1,223 research outputs found
Hadronic Light-by-Light Contribution to Muon g-2 in Chiral Perturbation Theory
We compute the hadronic light-by-light scattering contributions to the muon
anomalous magnetic moment, \amulbl, in chiral perturbation theory that are
enhanced by large logarithms and a factor of . They depend on a low-energy
constant entering pseudoscalar meson decay into a charged lepton pair. The
uncertainty introduced by this constant is , which is
comparable in magnitude to the present uncertainty entering the leading-order
vacuum polarization contributions to the anomalous moment. It may be reduced to
some extent through an improved measurement of the branching
ratio. However, the dependence of \amulbl on non-logarithmically enhanced
effects cannot be constrained except through the measurement of the anomalous
moment itself. The extraction of information on new physics would require a
future experimental value for the anomalous moment differing significantly from
the 2001 result reported by the E821 collaboration.Comment: 7 pages, 2 figure
Spiders (Araneae) from Agricultural fields near foothill of Satpura Mountain ranges of Amravati District, Maharashtra, India.
This paper deals with the study of spider distribution in agricultural fields adjoining the Satpura Mountain Ranges of the Amravati district. The total collection of spiders comprises 12 families, 37 genera and 76 species. The Araneidae and Thomisidae families were dominant, followed by Saltisidae from the selected agricultural area. Lycosidae and Tetragnathidae were also found in a decreasing number of species due to their specific habitation. The analysis of guild structure revealed six feeding guilds. Orb web weavers and Ambushers constituted the dominant feeding guild representing 33% and 22% of the total collection respectively. Stalkers and ground runners represent 20% and 17% and foliage hunters and sheet web weavers represent 5% and 3% respectively. A new species of genus Sassacus (Beetle like spider), family Saltisidae was found for the first time in the Vidarbha region. The richness of spider diversity is a sign of the overall biodiversity which is a useful indicator of the species richness of the agro-ecosystem.

Hadronic light-by-light scattering contribution to the muon g-2: an effective field theory approach
The hadronic light-by-light contribution to a_{mu}, the anomalous magnetic
moment of the muon, is discussed from the point of view of an effective
low-energy theory. As an application, the coefficient of the leading logarithm
arising from the two-loop graphs involving two anomalous vertices is computed,
and found to be positive. This corresponds to a positive sign for the pion-pole
contribution to the hadronic light-by-light correction to a_{mu}, and to a
sizeable reduction of the discrepancy between the present experimental value of
a_{mu} and its theoretical counterpart in the standard model.Comment: 4 pages, 1 figure. v2: published versio
The Muon g-2 Revisited
I present a short review of the present status of the Standard Model
prediction of the anomalous magnetic moment of the muon, with special emphasis
on the hadronic contributions.Comment: Invited talk at the XVI Rencontres de Physique at La Thuil
Comment on the Pion Pole Part of the Light-by-Light Contribution to the Muon
We comment on the recent calculations of the pion pole part of the
light-by-light contribution to the muon anomalous magnetic moment and we point
out where the analysis in our previous work was mistaken.Comment: 2 page
The Standard Model and low-energy experiments: from lepton-flavour violation to dark photons
This note is a concise theoretical summary of the first session on new
physics searches at the high-intensity frontier of the IFAE2017 Conference.
Recent theoretical developments related to muonic lepton-flavour violation and
are reviewed.Comment: 5 pages, IFAE2017 Conferenc
Towards a data-driven analysis of hadronic light-by-light scattering
The hadronic light-by-light contribution to the anomalous magnetic moment of
the muon was recently analyzed in the framework of dispersion theory, providing
a systematic formalism where all input quantities are expressed in terms of
on-shell form factors and scattering amplitudes that are in principle
accessible in experiment. We briefly review the main ideas behind this
framework and discuss the various experimental ingredients needed for the
evaluation of one- and two-pion intermediate states. In particular, we identify
processes that in the absence of data for doubly-virtual pion-photon
interactions can help constrain parameters in the dispersive reconstruction of
the relevant input quantities, the pion transition form factor and the helicity
partial waves for .Comment: 7 pages, 4 figures, 2 tables, journal versio
Rescattering effects in the hadronic-light-by-light contribution to the anomalous magnetic moment of the muon
We present a first model-independent calculation of intermediate
states in the hadronic-light-by-light (HLbL) contribution to the anomalous
magnetic moment of the muon that goes beyond the scalar QED pion
loop. To this end we combine a recently developed dispersive description of the
HLbL tensor with a partial-wave expansion and demonstrate that the known
scalar-QED result is recovered after partial-wave resummation. Using dispersive
fits to high-statistics data for the pion vector form factor, we provide an
evaluation of the full pion box, . We then construct suitable input for the
helicity partial waves based on a pion-pole left-hand cut and show that for the
dominant charged-pion contribution this representation is consistent with the
two-loop chiral prediction and the COMPASS measurement for the pion
polarizability. This allows us to reliably estimate -wave rescattering
effects to the full pion box and leads to our final estimate for the sum of
these two contributions: .Comment: 7 pages, 1 figure; version to appear in PR
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