Search

Recently, it has been shown that the theory in the quadratic gauge on 4-sphere, 4 consists of two phases namely, the confined and the deconfined phases. A suitable finite field-dependent Becchi–Rouet–Stora–Tyutin (FFBRST) transformation interrelates two different gauge fixed theories. In this paper, we use the FFBRST technique on the curved space for the first time and elaborate a novel application of it. We propose two different formulations of this technique that transform the deconfined phase action on sphere to the confined phase action on sphere inside the quadratic gauge. Both proposed passages change the phase with BRST invariance to the phase without BRST invariance unlike usual connections where the FFBRST operation leaves the BRST symmetry intact and there is a unique field theoretic essence of them, which makes them particularly important to study. Thus, the two different field redefinitions act as a new mechanism that execute phase transition between two real QCD phases on 4-sphere other than ghost condensation process. [ABSTRACT FROM AUTHOR]

In this paper, we tentatively assign the Y (4 2 3 0) as the vector tetraquark state with a relative P-wave between the scalar diquark pair, and explore the three-body strong decays Y (4 2 3 0) → D ̄ ∗ − D ∗ 0 π + , D ̄ ∗ − D 0 π + , J ∕ ψ π + π − and J ∕ ψ K + K − with the light-cone QCD sum rules by assuming contact four-meson coupling constants. The resulting partial decay widths are too small to account for the experimental data, and we expect those decays take place through an intermediate meson. We can search for the intermediate states and precisely measure the branching fractions to diagnose the nature of the Y states. [ABSTRACT FROM AUTHOR]

Among the known elementary particles, 15 are not massless. In the Lagrangian of the standard model, the Higgs particle couples to all 15 of them to give them their respective masses. In this paper, a new model is proposed, where in the Lagrangian, the Higgs particle couples only to the four heaviest known elementary particles t , H , Z and W , all with masses in the vicinity of 1 0 0 GeV ∕ c 2 , but not to the other 11. In this model, the masses of these 11 elementary particles that do not couple directly to the Higgs particle are generated by radiative corrections. Because of the reduction of the number of terms in the Lagrangian, this model is referred to as the basic standard model. By studying how the bottom quark can acquire a mass, it is found that there must be a relation between the three gauge coupling constants of the gauge group U (1) × S U (2) × S U (3). This relation between these coupling constants is the first prediction, on purely theoretical grounds without using any experimental input, of the basic standard model, and is studied in some detail. In particular, this new prediction is found to be in good agreement with experimental measurements. [ABSTRACT FROM AUTHOR]

Understanding the phase diagram of the QCD matter is one of the ultimate goals in high-energy nuclear physics. Event-by-event fluctuations of conserved charges are believed to be sensitive to the QCD phase structures. In this paper, we will review the measurements carried out in the Beam Energy Scan program at RHIC. Our focus will be on the technical details to overcome various difficulties of the measurements. We will also discuss about the current interpretations on the results and future prospects. [ABSTRACT FROM AUTHOR]

This paper presents a method for extracting the parton distribution functions (PDFs) at small momentum fractions x and at the next-to-leading order (NLO) accuracy in perturbative quantum chromodynamics. It turns out that the PDFs can be described by the "Fractal" or self-similar distributions at low x below x < 0. 0 1. To this end, a simple parametrization for the unintegrated PDFs based on the "Fractal" approach is considered. These functions have self-similar behavior at low x and k t 2 for sea quarks and have self-similar behavior at low x for gluon distribution. By integration from these transverse momentum distributions (TMDs), the initial input densities are obtained and the model's free parameters are then calculated using the experimental data released by the HERA experiment. The small- x experimental datasets on electron–proton ( e − p) and positron–proton ( e + p) for natural current (NC) interactions in deep inelastic scattering (DIS) processes at HERA for the range of 1. 2 < Q 2 < 5 0 0 (GeV2) and x < 0. 0 1 are included in this analysis. The uncertainty estimations in this analysis are carried out using the standard "Hessian" method. Considering the overall value of χ 2 ∕ dof and theory-to-data comparisons, the results indicate good agreements between the experimental datasets and the theoretical predictions. A detailed comparison is also presented between the model's predictions for the relevant small- x observable and recent parametrizations for the PDFs. [ABSTRACT FROM AUTHOR]

