Leptophobic $Z^\prime$ in supersymmetry and where to find them
Jack Y. Araz
备注：
8 pages (10 with ref.), 6 figures. Text of the presentation at the 11th Int. Symposium Quantum Theory and Symmetries (July 1st to 5th, 2019, CRM, Univ. of Montreal), to be published in the proceedings (CRM Series on Mathematical Physics, Springer, 2020)
发表信息：
"Quantum Theory and Symmetries", edited by M. B. Paranjape et al. (CRM Series in Mathematical Physics, Springer, 2021), pp. 559-567
This report presents possible loopholes in heavy $Z^\prime$ searches which are concentrated around high mass resonances. We present a scenario where massive neutral vector boson $Z^\prime$, predicted by $E_6$-inspired $U(1)^\prime$ models, can become leptophobic due to kinetic mixing between $Z-Z^\prime$. Such a scenario can avoid high-mass dilepton resonance searches. Furthermore, we propose a channel through supersymmetric cascade decays to observe leptophobic $Z^\prime$. We show that it is possible to reach up to $8σ$ at $\sqrt{s} = 14$ TeV and 3 ab$^{-1}$ integrated luminosity. This report follows the steps of the work that has been conducted in ref. [arXiv:1711.06302].
We consider the exclusive flavor changing neutral current processes B -> M ν\barν (M= π, K, ρ, K^*) in the leptophobic Z^\prime model, in which the charged leptons do not couple to the extra Z^\prime boson. We find that these exclusive modes are very effective to constrain the leptophobic Z^\prime model. In the leptophobic Z^\prime model, additional right-handed neutrinos are introduced and they can contribute to the missing energy signal in B -> M + E_missing decays. Through the explicit calculations, we obtain quite stringent bounds on the model parameters, |U_{sb}^{Z^\prime}| \leq 0.29 and …
We study the exclusive flavor chancing neutral current process Lambda(b)-->Lambda neutrino antineutrino in the leptophobic Z-prime model, where charged leptons do not couple to the extra Z-prime boson. The branching ratio, as well as, the longitudinal,transversal and normal polarizations are calculated. It has been shown that all these physical observables are very sensitive to the existence of new physics beyond the standard model and their experimental measurements can give valuable information about it.
We consider the leptophobic $Z^\prime$ model which can appear naturally in the flipped SU(5) or string-inspired $E_6$ models. This model can be constrained by measurements of the $B\to M ν\barν$ decays and $Δm_s$. We find that although the latter give much stronger constraints on the coupling than the former, they are complementary to each other.
We consider a leptophobic Z^\prime scenario in a flipped SU(5) grand unified theory obtained from heterotic string theory. We show that the allowed Z^\prime mass, flavor conserving and flavor changing couplings of the Z^\prime to the down-type quarks are strongly constrained by the mass difference in B_s-\bar{B}_s system and the four branching ratios of B -> πK decays. It is shown that even under these constraints large deviations in direct and/or indirect CP asymmetries of B \to πK decays from the SM expectations are allowed. Especially it is possible to accommodate the apparent puzzling data…
Leptophobic Z^\prime gauge boson appears naturally in many grand unified theories, such as flipped SU(5) or string-inspired E_6 models. This elusive particle easily escapes the direct/indirect detections because it does not couple to charged leptons. However, it can generate flavor changing neutral current at tree level. In this letter, we show that the recently measured mass difference, Δm_s, in the B_s^0 -\bar{B}_s^0 system improves the previous bound of flavor changing effective coupling by about one order of magnitude, i.e irrespective of its phase, |U_{sb}^{Z^\prime}| \leq 0.036 for M_{Z^…
Searching for heavy vector bosons $Z^\prime$, predicted in models inspired by Grand Unification Theories, is among the challenging objectives of the LHC. The ATLAS and CMS collaborations have looked for $Z^\prime$ bosons assuming that they can decay only into Standard Model channels, and have set exclusion limits by investigating dilepton, dijet and to a smaller extent top-antitop final states. In this work we explore possible loopholes in these $Z^\prime$ searches by studying supersymmetric as well as leptophobic scenarios. We demonstrate the existence of realizations in which the $Z^\prime$ …
We perform a comprehensive analysis of the secluded UMSSM model, consistent with present experimental constraints. We find that in this model the additional $Z^\prime$ gauge boson can be leptophobic without resorting to gauge kinetic mixing and, consequently, also $d$-quark-phobic, thus lowering the LHC bounds on its mass. The model can accommodate very light singlinos as DM candidates, consistent with present day cosmological and collider constraints. Light charginos and neutralinos are responsible for muon anomalous magnetic predictions within 1$σ$ of the measured experimental value. Finally…
We consider the phenomenology of a naturally leptophobic $Z$-prime boson in the 1 to 10 GeV mass range. The $Z$-prime's couplings to leptons arise only via a radiatively-generated kinetic mixing with the $Z$ and photon, and hence are suppressed. We map out the allowed regions of the mass-coupling plane and show that such a $Z$-prime that couples to quarks with electromagnetic strength is not excluded by the current data. We then discuss possible signatures at bottom and charm factories.
