Color-octet scalars at the LHC
Elements of the phenomenology of color-octet scalars (sgluons), as predicted in the hybrid N=1/N=2 supersymmetric model, are discussed in the light of forthcoming experiments at the CERN Large Hadron Collider.
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arXiv subjects
J. Kalinowski
Publications and source records attributed to J. Kalinowski.
Pinning Down the Invisible Sneutrino at the ILC
Using the event generator WHIZARD we study in a realistic ILC environment the prospects of measuring properties of sneutrinos that decay invisibly into the lightest neutralino and the neutrino.
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Color-Octet Scalars of N=2 Supersymmetry at the LHC
The color gauge hyper-multiplet in N=2 supersymmetry consists of the usual N=1 gauge vector/gaugino super-multiplet, joined with a novel gaugino/scalar super-multiplet. Large cross sections are predicted for the production of pairs of the color-octet scalars $σ$ [sgluons] at the LHC: $gg, q\bar{q} \to σσ^{\ast}$. Single $σ$ production is possible at one-loop level, but the $g g\to σ$ amplitude vanishes in the limit of degenerate $L$ and $R$ squarks. When kinematically allowed, $σ$ decays predominantly into two gluinos, whose cascade decays give rise to a burst of eight or more jets together with four LSP's as signature for $σ$ pair events at the LHC. $σ$ can also decay into a squark-antisquark pair at tree level. At one-loop level $σ$ decays into gluons or a $t \bar t$ pair are predicted, generating exciting resonance signatures in the final states. The corresponding partial widths are very roughly comparable to that for three body final states mediated by one virtual squark at tree level.
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Dark Matter in the USSM
We discuss the neutralino dark matter within classes of extended supersymmetric models, referred to as the USSM, containing one additional SM singlet Higgs plus an extra Z', together with their superpartners the singlino and bino'.
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Neutralino Dark Matter in the USSM
This paper provides a comprehensive discussion of neutralino dark matter within classes of extended supersymmetric models referred to as the USSM containing one additional SM singlet Higgs plus an extra $Z'$, together with their superpartners the singlino and bino'. These extra states of the USSM can significantly modify the nature and properties of neutralino dark matter relative to that of the minimal (or even next-to-minimal) supersymmetric standard models. We derive the Feynman rules for the USSM and calculate the dark matter relic abundance and direct detection rates for elastic scattering in the USSM for interesting regions of parameter space where the largest differences are expected.
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Pinning down the Invisible Sneutrino
For points in SUSY parameter space where the sneutrino is lighter than the lightest chargino and next-to-lightest neutralino, its direct mass determination from sneutrino pair production process at e+e- collider is impossible since it decays invisibly. In such a scenario the sneutrino can be discovered and its mass determined from measurements of two-body decays of charginos produced in pairs at the ILC. Using the event generator WHIZARD we study the prospects of measuring sneutrino properties in a realistic ILC environment. In our analysis we include beamstrahlung, initial state radiation, a complete account of reducible backgrounds from SM and SUSY processes, and a complete matrix-element calculation of the SUSY signal which encompasses all irreducible background and interference contributions. We also simulate photon induced background processes using exact matrix elements. Radiation effects and the cuts to reduce background strongly modify the edges of the lepton energy spectra from which the sneutrino and chargino mass are determined. We discuss possible approaches to measure the sneutrino mass with optimal precision.
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(N)LO Simulation of Chargino Production and Decay
We consider NLO chargino production and decays at the ILC. For this, we present an NLO extension of the Monte Carlo Event Generator Whizard including the NLO production. For photonic corrections, we use both a fixed order and a resummation approach. The latter method evades the problem of negative event weights and automatically includes leading higher order corrections. We present results for cross sections and event generation for both methods. As a first step towards a full NLO Monte Carlo, we consider a LO implementation of the chargino production and subsequent leptonic decay and investigate the precision of the sneutrino mass determination by means of lepton energy distributions in chargino decays. The SM and SUSY backgrounds are included in our study using full matrix elements as well as smearing effects from ISR and beamstrahlung. Without using energy distribution fits, the sneutrino mass can be determined with an error in the percent regime.
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LHC/ILC interplay for challenging SUSY scenarios
Combined analyses at the Large Hadron Collider and at the International Linear Collider are important to unravel a difficult region of supersymmetry that is characterized by scalar SUSY particles with masses around 2 TeV. Precision measurements of masses, cross sections and forward-backward asymmetries allow to determine the fundamental supersymmetric parameters even if only a small part of the spectrum is accessible. Mass constraints for the heavy particles can be derived.
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Heavy sfermions in SUSY analysis at LHC and ILC
The physics potential of the Large Hadron Collider in combination with the planned International Linear Collider is discussed for a difficult region of supersymmetry that is characterized by scalar SUSY particles with masses around 2 TeV. Precision measurements of masses, cross sections and forward-backward asymmetries allow to determine the fundamental supersymmetric parameters even if only a small part of the spectrum is accessible. No assumptions on a specific SUSY-breaking mechanism are imposed. Mass contraints for the kinematically inaccessible particles can be derived.
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Speculations on Isolated Lepton Events at HERA
Speculations on mechanisms which might be responsible for events with an isolated high p_T lepton, a hadron jet and missing energy, as observed in the H1 experiment at HERA, are discussed.
