arXiv subjects

Pran Nath

Publications and source records attributed to Pran Nath.

At least 163 records · Page 9Linked to original sources

arXiv2003

Weak Isospin Violations in Charged and Neutral Higgs Couplings from SUSY Loop Corrections

Supersymmetric QCD and supersymmetric electroweak loop corrections to the violations of weak isospin to Yukawa couplings are investigated. Specifically it involves an analysis of the supersymmetric loop corrections to the Higgs couplings to the third generation quarks and leptons. Here we analyze the SUSY loop corrections to the charged Higgs couplings which are then compared with the supersymmetric loop corrections to the neutral Higgs couplings previously computed. It is found that the weak isospin violations can be quite significant, i.e, as much as 40-50% or more of the total loop correction to the Yukawa coupling. The effects of CP phases are also studied and it is found that these effects can either enhance or suppress the weak isospin violations. We also investigate the weak isospin violation effects on the branching ratio $BR(H^-\to\bar t b)/ BR(H^-\to \barν_ττ^-)$ and show that the effects are sensitive to CP phases. Thus an accurate measurement of this branching ratio along with the branching ratio of the neutral Higgs boson decays can provide a measure of weak isospin violation along with providing a clue to the presence of supersymmetry.

hep-ph↗

arXiv2003

WMAP Data and Recent Developments in Supersymmetric Dark Matter

A brief review is given of the recent developments in the analyses of supersymmetric dark matter. Chief among these is the very accurate determination of the amount of cold dark matter in the universe from analyses using WMAP data. The implications of this data for the mSUGRA parameter space are analyzed. It is shown that the data admits solutions on the hyperbolic branch (HB) of the radiative breaking of the electroweak symmetry. A part of the hyperbolic branch lies in the so called inversion region where the LSP neutralino $χ_1^0$ becomes essentially a pure Higgsino and degenerate with the next to the lightest neutralino $χ_2^0$ and the light chargino $χ_1^{\pm}$. Thus some of the conventional signals for the observation of supersymmetry at colliders (e.g., the missing energy signals) do not operate in this region. On the other hand the inversion region contains a high degree of degeneracy of $χ_1^0$, $χ_2^0$, $χ_1^{\pm}$ leading to coannihilations which allow for the satisfaction of the WMAP relic density constraints deep on the hyperbolic branch. Further, an analysis of the neutralino-proton cross sections in this region reveals that this region can still be accessible to dark matter experiments in the future. Constraints from $g_μ-2$ and from $B^0_s\to μ^+μ^-$ are discussed. Future prospects are also discussed.

hep-ph↗

arXiv2003

Coupling the Supersymmetric 210 Vector Multiplet to Matter in SO(10)

An analysis of the couplings of the 210 dimensional SO(10) vector multiplet to matter is given. Specifically we give an $SU(5)\times U(1)$ decomposition of the vector couplings $\bar{16}_{\pm}-16_{\pm}-210$, where $16_{\pm}$ is the semispinor of SO(10) chirality ${\pm}$, using a recently derived basic theorem. The analysis is carried out using the Wess-Zumino gauge. However, we also consider the more general situation where all components of the vector multiplet enter in the couplings with the chiral fields. Here elimination of the auxiliary fields leads to a sigma model type nonlinear Lagrangian. Interactions of the type analysed here may find applications in effective theories with the 210 vector arising as a condensate. The analysis presented here completes the explicit computation of all lowest order couplings involving the $16_{\pm}$ of spinors with Higgs and vectors multiplets using the basic theorem.

hep-th↗

arXiv2003

Corrections to b, t quark masses and $τ$ lepton mass in SUGRA including CP phases

A brief review is given of recent analyses of the effects of CP phases on the supersymmetric QCD and supersymmetric electroweak contibutions to the $b$ and $t$ quark masses and to the $τ$ lepton mass in SUGRA models. The effects of CP phases on the supersymmetric contributions are found to be significanlty large for the b quark mass as they can change both its sign and its magnitude. Thus with the inclusion of CP phases the supersymmetric correction to the b quark mass can be as much as fifty percent or more of the total b quark mass. For the case of the $τ$ lepton, the effects of CP phases on the supersymmetric correction is also relatively large as it can again affect both the sign and the magnitude of the $τ$ mass correction. However, in this case the overall correction is found to be only a few percent. The effect of CP phases on SUSY contribution to the $t$ quark mass was also investigated. However, in this case the overall correction is less than a percent with or without the inclusion of phases. These results have important implications for $b-τ$ unification and for $b-t-τ$ unification in the context of unified theories.

hep-ph↗

arXiv2003

WMAP Constraints, SUSY Dark Matter and Implications for the Direct Detection of SUSY

