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Hye-Sung Lee

Publications and source records attributed to Hye-Sung Lee.

At least 73 records · Page 4Linked to original sources
arXiv2010

Gauged B-x_i L origin of R parity and its implications

Gauged B-L is a popular candidate for the origin of the conservation of R parity, i.e. R = (-)^{3B+L+2j}, in supersymmetry, but it fails to forbid the effective dimension-five terms arising from the superfield combinations QQQL, uude, and uddN, which allow the proton to decay. Changing it to B-x_i L, where x_e+x_μ+x_τ=3 (with x_i not equal to 1) for the three families, would forbid these terms while still serving as a gauge origin of R parity. We show how this is achieved in two minimal models with realistic neutrino mass matrices, and discuss their phenomenological implications.

hep-ph↗
arXiv2010

Bound on Z' Mass from CDMS II in the Dark Left-Right Gauge Model II

With the recent possible signal of dark matter from the CDMS II experiment, the Z' mass of a new version of the dark left-right gauge model (DLRM II) is predicted to be at around a TeV. As such, it has an excellent discovery prognosis at the operating Large Hadron Collider.

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arXiv2009

Six-Lepton Z' Resonance at the Large Hadron Collider

New physics models admit the interesting possibility of a Z' weak boson associated with an extra U(1) gauge symmetry and a Higgs boson that is heavy enough to decay into a pair of Z bosons. Then Z' production and decay via Z' -> ZH -> ZZZ has a distinctive LHC signal that is nearly background free and reconstructs the H and Z' masses and widths. The Z' decay to 3 pairs of leptons is especially distinctive. The ZH decay mode exists even if the Z' is decoupled from leptons, which motivates an independent 6-lepton resonance search regardless of the dilepton search results.

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arXiv2009

New physics search at the LHC via Z' resonance

A new Abelian gauge symmetry U(1)' is well motivated to extend the standard model or supersymmetric standard model. Leptonic Z' resonances are clean signals even at the hadron colliders. We discuss how 4-lepton and 6-lepton Z' resonances can help the search for Supersymmetry and Higgs, respectively, at the LHC.

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arXiv2009

Dileptons and four leptons at Z' resonance in the early stage of the LHC

The LHC era just began. The first discovery at the LHC experiment would be arguably a new resonance pole at TeV scale, if it exists. While the discovery of the Z' would be exciting by itself, it may also suggest what other new physics signals should be looked for while the LHC experiment is still at its early stage. We argue that the four lepton resonance at the Z' pole is a well-motivated and promising signal especially in supersymmetry framework, which can serve as a supersymmetry search scheme even in the early stage of the LHC experiment.

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arXiv2009

Generalized Lepton Number and Dark Left-Right Gauge Model

In a left-right gauge model of particle interactions, the left-handed fermion doublet (nu,e)_L is connected to its right-handed counterpart (n,e)_R through a scalar bidoublet so that e_L pairs with e_R, and nu_L with n_R to form mass terms. Suppose the latter link is severed without affecting the former, then n_R is not the mass partner of nu_L, and as we show in this paper, becomes a candidate for dark matter which is relevant for the recent PAMELA and ATIC observations. We accomplish this in a specific nonsupersymmetric model, where a generalized lepton number can be defined, so that n_R and W_R are odd under R = (-1)^{3B+L+2j}. Fermionic leptoquarks are also predicted.

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arXiv2009

Common gauge origin of discrete symmetries in observable sector and hidden sector

An extra Abelian gauge symmetry is motivated in many new physics models in both supersymmetric and nonsupersymmetric cases. Such a new gauge symmetry may interact with both the observable sector and the hidden sector. We systematically investigate the most general residual discrete symmetries in both sectors from a common Abelian gauge symmetry. Those discrete symmetries can ensure the stability of the proton and the dark matter candidate. A hidden sector dark matter candidate (lightest U-parity particle or LUP) interacts with the standard model fields through the gauge boson Z', which may selectively couple to quarks or leptons only. We make a comment on the implications of the discrete symmetry and the leptonically coupling dark matter candidate, which has been highlighted recently due to the possibility of the simultaneous explanation of the DAMA and the PAMELA results. We also show how to construct the most general U(1) charges for a given discrete symmetry, and discuss the relation between the U(1) gauge symmetry and R-parity.

hep-ph↗
arXiv2009

R-parity violating U(1)'-extended supersymmetric standard model

Supersymmetry is one of the best motivated new physics scenarios. To build a realistic supersymmetric standard model, however, a companion symmetry is necessary to address various issues. While R-parity is a popular candidate that can address the proton and dark matter issues simultaneously, it is not the only option for such a property. We review how a TeV scale U(1)' gauge symmetry can replace the R-parity. Discrete symmetries of the U(1)' can make the model still viable and attractive with distinguishable phenomenology. For instance, with a residual discrete symmetry of the U(1)', Z6 = B3 x U2, the proton can be protected by the baryon triality (B3) and a hidden sector dark matter candidate can be protected by the U-parity (U2).

