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Diboson anomaly: Heavy Higgs resonance and QCD vector-like exotics Aristizabal Sierra, Diego ; ; et al in Physical Review. D : Particles and Fields (2016), 93 The ATLAS collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region 1.8−2.2 TeV. In the light of these ... [more ▼] The ATLAS collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region 1.8−2.2 TeV. In the light of these results, we argue that such signal might be the first manifestation of the production and further decay of a heavy CP-even Higgs resulting from a type-I Two Higgs Doublet Model. We demonstrate that in the presence of colored vector-like fermions, its gluon fusion production cross section is strongly enhanced, with the enhancement depending on the color representation of the new fermion states. Our findings show that barring the color triplet case, any QCD "exotic" representation can fit the ATLAS result in fairly large portions of the parameter space. We have found that if the diboson excess is confirmed and this mechanism is indeed responsible for it, then the LHC Run-2 should find: (i) a CP-odd scalar with mass below ∼2.3 TeV, (ii) new colored states with masses below ∼2 TeV, (iii) no statistically significant diboson events in the W±Z channel, (iv) events in the triboson channels W±W∓Z and ZZZ with invariant mass amounting to the mass of the CP-odd scalar. [less ▲] Detailed reference viewed: 20 (0 ULg)Explaining the CMS Higgs lepton-flavor violating Aristizabal Sierra, Diego ; Vicente, Avelino in Physical Review. D : Particles and Fields (2014), 90(11), 115004 Direct searches for lepton flavor violating Higgs boson decays in the τ μ channel have been recently reported by the CMS collaboration. The results display a slight excess of signal events with a ... [more ▼] Direct searches for lepton flavor violating Higgs boson decays in the τ μ channel have been recently reported by the CMS collaboration. The results display a slight excess of signal events with a significance of 2.5σ, which translates into a branching ratio of about 1%. By interpreting these findings as a hint for beyond the standard model physics, we show that the Type-III 2HDM is capable of reproducing such signal while at the same time satisfying vacuum stability, perturbativity, electroweak precision data, measured Higgs standard decay modes and low-energy lepton flavor violating constraints. We have found that the allowed signal strength ranges for the bb, WW* and ZZ* standard channels shrink as soon as BR(h→τμ)∼ 1% is enforced. Thus, we point out that if the excess persists, improved measurements of these channels may be used to test our Type-III 2HDM scenario. [less ▲] Detailed reference viewed: 16 (2 ULg)Twist-2 generalized transverse-momentum dependent parton distributions and the spin/orbital structure of the nucleon ; Lorce, Cédric ; et al in Physical Review. D : Particles and Fields (2014) Detailed reference viewed: 10 (0 ULg)[70,l+] baryons in large Nc QCD revisited: The effect on Regge trajectories ; Stancu, Floarea in Physical Review. D : Particles and Fields (2013), 87(April), 076012 A simple procedure within the 1/N_c expansion method where all the N_c quarks are treated on the same footing has been found successful in describing mixed symmetric negative parity baryon states ... [more ▼] A simple procedure within the 1/N_c expansion method where all the N_c quarks are treated on the same footing has been found successful in describing mixed symmetric negative parity baryon states belonging to the [{\bf 70},\ell^-] multiplets of the N = 1 and 3 bands. Presently it is applied to mixed symmetric positive parity [{\bf 70},0^+] and [{\bf 70},2^+] multiplets of the N = 2 band. We search for the most dominant terms in the mass formula. The results are compared to those obtained in the procedure where the system is separated into a core and an excited quark. We find that both the spin and isospin operators of the entire system of N_c quarks play dominant roles in describing the data, like for negative parity states. As a by-product we present the contribution of the leading spin-isospin singlet term as a function of the band number, which hints at distinct Regge trajectories for the symmetric and mixed symmetric states. [less ▲] Detailed reference viewed: 16 (4 ULg)Accessing baryon to meson transition distribution amplitudes in meson production in association with a high invariant mass lepton pair at GSI-FAIR with P̅ ANDA Lansberg, Jean-Philippe ; ; Semenov-Tyan-Shanskiy, Kirill et al in Physical Review. D : Particles and Fields (2012), 86 Nucleon-antinucleon annihilation into a near backward- (or forward-) produced meson and a high invariant mass lepton pair admits a factorized description in terms of antinucleon (or nucleon) distribution ... [more ▼] Nucleon-antinucleon annihilation into a near backward- (or forward-) produced meson and a high invariant mass lepton pair admits a factorized description in terms of antinucleon (or nucleon) distribution amplitudes (DAs) and nucleon to meson (or antinucleon to meson) transition distribution amplitudes (TDAs). We estimate the cross section of backward (and forward) pion and eta-meson production in association with a high invariant mass lepton pair for the kinematical conditions