| 1. |
- Aydemir, Ufuk, et al.
(författare)
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Addressing the R-D(*) anomalies with an S-1 leptoquark from SO(10) grand unification
- 2020
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 101:1
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Tidskriftsartikel (refereegranskat)abstract
- Motivated by the R-D(*) anomalies, we investigate an SO(10) grand unification scenario where a charge -1/3 scalar leptoquark (S-1) remains as the only new physics candidate at the TeV scale. This leptoquark along with the Standard Model (SM) Higgs doublet originates from the same ten-dimensional real scalar multiplet in the SO(10) grand unification framework taking its mass close to the electroweak scale. We explicitly show how the gauge coupling unification is achieved with only one intermediate symmetrybreaking scale at which the Pati-Salam gauge group is broken into the SM group. We investigate the phenomenological implications of our scenario and show that an S-1 with a specific Yukawa texture can explain the R-D(*) anomalies. We perform a multiparameter scan considering the relevant flavor constraints on R-D(*), F-L(D*), P-tau(D*) and R-K(*)(vv) as well as the constraint coming from the Z -> tau tau decay and the latest Dr resonance search data at the LHC. Our analysis shows that a single leptoquark solution to the observed R-D(*) anomalies with S-1 is still a viable solution.
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| 2. |
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| 3. |
- Aydemir, Ufuk, et al.
(författare)
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LHC Probes of TeV-Scale Scalars in SO(10) Grand Unification
- 2017
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Ingår i: Advances in High Energy Physics. - : HINDAWI LTD. - 1687-7357 .- 1687-7365.
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the possibility of TeV-scale scalars as low energy remnants arising in the nonsupersymmetric SO(10) grandunification framework where the field content is minimal.We consider a scenario where the SO(10) gauge symmetry is broken intothe gauge symmetry of the Standard Model (SM) through multiple stages of symmetry breaking, and a colored and hyperchargedscalar ? picks a TeV-scale mass in the process. The last stage of the symmetry breaking occurs at the TeV-scale where the leftrightsymmetry, that is, SU(2)? ⊗ SU(2)? ⊗ U(1)?−? ⊗ SU(3)?, is broken into that of the SM by a singlet scalar field S of mass?S ∼ 1TeV, which is a component of an SU(2)?-triplet scalar field, acquiring a TeV-scale vacuum expectation value. For the LHCphenomenology, we consider a scenario where S is produced via gluon-gluon fusion through loop interactions with ? and alsodecays to a pair of SM gauge bosons through ? in the loop.We find that the parameter space is heavily constrained from the latestLHC data.We use a multivariate analysis to estimate the LHC discovery reach of S into the diphoton channel.
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| 4. |
- 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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| 5. |
- Bhardwaj, Akanksha, et al.
(författare)
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Probing the inert doublet model using jet substructure with a multivariate analysis
- 2019
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 100:5
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Tidskriftsartikel (refereegranskat)abstract
- We explore the challenging but phenomenologically interesting hierarchical mass spectrum of the inert doublet model where relatively light dark matter along with much heavier scalar states can fully satisfy the constraints on the relic abundance and also fulfill other theoretical as well as collider and astrophysical bounds. To probe this region of parameter space at the LHC, we propose a signal process that combines up to two large radius boosted jets along with substantial missing transverse momentum. Aided by our intuitive signal selection, we capture a hybrid process where the di-fatjet signal is significantly enhanced by the mono-fatjet contribution with minimal effects on the SM di-fatjet background. Substantiated by the sizable mass difference between the scalars, these boosted jets, originally produced from the hadronic decay of massive vector bosons, still carry the inherent footprint of their root. These features implanted inside the jet substructure can provide additional handles to deal with a large background involving QCD jets. We adopt a multivariate analysis using a boosted decision tree to provide a robust mechanism to explore the hierarchical scenario, which would bring almost the entire available parameter space well within reach of the 14 TeV LHC runs with high luminosity.
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| 6. |
- Camargo-Molina, José Eliel, et al.
