The members of the CMS group at the University of Maryland were impressed when they learned of Sascha Mehlhase’s LEGO model of the ATLAS detector. They were also jealous, and so a group led by Jeff Temple, Marguerite Tonjes, and Jaime Gomez decided to build a matching LEGO model of CMS. The model has recently been completed, and is the centerpiece of a new display highlighting CMS research at the University of Maryland.

The model is built to a 1:48 scale, with a diameter of 30 cm and total length of nearly 60 cm. The central region of the model contains replicas of the silicon strip tracker, the electromagnetic and hadron calorimeters, CMS solenoid and return yoke, and barrel muon chambers. As with the actual CMS apparatus, the barrel yoke is separated into five rings, with twelve sectors per ring. The LEGO model also includes copies of the endcap calorimeters, muon endcaps, forward hadron calorimeters, and the ZDC.

Approximately 14,000 LEGO pieces were used to construct the model. These pieces were purchased from the LEGO “Pick A Brick” web site as well as numerous secondary market vendors at The model’s total cost of $2300 was funded through the generosity of the University of Maryland Physics Department. Jeff, Marguerite, and Jaime spent roughly 50 hours designing the model, and another 70 hours building it. The bulk of the construction took place over a single weekend, with help from Prof. Sarah Eno, grad student Kevin Pedro, former CMS member Ellie Twedt, and numerous friends and family members. Sarah’s son Fred and his friend Charlie were excited to lend their assistance to the project, though perhaps less excited once they learned that they needed to build sixty copies of the same muon sector.

The construction of the model is detailed on the web page . In addition to the main model, the group also built pixelated versions of the CMS and CERN logos, as well as LEGO “doppelgangers” for each UMD scientist working on CMS. Kevin and Jeff designed a “mini-scale” CMS model to match the 1:200 ATLAS scale model built by Sascha. The mini-scale CMS is made up of 300 pieces, and instructions to build that model are available on the web page. We hope to be able to provide instructions for the full model, as well as a means of easily ordering all the parts for the model, in the future.

Our model currently resides in the main display case of the John Toll Physics building at the University of Maryland. The display details the construction of both the real and LEGO versions of the CMS detector, and a rotating set of posters highlights our students’ recent contributions to CMS. A QR tag (made of LEGOs, naturally) lets passing students access this information directly with their cell phones.

Now that the LEGO CMS model has been constructed, LHCb and ALICE, the ball (er, brick) is in your court!

Submitted by Marguerite Tonjes and Jeff Temple