Semileptonic meson decays in point-form relativistic quantum mechanics: Unambiguous extraction of weak form factors

Abstract

The point-form version of the Bakamjian-Thomas construction is applied to the description of several semileptonic decays of mesons. Weak form factors are extracted without ambiguity for pseudoscalar-to-pseudoscalar as well as for pseudoscalar-to-vector transitions of mesons from the most general covariant decomposition of the weak current. No manifestation of cluster-separability violation appears in the form of non-physical contributions to the structure of such a current, in contrast to what happens in the electromagnetic case. Moreover, no frame dependence is observed when we extract the form factors from the most general covariant decomposition of the current, which contrasts with analogous front-form calculations that involve vector mesons in the transition. We present our results for heavy-light meson decays, i.e. B → D, as well as for B and D mesons decaying into π, ρ and K ( * ) and perform a numerical comparison with the analogous front-form approach. Differences between point and front forms that are not seen in the heavy-quark limit of qQ-systems appear. These differences are attributed to the different role that the non-valence contributions play in the description of hadronic reactions in each form. It is argued how contributions from missing Z-graphs can be estimated.

Weak transition form factors of heavy-light pseudoscalar mesons for space- and timelike momentum transfers

“…This paper continues previous work in which semileptonic weak B → D, π and D → K, π decays [1,2] have been investigated within a constituent-quark model making use of the point-form of relativistic quantum mechanics [3][4][5][6]. In this paper we study B → D, π and D → K, π transition form factors for space-and time-like momentum transfers, as can be measured in neutrino scattering and semileptonic weak decays.…”

“…For elastic scattering of an electron by a pseudoscalar meson it turned out that a complete covariant decomposition of the (conserved) current requires one additional spurious covariant, namely the sum of the incoming and outgoing electron fourmomenta [1,8]. 2 In addition, the form factors are ob- 2 The occurrence of an additional covariant parallels the spurious dependence of currents on the orientation of the light front in the covariant light-front approach discussed in Ref. [11].…”

“…Primed momenta with tilde are related to the corresponding momenta without tilde by means of a canonical boost, i.e. 2 . Note that due to the decay kinematics k b = kb and k ū = kū .…”

Aspects of open-flavour mesons in a comprehensive DSBSE study

“…From the theory point of view, one needs a thorough understanding of nonperturbative QCD, which is sought via different approaches such as the traditional quark model in relativistic forms [3][4][5][6][7][8][9][10][11], effective field theories [12][13][14][15], QCD sum rules (QSRs) [16][17][18][19], latticeregularized QCD [20][21][22][23][24], and covariant approaches to QCD bound states at various levels of sophistication and aspects pertaining thereto [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41].…”

Описание Радиационных Распадов В Рамках Мгновенной Формы Релятивистской Квантовой Механики

“…Эта конструкция позволяет добавлять взаимодействие пуанкаре-инвариантным способом. Конструкция оказалась весьма удачной и многократно применялась в разного рода задачах (см., например, работы [10]- [12] и приведенные там ссылки). В настоящей работе используется мгновенная форма РКМ.…”