共查询到20条相似文献,搜索用时 31 毫秒
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V. Fanti A. Lai L. Musa A. Nappi M.G. Setzu 《Zeitschrift fur Physik C Particles and Fields》1997,76(4):653-657
The rate of the decay of the neutral K meson into K L 0 → μμγ has been measured with the NA48 detector at the CERN SPS. A total of 59 events has been observed with an estimated background of 14 events. The overall Kaon flux was determined to be 1.2 × 109. This observation corresponds to a branching ratio of (3.4 ± 0.6stat ± 0.4sys × 10-7. Using this branching ratio the parameter αK* describing the relative strength of the two contributing amplitudes to this decay, through intermediate pseudoscalar or vectorlike mesons, was measured to be αK* = -0.04+ -0.21 +0.24 . 相似文献
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《Physics Reports》2002,370(6):537-680
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《Physics letters. [Part B]》1987,199(1):139-146
The decay rates of KL → 2γ and KS → 2γ have been measured at the CERN SPS. The results are Γ(KL→2γ)/χ(KL→2π0)=0.632±0.004±0.008 and Γ(KS→2γ)/Γ(KL→2γ)=2.3 ±1.0±0.4. This is the first observation of KS→2γ decays. 相似文献
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I. V. Ajinenko S. A. Akimenko G. A. Akopdzhanov K. S. Belous G. I. Britvich I. G. Britvich A. P. Filin V. N. Govorun A. V. Inyakin V. A. Khmelnikov A. S. Konstantinov V. F. Konstantinov I. Ya. Korolkov V. M. Leontiev V. P. Novikov V. F. Obraztsov V. A. Polyakov V. I. Romanovsky V. M. Ronjin V. A. Senko N. A. Shalanda M. M. Shapkin V. I. Shelikhov N. E. Smirnov A. A. Sokolov O. G. Tchikilev E. V. Vlasov O. P. Yushchenko V. N. Bolotov S. V. Laptev A. Yu. Polyarush V. E. Postoev S. V. Yashchenko B. Zh. Zalikhanov V. Z. Serdyuk 《Physics of Atomic Nuclei》2002,65(11):2064-2069
The decay K ? → e ? νπ 0 has been studied using in-flight decays detected with the ISTRA+ setup working at the 25-GeV negative secondary beam of the U-70 PS. About 130K events were used for the analysis. The λ + parameter of the vector form factor has been measured: λ +=0.0293±0.0015(stat.)±0.002(syst.). The limits on the possible tensor and scalar couplings have been derived: f T/f +(0)=?0.045±0.060(stat.) and f S/f +(0)=?0.019 ?0.016 +0.025 (stat.). 相似文献
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Alexander Nehrkorn 《Hyperfine Interactions》2016,237(1):96
The tau lepton and its reconstruction at CMS are briefly described. This is followed by a summary of the searches for a standard model Higgs boson and neutral Higgs bosons from the minimal supersymmetric extension of the standard model decaying into pairs of tau leptons performed by the CMS Collaboration. The data samples used in these searches were collected during the first running period of the LHC and contain 4.9 fb?1 at \(\sqrt {s}=7\,\text {TeV}\) and 19.7 fb?1 at \(\sqrt {s}=8\,\text {TeV}\). 相似文献
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《Nuclear Physics B》1998,513(3):555-572
We have measured the branching ratio of the radiative decay π → μνγ. The energies of the gamma-ray and of the muon were both measured and the Dalitz-plot distribution of the decay was obtained. The data agree well with the theoretical prediction (QED internal bremsstrahlung) down to a γ-ray energy of 1 MeV. The discrepancy reported in a previous experiment is not confirmed. 相似文献
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We have studied \(D_s^ + \to K_0^{* + } \bar K^0\) and \(D_s^ + \to \bar K_0^{*0} K^ +\) decays in the factorization of the hadron currents approximation. The spectator model leads the decays have different but negligible branching ratios. We show, however, that the inclusion of annihilation contribution can enhance the branching ratios. We predict that \(B(D_s^ + \to \bar K_0^{*0} K^ + )\) and \(B(D_s^ + \to K_0^{* + } \bar K^0 )\) could be around 2%. 相似文献
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The observation potential of the decay B+ K+K+– with the ATLAS detector at LHC is described in this paper. In the Standard Model this decay mode is highly suppressed, while in models beyond the Standard Model it could be significantly enhanced. To improve the selection of the K+K+– final state, a charged hadron identification using Time-over-Threshold measurements in the ATLAS Transition Radiation Tracker was developed and used. 相似文献
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The exclusive decay of B + → D + K 0 is calculated by the QCD factorization method (QCDF) and final state interaction (FSI). First, the B + → D + K 0 decay is calculated via QCDF method. The result that is found by using the QCDF method is less than the experimental result. So FSI is considered to solve the B + → D + K 0 decay. For this decay, the D s + π0, D s + *ρ0, D s + *? via the exchange of \(\bar K^0\) , \(\bar K^{0*} \) , D ?, and D ?* mesons are chosen for the intermediate states. The above intermediate states are calculated by using the QCDF method. In the FSI effects, the results of our calculations depend on η as the phenomenological parameter. The range of this parameter is selected from 2 to 2.4. It is found that if η = 2.4 is selected, the numbers of the branching ratio are placed in the experimental range. The experimental branching ratio of this decay is less than 2.9 × 10?6 and our results calculated by QCDF and FSI are (0.16 ± 0.04) × 10?6 and (2.8 ± 0.09) × 10?6, respectively. 相似文献
