Tiny solenoid looking for new physics

CMS on the lookout for new physics

CMS detector point of view. credit: CERN

As the third round of the Large Hadron Collider (LHC) approaches, the LHC experiments are still publishing new results based on previous operating data. Although no new discoveries were announced, small deviations from expectations appear in a small number of analyses. At the current level, these aberrations can still be attributed to random fluctuations in the data, but they do indicate areas that need to be examined more closely once the stream of new collisions arrives. Here are some examples recently published by the chiral co-operation of the compressed muon (CMS).

In 2017, CMS recorded an amazing collision event that contained four end-state particle jets. The constant mass of all four jets was 8 MeV and the jets could be divided into two pairs with a constant mass of 1.9 TeV each. Such a configuration can be produced if a new particle with a mass of 8 MeV is created in the collision of proton beams, and then decays into a pair of new particles with a mass of 1.9 TeV. In a new analysis recently published by CMS, a search was conducted for pairs of jets with fixed masses matching the data collected up to the end of the run of the LHC Run 2. Surprisingly, a second event with similar amazing properties was found, with a 4 – 8.6 tera jet mass electron volts and the mass of the jet is 2.15 electron volts. These two events can be clearly seen in the graph below, where the events of 4 jets are plotted as a function of the mass of 2 and 4 jets.

While nearly all of the events observed with two pairs of aircraft were produced by strong interactions Among the colliding photons, events with high fixed masses are extremely unlikely. The probability of seeing two events at these masses without any new phenomena is on the order of 1 in 20,000, which corresponds to a local significance of 3.9. While this may seem a very strong signal at first, since the area of ​​the blocks being analyzed is large, it is also important to consider global significance, which indicates that a surplus may be observed anywhere in the analyzed area. For the two events, the global significance is only 1.6 degrees.

CMS on the lookout for new physics

Number of events observed (color scale), plotted as a function of the mass of four jets and the average mass of the two systems. The two dots in the upper right correspond to the two interesting events. Credit: CMS

Two other searches for new heavy particles indicate slight data overruns. In the search for a high-mass resonance that decays into a pair of W bosons (which then decays into leptons), the highest deviation corresponds to the hypothesis of a signal with a mass of 650 GeV, with a local significance of 3.8 and a global significance of 2.6. In the search for heavy particles that decay into pairs of bosons (WW, WZ or other groups, also including Higgs bosons) which subsequently decay into pairs of jets, the data on the predictions diverge in two places. The hypothesis of the signal is a W boson with a mass of 2.1 or 2.9 TeV, which decays into a WZ pair and the highest local significance is 3.6, with a global significance of 2.3.

Another new result comes from searches for additional Higgs boson particles that decay into tau pairs. to new particle With a mass of 100 GeV, a slight excess is observed in the data of local significance 3.1 and global 2.7. Interestingly, this coincides with a similar excess seen by CMS in a previous search for low-mass resonance in the two-photon end state. Another excess is visible in the high mass range, with the largest deviation from expectation observed for a mass of 1.2 TeV with a local (global) significance of 2.8° (2.4 °C).

The final state of the tau pair has also been used to search for new hypothetical particles called leptoquarks. This is of particular interest as leptoquarks can explain the flavor anomalies observed with the LHCb experiment, so if the aberrations are indeed a manifestation of some new phenomenon, this would be a way of looking independently at these phenomena from a different angle. No excess has been found by CMS so far, but the analysis is just beginning to be sensitive to the range of leptoquark variables that can fit in with flavor anomalies, so more data is needed to fully explore the leptoquark hypothesis.

The new data-taking period for the LHC is set to begin in July, with higher power and with significantly upgraded detectors, promising a new stream of data for searches for new phenomena.


The Atlas experiment is looking for a rare Higgs boson that decays into a photon and a Z boson


more information:
More details at CERN Courier: cerncourier.com/a/dijet-excess-intrigues-at-cms/

the quote: Muon solenoid compressed in search of new physics (2022, June 20) Retrieved June 21, 2022 from https://phys.org/news/2022-06-compact-muon-solenoid-lookout-physics.html

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