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Pran Nath

Publications and source records attributed to Pran Nath.

At least 217 records · Page 12Linked to original sources
arXiv1997

Non-Universality Effects and Dark Matter in Gravity Mediated SUSY Breaking

Dark matter detection rates for supergravity models with R parity where supersymmetry is broken at a scale >~M_G are discussed. Non-universal soft breaking masses in both the Higgs and squark sectors are considered, and it is seen that these can effect rates by a factor of 10-100 when m_X <~ 65 GeV (X=lightest neutralino) but otherwise make relatively small corrections. The b->s+γbranching ratio is seen to correlate with detector event rates, large (small) branching ratios corresponding to small (large) event rates. Effects of precision determinations of cosmological parameters or event rate predictions by future satellite experiments are discussed for the LCDM and the vCDM 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.

hep-ph↗
arXiv1997

R_b in Supergravity Grand Unification with Non-universal Soft SUSY Breaking

An analysis of supersymmetric contributions to R_b in supergravity grand unification with non-universal boundary conditions on soft SUSY breaking in the scalar sector is given. Effects on R_b of Planck scale corrections on gaugino masses are also analysed. It is found that there exist regions of the parameter space where positive corrections to R_b of size $\sim 1 σ$ can be gotten. The region of the parameter space where enhancement of R_b occurs is identified. Prediction of the full sparticle spectrum for the maximal R_b case is given. The analysis has implications for the discovery of supersymmetric particles at colliders.

hep-ph↗
arXiv1997

Detecting Physics At The Post-GUT And String Scales By Linear Colliders

The ability of linear colliders to test physics at the post-GUT scale is investigated. Using current estimates of measurements available at such accelerators, it is seen that soft breaking masses can be measured with errors of about (1-20)%. Three classes of models in the post-GUT region are examined: models with universal soft breaking masses at the string scale, models with horizontal symmetry, and string models with Calabi-Yau compactifications. In each case, linear colliders would be able to test directly theoretical assumptions made at energies beyond the GUT scale to a good accuracy, distinguish between different models, and measure parameters that are expected to be predictions of string models.

hep-ph↗
arXiv1997

Non-Universal Soft SUSY Breaking and Dark Matter

An analysis is given of the effects of non-universal soft SUSY breaking masses in the Higgs sector and in the third generation squark sector, and it is shown that they are highly coupled. Analytic expressions are obtained for their effects on the parameters $μ,m_A$ and on the third generation squark masses. Non-universality effects on dark matter event rates in neutralino-nucleus scattering are analysed. It is found that the effects are maximal in the range $m_{\tildeχ_1}\leq 65$~GeV where the relic density is governed by the Z and Higgs poles. In this range the minimum event rates can be increased or decreased by factors of O(10) depending on the sign of non-universality. Above this range Landau pole effects arising from the heavy top mass tend to suppress the non-universality effects. The effect of more precise measurements of cosmological parameters on event rates, which is expected to occur in the next round of COBE like sattelite experiments, is also investigated. Implications for the analysis for dark matter searches are discussed.

hep-ph↗
arXiv1996

Textured Minimal and Extended Supergravity Unification and Implications for Proton Stability

We construct a class of textured supergravity unified SU(5) models using Planck scale corrections. We show that the texture constraints in the Higgs doublet sector are insufficient in general to fully determine the textures in the Higgs triplet sector. A classification of textured minimal parameter models is given and their Higgs triplet textures computed under the constraint that they possess the Georgi-Jarlskog textures in the Higgs doublet sector. It is argued that additional dynamical assumptions are needed to remove the ambiguity.The recently proposed extension of supergravity unification to include a minimal exotic sector is free of this ambiguity and leads to unique textures in the Higgs triplet sector. Implications for proton stability are discussed.

