Searches for B → Dμ+μ− decays and test-beam studies of TORCH detector prototypes
<p>Two complementary pieces of research, linked by the LHCb experiment, are presented. The first uses 8.7 fb<sup>−1</sup> of LHCb data to search for a set of rare decays in the B → Dμ<sup>+</sup>μ<sup>-</sup> family: B<sup>0</sup> → D<sup>...
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| Format: | Thesis |
| Language: | English |
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2020
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| _version_ | 1817932987415658496 |
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| author | Hancock, TH |
| author2 | Harnew, N |
| author_facet | Harnew, N Hancock, TH |
| author_sort | Hancock, TH |
| collection | OXFORD |
| description | <p>Two complementary pieces of research, linked by the LHCb experiment, are presented. The first uses 8.7 fb<sup>−1</sup> of LHCb data to search for a set of rare decays in the B → Dμ<sup>+</sup>μ<sup>-</sup> family: B<sup>0</sup> → D<sup>0</sup>μ<sup>+</sup>μ<sup>−</sup>, B<sup>0</sup> → D<sup>0</sup>J/ψ , B<sub>s</sub><sup>0</sup> → D<sup>0</sup>μ<sup>+</sup>μ<sup>-</sup>, B<sub>s</sub><sup>0</sup> → D0J/ψ, B+ → Ds<sup>+</sup>μ<sup>+</sup>μ−, B<sup>+</sup> → D<sub>s</sub><sup>+</sup>J/ψ, and B<sub>c</sub><sup>+</sup> → Ds<sup>+</sup>μ<sup>+</sup>μ<sup>-</sup>. Although no signals are observed, the following world-best upper limits are set on the branching ratios at the 95% confidence level: </p>
<p>B(B<sup>0</sup> → D<sup>0</sup>μ<sup>+</sup>μ<sup>-</sup>) < 6.1 × 10<sup>−8</sup>, </p>
<p>B(B<sup>0</sup> → D0J/ψ) < 1.4 × 10<sup>−6</sup>, </p>
<p>B(B<sub>s</sub><sup>0</sup> → D0μ<sup>+</sup>μ<sup>-</sup>) < 1.8 × 10<sup>−7</sup>, </p>
<p>B(B<sub>s</sub><sup>0</sup> → D0J/ψ) < 1.4 × 10<sup>−6</sup>, </p>
<p>B(B<sup>+</sup> → Ds<sup>+</sup>μ<sup>+</sup>μ<sup>-</sup>) < 3.2 × 10<sup>−8</sup>, </p>
<p>B(B<sup>+</sup> → Ds<sup>+</sup>J/ψ) < 3.5 × 10<sup>−7</sup>, </p>
<p>and (fc/fu).B(Bc+ → Ds<sup>+</sup>μ<sup>+</sup>μ<sup>-</sup>) < 9.6 × 10<sup>−8</sup>, </p>
<p>where fc and fu are the probabilities that a b quark will hadronize into a Bc+ or B+ mesons respectively. Additionally, the branching ratio of the previously-observed B<sub>c</sub><sup>+</sup> → D<sub>s</sub><sup>+</sup>J/ψ decay is measured to be </p>
<p>(fc/fu).B(B<sub>c</sub><sup>+</sup> → D<sub>s</sub><sup>+</sup>J/ψ ) = (1.63 ± 0.15 ± 0.13) × 10<sup>−5</sup>, </p>
<p>where the first error is statistical and the second systematic. </p>
<p>The second piece of research details test-beam studies of novel time-of-flight detector for a future upgrade of LHCb, prototypes of the so-called TORCH detector. Three test-beam campaigns have been undertaken, two with a small- scale demonstrator and one with a half-sized LHCb module. Single-photon time resolutions better than 100 ps have been measured; a plan of future work required to reach the target 70 ps is discussed. The photon-counting efficiency of the half- sized demonstrator is also presented. A deficit of photons compared to the LHCb benchmark is seen, however with MCP-PMT photon detectors of improved quantum efficiency, photon yields close to requirement should be anticipated.</p> |
| first_indexed | 2024-03-06T21:37:10Z |
| format | Thesis |
| id | oxford-uuid:46a32200-c506-488e-8ad3-f836d558e37b |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:46:39Z |
| publishDate | 2020 |
| record_format | dspace |
