arXiv subjects

Abdesslam Arhrib

Publications and source records attributed to Abdesslam Arhrib.

At least 73 records · Page 4Linked to original sources

arXiv2010

Forward-backward asymmetry of top quark in diquark models

Motivated by the recent unexpected large forward-backward asymmetry (FBA) of the top quark observed by D$Ø$ and CDF at the Tevatron, we investigate a possible explanation for the anomaly within the framework of diquark models. Unlike other mechanisms induced by s-channel or t-channel, the top-quark pair production in the diquark models is dictated by the u-channel diagram. We find that the color-triplet diquark can generate the FBA of 20% when the constraint from the cross section of the top-quark pair production is taken into account.

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arXiv2010

Lepton flavor violating tau decays in type-III seesaw mechanism

In this paper, the lepton flavor violating $τ\to \ell P(V)$ ($P,V= π^0, η, η^{\prime}, ρ^0, ω, ϕ$) and $τ\to 3\ell$ ($\ell = e, μ$) decays are studied in the framework of the type-III seesaw model, in which new triplet fermions with a zero hypercharge (Y=0) interact with ordinary lepton doublets via Yukawa couplings, and affect tree-level leptonic Z-boson couplings. We investigate the experimental bound from the leptonic Z decay to get contraint on the exsiting parameters space. We predict that the upper limits on the branching ratios of $τ\to \ell P(V)$ and $τ\to 3\ell$ can reach the experimental current limits.

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arXiv2010

Double Neutral Higgs production in the Two-Higgs doublet model at the LHC

In this work we study the production and decay of two CP-even Higgs bosons in the general CP-conserving two-Higgs doublet model at the LHC. We also study the limiting case of the decoupling scenario. For each Yukawa version of the model, we look for the region of the parameter space where a signal would be seen at the LHC. Taking into account theoretical and experimental constraints on the two Higgs doublet model parameters, we show that the cross section can be two orders of magnitude above the corresponding Standard Model cross section. We have also studied in detail the decay profile of the Higgs bosons and showed that interesting signatures may emerge for some particular values of the parameters. In some scenarios, specific triple Higgs could be measured.

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arXiv2009

Higgs boson enhancement effects on squark-pair production at the LHC

We study the Higgs boson effects on third-generation squark-pair production in proton-proton collision at the CERN Large Hadron Collider (LHC), including $\Stop \Stop^*$, $\Stop\Sbot^*$, and $\Sbot \Sbot^*$. We found that substantial enhancement can be obtained through s-channel exchanges of Higgs bosons at large $\tanβ$, at which the enhancement mainly comes from $b\bar b$, $b\bar c$, and $c\bar b$ initial states. We compute the complete set of electroweak (EW) contributions to all production channels. This completes previous computations in the literature. We found that the EW contributions can be significant and can reach up to 25% in more general scenarios and at the resonance of the heavy Higgs boson. The size of Higgs enhancement is comparable or even higher than the PDF uncertainties and so must be included in any reliable analysis. A full analytical computation of all the EW contributions is presented.

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arXiv2009

CP Violation in Fourth Generation Quark Decays

We show that, if a fourth generation is discovered at the Tevatron or LHC, one could study CP violation in b' \to s decays. Asymmetries could reach 30% for b'\to sZ for m_{b'} \lesssim 350 GeV, while it could be greater than 50% for b'\to sγand extend to higher m_{b'}. Branching ratios are 10^{-3}--10^{-5}, and CPV measurement requires tagging. Once measured, however, the CPV phase can be extracted with little theoretical uncertainty.

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arXiv2009

Neutral Higgs boson pair production in photon-photon annihilation in the Two Higgs Doublet Model

We study double Higgs production in photon-photon collisions as a probe of the new dynamics of Higgs interactions in the framework of two Higgs Doublet Models. We analyze neutral Higgs bosons production and decay in the fusion processes, $γγ\to S_iS_j$, $S_i=h^0, H^0, A^0$, and show that both $h^0h^0$ and $A^0A^0$ production can be enhanced by threshold effects in the region $E_{γγ}\approx 2 m_{H\pm}$. Resonant effects due to the heavy Higgs, $H^0$, can also play a role in the cross section enhancement when it is allowed to decay to two light CP-even $h^0$ or to two light CP-odd $A^0$ scalars. We have scanned the allowed parameter space of the Two Higgs Doublet Model and found a vast region of the parameter space where the cross section is two orders of magnitude above the Standard Model cross section. We further show that the Standard Model experimental analysis can be used to discover or to constraint the two Higgs doublet model parameter space.

