Measurement of the Neutral B Meson-B Bar Meson Oscillation Frequency Using Dilepton Events at BABAR. PDF Download
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Author: Ming Chao
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Languages : en
Pages : 165
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This dissertation describes the measurement of the B{sup 0}{bar B}{sup 0} oscillation frequency {Delta}m{sub d} with a sample of 122 x 10{sup 6} B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at the Stanford Linear Accelerator Center. A fully inclusive approach is used to select dilepton events in which B meson decays semileptonically and the lepton's charge is employed to identify the flavor of each B meson. The oscillation frequency {Delta}m{sub d} is extracted from the time evolution of the dilepton events. A maximum likelihood fit to the same sign and opposite sign events simultaneously gives {Delta}m{sub d} = (0.485 {+-} 0.009(stat.) {+-} 0.010(syst.)) ps{sup 1} where the first uncertainty is statistical and the second is systematic. This is one of the single most precise measurements of the B{sup 0}{bar B}{sup 0} oscillation frequency to date.
Author: Ming Chao
Publisher:
ISBN:
Category :
Languages : en
Pages : 165
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Book Description
This dissertation describes the measurement of the B{sup 0}{bar B}{sup 0} oscillation frequency {Delta}m{sub d} with a sample of 122 x 10{sup 6} B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at the Stanford Linear Accelerator Center. A fully inclusive approach is used to select dilepton events in which B meson decays semileptonically and the lepton's charge is employed to identify the flavor of each B meson. The oscillation frequency {Delta}m{sub d} is extracted from the time evolution of the dilepton events. A maximum likelihood fit to the same sign and opposite sign events simultaneously gives {Delta}m{sub d} = (0.485 {+-} 0.009(stat.) {+-} 0.010(syst.)) ps{sup 1} where the first uncertainty is statistical and the second is systematic. This is one of the single most precise measurements of the B{sup 0}{bar B}{sup 0} oscillation frequency to date.
Author: Naveen Jeevaka Wickramasinghe Gunawardane
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Category :
Languages : en
Pages :
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Languages : en
Pages :
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The B[sup 0]-[bar B][sup 0] oscillation frequency has been measured with a sample of 23 million B[bar B] pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives[Delta]m[sub d]= 0.493[+-] 0.012 (stat)[+-] 0.009 (syst) ps[sup -1].
Author: Ming Chao
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ISBN:
Category : B mesons
Languages : en
Pages : 330
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Languages : en
Pages : 149
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This thesis reports on a measurement of the neutral B meson mixing parameter, [Delta]md, at the BABAR experiment and the work carried out on the electromagnetic calorimeter (EMC) data acquisition (DAQ) system and simulation software.
![Simultaneous Measurement of the B0 Meson Lifetime and Mixing Frequency with B0 --] D*- 1+ Nu Decays PDF](https://books.google.com/books/content/images/frontcover/j5hPAQAACAAJ?fife=w80-h100)
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Languages : en
Pages : 23
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We measure the B° lifetime [tau]{sub b°} and the B°-{bar B}° oscillation frequency [Delta]m{sub d} with a sample of approximately 14,000 exclusively reconstructed B{sup 0} 2!D*− l [nu]{sub {ell}} signal events, selected from 23 million B{bar B} pairs recorded at the [Upsilon](4S) resonance with the BABAR detector at the Stanford Linear Accelerator Center. The decay position of the other B is determined with the remaining tracks in the event, and its b-quark flavor at the time of decay is determined with a tagging algorithm that exploits the correlation between the flavor of the b-quark and the charges of its decay products. The lifetime and oscillation frequency are measured simultaneously with an unbinned maximum-likelihood ([Delta]t) that uses, for each event, the measured difference in decay times of the two B mesons ([Delta]t), the calculated uncertainty on [Delta]t, the signal and background probabilities, and b-quark tagging information for the other B. The results are [tau]{sub B{sup 0}} = (1.523{sub -0.023}{sup +0.024} ± 0.022) ps and [Delta]m{sub d} = (0.492 ± 0.018 ± 0.013) ps−1.
