UConn Physics graduate student Mohammed (Mo) Akhshik works on data gathered using the Hubble Space Telescope (HST) and has led to exciting discoveries, some while he served as the science Principle Investigator of the REQUIEM HST program from which he is co-author on two publications, one in Natureand one in Nature Astronomy. Akhshik is also a recipient of a national fellowship as a NASA FINESST Future Investigator.
Akhshik gleans new information about very distant galaxies using a phenomenon called gravitational lensing. Due to the forces of gravity, light from distant galaxies is focused to appear brighter, and the images appear in different parts of the sky at different times, explains Akhshik. The researchers were also able to detect new details of distant galaxies through observations from different telescopes, which Akhshik says is almost like layering different filters on the same image.
At the center of galaxies, like our own Milky Way, lie massive black holes surrounded by spinning gas. Some shine brightly, with a continuous supply of fuel, while others go dormant for millions of years, only to reawaken with a serendipitous influx of gas. It remains largely a mystery how gas flows across the universe to feed these massive black holes. UConn Assistant Professor of Physics Daniel Anglés-Alcázar, lead author on a paper published in The Astrophysical Journal, addresses some of the questions surrounding these massive and enigmatic features of the universe by using new, high-powered simulations.
Prof. Emeritus Winthrop Smith and former student Prof. Douglas Goodman (Quinnipiac University) Edit Special Issue of Open Access Journal Atoms, on Low Energy Interactions between Ions and Ultracold Atoms
The Special Issue of the online journal Atoms is a collection of current peer-reviewed articles by experts in the field of ultracold collisions and reactions involving ions and atoms co-trapped by electromagnetic fields in a common volume (a hybrid ion-neutral trap). Prof. Goodman, a recent UConn Ph.D. student of Prof. Smith (2015) who worked with hybrid traps for his dissertation, is now on the faculty of Quinnipiac University in Hamden, CT.
Prof. Smith’s research, on which he supervised four doctoral dissertations over the last few years, centers around the study of low-energy ion-neutral collisions. At long range, universal types of charge-induced polarization effects produce very large elastic, inelastic, reactive, and charge-transfer cross-sections leading to a high interaction probability between ions and neutral atoms at low temperature. The Special Issue articles highlight recent experimental and simulation work in this field and discuss the outlook for future developments.
Two of the manuscripts in this Special Issue explore recent advances in hybrid trap technology. The paper by Prof. Karpa explains the use of bichromatic optical dipole traps, which can be used instead of the previously developed hybrid rf ion trap and magneto-optic trap. This remarkable new technique avoids the use of rf fields and associated micromotion heating limitations and allows access to the long-sought quantum-dominated regime of interaction.
Karpa, L. Interactions of Ions and Ultracold Neutral Atom Ensembles inComposite Optical Dipole Traps: Developments and Perspectives. Atoms2021, 9(3), 39; https://doi.org/10.3390/atoms9030039The manuscript included by Prof. Denschlag’s team, early practitioners of hybrid-trap ion-neutral studies, introduces a novel type of low-energy reaction. Denschlag’s group discusses the interaction between an atomic ion and an atom with a valence electron in a highly excited Rydberg state that reacts to yield a long-range atom-ion Rydberg molecule, with binding lengths up to the micrometer scale.Deiß, M.; Haze, S.; Hecker Denschlag, J. Long-Range Atom–Ion RydbergMolecule: A Novel Molecular Binding Mechanism. Atoms 2021, 9(2), 34;https://doi.org/10.3390/atoms9020034 https://www.mdpi.com/2218-2004/9/2/34
The remaining two manuscripts in this Special Issue address important phenomenology of rf Paul traps as they are used in ion-neutral interaction experiments. The paper by Prof. Blumel analyzes the properties of ion clouds loaded from a magneto-optical trap in a hybrid ion-neutral system. He develops theoretical predictions for optimal loading conditions for hybrid-trap experiments, which are supported by numerical simulations. Additionally, he predicts the existence of a new type of ion heating mechanism caused by the increase in Coulomb energy associated with each newly loaded ion within the existing ion-cloud volume.