Recently, WMAP has measured the cosmological parameters to a much greater accuracy. We analyze the implications of this more precise measurement for supersymmetric dark matter and for the direct detection of supersymmetry at accelerators. We consider mSUGRA including also the hyperbolic branch in the radiative breaking of the electroweak symmetry. On the part of the hyperbolic branch where the lightest neutralino is dominantly a higgsino rather than being mostly a bino, the relic density constraints are satisfied by coannihilation with the next lightest neutralino and the light chargino. Including this branch the lightest neutralino mass satisfies $m_{χ_1^0}\leq 1200$ GeV for $\tanβ\leq 50$. Constraints of $b\to s+γ$ and of $g_μ-2$ are also analyzed. It is shown that the neutralino-proton cross section in each case will fall within the reach of dark matter experiments. Possibility for the direct detection of supersymmetry is discussed in the allowed regions of the parameter space consistent with WMAP constraints. A brief discussion of the hyperbolic branch and focus point region (HB/FP) is also given.

hep-ph↗

arXiv2003

Twenty Years of SUGRA

A brief review is given of the developments of mSUGRA and its extensions since the formulation of these models in 1982. Future directions and prospects are also discussed.

hep-ph↗

arXiv2003

Decays of Higgs to $b\bar b$, $τ\barτ$ and $c\bar c$ as Signatures of Supersymmetry and CP Phases

The branching ratio of the lightest Higgs decay into $b\bar b$, $τ\barτ$ and $c\bar c$ is sensitive to supersymmetric effects. We include in this work the effects of CP phases on the Higgs decays. Specifically we compute the deviation of the CP phase dependent branching ratio from the standard model result. The analysis includes the full one loop corrections of fermion masses including CP phases involving the gluino, the chargino and the neutralino exchanges. The analysis shows that the supersymmetric effects with CP phases can change the branching ratios by as much as 100% for the lightest Higgs decay into $b\bar b$ and $τ\barτ$ with similar results holding for the heavier Higgs decays. A detailed analysis is also given of the effects of CP phases on the Higgs decays into $c\bar c$. The deviations of $R_{b/τ}$ and $R_{b/c}$ from the standard model result are investigated as a possible signature of supersymmetry and CP effects. Thus a measurement of the decays of the higgs into $b\bar b$, $τ\bar τ$ and $c\bar c$ may provide important clues regarding the existence of supersymmetry and CP phases.

hep-ph↗

arXiv2003

SUSY QCD and SUSY Electroweak Loop Corrections to $b, t$ and $τ$ Masses Including the Effects of CP Phases

We compute supersymmetric QCD and supersymmetric electroweak corrections to the b and t quark masses and to the $τ$ lepton mass in the presence of CP phases valid for all $\tanβ$. The analysis includes one loop diagrams arising from the exchange of gluinos, charginos and neutralinos. We find that the CP effects can change both the magnitude as well as the sign of the supersymmetric loop correction. In the region of parameter space studied we found that the numerical size of the correction to the b quark mass can be as large as 30 percent and to the $τ$ lepton mass as much as 5 percent. For the top quark mass the correction is typically less than a percent. These corrections are of importance in unified models since $b-τ$ and $b-t-τ$ unification is strongly affected by the size of these corrections. More generally these results will be of importance in analyses of quark-lepton textures with the inclusion of CP phases. Further, the analysis presented here is relevant in a variety of low energy phenomena where supersymmetric QCD and supersymmetric electroweak corrections on b mass enter prominently in B physics, e.g., in processes such as $B^0_{s,d}\to l^+ł^-$.

hep-ph↗

arXiv2002

CP Violation Effects on $B^0_{s,d}\to \it l^+\it l^-$ in Supersymmetry at Large $\tanβ$

An analytic analysis of the CP violating effects arising from the soft SUSY breaking parameters on the decays $B^0_{s,d}\to \it l^+\it l^-$ at large $\tanβ$ is given. It is found that the phases have a strong effect on the branching ratio and in some regions of the parameter space they can lead to a variation of the branching ratio by as much as 1-2 orders of magnitude. These results have important implications for the discovery of the $B^0_{s}\to μ^+μ^-$ signal in RUNII of the Tevatron and further on how the parameter space of SUSY models will be limited once the signal is found.

hep-ph↗

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.

hep-ph↗

arXiv2002

Modular Invariance, Soft Breaking, $μ$ and $\tanβ$ in Superstring Models

We go beyond parameterizations of soft terms in superstring models and investigate the dynamical assumptions that lead to the relative strength of the dilaton {\it vs} the moduli contributions in the soft breaking. Specifically, we discuss in some simple heterotic orbifold models sufficient conditions to achieve dilaton dominance. Assuming self-dual points to be minima we find multiple solutions to the trilinear and bilinear soft parameters $A_0$ and $B_0$. We discuss the constraints on $μ$ and $\tanβ$ in superstring models in the context of radiative breaking of the electroweak symmetry. We show that string models prefer a small to a moderate value of $\tanβ$, {\it i.e}. $\tanβ\leq 10$, and a value much larger than this requires a high degree of fine tuning. Further, we show that for large $\tanβ$ the radiative electroweak symmetry breaking constraint leads to a value $α_{string}=g_{string}^2/4π$ which is typically an order of magnitude smaller than implied by the LEP data and the heterotic superstring relation $g_{string}=k_ig_i$, where $g_i$ is the gauge coupling constant for the gauge group $G_i$ and $k_i$ is the corresponding Kac-Moody level in the class of models considered. This situation can be overcome by another fine tuned cancellation between the dilaton and the moduli contributions in the soft parameters.

