Short intro

I am a research professor (ZAP-BOF hoofddocent) at the Vrije Universiteit Brussel (VUB), in Belgium.
I work at the Interuniversity Institute for High Energies (IIHE), a joint institute between the VUB and ULB universities.

My field of research is experimental high-energy physics. I am since long a member of the CMS experiment at the LHC collider at the CERN laboratory near Geneva, Switzerland. Since a few years I also joined the milliQan experiment.
With my research, I've built expertise in supersymmetry, dark matter and exotic long-lived particles. Through numerous searches for new physics, I explore nature at its smallest scales, thrilled by the possibility to find something new, something unexpected, something that teaches us more about the universe we live in.

Since the start of the LHC, I have also developed a passion for detector instrumentation and operation. The detectors we use are our doorway to in-depth understanding of the data, our foundation for complex but robust precision measurements and searches for unexpected new physics. I'm a long-time contributor to the impressive current CMS silicon strip tracker, and the upcoming next-generation silicon outer tracker. A significant part of the latter will be constructed in the IIHE labs.

Via the menu on the right, you may find more info about my research, my team, my teaching, my outreach, and myself.

Contact information

Postal address:	Vrije Universiteit Brussel Dienst ELEM Pleinlaan 2 1050 Brussel Belgium
Office:	G.0.13
Phone:	(+32) 2 629 32 18
E-mail:	steven.lowette@cern.ch steven.lowette@vub.be
Mastodon:	@StevenLowette@mstdn.social
Twitter:	@StevenLowette
Also on Skype and Strava.

Thesis topics

If you're a student looking for a topic for a bachelor or master thesis at the VUB, take a look at this 2-slide presentation from the 2023 student welcome moment.

The topics presented are either in data analysis (the CMS experiment, next year also milliQan) or in instrumentation (both CMS tracker upgrade and milliQan). To get a better idea of what that can mean, check out current and past examples of subjects, or get in contact.

Teaching

I teach several courses at VUB in the bachelor Fysica en Sterrekunde and in the English-taught master Physics and Astrophysics.

Currently I'm responsible for these courses:

• Seminarie Actuele Wetenschappen en Samenleving (BA1, 3 ECTS)
  This compulsory course in the first year of the bachelor education consists of 3 parts: 1/ mathematics drill exercises in the first weeks, to bring all students to the necessary level; 2/ excursions and colloquia or seminars to bring the students in contact with physics and its position in society; and 3/ student presentations, where the students present a physics topic of choice to their peers.
  More details


• Experimental Techniques in Particle Physics (MA1/2, 6 ECTS)
  This is a master's course at the VUB (and UA and UGent) jointly with Prof. Albert De Roeck at UAntwerpen.
  It is an advanced course on general techniques used in particle physics to conduct experiments. This includes a part on the physics of detection techniques and a part on reconstruction and analysis aspects of particle collisions.
  To reduce the need to travel for non-VUB students, my part of the lectures is bundled in 3 times 4-hour lectures. All course material is in English.
  More details


• Extensions of the Standard Model (MA2, 6 ECTS)
  This is a master-level course at the VUB (and UGent), jointly with ULB. In 2022-2023 this was for the theoretical part together with Prof. Michael Tytgat (ULB), in 2023-2024 this will be with Prof. Thomas Hambye.
  The course introduces diverse aspects of physics models beyond the Standard Model of particle physics. The course is rather for the second master year, after having followed a course on the Standard Model of particle physics including electroweak theory (with field theory).
  The lectures run every week on Wednesday afternoon. My part of the lectures is bundled in 3 times 4-hour lectures. All course material is in English.
  More details


• Simulation of Physics Phenomena and Detectors in Modern Physics (MA1/2, 6 ECTS)
  This master-level course approaches simulation problems related to detection via hands-on exercises and a self-proposed larger project. Having followed the course on Experimental Techniques in Particle Physics mentioned above, is recommended, but not a must. This is a very interactive course with continuous participation with flipped-classroam style.
  More details


• Mobility A & B (MA1/2, 6+6 ECTS, with Prof. Mariotti)
  This is not a course as such, but rather the planning and evaluation of the student mobility in the master years. As part of our master's programme, students have to take up 10 ECTS in mobility, which in practise typically amounts to 12 ECTS. This can happen through an internship (encouraged), which we evaluate with a written report and presentation. Or it can be a course taken up at another university, for which the evaluation is taken from that course.
  More details

Research

I am a professor and researcher at the Vrije Universiteit Brussel (VUB), in the joint Inter-university Institute for High Energies (IIHE). My field of research is experimental particle physics, where I'm working on the CMS experiment and the milliQan experiment at the LHC collider at the CERN laboratory near Geneva, Switzerland.

