Measurement of the [Lambda]0b Lifetime in [Lambda]0b 2![Lambda]+c[pi]- Decays at the Collider Detector at Fermilab
Measurement of the [Lambda]0b Lifetime in [Lambda]0b 2![Lambda]+c[pi]- Decays at the Collider Detector at Fermilab

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Published: 2008

Total Pages: 214

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The lifetime of the [Lambda]0b baryon (consisting of u, d and b quarks) is the theoretically most interesting of all b-hadron lifetimes. The lifetime of [Lambda]0b probes our understanding of how baryons with one heavy quark are put together and how they decay. Experimentally however, measurements of the [Lambda]0b lifetime have either lacked precision or have been inconsistent with one another. This thesis describes the measurement of [Lambda]0b lifetime in proton-antiproton collisions with center of mass energy of 1.96 TeV at Fermilab's Tevatron collider. Using 1070 ± 60pb-1 of data collected by the Collider Detector at Fermilab (CDF), a clean sample of about 3,000 fully-reconstructed [Lambda]0b →[Lambda]c+[pi]- decays (with [Lambda]+c subsequently decaying via [Lambda]+c → p+ K- [pi]+) is used to extract the lifetime of the [Lambda]0b baryon, which is found to be c[tau]([Lambda]0b) = 422.8 ± 13.8(stat) ± 8.8(syst)[mu]m. This is the most precise measurement of its kind, and is even better than the current world average. It also settles the recent controversy regarding the apparent inconsistency between CDF's other measurement and the rest of the world.

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 Lambda0(b) Lifetime in Lambda0(b) ---] J/psi Lambda0 in P Anti-p Collisions at S**1/2
Measurement of the Lambda0(b) Lifetime in Lambda0(b) ---] J/psi Lambda0 in P Anti-p Collisions at S**1/2

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Published: 2006

Total Pages: 7

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The authors report a measurement of the [Lambda]{sub b}° lifetime in the exclusive decay [Lambda]{sub b}° → J/[psi][Lambda]° in p{bar p} collisions at √s = 1.96 TeV using an integrated luminosity of 1.0 fb−1 of data collected by the CDF II detector at the Fermilab Tevatron. Using fully reconstructed decays, they measure [tau]([Lambda]{sub b}°) = 1.593{sub -0.078}{sup +0.083}(stat.) ± 0.033(syst.) ps. This is the single most precise measurement of [tau]([Lambda]{sub b}°) and is 3.2 [sigma] higher than the current world average.

Measurement of the Lambda 0(b) -] Lambda +(c) Pi- Branching Ratio
Measurement of the Lambda 0(b) -] Lambda +(c) Pi- Branching Ratio

Author: Yi Le

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Published: 2003

Total Pages: 155

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The authors present a measurement of the {Lambda}{sub b}{sup 0} {yields} {Lambda}{sub c}{sup +} {pi}{sup -} branching ratio in p{bar p} collisions at {radical}s = 1.96 TeV using 65 pb{sup -1} data collected by the Collider Detector at Fermilab (CDF). The measurement starts from reconstructing two decay modes: {Lambda}{sub b}{sup 0} {yields} {Lambda}{sub c}{sup +}{pi}{sup -}, where {Lambda}{sub c}{sup +} {yields} p K{sup -} {pi}{sup +}; and {bar B}{sup 0} {yields} D{sup +}{pi}{sup -}, where D{sup +} {yields} {pi}{sup +} K{sup -} {pi}{sup +}. The authors obtained 96 {+-} 13 {Lambda}{sub b}{sup 0} and 321 {+-} 22 {bar B}{sup 0} candidates from the CDF Run II Two-Track Hadronic Trigger data sample. The relative branching ratio of the two decays is then measured based on the equation: f{sub {Lambda}{sub b}} BR({Lambda}{sub b} {yields} {Lambda}{sub c}{sup +} {pi}{sup -})/f{sub d} BR({bar B}{sup 0} {yields} D{sup +} {pi}{sup -}) = BR(D{sup +} {yields} K{pi}{pi}) N{sub {Lambda}{sub b}} {epsilon}{sub B{sup 0}}/BR({Lambda}{sub c}{sup +} {yields} pK{pi}) N{sub {bar B}{sup 0}} {epsilon}{sub {Lambda}{sub b}}. The measurement gives f{sub {Lambda}{sub b}} BR({Lambda}{sub b} {yields} {Lambda}{sub c}{sup +}{pi}{sup -})/f{sub d} BR({bar B}{sup 0} {yields} D{sup +}{pi}{sup -}) = 0.66 {+-} 0.11(stat) {+-} 0.09(syst) {+-} 0.18(BR). The {Lambda}{sub b}{sup 0} {yields} {Lambda}{sub c}{sup +}{pi}{sup -} branching ratio is then extracted, giving BR({Lambda}{sub b}{sup 0} {yields} {Lambda}{sub c}{sup +}{pi}{sup -}) = (6.6 {+-} 1.2(stat.) {+-} 0.9(syst.) {+-} 2.3(BR+FR)) x 10{sup -3}. The {Lambda}{sub b}{sup 0} sample they reconstructed in this analysis is the largest fully reconstructed {Lambda}{sub b}{sup 0} sample in existence. The result they report here on the {Lambda}{sub b}{sup 0} {yields} {Lambda}{sub c}{sup +}{pi}{sup -} branching ratio is the world's first such measurement.