(författare)
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Heavy charged scalars from cs̄ fusion : a generic search strategy applied to a 3HDM with U(1) x U(1) family symmetry
- 2018
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :3
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Tidskriftsartikel (refereegranskat)abstract
- We describe a class of three Higgs doublet models (3HDMs) with a softly broken U(1) x U(1) family symmetry that enforces a Cabibbo-like quark mixing while forbidding tree-level flavour changing neutral currents. The hierarchy in the observed quark masses is partly explained by a softer hierarchy in the vacuum expectation values of the three Higgs doublets. As a consequence, the physical scalar spectrum contains a Standard Model (SM) like Higgs boson h(125) while exotic scalars couple the strongest to the second quark family, leading to rather unconventional discovery channels that could be probed at the Large Hadron Collider. In particular, we describe a search strategy for the lightest charged Higgs boson H-+/-, through the process cs̄ -> H+ -> W+ h(125), using a multivariate analysis that leads to an excellent discriminatory power against the SM background. Although the analysis is applied to the proposed class of 3HDMs, we employ a model-independent formulation such that it can be applied to any other model with the same discovery channel.
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| 7. |
- Chandak, Kushagra, et al.
(författare)
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Hunting for scalar leptoquarks with boosted tops and light leptons
- 2019
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 100:7
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Tidskriftsartikel (refereegranskat)abstract
- The LHC search strategies for leptoquarks that couple dominantly to a top quark are different than for the ones that couple mostly to the light quarks. We consider charge 1/3 (phi(1)) and 5/3 (phi(5)) scalar leptoquarks that can decay to a top quark and a charged lepton (tl) giving rise to a resonance system of a boosted top and a high-p(T) lepton. We introduce simple phenomenological models suitable for bottom-up studies and explicitly map them to all possible scalar leptoquark models within the Buchmuller-Ruckl-Wyler classifications that can have the desired decays. We study pair and single productions of these leptoquarks. Contrary to the common perception, we find that the single production of top-philic leptoquarks phi = {phi(1), phi(5)} in association with a lepton and jets could be significant for order one phi tl coupling in certain scenarios. We propose a strategy of selecting events with at least one hadronic-top and two high-p(T) same flavor opposite sign leptons. This captures events from both pair and single productions. Our strategy can significantly enhance the LHC discovery potential especially in the high-mass region where single productions become more prominent. Our estimation shows that a scalar leptoquark as heavy as similar to 1.7 TeV can be discovered at the 14 TeV LHC with 3 ab(-1) of integrated luminosity in the tll + X channel for 100% branching ratio in the phi -> tl decay mode. However, in some scenarios, the discovery reach can increase beyond 2 TeV even though the branching ratio comes down to about 50%.
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| 8. |
- Choudhury, Debajyoti, et al.
(författare)
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Neutrino and Z′ phenomenology in an anomaly-free U(1) extension : role of higher-dimensional operators
- 2020
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Ingår i: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :6
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Tidskriftsartikel (refereegranskat)abstract
- We consider an anomaly-free U(1) extension of the Standard Model with three right-handed neutrinos (RHNs) and two complex scalars, wherein the charge assignments preclude all tree-level mass terms for the neutrinos. Considering this setup, in turn, to be only a low-energy effective theory, we introduce higher-dimensional termsa laFroggatt-Nielsen to naturally generate tiny neutrino masses. One of the RHNs turns out to be very light, thereby constituting the main decay mode for theZ ' and hence relaxing the LHC dilepton resonance search constraints. The lightest RHN has a lifetime comparable to or bigger than the age of the Universe, and, hence, could account for a non-negligible fraction of the dark matter.
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| 9. |
- Danielsson, Ulf, et al.
(författare)
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Varying gauge couplings and collider phenomenology
- 2019
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Ingår i: Physical Review D. Particles and fields. - : American Physical Society. - 0556-2821 .- 1089-4918. ; 100:5
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate a natural extension of the Standard Model that involves varying coupling constants. This is a general expectation in any fundamental theory such as string theory, and there are good reasons for why new physics could appear at reachable energy scales. We investigate the collider phenomenology of models with varying gauge couplings where the variations are associated with real singlet scalar fields. We introduce three different heavy scalar fields that are responsible for the variations of the three gauge couplings of the Standard Model. This gives rise to many interesting collider signatures that we explore, resulting in exclusion limits based on the most recent LHC data, and predictions of the future discovery potential at the high-luminosity LHC.
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| 10. |
- 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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