arXiv subjects

Y. Santoso

Publications and source records attributed to Y. Santoso.

18 recordsLinked to original sources

arXiv2003

Phenomenological Constraints on Patterns of Supersymmetry Breaking

Specific models of supersymmetry breaking predict relations between the trilinear and bilinear soft supersymmetry breaking parameters A_0 and B_0 at the input scale. In such models, the value of tan beta can be calculated as a function of the scalar masses m_0 and the gaugino masses m_{1/2}, which we assume to be universal. The experimental constraints on sparticle and Higgs masses, b to s gamma decay and the cold dark matter density Omega_{CDM} h^2 can then be used to constrain tan beta in such specific models of supersymmetry breaking. In the simplest Polonyi model with A_0 = (3 - sqrt{3})m_0 = B_0 + m_0, we find 11 < tan beta < 20 (tan beta ~ 4.15) for mu > 0 (mu < 0). We also discuss other models with A_0 = B_0 + m_0, finding that only the range -1.9 < A_0/m_0 < 2.5 is allowed for mu > 0, and the range 1.25 < A_0/m_0 < 4.8 for mu < 0. In these models, we find no solutions in the rapid-annihilation `funnels' or in the `focus-point' region. We also discuss the allowed range of tan beta in the no-scale model with A_0 = B_0 = 0. In all these models, most of the allowed regions are in the chi - stau_1 coannihilation `tail'.

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arXiv2003

Supersymmetric Dark Matter in Light of WMAP

We re-examine the parameter space of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), taking account of the restricted range of Ω_{CDM} h^2 consistent with the WMAP data. This provides a significantly reduced upper limit on the mass of the lightest supersymmetric particle LSP: m_χ< 500 GeV for \tan β< 45 and μ> 0, or \tan β< 30 and μ< 0, thereby improving the prospects for measuring supersymmetry at the LHC, and increasing the likelihood that a 1-TeV linear e^+ e^- collider would be able to measure the properties of some supersymmetric particles.

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arXiv2003

Direct Detection of Dark Matter in the MSSM with Non-Universal Higgs Masses

We calculate dark matter scattering rates in the minimal supersymmetric extension of the Standard Model (MSSM), allowing the soft supersymmetry-breaking masses of the Higgs multiplets, m_{1,2}, to be non-universal (NUHM). Compared with the constrained MSSM (CMSSM) in which m_{1,2} are required to be equal to the soft supersymmetry-breaking masses m_0 of the squark and slepton masses, we find that the elastic scattering cross sections may be up to two orders of magnitude larger than values in the CMSSM for similar LSP masses. We find the following preferred ranges for the spin-independent cross section: 10^{-6} pb \ga σ_{SI} \ga 10^{-10} pb, and for the spin-dependent cross section: 10^{-3} pb \ga σ_{SD}, with the lower bound on σ_{SI} dependent on using the putative constraint from the muon anomalous magnetic moment. We stress the importance of incorporating accelerator and dark matter constraints in restricting the NUHM parameter space, and also of requiring that no undesirable vacuum appear below the GUT scale. In particular, values of the spin-independent cross section another order of magnitude larger would appear to be allowed, for small \tan β, if the GUT vacuum stability requirement were relaxed, and much lower cross-section values would be permitted if the muon anomalous magnetic moment constraint were dropped.

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arXiv2002

Exploration of the MSSM with Non-Universal Higgs Masses

We explore the parameter space of the minimal supersymmetric extension of the Standard Model (MSSM), allowing the soft supersymmetry-breaking masses of the Higgs multiplets, m_{1,2}, to be non-universal (NUHM). Compared with the constrained MSSM (CMSSM) in which m_{1,2} are required to be equal to the soft supersymmetry-breaking masses m_0 of the squark and slepton masses, the Higgs mixing parameter mu and the pseudoscalar Higgs mass m_A, which are calculated in the CMSSM, are free in the NUHM model. We incorporate accelerator and dark matter constraints in determining allowed regions of the (mu, m_A), (mu, M_2) and (m_{1/2}, m_0) planes for selected choices of the other NUHM parameters. In the examples studied, we find that the LSP mass cannot be reduced far below its limit in the CMSSM, whereas m_A may be as small as allowed by LEP for large tan β. We present in Appendices details of the calculations of neutralino-slepton, chargino-slepton and neutralino-sneutrino coannihilation needed in our exploration of the NUHM.

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arXiv2002

Dark Matter in SUSY Models

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\to sγconstraints 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.

