0000000000098968
AUTHOR
Werner Porod
LHC phenomenology of the mu nu SSM
The $\mu\nu$SSM has been proposed to solve simultaneously the $\mu$-problem of the MSSM and explain current neutrino data. The model breaks lepton number as well as R-parity. In this paper we study the phenomenology of this proposal concentrating on neutrino masses and the decay of the lightest supersymmetric particle (LSP). At first we investigate in detail the $\mu\nu$SSM with one generation of singlets, which can explain all neutrino data, once 1-loop corrections are taken into account. Then we study variations of the model with more singlets, which can generate all neutrino masses and mixings at tree-level. We calculate the decay properties of the lightest supersymmetric particle, assum…
Testing the mechanism of R-parity breaking with slepton LSP decays
In supersymmetric models R-parity can be violated through either bilinear or trilinear terms in the superpotential, or both. If charged scalar leptons are the lightest supersymmetric particles, their decay properties can be used to obtain information about the relative importance of these couplings. We show that in some specific scenarios it is even possible to decide whether bilinear or trilinear terms give the dominant contribution to the neutrino mass matrix.
Probing neutralino properties in minimal supergravity with bilinear R-parity violation
Supersymmetric models with bilinear R-parity violation (BRPV) can account for the observed neutrino masses and mixing parameters indicated by neutrino oscillation data. We consider minimal supergravity versions of BRPV where the lightest supersymmetric particle (LSP) is a neutralino. This is unstable, with a large enough decay length to be detected at the CERN Large Hadron Collider (LHC). We analyse the LHC potential to determine the LSP properties, such as mass, lifetime and branching ratios, and discuss their relation to neutrino properties.
Light charged Higgs at the beginning of the LHC era
The terascale will be explored with the start of the LHC. One of the most fundamental questions which we expect to be answered is the root of electroweak symmetry breaking and whether the Higgs mechanism is realized in nature or not. In this context we pose the question if existing experimental data still allow for a light non-minimal Higgs sector. We tackle this question first in the context of the two Higgs doublet model and then we concentrate in two supersymmetric models, the constrained MSSM and the MSSM with non-universal Higgs masses. In both supersymmetric scearios, light pseudoscalar and light charged-Higgs bosons are still viable provided tan beta is large. In this regime, we emph…
Flavour violation at the LHC: type-I versus type-II seesaw in minimal supergravity
20 pages, 13 figures.-- ISI article identifier:000267789100003.-- ArXiv pre-print avaible at:http://arxiv.org/abs/0903.1408
R-parity violating sneutrino decays
R-parity can be violated through either bilinear and/or trilinear terms in the superpotential. The decay properties of sneutrinos can be used to obtain information about the relative importance of these couplings provided sneutrinos are the lightest supersymmetric particles. We show that in some specific scenarios it is even possible to decide whether bilinear or trilinear terms give the dominant contribution to the neutrino mass matrix.
Majoron emission in muon and tau decays revisited
9 pages, 4 figures.-- ISI article identifier:000264762400078.-- ArXiv pre-print avaible at: http://arxiv.org/abs/0902.0525
General flavor blind minimal supersymmetric standard model andCPviolation
We study the implications on flavor changing neutral current and $\mathrm{CP}$ violating processes in the context of supersymmetric theories without a new flavor structure (flavor blind supersymmetry). The low-energy parameters are determined by the running of the soft breaking terms from the grand unified scale with supersymmetric (SUSY) phases consistent with the electric dipole moment constraints. We find that the $\mathrm{CP}$ asymmetry in $\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma}$ can reach large values potentially measurable at B factories, especially in the low $BR(\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma})$ region, while the contributions to electr…
Collider signals of gravitino dark matter in bilinearly broken R-parity
