Eur. Phys. J. A (2012) 48: 73
https://doi.org/10.1140/epja/i2012-12073-x

Regular Article - Theoretical Physics

Analysis of the Λ_b → Λℓ⁺ℓ⁻ transition in the SM4 using form factors from full QCD

Physics Department, Doğuş University, Acıbadem-Kadıköy, 34722, Istanbul, Turkey

^* e-mail: kazizi@dogus.edu.tr

Received: 19 March 2012
Accepted: 9 April 2012
Published online: 25 May 2012

Abstract

Using the responsible form factors calculated via full QCD, we analyze the Λ _b → Λℓ⁺ℓ⁻ transition in the standard model containing fourth-generation quarks (SM4). We discuss the effects of the presence of the t’ fourth-family quark on related observables like branching ratio, forward-backward asymmetry, baryon polarization as well as double-lepton polarization asymmetries. We also compare our results with those obtained in the SM as well as with predictions of the SM4 but using form factors calculated within heavy-quark effective theory. The obtained results on the branching ratio indicate that the ℓ transition is more probable in full QCD comparing to the heavy-quark effective theory. It is also shown that the results on all considered observables in the SM4 deviate considerably from the SM predictions when m _t′ ≥ 400 GeV.