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article__header__reduce_padding_bottom-lno25"><div class="article_date_and_read_time-yLEUt"><p class="article_pub_date-EsKM-">October 1, 1978</p><p class="article_read_time-zEJJG">1 min read</p></div><h1 class="article_hed-9vUZD"><p>The Upsilon Particle</p></h1><div class="article_dek-bmjfm"><p>Its unexpected discovery as the heaviest particle has prompted physicists to introduce a massive new quark, raising the number of these unobserved elementary subparticles from four to five</p></div><p class="article_authors-s5nSV">By <a class="article_authors__link--mMFB" href="/author/leon-m-lederman/">Leon M. Lederman</a></p><div class="article_eyebrows-BqeOV"><div class="eyebrows_container-QeE5W eyebrows_container__margin_top-8RQXq"></div></div></div><div class="columnSignup-ztftf"><form class="form-iuY8H"><p class="columnSignup__hdr__text-txjdh">Join Our Community of Science Lovers!</p><button class=""><span class="columnDropdownTxt-vmLrQ">Sign Up for Our Free Daily Newsletter</span></button><div class="columnDropdownWrap-EOZlf"><div><label for="email-:R8p:" class="sr-only">Email Address</label><input id="email-:R8p:" class="input-DHdro input-QLKSA" type="email" name="email" placeholder="Enter your email" required=""/></div><div><label for="consent-:R8p:" class="checkboxLabel-zVwTj"><input id="consent-:R8p:" class="input-DHdro input-QLKSA checkbox-tNiTj" type="checkbox" name="consent" required=""/><span>I agree my information will be processed in accordance with the Scientific American and Springer Nature Limited <a href="/page/privacy-policy">Privacy Policy</a>.</span></label></div><input type="hidden" name="lists" value="today_in_science"/><button class="button-yNos0" type="submit">Sign Up</button></div></form></div><div class="body-n28ll prose-Yw0x0 prose-v4bYC article__body-ivA3W">00</div><footer class="footer-u1I4n"><div class="divide-L7a-x"><div class="rights-Y0o9k"></div></div><div class="divide-L7a-x"></div><div class="divide-L7a-x"><div class="subdivide-5Zp4J"><a href="/author/leon-m-lederman/">More by <span>Leon M. Lederman</span></a></div></div><div class="divide-L7a-x"><div class="viewIssue-pzfFx"><a class="issueThumb-BLiKJ" href="/issue/sa/1978/10-01/"><img class="thumb-gcwPd" src="https://static.scientificamerican.com/sciam/cache/file/9430BAA1-065D-4668-95C45FF20FA79764_source.jpg" alt="Scientific American Magazine Vol 239 Issue 4" srcSet="https://static.scientificamerican.com/sciam/cache/file/9430BAA1-065D-4668-95C45FF20FA79764_source.jpg?w=300 300w, https://static.scientificamerican.com/sciam/cache/file/9430BAA1-065D-4668-95C45FF20FA79764_source.jpg?w=600 600w, https://static.scientificamerican.com/sciam/cache/file/9430BAA1-065D-4668-95C45FF20FA79764_source.jpg?w=900 900w" sizes="300px" width="300" loading="lazy"/></a><cite class="issueInfo-xUoIO">This article was originally published with the title “<span>The Upsilon Particle</span>” in <span class="citation-yDArp"><i>Scientific American Magazine</i> Vol. 239 No. 4 (<time dateTime="1978-10-01">October 1978</time>), p. 72</span><br/><small 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