We study the reach of the Large Hadron Collider with 1/fb of data at sqrt{s} = 7 TeV for several classes of supersymmetric models with compressed mass spectra, using jets and missing transverse energy cuts like those employed by ATLAS for Summer 2011 data. In the limit of extreme compression, the best limits come from signal regions that do not require more than 2 or 3 jets and that remove backgrounds by requiring more missing energy rather than higher effective mass.
Diagnostic signals of the minimal model of anomaly mediated supersymmetry breaking are discussed in the context of a $\sqrt{s}$ = 1 TeV $e^+e^-$ linear collider.
Top squark-mediated annihilation of bino-like neutralinos to top-antitop pairs can play the dominant role in obtaining a thermal relic dark matter abundance in agreement with observations. In a previous paper, it was argued that this can occur naturally in models of compressed supersymmetry, which feature a running gluino mass parameter that is substantially smaller than the wino mass parameter at the scale of apparent gauge coupling unification. Here I study in some more detail the parameter space in which this is viable, and compare to other scenarios for obtaining the observed dark matter d…
While it is natural for supersymmetric particles to be well within the mass range of the large hadron collider, it is possible that the sparticle masses could be very heavy. Signatures are examined at a very high energy hadron collider and an very high luminosity option for the Large Hadron Collider in such scenarios.
We consider the collider phenomenology of split-supersymmetry models. We show that despite the challenging nature of the signals in these models the long-lived gluino can be discovered with masses in excess of 2 TeV at the LHC. At a future linear collider we will be able to observe the renormalization group effects from split supersymmetry, using measurements of the neutralino and chargino masses and cross sections.
We show the usefulness of an $e^-γ$ collider with backscattered laser photons in unveiling the signatures of Gauge-Mediated Supersymmetry Breaking models, with a right selectron as the next LSP. We also show how the signal can be distinguished from the Standard Model background as well as from signals of minimal supersymmetry.
We present here the results for Higgs and Supersymmetry prospective searches at the Large Hadron Collider. We show that for one year at high luminosity, Standard Model and MSSM Higgs should be observed within the theoretically expected mass range. MSUGRA and restricted phenomenological MSSM searches lead to discovery of up to 2.5 TeV squarks and gluinos.
We study the signatures of minimal anomaly mediated supersymmetry breaking in an e^- gamma collider. We demonstrate that the associated production of a sneutrino with the lightest chargino leads to a substantially large signal size. The background is negligibly small, though. Even more interestingly, a measurement of the fundamental supersymmetry breaking parameters could be possible.
We show how to differentiate the minimal supersymmetric extension of the standard model from black hole events at the Large Hadron Collider. Black holes are simulated with the CATFISH generator. Supersymmetry simulations use a combination of PYTHIA and ISAJET. Our study, based on event shape variables, visible and missing momenta, and analysis of dilepton events, demonstrates that supersymmetry and black hole events at the LHC can be easily discriminated.
The theoretical expectations for the supersymmetric particle spectrum is reviewed and a brief overview on present constraints on supersymmetric models from collider experiments is presented. Finally, we discuss the discovery potential of future collider experiments.
We classify the variety of low-energy supersymmetric signatures that can be probed at future colliders. We focus on phenomena associated with the minimal supersymmetric extension of the Standard Model. The structure of the supersymmetry-breaking introduces additional model assumptions. The approaches considered here are supergravity-mediated and gauge-mediated supersymmetry-breaking. Alternative phenomenologies arising in non-minimal and/or R-parity-violating approaches are also briefly examined.
In compressed supersymmetry, a light top squark naturally mediates efficient neutralino pair annihilation to govern the thermal relic abundance of dark matter. I study the LHC signal of same-sign leptonic top-quark decays from gluino and squark production, which follows from gluino decays to top plus stop followed by the stop decaying to a charm quark and the LSP in these models. Measurements of the numbers of jets with heavy-flavor tags in the same-sign lepton events can be used to confirm the origin of the signal. Summed transverse momentum observables provide an estimate of an effective sup…
We consider the collider phenomenology of split-supersymmetry models. Despite the challenging nature of the signals in these models the long-lived gluino can be discovered with masses above 2 TeV at the LHC. At a future linear collider we will be able to observe the renormalization group effects from split supersymmetry on the chargino/neutralino mixing parameters, using measurements of the neutralino and chargino masses and cross sections. This indirect determination of chargino/neutralino anomalous Yukawa couplings is an important check for supersymmetric models in general.
