CPviolation in hyperon decays from supersymmetry

Abstract

It was pointed out recently that supersymmetry can generate flavor-changing gluonic dipole operators with sufficiently large coefficients to dominate the observed value of ⑀Ј/⑀. We point out that the same operators contribute to direct CP violation in hyperon decay and can generate a CP violating asymmetry A(⌳ Ϫ 0 ) in the range probed by the current E871 experiment. Interestingly, models that naturally reproduce the relation ϭͱm d /m s do not generate ⑀Ј/⑀ but could lead to an A(⌳ Ϫ 0 ) of O(10 Ϫ3 ).The origin of CP violation remains one of the outstanding problems in particle physics. Until recently the only observation of CP violation was in the neutral kaon mixing, with a value of ⑀Ϸ2.27ϫ10 Ϫ3 exp(i/4) ͓1,2͔. The KTeV and NA48 Collaborations have now reported observations of direct CP violation in the neutral kaon decay amplitudes ͓3͔, with the world average value being Re(⑀Ј/⑀)ϭ(21.2Ϯ4.6) ϫ10 Ϫ4 ͓4͔.Although this result is not inconsistent with the standard model prediction, it can be used to constrain other models of CP violation ͓5-7͔. In particular, it has been found that there can be large supersymmetric contributions to ⑀Ј/⑀ ͓5,6͔. Depending on which new contributions are large, there are different consequences for other processes such as rare kaon decays ͓8͔ and hyperon decays.In this Rapid Communication we concentrate on the supersymmetric scenario in which the gluonic dipole operators can have large coefficients. In this case there are potentially large contributions to both ⑀Ј/⑀ ͓5͔ and to the CP-violating asymmetry A(⌳ Ϫ 0 ) in hyperon nonleptonic decays. Experiment E871 at Fermilab is expected to reach a sensitivity of 2ϫ10 Ϫ4 for the observable ͓A(⌳ Ϫ 0 )ϩA(⌶ Ϫ Ϫ )͔ ͓9͔. The CP-violating asymmetry A(⌳ Ϫ 0 ) compares the decay parameter ␣ from the reaction ⌳ 0 →p Ϫ to the corresponding parameter ␣ in ⌳ 0 →p ϩ whereas A(⌶ Ϫ Ϫ ) is the corresponding asymmetry for the mode ⌶ Ϫ →⌳ 0 Ϫ . These asymmetries have a very simple form when one neglects the small ⌬Iϭ3/2 amplitude, for example ͓10͔,where ␦ 1 ϭ6°, ␦ 11 ϭϪ1.1°are the final state N interaction phases for S and P wave amplitudes with Iϭ1/2, respectively ͓11͔. s,p are the corresponding CP-violating weak phases. Recent calculations suggest that the strong scattering phases in the ⌳ 0 final state of the ⌶ decay are small ͓12͔, and, therefore, the current theoretical prejudice is that ͉A(⌳ Ϫ 0 )͉ will dominate the measurement. The standard model prediction for this quantity is around 3ϫ10 Ϫ5 , albeit with large uncertainty ͓10,13͔. This suggests that a nonzero measurement by E871 will be an indication for new physics.A model independent study of new CP-violating interactions has shown that A(⌳ Ϫ 0 ) could be ten times larger than in the standard model and within reach of E871 ͓14͔. A particular example of an operator in which A(⌳ Ϫ 0 ) can be this large is precisely the gluonic dipole operator ͓14͔. The results of E871, therefore, can have a direct impact on supersymmetric models.The short distance effective Hamiltonian for the gluonic dipole operator...

CP-violating asymmetry in p in the Skyrme model

“…It is found that the result is consistent with that given in Ref. [1], and A(Λ 0 − ) could be range of O(10 −3 ).…”

“…[1] that B p and B s quantify the uncertainty in the matrix elements analysis, we can therefore expect that A(Λ 0 − ) could also be O(10 −3 ) in the present letter. In conclusion, we have restudied the supersymmetric contribution to the CP -violating asymmetry in hyperon non-leptonic decay Λ → pπ.…”

“…An example of an operator is precisely the gluonic dipole operator [1,6], in which A(Λ 0 − ) would be enhanced and could reach around O(10 −3 ) [1]. *…”

Search for DirectCPViolation in Nonleptonic Decays of ChargedΞandΛHyperons

“…A Λ is estimated to be (2 − 5) × 10 −5 in the standard model [9,11], but it can be as large as a few times 10 −4 in the other models [12][13][14]. For the charged Ξ → Λπ decay, A Ξ is expected to be smaller than A Λ by about a factor of ten because the strong phase shifts of the Λπ final state are predicted to be small [15].…”

Intensity-Frontier Antiproton Physics with The Antiproton Annihilation Spectrometer (TAPAS) at Fermilab

“…The baryon asymmetry of the universe can in principle be understood in terms of CP violation [6], but the CKM contribution to CPV is too small by many orders of magnitude [7], suggesting that additional contributions from new physics were at play in the early universe. Proposed Standard Model extensions (e.g., non-minimal SUSY [8], multi-Higgs models [9], left-right-symmetric models [10,11], and the SME of Kostelecký et al [12]) abound in possible new, CP-violating phases, which could account for the baryon asymmetry and could show up in sensitive heavy-quark experiments. These issues have motivated substantial, world-wide efforts seeking to discover physics beyond the Standard Model in neutral-meson mixing and CPV.…”