Dong-Won Jung

Model independent analysis of the forward-backward asymmetry of top quark production at the Tevatron

Abstract Motivated by a possible anomaly in the forward–backward (FB) asymmetry of top quark ( A FB ) observed at the Tevatron, we perform a model independent analysis on q q ¯ → t t ¯ using an effective Lagrangian with dim-6 four-quark operators. We derive necessary conditions on new physics structures and the couplings that are consistent with the t t ¯ production cross section and A FB measured at the Tevatron, and discuss possible new physics scenarios that could generate such dim-6 operators.

Electroweak symmetry breaking and cold dark matter from strongly interacting hidden sector

We consider a hidden sector with a vectorlike confining gauge theory like QCD with Nh,c colors and Nh,f light quarks Qh in the hidden sector. Then a scale ΛH would be generated by dimensional transmutation, and chiral symmetry breaking occurs in the hidden sector. This scale ΛH can play a role of the SM Higgs mass parameter, triggering electroweak symmetry breaking (EWSB). Furthermore the lightest mesons in the hidden sector is stable by flavor conservation of the hidden sector strong interaction, and could be a good cold dark matter (CDM). We study collider phenomenology, and relic density and direct detection rates of the CDM of this model.

Longitudinal top polarization as a probe of a possible origin of forward–backward asymmetry of the top quark at the Tevatron

Abstract If the forward–backward (FB) asymmetry of top quark ( A FB ) observed at the Tevatron deviates from the SM prediction, there must be P -violating interactions in q q ¯ → t t ¯ . This new interaction will necessarily affect the top spin polarization. In this Letter, we perform a model independent analysis on the longitudinal (anti)top polarization ( P L and P ¯ L ) using an effective lagrangian with dim-6 four-quark operators relevant for q q ¯ → t t ¯ , and show that the P -odd observable corresponding to the polarization difference ( P L − P ¯ L ) gives important informations on the chiral structures of new physics that might be relevant to the A FB .

Possible Common Origin of the Top Forward-backward Asymmetry and the CDF Dijet Resonance

A color-singlet neutral vector boson is considered as a possible common origin of the top forward-backward asymmetry and the CDF dijet resonance. We identify chiral and flavor structures of the couplings of this new vector boson to the standard model quarks for which one could accommodate both data. We also demonstrate that non-vanishing observables involving longitudinal top polarizations can provide useful criteria for the possible existence of parity violating new physics in the q q^bar -> t t^bar process, and discrimination between the flavor-conserving and flavor-violating cases.

Higgs–dilaton(radion) system confronting the LHC Higgs data

Abstract We consider the Higgs–dilaton(radion) system using the trace of energy–momentum tensor ( T μ μ ) with the full Standard Model (SM) gauge symmetry G SM ≡ SU ( 3 ) c × SU ( 2 ) L × U ( 1 ) Y , and find out that the resulting phenomenology for the Higgs–dilaton(radion) system is distinctly different from the earlier studies based on the T μ μ with the unbroken subgroup H SM ≡ SU ( 3 ) c × U ( 1 ) em of G SM . After electroweak symmetry breaking (EWSB), the SM Higgs boson and dilaton(radion) will mix with each other, and there appear two Higgs-like scalar bosons and the Higgs–dilaton mixing changes the scalar phenomenology in interesting ways. The signal strengths for the gg-initiated channels could be modified significantly compared with the SM predictions due to the QCD scale anomaly and the Higgs–dilaton(radion) mixing, whereas anomaly contributions are almost negligible for other channels. We also discuss the self-couplings and the signal strengths of the 126 GeV scalar boson in various channels and possible constraints from the extra light/heavy scalar boson. The Higgs–dilaton(radion) system considered in this work has a number of distinctive features that could be tested by the upcoming LHC running and at the ILC.

