arXiv subjects

Tarek Ibrahim

Publications and source records attributed to Tarek Ibrahim.

54 records · Page 3Linked to original sources

arXiv2002

Phases and CP Violation in SUSY

We discuss CP violation in supersymmetric theories and show that CP phenomena can act as a probe of their origins, i.e., compactification and spontaneous supersymmetry breaking. CP violation as a probe of the flavor structure of supersymmetric theories is also discussed. A brief overview is given of several low energy phenomena where CP phases can produce new effects. These include important CP effects in processes involving sparticles and CP mixing effects in the neutral Higgs boson system. We also discuss the possibility of violations of scaling in the electric dipole moments (EDMs) due to the presence of nonuniversalities and show that with inclusion of nonuniversalities the muon EDM could be up to 1-2 orders of magnitude larger than implied by scaling and within reach of the next generation of experiments. Thus the EDMs are an important probe of the flavor structure of supersymmetric theories.

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arXiv2002

CP Violation in SUSY, Strings and Branes

A review is given of CP violation in a broad class of models based on supersymmetry, superstrings and brane models. Such models contain typically large CP violating phases which affect a variety of supersymmetric phenomenon at low energies and affect search for supersymmetry at colliders and in dark matter experiments. We focus here on few such phenomena, specifically the mixing of the CP even and the CP odd Higgs bosons which can be induced by loop corrections and on CP violation in the muon sector. Possible signals for the observation of CP violation are also discussed.

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arXiv2002

Neutralino Exchange Corrections to the Higgs Boson Mixings with Explicit CP Violation

A calculus for the derivatives of the eigen values of the neutralino mass matrix with respect to the CP violating background fields is developed and used to compute the mixings among the CP even and the CP odd Higgs sectors arising from the inclusion of the neutralino sector consisting of the neutralino, the Z boson, and the neutral Higgs bosons ($χ^0_i-Z-h^0-H^0$) exchange in the loop contribution to the effective potential including the effects of large CP violating phases. Along with the stop, sbottom, stau and chargino-W-charged Higgs ($χ^+-W-H^+$) contributions computed previously the present analysis completes the one loop corrections to the Higgs boson mass matrix in the presence of large phases. CP violation in the neutral Higgs sector is discussed in the above framework with specific focus on the mixings of the CP even and the CP odd sectors arising from the neutralino sector. It is shown that numerically the effects of the neutralino exchange contribution on the mixings of the CP even and the CP odd sectors are comparable to the effects of the stop and of the chargino exchange contributions and thus the neutralino exchange contribution must be included for a realistic analysis of mixings in the CP even and the CP odd sectors. Phenomenological implications of these results are discussed.

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arXiv2001

Large Phases and CP Violation in SUSY

A brief overview is given of recent developments in the analyses of large phases and CP violation in supersymmetric unified models. The problem of experimental electric dipole moment constraints and large phases is discussed. Implications of large phases on supersymmetric phenomena are reviewed. The possibility of generating a muon electric dipole moment much larger than implied by the scaling relation $d_μ/d_e\simeq m_μ/m_e$ from lepton flavor nonuniversality and within reach of the recently proposed Brookhaven experiment for a sensitive probe of $d_μ$ is also discussed.

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arXiv2001

Mixing of the CP Even and the CP Odd Higgs Bosons and the EDM Constraints

The mixing among the CP even and the CP odd neutral Higgs bosons of MSSM by one loop induced effects in the presence of CP phases is investigated using three different mechanisms to satisfy the EDM constraints, i.e., a fine tuning of phases, a heavy sparticle spectrum, and the cancellation mechanism. It is shown that if a mixing effect among the CP even and the CP odd Higgs bosons is observed experimentally, then it is only the cancellation mechanism that can survive under the naturalness constraint.

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arXiv2001

Slepton Flavor Nonuniversality, the Muon EDM and its Proposed sensitive Search at Brookhaven

We analyze the electric dipole moment of the electron ($d_e$), of the neutron ($d_n$) and of the muon ($d_μ$) using the cancellation mechanism in the presence of nonuniversalities of the soft breaking parameters. It is shown that the nonuniversalities in the slepton sector produce a strong violation of the scaling relation $d_μ/d_e\simeq m_μ/m_e$ in the cancellation region. An analysis of $d_e, d_n$ and $d_μ$ under the constraints of the current experimental limits on $d_e$ and $d_n$ and under the constraints of the recent Brookhaven result on $g_μ-2$ shows that in the non-scaling region $d_μ$ can be as large as ($10^{-24}-10^{-23}$)ecm and thus within reach of the recently proposed Brookhaven experiment for a sensitive search for $d_μ$ at the level of $10^{-24}$ ecm.

