arXiv subjects

Tarek Ibrahim

Publications and source records attributed to Tarek Ibrahim.

At least 19 recordsLinked to original sources

arXiv2026

Higgs Mass and CP violating Phases Implications on the SUSY Breaking Scale in MSSM

The large Higgs mass $m_h \approx 125 GeV$ can raise the values of the SUSY breaking parameters in the Minimal Supersymmetric Standard Model MSSM to the range of several TeV scale. The CP violating phases in the MSSM can induce EDMs of the fermions in the theory already in conflict with the current experimental upper limit unless the masses of the SUSY partners are on the heavy side. We invistigate the implications of both constraints, the Higgs Mass and the complete set of SUSY CP violating phases in the analysis of the electric dipole moments EDMs on the SUSY breaking parameters and thus on the SUSY mass spectrum. We use the electric dipole moments of the electron, the neutron and the proton as our probes in this study.

hep-ph↗

arXiv2025

LookWhere? Efficient Visual Recognition by Learning Where to Look and What to See from Self-Supervision

Vision transformers are ever larger, more accurate, and more expensive to compute. The expense is even more extreme at high resolution as the number of tokens grows quadratically with the image size. We turn to adaptive computation to cope with this cost by learning to predict where to compute. Our LookWhere method divides the computation between a low-resolution selector and a high-resolution extractor without ever processing the full high-resolution input. We jointly pretrain the selector and extractor without task supervision by distillation from a self-supervised teacher, in effect, learning where and what to compute simultaneously. Unlike prior token reduction methods, which pay to save by pruning already-computed tokens, and prior token selection methods, which require complex and expensive per-task optimization, LookWhere economically and accurately selects and extracts transferrable representations of images. We show that LookWhere excels at sparse recognition on high-resolution inputs (Traffic Signs), maintaining accuracy while reducing FLOPs by up to 34x and time by 6x. It also excels at standard recognition tasks that are global (ImageNet classification) or local (ADE20K segmentation), improving accuracy while reducing time by 1.36x. See https://github.com/antofuller/lookwhere for the code and weights.

cs.CV↗

arXiv2021

A decaying neutralino as dark matter and its gamma ray spectrum

It is shown that a decaying neutralino in a supergravity unified framework is a viable candidate for dark matter. Such a situation arises in the presence of a hidden sector with ultraweak couplings to the visible sector where the neutralino can decay into the hidden sector's lightest supersymmetric particle (LSP) with a lifetime larger than the lifetime of the universe. We present a concrete model where the MSSM/SUGRA is extended to include a hidden sector comprised of $U(1)_{X_1} \times U(1)_{X_2}$ gauge sector and the LSP of the hidden sector is a neutralino which is lighter than the LSP neutralino of the visible sector. We compute the loop suppressed radiative decay of the visible sector neutralino into the neutralino of the hidden sector and show that the decay can occur with a lifetime larger than the age of the universe. The decaying neutralino can be probed by indirect detection experiments, specifically by its signature decay into the hidden sector neutralino and an energetic gamma ray photon. Such a gamma ray can be searched for with improved sensitivity at Fermi-LAT and by future experiments such as the Square Kilometer Array (SKA) and the Cherenkov Telescope Array (CTA). We present several benchmarks which have a natural suppression of the hadronic channels from dark matter annihilation and decays and consistent with measurements of the antiproton background.

hep-ph↗

arXiv2018

Observables of low-lying supersymmetric vectorlike leptonic generations via loop corrections

A correlated analysis of observables arising from loop induced effects from a vectorlike generation is given. The observables include flavor changing radiative decays $μ\to e γ, τ\to μγ, τ\to e γ$, electric dipole moments of the charged leptons $e,μ, τ$, and corrections to magnetic dipole moments of $g_μ-2$ and $g_e-2$. In this work we give a full analysis of the corrections to these observables by taking into account both the supersymmetry loops as well as the exchange of a vectorlike leptonic generation. Thus the fermion mass matrix involves a $5\times 5$ mixing matrix while the scalar sector involves a $10\times 10$ mixing matrix including the CP violating phases from the vectorlike sector. The analysis is done under the constraint of the Higgs boson mass at the experimentally measured value. The loops considered include the exchange of $W$ and $Z$ bosons and of leptons and a mirror lepton, and the exchange of charginos and neutralinos, sleptons and mirror sleptons. The correction to the diphoton decay of the Higgs $h\to γγ$ including the exchange of the vectorlike leptonic multiplet is also computed.

