scholarly journals Soft spectator scattering in the nucleon form factors at largeQ2within the soft collinear effective theory approach

2011 ◽  
Vol 83 (9) ◽  
Author(s):  
Nikolai Kivel ◽  
Marc Vanderhaeghen
Keyword(s):  
Form Factors ◽  
Effective Theory ◽  
Theory Approach ◽  
Soft Collinear Effective Theory ◽  
Nucleon Form Factors

scholarly journals Consistent treatment of rapidity divergence in soft-collinear effective theory

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Junegone Chay ◽  
Chul Kim
Keyword(s):  
Heavy Quark ◽  
Soft Mode ◽  
Form Factors ◽  
Effective Theory ◽  
Large Rapidity ◽  
Soft Modes ◽  
Heavy Quark Mass ◽  
Soft Collinear Effective Theory ◽  
Matching Procedure ◽  
Consistent Treatment

Abstract In soft-collinear effective theory, we analyze the structure of rapidity divergence due to the collinear and soft modes residing in disparate phase spaces. The idea of an effective theory is applied to a system of collinear modes with large rapidity and soft modes with small rapidity. The large-rapidity (collinear) modes are integrated out to obtain the effective theory for the small-rapidity (soft) modes. The full SCET with the collinear and soft modes should be matched onto the soft theory at the rapidity boundary, and the matching procedure becomes exactly the zero-bin subtraction. The large-rapidity region is out of reach for the soft mode, which results in the rapidity divergence. The rapidity divergence in the collinear sector comes from the zero-bin subtraction, which ensures the cancellation of the rapidity divergences from the soft and collinear sectors. In order to treat the rapidity divergence, we construct the rapidity regulators consistently for all the modes. They are generalized by assigning independent rapidity scales for different collinear directions. The soft regulator incorporates the correct directional dependence when the innate collinear directions are not back-to-back, which is discussed in the N-jet operator. As an application, we consider the Sudakov form factor for the back-to-back collinear current and the soft-collinear current, where the soft rapidity regulator for a soft quark is developed. We extend the analysis to the boosted heavy quark sector and exploit the delicacy with the presence of the heavy quark mass. We present the resummed results of large logarithms in the form factors for various currents with the light and the heavy quarks, employing the renormalization group evolution on the renormalization and the rapidity scales.

Symmetry-breaking corrections to the form factors for heavy-to-heavy B-meson at large recoil

2019 ◽  
Vol 34 (08) ◽  
pp. 1950046
Author(s):  
Saba Shafaq ◽  
Ishtiaq Ahmed ◽  
M. Jamil Aslam
Keyword(s):  
Perturbation Theory ◽  
Symmetry Breaking ◽  
Heavy Quark ◽  
B Meson ◽  
Form Factors ◽  
Heavy Meson ◽  
Effective Theory ◽  
Vertex Corrections ◽  
Soft Collinear Effective Theory ◽  
Heavy Quark Limit

The present study investigates the decay of B to heavy meson using the soft collinear effective theory. By assigning different loop momenta, the factorization has been tested and it is found to be valid to all orders in the perturbation theory. It is noted that theory contains one hard collinear and two soft modes depending upon virtuality of different momenta. In the next step, symmetry-conserving relations (in heavy quark limits) to the form factors have been studied. These relations are then used to parametrize the form factors to get symmetry-breaking corrections. These symmetry-breaking corrections can be calculated using perturbative (vertex corrections) as well as nonperturbative (hard spectator interactions) QCD. It is found that in the heavy quark limit, these symmetry contributions do not contribute to the form factors that appear in physical observables for the case of [Formula: see text] decays which are contrary to the heavy-to-light meson decays.

scholarly journals Precision calculations of B→V form factors from soft-collinear effective theory sum rules on the light-cone

2020 ◽  
Vol 101 (7) ◽  
Author(s):  
Jing Gao ◽  
Cai-Dian Lü ◽  
Yue-Long Shen ◽  
Yu-Ming Wang ◽  
Yan-Bing Wei
Keyword(s):  
Light Cone ◽  
Sum Rules ◽  
Form Factors ◽  
Effective Theory ◽  
Soft Collinear Effective Theory

scholarly journals Precision calculations of the double radiative bottom-meson decays in soft-collinear effective theory

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Yue-Long Shen ◽  
Yu-Ming Wang ◽  
Yan-Bing Wei
Keyword(s):  
Equations Of Motion ◽  
Form Factors ◽  
Bottom Meson ◽  
Photon Radiation ◽  
Effective Theory ◽  
Tree Level ◽  
Meson Decay ◽  
Neutral Meson ◽  
Power Correction ◽  
Soft Collinear Effective Theory

Abstract Employing the systematic framework of soft-collinear effective theory (SCET) we perform an improved calculation of the leading-power contributions to the double radiative Bd,s-meson decay amplitudes in the heavy quark expansion by including the perturbative resummation of enhanced logarithms of mb/ΛQCD at the next-to-leading-logarithmic accuracy. We then construct the QCD factorization formulae for the subleading power contributions arising from the energetic photon radiation off the constituent light-flavour quark of the bottom meson at tree level. Furthermore, we explore the factorization properties of the subleading power correction from the effective SCET current "Image missing" at $$ \mathcal{O}\left({\alpha}_s^0\right) $$ O α s 0 by virtue of the operator identities due to the classical equations of motion. The higher-twist contributions to the Bd,s→ γγ helicity form factors from the two-particle and three-particle bottom-meson distribution amplitudes are evaluated with the perturbative factorization technique, up to the twist-six accuracy. In addition, the subleading power weak-annihilation contributions from both the current-current and QCD penguin operators are taken into account at the one-loop accuracy. We proceed to apply the operator-production-expansion-controlled dispersion relation for estimating the power-suppressed soft contributions to the double radiative Bd,s-meson decay form factors, which cannot be factorized into the light-cone distribution amplitudes of the heavy-meson and the resolved photon as well as the hard-scattering kernel calculable in perturbation theory canonically. Phenomenological explorations of the radiative Bd,s→ γγ decay observables in the presence of the neutral-meson mixing, including the CP-averaged branching fractions, the polarization fractions and the time-dependent CP asymmetries, are carried out subsequently with an emphasis on the numerical impacts of the newly computed ingredients together with the theory uncertainties from the shape parameters of the HQET bottom-meson distribution amplitudes.

IMPACT OF POSITIVE PARITY HEAVY MESONS ON CHARM MESON DECAYS

2008 ◽  
Vol 23 (21) ◽  
pp. 3196-3199 ◽  
Author(s):  
SVJETLANA FAJFER ◽  
JERNEJ F. KAMENIK
Keyword(s):  
Heavy Quark ◽  
Form Factors ◽  
Negative Parity ◽  
Heavy Meson ◽  
Effective Theory ◽  
Charm Meson ◽  
Soft Collinear Effective Theory ◽  
Heavy Quark Symmetry ◽  
The Impact

We discuss strong decays of positive and negative parity charmed mesons within heavy meson chiral perturbation theory and study the impact of excited charm states on the determination of the effective meson couplings. Motivated by recent experimental results we also reconsider semileptonic D → Plνl and D → Vlνl decays within a model which combines heavy quark symmetry and properties of the chiral Lagrangian. Using limits of soft collinear effective theory and heavy quark effective theory we parametrize the semileptonic form factors. We include excited charm meson states in our Lagrangian and determine their impact on the charm meson semileptonic form factors.

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