Higgs particle: associated production

Top PDF Higgs particle: associated production:

Uncertainties on exclusive diffractive Higgs boson and jet production at the LHC

Uncertainties on exclusive diffractive Higgs boson and jet production at the LHC

I. INTRODUCTION The Higgs boson is the last particle of the Standard Model remaining to be confirmed experimentally. Inclu- sive searches in decay channels such as b¯b, W + W − , ZZ, γγ and associated production have been performed at the Tevatron and are being started at the LHC. However the search for the Higgs boson at low mass is complicated due to the huge background coming from QCD jet events. Especially the b¯b channel, dominant for mH = 120 GeV, is very difficult at the Tevatron and literally impossible at the LHC. Thus other possibilities have been investigated, in particular using the exclusive diffractive production [1, 2]. In such processes both incoming hadrons, p¯ p at the Tevatron and pp at the LHC, remain intact after the interaction and the Higgs decays in the central region. The process involves the exchange of a color singlet and large rapidity gaps remain between the Higgs and the outgoing hadrons. At the Tevatron it is not possible to produce exclusively the Higgs boson due to the tiny cross section. However other particles, or systems of particles, can be produced, i.e. a pair of jets (a dijet), χc or γγ, as long as they have 0 ++ quantum numbers.
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Search for the Standard Model Higgs boson with the ATLAS experiment at the LHC leading to the observation of a new particle compatible with the Higgs boson

Search for the Standard Model Higgs boson with the ATLAS experiment at the LHC leading to the observation of a new particle compatible with the Higgs boson

for pp collisions at √ s = 7 TeV. They correspond to next-to-next-to-leading order (NNLO) in QCD for the gluon fusion [47–52] and vector boson fusion [53] and the associated production with a W or Z boson [54] processes. In addition, QCD soft- gluon resummations up to next-to-next-to-leading log (NNLL) are available for the gluon fusion process [55], while the NLO electroweak corrections are applied to the gluon fusion [56, 57], the vector-boson fusion [58, 59] and the associated production with a W or Z boson [60] processes. These cross section calculations do not take into account the width of the Higgs boson, which is implemented through a Breit-Wigner line shape applied at the event generator level. The Higgs boson decay branching ratio to the four-lepton final state is predicted by prophecy4f [18,61], including the complete NLO QCD and EW corrections with all interference and leading two-loop heavy Higgs boson corrections to the four-fermion width.
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Search for the associated production of the Higgs boson with a top quark pair in multilepton final states with the ATLAS detector

Search for the associated production of the Higgs boson with a top quark pair in multilepton final states with the ATLAS detector

category or a dilepton t¯t event to the 3` or 2`1τ had categor- ies. These backgrounds in the signal regions are expected to be dominated by t¯t or single top quark production with leptons produced in decays of heavy-flavour hadrons. Production of t¯t with an additional photon which converts in the detector mater- ial is a subdominant contribution. With the tight object selec- tion requirements applied in this analysis, almost all reconstruc- ted electron and muon objects correspond to real electrons and muons; the fraction arising from incorrect particle identification is negligible. Estimates of these backgrounds are obtained from data. Each channel has a slightly di fferent procedure, motivated by the specific event topology and the statistical power avail- able in the control regions. The methods are discussed below, and the expected non-prompt lepton contributions to the vari- ous categories are shown in Table 3 . In the following, a tight lepton is a lepton that passes the nominal selection, a sideband lepton is defined as a lepton candidate which satisfies di fferent criteria than the tight lepton selection (identification selection, isolation, or p T ), and (sideband) control regions either require
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Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector

Evidence for the associated production of the Higgs boson and a top quark pair with the ATLAS detector

