1,721,330 research outputs found
FeynHiggs: A program for the calculation of MSSM Higgs-boson observables - Version 2.6.5
No full textFeynHiggs is a Fortran code for the calculation of physical observables in the field of high-energy physics. FeynHiggs calculates various observables in the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) for real or complex parameters. These observables comprise Higgs-boson masses, mixing angles, couplings, Tevatron/LHC production cross-sections, branching ratios, as well as some additional observables such as ρ, MW, the effective leptonic weak mixing angle, (g − 2)μ, BR(b → sγ), electric dipole moments.Peer reviewe
FeynHiggs: A program for the calculation of MSSM Higgs-boson observables – Version 2.6.5
No full textTitle of program: FeynHiggs v2.6.5
Catalogue Id: ADKT_v2_0FeynHiggs is a Fortran code for the calculation of physical observables in the field of high-energy physics. FeynHiggs calculates various observables in the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM) for real or complex parameters. These observables comprise Higgs-boson masses, mixing angles, couplings, Tevatron/LHC production cross-sections, branching ratios, as well as some additional observables such as Δρ, M_W , the effective leptonic weak mixing angle, ( g − 2 )_μ ,...Nature of problem: The experimental searches for Higgs bosons have to be compared with theory predictions at a high level of accuracy. Radiative corrections are especially important in the Minimal Supersymmetric Standard Model (MSSM).Peer reviewe
Precise Predictions for Higgs Physics in the Next-to-Minimal Supersymmetric Standard Model (NMSSM)
No full textWithin this thesis a precise mass-prediction for the Higgs fields of the Next-to-Minimal Supersymmetric Standard Model (NMSSM) is obtained with Feynman-diagrammatic methods. The results are studied numerically for sample scenariosthat are in agreement with current New Physics searches at the LHC. Furthermorea comparison between the obtained results and different calculations is performed asa first step in order to obtain an estimation for the theoretical uncertainties of theHiggs-mass prediction in the NMSSM.The precise mass-prediction includes the full NMSSM one-loop corrections sup-plemented with the dominant and sub-dominant two-loop corrections within theMinimal Supersymmetric Standard Model (MSSM). These include contributions atthe orders O(α_t α_s , α_b α_s , α_t^2 , α_t α_b ), as well as a resummation of leading and subleadinglogarithms from the top/scalar top sector. Higher-order corrections are essential forthe NMSSM in order to provide a Higgs particle that is consistent with the availabledata, including the observed neutral, CP-even Higgs field with a mass of about125 GeV. We explored the validity of the applied approximation at the two-looplevel and found that it is reliable for a wide range of scenarios within the NMSSM.This is especially true for the mass of the observed (MS)SM-like Higgs field. Theresult of this work will be included in a future extension of the program FeynHiggs.We also compared our results with the program NMSSMCalc that also performsa Feynman-diagrammatic calculation of the Higgs-masses with a slightly differentrenormalization scheme. The comparison reveals that for the mass of the (MS)SM-likeHiggs field the genuine NMSSM-effects induced by the choice of the renormalization scheme are by far minor compared to similar effects observed in the MSSM
Das Higgs-Potenzial erschließen: Von Teilchenbeschleunigern zum Kosmos
No full textThe upcoming decades in particle physics will offer an unprecedented amount of data, opening new avenues to deepen our understanding of the fundamental laws of nature. On one hand, the High-Luminosity Large Hadron Collider (HL-LHC) will significantly enhance our experimental reach at the energy frontier. On the other hand, the Laser Interferometer Space Antenna (LISA) will inaugurate the era of the early Universe gravitational wave astronomy. The data they will collect may shed light on some of the most profound open questions in physics. At the centre of many unresolved questions in the Standard Model (SM), which include the origin of electroweak symmetry breaking, the matter-antimatter asymmetry, and the nature of dark matter, lies the scalar potential. In particular, the trilinear Higgs self-coupling offers a unique window to determine the shape of this potential. While collider experiments probe it as realised today, cosmological observations can provide insights into its evolution in the early Universe. Together, they offer complementary perspectives on one of the most fundamental ingredients of particle physics.
