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H. Anlauf H. D. Dahmen P. Manakos T. Mannel T. Ohl 《Zeitschrift fur Physik C Particles and Fields》1991,52(4):655-658
We estimate the higher order QED corrections to the QED Compton events at HERA employing the leading logarithmic approximation to all orders in α. The Compton events are events of the typee+p→e′+γ+ Hadrons, wheree′ and γ have nearly balancedp T . 相似文献
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H. D. Dahmen P. Manakos T. Mannel T. Ohl 《Zeitschrift fur Physik C Particles and Fields》1989,44(1):139-147
The photon two-point function is calculated using the exponential representation for the time-evolution operator taking into account terms up to second order ine in the exponent. The limiting case of vanishing electron mass is examined and it is shown that mass singularities cancel by means of unitarity. Near mass shell the causal Green function exhibits in the limit of vanishing electron mass the expected cut behaviour, off mass shell we recover the result of the usual perturbation theory. 相似文献
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Frabetti PL Cheung HW Cumalat JP Dallapiccola C Ginkel JF Greene SV Johns WE Nehring MS Butler JN Cihangir S Gaines I Garren L Garbincius PH Gourlay SA Harding DJ Kasper P Kreymer A Lebrun P Shukla S Bianco S Fabbri FL Sarwar S Zallo A Culbertson R Gardner RW Greene R Wiss J Alimonti G Bellini G Caccianiga B Cinquini L Di Corato M Giammarchi M Inzani P Leveraro F Malvezzi S Menasce D Meroni E Moroni L Pedrini D Perasso L Sala A Sala S Toretta D Vittone M Buchholz D Claes D Gobbi B O'Reilly B 《Physical review letters》1993,70(12):1755-1758
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T. Mannel B. D. Pecjak A. A. Pivovarov 《The European Physical Journal C - Particles and Fields》2011,71(4):1607
We use QCD sum rules to compute the matrix elements of the ΔB=2 operators appearing in the heavy-quark expansion of the width difference of the B
s
mass eigenstates. The main focus of our analysis is on the subleading operators R
2 and R
3, which appear at next-to-leading order in the 1/m
b
expansion. The matrix elements of these operators are already essential for precise phenomenology, but their calculation
in lattice QCD is lacking and the values given here provide a first estimate of their values. We conclude that the violation
of the factorization approximation for these matrix elements due to non-perturbative vacuum condensates is as low as 1–2%. 相似文献
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We calculate branching ratios and the polarization in the decay ofB mesons to two vector mesons using heavy quark symmetries to evaluate the current matrix elements. 相似文献
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Hans D. Dahmen Thomas Mannel Panagiotis Manakos 《Zeitschrift fur Physik C Particles and Fields》1988,40(3):435-441
A unitary approximation for the time-evolution operator given through the exponential representation is used to calculate the renormalization constants of QED. The results obtained by this method are the same as the renormalization group improvement of the usual perturbation series taking into account terms up to the second order ine. 相似文献
9.
A manifestly non-renormalizable effective Lagrangian with four fermion coupling is proposed for relativistic Hartree Fock calculations. It is briefly compared with other field theoretic models. 相似文献
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We consider an effective theory (ET) approach to flavor-violating processes beyond the standard model, where the breaking of flavor symmetry is described by spurion fields whose low-energy vacuum expectation values are identified with the standard model Yukawa couplings. Insisting on canonical mass dimensions for the spurion fields, the large top-quark Yukawa coupling also implies a large expectation value for the associated spurion, which breaks part of the flavor symmetry already at the UV scale Lambda of the ET. Below that scale, flavor symmetry in the ET is represented in a nonlinear way by introducing Goldstone modes for the partly broken flavor symmetry and spurion fields transforming under the residual symmetry. As a result, the dominance of certain flavor structures in rare quark decays can be understood in terms of the 1/Lambda expansion in the ET. 相似文献