arXiv subjects

Mandeep Kaur

Publications and source records attributed to Mandeep Kaur.

At least 19 recordsLinked to original sources

arXiv2025

Two-loop helicity amplitudes for diphoton production with massive quark loop

We compute two-loop helicity amplitudes in QCD for diphoton production through quark- and gluon-initiated channels, accounting for a massive internal quark loop by keeping its full mass dependence. Using physical projectors, we directly decompose the amplitude into its helicity components. By renormalising the heavy quark mass in on-shell, and other quantities in $\overline{\rm MS}$ schemes, we obtain finite remainders. This work paves the way for calculating the cross-section for diphoton production at higher orders in QCD with a massive quark loop, employing different subtraction schemes. The effect of a heavy quark is expected to play a crucial role in high-luminosity LHC.

hep-ph↗

arXiv2024

QCD corrections to the Golden decay channel of the Higgs boson

Precision studies within the Higgs sector of the Standard Model are crucial to deepen our understanding of the fundamental interactions and uncovering new physics phenomena beyond the Standard Model. To fully leverage the potential of future precision machines aiming to provide highly precise experimental measurements of the Higgs properties, it is crucial to minimize theoretical errors in the Higgs sector observables, such as production and decay rates. In this thesis, we focus on providing precise predictions for observables associated with the Golden decay channel of the Higgs boson. We improve theoretical predictions for the partial decay width of this channel, specifically $H \to Z^{(*)}Z^{(*)} \to e^+ e^- μ^+ μ^-$, by incorporating NNLO mixed QCD-electroweak corrections in perturbation theory. We also describe the full analytical evaluation of the two-loop master integrals appearing in the $\mathcal{O}(αα_s)$ corrections to the $HZZ$ vertex with both $Z$-bosons being off-shell, employing the method of differential equations retaining full mass dependence. The analytic results for all the master integrals are obtained in terms of Chen's iterated integrals with logarithmic kernels order-by-order in the dimensional regularization parameter $ε$, along with analytic boundary constants. This thesis also presents a phenomenological study of the $H \to e^+ e^- μ^+ μ^-$ decay at $\mathcal{O}(αα_s)$ by implementing the entire calculation of the decay amplitude in the public code Hto4l to perform the phase space integration over final state leptons. We study the impact of these mixed QCD-electroweak corrections on the invariant mass distribution of the final-state leptons and angular variables, specifically the angle between the decay planes of the intermediate $Z$-bosons relative to leading-order predictions and NLO electroweak corrections.

hep-ph↗

arXiv2024

QCD corrections to the Golden decay channel of the Higgs boson

Future colliders aim to provide highly precise experimental measurements of the properties of the Higgs boson. In order to benefit from these precision machines, theoretical errors in the Higgs sector observables have to match at least the experimental uncertainties. The theoretical uncertainties in the Higgs sector observables can be reduced by including missing higher-order terms in their perturbative calculations. In this direction, we compute the mixed QCD-electroweak corrections at ${\mathcal O}(αα_s)$ to the Higgs decay into four charged leptons by considering the golden decay channel, $ H \to e^+e^-μ^+μ^-$. Due to color conservation, these corrections receive contributions only from the two-loop virtual diagrams. In the complex mass scheme, we find that the mixed QCD-electroweak corrections to the partial decay width, relative to the leading order predictions, are positive and about $0.27\%$ for $α_s(M_Z)$. Relative to the next-to-leading order electroweak corrections, the mixed QCD-electroweak corrections are found to be approximately $18\%$ for $α_s(M_Z)$. With respect to the leading order, we observe a flat effect of the mixed QCD-electroweak corrections on the invariant mass distribution of the lepton pairs with fixed QCD coupling. The $ϕ$ distribution, due to the mixed QCD-electroweak corrections, follows a $(1-\cos ϕ)$ dependence.

