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Ahmed Rashed

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Published work

14 published item(s)

preprint2026arXiv

Rethinking Convolutional Networks for Attribute-Aware Sequential Recommendation

Attribute-aware sequential recommendation entails predicting the next item a user will interact with based on a chronologically ordered history of past interactions, enriched with item attributes. Existing methods typically leverage self-attention mechanisms to aggregate the entire sequence into a unified representation used for next-item prediction. While effective, these models often suffer from high computational complexity and memory consumption, limiting their ability to process long user histories. This constraint restricts the model's capacity to fully capture long-term user preferences. In some scenarios, modeling item interactions purely through attention may also not be the most effective approach to extract sequential patterns. In this work, we propose ConvRec, an alternative method with linear computational and memory complexity that employs convolutional layers in a hierarchical, down-scaled fashion to generate compact, yet expressive sequence representations. To further enhance the model's ability to capture diverse sequential patterns, each layer aggregates the neighboring items gradually to reach a comprehensive sequence representation. Extensive experiments on four real-world datasets demonstrate that our approach outperforms state-of-the-art sequential recommendation models, highlighting the potential of convolution-based architectures for efficient and effective sequence modeling in recommendation systems. Our implementation code and datasets are available here https://github.com/ismll-research/ConvRec.

preprint2022arXiv

A.I. and Data-Driven Mobility at Volkswagen Financial Services AG

Machine learning is being widely adapted in industrial applications owing to the capabilities of commercially available hardware and rapidly advancing research. Volkswagen Financial Services (VWFS), as a market leader in vehicle leasing services, aims to leverage existing proprietary data and the latest research to enhance existing and derive new business processes. The collaboration between Information Systems and Machine Learning Lab (ISMLL) and VWFS serves to realize this goal. In this paper, we propose methods in the fields of recommender systems, object detection, and forecasting that enable data-driven decisions for the vehicle life-cycle at VWFS.

preprint2022arXiv

The Dark $Z'$ and Sterile Neutrinos Behind Current Anomalies

We show how, in the $B-L$ extension of the SM (BLSM) with an Inverse Seesaw (IS) mechanism for neutrino mass generation, a light $Z'$ state with moderate couplings to SM objects, hence `dark' in its nature, can be associated, in conjunction with light sterile neutrinos, to some present day data anomalies, such as the anomalous magnetic moment of the muon as well as a possible signal indicating the existence of sterile neutrinos in neutrino beam experiments.

preprint2020arXiv

Probing $Z^\prime$ Mediated Charged Lepton Flavor Violation with Taus at the LHeC

While charged lepton flavor violation (cLFV) with taus is often expected to be largest in many extensions of the Standard Model (SM), it is currently much less constrained than cLFV with electrons and muons. We study the sensitivity of the LHeC to $e$-$τ$ (and $e$-$μ$) conversion processes $p e^- \to τ^- + j$ (and $p e^- \to μ^- + j$) mediated by a $Z'$ with flavor-violating couplings to charged leptons in the $t$-channel. Compared to current tests at the LHC, where cLFV decays of the $Z'$ (produced in the s-channel) are searched for, the LHeC has sensitivity to much higher $Z'$ masses, up to O(10) TeV. For cLFV with taus, we find that the LHeC sensitivity from the process $p e^- \to τ^- + j$ can exceed the current limits from collider and non-collider experiments in the whole considered $Z'$ mass range (above $500$ GeV) by more than two orders of magnitude. In particular for extensions of the SM with a heavy $Z'$, where direct production at colliders is kinematically suppressed, $e-τ$ conversion at LHeC provides an exciting new discovery channel for this type of new physics.

preprint2016arXiv

Probing lepton non-universality in tau neutrino Scattering

Recently hints of lepton flavor non-universality emerged in the BaBar and LHCb experiments. In this paper we propose tests of lepton universality in $ν_τ$ scattering. To parametrize the new physics we adopt an effective Lagrangian approach and consider the neutrino deep inelastic scattering processes $ν_τ+ N \to τ+ X$ and $ν_μ+ N \to μ+ X$ where we assume the largest new physics effects are in the $τ$ sector. We also consider an explicit leptoquark model in our calculations. In order to make comparison with the standard model and also in order to cancel out the uncertainties of the parton distribution functions, we consider the ratio of total and differential cross sections of tau-neutrino to muon-neutrino scattering. We find new physics effects that can possibly be observed at the proposed Search for Hidden Particles (SHiP) experiment at CERN.

preprint2013arXiv

Deviation from Tri-Bimaximal Mixing and Large Reactor Mixing Angle

Recent observations for a non-zero $θ_{13}$ have come from various experiments. We study a model of lepton mixing with a 2-3 flavor symmetry to accommodate the sizable $θ_{13}$ measurement. In this work, we derive deviations from the tri-bimaximal (TBM) pattern arising from breaking the flavor symmetry in the neutrino sector, while the charged leptons contribution has been discussed in a previous work. Contributions from both sectors towards accommodating the non-zero $θ_{13}$ measurement are presented.

preprint2013arXiv

Nonstandard interactions of tau neutrino via charged Higgs and $W'$ contribution

We consider charged Higgs and $W'$ gauge boson contributions to the quasielastic scattering $ν_τ+ n \rightarrow τ^- + p$ and $\barν_τ+ p \rightarrow τ^+ + n$ . These effects modify the standard model cross section for these processes and thus impact the extraction of the neutrino mixing angles $θ_{23}$ and $θ_{13}$ . We include form factor effects in our calculations and find the deviation of the actual mixing angle from the measured one, assuming the standard model cross section, can be significant and can depend on the energy of the neutrino.