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arXiv2001

Electron and Neutron Electric Dipole Moments in the Focus Point Scenario of SUGRA Model

We estimate the electron and neutron electric dipole moments in the focus point scenario of the minimal SUGRA model corresponding to large sfermion masses and moderate to large $\tanβ$. There is a viable region of moderate fine-tuning in the parameter space, around $\tanβ\simeq 5$, where the experimental limits on these electric dipole moments can be satisfied without assuming unnaturally small phase angles. But the fine-tuning constraints become more severe for $\tanβ> 10$.

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arXiv2001

Constraints on Explicit CP Violation from the Brookhaven Muon g-2 Experiment

We use the recently derived CP phase dependent analytic results for the supersymmetric electro-weak correction to $g_μ-2$ to constrain the explicit CP phases in softly broken supersymmetry using the new physics effect seen in the g-2 Brookhaven measurement. It is shown that the BNL data strongly constrains the CP violating phase $θ_μ$ (the phase of the Higgs mixing parameter $μ$) and $ξ_2$ (the phase of the SU(2) gaugino mass $\tilde m_2$) and as much as 60-90% of the region in the $ξ_2-θ_μ$ plane is eliminated over a significant region of the MSSM parameter space by the BNL constraint. The region of CP phases not excluded by the BNL experiment allows for large phases and for a satisfaction of the EDM constraints via the cancellation mechanism. We find several models with large CP violation which satisfy the EDM constraint via the cancellation mechanism and produce an $a_μ^{SUSY}$ consistent with the new physics signal seen by the Brookhaven experiment. The sparticle spectrum of these models lies within reach of the planned accelerator experiments.

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arXiv2000

Corrections to the Higgs Boson Masses and Mixings from Chargino, W and Charged Higgs Exchange Loops and Large CP Phases

One loop contributions to the Higgs boson masses and mixings from the chargino sector consisting of the chargino, the W, and the charged Higgs boson ($χ^+-W-H^+$) exchanges and including the effects of large CP violating phases are computed. It is found that the chargino sector makes a large contribution to the mixings of the CP even and the CP odd Higgs sectors through the induced one loop effects and may even dominate the mixing generated by the stop and the sbottom sectors. Effects of the chargino sector contribution to the Higgs boson masses are also computed. It is found that the sum of the $χ^+-W-H^+$ exchange contribution lowers the lightest Higgs boson mass and worsens the fine tuning problem implied by the LEP data. Phenomenological implications of these results are discussed.

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arXiv2000

Effects of Large CP Phases on the Proton Lifetime in Supersymmetric Unification

The effects of large CP violating phases arising from the soft SUSY breaking parameters on the proton lifetime are investigated in supersymmetric grand unified models. It is found that the CP violating phases can reduce as well as enhance the proton lifetime depending on the part of the parameter space one is in. Modifications of the proton lifetime by as much as a factor of 2 due to the effects of the CP violating phases are seen. The largest effects arise for the lightest sparticle spectrum in the dressing loop integrals and the effects decrease with the increasing scale of the sparticle masses. An analysis of the uncertainties in the determination of the proton life time due to uncertainties in the quark masses and in the other input data is also given. These results are of import in the precision predictions of the proton lifetime in supersymmetric unification both in GUT and in string models when the soft SUSY breaking parameters are complex.

hep-ph↗

arXiv2000

CP Violation and Dark Matter

A brief review is given of the effects of CP violation on the direct detection of neutralinos in dark matter detectors. We first summarize the current developments using the cancellation mechanism which allows for the existence of large CP violating phases consistent with experimental limits on the electron and on the neutron electric dipole moments in a broad class of SUSY, string and D brane models. We then discuss their effects on the scattering of neutralinos from quarks and on the event rates. It is found that while CP effects on the event rates can be enormous such effects are reduced significantly with the imposition of the EDM constraints. However, even with the inclusion of the EDM constraints the effects are still very significant and should be included in a precision prediction of event rates in any SUSY, string or D brane model.

hep-ph↗

arXiv2000

Large CP Phases and the Cancellation Mechanism in EDMs in SUSY, String and Brane Models

We show that EDMs obey a simple approximate scaling under the transformation $m_0\to λm_0,m_{1/2}\to λm_{1/2}$ in the large $μ$ region when $μ$ itself obeys the same scaling, ie., $μ\to λμ$. In the scaling region the knowledge of a single point in the MSSM parameter space where the cancellation in the EDMs occur allows one to generate a trajectory in the $m_0-m_{1/2}$ plane where the cancellation mechanism holds and the EDMs are small. We illustrate these results for MSSM with radiative electro-weak symmetry breaking constraints. We also discuss a class of D brane models based on Type IIB superstring compactifications which have non-universal phases in the gaugino mass sector and allow large CP violating phases consistent with the EDM constraints through the cancellation mechanism. The scaling in these D brane models and in a heterotic string model is also discussed.