The discovery of hot and dense quantum chromodynamics (QCD) matter, known as Quark–Gluon Plasma (QGP), is an essential milestone in understanding the finite temperature QCD medium. Experimentalists around the world collect an unprecedented amount of data in heavy ion collisions, at Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory (BNL) in New York, USA, and at the Large Hadron Collider (LHC), at CERN in Geneva, Switzerland. The experimentalists analyze these data to unravel the mystery of this new phase of matter that filled a few microseconds old universe just after the Big Bang. Recent advancements in theory, experimental techniques, and high computing facilities help us to better interpret experimental observations in heavy ion collisions. The exchange of ideas between experimentalists and theorists is crucial for the characterization of QGP. The motivation of this first conference, named Hot QCD Matter 2022 is to bring the community together to have a discourse on this topic. In this paper, there are 36 sections discussing various topics in the field of relativistic heavy ion collisions and related phenomena that cover a snapshot of the current experimental observations and theoretical progress. This paper begins with the theoretical overview of relativistic spin-hydrodynamics in the presence of the external magnetic field, followed by the Lattice QCD results on heavy quarks in QGP. Finally, it concludes with an overview of experimental results. [ABSTRACT FROM AUTHOR]

In this paper, we obtain the integrated flavor asymmetry of the sea quarks in the proton, ∫ 0 1 (d ̄ − ū) d x , with the help of the truncated moments approach elaborated in our previous papers. We use the difference between the light sea-quark distributions d ̄ − ū extracted from Drell–Yan (DY) NuSea/E866 measurements of the cross-section ratio σ p d / σ p p and from the recent global analysis of deep inelastic scattering (DIS) F 2 p − n data incorporating the reanalyzed neutron structure function. In our analysis, we also include the most recent DY data from the Fermilab SeaQuest/E906 experiment. [ABSTRACT FROM AUTHOR]

Construction of future Muon Collier (or dedicated μ -ring) tangential to the energy frontier h h colliders will give opportunity to realize μ p and μ A collisions at multi-TeV center-of-mass energies with sufficiently high luminosities. Obviously, such colliders will essentially enlarge the physics search potential of corresponding muon and hadron colliders for both the SM (especially for clarifying QCD basics and confinement hypothesis) and BSM phenomena. In addition, they will provide parton distribution functions for adequate interpretation of energy frontier h h colliders' and cosmic ray experiments data. This paper is devoted to review of main parameters of μ h colliders proposed until now. [ABSTRACT FROM AUTHOR]

In this paper, a next-to-next-to-leading order (NNLO) quantum chromodynamics (QCD) calculation of gluon distribution function at small- x is presented. The gluon distribution function is explored analytically in the Dokshitzer–Gribov–Lipatov–Altarelli–Parisi approach by a Taylor expansion at small- x as two first-order partial differential equations in two variables: Bjorken x and t (t = ln ( Q 2 Λ 2 )). We have solved the system of equations at LO, NLO and NNLO, respectively, by Lagrange's method. The resulting analytical expressions are compared with the available global parton distribution function fits as well as with the results of the Block–Durand–McKay model. We have further performed an χ 2 test to check the compatibility of our predictions and observed that our results can be consistently described in the context of perturbative QCD. A comparative analysis of the obtained results at LO, NLO and NNLO reveals that the NNLO approximation has a significant contribution to the gluon distribution function particularly in the small- x region. [ABSTRACT FROM AUTHOR]

In this paper, we apply the method of QCD sum rules to study the doubly heavy tetraquark states Q Q q ̄ n ̄ with spin-parity J P = 1 + and strangeness S = 0 , − 1 using careful estimates of the Borel and threshold parameters involved. Masses of the doubly bottom and charmed tetraquarks with isospin I = 0 , 1 / 2 , 1 are computed precisely via taking into account multifarious condensates up to dimension 10. Compared with the two-heavy meson thresholds, we find that all nonstrange doubly-bottom tetraquarks and a doubly-charmed tetraquarks associated with J 3 with J P = 1 + are stable against strong decay into two bottom mesons while a doubly-charmed tetraquark associated with current J 2 is unstable against strong decay. By the way, weak decay widths of the doubly bottom tetraquarks are also given. [ABSTRACT FROM AUTHOR]

In the paper, we construct eight color singlet–singlet-type five-quark currents with distinguished isospins to study the D ̄ Ξ ′ , D ̄ Ξ c ∗ , D ̄ ∗ Ξ c ′ and D ̄ ∗ Ξ c ∗ molecular states with strangeness via the QCD sum rules. Numerical results show that the central values of the pentaquark masses with higher (lower) isospin are slightly above (below) the thresholds of the corresponding meson–baryon pairs, and support assigning the P c s (4 4 5 9) as the D ̄ Ξ c ∗ molecular state with the quantum numbers I J P = 0 3 2 − . The other predictions can be confronted to the experimental data in the future. [ABSTRACT FROM AUTHOR]

