共查询到20条相似文献,搜索用时 109 毫秒
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基于扩展的Su-Schrieffer-Heeger紧束缚模型和非绝热动力学方法, 研究了共轭聚合物材料中均匀无序效应对极化子输运动力学的影响. 研究发现: 极化子的动力学输运过程由外加电场和均匀无序效应共同决定; 在大部分电场范围下, 均匀无序效应对极化子输运的影响不太明显, 几乎可以忽略; 但在弱电场下, 均匀无序效应不利于极化子输运. 与高斯型无序效应下极化子的输运过程相比, 具有均匀无序的薄膜形貌更有利于极化子输运. 相似文献
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“标准模型”是用来描写一种量子理论的术语,这种理论包括了强相互作用理论(量子色动力学)和弱电统一理论.图中也把引力相互作用包括了进来,尽管它不属于标准模型. 相似文献
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“标准模型”是用来描写一种量子理论的术语,这种理论包括了强相互作用理论(量子色动力学)和弱电统一理论.图中也把引力相互作用包括了进来,尽管它不属于标准模型. 相似文献
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利用QCD因子化方法,并采用具有质量的有效胶子传播子来消除端点发散,计算了纯湮没衰变( ̄Bs)→π π-过程的CP平均分支比并对该过程的CP破坏进行了具体研究.结果表明:该过程的CP平均分支比为1.24×10-7,同时企鹅图对该过程起着主要贡献;( ̄Bs)→π π-过程中直接CP破坏参数Cππ估算为-0.05,混合CP破坏参数Sππ比较大,可达到0.18.该过程在未来的LHC-b物理实验上是完全有可能被测量到的,通过对该过程的研究能够使我们更好地了解B介子无璨衰变的动力学机制和胶子的性质. 相似文献
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N. G. Deshpande Xiao-Gang He Sechul Oh 《Zeitschrift fur Physik C Particles and Fields》1997,74(2):359-368
We study the influence of penguin (especially, electroweak penguin) effects on some methods of measuring the angles α, β, and γ in the CKM unitarity triangle. We use next-to-leading order effective Hamiltonian, and present numerical estimates based on the factorization approximation. We find that some techniques suggested in the literature, especially for α determination, are not workable in light of the electroweak penguin effects. Nevertheless, there are methods that would work for each angle determination. For angle β we consider B → D +D~ - mode and estimate the penguin contamination. For angle γ we consider a method based on SU(3) symmetry and carefully consider SU(3) breaking effects. We point out regions in the parameter space where this method could be used reliably. 相似文献
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The influence of strong and electroweak penguin amplitudes in B/B→π+π- is investigated in connection with the determination of the unitarity triangle angle a of the CKM matrix. A relation between the observable asymmetry, the angle α, and the penguin amplitude is established. A model calculation of the penguin amplitude shows that the CP asymmetry in B0→π+π- decays is only mildly influenced by the penguin amplitudes. Experimental limits on pure penguin and penguin dominated processes are consistent with the model. This information also suggests in a rather model-independent way that penguin amplitudes will not be a serious complicating factor in the determination ofa from the π+π- time-dependent asymmetry. 相似文献
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Dong-Sheng Du Zheng-Tao Wei 《The European Physical Journal C - Particles and Fields》1998,5(4):705-709
The space-like penguin contributions to branching ratios and CP asymmetries in charmless decays of to two pseudoscalar mesons are studied using the next-to-leading order low energy effective Hamiltonian and factorization
approximation. Both the gluonic penguin and the electroweak penguin diagrams are considered. In addition the annihilation
diagram contributions are also taken in account. We find that the space-like penguin effects are significant.
Received: 15 December 1997 / Published online: 23 June 1998 相似文献
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Using the next-to-leading order low energy effective Hamiltonian for |ΔB|=1, ΔC=ΔU=0 transitions, the contributions of electroweak penguin operators in charmless B ±,0→PP and PV decays are estimated in the standard model. We find that, for some channels, the electroweak penguin effects can enhance or reduce the QCD penguin and/or tree level contributions by at least 30%, and can even play a dominant role. 相似文献
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We present a general parametrization of , and , decays, taking into account both electroweak penguin and rescattering effects. This formalism allows – among other things
– a generalized implementation of the strategies that were recently proposed by Neubert and Rosner to probe the CKM angle
with the help of , decays. In particular, it allows us to investigate the sensitivity of the extracted value of to the basic assumptions of their approach. We find that certain rescattering processes may have an important impact and
emphasize that additional hadronic uncertainties may be due to non-factorizable SU(3)-breaking effects. The former can be controlled by using SU(3) flavour symmetry arguments and additional experimental information provided by modes. We propose a new strategy to probe the angle with the help of the neutral decays , , which is theoretically cleaner than the , approach. Here rescattering processes can be taken into account by just measuring the CP-violating observables of the decay
. Finally, we point out that an experimental analysis of modes would also be very useful to probe the CKM angle , as well as electroweak penguins, and we critically compare the virtues and weaknesses of the various approaches discussed
in this paper. As a by-product, we point out a strategy to include the electroweak penguins in the determination of the CKM
angle from decays.