This review illustrates by means of sample reactions the potential of a future global e+e- Linear Collider (LC) for precision measurements of Supersymmetric particles with emphasis on recent studies and addressing major research directions.
The physics potential of discovering and exploring supersymmetry at future e^+e^- linear colliders is reviewed. Such colliders are planned to start to operate at a center-of-mass energy of 500 GeV to 800 GeV, with a final energy of about 2 TeV expected. They are ideal facilities for the discovery of supersymmetric particles. High precision measurements of their properties and interactions will help to uncover the mechanism of supersymmetry breaking and will allow for tests of grand unification scenarios.
Search for supersymmetry is carried out in the framework of the Minimal Supersymmetric Standard Model (MSSM). Using the software programs SOFTSUSY and PROSPINO, the mass spectrum and the production cross-sections of superpartners are calculated. The results obtained are of importance for searching the new physics at the LHC.
In this contribution we present a discussion of some aspects of the capabilities of a photon collider to probe physics beyond the standard model. I will take a few examples from Higgs physics, supersymmetry, extra dimensional theories as well as unparticles, pointing out the special rôle that a photon collider can play in each case.
The lack of evidence for the production of colored supersymmetric particles at the LHC has increased interest in searches for superpartners of the electroweak SM gauge bosons, namely the neutralinos and charginos. These are challenging due to the weak nature of the production process, and the existing discovery reach has significant gaps in due to the difficulty of separating the supersymmetric signal from SM diboson events that produce similar final states and kinematics. We apply the Recursive Jigsaw Reconstruction technique to study final states enriched in charged leptons and missing trans…
Using the facts that in Gauge-Mediated Supersymmetry Breaking schemes, masses of the right and the left sfermions can differ widely, and the gravitino is the Lightest Supersymmetric Particle, we show that it is possible to obtain unambiguous signatures of such schemes in a high energy $e^+e^-$ collider if one looks at the asymmetries in the cross-sections for certain final states with left-and right-polarized beams.
Up to now, almost all discussion of supersymmetry at future colliders has been concerned with particle searches. However, if candidates for supersymmetric particles are found, there is much more that we will want to know about them. Supersymmetry predicts quantitative relations among the couplings and masses of supersymmetric particles. We discuss the prospects for testing such relations at a future $e^+e^-$ linear collider, using measurements that exploit the availability of polarized beams. Precision tests from chargino production are investigated in two representative cases, and sfermion an…
The phenomenology of a low-energy supersymmetry at hadron colliders is discussed with consideration of the minimal supergravity model, with a large top quark Yukawa coupling at the grand unification mass scale, and gauge mediated symmetry breaking models. Possible supersymmetry interpretations of some unexplained events are mentioned.
The experimental potential of e+e- Linear Colliders to explore the properties of supersymmetric particles is reviewed. High precision measurements of masses, spin-parity, gauge quantum numbers, couplings and mixings, production and decay properties will be possible in a clean environment. These achievements will allow the underlying supersymmetry breaking scheme to be revealed, the parameters of the fundamental theory to be determined and to test their unification through extrapolation to very high energie scales.
The production of a charged lepton (e/mu) pair with a large missing energy at a linear collider is discussed as a means of distinguishing the minimal supersymmetry (MSSM) scenario from that with large extra dimensions (ADD) for parameter ranges where the total cross sections are comparable for both. Analyses in terms of event shape variables, specifically sphericity and thrust, are shown to enable a clear discrimination in this regard.
