CERN: Content tagged with Higgs boson https://home.cern/ en Leptoquarks, the Higgs boson and the muon’s magnetism https://home.cern/news/news/physics/leptoquarks-higgs-boson-and-muons-magnetism <span>Leptoquarks, the Higgs boson and the muon’s magnetism</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 06/14/2021 - 14:44</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>Zoom into an online particle physics conference, and the chances are you’ll hear the term muon anomaly. This is a longstanding tension with the <a href="https://home.cern/science/physics/standard-model">Standard Model</a> of particle physics, seen in the magnetism of a heavier cousin of the electron called a muon, that has recently been <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">strengthened by measurements made at Fermilab in the US</a>.</p> <p>In a <a href="https://arxiv.org/abs/2008.02643">paper</a> accepted for publication in <em>Physical Review Letters</em>, a trio of theorists including Andreas Crivellin of CERN shows that a class of new unknown particles that could account for the muon anomaly, known as leptoquarks, could also affect the transformation, or “decay”, of the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a> into muons.</p> <p>Leptoquarks are hypothetical particles that connect quarks and leptons, the two types of particles that make up matter at the most fundamental level. They are a popular explanation for the muon anomaly and other <a href="https://cerncourier.com/a/the-flavour-of-new-physics/">anomalies</a> seen in certain decays of particles called B mesons.</p> <p>In their new study, Crivellin and his colleagues explored how two kinds of leptoquarks that could explain the muon anomaly would affect the rare decay of the Higgs boson into muons, of which the ATLAS and CMS experiments recently <a href="https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process">obtained</a> the first indications.</p> <p>They found that one of the two kinds of leptoquarks increases the rate at which this Higgs decay takes place, while the other one decreases it.</p> <p>“The current measurements of the Higgs decay to muons are not sufficient to see this increase or decrease, and the muon anomaly has yet to be confirmed,” says Crivellin. “But if future measurements, at the LHC or future colliders, display such a change, and the muon anomaly is confirmed, it will be possible to pick out which of the two kinds of leptoquarks would be more likely to explain the muon anomaly.”</p> </div> Mon, 14 Jun 2021 12:44:58 +0000 abelchio 157201 at https://home.cern Leptoquarks, the Higgs boson and the muon’s magnetism https://home.cern/news/news/physics/leptoquarks-higgs-boson-and-muons-magnetism <span>Leptoquarks, the Higgs boson and the muon’s magnetism</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 06/14/2021 - 14:44</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>Zoom into an online particle physics conference, and the chances are you’ll hear the term muon anomaly. This is a longstanding tension with the <a href="https://home.cern/science/physics/standard-model">Standard Model</a> of particle physics, seen in the magnetism of a heavier cousin of the electron called a muon, that has recently been <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">strengthened by measurements made at Fermilab in the US</a>.</p> <p>In a <a href="https://arxiv.org/abs/2008.02643">paper</a> accepted for publication in <em>Physical Review Letters</em>, a trio of theorists including Andreas Crivellin of CERN shows that a class of new unknown particles that could account for the muon anomaly, known as leptoquarks, could also affect the transformation, or “decay”, of the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a> into muons.</p> <p>Leptoquarks are hypothetical particles that connect quarks and leptons, the two types of particles that make up matter at the most fundamental level. They are a popular explanation for the muon anomaly and other <a href="https://cerncourier.com/a/the-flavour-of-new-physics/">anomalies</a> seen in certain decays of particles called B mesons.</p> <p>In their new study, Crivellin and his colleagues explored how two kinds of leptoquarks that could explain the muon anomaly would affect the rare decay of the Higgs boson into muons, of which the ATLAS and CMS experiments recently <a href="https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process">obtained</a> the first indications.