An observation made by the CMS experiment at CERN unambiguously demonstrates the interaction of the Higgs boson and top quarks, which are the heaviest known subatomic particles. This major milestone is an important step forward in our understanding of the origins of mass. Physicists at the University of Zurich made central contributions by incorporating sophisticated data analysis methods that allowed this benchmark to be reached much earlier than expected.
On 4 July 2012, two of the experiments at the CERN’s Large Hadron Collider (LHC), ATLAS (A Toroidal LHC ApparatuS) and CMS (Compact-Muon-Solenoid), reported independently the discovery of the Higgs boson.
The discovery confirmed the existence of the last missing elementary particle of the Standard Model, half a century after the Higgs boson was predicted theoretically. At the same time the discovery marked also the beginning of an experimental programme aimed to determine the properties of the newly discovered particle. Now, the CMS collaboration achieved an important milestone in that programme.
Higgs boson and top quark-antiquark pair produced
In the Standard Model, the Higgs boson can couple to the particles of matter called fermions, with a coupling strength proportional to the fermion mass. While associated decay processes have been observed, the decay into top quarks, the heaviest known fermions, is kinematically impossible.
Therefore, alternative routes for directly probing the coupling of the Higgs boson to the top quark are needed. One is through the production of a Higgs boson and a top quark-antiquark pair. This is the production mechanism that has now been observed for the first time, and in doing so, the CMS collaboration accomplished one of the primary objectives of the Higgs physics programme.
New techniques speed up data extraction
The extraction of these events from the LHC data is challenging as there are many mundane type of events that can mimic them. Identifying these events requires measurements from all CMS subdetectors, which makes the reconstruction quite complex.
The team of Prof. Florencia Canelli of the Department of Physics at the University of Zurich developed, in collaboration with the CMS group of the ETH, sophisticated techniques that allowed CMS to increase the sensitivity to these events. As consequence, this milestone has been passed considerably earlier than expected. «The development of these techniques also open the possibility of increasing the sensitivity in many other areas of research at the LHC», says Canelli, who is also co-leading the physics group that studies top quarks.
Search for physics beyond the Standard Model
The present achievement is a case in point. With the observation of the coupling between the two heaviest elementary particles of the Standard Model, the LHC physics programme to characterize and more fully understand the Higgs boson has taken an important step.
While the strength of the measured coupling is consistent with the Standard Model expectation, the precision of the measurement still leaves room for contributions from new physics. «In the coming years, much more data will be collected and the precision will be improved, in order to see if the Higgs boson reveals the presence of physics beyond the Standard Model», adds Florencia Canelli.
A. M. Sirunyan et al. (CMS Collaboration). Observation of t¯tH Production. Physical Review Letters. June 4, 2018. DOI: 0.1103/PhysRevLett.120.231801
Prof. Dr. Florencia Canelli
Department of Physics
University of Zürich
Phone: +41 44 635 57 84
Kurt Bodenmüller | Universität Zürich
New material for splitting water
19.06.2018 | American Institute of Physics
Carbon nanotube optics provide optical-based quantum cryptography and quantum computing
19.06.2018 | DOE/Los Alamos National Laboratory
Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
19.06.2018 | Physics and Astronomy
19.06.2018 | Life Sciences
19.06.2018 | Physics and Astronomy