arXiv subjects

G. R. Boroun

Publications and source records attributed to G. R. Boroun.

At least 91 records · Page 5Linked to original sources

arXiv2015

Geometrical scaling behavior of the top structure functions ratio at the LHeC

We consider the ratio of the top structure functions $R^{t}(τ_{t})$ in top pair production as a probe of the top content of the proton at the LHeC project. We study the top structure functions with the geometrical scaling of gluon distribution at small $x$ and show that top reduced cross section exhibits geometrical scaling in a large range of photon vitualities. This analysis shows that top longitudinal structure function has sizeable impact on the top reduced cross section at $Q^{2}{\approx}~ 4m_{t}^{2}$.

hep-ph↗

arXiv2014

A Phenomenological Solution Small $x$ to the Longitudinal Structure Function Dynamical Behavior

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, $k_{T}$ factorization and H1 data.

hep-ph↗

arXiv2014

Top structure function at the LHeC

The proposed linear and nonlinear behavior for the top structure function at the LHeC is considered. We present the conditions necessary to prediction the top structure function $F_{2}^{t}(x,Q^{2})$ with respect to the different predictions for the bahavior of the gluon at low $x$.

hep-ph↗

arXiv2014

Geometrical scaling in charm structure function ratios

By using a Laplace-transform technique, we solve the next-to-leading-order master equation for charm production and derive a compact formula for the ratio $R^{c}=\frac{F^{^{c\overline{c}}}_L}{F^{^{c\overline{c}}}_2}$, which is useful for extracting the charm structure function from the reduced charm cross section, in particular, at DESY HERA, at small x. Our results show that this ratio is independent of xat small x. In this method of determining the ratios, we apply geometrical scaling in charm production in deep inelastic scattering (DIS). Our analysis shows that the renormalization scales have a sizable impact on the ratio Rcat high $Q^{2}$. Our results for the ratio of the charm structure functions are in a goodagreement with some phenomenological models.

hep-ph↗

arXiv2014

The ratio of the beauty structure functions $R^b = F^b_L/F^b_2$ at low x

We study the structure functions $F_{k}^{b}(x,Q^{2})$ ($k=2, L$) and the reduced cross section $σ_{r}^{b}(x,Q^{2})$ for small values of Bjorken$^{,}$s $x$ variable with respect to the hard (Lipatov) pomeron for the gluon distribution and provide a compact formula for the ratio $R^{b}$ that is useful to extract the beauty structure function from the beauty reduced cross section, in particular at DESY HERA. Also we show that the effects of the nonlinear corrections to the gluon distribution tame the behavior of the beauty structure function and the beauty reduced cross section at low $x$.

hep-ph↗

arXiv2014

Dynamical behavior connection of the gluon distribution and the proton structure function at small $x$

We make a critical study of the relationship between the singlet structure function $F_{2}^{S}$ and the gluon distribution $G(x,Q^{2})$ proposed in the past two decades, which is frequently used to extract the gluon distribution from the proton structure function. We show that a simple relation is not generally valid in the simplest state. We complete this relation by using a Laplace transform method and hard-pomeron behavior at LO and NLO at small $x$. Our study shows that this relation is dependent on the splitting functions and initial conditions at $Q^{2} = Q^{2}_{0}$ and running coupling constant at NLO. The resulting analytic expression allows us to predict the proton structure function with respect to the gluon distributions and to compare the results with H1 data and a QCD analysis fit. Comparisons with other results are made and predictions for the proposed best approach are also provided.

hep-ph↗

arXiv2014

Analytic Approach to the Approximate Solution of the Independent DGLAP Evolution Equations with Respect to the Hard-Pomeron Behavior

We show that it is possible to use hard-Pomeron behavior to the gluon distribution and singlet structure function at low $x$. We derive a second-order independent differential equation for the gluon distribution and the singlet structure function. In this approach, both singlet quarks and gluons have the same high-energy behavior at small $x$. These equations are derived from the next-to-leading order DGLAP evolution equations. All results can be consistently described in the framework of perturbative QCD, which shows an increase of gluon distribution and singlet structure functions as $x$ decreases.