The $Z'$-portal is one of most popular and well-explored scenarios of dark matter (DM). To avoid the strong constraints coming from dilepton resonance searches at the LHC and direct detection of DM, it is usually required that in addition to being leptophobic, the $Z'$ is axially coupled to either the (fermionic) DM or the standard model (SM) quarks. The first possibility has been extensively studied both in the context of simplified model and UV complete scenarios. However, the studies on the second possibiliy are largely confined to simplified models only. Here, we construct the minimal UV c…
The $U(1)$ extensions of the Standard Model contain a heavy neutral gauge boson $Z^\prime$. If leptophobic, the boson can evade the stringent bounds from the dilepton resonance searches. We consider two theoretically well-motivated examples of leptophobic $U(1)$ extensions in which the $Z'$ decays to right-handed neutrinos (RHNs) with substantial branchings. The coexistence of a leptophobic $Z^\prime$ and the RHNs opens up a new possibility of searching for these particles simultaneously through the production of a $Z^\prime$ at the LHC and its decay to a RHN pair. For this decay to occur, the…
The decays of $η$ and $η^\prime$ mesons provide unique opportunities for testing the properties of low energy Quantum Chromodynamics and for the search of new physics beyond the Standard Model. However, recent experimental results on the rare decays of $η^{\left(\prime\right)}\rightarrowπ^0\left(η\right)γγ$ cannot be self-consistently described by the combination of the Vector Meson Dominance and Linear Sigma Model employing the same set of parameters. We show that this tension can be attributed to the presence of a leptophobic dark photon $\mathcal{B}$, and find representative values of the p…
We discuss the 750 GeV diphoton excess at the LHC@13TeV in the framework of leptophobic U(1)$^\prime$ model inspired by $E_6$ grand unified theory (GUT). In this model, the Standard Model (SM) chiral fermions carry charges under extra U(1)$^\prime$ gauge symmetry which is spontaneously broken by a U(1)$^\prime$-charged singlet scalar ($Φ$). In addition, extra quarks and leptons are introduced to achieve the anomaly-free conditions, which is a natural consequence of the assumed $E_6$ GUT. These new fermions are vectorlike under the SM gauge group but chiral under new U(1)$^\prime$, and their ma…
The sensitivity of the rare decays $η^{(\prime)}\toπ^{0}γγ$ and $η^{\prime}\toηγγ$ to signatures of a leptophobic $B$ boson in the MeV-GeV mass range is analyzed in this work. By adding an explicit $B$-boson resonance exchange, $η\to Bγ\toπ^{0}γγ$, to the Standard Model contributions from vector and scalar meson exchanges, and employing experimental data for the associated branching ratios, it allows us to improve the current constraints on the $B$-boson mass $m_{B}$ and coupling to Standard Model particles $α_{B}$. From these constraints and the analysis of the available experimental $γγ$ inv…
The resonant excesses around 2 TeV reported by the ATLAS Collaboration can be explained in the left-right model, and the tight constraints from lepton plus missing energy searches can be evaded if the $SU(2)_R$ gauge symmetry is leptophobic. We for the first time propose an anomaly free leptophobic left-right model with gauge symmetry $SU(3)_C \times SU(2)_L \times SU(2)_R \times U(1)_{X}$ where the SM leptons are singlets under $SU(2)_R$. The gauge anomalies are cancelled by introducing extra vector-like quarks. The mass of $Z^\prime$ gauge boson, which cannot be leptophobic, is assumed to be…
A broad class of supersymmetric extensions of the standard model predict a Z' vector boson whose mass is naturally in the range 250 GeV < M_Z' < 2 TeV. To avoid unacceptably large mixing with the Z, one requires either a discrete tuning of the U(1)' charges or a leptophobic Z'. Both cases are likely to arise as the low energy limits of heterotic string compactifications, but a survey of existing realistic string models provides no acceptable examples. A broken U(1)' leads to additional D-term contributions to squark, slepton, and Higgs masses, which depend on the U(1)' charge assignments and t…
In light of the recent experimental data from $B$ factories, We try to explain the large branching ratio (compared to the Standard Model prediction) of the decay $B^{\pm}\to η' K^{\pm}$ in the context of R-parity violating ($\rpv$) supersymmetry. We investigate other observed $η^{(\prime)}$ modes and find that only two pairs of $\rpv$ coupling can satisfy the requirements without affecting the other $B \to PP$ and $B \to VP$ decay modes except the mode $B \to ϕK$. We also calculate the CP asymmetry for the observed decay modes affected by the new couplings.
