Study Of Hadron Production Research Articles

Recent results from LHCb for astroparticle physics

The LHCb experiment is a general-purpose forward spectrometer designed for the study of heavy flavour physics at the LHC. The acceptance in the pseudorapidity range 2 < \eta < 52<η<5 with full tracking and particle identification capabilities down to very small transverse momentum make LHCb also ideal to study hadron production in the forward region. Measuring and modelling these processes is essential for the simulation of interactions of high-energy cosmic rays with matter, like Earth’s atmosphere or the interstellar medium. We present recently published analyses from the LHCb collaboration relevant for this application.

Multiplicity of charged and identified particles within jets

Jets are commonly used to study Quantum Chromodynamics and search for physics beyond the Standard model. Recent experimental results are analyzed to study hard and soft hadron production mechanisms within and out of the jets. The result of this work is the study of hadron production within and out of the jets produced in proton-proton collisions generated using Pythia 8.3 event generator. We report color reconnection effects on jet multiplicity, multiplicity for identified particles within the jets and transverse momenta distributions at 7 and 13 TeV.

Study of hadron production through pair annihilation in the noncommutative standard model

Study of hadron production through pair annihilation in the noncommutative standard model

Hadron production with collinearly-improved unintegrated gluon distributions in high energy proton-proton collisions * *Supported by the National Natural Science Foundation of China (12165004, 12061141008, 11975005), Guizhou Provincial Science and Technology Projects ([2019]5103, [2019]5653), the Education Department of Guizhou Province (KY[2021]131), the National Key Research and Development Program of China (2018YFE0104700, 2018YFE01014800)

The collinearly-improved Balitsky-Kovchegov (ciBK) equation evolved unintegrated gluon distribution (UGD) is used for the first time to study hadron production in high energy proton-proton collisions in order to improve the predictive power of the Color Glass Condensate effective theory. We show that the ciBK equation evolved UGD provides a relatively better description of LHC data on the transverse momentum and integrated multiplicity distributions of charged hadron and neutral pion production for several collision energies compared with the running coupling Balitsky-Kovchegov (rcBK) equation evolved UGD. This is because the ciBK evolved UGD has a sharper transverse momentum distribution than the rcBK UGD. The impact of running coupling prescriptions on hadron production is studied, and it is found that the parent dipole and smallest dipole running coupling prescriptions provide similar depictions of the data. Moreover, the scale dependence of the fragmentation function is investigated by taking three typical values of scale. We find that the differences resulting from the scale dependence of the fragmentation function can be fully absorbed into the normalization factor, which lumps higher order corrections.

Hadronic resonance production and interaction in p−Pb collisions at LHC energies in EPOS3

Using the EPOS3 model with UrQMD to describe the hadronic phase, we study the production of short-lived hadronic resonances and the modification of their yields and $p_{T}$ spectra in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. High-multiplicity p-Pb collisions exhibit similar behavior to mid-peripheral Pb-Pb collisions at LHC energies, and we find indications of a short-lived hadronic phase in p-Pb collisions that can modify resonance yields and $p_{T}$ spectra through scattering processes. The evolution of resonance production is investigated as a function of the system size, which is related to the lifetime of the hadronic phase, in order to study the onset of collective effects in p-Pb collisions. We also study hadron production separately in the core and corona parts of these collisions, and explore how this division affects the total particle yields as the system size increases.

