arXiv subjects

Tajdar Mufti

Publications and source records attributed to Tajdar Mufti.

12 recordsLinked to original sources

arXiv2025

Two and three point functions in real singlet and complex doublet scalar model

We study dynamics of an interacting theory of a real singlet scalar and an $SU(2)$ symmetry preserving complex doublet scalar fields using lattice simulations over a broad region of the parameter space. The model contains all $SU(2)$-preserving quartic and a real singlet-$SU(2)$ invariant doublet field Yukawa interactions. The field propagators and the Yukawa vertex are the central structures for the study. We complement the study by implementing machine learning routines to the correlation functions in order to probe the underlying physics. The model reveals the role of nonperturbative effects in terms of infrared enhanced field propagators with a stable amputated Yukawa vertex, and a continuum-like scaling window in the parameter space with large regulator. The ultraviolet effects are visible in terms of an scaling structure appearing in a composite operator of mixed scalar interactions and the singlet expectation value.

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arXiv2021

Dynamical generation of scalar mass in two Higgs doublet model under Yukawa interactions

Light scalars are among the expected particles in nature. If they indeed exist, dynamical generation of masses becomes an important phenomenon to investigate in scalar interactions. A two Higgs doublet model containing two complex doublet scalar fields, conveniently called the standard model Higgs and the second Higgs fields, is studied to explore the extent of dynamical mass generation and the field propagators in the model at different cutoff values. Both Higgs fields are coupled with each other by a real singlet scalar field through a modelled Yukawa interaction. The model is studied for various renormalized masses of the second Higgs field at various coupling strength. The renormalized mass of the standard model Higgs boson is kept at $125.09$ GeV. The model has strong indication of existence of critical coupling below $10^{-3}$ GeV. The observed dynamical masses are generally within $200$ MeV. The two Higgs propagators are found to be considerably stable compared to scalar singlet propagators despite cutoff effects. No phase structure in the parameter space was observed. The model is found non-trivial.

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arXiv2021

Two Higgs Doublet Model with Scalar Mediation via Yukawa Interactions

Scalar sector offers a valuable avenue to explore its implications in the particle physics phenomenology for new physics and several model dependent phenomena. Two Higgs doublet models are among the promising models for such explorations. In the presence of a standard model Higgs, a two Higgs doublet model is studied in which the two Higgs fields are connected with each other via a scalar singlet field. The study is conducted using Dyson Schwinger equations under the Yukawa vertices set at their tree level form up to certain constants. Among the field propagators, the two Higgs propagators are found to be least effected in the parameter space which also reflects in the insignificant beyond the bare mass contributions to the renormalized Higgs masses. Evidence of universality in terms of identical coupling for both Higgs is found in the model. The model is found to be non-trivial in the explored parameter space. There are cutoff effects in the model. Stability in the calculated correlation functions and parameters generally ensues beyond 100 TeV cutoff.

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arXiv2021

Dynamical Mass Generation in Wick Cutkosky Model

Studying extent of dynamical generation of mass in a quantum field theory, which may have non-perturbative attributes, is an essential step towards complete understanding of the theory. It has historic relevance to interactions including fermions. However, as search of further fundamental scalars continues, inquiring into the possibility of dynamical generation of mass becomes crucial for scalars with masses much lower than the electroweak scale. This paper addresses Yukawa interaction between a complex doublet field, conveniently named the Higgs, and a scalar singlet studied in terms of correlation functions and the dynamical masses produced in the parameter space of the model. The study is conducted using the method of Dyson Schwinger equation. The Higgs is found to be receiving negative squared masses while the scalar singlet field receives positive squared mass. Higgs propagators are found to be significantly more sensitive to couplings in comparison to the scalar propagators. The vertices are relatively more stable against the cutoff used in comparison to the propagators and dynamically generated masses. No indication of a critical coupling is found within the explored range of coupling values. The model is found to have strong cutoff effects until the cutoff is raised to 100 TeV. The model suggests no sign of triviality.

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arXiv2019

Exploring Higgs boson Yukawa interactions with a scalar singlet using Dyson-Schwinger equations

Higgs, being the first discovery of a fundamental scalar field in the standard model (SM), opens the possibility of existence of other scalar or pseudo scalar particles in nature. Though it does not conclusively fulfill the role of inflaton, it does provide motivation for experimental searches involving interactions of scalar (or pseudo scalar) particles as well as implications of such particles' existence from the perspective of theoretical understanding. Yukawa interactions are among the possible interactions. The considered model addresses Yukawa interaction among the Higgs (and Higgs bar) and a real singlet scalar field using Dyson Schwinger equations (DSEs) over a range of bare coupling values relevant to inflation-related physics for several scalar bare masses and cutoff values. The Higgs mass is kept fixed at two values for two different scenarios. It is found that Higgs propagators are tree level dominated while scalar propagators, despite their dependence on parameter region, do not degenerate over the whole parameter space. The interaction vertices show significant deviations from tree level expression for a number of parameters and exhibit two distinct behaviors. Furthermore, the theory does not show any conclusive sign of triviality over the explored parameter space, despite suppressed vertices for some parameters, particularly for small coupling values in a certain region of parameter space.

hep-ph↗

arXiv2018

Studies of Wick Cutkosky model in light of its classical ground state using Dyson Schwinger equations

