Jul 25, 2018

Ep 45: Steven Goldfarb - Atlas Experiment (Large Hadron Collider), CERN

Atlas Experiment (Large Hadron Collider)
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Q1: How did you become interested in physics?

A1: Steven Goldfarb’s natural curiosity about the world around him and the influence of great science teachers eventually led him to a career in physics. Goldfarb started out at the University of Michigan in a few different programs, and discovered that he liked math as it connected to nature. During his time as a Physics PhD student at the University of Michigan, Goldfarb was invited to spend time at CERN in Switzerland to help prepare equipment for testing. Steven Goldfarb now works on the Atlas Experiment at CERN.

Q2: What were you first involved in at CERN?

A2: Steven Goldfarb joined CERN as they were building equipment for a new experiment, the Large Electron-Positron (LEP) Collider. This collider was built in a large, circular underground tunnel, which was necessary due to the radiation released as the electrons moved around curves. Carl Anderson’s discovery of antimatter and cosmic rays has influenced physics theories and experiments for decades after his work. Positrons are the antimatter counterparts to the electrons. These particles were collided at extremely high speeds to create photons.

Q3: What is the process of developing a physics theory and performing an experiment?

A3: Steven Goldfarb sees advancements in physics evolve from theories in two different ways. First, scientists measure patterns in nature and theorists try to explain the symmetry of the nature’s patterns and provide predictions. Sometimes these theories are tested with further measurement and sometimes these theories provide directions for exploration. Steven Goldfarb’s group at LEP was responsible for building one specific part of the Collider.

Q4: As a particle gets closer to the speed of light, does the mass increase?

A4: As a particle gets closer to the speed of light, the effective mass increases, which Steven Goldfarb simply describes as energy. This observation is a relativistic effect. The accelerator takes the light particles and gives them energy at high speed so that the fundamental particles interact with each other, either by exchanging a particle or becoming another particle. The particles are accelerated through each other thousands of times, while sensors record the interesting and more complex interactions, but ignore the more common quirks of the interaction.

Q5: How do you plan ahead for future technology available by the time the sensor gets built and implemented in the experiments?

A5: Steven Goldfarb and the physics research community pushes industry to develop technology and make electronics fast enough and small enough to achieve the results needed in sensors. As a PhD student, Goldfarb was involved with the construction of the detector at CERN and took data from LEP during production of Z bosons. New experiments are always under way, even during construction of upcoming experiments, and allow technology to evolve with the testing.

Q6: What do scientists do in between experiments?

A6: Steven Goldfarb and the other team members at CERN are constantly working on building or deconstructing experiments and processing data in between. More precise data comes from repetition of experiments, so there is always lots of data analysis and new methods are always needed for advanced experiments. The unknowns about dark matter and expansion of the universe will push further experiments, as did the unknowns about neutrinos.

Q7: What detectors are used in the physics experiments?

A7: CERN uses its own detectors in collisions, four in total (such as the Atlas detector that Steven Goldberg currently works on), which surround the points in which the beams cross paths. The beam is divided into packets of protons, each which contain 100 billion protons, and beams are crossed 40 million times per second. When two packets cross, there are about 40-50 head-on collisions, but not all collisions interact. The detectors snap pictures when interesting interactions happen, which can be later analyzed. Goldfarb stresses that CERN cannot process all the data independently, and instead depend on institutions all across the world to analyze data and return plots of events back to CERN.

Q8: What are you looking for in the data pulled from the physics experiments?

A8: Steven Goldfarb currently spends a lot of time studying the Higgs boson particle and measuring its properties. His overall goal is to observe something new, with a special interest in dark matter. Goldfarb is less involved in the analysis side of the experiments, but works with many student groups at different times of the year who visit CERN to study. Steven Goldfarb’s role now is more centered around educating others about science and how to make decisions based on data.

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