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Pran Nath

Publications and source records attributed to Pran Nath.

At least 199 records · Page 11Linked to original sources
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↗
arXiv1999

Probing the Nature of Compactification with Kaluza-Klein Excitations at the Large Hadron Collider

It is shown that the nature of compactification of extra dimensions in theories of large radius compactification can be explored in several processes at the Large Hadron Collider (LHC). Specifically it is shown that the characteristics of the Kaluza-Klein (KK) excitations encode information on the nature of compactification, i.e., on the number of compactified dimensions as well as on the type of compactification, e.g., of the specific orbifold compactification. The most dramatic signals arise from the interference pattern involving the exchange of the Standard Model spin 1 bosons ($γ$ and Z) and their Kaluza-Klein modes in the dilepton final state $pp\to l^+l^-X$. It is shown that LHC with 100$fb^{-1}$ of luminosity can discover Kaluza-Klein modes up to compactification scales of $\approx 6$ TeV as well as identify the nature of compactification. Effects of the Kaluza-Klein excitations of the W boson and of the gluon are also studied. Exhibition of these phenomena is given for the case of one extra dimension and for the case of two extra dimensions with $Z_2\times Z_2, Z_3$, and $Z_6$ orbifold compactifications.

hep-ph↗
arXiv1999

Out-going Muon Flux from Neutralino Annihilation in the Sun and the Earth in Supergravity Unification

Predictions for the out-going muon fluxes from the annihilation of neutralinos in the center of the Sun and the Earth in supergravity unification are given. Effects of uncertainties of the input data are analysed. It is shown that the out-going muon flux measurements from the Sun and the Earth are complementary, with the Earth providing a larger flux for low values of fine tuning and the Sun providing a larger flux for high values of fine tuning, and that only a combination of the two can compete favorably with the direct detection measurements. The predictions are compared with the recent limits from BAIKAL NT-96, MACRO, and BAKSAN.

hep-ph↗
arXiv1999

Effects of Kaluza-Klein Excitations on g_μ-2

An analysis of the effects associated with the Kaluza-Klein excitations of the photon and of the W and Z bosons on g_μ-2 for d number of extra dimensions with large radius compactifications is given. The Kaluza-Klein effects on g_μ-2 are found to be very sensitive to the number of extra dimensions. For models where the quark-lepton generations live on the 4D wall, it is shown that when the constraints from the Kaluza-Klein corrections to the Fermi constant are included, the effects of the Kaluza-Klein excitations to g_μ-2 become too small to be observable. A model which evades Kaluza-Klein corrections to the muon decay μ\to e\barν_eν_μ without suppression of their effects on g_μ-2 is discussed.

hep-ph↗
arXiv1999

Effects of Extra Space-time Dimensions on the Fermi Constant

Effects of Kaluza-Klein excitations associated with extra dimensions with large radius compactifications on the Fermi constant are explored. It is shown that the current precision determinations of the Fermi constant, of the fine structure constant, and of the W and Z mass put stringent constraints on the compactification radius. The analysis excludes one extra space time dimension below $\sim 1.6$ TeV, and excludes 2, 3 and 4 extra space dimensions opening simultaneously below $\sim$ 3.5 TeV, 5.7 TeV and 7.8 TeV at the $90% CL$. Implications of these results for future collider experiments are discussed.

hep-ph↗
arXiv1999

Annual Modulation Signature for the Direct Detection of Milky Way Wimps and Supergravity Models

An analysis is given of the annual modulation signal for the direct detection of relic neutralinos within the framework of supergravity unified models. It is shown that both the minimal and the non-minimal SUGRA models can generate neutralino-proton cross-sections at the level compatible with the signals reported in the DAMA experiment at the Gran Sasso National Laboratory. Effects of proton stability on the analysis of the DAMA data in the minimal and the non-minimal SUGRA models are also discussed.

hep-ph↗
arXiv1998

Grand Unification and B & L Conservation

A review of baryon and lepton conservation in supersymmetric grand unified theories is given. Proton stability is discussed in the minimal SU(5) supergravity grand unification and in several non-minimal extensions such as the $SU(3)^3$, SO(10) and some string based models. Effects of dark matter on proton stability are also discussed and it is shown that the combined constraints of dark matter and proton stability constrain the sparticle spectrum. It is also shown that proton lifetime limits put severe constraints on the event rates in dark matter detectors. Future prospects for the observation of baryon and lepton number violation are also discussed.

