arXiv subjects

Asmita Mukherjee

Publications and source records attributed to Asmita Mukherjee.

At least 37 records · Page 2Linked to original sources

arXiv2023

Azimuthal asymmetries in $D$-meson and jet production at the EIC

We study the azimuthal asymmetries in back-to-back leptoproduction of $D$-meson and jet to probe the gluon TMDs in an unpolarized and transversely polarized electron-proton collision at the kinematics of EIC. We give predictions for unpolarized cross-sections within the TMD factorization framework. In $D$-meson and jet formation, the only leading order contribution comes from the photon gluon fusion process. We give numerical estimates of the upper bound on the azimuthal asymmetries with the saturation of positivity bounds; also, we present the asymmetries using a Gaussian parameterization of TMDs. We obtain sizable asymmetries in the kinematics that will be accessible at EIC.

hep-ph↗

arXiv2023

Sum rules for the Gravitational Form Factors using light-front dressed quark state

We consider a light-front dressed quark state, per se, instead of a proton state, we consider a simple composite spin-1/2 state of a quark dressed with a gluon. This perturbative model incorporates gluonic degrees of freedom, which enable us to evaluate the gravitational form factors (GFFs) of the quark as well as the gluon in this model \cite{More:2021stk, More:2023pcy}. We employ the Hamiltonian framework and choose the light-front gauge $A^+=0$. We calculate the four GFFs and corroborate the sum rules that GFFs satisfy. The GFF $D$ is attributed to information like pressure, shear, and energy distributions. We analyze some of these distributions for a dressed quark state at one loop in QCD.

hep-ph↗

arXiv2023

The case for an EIC Theory Alliance: Theoretical Challenges of the EIC

We outline the physics opportunities provided by the Electron Ion Collider (EIC). These include the study of the parton structure of the nucleon and nuclei, the onset of gluon saturation, the production of jets and heavy flavor, hadron spectroscopy and tests of fundamental symmetries. We review the present status and future challenges in EIC theory that have to be addressed in order to realize this ambitious and impactful physics program, including how to engage a diverse and inclusive workforce. In order to address these many-fold challenges, we propose a coordinated effort involving theory groups with differing expertise is needed. We discuss the scientific goals and scope of such an EIC Theory Alliance.

hep-ph↗

arXiv2023

Gluon distributions in the proton in a light-front spectator model

We formulate a light-front spectator model for the proton incorporating the gluonic degree of freedom. In this model, at high energy scattering of the proton, the active parton is a gluon and the rest is viewed as a spin-$\frac{1}{2}$ spectator with an effective mass. The light front wave functions of the proton are constructed using a soft wall AdS/QCD prediction and parameterized by fitting the unpolarized gluon distribution function to the NNPDF3.0nlo data set. We investigate the helicity distribution of gluon in this model. We find that our prediction for the gluon helicity asymmetry agrees well with existing experimental data and satisfies the perturbative QCD constraints at small and large longitudinal momentum regions. We also present the transverse momentum dependent distributions (TMDs) for gluon in this model. We further show that the model-independent Mulders-Rodrigues inequalities are obeyed by the TMDs computed in our model.

hep-ph↗

arXiv2023

3D EMT distributions as an Abel image of 2D EMT distributions on the light-front

The energy-momentum tensor (EMT) and corresponding gravitational form factors (GFFs) provide us information about the internal structure like spin, mass and spatial densities of the proton. The Druck gravitational (D-term) form factor is related to the mechanical stability of the proton and gives information about the spatial distributions of the forces inside the hadron. In this work, we study the GFFs in the framework of the light-front quark diquark model. The model has been successful to derive various properties of protons. We investigate the three-dimensional spatial distributions of proton as an Abel image of two-dimensional distributions in this model[1]. We explicitly show the global and local stability conditions which are satisfied by both 2D and 3D distributions in our model. We compare our results with the chiral quark soliton model, JLab and lattice data.