hep-ph↗

arXiv2024

Two-loop non-planar four-point topology with massive internal loop

We study a set of two-loop non-planar master integrals needed for the NNLO QCD corrections to diphoton and dijet production at hadron colliders. The top-sector topology contains an internal massive fermion loop and is known to contain elliptic curves. Leveraging the method of differential equations, we provide a comprehensive discussion for deriving an $ε$-factorized differential equation related to the most intricate sector within the Feynman integral family. Despite the dependence on multiple scales and the presence of two elliptic sectors, we demonstrate how to leverage the properties of their maximal cuts and the factorization of the Picard-Fuchs operator to deal with the complexity of the analytic computation. In particular, we construct a transformation matrix that brings the differential equations into a format enabling the convenient expression of analytic results in terms of Chen's iterated integrals.

hep-th↗

arXiv2022

Master integrals for ${\cal O}(αα_s)$ corrections to $H \to ZZ^*$

We present analytic results for all the Feynman integrals relevant for ${\mathcal O}(αα_s)$ virtual corrections to $H \rightarrow ZZ^*$ decay. We use the method of differential equations to solve the master integrals while keeping the full dependence on the masses of all the particles including internal propagators. Due to the presence of four mass scales we encounter multiple square roots. We argue that all the occurring square roots can not be rationalized at the same time as a simultaneous rationalization brings us to integrals over $CY_3$ manifolds. Hence we rationalize only three square roots simultaneously and construct suitable ansätze to obtain dlog-forms containing the square root, after obtaining an epsilon-factorised form for the differential equations. We present the alphabet and the analytic form of all the boundary constants that appear in the solutions of the differential equations. The results for master integrals are expressed in terms of Chen's iterated integrals with dlog one-forms.

hep-ph↗

arXiv2022

Tune-out and magic wavelengths, and electric quadrupole transition properties of the singly charged alkaline-earth metal ions

In continuation to our earlier reported data on the electric dipole (E1) matrix elements and lifetimes of the metastable states of the alkaline earth ions in [Atomic Data and Nuc. Data Tables {\bf 137} (2021) 101381], we present here the tune-out and magic wavelengths of the Mg$^+$, Ca$^+$, Sr$^+$ and Ba$^+$ alkaline earth-metal ions by determining dynamic E1 polarizabilities. Furthermore, we have evaluated the electric quadrupole (E2) matrix elements of a large number of forbidden transitions using an all-order relativistic many-body method and compare them with the previously reported values for a few selective transitions. Compilation of both the E1 and E2 transition matrix elements, will now provide a more complete knowledge about the transition properties of the considered singly charged alkaline earth-metal ions. Similarly, the listed precise values of tune-out and magic wavelengths due to the dominant E1 polarizabilities can be helpful to conduct experiments using the above ions with reduced systematics. Therefore, all these data will be immensely useful for various applications for carrying out the high-precision experiments and laboratory simulations in atomic physics, and interpreting transition lines in the astrophysical observations.

physics.atom-ph↗

arXiv2022

Spectroscopic data of Rb-isoelectronic Zr and Nb ions for astrophysical applications

We present high-accuracy spectroscopy data of line strengths, transition probabilities and oscillator strengths for the allowed transitions among the $nS_{1/2}$, $nP_{1/2,3/2}$ and $n'D_{3/2,5/2}$ states with $n=5$ to $10$ and $n'=4$ to $10$ of the Rb-isoelectronic Zr (Zr IV) and Nb (Nb V) ions. %\textcolor{red}{except for a few transitions that seem to be unreliable.} They can serve to analyse various astrophysical phenomena undergoing inside the heavenly bodies containing Zr and Nb elements. Since there is a lack of precise observational and calculated data for the spectroscopic properties in the above ions, their accurate determinations are of immense interest. The literature data, that are available only for a few selected low-lying transitions, have large discrepancies and they cannot be used reliably for the above purpose. After accounting for electron interactions through random phase approximation, Brückner orbitals, structural radiations and normalizations of wave functions in the relativistic many-body methods, we have evaluated the electric dipole amplitudes precisely. Combining these values with the observed wavelengths, the above transition properties and lifetimes of a number of excited states of the Zr IV and Nb V ions are determined and compared with the literature data.

