And beyond

Taking a closer look at LHC

Although the Standard Model has been very successful in accounting for all experimental phenomena, it is not expected to be the ultimate theory because of its great complexity and the many questions it leaves unanswered.

For example, if forces and matter particles are all there are, it says all particles must travel at the speed of light–but that is not what is being observed. To slow them down, is neccesary the Higgs field. In 2013, ATLAS e CMS, detectors in LHC, have shown the existence of this field. 

It does not include the force of gravity and does not encompass the General Theory of Relativity.

Also, physicists now understand that 96 percent of the universe is not made of matter as we know it, and thus it does not fit into the Standard Model.

How to extend the Standard Model to account for these mysteries is an open question to be answered by current and future experiments.


As we indicated at the beginning of this section, the Standard Model cannot be the final theory of particle physics. There are several theoretical models that evade the limitations of the Standard Model, and their study is one of the goals of the LHC experiments (detectors).

For decades, so-called Supersymmetry Theories (SUSY) appeared as attempts to solve the constraints of the Standard Model. The essential idea was that for each type of particle there would be an associated - supercompanion - particle of large mass. This would be a boson replica if the "normal" particle is a fermion and vice versa.

Currently, these supersymmetry theories have been taken over by models involving "dark sectors", which include particles that are barely related to their Standard Model companions, making their detection very complex.

There are many variants of models with dark sectors, and each of them predicts different phenomenologies. One example is that of "long-lived" particles, which can fly macroscopic distances before disintegrating. We can generalise by pointing out that to find these particles requires either accumulating many collisions, since they occur very infrequently, or reaching very large collision energies, since their mass is much higher than that of the particles known so far.

One of the advantages of these dark sector models is that they typically include neutral, massive, almost non-interacting particles. Such particles are excellent candidates for dark matter. This, together with other more formal theoretical reasons, makes such models tremendously attractive.

In this dark sector of particle physics we could have a dark Higgs boson counterpart. Like the normal Higgs boson, this particle would be connected to the mechanism that gives mass to particles in the dark sector.

The energy currently available in proton-proton collisions at the LHC may be sufficient to produce this kind of particle according to such theoretical models. Three of the LHC's largest experiments (ATLAS, CMS and LHCb) have a very extensive search programme for dark-sector particles, designed to, if these theories are correct, detect their signal.

 

(Taken from https://cms.cern/news/searching-dark-side-universe)

In the picture we have a visualisation of a particle collision event recorded at the CMS detector, with the initial collision of two protons, coming in opposite directions, occurring in the centre of the picture. As a result, a pair of high-energy charged leptons (a muon in red and an electron in green on the left side of the image) is created, resulting in a significant transverse momentum imbalance (pink arrow on the right side of the image), which would point in the direction in which the undetected dark matter particles could have gone.


 


http://lhcb.web.cern.ch/

AUTHORS


Xabier Cid Vidal, PhD in experimental Particle Physics for Santiago University (USC). Research Fellow in experimental Particle Physics at CERN from January 2013 to Decembre 2015. He was until 2022 linked to the Department of Particle Physics of the USC as a "Juan de La Cierva", "Ramon y Cajal" fellow (Spanish Postdoctoral Senior Grants), and Associate Professor. Since 2023 is Senior Lecturer in that Department.(ORCID).

Ramon Cid Manzano, until his retirement in 2020 was secondary school Physics Teacher at IES de SAR (Santiago - Spain), and part-time Lecturer (Profesor Asociado) in Faculty of Education at the University of Santiago (Spain). He has a Degree in Physics and in Chemistry, and he is PhD for Santiago University (USC) (ORCID).

CERN


CERN WEBSITE

CERN Directory

CERN Experimental Program

Theoretical physics (TH)

CERN Experimental Physics Department

CERN Scientific Committees

CERN Structure

CERN and the Environment

LHC


LHC

Detector CMS

Detector ATLAS

Detector ALICE

Detector LHCb

Detector TOTEM

Detector LHCf

Detector MoEDAL

Detector FASER

Detector SND@LHC

 


 IMPORTANT NOTICE

 For the bibliography used when writing this Section please go to the References Section


© Xabier Cid Vidal & Ramon Cid - rcid@lhc-closer.es  | SANTIAGO (SPAIN) |

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