Blümel, R. Loading a Paul Trap: Densities, Capacities, and Scaling inthe Saturation Regime. Atoms 2021, 9(1), 11; https://doi.org/10.3390/atoms9010011https://www.mdpi.com/2218-2004/9/1/11
Last, the manuscript by Prof. Rangwala’s group, numerically and analytically explores the benefits of using linear multipole rf traps for studying low-energy ion-neutral collisions, as opposed to the conventional quadrupole ion-trap configuration. Using new analyses of the heating effects, Rangwala’s group shows that the higher-order multipolar trap configurations reduce unwanted heating in the ion-neutral system. In doing so, they develop a methodology for comparing and optimizing hybrid trap designs.
Niranjan, M.; Prakash, A.; Rangwala, S. Analysis of Multipolar Linear
Paul Traps for Ion–Atom Ultracold Collision Experiments. Atoms 2021,
The Physics Department welcomes our newest faculty member, Dr. Anh-Thu Le, although he prefers to be called simply AT. AT worked for many years at the well-known James R. Macdonald Laboratory, rising to the rank of Research Professor. He worked alongside a world-known theorist, Dr. Chii-Dong Lin. Dr. Le went on to become an Assistant Professor at Missouri University of Science and Technology before coming to UConn. Dr. Le is well-versed in current theoretical methods for exploring the interaction of ultrafast lasers with atoms and molecules. He has a strong overlap with the ultrafast AMO experimental programs at UConn and has collaborated with high-profile experimental groups.
Dr. Le has a thoroughly international and diverse background, having grown up in the Vietnamese countryside. His research career has taken him from Vietnam to the Republic of Belarus, Germany, Canada, and ultimately the US. This has left him with a lasting commitment to serving diverse populations, both in the classroom and in his research.
The UConn group on the floor of Hall A during the SBS installation. From left to right: Postdoctoral Research Associate Dr. Eric Fuchey, Professor Andrew Puckett, and Graduate Research Assistants Provakar Datta and Sebastian Seeds. Click the image for a slideshow of additional installation photos and for more details about the experiment.
Professor Andrew Puckett’s research group is currently leading, as part of a collaboration of approximately 100 scientists from approximately 30 US and international institutions, the installation in Jefferson Lab’s Experimental Hall A of the first of a series of planned experiments known as the Super BigBite Spectrometer (SBS) Program, with beam to Hall A tentatively scheduled to begin in early September of 2021. Jefferson Lab, located in Newport News, Virginia, is a national user facility operated by the US Department of Energy, and is the world’s premiere laboratory for imaging the subatomic (and subnuclear) quark-gluon structure of protons, neutrons, and nuclei using its continuous, polarized electron beam. In addition to Professor Puckett, the UConn researchers involved in this effort are Postdoctoral Research Associate Eric Fuchey, and Graduate Research Assistants Provakar Datta and Sebastian Seeds. The first set of experiments in the SBS program, slated to run during Fall 2021, is focused on the measurement of neutron electromagnetic form factors at very large values of the momentum transfer Q2, which essentially probe the spatial distributions of electric charge and magnetism inside the neutron at very small distance scales of order 0.05-0.1 fm (1 fm = one femtometer = 10-15 m = 0.000 000 000 000 001 m), approximately 10-20 times smaller than the size of the proton and approximately 1 million times smaller than the size of a typical atom.
Electrons from Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF), with energies of up to 10 GeV (=10 billion electron-volts), will scatter elastically from protons and neutrons in a liquid deuterium target in Hall A. Scattered electrons will be detected in the BigBite Spectrometer, located on the left side of the beam, while the high-energy protons and neutrons recoiling from the “hard” collisions with the beam electrons will be detected in the SBS by the newly constructed Hadron Calorimeter (HCAL), located on the right side of the beam. The SBS dipole magnet will provide a small vertical deflection of the scattered protons, which allows HCAL to distinguish them from scattered neutrons, which are undeflected by the magnetic field, but produce otherwise identical signals in HCAL.
The first group of SBS experiments, collectively known as the “GMN run group”, will answer several important questions about the “femtoscopic” structure of the neutron, including:
What is the behavior of the neutron’s magnetic form factor at large momentum transfers? The SBS experiment will dramatically expand the Q2 reach of neutron magnetic form factor data compared to all previously existing measurements, from approximately 4 –> 14 (GeV/c)2. See original experiment proposal here.