physics.atom-ph↗

arXiv2020

Accessing topological surface states and negative MR in sculpted nanowires of Bi2Te3 at ultra-low temperature

Milling of 2D flakes is a simple method to fabricate nanomaterial of any desired shape and size. Inherently milling process can introduce the impurity or disorder which might show exotic quantum transport phenomenon when studied at the low temperature. Here we report temperature dependent weak antilocalization (WAL) effects in the sculpted nanowires of topological insulator in the presence of perpendicular magnetic field. The quadratic and linear magnetoconductivity (MC) curves at low temperature indicate the bulk contribution in the transport. A cusp feature in magnetoconductivity curves (positive magnetoresistance) at ultra low temperature and at magnetic field, less than 1T represent the WAL indicating the transport through surface states. The MC curves are discussed by using the 2D Hikami Larkin Nagaoka theory. The crossover interplay nature of positive and negative magnetoresistance observed in the MR curve at ultra low temperature. Our results indicate that transport through topological surface states (TSS) in sculpted nanowires of Bi2Te3 can be achieved at mK range and linear MR observed at 2 K could be the coexistence of electron transport through TSS and contribution from the bulk band.

cond-mat.mtrl-sci↗

arXiv2020

Radiative Transition Properties of Singly Charged Magnesium, Calcium, Strontium and Barium Ions

Accurate values of electric dipole (E1) amplitudes along with their uncertainties for a number of transitions among low-lying states of Mg$^+$, Ca$^+$, Sr$^+$, and Ba$^+$ are listed by carrying out calculations using a relativistic all-order many-body method. By combining experimental wavelengths with these amplitudes, we quote transition probabilities, oscillator strengths and lifetimes of many short-lived excited states of the above ions. The uncertainties in these radiative properties are also quoted. We also give electric quadrupole (E2) and magnetic dipole (M1) amplitudes of the metastable states of the Ca$^+$, Sr$^+$, and Ba$^+$ ions by performing similar calculations. Using these calculated E1, E2 and M1 matrix elements, we have estimated the transition probabilities, oscillator strengths and lifetimes of a number of allowed and metastable states. These quantities are further compared with the values available from the other theoretical studies and experimental data in the literature. These data will be immensely useful for the astrophysical observations, laboratory analysis and simulations of spectral properties in the above considered alkaline-earth metal ions.

physics.atom-ph↗

arXiv2020

Accurate determination of energy levels, hyperfine structure constants, lifetimes and dipole polarizabilities of triply ionized tin isotopes

We have investigated energies, magnetic dipole hyperfine structure constants ($A_{hyf}$) and electric dipole (E1) matrix elements of a number of low-lying states of the triply ionized tin (Sn$^{3+}$) by employing relativistic coupled-cluster theory. Contributions from the Breit interaction and lower-order quantum electrodynamics (QED) effects in determination of above quantities are also given explicitly. These higher-order relativistic effects are found to be important for accurate evaluation of energies, while QED contributions are seen to be contributing significantly to the determination of $A_{hyf}$ values. Our theoretical results for energies are in agreement with one of the measurements but show significant differences for some states with another measurement. Reported $A_{hyf}$ will be useful in guiding measurements of hyperfine levels in the stable isotopes of Sn$^{3+}$. The calculated E1 matrix elements are further used to estimate oscillator strengths, transition probabilities and dipole polarizabilities ($α$) of many states. Large discrepancies between present results and previous calculations of oscillator strengths and transition probabilities are observed for a number of states. The estimated $α$ values will be useful for carrying out high precision measurements using Sn$^{3+}$ ion in future experiments.

