Gravitino is one feasible candidate for the dark matter in supergravity models. With its coupling... more Gravitino is one feasible candidate for the dark matter in supergravity models. With its couplings being suppressed by the Plank mass, gravitino interacts very weakly with other particles, making its direct detection, or production at colliders practically impossible. The signatures of this scenario mainly arise from the next lightest supersymmetric particle (NLSP) which is metastable due to the very weak coupling. There are many possibilities for the NLSP, and here I will review the feasibility of stop particle as the NLSP and discuss its phenomenology.
We consider the neutralino proton cross section for detection of Milky Way dark matter for a numb... more We consider the neutralino proton cross section for detection of Milky Way dark matter for a number of supergravity models with gauge unification at the GUT scale: models with universal soft breaking (mSUGRA), models with nonuniversal soft breaking, and string inspired D-brane models. The parameter space examined includes m 1/2 <1 TeV and tan β < 50, and the recent Higgs bound of m h >114 GeV is imposed. (For grand unified models, this bound is to be imposed for all tan β.) All coannihilation effects are included as well as the recent NLO corrections to b → sγ for large tan β, and coannihilation effects are shown to be sensitive to A 0 for large tan β. In all models, current detectors are sampling parts of the paramater space i. e. tan β > ∼ 25 for mSUGRA, tan β > ∼ 7 for nonuniversal models, and tan β > ∼ 20 for D-brane models. Future detectors should be able to cover almost the full parameter space for µ > 0. For µ < 0, cancellations can occur for m 1/2 > ∼ 450 GeV, allowing the cross sections to become < ∼ 10 −10 pb for limited ranges of tan β. (The positions of these cancellations are seen to be sensitive to the value of σ πN .) In this case, the gluino and squarks lie above 1 TeV, but still should be accessible to the LHC if m 1/2 < 1 TeV.
We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the St... more We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the Standard Model. We consider minimal supergravity motivated models (mSUGRA)/CMSSM and grand unified models, SU(5) and SO(10). In the grand unified models, the neutrino mixings provide an additional source of squark flavor violation through the quark-lepton unification. In the context of minimal SU(5) model, we find that the new CDF measurement has imposed a lower bound on the branching ratio of τ → µγ for a large CP phase in the B s-B s mixing. Recall that there have been indication for a large CP phase in B s mixing from B s → J/ψφ (Tevatron and LHCb) and dimuon asymmetry (D0). We also predict Br(τ → µη) for the possible range of values of Br(τ → µγ).
The range of neutralino-proton cross sections for R-parity preserving supergravity models with GU... more The range of neutralino-proton cross sections for R-parity preserving supergravity models with GUT scale unification of the gauge coupling constants is examined. The models considered here are mSUGRA, models with non universal soft breaking and D-brane models. It is found that the current dark matter detectors are sampling significant parts of the SUSY parameter space and future detectors could sample almost the entire space. The special regions of parameter space that may be inaccessible to future detectors are seen to have a squark/gluino spectra beyond 1 TeV, but observable at the LHC.
We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the St... more We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the Standard Model. We consider minimal supergravity motivated models (mSUGRA)/CMSSM and grand unified models, SU(5) and SO(10). In the grand unified models, the neutrino mixings provide an additional source of squark flavor violation through the quark-lepton unification. In the context of minimal SU(5) model, we find that the new CDF measurement has imposed a lower bound on the branching ratio of τ → µγ for a large CP phase in the B s-B s mixing. Recall that there have been indication for a large CP phase in B s mixing from B s → J/ψφ (Tevatron and LHCb) and dimuon asymmetry (D0). We also predict Br(τ → µη) for the possible range of values of Br(τ → µγ).
Supersymmetry and Unification of Fundamental Interactions, 2002
The SUSY contribution to the muon magnetic moment anomaly, a SUGRA µ , and the electron electric ... more The SUSY contribution to the muon magnetic moment anomaly, a SUGRA µ , and the electron electric dipole moment, de, is discussed within the framework of a modified mSUGRA model where the magnitudes of the soft breaking masses are universal, but arbitrary phases are allowed. It is shown analytically how the cancellation mechanism can allow for large phases (i.e. θ B < ∼ 0.4) and still suppress the value of de below its current experimental bound. The dependence of a SUGRA µ on the CP violating phases are analytically examined, and seen to decrease it but by at most a factor of about two. This reduction would then decrease the upper bound on m 1/2 due to the lower bound of Brookhaven data, and hence lower the SUSY mass spectrum, making it more accessible to accelerators. At the electroweak scale, the phases have to be specified to within a few percent to satisfy the experimental bound on de, but at the GUT scale, fine tuning below 1% is required for lower values of m 1/2. This fine tuning problem will become more serious if the bound on de is decreased.
