The first seek for mushy unclustered power patterns in proton–proton collisions at 13TeV

A key goal of many physics research is to experimentally observe unique phenomena past the Standard Model (SM) which might be predicted by theoretical fashions. These embrace hidden valley fashions, which predict the existence of a darkish sector through which particles and interactions are ruled by a darkish, sturdy drive. The particles and interactions predicted by these fashions may have distinctive decay signatures.

In a latest paper revealed in Physical Review Letters, the massive staff of particle physicists concerned within the CMS (Compact Muon Solenoid) experiment at CERN revealed the outcomes of the primary seek for mushy unclustered power patterns (SUEPs), a particular sign that hidden valley fashions predict would emerge from high-energy particle collisions.

“SUEPs are a part of an even bigger household of theories that search to increase the Standard Model to cowl the unexplained phenomena we observe in our universe: darkish matter, matter-antimatter asymmetry, and so on.,” Luca Lavezzo, from the CMS search staff, advised Phys.org.

“In explicit, they’re one of many many predictions that come up out of hidden valley theories. First proposed by Matt Strassler and Kathryn Zurek virtually 20 years in the past, these theories posit a ‘darkish sector’ separate from the SM, with its personal sturdy, ‘confining’ drive, akin to the sturdy drive that within the SM that binds quarks and gluons into states like protons, neutrons, and different hadrons.”

Hidden valley fashions make attention-grabbing theoretical predictions, most of which haven’t been examined experimentally but. This is as a result of when these theories have been first launched, trying to find the darkish sectors they predicted utilizing current experimental strategies was deemed unattainable, thus these searches have been postponed for future analysis.

“A few years in the past, as searches for advanced darkish sectors picked up extra curiosity in the neighborhood, theorists and experimentalists once more thought-about the unusual predictions from hidden valley theories, and it was realized that some have been lastly accessible at colliders,” stated Lavezzo.

“Soft unclustered power patterns or SUEPs, semivisible jets, and rising jets have been the primary technology of searches which have focused particular hidden valley predictions, which have all been revealed within the final couple of years.”

Hidden valley fashions predict that high-energy particle collisions may give rise to particular signatures, specifically SUEPs. In particle colliders, such because the one amassing information for the CMS experiment, these signatures would seem as many low-momentum particles distributed in a spherical sample.

“This is a fairly distinct signature in comparison with what we anticipate to see from the SM, however it may be troublesome to tell apart a SUEP in a typical collider occasion, as a result of there are a number of dozen simultaneous collisions, every of which produce many low-energy particles,” defined Lavezzo.

“Furthermore, our triggers (i.e., standards used to determine whether or not a proton–proton collision is attention-grabbing sufficient to be saved) are essentially designed to avoid wasting solely occasions with extremely energetic particles produced, and subsequently they’ve issue deciding on occasions with inherently low power.”

To circumvent the challenges that prevented researchers from trying to find these particles prior to now, the CMS Collaboration first had to make sure that the particle producing a SUEP (i.e., the “portal” connecting the SM and Hidden Valley fashions), is recoiling in opposition to an SM particle, which within the case of the staff’s experiment was a jet. This recoil produces an occasion through which each particles have sizable and but balanced power ranges, which could be triggered on the SM jet.

“With this technique, the SUEP turns into much less spherical and begins to resemble a wider model of an SM jet, which is a bathe of particles from a gluon or quark,” stated Lavezzo. “The sport now grew to become to tell apart between SM jets and SUEPs. However, it’s fairly laborious to get dependable predictions utilizing our conventional methods in these difficult environments and occasions, which is critical to check our measurement to concept in order that we are able to determine whether or not there’s proof of SUEPs or all the things is because the SM predicts.”

To conduct their search, the CMS collaboration determined to estimate the contribution of SM occasions straight from the the info they noticed. In doing this, they used the extended-ABCD technique, an strategy for estimating the SM contribution within the sign area.

“We are the primary seek for SUEPs at colliders and we have been capable of exclude a lot of the obtainable section house for SUEP theories, and have offered a set of methods that can hopefully be expanded in future analysis,” stated Lavezzo. “When presenting these outcomes, we obtained plenty of attention-grabbing suggestions from theorists (even from Matt Strassler, who first theorized SUEPs) who have been excited that we had been capable of get some experimental outcomes for these fashions and that now extra concepts could possibly be examined.”

The latest search carried out by this analysis group units new constraints that would information future efforts at observing SUEPs in particle colliders. While hidden valley fashions assume that SUEPs will probably be totally seen (i.e., all darkish sector particles decay again to the SM), this won’t essentially be the case.

“SUEPs may decay to the SM after some lifetime, or a few of them could possibly be secure and invisible, which would seem as totally different signatures that will have evaded earlier searches,” added Lavezzo. “More focused searches may be carried out the place ours was not optimized; particularly, low-mass portals stay pretty unconstrained.”

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