arXiv subjects

Utpal Chattopadhyay

Publications and source records attributed to Utpal Chattopadhyay.

50 records · Page 3Linked to original sources

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

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

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↗

arXiv2001

Muon g-2 and Implications for Supersymmetry

A brief review is given of the implications of the recent Brookhaven result on the muon anomaly ($a_μ$) for supersymmetry. We focus mainly on the implications of the recent results for the minimal supergravity unified model. We show that the observed difference implies the existence of sparticles most of which should become observable at the Large Hadron Collider. Further, as foreseen in works prior to the Brookhaven experiment the sign of the difference between experimental prediction of $a_μ$ and its Standard Model value determines the sign of the Higgs mixing parameter $μ$. The $μ$ sign has important implications for the direct detection of dark matter. Implications of the Brookhaven result for other low energy phenomena are also discussed.

hep-ph↗

arXiv2001

Upper Limits on Sparticle Masses from g-2 and the Possibility for Discovery of Supersymmetry at Colliders and in Dark Matter Searches

We analyze the implications of the new physics effect seen in the $g-2$ Brookhaven measurement and show that if the effect arises from supersymmetry, then the sign of the Higgs mixing parameter $μ$ is determined to be positive in the standard sign convention. Further, analyses within the minimal supergravity model show that the Brookhaven result leads to upper limits on the universal gaugino and scalar masses of $m_{1/2}\leq 800$ GeV and $m_0\leq 1.5$ TeV for $\tanβ\leq 55$. Our analysis strongly suggests that supersymmetry via production of sparticles must be found at the Large Hadron Collider. Further, sign($μ$) positive is favorable for the discovery of supersymmetric cold dark matter.

hep-ph↗

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 $\tanβ> 10$.

hep-ph↗

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.

hep-ph↗

arXiv2000

Constraining Anomaly Mediated Supersymmetry Breaking Framework via Ongoing Muon g-2 Experiment at Brookhaven

The ongoing high precision E821 Brookhaven National Laboratory experiment on muon g-2 is promising to probe a theory involving supersymmetry. We have studied the constraints on the minimal Anomaly Mediated Supersymmetry Breaking (AMSB) model using the current data of muon g-2 from Brookhaven. A scenario of seeing no deviation from the Standard Model is also considered, within a $2σ$ limit of the combined error from the Standard Model result and the Brookhaven predicted uncertainty level. The resulting constraint is found to be complementary to what one obtains from $b \to s+ γ$ bounds within the AMSB scenario, since only a definite sign of $μ$ is effectively probed via $b \to s+ γ$. A few relevant generic features of the model are also described for disallowed regions of parameter space.

hep-ph↗

arXiv2000

LHC Signature of the Minimal SUGRA Model with a Large Soft Scalar Mass

Thanks to the focus point phenomenon, it is quite {\it natural} for the minimal SUGRA model to have a large soft scalar mass m_0 > 1 TeV. A distinctive feature of this model is an inverted hierarchy, where the lighter stop has a significantly smaller mass than the other squarks and sleptons. Consequently, the gluino is predicted to decay dominantly via stop exchange into a channel containing 2b and 2W along with the LSP. We exploit this feature to construct a robust signature for this model at the LHC in leptonic channels with 3-4 b-tags and a large missing-E_T.

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↗

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

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.

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