Sources and Detection of Dark Matter and Dark Energy in the Universe, 2001
Neutralino proton cross sections are examined for models with R-parity invariance with universal ... more Neutralino proton cross sections are examined for models with R-parity invariance with universal soft breaking (mSUGRA) models, nonuniversal SUGRA models, and D-brane models. The region of parameter space where current dark matter detectors are sensitive, i.e. 1 × 10 −6 pb, is examined. For mSUGRA models, detectors are sampling parts of the parametr space for tanβ > ∼ 25. The nonuniversal models can achieve cross sections that are a factor of 10-100 bigger or smaller then the universal one and in the former case sample regions tanβ > ∼ 4. The D-brane models considered require tanβ > ∼ 15. The inclusion of CP violating phases reduces the cross section by a factor of ∼ 2-3 (but also requires considerable fine tuning at the GUT scale). The expected particle spectra at accelerators are examined and seen to differ for each model. Three new regions of possible coannihilation are noted.
We consider neutralino-proton cross sections for halo dark matter neutralinos (χ 0 1) within the ... more We consider neutralino-proton cross sections for halo dark matter neutralinos (χ 0 1) within the framework of supergravity models with R-parity invariance for models with universal soft breaking (mSUGRA) and models with nonuniversal soft breaking. The analysis includes the necessary corrections to treat the large tanβ region (i.e. L-R mixing in the squark and slepton mass matrices, loop corrections to the b and τ masses,etc) and includes all coannihilation phenomena. For mSUGRA, dark matter detectors with current sensitivity are seen to be probing the region where tanβ > ∼25, Ωχ0 1 h 2 < 0.1, mχ0 1 < ∼ 90 GeV, and for the light Higgs, m h < ∼ 120 GeV. Nonuniversal models can have a much larger cross section, and current detectors can probe part of the parameter space where tanβ > ∼ 4. Minimum cross sections are generally greater than 10 −9 pb to 10 −10 pb for m 1/2 < 600 GeV (and hence accessible to planned future detectors), with the exception of a region when µ < 0 where for m 1/2 > ∼ 450 GeV, 4 < ∼ tan β < ∼ 20, the cross section drops to a minimum of about 1 × 10 −12 pb at m 1/2 = 600 GeV, tan β ≃ 10. In this region, the gluino and squarks lie above 1 TeV, but should still be accessible to the LHC.
We consider here the spin independent neutralino-proton cross section for a variety of SUGRA and ... more We consider here the spin independent neutralino-proton cross section for a variety of SUGRA and D-brane models with R-parity invariance. The minimum cross section generally is >~ 1\times 10^{-(9-10)} pb (and hence accessible to future detectors) except for special regions of parameter space where it may drop to =~ 10^{-12} pb. In the latter case the gluino and squarks will be heavy (>~ 1 TeV).
Direct detection experiments for neutralino dark matter in the Milky Way are examined within the ... more Direct detection experiments for neutralino dark matter in the Milky Way are examined within the framework of SUGRA models with R-parity invariance and grand unification at the GUT scale, M G. Models of this type apply to a large number of phenomena, and all existing bounds on the SUSY parameter space due to current experimental constraints are included. For models with universal soft breaking at M G (mSUGRA), the Higgs mass and b → sγ constraints imply that the gaugino mass, m 1/2 , obeys m 1/2 >(300-400)GeV putting most of the parameter space in the co-annihilation domain where there is a relatively narrow band in the m 0 − m 1/2 plane. For µ > 0 we find that the neutralino-proton cross section > ∼ 10 −10 pb for m 1/2 < 1 TeV, making almost all of this parameter space accessible to future planned detectors. For µ < 0, however, there will be large regions of parameter space with cross sections < 10 −12 pb, and hence unaccessible experimentally. If, however, the muon magnetic moment anomaly is confirmed, then µ > 0 and m 1/2 < ∼ 800 GeV. Models with non-universal soft breaking in the third generation and Higgs sector can allow for new effects arising from additional early universe annihilation through the Z-channel pole. Here cross sections that will be accessible in the near future to the next generation of detectors can arise, and can even rise to the large values implied by the DAMA data. Thus dark matter detectors have the possibility of studying the the post-GUT physics that control the patterns of soft breaking.
