1 General FAQ's for BL4S

Are there any costs involved in taking part in the competition?

There are no fees or anything similar, taking part is completely free. For the winning teams, BL4S will cover the full costs of the winners' participation to the competition, including travel, accommodation and three meals per day.

Where do I find the rules and conditions of the competition?

The description of the competition, the rules, the timeline, and the prizes is available in the invitation letter.

Who is eligible?

High-school students from all over the world aged 16 and older on the first day of their visit at the laboratory (usually September or October of the year of the competition) are eligible. Younger students may be part of a team, but they cannot be invited on site in case of winning the competition. Participants must be in high/secondary school when submitting the proposal.

Is it possible for students under the age of 16 to participate in the competition?

Yes, but... For the participation to the competition there is no age limit. Students under the age of 16 can be members of a team and will receive certificates. The only limitation is that if team wins, only students that are at least 16 years old in September (i.e. by the first day of the experimental time) can be invited.

Who can be a team coach?

The team coach needs to be an adult. Very often this person is a teacher at the students’ school, but this is not mandatory. The coach can be a mentor from another institution or even a parent or student at university. Please keep in mind that, in case of winning the competition, the team coach will need to obtain the consent of the parents of all minors in the team, and probably also of the school(s) the team members are enrolled in.

What is the prize?

The participants in BL4S 2023 have the chance to win a trip to CERN or DESY  (free of expenses) and conduct a student-led particle physics experiment at a world-leading accelerator centre. Before coming to CERN or DESY the winning teams will have the opportunity to work together with scientists on their ideas on how to use the beam line and plan out a particle physics experiment. A selection of up to 30 teams will receive special prizes to recognize the quality of their work. One team will win an award for the best video, and seven teams will receive a telescope offered by the "Stars shine for everyone" project. More information are available here. All the members of the teams that submit a proposal will receive a participation certificate. Please note that all prizes on this website are indicative. CERN reserves the right to modify or exchange the prize should it so require. CERN also does not bear any responsibilities for lost prizes during the course of shipping.

Where will it happen?

In 2023 BL4S will take place at the fixed-target beam facilities of CERN and DESY.


When will it happen?

The registration opens the year before the competition. in 2023 proposals can be submitted between January 2023 and the deadline: midnight CET on 12 April. The winning teams are notified in June. The winning teams will be invited to the research laboratory at the end of September.

Why are CERN and DESY doing this?

BL4S is an ideal opportunity to expose today’s cutting-edge physics to tomorrow’s scientists. The competition began in 2014 to celebrate CERN’s 60th Anniversary and had already nine successful runs.

How do we enter?

Have a look at how to apply  and at our useful documents and follow the instructions you’ll find there. Remember, you must submit your written proposal by midnight CET on 15 April 2022.

Who can be part of a team?

Students can be from a single school, from multiple classes, from different schools or even countries. Each team has to have at least 5 members and has to be represented by an adult coach.

Can one person be the coach of multiple teams?

Yes, a coach can represent more than one team.

Can the same students form multiple teams, and can these teams participate in BL4S as different teams?

Yes, the same student(s) can technically be part of multiple teams, but we suggest you to focus on one proposal rather than working on multiple proposals at the same time.

Can multiple research proposals be given in one research proposal?

No, a proposal should include only one idea.

Can a team submit multiple research proposals?

Technically the same participants can send different proposals (using different team names), but we advise against it. Preparing a research proposal is complicated and we recommend that you focus on one idea and develop it as well as possible.

How many people per team?

The minimum is 5. For the winners a maximum of nine students and two coaches will be invited. Data transmission and web link-ups will allow additional students to participate and analyse data remotely.

Can we use the logos in our written proposal and video?

The CERN logo is legally protected and any use by third parties is forbidden. However, the BL4S logo could be used if desired.

How do we submit videos?

Publish your video on a platform such as Vimeo or YouTube and submit your full proposal via the submission form including the link to your video. Note that the video is not mandatory, but encouraged.

In what languages can we submit our proposals?

All submissions must be made in English. Please note that we cannot consider submissions made in other languages. 

What kind of experiments can we do?

