Center for Particles and Fields (original) (raw)

Research (Click here for more information.)

I am experimental particle physicist and faculty at the University of Texas at Austin. Together with my group I conduct research that focuses on studies of neutrinos, development of particle detectors, and medical imaging. We are involved in the neutrino program at Fermilab in the US and the LSM and LNGS labs in Europe. Click on this link illustrating activities of our group.

At Fermilab, we are involved in the MINOS, MINOS+, and NOvA - long baseline experiments which pursue neutrino oscillations and neutrino physics using a NuMI beam and two detectors.

The on-axis MINOS Near Detector was located about 1km from the proton target at Fermilab, and the MINOS Far Detector was built 735km away in the Soudan Underground Laboratory in Northern Minnesota. MINOS took data between 2005 and 2012 and has set some of the most stringent constraints for the "atmospheric" neutrino mass splitting and mixing, reported in 2013 . The search for appearance of electron-neutrinos in the muon-neutrino NuMI beam has also yielded some of the first hints for θ13 and later reported these appearance results using the full MINOS data set. MINOS has published results that use together all MINOS beam and atmospheric data in a three-flavor analysis framework. These combined results set the most precise value for the atmospheric mass splitting to date. MINOS data were also used to search for sterile neutrino. This work is now reported in two interesting papers, one by MINOS (MINOS sterile search) and one by MINOS with the Daya Bay and the Bugey experiments (see MINOS, Daya Bay, Bugey-3 sterile search) excluding a large portion of available phase space for existence of a light sterile neutrinos.

Between 2013 and 2016, MINOS took data with the NuMI beam optimized for the off-axis NOvA experiment. The experiment was called MINOS+ and the collaboration was slightly reshaped. In addition to high-statistics testing of the disappearance of muon neutrinos at higher energies (4-8 GeV rather than 1-5 GeV), the experiment has unprecedented sensitivities to searches for sterile neutrinos, non standard neutrino interactions, and large extra dimensions. Both MINOS detectors are now dismantled. The end of MINOS era (that started about 25 years ago in 1995) and MINOS+ was celebrated by the entire Fermilab community (see the link about the end of MINOS) ... Data taken by MINOS and MINOS+ have been used to set unprecedented constraints on sterile neutrinos using the disappearance of muon neutrinos , and by combining with the Daya Bay and Bugey-3 disappearance of reactor antineutrinos, the three experiments provide a stringent constraint on the appearance of electron neutrinos. . New results also improve improve the standard oscillations parameter and the parameter space for Large Extra Dimensions.

We are also involved in the NOvA Experiment at Fermilab, and in the future long baseline the DUNE experiment that will use a new long-baseline LBNE beam line. NOvA uses two low-density off-axis detectors on a 810km baseline from Fermilab to Ash River, Minnesota and it is now one of the flagship experiments at Fermilab. Both, NOvA now and DUNE in the future, continue improving precision of neutrino and antineutrino oscillation parameters and are expected to yield tight constraints on the neutrino mass hierarchy, the θ23 octant, and the δCP angle of the Pontecorvo-Maki-Nakagawa-Sakata matrix and possibly resolve the mass ordering and neutrino CP problem (see., e.g., here). NOvA makes great leaps in this program, as reported in these recent publications in 2017a and 2017b, 2018, and2019 .

At Laboratoire Souterrain de Modane in France, we have been contributing to the NEMO-3 experiment and its future reincarnation SuperNEMO. These are experiments designed to search for neutrinoless double beta decay which, if observed, would demonstrate that neutrinos are Majorana particles (i.e., that neutrinos and antineutrinos represent the same fundamental field). NEMO-3 has recently published results on a search for a neutrinoless double beta of Mo-100 . The lower limit on the half-life for this process gives some of the tightest upper bounds on the effective Majorana neutrino mass mββ. Since 2019 we are also beginning to contribute to the LEGEND-200 Experiment at LNGS and its later phase LEGEND. If down-selected, LEGEND will be a world-leading effort searching for neutrinoless double beta decay using enriched germanium 76 high purity crystals. The experiment will have the sensitivity to reach meV effective neutrino masses.

In our group we maintain R&D of particle detectors and calibration systems. Examples include large water Cherenkov detectors, as described in here, Bi-207 calibration and light injection system for SuperNEMO, and currently a Positron Emission Tomography scanner to assist in the Proton Therapy treatment.

Teaching

I often teach introductory physics tailored for pre-meds, biology, and chemistry majors (PHY 317K and PHY 317L). I also teach Modern Physics (or "Junior") Laboratory course (PHY 353) and Advanced (or "Senior") Laboratory course (PHY 474). Every semester I give lectures on particle radiation detectors as a quarter part of the Physics of Sensors class (PHY 386K).

I strongly believe and support education through research. This is why I have been always engaging undergraduate students in my research activities. This has led many of them to their successful graduate careers or excellent employment opportunities after graduation.