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Insights into Particle Physics: Electrons, Quarks, Higgs Boson, and the Large Hadron Collider
Discovery of the Higgs Boson at the Large Hadron Collider
The discovery of the Higgs boson at the Large Hadron Collider (LHC) marked a significant milestone in particle physics. The CMS Collaboration observed a new particle with a mass of about 125 GeV, consistent with the Higgs boson predicted by the Standard Model. This discovery was made through proton-proton collisions, with the strongest evidence found in the diphoton and four-lepton final states1. The statistical significance of this observation was five standard deviations, indicating a very low probability of the result being a random fluctuation1.
Higgs Boson Decays and Production Mechanisms
Decays into Low-Mass Spin-0 Particles
Research has also focused on beyond the Standard Model decays of the Higgs boson. One study investigated the decay of the Higgs boson into two new low-mass spin-0 particles, which subsequently decay into b-quark pairs. This search, conducted using the ATLAS detector, targeted a mass range of 15-30 GeV for the new particles2. The study employed a novel strategy to enhance the detection efficiency for closely collimated decay products2.
Heavy Higgs Bosons Decaying to Top Quark Pairs
Another area of research involves heavy pseudoscalar (A) and scalar (H) Higgs bosons decaying into top quark pairs. The ATLAS experiment conducted a search for these decays using data from proton-proton collisions at a center-of-mass energy of 8 TeV. The results showed no significant deviation from the Standard Model predictions, and exclusion limits were set on the signal strength as a function of the mass and the ratio of vacuum expectation values of the two Higgs fields3.
Higgs Boson Production via Bottom-Quark Fusion
Higgs bosons with enhanced coupling to bottom quarks are produced via bottom-quark fusion at hadron colliders. This production mechanism is significant for large values of tanβ, a parameter in certain extensions of the Standard Model. The next-to-leading-order cross section for this process was recalculated, showing improved convergence of the perturbation series and mild factorization-scale dependence4.
QCD Corrections and Higgs Boson Pair Production
Gluon Fusion and QCD Corrections
Gluon fusion is the primary production mechanism for Higgs bosons in proton-proton collisions at the LHC. QCD corrections to the fusion cross section increase the production rate by a factor of 1.5 to 1.7, enhancing the prospects for Higgs boson discovery6. These corrections apply to both the Standard Model and its extensions, such as supersymmetric theories6.
Neutral Higgs-Boson Pair Production
The production of neutral Higgs-boson pairs provides an opportunity to study trilinear Higgs couplings. QCD corrections to gluon-initiated processes and Drell-Yan-like pair production significantly enhance the total cross sections, making this an important area of study for future high-energy colliders8.
Future Prospects and Collider Developments
Compact Linear Collider (CLIC)
Looking ahead, the Compact Linear Collider (CLIC) is a proposed future collider that aims to provide precision measurements of the Higgs boson and the top quark. CLIC would operate at center-of-mass energies ranging from 380 GeV to 3 TeV, offering a complementary approach to the LHC's High-Luminosity upgrade. This collider could reveal new physics through deviations from Standard Model expectations10.
Higgs Boson Couplings
Ongoing and future experiments continue to refine our understanding of the Higgs boson couplings with other particles. These measurements are crucial for testing the Standard Model and exploring potential new physics. The ATLAS and CMS collaborations have made significant progress in this area, and future collider developments are expected to provide even more precise and accurate measurements9.
Conclusion
The discovery and ongoing study of the Higgs boson at the LHC have profoundly impacted our understanding of particle physics. From its production mechanisms and decay channels to the exploration of new physics beyond the Standard Model, the research conducted at the LHC and future colliders like CLIC will continue to push the boundaries of our knowledge. The intricate relationships between the Higgs boson, quarks, leptons, and other fundamental particles remain a central focus in the quest to unravel the mysteries of the universe.
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Most relevant research papers on this topic
A New Boson with a Mass of 125 GeV Observed with the CMS Experiment at the Large Hadron Collider
The CMS experiment has observed a new particle with a mass of 125 GeV in proton-proton collisions at CERN, suggesting it may be a new Higgs boson.
Highly CitedSearch for Higgs boson decays into two new low-mass spin-0 particles in the 4$b$ channel with the ATLAS detector using $pp$ collisions at $\sqrt{s}= 13$ TeV
This paper describes a search for beyond the Standard Model decays of the Higgs boson into a pair of new spin-0 particles subsequently decaying into b -quark pairs, H → aa → ð b ¯ b Þð b ¯ b Þ , using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider at center-of-mass energy ffiffiffi s p ¼ 13 TeV. This search focuses on the range 15 GeV ≤ m a ≤ 30 GeV, where the decay products are collimated; it is complementary to a previous search in the same final state targeting the range 20 GeV ≤ m a ≤ 60 GeV, where the decay products are well separated. A novel strategy for the identification of the a → b ¯ b decays is deployed to enhance the efficiency for topologies with small separation angles. The search is performed with 36 fb − 1 of integrated luminosity collected in 2015 and 2016 and sets upper limits on the production cross section of H → aa → ð b ¯ b Þð b ¯ b Þ , where the Higgs boson is produced in association with a Z boson.
Search for Heavy Higgs Bosons A/H Decaying to a Top Quark Pair in pp Collisions at sqrt[s]=8 TeV with the ATLAS Detector.
The ATLAS experiment has found no significant deviation from the standard model prediction for heavy Higgs bosons decaying into a top quark pair in proton-proton collisions at 8 TeV.
Higgs-boson production via bottom-quark fusion
The appropriate factorization scale for b distribution functions in hadron colliders is approximately $m_h/4,$ improving the convergence of perturbation series and enhancing the prospects for Higgs-boson discovery at large values of $mathrmtanensuremath
Highly CitedQCD corrections to Higgs-boson production at proton-proton colliders.
QCD corrections to gluon fusion cross sections in proton-proton collisions increase the cross section by about 1.5 to 1.7, potentially enabling the production of CP-even Higgs particles in supersymmetric theories.
Highly CitedSearch for single production of a vectorlike T quark decaying into a Higgs boson and top quark with fully hadronic final states using the ATLAS detector
The ATLAS detector has identified no significant excess above background in 13 TeV proton-proton collisions, setting limits on the production cross section of a singlet T quark at 95% confidence level.
Neutral Higgs-Boson Pair Production at Hadron Colliders: QCD Corrections
QCD corrections significantly enhance the total cross sections for neutral Higgs-boson production at future high-energy colliders, providing a potential study of trilinear Higgs couplings.
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