Spin correlations in production and decay of charginos

Abstract

We study the production of charginos e + e − →χ + iχ − j , (i, j = 1, 2) with polarized beams and the subsequent decaysχ. . , 4), including the complete spin correlations between production and decay. Analytical formulae are presented for the joint spin-density matrix of the charginos, for the chargino decay matrix and for the differential cross section of the combined processes of production and decays. We present numerical results for pair production of the lighter chargino with unpolarized beams and the leptonic decay ofχ − 1 into the lightest neutralinoχ 0 1 . The lepton angular distribution and the forward-backward asymmetry are studied in four representative scenarios for √ s = 192 GeV and √

Physics possibilities at a linear collider

“…. 4, at a linear collider with polarised beams with subsequent leptonic tree-body decaysχ [31]. Since observables like decay angular distributions and T-odd triple product correlations depend on the polarisation of the decaying neutralinos [32] the full spin correlations between production and decay are included.…”

“…Since observables like decay angular distributions and T-odd triple product correlations depend on the polarisation of the decaying neutralinos [32] the full spin correlations between production and decay are included. In [31] the complete analytical formulae for longitudinal polarised beams are given, including complex couplings to allow the study of CP violating phenomena. In figure 5 in the scenario SPS1a [33] for unpolarised beams (solid) and beam polarisations P e − = −0.8, P e + = +0.6 (dashed), P e − = +0.8, P e + = −0.6 (dotted).…”

Chargino production and decay in photon–photon collisions

“…with complete spin correlations are calculated using the same formalism as in [3] for e + e − -annihilation.…”

“…2) are given in [3,4]. They depend on the gaugino mass parameters M 1 , M 2 , the higgsino mass parameter µ, the ratio tan β of the vacuum expectation values of the neutral Higgs fields and the left selectron and the sneutrino mass.…”

“…The analytical formulae for the quantities P αβ , Σ a P,αβ , Σ ′b P,αβ and Σ ab P,αβ are given in the next section. Analytical expressions for the decay matrices for the leptonic decays (2) and (3) can be found in [3,4].…”