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R. Arnowitt

Publications and source records attributed to R. Arnowitt.

At least 73 records · Page 4Linked to original sources
arXiv1997

Dark Matter Predictions With Non-Universal Soft Breaking Masses

The effect of non-universal SUSY soft breaking on predictions of dark matter detector event rates are surveyed for supergravity models with gravity mediated soft breaking. For universal soft breaking in the first two generations and tan(beta)<=20, non-universal effects can be characterized by four parameters (two for Higgs and two for third generation squarks) in addition to those of the minimal model (MSGM). These can increase or decrease event rates by a factor of 10-100 in the domain m_{χ_1^0}<60 GeV (χ_1^0= lightest neutralino) but produce generally small effects at higher masses. The value of the top mass and b->s+γbranching ratio eliminates most of the parameter space for μ<0, causing event rates for μ<0 to be a factor approximately 100 smaller than for mu>0. A correlation between large (small) event rates and small (large) b-> s+γbranching ratio is observed. The effect of future satellite (MAP and PLANCK) precision determinations of cosmological parameters on predicted event rates is examined for examples of the ΛCDM and νCDM models. It is seen that these could sharpen the event rate predictions and also restrict the allowed gaugino mass ranges, thus influencing predictions for accelerator SUSY searches.

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↗
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

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

Proton Decay and the Dimopoulos-Wilczek Mechanism in Minimal SO(10) Models

Proton decay is examined within the framework of certain SO(10) models which have low dimension representations compatible with the recently found constraints coming from string theory, and which use the Dimopoulos-Wilczek mechanism to solve the doublet-triplet splitting problem. It is found that the mass parameter that controls proton decay rate is intimately related to the low energy data via the coupling unification condition, and that a suppression of proton decay is achieved at the cost of large threshold effects. Furthermore, in cases where there are states with intermediate masses, the threshold effects further enhance proton decay. The experimental bound then severely constrains the parameter space of these models. Some possible solutions are suggested.

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

Gravitational GUT Breaking and the GUT-Planck Hierarchy

It is shown that non-renormalizable gravitational interactions in the Higgs sector of supersymmetric grand unified theories (GUT's) can produce the breaking of the unifying gauge group $G$ at the GUT scale $M_{\rm GUT} \sim 10^{16}$~GeV. Such a breaking offers an attractive alternative to the traditional method where the superheavy GUT scale mass parameters are added ad hoc into the theory. The mechanism also offers a natural explanation for the closeness of the GUT breaking scale to the Planck scale. A study of the minimal SU(5) model endowed with this mechanism is presented and shown to be phenomenologically viable. A second model is examined where the Higgs doublets are kept naturally light as Goldstone modes. This latter model also achieves breaking of $G$ at $M_{\rm GUT}$ but cannot easily satisfy the current experimental proton decay bound.

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

Planck Scale Physics and the Testability of SU(5) Supergravity GUT

GUT scale threshold corrections in minimal SU(5) supergravity grand unification are discussed. It is shown that predictions may be made despite uncertainties associated with the high energy scale. A bound relating the strong coupling constant to the mass scales associated with proton decay and supersymmetry is derived, and a sensitive probe of the underlying theory is outlined. In particular, low energy measurements can in principle determine the presence of Planck scale ($ 1 / {{\rm M}_{\rm Pl}} $) terms.

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.}

hep-ph↗
arXiv1994

Event Rates in Dark Matter Detectors For Neutralinos Including Constraints From The $b\rightarrow sγ$ Decay

Event rates for dark matter detectors in neutralino--nucleus scattering are studied for supergravity unified models, including the constraint arising from the $b\rightarrow sγ$ experiment. The recent experimental measurement of this decay by the CLEO Collaboration leads to strong constraints on the SUSY particle spectrum,and also significantly affects the event rates in dark matter detectors. The analysis given here uses the accurate method for the computation of the relic density and leads to a dip in the event rate when the neutralino mass is $\sim M_Z/2$ due to the $Z$-pole, and similar results hold when the neutralino mass is $\sim m_h/2$ due to the Higgs pole . Implication of these results for dark matter detectors are discussed.

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