Seen and anticipated exclusion contours, at 90% CL, within the airplane (MA′ , ε) for the mixed A′ → e+e− and A′ → μ+μ− analyses (proper) at the side of the predicted +/-1σ (inexperienced) and +/-2σ (yellow) bands. Earlier effects are proven in grey. The NA62 A′ → μ+μ− result’s proven with a dot-dashed line in the correct panel. Credit score: NA62 Collaboration.
Darkish photons are hypothetical debris that resemble mild debris (i.e., photons), however have interaction weakly with customary subject, which might lead them to unattainable or very tough to discover the usage of typical experimental strategies. Those debris are darkish subject applicants, which means that they may give a contribution to the invisible and elusive type of subject accounting for roughly 85% of the universe’s mass.
The NA62 Collaboration, a big analysis collaboration involving scientists at quite a lot of institutes international, has printed the result of a brand new seek for darkish photons, in particular for his or her leptonic decays. Their findings, printed in Bodily Overview Letters, had been derived through examining information accrued through the NA62 detector at CERN configured in beam-dump mode.
“Darkish subject searches are these days probably the most sizzling subjects within the prime power physics neighborhood. We search for weakly interacting debris in plenty of other amenities starting from accelerator experiments to tabletop laboratory setups,” Alina Kleimenova and Stefan Ghinescu, a part of the NA62 Collaboration, informed Phys.org.
“Whilst LHC experiments depend at the prime collision power, smashing protons at about 14 trillion electron volts, NA62, being a fixed-target experiment, specializes in the prime depth means with a quintillion (1018) of protons heading in the right direction according to 12 months. This depth creates a singular alternative to probe quite a lot of uncommon processes and past Same old Type eventualities.”
Darkish photons, additionally known as A’, are some of the hypothetical debris past the Same old Type whose life might be probed through the NA62 detector. Those debris may act as mediators between recognized visual subject and darkish subject.
Particularly, darkish photons would possibly couple to atypical subject, as they may combine with photons described through the Same old Type. The coupling, alternatively, can be extraordinarily susceptible, which might provide an explanation for why they have got no longer been detected thus far.
“This feeble interplay interprets into an extended lifetime, which means in NA62 settings, A’ would trip from tenths of centimeters to loads of meters earlier than decaying,” mentioned Kleimenova and Ghinescu.
“Theoretically, if the darkish photon is the lightest darkish subject particle and has a mass underneath roughly 700 MeV, it might essentially decay into lepton pairs, comparable to electrons or muons. NA62 has all of the important components with the intention to most likely see those decay signatures, that includes an overly lengthy beam line (over 80 m from the objective to the decay quantity), actual monitoring, timing and particle id techniques and the chance to gather those information in a virtually background-free mode.”
The principle purpose of the new learn about through the NA62 Collaboration was once to research the sensitivity of the NA62 detector at CERN to darkish photon decays. By means of examining the knowledge accrued through the detector whilst it was once configured in so-called unload mode, the workforce was hoping to spot alerts that may be related to darkish photons.
Credit score: NA62 Collaboration.
“NA62 is a kaon experiment devoted to precision measurements and research of uncommon kaon decays,” defined the authors. “The experiment can be operated in ‘unload mode.’ On this mode, we will take away the objective used to provide kaons and unload the 400 GeV proton beam onto an absorber at two times the standard depth.”
Theoretical predictions recommend that interactions between protons and unload subject material within the NA62 detector may produce quite a lot of debris in hidden sectors of the sunshine spectrum with plenty round 1 GeV, together with darkish photons. Those debris may then trip and rot within the instrumented area of the NA62 experiment.
“What we seek for in our research is an match with handiest two reverse charged lepton tracks, which shape a vertex throughout the NA62 instrumented area,” mentioned the authors. “Since this match will have to originate from the proton-dump collision, we hint the two-lepton vertex 80 meters again to the entrance airplane of the absorber and take a look at if this traced place is suitable with the positioning of the principle proton interplay level.”
As a part of their fresh learn about, the researchers analyzed a knowledge pattern of one.4×1017 protons on unload accrued through the NA62 detector in 2021. Within the intervening time, alternatively, the detector has accrued further information and is predicted to achieve roughly 1018 protons on unload through the tip of the NA62 experiment.
“Sadly, we didn’t to find any proof of darkish photons, however we controlled to exclude new areas at nighttime photon mass and interplay energy parameter house,” mentioned the authors. “As well as, our effects will also be reinterpreted inside of different fashions, for instance the ones involving axion-like debris.”
Whilst the workforce didn’t discover darkish photon decays but, their fresh findings may tell long term searches for those elusive debris. Kleimenova, Ghinescu and their colleagues are actually operating on combining their effects with the findings of the collaboration’s hadronic ultimate states research.
“This present effort would conclude a complete seek for darkish subject mediators the usage of information accrued through NA62 in 2021,” upload the authors.
“Our final purpose is to increase this research to all the NA62 unload dataset. Moreover, there are a couple of extra Hidden sector eventualities which might be investigated through NA62, for instance, Heavy Impartial Leptons (HNLs). HNLs are specifically attention-grabbing as a result of they are able to deal with a number of key issues in particle physics and cosmology, such because the beginning of neutrino plenty, the matter-antimatter asymmetry within the universe, and the character of darkish subject.”
Additional info:
E. Cortina Gil et al, Seek for Leptonic Decays of Darkish Photons at NA62, Bodily Overview Letters (2024). DOI: 10.1103/PhysRevLett.133.111802.
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