peripheral collisions.

Role of quarks in hadroproduction in high energy collisions

A qualitative model for hadroproduction in high energy collisions considering two components (“thermal” and “hard”) to hadroproduction is proposed. Inclusive pseudorapidity distributions, dσ/dη, and transverse momentum spectra, d2σ/(dηdpT2), measured by different collaborations are considered in terms of this model. The shapes of the pseudorapidity distributions agree with that one can expect from the qualitative picture introduced. The model is used to provide predictions for the LHC. Data up to a centre-of-mass energy of 7 TeV are well described and predictions for higher energies await new data. Finally, the differences between charged particle spectra produced in inclusive and diffractive events are discussed and the absence of the “thermal” component in the latter is observed.

Momentum flow relative to the dijet system in PbPb collisions

Abstract The difference in charged particle multiplicity and momentum flow carried by charged particles near the leading and the subleading jet in dijet events is measured in PbPb and pp collisions. In PbPb collisions, there is an increase in the fraction of dijet events with large momentum asymmetry between the leading and subleading jets compared to what is seen in pp collisions. In this analysis, the radiation balancing the dijet asymmetry is characterized in terms of the multiplicity, angular (up to Δ R = 1.8 ) and momentum spectra of charged particles with p T > 0.5 GeV / c . The measurement is done as a function of PbPb collision centrality and dijet asymmetry.

Jet and charged hadron nuclear modification factors in pPb collisions with CMS

One of the signatures of the strongly interacting medium produced in central PbPb collisions is the suppression of high- p T jets and charged particles . In order to disentangle the initial state and final state effects in heavy ion collisions , the nuclear modification factor of both jets and of charged-particles in pPb ( R pPb ) collisions is presented. The spectra of both jets and charged-particles in pPb collisions at s N N = 5.02 TeV , have been measured with the CMS detector using high statistics samples. The R pPb of charged particles is determined by dividing the measured pPb spectrum by a pp reference spectrum constructed using interpolation methods, or alternatively from PYTHIA simulations.