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We study the rare B decay B→K*ℓ+ℓ- using soft-collinear effective theory (SCET). At leading power in 1/mb, a factorization formula is obtained valid to all orders in αs. For phenomenological application, we calculate the decay amplitude including order αs corrections, and resum the logarithms by evolving the matching coefficients from the hard scale
down to the scale
. The branching ratio for B→K*ℓ+ℓ- is uncertain due to the imprecise knowledge of the soft form factors ζ⊥(q2) and ζ∥(q2). Constraining the soft form factor ζ⊥(q2=0) from data on B→K*γ yields ζ⊥(q2=0)=0.32±0.02. Using this input, together with the light-cone sum rules to determine the q2-dependence of ζ⊥(q2) and the other soft form factor ζ∥(q2), we estimate the partially integrated branching ratio in the range 1 GeV2≤q2≤7 GeV2 to be (2.92+0.67
-0.61)×10-7. We discuss how to reduce the form factor related uncertainty by combining data on B→ρ(→ππ)ℓνℓ and B→K*(→Kπ)ℓ+ℓ-. The forward-backward asymmetry is less sensitive to the input parameters. In particular, for the zero-point of the forward-backward
asymmetry in the standard model, we get q0
2=(4.07+0.16
-0.13)
GeV2. The scale dependence of q0
2 is discussed in detail.
PACS 13.25.Hw, 12.39.St, 12.38.Bx 相似文献
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Aaij R Abellan Beteta C Adeva B Adinolfi M Adrover C Affolder A Ajaltouni Z Albrecht J Alessio F Alexander M Alkhazov G Alvarez Cartelle P Alves AA Amato S Amhis Y Anderson J Appleby RB Aquines Gutierrez O Archilli F Arrabito L Artamonov A Artuso M Aslanides E Auriemma G Bachmann S Back JJ Bailey DS Balagura V Baldini W Barlow RJ Barschel C Barsuk S Barter W Bates A Bauer C Bauer T Bay A Bediaga I Belogurov S Belous K Belyaev I Ben-Haim E Benayoun M Bencivenni G Benson S Benton J Bernet R 《Physical review letters》2012,108(18):181806
The angular distributions and the partial branching fraction of the decay B0 → K*0 μ+ μ- are studied by using an integrated luminosity of 0.37 fb(-1) of data collected with the LHCb detector. The forward-backward asymmetry of the muons, A(FB), the fraction of longitudinal polarization, F(L), and the partial branching fraction dB/dq2 are determined as a function of the dimuon invariant mass. The measurements are in good agreement with the standard model predictions and are the most precise to date. In the dimuon invariant mass squared range 1.00-6.00 GeV2/c4, the results are A(FB)=-0.06(-0.14)(+0.13)±0.04, F(L)=0.55±0.10±0.03, and dB/dq2=(0.42±0.06±0.03)×10(-7) c4/GeV2. In each case, the first error is statistical and the second systematic. 相似文献
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It has been claimed in a recent paper that the result given by the axial anomaly for the process 0 2 can be reproduced with the pion wave function calculated from a QCD sum rule. We examine the method and discover several deficiencies. In particular, the result does not coincide with the correct value given by the anomaly, but has an opposite sign. 相似文献
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Stefano Bertolini Francesco Vissani 《Zeitschrift fur Physik C Particles and Fields》1995,67(3):513-524
We present an update study of the penguin induced transitionbs in the minimalN=1 supersymmetric extension of the Standard Model with radiative breaking of the electroweak group. We include the effects of one-loop corrections to the Higgs potential and scalar masses, and perform a detailed analysis of the implications of the recently advocated relation |B|2 for the bilinear SUSY soft breaking parameter in grand unified theories. We show that the present upper and lower experimental limits on the inclusive decay sharply constrain the parameter space of the model for a wide range of tan values. 相似文献
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《Physics letters. [Part B]》1997,415(4):395-401
The short distance QCD corrections to b→sγγ are calculated in the leading logarithmic approximation. The equivalence of operator basis reduction for S-matrix elements by using the equations of motion or by proving a low energy theorem is discussed. We apply the above results to the exclusive Bs→γγ decay. The branching ratio of this decay is found to be 5×10−7 in the Standard Model. We also found that QCD corrections modify considerably the ratio between CP-even and CP-odd two-photon amplitudes. 相似文献