This thesis investigates the phenomenological implications of deviations in the Higgs trilinear self-coupling within well-motivated Beyond the Standard Model (BSM) scenarios featuring extended scalar sectors, with a particular focus on the Two Higgs Doublet Model (2HDM). We perform a detailed study of Higgs pair production at the HL-LHC, the process most directly sensitive to trilinear scalar couplings, examining the effects of additional scalar states both through direct resonant production channels and through radiative corrections to the trilinear Higgs coupling. Our results show that interference effects between resonant and non-resonant contributions, affected by loop-induced modifications to scalar self-interactions, can significantly alter both the total production cross section and the invariant mass distribution, while remaining consistent with all current experimental and theoretical constraints. To account for these effects, we develop and apply dedicated computational frameworks that enable precision BSM analyses incorporating these significant loop effects.
Turning to the early Universe, we examine the thermal evolution predicted by BSM scenarios and identify conditions required for a strong first-order electroweak phase transition, which is a necessary ingredient for electroweak baryogenesis. We analyse the characteristic mass hierarchies that favour such transitions and identify the most important collider signatures capable of probing the relevant parameter space. At the same time, we explore the complementary reach of cosmological observables, focusing on stochastic gravitational wave (GW) backgrounds that may be sourced by such strong transitions. We find that space-based GW astronomy could become a complementary tool for exploring fundamental questions of particle physics
Exploring Models of Electroweak Symmetry Breaking at the LHC and Beyond
No full textWe explore different scenarios of electroweak symmetry breaking by studying the phenomenology of several models that extend the scalar sector of the Standard Model (SM). We investigate resonant multiscalar production in a singlet extension of the SM. The resulting benchmark scenarios illustrate many previously unstudied signatures of Higgs-to-Higgs decays that could serve as discovery channels for additional scalars. While many properties of 125 GeV Higgs bosons () are precisely measured, it could nevertheless be a CP-mixed state with a sizeable CP-odd admixture. We investigate this possibility in the CP-violating two Higgs doublet model (2HDM) and discuss the impact of bounds from fermionic electric dipole moments. We find that maximally CP-violating Yukawa couplings of are compatible with current measurements. The Higgs sector could also contain CP violation that is confined to a dark sector. In the minimal model that allows this possibility, we find that the CP violation is in principle observable through loop-induced anomalous triple gauge couplings. However, the CP-violating form factor and the resulting asymmetries are strongly suppressed, making them challenging to observe even for maximally CP-violating scenarios. In many beyond the SM (BSM) models with extended scalar sectors — for example in this dark sector model — the scalar potential is so complicated that its vacuum structure can only be studied numerically. We present a novel approach to vacuum stability constraints that aims at an efficient and reliable evaluation for use in large parameter scans of BSM models. We study the vacuum structure of the next-to 2HDM (N2HDM) — an extension of the 2HDM by a real scalar singlet. We show analytically that — in contrast to the 2HDM — the electroweak vacuum of the N2HDM is not necessarily stable against charge- or CP-breaking vacua. Using our numerical approach, we study the phenomenological consequences of the intricate N2HDM vacuum structure and find a direct constraint from vacuum stability on the predictions for the decay of into two photons. We finally derive vacuum stability constraints on benchmark scenarios in the minimal supersymmetric extension of the SM. We validate our approach against results in the literature and find good agreement. In particular, we show that the better numerical stability of our approach can lead to more reliable results in a fraction of the runtime of alternative methods. The phenomenological studies carried out in this thesis aim to contribute to a better understanding of electroweak symmetry breaking and facilitate the exploration of models with extended scalar sectors using future experimental results
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Interplay of Higgs Phenomenology and New Physics in Supersymmetric Theories