The motivations for low-energy supersymmetry and the main features of the minimal supersymmetric extension of the Standard Model are reviewed. Possible non-minimal models and the issue of gauge coupling unification are also discussed. Theoretical results relevant for supersymmetric particle searches at present and future accelerators are presented, with emphasis on the role of a proposed $\epem$ collider with $\sqrt{s} = 500 \gev$. In particular, recent results on radiative corrections to supersymmetric Higgs boson masses and couplings are summarized, and their implications for experimental se…
If new particles are discovered, it will be important to determine if they are the supersymmetric partners of standard model bosons and fermions. Supersymmetry predicts relations among the couplings and masses of these particles. We discuss the prospects for testing these relations at a future $e^+e^-$ linear collider with measurements that exploit the availability of polarized beams.
Experimental searches for supersymmetry are entering a new era. As future experiments explore the mass range above the current lower bounds on superpartner masses, a failure to observe signals of superpartner production will begin to erode the central motivation for supersymmetry at the weak scale. In this article we present a detailed examination of which regions of supersymmetric parameter space are most natural and the extent to which weak-scale supersymmetry becomes unnatural if no superpartners are observed at LEP-II, the Tevatron, possible upgrades of these machines, and the LHC.
We investigate the production of charginos and neutralinos at a 500 GeV e^+e^- collider (NLC) and study their decays to the lightest neutralino, which then decays into multi-fermion final states through couplings which do not conserve R-parity. These couplings are assumed to affect only the decay of the lightest neutralino. Detailed analyses of the possible signals and backgrounds are performed for five selected points in the parameter space.
Light bottom squarks and gluinos have been invoked to explain the b quark pair production excess at the Tevatron. We investigate the associated production of ttbb at hadron colliders in this scenario, and find that the rates for this process are enhanced over the Standard Model prediction. If light gluinos exist, it may be possible to detect them at the Tevatron, and they could easily be observed at the LHC.
Martin has proposed a scenario dubbed ``compressed supersymmetry'' (SUSY) where the MSSM is the effective field theory between energy scales M_{\rm weak} and M_{\rm GUT}, but with the GUT scale SU(3) gaugino mass M_3<< M_1 or M_2. As a result, squark and gluino masses are suppressed relative to slepton, chargino and neutralino masses, leading to a compressed sparticle mass spectrum, and where the dark matter relic density in the early universe may be dominantly governed by neutralino annihilation into ttbar pairs via exchange of a light top squark. We explore the dark matter and collider signa…
The properties of the light charged sleptons in $\ser\ser$, $\smur\smur$ and $\stau_1\stau_1$ production are studied within the mSUGRA scenario SPS 1a. Various method are presented to determine very precisely masses, angular distributions, spin and couplings as well as the $\stau_1$ polarisation and mixing parameter in the $\stau$ sector. The analysis is based on a complete simulation of signal and background reactions assuming experimental conditions of the TESLA $e^+e^-$ Linear Collider.
The parameters of the Minimal Supersymmetric Standard Model appear to require uncomfortably precise adjustment in order to reconcile the electroweak symmetry breaking scale with the lower mass limits on a neutral Higgs scalar boson. This problem can be significantly ameliorated in models with a running gluino mass parameter that is smaller than the wino mass near the scale of unification of gauge couplings. A "compressed" superpartner mass spectrum results; compared to models with unified gaugino masses, the ratios of the squark and gluino masses to the lightest superpartner mass are reduced. …
We examine the possibility of detecting signals of split supersymmetry in the loop-induced decay h --> gamma gamma of the Higgs boson at the Large Hadron Collider, where charginos, as surviving light fermions of the supersymmetric spectrum, can contribute in the loop. We perform a detailed study of uncertainties in various parameters involved in the analysis, and thus the net uncertainty in the standard model prediction of the rate. After a thorough scan of the parameter space, taking all constraints into account, we conclude that it will be very difficult to infer about split supersymmetry fr…
