arXiv subjects

Shakeel Mahmood

Publications and source records attributed to Shakeel Mahmood.

9 recordsLinked to original sources

arXiv2026

Neutral-current neutrino-nucleus scattering off I (127) and Cs (133): Coherent and incoherent contributions with electroweak refinements for odd-A nuclei

Calculations of neutral-current neutrino-nucleus scattering cross sections are important for interpreting low- and intermediate-energy neutrino data, where terrestrial measurements remain limited. The first observation of coherent elastic neutrino-nucleus scattering (CEvNS) in 2017 with a CsI[Na] detector at the Spallation Neutron Source reported results consistent with Standard Model expectations, motivating improved theoretical descriptions beyond the purely coherent regime. In this work, we calculate neutral-current scattering cross sections for 127I and 133Cs within a unified analytical framework that consistently incorporates coherent elastic, incoherent excitation, and spin-dependent axial contributions relevant for odd-A nuclei. A consistent distinction between nuclear and nucleon form factors is maintained throughout the formalism. The incoherent contribution is evaluated using structure-function methods, providing a physically motivated decomposition of the total cross section. Electroweak effects are included through momentum-transfer-dependent sin^2(theta_W) corrections in the MS-bar scheme together with flavor-dependent neutrino charge-radius contributions implemented consistently in the vector couplings. Cross sections are presented as functions of neutrino energy and for decay-at-rest neutrino spectra in the low-to-intermediate energy region where elastic and quasi-elastic processes dominate. Inclusion of incoherent and axial contributions enhances the total cross section near Enu ~ 10 MeV, while the incoherent component becomes dominant around Enu ~ 50 MeV. Expected interaction rates for decay-at-rest neutrinos are of order 0.1 events kg^-1 yr^-1 near a 40 keV recoil threshold. The results provide a systematic assessment of subleading contributions relevant for CsI-based detectors and astrophysical neutrino applications.

hep-ph↗

arXiv2024

The 3-3-1 model with exotic electric charges, right-handed neutrinos with type-I+II seesaw mechanism and its effects on LFV

In this research, we propose a modified version of the 3-3-1 model, incorporating a type I+II seesaw mechanism and Z4 discrete symmetry, as a framework for investigating lepton flavor-violating (LFV) decays. This model successfully yields the left-handed neutrinos mass square difference in the eV scale, with specific values of mass square differences; and generates mixing angles that align with experimental data. Furthermore, we develop SARAH and SPheno algorithms tailored for our modified model, enabling us to estimate the magnitude of LFV observables. Our calculations indicate favorable results for various LFV branching ratios. These findings demonstrate improved agreement with experimental measurements compared to previously reported results, which typically fall within the range of 10^-2 to 10^-6.

hep-ph↗

arXiv2023

Isospin Decomposition of D Mesons

This work focuses on decomposition of isospin amplitude of D meson non-leptonic decays. Isospin vector algebra is used to show the equivalency of two amplitude decompositions. We restrict to the transitions involving only Del I = 1 and Del I = 0: The isospin symmetry is relating charge channel (D+ -> K+,Pi+ Pi-; D+ -> K+, Pi0, Pi0 and D+-> K0, Pi0,Pi+); and neutral channel (D0 -> K0,Pi+,Pi- D0 -> K0, Pi0, Pi0 and D0 -> K+, Pi0, Pi-) with each other. Equivalent triangle relations are obtained for both channels.

hep-ph↗

arXiv2022

Electron-Neutrino Scattering a Strong Aspirant for Precision Measurements

This work focuses on the study of electron and neutrino scattering in the frame work of physics beyond the standard model (SM) called new physics (NP). Both Model Independent (MI) and Model Depen-dent (MD) ways are used to constrain NP. R-parity violating Supersymmetry ( /Rp SUSY) Model is used to perform MD analysis, where the scattering cross-section is infuenced by new s-bosons. For MI way non-standard neutrino intections (NSI) are used where there is no need of introducing any new particle. LSND and LAMPF-E225 data is used to identify the physically allowed and forbidden regions for nonunivarsal NSI parameters and nonunivarsal SUSY parameters. Similarly, CHARM-II, BNL-COL and BNL-E734 experimental is used to explore allowed and forbidden regions and limits are established. Furthermore, we establish a relationship between MI and MD coupling parameters.

hep-ph↗

arXiv2021

Study of Nonstandard Interactions in Rare Decays of Hyprons with Missing Energy

We study rare decays of hyperons involving di-neutrinos in the final state in the standard model and compare them with other models. It is claimed that the branching ratio calculated in this article are 2 times the values of 331 model and exceptionally large than the previously calculated values. We explore the nonstandard neutrino interactions (NSI) and constrain NSIs free parameter with these decays. We obtain stringent bounds on of O(0.01). We show that branching ratios (Br) could be in the range of BES III if constraints are O(0.3).

hep-ph↗

arXiv2017

Study of rare mesonic decays involving di-neutrinos in their final state

We have carried out phenomenological implication of R-parity violating ($\NEG% {R}_{p}$) Minimal Supersymmetric Model (MSSM) via analyses of pure leptonic($% M\rightarrow ν\barν$) and semileptonic decays of pseudo-scalar mesons(% $M\rightarrow Xν\barν$). These analyses involve prediction of branching fraction of pure leptonic decays by using experimental limits/bounds derived from the study of semileptonic decays on $\NEG{R}_{p}$ parameters. We have found, in general that $\NEG{R}_{p}$ contribution dominates over the SM contribution i.e., by a factor of $10^{2}$ for the semleptonic decays of $K^{0}$, $10$ for the pure leptonic decays of $K_{L,S}$ , while $10^{2}~$\& $10^{4}$ in case of $B_{s}$ and $B_{d}$ respectively. This demonstrates the role of $\NEG{R}_{p}$ as a viable model for the study of NP contribution in rare decays.

hep-ph↗

arXiv2015

The study of NSIs in B and KL rare decays with three generations of quarks and interference effects between the standard model and NSIs

We study the rare decays of B meson. We want to constraint the NSIs by using these reactions. We show that there is a strong dependence of these reactions on new physics parameter. We include second and third generation of quarks in the loop for these decays. We further point out that the constraints for second generation are more precise as compared to second and third. We further point out that for inclusive decay, the u quark induce NSIs are giving very very small contribution. We also study KL rare decay to pi zero, neutrino and anti-neutrino. We also study the interference between the standard model and NSIs.

hep-ph↗

arXiv2014

New Physics Through Rare Decays Of Mesons

We study the contribution of 2nd generation of quarks in NSIs. We investigate it through the rare decays of mesons involving neutrinos in the final state. We show the C and s quarks can effect NSIs just like u and s. We explore constraints on free parameter of NSIs. For this purpose we select 6 FCNC semi-leptonic processes of B, D and K mesons having neutrinos in the final state

hep-ph↗

arXiv2014

New Physics from NSIs in charm Decays

We study rare decays of Charm in NSIs. We calculate the NSIs Branching ratios of these decays. There is a strong dependence of these on new physics parameter. They provide, stringent constraints on free parameter in tau.

hep-ph↗