scholarly journals Short-distance constraints for the longitudinal component of the hadronic light-by-light amplitude: an update

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
G. Colangelo ◽  
F. Hagelstein ◽  
M. Hoferichter ◽  
L. Laub ◽  
P. Stoffer
Keyword(s):  
Anomalous Magnetic Moment ◽  
Short Distance ◽  
Numerical Estimate ◽  
Longitudinal Component ◽  
Quark Loop ◽  
Distance Constraints ◽  
Axial Anomaly ◽  
Massless Quark ◽  
The Impact ◽  
Perturbative Corrections

AbstractWe reassess the impact of short-distance constraints for the longitudinal component of the hadronic light-by-light amplitude on the anomalous magnetic moment of the muon, $$a_\mu =(g-2)_\mu /2$$ a μ = ( g - 2 ) μ / 2 , by comparing different solutions that have recently appeared in the literature. In particular, we analyze the relevance of the exact axial anomaly and its impact on $$a_\mu $$ a μ and conclude that it remains rather limited. We show that all recently proposed solutions agree well within uncertainties on the numerical estimate of the impact of short-distance constraints on $$a_\mu $$ a μ , despite differences in the concrete implementation. We also take into account the recently calculated perturbative corrections to the massless quark loop to update our estimate and outline the path towards future improvements.

scholarly journals The two-loop perturbative correction to the (g − 2)μ HLbL at short distances

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Johan Bijnens ◽  
Nils Hermansson-Truedsson ◽  
Laetitia Laub ◽  
Antonio Rodríguez-Sánchez
Keyword(s):  
Electromagnetic Field ◽  
Perturbative Qcd ◽  
Operator Product Expansion ◽  
Short Distance ◽  
Operator Product ◽  
Quark Loop ◽  
Perturbative Correction ◽  
Massless Quark ◽  
Leading Term ◽  
Perturbative Corrections

Abstract The short-distance behaviour of the hadronic light-by-light (HLbL) contribution to (g − 2)μ has recently been studied by means of an operator product expansion in a background electromagnetic field. The leading term in this expansion has been shown to be given by the massless quark loop, and the non-perturbative corrections are numerically very suppressed. Here, we calculate the perturbative QCD correction to the massless quark loop. The correction is found to be fairly small compared to the quark loop as far as we study energy scales where the perturbative running for the QCD coupling is well-defined, i.e. for scales μ ≳ 1 GeV. This should allow to reduce the large systematic uncertainty associated to high-multiplicity hadronic states.

scholarly journals Short-distance constraints on hadronic light-by-light scattering in the anomalous magnetic moment of the muon

2020 ◽  
Vol 101 (5) ◽  
Author(s):  
Gilberto Colangelo ◽  
Franziska Hagelstein ◽  
Martin Hoferichter ◽  
Laetitia Laub ◽  
Peter Stoffer
Keyword(s):  
Light Scattering ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Short Distance ◽  
Distance Constraints

scholarly journals Short-distance constraints for HLbL in muon g-2

2022 ◽  
Vol 258 ◽  
pp. 06005
Author(s):  
Johan Bijnens ◽  
Nils Hermansson-Truedsson ◽  
Antonio Rodríguez-Sánchez
Keyword(s):  
Operator Product Expansion ◽  
Short Distance ◽  
Operator Product ◽  
Quark Loop ◽  
Distance Constraints ◽  
Analytic Evaluation ◽  
Power Corrections ◽  
Low Energies ◽  
Model Independent

Model-independent short-distance constraints allow for a reduction of theoretical uncertainties associated to the analytic evaluation of Hadronic Light-by-Light contributions to the muon g-2. In this talk we focus on the region where the three loop virtualities are large. Even when the fourth photon leg is soft, we show how a precise Operator Product Expansion can be applied in that region. The leading contribution is found to be given by the quark loop, while the evaluation of both gluonic and power corrections show how the expansion is well behaved at relatively low energies, where significant contributions to the muon g-2 remain. Numerical values for them are also presented.

scholarly journals Short-distance constraints for the HLbL contribution to the muon anomalous magnetic moment