In this paper, we present the charged particles jet cross-section study in p p and p P b collisions at s N N = 5. 0 2 ,TeV using PYTHIA8 (PYTHIA8.186 and PYTHIA8.306) and HIJING 2.0 models, in kinematic range of 5 < p T < 1 0 0 ,GeV/c for p p collisions and 2 0 < p T < 1 2 0 ,GeV/c for p P b collisions. The jets are reconstructed for R = 0. 2 , 0.3, 0.4 and 0.6 for the pseudorapidity interval of | η | < 0.9-R. The jets algorithms: cell jet and slow jet inside PYTHIA8.186 and anti- k T algorithm using HIJING 2.0 have been used for Monte Carlo simulations. The simulation results are then compared with measurements of the ALICE experiment. It is observed that all models' predictions are lower than experimental data up to p T = 2 0 ,GeV/c; after that, the Monte Carlo study of Cell and slow jet satisfies the experimental data. The CR tunes could not explain the ALICE data at high p T values due to nonperturbative QCD effects. We have also calculated the nuclear modification factor R p P b , and no clear suppression has been seen in the case of p P b collisions. The results from the models indicate that the QGP is not formed and that the cold nuclear matter effect exists in pPb collisions. [ABSTRACT FROM AUTHOR]

The prediction of properties of the low-energy portion of the hadronic spectrum is a challenging task which, up to day, is still tentatively given due to the nonperturbative nature of quantum chromodynamics (QCD) at low energies. In this paper, we are exploring the validity of the SO(4) scheme, as a representative of the fundamental QCD structure of meson-like states in the region below 2.5 GeV. We have focused our attention on the calculation of the energy and width of meson states of various spin, isospin and parities. [ABSTRACT FROM AUTHOR]

In this paper, we construct the diquark–diquark–diquark-type vector six-quark currents to investigate the vector and scalar hexaquark states in the framework of the QCD sum rules in a consistent way, and make predictions for the hexaquark masses. We can search for the fully heavy hexaquark states in the di- Ω c c c and di- Ω b b b invariant mass spectra in the future. Combined with our previous works on the fully heavy tetraquark states and pentaquark states, the present predictions can shed light on the nature of the fully heavy multiquark states. [ABSTRACT FROM AUTHOR]

In this paper, we present here a detailed study of several observables as a function of pseudorapidity from several hadron production models commonly used for extended air shower simulations and compare these predictions with p p collisions measured by the CMS experiment at s = 1 3 TeV. To facilitate the model/data comparisons, the pseudorapidity binning used in the energy density spectra data was also applied to the Monte Carlo analysis (3. 1 5 < η < 5. 2 and − 6. 6 < η < − 5. 2). Given that no model currently describes the full breadth of available hadronic collision data, four independent models were used in the comparison study, each with differences in the handling of soft quantum chromodynamics processes, in particular. The analysis results show that predictions from EPOS-LHC provide good agreement with the data, in contrast with the other models used in the study (QGSJETII-04, DPMJET-3.19, Sibyll2.3d). Significant modifications may be required in the rest of the model-based generators for them to provide a better description of the experimental observations. [ABSTRACT FROM AUTHOR]

In this paper, we study the pion-nucleon sigma term in Dyson–Schwinger equations approach of QCD with a three-constituent-quark approximation. The constituent quark mass is defined by the quark mass function obtained from the quark gap equation with various quark-gluon vertex and effective interaction models. We investigate the parameter dependence of the numerical results with fixed values of chiral condensate. We found that in all cases the numerical results of the pion-nucleon sigma term decrease with increasing constituent quark mass. Quantitatively, the dependence is insensitive to different interaction models, but is quite different with different quark-gluon vertices. Concerning the experimental results, we give the proper model and parameter range with which the theoretical value of pion-nucleon sigma term is consistent with the experiments. [ABSTRACT FROM AUTHOR]

In this paper, we examine, in the 't Hooft renormalization scheme, the analytic running coupling α ̄ t (Q 2) in QCD, using the two-loop β -function with positive expansion parameters β 0 and β 1 . An exact integral representation is derived for this causal coupling, which is fully expressed in terms of the imaginary part of the Lambert function W. This integral form manifestly accounts for the universal value of the infrared limit α ̄ t (Q 2 = 0) = 4 π / β 0 . [ABSTRACT FROM AUTHOR]

In this paper, a search for power-law fluctuations with fractality and intermittency analysis to explore the QCD phase diagram and the critical point is summarized. Experimental data on self-similar correlations and fluctuations with respect to the size of phase–space volume in various high energy heavy-ion collisions are presented, with special emphasis on background subtraction and efficiency correction of the measurement. Phenomenological modeling and theoretical work on the subject are discussed. Finally, we highlight possible directions for future research. [ABSTRACT FROM AUTHOR]

