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Title: Search for B$$0\atop{s}$$ oscillations at D0

Abstract

Measurement of the B$$0\atop{s}$$ oscillation frequency via B$$0\atop{s}$$ mixing analyses provides a powerful constraint on the CKM matrix elements. A search for B$$0\atop{s}$$ oscillations was performed using data collected by the DØ detector during the period 2002-2005 at the Fermilab Tevatron. Approximately 610 pb -1 of data was analyzed to reconstruct a large set of B0 s mesons in different semileptonic decay modes. Opposite-side flavor tagging algorithms that were tested on semileptonic B0 d decays with the measurement of the B$$0\atop{d}$$ mixing frequency were used to determine the initial state flavor of the reconstructed B0 s meson. No significant signal for any particular value of the oscillation frequency was found. A 95% confidence level limit on the B$$0\atop{s}$$ oscillation frequency Δm s > 7.3 ps -1 and a sensitivity of 9.5 ps -1 were obtained.

Authors:
 [1]
  1. Columbia Univ., New York, NY (United States)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
879115
Report Number(s):
FERMILAB-THESIS-2005-64
TRN: US0700909
DOE Contract Number:
AC02-76CH03000
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ALGORITHMS; FERMILAB TEVATRON; MATRIX ELEMENTS; MESONS; OSCILLATIONS; SEMILEPTONIC DECAY; SENSITIVITY; Experiment-HEP