Many theoretical and experimental results on the reach of the Large Hadron Collider are based on the mSUGRA-inspired scenario with universal soft supersymmetry breaking parameters at the apparent gauge coupling unification scale. We study signals for supersymmetric models in which the sparticle mass range is compressed compared to mSUGRA, using cuts like those employed by ATLAS for 2010 data. The acceptance and the cross-section times acceptance are found for several model lines that employ a compression parameter to smoothly interpolate between the mSUGRA case and the extreme case of degenera…
Signatures of anomaly mediated supersymmetry breaking in linear colliders are briefly reviewed after presenting an outline of the theoretical framework. A unique and distinct feature of a large class of models of this type is a winolike chargino which is very closely degenerate in mass with the lightest neutralino. The very slow decay of this chargino results in a heavily ionizing charged track and one soft charged pion with a characteristic momentum distribution, leading to unique signals in linear colliders which are essentially free of background. The determination of chargino and slepton m…
In these Lectures, we present a pedagogical introduction to weak scale supersymmetry phenomenology. A basic understanding of the Standard Model and of the ideas behind Grand Unification, but no prior knowledge of supersymmetry, is assumed. Topics covered include: What is supersymmetry and why do we bother with it? Working with a supersymmetric theory: A toy example Construction of supersymmetric Lagrangians The Minimal Supersymmetric Model The mSUGRA Model: A paradigm for SUSY phenomenology Decays of supersymmetric particles Production of supersymmetric particles at colliders Observational con…
We contrast the experimental signatures of low energy supersymmetry and the model of Universal Extra Dimensions and discuss various methods for their discrimination at hadron and lepton colliders. We study the discovery reach of hadron colliders for level 2 Kaluza-Klein modes, which would indicate the presence of extra dimensions. We also investigate the possibility to differentiate the spins of the superpartners and KK modes by means of the asymmetry method of Barr. We then review the methods for discriminating between the two scenarios at a high energy linear collider such as CLIC. We consid…
The potential of muon colliders to study a low-energy supersymmetry is addressed in the framework of the minimal supergravity model, whose predictions are first briefly surveyed. Foremost among the unique features of a muon collider is s-channel production of Higgs bosons, by which Higgs boson masses, widths, and couplings can be precisely measured to test the predictions of supersymmetry. Measurements of the threshold region cross sections of W^+ W^-, t t-bar, Zh, chargino pairs, slepton and sneutrino pairs will precisely determine the corresponding masses and test supersymmetric radiative co…
The identity of Dark Matter (DM) is one of the most captivating topics in particle physics today. The R-parity conserving Minimal Supersymmetric Standard Model (MSSM), which naturally provides a DM candidate in the form of the lightest neutralino ($\tildeχ_{1}^{0}$), is used as a benchmark scenario to show that a measurement of $Ω_{\tildeχ_{1}^{0}}h^{2}$ can be achieved from measurements at the CERN Large Hadron Collider. Focus is placed on compressed mass spectra regions, where the mass difference between the $\tildeχ_{1}^{0}$ and the $\tildeτ_{1}$ is small and where the $\tildeτ_{1}$-$\tilde…
The prospects for the discovery and exploration of low-energy Supersymmetry at future colliders, the Large Hadron Collider (LHC) and the future international linear electron positron collider (ILC) are summarized. The focus is on the experimental techniques that will be used to discover superpartners and to measure their properties. Special attention is given to the question how the results from both machines could influence each other, in particular when they have overlapping running time.
Motivated by the recent Super-Kamiokande results on atmospheric neutrinos, we incorporate massive neutrinos, with large angle oscillation between the second and third generations, in a scenario with R-parity violating supersymmetry. We emphasize the testability of such models through the observation of comparable numbers of muons and taus, produced together with the W-boson, in decays of the lightest neutralino. A distinctly measurable decay gap is another remarkable feature of such a scenario.