hep-ph↗

arXiv2023

Real and virtual photons within basis light-front quantization

We compute the structure function, transverse momentum dependent parton distributions (TMDs), and generalized parton distributions (GPDs) for the physical photon from the light-front quantum electrodynamics (QED) Hamiltonian, determined for its constituent bare photon and electron-positron Fock components within the Basis Light-Front Quantization framework. After performing nonperturbative renormalization, we obtain a good quality description of the perturbative QED properties of the photon, as well as good agreement with the experimental data for the photon's structure function. We also investigate the TMDs and GPDs of the space-like and the time-like virtual photon by incorporating a nonzero photon mass.

hep-ph↗

arXiv2023

Gluon contribution to the mechanical properties of a dressed quark in light-front Hamiltonian QCD

We calculate the contribution to the gravitational form factors (GFFs) from the gluon part of the energy-momentum tensor in QCD. We take a simple spin $1/2$ composite state, namely a quark dressed with a gluon. We use the light-front Hamiltonian QCD approach in the light-front gauge. We also present the effect of the gluon on the mechanical properties like the pressure, shear and energy distributions of the dressed quark state.

hep-ph↗

arXiv2022

Azimuthal asymmetries in $J/ψ$-photon production at the EIC

We calculate azimuthal asymmetries in back-to-back production of $J/ψ$ and a photon in electron-proton scattering process at the future electron-ion collider (EIC) using TMD factorization framework. We consider the cases where the proton is unpolarized or transversely polarized. For the formation of $J/ψ$, non-relativistic QCD (NRQCD) is used. We find that the cross-section gets contribution from only one color octet state, as a result, the azimuthal modulations become independent of the long-distance matrix elements (LDMEs), and thus can be used to probe, in particular the gluon TMDs which are dominant in this kinematics. We show estimates of the upper bounds of different azimuthal asymmetries using the positivity bounds on TMDs. In addition, we show estimate of asymmetries using the Gaussian parametrization of the TMDs.

hep-ph↗

arXiv2022

Superkicks and momentum density tests via micromanipulation

There is an unsettled problem in choosing the correct expressions for the local momentum density and angular momentum density of electromagnetic fields (or indeed, of any non-scalar field). If one only examines plane waves, the problem is moot, as the known possible expressions all give the same result. The momentum and angular momentum density expressions are generally obtained from the energy-momentum tensor, in turn obtained from a Lagrangian. The electrodynamic expressions obtained by the canonical procedure are not the same as the symmetric Belinfante reworking. For the interaction of matter with structured light, for example, twisted photons, this is important; there are drastically different predictions for forces and angular momenta induced on small test objects. We show situations where the two predictions can be checked, with numerical estimates of the size of the effects.

physics.optics↗

arXiv2022

Vorticity of Twisted Spinor Fields

Spinor fields with a vortex structure in free space that allow them to have arbitrary integer orbital angular momentum along the direction of motion have been studied for some time. Relatively new is the observation in a certain context that the vortex center of this field structure is, unlike a classical whirlpool, not singular. We point out that there are several ways to calculate the local velocity of the spinor field and that all but one show a singular vorticity at the vortex line. That one, using the Dirac bilinear current with no derivatives, is the only one so far (to our knowledge) studied in the literature in this context and we further show how to understand an apparent conflict in the existing results.

quant-ph↗

arXiv2022

$\cos2ϕ_t$ azimuthal asymmetry in back-to-back $J/ψ$-jet production in $e~p\rightarrow e~J/ψ~Jet~ X$ at the EIC

In this article, we investigate the $\cos2ϕ_t$ azimuthal asymmetry in $e ~p\rightarrow e ~J/ψ~Jet~ X$, where the $J/ψ$-jet pair is almost back-to-back in the transverse plane, within the framework of the generalized parton model(GPM). We use non-relativistic QCD(NRQCD) to calculate the $J/ψ$ production amplitude and incorporate both color singlet(CS) and color octet(CO) contributions to the asymmetry. We estimate the asymmetry using different parameterizations of the gluon TMDs in the kinematics that can be accessed at the future electron-ion collider (EIC) and also investigate the impact of transverse momentum dependent (TMD) evolution on the asymmetry. We present the contributions coming from different states to the asymmetry in NRQCD.