We examine the discovery potential for SUSY new physics at a pp collider upgrade of Tevatron with... more We examine the discovery potential for SUSY new physics at a pp collider upgrade of Tevatron with √ s = 5.4 TeV and luminosity L ≃ 4× 10 32 cm −2 s −1 (the Tripler). We consider the reach for gluinos (g) and squarks (q) using the experimental signatures with large missing transverse energy (E / T) of jets + E / T and 1ℓ + jets + E / T (where ℓ=electron or muon) within the framework of minimal supergravity. The Tripler's strongest reach for the gluino is 1060 GeV for the jets + E / T channel and 1140 GeV for the 1ℓ + jets + E / T channel for 30 fb −1 of integrated luminosity (approximately two years running time). This is to be compared with the Tevatron where the reach is 440(460) GeV in the jets + E / T channel for 15(30) fb −1 of integrated luminosity.
We consider the prospects of supersymmetric dark matter in light of the recent results announced ... more We consider the prospects of supersymmetric dark matter in light of the recent results announced by the CDMS experiment. In this paper, we investigate the status of: (i) neutralino dark matter in models of minimal supergravity, (ii) neutralino dark matter in models with nonuniversal Higgs masses, and (iii) sneutrino dark matter in the U (1)B−L extension of the minimal supersymmetric standard model; and discuss the predictions of these models for the LHC, Tevatron, IceCube and PAMELA.
We revisit sneutrino dark matter in light of the recent results from the PAMELA and ATIC experime... more We revisit sneutrino dark matter in light of the recent results from the PAMELA and ATIC experiments. In the U (1)B−L extension of the minimal supersymmetric standard model the righthanded sneutrino is a natural candidate for thermal dark matter. Sneutrino annihilation at the present time can be considerably enhanced due to the exchange of the lightest field in the Higgs sector that breaks U (1)B−L. The annihilation mainly produces taus (or muons) by the virtue of B − L charges. A sneutrino mass in the 1 − 2 TeV range provides a good fit to the PAMELA data and a reasonable fit to the ATIC data. Within this mass range the sneutrino-nucleon elastic scattering cross section is 10 −11 − 10 −9 pb, which might be probed by upcoming and future direct detection experiments. In addition, if (at least) one of the neutrinos is dominantly a Dirac fermion, the sneutrino can provide a unified picture of dark matter and inflation.
We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the St... more We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the Standard Model. We consider minimal supergravity motivated models (mSUGRA)/CMSSM and grand unified models, SU(5) and SO(10). In the grand unified models, the neutrino mixings provide an additional source of squark flavor violation through the quark-lepton unification. In the context of minimal SU(5) model, we find that the new CDF measurement has imposed a lower bound on the branching ratio of τ → µγ for a large CP phase in the B s-B s mixing. Recall that there have been indication for a large CP phase in B s mixing from B s → J/ψφ (Tevatron and LHCb) and dimuon asymmetry (D0). We also predict Br(τ → µη) for the possible range of values of Br(τ → µγ).
Inflation can occur near a point of inflection in the potential of flat directions of the Minimal... more Inflation can occur near a point of inflection in the potential of flat directions of the Minimal Supersymmetric Standard Model. In this paper we elaborate on the complementarity between the bounds from Cosmic Microwave Background measurements, dark matter and particle physics phenomenology in determining the underlying parameters of MSSM inflation by specializing to the Minimal Supergravity scenario. We show that the future measurements from the Large Hadron Collider in tandem with all these constraints will significantly restrict the allowed parameter space. We also suggest a new perspective on the fine tuning issue of MSSM inflation. With quantum corrections taken into account, the necessary condition between the soft supersymmetry breaking parameters in the inflaton potential can be satisfied at scales of interest without a fine tuning of their boundary values at a high scale. The requirement that this happens at the inflection point determines a dimensionless coupling, which is associated with a non-renormalizable interaction term in the Lagrangian and has no bearing for phenomenology, to very high accuracy.
We propose a simple model of supersymmetric dark matter that can explain recent results from PAME... more We propose a simple model of supersymmetric dark matter that can explain recent results from PAMELA and ATIC experiments. It is based on a U (1)B−L extension of the minimal supersymmetric standard model. The dark matter particle is a linear combination of the U (1)B−L gaugino and Higgsino partners of Higgs fields that break the B − L around one TeV. The dominant mode of dark matter annihilation is to the lightest of the new Higgs fields, which has a mass in the GeV range, and its subsequent decay mainly produces taus or muons by the virtue of B − L charges. This light Higgs also results in Sommerfeld enhancement of the dark matter annihilation cross section, which can be > ∼ 10 3. For a dark matter mass in the 1 − 2 TeV range, the model provides a good fit to the PAMELA data and a reasonable fit to the ATIC data. We also briefly discuss the prospects of this model for direct detection experiments and the LHC.
