CUSPS IN THE KAON DECAYS

We consider two ways of the experimental determination of the S-wave ππ scattering lengths: from K → 3π decays and from Ke4 decays. In both cases the unitary cusps, which emerge due to the difference in the charged and neutral pion masses, play a crucial role. We construct a systematic effective field theory framework which can be used to describe decay amplitudes in the cusp region.

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The S-wave pion–nucleon scattering lengths from pionic atoms using effective field theory

Nuclear Physics A ◽

10.1016/s0375-9474(03)01008-x ◽

2003 ◽

Vol 720 (3-4) ◽

pp. 399-415 ◽

Cited By ~ 55

Author(s):

S.R. Beane ◽

V. Bernard ◽

E. Epelbaum ◽

Ulf-G. Meißner ◽

D.R. Phillips

Keyword(s):

Field Theory ◽

Effective Field Theory ◽

Effective Field ◽

S Wave ◽

Nucleon Scattering ◽

Pion Nucleon ◽

Pionic Atoms ◽

Scattering Lengths

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Effective field theory calculations of NN → NNπ

International Journal of Modern Physics E ◽

10.1142/s0218301314300045 ◽

2014 ◽

Vol 23 (04) ◽

pp. 1430004 ◽

Cited By ~ 16

Author(s):

Vadim Baru ◽

Christoph Hanhart ◽

Fred Myhrer

Keyword(s):

Field Theory ◽

Effective Field Theory ◽

Pion Production ◽

Mass Difference ◽

Effective Field ◽

S Wave ◽

Chiral Effective Field Theory ◽

Charge Symmetry ◽

Pion Nucleon ◽

Scattering Lengths

In this review, we present the recent advances for calculations of the reactions NN → NNπ using chiral effective field theory χEFT. Discussed are the next-to-next-to leading order (N2LO) loop contributions with nucleon and Delta-isobar for near threshold s-wave pion-production. Results of recent experimental pion-production data for energies close to the threshold are analyzed. Several particular applications are discussed: (i) it is shown how the measured charge symmetry (CS) violating pion-production reaction can be used to extract the strong interaction contribution to the proton–neutron mass difference; (ii) the role of NN → NNπ for the extraction of the pion–nucleon scattering lengths from pionic atoms data is illuminated.

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Non-equilibrium effective field theory and second sound

Journal of High Energy Physics ◽

10.1007/jhep04(2021)213 ◽

2021 ◽

Vol 2021 (4) ◽

Author(s):

Michael J. Landry

Keyword(s):

Field Theory ◽

Effective Field Theory ◽

Sound Wave ◽

Effective Field ◽

Second Sound ◽

Gauge Symmetries ◽

Sound Modes ◽

State Of Matter ◽

The Difference ◽

Non Equilibrium

Abstract We investigate the phenomenon of second sound in various states of matter from the perspective of non-equilibrium effective field theory (EFT). In particular, for each state of matter considered, we find that at least two (though sometimes multiple) qualitatively different EFTs exist at finite temperature such that there is always at least one EFT with a propagating second-sound wave and at least one with no such second-sound wave. To aid in the construction of these EFTs, we use the method of cosets developed for non-equilibrium systems. It turns out that the difference between the EFTs with and without second-sound modes can be understood as arising from different choices of a new kind of inverse Higgs constraint. Finally, we demonstrate that it is possible to bypass the need for new inverse Higgs constraints by formulating EFTs on a new kind of manifold that is like the usual fluid worldvolume, but with reduced gauge symmetries.

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Charged lepton flavour violating processes

10.21468/scipostphysproc.1.014 ◽

2019 ◽

Author(s):

Adrian Signer

Keyword(s):

Effective Field Theory ◽

Charged Lepton ◽

Experimental Situation ◽

Specific Model ◽

Effective Field ◽

Charged Scalar ◽

The Standard Model ◽

Doubly Charged ◽

Theory Framework ◽

Lepton Flavour

Charged lepton flavour violating processes are naturally present in many extensions of the Standard Model. After a brief overview on the experimental situation, an effective-field-theory framework is described that allows to interpret and compare the various experiments in a consistent way. The usefulness of this approach is then illustrated in the context of a specific model with a doubly charged scalar.

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Elementary Particle Scattering Lengths and Resonances

Australian Journal of Physics ◽

10.1071/ph740013 ◽

1974 ◽

Vol 27 (1) ◽

pp. 13

Author(s):

DC Peaslee

Keyword(s):

Optical Potential ◽

Scattering Length ◽

Compound System ◽

Zero Energy ◽

S Wave ◽

Nucleon System ◽

Level Shifts ◽

Wave States ◽

Scattering Lengths

An investigation is made of the relation between scattering lengths and resonances in a two-nucleon system. For resonances Eo near zero energy the usual determination of an effective optical potential in mesonic atoms is limited, and it is shown here that the scattering length can only be represented usefully as a sum over resonances of the compound system if the condition IEolDI ~ (PDo)! Is satisfied, where D is the average spacing of s-wave states, p the density of target nucleons and Do the Compton volume of the reduced system. This condition is seen to be valid for mr:, nK and KK interactions and these systems are considered in some detail. It is shown that knowledge of the level shifts of each of these examples can help resolve present uncertainties in associated boson structure.

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