119099687
Pad\'e expansion and nucleon-nucleon scattering in coupled channels
Since the significant effective field theory (EFT) approach to nucleon systems[1, 2], there has been creating controversies about the consistent renormalization and EFT power counting in nonperturbative regime[3, 4]. The main difficulty is due to the nontrivial prescription dependence developed in nonperturbative regime, where some wisdoms about renormalization established within perturbative regimes cease to apply directly[5]. Therefore, the nonperturbative prescription dependence must be removed through imposing appropriate boundary conditions which are usually implemented through various forms of data fitting either explicitly or implicitly[6, 7, 8, 9, 10, 11, 12, 13]. In more recent literature, nonperturbative counter terms, or equivalently, nonperturbative parametrization of the renormalization prescription has been the main focus[14, 15]. That is, due to the difficulty in treating the issues in nonperturbative regimes, the key issue is to find more efficient parametrization of nonperturbative prescription. In this regard, we have performed an analysis and treatment of the nonperturbative prescription dependence basing on Padé approximant of an important nonperturbative factor of T -matrix for nucleon-nucleon (NN) scattering in uncoupled channles[16, 17, 18]. In this report, we will extend our analysis to coupled channels. Some general theoretical and technical issues associated with coupled channels will be addressed first, then we will illustrate our method in D3−G3. The object under consideration is the T -matrix for nucleon-nucleon scattering processes at low energies. According to Weinberg’s proposal[19], this T -matrix should be solved from Lippmann-Schwinger (LS) equation with the potential to be systematically constructed using χPT as the low energy effective theory of QCD. For coupled channels, such LSE’s read,
14239579
Confinement of Higgs bosons from hidden symmetry and convexity
In the full effective potential (EFP) approach, we find that spontaneous symmetry breaking (SSB) can, with the convexity of the full EFP, lead to the prediction of the IR confinement of Higgs particles, adding difficulty to the experimental identification of Higgs particles. The short distance behaviors remain intact. The whole presentation is given in the understanding that any QFT becomes UV well defined in a more complete underyling theory according to a recently proposed strategy.
15356070
Can QFT be UV finite as well as effective
A new attempt is demonstrated that QFTs can be UV finite if they are viewed as the low energy effective theories of a fundamental underlying theory (complete and well-defined in all respects) according to the modern standard point of view. This approach is much simpler in principle and in technology comparing to any known renormalization program. Some subtle and difficult issues can be easily resolved. The importance of the procedure for defining the ambiguities is fully appreciated in the new approach. Some simple but important nonperturbative examples are discussed to show the power and plausibility of the new approach.
13049479
A new kind of constraints on renormalization schemes
We derive a new kind of physical constraints on the subtraction schemes for theories with massive particles in addition to the Ward identities for gauge symmetries. The momentum subtraction scheme fails this criterion. The decoupling of heavy fields is discussed in the context of Callan-Symanzik equations where all schemes (including MOM) lead to the same pattern of decoupling with inevitable discontinuities in beta function across heavy field thresholds. PACS number(s): 11.10.Gh; 11.10.Hi; 12.39.Hg
119670186
Padé Expansion and the Renormalization of Nucleon–Nucleon Scattering
The importance of imposing physical boundary conditions on the T-matrix to remove the nonperturbative renormalization prescription dependence is stressed and demonstrated in two diagonal channels 1P1 and 1D2, with the help of Pade expansion.
14573379
Harmonic scaling laws and underlying structures
Based on the effective field theory philosophy, a universal form of the scaling laws could be easily derived with the scaling anomalies naturally clarified as the decoupling effects of underlying physics. In the novel framework, the conventional renormalization group equations and Callan-Symanzik equations could be reproduced as special cases and a number of important and difficult issues around them could be clarified. The underlying theory point of view could envisage a harmonic scaling law that help to fix the form of the loop amplitudes through anomalies, and the heavy field decoupling can be incorporated in this underlying theory approach in a more unified manner.
119340871
PHASE-STRUCTURE OF LATTICE-Z (2) GAUGE-HIGGS THEORY BY VARIATIONAL CUMULANT EXPANSION
Abstract We use the variational cumulant expansion method to study the four-dimensional lattice Z(2) gauge theory coupled to a radially varied scalar field which is assumed to take discrete values. Its phase structure is given in different cases. The comparison with the results from other approaches is also presented.
119115457
Light dark matter in NMSSM and implication on Higgs phenomenology
For the experimental search of neutralino dark matter, it is important to know its allowed mass and scattering cross section with the nucleon. In order to figure out how light a neutralino dark matter can be predicted in low energy supersymmetry, we scan over the parameter space of the NMSSM (next-to-minimal supersymmetric model), assuming all the relevant soft mass parameters to be below TeV scale. We find that in the parameter space allowed by current experiments the neutralino dark matter can be as light as a few GeV and its scattering rate off the nucleon can reach the sensitivity of XENON100 and CoGeNT. As a result, a sizable parameter space is excluded by the current XENON100 and CoGeNT data (the plausible CoGeNT dark matter signal can also be explained). The future 6000 kg-days exposure of XENON100 will further explore (but cannot completely cover) the remained parameter space. Moreover, we find that in such a light dark matter scenario a light CP-even or CP-odd Higgs boson must be present to satisfy the measured dark matter relic density. Consequently, the SM-like Higgs boson h(SM) may decay predominantly into a pair of light Higgs bosons or a pair of neutralinos so that the conventional decays like h(SM) -> gamma gamma is much suppressed. (C) 2011 Elsevier B.V. All rights reserved.
118536637
Lepton flavor violating Z-boson decays at GigaZ as a probe of supersymmetry
AbstractThis paper briefly reviews the lepton flavor violating Z-decays at GigaZ as a probe of supersymmetry by focusing on Z → ℓi$$
\bar \ell 
$$j in two representative supersymmetric models: the minimal supersymmetric model without R-parity and the supersymmetric seesaw model. The work concludes that under the current experimental constraints from LEP and ℓi → ℓjγ, these rare decays can still be enhanced to reach the sensitivity of the GigaZ. Therefore, supersymmetry can be probed via these decays at GigaZ.
119235151
Higgs decay to dark matter in low energy SUSY: is it detectable at the LHC?
A bstractDue to the limited statistics so far accumulated in the Higgs boson search at the LHC, the Higgs boson property has not yet been tightly constrained and it is still allowed for the Higgs boson to decay invisibly to dark matter with a sizable branching ratio. In this work, we perform a comparative study for the Higgs decay to neutralino dark matter by considering three different low energy SUSY models: the minimal supersymmetric standard model (MSSM), the next-to-minimal supersymmetric standard models (NMSSM) and the nearly minimal supersymmetric standard model (nMSSM). Under current experimental constraints at 2σ level (including the muon g − 2 and the dark matter relic density), we scan over the parameter space of each model. Then in the allowed parameter space we calculate the branching ratio of the SM-like Higgs decay to neutralino dark matter and examine its observability at the LHC by considering three production channels: the weak boson fusion VV → h, the associated production with a Z-boson pp → hZ + X or a pair of top quarks $pp \to ht\overline t + X$. We find that in the MSSM such a decay is far below the detectable level; while in both the NMSSM and nMSSM the decay branching ratio can be large enough to be observable at the LHC. We conclude that at the LHC the interplay of detecting such an invisible decay and the visible di-photon decay may allow for a discrimination of different SUSY models.
15143546
Top quark at the upgraded Tevatron to prove new physics
This talk is a review of the recent studies on probing new physics through single top quark processes and probing exotic top quark decays at the upgraded Tevatron.