Tag Archives: Higgs

Exploring the Production of Higgs Boson Pairs in Proton-Proton Collisions with the CMS Experiment

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CMS Collaboration physicists used data from high-energy proton-proton collisions from Experiment 2 at CERN’s Large Hadron Collider (LHC) to released The latest research into the production of Higgs boson pairs, known as De-Higgs, has placed constraints on the rate of their formation.

Event display of candidate events for Higgs pair generation. Image credit: CERN.

According to physicists, Higgs particle pair can be created in two main ways.

The first is called gluon-gluon fusion, in which gluons (particles inside colliding protons) interact to produce the Higgs boson. This process allows scientists to study the interaction between one so-called intermediate state Higgs boson and two final state Higgs bosons.

The second method involves quarks, also inside the colliding protons, which emit two vector bosons. These vector particles interact to form a Higgs particle, allowing the study of the interaction between two Higgs particles and two vector particles.

CMS physicists performed the latest analysis by exploring multiple ways DeHiggs could collapse.

These final states resulted from the decay of Higgs boson pairs into bottom quarks, W particles, tau leptons, and photons.

By combining these searches and analyzing all the data simultaneously using advanced analytics techniques such as boosted decision trees and deep neural networks, the collaboration was able to extract more information than ever before. .

This study allowed the researchers to set an upper bound on the Higgs pair production rate with a 95% confidence level.

The measured limits are now 3.5 times higher than the Standard Model’s prediction for total DeHiggs production and 79 times higher than the Standard Model’s prediction for DeHiggs production by vector boson fusion.

The LHC’s Run 3 data acquisition era is underway, and the amount of data collected by CMS experiments has already doubled, and CMS researchers are making progress in analyzing it.

One of the most exciting prospects for measuring the self-interactions of the Higgs boson is the upcoming High-Luminosity LHC (HL-LHC), scheduled to become operational in 2030.

In this new phase, the accelerator will provide CMS with the highest luminosity ever reached in a collider.

Considering luminosity predictions and systematic uncertainties, scientists estimate that the first evidence of Higgs formation may begin to appear in about half of the HL-LHC data.

“We look forward to further investigating this rare and exciting phenomenon,” they said.

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CMS cooperation. 2024. Combined search for non-resonant Higgs boson pair production in proton-proton collisions at √s=13 TeV. CMS-PAS-HIG-20-011

Source: www.sci.news

CERN Scientists Aim to Produce Enigmatic Higgs Particle Duplicates

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Physicists from the ATLAS Collaboration at the Large Hadron Collider (LHC) at CERN have announced the results of the most sensitive search to date for double Higgs production and self-coupling, achieved by combining five double Higgs studies from LHC Run 2 data.

Event display of a double Higgs candidate event, photographed in 2017. Image courtesy of ATLAS Collaboration / CERN.

Remember how hard it was to find one Higgs boson? Now try and find two of them in the same place at the same time.

This intriguing process, known as double Higgs production, can teach scientists about the Higgs particle's self-interaction.

By studying it, physicists can measure the strength of the Higgs particle's self-binding, a fundamental aspect of the Standard Model that links the Higgs mechanism to the stability of the universe.

Searching for the creation of double Higgs particles is a particularly challenging task.

This is an extremely rare process, about 1,000 times rarer than the creation of a single Higgs particle.

While LHC Run 2 produced 40 million collisions per second, ATLAS is expected to produce just a few thousand double Higgs events.

So how can physicists find these rare needles in a mountain of data?

One way to make it easier to find double Higgs production is to search in multiple locations.

By investigating the different ways in which the double Higgs decay (decay modes) and combining them, physicists can maximise their chances of discovering and studying the creation of the double Higgs.

The new results from the ATLAS collaboration are the most comprehensive search to date, covering more than half of all possible double Higgs events with ATLAS.

Each of the five individual studies in this combination focuses on a different mode of damping, each with its own strengths and weaknesses.