</p> <p>They found that one of the two kinds of leptoquarks increases the rate at which this Higgs decay takes place, while the other one decreases it.</p> <p>“The current measurements of the Higgs decay to muons are not sufficient to see this increase or decrease, and the muon anomaly has yet to be confirmed,” says Crivellin. “But if future measurements, at the LHC or future colliders, display such a change, and the muon anomaly is confirmed, it will be possible to pick out which of the two kinds of leptoquarks would be more likely to explain the muon anomaly.”</p> </div> Mon, 14 Jun 2021 12:44:58 +0000 abelchio 157201 at https://home.cern Leptoquarks, the Higgs boson and the muon’s magnetism https://home.cern/news/news/physics/leptoquarks-higgs-boson-and-muons-magnetism <span>Leptoquarks, the Higgs boson and the muon’s magnetism</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 06/14/2021 - 14:44</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>Zoom into an online particle physics conference, and the chances are you’ll hear the term muon anomaly. This is a longstanding tension with the <a href="https://home.cern/science/physics/standard-model">Standard Model</a> of particle physics, seen in the magnetism of a heavier cousin of the electron called a muon, that has recently been <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">strengthened by measurements made at Fermilab in the US</a>.</p> <p>In a <a href="https://arxiv.org/abs/2008.02643">paper</a> accepted for publication in <em>Physical Review Letters</em>, a trio of theorists including Andreas Crivellin of CERN shows that a class of new unknown particles that could account for the muon anomaly, known as leptoquarks, could also affect the transformation, or “decay”, of the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a> into muons.</p> <p>Leptoquarks are hypothetical particles that connect quarks and leptons, the two types of particles that make up matter at the most fundamental level. They are a popular explanation for the muon anomaly and other <a href="https://cerncourier.com/a/the-flavour-of-new-physics/">anomalies</a> seen in certain decays of particles called B mesons.</p> <p>In their new study, Crivellin and his colleagues explored how two kinds of leptoquarks that could explain the muon anomaly would affect the rare decay of the Higgs boson into muons, of which the ATLAS and CMS experiments recently <a href="https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process">obtained</a> the first indications.</p> <p>They found that one of the two kinds of leptoquarks increases the rate at which this Higgs decay takes place, while the other one decreases it.</p> <p>“The current measurements of the Higgs decay to muons are not sufficient to see this increase or decrease, and the muon anomaly has yet to be confirmed,” says Crivellin. “But if future measurements, at the LHC or future colliders, display such a change, and the muon anomaly is confirmed, it will be possible to pick out which of the two kinds of leptoquarks would be more likely to explain the muon anomaly.”</p> </div> Mon, 14 Jun 2021 12:44:58 +0000 abelchio 157201 at https://home.cern Leptoquarks, the Higgs boson and the muon’s magnetism https://home.cern/news/news/physics/leptoquarks-higgs-boson-and-muons-magnetism <span>Leptoquarks, the Higgs boson and the muon’s magnetism</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 06/14/2021 - 14:44</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>Zoom into an online particle physics conference, and the chances are you’ll hear the term muon anomaly. This is a longstanding tension with the <a href="https://home.cern/science/physics/standard-model">Standard Model</a> of particle physics, seen in the magnetism of a heavier cousin of the electron called a muon, that has recently been <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">strengthened by measurements made at Fermilab in the US</a>.</p> <p>In a <a href="https://arxiv.org/abs/2008.02643">paper</a> accepted for publication in <em>Physical Review Letters</em>, a trio of theorists including Andreas Crivellin of CERN shows that a class of new unknown particles that could account for the muon anomaly, known as leptoquarks, could also affect the transformation, or “decay”, of the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a> into muons.</p> <p>Leptoquarks are hypothetical particles that connect quarks and leptons, the two types of particles that make up matter at the most fundamental level. They are a popular explanation for the muon anomaly and other <a href="https://cerncourier.com/a/the-flavour-of-new-physics/">anomalies</a> seen in certain decays of particles called B mesons.