35 ]. This article reports the results of a search for t ¯tH production using a dataset corresponding to an integrated luminosity of 36.1 fb −1 collected with the ATLAS detector at √ s = 13 TeV during 2015 and 2016. Examples of tree-level Feynman diagrams are given in Figure 1 where the Higgs boson is shown decaying to WW ∗ /Z Z ∗ or ττ. The search uses seven final states distinguished by the number and flavor of charged-lepton (electron, muon and hadronically decaying τ lepton) candidates, denoted l. In the following, the term “light lepton”, denoted `, refers to either electrons or muons and is understood to mean both particle and antiparticle as appropriate. These signatures are primarily sensitive to the decays H → WW ∗ (with subsequent decay to l νl ν or l νqq), H → τ + τ − and H → Z Z ∗ (with subsequent decay to ll νν or llqq), and their selection is designed to avoid any overlap with the ATLAS searches for t ¯tH production with H → b ¯ b [ 36 ], H → γγ [ 37 ] and H → Z Z ∗ → 4` [ 38 ] decays. Backgrounds to the signal arise from associated production of a top quark pair and a W or Z (henceforth V ) boson. Additional backgrounds arise from t ¯t production with leptons from heavy-flavor hadron decays and additional jets (non-prompt leptons), and other processes where the electron charge is incorrectly assigned (labeled as “q mis-id") or where jets are incorrectly identified as τ candidates. Backgrounds are estimated with a combination of simulation and data-driven techniques (labeled as “Pre-Fit”), and then a global fit to the data, in all final states, is used to extract the best estimate for the t ¯tH production rate and adjust the background predictions (labeled as “Post-Fit”).
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Particle Production in a Hadron Collider Rapidity Gap: The Higgs Case

Particle Production in a Hadron Collider Rapidity Gap: The Higgs Case

quarks are suppressed by a factor ∼ (25 GeV −2 )µ 2 0 with respect to those in which the gluons couple to the same quark line, and factorisation can be restored, for µ 0 ∼ 1 GeV. This kind of picture has recently been questioned on theoretical grounds [18], but it seems to remain the only one available which reproduces the observed properties of the pomeron. In the following, rather than worrying about the ultimate nature of the pomeron, we shall adopt the following pragmatic approach: we are after rates for the production of rare particles produced in a rapidity gap. This is very similar to single-diffractive processes and elastic processes, except that we need to insert a rare particle production vertex in the diagram. The best phenomenological description of such processes is two-gluon ex- change, multiplied by a pomeron s-dependence given by Eq. (2.1). We shall first set up the lowest-order perturbative calculation of Higgs production via two-gluon exchange. We shall then evaluate the importance of the IR region by using a constituent-gluon propagator which matches to the perturbative one at high k 2 [19]. The model hence contains several
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Hepatic stress associated with pathologies characterized by disturbed glucose production

Hepatic stress associated with pathologies characterized by disturbed glucose production

Mitochondrial dysfunction and ROS Mouse models have generated interesting data in regards to cell stress associated with GSDI. As previously men- tioned, G6Pase deficiency leads to hepatocyte metabolism characterized by the activation of glycolysis, de novo lipo- genesis, PPP and glycogen synthesis [22, 23]. Interestingly, hepatic mitochondrial dysfunction was reported, along with a striking decrease in basal respiration, ATP turnover, maximal respiration, and spare mitochondrial capacity [84]. The structure of mitochondria was abnormal and the mito- chondrial content was also decreased, probably due to decreased biogenesis. Another study confirmed this result in L.G6pc-/- mice, showing that lipid-mediated Sirtuin1 (SirT1) down-regulation entails a decrease in peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), and thus alters mitochondrial integrity, biogenesis, and function in GSDI hepatocytes [85]. The mitochondrial apop- tosis pathway is also activated [84]. Indeed, an increase in cytochrome c release, as well as activation of caspases 9 and 3 were reported in G6pc-knock down cells. Finally, mitochondrial dysfunction was linked to insulin resistance [80]. Despite this pathological mitochondrial phenotype, ROS levels were not increased in the cells, leaving room to speculate that oxidative stress might not be present in the case of GSDI. Furthermore, increased circulating levels of antioxidants reported in GSDI patients could contribute to the protection against oxidative stress [86]. Elevated circu- lating antioxidants could also protect GSDI patients against atherosclerosis, despite hyperlipidemia [87, 88]. It is note- worthy that hyperuricemia, albeit a pathological state, can also provide antioxidant defense, since plasma uric acid is also a potent low-molecular-weight antioxidant. However, within the cell, uric acid can have pro-oxidative roles as well, by forming radicals with other oxidants, rendering the effect of this metabolite in GSDI complex [89].
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Mesopelagic microbial carbon production correlates with diversity across different marine particle fractions

