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Bottom quark
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<h2 id="name-and-history">Name and history</h2> <p>The bottom quark was first described theoretically in 1973 by physicists <a href="/facts/Makoto_Kobayashi_(physicist)/5TkD1h41">Makoto Kobayashi</a> and <a href="/facts/Toshihide_Maskawa/TJEuQLAv">Toshihide Maskawa</a> to explain <a href="/facts/CP_violation/Nu5lCsPI">CP violation</a>.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> The name "bottom" was introduced in 1975 by <a href="/facts/Haim_Harari/qSJRM2Gr">Haim Harari</a>.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a><a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p><p>The evidence for the bottom quark was first obtained in 1977 by the <a href="/facts/Fermilab/8yyTx3oj">Fermilab</a> E288 experiment team led by <a href="/facts/Leon_M._Lederman/3UT17nBB">Leon M. Lederman</a>, when proton-nucleon collisions produced <a href="/facts/Bottomonium/YxVtcTd3">bottomonium</a> decaying to pairs of <a href="/facts/Muon/BP2fLVIR">muons</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> The discovery was confirmed about a year later by the PLUTO and DASP2 Collaborations at the electron-positron collider <a href="/facts/DORIS_(particle_accelerator)/tjGYFtoq">DORIS</a> at <a href="/facts/DESY/pShcLjpM">DESY</a>.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a><a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> It was reported at the time that DESY scientists were in favor of the name "beauty", while the American scientists tended towards "bottom".<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p><p>Kobayashi and Maskawa won the 2008 <a href="/facts/Nobel_Prize_in_Physics/o6w1nCbr">Nobel Prize in Physics</a> for their explanation of CP-violation.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p><p>While the name "beauty" is sometimes used, "bottom" became the predominant usage by analogy of <a href="/facts/Top_quark/82qd7NPI">"top"</a> and "bottom" to <a href="/facts/Up_quark/Aw3Vp3vk">"up"</a> and <a href="/facts/Down_quark/Nq10ayEE">"down"</a>. </p> <h2 id="distinct-character">Distinct character</h2> <p>The bottom quark's <a href="/facts/Quark/hwuuVkV5">"bare" mass</a> is around 4.18 <a href="/facts/Electronvolt/YMT1fqX9">GeV/<i>c</i>2</a><a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> – a bit more than four times the mass of a <a href="/facts/Proton/clCjepXP">proton</a>, and many orders of magnitude larger than common "light" quarks. </p><p>Although it almost exclusively transitions from or to a <a href="/facts/Top_quark/82qd7NPI">top quark</a>, the bottom quark can decay into either an <a href="/facts/Up_quark/Aw3Vp3vk">up quark</a> or <a href="/facts/Charm_quark/RLduBtpL">charm quark</a> via the <a href="/facts/Weak_interaction/f6upmKMs">weak interaction</a>. <a href="/facts/CKM_matrix/7ckdsIcX">CKM matrix</a> elements Vub and Vcb specify the rates, where both these decays are suppressed, making lifetimes of most bottom particles (~10−12 s) somewhat longer than those of charmed particles (~10−13 s), but shorter than those of strange particles (from ~10−10 to ~10−8 s).<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p>The combination of high mass and low transition rate gives experimental <a href="/facts/Particle_collider/j6wTDohV">collision</a> byproducts containing a bottom quark a distinctive signature that makes them relatively easy to identify using a technique called "<a href="/facts/B-tagging/P36ynqcd">B-tagging</a>". For that reason, <a href="/facts/Meson/9R0kIc1q">mesons</a> containing the bottom quark are exceptionally long-lived for their mass, and are the easiest particles to use to investigate <a href="/facts/CP_violation/Nu5lCsPI">CP violation</a>. Such experiments are being performed at the <a href="/facts/BaBar_experiment/qh6z0s5M">BaBar</a>, <a href="/facts/Belle_Experiment/hor4Nxnp">Belle</a> and <a href="/facts/LHCb/PAlpBtnl">LHCb</a> experiments. </p> <h2 id="hadrons-containing-bottom-quarks">Hadrons containing bottom quarks</h2> <p class="note">Main articles: <a href="/facts/List_of_baryons/JYauAREa">list of baryons</a> and <a href="/facts/List_of_mesons/e1wtI89p">list of mesons</a></p> <p>Some of the <a href="/facts/Hadron/C0sd1zty">hadrons</a> containing bottom quarks include: </p> <ul><li><a href="/facts/B_meson/4669MSRM">B mesons</a> contain a bottom quark (or its <a href="/facts/Antiparticle/7Ic43ThI">antiparticle</a>) and an <a href="/facts/Up_quark/Aw3Vp3vk">up</a> or <a href="/facts/Down_quark/Nq10ayEE">down quark</a>.