arXiv subjects

Jari Laamanen

Publications and source records attributed to Jari Laamanen.

16 recordsLinked to original sources

arXiv2012

Comparison of neutralino and sneutrino dark matter in a model with spontaneous CP violation

Supersymmetric extensions to the standard model provide viable dark matter candidates, and can introduce additional charge-parity (CP) violation, needed for obtaining the observed baryon asymmetry of the universe. We study the possibilities of scalar and neutralino dark matter with spontaneous CP violation in the next-to-minimal supersymmetric standard model with a right handed neutrino. The observed relic density can be produced both by neutralino and right handed sneutrino as the lightest supersymmetric particle, but when CP is violated, the new annihilation channels lower the achieved relic density in general. We consider collider phenomenology in a number of benchmark points, in which all experimental constraints are satisfied, and either the neutralino or the right handed sneutrino contribute to the dark matter abundance.

hep-ph↗

arXiv2012

Top jets as a probe of degenerate stop-NLSP LSP scenario in the framework of cMSSM

The degenerate stop NLSP and neutralino LSP scenario is well motivated but hard to detect at the collider experiments. We propose a novel signature for detection this scenario at the Large Hadron Collider (LHC) and demonstrate its feasibility.

hep-ph↗

arXiv2012

Higgs and non-universal gaugino masses: no SUSY signal expected yet?

So far, no supersymmetric particles have been detected at the Large Hadron Collider (LHC). However, the recent Higgs results have interesting implications for the SUSY parameter space. In this paper, we study the consequences of an LHC Higgs signal for a model with non-universal gaugino masses in the context of SU(5) unification. The gaugino mass ratios associated with the higher representations produce viable spectra that are largely inaccessible to the current LHC and direct dark matter detection experiments. Thus, in light of the Higgs results, the non-observation of SUSY is no surprise.

hep-ph↗

arXiv2011

Stop as a next-to-lightest supersymmetric particle in constrained MSSM

So far the squarks have not been detected at the LHC indicating that they are heavier than a few hundred GeVs, if they exist. The lighter stop can be considerably lighter than the other squarks. We study the possibility that a supersymmetric partner of the top quark, stop, is the next-to-lightest supersymmetric particle in the constrained supersymmetric standard model. Various constraints, on top of the mass limits, are taken into an account, and the allowed parameter space for this scenario is determined. Observing stop which is the next-to-lightest supersymmetric particle at the LHC may be difficult.

hep-ph↗

arXiv2010

A large Muon Electric Dipole Moment from Flavor?

We study the prospects and opportunities of a large muon electric dipole moment (EDM) of the order (10^{-24} - 10^{-22}) ecm. We investigate how natural such a value is within the general minimal supersymmetric extension of the Standard Model with CP violation from lepton flavor violation in view of the experimental constraints. In models with hybrid gauge-gravity mediated supersymmetry breaking a large muon EDM is indicative for the structure of flavor breaking at the Planck scale, and points towards a high messenger scale.

hep-ph↗

arXiv2010

Implications of different supersymmetry breaking patterns for the spectrum and decay of neutralinos and charginos

We consider different patterns of supersymmetry breaking gaugino masses, and implications of these patterns for the phenomenology of neutralinos and charginos in models of low energy supersymmetry. We outline a general procedure for obtaining approximate values for the neutralino masses relevant for our analysis, and describe the constraints on the gaugino mass parameters which follow from the present experimental limits on the mass of the lightest chargino. We evaluate an upper bound on the mass of the lightest neutralino that follows from the structure of the mass matrix in different models for the gaugino mass parameters. Using the experimental lower limit for the chargino mass, we examine the lower bound for the neutralino masses. Using a sum rule for the squared masses of charginos and neutralinos, we discuss how to distinguish between different models for the supersymmetry breaking scenarios. We discuss in detail the decay modes of neutralinos and charginos in different models of supersymmetry breaking. Our analysis shows that by measuring the masses and decay properties of the neutralinos, one can distinguish between different patterns of supersymmetry breaking in the gaugino sector. We then compare the dark matter characteristics that arise in different models of supersymmetry breaking.

hep-ph↗

arXiv2009

Relic density in nonuniversal gaugino mass models with SO(10) GUT symmetry

Non-universal boundary conditions in grand unified theories can lead to nonuniversal gaugino masses at the unification scale. In R-parity preserving theories the lightest supersymmetric particle is a natural candidate for the dark matter. The composition of the lightest neutralino and the identity of the next-to-lightest supersymmetric particle are studied, when nonuniversal gaugino masses come from representations of SO(10). In these cases, the thermal relic density compatible with the Wilkinson Microwave Anisotropy Probe observations is found. Relic densities are compared with the universal case. Mass spectra in the studied cases are discussed.

hep-ph↗

arXiv2008

Relic density in SO(10) SUSY GUT models

hep-ph↗

arXiv2008

Search for Higgs Bosons in SUSY Cascades in CMS and Dark Matter with Non-universal Gaugino Masses