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arXiv2001

Effects of the Muon g-2 Anomaly on Dark Matter and Accelerator Physics

The effect of the recently observed 2.6 sigma deviation of the muon anomalous magnetic moment (a_mu = (g_mu -2)/2) from its Standard Model prediction is examined within the framework of supergravity models with grand unification and R parity invariance. The constraints of the Higgs mass bounds, the b -> s gamma bounds (including the large tan beta NLO corrections) and the cosmological relic density of light neutralinos (including all slepton neutralino coannihilation effects) are included in the analysis. For universal soft breaking, the Higgs and b -> s gamma bounds puts a lower bound m_1/2 >~ 300 GeV, most of the parameter space now falling in the co-annihilation region. The 2 sigma lower bound on the magnetic moment anomaly places an upper bound of m_1/2 ~< 800 GeV. It is seen that mSUGRA requires that a_mu ~< 50 \times 10^{-10}. One finds for m_h > 114 GeV, that tan beta > 5(7) for A_0 = 0(-4 m_1/2) and for m_h > 120 GeV, one has tan beta > 15 (10) for A_0 = 0(-4m_1/2). The sparticle spectrum is now much constrained, and the reaches of the Tevatron RUN II, NLC, and LHC for new physics discovery are discussed. Dark matter detection rates are examined, and it is seen that future detectors now would be able to scan most of the parameter space. Models with non-universal soft breaking in the Higgs and third generation of squarks and sleptons are exmained, and it is seen that a new Z s-channel annihilation of neutralinos in the early universe is possible with dark matter detection rates accessible to the next round of detectors.

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arXiv2001

Muon g-2 and Electric Dipole Moments in SUGRA Models

The SUSY contribution to the muon magnetic moment anomaly, a_mu^SUGRA, and the electron electric dipole moment, d_e, 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. theta_B <~ 0.4) and still suppress the value of d_e below its current experimental bound. The dependence of a_mu^SUGRA 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 d_e, 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 d_e is decreased.

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arXiv2001

SUSY Phases, the Electron Electric Dipole Moment and the Muon Magnetic Moment

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 2 π) 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 -> s γ, etc.) and relic density constraints with all stau-neutralino co-annihilation processes are included in the analysis.

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arXiv2001

Coannihilation Effects in Supergravity and D-Brane Models

Coannihilation effects in neutralino relic density calculations are examined for a full range of supersymmetry parameters including large \tanβand large A_0 for stau, chargino, stop and sbottom coannihilation with the neutralino. Supergravity models possessing grand unification with universal soft breaking (mSUGRA), models with nonuniversal soft breaking in the Higgs and third generation sparticles, and D-brane models with nonuniversal gaugino masses were analysed. Unlike low \tanβwhere m_0 is generally small, stau coannihilation corridors with high \tanβare highly sensitive to A_0, and large A_0 allows m_0 to become as large as 1TeV. Nonuniversal soft breaking models at high \tanβalso allow the opening of a new annihilation channel through the s-channel Z pole with acceptable relic density, allowing a new wide band in the m_0-m_{1/2} plane with m_{1/2} >~ 400 GeV and $m_0$ rising to 1 TeV. The D-brane models considered possess stau coannihilations regions similar to mSUGRA, as well as small regions of chargino coannihilation. Neutralino-proton cross sections are analysed for all models and it is found that future detectors for halo wimps will be able to scan essentially the full parameter space with m_{1/2} < 1 TeV except for a region with μ< 0 where accidental cancellations occur when 5 ~<\tanβ~< 30. Analytic explanations of much of the above phenomena are given. The above analyses include current LEP bounds on the Higgs mass, large \tanβNLO correction to the b \to s γdecay, and large \tanβSUSY corrections to the b and τmasses.

