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71.
S. Baeßler F. Ayala Guardia M. Borg F. Glück W. Heil G. Konrad I. Konorov R. Muñoz Horta G. Petzoldt D. Rich M. Simson Yu. Sobolev H. -F. Wirth O. Zimmer 《The European Physical Journal A - Hadrons and Nuclei》2008,38(1):17-26
The neutron decay spectrometera SPECT has been built to perform a precise measurement of the proton spectrum shape in the decay of free neutrons. Such a
measurement allows a determination of the neutrino electron angular-correlation coefficienta . The present best experiments have an uncertainty of Δa/a = 5% and since the seventies there is no substantial improvement. Witha SPECT, we aim for an uncertainty which is lower by more than an order of magnitude, thus enabling us to perform several precise
tests of the Standard Model. In our first beam time at the particle physics beam MEPHISTO at the Forschungsneutronenquelle
Heinz Maier-Leibnitz, we studied the properties of the spectrometer. The most serious problem turned out to be the situation-
and time-dependent behavior of the background. From the data sets from this beam time in which a background problem was not
obvious, we could extract a value ofa = - 0.1151±0.0040stat , but we could not quantify the background uncertainty. We show ways to deal with the background and other problems for future
beam times. 相似文献
72.
We study the CP-averaged branching fractions and the CP-violating asymmetries in the pure annihilation decays ofB _s~0→a_0~+a _0~-andB _d~0→K_0~(*+)K_0~(*-),where a_0[K_0~*]denotes the scalar a_0(980) and a_0(1450)[K_0~*(800)(ork)and K_0~*(1430)],with the perturbative QCD factorization approach under the assumption of two-quark structure for the a_0and K_0~*states.The numerical results show that the branching ratios of theB _d~0→K_0~(*+)K_0~(*-)decays are in the order of 10~(-6),while the decay rates of theB_s~0→a_0~+a _0~-modes are in the order of 10~(-5).In light of the measured modes with the same quark components in the pseudoscalar sector,namely,B _d~0→K~+K~-and B_s~0→p p~(+-),the predictions for the considered decay modes in this work are expected to be measured at the Large Hadron Collider beauty and/or Belle-Ⅱ experiments in the (near) future.Meanwhile,it is of great interest to find that the twist-3 distribution amplitudes φ~S and φ~T with inclusion of the Gegenbauer polynomials for the scalar a_0(1450) and K_0~*(1430)states in scenario2 contribute slightly to the branching ratios while significantly to the CP violations in the B_d~0→K_0~*(14 30)~+K_0*(14 30)~-and B_s~0→a_0(1450)~+a_0(1450)~-decays,which indicates that,compared to the asymptotic φ~Sand φ~T,these Gegenbauer polynomials could change the strong phases evidently in these pure annihilation decay channels.These predictions await for the future confirmation experimentally,which could further provide useful information to help explore the inner structure of the scalars and shed light on the annihilation decay mechanism. 相似文献
73.
By studying the \begin{document}$\eta_c$\end{document} ![]()
![]()
exclusive decay to double glueballs, we introduce a model to phenomenologically mimic the gluon-pair-vacuum interaction vertices, namely the \begin{document}$0^{++}$\end{document} ![]()
![]()
model. Based on this model, we study glueball production in pseudoscalar quarkonium decays, explicitly \begin{document}$\eta_c \to f_0(1500)\eta(1405)$\end{document} ![]()
![]()
, \begin{document}$\eta_b\to f_0(1500)\eta(1405)$\end{document} ![]()
![]()
, and \begin{document}$\eta_b\to f_0(1710)\eta(1405)$\end{document} ![]()
![]()
processes. Among them \begin{document}$f_0(1500)$\end{document} ![]()
![]()
and \begin{document}$f_0(1710)$\end{document} ![]()
![]()
are well-known scalars possessing large glue components, while \begin{document}$\eta(1405)$\end{document} ![]()
![]()
is a potential candidate for a pseudoscalar glueball. The preliminary calculation results indicate that these processes are marginally accessible in the presently running experiments BES III, BELLE II, and LHCb. 相似文献
74.