The conventional quark mass is not continuous at thresholds. In this paper, we derive matching-invariant quark masses which are continuous everywhere. They are generally expanded as an obvious function of the logarithmic Λ scaled energy. The expansion coefficients are related to the gamma and beta functions, with concretization to four-loop level. Due to the maximal elimination of their direct dependence on the coupling with large uncertainties, the new expressions for quark masses converge much fast and accurate. [ABSTRACT FROM AUTHOR]

Quantum chromodynamics is a fundamental non-Abelian gauge theory of strong interactions. The physical quantum chromodynamics vacuum state is a linear superposition of the n -vacua states with different topological numbers. Because of the configuration of the gauge fields, the tunneling events can induce the local parity-odd domains. Those interactions that occur in these domains can be affected by these effects. Considering the hadron (nucleon) system, we introduce the parity-odd parton distribution functions in order to describe the parity-odd structures inside the hadron in this paper. We obtain 8 parity-odd parton distribution functions at leading twist for spin-1/2 hadrons and present their properties. By introducing the parity-odd quark–quark correlator, we find the parity-odd effects vanish from the macroscopic point of view. In this paper, we consider the high energy semi-inclusive deeply inelastic scattering process to investigate parity-odd effects by calculating the spin asymmetries. [ABSTRACT FROM AUTHOR]

In this paper, we use the self-consistent mean field approximation to study the Quantum Chromodynamics (QCD) phase transition. In the self-consistent mean field approximation of the Nambu–Jona-Lasinio (NJL) model, a parameter α is introduced, which reflects the weight of "direct" channel and the "exchange" channel and needs to be determined by experiments (as mentioned in a recent work [T. Zhao, W. Zheng, F. Wang, C.-M. Li, Y. Yan, Y.-F. Huang and H.-S. Zong, Phys. Rev. D100, 043018 (2019)], the results with α = 0. 9 are in good agreement with astronomical observation data on the latest binary neutron star merging. This indicates that the contribution of "exchange" channel should be considered, and α = 0. 9 is a possible choice). By comparing the results with different parameter α 's (α = 0 , α = 0. 5 and α = 0. 9), we study the influence of "exchange" channel on the behavior of the solutions of the quark gap equation and the critical point of chiral phase transition. Our results show that the second-order chiral phase turns to the crossover from the chiral limit to the non-chiral limit around μ = 3 6 0 MeV in the case of α = 0. 9. The difference of the quark mass with different α 's mainly occurs in the intermediate temperatures for the different fixed chemical potentials. At zero temperature and the chemical potential μ = 3 3 4 MeV there will be two solutions (including a meta-stable solution) of gap equation with α = 0 , and as α increases it will be only one solution left (the meta-stable solution will disappear until α = 0. 5). Besides, the discrepancy of the critical temperature (above which the pseudo-Wigner solution and negative Nambu solution will disappear) in the three cases of α = 0 , 0. 5 , 0. 9 will become large when the chemical potential increases. [ABSTRACT FROM AUTHOR]

In this paper, we put our focus towards describing the nonperturbative effects in the properties of hadrons made from the light-heavy and the heavy–heavy quarks in the framework of Instanton Liquid Model (ILM) of QCD vacuum. The main features of ILM and its applicability in the heavy quark sector are briefly discussed. The properties of gluonic systems, the light and heavy quark correlators in the instanton background are also analyzed. We demonstrate that the consideration of both, perturbative and nonperturbative, gluon effects in the instanton background for a single heavy quark leads to the mass shift due to the direct-instanton nonperturbative and ILM modified perturbative contributions, respectively. For the interacting heavy quark and heavy anti-quark, the potential consists of the direct instanton-induced part and the one-gluon exchange (OGE) perturbative part. OGE interactions are screened at large distances due to the nonperturbative dynamics. The estimation of instanton contributions in the phenomenological Cornell-type potential model is presented. In relation to the experimental data, the charmonium properties, the role of instanton effects in their spectra and transitions are discussed. The main features of heavy-light quark systems in the instanton generated background are also discussed. As an example, we consider the process of pion emissions by the exited heavy quarkonium. We show that there is a sizable correction (∼ 2 0 %) to the dipole approximation for the process ψ (2 S) → J / ψ π + π − . [ABSTRACT FROM AUTHOR]

In this paper, the mass spectra of mesons with one or two heavy quarks and their diquarks partners are estimated within a nonrelativistic framework by solving Schrödinger equation with an effective potential inspired by a symmetry preserving Poincaré covariant vector–vector contact interaction model of quantum chromodynamics. Matrix Numerov method is implemented for this purpose. In our survey of mesons with heavy quarks, we fix the model parameter to the masses of groundstates and then extend our calculations for radial excitations and diquarks. The potential model used in this work gives results which are in good agreement with experimental data and other theoretical calculations. [ABSTRACT FROM AUTHOR]