hep-ph↗

arXiv2001

Muon g-2, Dark Matter Detection and Accelerator Physics

We examine the recently observed deviation of the muon g - 2 from the Standard Model prediction within the framework of gravity mediated SUGRA models with R parity invariance. Universal soft breaking (mSUGRA) models, and models with non-universal Higgs and third generation squark/slepton masses at M_G are considered. All relic density constraints from stau-neutralino co-annihilation and large \tanβNLO corrections for b \to sγdecay are included, and we consider two possibilities for the light Higgs: m_h > 114 GeV and m_h > 120 GeV. The combined m_h, b \to sγand a_μ bounds give rise to lower bounds on \tanβand m_{1/2}, while the lower bound on a_μ gives rise to an upper bounds on m_{1/2}. These bounds are sensitive to A_0, e.g. for m_h > 114 GeV, the 95% C.L. is \tanβ> 7(5) for A_0 = 0(-4m_{1/2}), and for m_h > 120 GeV, \tanβ> 15(10). The positive sign of the a_μ deviation implies μ> 0, eliminating the extreme cancellations in the dark matter neutralino-proton detection cross section so that almost all the SUSY parameter space should be accessible to future planned detectors. Most of the allowed parts of parameter space occur in the co-annihilation region where m_0 is strongly correlated with m_{1/2}. The lower bound on a_μ then greatly reduces the allowed parameter space. Thus using 90% C. L. bounds on a_μ we find for A_0 = 0 that \tanβ\geq 10 and for \tanβ\leq 40 that m_{1/2} = (290 - 550) GeV and m_0 = (70 - 300) GeV. Then the tri-lepton signal and other SUSY signals would be beyond the Tevatron Run II (except for the light Higgs), only the \tildeτ_1 and h and (and for part of the parameter space) the \tilde{e}_1 will be accessible to a 500 GeV NLC, while the LHC would be able to see the full SUSY mass spectrum.

hep-ph↗

arXiv2001

Neutralino Proton Cross Section and Dark Matter Detection

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\to sγfor 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 tanβ. (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.

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arXiv2000

Prospect for Searches for Gluinos and Squarks at a Tevatron Tripler

We examine the discovery potential for SUSY new physics at a p{\bar p} collider upgrade of Tevatron with \sqrt s = 5.4 TeV and luminosity L ~= 4\times 10^{32} cm^{-2}s^{-1} (the Tripler). We consider the reach for gluinos and squarks using the experimental signatures with large missing transverse energy (\met) of jets + \met and 1l + jets + \met (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 + \met channel and 1140 GeV for the 1l + jets + \met 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 + \met channel for 15(30) fb^{-1} of integrated luminosity.

hep-ph↗

arXiv2000

Neutralino Proton Cross Sections in SUGRA and D-BRANE Models

We calculate the spin independent neutralino-proton cross section for universal SUGRA, non universal SUGRA and D-brane models with R-parity invariance. The regions of maximum cross section in these models has started to be probed by the current detectors. The minimum cross section generally is >~1\times 10^{-(9-10)}pb and hence will be accessible in the future detectors, barring special regions of parameter space where it can reduce to =~10^{-12}pb. However, the squarks and gluinos will be heavy (>~1 TeV) in the latter case, but still accessible at the LHC.

hep-ph↗

arXiv2000

Dark Matter in Supergravity

We consider neutralino-proton cross sections for halo dark matter neutralinos 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 tanbeta region (i.e. L-R mixing in the squark and slepton mass matrices, loop corrections to the b and tau masses,etc) and includes all coannihilation phenomena. For mSUGRA, dark matter detectors with current sensitivity are seen to be probing the region where tanbeta>~25, Omega h^2 <0.1, m_{chi_1^0}~<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 tan>~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 mu <0 where for m_{1/2}>~450 GeV, 4~< tanbeta~<20, the cross section drops to a minimum of about 1\times10^{-12} pb at m_{1/2}=600 GeV, tan beta=~10. In this region, the gluino and squarks lie above 1 TeV, but should still be accessible to the LHC.

hep-ph↗

arXiv2000

Dark Matter and Detector Cross Sections

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).

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arXiv2000

Maximum And Minimum Dark Matter Detection Cross Sections

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.

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arXiv2000

Neutralino Proton Cross Sections For Dark Matter In SUGRA And D-BRANE Models

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. $1\times 10^{-6}$ pb, is examined. For mSUGRA models, detectors are sampling parts of the parametr space for tan$β>\sim 25$. 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 tan$β>\sim 4$. The D-brane models considered require tan$β>\sim 15$. The inclusion of CP violating phases reduces the cross section by a factor of $\sim$ 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.

hep-ph↗

arXiv2000

Neutralino Proton Cross Sections In Supergravity Models

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. $(0.1-10)\times 10^{-6}$ pb, is examined. For universal soft breaking (mSUGRA), detectors with sensitivity $σ_{\tildeχ_{1}^{0}-p} \geq 1 \times 10^{-6}$ pb will be able to sample parts of the parameter space for $\tan β\stackrel{>}{\sim} 25$. Current relic density bounds restrict $m_{\tildeχ_{1}^{0}} \leq 120$ 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 $\tan β\stackrel{>}{\sim} 4$. 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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