Received: 14 June 1999 / Published online: 28 September 1999 相似文献
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Wagner A Muntz C Oeschler H Sturm C Barth R Cieslak M D&ecedil;bowski M Grosse E Koczon P Laue F Mang M Miskowiec D Schwab E Senger P Beckerle P Brill D Shin Y Strobele H Walus W Kohlmeyer B Puhlhofer F Speer J Yoo IK 《Physical review letters》2000,84(1):18-21
Recent results from CLEO on B-->Kpi indicate that the phase gamma may be substantially different from that obtained from other fit to the KM matrix elements in the standard model. We show that gamma extracted using B-->Kpi,pipi is sensitive to new physics occurring at loop level. It provides a powerful method to probe new physics in electroweak penguin interactions. Using effects due to anomalous gauge couplings as an example, we show that within the allowed ranges for these couplings information about gamma obtained from B-->Kpi,pipi can be very different from the standard model prediction. 相似文献
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Surath Kumar Biswas V.P. Gautam 《The European Physical Journal C - Particles and Fields》1998,4(2):269-275
The effective vertex may be influenced by tree vertex formed by a mixing with heavy exotic isosinglet down type quarks. To study that the electroweak penguin diagrams involving
one insertion of the vertex have been considered and we have calculated the contribution arising out of those diagrams using the Fourth Generation
CKM matrix elements; also the applicability of the generalized GIM mechanism is considered. The additional effects of the heavy isosinglets are compared with the effects of exotic heavy isodoublets
appearing in multi-generational models. We see that in the effective vertex amplitude, the down flavour changing contribution
interferes constructively with the one loop penguin diagrams and experimental data may put constraint on the fourth generation
down quark mass.
Received: 21 March 1997 / Revised version: 19 August 1997 / Published online: 20 February 1998 相似文献
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We study B meson decays to two charmless baryons in the diquark model, including strong and electroweak penguins as well as the tree
operators. It is shown that penguin operators can enhance considerably, but affect only slightly, where and are non-strange and strange baryons, respectively. The dependence of the decay rates due to tree–penguin interference is illustrated. In principle, some of the modes could dominate over for , but in general the effect is milder than their mesonic counterparts. This is because the operator can only produce vector but not scalar diquarks, while the opposite is true for and . Predictions from the diquark model are compared to those from the sum rule calculation. The decays and inclusive baryonic decays are also discussed.
Received: 27 December 2001 / Published online: 5 April 2002 相似文献
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The measured B-->pipi,piK branching ratios (BRs) exhibit puzzling patterns. We point out that the B-->pipi hierarchy can be nicely accommodated in the standard model (SM) through nonfactorizable hadronic interference effects, whereas the B-->piK system may indicate new physics (NP) in the electroweak (EW) penguin sector. Using the B-->pipi data and the SU(3) flavor symmetry, we fix the hadronic B-->piK parameters and show that any currently observed feature of the B-->piK system can be easily explained through enhanced EW penguin diagrams with a large CP-violating NP phase. This in turn implies in particular an enhancement of the K(L)-->pi(0)nunu rate by 1 order of magnitude, with BR(K(L)-->pi(0)nunu) approximately 4BR(K+-->pi(+)nunu), BR(K(L)-->pi(0)e(+)e(-))=O(10(-10)), and (sin(2beta)(pinunu)<0. We address also other rare K and B decays and B(d)-->phiK(S). 相似文献
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John M. Losecco 《Pramana》2004,62(3):583-586
We summarize results on a number of observations of penguin dominated radiative decays of theB meson. Such decays are forbidden at tree level and proceed via electroweak loops. As such they may be sensitive to physics
beyond the standard model. The observations have been made at the BaBar experiment at PEP-II, the asymmetricB factory at SLAC. 相似文献