Polarization in (quasi-)two-body decays and new physics

Ajaltouni, Z.; Salvo, E. Di

doi:10.1140/epjc/s10052-019-7506-9

Cited by 4 publications

(10 citation statements)

References 75 publications

(122 reference statements)

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“…Last, we have illustrated some applications; two of them, which concern the decays t → b W [20,21] and Λ b → Λ c l + ν l [44][45][46]22], are very interesting from the viewpoint of the search for new physics beyond the Standard Model.…”

Section: Discussionmentioning

confidence: 99%

“…The off-diagonal elements are parametrized according to Eq. ( 19), taking account of the relationship (22).…”

Section: Parity Conserving Processesmentioning

confidence: 99%

“…We consider the two cases, in order to simulate a resonance-background interference in strong decays of vector mesons; these were already considered many years ago [8], but with a different approach. One has to take account of the relation (22). a) In the case that R includes the states 1 − and 0 − , we have η ′ = η, therefore…”

Section: Two Spins: 1 − and 0 ∓ -Parity Conservationmentioning

confidence: 99%

“…Moreover, the suggestion of exploiting the rank condition for reducing the number of parameters of the SDM [11,8] needs implementation; this problem is especially important when higher spins or more than one spin are involved. Last, the parametrizations, which were proposed in the past, concern essentially resonances which are produced in strong interactions, whereas, in the last years, one has to do with structures which arise from weak decays [20,21,22]: a systematic study of such cases has not yet been performed.…”

Section: Introductionmentioning

confidence: 99%

“…The spin density matrix (SDM), which was introduced long time ago [1] to describe a mixture of pure spin states, is an essential tool for various aims, like determining the spin and the parity of the resonances [2][3][4][5][6][7][8][9], singling out some exchange mechanisms in the production reactions [8,[10][11][12][13][14][15][16][17][18][19] and finding possible hints to new physics [20][21][22]. It concerns unstable states -to be denoted as R in the following -which are produced in some reactions, usually of the type…”

Section: Introductionmentioning

confidence: 99%

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Parametrizations of the Spin Density Matrix

Di Salvo,

Ajaltouni

2020

Preprint

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We propose for the spin density matrix two parametrizations which automatically fulfil the non-negativity conditions, without setting any bound on the parameters. The first one relies on a theorem, that we prove, and it is rather simple and easily adaptable to some specific reactions, where, for example, parity is conserved or angular momentum conservation entails selection rules. Moreover, in the case when the rank is less than the order of the density matrix, we show how to improve the fits to the data, either by implementing previous suggestions, or by elaborating an alternative method, for which we prove a second theorem. Our second parametrization is a variant of previous treatments, it appears suitable for some particular processes. Moreover, we discuss about the possibility of inferring the elements of the density matrix from the differential decay width. Last, we illustrate various examples of current interest, both in strong and weak decays; some of them may be helpful in the investigation of physics beyond the standard model.

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