Supersymmetry Reach of Tevatron Upgrades: The Large tan⁡β\tan\beta Case

The Yukawa couplings of the tau lepton and the bottom quark become comparable to, or even exceed, electroweak gauge couplings for large values of the SUSY parameter $\tan\beta$. As a result, the lightest tau slepton \ttau_1 and bottom squark \tb_1 can be significantly lighter than corresponding sleptons and squarks of the first two generations. Gluino, chargino and neutralino decays to third generation particles are significantly enhanced when $\tan\beta$ is large. This affects projections for collider experiment reach for supersymmetric particles. In this paper, we evaluate the reach of the Fermilab Tevatron $p\bar p$ collider for supersymmetric signals in the framework of the mSUGRA model. We find that the reach via signatures with multiple isolated leptons ($e$ and $\mu$) is considerably reduced. For very large $\tan\beta$, the greatest reach is attained in the multi-jet+\eslt signature. Some significant extra regions may be probed by requiring the presence of an identified $b$-jet in jets+\eslt events, or by requiring one of the identified leptons in clean trilepton events to actually be a hadronic 1 or 3 charged prong tau. In an appendix, we present formulae for chargino, neutralino and gluino three body decays which are valid at large $\tan\beta$.Comment: 31 page Revtex file including 10 PS figure

Hidden SUSY at the LHC: the light higgsino-world scenario and the role of a lepton collider

While the SUSY flavor, CP and gravitino problems seem to favor a very heavy spectrum of matter scalars, fine-tuning in the electroweak sector prefers low values of superpotential mass \mu. In the limit of low \mu, the two lightest neutralinos and light chargino are higgsino-like. The light charginos and neutralinos may have large production cross sections at LHC, but since they are nearly mass degenerate, there is only small energy release in three-body sparticle decays. Possible dilepton and trilepton signatures are difficult to observe after mild cuts due to the very soft p_T spectrum of the final state isolated leptons. Thus, the higgsino-world scenario can easily elude standard SUSY searches at the LHC. It should motivate experimental searches to focus on dimuon and trimuon production at the very lowest p_T(\mu) values possible. If the neutralino relic abundance is enhanced via non-standard cosmological dark matter production, then there exist excellent prospects for direct or indirect detection of higgsino-like WIMPs. While the higgsino-world scenario may easily hide from LHC SUSY searches, a linear e^+e^- collider or a muon collider operating in the \sqrt{s}\sim 0.5-1 TeV range would be able to easily access the chargino and neutralino pair production reactions.Comment: 20 pages including 12 .eps figure

The Reach of the Fermilab Tevatron and CERN LHC for Gaugino Mediated SUSY Breaking Models

In supersymmetric models with gaugino mediated SUSY breaking (inoMSB), it is assumed that SUSY breaking on a hidden brane is communicated to the visible brane via gauge superfields which propagate in the bulk. This leads to GUT models where the common gaugino mass $m_{1/2}$ is the only soft SUSY breaking term to receive contributions at tree level. To obtain a viable phenomenology, it is assumed that the gaugino mass is induced at some scale $M_c$ beyond the GUT scale, and that additional renormalization group running takes place between $M_c$ and $M_{GUT}$ as in a SUSY GUT. We assume an SU(5) SUSY GUT above the GUT scale, and compute the SUSY particle spectrum expected in models with inoMSB. We use the Monte Carlo program ISAJET to simulate signals within the inoMSB model, and compute the SUSY reach including cuts and triggers approriate to Fermilab Tevatron and CERN LHC experiments. We find no reach for SUSY by the Tevatron collider in the trilepton channel. %either with or without %identified tau leptons. At the CERN LHC, values of $m_{1/2}=1000$ (1160) GeV can be probed with 10 (100) fb$^{-1}$ of integrated luminosity, corresponding to a reach in terms of $m_{\tg}$ of 2150 (2500) GeV. The inoMSB model and mSUGRA can likely only be differentiated at a linear $e^+e^-$ collider with sufficient energy to produce sleptons and charginos.Comment: 17 page revtex file with 9 PS figure

Reach of the Fermilab Tevatron for minimal supergravity in the region of large scalar masses

The reach of the Fermilab Tevatron for supersymmetric matter has been calculated in the framework of the minimal supergravity model in the clean trilepton channel. Previous analyses of this channel were restricted to scalar masses m_0<= 1 TeV. We extend the analysis to large values of scalar masses m_0\sim 3.5 TeV. This includes the compelling hyperbolic branch/focus point (HB/FP) region, where the superpotential \mu parameter becomes small. In this region, assuming a 5\sigma (3\sigma) signal with 10 (25) fb^{-1} of integrated luminosity, the Tevatron reach in the trilepton channel extends up to m_{1/2}\sim 190 (270) GeV independent of \tan\beta . This corresponds to a reach in terms of the gluino mass of m_{\tg}\sim 575 (750) GeV.Comment: 11 page latex file including 6 EPS figures; several typos corrected and references adde

Ground-state degeneracies leave recognizable topological scars in the one-particle density

In Kohn-Sham density functional theory (KS-DFT) a fictitious system of non-interacting particles is constructed having the same ground-state (GS) density as the physical system of interest. A fundamental open question in DFT concerns the ability of an exact KS calculation to spot and characterize the GS degeneracies in the physical system. In this article we provide theoretical evidence suggesting that the GS density, as a function of position on a 2D manifold of parameters affecting the external potential, is "topologically scarred" in a distinct way by degeneracies. These scars are sufficiently detailed to enable determination of the positions of degeneracies and even the associated Berry phases. We conclude that an exact KS calculation can spot and characterize the degeneracies of the physical system