We investigate the effect of the dimuon CP asymmetry from the B decay modes, recently observed at... more We investigate the effect of the dimuon CP asymmetry from the B decay modes, recently observed at 3.2 σ deviation from the Standard Model (SM) by the D0 collaboration, in the context of SU(5) and SO(10) GUT models. We exhibit that a large amount of flavor violation between the second and the third generation is generated due to the large neutrino atmospheric mixing angle and this flavor violation can be responsible for the observed large CP asymmetry due to the presence of new phases (not present in the CKM matrix) in the Yukawa couplings. We also study the implication of the parameter space in these GUT models with large CP violating lepton asymmetry for different phenomenologies, e.g., Br(τ → µγ), Br(B s → µµ) at the Fermilab, direct detection of dark matter (DM) in the ongoing detectors and measurement of muon flux from solar neutrinos at the IceCube experiment.
We combine the analyses for flavor changing neutral current processes and dark matter solutions i... more We combine the analyses for flavor changing neutral current processes and dark matter solutions in minimal-type supersymmetric grand unified theory (GUT) models, SO(10) and SU(5), with a large B s-B s mixing phase and large tan β. For large tan β, the double penguin diagram dominates the SUSY contribution to the B s-B s mixing amplitude. Also, the Br(B s → µµ) constraint becomes important as it grows as tan 6 β, although it can still be suppressed by large pseudoscalar Higgs mass m A. We investigate the correlation between B s → µµ and the dark matter direct detection cross-section through their dependence on m A. In the minimal-type of SU(5) with type I seesaw, the large mixing in neutrino Dirac couplings results in large lepton flavor violating decay process τ → µγ, which in turn sets upper bound on m A. In the SO(10) case, the large mixing can be chosen to be in the Majorana couplings instead, and the constraint from Br(τ → µγ) can be avoided. The heavy Higgs funnel region turns out to be an interesting possibility in both cases and the direct dark matter detection should be possible in the near future in these scenarios.
The electron electric dipole moment (d e) and the muon magnetic moment anomaly (a µ) recently obs... more The electron electric dipole moment (d e) and the muon magnetic moment anomaly (a µ) recently observed at BNL are analyzed within the framework of SUGRA models with CP violating phases at the GUT scale. It is seen analytically that even if d e were zero, there can be a large Bino mass phase (ranging from 0 to 2π) with a corresponding large B soft breaking mass phase (of size < ∼ 0.5 with sign fixed by the experimental sign of a µ). The dependence of the B phase on the other SUSY parameters, gaugino mass m 1/2 , tan β, A 0 , is examined. The lower bound of a µ determines the upper bound of m 1/2. It is shown analytically how the existence of a non-zero Bino phase reduces this upper bound (which would correspondingly lower the SUSY mass spectra). The experimental upper bound on d e determines the range of allowed phases, and the question of whether the current bound on d e requires any fine tuning is investigated. At the electroweak scale, the phases have to be specified to within a few percent. At the GUT scale, however, the B phase requires fine tuning below the 1% level over parts of the parameter space for low m 1/2 , and if the current experimental bound on d e were reduced by only a factor of 3−4, fine tuning below 1% would occur at both the electroweak and GUT scale over large regions of the parameter space. All accelerator constraints (m h > 114 GeV, b → sγ, etc.) and relic density constraints with all stau-neutralino co-annihilation processes are included in the analysis.
The neutralino-proton cross section is examined for supergravity models with R-parity invariance ... more The neutralino-proton cross section is examined for supergravity models with R-parity invariance with universal and non-universal soft breaking. The region of parameter space that dark matter detectors are currently (or will be shortly) sensitive i.e. (0.1 − 10) × 10 −6 pb, is examined. For universal soft breaking (mSUGRA), detectors with sensitivity σχ0 1 −p ≥ 1 × 10 −6 pb will be able to sample parts of the parameter space for tan β > ∼ 25. Current relic density bounds restrict mχ0 1 ≤ 120 GeV for the maximum cross sections, which is below where astronomical uncertainties about the Milky Way are relevant. Nonuniversal soft breaking models can allow much larger cross sections and can sample the parameter space for tan β > ∼ 4. In such models, m 0 can be quite large reducing the tension between proton decay bounds and dark matter analysis. We note the existance of two new domains where coannihilation effects can enter, i.e. for mSUGRA at large tan β, and for nonuniversal models with small tan β.