In models with gauge mediated supersymmetry breaking the gravitino is the lightest supersymmetric particle. If R-parity is violated the gravitino decays, but with a half-live far exceeding the age of the universe and thus is, in principle, a candidate for the dark matter. We consider the decays of the next-to-lightest supersymmetric particle, assumed to be the neutralino. We show that in models where the breaking of R-parity is bilinear, the condition that R-parity violation explains correctly the measured neutrino masses fixes the branching ratio of the decay ${\tilde \chi}^0_1 \to {\tilde G}\gamma$ in the range $10^{-3}-10^{-2}$, if the gravitino mass is in the range required to solve the…
General Flavor Blind MSSM and CP Violation
We study the implications on flavor changing neutral current and CP violating processes in the context of supersymmetric theories without a new flavor structure (flavor blind supersymmetry). The low energy parameters are determined by the running of the soft breaking terms from the grand unified scale with SUSY phases consistent with the EDM constraints. We find that the CP asymmetry in b --> s gamma can reach large values potentially measurable at B factories, especially in the low BR(b --> s gamma) region. We perform a fit of the unitarity triangle including all the relevant observables. In this case, no sizeable deviations from the SM expectations are found. Finally we analyze the …
Probing minimal supergravity in the type-I seesaw mechanism with lepton flavour violation at the CERN LHC
The most general supersymmetric seesaw mechanism has too many parameters to be predictive and thus can not be excluded by any measurements of lepton flavour violating (LFV) processes. We focus on the simplest version of the type-I seesaw mechanism assuming minimal supergravity boundary conditions. We compute branching ratios for the LFV scalar tau decays, ${\tilde \tau}_2 \to (e,\mu) + \chi^0_1$, as well as loop-induced LFV decays at low energy, such as $l_i \to l_j + \gamma$ and $l_i \to 3 l_j$, exploring their sensitivity to the unknown seesaw parameters. We find some simple, extreme scenarios for the unknown right-handed parameters, where ratios of LFV branching ratios correlate with neu…
Impact of squark generation mixing on the search for squarks decaying into fermions at LHC
We study the effect of squark generation mixing on squark production and decays at LHC in the Minimal Supersymmetric Standard Model (MSSM). We show that the effect can be very large despite the very strong constraints on quark flavour violation (QFV) from experimental data on B mesons. We find that the two lightest up-type squarks su_{1,2} can have large branching ratios for the decays into 'c-quark + neutralino_1' and 't-quark + neutralino_1' at the same time due to squark generation mixing, leading to QFV signals 'pp -> c bar{t} (t bar{c}) + missing-E_T + X' with a significant rate. The observation of this remarkable signature would provide a powerful test of supersymmetric QFV at LHC.…
The electroweak sector of the NMSSM at the one-loop level
We present the electroweak spectrum for the Next-to-Minimal Supersymmetric Standard Model at the one-loop level, e. g. the masses of Higgs bosons, sleptons, charginos and neutralinos. For the numerical evaluation we present a mSUGRA variant with non-universal Higgs mass parameters squared and we compare our results with existing ones in the literature. Moreover, we briefly discuss the implications of our results for the calculation of the relic density.
Neutrino masses and mixings from supersymmetry with bilinear R-parity violation: A theory for solar and atmospheric neutrino oscillations
The simplest unified extension of the MSSM with bi-linear R--Parity violation naturally predicts a hierarchical neutrino mass spectrum, in which one neutrino acquires mass by mixing with neutralinos, while the other two get mass radiatively. We have performed a full one-loop calculation of the neutralino-neutrino mass matrix in the bi-linear \rp MSSM, taking special care to achieve a manifestly gauge invariant calculation. Moreover we have performed the renormalization of the heaviest neutrino, needed in order to get meaningful results. The atmospheric mass scale and maximal mixing angle arise from tree-level physics, while solar neutrino scale and oscillations follow from calculable one-lo…
Signatures of Spontaneous Breaking of R-Parity in Gluino Cascade Decays at LHC
We study the pattern of gluino cascade decays in a class of supersymmetric models where R-parity is spontaneously broken. We give a detailed discussion of the R-parity violating decays of the lightest neutralino, the second lightest neutralino and the lightest chargino. The multi-lepton and same-sign dilepton signal rates expected in these models are compared with those predicted in the Minimal Supersymmetric Standard Model. We show that these rates can be substantially enhanced in broken R-parity models.
