Effects Of Dis Research Articles

Higher twists effects in DIS on nuclei at the EIC and LHeC: a phenomenological analysis

In this paper we investigate the impact of the higher - twist effects, resummed by the non - linear approaches for the QCD dynamics, on the inclusive observables that will be measured in future electron - ion colliders. We assume a phenomenological model for the dipole - nucleus scattering amplitude which takes into account the non - linear corrections and estimate the contribution of the different twists for $F_2^A(x,Q^2)$, $F_L^A(x,Q^2)$ and $\partial F_2^A /\partial ln Q^2$ considering different values of the Bjorken - $x$ variable, photon virtuality $Q^2$ and atomic number $A$. A comparison with the full predictions is performed and the impact of the distinct twists is estimated. Our results indicate that a future analysis of the logarithmic $Q^2$ slope and longitudinal structure function will allow us to probe the presence of the non - linear effects on the QCD dynamics.

Disulfiram Inhibits M. tuberculosis Growth by Altering Methionine Pool, Redox Status and Host-Immune Response

Methionine biosynthetic pathway, essential for the growth of Mycobacterium tuberculosis (Mtb) in the host, represents an attractive target for the development of novel anti-tuberculars. Here, we have biochemically characterized homoserine acetyl transferase (HSAT viz. MetA) of Mtb, which catalyses the first committed step of methionine and S-adenosylmethionine (SAM) biosynthesis. High-throughput screening of a 2300 compound library resulted in identification of thiram, an anti-fungal organosulfur compound, as the most potent MetA inhibitor. Further analysis of thiram analogs led to the identification of orally bioavailable disulfiram (DIS, an anti-alcoholism FDA approved drug) as a novel inhibitor of MetA. Both thiram and DIS restricted the growth of drug-sensitive and drug-resistant Mtb strains in a bactericidal manner. ThermoFlour assay demonstrated direct binding of DIS with MetA. Metabolomic and transcriptomic studies showed DIS mediated perturbation of methionine and redox homeostasis, respectively, in Mtb. In concordance, the effect of DIS on Mtb growth was partially rescued by supplementation with either L-methionine as well as N-acetyl cysteine, suggesting a multi-target killing mechanism. In Mtb-infected mice, DIS administration restricted bacterial growth, increased efficacy of isoniazid, ameliorated lung pathology, modulated lung immune cell landscape and protective immune response. Taken together, our results demonstrate that DIS can be repurposed for designing an effective anti-tubercular therapy. Funding Statement: The research fellowship to D.C. and T.P.G. from Department of Biotechnology, Govt. of India is acknowledged. Ava.S. fellowship was supported by the University of Grants commission. R.B. acknowledges Department of Science and Technology India and FICCI for providing C.V. Raman International fellowship. R.S. acknowledge THSTI, and Department of Biotechnology, Govt. of India (BT/PR29075/BRB/10/1699/2018) for funding. This research was supported by SIgN A*STAR, A*STAR JCO-CDA grant (#1518251030), and Singapore-India Joint grant (#1518224018) to A.S. Declaration of Interests: None. Ethics Approval Statement: The proposed animal experiments were approved by the institutional animal ethics committee of Defence Science Organization (DSO), Singapore.

Nonperturbative approach to the parton model

In this paper, the nonperturbative parton distributions, obtained from the Lorentz contracted wave functions, are analyzed in the formalism of many-particle Fock components and their properties are compared to the standard perturbative distributions. We show that the collinear and IR divergencies specific for perturbative evolution treatment are absent in the nonperturbative version, however for large momenta [Formula: see text] (string tension), the bremsstrahlung kinematics is restored. A preliminary discussion of possible nonperturbative effects in DIS and high energy scattering is given, including in particular a possible role of multihybrid states in creating ridge-type effects.

Charm in deep-inelastic scattering

We show how to extend systematically the FONLL scheme for inclusion of heavy quark mass effects in DIS to account for the possible effects of an intrinsic charm component in the nucleon. We show that when there is no intrinsic charm, FONLL is equivalent to S-ACOT to any order in perturbation theory, while when an intrinsic charm component is included FONLL is identical to ACOT, again to all orders in perturbation theory. We discuss in detail the inclusion of top and bottom quarks to construct a variable flavour number scheme, and give explicit expressions for the construction of the structure functions $F^c_2$, $F^c_L$ and $F^c_3$ to NNLO.

