Measurement of the $\Lambda^0_b$ Lifetime in the Exclusive Decay $\Lambda^0_b \rightarrow J/\psi \Lambda^0$ with the \D0~detector

Measurement of the $\Lambda^0_b$ Lifetime in the Exclusive Decay $\Lambda^0_b \rightarrow J/\psi \Lambda^0$ with the \D0~detector

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Published: 2012

Total Pages: 130

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In this work we report a measurement of the [Lambda]0b baryon lifetime using the exclusive decay [Lambda]0b→ J/ [Psi][Lambda]0. The B0 meson lifetime is also measured in the topologically similar channel B0→ J/ K0S , which provides a crosscheck of the measurement procedure, and allows a direct determination of the ratio of the [Lambda]0b and the B0 lifetimes. The data used in this analysis were collected with the DØ detector during the complete Run II of the Fermilab Tevatron Collider, from 2002 to 2011, and correspond to an integrated luminosity of 10.4 fb-1 of proton-antiproton collisions at a center of mass energy √s = 1.96 TeV. We obtain [tau] ([Lambda]0b ) = 1.303 ± 0.075 (stat.) ± 0.035 (syst.) ps, [tau] (B0) = 1.508±0.025 (stat.)±0.043 (syst.) ps and [tau] ([Lambda]0b )/[tau] (B0) = 0.864± 0.052 (stat.)±0.033 (syst.). These measurements supersede previous results of the DØ Collaboration using the same decay channels. Our measurement of the lifetime ratio is in excellent agreement with theoretical predictions and compatible with the current world-average, but differs with the latest measurement of the CDF Collaboration in more than 2 standard deviations.


Measurement of the Lambda(b) Lifetime in the Exclusive Decay Lambda(b) ---] J

Measurement of the Lambda(b) Lifetime in the Exclusive Decay Lambda(b) ---] J

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Published: 2007

Total Pages: 7

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We have measured the?{sub b} lifetime using the exclusive decay?{sub b}→J/??, based on 1.2 fb−1 of data collected with the D0 detector during 2002-2006. From 171 reconstructed?{sub b} decays, where the J/? and? are identified via the decays J/??????????− and????????p?, we measured the?{sub b} lifetime to be?(?{sub b})=1.218{sub -0.115}{sup +0.130}(stat)±0.042(syst) ps. We also measured the B° lifetime in the decay B°→J/?(?+?−)K{sub S}°(?+?−) to be?(B°)=1.501{sub -0.074}{sup +0.078}(stat)±0.050(syst) ps, yielding a lifetime ratio of?(?{sub b})/?(B°)=0.811{sub -0.087}{sup +0.096}(stat)±0.034(syst =).


A Measurement of the Lambda-c Baryon Decays to Proton Kaon( - ) Pion(+) Absolute Branching Fraction with the BaBar Detector

A Measurement of the Lambda-c Baryon Decays to Proton Kaon( - ) Pion(+) Absolute Branching Fraction with the BaBar Detector

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Published: 2004

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A measurement of [Beta]([Lambda][sub c][sup +] [yields] pK[sup -] [pi][sup +]) is presented based on data collected with the BaBar detector at the Stanford Linear Accelerator Center. Branching fraction measurements represent a large portion of what is known about short-lived particles, the strong force that binds them, and the weak force that causes them to decay. While the majority of branching fraction measurements are done as ratios between two decay modes, it is the absolute measurements of a few particular decay modes that set the scale for these relative measurements. The [Lambda][sub c][sup +] particle is one of the four weakly decaying hadrons into which more than 90% of the known heavy quark hadrons will eventually decay. Thus, an absolute measurement of the branching fraction for [Lambda][sub c][sup +] [yields] pK[sup -][pi][sup +] is important for many studies of the heavy quark sector, from spectroscopy to B meson decays. The number of produced [Lambda][sub c][sup +]'s is inferred from the number of events reconstructed with an antiproton and an accompanying D meson. The final result of [Beta]([Lambda][sub c][sup +] [yields] pK[sup -] [pi][sup +]) = [6.12 [+-] 0.31(stat.) [+-] 0.42(syst.)]% represents more than a two-fold improvement in precision over the world average. The dominant source of systematic uncertainty is the irreducible background of [Xi][sub c] baryons.