Quantum chromodynamics (QCD), the theory of the strong interactions, involves quarks interacting with non-Abelian gluon fields. This theory has many features that are difficult to impossible to see in conventional diagrammatic perturbation theory. This includes quark confinement, mass generation and chiral symmetry breaking. This paper is a colloquium level overview of the framework for understanding how these effects come about. [ABSTRACT FROM AUTHOR]

In this paper, we give a brief review of recent theoretical studies of double prompt J / ψ production at the FNAL Tevatron and the CERN LHC, to which both single- and double-parton-scattering processes contribute. In single parton scattering, we mainly present the results computed within the framework of non-relativistic quantum chromodynamics factorization combined with one of the two approaches to describe the parton inside the (anti)proton, the collinear parton model and the parton Reggeization approach. The contributions from double parton scattering calculated with different values of σ eff are also discussed. We conclude that, in double prompt J / ψ hadroproduction, there remain some differences between theoretical predictions and experimental measurements. [ABSTRACT FROM AUTHOR]

When tunneling events induced by nontrivial configurations of the quantum chromodynamics gauge fields are taken into consideration, parity violating quantities emerge. Based on this consideration, parity-odd fragmentation functions can be introduced in the high energy reactions. In this paper, we calculate the differential cross-section in terms of both the parity-even and parity-odd fragmentation functions in semi-inclusive electron positron annihilation process. Semi-inclusive implies that not only a vector meson in one jet but also the back-to-back jet is measured in this reaction. According to the differential cross-section, we further calculate the azimuthal asymmetries and hadron polarizations in terms of fragmentation functions. A method of measuring the parity violating effects in the semi-inclusive annihilation process is suggested. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the mass spectrum of the ground state hidden-charm tetraquark molecular states without strange, with strange and with hidden-strange via the QCD sum rules in a comprehensive way and revisit the assignments of the X , Y , Z states in the scenario of tetraquark molecular states consistently based on the QCD sum rules. [ABSTRACT FROM AUTHOR]

In this paper, one uses a damped potential to present a description of the running coupling constant of QCD in the confinement phase. Based on a phenomenological perspective for the Debye screening length, one compares the running coupling obtained here with both the Brodsky–de Téramond–Deur and the Richardson approaches. The results seem to indicate the model introduced here corroborate the Richardson approach. Moreover, the Debye screening mass in the confinement phase depends on a small parameter, which tends to vanish in the nonconfinement phase of QCD. [ABSTRACT FROM AUTHOR]

In this paper, we study the scalar-diquark–scalar-diquark–antiquark-type u d s c c ̄ pentaquark state with the QCD sum rules, the predicted mass M P = 4. 4 7 ± 0. 1 1 GeV is in excellent agreement with the experimental data 4 4 5 8. 8 ± 2. 9 − 1. 1 + 4. 7 MeV from the LHCb collaboration, and supports assigning the P c s (4 4 5 9) to be the hidden-charm pentaquark state with the spin-parity J P = 1 2 − . We take into account the flavor S U (3) mass-breaking effect, and estimate the mass spectrum of the diquark–diquark–antiquark-type u d s c c ̄ pentaquark states with the strangeness S = − 1. [ABSTRACT FROM AUTHOR]

In this paper, production of charmonium state 𝒬 in exclusive W → 𝒬 D s (∗) decays is analyzed in the framework of both leading order Non-relativistic Quantum Chromodynamics (NRQCD) and light-cone (LC) expansion models. Analytical and numerical predictions for the branching fractions of these decays in both the approaches are given. The typical value of the branching fractions is ∼ 1 0 − 1 1 and it turns out that the LC results are significantly larger than NRQCD ones (approximately two or four times increase depending on the quantum numbers of the final particles), so the effect of internal quark motion should be taken into account. Some rough estimates of color-octet contributions are presented and it is shown that these contributions could be comparable with color-singlet results. [ABSTRACT FROM AUTHOR]

