Research Highlights
Cover Article: Instrumental uncertainties in radiative corrections for the MUSE experiment
Dr. Bernauer, an assistant professor in our department, along with collaborators,
have published a paper in the EPJA that has been selected as the cover article, increasing the visibility of this important
work!
A sketch of the MUSE experimental set-up at the Paul Scherrer Institute in Switzerland.
The MUon proton Scattering Experiment (MUSE) based in Switzerland has made significant headway in accurately measuring the size of protons -- positively charged particles at the heart of any atom. The MUSE experiment measures the proton radius through scattering muons -- particles that behave almost like electrons, except that they are almost 200 times heavier!
The particle beam the MUSE experiment uses for its scattering measurements contains a mix of electrons, muons, and pions, a different type of subatomic particle. The incident particles bass through various detectors for timing measurements and to identify which particles are which. They then collide with the target and scatter. The distribution of the scattering particles gives us information about the size of the target particles -- namely, the size of the proton!
Visualizing Quantum Particles at the Sub-nanometer Scale
A recent work, spearheaded by members of our Physics and Astronomy department with
collaborators from Columbia University and UC San Diego, unveiled a new tool that
can image quantum particles. The particles, called Dirac magnetoexcitons (DiMEs),
were seen at infrared frequencies for the first time!
Magneto infrared optics now goes nano. Credit: Michael Dapolito, Xinzhong Chen, Mengkun
Liu
The new imaging tool combines a cryogenic scattering-type scanning near-field optical microscopy (SNOM) with high magnetic fields. The SNOM technique is commonly used to study quantum particles smaller than the diffraction limit of light. However, to fully probe the properties of these particles, researchers needed to cool the microscopes to cryogenic temperatures and operate them under strong magnetic fields.
"Electrons in a magnetic field do strange things that we haven’t seen before, because
the resolution of existing tools that are compatible with magnetic fields hasn’t been
good enough. These results should be the first of many with this monumental new tool."
-- Dmitri Basov, co-author
The paper, published in Nature, may be found here. A highlight article published by Columbia may be read here.
Proton "Spin Crisis" Solved at BNL's RHIC
Former department graduate student Zhongling Ji, advised by Dr. Deshpande, was fundamental
in this resolution. Measurements at the Relativistic Heavy Ion Collider (RHIC) at
Brookhaven National Laboratory (BNL) carried out by Dr. Ji were the key to solving
this "crisis."
Zhongling Ji (left) and Abhay Deshpande (right) at Dr. Ji's thesis defense.
The problem of how much a proton's quarks contribute to its spin has been around since
1987. At that time, experiments at CERN found that the spin of the proton's internal quarks couldn't account for the full
spin of the proton itself -- igniting the so-called "spin crisis."
To find the missing spin, researchers began looking at the photons produced by interactions between quarks and gluons in proton collisions.
"...one of the major obstacles in this analysis is effectively removing the considerable
background of photons that come from the decay of other particles produced in RHIC’s
collisions,"
-- Zhongling Ji
The paper, published in PRL, may be found here. A press release from BNL about the discovery may be read here, and one from Stony Brook University may be read here.
Research Groups and Connected Research Centers