Gravitino is one feasible candidate for the dark matter in supergravity models. With its coupling... more Gravitino is one feasible candidate for the dark matter in supergravity models. With its couplings being suppressed by the Plank mass, gravitino interacts very weakly with other particles, making its direct detection, or production at colliders practically impossible. The signatures of this scenario mainly arise from the next lightest supersymmetric particle (NLSP) which is metastable due to the very weak coupling. There are many possibilities for the NLSP, and here I will review the feasibility of stop particle as the NLSP and discuss its phenomenology.
We consider the neutralino proton cross section for detection of Milky Way dark matter for a numb... more We consider the neutralino proton cross section for detection of Milky Way dark matter for a number of supergravity models with gauge unification at the GUT scale: models with universal soft breaking (mSUGRA), models with nonuniversal soft breaking, and string inspired D-brane models. The parameter space examined includes m 1/2 <1 TeV and tan β < 50, and the recent Higgs bound of m h >114 GeV is imposed. (For grand unified models, this bound is to be imposed for all tan β.) All coannihilation effects are included as well as the recent NLO corrections to b → sγ for large tan β, and coannihilation effects are shown to be sensitive to A 0 for large tan β. In all models, current detectors are sampling parts of the paramater space i. e. tan β > ∼ 25 for mSUGRA, tan β > ∼ 7 for nonuniversal models, and tan β > ∼ 20 for D-brane models. Future detectors should be able to cover almost the full parameter space for µ > 0. For µ < 0, cancellations can occur for m 1/2 > ∼ 450 GeV, allowing the cross sections to become < ∼ 10 −10 pb for limited ranges of tan β. (The positions of these cancellations are seen to be sensitive to the value of σ πN .) In this case, the gluino and squarks lie above 1 TeV, but still should be accessible to the LHC if m 1/2 < 1 TeV.
We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the St... more We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the Standard Model. We consider minimal supergravity motivated models (mSUGRA)/CMSSM and grand unified models, SU(5) and SO(10). In the grand unified models, the neutrino mixings provide an additional source of squark flavor violation through the quark-lepton unification. In the context of minimal SU(5) model, we find that the new CDF measurement has imposed a lower bound on the branching ratio of τ → µγ for a large CP phase in the B s-B s mixing. Recall that there have been indication for a large CP phase in B s mixing from B s → J/ψφ (Tevatron and LHCb) and dimuon asymmetry (D0). We also predict Br(τ → µη) for the possible range of values of Br(τ → µγ).
The range of neutralino-proton cross sections for R-parity preserving supergravity models with GU... more The range of neutralino-proton cross sections for R-parity preserving supergravity models with GUT scale unification of the gauge coupling constants is examined. The models considered here are mSUGRA, models with non universal soft breaking and D-brane models. It is found that the current dark matter detectors are sampling significant parts of the SUSY parameter space and future detectors could sample almost the entire space. The special regions of parameter space that may be inaccessible to future detectors are seen to have a squark/gluino spectra beyond 1 TeV, but observable at the LHC.
We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the St... more We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the Standard Model. We consider minimal supergravity motivated models (mSUGRA)/CMSSM and grand unified models, SU(5) and SO(10). In the grand unified models, the neutrino mixings provide an additional source of squark flavor violation through the quark-lepton unification. In the context of minimal SU(5) model, we find that the new CDF measurement has imposed a lower bound on the branching ratio of τ → µγ for a large CP phase in the B s-B s mixing. Recall that there have been indication for a large CP phase in B s mixing from B s → J/ψφ (Tevatron and LHCb) and dimuon asymmetry (D0). We also predict Br(τ → µη) for the possible range of values of Br(τ → µγ).
Supersymmetry and Unification of Fundamental Interactions, 2002
The SUSY contribution to the muon magnetic moment anomaly, a SUGRA µ , and the electron electric ... more The SUSY contribution to the muon magnetic moment anomaly, a SUGRA µ , and the electron electric dipole moment, de, is discussed within the framework of a modified mSUGRA model where the magnitudes of the soft breaking masses are universal, but arbitrary phases are allowed. It is shown analytically how the cancellation mechanism can allow for large phases (i.e. θ B < ∼ 0.4) and still suppress the value of de below its current experimental bound. The dependence of a SUGRA µ on the CP violating phases are analytically examined, and seen to decrease it but by at most a factor of about two. This reduction would then decrease the upper bound on m 1/2 due to the lower bound of Brookhaven data, and hence lower the SUSY mass spectrum, making it more accessible to accelerators. At the electroweak scale, the phases have to be specified to within a few percent to satisfy the experimental bound on de, but at the GUT scale, fine tuning below 1% is required for lower values of m 1/2. This fine tuning problem will become more serious if the bound on de is decreased.