2019 ◽  
Vol 798 ◽  
pp. 134994 ◽  
Author(s):  
Johan Bijnens ◽  
Nils Hermansson-Truedsson ◽  
Antonio Rodríguez-Sánchez
Keyword(s):  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Short Distance ◽  
Muon Anomalous Magnetic Moment ◽  
Distance Constraints

scholarly journals Soft-drop grooming for hadronic event shapes

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Jeremy Baron ◽  
Daniel Reichelt ◽  
Steffen Schumann ◽  
Niklas Schwanemann ◽  
Vincent Theeuwes
Keyword(s):  
Event Generator ◽  
Experimental Measurements ◽  
Event Shape ◽  
Matrix Elements ◽  
Underlying Event ◽  
Hadronic Event ◽  
Wide Range ◽  
Event Shapes ◽  
The Impact ◽  
Perturbative Corrections

Abstract Soft-drop grooming of hadron-collision final states has the potential to significantly reduce the impact of non-perturbative corrections, and in particular the underlying-event contribution. This eventually will enable a more direct comparison of accurate perturbative predictions with experimental measurements. In this study we consider soft-drop groomed dijet event shapes. We derive general results needed to perform the resummation of suitable event-shape variables to next-to-leading logarithmic (NLL) accuracy matched to exact next-to-leading order (NLO) QCD matrix elements. We compile predictions for the transverse-thrust shape accurate to NLO + NLL′ using the implementation of the Caesar formalism in the Sherpa event generator framework. We complement this by state-of-the-art parton- and hadron-level predictions based on NLO QCD matrix elements matched with parton showers. We explore the potential to mitigate non-perturbative corrections for particle-level and track-based measurements of transverse thrust by considering a wide range of soft-drop parameters. We find that soft-drop grooming indeed is very efficient in removing the underlying event. This motivates future experimental measurements to be compared to precise QCD predictions and employed to constrain non-perturbative models in Monte-Carlo simulations.

scholarly journals Factorization at subleading power and endpoint divergences in h → γγ decay. Part II. Renormalization and scale evolution

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Ze Long Liu ◽  
Bianka Mecaj ◽  
Matthias Neubert ◽  
Xing Wang
Keyword(s):  
Decay Amplitude ◽  
Factorization Theorem ◽  
Effective Theory ◽  
Operator Matrix ◽  
Quark Loop ◽  
Perfect Agreement ◽  
Soft Collinear Effective Theory ◽  
Convolution Integrals ◽  
Factorization Formula ◽  
Massless Quark

Abstract Building on the recent derivation of a bare factorization theorem for the b-quark induced contribution to the h → γγ decay amplitude based on soft-collinear effective theory, we derive the first renormalized factorization theorem for a process described at subleading power in scale ratios, where λ = mb/Mh « 1 in our case. We prove two refactorization conditions for a matching coefficient and an operator matrix element in the endpoint region, where they exhibit singularities giving rise to divergent convolution integrals. The refactorization conditions ensure that the dependence of the decay amplitude on the rapidity regulator, which regularizes the endpoint singularities, cancels out to all orders of perturbation theory. We establish the renormalized form of the factorization formula, proving that extra contributions arising from the fact that “endpoint regularization” does not commute with renormalization can be absorbed, to all orders, by a redefinition of one of the matching coefficients. We derive the renormalization-group evolution equation satisfied by all quantities in the factorization formula and use them to predict the large logarithms of order $$ {\alpha \alpha}_s^2{L}^k $$ αα s 2 L k in the three-loop decay amplitude, where $$ L=\ln \left(-{M}_h^2/{m}_b^2\right) $$ L = ln − M h 2 / m b 2 and k = 6, 5, 4, 3. We find perfect agreement with existing numerical results for the amplitude and analytical results for the three-loop contributions involving a massless quark loop. On the other hand, we disagree with the results of previous attempts to predict the series of subleading logarithms $$ \sim {\alpha \alpha}_s^n{L}^{2n+1} $$ ∼ αα s n L 2 n + 1 .

scholarly journals Effects of longitudinal short-distance constraints on the hadronic light-by-light contribution to the muon $$\mathbf {g-2}$$

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Jan Lüdtke ◽  
Massimiliano Procura
Keyword(s):  
Short Distance ◽  
Independent Method ◽  
Recent Model ◽  
Low Energy ◽  
Muon Anomalous Magnetic Moment ◽  
Distance Constraints ◽  
Independent Information ◽  
Intermediate States ◽  
Model Independent ◽  
Interpolation Functions

