Hadron Lifetimes Research Articles

The lifetimes of B states in Z decays

The lifetimes of B states have been investigated by the ALEPH experiment at LEP, using a sample of 1.7 × 10 5 hadronic Z decays. The average B hadron lifetime is determined from a fit to the impact parameter distribution of leptons with high transverse momentum, to be 1.29±0.06±0.10 ps. A first study is made of the exclusive B 0 and B + lifetimes using events that contain both a lepton and a reconstructed D a or D 0 candidate. The ratio of lifetimes for the two states is measured to be τ B+ / τ B 0 = 0.96 −0.44−0.25 +0.69+0.58.

Inclusive [formula omitted] and D ∗ production in hadronic Z 0 decays with the OPAL detector

The inclusive production of J/ψ and D ∗ mesons has been observed in a sample of roughly 150, 000 multihadronic Z 0 decays with the OPAL detector. Based on 115 D ∗± mesons with x > 0.2 , the average energy of D ∗'s and the partial width Γ(Z 0 → c c) is determined. From a sample of approximately 45 reconstructed J/ψ mesons in the e +e − and μ +μ − final states, the inclusive branching ratio is determined. The average B hadron lifetime is calculated from the measured distances between the primary and J ψ vertices.

Measurement of the average B hadron lifetime in Z 0 decays

A sample of 689 muon candidates and 665 electron candidates identified in multihadronic Z 0 decays has been used to measure the average B hadron lifetime. These data were recorded with the OPAL detector during 1990. Maximum likelihood fits to the distributions of the lepton impact parameters yield an average B hadron lifetime of τ b = 1.37 ± 0.07 ± 0.06 ps, where the first error is statistical and the second systematic. This result is a weighted average over the semileptonic branching fractions and production rates of the B hadrons produced in Z 0 decays.

Observation of J/Ψ production in multihadronic Z 0 decays

The production of J/ψ mesons in multihadronic Z 0 decays has been observed in the e +e − and β +β − final states. From a sample of approximately 45 reconstructed J ψ mesons, the inclusive branching fraction is measured to be Br(Z 0→J/ ψ + X) = (4.5±0.8±0.4±0.6) × 10 −3, where the first error is statistical, the second systematic, and the third error is due to the uncertainty in the leptonic decay rate of the J/ψ. The J/ψ energy distribution is consistent with the distribution expected from B hadron decays. The average B hadron lifetime is calculated from the measured distances between the primary and J/ψ vertices, resulting in τ B = 1.32 −0.25 +0.31±0.15 ps, where the first error is statistical and the second systematic.

Refined measurement of the B-hadron lifetime.

We report a new measurement of the average lifetime of hadrons containing bottom quarks. The B-hadron decays are tagged by identifying leptons at high transverse momentum. From a fit to the lepton impact-parameter distribution, the average B-hadron lifetime is found to be (0.98 0.12 0.13)×10-12 sec. © 1989 The American Physical Society.

Measurement of the B Hadron Lifetime from Mark II at PEPa

Using data taken by the Mark II detector at PEP, the decays of B hadrons are tagged by identifying leptons at high transverse momentum. By means of a precision inner drift chamber, the impact parameters of these leptons are measured with respect to the B production point. From this impact parameter distribution, the B hadron lifetime is found to be 0.98 f 0.12 f 0.13 ps. This measurement can be used to place constraints models of quark mixing.

Measurement of the average lifetime of hadrons containing bottom quarks.

This thesis reports a measurement of the average lifetime of hadrons containing bottom quarks. It is based on data taken with the DELCO detector at the PEP e/sup +/e/sup -/ storage ring at a center of mass energy of 29 GeV. The decays of hadrons containing bottom quarks are tagged in hadronic events by the presence of electrons with a large component of momentum transverse to the event axis. Such electrons are identified in the DELCO detector by an atmospheric pressure Cherenkov counter assisted by a lead/scintillator electromagnetic shower counter. The lifetime measured is 1.17 psec, consistent with previous measurements. This measurement, in conjunction with a limit on the non-charm branching ratio in b-decay obtained by other experiments, can be used to constrain the magnitude of the V/sub cb/ element of the Kobayashi-Maskawa matrix to the range 0.042 (+0.005 or -0.004 (stat.), +0.004 or -0.002 (sys.)), where the errors reflect the uncertainty on tau/sub b/ only and not the uncertainties in the calculations which relate the b-lifetime and the element of the Kobayashi-Maskawa matrix.

Measurement of the lifetime of hadrons containing the b-quark

Data collected with the High Resolution Spectrometer at PEP, corresponding to an integrated luminosity of 200 pb −1 of e +e − annihilation at 29 GeV, were used to measure the mean lifetime of hadrons containing the bottom quark. The lifetime was determined using the impact parameter method on events containing a high-transverse-momentum electron. The result, based on a sample of 301 events, is τ B = 1.02 ± 0.39 0.42 ps, where the indicated errors include both statistics and systematics.

Determination of the lifetime of bottom hadrons.

We have measured the mean lifetime of the hadrons containing b quarks that are produced in e+e− annihilation at √s =29 GeV. We use the full sample of data collected by the MAC detector at the SLAC storage ring, PEP, including those recently acquired with a precision vertex detector. The result is τb=[1.29±0.20(stat) ±0.07(syst) ps]×(1.00±0.15), where the last factor is the systematic uncertainty in the scale.Received 27 October 1986DOI:https://doi.org/10.1103/PhysRevLett.58.640©1987 American Physical Society

Determination of the average lifetime of bottom hadrons

We have determined the average lifetime of hadrons containing b quarks produced in e +e − annihilation to be τ B = 1.83 +0.83 +0.37 − −0.34 ×10 −12s . Our method uses charged decay products from both non-leptonic and semileptonic decay modes.

Measurement of the AverageB- Hadron Lifetime

Results are reported from a study of the impact parameters of electrons in hadronic events produced at the PEP ${e}^{+}{e}^{\ensuremath{-}}$ storage ring. Electrons in hadronic events are produced by bottom and charm decay and their impact parameters show hadrons containing bottom quarks to have a lifetime of ${1.16}_{\ensuremath{-}0.34}^{+0.37}$(stat.) \ifmmode\pm\else\textpm\fi{}0.23 (syst.) psec. This result is used to constrain elements of the Kobayashi-Maskawa mixing matrix.

Measurement of the Lifetime of Bottom Hadrons

The average lifetime of bottom hadrons was measured with the Mark II vertex detector at the storage ring PEP. The lifetime was determined by measuring the impact parameters of leptons produced in bottom decays. τb=(12.0-3.6+4. 5±3.0)×10-13 sec was found. © 1983 The American Physical Society.

Fit of the mixing angles in the six quark model and predictions on theB meson lifetime

Experimental data are used to constrain the parameters of the six quark mixing model and of a composite quark model. A combined fit of the mixing angles in the Kobayashi-Maskawa scheme gives sinθ1=0.228±0.011 and error contours around the best values sinθ2=0.12 and sinθ3≈0. From this, a limit of τ B >0.35×10−13s for the mean lifetime of bottom-flavoured hadrons is obtained. For the composite quark model of Katsumata and Tomozawa, a value of τ B =(0.22−0.23)10−13s is derived.