Supersymmetry Scenario Research Articles

Hierarchically split supersymmetry with Fayet–Iliopoulos D-terms in string theory

We show that in string theory or supergravity with supersymmetry breaking through combined F-terms and Fayet–Iliopoulos D-terms the masses for charged scalars and fermions can be hierarchically split. The mass scale for the gauginos and higgsinos of the MSSM is controlled by the gravitino mass m 3 / 2 , as usual, while the scalars get extra contributions from the D-terms of extra Abelian U ( 1 ) factors, which can make them much heavier. The vanishing of the vacuum energy requires that their masses lie below m 3 / 2 M Pl , which for m 3 / 2 = O ( TeV ) sets a bound of 10 10 – 13 GeV . Thus, scalars with non-vanishing U ( 1 ) charges typically become heavy, while others remain light, producing a spectrum of scalars with masses proportional to their charges, and therefore non-universal. This is a modification of the split supersymmetry scenario, but with a light gravitino. We discuss how Fayet–Iliopoulos terms of this size can arise in orientifold string compactifications with D-branes. Furthermore, within the frame work of D-term inflation, the same vacuum energy that generates the heavy scalar masses can be responsible for driving cosmological inflation.

Sparticle spectrum and phenomenology in split supersymmetry: Some possibilities

We investigate the split supersymmetry (SUSY) scenario recently proposed by Arkani-Hamed and Dimopoulos, where the scalars are heavy but the fermions are within the TeV range. We show that the sparticle spectrum in such a case crucially depends on the specific details of the mechanism underlying the SUSY breaking scheme, and the accelerator signals are also affected by it. In particular, we demonstrate in the context of a braneworld-inspired model, used as illustration in the original work, that a new fermion ${\ensuremath{\psi}}_{X}$, arising from the SUSY breaking sector, is shown to control low-energy phenomenology in several cases. Also, SUSY signals are characterized by the associated production of the light neutral Higgs. In an alternative scenario where the gauginos are assumed to propagate in the bulk, we find that gluinos can be heavy and short-lived, and the SUSY breaking scale can be free of cosmological constraints.

Testing soft electroweak supersymmetry breaking from neutralino, chargino, and charged Higgs boson pair production at linear colliders

We consider the production of neutralino, chargino, and charged Higgs boson pairs in the Minimal Supersymmetric Standard Model (MSSM) framework at future ${e}^{+}{e}^{\ensuremath{-}}$ colliders. We show that, for c.m. energies in the 1 TeV range and in a moderately light supersymmetry (SUSY) scenario, a combined analysis of the slopes of these production cross sections could lead to a strong consistency test involving the soft supersymmetric breaking parameters ${M}_{1}$, ${M}_{2}$, the Higgsino parameter $\ensuremath{\mu}$, and $\mathrm{tan}\ensuremath{\beta}$.

Signatures of long-lived gluinos in split supersymmetry

We examine the experimental signatures for the production of gluinos at colliders and in cosmic rays within the split supersymmetry scenario. Unlike in the MSSM, the gluinos in this model are relatively long-lived due to the large value of the squark masses which mediate their decay. Searches at colliders are found to be sensitive to the nature of gluino fragmentation as well as the gluino-hadron interactions with nuclei and energy deposition as it traverses the detector. We find that the worst-case scenario, where a neutral gluino-hadron passes through the detector with little energy deposition, is well described by a monojet signature. For this case, using Run I data we obtain a bound of $m_{\tilde g} > 170$ GeV; this will increase to 210(1100) GeV at Run II(LHC) if no excess events are observed. In the opposite case, where a charged gluino-hadron travels through the detector, a significantly greater reach is obtained via stable charged particle search techniques. We also examine the production of gluino pairs in the atmosphere by cosmic rays and show they are potentially observable at IceCube; this would provide a cross-check for observations at hadron colliders.

Can there be a heavy sbottom hidden in three-jet data at CERN LEP?

A low-energy supersymmetry scenario with a light gluino of mass 12--16 GeV and light sbottom $({b}_{1})$ of mass 2--6 GeV has been used to explain the apparent overproduction of b quarks at the fermilab Tevatron. In this scenario the other mass eigenstate of the sbottom, i.e., ${b}_{2},$ is favored to be lighter than 180 GeV due to constraints from electroweak precision data. We survey its decay modes in this scenario and show that decay into a b quark and gluino should be dominant. Associated sbottom production at CERN LEP via ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{Z}^{*}\ensuremath{\rightarrow}{b}_{1}{b}_{2}^{*}+{b}_{1}^{*}{b}_{2}$ is studied and we show that it is naturally a three-jet process with a small cross section, increasingly obscured by a large standard model background for heavier ${b}_{2}.$ However we find that direct observation of a ${b}_{2}$ at the $5\ensuremath{\sigma}$ level is possible if it is lighter than 110--129 GeV, depending on the sbottom mixing angle $|\mathrm{cos}{\ensuremath{\theta}}_{b}|=0.30--0.45.$ We also show that ${b}_{2}$-pair production can be mistaken for production of neutral minimal supersymmetric standard model Higgs bosons in the channel ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{h}^{0}{A}^{0}\ensuremath{\rightarrow}b\overline{b}b\overline{b}.$ Using searches for the latter we place a lower mass limit of 90 GeV on ${b}_{2}.$

Search for pair production of scalar top quarks in R-parity violating decay modes in pp collisions at square root of s=1.8 TeV.

We present the results of a search for pair production of scalar top quarks (t(1)) in an R-parity violating supersymmetry scenario in 106 pb(-1) of pp collisions at square root of s=1.8 TeV collected by the Collider Detector at Fermilab. In this mode each t(1) decays into a tau lepton and a b quark. We search for events with two tau's, one decaying leptonically (e or mu) and one decaying hadronically, and two jets. No candidate events pass our final selection criteria. We set a 95% confidence level lower limit on the t(1) mass at 122 GeV/c(2) for Br(t(1)-->tau b)=1.