| spelling | oxford-uuid:46a32200-c506-488e-8ad3-f836d558e37b2024-12-08T09:09:24ZSearches for B → Dμ+μ− decays and test-beam studies of TORCH detector prototypesThesishttp://purl.org/coar/resource_type/c_db06uuid:46a32200-c506-488e-8ad3-f836d558e37bParticle PhysicsEnglishHyrax Deposit2020Hancock, THHarnew, N <p>Two complementary pieces of research, linked by the LHCb experiment, are presented. The first uses 8.7 fb<sup>−1</sup> of LHCb data to search for a set of rare decays in the B → Dμ<sup>+</sup>μ<sup>-</sup> family: B<sup>0</sup> → D<sup>0</sup>μ<sup>+</sup>μ<sup>−</sup>, B<sup>0</sup> → D<sup>0</sup>J/ψ , B<sub>s</sub><sup>0</sup> → D<sup>0</sup>μ<sup>+</sup>μ<sup>-</sup>, B<sub>s</sub><sup>0</sup> → D0J/ψ, B+ → Ds<sup>+</sup>μ<sup>+</sup>μ−, B<sup>+</sup> → D<sub>s</sub><sup>+</sup>J/ψ, and B<sub>c</sub><sup>+</sup> → Ds<sup>+</sup>μ<sup>+</sup>μ<sup>-</sup>. Although no signals are observed, the following world-best upper limits are set on the branching ratios at the 95% confidence level: </p> <p>B(B<sup>0</sup> → D<sup>0</sup>μ<sup>+</sup>μ<sup>-</sup>) < 6.1 × 10<sup>−8</sup>, </p> <p>B(B<sup>0</sup> → D0J/ψ) < 1.4 × 10<sup>−6</sup>, </p> <p>B(B<sub>s</sub><sup>0</sup> → D0μ<sup>+</sup>μ<sup>-</sup>) < 1.8 × 10<sup>−7</sup>, </p> <p>B(B<sub>s</sub><sup>0</sup> → D0J/ψ) < 1.4 × 10<sup>−6</sup>, </p> <p>B(B<sup>+</sup> → Ds<sup>+</sup>μ<sup>+</sup>μ<sup>-</sup>) < 3.2 × 10<sup>−8</sup>, </p> <p>B(B<sup>+</sup> → Ds<sup>+</sup>J/ψ) < 3.5 × 10<sup>−7</sup>, </p> <p>and (fc/fu).B(Bc+ → Ds<sup>+</sup>μ<sup>+</sup>μ<sup>-</sup>) < 9.6 × 10<sup>−8</sup>, </p> <p>where fc and fu are the probabilities that a b quark will hadronize into a Bc+ or B+ mesons respectively. Additionally, the branching ratio of the previously-observed B<sub>c</sub><sup>+</sup> → D<sub>s</sub><sup>+</sup>J/ψ decay is measured to be </p> <p>(fc/fu).B(B<sub>c</sub><sup>+</sup> → D<sub>s</sub><sup>+</sup>J/ψ ) = (1.63 ± 0.15 ± 0.13) × 10<sup>−5</sup>, </p> <p>where the first error is statistical and the second systematic. </p> <p>The second piece of research details test-beam studies of novel time-of-flight detector for a future upgrade of LHCb, prototypes of the so-called TORCH detector. Three test-beam campaigns have been undertaken, two with a small- scale demonstrator and one with a half-sized LHCb module. Single-photon time resolutions better than 100 ps have been measured; a plan of future work required to reach the target 70 ps is discussed. The photon-counting efficiency of the half- sized demonstrator is also presented. A deficit of photons compared to the LHCb benchmark is seen, however with MCP-PMT photon detectors of improved quantum efficiency, photon yields close to requirement should be anticipated.</p> |
| spellingShingle | Particle Physics Hancock, TH Searches for B → Dμ+μ− decays and test-beam studies of TORCH detector prototypes |
| title | Searches for B → Dμ+μ− decays and test-beam studies of TORCH detector prototypes |
| title_full | Searches for B → Dμ+μ− decays and test-beam studies of TORCH detector prototypes |
| title_fullStr | Searches for B → Dμ+μ− decays and test-beam studies of TORCH detector prototypes |
| title_full_unstemmed | Searches for B → Dμ+μ− decays and test-beam studies of TORCH detector prototypes |
| title_short | Searches for B → Dμ+μ− decays and test-beam studies of TORCH detector prototypes |
| title_sort | searches for b dμ μ decays and test beam studies of torch detector prototypes |
| topic | Particle Physics |
| work_keys_str_mv | AT hancockth searchesforbdmmdecaysandtestbeamstudiesoftorchdetectorprototypes |