How is the charge and magnetism of the proton shared among its “up” and “down” quark constituents as a function of Q2? The proton magnetic form factor has been measured over a much wider range of Q2 than the neutron, and combined proton and neutron measurements can be used to disentangle the contributions of “up” and “down” quarks (and diquark correlations) to the proton’s structure, under the assumption of charge symmetry of the strong interactions (see, e.g., https://inspirehep.net/literature/1812076)
How important and/or significant is the contribution of two-photon-exchange to elastic electron-neutron scattering? The first SBS experiment group will perform measurements of the electric/magnetic form factor ratio for the neutron using two different techniques known as “Rosenbluth Separation” and “Polarization Transfer”, at a Q2 where these two techniques have shown significant disagreement for the proton. Both measurements will be the first of their kind for the neutron at such large Q2 values (see, e.g., Polarization Transfer Proposal and Rosenbluth Separation Proposal)
The GMN run group will start in early September and run through the fall of 2021. The broader SBS program will continue in Hall A through at least 2023, and will drastically improve our understanding of the femtoscopic quark-gluon structure of protons, neutrons, and atomic nuclei. Professor Puckett’s research in the SBS and Hall A Collaborations is supported by the US Department of Energy, Office of Science, Office of Nuclear Physics. Stay tuned!
Physics major Nicole Khusid, a rising senior at UConn, was featured in a UConn Today article about her research. Nicole has been working on gravitional lensing of distant sources of gravitational waves, seeking to understand their multimessenger signals and detectability by future astrophysics facilities. Nicole was awarded a SURF (Summer Undergraduate Research Fund) award to perform this research wtih Prof. Chiara Mingarelli. For the full story, see the article in UConn Today.
The following article appeared in UConn Today on May 20, 2021 under by-line Elaina Hancock– UConn Communications
Physicists are one step closer to describing an anomaly, called the Muon g-2, that could challenge the fundamental laws of physics. It seems the muon may be breaking what have been understood as the laws of physics, and the findings announced on April 7th were met with much excitement and speculation at what this might mean. UConn physics researchers Professor Thomas Blum and Assistant Professor Luchang Jin helped pioneer the theoretical physics behind the findings, and they recently met with UConn Today to help explain the excitement.
What is a muon, and how do you study them?
Blum: A muon is a “fundamental particle,” meaning it’s an elementary particle like an electron or a photon. Muons are unstable, so they don’t live very long. Unlike an electron, where we can focus on them as long as we want and do measurements, we only have a little bit of time to take measurements of muons.
The way researchers perform the experiment is by slamming particles into other particles to create the muons, and they eventually collect them into a beam. This beam of muons travels at almost the speed of light where they live a little bit longer than they would if they were at rest. That’s Einstein’s theory of relativity in action.
The researchers put the muons into what’s called a storage ring where, eventually, they decay into other particles, and it’s those other particles that are detected in the experiment.
Muons have a property called a magnetic moment, which is like a little compass that points in the direction of the magnetic field that it’s in. In the storage ring, there’s a uniform magnetic field, and as the muons are going around in the storage ring, their magnetic moment, which would be perfectly aligned with their direction of travel if there were no anomaly, actually precesses with respect to the direction of travel as it goes around the ring, because of the interaction with the magnetic field.
It’s that precession that they’re measuring, because the precession is proportional to the strength of the magnetic moment. We can measure this magnetic moment extremely precisely in experiments, and we can calculate its value theoretically very precisely, to less than one-half part per million. Then we can compare the two and see how well they agree.
Can you explain the excitement surrounding these results?
Blum: For a long time — almost 20 years — the best measurement had been done at Brookhaven National Lab on Long Island, where they measured this magnetic moment very precisely, and found that it didn’t agree with our best fundamental theory, which is called the Standard Model of particle physics. The discrepancy wasn’t big enough to say that there was definitely something wrong with the Standard Model or not.
The new results are from a new experiment done to measure the magnetic moment even more precisely. That effort has been going on at Fermilab outside of Chicago for a few years now, and they just announced these results in early April. Their measurement is completely compatible with the Brookhaven value, and if you take the two together, then the disagreement with the Standard Model gets even worse: it now stands at 4.2 standard deviations.
People are very excited, because this could possibly signal that there is new physics in the universe that that we don’t know about yet. The new physics could be new particles that we’ve never seen before, or new interactions beyond the ones we know about already and that could explain the difference between what’s measured and what’s calculated. So that’s what everybody’s excited about.