Combining anomaly with $Z^\prime$ mediation allows us to solve the tachyonic problem of the former and avoid fine tuning in the latter. This model includes an extra $U(1)^\prime$ gauge symmetry and extra singlet scalar $S$ which provides a solution to the `$μ$ problem' of the Minimal Supersymmetric Standard Model (MSSM). The low-energy particle spectrum is calculated from the UV inputs using the Renormalization Group Equations. The benchmark points considered in the original model, suggested before the Higgs discovery, predicted a Higgs mass heavier than the generic MSSM value. In 2012, the Hi…
The R-parity non-conservation phenomenology within the minimal supersymmetric standard model with gauge mediated supersymmetry breaking has been studied. New constraints on the lepton number violating constant $λ_{111}^\prime$ were imposed by non-observability of the neutrinoless double beta decay. We find that $λ_{111}^\prime$ depends strongly on the effective supersymmetry breaking scale $Λ$ only and deduce limits which are much stronger than those previously found in literature.
I give a pedagogical introduction into flavour-changing neutral current interactions of kaons and their role to reveal or constrain physics beyond the Standard Model (SM). Then I discuss the measure $ε_K^\prime$ of direct CP violation in $K\to ππ$ decays, which deviates from the SM prediction by $2.8σ$. A supersymmetric scenario with flavour mixing among left-handed squarks can accomodate the measured value of $ε_K^\prime$ even for very heavy sparticles, outside the reach of the LHC. The considered scenario employs mass splittings among the right-handed up and down squarks (to enhance $ε_K^\pr…
We present a new technique for tagging heavy-flavor jets with p_T > 500 GeV called "mu_x tagging." Current track-based methods of b-jet tagging lose efficiency and experience a large rise in fake rate in the boosted regime. Using muons from B hadron decay, we combine angular information and jet substructure to tag b jets, c jets, light jets, and "light-heavy" jets (those containing B hadrons from gluon splitting). We find tagging efficiencies of epsilon_b = 14%, epsilon_c = 6.5%, epsilon_{light-light} = 0.14%, and epsilon_{light-heavy} = 0.5%, respectively, that are nearly independent of trans…
The quantities $ε_K^\prime$ and $ε_K$ measure the amount of direct and indirect CP violation in $K\to ππ$ decays, respectively. Using the recent lattice results from the RBC and UKQCD Collaborations and a new compact implementation of the $ΔS=1$ renormalization group evolution we predict $ \mbox{Re}\, \frac{ε_{K}'}{ε_{K}} = \left(1.06 \pm 5.07 \right) \times 10^{-4}$ in the Standard Model. This value is $2.8\,σ$ below the experimental value of $ \mbox{Re}\, \frac{ε_{K}'}{ε_{K}} = \left(16.6 \pm 2.3 \right) \times 10^{-4}.$ In generic models of new physics the well-understood $ε_K$ precludes la…
A supersymmetric extension of the $U(1)\times U(1)^{\prime }$-Higgs bosonic superconducting cosmic string model is considered,and the constraints imposed upon such a model due to renormalizability, supersymmetry, and gauge invariance are examined. For a simple model with a single $U(1)$ chiral superfield and a single $% U(1)^{\prime }$ chiral superfield, the Witten mechanism for bosonic superconductivity (giving rise to long range gauge fields outside of the string) does not exist. The simplest model that can accommodate the requisite interactions requires five chiral supermultiplets. This sup…
We present a detailed analysis together with exact numerical calculations on one-loop contributions to neutron electric dipole moment from supersymmetry without R-parity, focusing on the gluino, chargino, and neutralino contributions. Apart from the neglected family mixing among quarks, complete formulae are given for the various contributions, through the quark dipole operators, to which the present study is restricted. We discuss the structure and main features of the R-parity violating contributions and the interplay between the R-parity conserving and violating parameters. In particular, t…
I present a new scheme for tagging boosted heavy flavor jets called "$μ_x$ tagging" and its application to TeV-scale physics beyond the Standard Model. Using muons from B hadron decay to define a particular combination "x" of angular information, and jet substructure variables, we identify a clean ($ε_{\mathrm{fake}}/ε_b\sim 1/100$) good efficiency ($ε_b = 14\%$) tag. I demonstrate the usefulness of this new scheme by showing the reach for discovery of leptophobic $Z^\prime\to b\bar b$ and $tH^\pm\to t t b$.