Mesopelagic microbial carbon production correlates with diversity across different marine particle fractions

less attention despite their known biogeochemical and cli- matic importance [ 23 ]. To date, concepts in ecological processes such as the relationships between secondary production and community diversity remain poorly studied. Here, we provide the first assessment of remineralization rates of heterotrophic prokaryotes coupled to their diversity associated to the non-sinking and fast-sinking fractions at four depths horizons of the mesopelagic zone in the North Atlantic Ocean. Thereby, the “non-sinking fraction” com- prises free-living prokaryotes and those attached to sus- pended particles, and the “fast-sinking fraction” refers to prokaryotes attached to fast-sinking particles (i.e., gravita- tional sinking particles) retrieved from the MSC. Measured PHP was used as an indicator of remineralization rates on fast-sinking and non-sinking prokaryotic fractions. Using 16 S rRNA sequencing, we identi fied key prokaryotic players and their potential ecological and metabolic func- tions to further predict prokaryotic processes involved in mesopelagic particle remineralization. In this study, we coupled cell-speci fic PHP rates (and further estimates of prokaryotic C loss rates) to prokaryotic species richness. Our results show that cell-speci fic rates vary little with depth on fast-sinking particles while they decrease strongly on non-sinking particles. Interestingly, microbial species richness decreases with depth for the fast-sinking particles while increases for non-sinking particles despite energetic resources being potentially available in fast-sinking parti- cles. Finally, we found a strong negative relationship between cell-speci fic PHP rates and species richness. While the underlying mechanisms driving such a pattern are still unclear, our results suggest this negative correlation may be a widespread ecological trait of mesopelagic prokaryotic communities. This potentially increases C sequestration as the ability of the fast-sinking particle prokaryotic commu- nity to degrade organic C may not be as ef ficient as the ability of the more diverse community observed in the non- sinking fraction at any depths.
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A-t-on trouvé le boson de Higgs ?

A-t-on trouvé le boson de Higgs ?

avancées en physique fondamentale, la presse a fait ses choux gras de la découverte possible du boson de Higgs, tout cela parce que cette particule avait été dénommée « Particule de Dieu » par le prix Nobel Leon M. Lederman dans son ouvrage de 1993 avec Dick Teresi, « The God Particle : If the Universe Is the Answer, What Is the Question ? ». Ce titre provocateur avait été plus ou moins imposé par l’éditeur. Les auteurs auraient plutôt penché pour la « Goddamn Particle » mais ils n’ont pas reculé devant un titre accrocheur et la perspective de meilleures ventes. Le boson de Higgs est un élément aussi insaisissable qu’es- sentiel pour la compréhension de la structure de la matière, et son importance, conjuguée à son intangibilité, peuvent en justifier une espèce de divinisation. C’est donc Dieu qui a
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The Quantum Critical Higgs

The Quantum Critical Higgs

Within the SM one does not expect large deviations from mean-field theory in the electroweak symmetry breaking sector: any such deviation would be the result of small quantum loop corrections involving perturbative couplings. As a consequence, non-trivial momentum dependence in the SM is typically sub-dominant, leading to form factors that are constant up to small corrections. Once the effects of the strong sector leading to the QPT are added via its n-point functions, deviations from mean-field theory are possible. By now the Higgs boson has been observed in several different channels at the LHC, with all results in agreement with the SM predictions. When the Higgs is embedded into a strong conformal sector, one therefore needs to ensure that the resulting deviations from the SM are not too large. We first present a general parameterization of the relevant Higgs amplitudes in terms of form factors, and then explore specific realizations of the strong conformal sector and their contributions to these form factors. We focus on those implementations where the corrections to already measured Higgs observables are expected to be small. The amplitudes can be divided into two sets: those where the measurement is made with all the legs on-shell (and the form factor reduces to a constant), and those measured with off-shell information, where additional momentum dependence is expected to appear.
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Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs

Constraints on the Higgs boson width from off-shell production and decay to Z-boson pairs

