Light-cone distribution amplitudes (LCDAs) of heavy meson within heavy quark effective theory (HQET) are crucial for predicting physical observables in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi></math> decays, but unfortunately there is no first-principle result due to severe challenges. After analyzing these challenges, we propose a realistic method to determine heavy meson LCDA. We utilize equal-time correlations and incorporate a dynamic quark field for a fast moving heavy quark. To verify this method, we make use of lattice QCD simulation on a lattice ensemble with spacing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>a</mi><mo>=</mo><mn>0.05187</mn><mtext> </mtext><mtext> </mtext><mi>fm</mi></math>. The preliminary findings for HQET LCDAs qualitatively align with phenomenological models, and the fitted result for the first inverse moment <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>λ</mi><mi>B</mi><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></math> is consistent with the experimentally constrained region from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo stretchy="false">→</mo><mi>γ</mi><mo>ℓ</mo><msub><mi>ν</mi><mo>ℓ</mo></msub></math>. We explore how our findings can reduce model uncertainties in predictions of heavy-to-light form factors at large recoil. These results demonstrate the promise of our method in providing first-principle predictions for heavy meson LCDAs.

China

Xue-Ying Han

Jun Hua

United States

Xiangdong Ji

Cai-Dian Lü

Wei Wang

Ji Xu

Qi-An Zhang

Shuai Zhao

Realistic method to access heavy meson light-cone distribution amplitudes from first-principle

The semi-inclusive decay processes of a top quark into a charged pseudoscalar meson and a jet are studied within the framework of QCD factorization. The leading power of the decay matrix elements can be factorized into heavy-to-light quark transition current and a hadron matrix element up to next-to-leading-order QCD corrections. We calculate one-loop virtual corrections together with real gluon emission corrections at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>α</mi></mrow><mrow><mi>s</mi></mrow></msub></mrow></math> order. The numerical results of the branching ratios are presented for the sum of two- and three-body decays. We also study the energy cutoff dependence of the gluon jet. These processes are hopeful to be detected in near future experiments, which can serve as probes for new physics.

Long-Shun Lu

Lei-Yi Li

Study of rare top quark decays into a jet plus a charged pseudoscalar meson

We develop an approach for calculating heavy quark effective theory (HQET) light-cone distribution amplitudes (LCDAs) by employing a sequential effective theory methodology. The theoretical foundation of the framework is established, elucidating how the quasidistribution amplitudes (quasi-DAs) with three scales can be utilized to compute HQET LCDAs. We provide theoretical support for this approach by demonstrating the rationale behind devising a hierarchical ordering for the three involved scales, discussing the factorization at each step, clarifying the underlying reason for obtaining HQET LCDAs in the final phase, and addressing potential theoretical challenges. The lattice QCD simulation aspect is explored in detail, and the computations of quasi-DAs are presented. We employ three fitting strategies to handle contributions from excited states and extract the bare matrix elements. For renormalization purposes, we apply hybrid renormalization schemes at short and long distance separations. To mitigate long-distance perturbations, we perform an extrapolation in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>λ</mi><mo>=</mo><mi>z</mi><mo>·</mo><msup><mi>P</mi><mi>z</mi></msup></math> and assess the stability against various parameters. After two-step matching, our results for HQET LCDAs are found in agreement with existing model parametrizations. The potential phenomenological implications of the results are discussed, shedding light on how these findings could impact our understanding of the strong interaction dynamics and physics beyond the standard model. It should be noted, however, that systematic uncertainties have not been accounted for yet.

Germany

Andreas Schäfer

Yushan Su

Yibo Yang

Jian-Hui Zhang

Calculation of heavy meson light-cone distribution amplitudes from lattice QCD

The similar densities of dark matter and baryons in the universe imply that they may arise from the same ultraviolet model. B-Mesogenesis, which assumes dark matter is charged under the baryon number, attempts to simultaneously explain the origin of baryon asymmetry and dark matter in the universe. In particular, B-Mesogenesis may induce bottom-baryon decays into invisible or semi-invisible final states, which provide a distinctive signal for probing this scenario. In this work, we systematically study the invisible decays of bottom baryons into dark matter and the semi-invisible decays of bottom baryons into a meson or a photon together with a dark matter particle. In particular, the fully invisible decay can reveal the stable particles in B-Mesogenesis. Some QCD-based frameworks are used to calculate the hadronic matrix elements under the B-Mesogenesis model. We estimate the constraints on the Wilson coefficients or the product of some new physics couplings with the Wilson coefficients according to the semi-invisible and invisible decays of bottom baryons detectable at future colliders.