Can you tell us about the Standard Model?
Jin: The Standard Model describes electromagnetic interactions between charged particles. It also describes the so called weak interactions, which is responsible for nuclear decay. The weak interactions become more important in high energy collisions, and unifies with the electromagnetic interactions. Lastly, the Standard Model describes the strong interactions, which bind quarks into nucleons and nuclei.
Basically, the Standard Model describes everything around us, ranging from things happening in our daily lives to the high-energy proton collisions in the Large Hadron Collider, with the major exception being gravity, which is only sort of visible, but we can feel it because gravity forces always add up, and there are a lot of other massive objects around us. It also doesn’t include dark matter, if we actually do have that in the universe.
People believe, and I think this is really true, that the Standard Model cannot possibly describe everything to extremely high precision, especially when we accelerate subatomic particles to very high energies. However, it was not very clear how high the energy or the precision has to be before we can see some discrepancies. We know the upper bound — usually referred to as the Planck scale, where the Standard Model has to fail due to the omission of gravity. But the Planck scale is so high that there is little hope to be able to perform experiments at that high energy. It is very nice to find a concrete example that the Standard Model actually misses something, and the g-2 anomaly is a very good candidate.
What roles did you each have in this research?
Jin: Theoretically, we decomposed the g-2 into contributions from the different types of interactions. At present, most of the values are obtained by analytic calculations of the various contributions. Other experimentally measurable quantities that have little to do with the muon magnetic moment experiments in terms of what they measure can be related through the Standard Model to the Muon g-2 value. So, to a large extent, this can still be viewed as a theory prediction. Blum pioneered the first lattice calculation for a certain g-2 contribution called the hadronic vacuum polarization, which doesn’t use experimental data at all.
Blum: Jin came up with new methods to compute the Hadronic Light-by-Light contribution which allowed us – with colleagues at Brookhaven National Lab, Columbia University, and Nagoya University – to compute it completely for the first time without experimental input. What Jin and I are doing, along with a host of other theorists around the world, is trying to better calculate the value of this magnetic moment from the theory side, so that we can have an even better comparison with the experimental measurements.
Jin: The Standard Model itself has a few parameters, which for most, we know very, very precisely. This includes the masses of the fundamental particles. In principle, as one might imagine, the theory prediction of the Muon g-2 is a very complicated expression just in terms of these numbers. We are not able to do that yet, but maybe soon we can. We expect that if we continue to improve our calculations, and as computers continue to get faster, the last digit determination may become more accurate.
To dig deeper into the science behind the findings, read Blum and Jin’s feature article on the findings in CERN Courier.
Prof. Battersby’s work focuses on describing and studying the center of the Milky Way galaxy, which she calls an “experimental playground” for the distant cosmos. Her work described the spectroscopy of the galaxy’s center, which analyzes imagery to understand the chemical makeup of the area, as well as its temperature and the velocity of objects.
Battersby works on data from the Submillimeter Array facility, a collection of eight powerful telescopes situated atop Mount Maunakea in Hawaii. The telescope can collect up to a terabyte of data every day, and Battersby’s project used 61 days of data.
Battersby refers to her computer as “her laboratory,” and ensures the students in her classes do, too. In her courses, she often assigns programming and analysis problems, like using a large data set to determine the material composition of the Sun.
“We have a lot of the tools to train students in data science,” she says. “Research is moving in that direction, and students in our programs are prepared for it.”
New Physics PhD graduate Yasaman Homayouni is featured in a story on the class of 2021 from the College of Liberal Arts and Sciences (CLAS). For the full story of what inspired Yasaman and other students during their time at UConn, see the article in UConn Today.
The Fermilab E989 experiment announced the first new result on the muon’s anomalous magnetic moment in almost 20 years. The new measurement, combined with Brookhaven’s E821, has increased the discrepancy with the Standard Model value to 4.2 standard deviations. UConn Professors Tom Blum and Luchang Jin explain the theory calculations in a feature story in the Cern Courier.
Jin: The Standard Model describes electromagnetic interactions between charged particles. It also describes the so called weak interactions, which is responsible for nuclear decay. The weak interactions become more important in high energy collisions, and unifies with the electromagnetic interactions. Lastly, the Standard Model describes the strong interactions, which bind quarks into nucleons and nuclei.