In this Letter, we present constraints on the Higgs boson width using its off-shell production and decay to Z-boson pairs, in the fi- nal states where one Z boson decays to an electron or a muon pair and the other to either an electron or a muon pair, H → ZZ → 4  (4  channel), or a pair of neutrinos, H → ZZ → 2  2 ν (2  2 ν chan- nel). Relying on the observed Higgs boson signal in the resonance peak region [7] , the simultaneous measurement of the signal in the high-mass region leads to constraints on the Higgs boson width Γ H in the 4  decay channel. The 2  2 ν decay channel, which ben- efits from a higher branching fraction [16,17] , is used in the high- mass region to further increase the sensitivity to the Higgs boson width. The analysis is performed for the tree-level HVV coupling of a scalar Higgs boson, consistent with our observations [4,7] , and implications for the anomalous HVV interactions are discussed. The Higgs boson mass is set to the measured value in the 4  decay channel of m H = 125 . 6 GeV [7] and the Higgs boson width is set to the corresponding expected value in the SM of Γ H SM = 4 . 15 MeV [8,9] .
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Extrapolating W-Associated Jet-Production Ratios at the LHC

Extrapolating W-Associated Jet-Production Ratios at the LHC

transverse momentum p V T , the matrix element would be maximized for an asymmetric con- figuration of jets, corresponding to a near-singular configuration of the partons. A typical configuration, for example, would have one hard jet recoiling against the vector boson, and additional jets (if any) with small transverse momenta just above the minimum jet transverse momentum. In these configurations, the short-distance matrix element will factorize into a matrix element for production of one hard gluon, and a singular factor (a splitting function in collinear limits, or an eikonal one in soft limits). The phase-space integrals over these near-singular configurations give rise to potentially large logarithms. Because the minimum jet–jet distance R is relatively large, collinear logarithms should not play an important role;
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Evidence for a Standard Model Higgs boson like particle decaying into four leptons with the CMS detector

Evidence for a Standard Model Higgs boson like particle decaying into four leptons with the CMS detector

6.1. Electrons This ECAL driven electron seeding strategy is very efficient for isolated electrons with p T e > 10 GeV. At lower p e T , the φ window used for the superclusters starts to be too small and some electrons which radiates lead to electron and photon clusters separated more than 0.3 rad in the magnetic field. Moreover, for the cases of electrons in jets, the energy collected in the superclusters may include some neutral contribution from the jets therefore biasing the energy measurement used to seed electron tracks. For these reasons, the above seeding strategy is complemented by a tracker driven algorithm, developed in the context of the Particle Flow (PF) event reconstruction [69]. The tracker driven seeding starts from the high purity tracks, and makes use of the particle flow clustering which exploits the fine ECAL granularity. The tracker driven seeding algorithm, described in details in [70], can be illustrated with two extreme cases. When an electron does not radiate energy by bremsstrahlung while traversing the tracker, it gives rise to a single cluster in the ECAL and its track is often well reconstructed by the standard Kalman Filter which is able in these cases to collect hits up to the ECAL entrance. The track can then be matched with a particle flow cluster, and its momentum compared to the cluster energy forming an E /p ratio. If this ratio is close to unity, the seed of the track is promoted to electron seed. Alternatively, when an electron undergoes a significant bremsstrahlung, the standard Kalman Filter is not able to follow the change of curvature, and the track has a small number of hits, and a large χ 2 . Thus, using the tracker as a preshower, and exploiting the differences of characteristics between a pion track and an electron track reconstructed with the standard Kalman Filter algorithm, the electron tracks can be selected. The variety of situations between the two extreme cases illustrated here require a treatment more sophisticated than what was just described. In practice, a refined treatment of the track is applied, and the pure tracking observables are combined with the ECAL-track matching quality variables in a single discriminator with a multivariate analysis.
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Search for doubly charged Higgs boson pair production in ppbar collisions at sqrt{s} = 1.96 TeV

Search for doubly charged Higgs boson pair production in ppbar collisions at sqrt{s} = 1.96 TeV