hep-ph↗
arXiv1995

Supersymmetric Dark Matter

A review of supersymmetric dark matter in minimal supergravity unification with R-parity invariance and with radiative breaking of the electro-weak symmetry is given. The analysis shows the lightest neutralino is the LSP over most of the parameter space of the supergravity model. The event rates in neutralino- nucleus scattering in dark matter detectors are also discussed.It is found that the event rates are sensititive to the constraint from the $b\rightarrow sγ$ experiment.It is also found that the event rates are sensitive to the constraints of relic density and in our analysis we have used the accurate method for the computation of the neutralino relic density. Finally,the effect of the new results on quark polarizabilities, from the data of the Spin Muon Collaboration, on event rates is also discussed.The analysis shows that the event rates for the Ge detectors and for other detectors which use heavy targets are only negligibly affected.

hep-ph↗
arXiv1995

Hierarchies and Textures in Supergravity Unification

It is proposed that supergravity unified models contain in addition to the hidden and the visible sectors, a third sector which contains exotic matter with couplings to the fields of both the visible and the hidden sectors. After spontaneous breaking of supersymmetry exotic matter becomes superheavy and its elimination leads to quark-lepton textures at the GUT scale with a hierarchy in powers of $M_G/M_P$.Textures in the Higgs triplet sector are also computed and it is shown that they modify predictions of proton decay in unified models.

hep-ph↗
arXiv1995

Predictions of Neutralino Dark Matter Event Rates in Minimal Supergravity Unification

A detailed analysis of dark matter event rates in minimal supergravity models (MSGM) is given. It is shown analytically that the lightest neutralino the ${{\tilde {Z}_{1}}}$ is the LSP over almost all of the parameter space, and hence the natural candidate for cold dark matter (CDM). The radiative breaking of $SU(2)\times U(1)$ constraints are shown to be crucial in determining the expected event rates. Approximate analytic formulae are obtained to determine the gaugino-higgsino content of the ${{\tilde{Z}_{1}}}$ particle.From this one can deduce the behavior of the event rates as one varies the SUSY soft breaking parameters and tan $β$. The constraint on the event rates due to the recently measured $b\rightarrow s+γ$ decay is calculated. It is seen that this data eliminates most of the parameter space where $μ$ (the Higgs mixing parameter) and $A_t$ (the t-quark cubic soft breaking parameter) have the same sign. Since the t-quark is close to its Landau pole, $A_t$ is restricted to be mostly positive, and so most of the $μ>0$ part of the parameter space is eliminated...

hep-ph↗
arXiv1995

Probing Supergravity Grand Unification in the Brookhaven g-2 Experiment

A quantitative analysis of $\amu\equiv{1\over 2}(g-2)_μ$ within the framework of Supergravity Grand Unification and radiative breaking of the electro-weak symmetry is given. It is found that $a_μ^{SUSY}$ is dominated by the chiral interference term from the light chargino exchange, and that this term carries a signature which correlates strongly with the sign of $μ$. Thus as a rule $a_μ^{SUSY}>0$ for $μ>0$ and $a_μ^{SUSY}<0$ for $μ<0$ with very few exceptions when tan$β\sim 1$. At the quantitative level it is shown that if the E821 BNL experiment can reach the expected sensitivity of $4\times 10^{-10}$ and there is a reduction in the hadronic error by a factor of four or more, then the experiment will explore a majority of the parameter space in $ m_0-m_{\tilde g}$ plane in the region $m_0\lsim 400$ GeV, $m_{\tilde g}\lsim 700$ GeV for $\tanbeta \gsim 10$ assuming the experiment will not discard the Standard Model result within its $2σ$ uncertainty limit. For smaller $\tanbeta$, the SUSY reach of E821 will still be considerable. Further, if no effect within $2 σ$ limit of the Standard Model value is seen, then large $\tanbeta$ scenarios will be severely constrained within the current naturalness criterion, ie., $m_0, m_{\tilde g}\lsim 1$ TeV.

