17 research outputs found
レプトン-ハドロンオヨビハドロン-ハドロンハンノウニオケルチャームリュウシツイセイセイコウカノタンサク
No full text京都大学0048新制・課程博士理学博士甲第2341号理博第622号新制||理||331(附属図書館)6452UT51-55-E17京都大学大学院理学研究科物理学第二専攻(主査)教授 町田 茂, 教授 田中 正, 教授 三宅 弘三学位規則第5条第1項該当Kyoto UniversityDA
Probing top quark couplings at polarized NLC
No full textThe energy spectrum of the lepton(s) in at next linear colliders (NLC) is studied for arbitrary longitudinal beam polarizations as a possible test of new physics in top-quark couplings. The most general non-standard couplings for gamma-tt-bar, Ztt-bar and Wtb vertices are considered. Expected precision of the non-standard-parameter determination is estimated applying the optimal-observable procedure
New hints for testing anomalous top-quark interactions at future linear colliders
No full textAngular and energy distributions for leptons and bottom quarks in the process have been calculated assuming the most general top-quark couplings. The double distributions depend both on modification of the t t ̄ production and t (−) → b (−) W decay vertices. However, the leptonic angular distribution turned out to be totally insensitive to non-standard parts of Wtb vertex. Distributions of decay products for polarized top quark in its rest frame have been also calculated. It has been found that the factorization of energy and angular dependence for the double leptonic distribution noticed earlier for the Standard Model survives even if one allows for deviations from the V–A interactions, and the SM angular leptonic distribution turned out to be preserved by anomalous decay vertex
Four Fermi effective operators in top quark production and decay
No full textEffects of four-Fermi-type new interactions are studied in top-quark pair production and their subsequent decays at future colliders. Secondary-lepton-energy distributions are calculated for arbitrary longitudinal beam polarizations. An optimal-observables procedure is applied for the determination of new parameters
Optimal-Observable Analysis of Possible New Physics Using the b-quark in
No full textWe study possible anomalous top-quark couplings generated by SU(2) x U(1) gauge invariant dimension-6 effective operators, using the final b-quark momentum distribution in gamma gamma -> tt -> bX. Taking into account non-standard tt gamma, tbW and gamma gamma H couplings, we perform an optimal-observable analysis in order to estimate the precision for the determination of all relevant non-standard couplings
Probing Anomalous Top-Quark Couplings Induced by Dim.6 Operators at Photon Colliders
No full textPossible anomalous top-quark couplings induced by SU(2) x U(1) gauge-invariant dimension-6 effective operators were studied in the process of t t-bar productions and decays at polarized gamma gamma colliders. Two CP-violating asymmetries, a linear-polarization asymmetry and a circular-polarization asymmetry, were computed including both non-standard [t t-bar gamma] and [gamma gamma H] couplings. An optimal-observable analysis for the process gamma gamma --> t t-bar --> l^{+-} ... was performed in order to estimate the precision for determination of all relevant non-standard couplings, including the anomalous tbW coupling.Possible anomalous top-quark couplings induced by SU (2)× U (1) gauge-invariant dimension-6 effective operators were studied in the process of t t ̄ productions and decays at polarized γγ colliders. Two CP -violating asymmetries, a linear-polarization asymmetry and a circular-polarization asymmetry, were computed including both non-standard t t ̄ γ and γγH couplings. An optimal-observable analysis for the process γγ→t t ̄ →l ± ⋯ was performed in order to estimate the precision for determination of all relevant non-standard couplings, including the anomalous tbW coupling.Possible anomalous top-quark couplings induced by SU(2) x U(1) gauge-invariant dimension-6 effective operators were studied in the process of t t-bar productions and decays at polarized gamma gamma colliders. Two CP-violating asymmetries, a linear-polarization asymmetry and a circular-polarization asymmetry, were computed including both non-standard [t t-bar gamma] and [gamma gamma H] couplings. An optimal-observable analysis for the process gamma gamma --> t t-bar --> l^{+-} ... was performed in order to estimate the precision for determination of all relevant non-standard couplings, including the anomalous tbW coupling
Decoupling theorem in top productions/decays revisited : To what extent can we understand it visually?
No full textI revisit here the decoupling theorem in top-quark productions/decays, which states that the angular distribution of any final-particle produced in those processes does not depend on any possible nonstandard top-quark decay interactions at their leading order when certain conditions are satisfied. Toward a simple, intuitive and visual understanding of this theorem, I will study to what extent we could explain why such a theorem holds without relying on any specific/detailed calculations.journal articl
