| 1. |
- Camargo-Molina, José Eliel, et al.
(författare)
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A new perspective on the electroweak phase transition in the Standard Model Effective Field Theory
- 2021
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2021
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Tidskriftsartikel (refereegranskat)abstract
- A first-order Electroweak Phase Transition (EWPT) could explain the observed baryon-antibaryon asymmetry and have a detectable gravitational wave signature, but this is not possible in the Standard Model. We therefore study the EWPT in the Standard Model Effective Field Theory (SMEFT) including dimension-six operators. A first-order EWPT has previously been shown to be possible in the SMEFT in scenarios with a tree-level barrier between minima, which requires a negative Higgs quartic coupling and a new physics scale low enough to raise questions about the validity of the EFT approach. In this work we show that a first-order EWPT is possible in a novel scenario where the barrier between minima is generated radiatively, the quartic coupling is positive, the scale of new physics is higher, and there is good agreement with experimental bounds. Our calculation is done in a consistent, gauge-invariant way, and we carefully analyze the scaling of parameters necessary to generate a barrier in the potential. We perform a global fit in the relevant parameter space and explicitly find the points with a first-order transition that agree with experimental data. We also briefly discuss the prospects for probing the allowed parameter space using di-Higgs production in colliders.
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| 2. |
- Ekstedt, Andreas, et al.
(författare)
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Constraining minimal anomaly free U(1) extensions of the Standard Model
- 2016
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; 1611
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Tidskriftsartikel (refereegranskat)abstract
- We consider a class of minimal anomaly free U(1) extensions of the Standard Model with three generations of right-handed neutrinos and a complex scalar. Using electroweak precision constraints, new 13 TeV LHC data, and considering theoretical limitations such as perturbativity, we show that it is possible to constrain a wide class of models. By classifying these models with a single parameter, κ, we can put a model independent upper bound on the new U(1) gauge coupling gz. We find that the new dilepton data puts strong bounds on the parameters, especially in the mass region MZ′≲3 TeV.
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| 3. |
- Ekstedt, Andreas, et al.
(författare)
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Minimal anomalous U(1) theories and collider phenomenology
- 2018
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; 1802, s. 152-
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Tidskriftsartikel (refereegranskat)abstract
- We study the collider phenomenology of a neutral gauge boson Z′ arising in minimal but anomalous U(1) extensions of the Standard Model (SM). To retain gauge invariance of physical observables, we consider cancellation of gauge anomalies through the Green-Schwarz mechanism. We categorize a wide class of U(1) extensions in terms of the new U(1) charges of the left-handed quarks and leptons and the Higgs doublet. We derive constraints on some benchmark models using electroweak precision constraints and the latest 13 TeV LHC dilepton and dijet resonance search data. We calculate the decay rates of the exotic and rare one-loop Z′ decays to ZZ and Z-photon modes, which are the unique signatures of our framework. If observed, these decays could hint at anomaly cancellation through the Green-Schwarz mechanism. We also discuss the possible observation of such signatures at the LHC and at future ILC colliders.
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| 4. |
- Enberg, Rikard, et al.
(författare)
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Higgs phenomenology in the Stealth Doublet Model
- 2015
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 91
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Tidskriftsartikel (refereegranskat)abstract
- We analyze a model for the Higgs sector with two scalar doublets and a softly broken Z2 symmetry. One of the doublets breaks the electroweak symmetry and has tree-level Yukawa couplings to fermions. The other doublet has no vacuum expectation value and no tree-level couplings to fermions. Because the Z2 parity is broken the two doublets can mix, which leads to a distinct and novel phenomenology. This Stealth Doublet Model can be seen as a generalization of the Inert Doublet Model with a broken Z2 symmetry. We outline the model and present constraints from theory, electroweak precision tests and collider searches, including the recent observation of a Higgs boson at the LHC. The CP-odd scalar A and the charged scalar H± couple to fermions at one-loop level. We compute the decays of A and H± and in particular the one-loop decays A→ff¯, H±→ff¯′, H±→W±Z and H±→W±γ. We also describe how to calculate and renormalize such processes in our model. We find that if one of H± or A is the lightest scalar, H±→W±γ or A→bb¯ are typically their respective dominating decay channels. Otherwise, the dominating decays of H± and Aare into a scalar and a vector. Due to the absence of tree-level fermion couplings for H± and A, we consider pair production and associated production with vector bosons and scalars at the LHC. If the parameter space of the model that favors H±→W±γ is realized in Nature, we estimate that there should be a considerable amount of such events in the present LHC data.
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| 5. |
- Enberg, Rikard, et al.
