supersymmetry

Breaking “R-parity” in new searches for supersymmetry

At the recent ICHEP 2024 conference held in Prague (Czech Republic), ATLAS physicists presented two innovative searches for R-parity-violating SUSY using data collected during the Run 2 of the LHC (2015 to 2018).

25 July 2024

Searching for supersymmetric needles in the LHC haystack

The ATLAS Collaboration has published three new results in this challenging area, using Boosted Decision Trees (BDTs) to isolate potential signals and ultimately set stringent constraints on the masses of SUSY particles.

20 November 2023

ATLAS releases comprehensive review of supersymmetric dark matter

In new results presented today, the ATLAS Collaboration provides its most comprehensive overview of the searches for weakly-interacting supersymmetric particles. By developing new search algorithms and exploiting machine learning techniques, researchers have probed deep into this difficult-to-reach territory.

22 August 2023

ATLAS strengthens its search for supersymmetry

Where is all the new physics? Could it be sneaking past the standard searches? ATLAS researchers have developed innovative ways to search for new particles, improving their search programme to ensure they have the best chance of discovering new physics in Run 3 of the LHC.

29 March 2022

Search for new physics in Higgs boson decays with displaced photons

The ATLAS Collaboration performed a new search for exotic Higgs-boson decays using the full dataset of 13 TeV proton-proton collisions delivered by the LHC between 2015 and 2018.

28 March 2022

The hunt for higgsinos reaches new limits

The ATLAS Collaboration has released three new searches for "higgsinos" - the super-partner of the Higgs boson.

10 June 2021

Better late than never: ATLAS searches for late-decaying new particles

A new result from the ATLAS Collaboration – debuted at the virtual Moriond Electroweak conference – sets itself apart from more traditional LHC searches. Typically, physicists will look for new particles produced in LHC collisions that immediately decay to known or invisible particles. This analysis, in contrast, looks for new particles that live for roughly a hundred nanoseconds or more before decaying.

23 March 2021

The supersymmetric bottom quark and its friends

The special status of the top and bottom quarks makes them key players in the search for phenomena not foreseen by the Standard Model. New ATLAS results set strong constraints on the production of supersymmetric bottom quarks and of possible dark-matter particles.

16 March 2021

Higgs boson probes for new phenomena

ATLAS scientists are implementing a new strategy in the search for physics beyond the Standard Model – one that combines measurements across the full spectrum of the Collaboration's research programme.

28 October 2020

ATLAS Live talk: Physics Through the Looking Glass with Dr. Laura Jeanty

On Thursday 28 May, Dr. Laura Jeanty gave a public talk live on YouTube on the underlying symmetries of the Universe, and how they are studied by particle physics experiments.

29 May 2020

Fantastic decays and where to find them

Supersymmetry offers an elegant solution to the limitations of the Standard Model, extending it to give each elementary particle a “superpartner” with different spin properties. Yet SUSY also contains interactions that would cause phenomena not observed in nature, such as the decay of protons. This has traditionally been avoided by requiring the conservation of a property known as “R-parity” (or “matter-parity”), which incorporates the baryon number, lepton number and spin. ATLAS physicists are also considering SUSY models with R-parity violation (or “RPV”), which would allow the lightest SUSY particle to be observed decaying directly into Standard Model particles.

27 May 2020

Searching for natural supersymmetry using novel techniques

In new results presented today at CERN, the ATLAS Experiment’s search for supersymmetry (SUSY) reached new levels of sensitivity. The results examine a popular SUSY extension studied at the Large Hadron Collider (LHC): the “Minimal Supersymmetric Standard Model” (MSSM), which includes the minimum required number of new particles and interactions to make predictions at the LHC energies.

18 February 2020

ATLAS releases new search for strong supersymmetry

New particles sensitive to the strong interaction might be produced in abundance in the proton-proton collisions generated by the LHC – provided that they aren’t too heavy. These particles could be the partners of gluons and quarks predicted by supersymmetry (SUSY), a proposed extension of the Standard Model of particle physics that would expand its predictive power to include much higher energies. In the simplest scenarios, these “gluinos” and “squarks” would be produced in pairs, and decay directly into quarks and a new stable neutral particle (the “neutralino”), which would not interact with the ATLAS detector. The neutralino could be the main constituent of dark matter.

5 August 2019

In conversation with Zachary Marshall, a leading voice in the search for new physics

Simulation and supersymmetry, two things that have defined Zachary Marshall’s career. Zach is a researcher with Lawrence Berkeley National Lab. He is currently the co-convener of the ATLAS Supersymmetry group, leading the team searching for supersymmetry and all its various manifestations, building on his previous work as convenor of the ATLAS Simulation group.

5 July 2019

Searching for Electroweak SUSY: not because it is easy, but because it is hard

Today, at the Large Hadron Collider Physics (LHCP) conference in Puebla, Mexico, and at the SUSY2019 conference in Corpus Christi, USA, the ATLAS Collaboration presented numerous new searches for SUSY based on the full Run-2 dataset (taken between 2015 and 2018), including two particularly challenging searches for electroweak SUSY. Both target particles that are produced at extremely low rates at the LHC, and decay into Standard Model particles that are themselves difficult to reconstruct. The large amount of data successfully collected by ATLAS in Run 2 provides a unique opportunity to explore these scenarios with new analysis techniques.