It is up to you and your team to decide how you want to use the beam line facility. The beamline will be fully equipped; with a pre-determined set of detectors that you can choose from to design your own experiment. Have a look at the beam and detector document in our useful documents to learn more about the beamline facilities and its possibilities. In addition to the equipment provided, you may also bring your own detectors (maybe you can even build one yourself as previous winners have done).

How are the proposals judged?

We will evaluate the proposals on these criteria:

  • The feasibility of the experiment
  • Your ability to follow the scientific method
  • The motivation of the experiment and why you want to come to CERN or DESY
  • The creativity of the experiment

We are not expecting fully developed experimental proposals. Your motivation and creativity are very important to us.

We don’t know much about particle physics. Is this a problem?

All students enthusiastic about learning are encouraged to participate. We recognize that most students have little to no experience with particle physics when they begin the competition, but will learn as they progress through the competition. Volunteers are available for providing help to the team. In addition CERN’s website has several resources for introducing particle physics.

Who will evaluate our experiment proposal?

A group of physicists and engineers will pre-select the proposals. Most of the people taking part in the selection are members of the SPSC, the committee that validates all proposals for experiments at the CERN’s Super Proton Synchrotron (SPS) and Proton Synchrotron (PS) accelerators.


What is the CERN PS accelerator?

The Proton Synchrotron (PS) is a particle accelerator, in operation since 1959, and probably the most versatile of CERN. It is part of the CERN accelerator complex and it pre-accelerates particles for the large LHC ring, it delivers particles to the Anti-Matter Factory, and it also provides beams to a number of experimental areas. One of them, called “T9”, and it is the place where the BL4S experiments are going to take place.

Which kind of particles does the PS provide? What is their energy?

The PS itself accelerates protons (as its name suggests) up to an energy of 26 GeV. By directing these protons at a target, the debris resulting from this collision can be separated into beams of different particles, called "secondary beams", available for the experiments. The beam contains electrons, protons, pions, kaons and muons as well as their anti-particles. The energies of these secondary particles vary from 200 MeV to 15 GeV.

Can we get an antimatter beam?

Yes. The secondary beam of the PS contains for example anti-electrons and anti-protons as described in our beam and detectors document

Can atoms or molecules be accelerated at the PS?

No. The PS can accelerate only protons. You can, however, shoot these particles at a target of your choice and study how they interact with the atoms or molecules in that target.

What are the professional physicists at CERN and DESY doing with the beam?

Most of the time we use the beam to test prototypes of new detectors before their installation in the large experiments. We are evaluating the performance of new detector designs and test if they are sufficiently resistant to radiation. One of the beamlines of the PS is reserved to the CLOUD experiment that studies how galactic cosmic rays can lead to cloud formation in the upper atmosphere.

Can we bring our own equipment/detectors to the beam?

In principle, this is possible, but we have to evaluate it individually, in particular if the material has potential hazards (e.g. fire, toxicity, etc..). Please contact us during your early planning phase if you think of bringing your equipment to CERN or DESY.

Do we have to prepare in advance the data acquisition and analysis softwares?

No, the winning teams will receive full support to set-up their data acquisition system and to start their data analysis during the experiment preparation time, and during their stay at CERN or DESY.

Is it possible to use a virus sample or bacteria in the experiment? What about other biological material?

Unfortunately is not possible to irradiate any kind of samples that contain living organisms including seeds, roots or cells. Inactive organic material such as wood or leather can be exposed to the beam.

Can we have a dipole magnet in the experimental area?

In previous editions of BL4S, dipole electro-magnets were used to deflect charged particles. This option, unfortunately, is no longer possible.

Can we find a Higgs boson? What about neutrinos?

No. Higgs bosons can only be observed in the Large Hadron Collider (LHC) at CERN, the largest accelerator in the world. The beams provided by the PS does not have enough energy for the production of Higgs particles. The beam of the PS does contain neutrinos (for example produced by the decay of pions) but detecting them is extremely difficult and beyond the reach of a BL4S experiment.

I still have some technical questions. Who can I ask for help?

Please feel free to send us your questions to bl4s.team@cern.ch. For obtaining quickly the most useful answer, you should include some short information about your ideas/your proposal and how our answers would influence your experiment.