The explanation of the small neutrino mass can be depicted using some handsome models like type-I and inverse seesaw where the Standard Model gauge singlet heavy right-handed neutrinos are deployed. The common thing in these two models is a lepton number violating parameter, however, its order of magnitude creates a striking difference between them making the nature of the right-handed heavy neutrinos a major play factor. In the type-I seesaw a large lepton number violating parameter involves the heavy right-handed neutrinos in the form of Majorana fermions while a small lepton number violating parameter being involved in the inverse seesaw demands the pseudo-Dirac nature of the heavy right-handed neutrinos. Such heavy neutrinos are accommodated in these models through the sizable mixings with the Standard Model light neutrinos. In this paper we consider the purely inverse seesaw scenario to study the pair production of the pseudo-Dirac heavy neutrinos followed by their various multilepton decay modes through the leading branching fraction at the leading order and next-to-leading order QCD at the LHC with a center-of-mass energy of 13 TeV and a luminosity of 3000 fb − 1 . We also consider a prospective 100 TeV hadron collider with luminosities of 3000 fb − 1 and 30,000 fb − 1 , respectively to study the process. Using anomalous multilepton search performed by the CMS at the 8 TeV with 19.5 fb − 1 luminosity we show prospective search reaches of the mixing angles for the three lepton and four lepton events at the 13 TeV LHC and 100 TeV hadron collider. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a relative P -wave to construct the doubly-charm axialvector diquark operator, then take the doubly-charm axialvector (anti-)diquark operator as the basic constituent to construct the scalar and tensor tetraquark currents to study the scalar, axialvector and tensor fully-charm tetraquark states with the QCD sum rules. We observe that the ground state à à -type tetraquark states and the first radial excited states of the A A -type tetraquark states have almost degenerated masses, where the à and A stand for the diquark operators with and without the relative P -wave, respectively, the broad structure above the J / ψ J / ψ threshold maybe consist of several diquark–antidiquark-type fully-charm tetraquark states. [ABSTRACT FROM AUTHOR]

Deep inelastic scattering is one of the best place to study hadron structures. In this paper we consider the target fragmentation region deep inelastic scattering process at leading twist. The calculations are carried out by applying the collinear expansion. In the collinear expansion formalism the multiple gluon scattering is taken into account and gauge links are obtained systematically and automatically. Quantum chromodynamics is a non-Abelian gauge theory of strong interactions in which parity symmetry can be violated by the nontrivial 𝜃 -vacuum tunneling effects. As a result, the axial vector current is induced. By defining and decomposing the parity-odd correlator we calculate both the parity-even and parity-odd contributions to the cross-section of the target fragmentation region deep inelastic scattering. We also present the positivity bounds for these fracture functions. [ABSTRACT FROM AUTHOR]

In this paper, I review recent progress in lattice-QCD calculations of hadron structure with an emphasis on nucleon structure. A wide range of nucleon observables are being studied in modern lattice calculations, and important progress has been made at physical pion mass, including the spin decomposition of the nucleon and the Bjorken- x dependence of hadron structure. Challenges and perspectives for future lattice hadron-structure calculations will be discussed. [ABSTRACT FROM AUTHOR]

Quantum chromodynamics is a non-Abelian gauge theory of strong interactions, in which the parity symmetry can be violated by the nontrivial 𝜃 -vacuum tunneling effects. The 𝜃 -vacuum induces the local parity-odd domains. Those reactions that occur in these domains can be affected by the tunneling effects and quantities become parity-odd. In this paper we consider the fragmentation process where parity-odd fragmentation functions are introduced. We present the fragmentation functions by decomposing the quark–quark correlator. Among the total 16 fragmentation functions, eight of them are parity conserved, and the others are parity violated. They have a one-to-one correspondence. Positivity bounds of these one-dimensional fragmentation functions are shown. To be explicit, we also introduce an operator definition of the parity-odd correlator. According to the definition, we give a proof that the parity-odd fragmentation functions are local quantities and vanish when sum over all the hadrons h. [ABSTRACT FROM AUTHOR]

In this paper, we consider a deformed AdS background and study the effect of deformation parameter on the pair production rate of the Schwinger effect. The electrostatic potential is important for the pair production in the holographic Schwinger effect. In this paper, we analyze the electrostatic potential in a deformed AdS background and investigate the effect of deformation parameter which may be useful to test the AdS/QCD. In the case of zero temperature, we find that the larger value of the deformation parameter leads to a smaller value of separation length of the test particles on the probe. Also, we find a finite maximum of separation length in the presence of modification parameter. [ABSTRACT FROM AUTHOR]