</li> <li>Bc and Bs mesons contain a bottom quark along with a <a href="/facts/Charm_quark/RLduBtpL">charm quark</a> or <a href="/facts/Strange_quark/VDWd3ky0">strange quark</a> respectively.</li> <li>There are many <a href="/facts/Bottomonium/YxVtcTd3">bottomonium</a> states, for example the <a href="/facts/Upsilon_meson/Ap9wz1cs">ϒ meson</a> and <a href="/facts/Chi_b_(3P)/YxVtcTd3">χb(3P)</a>, the first particle discovered in <a href="/facts/Large_Hadron_Collider/XWJCFSqT">LHC</a>. These consist of a bottom quark and its antiparticle.</li> <li>Bottom <a href="/facts/Baryon/QFwAUWK2">baryons</a> have been observed, and are named in analogy with strange baryons (e.g. Λ0b).</li></ul> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Quark_model/mmaanHvp">Quark model</a></li> <li><a href="/facts/B-factory/NJUkVHbs">B-factory</a></li> <li><a href="/facts/B_meson/4669MSRM">B meson</a></li></ul> <h2 id="further-reading">Further reading</h2> <ul><li>L. Lederman (1978). "The Upsilon Particle". <i><a href="/facts/Scientific_American/jkl8bhUN">Scientific American</a></i>. 239 (4): 72–81. <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/1978SciAm.239d..72L">1978SciAm.239d..72L</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1038%2Fscientificamerican1078-72">10.1038/scientificamerican1078-72</a>.</li> <li>R. Nave. <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/quark.html">"Quarks"</a>. <i><a href="/facts/HyperPhysics/KWfaNNm8">HyperPhysics</a></i>. <a href="/facts/Georgia_State_University/uNoDS9om">Georgia State University</a>, Department of Physics and Astronomy. Retrieved 29 June 2008.</li> <li>A. Pickering (1984). <i>Constructing Quarks</i>. <a href="/facts/University_of_Chicago_Press/6se0Ezfb">University of Chicago Press</a>. pp. 114–125. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-226-66799-7.</li> <li>J. Yoh (1997). <a href="http://lss.fnal.gov/archive/1997/conf/Conf-97-432-E.pdf"><i>The Discovery of the b Quark at Fermilab in 1977: The Experiment Coordinator's Story</i></a> (PDF). Proceedings of Twenty Beautiful Years of Bottom Physics. AIP Conference Proceedings. Vol. 424. pp. 29–42. <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/1998AIPC..424...29Y">1998AIPC..424...29Y</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1063%2F1.55114">10.1063/1.55114</a>.</li> <li><a href="/facts/Sheldon_Stone/UFN6VAX7">Stone, Sheldon</a> (1994). <a href="https://doi.org/10.1142/1441"><i>B Decays</i></a> (2nd ed.). <a href="/facts/Syracuse_University/UhpgUjmb">Syracuse University</a>: <a href="/facts/World_Scientific/qJPTP0Yk">World Scientific</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1142%2F1441">10.1142/1441</a>. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-981-02-0708-3. <a href="/facts/OCLC_(identifier)/Yqad8waq">OCLC</a> <a href="https://search.worldcat.org/oclc/636743000">636743000</a>.</li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://history.fnal.gov/botqrk.html">History of the discovery of the bottom quark / Upsilon meson</a> <a href="https://web.archive.org/web/20170824104835/http://history.fnal.gov/botqrk.html">Archived</a> 24 August 2017 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Kobayashi, M.; Maskawa, T. (1973). "CP-Violation in the Renormalizable Theory of Weak Interaction". Progress of Theoretical Physics. 