</p> <p>In their new study, Crivellin and his colleagues explored how two kinds of leptoquarks that could explain the muon anomaly would affect the rare decay of the Higgs boson into muons, of which the ATLAS and CMS experiments recently <a href="https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process">obtained</a> the first indications.</p> <p>They found that one of the two kinds of leptoquarks increases the rate at which this Higgs decay takes place, while the other one decreases it.</p> <p>“The current measurements of the Higgs decay to muons are not sufficient to see this increase or decrease, and the muon anomaly has yet to be confirmed,” says Crivellin. “But if future measurements, at the LHC or future colliders, display such a change, and the muon anomaly is confirmed, it will be possible to pick out which of the two kinds of leptoquarks would be more likely to explain the muon anomaly.”</p> </div> Mon, 14 Jun 2021 12:44:58 +0000 abelchio 157201 at https://home.cern Leptoquarks, the Higgs boson and the muon’s magnetism https://home.cern/news/news/physics/leptoquarks-higgs-boson-and-muons-magnetism <span>Leptoquarks, the Higgs boson and the muon’s magnetism</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 06/14/2021 - 14:44</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>Zoom into an online particle physics conference, and the chances are you’ll hear the term muon anomaly. This is a longstanding tension with the <a href="https://home.cern/science/physics/standard-model">Standard Model</a> of particle physics, seen in the magnetism of a heavier cousin of the electron called a muon, that has recently been <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">strengthened by measurements made at Fermilab in the US</a>.</p> <p>In a <a href="https://arxiv.org/abs/2008.02643">paper</a> accepted for publication in <em>Physical Review Letters</em>, a trio of theorists including Andreas Crivellin of CERN shows that a class of new unknown particles that could account for the muon anomaly, known as leptoquarks, could also affect the transformation, or “decay”, of the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a> into muons.</p> <p>Leptoquarks are hypothetical particles that connect quarks and leptons, the two types of particles that make up matter at the most fundamental level. They are a popular explanation for the muon anomaly and other <a href="https://cerncourier.com/a/the-flavour-of-new-physics/">anomalies</a> seen in certain decays of particles called B mesons.</p> <p>In their new study, Crivellin and his colleagues explored how two kinds of leptoquarks that could explain the muon anomaly would affect the rare decay of the Higgs boson into muons, of which the ATLAS and CMS experiments recently <a href="https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process">obtained</a> the first indications.</p> <p>They found that one of the two kinds of leptoquarks increases the rate at which this Higgs decay takes place, while the other one decreases it.</p> <p>“The current measurements of the Higgs decay to muons are not sufficient to see this increase or decrease, and the muon anomaly has yet to be confirmed,” says Crivellin. “But if future measurements, at the LHC or future colliders, display such a change, and the muon anomaly is confirmed, it will be possible to pick out which of the two kinds of leptoquarks would be more likely to explain the muon anomaly.”</p> </div> Mon, 14 Jun 2021 12:44:58 +0000 abelchio 157201 at https://home.cern Leptoquarks, the Higgs boson and the muon’s magnetism https://home.cern/news/news/physics/leptoquarks-higgs-boson-and-muons-magnetism <span>Leptoquarks, the Higgs boson and the muon’s magnetism</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 06/14/2021 - 14:44</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>Zoom into an online particle physics conference, and the chances are you’ll hear the term muon anomaly. This is a longstanding tension with the <a href="https://home.cern/science/physics/standard-model">Standard Model</a> of particle physics, seen in the magnetism of a heavier cousin of the electron called a muon, that has recently been <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">strengthened by measurements made at Fermilab in the US</a>.