Determination of |Vub|/|Vcb| with DELPHI at LEP

Abstract

The ratio of the CKM quark-mixing matrix elements |V ub |/|V cb | has been measured using B hadron semileptonic decays. The analysis uses the reconstructed mass M X of the secondary hadronic system produced in association with an identified lepton. Since B → X u ℓν transitions are characterised by hadronic masses below those of the D mesons produced in B → X c ℓν transitions, events with a reconstructed value of M X significantly below the D mass are selected. Further signal enrichments are obtained using the topology of reconstructed decays and hadron identification. A fit to the numbers of decays in the b → u enriched and depleted samples with M X above and below 1.6 GeV/c 2 and to the shapes of the lepton energy distribution in the B rest frame gives |V ub |/|V cb | = 0.103 +0.011 −0.012 (stat.) ± 0.016 (syst.) ± 0.010 (model) and, correspondingly, a charmless semileptonic B decay branching fraction of BR(B → X u ℓν) = (1.57 ± 0.35 (stat.) ± 0.48 (syst.) ± 0.27 (model)) × 10 −3 .

One-loop contributions to neutral Higgs decay h→μτ

“…Another indirect search is the one-loop contribution, where sleptons and N run in loops, to lepton pair production, e + e − → l + i l − i , and multiflavor lepton final state e + e − → l + i l − j (i = j) [45]. Recent bounds of new particle masses obtained from the LEP are a few hundred GeV [45,51,52], which is consistent with results obtained from the LHC.…”

B physics at the Z0resonance

“…A somewhat different approach is taken by DELPHI [41]. Here, the selected events are divided into 4 classes, depending on the reconstructed hadronic mass (above or below 1.6 GeV) and an enrichment or depletion in b → u decays.…”

“…The measurements from ALEPH [39], DELPHI [41] and L3 [40] have been combined to give a result of where the first error includes statistical and uncorrelated systematic contributions, the second is associated with modelling b → c decays and the third with modelling b → u decays [7].…”

Measurement of the inclusive electron spectrum from B meson decays and determination of |Vub|

“…The best estimate of this BF has been derived by HFAG [3], based on a global fit to moments of the lepton momentum and hadron mass spectra in B → Xeν decays (corrected for B → X u eν decays) either with a constraint on the c-quark mass or by including photon energy moments in B → X s γ decays in the fit. Inclusive measurements of jV ub j have been performed at the ϒð4SÞ resonance, by ARGUS [5], CLEO [6,7], BABAR [8] and Belle [9], and experiments at LEP operating at the Z 0 resonance, L3 [10], ALEPH [11], DELPHI [12], and OPAL [13]. Among the jV ub j measurements based on exclusive semileptonic decays [2], the most recent by the LHCb experiment at the LHC is based on the baryon decay Λ b → pμν [14].…”