Probing neutrino properties with charged scalar lepton decays
Supersymmetry with bilinear R-parity violation provides a predictive framework for neutrino masses and mixings in agreement with current neutrino oscillation data. The model leads to striking signals at future colliders through the R-parity violating decays of the lightest supersymmetric particle. Here we study charged scalar lepton decays and demonstrate that if the scalar tau is the LSP (i) it will decay within the detector, despite the smallness of the neutrino masses, (ii) the relative ratio of branching ratios Br({tilde tau}_1 --> e sum nu_i)/ Br({tilde tau}_1 --> mu sum nu_i) is predicted from the measured solar neutrino angle, and (iii) scalar muon and scalar electron decays wi…
Analysis of enhancedβeffects in minimal flavor violation GUT scenarios
Long-range forces between macroscopic objects are mediated by light particles that interact with the electrons or nucleons, and include spin-dependent static components as well as spin- and velocity-dependent components. We parametrize the long-range potential between two fermions assuming rotational invariance, and find 16 different components. Applying this result to electrically neutral objects, we show that the macroscopic potential depends on 72 measurable parameters. We then derive the potential induced by the exchange of a new gauge boson or spinless particle, and compare the limits set by measurements of macroscopic forces to the astrophysical limits on the couplings of these partic…
FCNC and CP violation observables in an SU(3)-flavoured MSSM
A non-Abelian flavour symmetry in a minimal supersymmetric standard model can explain the flavour structures in the Yukawa couplings and simultaneously solve the SUSY flavour problem. Similarly the SUSY CP problem can be solved if CP is spontaneously broken in the flavour sector. In this work, we present an explicit example of these statements with a SU(3) flavour symmetry and spontaneous CP violation. In addition, we show that it is still possible to find some significant deviation from the SM expectations as far as FCNC and CP violation are concerned. We find that large contributions can be expected in lepton flavour violating decays, as � ! e and � ! � , electric dipole moments, de and d…
Dark matter and LHC phenomenology in a left-right supersymmetric model
Left-right symmetric extensions of the Minimal Supersymmetric Standard Model can explain neutrino data and have potentially interesting phenomenology beyond that found in minimal SUSY seesaw models. Here we study a SUSY model in which the left-right symmetry is broken by triplets at a high scale, but significantly below the GUT scale. Sparticle spectra in this model differ from the usual constrained MSSM expectations and these changes affect the relic abundance of the lightest neutralino. We discuss changes for the standard stau (and stop) co-annihilation, the Higgs funnel and the focus point regions. The model has potentially large lepton flavour violation in both, left and right, scalar l…
Neutralino phenomenology at LEP2 in supersymmetry with bilinear breaking of R-parity
We discuss the phenomenology of the lightest neutralino in models where an effective bilinear term in the superpotential parametrizes the explicit breaking of R-parity. We consider supergravity scenarios where the lightest supersymmetric particle (LSP) is the lightest neutralino and which can be explored at LEP2. We present a detailed study of the LSP decay properties and general features of the corresponding signals expected at LEP2. We also contrast our model with gauge mediated supersymmetry breaking.
Running soft parameters in SUSY models with multiple U(1) gauge factors
Abstract We generalize the two-loop renormalization group equations for the parameters of the softly broken SUSY gauge theories given in the literature to the most general case when the gauge group contains more than a single Abelian gauge factor. The complete method is illustrated at two-loop within a specific example and compared to some of the previously proposed partial treatments.
Top-quark phenomenology in models with bilinearly and spontaneously broken R-parity
We study unconventional decays of the top-quark in the framework of SUSY models with spontaneously broken R-parity. In particular we discuss an effective theory which consists of the MSSM plus bilinearly broken R-parity. We demonstrate that the decay modes t -> stau + b and t -> tau + sbottom can have large branching ratios even in scenarios where the tau-neutrino mass is very small. We show that existing Tevatron data already probe the theoretical parameters, with promising prospects for further improvement at the Run 2 of the Tevatron.
Signatures of bosonic squark decays in non-minimally flavour-violating supersymmetry
We investigate couplings of squarks to gauge and Higgs-bosons within the framework of non-minimal flavour violation in the Minimal Supersymmetric Standard Model. Introducing non-diagonal elements in the mass matrices of squarks, we first study their impact on the self-energies and physical mass eigenvalues of squarks. We then present an extensive analysis of bosonic squark decays for variations of the flavour-violating parameters around the two benchmark scenarios SPS1a' and SPS1b. Signatures, that would be characteristic for a non-minimal flavour structure in the squark sector, can be found in wide regions of the parameter space.