</p> <p>In a <a href="https://arxiv.org/abs/2008.02643">paper</a> accepted for publication in <em>Physical Review Letters</em>, a trio of theorists including Andreas Crivellin of CERN shows that a class of new unknown particles that could account for the muon anomaly, known as leptoquarks, could also affect the transformation, or “decay”, of the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a> into muons.</p> <p>Leptoquarks are hypothetical particles that connect quarks and leptons, the two types of particles that make up matter at the most fundamental level. They are a popular explanation for the muon anomaly and other <a href="https://cerncourier.com/a/the-flavour-of-new-physics/">anomalies</a> seen in certain decays of particles called B mesons.</p> <p>In their new study, Crivellin and his colleagues explored how two kinds of leptoquarks that could explain the muon anomaly would affect the rare decay of the Higgs boson into muons, of which the ATLAS and CMS experiments recently <a href="https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process">obtained</a> the first indications.</p> <p>They found that one of the two kinds of leptoquarks increases the rate at which this Higgs decay takes place, while the other one decreases it.</p> <p>“The current measurements of the Higgs decay to muons are not sufficient to see this increase or decrease, and the muon anomaly has yet to be confirmed,” says Crivellin. “But if future measurements, at the LHC or future colliders, display such a change, and the muon anomaly is confirmed, it will be possible to pick out which of the two kinds of leptoquarks would be more likely to explain the muon anomaly.”</p> </div> Mon, 14 Jun 2021 12:44:58 +0000 abelchio 157201 at https://home.cern Leptoquarks, the Higgs boson and the muon’s magnetism https://home.cern/news/news/physics/leptoquarks-higgs-boson-and-muons-magnetism <span>Leptoquarks, the Higgs boson and the muon’s magnetism</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 06/14/2021 - 14:44</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>Zoom into an online particle physics conference, and the chances are you’ll hear the term muon anomaly. This is a longstanding tension with the <a href="https://home.cern/science/physics/standard-model">Standard Model</a> of particle physics, seen in the magnetism of a heavier cousin of the electron called a muon, that has recently been <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">strengthened by measurements made at Fermilab in the US</a>.</p> <p>In a <a href="https://arxiv.org/abs/2008.02643">paper</a> accepted for publication in <em>Physical Review Letters</em>, a trio of theorists including Andreas Crivellin of CERN shows that a class of new unknown particles that could account for the muon anomaly, known as leptoquarks, could also affect the transformation, or “decay”, of the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a> into muons.</p> <p>Leptoquarks are hypothetical particles that connect quarks and leptons, the two types of particles that make up matter at the most fundamental level. They are a popular explanation for the muon anomaly and other <a href="https://cerncourier.com/a/the-flavour-of-new-physics/">anomalies</a> seen in certain decays of particles called B mesons.</p> <p>In their new study, Crivellin and his colleagues explored how two kinds of leptoquarks that could explain the muon anomaly would affect the rare decay of the Higgs boson into muons, of which the ATLAS and CMS experiments recently <a href="https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process">obtained</a> the first indications.</p> <p>They found that one of the two kinds of leptoquarks increases the rate at which this Higgs decay takes place, while the other one decreases it.</p> <p>“The current measurements of the Higgs decay to muons are not sufficient to see this increase or decrease, and the muon anomaly has yet to be confirmed,” says Crivellin. “But if future measurements, at the LHC or future colliders, display such a change, and the muon anomaly is confirmed, it will be possible to pick out which of the two kinds of leptoquarks would be more likely to explain the muon anomaly.”