hep-ph↗

arXiv2022

Superkicks and the photon angular and linear momentum density

We address a problem of proper definition of momentum density for spatially structured electromagnetic fields. We show that the expressions for the momentum and angular momentum obtained locally are not the same when one uses the canonical energy-momentum tensor instead of the symmetric Belinfante energy-momentum tensor in electrodynamics. This has important consequences for interaction of matter with structured light, for example, twisted photons; and would give drastically different results for forces and angular momenta induced on small test objects. We show, with numerical estimates of the size of the effects, situations where the canonical and symmetrized forms induce very different torques or (superkick) recoil momenta on small objects or atomic rotors, over a broad range of circumstances.

quant-ph↗

arXiv2022

Gravitational Form Factors and Mechanical Properties of the Proton : Connection Between Distributions in 2D and 3D

The gravitational form factors which are obtained from the matrix elements of the energy-momentum tensor provide us information about internal distributions of mass, energy, pressure and shear. The Druck term is the least understood among all the gravitational form factors. In a light front quark-diquark model of proton, we investigate the Druck form factor. Using Abel transformation, we evaluate the 3D distribution in the Breit frame from the 2D light front distributions. The results are compared with other models and lattice predictions.

hep-ph↗

arXiv2022

Basis light-front quantization approach to photon

We solve for the light-front wave functions (LFWFs) of the physical photon from the eigenvectors of the light-front quantum electrodynamics (QED) Hamiltonian with the aim to determine its bare photon and electron-positron Fock components. We then employ the resulting LFWFs to compute the transverse momentum dependent parton distributions (TMDs) and the generalized parton distributions (GPDs) of the photon. The TMDs are found to be in excellent agreement with the lowest-order perturbative results calculated using the electron-positron quantum fluctuation of the photon. The GPDs are also consistent with the perturbative calculations.

hep-ph↗

arXiv2021

Gravitational form factors and mechanical properties of a quark at one loop in light-front Hamiltonian QCD

We calculate the gravitational form factors (GFFs) and pressure, shear and energy distributions for a quark state dressed with a gluon at one loop in QCD. We use the light-front Hamiltonian approach. In the light-front gauge, we use a two-component formalism to eliminate the constrained fields. The state may be thought of as a perturbative model for a relativistic spin $1/2$ composite system having a gluonic degree of freedom. We compare the results with model calculations for a nucleon.

hep-ph↗

arXiv2021

Sivers asymmetry in inelastic $J/ψ$ leptoproduction at the EIC

We study the Sivers asymmetry in inelastic $J/ψ$ leptoproduction, $ep^\uparrow \to e+ J/ψ+X$, within a transverse momentum dependent scheme, the so-called generalized parton model (GPM). The effects of final-state interactions are properly taken into account by employing the color-gauge invariant GPM (CGI-GPM). For the $J/ψ$ formation the non-relativistic QCD (NRQCD) framework is adopted. Predictions for unpolarized cross sections and maximized Sivers asymmetries at EIC energies are given.

hep-ph↗

arXiv2021

Proton gravitational form factors in a light-front quark-diquark model

We present a recent calculation of the gravitational form factors (GFFs) of proton using the light-front quark-diquark model constructed by the soft-wall AdS/QCD. The four GFFs $~A(Q^2)$ , $B(Q^2)$ , $C(Q^2)$ and $\bar{C}(Q^2)$ are calculated in this model. We also show the pressure and shear distributions of quarks inside the proton. The GFFs, $A(Q^2)$ and $B(Q^2)$ are found to be consistent with the lattice QCD, while the qualitative behavior of the $D$-term form factor is in agreement with the extracted data from the deeply virtual Compton scattering (DVCS) experiments at JLab, the lattice QCD, and the predictions of different phenomenological models.

hep-ph↗

arXiv2021

A new method to extract the valence transversity distributions

A new method is suggested for the extraction of $u$-quark and $d$-quark transversity distributions, using single spin asymmetry (SSA) data in semi-inclusive deep inelastic scattering (SIDIS) processes, where they couple to the Collins or the di-hadron fragmentation functions. We discuss a recent suggestion to extract the transversity distribution using the concept of difference asymmetries and their ratios, which avoids the requirement of Collins function. We suggest new measurements, involving ratios of polarized cross-sections, that would directly probe the ratio $h_1^{d_v}/h_1^{u_v}$. We also show some numerical estimates.

hep-ph↗