I explore the phenomenology of Supersymmetry models in which the gauginos are much heavier then that scalar particles of the MSSM. In these models, the gauginos are inaccessible to colliders while the scalar spectrum is compressed. I give several examples of models which exhibit this phenomenology built in the class of General Gauge Mediated Models. I explore possible LSP and NLSP candidates in these scenarios including Higgsino, stau, and sneutrino candidates. Collider signatures for these models include multi-particle decay chains, many taus in the final state, and possible displaced vertice…
Measurements of supersymmetric particle couplings provide important verification of supersymmetry. If some of the superpartners are at the multi-TeV scale, they will escape direct detection at planned future colliders. However, such particles induce nondecoupling corrections in processes involving the accessible superparticles through violations of the supersymmetric equivalence between gauge boson and gaugino couplings. These violations are analogous to the oblique corrections in the electroweak sector of the standard model, and can be parametrized in terms of super-oblique parameters. The $e…
In split supersymmetry, gauginos and Higgsinos are the only supersymmetric particles which are possibly accessible at foreseeable colliders. While the direct experimental searches, such as LEP and Tevatron experiments, gave robust lower bounds on the masses of these particles, the cosmic dark matter can give some upper bounds and thus have important implications for the searches at future colliders. In this work we scrutinize such dark matter constraints and show the allowed mass range for charginos and neutralinos (the mass eigenstates of gauginos and Higgsinos). We find that the lightest cha…
In the minimal supersymmetric standard model with R-parity violation, the lepton number violating top quark interactions can contribute to the top pair production at a linear collider via tree-level u-channel squark exchange diagrams. We calculate such contributions and find that in the allowed range of these R-violating couplings, the top pair production rate as well as the top quark polarization and the forward-backward asymmetry can be significantly altered. By comparing the unpolarized beams with the polarized beams, we find that the polarized beams are more powerful in probing such new ph…
We consider a large number of pair production processes at future colliders (LHC, ILC) for values of the c.m. energy in the TeV range, where a logarithmic expansion of Sudakov kind would provide a reliable description of Split supersymmetric electroweak effects. We calculate all the leading and next to leading terms of the expansions, that would differ drastically in the considered domain from those of an extreme "light" scenario. We imagine then two possible competitive future situations, at LHC and at ILC, where the determination of the energy dependence of the cross sections of certain proc…
If supersymmetry (SUSY) is realized at the electroweak scale, its underlying structure and breaking mechanism may be explored with great precision by a future linear $e^+ e^-$ collider (LC) with a clean environment, tunable collision energy, high luminosity polarized beams, and additional $e^-e^-$, $eγ$ and $γγ$ modes. In this report we summarize four papers submitted to the ICHEP04 conference about the precise measurements of the top squark parameters and $\tanβ$, the impacts of the CP phases on the search for top/bottom squarks, the Majorana nature and CP violation in the neutralino system, …
We investigate the experimental implications of the minimal gauge-mediated low energy supersymmetry breaking (GMLESB) model for Fermilab Tevatron collider experiments. We map out the regions of parameter space of this model that have already been excluded by collider searches and by limits on $b\to sγ$. We use ISAJET to compute the cross sections for a variety of topological signatures which include photons in assocation with multiple leptons, jets and missing transverse energy. The reach in the parameter $Λ$, which fixes the scale of sparticle masses, is estimated to be $\sim 60$, 100 and 135…
If the parameter $tan β$ of the minimal supersymmetric model is large, then $b$ and $τ$ Yukawa interactions are important. These can significantly modify the masses and decays of sparticles. We describe new calculations which allow a reliable exploration of large $tan β$ values, and discuss implications for collider experiments. For large values of $tan β$, charginos and neutralinos may dominantly decay to $τ$-leptons or $b$-quarks. The usual cross sections for multilepton signatures may be greatly reduced, but SUSY may be detectable via new signals involving $τ$'s or $b$'s in the final state.
We investigate the collider signals associated with scalar quirks ("squirks") in folded supersymmetric models. As opposed to regular superpartners in supersymmetric models these particles are uncolored, but are instead charged under a new confining group, leading to radically different collider signals. Due to the new strong dynamics, squirks that are pair produced do not hadronize separately, but rather form a highly excited bound state. The excited ``squirkonium'' loses energy to radiation before annihilating back into Standard Model particles. We calculate the branching fractions into vario…
We address the complementarity of the CERN Large Hadron Collider and an $e^+ e^-$ Linear Collider in determining SUSY model parameters for a particular SO(10) SUSY GUT case study.
