Calculation of the Gluon Distribution Function Using Alternative Method for the Proton Structure Function

A calculation of the proton structure function F2(x,Q^2) is reported with an approximation method that relates the reduced cross section derivative and the F2(x, Q^2) scaling violation at low x by using quadratic form for the structure function. This quadratic form approximation method can be used to determine the structure function F2 (x, Q^2) from the HERA reduced cross section data taken at low x. This new approach can determine the structure functions F2(x,Q^2) with reasonable precision even for low x values which have not been investigated. We observe that the Q^2 dependence is quadratic over the full kinematic covered range. To test the validity of our new determined structure functions, we find the gluon distribution function in the leading order approximation with our new calculation for the structure functions and compare them with the QCD parton distribution functions.     

Extraction of Structure Function and Gluon Distribution Function at Low-x from Cross Section Derivative by Regge Behavior

An approximation method based on Regge behavior is presented. This new method relates the reduced cross section derivative and the structure function Regge behavior at low x. With the use of this approximation method, the C and λ parameters are calculated from the HERA reduced cross section data taken at low-x. Also, we calculate the structure functions F₂(x,Q²) even for low-x values, which have not been investigated. To test the validity of calculated structure functions, we find the gluon distribution function in the Leading order approximation based on Regge behaviour of structure function and compare to the NLO QCD fit to H1 data and NLO parton distribution function.     

Nuclear Effect Study Under K Factor's Nonconstancy

A consistent approach to estimating nuclear effect functions R_v^A(x₂) and R_s^A(x₂) based on numerical iteration technique is presented in the quark-parton model when taking into account the nonconstancy of quantum chromodynamics correction factor K. R_v^A(x₂) and R_s^A(x₂) correspond respectively to the valence quark distributions for one bound nucleon within the nucleus and to the sea quark ones. Related numerical analysis is given for nuclei ₆C¹², ₂₀Ca⁴⁰, and ₂₆Fe⁵⁶. As the basis, it adopts both experimental data of the high energy proton-nucleus Drell-Yan process and of the high energy lepton-nucleus deep inelastic scattering.     

On the Nuclear Effects of Valence Quark Distributions and Sea Quark Distributions

In this paper we present a method which may be used to get the nuclear effect functions R_υ^A(x_t) and R_s^A(x_t) for valence quark distributions and sea quark distributions in the light of the data of 1-A deep inelastic scattering and nuclear Drell-Yan process. Both the functions may be used to test the theoretical models explaining the nuclear effects. With nuclei Fe, Ca and C as examples, the results are shown.     

Nuclear Effect on Nucleon Structure Function in the Extended x-Rescaling Model with Parton Recombination Effect

The extended x-rescaling model is tested by taking into account the parton recombination effect to explain the nuclear effects including the EMC effect, nuclear Drell-Yan ratios and the nuclear gluon distributions in the ⁵⁶Fe nucleus. The calculated results satisfactorily agree with the data of the EMC effect, nuclear Drell-Yan ratio and nuclear gluon distributions.     

A Lower Bound on Longitudinal Structure Function at Small x from a Self-Similarity Based Model of Proton

Self-similarity based model of proton structure function at small x was reported in the literature sometime back. The phenomenological validity of the model is in the kinematical region 6.2 × 10-7 ≤ x ≤ 10-2 and 0.045 ≤ Q2 ≤ 120 GeV2. We use momentum sum rule to pin down the corresponding self-similarity-based gluon distribution function valid in the same kinematical region. The model is then used to compute bound on the longitudinal structure function FL（X, Q2） for A1tarelli-Martinelli equation in QCD and is compared with the recent HERA data.     

Demonstration of the Double Q2-Rescaling Model

In this paper we have demonstrated the double Q²-rescaling model (DQ²RM) of parton distribution functions of nucleon bounded in nucleus. For different χ regions in I-A deep inelastic scattering process we take different approaches: in high χ region (0.1 ≤ χ ≤ 0.7)we use the distorted QCD vacuum model which resulted from topologically multi-connected domain vacuum structure of nucleus; in low χ region (10^-4 ≤ χ ≤ 10^-3) we adopt the Glauber (Mueller) multi-scat tering formula for gluon coherently rescat tering in nucleus. From these two approaches we show that the rescaling parton distribution functions in bound nucleon are in good agreement with those we got from DQ²RM, thus the validity for this phenomenological model is demonstrated.     

xF3(x,Q2) Structure Function and Gross-Llewellyn Smith Sum Rule with Nuclear Effect and Higher Twist Correction

We present an analysis of the xF₃(x,Q²) structure function and Gross-Llewellyn Smith(GLS) sum rule taking into account the nuclear effects and higher twist correction. This analysis is based on the results presented in[N.M. Nath, et al., Indian J. Phys. 90 (2016) 117]. The corrections due to nuclear effects predicted in several earlier analysis are incorporated to our results of xF₃(x,Q²) structure function and GLS sum rule for free nucleon, corrected upto next-next-to-leading order (NNLO) perturbative order and calculate the nuclear structure function as well as sum rule for nuclei. In addition, by means of a simple model we have extracted the higher twist contributions to the non-singlet structure function xF₃(x,Q²) and GLS sum rule in NNLO perturbative orders and then incorporated them to our results. Our NNLO results along with nuclear effect and higher twist corrections are observed to be compatible with corresponding experimental data and other phenomenological analysis.     

What About the Contribution from Reggeons in Hard Process of Strong Interactions?