For example, the most likely double-Higgs decay mode is the decay into four bottom quarks.

However, the Standard Model QCD process likely also produces four bottom quarks, making it difficult to distinguish this background process from a double Higgs event.

The double-Higgs decay into two bottom quarks and two tau leptons involves moderate background contamination, but it occurs five times less frequently and there are neutrinos that escape undetected, complicating physicists' efforts to recreate the decay.

Decays into multiple leptons are not uncommon, but they have complex characteristics.

Other double Higgs decays are even rarer, such as the decay into two bottom quarks and two photons.

This final state accounts for only 0.3% of all double Higgs decays, but has a cleaner signature and much smaller background contamination.

Combining their findings for each of these decays, ATLAS physicists were able to find that the probability of producing two Higgs particles rules out more than 2.9 times the Standard Model prediction.

This result has a confidence level of 95% and an expected sensitivity of 2.4 (assuming this process does not exist in nature).

They were also able to provide constraints on the strength of the Higgs particle's self-coupling, achieving the highest sensitivity to date for this important observable.

They found that the magnitude of the Higgs self-coupling constant and the strength of the interaction between two Higgs particles and two vector particles are consistent with the Standard Model predictions.

“This overall result marks a milestone in the study of double Higgs particle production,” the researchers said.

their result will be published in journal Physics Review Letter.

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ATLAS Collaboration. 2024. Combined search for Higgs pair production in pp collisions at s√=13 TeV with the ATLAS detector. Physiotherapy Rev Lett,in press; arXiv:2406.09971

Source: www.sci.news

Physicists at CERN release data on the discovery of the Higgs particle

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Physicist from CMS cooperation at CERN just published the combination of CMS measurements that helped establish the discovery of the Higgs boson in 2012.

CMS event display showing a Higgs boson candidate decaying into two photons. It is one of two decay channels that were key to the particle’s discovery. Image credit: CERN.

“Physical measurements based on data from CERN’s Large Hadron Collider (LHC) are typically reported as central values and corresponding uncertainties,” the CMS physicists said.

“For example, shortly after observing the Higgs boson in the LHC’s proton-proton collision data, CMS determined its mass to be 125.3 plus or minus 0.6 GeV (the mass of a proton is about 1 GeV).”

“But this figure is just a quick summary of the measurements, and is like the title of a book.”

In measurement, the complete information extracted from the data is encoded into a mathematical function known as a likelihood function. This function includes measurements of quantities and dependence on external factors.

“For CMS measurements, these factors include the calibration of the CMS detector, the accuracy of the CMS detector simulation used to facilitate the measurements, and other systematic effects,” the researchers said.

“To fully understand the nasty collisions that occur at the LHC, many aspects need to be determined, so the likelihood function for measurements based on LHC data can be complex.”

“For example, the likelihood function for the combined CMS Higgs boson discovery measurement that CMS just released in electronic form has nearly 700 parameters for a fixed value of the Higgs boson mass.”

“Only one of these, the number of Higgs bosons found in the data, is an important physical parameter, and the rest model systematic uncertainties.”

“Each of these parameters corresponds to a dimension of a multidimensional abstract space in which the likelihood function can be drawn.”

“It is difficult for humans to visualize spaces that contain multiple dimensions, much less spaces that contain many dimensions.”

The new release of the CMS Higgs boson discovery measurement likelihood function, the first publicly available likelihood function from this collaboration, allows researchers to avoid this problem.

Using a publicly accessible likelihood function, physicists outside the CMS Collaboration can now accurately incorporate CMS Higgs boson discovery measurements into their studies.

“The release of this likelihood function and the Combine software used to model likelihood and fit data marks another milestone in CMS’s 10-year commitment to fully open science.” said the people.

“This joins hundreds of open access publications, the release of nearly 5 petabytes of CMS data on the CERN Open Data Portal, and the publication of the entire software framework on GitHub.”

Source: www.sci.news