119090694
Probing topcolor-assisted technicolor from like-sign top pair production at CERN LHC
The topcolor-assisted technicolor (TC2) theory predicts tree-level flavor-changing neutral-current (FCNC) top quark Yukawa couplings with top-pions. Such FCNC interactions will induce like-sign top quark pair productions at CERN Large Hadron Collider (LHC). While these rare productions are far below the observable level in the Standard Model and other popular new physics models such as the Minimal Supersymmetric Model, we find that in a sound part of parameter space the TC2 model can enhance the production cross sections to several tens of fb and thus may be observable at the LHC due to rather low backgrounds. Searching for these productions at the LHC will serve as an excellent probe for the TC2 model.
119516872
Muon anomalous magnetic moment in technicolor models
Contributions to the muon anomalous magnetic moment are evaluated in the technicolor model with scalars and topcolor assisted technicolor model, In the technicolor model with scalers, the additional contributions come from the loops of scalers, which were found sizable only for a very large f/f' disfavored by the experiment of h --> s gamma. The topcolor effect is also found to be large only for an unnaturally large tan theta', and thus the previously evaluated loop effects of extended technicolor bosons, suppressed by m(mu)(2)/M-ETC(2), must be resorted to account for the E821 experiment. So, if the E821 experiment result persists, it would be a challenge to technicolor models. (C) 2001 Published by Elsevier Science B.V.
40224148
Virtual effects of split-SUSY in Higgs productions at linear colliders
In split supersymmetry, gauginos and higgsinos are the only supersymmetric particles possibly accessible at foreseeable colliders like the CERN Large Hadron Collider (LHC) and the International Linear Collider (ILC). In order to account for the cosmic dark matter measured by WMAP, these gauginos and higgsinos are stringently constrained and could be explored at the colliders through their direct productions and/or virtual effects in some processes. The clean environment and high luminosity of the ILC render the virtual effects at percent level meaningful in unraveling the new physics effects. In this work we assume split supersymmetry and calculate the virtual effects of the WMAP-allowed gauginos and higgsinos in the Higgs productions e+e-→Zh and e+e-→νeν̄eh through WW fusion at the ILC. We find that the production cross section of e+e-→Zh can be altered by a few percent in some part of the WMAP-allowed parameter space, while the correction to the WW fusion process e+e-→νeν̄eh is below 1%. Such virtual effects are correlated with the cross sections of chargino pair productions and can offer complementary information in probing split supersymmetry at the colliders.
15720470
Supersymmetric electroweak corrections to single top quark production at the Fermilab Tevatron
We calculate the O({alpha}{sub ew}M{sub t}{sup 2}/M{sub W}{sup 2}) supersymmetric (SUSY) electroweak corrections to single top quark production via q{bar q}{sup {prime}}{r_arrow}t{bar b} at the Fermilab Tevatron in the minimal supersymmetric model. The supersymmetric electroweak corrections to the cross section are at most a few percent for tan{beta} {gt} 1, but can exceed 10{percent} for tan{beta} {lt} 1. The combined effects of SUSY electroweak corrections and the Yukawa corrections can exceed 10{percent} for favorable parameter values, which might be observable at a high-luminosity Tevatron. {copyright} {ital 1997} {ital The American Physical Society}
119233750
Di-photon Higgs signal at the LHC: A comparative study in different supersymmetric models
As the most important discovery channel for a light Higgs boson at the LHC the di-photon signal gg --> h --> gamma gamma is sensitive to underlying physics. In this work we investigate such a signal in a comparative way by considering three different supersymmetric models, namely the minimal supersymmetric standard model (MSSM), the next-to-minimal supersymmetric standard model (NMSSM) and the nearly minimal supersymmetric standard model (nMSSM). Under the current collider and cosmological constraints we scan over the parameter space and obtain the following observation in the allowed parameter space: (i) In the nMSSM the signal rate is always suppressed; (ii) In the MSSM the signal rate is suppressed in most cases, but in a tiny corner of the parameter space it can be enhanced (maximally by a factor of 2); (iii) In the NMSSM the signal rate can be enhanced or suppressed depending on the parameter space, and the enhancement factor can be as large as 7. (C) 2011 Elsevier B.V. All rights reserved.