In this paper, the non-leptonic three-body decays B → K ∗ (8 9 2) K π , π π , K K are studied by introducing two-meson distribution amplitude for the K π , π π and K K pairs in naive and QCD factorization (QCDF) approaches, such that the analysis is simplified into quasi-two body decays. By considering that the vector meson is being ejected in factorization, the resonant and non-resonant contributions are analyzed by using intermediate mesons in Breit–Wigner resonance formalism and the heavy meson chiral perturbation theory (HMChPT), respectively. The calculated values of the resonant and non-resonant branching ratio of B → K ∗ (8 9 2) π π , B → K ∗ (8 9 2) K π and B → K ∗ (8 9 2) K K decay modes are compared with the experimental data. For B → K 0 ∗ (8 9 2) π + π − and B → K 0 ∗ (8 9 2) K + K − , the non-resonant contributions are about 70–80% of experimental data, for which the total results by considering resonant contributions are in good agreement with the experiment. [ABSTRACT FROM AUTHOR]

In this paper we derive Dyson–Schwinger hierarchy of the equations for the correlators of reggeized gluon fields in the framework of Lipatov's high energy QCD effective action formalism. 1 – 1 0 The explicit perturbative expressions for the correlators till correlator of four Reggeon fields inclusively are obtained and different perturbative schemes for the solutions of the equation for the two-field correlator are discussed. A correspondence between the correlators of reggeized gluon fields and Wilson line operators of longitudinal gluon field is established with the help of the results of Ref. 10. The connection between the JIMWLK-Balitsky formalism and Lipatov's effective action approach and applications of the obtained results are also discussed. [ABSTRACT FROM AUTHOR]

The understanding of the basic properties of the ultrahigh-energy extensive air showers is dependent on the description of hadronic interactions in an energy range beyond that probed by the LHC. One of the uncertainties present in the modeling of air showers is the treatment of diffractive interactions, which are dominated by nonperturbative physics and usually described by phenomenological models. These interactions are expected to affect the development of the air showers, since they provide a way of transporting substantial amounts of energy deep in the atmosphere, modifying the global characteristics of the shower profile. In this paper, we investigate the impact of diffractive interactions in the observables that can be measured in hadronic collisions at high energies and ultrahigh-energy cosmic ray interactions. We consider three distinct phenomenological models for the treatment of diffractive physics and estimate the influence of these interactions on the elasticity, number of secondaries, longitudinal air shower profiles and muon densities for proton-air and iron-air collisions at different primary energies. Our results demonstrate that even for the most recent models, diffractive events have a non-negligible effect on the observables and that the distinct approaches for these interactions, present in the phenomenological models, still are an important source of theoretical uncertainty for the description of the extensive air showers. [ABSTRACT FROM AUTHOR]

In the previous work [A. P. Balachandran and S. Vaidya, Eur. Phys. J. Plus 128, 118 (2013)], we have argued that the algebra of non-Abelian superselection rules is spontaneously broken to its maximal Abelian subalgebra, that is, the algebra generated by its completing commuting set (the two Casimirs, isospin and a basis of its Cartan subalgebra). In this paper, alternative arguments confirming these results are presented. In addition, Lorentz invariance is shown to be broken in quantum chromodynamics (QCD), just as it is in quantum electrodynamics (QED). The experimental consequences of these results include fuzzy mass and spin shells of coloured particles like quarks, and decay life times which depend on the frame of observation [D. Buchholz, Phys. Lett. B 174, 331 (1986); D. Buchholz and K. Fredenhagen, Commun. Math. Phys. 84, 1 (1982; J. Fröhlich, G. Morchio and F. Strocchi, Phys. Lett. B 89, 61 (1979); A. P. Balachandran, S. Kürkçüoğlu, A. R. de Queiroz and S. Vaidya, Eur. Phys. J. C 75, 89 (2015); A. P. Balachandran, S. Kürkçüoğlu and A. R. de Queiroz, Mod. Phys. Lett. A 28, 1350028 (2013)]. In a paper under preparation, these results are extended to the ADM Poincaré group and the local Lorentz group of frames. The renormalisation of the ADM energy by infrared gravitons is also studied and estimated. [ABSTRACT FROM AUTHOR]

In this paper, the evolutions of longitudinal proton structure function have been obtained at small x up to next-to-next-to-leading order using a hard Pomeron behavior. In our paper, evolutions of gluonic as well as heavy longitudinal structure functions have been obtained separately and the total contributions have been calculated. The total longitudinal structure functions have been compared with results of Donnachie-Landshoff (DL) model, Color Dipole (CD) model, kT factorization and H1 data. [ABSTRACT FROM AUTHOR]

This paper is devoted to systematic analysis of double charmonium production in exclusive Z-boson decays in the framework of non-relativistic quantum chromodynamics (NRQCD) and leading twist light-cone (LC) models. Theoretical predictions for branching fractions of all considered decays are presented. According to the obtained results in the case of the allowed helicity suppression rule processes, the effect of internal quark motion increases the branching fractions by a factor 1.5, while for forbidden reactions the LC predictions are strictly zero, while NRQCD ones are significantly smaller than for allowed. [ABSTRACT FROM AUTHOR]

