Hadronic light-by-light scattering in the muon g-2: a new short-distance  constraint on pion exchange

Nyffeler, Andreas

doi:10.22323/1.086.0080

Cited by 17 publications

(30 citation statements)

References 51 publications

(222 reference statements)

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“…2 we demonstrated an agreement of the Monte Carlo simulation of e + e − → e + e − π 0 in the "single-tag" mode with the experimental data from CLEO [18] and BaBar [19]. We conclude that the matrix element is well under control and the applied pion transition form factor (LMD+V) [24] is in agreement with data. The procedure of the phase space generation was validated by means of the high statistics phase space volume calculation in EKHARA and comparison of the result with that from the independent dedicated numerical calculation.…”

Section: Validation Of the Generatorsupporting

confidence: 77%

“…2 we demonstrate an agreement of the Monte Carlo simulation with the "single-tag" experimental data from CLEO [18] and BaBar [19]. For simulation we use the matrix element (3) with the form factor of the lowest meson dominance model with two vector resonances (LMD+V), fitted [24] to the BABAR data [19]. A number of other expressions for the form factor are also available for the user of EKHARA.…”

Section: The Matrix Elementmentioning

confidence: 99%

“…5 (LMD+V new) the form factor of the lowest meson dominance model with two vector resonances fitted [24] to the BABAR data [19]. This is the recommended form factor; 6 (quark) the form factor given in [25].…”

Section: Input Filesmentioning

confidence: 99%

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EKHARA: A Monte Carlo generator for and processes

Czyż

Ivashyn

2011

Computer Physics Communications

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We present EKHARA Monte Carlo event generator of reactions e + e − → e + e − π 0 and e + e − → e + e − π + π − . The newly added channel (e + e − → e + e − π 0 ) is important for γ * γ * physics and can be used for the pion transition form factor studies at meson factories.Keywords: Monte Carlo generator, Pion transition form factor, Pion pair production, Two-photon processes, e + e − annihilation and Empirical Models and Theories Nature of problem: PROGRAM SUMMARYThe first version of EKHARA [1,2] was developed to simulate background for the pion form factor measurement at meson factories coming from the process e + e − → e + e − π + π − . The newly added channel e + e − → e + e − π 0 will help in the pion transition from factor studies at meson factories [3]. Solution method:Events consisting of the momenta of the outgoing particles are generated by Monte Carlo methods. The generated events are distributed accordingly to the theoretical cross section. For the e + e − → e + e − π 0 mode the Monte Carlo sampling developed in [4] was adopted. Restrictions:In order to compile the code, the FORTRAN 77 compiler should support quadruple precision numbers. Unusual features:Calculations are carried in quadruple precision, in order to avoid numerical cancellations in e + e − → e + e − π + π − mode. Running time:Depends on the requested mode and applied kinematic cuts. Example: on Intel Core2 Quad CPU Q6600 @ 2.40GHz, using only one thread,• 10 5 unweighted e + e − π 0 events are generated in 78 seconds (no cuts),• 10 5 weighted e + e − π + π − events are generated in 38 seconds (with cuts [2]).

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Section: Validation Of the Generatorsupporting

confidence: 77%

Section: The Matrix Elementmentioning

confidence: 99%

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EKHARA: A Monte Carlo generator for and processes

Czyż

Ivashyn

2011

Computer Physics Communications

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“…This range in ∆(g − 2) µ is the union of the 3σ intervals around the SM value, (0.0 ± 5.9) × 10 −10 from combining [89] the results of refs. [90][91][92] and the experimental measurement [93,94] corrected to an updated value of the muon to proton magnetic moment ratio [95,96] giving ∆(g − 2) µ,exp = (24.9 ± 6.3) × 10 −10 . Three-sigma intervals are used to obtain a continuous range from the union.…”

Section: Jhep10(2015)134mentioning

confidence: 99%

Summary of the ATLAS experiment’s sensitivity to supersymmetry after LHC Run 1 — interpreted in the phenomenological MSSM