Yong Zheng

Jian-Nan Ding

Dong-Hao Li

Fu-Sheng Yu

Invisible and semi-invisible decays of bottom baryons  

We calculate the form factors for the baryon number violation processes of a heavy-flavor baryon decaying into a pseudoscalar meson and a lepton. In the framework of the Standard Model effective field theory, the leptoquark operators at the bottom quark scale, whose matrix elements define the form factors, are derived by integrating out the high energy physics. Under the quantum chromodynamics (QCD) factorization approach, the form factors of the baryon number violation processes at leading power can be factorized into the convolution of the long-distance hadron wave functions as well as the short-distance hard and jet functions representing the hard scale and hard-collinear scale effects, separately. Based on measurements of the baryon number violation processes by LHCb, we further impose constraints on the new physics constants of leptoquark operators.

Jin Wang

Yan-Bing Wei

<math><mrow><msub><mrow><mi>Λ</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>→</mo><mi>P</mi><mo>ℓ</mo></mrow></math> factorization in QCD

We calculate the next-to-leading order QCD corrections to B to scalar meson form factors from QCD light-cone sum rules with B meson light-cone distribution amplitudes. We demonstrate that the B meson-to-vacuum correlation functions can be factorized into the convolution of short-distance coefficients and light-cone distribution amplitudes at the one-loop level and find that only <math> <msubsup> <mi>ϕ</mi> <mi>B</mi> <mo>+</mo> </msubsup> </math> $$ {\phi}_B^{+} $$ (ω, μ) contributes to the form factors. We then employ the z-parameterization combined with constraints from strong coupling constants to reconstruct the q 2 dependence of the form factors in the whole kinematic allowed regions. Due to the large cancellations between the hard functions and the jet functions, the next-to-leading order results show a modest increase of approximately 5% compared to the leading order results. Based on the results of form factors, we predict the branching ratios of semi-leptonic B → <math> <mi>S</mi> <mi>ℓ</mi> <msub> <mover> <mi>ν</mi> <mo>¯</mo> </mover> <mi>ℓ</mi> </msub> </math> $$ S\ell {\overline{\nu}}_{\ell } $$ and B → <math> <mi>S</mi> <msub> <mi>ν</mi> <mi>ℓ</mi> </msub> <msub> <mover> <mi>ν</mi> <mo>¯</mo> </mover> <mi>ℓ</mi> </msub> </math> $$ S{\nu}_{\ell }{\overline{\nu}}_{\ell } $$ processes, as well as several angular observables, such as forward-backward asymmetries, “flat terms” and lepton polarization asymmetries. We compare these results with calculations from other methods. Experimental verification of these results is required in future experiments.

Yue-Long Shen

Bo-Xuan Shi

Next-to-leading order QCD corrections to the form factors of B to scalar meson decays

We analyze quasi-two-body charmless <math><mrow><mi>B</mi></mrow></math> decays <math><msub><mi>B</mi><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></msub><mo>→</mo><msub><mi>P</mi><mn>1</mn></msub><mi>V</mi><mo>→</mo><msub><mi>P</mi><mn>1</mn></msub><msub><mi>P</mi><mn>2</mn></msub><msub><mi>P</mi><mn>3</mn></msub></math> with <math><mi>V</mi></math> representing a vector resonant, and <math><msub><mi>P</mi><mrow><mn>1</mn><mo>,</mo><mn>2</mn><mo>,</mo><mn>3</mn></mrow></msub></math> as a light pseudoscalar meson, pion, kaon, or <math><mrow><msup><mrow><mi>η</mi></mrow><mrow><mo>(</mo><mo>′</mo><mo>)</mo></mrow></msup></mrow></math>. The intermediate processes <math><msub><mi>B</mi><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></msub><mo>→</mo><msub><mi>P</mi><mn>1</mn></msub><mi>V</mi></math> are calculated in the factorization-assisted topological-amplitude approach and the vector resonant effects are described by the Breit-Wigner propagator, which successively decay to <math><msub><mi>P</mi><mn>1</mn></msub><msub><mi>P</mi><mn>2</mn></msub></math> via strong interaction. Taking into account of all vector resonances in ground state, <math><mrow><mi>ρ</mi><mo>,</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>*</mo></mrow></msup><mo>,</mo><mi>ω</mi><mo>,</mo><mi>ϕ</mi></mrow></math>, we present the related branching fractions, and calculate the virtual effects for <math><msub><mi>B</mi><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></msub><mo>→</mo><mi>π</mi><mo>,</mo><mi>K</mi><mo>(</mo><mi>ρ</mi><mo>,</mo><mi>ω</mi><mo>→</mo><mo>)</mo><mi>K</mi><mi>K</mi></math>. We also predict direct <math><mrow><mi>C</mi><mi>P</mi></mrow></math> asymmetries of three-body <math><mi>B</mi></math> decay modes with <math><mi>ρ</mi><mo>,</mo><msup><mi>K</mi><mo>*</mo></msup></math> resonances as intermediate states. Our predicted branching fractions of decay modes dominated by the color-favored tree diagram or the color-favored penguin diagram are consistent with the perturbative QCD approach’s predictions as well as the QCD factorization approach. While for those nonperturbative contribution dominated decay modes, the branching ratios in this work are in better agreement with current experimental data than the perturbative QCD (PQCD) predictions and the QCD factorization results due to their shortage of the nonperturbative contributions or <math><mn>1</mn><mo>/</mo><msub><mi>m</mi><mi>b</mi></msub></math> power corrections. Many of the decays channels, especially for direct <math><mrow><mi>C</mi><mi>P</mi></mrow></math> asymmetries, are waiting for the future experiments.

