Transverse Momentum Distributions Research Articles

Thermodynamic signatures and phase transitions in high-energy Au–Au collision

In this study, we systematically investigate the dynamics of various hadrons namely π +, π −, K +, K −, p, p¯ , Λ, Λ¯ , Ξ− and Ξ¯+ produced in central Au–Au collisions. We analyze data of AGS and RHIC, which span a broad range of collision energies, ranging from sNN = 1.9 to 200 GeV. To analyze the transverse momentum (p T ) and transverse mass (m T ) distributions, we employ a two-component standard distribution function, achieving a very good representation of the experimental data across these energy regimes. We extract key thermodynamic parameters, including the effective temperature T, the mean transverse momentum 〈p T 〉, and the initial temperature T i , and analyze their dependence on the values of collision energy and particle mass. Our findings reveal a distinct transition behaviour around sNN=19.6GeV . Below sNN=19.6GeV , the values of T, 〈p T 〉, and T i increase monotonically for all hadrons due to higher energy transfer into the system. Above this energy threshold, these extracted parameters plateau, suggesting that the additional energy is utilized as latent heat for phase transition rather than increasing the system’s temperature. These observations delineate two distinct regions: a hadron-dominated region at lower energies and a parton-dominated region at higher energies, each potentially indicative of different phases of matter, with the latter possibly signalling the onset of a quark–gluon plasma. The study thus provides critical insights into the complex interplay of thermodynamics, phase transitions, and particle interactions in high-energy Au–Au collisions.

Extraction of unpolarized transverse momentum distributions from the fit of Drell-Yan data at N4LL

We present an extraction of unpolarized transverse momentum dependent parton distributions functions (TMDPDFs) and Collins-Soper kernel from the fit of Drell-Yan and weak-vector boson production data. The TMDPDF are parameterized, as commonly done, using their (large transverse momentum) asymptotic matching to PDF. The analysis is done at the next-to-next-to-next-to-next-to leading logarithmic accuracy (N4LL) (performed only approximately because PDF evolution is known so far at next-to-next-to leading order (NNLO)). The non-perturbative model used for TMDPDF is flavor dependent to reduce the colllinear PDF bias. The estimation of uncertainties is done with the replica method and, for the first time, it includes the propagation of uncertainties due to the collinear distributions.

Soft-gluon corrections in [formula omitted] production

We study higher-order QCD corrections for the associated production of a top-antitop quark pair and a W boson (tt¯W production) in proton-proton collisions. We calculate approximate NNLO (aNNLO) and approximate N3LO (aN3LO) cross sections, with second-order and third-order soft-gluon corrections added to the exact NLO QCD result, and we also include electroweak (EW) corrections through NLO. We calculate uncertainties from scale dependence, which are reduced at higher orders, and from parton distributions, and we also provide separate results for tt¯W+ and tt¯W− production. We compare our results to recent measurements from the LHC, and we find that the aN3LO QCD + NLO EW predictions provide improved agreement with the data. We also calculate differential distributions in top-quark transverse momentum and rapidity and find significant enhancements from the higher-order corrections. This is the first calculation of soft-gluon corrections in single-particle-inclusive kinematics for a 2→3 process where all final-state particles are massive.

Correlation of the hyperon potential stiffness with hyperon constituents in neutron stars and heavy-ion collisions

The breaking of SU(6) symmetry to a more general flavor SU(3) symmetry could serve as a potential explanation for the “hyperon puzzle” of neutron stars by adjusting the hyperon potentials. Specifically, when the soft relativistic mean-field (RMF) Λ hyperon potentials fall within the domains of chiral SU(3) interactions NLO13 with two-body forces, the maximum mass of neutron stars is expected to be lower than 2.0 M⊙, whereas it can exceed 2.0M⊙ if the RMF Λ hyperon potentials are sufficiently stiff to be consistent with those from chiral SU(3) interactions NLO13 with three-body forces. In our investigation involving these two types of Λ hyperon potentials, we explore how the hyperon yields and flows are affected in heavy-ion collisions. We find that the inclusion of hyperon potentials results in better agreement of the Λ directed flows with data but without clear differentiation in the stiffness of the hyperon potentials. Similarly negligent is the disparity in the rapidity distributions of the Λ collective flows predicted by the stiff and soft hyperon potentials. In contrast, the Λ collective flows beyond the central rapidity region turn out to be sensitive to the stiffness of the RMF equation of state (EOS) with the preference of a soft RMF EOS to a stiff one. Notably, the transverse momentum distributions of Λ hyperon production are sensitive to both the stiffness of the RMF EOS and Λ hyperon potential at high transverse momenta.