We propose a supersymmetric SU(5) orbifold GUT in 5 dimensions in which supersymmetry breaking at the boundaries give rise to split supersymmetry spectrum. The extra dimension is compactified on a $S^1/Z_2 \times Z_2^\prime$ orbifold having two fixed points. The standard model fermions are localized in the standard model brane, where supersymmetry is broken by the nonvanishing of the F-term of a superfield X at some intermediate scale. All scalar superpartners acquires mass at this stage. The standard model gauginos and higgsinos remain light, since their masses are protected by R-symmetry and…
We present a systematic analysis of all the contributions at the leading log order to the branching ratio of the inclusive radiative B decay, B --> X_s + gamma in the framework of supersymmetry without R-parity. The relevant set of four-quark operators involved in QCD running are extended from 6 (within SM and MSSM) to 24, with also many new contributions to the Wilson coefficients of (chromo)magnetic penguins for either chiral structure. We present complete analytical results here without any a priori assumptions on the form of R-parity violation. Mass eigenstate expressions are given, hence …
We study the corrections to $ε^\prime /ε$ in the minimal supersymmetric model at the leading order in QCD and QED. Supersymmetry can increase the standard model prediction for $ε^\prime /ε$ by at most 40\% for $m_t=174$ GeV, an enhancement which is indistinguishable from the present theoretical uncertainties. The most conspicuous effect of supersymmetry is a strong depletion of $ε^\prime /ε$. For certain choices of supersymmetric parameters, vanishing and even small negative values of $ε^\prime /ε$ can be obtained for the top quark in the CDF range.
We present a detailed analysis of the neutron, deuteron and mercury electric dipole moment from supersymmetry without R parity, focusing on the quark-scalar loop contributions. Being proportional to top Yukawa and top mass, such contributions are often large. Analytical expressions illustrating the explicit role of the R-parity violating parameters are given following perturbative diagonalization of mass-squared matrices for the scalars. Dominant contributions come from the combinations $B_i λ^{\prime}_{ij1}$ for which we obtain robust bounds. It turns out that neutron and deuteron EDMs receiv…
It is a well--known problem that in supersymmetric models there are new CP--violating phases which, if unsuppressed, would give a neutron electric dipole moment $10^2$ to $10^3$ times the present experimental limit. Here we propose that these new phases are suppressed by CP invariance, which is broken spontaneously at a high scale and that this breaking shows up at low energies only through a universal phase of the gaugino masses. It is shown that this can well fit both $ε$ and $ε^\prime$ of the neutral Kaon system. The electric dipole moments of the neutron and the electron should be not much…
We propose that the $γ+ E \hspace{-.5em}/\;\:$ signal at the Belle-II will be a smoking gun for supersymmetry (SUSY) in the presence of a gauged $U(1)_{L_μ-L_τ}$ symmetry. A striking consequence of breaking the enhanced symmetry in the limit of degenerate (s)leptons is the nondecoupling of the radiative contribution of heavy charged sleptons, appearing in SUSY, to the $γ- Z^\prime$ kinetic mixing. The signal process, $e^+ e^- \rightarrow γZ^\prime \rightarrow γ+ E \hspace{-.5em}/\;\:$, is an outcome of this ubiquitous feature. We take into account the severe constraints on gauged $U(1)_{L_μ-L_…
The severe constraints imposed on the parameter space of the minimal split supersymmetry model by the infrared fixed point solution of the top Yukawa coupling $Y_t$ are studied in detail in terms of the value of the top quark mass measured at the Tevatron together with the lower bound on the lightest Higgs mass established by LEP. The sensitive dependence of the higgsino mass parameter $μ$ and of the gaugino coupling strengths ${\tilde g}_{u,d}$, ${\tilde g}^\prime_{u,d}$ on the value of $Y_t$ in the vicinity of the Landau pole is a remarkable consequence. A few other interesting features emer…