Si-Hong Zhou

Xin-Xia Hai

Run-Hui Li

Analysis of three-body charmless <math><mi>B</mi></math>-meson decays under the factorization-assisted topological-amplitude approach

We identify a novel leading-power contribution to the pure weak annihilation non-leptonic B-meson decay amplitudes, which arises from the hard-collinear gluon exchange between the light quark of the bottom meson and the final-state active partons. This interesting observation is naturally expected to shed new light on deciphering rapidity divergences in the convolution integrals of the soft-collinear factorization formulae. Subsequently we explore an intriguing enhancement mechanism due to the penguin contractions of the current-current operators from the weak effective Hamiltonian, which yields the significant impacts on the CP violating observables.

Chao Wang

Yu-Ming Wang

Shedding new light on weak annihilation -meson Decays

The perturbative quantum chromodynamics (PQCD) approach based on   $ k_T $   factorization has resulted in great achievements in the QCD calculation of hadronic B decays. By regulating the endpoint divergence by the transverse momentum of quarks in the propagators, one can perform the perturbation calculation for various diagrams, including annihilation type diagrams. In this paper, we review the current status of the PQCD factorization calculation of two-body charmless   $ k_T $  U decays up to next-to-leading order (NLO) QCD corrections. Two new power suppressed terms in the decaying amplitudes are also considered. Using universal input (non-perturbative) parameters, we collect the branching ratios and   $ k_T $   asymmetry parameters of all charmless two body B decays, which are calculated in the PQCD approach up to NLO. The results are compared with those of the QCD factorization approach, soft-collinear effective theory approach, and current experimental measurements. For most of the considered B meson decays, the PQCD results for branching ratios agree well with those of other approaches and experimental data. The PQCD predictions for the   $ k_T $   asymmetry parameters of many of the decay channels do not agree with those of other approaches but have better agreement with experimental data. The longstanding   $ k_T $   puzzle regarding the pattern of the direct CP asymmetries of penguin-dominated   $ k_T $   decays can be understood after the inclusion of NLO contributions in PQCD. The NLO corrections and power suppressed terms play an important role in color suppressed and pure annihilation type B decay modes. These rare decays are more sensitive to different types of corrections, providing an opportunity to examine the factorization approach with more precise experimental measurements.

Jian Chai

Shan Cheng

Yao-hui Ju

Da-Cheng Yan

Zhen-Jun Xiao

Charmless two-body meson decays in the perturbative QCD factorization approach  

In this paper we investigate the next-to-leading power contribution to the <math><mrow><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><mi>γ</mi><mi>γ</mi></mrow></math> and <math><mrow><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><mi>γ</mi><mo>ℓ</mo><mover><mrow><mo>ℓ</mo></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> decays from the strange quark mass effect with the dispersion approach which is QCD inspired and more predictive. We present the analytic expression of the quark mass contribution in the <math><msub><mi>B</mi><mi>s</mi></msub><mo>→</mo><mi>γ</mi><mi>γ</mi></math> and <math><mrow><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><mi>γ</mi><mo>ℓ</mo><mover><mrow><mo>ℓ</mo></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> decays, together with a new term that is missed in the previous study. We also evaluate the resolved photon contribution from the A-type amplitude in <math><mrow><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><mi>γ</mi><mo>ℓ</mo><mover><mrow><mo>ℓ</mo></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> decay. The numerical results of the strange quark mass contribution to the <math><mrow><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><mi>γ</mi><mi>γ</mi></mrow></math> decay is about 6% relative to the total branching ratio, while it is relatively small in the <math><mrow><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><mi>γ</mi><mo>ℓ</mo><mover><mrow><mo>ℓ</mo></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> decay due to the large resonance contribution.

Strange quark mass effect in <math><mrow><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><mi>γ</mi><mi>γ</mi><mo>,</mo><mtext> </mtext><mi>γ</mi><mo>ℓ</mo><mover><mrow><mo>ℓ</mo></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> decays