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CP violation at one loop in the polarization-independent chargino production in e+e- collisions
Recently Osland and Vereshagin noticed, based on sample calculations of some box diagrams, that in unpolarised e+e- collisions CP-odd effects in the non-diagonal chargino-pair production process are generated at one-loop. Here we perform a full one-loop analysis of these effects and point out that in some cases the neglected vertex and self-energy contributions may play a dominant role. We also show that CP asymmetries in chargino production are sensitive not only to the phase of mu parameter in the chargino sector but also to the phase of stop trilinear coupling A_t.
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Dark Matter in the U(1) Extended SUSY
The neutralino sector of the U(1) extended SUSY is presented and some collider and cosmology-related phenomenology discussed.
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Isolated Lepton Events at HERA: SUSY R-Parity Violation?
Events with an isolated high $p_T$ lepton, a hadron jet and missing energy as observed in the H1 experiment at HERA, are potentially associated with R-parity violation in supersymmetric theories. However, stringent kinematic constraints must be fulfilled if the production of supersymmetric particles in R-parity violating scenarios were the correct path for explaining these puzzling events. A reference point \RF is specified for which these constraints are illustrated and implications of the supersymmetric interpretation for new classes of multi-lepton events are indicated.
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The Neutralino Sector in the U(1)-Extended Supersymmetric Standard Model
Motivated by grand unified theories and string theories we analyze the general structure of the neutralino sector in the USSM, an extension of the Minimal Supersymmetric Standard Model that involves a broken extra U(1) gauge symmetry. This supersymmetric U(1)-extended model includes an Abelian gauge superfield and a Higgs singlet superfield in addition to the standard gauge and Higgs superfields of the MSSM. The interactions between the MSSM fields and the new fields are in general weak and the mixing is small, so that the coupling of the two subsystems can be treated perturbatively. As a result, the mass spectrum and mixing matrix in the neutralino sector can be analyzed analytically and the structure of this 6-state system is under good theoretical control. We describe the decay modes of the new states and the impact of this extension on decays of the original MSSM neutralinos, including radiative transitions in cross-over zones. Production channels in cascade decays at the LHC and pair production at $e^+e^-$ colliders are also discussed.
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Combined LHC/ILC analysis of a SUSY scenario with heavy sfermions
We discuss the potential of combined analyses at the Large Hadron Collider and the planned International Linear Collider to explore low-energy supersymmetry in a difficult region of the parameter space characterized by masses of the scalar SUSY particles around 2 TeV. Precision analyses of cross sections for light chargino production and forward--backward asymmetries of decay leptons and hadrons at the ILC, together with mass information on chi^0_2 and squarks from the LHC, allow us to determine the underlying fundamental gaugino/higgsino MSSM parameters and to constrain the masses of the heavy, kinematically inaccessible sparticles. No assumptions on a specific SUSY-breaking mechanism are imposed. For this analysis the complete spin correlations between production and decay processes are taken into account.
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CP Studies and Non-Standard Higgs Physics
There are many possibilities for new physics beyond the Standard Model that feature non-standard Higgs sectors. These may introduce new sources of CP violation, and there may be mixing between multiple Higgs bosons or other new scalar bosons. Alternatively, the Higgs may be a composite state, or there may even be no Higgs at all. These non-standard Higgs scenarios have important implications for collider physics as well as for cosmology, and understanding their phenomenology is essential for a full comprehension of electroweak symmetry breaking. This report discusses the most relevant theories which go beyond the Standard Model and its minimal, CP-conserving supersymmetric extension: two-Higgs-doublet models and minimal supersymmetric models with CP violation, supersymmetric models with an extra singlet, models with extra gauge groups or Higgs triplets, Little Higgs models, models in extra dimensions, and models with technicolour or other new strong dynamics. For each of these scenarios, this report presents an introduction to the phenomenology, followed by contributions on more detailed theoretical aspects and studies of possible experimental signatures at the LHC and other colliders.
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The Challenge of Determining SUSY Parameters in Focus-Point-Inspired Cases
We discuss the potential of combined LHC and ILC experiments for SUSY searches in a difficult region of the parameter space, in which all sfermion masses are above the TeV scale. Precision analyses of cross sections of light chargino production and forward--backward asymmetries of decay leptons and hadrons at the ILC, together with mass information on \tildeχ^0_2 and squarks from the LHC, allow us to fit rather precisely the underlying fundamental gaugino/higgsino MSSM parameters and to constrain the masses of the heavy virtual sparticles. For such analyses the complete spin correlations between the production and decay processes have to be taken into account. We also took into account expected experimental uncertainties.
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Analysis of the Neutralino System in Three--Body Leptonic Decays of Neutralinos
Neutralinos $\tildeχ^0$ in supersymmetric theories, the spin--1/2 Majorana--type superpartners of the U(1) and SU(2) neutral electroweak gauge bosons and SU(2) neutral Higgs bosons, are expected to be among light supersymmetric particles so that they can be produced copiouslyvia direct pair production and/or from cascade decays of other sparticles such as sleptons at the planned Large Hadron Collider and the prospective International Linear Collider. Considering the prospects of having both highly polarized neutralinos and possibility of reconstructing their decay rest frames, we provide a systematic investigation of the three--body leptonic decays of the neutralinos in the minimal supersymmetric standard model and demonstrate alternative ways for probing the Majorana nature of the neutralinos and CP violation in the neutralino system.
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