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arXiv2009

Collider Signatures for Heavy Lepton Triplet in Type I+III Seesaw

The minimal SU(5) theory augmented by the fermionic adjoint representation restores the coupling constant unification and gives realistic neutrino masses and mixing through the hybrid Type I and Type III seesaw. The crucial prediction of the theory is an SU(2) lepton triplet with the mass below TeV. We study the signature of these heavy leptons and propose the strategy to test this mechanism at the hadron and lepton colliders. The smoking gun evidence of the theory is Delta L=2 lepton number violation through events of a pair of like-sign leptons plus four jets without significant missing energy at hadron colliders. We find that via this unique channel, the heavy lepton can be searched for up to a mass of 200 GeV at the Tevatron with 8 fb^-1, and up to 450 (700) GeV at the LHC of 14 TeV C.M.energy with 10 (100) fb^-1. The signal rate at the 10 TeV LHC is reduced to 60-35% for a mass of 200-700 GeV. We also comment on how to distinguish this theory from other models with similar heavy leptons. Finally, we compare the production rates and angular distributions of heavy leptons in e+e- collisions for various models.

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arXiv2008

Charged Higgs in the NMSSM

The charged Higgs boson decays $H^\pm\to W^\pm A_1$ and $H^\pm\to W^\pm h_i$ are studied in the framework of the next-to Minimal Supersymmetric Standard Model (NMSSM). It is found that the decay rate for H^\pm\to W^\pm A_1 can dominate both below and above the top-bottom threshold. We suggest that p p\to H^\pm A_1 is a promising discovery channel for a light charged Higgs boson in the NMSSM with small or moderate \tanβand dominant decay mode H^\pm \to W^\pm A_1 which leads to W^\pm A_1 A_1. This W^\pm A_1 A_1 signature can also arise from the Higgsstrahlung process pp\to W^\pm h_1 followed by the decay h_1\to A_1 A_1. It is shown that there exist regions of parameter space where these processes can have comparable cross sections and we suggest that their respective signals can be distinguished at the LHC by using appropriate reconstruction methods.

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arXiv2008

Search for a light fermiophobic Higgs boson produced via gluon fusion at Hadron Colliders

In this study, we propose new Higgs production mechanisms with multi-photon final states in the fermiophobic limit of the Two Higgs Doublet Model. The processes are: gg -> hh, gg -> H h followed by H -> h h and gg -> A h followed by A -> h Z. In the fermiophobic limit, gg -> h h and gg -> A h -> h h Z would give rise to 4 photon signature while gg -> H h -> h h h can give a 6 photon final state. We show that both the Fermilab Tevatron and CERN's Large Hadron Collider can probe a substantial slice of the parameter space in this fermiophobic scenario of the Two Higgs Doublet Model. If observed the above processes can give some information on the triple Higgs couplings involved.

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arXiv2008

Probing triple Higgs couplings of the Two Higgs Doublet Model at Linear Collider

We study double Higgs production at the future Linear Collider in the framework of the Two Higgs Doublet Models through the following channels: $e^+e^- \to Φ_i Φ_j Z$, $Φ_i=h^0, H^0, A^0, H^\pm$. All these processes are sensitive to triple Higgs couplings. Hence observations of them provide information on the triple Higgs couplings that help reconstructing the scalar potential. We also discuss the double Higgs-strahlung $e^+e^- \to h^0 h^0 Z$ in the decoupling limit where $h^0$ mimics the SM Higgs boson. The processes $e^+e^- \to h^0 h^0 Z$ and $e^+e^- \to h^0 H^0 Z$ are also discussed in the fermiophobic limit where distinctive signatures such as $4γ+X$, $2γ+X$ and $6γ+X$ are expected in the Type-I Two Higgs Doublet Model.

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arXiv2008

Charged Higgs bosons in the Next-to MSSM (NMSSM)

The charged Higgs boson decays $H^\pm\to W^\pm A_1$ and $H^\pm\to W^\pm h_i$ are studied in the framework of the next-to Minimal Supersymmetric Standard Model (NMSSM). It is found that the decay rate for $H^\pm\to W^\pm A_1$ can exceed the rates for the $τ^\pmν$ and $tb$ channels both below and above the top-bottom threshold. The dominance of $H^\pm\to W^\pm A_1$ is most readily achieved when $A_1$ has a large doublet component and small mass. We also study the production process $pp\to H^\pm A_1$ at the LHC followed by the decay $H^\pm\to W^\pm A_1$ which leads to the signature $W^\pm A_1 A_1$. We suggest that $p p\to H^\pm A_1$ is a promising discovery channel for a light charged Higgs boson in the NMSSM with small or moderate $\tanβ$ and dominant decay mode $H^\pm \to W^\pm A_1$. This $W^\pm A_1 A_1$ signature can also arise from the Higgsstrahlung process $pp\to W^\pm h_1$ followed by the decay $h_1\to A_1 A_1$. It is shown that there exist regions of parameter space where these processes can have comparable cross sections and we suggest that their respective signals can be distinguished at the LHC by using appropriate reconstruction methods.

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arXiv2007

H-> WZ and H->Wgamma in the MSSM

We study the complete one loop contribution to $H^\pm\to W^\pm Z$ and $H^\pm \to W^\pm γ$ in the Minimal Supersymmetric Standard Model (MSSM).