hep-ph↗

arXiv2014

Shadowing correction to the gluon distribution behavior at small x

We determined the saturation exponent of the gluon distribution using the solution of the QCD nonlinear Dokshitzer-Gribov-Lipatov-Altarelli-parisi (NLDGLAP) evolution equation at small $x$. The very small $x$ behavior of the gluon distribution is obtained by solving the Gribov, Levin, Ryskin, Mueller and Qiu (GLR-MQ) evolution equation with the nonlinear shadowing term incorporated. The form of initial condition for the equation is determined. We find, with decreasing $x$, the emergence of a singular behavior and the eventual taming (at $R=5\hspace{0.1cm}GeV^{-1}$) and the essential taming (at $R=2\hspace{0.1cm}GeV^{-1}$) of this singular behavior by shadowing term. The nonlinear gluon density functions are calculated and compared with the results for the integrated gluon density from the Balitsky- Kovchegov(BK) equation for the different values of $Q^{2}$. It is shown, that the results for the gluon density function are comparable with the results obtained from BK equation solution. Also we show that for each $x$, the $Q^{2}$ dependence of the data is well described by gluon shadowing corrections to GLR-MQ equation. The resulting analytic expression allow us to predict the logarithmic derivative $\frac{{\partial}F^{s}_{2}(x,Q^{2})}{{\partial}lnQ^{2}}$ and to compare the results with H1 data and a QCD analysis fit.

hep-ph↗

arXiv2014

Nonlinear correction to the longitudinal structure function at small x

We computed the longitudinal proton structure function $F_{L}$, using the nonlinear Dokshitzer-Gribov-Lipatov-Altarelli-parisi (NLDGLAP) evolution equation approach at small $x$. For the gluon distribution, the nonlinear effects are related to the longitudinal structure function. As, the very small $x$ behavior of the gluon distribution is obtained by solving the Gribov, Levin, Ryskin, Mueller and Qiu (GLR-MQ) evolution equation with the nonlinear shadowing term incorporated. We show, the strong rise that is corresponding to the linear QCD evolution equations, can be tamed by screening effects. Consequently, the obtained longitudinal structure function shows a tamed growth at small $x$. We computed the predictions for all detail of the nonlinear longitudinal structure function in the kinematic range where it has been measured by $H1$ collaboration and compared with computation Moch, Vermaseren and Vogt at the second order with input data from MRST QCD fit.

hep-ph↗

arXiv2014

An approximate approach to the nonlinear DGLAP evaluation equation

We determined the effects of the first nonlinear corrections to the gluon distribution using the solution of the QCD nonlinear Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (NLDGLAP) evolution equation at small x. By using a Laplace-transform technique, the behavior of the gluon distribution is obtained by solving the Gribov, Levin, Ryskin, Mueller and Qiu (GLR-MQ) evolution equation with the nonlinear shadowing term incorporated. We show that the strong rise that is corresponding to the linear QCD evolution equations at small x can be tamed by screening effects. Consequently, the nonlinear effects for the gluon distributions are calculated and compared with the results for the integrated gluon density from the Balitsky-Kovchegov (BK) equation. The resulting analytic expression allows us to predict the shadowing correction to the logarithmic derivative $F_{2}(x,Q^{2})$ with respect to $ln Q^{2}$ and to compare the results with H1 data and a QCD analysis fit.

hep-ph↗

arXiv2014

Evolution of the longitudinal structure function at small x

We derive an approximation approach to evolution of the longitudinal structure function, by using a Laplace-transform method. We solve the master equation and derive the longitudinal structure function as a function of the initial condition $F_{L}(x,Q^{2}_{0})$ at small x. Our results are independent of the longitudinal coefficient functions and extend from the leading order (LO) up to next-to-next-to-leading order (NNLO). The comparisons with H1 data and other parameterizations are made and results show that they are in agreement with H1 data and some phenomenological models.

hep-ph↗

arXiv2014

Hard- Pomeron behavior of the Longitudinal Structure Function $F_{L}$ in the Next- to- Leading- Order at low $x$

We present an analytic formula to extract the longitudinal structure function in the next- to -leading order of the perturbation theory at low $x$, from the Regge- like behavior of the gluon distribution and the structure function at this limit. In this approach, the longitudinal structure function has the hard- Pomeron behavior. The determined values are compared with the $H1$ data and MRST model. All results can consistently be described within the framework of perturbative QCD which essentially show increases as $x$ decreases.

hep-ph↗

arXiv2014

Analytical solution of the longitudinal structure function $F_{L}$ in the leading and next-to-leading-order analysis at low x with respect to Laguerre polynomials method