Aad

Bergeås

Brenner

et al. 2015

J. High Energ. Phys.

100

169

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A summary of the constraints from the ATLAS experiment on R-parityconserving supersymmetry is presented. Results from 22 separate ATLAS searches are considered, each based on analysis of up to 20.3 fb −1 of proton-proton collision data at centre-of-mass energies of √ s = 7 and 8 TeV at the Large Hadron Collider. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, in which the lightest supersymmetric particle is a neutralino, taking into account constraints from previous precision electroweak and flavour measurements as well as from dark matter related measurements. The results are presented in terms of constraints on supersymmetric particle masses and are compared to limits from simplified models. The impact of ATLAS searches on parameters such as the dark matter relic density, the couplings of the observed Higgs boson, and the degree of electroweak fine-tuning is also shown. Spectra for surviving supersymmetry model points with low fine-tunings are presented. The ATLAS collaboration 58 Keywords: Hadron-Hadron Scattering IntroductionDuring the first run of the Large Hadron Collider (LHC), the ATLAS [1] and CMS [2] Collaborations performed a wide range of searches for supersymmetry (SUSY) [3][4][5][6][7][8][9][10][11], using proton-proton (pp) collision data at centre-of-mass energies ( √ s) of 7 and 8 TeV. SUSY, a theoretically favoured framework for extending the Standard Model (SM), is able to address some of its unanswered questions, particularly the hierarchy problem [12][13][14][15], which is related to the fine-tuning needed to obtain the correct mass for the observed Higgs boson. SUSY can also provide credible dark matter candidates [16,17] and can improve the unification of the electroweak and strong interactions [18][19][20][21][22][23][24][25][26].The minimal supersymmetric extension of the Standard Model (MSSM) [27][28][29][30][31] predicts partners for each of the SM states. It predicts a pair of scalar partners -one for each fermion chirality -for each of the SM quarks and leptons. These spin-zero partner particles are known as squarks (q) and sleptons (˜ ) respectively. In the first two generations the pair of chiral partners is largely unmixed, so the mass states can be labelledẽ L andẽ R , where the L and R subscripts denote the scalar partners of the left-and right-handed Standard Model fermion states respectively. In the third generation of quarks and leptons the mixing between the scalars is larger, and the mixed states are labelled by their mass indices e.g.t 1 and t 2 , wheret 1 is lighter by construction. Each state in the SM gluon colour octet has a spinhalf partner known as a gluinog. There are a total of eight spin-half partners of the electroweak gauge and Higgs bosons: the neutral bino (superpartner of the U(1) gauge field); the winos, which are a charged pair and a neutral particle (superpartners of the W bosons of the SU(2) L gauge fields); and the Higgsinos, which are two neutral particles and a charged pai...

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“…It was noted in Ref. [15] that essentially all evaluations of the pion-exchange contribution use the normalization F π 0 * γ * γ * (m 2 π , 0, 0) = 1/(4π 2 F π ) for the form factor, as derived from the Wess-ZuminoWitten (WZW) term. Then the value F π = 92.4 MeV is used without any error attached to it, i.e.…”

Section: Introductionmentioning

confidence: 99%

Hadronic light-by-light scattering in the muong−2: impact of proposed measurements of theπ⁰→γγdecay width and theγ^*γ→π⁰transition form factor with the KLOE-2 experiment

Nyffeler

2012

EPJ Web of Conferences

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Hadronic light-by-light scattering in the muon g-2: a new short-distance constraint on pion exchange

Cited by 17 publications

References 51 publications

EKHARA: A Monte Carlo generator for and processes

EKHARA: A Monte Carlo generator for and processes

Summary of the ATLAS experiment’s sensitivity to supersymmetry after LHC Run 1 — interpreted in the phenomenological MSSM

Hadronic light-by-light scattering in the muong−2: impact of proposed measurements of theπ⁰→γγdecay width and theγ^*γ→π⁰transition form factor with the KLOE-2 experiment

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Hadronic light-by-light scattering in the muon g-2: a new short-distance constraint on pion exchange

Cited by 17 publications

References 51 publications

EKHARA: A Monte Carlo generator for and processes

EKHARA: A Monte Carlo generator for and processes

Summary of the ATLAS experiment’s sensitivity to supersymmetry after LHC Run 1 — interpreted in the phenomenological MSSM

Hadronic light-by-light scattering in the muong−2: impact of proposed measurements of theπ0→γγdecay width and theγ*γ→π0transition form factor with the KLOE-2 experiment

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Hadronic light-by-light scattering in the muong−2: impact of proposed measurements of theπ⁰→γγdecay width and theγ^*γ→π⁰transition form factor with the KLOE-2 experiment