Phenomenology of a supersymmetric U(1)(B-L) x U(1)(R) extension of the standard model with inverse seesaw mechanism
We discuss the minimal supersymmetric U(1)(B-L) X U(1)(R) extension of the standard model. Gauge couplings unify as in the minimal supersymmetric standard model (MSSM), even if the scale of U(1)(B-L) X U(1)(R) breaking is as low as order TeV and the model can be embedded into a SO(10) grand unified theory. The phenomenology of the model differs in some important aspects from the MSSM, leading potentially to rich phenomenology at the LHC. It predicts more light Higgs states and the mostly left CP-even Higgs having a mass that easily reaches 125 GeV, with no constraints on the supersymmetry spectrum. Right sneutrinos can be the lightest supersymmetric particle, changing all dark matter constr…
Supersymmetric type-III seesaw mechanism: Lepton flavor violation and LHC phenomenology
We study a supersymmetric version of the type-III seesaw mechanism considering two variants of the model: a minimal version for explaining neutrino data with only two copies of 24 superfields and a model with three generations of 24-plets. The latter predicts, in general, rates for mu -> e gamma inconsistent with experimental data. However, this bound can be evaded if certain special conditions within the neutrino sector are fulfilled. In the case of two 24-plets, lepton flavor violation constraints can be satisfied much more easily. After specifying the corresponding regions in the minimal supergravity parameter space, we show that under favorable conditions one can test the corresponding …
CP violation in decays of the lightest supersymmetric particle with bilinearly broken R parity
Supersymmetric models with broken R-parity induced by lepton number violating terms provide a calculable framework for neutrino masses and mixings. Within models with bilinear R-parity breaking six new physical phases appear which are potential sources of novel CP-violating phenomena compared to the minimal supersymmetric extension of the standard model. We consider CP-violating observables in the decays of the lightest supersymmetric particle in this class of models. We show that: (i) Neutrino physics requires a strong correlation between three different pairs of phases, thus reducing the effective number of new phases to three. (ii) CP-violating phenomena in decays of the lightest supersy…
More on higher order decays of the lighter top squark
We discuss the three-body decays stop_1 -> W^+ b neutralino_1, stop_1 -> H^+ b neutralino_1, stop_1 -> b slepton_i neutrino_l, and stop_1 -> b sneutrino_l l^+$ ($l =e,��,��$) of the lighter top squark within the minimal supersymmetric standard model. We give the complete analytical formulas for the decay widths and present a numerical study in view of an upgraded Tevatron, the CERN LHC, and a future lepton collider demonstrating the importance of these decay modes.
Impact of squark generation mixing on the search for gluinos at LHC
We study gluino decays in the Minimal Supersymmetric Standard Model (MSSM) with squark generation mixing. We show that the effect of this mixing on the gluino decay branching ratios can be very large in a significant part of the MSSM parameter space despite the very strong experimental constraints on quark flavour violation (QFV) from B meson observables. Especially we find that under favourable conditions the branching ratio of the QFV gluino decay (g) over tilde -> c (t) over tilde)((c) over tildet)(chi) over tilde (0)(1) can be as large as similar to 50%. We also find that the squark generation mixing can result in a multiple-edge (3- or 4-edge) structure in the charm-top quark invariant…
Spontaneous R-parity violation: Lightest neutralino decays and neutrino mixing angles at future colliders
We study the decays of the lightest supersymmetric particle (LSP) in models with spontaneously broken R-parity. We focus on the two cases that the LSP is either a bino or a neutral singlet lepton. We work out the most important phenomenological differences between these two scenarios and discuss also how they might be distinguished from explicit R-Parity breaking models. In both cases we find that certain ratios of decay branching ratios are correlated with either the solar or the atmospheric (and reactor) neutrino angle. The hypothesis that spontaneous R-Parity violation is the source of the observed neutrino masses is therefore potentially testable at the LHC.
