Search for exclusive B decays to J and η or π0 with the L3 detector

Abstract

A search for exclusive decays of Bt and Bf mesons has been performed in the channels Bi 4 Jq, Bz + Jq Bi 4 Jr0 and Bg -_) J.R'. The data sample consisted of more than three and half million hadronic Z decays collected by the L3 experiment at LEP from 1991 through 1995. No candidate events have been observed for any of the modes thus determining upper limits at 90% confidence level: 3.2 x low4 on Br(Bj --+ Jr') and the first experimental limits: Br(J3: -+ Jv) < 1.2 x 10w3, Br(Bt -+ 57) < 3.8 x 10p3, Br(By -+ Jr') < 1.2 X 10U3.

Revisiting non-perturbative effects in the jet broadenings

“…The results that we obtain are (fitting to data from [6,7,[15][16][17][18][19] and references in [20], partially based on a pre-existing compilation [21]) Figure 1 shows the a comparison between the data and the fits for B T and B W .…”

“…This factor is universal for all 1/Q jet observables considered in e + e − annihilation [2] and DIS processes [23] and reads 6 M = 1 + β −1 0 (1.575C A − 0.104n f ) = 1.490 (1.430) for n f = 3 (0) . (F. 15) The perturbative terms in (F.14) (proportional to α s and α 2 s ) represent the start of the series responsible for subtracting off the infrared renormalon divergence in the perturbative contribution to the observable.…”

Experimental Results on Two-Photon Physics from LEP

“…The second uncertainty is taken into account by using two models, namely PHOJET [2] and PYTHIA [3], for the description of the hadronic final state and for the correction from the accepted cross-section to σ γγ , leading to the largest uncertainty of the result. The published measurements of σ γγ by L3 [4] and by OPAL [5] are shown in Figure 2(left). Both results show a clear rise as a function of W .…”

“…[6] by a fit to older γγ data, including those of L3 from Ref. [4], are X 1γγ = (156 ± 18) nb and Y 1γγ = (320 ± 130) nb. Recently an additional hard pomeron component has been suggested in Ref.…”

“…The L3 data from Ref. [4] can be fitted using the old values for the exponents of ǫ 1 = 0.0790 ± 0.0011 and η 1 = 0.4678 ± 0.0059 from Ref. [9] leading to X 1γγ = (173 ± 7) nb and Y 1γγ = (519 ± 125) nb, Figure 2(right, c, dash).…”