preprint2013arXiv

Radiative Scaling Neutrino Mass with $A_4$ Symmetry

A new idea for neutrino mass was proposed recently, where its smallness is not due to the seesaw mechanism, i.e. not inversely proportional to some large mass scale. It comes from a one-loop mechanism with dark matter in the loop consisting of singlet Majorana fermions $N_i$ with masses of order 10 keV and neutrino masses are scaled down from them by factors of about $10^{-5}$. We discuss how this model may be implemented with the non-Abelian discrete symmetry $A_4$ for neutrino mixing, and consider the phenomenology of $N_i$ as well as the extra scalar doublet $(η^+,η^0)$.

preprint2013arXiv

Tau neutrino as a probe of nonstandard interaction

We study the $Δ$-resonance and deep inelastic scattering contributions in the tau-neutrino nucleon scattering $ν_τ+ N \to τ^- + X$ and $\barν_τ+ N \to τ^+ + X$ in the presence of a charged Higgs and a $W'$ gauge boson. The new physics effects to the quasielastic process have been discussed in a previous work. The extractions of the atmospheric mixing angle $θ_{23}$ rely on the standard model cross sections for $ν_τ+ N \to τ^- + X$ in $ν_τ$ appearance experiments. Corrections to the cross sections from the charged Higgs and $W'$ contributions modify the measured mixing angle. We include form factor effects in the new physics calculations and find the deviations of the mixing angle. If high-energy Long Base Line experiments are designed to measure $θ_{13}$ through tau neutrino appearance, the new physics effects to $ν_τ+ N \to τ^- + X$ and $\barν_τ+ N \to τ^+ + X$ can impact the extraction of this mixing angle. Finally, we investigate the new physics effects on the polarization of the $τ^\mp$ leptons produced in $ν_τ(\barν_τ)$ nucleon scattering.

preprint2013arXiv

Tau neutrino as a probe of nonstandard interactions via charged Higgs and $W'$ contribution

We discuss the impact of the presence of a charged Higgs and a $W'$ gauge boson on the tau-neutrino nucleon scattering $ν_τ+ N \rightarrow τ^- + X$ and $\barν_τ+ N \rightarrow τ^+ + X$. We show the effect of the new physics on the three subprocesses quasielastic, $Δ$-resonance, and deep inelastic scattering. The measurement of the atmospheric and reactor mixing angles $θ_{23}$ and $θ_{13}$, respectively, relies on the standard model cross section of the above processes if they have been measured in the appearance channels $ν_μ\rightarrow ν_τ$ and $\barν_e \rightarrow \barν_τ$ ($ν_e \rightarrow ν_τ$), respectively. Consideration of the new physics contributions to those reactions modifies the measured mixing angles, assuming the standard model cross section. We include form factor effects in the new physics calculations and find the deviations of the mixing angles which can be significant and can depend on the energy of the neutrino.

preprint2012arXiv

Scotogenic $A_4$ Neutrino Model for Nonzero $θ_{13}$ and Large $δ_{CP}$

Assuming that neutrinos acquire radiative seesaw Majorana masses through their interactions with dark matter, i.e. scotogenic from the Greek 'scotos' meaning darkness, and using the non-Abelian discrete symmetry $A_4$, we propose a model of neutrino masses and mixing with nonzero $θ_{13}$ and necessarily large leptonic CP violation, allowing both the normal and inverted hierarchies of neutrino masses, as well as quasi-degenerate solutions.

preprint2012arXiv

The charged lepton mass matrix and non-zero $θ_{13}$ with TeV scale New Physics

We provide an explicit structure of the charged lepton mass matrix which is 2-3 symmetric except for a single breaking of this symmetry by the muon mass. We identify a flavor symmetric limit for the mass matrices where the first generation is decoupled from the other two in the charged lepton sector while in the neutrino sector the third generation is decoupled from the first two generations. The leptonic mixing in the symmetric limit can be, among other structures, the bi-maximal (BM) or the tri-bimaximal (TBM) mixing. Symmetry breaking effects are included both in the charged lepton and the neutrino sector to produce corrections to the leptonic mixing and explain the recent $θ_{13}$ measurements. A model that extends the SM by three right handed neutrinos, an extra Higgs doublet, and two singlet scalars is introduced to generate the leptonic mixing.

preprint2011arXiv

The Top Forward Backward Asymmetry with general Z ' couplings

The measurement of the top forward-backward asymmetry in $\ttbar$ production measured at the Tevatron shows deviation from the Standard Model prediction. A $ u \to t$ transition via a flavor changing $Z^{\prime}$ can explain the data. We show that left handed $t_Lu_LZ^{\prime}$ couplings can be constrained from $B_{d,s}$ mixing while the constrains on the right handed couplings $t_R u_R Z^{\prime}$ vanish in the limit of $m_u \to 0$. We then consider the most general form of the $t uZ^{\prime}$ interaction which includes vector-axial vector as well as tensor type couplings and study how these couplings affect the top forward-backward asymmetry.

preprint2010arXiv

Probing light pseudoscalar, axial vector states through $η_{b} \toτ^{+}τ^{-}$

In this paper we explore the decay $η_b --> τ^+ τ^-$ as a probe for a light pseudoscalar or a light axial vector state. We estimate the standard model branching ratio for this decay to be $~4\times 10^{-9}$. We show that considerably larger branching ratios, up to the present experimental limit of ~8%, is possible in models with a light pseudoscalar or a light axial vector state. As we do not include possible mixing effects between the light pseudoscalar and the $η_b$, our results should be reliable when the pseudoscalar mass is away from the $η_b$ mass.