Broken R-parity, stop decays, and neutrino physics
We discuss the phenomenology of the lightest stop in models where R-parity is broken by bilinear superpotential terms. In this class of models we consider scenarios where the R-parity breaking two-body decay ~t_1->��^+b competes with the leading three-body decays such as ~t_1->W^+b~��^0_1. We demonstrate that the R-parity violating decay can be sizable and in some parts of the parameter space even the dominant one. Moreover we discuss the expectations for t_1->��^+b and ~t_1->e^+b. The recent results from solar and atmospheric neutrinos suggest that these are as important as the tau bottom mode. The t_1->l^+b decays are of particular interest for hadron colliders, as they may…
Supersymmetric mass spectra and the seesaw scale
Supersymmetric mass spectra within two variants of the seesaw mechanism, commonly known as type-II and type-III seesaw, are calculated using full 2-loop RGEs and minimal Supergravity boundary conditions. The type-II seesaw is realized using one pair of 15 and $\bar{15}$ superfields, while the type-III is realized using three copies of $24_M$ superfields. Using published, estimated errors on SUSY mass observables attainable at the LHC and in a combined LHC+ILC analysis, we calculate expected errors for the parameters of the models, most notably the seesaw scale. If SUSY particles are within the reach of the ILC, pure mSugra can be distinguished from mSugra plus type-II or type-III seesaw for…
Dark matter in minimal supergravity with type-II seesaw mechanism
We calculate the relic density of the lightest neutralino in a supersymmetric seesaw type-II (``triplet seesaw'') model with minimal supergravity boundary conditions at the grand unified theory (GUT) scale. The presence of a triplet below the GUT scale, required to explain measured neutrino data in this setup, leads to a characteristic deformation of the sparticle spectrum with respect to the pure minimal supergravity (mSUGRA) expectations, affecting the calculated relic dark matter (DM) density. We discuss how the DM allowed regions in the $({m}_{0},{M}_{1/2})$ plane change as a function of the (type-II) seesaw scale. We also compare the constraints imposed on the models parameter space fo…
Probing neutrino mass with multilepton production at the Tevatron in the simplest R-parity violation model
We analyze the production of multileptons in the simplest supergravity model with bilinear violation of R parity at the Fermilab Tevatron. Despite the small R-parity violating couplings needed to generate the neutrino masses indicated by current atmospheric neutrino data, the lightest supersymmetric particle is unstable and can decay inside the detector. This leads to a phenomenology quite distinct from that of the R-parity conserving scenario. We quantify by how much the supersymmetric multilepton signals differ from the R-parity conserving expectations, displaying our results in the $m_0 \otimes m_{1/2}$ plane. We show that the presence of bilinear R-parity violating interactions enhances…
Probing bilinear R-parity violating supergravity at the LHC
We study the collider phenomenology of bilinear R-parity violating supergravity, the simplest effective model for supersymmetric neutrino masses accounting for the current neutrino oscillation data. At the CERN Large Hadron Collider the center-of-mass energy will be high enough to probe directly these models through the search for the superpartners of the Standard Model (SM) particles. We analyze the impact of R-parity violation on the canonical supersymmetry searches - that is, we examine how the decay of the lightest supersymmetric particle (LSP) via bilinear R-parity violating interactions degrades the average expected missing momentum of the reactions and show how this diminishes the re…
Solar Neutrino Masses and Mixing from Bilinear R-Parity Broken Supersymmetry: Analytical versus Numerical Results
We give an analytical calculation of solar neutrino masses and mixing at one-loop order within bilinear R-parity breaking supersymmetry, and compare our results to the exact numerical calculation. Our method is based on a systematic perturbative expansion of R-parity violating vertices to leading order. We find in general quite good agreement between approximate and full numerical calculation, but the approximate expressions are much simpler to implement. Our formalism works especially well for the case of the large mixing angle MSW solution (LMA-MSW), now strongly favoured by the recent KamLAND reactor neutrino data.
A Supersymmetric Solution to the Solar and Atmospheric Neutrino Problems
The simplest unified extension of the Minimal Supersymmetric Standard Model with bi-linear R--Parity violation provides a predictive scheme for neutrino masses which can account for the observed atmospheric and solar neutrino anomalies in terms of bi-maximal neutrino mixing. The maximality of the atmospheric mixing angle arises dynamically, by minimizing the scalar potential, while the solar neutrino problem can be accounted for either by large or by small mixing oscillations. One neutrino picks up mass by mixing with neutralinos, while the degeneracy and masslessness of the other two is lifted only by loop corrections. Despite the smallness of neutrino masses R-parity violation is observab…
Testing neutrino mixing at future collider experiments
Low energy supersymmetry with bilinear breaking of R-parity leads to a weak-scale seesaw mechanism for the atmospheric neutrino scale and a radiative mechanism for the solar neutrino scale. The model has striking implications for collider searches of supersymmetric particles. Assuming that the lightest SUSY particle is the lightest neutralino we demonstrate that (i) The neutralino decays inside the detector even for tiny neutrino masses. (ii) Measurements of the neutrino mixing angles lead to predictions for the ratios of various neutralino branching ratios implying an independent test of neutrino physics at future colliders, such as the Large Hadron Collider or a Linear Collider.