AbstractWe present a model-independent method to estimate the effects of short-distance constraints (SDCs) on the hadronic light-by-light contribution to the muon anomalous magnetic moment $$a_\mu ^\text {HLbL}$$ a μ HLbL . The relevant loop integral is evaluated using multi-parameter families of interpolation functions, which satisfy by construction all constraints derived from general principles and smoothly connect the low-energy region with those where either two or all three independent photon virtualities become large. In agreement with other recent model-based analyses, we find that the SDCs and thus the infinite towers of heavy intermediate states that are responsible for saturating them have a rather small effect on $$a_\mu ^\text {HLbL}$$ a μ HLbL . Taking as input the known ground-state pseudoscalar pole contributions, we obtain that the longitudinal SDCs increase $$a_\mu ^\text {HLbL}$$ a μ HLbL by $$(9.1\pm 5.0) \times 10^{-11}$$ ( 9.1 ± 5.0 ) × 10 - 11 , where the isovector channel is responsible for $$(2.6\pm 1.5) \times 10^{-11}$$ ( 2.6 ± 1.5 ) × 10 - 11 . More precise estimates can be obtained with our method as soon as further accurate, model-independent information about important low-energy contributions from hadronic states with masses up to 1–2 GeV become available.

scholarly journals The impact of some morphological and motor characteristics in short distance running

2021 ◽  
Vol 11 (6) ◽  
pp. 109-119
Author(s):  
Q. Ramabaja ◽  
N. Rashiti ◽  
M. Shkodra ◽  
L. Ramadani
Keyword(s):  
Physical Education ◽  
Motor Skills ◽  
Short Distance ◽  
Morphological Development ◽  
Strong Impact ◽  
Distance Running ◽  
Anthropometric Parameters ◽  
Long Distance ◽  
Anthropometric Characteristics ◽  
The Impact

The knowledge of morphological development and their impact on motor skills in short-distance athletes should be one of the main concerns of athletics coaches, because any scientific research in the field of physical culture and sports is about proving the development and evaluation of anthropological characteristics which are responsible for achieving success in athletics. The purpose of this paper is to confirm the impact of some anthropometric characteristics in the execution of running speeds on short distances, specifically in running at 100, 200 and 400 meters to students aged 18 ± 6 years of the Faculty of Physical Education and Sports in Prishtina. The sample of this research has included a total of 60 students aged 18 years of the Faculty of Physical Education and Sports in Prishtina. The measurements were executed during September in the hall of the Faculty, while the 100, 200, and 400 meter runs in the stadium "Fadil Vokrri" Prishtina. The only condition that was used during the determination of the sample was: that the students are involved in regular physical education classes (and on the day of the measurement be healthy, without the flu, cold or other symptoms). The variables which are applied in this research have been 8 anthropometric variables and 3 motor-specific variables. The results obtained after their processing indicate that the impact of anthropometric variables is higher in running at 100, 200 and 400 meters. Short distance running and long distance running reduces the impact of anthropometric parameters whereas the influence of metabolic factors of energy production is increased.  These results were also confirmed using regression analysis, so that groups of predictors of anthropometric characteristics, specific motor skills that statistically significantly influenced each variable of individual criteria. The world records below the 10-second limit, in the 100 m, near the 9-meter limit, show not only the high level of sports, but also the strong impact on the growth, especially of strength indicators, speed-strength, explosive force, as main and applied motor skills in sports and athlete’s everyday life.

scholarly journals Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

2020 ◽  
Vol 2020 (3) ◽  
Author(s):  
Gilberto Colangelo ◽  
Franziska Hagelstein ◽  
Martin Hoferichter ◽  
Laetitia Laub ◽  
Peter Stoffer
Keyword(s):  
Short Distance ◽  
Distance Constraints

scholarly journals Next-to-leading-order QCD corrections to heavy quark fragmentation into $${}^1S^{(1,8)}_0$$ quarkonia

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Feng Feng ◽  
Yu Jia ◽  
Wen-Long Sang
Keyword(s):  
Heavy Quark ◽  
Fragmentation Function ◽  
Short Distance ◽  
Decomposition Method ◽  
Heavy Quarkonium ◽  
Leading Order ◽  
Quark Fragmentation ◽  
Definition Of ◽  
Perturbative Corrections ◽  
Operator Definition

AbstractWithin NRQCD factorization framework, in this work we compute, at the lowest order in velocity expansion, the next-to-leading-order (NLO) perturbative corrections to the short-distance coefficients associated with heavy quark fragmentation into the $${}^1S_0^{(1,8)}$$ 1 S 0 ( 1 , 8 ) components of a heavy quarkonium. Starting from the Collins and Soper’s operator definition of the quark fragmentation function, we apply the sector decomposition method to facilitate the numerical manipulation. It is found that the NLO QCD corrections have a significant impact.

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