A direct probe of Λ potential in nuclear medium

Using the Liège intranuclear-cascade model together with the ablation model ABLA, an investigation is conducted into the effects of Λ potential in Λ-nucleus and Λ-hypernucleus-nucleus collisions across various beam energies. The findings show that the angle and transverse-momentum distributions of scattered Λ hyperon, the scattering cross section of the Λ hyperon in Λ-nucleus collisions as well as the rapidity distribution of Λ hyperon in Λ-hypernucleus-nucleus collisions are significantly influenced by the strength of the Λ potential in these scattering reactions across various beam energies. These demonstrations, unhindered by the uncertainties of Λ and hypernuclei productions in nuclear medium, allow for a direct investigation of the Λ potential, especially its momentum dependence. The criticality of probing the Λ potential is closely associated with the resolution of the “hyperon puzzle” in neutron stars.

High-energy QCD dynamics from bottom flavor fragmentation at the Hi-Lumi LHC

We study the inclusive production of hadrons with bottom flavor at the LHC and its luminosity upgrade. We describe the collinear fragmentation of singly b-flavored hadrons, B mesons and Λb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda _b$$\\end{document} baryons, via the KKSS07 determination of fragmentation functions, while for charmed B mesons, Bc(1S0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c(^1S_0)$$\\end{document} and Bc(3S1)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c(^3S_1)$$\\end{document} particles, we employ the novel ZCFW22 set, built on the basis of state-of-the-art nonrelativistic QCD inputs. We use the Jethad multimodular working environment to analyze rapidity and transverse-momentum distributions for observables sensitive to the associated emission of two hadrons or a hadron-plus-jet system. Our reference formalism is the NLL/NLO+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm{NLL/NLO^+}$$\\end{document} hybrid collinear and high-energy factorization, where the standard collinear description is improved by the inclusions of energy logarithms resummed up to the next-to-leading approximation and beyond. We provide corroborating evidence that b-flavor emissions act as fair stabilizers of the high-energy resummation, thus serving as valuable tools for precision studies of high-energy QCD. As a bonus, we highlight that the predicted production-rate hierarchy between noncharmed b-hadrons and charmed Bc(1S0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_c(^1S_0)$$\\end{document} mesons is in line with recent LHCb estimates. This serves as simultaneous benchmark both for the hybrid factorization and for the single-parton fragmentation mechanism based on initial-scale inputs calculated via the nonrelativistic QCD effective theory.

Tight focusing of the vector optical field with polarization varying along complex curves of the Poincaré sphere.

Different from the scalar optical field with spatially uniform polarization, the vector optical field exhibits inhomogeneous distribution of polarization on the cross section. Manipulating the variation of polarization in a single optical beam is important to acquire a flexible and controllable focused optical field. Previous studies mainly focused on the vector optical field with its polarization varying along a circular trajectory of the Poincaré sphere. Here, we demonstrate the tight focusing behaviors of the vector optical field with the polarization varying along complex curves of the Poincaré sphere, which is generated by the joint modulation of azimuthal phase and amplitude distributions of orthogonally polarized components. The longitudinal polarization component with a multipolar pattern in rotational symmetry can be achieved with similar distribution of the total focused field. The transverse and longitudinal spin angular momentum distributions in the focal space are discussed. Approximately pure transverse spin angular momentum can be constructed and manipulated in the focal space, which provides the possibility to manipulate the 3D spin flux for the applications of nano and spin photonics.

A precise measurement of the Z-boson double-differential transverse momentum and rapidity distributions in the full phase space of the decay leptons with the ATLAS experiment at s=8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s}=8$$\\end{document} TeV