hep-ph↗

arXiv2000

CP Violation and the Muon Anomaly in N=1 Supergravity

The one loop supersymmetric electro-weak correction to the anomalous magnetic moment of the muon is derived in the minimal N=1 supergravity unification with two CP violating phases. A numerical analysis of the CP violating effects on $g_μ-2$ is carried out with the cancellation mechanism to guarantee the satisfaction of the experimental limits on the electric dipole moments of the electron and on the neutron. It is found that the effects of the CP phases can significantly affect the supersymmetric electro-weak correction to $g_μ-2$, and that the numerical size of such a correction can be as large or larger than the Standard Model electro-weak correction to $g_μ-2$. These results are of import for the new Brookhaven experiment which is expected to increase the sensitivity of the $g_μ-2$ measurements by a factor of 20 and allow for a test of the electro-weak correction in the near future.

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arXiv1999

Effects of Large CP violating phases on $g_{\m}-2$ in MSSM

Effects of CP violation on the supersymmetric electro-weak correction to the anomalous magnetic moment of the muon are investigated with the most general allowed set of CP violating phases in MSSM. The analysis includes contributions from the chargino and the neutralino exchanges to the muon anomaly. The supersymmetric contributions depend only on specific combinations of CP phases. The independent set of such phases is classified. We analyse the effects of the phases under the EDM constraints and show that large CP violating phases can drastically affect the magnitude of the supersymmetric electro-weak contribution to $a_μ$ and may even affect its overall sign.

hep-ph↗

arXiv1999

Effects of CP Violation on Event Rates in the Direct Detection of Dark Matter

A full analytic analysis of the effects of CP violating phases on the event rates in the direct detection of dark matter in the scattering of neutralinos from nuclear targets is given. The analysis includes CP violating phases in softly broken supersymmetry in the framework of the minimal supersymmetric standard model (MSSM) when generational mixings are ignored. A numerical analysis shows that large CP violating phases including the constraints from the experimental limits on the neutron and the electron electric dipole moment (EDM) can produce substantial effects on the event rates in dark matter detectors.

hep-ph↗

arXiv1998

The Neutron and the Lepton EDMs in MSSM, Large CP violating Phases, and the Cancellation Mechanism

An analysis of the electric dipole moment (EDM) of the neutron and of the leptons in the minimal supersymmetric standard model (MSSM) with the most general allowed set of CP violating phases without generational mixing is given. The analysis includes the contributions from the gluino, the chargino and the neutralino exchanges to the electric dipole operator, the chromoelectic dipole operator, and the CP violating purely gluonic dimension six operator. It is found that the EDMs depend only on certain combination of the CP phases. The independent set of such phases is classified. The analysis of the EDMs given here provides the framework for the exploration of the effects of large CP violating phases on low energy phenomena such as the search for supersymmetry at colliders, and in the analyses of dark matter consistent with the experimental limits on EDMs via the mechanism of internal cancellations.

hep-ph↗

arXiv1997

The Neutron and the Electron Electric Dipole Moment in N=1 Supergravity Unification

An analysis of the neutron EDM and of the electron EDM in minimal N=1 supergravity unification with two CP violating phases is given. For the neutron the analysis includes the complete one loop gluino, chargino, and neutralino exchange diagrams for the electric dipole and the chromoelectric dipole operators, and also the contribution of the purely gluonic dimension six operator. It is shown that there exist significant regions in the six dimensional parameter space of the model where cancellations between the gluino and the chargino exchanges reduce the electric and the chromoelectric contributions, and further cancellations among the electric, the chromoelectric, and the purely gluonic parts lead to a dramatic lowering of the neutron EDM sometimes below the electron EDM value. This phenomenon gives a new mechanism, i.e., that of internal cancellations, for the suppression of the neutron EDM in supersymmetric theories. The cancellation mechanism can significantly reduce the severe fine tuning problem associated with CP violating phases in SUSY and SUGRA unified models.

hep-ph↗

arXiv1997

The Chromoelectric and Purely Gluonic Operator Contributions to the Neutron Electric Dipole Moment in N=1 Supergravity

A complete one loop analysis of the chromoelectric dipole contribution to the electric dipole moment (edm) of the quarks and of the neutron in N=1 supergravity including the gluino, chargino and neutralino exchange contributions and exhibiting the dependence on the two CP violating phases allowed in the soft SUSY breaking sector of minimal supergravity models is given. It is found that in significant parts of the supergravity parameter space the chromoelectric dipole contribution to the neutron edm is comparable to the contribution from the electric dipole term and can exceed the contribution of the electric dipole term in certain regions of the parameter space. An analysis of the contribution of Weinberg's purely gluonic CP violating dimension six operator within supergravity unification is also given. It is found that this contribution can also be comparable to the contribution from the electric dipole term in certain regions of the supergravity parameter space.

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