LHC phenomenology of supersymmetric models beyond the MSSM
Contribution to the 16th International Symposium on Particles, Strings and Cosmology (PASCOS 2010). Valencia (Spain). July 19-23, 2010
WCxf: An exchange format for Wilson coefficients beyond the Standard Model
We define a data exchange format for numerical values of Wilson coefficients of local operators parameterising low-energy effects of physics beyond the Standard Model. The format facilitates interfacing model-specific Wilson coefficient calculators, renormalisation group (RG) runners, and observable calculators. It is designed to be unambiguous (defining a non-redundant set of operators with fixed normalisation in each basis), extensible (allowing the addition of new EFTs or bases by the user), and robust (being based on industry standard file formats with parsers implemented in many programming languages). We have implemented the format for the Standard Model EFT (SMEFT) and for the weak e…
LHC and lepton flavour violation phenomenology of a left-right extension of the MSSM
We study the phenomenology of a supersymmetric left-right model, assuming minimal supergravity boundary conditions. Both left-right and (B-L) symmetries are broken at an energy scale close to, but significantly below the GUT scale. Neutrino data is explained via a seesaw mechanism. We calculate the RGEs for superpotential and soft parameters complete at 2-loop order. At low energies lepton flavour violation (LFV) and small, but potentially measurable mass splittings in the charged scalar lepton sector appear, due to the RGE running. Different from the supersymmetric “pure seesaw” models, both, LFV and slepton mass splittings, occur not only in the left-but also in the right slepton sector. …
Determining Sneutrino Masses and Physical Implications
In some areas of supersymmetry parameter space, sneutrinos are lighter than the charginos and the next-to-lightest neutralino, and they decay into the invisible neutrino plus lightest-neutralino channel with probability one. In such a scenario they can be searched for in decays of charginos that are pair-produced in e+e- collisions, and in associated sneutrino-chargino production in photon-electron collisions. The sneutrino properties can be determined with high accuracy from the edges of the decay energy spectra in the first case and from threshold scans in the second. In the final part of the report we investigate the mass difference of sneutrinos and charged sleptons between the third an…
Supersymmetric type-III seesaw mechanism: Lepton flavor violating decays and dark matter
We study a supersymmetric version of the seesaw mechanism type III. The model consists of the minimal supersymmetric extension of the standard model particle content plus three copies of $\mathbf{24}$ superfields. The fermionic part of the $SU(2)$ triplet contained in the $\mathbf{24}$ is responsible for the type-III seesaw, which is used to explain the observed neutrino masses and mixings. Complete copies of $\mathbf{24}$ are introduced to maintain gauge coupling unification. These additional states change the beta functions of the gauge couplings above the seesaw scale. Using minimal Supergravity boundary conditions, we calculate the resulting supersymmetric mass spectra at the electrowea…
Neutrino properties and the decay of the lightest supersymmetric particle
Supersymmetry with broken R-parity can explain the neutrino mass squared differences and mixing angles observed in neutrino oscillation experiments. In the minimal model, where R-parity is broken only by bilinear terms, certain decay properties of the lightest supersymmetric particle (LSP) are correlated with neutrino mixing angles. Here we consider charginos, squarks, gluinos and sneutrinos being the LSP and calculate their decay properties in bilinear R-parity breaking supersymmetry. Together with the decays of charged scalars and neutralinos calculated previously this completes the proof that bilinear R-parity breaking as the source of neutrino masses will be testable at future colliders…
GHOSTLY BEACONS OF NEW PHYSICS
The article discusses the elementary particle of the neutrino, with information on research regarding its fundamental properties and how it differs from other particles. Topics include the connection between neutrinos and their antiparticles, the observation of the particles' activity during nuclear beta decay and their interactions, and the possible implications that an asymmetric relationship between neutrinos and their antimatter would suggest regarding the composition of the universe with a majority of matter.