Relativistic heavy-ion collisions provide an ideal environment to study the emergent phenomena in quantum chromodynamics (QCD). The chiral magnetic effect (CME) is one of the most interesting, arising from the topological charge fluctuations of QCD vacua, immersed in a strong magnetic field. Since the first measurement nearly a decade ago of the possibly CME-induced charge correlation, extensive studies have been devoted to background contributions to those measurements. Many new ideas and techniques have been developed to reduce or eliminate the backgrounds. This paper reviews these developments and the overall progress in the search for the CME. [ABSTRACT FROM AUTHOR]

Recently, electron vortices have attracted attention both experimentally and theoretically. A study on the Landau-Dirac problem is made to understand the nature of electron vortices. This line of investigation is motivated by the recent literature on the Landau problem that throws new insights on the nature of orbital angular momentum, i.e. canonical versus kinetic in the context of QCD. The significance of pure gauge vector potential, nontrivial topology and exchange of modular orbital angular momentum to understand the physical origin of electron vortices in the Landau-Dirac problem are new contributions of this paper. [ABSTRACT FROM AUTHOR]

The strong coupling constants not only are important to understand the strong interactions of the heavy baryons, but can also help us reveal the nature and structure of these baryons. Additionally, researchers indeed have made great efforts to calculate some of the strong coupling constants, , , , , , , , , , , , , , , , etc. In this paper, we analyze the strong vertices and using the three-point QCD sum rules under the Dirac structure of . We perform our analysis by considering the contributions of the perturbative part and the condensate terms of and . After the form factors are calculated, they are then fitted into analytical functions which are used to get the strong coupling constants for these two vertices. The final results are and . [ABSTRACT FROM AUTHOR]

In this paper, we describe our studies of the sigma meson, , using two-pion correlation functions. We use lattice quantum chromodynamics in the quenched approximation with so-called clover fermions. By working at unphysical pion masses we are able to identify a would-be resonance with mass less than , and then extrapolate to the physical point. We include the most important annihilation diagram, which is 'partially disconnected' or 'single annihilation'. Because this diagram is quite expensive to compute, we introduce a somewhat novel technique for the computation of all-to-all diagrams, based on momentum sources and a truncation in momentum space. In practice, we use only modes, so the method reduces to wall sources. At the point where the mass of the pion takes its physical value, we find a resonance in the two-pion channel with a mass of approximately MeV, consistent with the expected properties of the sigma meson, given the approximations we are making. [ABSTRACT FROM AUTHOR]

In this paper, we construct and calculate non-perturbative path integrals in a multiply-connected spacetime. This is done by summing over homotopy classes of paths. The topology of the spacetime is defined by Einstein-Rosen bridges (ERB) forming from the entanglement of quantum foam described by virtual black holes. As these 'bubbles' are entangled, they are connected by Planckian ERBs because of the conjecture. Hence, the spacetime will possess a large first Betti number . For any compact 2-surface in the spacetime, the topology (in particular the homotopy) of that surface is non-trivial due to the large number of Planckian ERBs that define homotopy through this surface. The quantization of spacetime with this topology - along with the proper choice of the 2-surfaces - is conjectured to allow non-perturbative path integrals of quantum gravity theory over the spacetime manifold. [ABSTRACT FROM AUTHOR]

A general, and very basic introduction to QCD sum rules is presented, with emphasis on recent issues to be described at length in other papers in this issue. Collectively, these papers constitute the proceedings of the International Workshop on Determination of the Fundamental Parameters of QCD, Singapore, March 2013. [ABSTRACT FROM AUTHOR]

In this paper, we report an analysis of partial momentum fractions carried by quarks and gluons in six alternative phenomenological models of proton structure function valid in limited small regions: , to 6; the limits being determined by phenomenological range of validity in each model. Since the physics of small is not completely understood at this point, we have considered both self-similarity-based as well as QCD-based models. The procedure by which one can determine the applicability ranges in and of the models is presented. We find that while the self-similarity-based models with linear rise in has limited phenomenological ranges of validity, an improved version with linear rise in has a wider phenomenological range. We then compare the partial momentum fractions in all the small models. Our analysis implies that the role of small sea quarks in calculating the second moments of parton distribution is minor one. We have also made a comprehensive comparison of all the phenomenological models considered to the available perturbative QCD, lattice QCD as well as Ads/QCD results. [ABSTRACT FROM AUTHOR]

Gerry Brown has played a major role in initiating and stimulating systematic work on the theories of nuclear forces. It is the purpose of this paper to review those theories - in his memory. [ABSTRACT FROM AUTHOR]