hep-ph↗

arXiv2017

Flavor violating top decays and flavor violating quark decays of the Higgs boson

In the standard model flavor violating decays of the top quark and of the Higgs boson are highly suppressed. Further, the flavor violating decays of the top and of the Higgs are also small in MSSM and not observable in current or in near future experiment. In this work we show that much larger branching ratios for these decays can be achieved in an extended MSSM model with an additional vector like quark generation. Specifically we show that in the extended model one can achieve branching ratios for $t\to h^0 c$ and $t\to h^0 u$ as large as the current experimental upper limits given by the ATLAS and the CMS Collaborations. We also analyze the flavor violating quark decay of the Higgs boson, i.e., $h^0\to b\bar s + \bar b s$ and $h^0\to b\bar d + \bar b d$. Here again one finds that the branching ratio for these decays can be as large as $O(1)\%$. The analysis is done with inclusion of the CP phases in the Higgs sector, and the effect of CP phases on the branching ratios is investigated. Specifically the Higgs sector spectrum and mixings are computed involving quarks and mirror quarks, squarks and mirror squarks in the loops consistent with the Higgs boson mass constraint. The resulting effective Lagrangian with inclusion of the vector like quark generation induce flavor violating decays at the tree level. The test of the branching ratios predicted could come with further data from LHC13 and such branching ratios could also be accessible at future colliders such as the Higgs factories where the Higgs couplings to fermions will be determined with greater precision.

hep-ph↗

arXiv2016

Flavor violating leptonic decays of the Higgs boson

Recent data from the ATLAS and CMS detectors at the Large Hadron Collider at CERN give a hint of possible violation of flavor in the leptonic decays of the Higgs boson. In this work we analyze the flavor violating leptonic decays $H^0_1\to l_i \bar l_j$ ($i\neq j$) within the framework of an MSSM extension with a vectorlike leptonic generation. Specifically we focus on the decay mode $H^0_1\to μτ$. The analysis is done including tree and loop contributions involving exchange of $W, Z$, charge and neutral higgs and leptons and mirror leptons, charginos and neutralinos and sleptons and mirror sleptons. It is found that a substantial branching ratio of $H^0_1\to μτ$, i.e., of as much a ${\cal{O}}(1)\%$, can be achieved in this model, the size hinted by the ATLAS and CMS data. The flavor violating decays $H^0_1\to eμ, eτ$ are also analyzed and found to be consistent with the current experimental limits. An analysis of the dependence of flavor violating decays on CP phases is given. The analysis is extended to include flavor decays of the heavier Higgs bosons. A confirmation of the flavor violation in Higgs boson decays with more data that is expected from LHC at $\sqrt s=13$ TeV will be evidence of new physics beyond the standard model.

hep-ph↗

arXiv2016

The Higgs boson mass constraint and the CP even-CP odd Higgs boson mixing in an MSSM extension

One loop contributions to the CP even-CP odd Higgs boson mixings arising from contributions due to exchange of a vectorlike multiplet are computed under the Higgs boson mass constraint. The vectorlike multiplet consists of a fourth generation of quarks and a mirror generation. This sector brings in new CP phases which can be large consistent with EDM constraints. In this work we compute the contributions from the exchange of quarks and mirror quarks $t_{4L}, t_{4R}, T_{L}, T_{R}$, and their scalar partners, the squarks and the mirror squarks. The effect of their contributions to the Higgs boson masses and mixings are computed and analyzed. The possibility of measuring the effects of mixing of CP even and CP odd Higgs in experiment is discussed. It is shown that the branching ratios of the Higgs bosons into fermion pairs are sensitive to new physics and specifically to CP phases.