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arXiv2007

CP violation in Charged Higgs Bosons decays $H^\pm \to W^\pm (γ, Z)$ in the Minimal Supersymmetric Standard Model (MSSM)

One loop mediated charged Higgs bosons decays $H^\pm\to W^\pm V$, $V= Z, γ$ are studied in the Minimal Supersymmetric Standard Model (MSSM) with and without CP violating phases. We evaluate the MSSM contributions to these processes taking into account $B\to X_sγ$ constraint as well as experimental constraints on the MSSM parameters. In the MSSM, we found that in the intermediate range of $\tanβ\la 10$ and for large A_t and large $μ$, where the lightest top squark becomes very light and hence non-decoupled, the branching ratio of $H^\pm \to W^{\pm} Z$ can be of the order 10^{-3} while the branching ratio of $H^\pm \to W^{\pm} γ$ is of the order 10^{-5}. We found also that the CP violating phases of soft SUSY parameters can modify the branching ratio by about one order of magnitude. We also show that MSSM with CP violating phases lead to CP-violating asymmetry in the decays $H^+ \to W^+V$ and $H^- \to W^-V$. Such CP asymmetry can be rather large and can reach 80% in some region of parameter space.

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arXiv2007

Flavor Changing Higgs Decays in Supersymmetry with Minimal Flavor Violation

We study the flavor changing neutral current decays of the MSSM Higgs bosons into strange and bottom quarks. We focus on a scenario of minimum flavor violation here, namely only that induced by the CKM matrix. Taking into account constraint from $b\to s γ$, $δρ$ as well as experimental constraints on the MSSM spectrum, we show that the branching ratio of $(Φ\to b\bar{s})$ and $(Φ\to \bar{b}s)$ combined, for $Φ$ being either one of the CP even Higgs states, can reach the order $10^{-4}$-$10^{-3}$ for large $\tanβ$, large $μ$, and large $A_t$. The result illustrates the significance of minimal flavor violation scenario which can induce competitive branching fraction for flavor changing Higgs decays. This can be compared with the previous studies where similar branching fraction has been reported, but with additional sources of flavor violations in squark mass matrices. We also discuss some basic features of the flavor violating decays in the generic case.

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arXiv2007

Left-Right squarks mixings effects in Charged Higgs Bosons decays $H^\pm \to W^\pm (γ, Z)$ in the MSSM

We study the complete one loop contribution to $H^\pm\to W^\pm V$, $V= Z, γ$, in the Minimal Supersymmetric Standard Model (MSSM). We evaluate the MSSM contributions taking into account $B\to X_sγ$ constraint as well as experimental constraints on the MSSM parameters. In the MSSM, we found that in the intermediate range of $\tanβ\la 10$ and for large $A_t$ and large $μ$, where lightest stop becomes very light and hence squarks contribution is not decoupling, the branching ratio of $H^\pm \to W^{\pm} Z$ can be of the order $10^{-3}$ while the branching ratio of $H^\pm \to W^{\pm} γ$ is of the order $10^{-5}$. We also study the effects of the CP violating phases of Soft SUSY parameters and found that they can modify the branching ratio by about one order of magnitude.

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arXiv2006

The light pseudoscalar Higgs boson in NMSSM

We study the associated production of a very light pseudoscalar Higgs boson with a pair of charginos. The novel signature involves a pair of charged leptons from chargino decays and a pair of photons from the pseudoscalar Higgs boson decay, plus large missing energy at the LHC and ILC. The signal may help us to distinguish the NMSSM from MSSM, provided that the experiment can resolve the two photons from the decay of the pseudoscalar Higgs boson.

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arXiv2006

Associated production of a light pseudoscalar Higgs boson with a chargino pair in the NMSSM

In the next-to-minimal supersymmetric standard model (NMSSM), the unique $λS H_u H_d$ in the superpotential gives rise to a coupling involving the lighter pseudoscalar Higgs boson and a pair of charged or neutral Higgsinos, even in the limit of zero mixing between the two pseudoscalar Higgs bosons. We study the associated production of a very light pseudoscalar Higgs boson with a pair of charginos. The novel signature involves a pair of charged leptons from chargino decays and a pair of photons from the pseudoscalar Higgs boson decay, plus large missing energy at the LHC and ILC. The signal may help us to distinguish the NMSSM from MSSM, provided that the experiment can resolve the two photons from the decay of the pseudoscalar Higgs boson.

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arXiv2006

Searching for a CP-odd Higgs via a pair of gauge bosons at the LHC

The CP-odd Higgs boson $A^0$ of the Minimal Supersymmetric Standard Model (MSSM) and Two Higgs Doublet Model (2HDM) will usually decay into the heaviest possible fermion -- antifermion pair available. The $A^0 \to VV$ decay where, $V =γ, Z, W^\pm$, and gluons are of particular interest as they are not allowed at tree level and hence they may offer information about the underlying new physics that enters at one loop level. In this paper all branching ratios of the CP-odd Higgs boson $A^0$ both in the MSSM and 2HDM are presented for this channel including all relevant Standard Model (SM) and MSSM particles. This discovery channel might provide an opportunity to search for a CP-odd Higgs boson at the Large Hadron Collider (LHC) and new physics beyond the Standard Model. Expressions for these decays are given in the Appendices.

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