physics.atom-ph↗

arXiv2019

Some results on vanishing coefficients in infinite product expansions

Recently, M. D. Hirschhorn proved that, if $\sum_{n=0}^\infty a_nq^n := (-q,-q^4;q^5)_\infty(q,q^9;q^{10})_\infty^3$ and $\sum_{n=0}^\infty b_nq^n:=(-q^2,-q^3;q^5)_\infty(q^3,q^7;q^{10})_\infty^3$, then $a_{5n+2}=a_{5n+4}=0$ and $b_{5n+1}=b_{5n+4}=0$. Motivated by the work of Hirschhorn, D. Tang proved some comparable results including the following: If $ \sum_{n=0}^\infty c_nq^n := (-q,-q^4;q^5)_\infty^3(q^3,q^7;q^{10})_\infty$ and $\sum_{n=0}^\infty d_nq^n := (-q^2,-q^3;q^5)_\infty^3(q,q^9;q^{10})_\infty$, then $c_{5n+3}=c_{5n+4}=0$ and $d_{5n+3}=d_{5n+4}=0$. In this paper, we prove that $a_{5n}=b_{5n+2}$, $a_{5n+1}=b_{5n+3}$, $a_{5n+2}=b_{5n+4}$, $a_{5n-1}=b_{5n+1}$, $c_{5n+3}=d_{5n+3}$, $c_{5n+4}=d_{5n+4}$, $c_{5n}=d_{5n}$, $c_{5n+2}=d_{5n+2}$, and $c_{5n+1}>d_{5n+1}$. We also record some other comparable results not listed by Tang.

math.NT↗

arXiv2019

Substrate Mediated Synthesis of Ti-Si-N Nano-and-Micro Structures for Optoelectronic Applications

Being one of the strongest materials, ternary TiSiN exhibits a very interesting family of binary transition metal nitride and silicide systems. A novel technique to fabricate morphologically fascinating nano and micro structures of TiSiN is reported here. The referred TiSiN films, majorly constituted with cubic TiN phase, are enriched with crystalline nanoparticles, micro-flowers and faceted micro-crystals which possess attractive functionalities towards plasmon mediated optoelectronic applications. Reactivity of titanium to silicon nitride based dielectric topping on the substrate at high temperature plays the key role in nitride formation for the demonstrated protocol. The optoelectronic response for these morphologically enriched composite films indicates an influential role of photo-induced surface plasmon polaritons on their dc transport properties. A plasmonically tuned resistive switching, controlled by the surface morphology in association with the film thickness, is observed under light illumination. Using Drudes modified frequency dependent bulk electron scattering rates and surface mediated SPPs-electron scattering rates, a generic model is proposed for addressing unambiguously the increased device resistance in response to light. The featured synthesis process opens a new direction towards the growth of transition metal nitrides while the proposed model serves as a basic platform to understand photo-induced electron scattering mechanisms in metal.

cond-mat.mtrl-sci↗

arXiv2018

Supervised Machine Learning for Extractive Query Based Summarisation of Biomedical Data

The automation of text summarisation of biomedical publications is a pressing need due to the plethora of information available on-line. This paper explores the impact of several supervised machine learning approaches for extracting multi-document summaries for given queries. In particular, we compare classification and regression approaches for query-based extractive summarisation using data provided by the BioASQ Challenge. We tackled the problem of annotating sentences for training classification systems and show that a simple annotation approach outperforms regression-based summarisation.

cs.CL↗

arXiv2018

New Congruences Modulo 2, 4, and 8 for the Number of Tagged Parts Over the Partitions with Designated Summands

Recently, Lin introduced two new partition functions PD$_t(n)$ and PDO$_t(n)$, which count the total number of tagged parts over all partitions of $n$ with designated summands and the total number of tagged parts over all partitions of $n$ with designated summands in which all parts are odd. Lin also proved some congruences modulo 3 and 9 for PD$_t(n)$ and PDO$_t(n)$, and conjectured some congruences modulo 8. Very recently, Adansie, Chern, and Xia found two new infinite families of congruences modulo 9 for PD$_t(n)$. In this paper, we prove the congruences modulo 8 conjectured by Lin and also find many new congruences and infinite families of congruences modulo some small powers of 2.