Sources and Detection of Dark Matter and Dark Energy in the Universe, 2001
Neutralino proton cross sections are examined for models with R-parity invariance with universal ... more Neutralino proton cross sections are examined for models with R-parity invariance with universal soft breaking (mSUGRA) models, nonuniversal SUGRA models, and D-brane models. The region of parameter space where current dark matter detectors are sensitive, i.e. 1 × 10 −6 pb, is examined. For mSUGRA models, detectors are sampling parts of the parametr space for tanβ > ∼ 25. The nonuniversal models can achieve cross sections that are a factor of 10-100 bigger or smaller then the universal one and in the former case sample regions tanβ > ∼ 4. The D-brane models considered require tanβ > ∼ 15. The inclusion of CP violating phases reduces the cross section by a factor of ∼ 2-3 (but also requires considerable fine tuning at the GUT scale). The expected particle spectra at accelerators are examined and seen to differ for each model. Three new regions of possible coannihilation are noted.
We consider neutralino-proton cross sections for halo dark matter neutralinos (χ 0 1) within the ... more We consider neutralino-proton cross sections for halo dark matter neutralinos (χ 0 1) within the framework of supergravity models with R-parity invariance for models with universal soft breaking (mSUGRA) and models with nonuniversal soft breaking. The analysis includes the necessary corrections to treat the large tanβ region (i.e. L-R mixing in the squark and slepton mass matrices, loop corrections to the b and τ masses,etc) and includes all coannihilation phenomena. For mSUGRA, dark matter detectors with current sensitivity are seen to be probing the region where tanβ > ∼25, Ωχ0 1 h 2 < 0.1, mχ0 1 < ∼ 90 GeV, and for the light Higgs, m h < ∼ 120 GeV. Nonuniversal models can have a much larger cross section, and current detectors can probe part of the parameter space where tanβ > ∼ 4. Minimum cross sections are generally greater than 10 −9 pb to 10 −10 pb for m 1/2 < 600 GeV (and hence accessible to planned future detectors), with the exception of a region when µ < 0 where for m 1/2 > ∼ 450 GeV, 4 < ∼ tan β < ∼ 20, the cross section drops to a minimum of about 1 × 10 −12 pb at m 1/2 = 600 GeV, tan β ≃ 10. In this region, the gluino and squarks lie above 1 TeV, but should still be accessible to the LHC.
We consider here the spin independent neutralino-proton cross section for a variety of SUGRA and ... more We consider here the spin independent neutralino-proton cross section for a variety of SUGRA and D-brane models with R-parity invariance. The minimum cross section generally is >~ 1\times 10^{-(9-10)} pb (and hence accessible to future detectors) except for special regions of parameter space where it may drop to =~ 10^{-12} pb. In the latter case the gluino and squarks will be heavy (>~ 1 TeV).
Direct detection experiments for neutralino dark matter in the Milky Way are examined within the ... more Direct detection experiments for neutralino dark matter in the Milky Way are examined within the framework of SUGRA models with R-parity invariance and grand unification at the GUT scale, M G. Models of this type apply to a large number of phenomena, and all existing bounds on the SUSY parameter space due to current experimental constraints are included. For models with universal soft breaking at M G (mSUGRA), the Higgs mass and b → sγ constraints imply that the gaugino mass, m 1/2 , obeys m 1/2 >(300-400)GeV putting most of the parameter space in the co-annihilation domain where there is a relatively narrow band in the m 0 − m 1/2 plane. For µ > 0 we find that the neutralino-proton cross section > ∼ 10 −10 pb for m 1/2 < 1 TeV, making almost all of this parameter space accessible to future planned detectors. For µ < 0, however, there will be large regions of parameter space with cross sections < 10 −12 pb, and hence unaccessible experimentally. If, however, the muon magnetic moment anomaly is confirmed, then µ > 0 and m 1/2 < ∼ 800 GeV. Models with non-universal soft breaking in the third generation and Higgs sector can allow for new effects arising from additional early universe annihilation through the Z-channel pole. Here cross sections that will be accessible in the near future to the next generation of detectors can arise, and can even rise to the large values implied by the DAMA data. Thus dark matter detectors have the possibility of studying the the post-GUT physics that control the patterns of soft breaking.