Implications of additional fundamental scalar fields are regarded as among the most important avenues to explore after the experimental discovery of the standard model Higgs, particularly when there already exist cogent arguments in favor of their existence. A peculiar observation in Higgs-scalar singlet system is tendency of scalar singlet field to have negative squared physical masses which may be a sign of either a tachyon field or symmetry breaking. Assuming that this feature is due to the presence of a phenomenon similar to the conventionally understood Higgs mechanism, Wick Cutkosky model is studied in the parameter space suggested by the classical ground state of the system at Higgs mass $125.09$ GeV with positive values for both squared bare masses. The results are found to have strong negative contributions to squared scalar masses. For higher cutoff values, the renormalized squared scalar masses and squared bare couplings are found to qualitatively favor a relationship similar to the one in the classical ground state of the system, upto an additive constant. Higgs propagators remain almost unaffected as observed in a previously explored region of parameter space. However, scalar singlet propagators are found to have relatively different qualitative features in comparison to the previous study of the model. Vertices are found to have qualitatively similar features. No sign of triviality is found.

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arXiv2015

A spectroscopical analysis of the phase diagram of Yang-Mills-Higgs theory

Yang-Mills-Higgs theory, being the standard-model Higgs sector for a suitable choice of gauge and custodial group, offers a rich set of physics. In particular, in some region of its parameter space it has QCD-like behavior, while in some other region it is Higgs-like. Therefore, it is possible to study a plethora of phenomena within a single theory. Here, the physics of the standard-model version is studied using lattice gauge theory. To this end, the low-lying spectrum in several different channels is obtained for more than 140 different sets of bare parameters throughout the phase diagram. The theory shows quite different behaviors in the different regions, from almost Yang-Mills-like to the one of an essentially free gas of massive photons. Especially, not always is the behavior as naively expected.

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arXiv2014

On the phase diagram and the singlet scalar channel in Yang-Mills-Higgs theory

Yang-Mills-Higgs theory is quite a remarkable theory in that it shows very different behaviors without phase transitions. It is dominated by the Brout-Englert-Higgs mechanism in some domain of the phase diagram, while it is essentially QCD-like in another. It is expected that albeit there is no qualitative difference, there are substantially quantitative differences throughout the spectrum. This is investigated using lattice theory for the case of the scalar singlet channel for more than a hundred different points in the phase diagram. It is found that the results deviate partly substantially from the expectations in some cases, but in others justify the picture of a weakly interacting theory - even in cases of rather strong interactions at the ultraviolet cutoff.

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arXiv2014

Two- and three-point functions in Landau gauge Yang-Mills-Higgs theory

Yang-Mills-Higgs theory offers a rich set of physics. In particular, in some region of its parameter space it has QCD-like behavior, while in some other range it is Higgs-like. Furthermore, for the choice of the gauge group SU(2) and an SU(2) Higgs flavor symmetry it is the Higgs sector of the standard model. Therefore, it is possible to study a plethora of phenomena within a single theory. Here the standard-model version is studied using lattice gauge theory. Choosing non-aligned minimal Landau gauge, its propagators and three-point vertices will be determined in both the QCD-like and Higgs-like domains. This permits to test various proposals for how confinement works, as well as how confinement and the Higgs effect differ. The correlations functions are found to exhibit a different behavior, depending on whether the lowest mass scalar flavor singlet is lighter than the vector triplet, heavier and stable, or unstable against decay into two vector triplets.

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arXiv2013

Correlation Functions and Confinement in Scalar QCD

The complete knowledge of a theory is encoded in its correlation functions. Thus non-perturbative effects, like confinement in QCD, is necessarily contained in these correlation functions. As a consequence, a number of confinement scenarios make predictions for the behavior of these correlation functions. Non-perturbative methods, like lattice calculations, permit to calculate the correlation functions and test these predictions. To avoid the entanglement with chiral symmetry breaking and the costs of full fermion simulations, here scalar QCD will be used as a role model, as it is expected that confinement operates in the same way. We present results on both two-point functions and three-point functions for the case of two colors and two flavors of scalars, and compare them to the predictions.

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arXiv2013

Exploring Higgs Sector Spectroscopy

The Higgs sector of the standard model is field-theoretically a very interesting theory. Because strong and weak coupling domains are continuously connected, only quantitative changes distinguish the various regions. Especially, this is true for the asymptotic spectrum, which can only consist out of gauge-invariant composite, i. e. bound, states. Since in some regions of parameter space even Regge trajectories are expected to exist, there is immediately the possibility that resonances may also be present in the parameter region characteristic of the standard model Higgs sector. This possibility is discussed in some detail, starting from the definition of the theory to spectroscopy, including excited state analysis, to some considerations whether this could have experimental consequences. The strongest limitation for this exploration turns out to be that the gauge coupling without fermions runs much faster, and the gauge sector is therefore potentially affected.

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arXiv2012

Non-perturbative aspects in a weakly interacting Higgs sector

Just like the weakly interacting QED can support non-perturbative phenomena, like atoms, so can the weak and Higgs interactions. Especially, there are strong field-theoretical arguments that only bound states can be the (quasi-)asymptotic physical degrees of freedom of this sector. After a brief review of these arguments, the 2-point, 3-point and 4-point correlation functions of the Higgs-W system are determined using lattice gauge theory. The results support a conjectured duality between elementary states and bound states for weak Higgs self-interactions. This leads to relations between the bound states and the experimentally observed particles. Interestingly, these may yield pseudo-scalar admixtures at the Higgs energy, and possibly a faint standard-model signal in the channel where a Kaluza-Klein graviton would be expected.

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