This Resource Book reviews the physics opportunities of a next-generation e+e- linear collider and discusses options for the experimental program. Part 2 reviews the possible experiments on Higgs bosons and supersymmetric particles that can be done at a linear collider.
A benchmark CP-violating supersymmetric scenario (known in the literature as `CPX-scenario') is studied in the context of the Large Hadron Collider (LHC). It is shown that the LHC, with low to moderate accumulated luminosity, will be able to probe the existing `hole' in the $m_{h_1}$-$\tanβ$ plane, which cannot be ruled out by the Large Electron Positron Collider data. This can be done through associated production of Higgs bosons with top quark and top squark pairs leading to the signal \emph{dilepton + $\leq{5}$ jets (including 3 b-jets) + missing ${p_T}$}. Efficient discrimination of such a…
The study of the Higgs boson properties offers compelling perspectives for testing the effects of physics beyond the Standard Model and has deep implications for the LHC program and future colliders. Accurate determinations of the Higgs boson properties can provide us with a distinctively precise picture of the Higgs sector, set tight bounds, and predict ranges for the values of new physics model parameters. In this paper, we discuss the constraints on supersymmetry that can be derived by a determination of the Higgs boson mass and couplings. We quantify these constraints by using scans of the…
Supersymmetry may be discovered at hadron colliders by searching for events similar to the top quark signal of two isolated leptons. In the case of gluino production, the most distinguishing feature is that in half the events the two leading leptons have the same sign. We demonstrate the remarkable sensitivity of this gluino signature at both the Fermilab Tevatron Collider and at the Superconducting Super Collider. Techniques for approximately determining the gluino mass are discussed.
We consider the production of chargino and charged Higgs boson pairs at future linear colliders for c.m. energies in the one TeV range. Working in the MSSM under the assumption of a "moderately" light SUSY scenario, we compute the leading (double) and next-to leading (linear) supersymmetric logarithmic terms of the so-called "Sudakov expansion" at one loop. We show that a combined analysis of the slopes of the chargino and of the charged Higgs production cross sections would offer a simple possibility for determining $\tanβ$ for large ($\gtrsim 10$) values and an allowed strip in the ($M_2,μ$)…
We review the status of searches for Supersymmetry at the Tevatron Collider. After discussing the theoretical aspects relevant to the production and decay of supersymmetric particles at the Tevatron, we present the current results for Runs Ia and Ib as of the summer of 1997. To appear in the book "Perspectives in Supersymmetry", edited by G.L. Kane, World Scientific.
We study the most promising signals of Constrained Minimal Supersymmetry detectable at a luminosity upgraded 2 TeV Fermilab Tevatron collider. Using a full event-level Monte Carlo based on Pythia/Jetset, we simulate the trilepton signal examining in detail the effect of constraints on the parameter space. We also simulate the monolepton and dilepton signals, the missing E_T + jets signal, and the signals of stop production in supersymmetry all with full Standard Model backgrounds with realistic detector cuts. We find that large fractions of parameter space can be probed (or eliminated if no si…
We examine signals for sparticle production at the CERN Large Hadron Collider (LHC) within the framework of gauge mediated supersymmetry breaking models with a low SUSY breaking scale for four different model lines, each of which leads to qualitatively different signatures. We first examine the reach of the LHC via the canonical E_T^miss and multilepton channels that have been advocated within the mSUGRA framework. Next, we examine special features of each of these model lines that could serve to further enhance the SUSY signal over Standard Model backgrounds. We use ISAJET to evaluate the SUS…
In the N=1 supersymmetric extension of the Standard Model, neutralinos associated in supermultiplets with the neutral electroweak gauge and Higgs bosons are, as well as gluinos, Majorana fermions. They can be paired with the Majorana fermions of novel gaugino/scalar supermultiplets, as suggested by extended N=2 supersymmetry, to Dirac particles. Matter fields are not extended beyond the standard N=1 supermultiplets in N=1/N=2 hybrid supersymmetry to preserve the chiral character of the theory. Complementing earlier analyses in the color sector, central elements of such an electroweak scenario …