CMS data analysis

I built my research career within the CMS experiment. That umbrella hosts a very rich diversity in research subjects I was active in over the years. On the data analysis side, I have evolved from top and Higgs physics and b-quark tagging in my PhD thesis, to a career concentrated on the search for new particles beyond our current theories: supersymmetry, dark matter, and long-lived exotics.

Currently, I'm working with my team on various searches:

• We're investigating whether particles with unexpected electric charge could possibly be produced and detected in the CMS detector.
• Furthermore, we're searching for hypothetical exotic decays of the Higgs boson, where a new light scalar particle "s" with mass below 2GeV could give rise to exclusive decays with kaons or pions (H → ss → μ⁺μ^- K⁺K^-/π⁺π^-).
• Finally, I'm working on a search for a hypothetical exotic form of dark matter, dubbed sexaquark, a bound state composed of six quarks of mass 2 GeV or just below. Such a discovery would be very unexpected but groundbreaking for the whole field. The image on the right shows how such a particle could show up in our detector (transverse view).

My leadership roles in and beyond CMS over the past years:

• 2020-2022: I was convener of the overall CMS Exotica search group, leading for 2 years about 20% of the CMS physics program.
• 2017-2019: convener of the Exotica long-lived particles analysis group, coordinating a variety of searches with long-lived particle signatures.
• 2016-2017: CMS delegate to the overarching CERN Dark Matter Working Group.
• 2016: convener of the Exotica MET+X analysis group, coordinating a variety of searches for dark matter.
• 2015: Co-organizer of the LHC Dark Matter Forum. that laid the groundwork for the searches for dark matter at the LHC in LHC Run-2 (2015-2018).
• 2014-2015: convener of the Exotica Monte Carlo & Interpretation group, providing a knowledge base of new-physics models to support new-physics simulation.

My recent relevant publications from CMS data analysis:

• CMS Collaboration, "Search for strongly interacting massive particles generating trackless jets in proton-proton collisions at sqrt(s) = 13 TeV", Eur.Phys.J. C 82 (2022) 3, 213, doi:10.1140/epjc/s10052-022-10095-5.
• CMS Collaboration, "Search for long-lived heavy neutral leptons with displaced vertices in proton-proton collisions at sqrt(s) =13 TeV", JHEP 07 (2022) 081, doi:10.1007/JHEP07(2022)081.
• CMS Collaboration, "Search for a Narrow Resonance Lighter than 200 GeV Decaying to a Pair of Muons in Proton-Proton Collisions at sqrt(s) = 13 TeV", Phys.Rev.Lett. 124 (2020) 13, 131802, doi:10.1103/PhysRevLett.124.131802.
• D. Abercrombie, et al., "Dark Matter benchmark models for early LHC Run-2 Searches: Report of the ATLAS/CMS Dark Matter Forum", Phys.Dark Univ. 27 (2020) 100371, doi:10.1016/j.dark.2019.100371.
• CMS Collaboration, "Search for invisible decays of a Higgs boson produced through vector boson fusion in proton-proton collisions at sqrt(s) = 13 TeV", Phys.Lett.B 793 (2019) 520, doi:10.1016/j.physletb.2019.04.025.
• CMS Collaboration, "Search for top squarks and dark matter particles in opposite-charge dilepton final states at sqrt(s) = 13 TeV", Phys.Rev.D 97 (2018) 3, 032009, doi:10.1103/PhysRevD.97.032009.
• CMS Collaboration, "Search for dark matter produced with an energetic jet or a hadronically decaying W or Z boson at sqrt(s) = 13 TeV", JHEP 07 (2017) 014, doi:10.1007/JHEP07(2017)014.

CMS tracker detector and instrumentation

I have a long-standing involvement in the CMS tracker, from instrumentation over detector operations, to data performance, which I have often linked to my data analysis topics. During the LHC startup, I served as a detector expert at the CMS site before and during the startup of the LHC. Once in Brussels, I supported many students to take up detector operation roles for periods of time, as well as offline tasks in data quality monitoring and calibrations. From 2015 onwards, I also started first activities in Brussels towards the CMS tracker upgrade, a very ambitious project where we engaged as well in data acquisition and electronics as towards eventual construction of one of the CMS endcaps by all Belgian teams.