We examine the discovery potential for SUSY new physics at a pp collider upgrade of Tevatron with... more We examine the discovery potential for SUSY new physics at a pp collider upgrade of Tevatron with √ s = 5.4 TeV and luminosity L ≃ 4× 10 32 cm −2 s −1 (the Tripler). We consider the reach for gluinos (g) and squarks (q) using the experimental signatures with large missing transverse energy (E / T) of jets + E / T and 1ℓ + jets + E / T (where ℓ=electron or muon) within the framework of minimal supergravity. The Tripler's strongest reach for the gluino is 1060 GeV for the jets + E / T channel and 1140 GeV for the 1ℓ + jets + E / T channel for 30 fb −1 of integrated luminosity (approximately two years running time). This is to be compared with the Tevatron where the reach is 440(460) GeV in the jets + E / T channel for 15(30) fb −1 of integrated luminosity.
We consider the prospects of supersymmetric dark matter in light of the recent results announced ... more We consider the prospects of supersymmetric dark matter in light of the recent results announced by the CDMS experiment. In this paper, we investigate the status of: (i) neutralino dark matter in models of minimal supergravity, (ii) neutralino dark matter in models with nonuniversal Higgs masses, and (iii) sneutrino dark matter in the U (1)B−L extension of the minimal supersymmetric standard model; and discuss the predictions of these models for the LHC, Tevatron, IceCube and PAMELA.
We revisit sneutrino dark matter in light of the recent results from the PAMELA and ATIC experime... more We revisit sneutrino dark matter in light of the recent results from the PAMELA and ATIC experiments. In the U (1)B−L extension of the minimal supersymmetric standard model the righthanded sneutrino is a natural candidate for thermal dark matter. Sneutrino annihilation at the present time can be considerably enhanced due to the exchange of the lightest field in the Higgs sector that breaks U (1)B−L. The annihilation mainly produces taus (or muons) by the virtue of B − L charges. A sneutrino mass in the 1 − 2 TeV range provides a good fit to the PAMELA data and a reasonable fit to the ATIC data. Within this mass range the sneutrino-nucleon elastic scattering cross section is 10 −11 − 10 −9 pb, which might be probed by upcoming and future direct detection experiments. In addition, if (at least) one of the neutrinos is dominantly a Dirac fermion, the sneutrino can provide a unified picture of dark matter and inflation.
We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the St... more We investigate the recent CDF measurement of the Br(B s → µ + µ −) which shows excess over the Standard Model. We consider minimal supergravity motivated models (mSUGRA)/CMSSM and grand unified models, SU(5) and SO(10). In the grand unified models, the neutrino mixings provide an additional source of squark flavor violation through the quark-lepton unification. In the context of minimal SU(5) model, we find that the new CDF measurement has imposed a lower bound on the branching ratio of τ → µγ for a large CP phase in the B s-B s mixing. Recall that there have been indication for a large CP phase in B s mixing from B s → J/ψφ (Tevatron and LHCb) and dimuon asymmetry (D0). We also predict Br(τ → µη) for the possible range of values of Br(τ → µγ).
Inflation can occur near a point of inflection in the potential of flat directions of the Minimal... more Inflation can occur near a point of inflection in the potential of flat directions of the Minimal Supersymmetric Standard Model. In this paper we elaborate on the complementarity between the bounds from Cosmic Microwave Background measurements, dark matter and particle physics phenomenology in determining the underlying parameters of MSSM inflation by specializing to the Minimal Supergravity scenario. We show that the future measurements from the Large Hadron Collider in tandem with all these constraints will significantly restrict the allowed parameter space. We also suggest a new perspective on the fine tuning issue of MSSM inflation. With quantum corrections taken into account, the necessary condition between the soft supersymmetry breaking parameters in the inflaton potential can be satisfied at scales of interest without a fine tuning of their boundary values at a high scale. The requirement that this happens at the inflection point determines a dimensionless coupling, which is associated with a non-renormalizable interaction term in the Lagrangian and has no bearing for phenomenology, to very high accuracy.
We propose a simple model of supersymmetric dark matter that can explain recent results from PAME... more We propose a simple model of supersymmetric dark matter that can explain recent results from PAMELA and ATIC experiments. It is based on a U (1)B−L extension of the minimal supersymmetric standard model. The dark matter particle is a linear combination of the U (1)B−L gaugino and Higgsino partners of Higgs fields that break the B − L around one TeV. The dominant mode of dark matter annihilation is to the lightest of the new Higgs fields, which has a mass in the GeV range, and its subsequent decay mainly produces taus or muons by the virtue of B − L charges. This light Higgs also results in Sommerfeld enhancement of the dark matter annihilation cross section, which can be > ∼ 10 3. For a dark matter mass in the 1 − 2 TeV range, the model provides a good fit to the PAMELA data and a reasonable fit to the ATIC data. We also briefly discuss the prospects of this model for direct detection experiments and the LHC.
