Flavour-changing neutral current decays of heavy baryons. The case

Abstract

We investigate the rare decay Λ b → Λγ which receives both short and long distance contributions. We estimate the long distance contributions and find them very small. The form factors are obtained from Λ c → Λℓν ℓ using heavy quark symmetry and a pole model. The short distance piece opens a window to new physics and we discuss the sensitivity of Λ b → Λγ to such effects.

Perturbative corrections to Λ b → Λ form factors from QCD light-cone sum rules

“…The pink (solid) and the blue (solid) curves refer to the predictions from the LCSR with an extrapolation and from the Lattice calculations [22], respectively, and the uncertainty bands are obtained by adding all separate theory uncertainties in quadrature. The HQET matrix element defined with an arbitrary Dirac structure of the leading-power effective current can be expressed by two Isgur-Wise functions at low hadronic recoil [63][64][65] 19) due to the heavy-quark spin symmetry. It is then straightforward to write 20) JHEP02 (2016)179 at low recoil.…”

Erratum: Exclusive rare decays of heavy baryons to light baryons:Λb→ΛγandHuang1, Yan2 2000Phys. Rev. D8681431View full textAdd to dashboardCite

“…Processes associated with the flavor-changing neutral current(FCNC) b → s transition have regained much attention since the measurement of FCNC decays of the type b → sγ by CLEO [1,2]. It is well known that these processes are forbidden at the tree level in the Standard Model(SM) and are strongly suppressed by the GIM mechanism, particularly for up type quarks.…”

Analysis of the radiativeΛb→Λγtransition in the standard model and scenarios with one or two universal extra dimensions

“…For comparison, we also give the results of other related works [55][56][57][58][59][60] in the same table as well as the upper limit from the Particle Data Group (PDG) [54]. From this table we see that, within the errors, our result is consistent with those of QCD sum rules [56,57] and a special current [59] and exactly the same with pole model's prediction [60]. However, our prediction differs considerably from these of light-cone QCD sum rules [55], covariant oscillator quark model (COQM) [58] and Ioffe current [59].…”

“…1, we see that there are distinctive differences between the SM predictions and those of the UED models, especially the UED6 for N KK ¼ 15, at small values of the [55] ð0:63 À 0:73Þ Â 10 À5 Three-point QCD sum rule [56] ð3:1 AE 0:6Þ Â 10 À5 QCD sum rule [57] ð3:7 AE 0:5Þ Â 10 À5 COQM [58] 0:23 Â 10 À5 Special current [59] ð1:99 þ0:34 À0:31 Þ Â 10 À5 Ioffe current [59] ð0:61 þ0:14 À0:13 Þ Â 10 À6 Pole model [60] ð1:0 À 4:5Þ Â 10 À5 PDG [54] <1:3 Â 10 À3 (CL ¼ 90%Þ compactification factor 1=R. These differences exist in the lower limits obtained by different FCNC transitions in the UED5 and UED6, cosmological constraints, electroweak precision tests [25,29,31,32], and the latest results of the Higgs search at the LHC and of the electroweak precision data for the S and T parameters [34]; however, they become small when 1=R approaches 1 TeV.…”