Medium effects in DIS from polarized nuclear targets

The behavior of the nucleon structure functions in lepton nuclei deep inelastic scattering, both polarized and unpolarized, due to nuclear structure effects is reanalyzed. The study is performed in two schemes: an x-rescaling approach, and one in which there is an increase of sea quark components in the in medium nucleon, related to the low energy N-N interaction. In view of a recent interesting experimental proposal to study the behavior of the proton spin structure functions in nuclei we proceed to compare these approaches in an effort to enlighten the possible phenomenological interest of such difficult experiment.

Impact of higher order and soft gluon corrections on the extraction of higher twist effects in DIS

The impact of recently calculated next-to-next-to-leading order QCD corrections and soft gluon resummations on the extraction of higher twist contributions to the deep-inelastic structure function F_2 is studied using the BCDMS and SLAC data. It is demonstrated to which extent the need for higher twist terms is diminishing due to these higher order effects in the kinematical region, 0.35 \le x \le 0.85 and Q^2>1.2 GeV^2, investigated. In addition, theoretical uncertainties in the extraction of higher twist contributions are discussed, and comparisons to results obtained previously are made.

Long-range Coulomb forces in DIS: missed radiative corrections?

The Born approximation, one photon exchange, used for DIS is subject to virtual radiative corrections which are related to the long-range Coulomb forces. They may be sizeable for heavy nuclei since Z\alpha is not a small parameter. So far these corrections are known only for two processes, elastic scattering and bremsstrahlung on the Coulomb field of a point-like target. While the former amplitude acquires only a phase, in the latter case the cross section is modified also. Although the problem of Coulomb corrections for DIS on nuclei is extremely difficult, it should be challenged rather than 'swept under the carpet'. The importance of these radiative corrections is questioned in present paper. We show that in the simplest case of a constant hadronic current the Coulomb corrections provide a phase to the Born amplitude, therefore the cross section remains the same. Inclusion of more realistic hadronic dynamics changes this conclusion. The example of coherent production of vector mesons off nuclei reveals large effects. So far a little progress has been made deriving exact lepton wave functions in the Coulomb field of an extended target. Employing available results based on the first-order approximation in Z\alpha, we conclude that the Coulomb corrections are still important for heavy nuclei. We also consider an alternative approach for extended nuclear targets, the eikonal approximation, which we demonstrate to reproduce the known exact results for Coulomb corrections. Calculating electroproduction of vector mesons we again arrive at a large deviation from the Born approximation. We conclude that one should accept with caution the experimental results for nuclear effects in DIS based on analyses done in the Born approximation.

Small $x$ QCD effects in DIS with a forward jet or a forward $\pi^{0}$

We compare predictions based on small x (QCD) dynamics with recent data for deep inelastic events containing forward jets or forward pi0 mesons. We quantify the effect of imposing the (higher order) consistency condition on the BFKL equation and study uncertainties inherent in the QCD predictions. We also estimate the cross-section for the forward production of two jets.

Unitarity effects in DIS

We argue that diffractive DIS, dominated by soft interactions, is probably the unique process which allows us to observe unitarity effects in DIS. Guided by a close analogy between the diffractive dissociation of a highly virtual photon and the elastic scattering of hadrons we propose a specific procedure to analyse the data in order to detect the onset of the unitarity limit. Lacking appropriate data, we use the predictions of a realistic model as an input for our analysis, to demonstrate that the output unitarity signal is sufficiently large to be detectable.

Recent results from Fermilab experiment E665

Fermilab experiment 665 (E665) has studied inelastic muon scattering from hydrogen as well as heavy nuclear targets. The emphasis of E665 has been on proton structure function measurements, nuclear effects in DIS and the study of hadronic final states. We present here proton structure function measurements, a determination of the gluon distribution of the nucleon, cross section ratio measurements and a measurement of the A-dependence of diffractive scattering.