hep-ph↗

arXiv2016

Leptonic $g-2$ moments, CP phases and the Higgs boson mass constraint

Higgs boson mass measurement at $\sim 125$ GeV points to a high scale for SUSY specifically the scalar masses. If all the scalars are heavy, supersymmetric contribution to the leptonic $g-2$ moments will be significantly reduced. On the other hand the Brookhaven experiment indicates a 3sigma deviation from the standard model prediction. Here we analyze the leptonic $g-2$ moments in an extended MSSM model with inclusion of a vector like leptonic generation which brings in new sources of CP violation. In this work we consider the contributions to the leptonic $g-2$ moments arising from the exchange of charginos and neutralinos, sleptons and mirror sleptons, and from the exchange of $W$ and $Z$ bosons and of leptons and mirror leptons. We focus specifically on the $g-2$ moments for the muon and the electron where sensitive measurements exist. Here it is shown that one can get consistency with the current data on $g-2$ under the Higgs boson mass constraint. Dependence of the moments on CP phases from the extended sector are analyzed and it is shown that they are sensitively dependent on the phases from the new sector. It is shown that the corrections to the leptonic moments arising from the extended MSSM sector will be non-vanishing even if the SUSY scale extends into the PeV region.

hep-ph↗

arXiv2015

Chromoelectric Dipole Moments of Quarks in MSSM Extensions

An analysis is given of the chromoelectric dipole moment of quarks and of the neutron in an MSSM extension where the matter sector contains an extra vectorlike generation of quarks and mirror quarks. The analysis includes contributions to the CEDM from the exchange of the $W$ and the $Z$ bosons, from the exchange of charginos and neutralinos and the gluino. Their contribution to the EDM of quarks is investigated. The interference between the MSSM sector and the new sector with vectorlike quarks is investigated. It is shown that inclusion of the vectorlike quarks can modify the quark EDMs in a significant way. Further, this interference also provides a probe of the vectorlike quark sector. These results are of interest as in the future measurements on the neutron EDM could see an improvement up to two orders of magnitude over the current experimental limits and provide a window to new physics beyond the standard model.

hep-ph↗

arXiv2015

$μ\to e γ$ Decay in an MSSM Extension

An analysis is given of the decay $μ\to e+ γ$ in an MSSM extension with a vectorlike generation. Here mixing with the mirrors allows the possibility of this decay. The analysis is done at the one loop level with the exchange of charginos and neutralinos and of sleptons and mirror sleptons in the loops. A one loop analysis with W and Z boson exchange and mirror leptons and neutrinos is also considered. The effects of CP violating phases from the new sector on the decay $μ\to e γ$ are analyzed in detail. The constraints arising from the current upper limit on the branching ratio ${\cal{B}}(μ\to {e} γ)$ from the MEG experiment of $2.4\times 10^{-12}$ (at 90\% CL) on the parameter space of SUSY models and on vectorlike models are explored. Further, the MEG experiment is likely to improve the upper limit by an order of magnitude in the coming years. The improved limits will allow one to probe a much larger domain of the parameter space of the extended models.

hep-ph↗

arXiv2015

The Neutron Electric Dipole Moment and Probe of PeV Scale Physics

The experimental limit on the neutron electric dipole moment is used as a possible probe of new physics beyond the standard model. Within MSSM we use the current experimental limit on the neutron EDM and possible future improvement as a probe of high scale SUSY. Quantitative analyses show that scalar masses as large as a PeV and larger could be probed in improved experiment far above the scales accessible at future colliders. We also discuss the neutron EDM as a probe of new physics models beyond MSSM. Specifically we consider an MSSM extension with a particle content including a vectorlike multiplet. Such an extension brings in new sources of CP violation beyond those in MSSM. These CP phases contribute to the EDM of the quarks and to the neutron EDM. These contributions are analyzed in this work where we include the supersymmetric loop diagrams involving the neutralinos, charginos, the gluino, squark and mirror squark exchange diagrams at the one loop level. We also take into account the contributions from the $W$, $Z$, quark and mirror quark exchanges arising from the mixings of the vectorlike generation with the three generations. It is shown that the experimental limit on the neutron EDM can be used to probe such new physics models. In the future one expects the neutron EDM to improve an order of magnitude or more allowing one to extend the probe of high scale SUSY and of new physics models. For the MSSM the probe of high scales could go up to and beyond PeV scale masses.

