Dr Harry Cliff - Rare beauty - seeking new physics at the LHCb experiment

Dr. Henry Clay, a physicist from the University of Cambridge and CERN's LHCb, is introduced as a guest speaker. He specializes in the research of particle decay and is renowned for his science communication skills, having given talks at prestigious institutions and authored a popular science book. His work involves high-energy physics, and he aims to discuss recent developments in his field, including the mysteries of the universe's fundamental building blocks and their governing laws.

The speaker's involvement with particle physics began in 2007 as a summer student at CERN, prior to the LHC's first operation. The excitement of the LHC's completion and the historical context of the project, dating back to discussions in the 1970s, are highlighted. The speaker shares his experiences and provides an overview of the Large Hadron Collider, the largest particle accelerator in the world, and its purpose to uncover the fundamental elements and laws of the universe.

The speaker gives a brief history of our understanding of the universe's composition, from the 90 different atoms of the early 20th century to the subatomic particles discovered later. The development of the Standard Model, which includes particles like quarks and electrons, is discussed. The speaker explains the model's success in describing the observable universe but also notes its limitations, such as the inability to explain dark matter and dark energy, which make up the majority of the universe.

The speaker discusses the need for physics beyond the Standard Model to explain phenomena such as dark matter, the observed matter-antimatter imbalance in the universe, and the Higgs boson's role in giving mass to particles. The Higgs field's non-zero vacuum expectation value and the fine-tuning problem it presents are also addressed. Supersymmetry, a popular solution to these issues, is introduced as a potential extension to the Standard Model that could explain dark matter and stabilize the Higgs field.

The speaker describes the operation of the Large Hadron Collider (LHC), including the process of accelerating protons to high energies and the detection of resulting collisions. The LHC's role in the discovery of the Higgs boson and its potential to reveal new physics, such as supersymmetry, is highlighted. The speaker also discusses the engineering marvel of the LHC, emphasizing its status as the world's largest cryogenic facility.

The speaker talks about the data collected by the LHC, particularly focusing on the search for supersymmetry. Despite initial excitement and expectations, there was no significant evidence found for supersymmetry. The speaker also mentions a temporary excitement over a small bump in a mass spectrum that was later explained as a statistical fluctuation. The search continues for new physics beyond the Standard Model, with intriguing results coming from the LHCb experiment.

The speaker explains the LHCb experiment's focus on studying beauty quarks and their decays as a way to indirectly search for new physics. The experiment looks for rare decays that could indicate the presence of new forces or particles not accounted for in the Standard Model. The speaker also discusses the theoretical background of quantum fields and how particle collisions in the LHC can be viewed as disturbances in these fields.

The speaker delves into the study of flavor-changing neutral currents, specifically the rare decay of a beauty quark into a strange quark and an electron-positron pair. The observed decay rates deviate from the Standard Model predictions, suggesting the possible influence of new, undiscovered particles or forces. The speaker emphasizes the significance of these anomalies and the excitement they generated in the physics community, leading to theoretical speculations about new physics models.

The speaker discusses how theorists have attempted to explain the observed anomalies in decay processes by introducing new particles such as Z' bosons and leptoquarks. These new physics models could potentially address multiple problems at once, including the hierarchy problem and the unification of forces. The speaker highlights the importance of continued theoretical and experimental work in refining our understanding of particle physics and the potential for groundbreaking discoveries.

The speaker underscores the importance of theoretical advancements in improving the precision of experimental predictions. The ongoing work in lattice QCD, a computational approach to quantum chromodynamics, is highlighted as crucial for refining theoretical predictions. The speaker also notes that any new experimental data can lead to a better understanding of the strong interaction and potentially reveal new aspects of physics models.

The speaker addresses the current status of supersymmetry as a theoretical model, noting that despite not being ruled out, it has not been detected at the LHC. The speaker also mentions other new physics models, such as quark-lepton unification models and Z' prime models, which aim to explain the observed anomalies in B physics. The potential implications of these models for understanding dark matter and the fundamental structure of the universe are discussed.

The speaker discusses the aesthetic appeal of a simple and symmetrical Standard Model, but cautions that nature does not necessarily conform to our preferences. The existence of symmetries within the Standard Model is acknowledged, but the speaker also notes that these may be fragments of a larger, yet undiscovered, symmetry. The potential for new particles or forces to reveal a more profound symmetry is considered, and the speaker expresses optimism for future discoveries.

The speaker describes the engineering aspects of the Large Hadron Collider, particularly the accommodation of thermal expansion and contraction in the machine's structure. The use of flexible bellows between magnets to allow for the contraction of the accelerator's length due to temperature changes is explained. The speaker also touches on the adjustments made to maintain the alignment of the accelerator's components.