The electroweak phase transition (EWPT) in the secluded-$U(1)'$-extended MSSM (sMSSM) is studied. Using the effective potential at zero and finite temperatures, we search for the non-MSSM-like EWPT in which the light stop mass is larger than the top quark mass. Scanning the parameters relevant to the EWPT, the upper limits of the Higgs boson masses, which are consistent with the strong first order EWPT, are derived. For the lightest CP-even and -odd Higgs bosons, we find $m_{H_1}<160$ GeV and $m_{A_1}<250$ GeV, respectively. In the sMSSM, the tree-level CP violation is possible by the complex …
Supersymmetry is a prime candidate for physics beyond the Standard Model because low-energy supersymmetry stabilizes the Higgs mass avoiding fine-tuning and leads to natural electroweak symmetry breaking. However, searches at the Large Hadron Collider (LHC) for supersymmetric particles have not found any signal and give strong limits on mass of gluino and squark. Also, the observed Higgs mass of 125 GeV is not easily accommodated in the minimal supersymmetric Standard Model (MSSM) where one has to rely on the radiative corrections to boost the Higgs mass accompanied with fine-tuning. I study a…
We consider the effects of R-parity violation due to the inclusion of a bilinear $μ^\prime L H_u$ superpotential term in high scale supersymmetric models with an EeV scale gravitino as dark matter. Although the typical phenomenological limits on this coupling (e.g. due to lepton number violation and the preservation of the baryon asymmetry) are relaxed when the supersymmetric mass spectrum is assumed to be heavy (in excess of the inflationary scale of $3 \times 10^{13}$ GeV), the requirement that the gravitino be sufficiently long-lived so as to account for the observed dark matter density, le…
We study minimal benchmark models of dark matter with an extra anomaly-free U(1)' gauge boson Z'. We find model parameters that give rise to the correct cosmological dark matter density while evading the latest direct detection searches for dark matter scattering produced by the XENON1T experiment, including the effects of Z-Z' mixing. We also find regions of parameter space that evade the constraints from LHC measurements of dileptons and dijets, precision electroweak measurements, and LHC searches for monojet events with missing transverse energy. We study two benchmark Z' models with Y-sequ…
Natural realisations of supersymmetry require light stops ${\tilde t}_1$, making them a prime target of LHC searches for physics beyond the Standard Model. Depending on the kinematic region, the main search channels are ${\tilde t_1}\to t \tilde χ^0_1$, ${\tilde t_1}\to W b \tilde χ^0_1$ and ${\tilde t_1}\to c \tilde χ^0_1$. We first examine the interplay of these decay modes with ${\tilde c_1}\to c \tilde χ^0_1$ in a model-independent fashion, revealing the existence of large regions in parameter space which are excluded for any ${\tilde t_1}\to c \tilde χ^0_1$ branching ratio. This effect is…
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The discovery of the long awaited Higgs boson is described using data from the CMS detector at the LHC. In the SM the masses of fermions and the heavy gauge bosons are generated by the interactions with the Higgs field, so all couplings are related to the observed masses. Indeed, all observed couplings are consistent with the predictions from the Higgs mechanism, both to vector bosons and fermions implying that masses are indeed consistent of being generated by the interactions with the Higgs field. However, on a cosmological scale the mass of the universe seems not to be related to the Higgs …
In the framework of R-parity violating (\rpv) supersymmetry, we try to find a consistent explanation for both recently measured CP asymmetry in B^0 --> phi K_S decay and the large branching ratio of B^{+/-} --> eta' K^{+/-} decay, which are inconsistent with the Standard Model (SM) prediction. We also investigate other charmless hadronic B --> PP and B --> VP decay modes whose experimental data favor the SM: for instance, recently measured CP asymmetries in B^0 --> eta^{prime} K_S and B^0 --> J / Psi K_S. We find that all the observed data can be accommodated for certain values of \rpv couplin…
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