hep-ph↗

arXiv2014

Electron EDM as a Sensitive Probe of PeV Scale Physics

We give a quantitative analysis of the electric dipole moments as a probe of high scale physics. We focus on the electric dipole moment of the electron since the limit on it is the most stringent. Further, theoretical computations of it are free of QCD uncertainties. The analysis presented here first explores the probe of high scales via electron EDM within MSSM where the contributions to the electric dipole moment (EDM) arise from the chargino and the neutralino exchanges in loops. Here it is shown that the electron EDM can probe mass scales from tens of TeV into the PeV range.The analysis is then extended to include a vectorlike generation which can mix with the three ordinary generations. Here new CP phases arise and it is shown that the electron EDM now has not only a supersymmetric contribution from the exchange of charginos and neutralinos but also a non-supersymmetric contribution from the exchange of W and Z bosons. It is further shown that the interference of the supersymmetric and the non-supersymmetric contribution leads to the remarkable phenomenon where the electron EDM as a function of the slepton mass first falls and become vanishingly small and then rises again as the slepton mass increases This phenomenon arises as a consequence of cancellation between the SUSY and the non-SUSY contribution at low scales while at high scales the SUSY contribution dies out and the EDM is controlled by the non-SUSY contribution alone. The high mass scales that can be probed by the EDM are far in excess of what accelerators will be able to probe. The sensitivity of the EDM to CP phases both in the SUSY and the non-SUSY sectors are also discussed.

hep-ph↗

arXiv2014

Probe of New Physics using Precision Measurement of the Electron Magnetic Moment

The anomalous magnetic moment of the electron is determined experimentally with an accuracy of $2.8\times 10^{-13}$ and the uncertainty may decrease by an order of magnitude in the future. While the current data is in excellent agreement with the standard model, the possible future improvement in the error in $Δa_e= a_e^{\text{exp}}- a_e^{\text{theory}}$ has recently drawn interest in the electron anomalous magnetic moment as a possible probe of new physics beyond the standard model. In this work we give an analysis of such physics in an extension of the minimal supersymmetric standard model with a vector multiplet. In the extended model the electroweak contribution to the anomalous magnetic moment of the electron include loop diagrams involving in addition to the exchange of W and Z, the exchange of charginos, sneutrinos and mirror sneutrinos, and the exchange of neutralinos, sleptons and mirror sleptons. The analysis shows that a contribution to the electron magnetic moment much larger than expected by $m_e^2/m_μ^2$ scaling of the deviation of the muon anomalous magnetic moment over the standard model prediction, i.e., $Δa_μ= 3 \times 10^{-9}$ as given by the Brookhaven experiment, can be gotten within the MSSM extension. Effects of CP violating phases in the extended MSSM model on the corrections to the supersymmetric electroweak contributions to $a_e$ are also investigated. The analysis points to the possibility of detection of new physics effects with modest improvement on the error in $Δa_e= a_e^{\text{exp}} - a_e^{\text{theory}}$.

hep-ph↗

arXiv2014

Large Neutrino Magnetic Dipole Moments in MSSM Extensions

An analysis of the Dirac neutrino magnetic moment with standard model interactions gives $μ_ν\sim 3 \times 10^{-19} μ_B (m_ν/1 eV)$. The observation of a significantly larger magnetic moment will provide a clear signal of new physics beyond the standard model. The current experimental limits on the neutrino magnetic moments are orders of magnitude larger than the prediction with the standard model interactions and thus its test appears out of reach. Here we give an analysis of the Dirac neutrino magnetic moments within the framework of a minimal supersymmetric standard model extension with a vectorlike lepton generation. Specifically we compute the moments arising from the exchange of W and the charged leptons in the loop, as well as from the exchange of charginos, charged sleptons and charged mirror sleptons. It is shown that the neutrino moment in this case can be several orders of magnitude larger than the one with standard model like interactions, lying close to and below the current experimental upper limits and should be accessible in improved future experiment. A correlated prediction of the heaviest neutrino lifetimes from radiative decays to the lighter neutrinos via exchange of charginos and sleptons in the loops is also made. The predicted lifetimes are several orders of magnitudes smaller than the one with the standard model interactions and also lie close to the current experimental limits from analyses using the cosmic background neutrino data.