Dynamics of QCD matter — current status

In this article, there are 18 sections discussing various current topics in the field of relativistic heavy-ion collisions and related phenomena, which will serve as a snapshot of the current state of the art. Section 1 reviews experimental results of some recent light-flavored particle production data from ALICE collaboration. Other sections are mostly theoretical in nature. Very strong but transient magnetic field created in relativistic heavy-ion collisions could have important observational consequences. This has generated a lot of theoretical activity in the last decade. Sections 2, 7, 9, 10 and 11 deal with the effects of the magnetic field on the properties of the QCD matter. More specifically, Sec. 2 discusses mass of [Formula: see text] in the linear sigma model coupled to quarks at zero temperature. In Sec. 7, one-loop calculation of the anisotropic pressure are discussed in the presence of strong magnetic field. In Sec. 9, chiral transition and chiral susceptibility in the NJL model is discussed for a chirally imbalanced plasma in the presence of magnetic field using a Wigner function approach. Sections 10 discusses electrical conductivity and Hall conductivity of hot and dense hadron gas within Boltzmann approach and Sec. 11 deals with electrical resistivity of quark matter in presence of magnetic field. There are several unanswered questions about the QCD phase diagram. Sections 3, 11 and 18 discuss various aspects of the QCD phase diagram and phase transitions. Recent years have witnessed interesting developments in foundational aspects of hydrodynamics and their application to heavy-ion collisions. Sections 12 and 15–17 of this article probe some aspects of this exciting field. In Sec. 12, analytical solutions of viscous Landau hydrodynamics in 1+1D are discussed. Section 15 deals with derivation of hydrodynamics from effective covariant kinetic theory. Sections 16 and 17 discuss hydrodynamics with spin and analytical hydrodynamic attractors, respectively. Transport coefficients together with their temperature- and density-dependence are essential inputs in hydrodynamical calculations. Sections 5, 8 and 14 deal with calculation/estimation of various transport coefficients (shear and bulk viscosity, thermal conductivity, relaxation times, etc.) of quark matter and hadronic matter. Sections 4, 6 and 13 deal with interesting new developments in the field. Section 4 discusses color dipole gluon distribution function at small transverse momentum in the form of a series of Bells polynomials. Section 6 discusses the properties of Higgs boson in the quark–gluon plasma using Higgs–quark interaction and calculate the Higgs decays into quark and anti-quark, which shows a dominant on-shell contribution in the bottom-quark channel. Section 13 discusses modification of coalescence model to incorporate viscous corrections and application of this model to study hadron production from a dissipative quark–gluon plasma.

Modification of hadron productions in small systems observed by PHENIX

Collisions of small systems exhibit evidence of collective behavior through various flow type measurements, which suggests that quark gluon plasma could be produced in these collisions. If so, there could also be evidence for energy loss in the plasma, which would present itself in the spectra of hadrons. Accordingly, the study of hadron production in highly asymmetric small systems may help to understand the role of initial and final state effects in the relativistic ion collisions. Therefore, PHENIX has studied the nuclear modification factors of various hadron species (π0, ϕ, and h±) as a function of transverse momentum, rapidity, system size in p+Al, p+Au, d+Au, and 3He+Au collisions at sNN=200GeV. Scaling of hadron production in small systems with Ncoll or Ncoll/Nprojpart and a hint of jet quenching in nuclear modification factors of π0 were observed.

Observation of a fine structure in e+e− → hadrons production at the nucleon-antinucleon threshold

A study of hadron production at the nucleon-antinucleon threshold has been performed with the CMD-3 detector at the VEPP-2000 e+e− collider. The very fast rise with about 1 MeV width has been observed in the e+e−→pp¯ cross section. A sharp drop in the e+e−→3(π+π−) cross section has been confirmed and found to have a less than 2 MeV width, in agreement with the observed fast rise of the e+e−→pp¯ cross section. For the first time a similar sharp drop is demonstrated in the e+e−→K+K−π+π− cross section. The behavior of the e+e−→3(π+π−),K+K−π+π− cross sections cannot be explained by an interference of any resonance amplitude with continuum, therefore this phenomenon cannot be due to a narrow near-threshold resonance. No such structure has been observed in the e+e−→2(π+π−) cross section.

The NNbar and multihadron production at the threshold at VEPP2000

A study of hadron production at the nucleon-antinucleon threshold has been performed with the CMD-3 detector at the VEPP-2000 e+e− collider. A very fast rise with an about 1 MeV width has been observed in the e+e−→ pp̅ cross section. A sharp drop in the e+ e−→ 3(π+π−) cross section has been con?rmed and found to have a width of less than 2 MeV, in agreement with the observed fast rise of the e+e−→ pp̅ cross section. For the ?rst time a similar sharp drop is demonstrated in the e+e−→ K+ K−π+π− cross section. The behavior of the e+e−→ 3(π+ π−), K+ K−π+π− cross sections cannot be explained by an interference of any resonance amplitude with continuum, therefore this phenomenon cannot be due to a narrow near-threshold resonance. No such structure has been observed in the e+e−→ 2(π+π−) cross section.

Measurements of Hadronic and Transition Form Factors at BESIII

Motivated by the need of experimental input to improve the Standard Model prediction of the anomalous magnetic moment of the muon aµ, the BESIII Collaboration started a dedicated program to measure hadronic cross sections as well as transition form factors (TFF) with high accuracy. The large data sets acquired by the BESIII Collaboration allow to exploit initial state radiation in order to study hadron production over a wide energy range, as well as two-photon collisions to study the momentum dependence of TFFs in the space like regime. The current status and ongoing investigations in both endeavors are discussed.

