| 1. |
- Arina, Chiara, et al.
(författare)
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Closing in on t-channel simplified dark matter models
- 2021
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 813
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive analysis of cosmological and collider constraints is presented for three simplified models characterised by a dark matter candidate (real scalar, Majorana fermion and real vector) and a coloured mediator (fermion, scalar and fermion respectively) interacting with the right-handed up quark of the Standard Model. Constraints from dark matter direct and indirect detection and relic density are combined with bounds originating from the re-interpretation of a full LHC run 2 ATLAS search targeting final states with multiple jets and missing transverse energy. Projections for the high-luminosity phase of the LHC are also provided to assess future exclusion and discovery reaches, which show that analogous future search strategies will not allow for a significant improvement compared with the present status. From the cosmological point of view, we demonstrate that thermal dark matter is largely probed (and disfavoured) by constraints from current direct and indirect detection experiments. These bounds and their future projections have moreover the potential of probing the whole parameter space when combined with the expectation of the high-luminosity phase of the LHC.
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| 2. |
- Banerjee, Avik, et al.
(författare)
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Vector-like quarks: status and new directions at the LHC
- 2024
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Tidskriftsartikel (refereegranskat)abstract
- Experimental searches for vector-like quarks have until now only considered their decays into Standard Model particles. However, various new physics scenarios predict additional scalars, so that these vector-like quarks can decay to new channels. These new channels reduce the branching ratios into Standard Model final states, significantly affecting current mass bounds. In this article, we quantitatively assess the relevance and observability of single and pair production processes of vector-like quarks, followed by decays into both standard and exotic final states. We highlight the importance of large widths and the relative interaction strengths with Standard Model particles and new scalars. Then, we review the post-Moriond 2024 status of these models in light of available LHC data and discuss potential future strategies to enhance the scope of vector-like quark searches.
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| 3. |
- Benbrik, R., et al.
(författare)
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Signatures of vector-like top partners decaying into new neutral scalar or pseudoscalar bosons
- 2020
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Ingår i: Journal of High Energy Physics. - : Springer Nature. - 1029-8479 .- 1126-6708. ; 2020:5
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Tidskriftsartikel (refereegranskat)abstract
- We explore the phenomenology of models containing one Vector-Like Quark (VLQ), t′, which can decay into the Standard Model (SM) top quark, t, and a new spin-0 neutral boson, S, the latter being either a scalar or pseudoscalar state. We parametrise the underlying interactions in terms of a simplified model which enables us to capture possible Beyond the SM (BSM) scenarios. We discuss in particular three such scenarios: one where the SM state is supplemented by an additional scalar, one which builds upon a 2-Higgs Doublet Model (2HDM) framework and another which realises a Composite Higgs Model (CHM) through partial compositeness. Such exotic decays of the t′ can be competitive with decays into SM particles, leading to new possible discovery channels at the Large Hadron Collider (LHC). Assuming t′ pair production via strong interactions, we design signal regions optimised for one t′ → S t transition (while being inclusive on the other t¯ ′ decay, and vice versa), followed by the decay of S into the two very clean experimental signatures S → γ γ and S → Z (→ ℓ+ℓ−)γ. We perform a dedicated signal- to-background analysis in both channels, by using Monte Carlo (MC) event simulations modelling the dynamics from the proton-proton to the detector level. Under the assumption of BR(t′ → S t) = 100%, we are therefore able to realistically quantify the sensitivity of the LHC to both the t′ and S masses, assuming both current and foreseen luminosities. This approach paves the way for the LHC experiments to surpass current VLQ search strategies based solely on t′ decays into SM bosons (W±, Z , h). © 2020, The Author(s).
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| 4. |
- Banerjee, Avik, 1992, et al.