Mass dependent top forward backward asymmetry in the effective Lagrangian approach: Addendum to `Model independent analysis of the forward-backward asymmetry of top quark production at the Tevatron'

Abstract Recently the CDF and the D0 Collaborations presented the data on the top forward–backward (FB) asymmetry A FB as functions of M t t ¯ and Δ y ≡ y t − y t ¯ . We study these observables in the effective Lagrangian approach with dimension-6 q q ¯ t t ¯ contact interactions, and compare with the CDF and D0 data. When we stay within the validity region of the effective Lagrangian approach, the mass dependent top FB asymmetry turns out to be smaller than the CDF data, more than 2- σ away. If this discrepancy remains in the future data with better statistics, it would imply that the effective Lagrangian approach is not adequate for the top FB asymmetry, and a new physics scale around a few hundred GeV in the t - or u -channel may be responsible for the observed top FB asymmetry.

Production of the charged Higgs bosons at the CERN Large Hadron Collider in the left-right symmetric model

We study the production of the charged Higgs boson at the CERN LHC in the left-right symmetric model. It is shown that there exists a lower bound of the cross section. We investigate that predicted cross sections of this model are generally larger than those of the two Higgs doublet model or the minimal supersymmetric model.

Dynamical Symmetry Breaking with Four-Superfield Interactions

A bstractWe investigate the dynamical mass generation resulted from interaction terms with four chiral superfields. The kind of interactions maybe considered a supersymmetric generalization of the four-fermion interactions of the classic Nambu-Jona-Lasinio model. A four-superfield interaction that contains a four-fermion interaction as one of its component terms has been the standard supersymmetrization of the NJL model for decades. Recently, we introduced a holomorphic variant with a dimension five interaction term instead. The latter is a main target of the present analysis. With the introduction of a new perspective on the superfield gap equation, we derive it for each one of the four-superfield interactions, using the supergraph technique. Through analyzing solutions to the gap equations, we illustrate the dynamical generation of superfield Dirac mass, including a supersymmetry breaking part. A dynamical symmetry breaking generally goes along with the dynamical mass generation, for which a bi-superfield condensate is responsible. The explicit illustration of dynamical symmetry breaking from the holomorphic dimension five interaction is reported for the first time. It has rich and novel features, which would be easily missed without the superfield approach developed here. We also discuss the nature of the bi-superfield condensate and its role of the effective Higgs superfield picture for both cases, illustrating their difference. Note that such a holomorphic quark superfield interaction term can successful account for the electroweak symmetry breaking with Higgs superfields as composites.

Majorana versus Dirac Mass from Holomorphic Supersymmetric Nambu-Jona-Lasinio Model

Abstract We study the theoretical features in relation to dynamical mass generation and symmetry break-ing for the recently proposed holomorphic supersymmetric Nambu–Jona-Lasinio model. The basicmodel has two different chiral superfields with a strongly coupled dimension five four-superfieldinteraction. In addition to the possibility of generation of Dirac mass between the pair establishedearlier, we show here the new option of generation of Majorana masses for each chiral superfield.We also give a first look at what condition may prefer Dirac over Majorana mass, illustrating thata split in the soft supersymmetry breaking masses is crucial. In particular, in the limit one of thesoft mass vanishes, we show that generation of the Majorana mass is no longer an option, while theDirac mass generation survives well. The latter is sensitive mostly to the average of the two softmasses. The result has positive implication on the application of the model framework towardsdynamical electroweak symmetry breaking with Higgs superfields as composites.

Anomaly-mediated supersymmetry breaking demystified

We reinterpret anomaly-mediated supersymmetry breaking from a field-theoretic perspective in which superconformal anomalies couple to either the chiral compensator or the U(1)R vector superfield. As supersymmetry in the hidden sector is spontaneously broken by non-vanishing vacuum expectation values of the chiral compensator F-term and/or the U(1)R vector superfield D-term, the soft breakdown of supersymmetry emerges in the visible sector. This approach is physically more understandable compared with the conventional approach where the chiral compensator is treated on the same footing as a spurion in gauge-mediated supersymmetry breaking scenario.