The aim of the present paper is to apply the Laguerre polynomials method for the analytical solution of the Altarelli- Martinelli equation. We use this method of the low $x$ gluon distribution to the longitudinal structure function using MRST partons as input. Having checked that this model gives a good description of the data to predict of the longitudinal structure function at leading and next to leading order analysis at low $x$

hep-ph↗

arXiv2014

NLO corrections to the hard pomeron behavior of the charm structure functions $F^{c}_{k} (k = 2,L)$ at low x

We show that the charm structure functions $F^{c}_{k}$ have a hard pomeron behavior at low x, as the gluon distribution is dominated by the hard (Lipatov) pomeron at small x and all $Q^{2}$ values. It is shown that the charm structure functions obtained, using the gluon distribution functions, are in agreement with data from HERA in the next-to-leading analysis (NLO). Having checked that this behavior gives the charm structure functions exponent independent of x. With respect to the hard (Lipatov) pomeron for the low-x gluon distribution, we provide a compact formula for the ratio $R^{c} = F^{c}_{L}/F^{c}_{2}$ that is approximately independent of x at low x and its independent of the input gluon distribution function at all $Q^{2}$ values.

hep-ph↗

arXiv2014

Longitudinal Structure Function $F_{L}$ from Charm Structure Function $F^{c}_{2}$

We predict the effect of the charm structure function on the longitudinal structure function at small x. In NLO analysis we find that the hard Pomeron behavior gives a good description of $F_{L}$ and $F^{c}_{k}$ (k = 2,L) at small x values. We conclude that a direct relation between $F_{L}/F^{c}_{2}$ would provide useful information on how to measure longitudinal structure function at high $Q^{2}$ values. Having checked that this model gives a good description of the data, when compared with other models.

hep-ph↗

arXiv2014

Analysis of the logarithmic slope of $F_{2}$ from the Regge gluon density behavior at small $x$

We study of the accuracy of the Regge behavior of the gluon distribution function for obtain an approximation relation, which is frequently used to extract the logarithmic slopes of the structure function from the gluon distribution at small $x$. We show that the Regge behavior analysis results are comparable with HERA data and also are better than other methods that expand of the gluon density at distinct points of expansion. Also we show that for $Q^{2}=22.4 GeV^{2}$, the $x$ dependence of the data is well described by gluon shadowing corrections to GLR-MQ equation. The resulting analytic expression allow us to predict the logarithmic derivative $\frac{{\partial}F_{2}(x,Q^{2})}{{\partial}lnQ^{2}}$ and to compare the results with H1 data and a QCD analysis fit with MRST parametrization input.

hep-ph↗

arXiv2014

The Ratio of the Charm Structure Functions $F^{c}_{k}(k = 2, L)$ at Low x in Deep Inelastic Scattering with Respect to the Expansion Method

We study the expansion method for the gluon distribution function at low x values and calculate the charm structure functions in the LO and NLO analysis. Our results provide a compact formula for the ratio $R^{c} =F^{c}_{L}/F^{c}_{2}$, which is approximately independent of x and the details of the parton distribution function at low x values. This ratio could be a good probe of the charm structure function $F^{c}_{2}$ in the proton deduced from the reduced charm cross sections at DESY HERA. These results show that the charm structure functions obtained are in agreement with HERA experimental data and other theoretical models.

hep-ph↗

arXiv2014

Decoupling of the DGLAP evolution equations at next-to-next-to-leading order (NNLO) at low-x

We present a set of formulas to extract two second-order independent differential equations for the gluon and singlet distribution functions. Our results extend from the LO up to NNLO DGLAP evolution equations with respect to the hard-Pomeron behavior at low-x. In this approach, both singlet quarks and gluons have the same high-energy behavior at low-x. We solve the independent DGLAP evolution equations for the functions $F^{s}_{2}(x,Q^{2})$ and $G(x,Q^{2})$ as a function of their initial parameterization at the starting scale $Q^{2}_{0}$ . The results not only give striking support to the hard-Pomeron description of the low-x behavior, but give a rather clean test of perturbative QCD showing an increase of the gluon distribution and singlet structure functions as x decreases. We compared our numerical results with the published BDM (Block et al. Phys. Rev. D 77:094003 (2008)) gluon and singlet distributions, starting from their initial values at $Q^{2}_{0} =1 GeV^{2}$.

hep-ph↗