L ) > 112 − 150 GeV, assuming 100% decays into the specified final state [13–16]. The results in this Letter are based on data collected with the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of up to 7.0 fb −1 . The D0 detector [17] comprises tracking detec- tors and calorimeters. Silicon microstrip detectors and a scintillating fiber tracker are used to reconstruct charged particle tracks within a 2 T solenoid. The uranium and liquid-argon calorimeters used to measure particle ener- gies consist of electromagnetic (EM) and hadronic sec- tions. Muons are identified by combining tracks in the central tracker with patterns of hits in the muon spec- trometer. Events are required to pass triggers that select at least one muon candidate.
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The bestest little Higgs

The bestest little Higgs

collective quartic coupling for the Higgs is generated with the help of the electroweak singlet, but this is not a dangerous singlet [8] because it transforms under a global symmetry. For the gauge sector, we employed a modular gauge structure in order to decouple the mass of the gauge partners from the Higgs and top partners. We introduced a new non-linear sigma field which is a singlet under all the global symmetries which protect the Higgs, but which transforms under the same gauge symmetries. This new sector has a decay constant F that is higher than the decay constant for the Higgses f . In this way, we can raise the mass of the new gauge bosons to a few TeV, above the bound from precision electroweak measurements, without introducing fine-tuning in the top and Higgs sectors. This method for implementing collective gauge couplings is completely generic, and can be used as a model building tool for any little Higgs model. In our case, the phenomenological implication of this modular gauge structure was the appearance of a set of uneaten PNGB modes which fill out a 6 of SO(4).
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Wave-particle interactions associated with Io’s auroral footprint: Evidence of Alfvén, ion cyclotron, and whistler modes

Wave-particle interactions associated with Io’s auroral footprint: Evidence of Alfvén, ion cyclotron, and whistler modes

We have presented field and particle observations during Juno’s PJ12 crossing of the Io’s flux tube and showed how they are related in the context of wave-particle processes of a moon- magnetosphere interaction. Our conclusions are the following:  Identification of Alfvénic magnetic turbulence across a large frequency range. This observation, in concert with broadband precipitating electron fluxes, underlines Alfvénic acceleration as Jupiter’s primary auroral mechanism, as observed throughout the main and satellite footprint tail aurorae by numerous works.  A commonly proposed mechanism for ion energization is the ion cyclotron
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Ion production rate in a boreal forest based on ion, particle and radiation measurements

Ion production rate in a boreal forest based on ion, particle and radiation measurements

( Kulmala et al. , 2000b ). TSCs cannot be observed directly by standard aerosol size dis- 10 tribution measurements because of their small size (of order 1 nm). If the background particle concentration is so high that it hinders the particle growth to observable sizes, there can still be enough particles to cause an additional ion sink which can be seen from the di fference of calculated and radon and external radiation based measure- ments. It has been previously found that TSC’s can form nearly every day, but they can 15

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Syndecan 4 is involved in mediating HCV entry through interaction with lipoviral particle-associated apolipoprotein E

Syndecan 4 is involved in mediating HCV entry through interaction with lipoviral particle-associated apolipoprotein E

Figure 1. Ectopic expression of apoE dose-dependently stimulates HCV production. (A) Schematic of apoE mutants and apoE-derived peptide sequence. Receptor binding domain (RBD: amino acids 136–150) and heparan sulfate proteoglycan binding domain (HSPG-BD: amino acids 142–147) are represented. Mutations of the apoE HSPG-BD (apoEDHSPG-BD, apoE K143A, K146A, and apoE R142A, R145A) were generated by site- directed mutagenesis. (B) Huh7.5.1 cells were either co-electroporated (Co-EP) with luciferase-encoding HCV RNA (Luc-Jc1) and siRNA targeting endogenous apoE expression (siApoE) (2–7) or mock-transfected (1). 24 h post-transfection, cells were transduced with adenoviruses expressing GFP (Ad-CTRL) as a control, or with increasing concentrations of adenoviruses expressing wt apoE (Ad-apoE-wt), representing 1:100–1:5 dilutions, and numbered from 2 to 7 according to increasing concentration. Three days post-transduction, intracellular apoE, actin and HCV core expression was determined by immunoblot of cell lysates. (C) Extracellular culture supernatants of the cells from (B) with corresponding number designations were concentrated by sucrose cushion. ApoE, HCV E2, and core expression were tested by Western blot. (D) HCV infection from apoE modulated cells was conducted by exposing naı¨ve Huh7.5.1 cells to culture media from cells transfected with HCV RNA and transduced with increasing concentrations of Ad-apoE-wt or with Ad-CTRL with number designations corresponding to (B) and (D). 3d post-infection, infectivity was measured by luciferase reporter activity. HCVcc infection is expressed as a percentage relative to apoE-silenced cells transduced with Ad-CTRL. Results are expressed as mean6SD of the experiment performed in triplicate (** = P,0.001).
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Jet-associated deuteron production in pp collisions at $\sqrt{s}=13$ TeV

