arXiv subjects

M. Rafi Alam

Publications and source records attributed to M. Rafi Alam.

At least 19 recordsLinked to original sources

arXiv2025

Neutrino-nucleon elastic scattering in presence of non-standard interactions: cross sections and nucleon polarizations

New physics beyond the Standard Model (SM) may appear in the form of non-standard neutrino interactions (NSI). We have studied neutral current (anti)neutrino-nucleon scattering in presence of NSI. We obtain that in this scenario, nucleon matrix elements depend not only on the isovector axial nucleon form factor but also on the isoscalar one. For the axial form factors we consequently rely on the quark flavor decomposition performed by QCD simulations in the lattice (LQCD). We have examined cross sections and polarization observables. For the current bounds on diagonal muon flavor NSI couplings we find substantial deviations from the SM predictions in cross sections and transverse polarizations of the outgoing nucleons. In view of the progress in the precision of LQCD determinations of nucleon properties, modern measurements of neutral current (anti)neutrino-nucleon scattering will be in the position to discover or significantly constrain NSI.

hep-ph↗

arXiv2024

Cabibbo suppressed hyperon production off nuclei induced by antineutrinos

In this work we study the production of $Σ$ and $Λ$ hyperons in strangeness changing $ΔS = -1$ charged current interactions of muon antineutrinos on nuclear targets. At the nucleon level, besides quasielastic scattering we consider the inelastic mechanism in which a pion is produced alongside the hyperon. Its relevance for antineutrinos with energies below 2 GeV is conveyed in integrated and differential cross sections. We observe that the distributions on the angle between the hyperon and the final lepton are clearly different for quasielastic and inelastic processes. Hyperon final state interactions, modeled with an intranuclear cascade, lead to a significant transfer from primary produced $Σ$'s into final $Λ$'s. They also cause considerable energy loss, which is apparent in hyperon energy distributions. We have investigated $Λ$ production off ${}^{40}$Ar in the conditions of the recently reported MicroBooNE measurement. We find that the $Λπ$ contribution, dominated by $Σ^*(1385)$ excitation, accounts for about one third of the cross section.

hep-ph↗

arXiv2021

Cabibbo suppressed single pion production off the nucleon induced by antineutrinos

In this work we study the $Σπ$ and $Λπ$ production off free nucleons driven by the strangeness-changing weak charged current. We calculate the total cross sections for all possible channels and estimate the flux-averaged total cross sections for experiments like MiniBooNE, SciBooNE, T2K, and Minerva. The model is based on the lowest order effective SU(3) chiral Lagrangians in the presence of an external weak charged current and contains Born and the lowest-lying decuplet resonant mechanisms that can contribute to these reaction channels. We also compare and discuss our results with others following similar and very different approaches.

hep-ph↗

arXiv2021

Weak Kaon Production off the nucleon and Watson's theorem

We have improved the tree-level model of Ref arXiv:1004.5484 [hep-ph] for weak production of kaons off nucleons by partially restoring unitarity. This is achieved by imposing Watson's theorem to the dominant vector and axial-vector contributions in appropriate angular momentum and isospin quantum number sectors. The observable consequences of this procedure are investigated.

hep-ph↗

arXiv2019

Weak production of strange $Ξ$ baryons off the nucleon

The charged current Cabibbo-supressed associated $K Ξ$ production off the nucleon induced by anti-neutrinos is studied at low and intermediate energies. The non-resonant terms are obtained using a microscopical model based on the SU(3) chiral Lagrangian. The basic parameters of the model are $f_π$, the pion decay constant, Cabibbo's angle, the proton and neutron magnetic moments and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. In addition, we also consider $Σ^\ast(1385)$ resonance, which can decay in $K Ξ$ final state when this channel is open. The studied mechanism is the prime source of $Ξ$ production at anti-neutrino energies around $2$ GeV and the calculated cross sections at these energies can be measured at the current and future neutrino experiments.