Since then, we achieved a multitude of milestones towards this biggest ever detector construction challenge in Belgium. We now routinely assemble fully functional detector modules, integrating all hyper-sensitive pieces of detector, electronics, mechanics, etc. One of my students also received a CMS Detector Award in 2018 for his outstanding contributions in the area of the data acquisition development and testing of electronics.

In the image, you can see a picture of a prototype tracker module assembled in Brussels. It is connected to high- and low-voltage power, and optical readout. Such modules are now routinely used in beam tests at other labs, but also by our own students for a various calibration studies.

Some recent publications from the CMS tracker side:

• W. Adam, et al. [CMS Tracker Group], "Beam test performance of prototype silicon detectors for the Outer Tracker for the Phase-2 Upgrade of CMS", JINST 15 (2020) no.03, P03014, doi:10.1088/1748-0221/15/03/P03014.
• K. Klein (ed.) et al., "The Phase-2 Upgrade of the CMS Tracker", CMS Technical Design Report CERN-LHCC-2017-009, CMS-TDR-014, doi:10.17181/CERN.QZ28.FLHW.

milliQan

The milliQan experiment is a small-scale array of bar-shaped scintillators read out by photo-multipliers, located in a small tunnel above the CMS experiment. Its goal is to search for particles of electric charge well below the electron charge e, being produced in the CMS interaction region and penetrating the many meters of rock that shield the detector from the large backgrounds that are present in and around CMS.

Early 2019, I joined the milliQan experiment, expanding my search interests in long-lived particles beyond CMS. At that time, a prototype detector (see picture) had taken data, published since, and plans started to be made towards construction of a more complete detector. Since 2021, a postdoc joined me partly on milliQan, and he has since taken part in the assembly at CERN of the detector that is now near completion. milliQan is now ready to start uninterrupted data taking during the LHC operations in 2023 and beyond, in search for signs of elusive low-charge particles.

Relevant publications so far:

• milliQan Collaboration, "Sensitivity to millicharged particles in future proton-proton collisions at the LHC with the milliQan detector", Phys.Rev.D 104 (2021) 3, 032002, doi:10.1103/PhysRevD.104.032002.
• A. Ball, et al., "Search for millicharged particles in proton-proton collisions at sqrt(s) = 13 TeV", Phys.Rev.D 102 (2020) 3, 032002, doi:10.1103/PhysRevD.102.032002.

Phenomenology work

At times, I also opportunistically work on projects that have a more phenomenological connection, outside of the direct experimental realm. The topics are diverse, as are the author teams. Most recently, I wrote a pedagogical review article on the subject of long-lived particle searches at the LHC.

My most relevant publications of phenomenological nature:

• S. Knapen and S. Lowette, "A guide to hunting long-lived particles at the LHC", Submitted on invitation to Annu.Rev.Nucl.Part.Sci., arXiv:2212.03883 [hep-ph].
• D. Abercrombie, et al., "Dark Matter benchmark models for early LHC Run-2 Searches: Report of the ATLAS/CMS Dark Matter Forum", Phys.Dark Univ. 27 (2020) 100371, doi:10.1016/j.dark.2019.100371.
• L. Calibbi, L. Lopez-Honorez, S. Lowette, A. Mariotti, "Singlet-Doublet Dark Matter Freeze-in: LHC displaced signatures versus cosmology", JHEP 09 (2018) 037, doi:10.1007/JHEP09(2018)037.
• N. Daci, I. De Bruyn, S. Lowette, M.H.G. Tytgat and B. Zaldivar, "Simplified SIMPs and the LHC", JHEP 11 (2015) 108, doi:10.1007/JHEP11(2015)108.

Current team

Postdocs

since 2021	David Vannerom	FWO postdoc on CMS and milliQan; former convener of the CMS JetMET POG MET group and expert in anomalous ionization signatures.
since 2022	Martin Delcourt	FWO postdoc on the CMS tracker upgrade, in particular regarding joing CMS-MUonE beam tests; current convener of the CMS Strip Tracker Calibration and Local Reconstruction group.
since 2022	Senne Van Putte	FWO IRI-supported postdoc on the CMS tracker upgrade.

PhD students

since 2020	Soumya Dansana (jointly with ULB)	PhD student on CMS with focus on displaced exotic Higgs decays. Joint PhD with ULB (w. Prof. Clerbaux)
since 2021	Wren Vetens	PhD student at UWisconsin-Madison - supervision of search for sexaquarks with CMS data.
since 2023	Jas Bierkens	PhD student on CMS with focus on rare Higgs decays to final states with charmed mesons.