No full textSupersymmetric (SUSY) theories such as the Minimal Supersymmetric Standard Model(MSSM) predict a new particle spectrum, including an extended Higgs sector, in orderto address fundamental questions that remain unanswered with the results obtained atthe Large Hadron Collider (LHC) so far. Despite an extensive programme to searchfor additional Higgs bosons at the LHC, no new Higgs-like particles have been observedbeyond the discovered signal at 125 GeV. Such searches have not taken into accountCP-violating effects in the Higgs sector, which are well-motivated in the light of the perceivedbaryon asymmetry in the universe, and which can induce significant deviations inthe phenomenology of the Higgs bosons. The search for additional Higgs bosons shouldtherefore account for the possibility that they may not necessarily be CP-eigenstates. Inthe most general case where the MSSM parameters can be complex, the three neutralHiggs bosons of the theory are the loop-corrected mass eigenstates {h1, h2, h3}, which areadmixtures of the tree-level CP-even and CP-odd Higgs states. This thesis focusses on theeffects of complex parameters on the production cross sections of these Higgs bosons andthe interference occurring between nearly mass-degenerate Higgs states. In the first partof this thesis, we discuss higher-order corrections in the Higgs sector which give rise toCP-violating mixing between the tree-level mass eigenstates, and present a computationof inclusive cross sections for the production of the CP-admixed Higgs bosons throughgluon fusion and bottom-quark annihilation. The predictions for the gluon-fusion processare based on an explicit calculation of the leading-order cross section for the generalcase of arbitrary complex parameters, supplemented by various higher-order corrections.The cross sections for the bottom-quark annihilation process are treated with a simplere-weighting procedure. In the next part, we describe the implementation of our crosssectionpredictions into an extension of the numerical code SusHi, named SusHiMi. Inour numerical analysis, we employ SusHiMi to study the effects of the phase of the softSUSY-breaking trilinear coupling of the Higgs with the top squark, and of the phaseof the gluino mass parameter on the neutral Higgs cross sections, masses, and mixings.We demonstrate that squark effects can be strongly dependent on the phases of thecomplex parameters, and emphasise the relevance of the resummation of squark effectsin the bottom-Yukawa coupling. Furthermore, we show that in a scenario where thetwo heavy Higgs bosons, h2 and h3, are strongly admixed and nearly mass-degenerate,experimentally resolving the two Higgs bosons as separate signals may not be possible.Only the sum of their cross sections including interference terms can be measured experimentally.Finally, we incorporate our cross section predictions into a formalism toaccount for the CP-violating interference between the Higgs bosons. In the prediction ofthe process b¯b ! h2, h3 ! +−, we show that strongly destructive interference arisesin the benchmark scenario defined in this thesis. Consequently, considerable parameterregions escape the exclusion bounds, which would be ruled out in LHC searches whichneglect these interference contributions
Complete electroweak O ( ) two-loop contributions to the Higgs boson masses in the MSSM and aspects of two-loop renormalisation
No full textPrecise predictions for Higgs physics in supersymmetric models
No full textIn the Minimal Supersymmetric Standard Model (MSSM), the mass of the SM-like Higgs boson can be predicted in terms of the model parameters and therefore used as a precision observable to constrain the MSSM parameter space. The precise prediction of the lightest MSSM Higgs boson mass in scenarios with one or several heavy supersymmetric particles requires the resummation of higher-order logarithmic contributions obtained within an effective-field-theory (EFT) approach. By combining the EFT calculation with a fixed-order calculation, a precise prediction also for low and intermediary SUSY scales can be obtained. This method is called the hybrid approach and is implemented, for instance, in the publicly available code FeynHiggs.We discuss various improvements to this hybrid framework. First, we consider the resummation of logarithmic contributions proportional to the bottom-Yukawa coupling, including two-loop -resummation. For large , this can lead to large upward shifts of the Higgs mass compared to the existing fixed-order calculations. Second, we improve the implemented EFT calculation by fully taking into account the effect of the phases of complex soft SUSY-breaking parameters. In addition, we discuss the inclusion of partial NLL resummation.After that, we turn to the case when there is a significant hierarchy between the gluino mass and the masses of the scalar top quarks. In such a situation, the current Higgs boson mass predictions so far have suffered from large theoretical uncertainties related to non-decoupling power-enhanced gluino contributions in the EFT employing the renormalization scheme. We demonstrate that the theoretical predictions in the heavy gluino region are vastly improved by the introduction of a more suitable renormalization scheme for the EFT calculation. It is shown that within this scheme, the large gluino contributions are absorbed into the model parameters, resulting in reliable and numerically stable predictions in the heavy-gluino region.The presented improvements will become publicly available as parts of FeynHiggs
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