DC Field | Value | Language |
---|---|---|
dc.contributor.advisor | Kim, Jae-Kwan | - |
dc.contributor.advisor | 김재관 | - |
dc.contributor.author | Kim, Yeong-Gyun | - |
dc.contributor.author | 김영균 | - |
dc.date.accessioned | 2011-12-14T07:27:12Z | - |
dc.date.available | 2011-12-14T07:27:12Z | - |
dc.date.issued | 1997 | - |
dc.identifier.uri | http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=112573&flag=dissertation | - |
dc.identifier.uri | http://hdl.handle.net/10203/47554 | - |
dc.description | 학위논문(박사) - 한국과학기술원 : 물리학과, 1997.2, [ iv, 71 p. ] | - |
dc.description.abstract | We study the some topics on the $b\bar{b}$ events in the $e^+e^-$ collision at Z resonance. According to the Standard Model, b quarks are produced almost completely longitudinally polarized at $\sqrt{s}\simeqM_Z$. Unfortunately, a measurement of $P_b$ is not as much straightforward. This is mainly due to hadronization and fragmentation properties b quarks that largely dilute and obscure b polarization effects in the observed final states. We suggest a strategy for detecting b polarization effects in the $e^+e^-$ collision on Z resonance. We select dilepton events in the $Z → b\bar{b}$ events, in which both b hadrons decay semileptonically. Then we catalog these events into the ``like-sign`` events in which leptons have same charge and the ``unlike-sign`` events in which leptons have different charge. Clearly the existence of the ``like-sign`` events is a signal of b-$\bar{B}$ mixing. In the ``like-sign`` events, one of the b hadrons must be a $B_s$ or $B_d$ meson. However this is not the case in the ``unlike-sign`` events. So the fractions of $∧_b$ would be different for each types of events. Then we have two types of inclusive leptonic samples with different $∧_b$ fractions. With these dileptonic events, the several polarization-dependent variables are calculated. Using this method, the b polarization effects may be detected without large uncertainties of b fragmentation and $∧_b$ decay model. The inclusive semi-leptonic decays of b mesons are attracting a lot of attention as testing ground for hadronic models and as a source for the weak parameters $V_ub$ and $V_cb$. In general there are two kinds of models which predict the lepton energy spectrum of inclusive decays of b meson. In the ACCMM model, the free quark decay picture is improved by taking into account the Fermi motion of the spectator in the b-meson. The second approach uses the parton model at an infinite momentum frame(IMF). It pictures the mesonic decay as the decay of the partons. The probabil... | eng |
dc.language | eng | - |
dc.publisher | 한국과학기술원 | - |
dc.title | $b\bar{b}$ events in the $e^+e^-$ collision at Z resonance | - |
dc.title.alternative | Z 공명에서의 $e^+e^-$ 충돌에 의한 $b\bar{b}$ 사건들 | - |
dc.type | Thesis(Ph.D) | - |
dc.identifier.CNRN | 112573/325007 | - |
dc.description.department | 한국과학기술원 : 물리학과, | - |
dc.identifier.uid | 000925065 | - |
dc.contributor.localauthor | Kim, Yeong-Gyun | - |
dc.contributor.localauthor | 김영균 | - |
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