hep-ph↗

arXiv2013

Radiative Decays of Cosmic Background Neutrinos in Extensions of MSSM with a Vector Like Lepton Generation

An analysis of radiative decays of the neutrinos $ν_j\to ν_l γ$ is discussed in MSSM extensions with a vector like lepton generation. Specifically we compute neutrino decays arising from the exchange of charginos and charged sleptons where the photon is emitted by the charged particle in the loop. It is shown that while the lifetime of the neutrino decay in the Standard Model is $\sim 10^{43}$ yrs for a neutrino mass of 50 meV, the current lower limit from experiment from the analysis of the Cosmic Infrared Background is $\sim 10^{12}$ yrs and thus beyond the reach of experiment in the foreseeable future. However, in the extensions with a vector like lepton generation the lifetime for the decays can be as low as $\sim 10^{12}- 10^{14}$ yrs and thus within reach of future improved experiments. The effect of CP phases on the neutrino lifetime is also analyzed. It is shown that while both the magnetic and the electric transition dipole moments contribute to the neutrino lifetime, often the electric dipole moment dominates even for moderate size CP phases.

hep-ph↗

arXiv2012

$τ\to μγ$ Decay in Extensions with a Vector Like Generation

An analysis is given of the decay $τ\to μ+ γ$ in MSSM extensions with a vector like generation. Here mixing with the mirrors allows the possibility of this decay. The analysis is done at one loop with the exchange of charginos and neutralinos and of sleptons and mirror sleptons in the loops. It is shown that a branching ratio ${\cal B}(τ\to μ+γ)$ in the range $4.4\times 10^{-8} -10^{-9}$ can be gotten which would be accessible to improved experiment such as at SuperB factories for this decay. The effects of CP violation on this decay are also analyzed.

hep-ph↗

arXiv2011

The Chromoelectric Dipole Moment of the Top Quark in Models with Vector Like Multiplets

The chromoelectric dipole moment of the top quark is calculated in a model with a vector like multiplet which mixes with the third generation in an extension of the MSSM. Such mixings allow for new CP violating phases. Including these new CP phases, the chromoelectric dipole moment that generates an electric dipole of the top in this class of models is computed. The top chromoelectric dipole moment operator arises from loops involving the exchange of the W, the Z as well as from the exchange involving the charginos, the neutralinos, the gluino, and the vector like multiplet and their superpartners. The analysis of the chromoelectric dipole moment operator of the top is more complicated than for the light quarks because the mass of the external fermion, in this case the top quark mass, cannot be ignored relative to the masses inside the loops. A numerical analysis is presented and it is shown that the contribution to the top EDM could lie in the range ($10^{-19}-10^{-18})$ ecm consistent with the current limits on the EDM of the electron, the neutron and on atomic EDMs. A top EDM of size $(10^{-19}-10^{-18})$ ecm could be accessible in collider experiments such as at the LHC and at the ILC.

hep-ph↗

arXiv2010

The top quark electric dipole moment in an MSSM extension with vector like multiplets

The electric dipole moment (EDM) of the top quark is calculated in a model with a vector like multiplet which mixes with the third generation in an extension of the MSSM. Such mixings allow for new CP violating phases. Including these new CP phases, the EDM of the top in this class of models is computed. The top EDM arises from loops involving the exchange of the W, the Z as well as from the exchange involving the charginos, the neutralinos, the gluino, and the vector like multiplet and their superpartners. The analysis of the EDM of the top is more complicated than for the light quarks because the mass of the external fermion, in this case the top quark mass cannot be ignored relative to the masses inside the loops. A numerical analysis is presented and it is shown that the top EDM could be close to $10^{-19} ecm$ consistent with the current limits on the EDM of the electron, the neutron and on atomic EDMs. A top EDM of size $10^{-19}ecm$ could be accessible in collider experiments such as the ILC.

hep-ph↗