This paper presents for the first time a precise measurement of the production properties of the Z boson in the full phase space of the decay leptons. This is in contrast to the many previous precise unfolded measurements performed in the fiducial phase space of the decay leptons. The measurement is obtained from proton–proton collision data collected by the ATLAS experiment in 2012 at s=8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s} = 8$$\\end{document} TeV at the LHC and corresponding to an integrated luminosity of 20.2 fb-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document}. The results, based on a total of 15.3 million Z-boson decays to electron and muon pairs, extend and improve a previous measurement of the full set of angular coefficients describing Z-boson decay. The double-differential cross-section distributions in Z-boson transverse momentum pT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p_{\ ext {T}}$$\\end{document} and rapidity y\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$y$$\\end{document} are measured in the pole region, defined as 80<mℓℓ<100\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$80< m^{\\ell \\ell }< 100$$\\end{document} GeV, over the range |y|<3.6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|y| < 3.6$$\\end{document}. The total uncertainty of the normalised cross-section measurements in the peak region of the pT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p_{\ ext {T}}$$\\end{document} distribution is dominated by statistical uncertainties over the full range and increases as a function of rapidity from 0.5–1.0% for |y|<2.0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|y| < 2.0$$\\end{document} to 2-7%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2-7\\%$$\\end{document} at higher rapidities. The results for the rapidity-dependent transverse momentum distributions are compared to state-of-the-art QCD predictions, which combine in the best cases approximate N4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^4$$\\end{document}LL resummation with N3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}LO fixed-order perturbative calculations. The differential rapidity distributions integrated over pT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p_{\ ext {T}}$$\\end{document} are even more precise, with accuracies from 0.2–0.3% for |y|<2.0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|y| < 2.0$$\\end{document} to 0.4–0.9% at higher rapidities, and are compared to fixed-order QCD predictions using the most recent parton distribution functions. The agreement between data and predictions is quite good in most cases.

System-size dependence of collective transverse flow in relativistic nuclear collisions

The transverse momentum distributions of identified hadrons (π±, K±, p, p, K0S, Λ, Λ, Ξ−, Ξ+, φ, Ω−, and Ω+) produced in Au+Au collisions at RHIC-BES energies are analyzed with Blast-Wave model and with Boltzmann-Gibbs statistics. The kinetic freeze-out temperature, the average transverse flow velocity and the flow profile exponent are extracted from the transverse momentum spectra of the particles. The study of system-size dependence of the kinetic freeze-out parameters showed that kinetic freeze-out temperature increases, while average transverse flow ve- locity decreases from central to peripheral collisions. The larger freeze-out temperature for peripheral collisions may indicate an earlier decoupling of the expanding system. For the same centrality class, it is observed that the transverse flow velocity and flow profile exponent have an increasing trend with increasing collision energy.

Comparative analysis of charged particle distributions in [formula omitted] collisions at [formula omitted] using Monte Carlo models and fitting functions

We conducted a detailed analysis of charged particle transverse momentum distributions using multiple Monte Carlo models – Pythia, HIJING, and QGSJET – compared against experimental data from the ATLAS detector in pp collisions at s=0.9TeV. Pythia emerged as the best among the models under study in representing most of the distributions due to its comprehensive modeling of parton showers, multiparton interactions, and underlying event dynamics, while QGSJET showed good results with the data in some of the distributions only. HIJING, however, was only able to replicate reduced phase-space distributions only.To further explore the collision medium and to extract important information about collective properties, we used the Tsallis-Pareto (TP) type function and the modified Hagedorn (MH) function. The Tsallis function enabled determination of the effective temperature (Teff) and the non-extensivity parameter (n1) while the MH function provided the kinetic freeze-out temperature (T0), transverse flow velocity (<βT>), and a secondary non-extensivity parameter (n2). Our investigation revealed changes in the effective freeze-out parameters based on event conditions. The Teff and <βT> derived from the TP and MH functions respectively exhibited higher values with a tighter pT cut of >500MeV compared to a more inclusive pT cut of >100MeV. Interestingly, the values of the non-extensivity parameters—n1 for the Tsallis function and n2 for the MH function were almost identical across both the experimental data and all three Monte Carlo models. These findings offer invaluable perspectives on the dynamics of charged particles in pp collisions at s=0.9TeV.

Analysis of charged hadrons’ transverse momentum distributions in p + Pb and Xe + Xe collisions at LHC energies

This paper is focused on comparative analysis of transverse momentum ( pT ) distributions across two different sets of experimental data from ALICE at the LHC, juxtaposing with the Monte-Carlo models EPOS-LHC and EPOS 1.99 simulations. The chosen collision sets have approximately same per nucleon energy. We analyze the transverse momentum spectra of hadrons ( π++π−, K++K− and p+p¯ ) in p+Pb collisions at sNN= 5.02 TeV, and Xe + Xe collisions at sNN= 5.44 TeV spanning a rapidity range of 0 < yCM < 0.5, centrality of 0 to 5% (the most central or head-on collisions). Analysis of the Hadrons yield is crucial for understanding the mechanism of underlying hadronization in the hot and dense quark matter produced in relativistic heavy ion collisions. The experimental results are compared with the predictions of hydrodynamic models EPOS-LHC and EPOS-1.99. It is notably found that the maximum yields of various particles occur at low pT. Furthermore, the comparison showed a slightly better agreement between experimental results and the predictions of the EPOS-LHC as opposed to that of EPOS-1.99. The EPOS-LHC model significantly shows an enhanced agreement with experimental results in the case of Xe+Xe collisions as compared to p+Pb collisions.