Supersymmetric type-III seesaw: lepton flavour violation and LHC phenomenology
We study a supersymmetric version of the seesaw mechanism type-III considering two variants of the model: a minimal version for explaining neutrino data with only two copies of 24-plet superfields and a model with three generations of 24-plets. The latter predicts in general rates for $\mu\to e\gamma$ inconsistent with experimental data. However, this bound can be evaded if certain special conditions within the neutrino sector are fulfilled. In case of two 24-plets lepton flavour violation constraints can be satisfied much easier. After specifying the corresponding regions in the CMSSM parameter space we show that under favorable conditions one can test the corresponding flavour structures …
The Hunt for New Physics at the Large Hadron Collider
233 páginas.-- AHEP Group: et al..-- El Pdf del artículo es la versión pre-print: arXiv.1001.2693v1.-- Trabajo presentado al "The International Workshop on Beyond the Standard Model Physics and LHC Signatures (BSM-LHC) celebrado en Boston (USA) del 2 al 4 de junio de 2009.
Proposal for generalised supersymmetry Les Houches Accord for see-saw models and PDG numbering scheme
The SUSY Les Houches Accord (SLHA) 2 extended the first SLHA to include various generalisations of the Minimal Supersymmetric Standard Model (MSSM) as well as its simplest next-to-minimal version. Here, we propose further extensions to it, to include the most general and well-established see-saw descriptions (types I/II/III, inverse, and linear) in both an effective and a simple gauged extension of the MSSM framework. In addition, we generalise the PDG numbering scheme to reflect the properties of the particles
Hefty MSSM-like light Higgs in extended gauge models
It is well known that in the MSSM the lightest neutral Higgs h^0 must be, at the tree level, lighter than the Z boson and that the loop corrections shift this stringent upper bound up to about 130 GeV. Extending the MSSM gauge group in a suitable way, the new Higgs sector dynamics can push the tree-level mass of h^0 well above the tree-level MSSM limit if it couples to the new gauge sector. This effect is further pronounced at the loop level and h^0 masses in the 140 GeV ballpark can be reached easily. We exemplify this for a sample setting with a low-scale U(1)_R x U(1)_B-L gauge symmetry in which neutrino masses can be implemented via the inverse seesaw mechanism.
Supersymmetry parameter analysis: SPA convention and project.
18 páginas, 6 figuras, 12 tablas.-- et al.
LHC phenomenology of the μνSSM
The $\mu\nu$SSM has been proposed to solve simultaneously the $\mu$-problem of the MSSM and explain current neutrino data. The model breaks lepton number as well as R-parity. In this paper we study the phenomenology of this proposal concentrating on neutrino masses and the decay of the lightest supersymmetric particle (LSP). At first we investigate in detail the $\mu\nu$SSM with one generation of singlets, which can explain all neutrino data, once 1-loop corrections are taken into account. Then we study variations of the model with more singlets, which can generate all neutrino masses and mixings at tree-level. We calculate the decay properties of the lightest supersymmetric particle, assum…
Probing neutrino oscillations in supersymmetric models at the Large Hadron Collider
The lightest supersymmetric particle may decay with branching ratios that correlate with neutrino oscillation parameters. In this case the CERN Large Hadron Collider (LHC) has the potential to probe the atmospheric neutrino mixing angle with sensitivity competitive to its low-energy determination by underground experiments. Under realistic detection assumptions, we identify the necessary conditions for the experiments at CERN's LHC to probe the simplest scenario for neutrino masses induced by minimal supergravity with bilinear R parity violation.
Supersymmetric type-II seesaw mechanism: CERN LHC and leptón flavor violating phenomenology
We study the supersymmetric version of the type-II seesaw mechanism assuming minimal supergravity boundary conditions. We calculate branching ratios for lepton flavor violating (LFV) scalar tau decays, potentially observable at the LHC, as well as LFV decays at low energy, such as l{sub i}{yields}l{sub j}+{gamma}, and compare their sensitivity to the unknown seesaw parameters. In the minimal case of only one triplet coupling to the standard model lepton doublets, ratios of LFV branching ratios can be related unambiguously to neutrino oscillation parameters. We also discuss how measurements of soft SUSY breaking parameters at the LHC can be used to indirectly extract information of the seesa…