Citation Formats

Bose, Tulika. Search for B$0\atop{s}$ oscillations at D0. United States: N. p., 2006. Web. doi:10.2172/879115.
Bose, Tulika. Search for B$0\atop{s}$ oscillations at D0. United States. doi:10.2172/879115.
Bose, Tulika. Sun . "Search for B$0\atop{s}$ oscillations at D0". United States. doi:10.2172/879115. https://www.osti.gov/servlets/purl/879115.
@article{osti_879115,
title = {Search for B$0\atop{s}$ oscillations at D0},
author = {Bose, Tulika},
abstractNote = {Measurement of the B$0\atop{s}$ oscillation frequency via B$0\atop{s}$ mixing analyses provides a powerful constraint on the CKM matrix elements. A search for B$0\atop{s}$ oscillations was performed using data collected by the DØ detector during the period 2002-2005 at the Fermilab Tevatron. Approximately 610 pb-1 of data was analyzed to reconstruct a large set of B0 s mesons in different semileptonic decay modes. Opposite-side flavor tagging algorithms that were tested on semileptonic B0 d decays with the measurement of the B$0\atop{d}$ mixing frequency were used to determine the initial state flavor of the reconstructed B0 s meson. No significant signal for any particular value of the oscillation frequency was found. A 95% confidence level limit on the B$0\atop{s}$ oscillation frequency Δms > 7.3 ps-1 and a sensitivity of 9.5 ps-1 were obtained.},
doi = {10.2172/879115},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Thesis/Dissertation:
Other availability
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  • We present a search for Bmore » $$0\atop{S}$$ oscillations using semileptonic B S → D sμX (D s → K$$0\atop{S}$$K). The data were collected using the D0 detector from events produced in √s = 1.96 TeV proton-antiproton collisions at the Fermilab Tevatron. The Tevatron is currently the only place in the world that produces B$$0\atop{S}$$ mesons and will be until early 2008 when the Large Hadron Collider begins operating at CERN. One of the vital ingredients for the search for B s oscillations is the determination of the flavor of the B$$0\atop{S}$$ candidate (B$$0\atop{S}$$ or $$\bar{B}$$$0\atop{S}$$ ) at the time of its production, called initial state flavor tagging. We develop an likelihood based initial state flavor tagger that uses objects on the side of the event opposite to the reconstructed B meson candidate. To improve the performance of this flavor tagger, we have made it multidimensional so that it takes correlations between discriminants into account. This tagging is then certified by applying it to sample of semimuonic B (0,+) decays and measuring the well-known oscillation frequency Δm d. We obtain Δm d = 0.486 ± 0.021 ps -1, consistent with the world average. The tagging performance is characterized by the effective efficiency, ϵD 2 = (1.90 ± 0.41)%. We then turn to the search for B$$0\atop{S}$$ oscillations in the above-named channel. A special two-dimensional mass fitting procedure is developed to separate kinematic reflections from signal events. Using this mass fitting procedure in an unbinned likelihood framework, we obtain a 95% C.L. of Δm s > 1.10 ps -1 and a sensitivity of 1.92 ps -1. This result is combined with other analyzed B$$0\atop{S}$$ decay channels at D0 to obtain a combined 95% C.L. of Δm s > 14.9 ps -1 and a sensitivity of 16.5 ps -1. The corresponding log likelihood scan has a preferred value of Δm s = 19 ps -1 with a 90% confidence level interval of 17 < Δms < 21 ps -1, assuming Gaussian uncertainties. A comparison of the change in the likelihood between Δm ss = 19 ps -1 and Δm s = ∞ yields an 8% expectation for a background fluctuation.« less
  • In this thesis, we report the study on one such particle called the Bmore » $$0\atop{s}$$ meson made up of a bottom and a strange quark. B$$0\atop{s}$$ mesons are currently produced in a great numbers only at the Tevatron and we report a study done to measure the mixing parameter Δm s between the B$$0\atop{s}$$ meson and its anti-particle $$\bar{B}$$$0\atop{s}$$. Mixing is the ability of a very few neutral mesons to change from their particle to their antiparticle and vice versa. Until recently there existed only a lower limit on this measurement, here we report an upper bound and a most probable value for the mixing parameter. In the following chapter, we discuss the theoretical motivation behind this study. The measurement technique and the different factors that effect the measurement are also given. In Chapter 3, we provide an overview of the experimental setup needed to perform the study. In Chapter 4, we present a new initial state flavor tagging algorithm using electrons and measurement of the B$$0\atop{d}$$ mixing parameter Δm d with the new technique. Details of the combined initial state tagging used in the B$$0\atop{s}$$ mixing study are also given. A detailed description of the B$$0\atop{s}$$ mixing analysis and the results are covered in Chapter 5. And finally the results from all the three channels and a bound on the mixing parameter are presented in Chapter 6.« less
  • This thesis describes a measurement of the Bmore » $$0\atop{d}$$ lifetime in the decay to (J/ΨK$$0\atop{S}$$), using 114 pb -1 of data collected by the D0 experiment at the Tevatron from October 15, 2002, to June 10, 2003. The measurement is motivated by the tests of the Standard Model that it makes possible. These include tests of Heavy Quark Effective Theory predicting B-meson lifetimes, and of the complex phase in the CKM-matrix as the source of CP-violation in B$$0\atop{d}$$ decays to (J/ΨK$$0\atop{S}$$).« less
  • In this thesis we present a search for oscillations of Bmore » $$0\atop{s}$$ mesons using semileptonic B$$0\atop{s}$$ → D$$-\atop{s}$$ℓ +v decays. Data were collected with the upgraded Collider Detector at Fermilab (CDFII) from events produced in collisions of 980 GeV protons and antiprotons accelerated in the Tevatron ring. The total proton-antiproton center-of-mass energy is 1.96 TeV. The Tevatron is the unique source in the world for B$$0\atop{s}$$ mesons, to be joined by the Large Hadron Collider at CERN after 2007. We establish a lower limit on the B$$0\atop{s}$$ oscillation frequency Δm s > 7.7 ps -1 at 95% Confidence Level. We also present a multivariate tagging algorithm that identifies semileptonic B → μX decays of the other B mesons in the event. Using this muon tagging algorithm as well as opposite side electron and jet charge tagging algorithms, we infer the B$$0\atop{s}$$ flavor at production. The tagging algorithms are calibrated using high statistics samples of B 0 and B + semileptonic B 0/+ → Dℓv decays. The oscillation frequency Δm d in semileptonic B 0 → Dℓv decays is measured to be Δm d = (0.501 ± 0.029(stat.) ± 0.017(syst.)) ps -1.« less
  • We present the first observation of the decaymore » $$\bar{B}$$$0\atop{s}$$→ D$$±\atop{s}$$ K∓ and measure the relative branching fraction of $$\bar{B}$$$0\atop{s}$$ → D$$±\atop{s}$$ K∓ to $$\bar{B}$$$0\atop{s}$$ → D$$+\atop{s}$$ π -. The measurement of the relative branching fraction is performed by applying a fit in invariant mass and specific ionization to 1.2 fb -1 of D s(φπ)X data collected with the CDF II detector in pp collisions at √ s = 1.96 TeV at the Fermilab Tevatron collider. We measure B $$\bar{B}$$$0\atop{s}$$ → D$$±\atop{s}$$ K∓ /B $$\bar{B}$$$0\atop{s}$$ → D$$+\atop{s}$$ π - = 0.107±0.019(stat)±0.008(sys). The statistical significance of the $$\bar{B}$$$0\atop{s}$$ → D$$±\atop{s}$$ K signal is 7.9σ. To cross-check our analysis method, we also measure B $$\bar{B0}$$→ D +K - /B $$\bar{B0}$$ → D +π - and B $$\bar{B0}$$ → D +*K - /B $$\bar{B0}$$ → D *+π - and verify that our results are in agreement with the world average.« less