20 May 2019

ATLAS sets strong constraints on supersymmetric dark matter

One of the most complete theoretical frameworks that includes a dark matter candidate is supersymmetry. Dark matter is an unknown type of matter present in the universe, which could be of particle origin. Many supersymmetric models predict the existence of a new stable, invisible particle - the lightest supersymmetric particle (LSP) – which has the right properties to be a dark matter particle. The ATLAS Collaboration has recently reported two new results on searches for an LSP where it exploited the experiment’s full “Run 2” data sample taken at 13 TeV proton-proton collision energy. The analyses looked for the pair production of two heavy supersymmetric particles, each of which decays to observable Standard Model particles and an LSP in the detector.

8 April 2019

The edge of SUSY

The ATLAS experiment has just completed a new search for evidence of supersymmetry (SUSY), a theory that predicts the existence of new “super-partner” particles, with different properties from their Standard Model counterparts. This search looks for SUSY particles decaying to produce two leptons and scrutinises the invariant mass distribution of these leptons, hoping to find a bump.

2 June 2018

Charming SUSY: running out of places to hide

Why is gravity so much weaker than the other forces of nature? This fundamental discrepancy, known as the “hierarchy problem”, has long been a source of puzzlement. Since the discovery of a scalar particle, the Higgs boson, with a mass of 125 GeV near that of the W and Z bosons mediating the weak force, the hierarchy problem is more acute than ever.

7 May 2018

Searching for supersymmetric Higgs bosons on the compressed frontier

The Standard Model has a number of puzzling features. For instance, why does the Higgs boson have a relatively low mass? Could its mass arise from a hidden symmetry that keeps it from being extremely heavy? And what about dark matter? While the Standard Model has some (almost) invisible particles, like neutrinos, those particles can’t account for all of the dark matter observed by cosmological measurements.

18 December 2017

Squeezing sleptons at the LHC

Supersymmetry (SUSY) is an extension of the Standard Model that predicts the existence of “superpartners” with slightly different properties compared to their Standard Model counterparts. Physicists have been searching for signs of SUSY for over forty years, so far without success, which makes us think that SUSY particles — should they exist — are also heavier than particles in the Standard Model. However, in order for SUSY to help mitigate some problems with the Higgs boson sector of the Standard Model, SUSY particles should not be too heavy. And if some SUSY particles are relatively light, then they should be produced copiously at CERN’s Large Hadron Collider (LHC). So for SUSY to remain an attractive theory of nature, it must be hiding in plain sight in LHC data.

15 December 2017

Broken symmetry: searches for supersymmetry at the LHC

A commentary by ATLAS physicists Paul de Jong and George Redlinger on the history, progress and future of the search for supersymmetry.

8 December 2017

ATLAS releases new results in search for weakly-interacting supersymmetric particles

Supersymmetry is an extension to the Standard Model that may explain the origin of dark matter and pave the way to a grand unified theory of nature. For each particle of the Standard Model, supersymmetry introduces an exotic new “super-partner,” which may be produced in proton-proton collisions. Searching for these particles is currently one of the top priorities of the LHC physics program. A discovery would transform our understanding of the building blocks of matter and the fundamental forces, leading to a paradigm shift in physics similar to when Einstein’s relativity superseded classical Newtonian physics in the early 20th century.

18 May 2017

Hunting for the superpartner of the top quark

Supersymmetry (SUSY) is one of the most attractive theories extending the Standard Model of particle physics. SUSY would provide a solution to several of the Standard Model’s unanswered questions, by more than doubling the number of elementary particles, giving each fermion a bosonic partner and vice versa. In many SUSY models the lightest supersymmetric particle (LSP) constitutes dark matter.

17 May 2017

Quest for the lost arc

Nature has surprised physicists many times in history and certainly will do so again. Therefore, physicists have to keep an open mind when searching for phenomena beyond the Standard Model.

21 March 2017

Particle-hunting at the energy frontier

There are many mysteries the Standard Model of particle physics cannot answer. Why is there an imbalance between matter and anti-matter in our Universe? What is the nature of dark matter or dark energy? And many more. The existence of physics beyond the Standard Model can solve some of these fundamental questions. By studying the head-on collisions of protons at a centre-of-mass energy of 13 TeV provided by the LHC, the ATLAS Collaboration is on the hunt for signs of new physics.

21 March 2017

Searching for signs of the “stop”

In new results presented at the Moriond Electroweak conference, the ATLAS Collaboration has sifted through the full available data sample of the LHC’s 13 TeV proton collisions in search of a specific SUSY particle: the heavy partner to the top quark, called the “top squark” or “stop”

21 March 2017

The search for super-particles continues!