Measurement of the ?0b Lifetime in ?0b {u2192} ?+c?- Decays at the Collider Detector at Fermilab
Measurement of the ?0b Lifetime in ?0b {u2192} ?+c?- Decays at the Collider Detector at Fermilab

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Published: 2008

Total Pages: 214

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The lifetime of the ?0b baryon (consisting of u, d and b quarks) is the theoretically most interesting of all b-hadron lifetimes. The lifetime of ?0b probes our understanding of how baryons with one heavy quark are put together and how they decay. Experimentally however, measurements of the ?0b lifetime have either lacked precision or have been inconsistent with one another. This thesis describes the measurement of ?0b lifetime in proton-antiproton collisions with center of mass energy of 1.96 TeV at Fermilab's Tevatron collider. Using 1070 ± 60pb-1 of data collected by the Collider Detector at Fermilab (CDF), a clean sample of about 3,000 fully-reconstructed ?0b →?c+?- decays (with ?+c subsequently decaying via ?+c → p+ K- ?+) is used to extract the lifetime of the ?0b baryon, which is found to be c?(?0b) = 422.8 ± 13.8(stat) ± 8.8(syst)?m. This is the most precise measurement of its kind, and is even better than the current world average. It also settles the recent controversy regarding the apparent inconsistency between CDF's other measurement and the rest of the world.

Measurement of the Lambda_b Lifetime in Lambda_b -] Lambda_c+ Pi- Decays in P-pbar Collisions at Sqrt(s)
Measurement of the Lambda_b Lifetime in Lambda_b -] Lambda_c+ Pi- Decays in P-pbar Collisions at Sqrt(s)

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Published: 2009

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We report a measurement of the lifetime of the?{sub b}° baryon in decays to the?{sub c}?− final state in a sample corresponding to 1.1 fb−1 collected in p{bar p} collisions at √s = 1.96 TeV by the CDF II detector at the Tevatron collider. Using a sample of about 3000 fully reconstructed?{sub b}° events we measure?(?{sub b}°) = 1.401 ± 0.046 (stat) ± 0.035 (syst) ps (corresponding to c?(?{sub b}°) = 420.1 ± 13.7 (stat) ± 10.6 (syst)?m, where c is the speed of light). The ratio of this result and the world average B° lifetime yields?(?{sub b}°)/?(B°) = 0.918 ± 0.038 (stat and syst), in good agreement with recent theoretical predictions.

Measurement of Lifetime and Decay-Width Difference in B0s -] J/psi Phi Decays
Measurement of Lifetime and Decay-Width Difference in B0s -] J/psi Phi Decays

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Published: 2007

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The authors measure the mean lifetime, [tau] = 2/([Lambda]{sub L} + [Lambda]{sub H}), and the decay-width difference, [Delta][Lambda] = [Lambda]{sub L} - [Lambda]{sub H}, of the light and heavy mass eigenstates of the B{sub s}° meson, B{sub sL}° and B{sub sH}°, in B{sub s}° → J/[psi][phi] decays using 1.7 fb−1 of data collected with the CDF II detector at the Fermilab Tevatron p{bar p} collider. Assuming CP conservation, a good approximation for the B{sub s}° system in the standard model, they obtain [Delta][Lambda] = 0.076{sub -0.063}{sup +0.059}(stat.) ± 0.006(syst.) ps−1 and [tau] = 1.52 ± 0.04(stat.) ± 0.02(syst.) ps, the most precise measurements to date. The constraints on the weak phase and [Delta][Lambda] are consistent with CP conservation.

B-lifetime Measurements at CDF.
B-lifetime Measurements at CDF.

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Published: 1993

Total Pages: 7

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The average b-hadron lifetime has been measured using a high statistics sample of B → J/?X decays recorded with the Collider Detector at Fermilab. The decay vertices of J/? →??− candidates have been reconstructed using information from a silicon vertex-detector. The measured B lifetime, which is the average over all b-hadrons produced in p{bar p} collisions at √s = 1.8 TeV, weighted by their branching ratios into J/? is:?B = 1.46 ± 0.06(stat.) ± 0.06(sys.)ps (preliminary); In addition we used the fully reconstructed final states B{sup ±} → J/?K{sup ±} and B° → J/?K°* to measure the exclusive lifetime of charged and neutral B-mesons. We measure:?{sub B}{sup ±} = 1.59 ± 0.27(stat.) ± 0.17(sys.) ps (preliminary);?{sub B}° = 1. 34 ± 0.31 (stat.) {plus_minus} 0.17 (sys.) ps (preliminary); From this we obtain the following result for the lifetime ratio:?{sub B}{sup {plus_minus}}/? {sub B}° = 1.19 {plus_minus} 0.35(stat.) {plus_minus} 0.12(sys.) (preliminary); This represents the first measurements of the b-lifetime at a hadron collider.

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 =).