Mixed Higgsino Dark Matter from a Large SU(2) Gaugino Mass

We observe that in SUSY models with non-universal GUT scale gaugino mass parameters, raising the GUT scale SU(2) gaugino mass |M_2| from its unified value results in a smaller value of -m_{H_u}^2 at the weak scale. By the electroweak symmetry breaking conditions, this implies a reduced value of \mu^2 {\it vis \`a vis} models with gaugino mass unification. The lightest neutralino can then be mixed Higgsino dark matter with a relic density in agreement with the measured abundance of cold dark matter (DM). We explore the phenomenology of this high |M_2| DM model. The spectrum is characterized by a very large wino mass and a concomitantly large splitting between left- and right- sfermion masses. In addition, the lighter chargino and three light neutralinos are relatively light with substantial higgsino components. The higgsino content of the LSP implies large rates for direct detection of neutralino dark matter, and enhanced rates for its indirect detection relative to mSUGRA. We find that experiments at the LHC should be able to discover SUSY over the portion of parameter space where m_{\tg} \alt 2350-2750 ~GeV, depending on the squark mass, while a 1 TeV electron-positron collider has a reach comparable to that of the LHC. The dilepton mass spectrum in multi-jet + \ell^+\ell^- + \eslt events at the LHC will likely show more than one mass edge, while its shape should provide indirect evidence for the large higgsino content of the decaying neutralinos.Comment: 36 pages with 26 eps figure

Yukawa-unified natural supersymmetry

Previous work on t-b-\tau Yukawa-unified supersymmetry, as expected from SUSY GUT theories based on the gauge group SO(10), tended to have exceedingly large electroweak fine-tuning (EWFT). Here, we examine supersymmetric models where we simultaneously require low EWFT ("natural SUSY") and a high degree of Yukawa coupling unification, along with a light Higgs scalar with m_h\sim125 GeV. As Yukawa unification requires large tan\beta\sim50, while EWFT requires rather light third generation squarks and low \mu\sim100-250 GeV, B-physics constraints from BR(B\to X_s\gamma) and BR(B_s\to \mu+\mu-) can be severe. We are able to find models with EWFT \Delta\lesssim 50-100 (better than 1-2% EWFT) and with Yukawa unification as low as R_yuk\sim1.3 (30% unification) if B-physics constraints are imposed. This may be improved to R_yuk\sim1.2 if additional small flavor violating terms conspire to improve accord with B-constraints. We present several Yukawa-unified natural SUSY (YUNS) benchmark points. LHC searches will be able to access gluinos in the lower 1-2 TeV portion of their predicted mass range although much of YUNS parameter space may lie beyond LHC14 reach. If heavy Higgs bosons can be accessed at a high rate, then the rare H, A\to \mu+\mu- decay might allow a determination of tan\beta\sim50 as predicted by YUNS models. Finally, the predicted light higgsinos should be accessible to a linear e+e- collider with \sqrt{s}\sim0.5 TeV.Comment: 18 pages, 7 figures, pdflatex; 3 references adde

Probing Neutralino Resonance Annihilation via Indirect Detection of Dark Matter

The lightest neutralino of R-parity conserving supersymmetric models serves as a compelling candidate to account for the presence of cold dark matter in the universe. In the minimal supergravity (mSUGRA) model, a relic density can be found in accord with recent WMAP data for large values of the parameter $\tan\beta$, where neutralino annihilation in the early universe occurs via the broad s-channel resonance of the pseudoscalar Higgs boson $A$. We map out rates for indirect detection of neutralinos via 1. detection of neutrinos arising from neutralino annihilation in the core of the earth or sun and 2. detection of gamma rays, antiprotons and positrons arising from neutralino annihilation in the galactic halo. If indeed $A$-resonance annihilation is the main sink for neutralinos in the early universe, then signals may occur in the gamma ray, antiproton and positron channels, while a signal in the neutrino channel would likely be absent. This is in contrast to the hyperbolic branch/focus point (HB/FP) region where {\it all} indirect detection signals are likely to occur, and also in contrast to the stau co-annihilation region, where {\it none} of the indirect signals are likely to occur.Comment: 12 pages including 4 eps figure

Probing Minimal Supergravity at the CERN LHC for Large tan⁡β\tan\beta

For large values of the minimal supergravity model parameter $\tan\beta$, the tau lepton and the bottom quark Yukawa couplings become large, leading to reduced masses of $\tau$-sleptons and $b$-squarks relative to their first and second generation counterparts, and to enhanced decays of charginos and neutralinos to $\tau$-leptons and $b$-quarks. We evaluate the reach of the CERN LHC $pp$ collider for supersymmetry in the mSUGRA model parameter space. We find that values of $m_{\tg}\sim 1500-2000$ GeV can be probed with just 10 fb$^{-1}$ of integrated luminosity for $\tan\beta$ values as high as 45, so that mSUGRA cannot escape the scrutiny of LHC experiments by virtue of having a large value of $\tan\beta$. We also perform a case study of an mSUGRA model at $\tan\beta =45$ where \tz_2\to \tau\ttau_1 and \tw_1\to \ttau_1\nu_\tau with $\sim 100$ branching fraction. In this case, at least within our simplistic study, we show that a di-tau mass edge, which determines the value of m_{\tz_2}-m_{\tz_1}, can still be reconstructed. This information can be used as a starting point for reconstructing SUSY cascade decays on an event-by-event basis, and can provide a strong constraint in determining the underlying model parameters. Finally, we show that for large $\tan\beta$ there can be an observable excess of $\tau$ leptons, and argue that $\tau$ signals might serve to provide new information about the underlying model framework.Comment: 22 page REVTEX file including 8 figure