Sabato D'Auria Paolo Bazzicalupo Mosé Rossi Ignacy Gryczynski Joseph R. Lakowicz 《Journal of fluorescence》2000,10(1):27-34
ASCUT-1 is a protein found in cuticlin, the insoluble residue of the cuticles of the nematode Ascaris lumbricoides. It contains the CUT-1-like domain which is shared by members of a novel family of components of extracellular matrices. The monomeric form of ASCUT-1 contains a single tryptophan residue. An understanding of the structure-function relationship of the protein under different chemical-physical conditions is of fundamental importance for an understanding of its structure and function in cuticles. In this paper we report the effect of the temperature and sodium dodecyl sulfate on the structural stability of this protein. The structure of the protein was studied in the temperature range 25–85°C in the absence and in the presence of sodium dodecyl sulfate by frequency-domain measurements of the intrinsic fluorescence intensity and anisotropy decays. The time-resolved fluorescence data in the absence of SDS indicated that the tryptophanyl emission decays were well described by a bimodal lifetime distribution, and that the temperature increases resulted in the sharpening and in the shortening of the tryptophanyl lifetime distribution. In the presence of SDS an unimodal fluorescence lifetime distribution as well as a marked decrease in the anisotropy decay values were observed. 相似文献
75.
A. Lusiani 《中国物理C(英文版)》2008,32(6):504-508
Since 1999, the BABAR collaboration has accumulated and studied large samples of tau lepton pairs. The main physics results are reported. 相似文献
76.
Hiroyasu Ejiri 《Progress in Particle and Nuclear Physics》2010,64(2):249-257
Neutrino-less double beta decays (0νββ), which violate the lepton number conservation law by ΔL=2, are unique and realistic probes for studying the Majorana nature of neutrinos, the ν mass spectrum and the absolute mass scale, the lepton sector CP and others beyond the standard electro-weak theory. Neutrino nuclear responses (nuclear matrix elements M0ν) are crucial to extract neutrino properties of the particle physics interests from experimental 0νββ rates. Subjects discussed include 0νββ processes and Majorana neutrinos, the present and future 0νββ experiments, and neutrino nuclear responses (M0ν) and charge exchange reactions. 相似文献
77.
Dong-Sheng Du Xue-Qian Li Zheng-Tao Wei Bing-Song Zou 《The European Physical Journal A - Hadrons and Nuclei》1999,4(1):91-96
We study the final-state interactions in B →π K decays through B → VV →π K processes where the inelastic rescattering occurs
via single pion exchange. The next-to-leading order low-energy effective Hamiltonian and Bauer-Stech-Wirbel (BSW) model are
used to evaluate the weak transition matrix elements and final-state interactions. We found that the final-state interaction
effects in B →ρ K*→π K processes are significant. The Fleischer-Mannel relation for the Cabibbo-Kobayashi-Maskawa (CKM) angle γ can be significantly
modified.
Received: 13 August 1998 相似文献
78.
The exclusive B→K(*) e+ e- decays are studied in the topcolor-assisted technicolor model and in the minimal technicolor model. We find that the angular distribution and the dilepton mass distribution in B→K(*) e+ e- which can be reliably predicted in the large dilepton mass region, are very sensitive to the actual form of the new interaction. This provides a good test to physics beyond the standard model. 相似文献
79.
In order to make a further confirmation of the assignments of the excited bottom and bottom-strange mesons B1(5721),B2^*(5747),Bs1(5830)and Bs2^*(5840)and identify possible assignments of BJ(5840)and BJ(5970),we study the strong decay of these states with the 3P0 decay model.Our analysis supports the assignments of B1(5721)and B2*(5747)as the 1P'1 and 1^3P2 states,and Bs1(5830)and Bs2^*(5840)as the strange partners of B1(5721)and B2^*(5747).Besides,we tentatively identify the recently observed BJ(5840)and BJ(5970)as the 2^3S1 and 13D3 states.It is noted that these conclusions need further confirmation by measurements of the decay channels BJ(5840)→Bπand BJ(5970)→Bπ. 相似文献
80.
Hsiang Nan Li 《Pramana》2006,67(5):755-762
I discuss some puzzles observed in exclusive B-meson decays, concentrating on the large difference between the direct CP asymmetries in the B
0 → π−
K
= and B
± → π0
K
± modes, the large B
0 → π0π0 branching ratio, and the large deviation of the mixing-induced CP asymmetries in the b → sqq penguins from those in the b → ccs trees. 相似文献