118505781
A SM-like Higgs near 125 GeV in low energy SUSY: a comparative study for MSSM and NMSSM
A bstractMotivated by the recent LHC hints of a Higgs boson around 125 GeV, we assume a SM-like Higgs with the mass 123-127 GeV and study its implication in low energy SUSY by comparing the MSSM and NMSSM. We consider various experimental constraints at 2σ level (including the muon g − 2 and the dark matter relic density) and perform a comprehensive scan over the parameter space of each model. Then in the parameter space which is allowed by current experimental constraints and also predicts a SM-like Higgs in 123-127 GeV, we examine the properties of the sensitive parameters (like the top squark mass and the trilinear coupling At) and calculate the rates of the di-photon signal and the V V* (V = W, Z) signals at the LHC. Our typical findings are: (i) In the MSSM the top squark and At must be large and thus incur some fine-tuning, which can be much ameliorated in the NMSSM; (ii) In the MSSM a light stau is needed to enhance the di- photon rate of the SM-like Higgs to exceed its SM prediction, while in the NMSSM the di-photon rate can be readily enhanced in several ways; (iii) In the MSSM the signal rates of pp → h → V V* at the LHC are never enhanced compared with their SM predictions, while in the NMSSM they may get enhanced significantly; (iv) A large part of the parameter space so far survived will be soon covered by the expected XENON100(2012) sensitivity (especially for the NMSSM).
119915103
Trace anomaly and mass independent rational terms
Abstract We perform a new investigation to show that the trace anomaly in Minkowskian spacetime is originated by a kind of mass independent rational term which is definite and nonlocal. Hence it is regularization independent and may provide more physical insight. A simple way for calculating trace anomalies is proposed and several examples are given.
120520076
Soliton mass and discrete coupling constants in the quantized sine-Gordon model
The soliton mass in the quantized sine-Gordon model over the whole range of the coupling constant (g2 from 0 to 8 pi ) is evaluated by means of the Gaussian effective potential method. The analytical expression with numerical results is presented. The authors find that the coupling constant g can only take discrete values. A new kind of soliton linking g Phi =0 to g Phi = pi emerges at a set of special coupling constants g.
648376
Harmonic scale transformation in effective QFTs with underlying structures
New equations governing the scale transformation behaviors of a QFT with underlying structures are derived. These equations, with their several equivalent versions, can yield some new and significant insights and results that are difficult to see in the conventional renormalization programs. Among the several equivalent versions, one is similar to the usual Callan-Symanzik equation and renormalization group equation but with different meanings. From another version, the anomalous equation of energy-momentum tensor trace can be easily obtained. It can be shown that with the new versions one could partially fix the scheme dependence and hence some renormalization schemes like momentum space subtractions are questionable. The asymptotic freedom for QCD is easily reproduced at one-loop level in our new version CSE. Finally the decoupling theorem a la Appelquist and Carazzone are discussed within our strategy.
14889402
Finite quantum field theory from a natural postulate
A new approach is demonstrated that QFTs can be UV finite if they are viewed as the low energy effective theories of a fundamental underlying theory (that is complete and well-defined in all respects) according to the nowaday's standard point of view. No subtraction procedure, counter terms and hence bare parameters are needed. It can also be viewed as a new formulation of the wilson's renormalization program. In contrast to the old ones, this new approach works for any interaction model and spacetime dimensions. Its important implications are sketched.
12618841
Antishadowing effects in the unitarized BFKL equation
Abstract A unitarized BFKL equation incorporating shadowing and antishadowing corrections of the gluon recombination is proposed. This equation reduces to the Balitsky–Kovchegov evolution equation near the saturation limit. We find that the antishadowing effects have a sizable influence on the gluon distribution function in the preasymptotic regime.