49 (2): 652–657. Bibcode:1973PThPh..49..652K. doi:10.1143/PTP.49.652. hdl:2433/66179. <a href="https://doi.org/10.1143%2FPTP.49.652" target="_blank">https://doi.org/10.1143%2FPTP.49.652</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Harari, H. (1975). "A new quark model for hadrons". Physics Letters B. 57 (3): 265–269. Bibcode:1975PhLB...57..265H. doi:10.1016/0370-2693(75)90072-6. <a href="/wiki/Physics_Letters_B" target="_blank">/wiki/Physics_Letters_B</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Staley, K. W. (2004). The Evidence for the Top Quark. Cambridge University Press. pp. 31–33. ISBN 978-0-521-82710-2. <a href="978-0-521-82710-2" target="_blank">978-0-521-82710-2</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"Discoveries at Fermilab – Discovery of the Bottom Quark" (Press release). Fermilab. 7 August 1977. Retrieved 24 July 2009. <a href="http://www.fnal.gov/pub/inquiring/physics/discoveries/bottom_quark_pr.html" target="_blank">http://www.fnal.gov/pub/inquiring/physics/discoveries/bottom_quark_pr.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Lederman, L. M. (2005). "Logbook: Bottom Quark". Symmetry Magazine. 2 (8). Archived from the original on 4 October 2006. <a href="https://web.archive.org/web/20061004101845/http://www.symmetrymagazine.org/cms/?pid=1000195" target="_blank">https://web.archive.org/web/20061004101845/http://www.symmetrymagazine.org/cms/?pid=1000195</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Herb, S. W.; Hom, D.; Lederman, L.; Sens, J.; Snyder, H.; Yoh, J.; Appel, J.; Brown, B.; Brown, C.; Innes, W.; Ueno, K.; Yamanouchi, T.; Ito, A.; Jöstlein, H.; Kaplan, D.; Kephart, R.; et al. (1977). "Observation of a Dimuon Resonance at 9.5 GeV in 400-GeV Proton-Nucleus Collisions". Physical Review Letters. 39 (5): 252. Bibcode:1977PhRvL..39..252H. doi:10.1103/PhysRevLett.39.252. OSTI 1155396. <a href="/w/index.php?title=John_Yoh&action=edit&redlink=1" target="_blank">/w/index.php?title=John_Yoh&action=edit&redlink=1</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>G. Flügge (1978). "Particle Spectroscopy". Proceedings of the 19th International Conference on High Energy Physics (Tokyo): 793–810. <a href="https://cds.cern.ch/record/870709/" target="_blank">https://cds.cern.ch/record/870709/</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Arthur L. Robinson (1978). "Particle Physics: New Evidence from Germany for Fifth Quark". Science. 200 (4345): 1033–1034. Bibcode:1978Sci...200.1033R. doi:10.1126/science.200.4345.1033. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Arthur L. Robinson (1978). "Particle Physics: New Evidence from Germany for Fifth Quark". Science. 200 (4345): 1033–1034. Bibcode:1978Sci...200.1033R. doi:10.1126/science.200.4345.1033. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>2008 Physics Nobel Prize lecture by Makoto Kobayashi <a href="http://nobelprize.org/nobel_prizes/physics/laureates/2008/kobayashi-lecture.html" target="_blank">http://nobelprize.org/nobel_prizes/physics/laureates/2008/kobayashi-lecture.html</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>2008 Physics Nobel Prize lecture by Toshihide Maskawa <a href="http://nobelprize.org/nobel_prizes/physics/laureates/2008/maskawa-lecture.html" target="_blank">http://nobelprize.org/nobel_prizes/physics/laureates/2008/maskawa-lecture.html</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>M. Tanabashi et al. (Particle Data Group) (2018). "Review of Particle Physics". Physical Review D. 98 (3): 030001. Bibcode:2018PhRvD..98c0001T. doi:10.1103/PhysRevD.98.030001. hdl:10044/1/68623. <a href="http://pdglive.lbl.gov/DataBlock.action?node=Q005M" target="_blank">http://pdglive.lbl.gov/DataBlock.action?node=Q005M</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Nave, C.R. (ed.). "Transformation of Quark Flavors by the Weak Interaction". Department of Physics and Astronomy. HyperPhysics. Atlanta, GA: Georgia State University. <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/qrkdec.html" target="_blank">http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/qrkdec.html</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> </ol>