hep-ph↗

arXiv2016

Quasielastic production of polarized hyperons in antineutrino--nucleon reactions

We have studied the differential cross section as well as the longitudinal and perpendicular components of polarization of final hyperon($Λ$,$Σ$) produced in the antineutrino induced quasielastic charged current reactions on nucleon and nuclear targets. The nucleon-hyperon transition form factors are determined from the experimental data on quasielastic $(ΔS =0)$ charged current (anti)neutrino--nucleon scattering and the semileptonic decay of neutron and hyperons assuming G--invariance, T--invariance and SU(3) symmetry. The vector transition form factors are obtained in terms of nucleon electromagnetic form factors for which various parameterizations available in literature have been used. A dipole parameterization for the axial vector form factor and the pseudoscalar transition form factor derived in terms of axial vector form factor assuming PCAC and GT relation extended to strangeness sector have been used in numerical evaluations. The flux averaged cross section and polarization observables corresponding to CERN Gargamelle experiment have been calculated for quasielastic hyperon production and found to be in reasonable agreement with the experimental observations. The numerical results for the flux averaged differential cross section$\frac{dσ}{dQ^2}$ and longitudinal(perpendicular) polarization $P_L(Q^2)(P_P(Q^2))$ relevant for the antineutrino fluxes of MINER$ν$A, MicroBooNE, and T2K experiments have been presented. This will be useful in interpreting future experimental results on production cross sections and polarization observables from the experiments on the quasielastic production of hyperons induced by antineutrinos and explore the possibility of determining the axial vector and pseudoscalar form factors in the strangeness sector.

hep-ph↗

arXiv2016

Weak Quasielastic Production of Hyperons

We present the results for antineutrino induced quasielastic hyperon production from nucleon and nuclear targets \cite{Alam:2014bya,Singh:2006xp}. The inputs are the nucleon-hyperon(N--Y) transition form factors determined from the analysis of neutrino-nucleon scattering and semileptonic decays of neutron and hyperons using SU(3) symmetry. The calculations for the nuclear targets are done in local density approximation. The nuclear medium effects(NME) like Fermi motion, Pauli blocking and final state interaction(FSI) effects due to hyperon-nucleon scattering have been taken into account. The hyperons giving rise to pions through weak decays also contribute to the weak pion production in addition to the $Δ$ excitation mechanism which dominates in the energy region of $<$ 0.7 GeV. We also present the results of longitudinal and perpendicular components of polarization of final hyperon \cite{Akbar:2016awk}. These measurements in the future accelerator experiments with antineutrinos may give some information on axial vector and pseudoscalar form factors in the strangeness sector.

hep-ph↗

arXiv2016

Lepton production cross sections in quasielastic $ν/\barν-$A scattering

We present the results of (anti)neutrino induced CCQE cross sections from some nuclear targets in the energy region of $E_ν\le 1 GeV$. The aim of the study is to confront electron and muon production cross sections relevant for $ν_μ\leftrightarrow ν_e$ or $\barν_μ\leftrightarrow \barν_e$ oscillation experiments. The effects due to lepton mass and its kinematic implications, second class currents and uncertainties in the axial and pseudoscalar form factors are discussed for (anti)neutrino induced reaction cross sections on free nucleon as well as the nucleons bound in a nucleus where nuclear medium effects influence the cross section. The calculations have been performed using local Fermi gas model with nucleon correlation effects. The details are given in Ref.[1].

nucl-th↗

arXiv2016

Pion production off the nucleon

We have studied charged current neutrino/antineutrino induced weak pion production from nucleon. For the present study, contributions from $Δ(1232)$-resonant term, non-resonant background terms as well as contribution from higher resonances viz. $P_{11}$(1440), $D_{13}$(1520), $S_{11}$(1535), $S_{11}$(1650) and $P_{13}$(1720) are taken. To write the hadronic current for the non-resonant background terms, a microscopic approach based on SU(2) non-linear sigma model has been used. The vector form factors for the resonances are obtained from the helicity amplitudes provided by MAID. Axial coupling in the case of $Δ(1232)$ resonance is obtained by fitting the ANL and BNL $ν$-deuteron reanalyzed scattering data. The results of the cross sections are presented and discussed for all the possible channels of single pion production induced by charged current interaction.