Status of light gaugino scenarios

I summarize recent developments in supersymmetry scenarios which leave some or all gauginos light. The emphasis is on experimental and phenomenological progress in the past year.

One-loop corrections to the Higgs sector in minimal supergravity models.

We study the Higgs spectrum of the minimal supersymmetric standard model in the context of supergravity models with radiative gauge-symmetry breaking, including the leading one-loop corrections. We find that, unlike in more general scenarios, these corrections cannot change the ordering of the Higgs-boson masses as predicted by tree-level expressions. Moreover, the upper bound on the mass of the lightest Higgs boson is reduced compared to the general case; however, even in the most restrictive supergravity model the Higgs sector might escape detection at the CERN Large Electron-Positron Collider LEP 200. We also present an expression for the one-loop-corrected charged-Higgs-boson mass, and describe an improved calculation of the bound on the lightest Higgs boson in general global supersymmetry scenarios.

Some remarks on a scenario of supersymmetry in quantum mechanics

We give some remarks on a recent paper of Lahiri, Kumar Roy and Bagchi who have constructed a scenario of supersymmetry in quantum mechanics by imposing a structure on the raising and lowering operators.

A scenario of supersymmetry in quantum mechanics

We construct a scenario of supersymmetry in quantum mechanics by imposing a structure on the raising and lowering operators. Possible consequences are worked out in one dimension which includes relating supersymmetry to the infinite deep well problem

Light-gluino scenario.

We investigate in detail the consequences of the supersymmetry scenario with a light (approx.5 GeV) gluino and heavy (approx.100 GeV) scalar quarks, including gluino distribution and fragmentation effects, proposed to explain large-missing-p/sub T/ events observed at the CERN pp-bar collider. The effective gluino distribution in the nucleon is evaluated using the Altarelli-Parisi equations. Ambiguities in evaluating scalar-quark production with the effective gluino distribution are discussed. A plausible gluino fragmentation function is deduced from heavy-quark fragmentation functions; scaling violations in the gluino fragmentation function are taken into account. Fragmentation effects drastically reduce the missing p/sub T/ in light-gluino jets. The present collider data do not rule out a light gluino with mass in the range of 3-5 GeV even if the g lifetime, from decay into a photino and a quark pair, is short.

Dimuons from gauge fermions produced inpp¯collisions

In a supersymmetry scenario with a mass hierarchy ${\mathrm{m}}_{\mathrm{g}\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}$\ensuremath{\approxeq}${\mathrm{m}}_{\mathrm{q}\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}$>${\mathrm{m}}_{\mathrm{\ensuremath{\omega}}\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}$>${\mathrm{m}}_{\mathrm{l}\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}$ , gluino-scalar quark pair production followed by the decay chain g\ifmmode \tilde{}\else \~{}\fi{}\ensuremath{\rightarrow}q\ifmmode \tilde{}\else \~{}\fi{} q\ifmmode\bar\else\textasciimacron\fi{}(q\ifmmode \tilde{}\else \~{}\fi{}\ifmmode\bar\else\textasciimacron\fi{}q), q\ifmmode \tilde{}\else \~{}\fi{}\ensuremath{\rightarrow}\ensuremath{\omega}\ifmmode \tilde{}\else \~{}\fi{}q, \ensuremath{\omega}\ifmmode \tilde{}\else \~{}\fi{}\ensuremath{\rightarrow}\ensuremath{\mu}\ifmmode \tilde{}\else \~{}\fi{}\ensuremath{\nu}(\ensuremath{\mu}\ensuremath{\nu}\ifmmode \tilde{}\else \~{}\fi{}), \ensuremath{\mu}\ifmmode \tilde{}\else \~{}\fi{}\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\gamma}\ifmmode \tilde{}\else \~{}\fi{} leads to like-sign and unlike-sign dimuons with comparable rates and possibly little accompanying hadronic activity; such events will often contain strange particles. Predictions are made for the dimuon distributions. The possible relevance to dimuon observations by Arnison et al. is addressed.

Testing supersymmetry interpretations of anomalous missing-pT events observed at the CERN pp-bar collider.

We compare predictions of three supersymmetry scenarios [(A) ${m}_{g\ifmmode \tilde{}\else \~{}\fi{}}$>${m}_{q\ifmmode \tilde{}\else \~{}\fi{}}$ \ensuremath{\simeq}50 GeV, (B) ${m}_{q\ifmmode \tilde{}\else \~{}\fi{}}$>${m}_{g\ifmmode \tilde{}\else \~{}\fi{}}$ \ensuremath{\simeq}50 GeV, and (C) ${m}_{q\ifmmode \tilde{}\else \~{}\fi{}}$ \ensuremath{\simeq}100 GeV, ${m}_{g\ifmmode \tilde{}\else \~{}\fi{}}$ \ensuremath{\simeq}3 GeV] proposed to explain large-missing-${p}_{T}$ events at the CERN pp\ifmmode\bar\else\textasciimacron\fi{} collider in terms of scalar-quark or gluino decays to a light photino. We evaluate fusion cross sections for monojets and multijets and present distributions in missing ${p}_{T}$, jet ${E}_{T}$, jet pseudorapidity, jet invariant mass, and cluster transverse mass. Scenarios A and B give about equal one-jet and two-jet event rates, soft missing-${p}_{T}$ and jet-${E}_{T}$ distributions and occasional prompt leptons; scenario B gives large jet invariant masses, even for monojets. Scenario C yields monojet dominance and Jacobian peaks in missing ${p}_{T}$ and jet ${E}_{T}$; the present UA1 data favor this latter description.