Forward backward multiplicity correlations: a tool to study properties of the proton-proton collisions

Forward-backward multiplicity correlations have been used to study hadron production mechanisms in electron-positron, proton-proton and more recently in leadlead collisions. The experimental results on this correlations and its comparison to different models reveals an incomplete agreement. In this work, we present an study of forward backward multiplicity correlations in proton-proton collisions using PYTHIA event generator, at LHC energies. Detailed analysis is presented in the case of soft and hard QCD processes, incorporating color reconnection model as part of hadronization mechanism and multiple parton interactions effects in the correlations. Our results and its comparison to available experimental data suggest that this kind of correlations are great tools to characterize the events and gives the possibility to disentangle phenomena in hard and soft QCD processes.

Study of radially excited Ds(21S0) and Ds(3P)**Supported by National Natural Science Foundation of China (11475111)

The unobserved JP = 0− radial excitation Ds(21S0) is anticipated to have mass 2650 MeV (denoted as Ds(2650)). Study of hadronic production is an important way to identify highly excited states. We study hadronic production of Ds(2650) from higher excited resonances in a 3P0 model. Relevant hadronic partial decay widths are found to be very small, which implies it is difficult to observe Ds(2650) in hadronic decays of higher excited resonances. Hadronic decay widths of radially excited Ds(3P) have also been estimated. The total decay widths of four Ds(3P) are large, but the branching ratios in the Ds(2650)η channel are very small, which implies that it seems impossible to observe Ds(2650) in hadronic decays of Ds(3P). The dominant decay channels of the four Ds(3P) have been pointed out, and D1(2420), D1(2430), , D(2550), D(2600), (11D2)D(2750) and are possible to observe in hadronic production from Ds(3P).

Processing of the signals from the Liquid Xenon Calorimeter for timing measurements

One of the goals of the Cryogenic Magnetic Detector at Budker Institute of Nuclear Physics SB RAS (Novosibirsk, Russia) is a study of hadron production in electron-positron collisions near threshold. The neutron-antineutron pair production events can be detected only by the calorimeters. In the barrel calorimeter the antineutron annihilation typically occurs about 5 ns or later after the beams crossing. For identification of such events it is necessary to measure the time of flight of particles to the LXe-calorimeter with an accuracy of about a few nanoseconds. The LXe-calorimeter consists of 14 layers of ionization chambers with two readout: anode and cathode. The duration of charge collection to the anodes is about 4.5 μs, while the required accuracy of measuring of the signal arrival time is less than 1/1000 of that (i.e. 4.5 ns). Besides, the signals' shapes differ substantially from event to event, so the signal arrival time is measured in two stages. In the paper we describ the development of the special electronics which performs waveform digitization and the on-line measurement of signals' arrival times and amplitudes.

Hadrons anti-hadrons production in reaction planes in relativistic heavy ion collisions on two common event generators: HIJING and HYDJET++

The study of hadron production in heavy ion collisions provides the researcher with valuable techniques to investigate the properties of quark gluon plasma (QGP). The hadron and anti-hadron production in the reaction plane, at relativistic heavy ion collisions are studied for the energy per nucleon available at the RHIC-STAR experiment of ∘ _(sNN) = 200 GeV. In order to test the models used for hadron and anti-hadron production, two common event generators (HIJING1.35 and HYDJET+ +2.0.2), established on Monte Carlo techniques, are discussed for hadron and anti-hadron production in the reaction plane for heavy ions 197Au79 −197Au79 collisions at √ ___SNN = 200 GeV. We find that, HYDJET+ + 2.0.2 is more realistic in comparing the results of simulations with those of the experimental data published by the STAR-Collaboration.

Hadrons anti-hadrons production in reaction planes in relativistic heavy ion collisions on two common event generators: HIJING and HYDJET++

The study of hadron production in heavy ion collisions provides the researcher with valuable techniques to investigate the properties of quark gluon plasma (QGP). The hadron and anti-hadron production in the reaction plane, at relativistic heavy ion collisions are studied for the energy per nucleon available at the RHIC-STAR experiment of ∘ _( s NN ) = 200 GeV. In order to test the models used for hadron and anti-hadron production, two common event generators ( HIJING 1.35 and HYDJET + +2.0.2), established on Monte Carlo techniques, are discussed for hadron and anti-hadron production in the reaction plane for heavy ions 197 Au 79 − 197 Au 79 collisions at √ ___ S NN = 200 GeV. We find that, HYDJET + + 2.0.2 is more realistic in comparing the results of simulations with those of the experimental data published by the STAR-Collaboration.

