分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-16
摘要： 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.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-16
摘要： We discuss single top quark production via u(i) (d) over bar(j)-->t (b) over bar at the Fermilab Tevatron in the minimal supersymmetric model with R-parity violation. We find that within the allowed range of coupling constants, the lepton-number-violating couplings can give rise to observable effects when the slepton mass lies in a specific narrow range. For the baryon number-violating couplings, the contribution to the production rate can be quite large in the presently allowed range of the coupling constants. We show that the measurement of single top quark production at the upgraded Tevatron can be used to constrain a linear combination of products of the R-parity-violating couplings.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-16
摘要： We list all possible dimension-six CP-violating SUc(3) x SUL(2) x U-Y(1)-invariant operators involving the third-family quarks, which can be generated by new physics at a higher energy scale. The expressions of these operators after electroweak symmetry breaking and the induced effective couplings Wt (b) over bar,Xb (b) over bar, and Xt (t) over bar (X = Z,gamma,g,H) are also presented. We evaluate sample contributions of these operators to CP-odd asymmetries of transverse polarization of the top quark in single top quark production at the upgraded Fermilab Tevatron, the same polarization effect in top-quark-top-antiquark pair production at the NLC, and the CP-odd observables of momentum correlations among the top quark decay products at the NLC. The energy and luminosity sensitivity in probing this CP-violating new physics is also studied.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-16
摘要： We list all possible dimension-six CP-conserving SUc(3)xSU(L)(2)xU(Y)(1)-invariant operators involving the third-family quarks which could be generated by new physics at a higher scale. Expressions for these operators after electroweak gauge symmetry breaking and the induced effective couplings Wt(b) over bar, Xb(b) over bar, and Xt(t) over bar (X = Z, gamma,g, H) are presented. Analytic expressions for the tree level contributions of all these operators to the observables R-b and A(FB)(b) at CERN LEP I, sigma(e(+)e(-) --> ) and A(FB)(b) at LEP II, sigma(e(+)e(-) --> ) and A(FB)(t) at the Next Linear Collider (NLC). as well as sigma( --> + X) at the Fermilab Tevatron upgrade, are provided. The effects of these operators on different electroweak observables are discussed and numerical examples presented. Numerical analyses show that in the coupling region allowed by R-b and A(FB)(b) at LEP I, some of the new physics operators can still have significant contributions at LEP II, the Tevatron, and the NLC.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-15
摘要： We propose to measure the CP phase delta(CP), the magnitude of the neutrino mixing matrix element \U-e3\ and the sign of the atmospheric scale mass-squared difference Deltam(31)(2) with a superbeam by the joint analysis of two different long baseline neutrino oscillation experiments. One is a long baseline experiment (LBL) at 300 km and the other is a very long baseline (VLBL) experiment at 2100 km. We take the neutrino source to be the approved high intensity proton synchrotron, HIPA. The neutrino beam for the LBL is the 2-degree off-axis superbeam, and for the VLBL a narrowband superbeam. Taking into account all possible errors, we evaluate the event rates required and the sensitivities that can be attained for the determination of delta(CP) and the sign of Deltam(31)(2). We arrive at a representative scenario for a reasonably precise probe of this part of neutrino physics.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-15
摘要： We examine the possibility of observing exotic top quark decays via R-parity violating SUSY interactions in e(+)e(-) collisions at roots = 500 GeV. We present cross-sections for tt production followed by the subsequent decay of either the t or (t) over bar via the R-parity violating interaction while the other undergoes the SM decay. We discuss kinematic cuts that allow the exotic SUSY decays to be detected over standard model backgrounds. Discovery limits for R-parity violating couplings in the top sector are presented assuming an integrated luminosity of 100 fb(-1). (C) 2001 Published by Elsevier Science B.V.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-15
摘要： We study the effects of dimension-six operators contributing to the gt(t) over bar vertex in top quark pair production at the Fermilab Tevatron collider. We derive both the limits from run 1 data and the potential bounds from future runs (runs 2 and 3). Although the current constraints are not very strong, the future runs are quite effective in probing these operators. We investigate the possibility of disentangling different operators with the tt invariant mass distribution and the top quark polarization asymmetry. We also study the effects of a different set of operators contributing to single top quark production via the Wt(b) over bar coupling. We derive the current and potential future bounds on these anomalous operators and find that the upgraded FermiIab Tevatron collider can improve the existing constraints from R-b for one of the operators. [S0556-2821(98)07121-5].
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