</p> </div> Mon, 14 Jun 2021 12:44:58 +0000 abelchio 157201 at https://home.cern Leptoquarks, the Higgs boson and the muon’s magnetism https://home.cern/news/news/physics/leptoquarks-higgs-boson-and-muons-magnetism <span>Leptoquarks, the Higgs boson and the muon’s magnetism</span> <div class="field field--name-field-p-news-display-byline field--type-entity-reference field--label-hidden field--items"> <div class="field--item">Ana Lopes</div> </div> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 06/14/2021 - 14:44</span> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p>Zoom into an online particle physics conference, and the chances are you’ll hear the term muon anomaly. This is a longstanding tension with the <a href="https://home.cern/science/physics/standard-model">Standard Model</a> of particle physics, seen in the magnetism of a heavier cousin of the electron called a muon, that has recently been <a href="https://news.fnal.gov/2021/04/first-results-from-fermilabs-muon-g-2-experiment-strengthen-evidence-of-new-physics/">strengthened by measurements made at Fermilab in the US</a>.</p> <p>In a <a href="https://arxiv.org/abs/2008.02643">paper</a> accepted for publication in <em>Physical Review Letters</em>, a trio of theorists including Andreas Crivellin of CERN shows that a class of new unknown particles that could account for the muon anomaly, known as leptoquarks, could also affect the transformation, or “decay”, of the <a href="https://home.cern/science/physics/higgs-boson">Higgs boson</a> into muons.</p> <p>Leptoquarks are hypothetical particles that connect quarks and leptons, the two types of particles that make up matter at the most fundamental level. They are a popular explanation for the muon anomaly and other <a href="https://cerncourier.com/a/the-flavour-of-new-physics/">anomalies</a> seen in certain decays of particles called B mesons.</p> <p>In their new study, Crivellin and his colleagues explored how two kinds of leptoquarks that could explain the muon anomaly would affect the rare decay of the Higgs boson into muons, of which the ATLAS and CMS experiments recently <a href="https://home.cern/news/press-release/physics/cern-experiments-announce-first-indications-rare-higgs-boson-process">obtained</a> the first indications.</p> <p>They found that one of the two kinds of leptoquarks increases the rate at which this Higgs decay takes place, while the other one decreases it.</p> <p>“The current measurements of the Higgs decay to muons are not sufficient to see this increase or decrease, and the muon anomaly has yet to be confirmed,” says Crivellin. “But if future measurements, at the LHC or future colliders, display such a change, and the muon anomaly is confirmed, it will be possible to pick out which of the two kinds of leptoquarks would be more likely to explain the muon anomaly.”</p> </div> Mon, 14 Jun 2021 12:44:58 +0000 abelchio 157201 at https://home.cern ATLAS searches for pairs of Higgs bosons in a rare particle decay https://home.cern/news/news/physics/atlas-searches-pairs-higgs-bosons-rare-particle-decay <span>ATLAS searches for pairs of Higgs bosons in a rare particle decay</span> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 03/29/2021 - 12:28</span> <div class="field field--name-field-p-news-display-list-cds field--type-cerncdsmedia field--label-hidden field--item"><figure class="cds-image" data-record-id="2759322" data-filename="event_display_HighResolution_long" id="ATLAS-PHOTO-2021-017-1"> <a href="//cds.cern.ch/images/ATLAS-PHOTO-2021-017-1" title="View on CDS"> <img alt="ATLAS Event Display: candidate pair of Higgs bosons decay in ATLAS" src="//cds.cern.ch/images/ATLAS-PHOTO-2021-017-1/file?size=medium"/> </a> <figcaption> ATLAS candidate event display of a pair of Higgs bosons decaying to two b-quarks and two photons (HH → bbɣɣ) in data taken in 2017. Charged-particle tracks are shown in green, the two candidate b-jets are shown as red cones, and the two candidate photons are shown as cyan towers. <span> (Image: CERN)</span> </figcaption> </figure></div> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p style="margin-bottom:16px">Since the <a href="/science/physics/higgs-boson">Higgs boson</a> was discovered in 2012, scientists at the <a href="/science/accelerators/large-hadron-collider">Large Hadron Collider</a> (LHC) have been studying the properties of this very special particle and its relation to the fundamental mechanism essential to the generation of mass of elementary particles. One property that remains to be experimentally verified is whether the Higgs boson is able to couple to itself, known as self-coupling. Such an interaction would contribute to the production of a pair of Higgs bosons in the LHC's high-energy proton–proton collisions, an incredibly rare process in the <a href="/science/physics/standard-model">Standard Model</a> – more than 1000 times rarer than the production of a single Higgs boson! Measuring a Higgs boson self-coupling that is different from the predicted value would have important consequences; the universe might be able to transition into a lower energy state and the laws that govern the interactions of matter could take a very different shape.