The transverse momentum distribution of J/ψ mesons produced in pp collisions at the LHC

The transverse momentum distribution of J/ψ mesons produced in pp collisions at the LHC

Forward dijet production at the LHC within an impact parameter dependent TMD approach

We investigate possible signatures of gluon saturation using forward p + A → j + j + X di-jet production processes at the Large Hadron Collider. In the forward rapidity region, this is a highly asymmetric process where partons with large longitudinal momentum fraction x in the dilute projectile are used as a probe to resolve the small x partonic content of the dense target. Such dilute-dense processes can be described in the factorization framework of Improved Transverse Momentum Distributions (ITMDs). We present a new model for ITMDs where we explicitly introduce the impact parameter (b) dependence in the ITMDs, to properly account for the nuclear enhancement of gluon saturation effects, and discuss the phenomenological consequences for p − Pb, p − Xe and p − O collisions at the LHC. While the case of p − p and e − p collisions is used to fix the model parameters, we find that, on average, the nuclear enhancement of the saturation scale is noticeably weaker than expected from naive scaling with a simple dependence on the atomic number. Since our model explicitly accounts for event-by-event fluctuations of the nuclear geometry, it can also be applied to study forward central correlations in p − A collisions.

Tunnelling of electrons via the neighboring atom

As compared to the intuitive process that the electron emits straight to the continuum from its parent ion, there is an alternative route that the electron may transfer to and be trapped by a neighboring ionic core before the eventual release. Here, we demonstrate that electron tunnelling via the neighboring atomic core is a pronounced process in light-induced tunnelling ionization of molecules by absorbing multiple near-infrared photons. We devised a site-resolved tunnelling experiment using an Ar-Kr+ ion as a prototype system to track the electron tunnelling dynamics from the Ar atom towards the neighboring Kr+ by monitoring its transverse momentum distribution, which is temporally captured into the resonant excited states of the Ar-Kr+ before its eventual releasing. The influence of the Coulomb potential of neighboring ionic cores promises new insights into the understanding and controlling of tunnelling dynamics in complex molecules or environment.

Determination of the strong-coupling constant from the Z-boson transverse-momentum distribution

The strong-coupling constant is determined from the low-momentum region of the transverse-momentum distribution of Z bosons produced through the Drell–Yan process, using predictions at third order in perturbative QCD. The analysis employs a measurement performed in proton-antiproton collisions at a centre-of-mass energy of s=1.96\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s} = 1.96$$\\end{document} TeV with the CDF experiment. The determined value of the strong coupling at the reference scale corresponding to the Z-boson mass is αS(mZ)=0.1191-0.0016+0.0013\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha _S(m_Z)= 0.1191^{+0.0013}_{-0.0016}$$\\end{document}.

Theoretical prediction of cosmic rays models for strange particles production at RHIC energy

This study conducts a comprehensive assessment of Monte Carlo models, including Sibyll, EPOS-LHC, and EPOS4, in the context of simulating strange and multi-strange hadron production within high-multiplicity proton–proton collisions at 200 GeV. The analysis reveals common trends across various particle types: models tend to overestimate low transverse momentum (pT) distributions and approach experimental data as pT increases. EPOS-LHC produce better predictions in the intermediate pT range. However, none of the models adequately reproduce pT distributions for Λ and Λ̄ particles, typically underpredicting the data. EPOS4_Hydro performs relatively better due to its ability to account for reduced particle multiplicity at high pT and energy redirection into flow. For Ξ and Ξ̄ particles, models underpredict distributions at high pT, except for EPOS4_Hydro, which consistently overpredicts. Additionally, the study delves into particle ratios, such as Λ̄/Λ and Ξ+/Ξ−, highlighting varying model performance. The mean transverse momentum increases with particle mass, and specific models demonstrate good fits for certain mass ranges. EPOS-LHC and EPOS4 with hydrodynamics were notably accurate for particles below 0.6 GeV. Within the mass range of 0.6 to 1.4 GeV, EPOS-LHC displayed the closest fit. However, particles surpassing 1.2 GeV showed higher accuracy with EPOS4 without hydrodynamics. These insights underscore the significance of selecting appropriate Monte Carlo models based on specific research requirements in high-energy physics.