of GSI-FAIR. The cross sections are found to be large enough to be measured with the PANDA detector. Interesting phenomenological applications of the approach are thus expected. [less ▲] Detailed reference viewed: 7 (0 ULg)Discrete symmetries in the three-Higgs-doublet model Ivanov, Igor ; in Physical Review. D : Particles and Fields (2012), 86(9), 0950305 N-Higgs-doublet models (NHDM) are among the most popular examples of electroweak symmetry breaking mechanisms beyond the Standard Model. Discrete symmetries imposed on the NHDM scalar potential play a ... [more ▼] N-Higgs-doublet models (NHDM) are among the most popular examples of electroweak symmetry breaking mechanisms beyond the Standard Model. Discrete symmetries imposed on the NHDM scalar potential play a pivotal role in shaping the phenomenology of the model, and various symmetry groups have been studied so far. However, in spite of all efforts, the classification of finite Higgs-family symmetry groups realizable in NHDM for any N>2 is still missing. Here, we solve this problem for the three-Higgs-doublet model by making use of Burnside’s theorem and other results from pure finite group theory which are rarely exploited in physics. Our method and results can also be used beyond high-energy physics, for example, in the study of possible symmetries in three-band superconductors. [less ▲] Detailed reference viewed: 13 (3 ULg)Negative parity baryons in the 1/Nc expansion: the three towers of states revisited. ; Stancu, Floarea in Physical Review. D : Particles and Fields (2012), D86 We discuss the compatibility between the quark-shell picture and the meson-nucleon scattering picture in large $N_c$ QCD for mixed symmetric $\ell$ = 1 states previously analyzed by using a simple ... [more ▼] We discuss the compatibility between the quark-shell picture and the meson-nucleon scattering picture in large $N_c$ QCD for mixed symmetric $\ell$ = 1 states previously analyzed by using a simple Hamiltonian including operators up to order $\mathcal{O}(N^0_c)$ defined in the standard ground state symmetric core + excited quark procedure. Here we introduce a Hamiltonian of order $\mathcal{O}(N^0_c)$ defined in a new approach where the separation of the system into two parts is not required. Three degenerate sets of states (towers) with the same quantum numbers as in the scattering picture and in the standard procedure are obtained. Thus the compatibility is equally achieved. The eigenvalues of the presently chosen Hamiltonian also have simple analytic expressions, depending linearly on the three dynamical coefficients entering the Hamiltonian. This reinforces the validity of the new approach which had already successfully described excited negative parity baryons in a large energy range. [less ▲] Detailed reference viewed: 18 (13 ULg)Z_p scalar dark matter from multi-Higgs-doublet models Ivanov, Igor ; Keus, Venus in Physical Review. D : Particles and Fields (2012), 86(1), 0160047 In many models, stability of dark matter particles is protected by a conserved Z_2 quantum number. However dark matter can be stabilized by other discrete symmetry groups, and examples of such models with ... [more ▼] In many models, stability of dark matter particles is protected by a conserved Z_2 quantum number. However dark matter can be stabilized by other discrete symmetry groups, and examples of such models with custom-tailored field content have been proposed. Here we show that electroweak symmetry breaking models with N Higgs doublets can readily accommodate scalar dark matter candidates stabilized by groups Z_p with any $p \le 2^{N-1}$, leading to a variety of kinds of microscopic dynamics in the dark sector. We give examples in which semi-annihilation or multiple semi-annihilation processes are allowed or forbidden, which can be especially interesting in the case of asymmetric dark matter. [less ▲] Detailed reference viewed: 20 (3 ULg)Highly excited negative parity baryons in the 1/Nc expansion. Matagne, Nicolas ; Stancu, Floarea in Physical Review. D : Particles and Fields (2012), D85 Detailed reference viewed: 9 (8 ULg)Cornering the axionlike particle explanation of quasar polarizations Payez, Alexandre in Physical Review. D : Particles and Fields (2012), 85(8), 087701 In a series of papers, it has been shown that the distribution of polarization position angles for visible light from quasars is not random in extremely large regions of the sky. As explained in a recent ... [more ▼] In a series of papers, it has been shown that the distribution of polarization position angles for visible light from quasars is not random in extremely large regions of the sky. As explained in a recent article, the measurement of vanishing circular polarization for such quasars is an important problem for a mechanism involving the mixing with axionlike particles in external magnetic fields. In this paper, we stress that a recent report of similar coherent orientations of polarization in radio waves further disfavors the need for such particles, as an effect at these wavelengths would be extremely suppressed or would directly contradict data. [less ▲] Detailed reference viewed: 33 (9 ULg)Measuring the phase of the scattering amplitude with vortex beams Ivanov, Igor in Physical Review. D : Particles and Fields (2012), 85(7), 