hep-ph↗

arXiv2016

Revisiting $ν_μ(\barν_μ)$ and $ν_e(\barν_e) $ Induced Quasielastic Scattering from Nuclei in Sub-GeV Energy Region

We present the results of charged current quasielastic(CCQE) scattering cross sections from free as well as bound nucleons like in $^{12}C$, $^{16}O$, $^{40}Ar$ and $^{208}Pb$ nuclear targets in $E_ν(_{\barν})~\le~ $1 GeV energy region. The results are obtained using local Fermi gas model with and without RPA effect. The differences those may arise in the electron and muon production cross sections due to the different lepton mass, uncertainties in the axial dipole mass $M_A$ and pseudoscalar form factor, and due to the inclusion of second class currents have been highlighted for neutrino/antineutrino induced processes.

nucl-th↗

arXiv2015

Quasielastic hyperon production in $\barν_μ-$Nucleus interactions

We have studied quasielastic charged current hyperon production induced by $\barν_μ$ on free nucleon and the nucleons bound inside the nucleus. The calculations are performed for several nuclear targets like $^{12}C$, $^{40}Ar$, $^{56}Fe$ and $^{208}Pb$ which are presently being used in various oscillation experiments using accelerator neutrinos. The inputs are the hyperon-nucleon transition form factors determined from neutrino-nucleon scattering as well as from semileptonic decays of neutron and hyperons using SU(3) symmetry. The calculations for the nuclear targets are done in local density approximation. The nuclear medium effects(NME) due to Fermi motion and final state interaction(FSI) effect due to hyperon-nucleon scattering have been taken into account.

hep-ph↗

arXiv2015

Electron and Muon production cross sections in quasielastic $ν(\barν)$-Nucleus scattering for $E_ν< 1~GeV$

In this work, we have studied (anti)neutrino induced charged current quasielastic scattering from some nuclear targets in the energy region of $E_ν< 1~GeV$. Our aim is to confront electron and muon production cross sections relevant for $ν_μ\leftrightarrow ν_e$ or $\barν_μ\leftrightarrow \barν_e$ oscillation experiments. The effects due to lepton mass and its kinematic implications, radiative corrections, second class currents and uncertainties in the axial and pseudoscalar form factors are calculated for (anti)neutrino induced reaction cross sections on free nucleon as well as the nucleons bound in a nucleus where nuclear medium effects influence the cross section. For the nuclear medium effects we have taken some versions of Fermi gas model(FGM) available in literature. The results for (anti)neutrino-nucleus scattering cross section per interacting nucleons are compared with the corresponding results in free nucleon case.

nucl-th↗

arXiv2015

Weak charged and neutral current induced one pion production off the nucleon

We present a study of neutrino/antineutrino induced charged and neutral current single pion production off the nucleon. For this, we have considered $P_{33}(1232)$ resonance, non-resonant background terms, other higher resonances like $P_{11}(1440)$, $S_{11}(1535)$, $D_{13}(1520)$, $S_{11}(1650)$ and $P_{13}(1720)$. For the non-resonant background terms a microscopic approach based on SU(2) non-linear sigma model has been used. The vector form factors for the resonances are obtained by using the relationship between the electromagnetic resonance form factors and helicity amplitudes provided by MAID. Axial coupling $C_5^{A}(0)$ in the case of $P_{33}(1232)$ resonance is obtained by fitting the ANL and BNL $ν$-deuteron reanalyzed scattering data. The results are presented with and without deuteron effect for the total scattering cross sections for all possible channels viz. $ν_l(\barν_l)~+~N\rightarrow l^-(l^+)~+~N^\prime~+~π^i$; $ν_l(\barν_l)~+~N\rightarrow ν_l(\barν_l)~+~N^\prime~+~π^i$, where $N, N^\prime=p,n$, $π^i=~π^\pm$ or $π^0$ and $l=e, μ$.