A high-energy QCD portal to exotic matter: Heavy-light tetraquarks at the HL-LHC

By taking advantage of the natural stability of the high-energy resummation, recently discovered in the context of heavy-flavor studies, we investigate the inclusive hadroproduction of a neutral heavy-light, hidden-flavored tetraquark (Xcuc¯u¯ or Xbsb¯s¯ state), in association with a heavy (single c- or b-flavored) hadron or a light jet at the (HL-)LHC. We make use of the JETHAD multi-modular working package to provide predictions for rapidity, azimuthal-angle and transverse-momentum distributions calculated via the hybrid high-energy and collinear factorization, where the Balitsky–Fadin–Kuraev–Lipatov resummation of energy logarithms is supplemented by collinear parton densities and fragmentation functions. We rely upon the single-parton fragmentation mechanism, valid in the large transverse-momentum regime, to describe the tetraquark production. Our study represents a first attempt at bridging the gap between all-order calculations of high-energy QCD and the exotics.

Transverse momentum dependent distribution functions in the threshold limit

We apply the joint threshold and transverse momentum dependent (TMD) factorization theorem to introduce new threshold-TMD distribution functions, including threshold-TMD parton distribution functions (PDFs) and fragmentation functions (FFs). We apply Soft-Collinear Effective Theory and renormalization group methods to carry out QCD evolution for both threshold-TMD PDFs and FFs. We show the universality of threshold-TMD functions among three standard processes, i.e. the Drell-Yan production in pp collisions, semi-inclusive deep-inelastic scattering and back-to-back two hadron production in e+e− collisions. In the end, we present the numerical predictions for different threshold-TMD functions and also transverse momentum distributions at pp, ep, and e+e− collisions.

Transverse momentum distributions of the identified particles in mini–bias non-single diffracted p＋p collisions at 200 GeV

The transverse momentum (pT) distributions of hadrons stem from the probability distributions of deconfined colored partons known as pT distributions. This provides insights into various stages of nuclear collisions, ranging from the initial partonic phase to the later stages, including the directly measurable hadronization process. The objective is to analyze the pT distributions of identified particles: π+, π−, K+, K−, K0s, p, p̄, Λ, Λ̄, Σ+, Σ−. These analyses are conducted in mini-bias non-single diffracted p+p collisions at an energy of 200GeV. The goal is to accurately determine the kinetic freezeout parameters and the extent of statistical nonextensivity. The measurements from the STAR experiment are merged with simulations using DPMJET, PYTHIA, and Sibyll.3d Monte–Carlo Event Generators. The predictions from these models and the actual measurements are compared using statistical distributions employing the Tsallis-type of non-extensive statistics. While Pythia8 displays a closer alignment with the data in certain instances, it was observed that none of the event generators could accurately replicate the data for all charged particles across the entire range of pT. We examined how the effective temperature correlates with the rest mass of different particles. Our analysis revealed that the freezeout process for heavier particles tends to occur at lower temperatures. This suggests that heavier particles might reach an equilibrium state relatively rapidly during the freezeout stage. Additionally, we observed a pattern where the non-extensive parameter q decreases as the mass of the produced particles increases. This implies that lighter particles tend to reach equilibrium after the heavier ones. Furthermore, the average transverse momentum (<pT>) is greater for heavier particles, leading to an enhanced radial flow compared to lighter particles. This rising trend also indicates the likelihood of mini-jet production, contributing to color string fragmentation that becomes more pronounced with the increasing mass of the particles.

Quantum entanglement in top quark pair production

Top quarks, the most massive particles in the standard model, attract considerable attention since they decay before hadronizing. This presents physicists with a unique opportunity to directly investigate their properties. In this letter, we expand upon the work of G. Iskander, J. Pan, M. Tyler, C. Weber and O. K. Baker to demonstrate that even with the most massive fundamental particle, we see the same manifestation of entanglement observed in both electroweak and electromagnetic interactions. We propose that the thermal component resulting from protons colliding into two top quarks emerges from entanglement within the two-proton wave function. The presence of entanglement implies the coexistence of both thermal and hard scattering components in the transverse momentum distribution. We use published ATLAS and CMS results to show that the data exhibits the expected behavior.