(författare)
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Heavy vector-like quarks decaying to exotic scalars: a case study with triplets
- 2024
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Ingår i: Journal of High Energy Physics. - : Springer. - 1029-8479 .- 1126-6708. ; 2024:1
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the pair production of a vector-like quark triplet with hypercharge 5/3 decaying into top quark and a complex scalar triplet with hypercharge 1 at the LHC. This novel scenario, featuring particles with exotic charges — two quarks with charge 8/3 and 5/3 and a scalar with charge 2 — serves as a unique window to models based on the framework of partial compositeness, where these particles naturally emerge as bound states around the TeV scale. Leveraging on the LHC data we establish exclusion limits on the masses of the vector-like quark and the scalar triplet. Subsequently, we design an analysis strategy aimed at improving sensitivity in the region which is still allowed. Our analysis focuses on two specific regions in the parameter space: the first entails a large mass gap between the vector-like quarks and the scalars, so that the vector-like quarks can decay into the scalars; the second involves a small mass gap, such that this decay is forbidden. To simplify the parameter space, both vector-like quarks and scalars are assumed to be degenerate or almost degenerate within the triplets, such that chain decays between fermions and scalars are suppressed. As a result, we found that final states characterized by a same-sign lepton pair, multiple jets, and high net transverse momentum (i.e. effective mass) will play a pivotal role to unveil this model and, more in general, models characterised by multiple vector-like quarks around the same mass scale during the high luminosity LHC phase.
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| 5. |
- Belyaev, A., et al.
(författare)
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Advancing LHC Probes of Dark Matter from the Inert two-Higgs Doublet Model with the Mono-jet Signal
- 2019
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 99:1
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Tidskriftsartikel (refereegranskat)abstract
- The inert 2-Higgs Doublet Model (i2HDM) is a well-motivated minimal consistent Dark Matter (DM) model, but it is rather challenging to test at the Large Hadron Collider (LHC) in the parameter space allowed by relic density and DM direct detection constraints. This is especially true when considering the latest XENON 1T data on direct DM searches which we use here to present the best current combined limit on the i2HDM parameter space. In this analysis, we present prospects to advance the exploitation of DM mono-jet signatures from the i2HDM at the LHC, by emphasising that a shape analysis of the missing transverse momentum distribution allows one to sizably improve the LHC discovery potential. As a key element of our analysis, we explore the validity of using an effective vertex, Hgg, for the coupling of the Higgs boson to gluons using a full one-loop computation. We have found sizeable differences between the two approaches, especially in the high missing transverse momentum region, and incorporated the respective K-factors to obtain the correct kinematical distributions. As a result, we delineate a realistic search strategy and present the improved current and projected LHC sensitivity to the i2HDM parameter space.
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| 6. |
- Cacciapaglia, Giacomo, et al.
(författare)
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Next-to-leading-order predictions for single vector-like quark production at the LHC
- 2019
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Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 793, s. 206-211
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Tidskriftsartikel (refereegranskat)abstract
- We propose simulation strategies for single production of third generation vector-like quarks at the LHC, implementing next-to-leading-order corrections in QCD and studying in detail their effect on cross sections and differential distributions. We also investigate the differences and the relative incertitudes induced by the use of the Four-Flavour Number Scheme versusthe Five-Flavour Number Scheme. As a phenomenological illustration, we concentrate on the production of vector-like quarks coupling to the third generation of the Standard Model in association with a jet and assuming standard couplings to gauge and Higgs bosons.
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| 7. |
- Corcella, Gennaro, et al.
(författare)
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Vector-like quarks decaying into singly and doubly charged bosons at LHC
- 2021
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Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :10
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the production of vector-like quarks with charge 5/3 at the LHC and their subsequent decays into new singly or doubly charged bosons plus a heavy quark (top or bottom). In particular, we explore final states with same-sign di-leptons (electron or muon pairs), with the leptons coming from the decay of the new bosons and, in the case of production of singly charged bosons, from top quarks as well. These processes are predicted by classes of models based on extensions of the gauge group of the Standard Model, such as the 331 Model, where the electroweak symmetry is described by SU(3)(L) x U(1)(X), X being a new abelian charge. For this purpose, a CMS search for vector-like partners with charge 5/3 decaying into Wt is recast to obtain model-independent bounds and projected reaches at future luminosity stages of the LHC. The results are then interpreted as mass bounds for the new particles predicted in the 331 Model and as a constraint on the scale of its spontaneous symmetry breaking. The complete set of model-independent results are provided as recast efficiencies, to allow for reinterpretation in different scenarios.