Master students

2023-2024

Fien Dewit

Master student developing scintillator instrumentation for tests of RPC muon chambers. (w. Prof. Dobur and Dr. Skovpen at UGent)

Bachelor students

Past team members

Postdocs

2020-2022	Alexander Morton
2018-2020	Simranjit Singh Chhibra
2016-2018	Giannis Flouris
2013-2016	Nadir Daci CMS Achievement Award 2016

PhD students

since 2018	A.R. Sahasransu	Thesis: Triggering and Data Scouting on Compressed Dark Matter Models at the CMS Experiment
2015-2020	Jarne De Clercq	Thesis: The upgraded outer tracker for the CMS detector at the high-luminosity LHC, and search for composite standard model dark matter with CMS at the LHC CMS Detector Award 2018 and Solvay Award 2020
2015-2019	David Vannerom (jointly with ULB)	Thesis: Search for new physics in the dark sector with the CMS detector
2013-2018	Isabelle De Bruyn	Thesis: Search for dark matter in the monojet and trackless jets final states with the CMS Detector at the LHC CMS Award 2016

Master students

2022-2023	Brent Danau	Thesis: The CMS tracker as an advanced lever to boost the search for sexaquarks
2020-2021	Caroline Bossuyt (UAntwerpen)	Thesis: A search for pair production of new light bosons through Higgs boson decay using muons and hadrons
2019-2020	Yens Elskens	Thesis: Background measurements for the milliQan experiment
2017-2018	Florian Partous	Thesis: The Standard Model strikes back: Searching for sexaquark dark matter at the LHC
2017-2018	Louis Dehennin	Thesis: Firmware Development And Characterization Of CMS Phase II Outer Tracker Prototype Modules

Bachelor students

2022-2023	Ono Feyens	Thesis: Noise investigation on 2S modules for the CMS silicon outer tracker upgrade in preparation for HL-LHC
2022-2023	Ruben Dillemans	Thesis: PMT studies with milliQan detectors
2021-2022	Alwia Badridin	Thesis: Noise measurement: CMS silicon strip detectyor phase-2 upgrade

Public outreach

I love the scientific journey and discovering how nature functions. And I really enjoy sharing this passion also to a broader community.

Do not hesitate to contact me in case you have some event where you would like to hear about particle physics.

Below is a list of my public engagement activities (mostly in Dutch).

• 2013-now: over 20 activities with high-school students. Ik kan ook naar jouw school komen: contacteer me gerust indien geinteresseerd!
• 2023: Lezing volkssterrenwacht Mira: Het Standaard Model in Vraag?
• 2022: VUB article at the occasion of 30 years since the space journey of Dirk Frimout
• 2020: Interview met volksterrenwacht Mira naar aanleiding van hun 50-jarig bestaan
• 2019: Lezing Volkssterrenwacht Armand Pien: De zoektocht naar donkere materie
• 2016: Science Bar Brussels, thema Donkere Materie (met Lieven Scheire)
• 2015: Bright Club Brussels, stand-up comedy, theme Dark Matter
• 2015: Lezing volkssterrenwacht Mira: Op zoek naar nieuwe deeltjes met de LHC deeltjesversneller
• 2014: Wetenschapscafe Turnhout: De bouwstenen van het heelal

Short bio sketch

A very concise version of my career path:

• 2019 onwards: Associate Professor ("hoofddocent") at the Vrije Universiteit Brussel.
• 2013 - 2018: Assistant Professor ("docent") at the Vrije Universiteit Brussel.
• 2007 - 2013: Post-doctoral researcher at the University of California, Santa Barbara, in the group of Joseph Incandela.
• 2001-2006: PhD in experimental particle physics, at the Vrije Universiteit Brussel. My PhD thesis can be found here. This thesis was awarded the CMS Thesis Award 2007.
• 1999-2003: Teacher's education for physics (for high-school level teaching in Belgium).
• 1997-2001: Bachelor and Master in physics, at the Vrije Universiteit Brussel. My Masters dissertation was conducted in the field of Statistical Physics.

Here's a list of some other academic activities:
I'm a regular speaker at conferences, workshops, and seminars on my research. I've also been a reviewer for the JHEP, EPJC, PLB, and IJMPA journals, as well for a variety of grant proposals. I've served on a multitude of Belgian and international thesis juries. Within VUB, I am or have been member of various committees, most notably the central research council (2019-2021) and the president/secretary of the examination committee VUB Bachelor/Master in physics and astronomy (2019-2021).