hep-ph↗

arXiv2015

Weak Production of Strange Particles and $η$ Mesons off the Nucleon

The strange particle production induced by (anti)neutrino off nucleon has been studied for $|ΔS|=0$ and $|ΔS|=1$ channels. The reactions those we have considered are for the production of single kaon/antikaon, eta and associated particle production processes. We have developed a microscopical model based on the SU(3) chiral Lagrangian. The basic parameters of the model are $f_π$, the pion decay constant, Cabibbo angle, the proton and neutron magnetic moments and the axial vector coupling constants for the baryons octet. For antikaon production we have also included $Σ^*$(1385) resonance and for eta production $S_{11}$(1535) and $S_{11}$(1650) resonances are included.

hep-ph↗

arXiv2015

Weak Quasielastic Production of Hyperons and Threshold Production of Two Pions

We have studied quasielastic charged current hyperon production induced by $\barν_μ$ on free nucleon and the nucleons bound inside the nucleus and the results are presented for several nuclear targets like $^{40}Ar$, $^{56}Fe$ and $^{208}Pb$. The hyperon-nucleon transition form factors are determined from neutrino-nucleon scattering and semileptonic decays of neutron and hyperons using SU(3) symmetry. The nuclear medium effects(NME) due to Fermi motion and final state interaction(FSI) effect due to hyperon-nucleon scattering have been taken into account. Also we have studied two pion production at threshold induced by neutrinos off nucleon targets. The contribution of nucleon, pion, and contact terms are calculated using Lagrangian given by nonlinear $σ$ model. The contribution of the Roper resonance has also been taken into account. The numerical results for the cross sections are presented and compared with the experimental results from ANL and BNL.

hep-ph↗

arXiv2013

Weak Strangeness and Eta Production

We have studied strange particle production off nucleons through $ΔS =0 $ and $|ΔS| = 1$ channels, and specifically single kaon/antikaon, eta, associated particle production for neutrino/antineutrino induced processes as well as antineutrino induced single hyperon production processes. We have developed a microscopical model based on the SU(3) chiral Lagrangians. The basic parameters of the model are $f_π$, the pion decay constant, Cabibbo angle, the proton and neutron magnetic moments and the axial vector coupling constants for the baryons octet. For antikaon production we have also included $Σ^*(1385)$ resonance and for eta production $S_{11}(1535)$ and $S_{11}(1650)$ resonances are included.

hep-ph↗

arXiv2013

${\barν}_l$ induced pion production from nuclei at $\sim$1 GeV

We have studied charged current $\barν_l$ induced one pion production from $^{12}$C and $^{16}$O nuclear targets at MiniBooNE and atmospheric antineutrino energies. The calculations have been done for the incoherent pion production process as well as for the pions coming from the hyperons in the quasielastic production of $Λ$ and $Σ$. The calculations are done in the local density approximation. For the inelastic processes the calculations have been done in the $Δ$ dominance model and we take into account the effect of Pauli blocking, Fermi motion of the nucleon and renormalization of $Δ$ properties in the nuclear medium. The effect of final state interaction(FSI) of pions is also taken into account. For the hyperon production, the nuclear medium effects due to Fermi motion and FSI effects due to hyperon-nucleon scattering have been taken into account. These results may be quite useful in the analysis of SciBooNE, MicroBooNE, MINER$ν$A, and ArgoNeuT experiments when the pion analysis is done by using antineutrino beams.

nucl-th↗

arXiv2013

Weak production of strange particles off the nucleon

The strange particle production off the nucleon induced by neutrinos and antineutrinos is investigated at low and intermediate energies. We develop a microscopic model based on the SU(3) chiral Lagrangian. The studied mechanisms are the main source of single kaon production for (anti)neutrino energies up to 1.5 GeV. Using this model we have also studied the associated production of kaons and hyperons. The cross sections are large enough to be measured by experiments such as MINER$ν$A, T2K and NO$ν$A.

hep-ph↗