We propose a novel approach to determine the leading hadronic corrections to the muon g-2. It consists in a measurement of the effective electromagnetic coupling in the space-like region extracted ...from Bhabha scattering data. We argue that this new method may become feasible at flavor factories, resulting in an alternative determination potentially competitive with the accuracy of the present results obtained with the dispersive approach via time-like data.
Theory for muon-electron scattering @ 10 ppm Banerjee, P.; Carloni Calame, C. M.; Chiesa, M. ...
The European physical journal. C, Particles and fields,
06/2020, Letnik:
80, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We review the current status of the theory predictions for elastic
μ
-
e
scattering, describing the recent activities and future plans of the theory initiative related to the proposed MUonE ...experiment.
We propose a new experiment to measure the running of the electromagnetic coupling constant in the space-like region by scattering high-energy muons on atomic electrons of a low-
Z
target through the ...elastic process
μ
e
→
μ
e
. The differential cross section of this process, measured as a function of the squared momentum transfer
t
=
q
2
<
0
, provides direct sensitivity to the leading-order hadronic contribution to the muon anomaly
a
μ
HLO
. By using a muon beam of 150 GeV, with an average rate of
∼
1.3
×
10
7
muon/s, currently available at the CERN North Area, a statistical uncertainty of
∼
0.3% can be achieved on
a
μ
HLO
after two years of data taking. The direct measurement of
a
μ
HLO
via
μ
e
scattering will provide an independent determination, competitive with the time-like dispersive approach, and consolidate the theoretical prediction for the muon
g
-2 in the Standard Model. It will allow therefore a firmer interpretation of the measurements of the future muon
g
-2 experiments at Fermilab and J-PARC.
The MUonE experiment aims at providing a novel determination of the leading hadronic contribution to the muon anomalous magnetic moment through the study of elastic muon-electron scattering. Since ...the initial-state electrons are bound in a low-Z atomic target, the interaction between the incoming muons and the nuclei is expected to be the main source of experimental background. In this article, we study the production of a real lepton pair from the muon-nucleus scattering, discussing its numerical impact in the MUonE kinematic configuration. The process is described as a scattering of a muon in an external Coulomb field with the addition of a form factor to describe the nuclear charge distribution. The calculation is implemented in the fully differential Monte Carlo event generator Mesmer, without introducing any approximation on the angular variables.
We present a high-precision QED calculation, with 0.1% theoretical accuracy, of two photon production in e+e− annihilation, as required by more and more accurate luminosity monitoring at flavour ...factories. The accuracy of the approach, which is based on the matching of exact next-to-leading order corrections with a QED Parton Shower algorithm, is demonstrated through a detailed analysis of the impact of the various sources of radiative corrections to the experimentally relevant observables. The calculation is implemented in the latest version of the event generator BabaYaga, available for precision simulations of photon pair production at e+e− colliders of moderately high energies.
The J/ψ meson has negative G parity so that, in the limit of isospin conservation, its decay into π+π− should be purely electromagnetic. However, the measured branching fraction B(J/ψ→π+π−) exceeds ...by more than 4.5 standard deviations the expectation computed according to BABAR data on the e+e−→π+π− cross section. The possibility that the two-gluon plus one-photon decay mechanism is not suppressed by G-parity conservation is discussed, even by considering other multipion decay channels. As also obtained by phenomenological computation, such a decay mechanism could be responsible for the observed discrepancy. Finally, we notice that the BESIII experiment, having the potential to perform an accurate measurement of the e+e−→π+π− cross section in the J/ψ mass energy region, can definitely prove or disprove this strong G-parity-violating mechanism by confirming or confuting the BABAR data.
Theory for muon-electron scattering @ 10 ppm Banerjee, P; Carloni Calame, C. M; Chiesa, M ...
The European physical journal. C, Particles and fields,
06/2020, Letnik:
80, Številka:
6
Journal Article
Recenzirano
Odprti dostop
We review the current status of the theory predictions for elastic Formula omitted-e scattering, describing the recent activities and future plans of the theory initiative related to the proposed ...MUonE experiment.
The Standard Model from LHC to future colliders Forte, S.; Nisati, A.; Passarino, G. ...
The European physical journal. C, Particles and fields,
11/2015, Letnik:
75, Številka:
11
Journal Article
Recenzirano
Odprti dostop
This review summarizes the results of the activities which have taken place in 2014 within the Standard Model Working Group of the “What Next” Workshop organized by INFN, Italy. We present a ...framework, general questions, and some indications of possible answers on the main issue for Standard Model physics in the LHC era and in view of possible future accelerators.
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