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arXiv2008

Discrete gauge symmetries and proton stability in the U(1)'-extended MSSM

The Minimal Supersymmetric Standard Model (MSSM) with conserved R-parity suffers from several fine-tuning problems, e.g. the mu-problem and the problem of proton decay through higher dimension operators. Both of these problems can be avoided by replacing R-parity with a non-anomalous U(1)' gauge symmetry which is broken at the TeV scale. The new gauge symmetry does not necessarily forbid all renormalizable R-parity violating interactions among the MSSM fields, and may allow for either lepton number or baryon number violation at the renormalizable level. However, the proton decay problem resurfaces with the introduction of new TeV-scale exotic fields which are required for gauge anomaly cancellations. In this paper we investigate the issue of proton stability in the presence of TeV-scale exotics. We show that there are large classes of models in which TeV exotics do not destabilize the proton. We classify the viable models according to the residual discrete symmetries after U(1)' and electroweak symmetry breaking. In some of our examples the residual U(1)' discrete gauge symmetry within the MSSM sector alone ensures that the proton is absolutely stable, for any exotic representations. In other cases the proton can be sufficiently long-lived, depending on the U(1)' and hypercharge discrete charge assignments for the exotic fields. Our analysis outlines a general scheme for ensuring proton stability in the presence of light exotics with baryon and lepton number violating interactions.

hep-ph↗
arXiv2008

Lightest U-parity Particle (LUP) dark matter

We suggest a U(1)' gauge symmetry as an alternative to the usual R-parity of supersymmetric standard models, showing that it can also work as a common source of stabilities of proton and dark matter in addition to other attractive features. The residual discrete symmetries of a single U(1)' can provide stabilities to both the MSSM sector (proton) and the hidden sector (new dark matter candidate, LUP). The LUP can expand the viability of many models such as R-parity violating models and gauge mediation models regarding dark matter issue.

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arXiv2008

U(1)' solution to the mu-problem and the proton decay problem in supersymmetry without R-parity

The Minimal Supersymmetric Standard Model (MSSM) is plagued by two major fine-tuning problems: the mu-problem and the proton decay problem. We present a simultaneous solution to both problems within the framework of a U(1)'-extended MSSM (UMSSM), without requiring R-parity conservation. We identify several classes of phenomenologically viable models and provide specific examples of U(1)' charge assignments. Our models generically contain either lepton number violating or baryon number violating renormalizable interactions, whose coexistence is nevertheless automatically forbidden by the new U(1)' gauge symmetry. The U(1)' symmetry also prohibits the potentially dangerous and often ignored higher-dimensional proton decay operators such as QQQL and UUDE which are still allowed by R-parity. Thus, under minimal assumptions, we show that once the mu-problem is solved, the proton is sufficiently stable, even in the presence of a minimum set of exotics fields, as required for anomaly cancellation. Our models provide impetus for pursuing the collider phenomenology of R-parity violation within the UMSSM framework.

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arXiv2007

A Supersymmetric U(1)' Model with Multiple Dark Matters

We consider a scenario where a supersymmetric model has multiple dark matter particles. Adding a U(1)' gauge symmetry is a well-motivated extension of the Minimal Supersymmetric Standard Model (MSSM). It can cure the problems of the MSSM such as the mu-problem or the proton decay problem with high-dimensional lepton number and baryon number violating operators which R-parity allows. An extra parity (U-parity) may arise as a residual discrete symmetry after U(1)' gauge symmetry is spontaneously broken. The Lightest U-parity Particle (LUP) is stable under the new parity becoming a new dark matter candidate. Up to three massive particles can be stable in the presence of the R-parity and the U-parity. We numerically illustrate that multiple stable particles in our model can satisfy both constraints from the relic density and the direct detection, thus providing a specific scenario where a supersymmetric model has well-motivated multiple dark matters consistent with experimental constraints. The scenario provides new possibilities in the present and upcoming dark matter searches in the direct detection and collider experiments.