Many of the most important unanswered questions in fundamental physics are related to mass. Why do elementary particles, which we have observed and measured at CERN and other laboratories, have the masses they do? And why are they so different, with the mass of the top quark more than three hundred thousand times that of the electron? The presence of dark matter in our universe is inferred because of its mass but, if it is a particle, what is it? While the Standard Model has been a tremendously successful theory in describing the interactions of sub-atomic particles, we must look to even larger masses in search of answers and, potentially, new supersymmetric particles

20 March 2017

Further progress in the quest for SUSY particles

ATLAS physicists have been eagerly searching the collected data for evidence of the production of the supersymmetric top quark (squark). Recent ATLAS results feature five separate searches for this elusive particle.

4 August 2016

Searching for new phenomena in final states with missing momentum and jets

The nature of dark matter remains one of the greatest mysteries in physics. While extraordinary, the Standard Model can not explain dark matter, whose existence is well established by cosmological measurements.

4 August 2016

Wanted: SUSY particle still at large

According to classical electrodynamics, the electromagnetic energy (and mass) of a point-like electron should be infinite. This is of course not the case! The solution of the riddle is antimatter - the ‘vacuum’ around every electron is filled with a cloud of electrons and anti-electrons and the combined energy turns out to be finite.

7 April 2016

Devouring dark matter theories

Most of the matter in the universe is made not of stuff we understand, but of invisible “dark matter” particles. We have yet to observe these mysterious particles on Earth, presumably because they interact so weakly with normal matter. The high energy collisions in the Large Hadron Collider provide our best current hope of making dark matter particles, and thus giving us a better understanding what most of the universe is made of.

24 August 2015

In search of super charm

If all the experimental evidence supports a theory, why should anyone want to dream up additional particles? Yet exactly this situation arose in the late 1960s. At that time, when the complete table of the known hadrons could be explained with just three quarks, theorists were already proposing a fourth, which they whimsically called “charm”.

9 January 2015

Searches for new physics with photons produced at vertices displaced from the collision point

Theories, such as supersymmetry, propose the existence of new types of particles to explain important questions about the universe, such as the nature of dark matter. ATLAS has performed a search for one such type – exotic heavy particles that have lifetimes long enough that they travel partway through the detector before decaying, at what is called a displaced vertex.

22 September 2014

Hunting for the top squark

Completion of the analysis of 2012 data recorded by the ATLAS detector at the LHC’s collision energy of 8 TeV has significantly improved our capability of finding a supersymmetric partner of the top quark – also known as the top squark or the stop.

5 July 2014

Is new physics running out of corners?

Friday was the last occasion for Moriond participants to see new results on specific physics topics since Saturday is reserved for summary talks. The topic was 'Beyond the Standard Model' -- a very large subject, which covers an incredible number of theoretical models, from Supersymmetry to Two-Higgs-Doublet Models, two of the most discussed topics of the day.

24 March 2014

Dark Matters

The winter conference season is well under way, and what better way to fill my first blog post than with a report from one of the premier conferences in particle and astroparticle physics: the Rencontres de Moriond.

24 March 2014
24 March 2014

So where is all the SUSY?

Supersymmetry (SUSY) is one of the most loved, and most hated, theories around that works as an extension of our beloved Standard Model.

4 October 2013

New searches for SUSY

ATLAS today presented new searches for Supersymmetry, a theory that could explain the large amount of dark matter in the universe.

20 July 2013

ATLAS Supersymmetry Searches and More at SUSY 2012 in Beijing

The 20th International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 2012) is taking place in Beijing, China on 13 -18 August 2012. SUSY is the theory which, if confirmed by experiment, will be the high energy extension of the Standard Model (SM). In SUSY, every particle should have a massive "shadow" particle or super-partner. Experimentalists have been looking for years for proof of the existence of these SUSY particles or sparticles.

13 August 2012

Moriond day 2: Inverse time dilation

I work with crazy particles. Dark matter is pretty weird, so are neutrinos seemingly, but what I search for blows it all away. Tuesday was the day of my presentation. The format for these young scientist presentations are 5 minutes and time for a single question afterwards. Trying to present a full picture of any analysis in that short a time is impossible; instead the idea is more like handing out a business card telling the audience what you work on in the hope that some will be interested and contact you informally afterwards.

6 March 2012

Philosophising physics

Last Monday (August 22), within a tight 35-minute allocation, ATLAS’ Henri Bachacou presented the entirety of the results from ‘Beyond the Standard Model’ searches for BOTH the ATLAS and CMS experiments, to the Lepton Photon conference in Mumbai, India. This included results of studies on Supersymmetry, strong gravity, heavy resonances and long-lived particles, and was a staggering amount of information to convey in an extremely limited amount of time. Henri did a great job, firing through slides, and guiding the audience through the most up-to-date results from the wide range of exotic topics. He did have one thing on his side, however… from each search, from each physics topic and from each experiment, the results came back the same: Has the LHC seen anything beyond the standard model yet? Nope.

3 September 2011

Is Nature Supersymmetric?

String Theory predicts a new symmetry, called "supersymmetry", that could shed light on some of today's mysteries of fundamental particles and interactions. In supersymmetry, every particle-type should have a "shadow" particle called a super-partner that (in general) has a much higher mass. The ATLAS Experiment has analyzed the first year of its LHC data and searched for evidence of these super-partners of ordinary matter.

24 May 2011