Jet-associated deuteron production in pp collisions at $\sqrt{s}=13$ TeV

statistical uncertainties, while the boxes show the total systematic uncertainty. Several independent sources of uncertainty associated with tracking, particle identification, sideband correction, and purity, as well as efficiency and acceptance were included into the total systematic uncer- tainty. Individual sources were estimated as follows: a) the DCA cut was narrowed from 0.5 (1.0) cm in the xy-plane (z-axis) to 0.1 (0.1) cm, b) the minimum number of TPC clusters for a track was increased from 70 to 90 hits, c) the TOF particle identification requirement on the mass-squared to be within 2 standard deviations of the mean mass was relaxed to 3 standard deviations, d) the mass-squared range used to select the sidebands was changed from 3–4 standard deviations from the mean to 4–5 standard deviations, e) the TPC particle identification requirement of agreement within three standard deviations was tightened to two standard deviations, f) the purity calculation from signal and background fit func- tions was compared to the purity found using bin-counting for the signal and a fit for the background, and g) the mixed-event correction in ∆ϕ was not applied. In addition, a ∆ϕ-independent uncertainty of 5% was applied to account for deficiencies in the deuteron efficiency and acceptance corrections. A separate purity and track selection efficiency was estimated for each change associated with the deuteron candidate track selection. The resulting variation (i.e. p/ε × A) was found to differ by less than 10% from the baseline value obtained using the standard selection.
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Le boson de Higgs et sa place dans le modèle standard

Le boson de Higgs et sa place dans le modèle standard

2) Des champs qui se ressentent Dans la partie traitant de la théorie quantique des champs, l’auteur introduit un paragraphe par : « Various fields – and the associated particles – may feel each other, i.e. they can interact ». Lorsque j’ai commencé la traduction, j’ai pensé qu’une traduction littérale, à savoir « Les champs peuvent se sentir les uns les autres » serait peu appropriée à un texte de ce niveau scientifique : donner un caractère trop « humain » aux champs ne servait pas vraiment le propos du texte. En réalité, c’est bien de cela dont il s’agit : les champs « ressentent leur présence mutuelle », c’est-à-dire qu’ils peuvent « savoir » si un autre champ est présent au point où ils sont. Ce concept fait référence au principe d’exclusion de Pauli, qui énonce que deux fermions ne peuvent pas se situer au même endroit au même moment 13 . Ce principe ne s’applique pas aux bosons, c’est-à-dire aux champs d’interaction. Il peut paraître difficile
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Constraints on anomalous Higgs boson couplings using production and decay information in the four-lepton final state

Constraints on anomalous Higgs boson couplings using production and decay information in the four-lepton final state

smaller number of parameters and fewer exotic-spin models, were obtained by ATLAS [17] . All the above studies considered the decay of an on-shell H bo- son to two vector bosons. The accumulated data in Run 1 were not sufficient for precision tests of anomalous interactions in as- sociated production, in off-shell production, or with fermions. Nonetheless, both CMS [14] and ATLAS [18] performed analyses of anomalous HVV interactions in VH and VBF production, respec- tively. Finally, the CMS experiment searched for anomalous HVV interactions in off-shell production of the H boson in pp → H → ZZ with Run 1 data [15] . Further measurements probing the tensor structure of the HVV and Hff interactions can test CP invariance
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