We investigate the effect of the dimuon CP asymmetry from the B decay modes, recently observed at... more We investigate the effect of the dimuon CP asymmetry from the B decay modes, recently observed at 3.2 σ deviation from the Standard Model (SM) by the D0 collaboration, in the context of SU(5) and SO(10) GUT models. We exhibit that a large amount of flavor violation between the second and the third generation is generated due to the large neutrino atmospheric mixing angle and this flavor violation can be responsible for the observed large CP asymmetry due to the presence of new phases (not present in the CKM matrix) in the Yukawa couplings. We also study the implication of the parameter space in these GUT models with large CP violating lepton asymmetry for different phenomenologies, e.g., Br(τ → µγ), Br(B s → µµ) at the Fermilab, direct detection of dark matter (DM) in the ongoing detectors and measurement of muon flux from solar neutrinos at the IceCube experiment.
We combine the analyses for flavor changing neutral current processes and dark matter solutions i... more We combine the analyses for flavor changing neutral current processes and dark matter solutions in minimal-type supersymmetric grand unified theory (GUT) models, SO(10) and SU(5), with a large B s-B s mixing phase and large tan β. For large tan β, the double penguin diagram dominates the SUSY contribution to the B s-B s mixing amplitude. Also, the Br(B s → µµ) constraint becomes important as it grows as tan 6 β, although it can still be suppressed by large pseudoscalar Higgs mass m A. We investigate the correlation between B s → µµ and the dark matter direct detection cross-section through their dependence on m A. In the minimal-type of SU(5) with type I seesaw, the large mixing in neutrino Dirac couplings results in large lepton flavor violating decay process τ → µγ, which in turn sets upper bound on m A. In the SO(10) case, the large mixing can be chosen to be in the Majorana couplings instead, and the constraint from Br(τ → µγ) can be avoided. The heavy Higgs funnel region turns out to be an interesting possibility in both cases and the direct dark matter detection should be possible in the near future in these scenarios.
The electron electric dipole moment (d e) and the muon magnetic moment anomaly (a µ) recently obs... more The electron electric dipole moment (d e) and the muon magnetic moment anomaly (a µ) recently observed at BNL are analyzed within the framework of SUGRA models with CP violating phases at the GUT scale. It is seen analytically that even if d e were zero, there can be a large Bino mass phase (ranging from 0 to 2π) with a corresponding large B soft breaking mass phase (of size < ∼ 0.5 with sign fixed by the experimental sign of a µ). The dependence of the B phase on the other SUSY parameters, gaugino mass m 1/2 , tan β, A 0 , is examined. The lower bound of a µ determines the upper bound of m 1/2. It is shown analytically how the existence of a non-zero Bino phase reduces this upper bound (which would correspondingly lower the SUSY mass spectra). The experimental upper bound on d e determines the range of allowed phases, and the question of whether the current bound on d e requires any fine tuning is investigated. At the electroweak scale, the phases have to be specified to within a few percent. At the GUT scale, however, the B phase requires fine tuning below the 1% level over parts of the parameter space for low m 1/2 , and if the current experimental bound on d e were reduced by only a factor of 3−4, fine tuning below 1% would occur at both the electroweak and GUT scale over large regions of the parameter space. All accelerator constraints (m h > 114 GeV, b → sγ, etc.) and relic density constraints with all stau-neutralino co-annihilation processes are included in the analysis.
The neutralino-proton cross section is examined for supergravity models with R-parity invariance ... more The neutralino-proton cross section is examined for supergravity models with R-parity invariance with universal and non-universal soft breaking. The region of parameter space that dark matter detectors are currently (or will be shortly) sensitive i.e. (0.1 − 10) × 10 −6 pb, is examined. For universal soft breaking (mSUGRA), detectors with sensitivity σχ0 1 −p ≥ 1 × 10 −6 pb will be able to sample parts of the parameter space for tan β > ∼ 25. Current relic density bounds restrict mχ0 1 ≤ 120 GeV for the maximum cross sections, which is below where astronomical uncertainties about the Milky Way are relevant. Nonuniversal soft breaking models can allow much larger cross sections and can sample the parameter space for tan β > ∼ 4. In such models, m 0 can be quite large reducing the tension between proton decay bounds and dark matter analysis. We note the existance of two new domains where coannihilation effects can enter, i.e. for mSUGRA at large tan β, and for nonuniversal models with small tan β.
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Papers by Yudi Santoso