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| 8. |
- Crivellin, Andreas, et al.
(författare)
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Searching for lepton flavor universality violation and collider signals from a singly charged scalar singlet
- 2021
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Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 103:7
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, evidence for lepton flavor universality violation beyond the Standard Model has been accumulated. In this context, a singly charged SU(2)(L) singlet scalar (phi(+/-)) is very interesting, as it can only have flavor off-diagonal couplings to neutrinos and charged leptons therefore necessarily violating lepton flavor (universality). In fact, it gives a (necessarily constructive) tree-level effect in l -> l'nu nu processes, while contributing to charged lepton flavor violating only at the loop level. Therefore, it can provide a common explanation of the hints for new physics in tau -> mu nu nu/tau(mu) -> e nu nu and of the Cabibbo Angle Anomaly. Such an explanation predicts Br[tau -> e gamma] to be of the order of a few times 10(-11), while Br[tau -> e mu mu] can be of the order of 10(-9) for order one couplings and therefore in the reach of forthcoming experiments. Furthermore, we derive a novel coupling-independent lower limit on the scalar mass of approximate to 200 GeV by recasting LHC slepton searches. In the scenario preferred by low energy precision data, the lower limit is even strengthened to approximate to 300 GeV, showing the complementary between LHC searches and flavor observables. Furthermore, we point out that this model can be tested by reinterpreting dark matter monophoton searches at future e(+)e(-) colliders.
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| 9. |
- Deandrea, Aldo, et al.
(författare)
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Single production of vector-like quarks : the effects of large width, interference and NLO corrections
- 2021
-
Ingår i: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2021:8
-
Tidskriftsartikel (refereegranskat)abstract
- We provide a comprehensive discussion, together with a complete setup for simulations, relevant for the production of a single vector-like quark at hadron colliders. Our predictions include finite width effects, signal-background interference effects and next-to-leading order QCD corrections. We explicitly apply the framework to study the single production of a vector-like quark T with charge 2/3, but the same procedure can be used to analyse the single production of vector-like quarks with charge -4/3, -1/3, 2/3 and 5/3, when the vector-like quark interacts with the Standard Model quarks and electroweak bosons. Moreover, this procedure can be straightforwardly extended to include additional interactions with exotic particles. We provide quantitative results for representative benchmark scenarios characterised by the T mass and width, and we determine the role of the interference terms for a range of masses and widths of phenomenological significance. We additionally describe in detail, both analytically and numerically, a striking feature in the invariant mass distribution appearing only in the T -> th channel.
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| 10. |
- Moretti, Stefano, et al.
(författare)
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Deconstructing squark contributions to di-Higgs production at the LHC
- 2023
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Ingår i: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 107:11
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel approach to the study of di-Higgs production via gluon-gluon fusion at the LHC. The relevant Feynman diagrams involving two Standard Model-like Higgs bosons hh are computed within a simplified model approach that enables one to interpret possible signals of new physics in a model-independent way as well as to map these onto specific theories. This is possible thanks to a decomposition of such a signal process into all its squared amplitudes and their relative interferences, each of which has a well-defined coupling structure. We illustrate the power of this procedure for the case of both a minimal and next-to-minimal representation of supersymmetry, for which the new physics effects are due to top squarks entering the loops of gg→hh. The squarks yield both a change of the integrated cross section and peculiar kinematic features in its differential distributions with respect to the Standard Model. These effects can in turn be traced back to the relevant diagrammatic and coupling structures and allow for a detailed analysis of the process. In order to do so, we perform systematic scans of the parameter spaces of such new physics scenarios and identify benchmark points which exhibit potentially observable features during the current and upcoming runs of the LHC.
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