In grand unified theories (GUT), non-universal boundary conditions for the gaugino masses may arise at the unification scale, and affect the observability of the neutral MSSM Higgs bosons (h/H/A) at the LHC. The implications of such non-universal gaugino masses are investigated for the Higgs boson production in the SUSY cascade decay chain gluino --> squark quark, squark --> neutralino_2 quark, neutralino_2 --> neutralino_1 h/H/A, h/H/A --> b b-bar produced in pp interactions. In the singlet representation with universal gaugino masses only the light Higgs boson can be produced in this cascade with the parameter region of interest for us, while with non-universal gaugino masses heavy neutral MSSM Higgs boson production may dominate. The allowed parameter space in the light of the WMAP constraints on the cold dark matter relic density is investigated in the above scenarios for gaugino mass parameters. We also demonstrate that combination of representations can give the required amount of dark matter in any point of the parameter space. In the non-universal case we show that heavy Higgs bosons can be detected in the studied cascade in parameter regions with the WMAP preferred neutralino relic density.

hep-ph↗

arXiv2007

Non-universal gaugino masses and implications on the dark matter and Higgs searches

Non-universal boundary conditions in grand unified theories can lead to non-universal gaugino masses at the unification scale. In R-parity preserving theories the lightest supersymmetric particle is a natural candidate for the dark matter. We have studied the composition of the lightest neutralino in non-universal gaugino mass cases from the SU(5), and implications on the dark matter. In the representations of SU(5) thermal relic density agreeing with WMAP is found. The possibility to observe the neutral MSSM Higgs bosons (h/H/A) at the LHC via neutralino cascades when the lightest neutralino is dark matter, is discussed for the representation 24, and the connection to dark matter is established.

hep-ph↗

arXiv2006

Phenomenology of non-universal gaugino masses and implications for the Higgs boson decay

Grand unified theories (GUTs) can lead to non-universal gaugino masses at the unification scale. We study the implications of such non-universal gaugino masses for the composition of the lightest neutralino in supersymmetric (SUSY) theories based on SU(5) gauge group. We also consider the phenomenological implications of non-universal gaugino masses for the phenomenology of Higgs bosons in the context of Large Hadron Collider.

hep-ph↗

arXiv2005

Phenomenology of non-universal gaugino masses in supersymmetric grand unified theories

Grand unified theories can lead to non-universal boundary conditions for the gaugino masses at the unification scale. We consider the implications of such non-universal boundary conditions for the composition of the lightest neutralino as well as for the upper bound on its mass in the simplest supersymmetric grand unified theory based on the SU(5) gauge group. We derive sum rules for neutralino and chargino masses in different representations of SU(5) which lead to different non-universal boundary conditions for the gaugino masses at the unification scale. We also consider the phenomenological implications of the non-universal gaugino masses arising from a grand unified theory in the context of Large Hadron Collider. In particular we investigate the detection of heavy neutral Higgs bosons $H^0, A^0$ from $H^0, A^0 \to \tildeχ_2^0 \tildeχ_2^0 \to 4l $, and study the possibilities of detecting the neutral Higgs bosons in cascade decays, including the decays $\tildeχ_i^0 \to h^0 (H^0, A^0) \tildeχ_1^0 \to b\bar{b} \tildeχ_1^0$.

hep-ph↗

arXiv2005

Infrared fixed point of the top Yukawa coupling in split supersymmetry

The severe constraints imposed on the parameter space of the minimal split supersymmetry model by the infrared fixed point solution of the top Yukawa coupling $Y_t$ are studied in detail in terms of the value of the top quark mass measured at the Tevatron together with the lower bound on the lightest Higgs mass established by LEP. The sensitive dependence of the higgsino mass parameter $μ$ and of the gaugino coupling strengths ${\tilde g}_{u,d}$, ${\tilde g}^\prime_{u,d}$ on the value of $Y_t$ in the vicinity of the Landau pole is a remarkable consequence. A few other interesting features emerge, though the model is found to be disfavored within the infrared fixed point scenario because of the need to have several fine tunings at work on account of the requirement of a low upper bound on $\tanβ$.

hep-ph↗

arXiv2005

Invisible Higgs in large extra dimensions

We discuss the possibility of detecting a Higgs boson in electron-positron collider experiments if large extra dimensions are realized in nature. In such a case, the Higgs boson can decay invisibly by oscillating into a graviscalar Kaluza-Klein (KK) tower. We show that the search for such a Higgs at an $e^+ e^-$ linear collider entails more complications than are usually thought of in relation to an invisibly decaying Higgs.

hep-ph↗

arXiv2004

Invisible Higgs in theories of large extra dimensions

We discuss the possibility of detecting a Higgs boson in future collider experiments if large extra dimensions are realized in nature. In such a case, the Higgs boson can decay invisibly by oscillating into a graviscalar Kaluza-Klein (KK) tower. We show that the search for such a Higgs at an $e^+ e^-$ linear collider entails more complications than are usually thought of in relation to an invisibly decaying Higgs, the main sources of such complications being the simultaneous presence of a continuum graviton production and the broadening of the Higgs peak. We discuss possible ways of overcoming such difficulties, and conclude that the detection of such a Higgs boson might still be a problem beyond the mass range of 250-300 GeV.

hep-ph↗

arXiv2003

Constraints on Sparticle Spectrum in different Supersymmetry Breaking Models

We derive sum rules for the sparticle masses in different models of supersymmetry breaking. This includes the gravity mediated models (SUGRA models) as well as models in which supersymmetry breaking terms are induced by super-Weyl anomaly (AMSB models). These sum rules can help in distinguishing between these models. In particular we obtain an upper bound on the mass of the lightest neutralino as a function of the gluino mass in SUGRA and AMSB models.

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