(författare)
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Higgs properties in a broken Inert Doublet Model
- 2013
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Berlin/Heidelberg. - 1126-6708 .- 1029-8479. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- We consider a model for the Higgs sector with two scalar doublets and a softly broken Z2 symmetry, the Stealth Doublet Model. This model can be seen as a generalization of the Inert Doublet Model. One of the doublets is the Higgs doublet that participates in electroweak symmetry breaking and couples to fermions. The other doublet does not couple to fermions at tree level and does not acquire a vacuum expectation value. The broken Z2 symmetry leads to interesting phenomenology such as mixing between the two doublets and charged and CP-odd scalars that can be light and have unusual decay channels. We present theoretical and experimental constraints on the model and consider the recent observation of a Higgs boson at the LHC. The data on the H→ γγ channel can be naturally accommodated in the model, with either the lightest or the heaviest CP-even scalar playing the role of the observed particle.
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| 6. |
- Enberg, Rikard, et al.
(författare)
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Higgs properties in a softly broken Inert Doublet Model
- 2013
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :8
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Tidskriftsartikel (refereegranskat)abstract
- We consider a model for the Higgs sector with two scalar doublets and a softly broken Z(2) symmetry, the Stealth Doublet Model. This model can be seen as a generalization of the Inert Doublet Model. One of the doublets is the Higgs doublet that participates in electroweak symmetry breaking and couples to fermions. The other doublet does not couple to fermions at tree level and does not acquire a vacuum expectation value. The broken Z(2) symmetry leads to interesting phenomenology such as mixing between the two doublets and charged and CP-odd scalars that can be light and have unusual decay channels. We present theoretical and experimental constraints on the model and consider the recent observation of a Higgs boson at the LHC. The data on the H -> gamma gamma channel can be naturally accommodated in the model, with either the lightest or the heaviest CP-even scalar playing the role of the observed particle.
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| 7. |
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| 8. |
- Haitina, Tatjana, et al.
(författare)
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Functional characterization of two melanocortin (MC) receptors in lamprey showing orthology to the MC1 and MC4 receptor subtypes
- 2007
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 7, s. 101-
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Tidskriftsartikel (refereegranskat)abstract
- Background The melanocortin (MC) receptors have a key role in regulating body weight and pigmentation. They belong to the rhodopsin family of G protein-coupled receptors (GPCRs). The purpose of this study was to identify ancestral MC receptors in agnathan, river lamprey. Results We report cloning of two MC receptors from river lamprey. The lamprey receptors, designated MCa and MCb, showed orthology to the MC1 and MC4 receptor subtypes, respectively. The molecular clock analysis suggested that lamprey MC receptor genes were not duplicated recently and diverged from each other more than 400 MYR ago. Expression and pharmacological characterization showed that the lamprey MCa receptor was able to bind and be activated by both lamprey and human MSH peptides. The lamprey MCa receptor had relatively high affinity for ACTH derived peptides similarly to the fish MC receptors. We found that both of the lamprey MC receptors were expressed in skin, while the MCb receptor was also found in liver, heart and skeletal muscle. Conclusion This study shows presence of MC receptors in agnathans indicating early signs of specific functions of melanocortin receptor subtypes.
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| 9. |
- Haitina, Tatjana, et al.
(författare)
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Further evidence for ancient role of ACTH peptides at melanocortin (MC) receptors; pharmacology of dogfish and lamprey peptides at dogfish MC receptors
- 2007
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Ingår i: Peptides. - : Elsevier BV. - 0196-9781 .- 1873-5169. ; 28:4, s. 798-805
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Tidskriftsartikel (refereegranskat)abstract
- The cloning of melanocortin (MC) receptors in distant species has provided us tools to get insight in how the ligand–receptors interactions in the MC system have evolved. We have however lacked studies on pharmacology of native ancient melanocortin peptides at the ancient MC receptors. In this paper we synthesized melanocortin peptides from both the sea lamprey (Petromyzon marinus) and spiny dogfish (Squalus acanthias) and tested them on the MC3 and MC4 receptors from spiny dogfish. The results show that both the dogfish and lamprey ACTH peptides have similar or higher affinity than the dogfish α-, β- and γ-MSH peptides to the dogfish MC3 and MC4 receptors. Moreover, both the dogfish and lamprey ACTH peptides have more than 10-fold higher affinity than α-MSH to the dogfish MC4 receptor. We also show that dogfish δ-MSH is able to bind to MC receptors and its potency is higher than of dogfish β-MSH, which is considered to be its precursor. Our results provide the first evidence that native ACTH ligands from dogfish and lamprey have a preference above native MSH peptides to ancient version of the MC3 and MC4 receptors. This further strengthens the hypotheses that the ligand contributing to the first version of the melanocortin ligand-receptor system resembled ACTH.
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| 10. |
- Ingelman, Gunnar, et al.
(författare)
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Rapidity gaps from colour string topologies
- 1999
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Ingår i: Nuclear physics B, Proceedings supplements. - 0920-5632 .- 1873-3832. ; 79:1-3, s. 386-388
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Tidskriftsartikel (refereegranskat)abstract
- Diffractive deep inelastic scattering at HERA and diffractive W and jet production at the Tevatron are well described by soft colour exchange models. Their essence is the variation of colour string-field topologies giving both gap and no-gap events, with a smooth transition and thereby a unified description of all final states.
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