The summer I played with the building blocks of the universe: Zareen Tahsin at CERN

On her first day at CERN, Zareen Tahsin Anjum felt the universe come closer—not as metaphor, but as matter in motion. Beneath her feet, subatomic particles raced at near-light speed through a 27-kilometre underground ring, while around her, scientists from across the world worked to answer fundamental questions about the nature of the universe.

For a young researcher from the Department of Nuclear Engineering at the University of Dhaka, the experience felt surreal. "It feels like a once-in-a-lifetime experience—something you cannot find anywhere else on Earth," she said.

CERN, the European Organization for Nuclear Research, is the world's largest and most advanced centre for particle physics. Home to the Large Hadron Collider (LHC), the most powerful particle accelerator ever built, it has produced some of the most significant discoveries in modern physics, including the 2012 confirmation of the Higgs boson—a key element of the Standard Model that explains how particles acquire mass.

Each summer, CERN invites a select group of students into this rarefied research environment through its highly competitive Summer Student Programme. More than 10,000 applicants compete annually for around 300 places in the two-month programme. 

In 2025, one of those selected was Zareen Tahsin Anjum, a postgraduate student from Dhaka University. She graduated with first-class first position and the highest CGPA in her undergraduate cohort, and recently received the Dean's Award 2025 from the Faculty of Engineering and Technology.

An early fascination with fundamentals

Zareen's interest in physics began early, rooted in a curiosity about energy, matter, and the laws governing the universe. That curiosity found direction when she enrolled in nuclear engineering at Dhaka University.

The discipline offered her a framework to explore phenomena ranging from subatomic interactions to large-scale energy systems. "The more I learned, the more my interest grew," she said. Far from being a narrow or purely applied field, nuclear engineering exposed her to a broad intellectual landscape connecting physics, mathematics, and technology.

CERN had long occupied a special place in her imagination. It is home to the LHC, the site of the Higgs boson discovery, and the birthplace of the World Wide Web. Yet it also felt distant. Bangladesh is not a CERN member state, and opportunities for direct engagement with its research ecosystem are limited.

That is what made the Summer Student Programme significant. Open to students from all countries, it remains one of the few structured pathways for researchers from non-member states to work at CERN. "As a non-member state, we generally don't have many opportunities," Zareen said. "I applied with the hope of experiencing this remarkable centre of scientific innovation."

Inside ATLAS: where collisions become clues

At CERN, Zareen was assigned to the ATLAS experiment, one of the four major detectors at the LHC and among the largest scientific instruments ever built. ATLAS (A Toroidal LHC Apparatus) is a general-purpose detector designed to record the debris produced when particle beams collide at extreme energies. These collisions, occurring millions of times per second, allow physicists to test existing theories and search for new particles.

ATLAS played a central role in the discovery of the Higgs boson in 2012, alongside the CMS detector. Yet major questions remain, including how the Higgs interacts with itself and how Higgs boson pairs decay—processes that could point to physics beyond the Standard Model.

Zareen's work focused on determining trigger efficiency for a specific decay channel related to di-Higgs production. Triggers are systems that decide which collision events are recorded for analysis. If a detector fails to trigger efficiently, crucial data can be lost.

Her task was to evaluate how effectively ATLAS could identify and record these rare events. Improving trigger efficiency increases the likelihood of detecting processes such as di-Higgs production, which are essential to probing the deeper structure of matter.

The work was technically demanding, but it also carried symbolic significance. The term "boson" traces back to Satyendra Nath Bose, the Bengali physicist whose collaboration with Einstein laid the foundation for Bose–Einstein statistics. Working at CERN, where that legacy continues to shape modern physics, added resonance to her experience.

Collaboration without borders

Beyond experiments and data, CERN offered something equally transformative: a culture of collaboration. Scientists from different countries and disciplines work together, driven by shared curiosity rather than competition.

"People are very welcoming," Zareen said. "There's an enthusiasm for learning that's contagious." In this environment, knowledge is exchanged freely and hierarchies give way to collective problem-solving.

For someone trained in a system with limited exposure to international research networks, the experience was perspective-shifting. She came to see scientific progress as a collective endeavour, shaped by dialogue across cultures and disciplines.

Dreams, constraints, and the road ahead

For many young Bangladeshi researchers, participation in global research hubs remains difficult. Limited funding, weak institutional linkages, and exclusion from major research networks often restrict academic trajectories.

Zareen is keenly aware of these constraints. "At present, direct participation in research at CERN feels unattainable for most Bangladeshi students," she said. Yet she believes visibility matters. Each instance of participation helps challenge the notion that such spaces are out of reach.

She hopes future progress will come through stronger collaborations, curriculum development, and institutional initiatives. At the departmental level, she sees scope for introducing courses in high-energy physics to bridge nuclear engineering with experimental particle physics. The overlap—detector technology, radiation measurement, and accelerator science—is substantial.

Such changes, she believes, would better prepare students for global research environments.

For those who aspire to institutions like CERN, her advice is straightforward: stay curious, understand the work being done, and prepare rigorously. The path is demanding, she acknowledges, but not impossible.

Her own journey reflects that reality. It was not defined by a single leap, but by steady progress shaped by persistence and imagination. Looking back, the distance from a classroom at Dhaka University to one of the world's most advanced research facilities does not feel like an endpoint. As she put it: "One step after another—and more steps to go."