arXiv subjects

Abolfazl Mirjalili

Publications and source records attributed to Abolfazl Mirjalili.

11 recordsLinked to original sources

arXiv2026

Nonlinear collective flow reveals the breakdown of quadrupole--hexadecapole scaling in heavy ion collisions

Determining the role of intrinsic hexadecapole deformation ($β_4$) in nuclear structure remains a long-standing challenge. Relativistic heavy-ion collisions provide a unique opportunity to address this problem by converting the initial nuclear geometry into the collective motion of the quark--gluon plasma (QGP). Using event-by-event viscous hydrodynamic simulations of ultra-central $^{238}$U+$^{238}$U collisions at $\sqrt{s_{NN}}=193$ GeV, we investigate whether higher-order collective flow can isolate the contribution of $β_4$ and test the $β_2-β_4$ correlation. We demonstrate that information carried by the sign of $β_4$ survives the QGP evolution and is enhanced through nonlinear hydrodynamic response: the fourth-order flow harmonic acquires its topology dependence predominantly from the linear response, whereas the sensitivity of the sixth-order harmonic originates almost entirely from nonlinear mode coupling. As a consequence, the nonlinear response coefficient $ξ_{6,222}$ cleanly separates the $(β_2,β_4)$ intrinsic nuclear topologies. These results establish the sign of $β_4$ as an experimentally accessible signature of deviations from the quadrupole--hexadecapole correlation, demonstrating that higher-order collective flow provides a direct probe of nuclear multipole structure while revealing how nonlinear QGP dynamics encode subtle higher-order geometric information into final-state observables.

nucl-th↗

arXiv2023

Recent data analysis to revisit the spin structure function of nucleon in Laplace space

Considering a fixed-flavor number scheme and based on laplace transdormation, we perform a leading-order and next-to-leading-order QCD analysis which are including world data on polarized structure functions $g_1$ and $g_2$. During our analysis, taking the DGLAP evolution, we employ the Jacobi polynomials expansion technique. In our recent analysis we utilize the recent available data and consequently include more data than what we did in our previous analysis. we obtain good agreements between our results for the polarized parton densities and nucleon structure functions with all available experimental data and some common parametrization models.

hep-ph↗

arXiv2022

Nucleon spin structure functions, considering target mass correction and higher twist effects at the NNLO accuracy and their transverse momentum dependence

Using recent and updated world data on polarized structure functions $g_1$ and $g_2$ we perform QCD analysis at the next-next-to-leading-order (NNLO) accuracy. We include also target mass correction and higher twist effect to get more precise results in our fitting procedure. To confirm the validity of our fitting results several sum rules are examined and we do a comparison for them with results from other models. In our analysis we employ Jacobi polynomials approach to obtain analytical solutions of the DGLAP evolution equations for parton distribution functions (PDFs). Using the extracted PDFs from our data analysis as input we also compute the $x$- and $\mathbf{p}_{T}$-dependence of some transverse momentum dependence (TMD) PDFs in polarized case, based on covariant parton model. These functions are naively even time-reversal (T-even) at twist-2 approximation. The results for TMDs are indicating proper and acceptable behaviour with respect to what are presented in other literatures.

hep-ph↗

arXiv2020

Mass corrections to the DGLAP equations

We propose a mass-dependent MOM scheme to renormalize UV divergence of unpolarized PDFs at one-loop order. This approach which is based on a once subtracted dispersion relation does not need any regulator. The overall counterterms are obtained from the imaginary part of large transverse momentum region in loop integrals. The mass-dependent characteristic of the scheme yields to mass-dependent splitting functions for the DGLAP evolution equations. While the flavor number is fixed at any renormalization scale, the decoupling theorem is automatically imposed by the mass-dependent splitting functions. The required symmetries are also automatically respected by our prescription.

hep-ph↗

arXiv2020

QCD analysis of non-singlet structure functions at NNLO accuracy, based on the Laplace transform

In this work, using the Laplace transformation technique we present our results for non-singlet quark distributions as well as nucleon structure function $F_2(x,Q^2)$ in unpolarized case at next-to-next-to-leading order (NNLO) QCD accuracy. We shall particularly compare our results for the sets of valence-quark parton distribution functions with the contemporary collaborations like CT14, CT18, MMHT14, MKAM16 and NNPDF. To construct the nucleon structure function we employ the expansion of Jacobi polynomials which is a suitable transform to convert the results of non-singlet structure function from the Laplace $s$-space to Bjorken $x$-space. We shall also consider the contributions of target mass correction as well as the higher twist effects at large-$x$ region for the proton and deuteron structure functions. Our results for the unpolarized quark distribution functions and nucleon structure functions are in good agreement with recent theoretical models and available experimental data.

hep-ph↗

arXiv2019

Nonsinglet polarized nucleon structure function in infrared-safe QCD

The polarized nucleon structure function in the nonsinglet case is investigated here by a new insight rather than conventional perturbative QCD (pQCD). For this purpose we note that the solution of the evolution equations in moment space involves noninteger powers of the coupling constant. Therefore it is possible to employ a new approach which is called fractional analytical perturbation theory Consequently, it is possible to remove the Landau singularities of the renormalized coupling, i.e., at the scales $Q \sim Λ$, using this approach. This provides an opportunity to continue the desired calculations toward small values of energy scales even less than the $Λ$ scale. To modify the analytical perturbation theory, a newer approach is introduced, called 2$δ$anQCD, in which the spectral function of the holomorphic coupling is parameterized in the low-energy region by two delta functions. This model gives us more reliable results for the considered QCD observables, even in the deep infrared region. We calculate the nonsinglet part of the polarized nucleon structure function, using the 2$δ$anQCD model, and compare it with the result from the underlying pQCD where both are in a new defined scheme, called the Lambert scheme. For this purpose we employ the anQCD package in the \textit{Mathematica} environment to establish the analytic (holomorphic) coupling constant. The results at various energy scales are also compared with the available experimental data, and it turns out that there is a good consistency between them. The results show that the obtained nucleon structure function at small energy scales has smoother behavior when using the 2$δ$anQCD model than the underlying pQCD. In fact the coupling constant in analytic QCD behaves moderately and it makes the result approach the available data in a better way.

