14236612
Late-decaying Q-ball with BBN lifetime
In the Affleck-Dine mechanism of baryogenesis, nontopological solitons called Q-balls can be formed. In this work we propose that such Q-balls decay during the BBN era and study the cosmological consequence of such late decays. We find that the late-decaying baryonic Q-balls with lifetime of about 10(3) s can provide a new developing mechanism for the BBN through a rolling baryon-to-photon ratio eta, which can naturally explain the discrepancy of the BBN prediction with the WMAP data on Li-7 abundance. For the late-decaying leptonic Q-balls with lifetime of about 10(6) s, we find that their decay product, gravitinos, can serve as a dark matter candidate and give an explanation for the approximate equality of dark and baryon matter densities. (C) 2004 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).
119293139
Probing topcolor-assisted technicolor from top charge asymmetry and triple-top production at the LHC
In a topcolor-assisted technicolor model (TC2) with large FCNC top quark couplings, we study its correlated contributions to the top quark forward-backward asymmetry (A(FB)) at the Tevatron, the top charge asymmetry (A(C)) and the triple-top production at the LHC. Under current constraints on the top quark from the LHC and Tevatron (such as the total and differential production rates), we scan the parameter space of such a TC2 model. We find that in the allowed parameter space the TC2 model can explain the Tevatron measured A(FB) at 2 sigma level, but meanwhile significantly enhance A(C) at the LHC. Such enhanced A(C), albeit currently allowed by the LHC measurement at 2 sigma level, will serve as a test of TC2 with the improvement of measurement precision at the LHC. Then with all the constraints (including the requirement to explain A(FB) at 2 sigma level and satisfying the current LHC measurement of A(C) at 2 sigma level), we find that the TC2 model can induce sizable triple-top production at the 14 TeV LHC (the production rate can maximally reach 16 pb). Due to the low SM backgrounds, the triple-top production can also be a good probe for TC2 model, complementary to A(C). (C) 2012 Elsevier B.V. All rights reserved.
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.
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.
45314613
Numerical evaluation of a two loop diagram in the cutoff regularization
Dimensional regularization [1] has become an efficient regularization scheme for theoretical calculations in high energy physics. It makes analytical results more available, and its gauge invariance almost decisively defeated the other schemes (say cutoff scheme) in QCD and other gauge theories. However, things are not so simple. It is very natural to anticipate that DR might fail sooner or later somewhere as it is just a special regularization but never a true theory of the short distance physics. Such event is now known: the MS scheme does not provide a physical prediction for low energy nucleons scattering in case of long scattering lengths [2] in nonperturbative context. To yield meaningful results, unconventional subtraction is devised and now known as PDS [2]. Since this is obtained with hindsight, we should not discard the cutoff scheme without further exploiting its virtues. There have recently been some further investigations over the relations between the divergences in DR and cutoff schemes and the associated limitations [4,5]. The conventional virtues of the DR scheme were shown to be due to an implicit subtraction [4]. In nonperturbative contexts involving multiloop corrections the DR might even make renormalization infeasible [5]. Traditionally, it is very hard to obtain analytical results for multiloop amplitudes within the cutoff scheme. In this report we show that one could achieve this goal numerically at a pretty good precision. We will make use of the dynamical symmetry breaking of λφ discussed in [6] to illustrate the numerical evaluation of the finite constant term in the two loop sunset diagram. Thus the report is organized as follows. First we quote some results of Ref. [6] in Sec. II as preparation. In Sec. III we present our strategy and procedures for doing the numerical analysis of the problem and its possible prospective significance. The result is also given there. In Sec. IV we revisit the problem introduced in Sec. II to show the significance of the new result obtained in Sec. III. The summary will also be given there.
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.
125789702
A nonperturbative scenario for EFT renormalization
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.
119429343
Comparative analysis of non-perturbative effects in B ---> X(u)l anti-nu(l) decays
In order to extract the Cabibbo-Kobayashi-Maskawa matrix element |V_{ub}| from B -> X_u l anti-nu_l decays, the overwhelming background from B -> X_c l anti-nu_l decays must be reduced by appropriate acceptance cuts. We study the non-perturbative effects due to the motion of the b quark inside the B meson on the phenomenologically relevant decay distributions of B -> X_u l anti-nu_l in the presence of such cuts in a comparative analysis based on shape functions and the parton model in the light-cone limit. Comparisons with recent data from the CLEO, BABAR, and BELLE collaborations favor the shape-function approach.