hep-ph↗
arXiv2007

Revival of the Thermal Sneutrino Dark Matter

The left-handed sneutrino in the Minimal Supersymmetric Standard Model (MSSM) has been ruled out as a viable thermal dark matter candidate, due to conflicting constraints from direct detection experiments and from the measurement of the dark matter relic density. The intrinsic fine-tuning problem of the MSSM, however, motivates an extension with a new U(1)' gauge symmetry. We show that in the U(1)'-extended MSSM the right-handed sneutrino becomes a good thermal dark matter candidate. We identify two generic parameter space regions where the combined constraints from relic density determinations, direct detection and collider searches are all satisfied.

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arXiv2006

Higgs Sector in Extensions of the MSSM

Extensions of the Minimal Supersymmetric Standard Model (MSSM) with additional singlet scalar fields solve the important mu-parameter fine tuning problem of the MSSM. We compute and compare the neutral Higgs boson mass spectra, including one-loop corrections, of the following MSSM extensions: Next-to-Minimal Supersymmetric Standard Model (NMSSM), the nearly-Minimal Supersymmetric Standard Model (nMSSM), and the U(1)'-extended Minimal Supersymmetric Standard Model (UMSSM) by performing scans over model parameters. We find that the Secluded U(1)'-extended Minimal Supersymmetric Standard Model (sMSSM) is identical to the nMSSM if three of the additional scalars decouple. The dominant part of the one-loop corrections are model-independent since the singlet field does not couple to MSSM particles other than the Higgs doublets. Thus, model-dependent parameters enter the masses only at tree-level. We apply constraints from LEP bounds on the Standard Model and MSSM Higgs boson masses and the MSSM chargino mass, the invisible Z decay width, and the Z-Z' mixing angle. Some extended models permit a Higgs boson with mass substantially below the SM LEP limit or above theoretical limits in the MSSM. Ways to differentiate the models via masses, couplings, decays and production of the Higgs bosons are discussed.

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arXiv2005

Properties of the Lightest Neutralino in MSSM Extensions

We study neutralino sectors in extensions of the MSSM that dynamically generate the mu-term. The extra neutralino states are superpartners of the Higgs singlets and/or additional gauge bosons. The extended models may have distinct lightest neutralino properties which can have important influences on their phenomenology. We consider constraints on the lightest neutralino from LEP, Tevatron, and (g-2)_mu measurements and the relic density of the dark matter. The lightest neutralino can be extremely light and/or dominated by its singlino component, which does not couple directly to SM particles except Higgs doublets.

hep-ph↗
arXiv2005

Lightest Neutralino in Extensions of the MSSM

We study neutralino sectors in extensions of the MSSM that dynamically generate the mu-term. The extra neutralino states are superpartners of the Higgs singlets and/or additional gauge bosons. The extended models may have distinct lightest neutralino properties which can have important influences on their phenomenology. We consider constraints on the lightest neutralino from LEP, Tevatron, and (g-2)_mu measurements and the relic density of the dark matter. The lightest neutralino can be extremely light and/or dominated by its singlino component which does not couple directly to SM particles except Higgs doublets.

hep-ph↗
arXiv2005

Muon Anomalous Magnetic Moment in a Supersymmetric U(1)' Model

We study the muon anomalous magnetic moment a_μ= (g_μ- 2)/2 in a supersymmetric U(1)' model. The neutralino sector has extra components from the superpartners of the U(1)' gauge boson and the extra Higgs singlets that break the U(1)' symmetry. The theoretical maximum bound on the lightest neutralino mass is much smaller than that of the Minimal Supersymmetric Standard Model (MSSM) because of the mixing pattern of the extra components. In a U(1)' model where the U(1)' symmetry is broken by a secluded sector (the S-model), tanβis required to be < 3 to have realistic electroweak symmetry breaking. These facts suggest that the a_μprediction may be meaningfully different from that of the MSSM. We evaluate and compare the muon anomalous magnetic moment in this model and the MSSM and discuss the constraints on tanβand relevant soft breaking terms. There are regions of the parameter space that can explain the experimental deviation of a_μfrom the Standard Model calculation and yield an acceptable cold dark matter relic density without conflict with collider experimental constraints.

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