hep-ph↗
arXiv1995

Landau Pole Effects and the Parameter Space of the Minimal Supergravity Model

It is shown that analyses at the electroweak scale can be significantly affected due to Landau pole effects in certain regions of the parameter space. This phenomenon arises due to a large magnification of errors of the input parameters $m_t$, $α_G$ which have currently a 10 percent uncertainty in their determination. The influence of the Landau pole on the constraint that the scalar SUSY spectrum be free of tachyons is also investigated.It is found that this constraint is very strong and eliminates a large portion of the parameter space.Under the above constraint the trilinear soft SUSY breaking term at the electroweak scale is found to lie in a restricted domain.

hep-ph↗
arXiv1995

Effects of Gravitational Smearing on Predictions of Supergravity Grand Unification

Limits on gravitational smearing from the dominant dimension 5 operator (with strength characterised by $cM/2M_{Planck}$) are obtained using the LEP data in supersymmetric SU(5) grand unification. Effects of c on the quasi infrared fixed point solutio ns of $m_b/m_τ$ unification are also analysed. It is found that $c>0$ softens and $c<0$ stiffens the fixed point constraint. The effect of c on the upper bound of the Higgs triplet mass is analysed and the existence of a scaling induced by c is discussed. Tests for the existence of gravitational smearing are discussed.

hep-ph↗
arXiv1994

The b->s +γDecay in Supergravity

The $b\rightarrow s+ γ$ decay is a powerful tool for testing models of new physics because the new physics diagrams enter in the same loop order as the Standard Model ones. The current experimental and theoretical status of this decay is reviewed. Predictions based on the minimal supergravity model (MSGM) in the leading order (LO) are discussed. It is shown that results are sensitive to the value of $m_{t}$ and $α_{G}$. The current experimental value for the $b\rightarrow s + γ$ rate already very likely eliminates part of the SUSY parameter space when both $m_{o}$ and $m_{\tilde{g}}$ are small and when $A_{t}$ and $μ$ have the same sign. Dark matter detection rates for $\tilde{Z}_{1}$ cold dark matter for $μ<0$ are only minimally affected by the current data, as are proton decay predictions for models consistent with current proton lifetime and $\tilde{Z}_{1}$ relic density bounds. [†Invited talk at ``Physics From Planck Scale to Electroweak Scale'', Warsaw, Sept. 21-24, 1994].

hep-ph↗
arXiv1994

The Decay b-s+gamma in SUSY Extensions of the Standard Model

A brief review is given of the decay b-s+gamma in SUSY extensions of the Standard Model.It is found that the recent CLEO results put strong constraints on the parameter space of the minimal N=1 Supergravity unified theory.Dark matter analyses are also strongly constrained for mu>0.

hep-ph↗
arXiv1994

Searching For SUSY Dark Matter

{\tenrm The possibility of detecting supersymmetric dark matter is examined within the framework of the minimal supergravity model (MSGM), where the $\tilde{Z}_{1}$ is the LSP for almost the entire parameter space. A brief discussion is given of experimental strategies for detecting dark matter. The relic density is constrained to obey 0.10 $\leq Ω_{\tilde{Z}_{1}}h^2 \leq$0.35, consistent with COBE data. Expected event rates for an array of possible terrestial detectors ($^3$He, CaF$_2$, Ge, GaAs, NaI and Pb) are examined. In general, detectors relying on coherrent $\tilde{Z}_{1}$-nucleus scattering are more sensitive than detectors relying on incoherrent (spin-dependent) scattering. The dependence of the event rates as a function of the SUSY parameters are described. The detectors are generally most sensitive to the small $m_0$ and small $m_{\tilde{q}}$ and large tan$β$ part of the parameter space. The current $b\rightarrow s+γ$ decay rate eliminates regions of large event rates for $μ>0$, but allows large event rates to still occur for $μ<0$. MSGM models that also possess SU(5)-type proton decay generally predict event rates below the expected sensitivity of current dark matter detectors.}

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