We discuss in this paper the possible contributions from IR_ρ (ρ-reggeon associated with ρ meson) in DIS process on protons. Using results from phenomenological analysis of high energy π-N charge-exchange scattering process, we get the expression of effective propagator of IR_ρ and the coupling constant β_ρ between IR_ρ and light quarks. As a simple and concrete example, we use them to evaluate the contributions of ρ to F₂(χ, Q²) from charge-exchange photoproduction quark-pair process, γ^* + p → n + q_u + q_d(→ n + X), in HERA kinematical regions. For comparison, we also evaluate contributions both from pomeron and partons in the same process. The ratio of contributions in F₂(χ, Q²) from IR_ρ versus IP is larger than 1%, therefore, the former may be tested experimentaly.     

On K-Factor's Non-Constancy for the Drell-Yan Process in Carbon-Carbon Nuclear Collision

The double Q²-rescaling model is used to compute the change of K-factor with x_A2 when the nucleus carbon-nucleus carbon collision occurs at different values of x_Al, where x are momentum fraction variables. In the calculation, the contributions of annihilations and Compton scattering have been considered for the Drell-Yan process. The calculated results show that the plots of K-factor versus X_A2 are very different for different values of x_Al. They are also compared with experimental data, which provides a test to the model of nuclear effect and the QCD theory itself     

Effects of QCD Vacuum and the Instanton Induced-Contributions to the Nucleon Structure Functions

The instanton induced cross section in deep inelastic kinematics is a subject which people are tendentious to investigate it. Instanton induced contributions are well defined for the nucleon structure function. The non-perturbative contribution to the quark distributions of structure function, F2 (x, Q2 ), is considered within an instanton model for the QCD vacuum. We find that the structure function may possess numerically large non-perterbative contributions which are related to the violation of chirality and correspond to the correction of parton distribution of the leading twist. It is shown that the instantons give a negative contribution to the structure function at the NLO approximation. A comparison between our results, considering instantaon effect, and the case when we do not take this effect is done. Taking into account the instanton size, ρ, via the modified running coupling constant we get to a good agreement between our results at the NLO and NNLO approximations and the available experimental data, specially at the low values of the Bjorken variable x0.1 which confirms the validity of our calculations.     

Nuclear Structure in High Energy Scattering Processes

We suggest that in hard scattering processes the nuclear medium can be viewed as a background parton sea where the bound nucleons are "soaked". The quark and gluon distributions in nuclei are investigated under this assumption. The comparisons of this model with the experimental data of the structure function ratio from charged lepton deep inelastic scattering, the gluon momentum distribution ratio from inelastic J/Ψ production, and the dimuon yield ratio from Drell-Yan dimuon production are present.     

QCD Predictions for Spin Dependence of Parton Distributions

We introduce the polarized valon distributions to describe the spin dependence of parton distributions. The polarized valon distributions in the proton and polarized parton distributions inside the valon can help to obtain polarized parton distribution in a proton. In order to be able to obtain the spin contribution of sea quarks, we need to improve the valon model. We employ the Bernstein polynomial averages to obtain the unknown parameters which exist in our calculations. Our results for the polarized proton structure function, xg^p₁, are in good agreement with the experimental data for some values of Q².     

INFRARED BEHAVIOR OF THE RUNNING COUPLING CONSTANT IN QCD

The infrared behavior of the running coupling constant in QCD has been studied using the Schwinger-Dyson equation of the gluon propagator based on the Slavnov-Taylor identities in axial gauge. It is shown that the infrared running coupling constant behavior g^-2(Q²)=g²(μ²/Q²) in the infrared limit Q²/μ²→0.     

Contribution of Quark Structure Term in Nucleon Electric and Magnetic Form Factors

The constituent quarks in the nucleon have always been considered as a point-like particle in the relativisticconstituent quark model. However its calculation results of GE^n agree poorly with the new experimental data. Theelectromagnetic structure of light front constituent quarks is considered in this paper. We find that the calculationresults have good agreement with the new experimental data of GE^n after considering the contribution of the quarkstructure term. This treatment seems to be able to improve the fit to experimental data of GEp/GMp,√Q2F2p/kpF1p,and GEn/GMn as well.     

Charged Pion Form Factor Determination in the Range of Q^2= 0.6-1.6 （GeV／c）^2

Using the most recent differential cross section data for e-p quasi-elastic scattering, the charged pion formation and its form factor Fπ is calculated in the energy range of 2.4-4 GeV at Q^2 = 0.6-1.6 (GeV/c)^2. The functional dependence of the charged pion form factor to the separated cross section aL is investigated and compared to the previously determined result.     

A Determination of Nucleon Form Factor Ratios Using Perturbative QCD

Using perturbative QCD in conjunction with CVC and standard electroweak theory, it is shown that at large Q², F₁ⁿ/F₁^P = F₂ⁿ/F₁^P = -0.69. The comparison with other results on form factor ratios from QCD sum rules and/or PQCD is carried out.     

Intrinsic luminescence centers in γ- and θ-alumina nanoparticles

In this study, we investigate the photoluminescence(PL) properties of γ and θ-alumina nanoparticles synthesized by the chemical wet method followed by annealing. The obtained experimental results indicate the presence of some favorable near ultraviolet(NUV)-orange luminescent centers for usage in various luminescence applications, such as oxygen vacancies(F, F~+_2, F~(2+)_2, and F_2centers), OH related defects, cation interstitial centers, and some new luminescence bands attributed to trapped-hole centers or donor–acceptor centers. The energy states of each defect are discussed in detail. The defects mentioned could alter the electronic structure by producing some energy states in the band gap that result in the optical absorption in the middle ultraviolet(MUV) region. Spectra show that photoionazation of F and F_2 centers plays a crucial role in providing either free electrons for the conduction band, or the photoconversions of aggregated oxygen vacancies into each other, or mobile electrons for electrons-holes recombination process by the Shockley–Read–Hall(SRH)mechanism.