</p> <p>At the ongoing <a href="http://moriond.in2p3.fr/2021/">Rencontres de Moriond</a> conference, the ATLAS collaboration presented the <a href="https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2021-016">result</a> of a study that further explores this question. ATLAS physicists looked for the two intimately related Higgs-pair production processes that could be present in LHC collisions, though only one of these is related to the Higgs boson self-coupling and contributes favourably to the production of Higgs pairs when their total mass is low. These two processes interfere quantum mechanically and suppress Higgs boson pair production in the Standard Model. If a new physics phenomenon is at play, it could change the Higgs boson self-coupling and ATLAS might see more pairs of Higgs bosons than expected – or in particle physics parlance, measure a higher cross-section.</p> <p>For their new study, ATLAS physicists have developed new analysis techniques to search for the rare process in which one of the two Higgs bosons decays to two photons and the other decays to two bottom quarks (HH → γγbb). First, they divided the proton–proton collision events into low and high mass regions, so as to optimise the sensitivity to the Higgs boson self-coupling. Then, using a machine-learning algorithm, they separated the events that look like the HH → γγbb process from those that don’t. Finally, they determined the cross-section for Higgs-pair production and observed how it varies as a function of the ratio of the Higgs boson self-coupling to its Standard Model value. This allowed ATLAS to constrain the Higgs boson self-coupling, between –1.5 and 6.7 times the Standard Model prediction, and also the Higgs-pair production cross-section. The result on the Higgs boson self-coupling is more than twice as powerful as the <a href="https://link.springer.com/article/10.1007%2FJHEP11%282018%29040">previous ATLAS</a> result in the same Higgs-pair decay channel.</p> <p>Although this result sets the world’s best constraints on the size of the Higgs boson self-coupling, the work is just beginning. This is a preview of what is to come, as much more data would be needed to observe the Higgs boson self-coupling if it were close to its Standa­­­rd Model prediction. Observing the Higgs boson self-coupling is indeed one of the <em>raisons d’être</em> of the <a href="/science/accelerators/high-luminosity-lhc">High-Luminosity LHC</a> (HL-LHC) programme, an upgrade to the LHC scheduled to begin operations in the late 2020s. The HL-LHC is expected to deliver a dataset more than 20 times larger than the one used in this analysis and to operate at higher collision energy. If Higgs-pair production is as predicted by the Standard Model, it should be observed in this huge dataset, and a more quantitative statement will be made on the strength of the Higgs boson coupling to itself.</p> <p>_____</p> <p><em>Read more on the <a class="bulletin" href="https://atlas.cern/updates/briefing/twice-higgs-twice-challenge">ATLAS website</a>.</em></p> </div> Mon, 29 Mar 2021 10:28:54 +0000 abelchio 156739 at https://home.cern ATLAS searches for pairs of Higgs bosons in a rare particle decay https://home.cern/news/news/physics/atlas-searches-pairs-higgs-bosons-rare-particle-decay <span>ATLAS searches for pairs of Higgs bosons in a rare particle decay</span> <span><span lang="" about="/user/159" typeof="schema:Person" property="schema:name" datatype="">abelchio</span></span> <span>Mon, 03/29/2021 - 12:28</span> <div class="field field--name-field-p-news-display-list-cds field--type-cerncdsmedia field--label-hidden field--item"><figure class="cds-image" data-record-id="2759322" data-filename="event_display_HighResolution_long" id="ATLAS-PHOTO-2021-017-1"> <a href="//cds.cern.ch/images/ATLAS-PHOTO-2021-017-1" title="View on CDS"> <img alt="ATLAS Event Display: candidate pair of Higgs bosons decay in ATLAS" src="//cds.cern.ch/images/ATLAS-PHOTO-2021-017-1/file?size=medium"/> </a> <figcaption> ATLAS candidate event display of a pair of Higgs bosons decaying to two b-quarks and two photons (HH → bbɣɣ) in data taken in 2017. Charged-particle tracks