hep-ph↗

arXiv2018

EMC effect in the next-to-leading order approximation based on the Laplace transformation

In this article, using Laplace transformation , an analytical solution is obtained for the DGLAP evolution equation at the next-to-leading order of perturbative QCD. The technique is also employed to extract, in the Laplace $s$-space, an analytical solution for the nuclear structure function, $F_2^A(x, Q^2)$. Firstly, the results for separate nuclear parton distributions for all parton types are presented which include valence quark densities, the anti-quark and strange sea PDFs and finally the gluon distribution. Based on the Laplace transformation, the obtained parton distribution functions and the nuclear structure function in the $x$-space are compared with the results from the [Phys.\ Rev.\ C series 86, 064301 (2012)] model. Our calculations are in good agreement with the available DIS experimental data as well as theoretical models which contain both small and large values of $x$-Bjorken variable. We compare our nuclear PDFs sets with those from other recent collaborations, in particular with the [ nCTEQ15 ] and [ HKN07] sets. The comparison between our results and those from the literature indicates a good agreement .

hep-ph↗

arXiv2017

Analytic derivation of the next-to-leading order proton structure function $F_2^p(x, Q^2)$ based on the Laplace transformation

An analytical solution based on the Laplace transformation technique for the DGLAP evolution equations is presented at next-to-leading order accuracy in perturbative QCD. This technique is also applied to extract the analytical solution for the proton structure function, $F_2^p(x, Q^2)$, in the Laplace $s$-space. We present the results for the separate parton distributions for all parton species, including valence quark densities, the anti-quark and strange sea parton distribution functions (PDFs), and the gluon distribution. We successfully compare the obtained parton distribution functions and the proton structure function with the results from {\tt GJR08} and {\tt KKT12} parametrization models as well as the $x$-space results using {\tt QCDnum} code. Our calculations show a very good agreement with the available theoretical models as well as the deep inelastic scattering (DIS) experimental data throughout the small and large values of $x$. The use of our analytical solution to extract the parton densities and the proton structure function is discussed in detail to justify the analysis method considering the accuracy and speed of calculations. Overall, the accuracy we obtain from the analytical solution using the inverse Laplace transform technique is found to be better than 1 part in 10$^{4}$ to 10$^{5}$. We also present a detailed QCD analysis of non-singlet structure functions using all available DIS data to perform global QCD fits. In this regard we employ the Jacobi polynomial approach to convert the results from Laplace $s$ space to Bjorken $x$ space. The extracted valence quark densities are also presented and compared to the {\tt JR14}, {\tt MMHT14}, {\tt NNPDF} and {\tt CJ15} PDFs sets. We evaluate the numerical effects of target mass corrections (TMCs) and higher twist (HT) terms on various structure functions, and compare fits to data with and without these corrections.

hep-ph↗

arXiv2016

Quark confinement due to creation of micro AdS black holes in quarkonium model

We use the solution of the Dirac equation for quarkonium atom in the 4D Anti de sitter (AdS$_{4}$) space to investigate the effect of the large negative cosmological constant on the phenomenon of quark confinement. We do the required calculations in the AdS$_{4}$ space to indicate that large cosmological constant can describe the quark confinement. In fact using the coulomb potential in Dirac equation while we employ the AdS metric will additionally lead us to a linear potential in the quark-antiquark interaction which can be considered to explain the quark confinement. This confining term is arising essentially from the geometrical features of the space. On the other hand the origin of the large cosmological constant can be justified by assuming the appearance of micro black holes in the recent hadronic collision process which is now current, for instance, at the LHC project.

physics.gen-ph↗

arXiv2016

Nucleon structure functions in noncommutative space-time

In the context of noncommutative space-time, we investigate the nucleon structure functions which plays an important role to identify the internal structure of nucleons. We use the corrected vertices and employ new vertices that appear in two approaches of noncommutativity and calculate the proton structure functions in terms of noncommutative tensor θ_{μν}. To check our result, we plot the nucleon structure function (NSF), F_2(x), and compare it with experimental data and the result coming out from the GRV, GJR and CT10 parametrization models. We show that new vertex which is arising the noncommutativity correction will lead us to better consistency between theoretical result and experimental data for NSF. This consistency would be better at small values of x-Bjorken variable. To indicate and confirm the validity of our calculations, we also act conversely and obtain an lower bound for the numerical values of Λ_{NC} scale which are corresponding to the recent reports.

hep-ph↗

arXiv2011

Pion mass dependence of the $K_{l3}$ semileptonic scalar form factor within finite volume

We calculate the scalar semileptonic kaon decay in finite volume at the momentum transfer $t_{m} = (m_{K} - m_π)^2$, using chiral perturbation theory. At first we obtain the hadronic matrix element to be calculated in finite volume. We then evaluate the finite size effects for two volumes with $L = 1.83 fm$ and $L= 2.73 fm$ and find that the difference between the finite volume corrections of the two volumes are larger than the difference as quoted in \cite{Boyle2007a}. It appears then that the pion masses used for the scalar form factor in ChPT are large which result in large finite volume corrections. If appropriate values for pion mass are used, we believe that the finite size effects estimated in this paper can be useful for Lattice data to extrapolate at large lattice size.

hep-ph↗