07600110 We show that colliding vortex beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the plane wave scattering amplitude changes with the scattering angle ... [more ▼] We show that colliding vortex beams instead of (approximate) plane waves can lead to a direct measurement of how the overall phase of the plane wave scattering amplitude changes with the scattering angle. Since vortex beams are coherent superpositions of plane waves with different momenta, their scattering amplitude receives contributions from plane wave amplitudes with distinct kinematics. These contributions interfere, leading to the measurement of their phase difference. Although interference exists for any generic wave packet collision, we show that using vortex beams dramatically enhances sensitivity to the phase in comparison with nonvortex beams. Since the overall phase is inaccessible in a plane wave collision, this measurement would be of great importance for a number of topics in hadronic physics, for example, meson production in the resonance region, physics of nucleon resonances, and small angle elastic hadron scattering. [less ▲] Detailed reference viewed: 18 (1 ULg)Consistent model for \pi N transition distribution amplitudes and backward pion electroproduction Lansberg, Jean-Philippe ; ; Semenov-Tian-Chanski, Kirill et al in Physical Review. D : Particles and Fields (2012), 85 The extension of the concept of generalized parton distributions leads to the introduction of baryon to meson transition distribution amplitudes (TDAs), nondiagonal matrix elements of the nonlocal three ... [more ▼] The extension of the concept of generalized parton distributions leads to the introduction of baryon to meson transition distribution amplitudes (TDAs), nondiagonal matrix elements of the nonlocal three quark operator between a nucleon and a meson state. We present a general framework for modeling nucleon to pion (\pi N) TDAs. Our main tool is the spectral representation for \pi N TDAs in terms of quadruple distributions. We propose a factorized Ansatz for quadruple distributions with input from the soft-pion theorem for \pi N TDAs. The spectral representation is complemented with a D-term like contribution from the nucleon exchange in the cross channel. We then study backward pion electroproduction in the QCD collinear factorization approach in which the nonperturbative part of the amplitude involves N TDAs. Within our two component model for N TDAs, we update previous leading-twist estimates of the unpolarized cross section. Finally, we compute the transverse target single spin asymmetry as a function of skewness. We find it to be sizable in the valence region and sensitive to the phenomenological input of our \pi N TDA model. [less ▲] Detailed reference viewed: 14 (0 ULg)Can axionlike particles explain the alignments of the polarizations of light from quasars? Payez, Alexandre ; Cudell, Jean-René ; Hutsemekers, Damien in Physical Review. D : Particles and Fields (2011), 84 The standard axion-like particle explanation of the observed large-scale coherent orientations of quasar polarisation vectors is ruled out by the recent measurements of vanishing of circular polarisation ... [more ▼] The standard axion-like particle explanation of the observed large-scale coherent orientations of quasar polarisation vectors is ruled out by the recent measurements of vanishing of circular polarisation. We introduce a more general wave-packet formalism and show that, although decoherence effects between waves of different frequencies can reduce significantly the amount of circular polarisation, the axion-like particle hypothesis is disfavoured given the bandwidth with which part of the observations were performed. Finally, we show that a more sophisticated model of extragalactic fields does not lead to an alignment of polarisations. [less ▲] Detailed reference viewed: 109 (53 ULg)Colliding particles carrying nonzero orbital angular momentum Ivanov, Igor in Physical Review. D : Particles and Fields (2011), 83(9), 093001 Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested ... [more ▼] Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some generic features of scattering processes involving twisted particles in the initial and/or final state. In order to avoid additional complications arising from nontrivial polarization states, we focus here on scalar fields only. We show that processes involving twisted particles allow one to perform a Fourier analysis of the plane-wave cross section with respect to the azimuthal angles of the initial particles. In addition, using twisted states, one can probe the autocorrelation function of the amplitude, which is inaccessible in the plane-wave collisions. Finally, we discuss prospects for experimental study of these effects. [less ▲] Detailed reference viewed: 11 (1 ULg)SU(6) [70,1-] baryon multiplet in the 1/N_c expansion ; Stancu, Floarea in Physical Review. D : Particles and Fields (2011), 83 The masses of excited states of mixed orbital symmetry of nonstrange and strange baryons belonging to the lowest $[{\bf 70},1^-]$ multiplet are calculated in the $1/N_c$ expansion to order $1/N_c$ with a ... [more ▼] The masses of excited states of mixed orbital symmetry of nonstrange and strange baryons belonging to the lowest $[{\bf 70},1^-]$ multiplet are calculated in the $1/N_c$ expansion to order $1/N_c$ with a new method which allows to considerably reduce the number of linearly independent operators entering the mass formula. This study represents an extension to SU(6) of our work on nonstrange baryons, the framework of which was SU(4). The conclusion regarding the role of the flavor operator, neglected in previous SU(6) studies, is reinforced. Namely, both the flavor and spin operators contribute dominantly to the flavor-spin breaking. [less ▲] Detailed reference viewed: 12 (3 ULg)Uncertainties on exclusive diffractive Higgs boson and jet production at the LHC Dechambre, Alice ; ; et al in Physical Review. D : Particles and Fields (2011), D83 Two theoretical descriptions of exclusive diffractive jets and Higgs production at the LHC were implemented into the FPMC generator: the Khoze, Martin, Ryskin model and the Cudell, Hern\'andez, Ivanov ... [more ▼] Two theoretical descriptions of exclusive diffractive jets and Higgs production at the LHC were implemented into the FPMC generator: the Khoze, Martin, Ryskin model and the Cudell, Hern\'andez, Ivanov, Dechambre exclusive model. We then study the uncertainties. We compare their predictions to the CDF measurement and discuss the possibility of constraining the exclusive Higgs production at the LHC with early measurements of exclusive jets. We show that the present theoretical uncertainties can be reduced with such data by a factor of 5. [less ▲] Detailed reference viewed: 9 (3 ULg)Negative parity baryons in the 1/N_c expansion : the quark excitation versus the meson-nucleon resonance picture ; Stancu, Floarea in Physical Review. D : Particles and Fields (2011), 84 In order to better understand the fundamental issue regarding the compatibility between the quark-shell picture and that of resonances in meson-nucleon scattering in large $N_c$ QCD we extend the work of ... [more ▼] In order to better understand the fundamental issue regarding the compatibility between the quark-shell picture and that of resonances in meson-nucleon scattering in large $N_c$ QCD we extend the work of Cohen and Lebed on mixed symmetric $\ell $ = 1 baryons to analyze excited states with $\ell $ = 3. We give an explicit proof on the degeneracy of mass eigenvalues of a simple Hamiltonian including operators up to order $\mathcal{O}(N^0_c)$ \emph{i. e.} neglecting $1/N_c$ corrections in the quark-shell picture in the large $N_c$ limit. We obtain three degenerate multiplets formed of $\ell = 3$ states, as in the case of $\ell $ = 1 baryons. The compatibility between this picture and that of resonances in meson-nucleon scattering is discussed in the light of the present results. [less ▲] Detailed reference viewed: 12 (2 ULg)pi N transition distribution amplitudes: Their symmetries and constraints from chiral dynamics ; Semenov-Tyan-Shanskiy, Kirill ; in Physical Review. D : Particles and Fields (2011), 84 Detailed reference viewed: 12 (0 ULg)Properties of the general N-Higgs-doublet model. I. The orbit space Ivanov, Igor ; in Physical Review. D : Particles and Fields (2010), 82(1), 0150141-16 We study the scalar sector of the general N-Higgs-doublet model via geometric constructions in the space of gauge orbits. We give a detailed description of the shape of the orbit space both for general N ... [more ▼] We study the scalar sector of the general N-Higgs-doublet model via geometric constructions in the space of gauge orbits. We give a detailed description of the shape of the orbit space both for general N and, in more detail, for N=3. We also comment on remarkable analogies between the N-Higgs-doublet model and quantum information theory. [less ▲] Detailed reference viewed: 22 (7 ULg)Group theoretical study of nonstrange and strange mixed symmetric baryon states [Nc-1,1] in the 1/Nc expansion ; Stancu, Floarea in Physical Review. D : Particles and Fields (2010), 81 Using group theory arguments we extend and complete our previous work by deriving all SU(6) exact wave functions associated with the spectrum of mixed symmetric baryon states [Nc-1,1] in the 1/Nc ... [more ▼] Using group theory arguments we extend and complete our previous work by deriving all SU(6) exact wave functions associated with the spectrum of mixed symmetric baryon states [Nc-1,1] in the 1/Nc expansion. The extension to SU(6) enables us to study the mass spectra of both strange and nonstrange baryons, while previous work was restricted to nonstrange baryons described by SU(4). The wave functions are specially written in a form to allow a comparison with the approximate, customarily used wave functions, where the system is separated into a ground state core and an excited quark. We show that the matrix elements of the flavor operator calculated with the exact wave functions acquire the same asymptotic form at large Nc, irrespective of the spin-flavor multiplet contained in [Nc-1,1], while with the approximate wave function one cannot obtain a similar behavior. The isoscalar factors of the permutation group of Nc particles derived here can be used in any problem where a given fermion system is described by the partition [Nc-1,1], and one fermion has to be separated from the rest. [less ▲] Detailed reference viewed: 22 (12 ULg) |
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