hep-ph↗

arXiv2002

Interpreting the New Brookhaven g_mu - 2 Result

The latest g_mu - 2 measurement by Brookhaven confirms the earlier measurement with twice the precision. However, interpretation of the result requires specific assumptions regarding the errors in the hadronic light by light (LbL) correction and in the hadronic vacuum polarization correction. Under the assumption that the analysis on LbL correction of Knecht and Nyffeler and the revised analysis of Hayakawa and Kinoshita are valid the new BNL result implies a deviation between experiment and the standard model of 1.6 sigma -2.6 sigma depending on the estimate of the hadronic vacuum polarization correction. We revisit the g_mu - 2 constraint for mSUGRA and its implications for the direct detection of sparticles at colliders and for the search for supersymmetric dark matter in view of the new evaluation.

hep-ph↗

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.

hep-ph↗

arXiv2002

Status of Supersymmetry in the Light of Recent Experiments

In this talk we discuss the constraints on supersymmetry arising from data from a number of recent experiments. There appears to be good cumulative evidence from experiment in favor of positivity of the sign of the Higgs mixing parameter $μ$. Implications of this result for Yukawa unification are discussed since Yukawa unification is sensitive to the $μ$ sign. An analysis of dark matter under the constraints of Yukawa unification is also given. It is shown that the simultaneous imposition of all existing constraints sharply defines the parameter space of models. Specifically models with nonuniversality of gaugino masses provide a simple resolution to the positivity of the $μ$ parameter and Yukawa unification. Implications of these results for colliders and for the next generation of dark matter searches are also discussed.

hep-ph↗

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.

hep-ph↗

arXiv2002

Theoretical Status of Muon (g-2)

The theoretical status of the muon anomaly is reviewed including the recent change in the light by light hadronic correction. Specific attention is given to the implications of the shift in the difference between the BNL experimental result and the standard model prediction for sparticle mass limits. The implication of the BNL data for Yukawa unification is discussed and the role of gaugino mass nonuniversalities in the satisfaction of Yukawa unification is explored. An analysis of the BNL constraint for the satisfaction of the relic density constraint and for the search for dark matter is also given.

hep-ph↗

arXiv2001

Supersymmetric Dark Matter and Yukawa Unification

An analysis of supersymmetric dark matter under the Yukawa unification constraint is given. The analysis utilizes the recently discovered region of the parameter space of models with gaugino mass nonuniversalities where large negative supersymmetric corrections to the b quark mass appear to allow $b-τ$ unification for a positive $μ$ sign consistent with the $b\to s+γ$ and $g_μ-2$ constraints. In the present analysis we use the revised theoretical determination of $a_μ^{SM}$ ($a_μ= (g_μ-2)/2$) in computing the difference $a_μ^{exp}-a_μ^{SM}$ which takes account of a reevaluation of the light by light contribution which has a positive sign. The analysis shows that the region of the parameter space with nonuniversalities of the gaugino masses which allows for unification of Yukawa couplings also contains regions which allow satisfaction of the relic density constraint. Specifically we find that the lightest neutralino mass consistent with the relic density constraint, $bτ$ unification for SU(5) and $b-t-τ$ unification for SO(10) in addition to other constraints lies in the region below 80 GeV. An analysis of the maximum and the minimum neutralino-proton scalar cross section for the allowed parameter space including the effect of a new determination of the pion-nucleon sigma term is also given. It is found that the full parameter space for this class of models can be explored in the next generation of proposed dark matter detectors.

hep-ph↗

arXiv2001

$b-τ$ Unification, $g_μ-2$, the $b\to s+γ$ Constraint and Nonuniversalities

An analysis is given of the $b-τ$ Yukawa coupling unification in view of the recent result from Brookhaven on $g_μ-2$ and under the constraint of $b\to s+γ$. We explore $b-τ$ unification under the above constraints for nonuniversal boundary conditions for the soft SUSY breaking parameters. We find new regions of the parameter space where significant negative supersymmetric contribution to the b quark mass can arise and $b-τ$ unification within SU(5) framework can occur with nonuniversal gaugino masses. Specifically we find that for the case where the gaugino mass matrix transforms like a 24 plet one finds a negative contribution to the b quark mass irrespective of the sign of the Higgs mixing parameter $μ$ when the supersymmetric contribution to $g_μ-2$ is positive. We exhibit regions of the parameter space where $b-τ$ unification occurs for $μ>0$ satisfying the constraints of $b\to s+γ$ and $g_μ-2$. The $μ<0$ case is also explored. The dependence of the accuracy of $b-τ$ unification defined by $|λ_b-λ_τ|/λ_τ$ on the parameter space is also investigated and it is shown that unification with an accuracy of a few percent can be achieved in significant regions of the parameter space. The allowed parameter space is consistent with the naturalness constraints and the corresponding sparticle spectrum is accessible at the Large Hadron Collider.

hep-ph↗