NA61/SHINE facility at the CERN SPS: beams and detector system

NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) is a multi-purpose experimental facility to study hadron production in hadron-proton, hadron-nucleus and nucleus-nucleus collisions at the CERN Super Proton Synchrotron. It recorded the first physics data with hadron beams in 2009 and with ion beams (secondary 7Be beams) in 2011.NA61/SHINE has greatly profited from the long development of the CERN proton and ion sources and the accelerator chain as well as the H2 beamline of the CERN North Area. The latter has recently been modified to also serve as a fragment separator as needed to produce the Be beams for NA61/SHINE. Numerous components of the NA61/SHINE set-up were inherited from its predecessors, in particular, the last one, the NA49 experiment. Important new detectors and upgrades of the legacy equipment were introduced by the NA61/SHINE Collaboration.This paper describes the state of the NA61/SHINE facility — the beams and the detector system — before the CERN Long Shutdown I, which started in March 2013.

Hadron physics at KLOE and KLOE-2

The KLOE experiment at the Frascati ϕ-factory collected large samples of light mesons, providing precise knowledge of their decay dynamics. The η → π+π−γ decay has been studied to search for a possible contribution from chiral anomaly, while a new preliminary high statistics Dalitz plot analysis of the η → π+π−π0 will increase the accuracy of the light quark mass ratio. Pseudoscalar production associated to internal conversion of the photon into a lepton pair allows the measurement of the form factor Fp(q12 = Mϕ2, q22 > 0) in the kinematical region of interest for the VMD model. Detailed study of such decays has been performed both for ϕ → ηe+e− and ϕ → π0e+e− processes. Moreover, data collected at √s have been used to study hadron production in γγ interactions, providing the most precise measurement of the Γ(η → γγ) partial width.

Centrality and transverse momentum dependencies of minijets and hadrons in Au-Au collisions

In the study of hadron production in Au-Au collisions at RHIC minijets play an important role in generating shower partons in the intermediate \ppt\ region. Momentum degradation of the hard and semihard partons as they traverse the inhomogeneous medium at various azimuthal angles results in a complicated convolution of geometrical, nuclear and dynamical factors that cannot usually be described in a transparent way. In this work a compact formula is found that represents the inclusive distributions of minijets of any parton type at the surface of the medium for any collision centrality. They take into account the contributions from all initiating partons created at any point in the medium. By comparing with the case of no energy loss, a ratio has been determined that is analogous to the nuclear modification factor for minijets. Phenomenological reality of such distributions is examined by calculating the hadronization of the minijets in the recombination model. Good fits of the data on pion, kaon and proton production throughout the intermediate \ppt\ region have been obtained by adjusting the parameters controlling the magnitude of the thermal partons and the degradation rates of the semihard partons. The result gives support to the minijet spectra at any centrality on the one hand, and the hadronization procedure used on the other. An important property made manifest in this study is that quarks and gluons must not lose energy in the same way because the partons form mesons and baryons differently by recombination and the momenta of quarks and gluons must be degraded at different rates in order to reproduce the experimental pion and proton spectra. This is a feature that renders invalid the notion of parton-hadron duality or other hadronization schemes based on similar ideas.

Jet Fragmentation via Recombination of Parton Showers

We study hadron production in jets by applying quark recombination to jet shower partons. With the jet showers obtained from PYTHIA and augmented by additional non-perturbative effects, we compute hadron spectra in e+ + e−− collisions at GeV. Including contributions from resonance decays, we find that the resulting transverse momentum spectra for pions, kaons, and protons reproduce reasonably those from the string fragmentation as implemented in PYTHIA.

Status and plans of the ion program of NA61 at the CERN SPS

Abstract The NA61/SHINE at the CERN SPS is a new experiment to study hadron production in p+p, p+A, h+A and A+A interactions. The main goal of the NA61 ion program is to explore the phase diagram (T − µB) of strongly interacting matter. In particular, we plan to study the properties of the onset of deconfinement and to search for the signatures of the critical point. A two-dimensional scan of the phase diagram will be performed by varying the energy (13A–158A GeV) and system size (p+p, Be+Be, Ar+Ca, Xe+La) of collisions. This paper summarizes the status and plans of the NA61/SHINE ion program. In particular the detector upgrades, data taking schedule and the first results on spectra and correlations are discussed.