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↗
arXiv1998

Naturalness, Weak Scale Supersymmetry and the Prospect for the Observation of Supersymmetry at the Tevatron and at the LHC

Naturalness bounds on weak scale supersymmetry in the context of radiative breaking of the electro-weak symmetry are analyzed. In the case of minimal supergravity it is found that for low tanβand for low values of fine tuning Phi, where Phi is defined essentially by the ratio μ^2/M_Z^2 where μis the Higgs mixing parameter and M_Z is the Z boson mass, the allowed values of the universal scalar parameter m_0, and the universal gaugino mass m_{1/2} lie on the surface of an ellipsoid with radii fixed by Φleading to tightly constrained upper bounds \sim \sqrtΦ.Thus for tanβ\leq 2(\leq 5) it is found that the upper limits for the entire set of sparticle masses lie in the range < 700 GeV (<1.5TeV) for any reasonable range of fine tuning (Φ\leq 20). However, it is found that there exist regions of the parameter space where the fine tuning does not tightly constrain m_0 and m_{1/2}. Effects of non- universalities in the Higgs sector and in the third generation sector on naturalness bounds are also analyzed and it is found that non-universalities can significantly affect the upper bounds. It is also found that achieving the maximum Higgs mass allowed in supergravity unified models requires a high degree of fine tuning. Thus a heavy sparticle spectrum is indicated if the Higgs mass exceeds 120 GeV. The prospect for the discovery of supersymmetry at the Tevatron and at the LHC in view of these results is discussed.

hep-ph↗
arXiv1998

Accurate Cosmological Parmeters and Supersymmetric Particle Properties

Future sattelite, balloon and ground based experiments will give precision determinations of the basic cosmological parameters and hence determine the amount of cold dark matter accurately. We consider here two cosmological models, the nuCDM model and the LambdaCDM model, and examine within the framework of supergravity grand unification the effect this will have for these models on supersymmetry searches at accelerators. In the former example the gluino (neutralino) mass has an upper bound of about 720(100) GeV and gaps (forbidden regions) may deveop at lower energies. In the latter case the upper bound occurs at gluino (neutralino) mass of about 520(70) GeV with squarks and selectron becoming light when gluino (neutralino) masses are greater than 420(55) GeV. Both models are sensitive to non-universal soft breaking masses, and show a correlation between large (small) dark matter detector rates and low (high) b -> s+ gamma branching ratio.

hep-ph↗
arXiv1998

Non-universal Soft SUSY Breaking and Dark Matter

A brief review of non-universalities in the soft SUSY breaking sector of supergravity grand unification is given. The effects of these non-universalities on the analysis of event rates in neutralino nucleus scattering are discussed. An analysis is also given of the implications of the simultaneous imposition of proton stability and dark matter constraints. One finds that these constraints put an upper limit on the gluino mass.

hep-ph↗
arXiv1998

Limits on SUSY particle Spectra from Proton Stability and Dark Matter Constraints

It is shown that the combined constraints on the amount of cold dark matter and of proton stability produce a stringent upper limit on the gluino mass $m_{\tilde g}$ (and hence on the lightest neutralino mass $m_{χ_1^0}\simeq m_{\tilde g}/7$) for a large class of gravity mediated supergravity unified models. One finds that for the minimal SU(5) model current data (Kamiokande) restricts $m_{\tilde g}\leq 400$ GeV for a scalar soft breaking mass $m_0\leq 1$ TeV. Expected future data from Super Kamionkande and ICARUS will be sensitive to the entire range of gluino mass for $m_0\leq 1$ TeV, and be able to exclude the region $m_{\tilde g}\geq 500$ GeV for $m_0\leq 5$ TeV. Effects of quark mass textures are studied and one finds that the bound $m_{\tilde g}\leq 500$ GeV holds when the experimental proton lifetime for the $p\to \bar νK^+$ mode becomes $\geq 5\times 10^{32}$ yr.Implications of these results for a test of these models at the Tevatron and at the LHC are discussed. The effects of non-universal soft breaking in the Higgs and the third generation squark sectors are also examined, and it is found that the proton lifetime is sensitive to these non-universal effects. The current data already eliminates some regions of non-universalities. The constraints of proton stability on the direct detection of dark matter are seen to reduce the maximum event rates by as much as a factor of $10^3$.

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

Supergravity Unified Models

The development of supergravity unified models and their implications for current and future experiments are discussed.

hep-ph↗
arXiv1997

Nucleon Instability in SUSY Models

A review of the current status of nucleon stability in SUSY unified models is given. The review includes analysis of nucleon stability in the minimal SU(5) supergravity model, and in extensions of the minimal model such as SO(10) models, and models including textures. Implications of the simultaneous constraint of the experimental limit on the proton lifetime and the constraint that dark matter not overclose the universe are also discussed.

hep-ph↗
arXiv1997

Seeing Planck Scale Physics At Accelerators

Much curent theoretical analysis is based on the hypothesis that the physics beyond the Standard Model is a consequence of new principles that occur at the Planck scale. The question arises whether such principles can ever be directly tested. We show here that for a significant class of models, hypotheses made at the string or Planck scale can indeed be directly tested to a relatively high degree of precision by linear colliders. Three classes of models are examined: those with universal SUSY soft breaking at the string scale, those with a horizontal symmetry at the string or Planck scale, and simple Calabi-Yau superstring models with dilaton and moduli SUSY breaking. (Invited talk at Orbis97.)

hep-ph↗