are shown in green, the two candidate b-jets are shown as red cones, and the two candidate photons are shown as cyan towers. <span> (Image: CERN)</span> </figcaption> </figure></div> <div class="field field--name-field-p-news-display-body field--type-text-long field--label-hidden field--item"><p style="margin-bottom:16px">Since the <a href="/science/physics/higgs-boson">Higgs boson</a> was discovered in 2012, scientists at the <a href="/science/accelerators/large-hadron-collider">Large Hadron Collider</a> (LHC) have been studying the properties of this very special particle and its relation to the fundamental mechanism essential to the generation of mass of elementary particles. One property that remains to be experimentally verified is whether the Higgs boson is able to couple to itself, known as self-coupling. Such an interaction would contribute to the production of a pair of Higgs bosons in the LHC's high-energy proton–proton collisions, an incredibly rare process in the <a href="/science/physics/standard-model">Standard Model</a> – more than 1000 times rarer than the production of a single Higgs boson! Measuring a Higgs boson self-coupling that is different from the predicted value would have important consequences; the universe might be able to transition into a lower energy state and the laws that govern the interactions of matter could take a very different shape.</p> <p>At the ongoing <a href="http://moriond.in2p3.fr/2021/">Rencontres de Moriond</a> conference, the ATLAS collaboration presented the <a href="https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2021-016">result</a> of a study that further explores this question. ATLAS physicists looked for the two intimately related Higgs-pair production processes that could be present in LHC collisions, though only one of these is related to the Higgs boson self-coupling and contributes favourably to the production of Higgs pairs when their total mass is low. These two processes interfere quantum mechanically and suppress Higgs boson pair production in the Standard Model. If a new physics phenomenon is at play, it could change the Higgs boson self-coupling and ATLAS might see more pairs of Higgs bosons than expected – or in particle physics parlance, measure a higher cross-section.</p> <p>For their new study, ATLAS physicists have developed new analysis techniques to search for the rare process in which one of the two Higgs bosons decays to two photons and the other decays to two bottom quarks (HH → γγbb). First, they divided the proton–proton collision events into low and high mass regions, so as to optimise the sensitivity to the Higgs boson self-coupling. Then, using a machine-learning algorithm, they separated the events that look like the HH → γγbb process from those that don’t. Finally, they determined the cross-section for Higgs-pair production and observed how it varies as a function of the ratio of the Higgs boson self-coupling to its Standard Model value. This allowed ATLAS to constrain the Higgs boson self-coupling, between –1.5 and 6.7 times the Standard Model prediction, and also the Higgs-pair production cross-section. The result on the Higgs boson self-coupling is more than twice as powerful as the <a href="https://link.springer.com/article/10.1007%2FJHEP11%282018%29040">previous ATLAS</a> result in the same Higgs-pair decay channel.</p> <p>Although this result sets the world’s best constraints on the size of the Higgs boson self-coupling, the work is just beginning. This is a preview of what is to come, as much more data would be needed to observe the Higgs boson self-coupling if it were close to its Standa­­­rd Model prediction. Observing the Higgs boson self-coupling is indeed one of the <em>raisons d’être</em> of the <a href="/science/accelerators/high-luminosity-lhc">High-Luminosity LHC</a> (HL-LHC) programme, an upgrade to the LHC scheduled to begin operations in the late 2020s. The HL-LHC is expected to deliver a dataset more than 20 times larger than the one used in this analysis and to operate at higher collision energy. If Higgs-pair production is as predicted by the Standard Model, it should be observed in this huge dataset, and a more quantitative statement will be made on the strength of the Higgs boson coupling to itself.</p> <p>_____</p> <p><em>Read more on the <a class="bulletin" href="https://atlas.cern/updates/briefing/twice-higgs-twice-challenge">ATLAS website</a>.</em></p> </div> Mon, 29 Mar 2021 10:28:54 +0000 abelchio 156739 at https://home.cern