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Languages : en
Pages :
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The Standard Model of particle physics describes the fundamental building blocks of the Universe and their basic interactions. The model naturally describes the time evolution of the basic particles, of which lifetime and mixing are two examples. The neutral B meson, consisting of a bottom quark and an oppositely charged down quark, enjoys a lifetime of about 1.5 ps and the special property of mixing with its antiparticle partner, the [bar B][sup 0]. That is, due to second order weak interactions, the B[sup 0] meson can change into a [bar B][sup 0] meson and back again as it evolves through time. The details of this behavior offer an opportunity to closely examine the Standard Model. In this dissertation, I report on a measurement of the lifetime and mixing frequency of the neutral B meson. Using the semileptonic decay channel B[sup 0] [yields] D*[sup -][ell][sup +][bar [nu]][sub [ell]], we select more than 68,000 signal and background candidates from about 23 million B[bar B] pairs collected in 1999-2000 with the BABAR detector located at the Stanford Linear Accelerator Center. The other B in the event is reconstructed inclusively. By constructing a master probability density function that describes the distribution of decay time differences in the sample, we use a maximum likelihood technique to simultaneously extract the B[sup 0] lifetime and mixing parameters with precision comparable to the year 2000 world average. The results are [tau][sub B[sup 0]] = (1.523[sub -0.023][sup +0.024] [+-] 0.022) ps and [Delta]m[sub d] = (0.492 [+-] 0.018 [+-] 0.013) ps[sup -1]. The statistical correlation coefficient between [tau][sub B[sup 0]] and [Delta]m[sub d] is -0.22. I describe in detail several cutting-edge strategies this analysis uses to study these phenomena, laying important groundwork for the future. I also discuss several extensions of this work to include possible measurements of higher order parameters such as [Delta][Lambda][sub d].
![A Measurement of the Neutral B Meson Lifetime Using Partially Reconstructed B0 -] D*-pi+ Decays PDF](https://books.google.com/books/content/images/frontcover/dLvVjwEACAAJ?fife=w80-h100)
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Languages : en
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The neutral B meson lifetime has been measured with the data collected by the BABAR detector at the PEP-II storage ring during the year 2000 for a total integrated luminosity of 20.3 fb[sup -1]. The B[sup 0][yields] D*[sup -][pi][sup+] decays have been selected with a partial reconstruction method in which only the fast pion from the B[sup 0] decay and the slow pion from D*[sup -][yields][bar D][sup 0][pi][sup -] are reconstructed. The B[sup 0] lifetime has been measured to be 1.510[+-] 0.040[+-] 0.038 ps with a sample of 6971[+-] 241 reconstructed signal events.
![Simultaneous Measurement of the B0 Meson Lifetime and Mixing Frequency with B0 -] D*- L+ NU{sub L} Decays PDF](https://books.google.com/books/content/images/frontcover/9OpXAQAACAAJ?fife=w80-h100)
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Category :
Languages : en
Pages : 29
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Book Description
We measure the B° lifetime [tau]{sub B°} and the B°-{bar B}° oscillation frequency [Delta]m{sub d} with a sample of approximately 14,000 exclusively reconstructed B{sup 0} 2!D*− l [nu]{sub {ell}} signal events, selected from 23 million B{bar B} pairs recorded at the [Upsilon](4S) resonance with the BABAR detector at the Stanford Linear Accelerator Center. The b-quark .avor of the other B at the time of decay and its decay position are determined inclusively. The lifetime and oscillation frequency are measured simultaneously with an unbinned maximum-likelihood fit that uses, for each event, the measured difference in B decay times ([Delta]t), the calculated uncertainty on [Delta]t, the signal and background probabilities, and b-quark tagging information for the other B. The preliminary results are [tau]{sub B{sup 0}} = (1.523{sub -0.023}{sup +0.024} ± 0.022) ps and [Delta]m{sub d} = (0.492 ± 0.018 ± 0.013) ps−1. The statistical correlation coefficient between [tau]{sub B{sup 0}} and [Delta]m{sub d} is -0.22.
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Languages : en
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A preliminary study of time dependence of B[sup 0][bar B][sup 0] oscillations using dilepton events is presented. The flavor of the B meson is determined by the charge sign of the lepton. To separate signal leptons from cascade and fake leptons we have used a method which combines several discriminating variables in a neural network. The time evolution of the oscillations is studied by reconstructing the time difference between the decays of the B mesons produced by the[Upsilon](4S) decay. With an integrated luminosity of 7.7 fb[sup -1] collected on resonance by BABAR at the PEP-II asymmetric B Factory, we measure the difference in mass of the neutral B eigenstates, [Delta]m[sub B[sup 0]], to be (0.507[+-] 0.015[+-] 0.022) x 10[sup 12][Dirac-h] s[sup -1].