math.NT↗

arXiv2018

Higher-component quadrupole polarizabilities: Estimations for the clock states of the alkaline earth-metal ions

Derivations for the higher tensor components of the quadrupole polarizabilities are given and their values for the metastable states of the Ca$^+$, Sr$^+$ and Ba$^+$ alkaline earth-metal ions are estimated. We also give the scalar quadrupole polarizabilities of the ground and metastable states of these ions to compare our results with the previously available theoretical and experimental results. Reasonably good agreement between our calculations with the previous values of scalar quadrupole polarizabilities demonstrate their correctness. The reported scalar and tensor quadrupole polarizabilities could be very useful to estimate the uncertainties due to the gradient of the electric fields in the clock frequencies of the above alkaline earth-metal ions when accuracies of these frequency measurements attain below 10$^{-19}$ precision level.

physics.atom-ph↗

arXiv2015

Decay analysis of compound nuclei with mass A$\sim 30-200$ formed in the reactions involving loosely bound projectiles

The dynamics of the reactions forming compound nuclei using loosely bound projectiles is analysed within the framework of dynamical cluster decay model (DCM) of Gupta and Collaborators. We have analysed different reactions with $^{7}Li$, $^{9}Be$ and $^{7}Be$ as neutron rich and neutron deficient projectiles, respectively, on different targets at the three $E_{lab}$ values, forming compound nuclei within the mass region A$\sim 30-200$. The contributions of light particles LPs ($A\le4$) cross sections $σ_{LP}$, energetically favoured intermediate mass fragments IMFs ($5 \le A_2 \le 20$) cross sections $σ_{IMF}$ as well as fusion-fission $\it{ff}$ cross sections $σ_{ff}$ constitute the $σ_{fus}$ (=$σ_{LP}$+$σ_{IMF}$+$σ_{ff}$) for these reactions. The contribution of the emitted LPs, IMFs and ff fragments is added for all the angular momentum upto the $\ell_{max}$ value, for the resepctive reactions. Interestingly, we find that the $ΔR^{emp}$, the only parameter of model and uniquely fixed to address the $σ_{fus}$ for all other reactions having $\it same$ loosely bound projectile at the chosen incident energy. It may be noted that the dynamical collective mass motion of preformed LPs, IMFs and ff fragments or clusters through the modified interaction potential barrier are treated on parallel footing. We see that the values of modified interaction barrier heights $ΔV_{B}^{emp}$ for such reactions are almost of the same amount specifically at the respective $\ell_{max}$ values.

nucl-th↗

arXiv2011

Influence of momentum dependent interactions on nuclear stopping in symmetric heavy-ion collisions

The role of momentum dependent interactions is studied in nuclear stopping at intermediate energy using an isospin-dependent quantum molecular dynamics model. Present calculations are performed at incident energy between 50 and 1000 MeV/nucleon. Our findings show that nuclear stopping is sensitive towards the impact parameter, incident energies as well as towards the mass of the colliding system. Further, the degree of stopping is suppressed by the inclusion of momentum dependent interactions, whereas the particle production is not affected by the MDI.

nucl-th↗

arXiv2011

Remarks on the non-equilibrium effects and collision dynamics in heavy-ion collisions

We study the beam energy dependence of equilibration process and space-time characteristics of participant and spectator matter. For this, we simulated the semi-central collisions of $^{40}Ca+ ^{40}Ca$ at incident energies of 400, 600 and 1000 AMeV within the \emph{quantum molecular dynamics} (QMD) approach. Our numerical calculations based on the molecular dynamics approach show that incident energy of the projectile influences the reaction observables drastically. The effect is more visible for transverse expansion of the nuclear matter and transparency behavior. The degree of thermalization of participant matter, however, remains independent of the incident energy. The characteristics of the trajectories followed by the nucleons suffering maximal and minimal binary collisions are also analyzed.

nucl-th↗