Scientists working on the Short-Baseline Near Detector (SBND) at Fermi National Accelerator Laboratory have identified the detector’s first neutrino interactions.
The SBND collaboration has been planning, prototyping and constructing the detector for nearly a decade.
“It isn’t every day that a detector sees its first neutrinos,” said David Schmitz, co-spokesperson for the SBND collaboration and associate professor of physics at the University of Chicago.
SBND is the final element that completes Fermilab’s Short-Baseline Neutrino (SBN) Program and will play a critical role in solving a decades-old mystery in particle physics.
SBND is the near detector for the Short Baseline Neutrino Program while ICARUS, which started collecting data in 2021, is the far detector.
The Short Baseline Neutrino Program at Fermilab differs from previous short-baseline measurements with accelerator-made neutrinos because it features both a near detector and far detector.
SBND will measure the neutrinos as they were produced in the Fermilab beam and ICARUS will measure the neutrinos after they’ve potentially oscillated.
The large data sample will allow researchers to study neutrino interactions with unprecedented precision.
But neutrinos won’t be the only particles SBND scientists will keep an eye out for.
The collaboration will continue operating the detector and analyzing the many millions of neutrino interactions collected for the next several years.
The first neutrino interactions detected by the Short-Baseline Near Detector (SBND) at Fermi National Accelerator Laboratory have been identified by scientists working on the device.
For almost ten years, the SBND collaboration has been designing, developing, and building the detector. Eventually, the moment they had all been waiting for arrived after several months of meticulously turning on each detector subsystem.
“Detectors don’t see their first neutrinos very often,” stated David Schmitz, an associate professor of physics at the University of Chicago and co-speaker for the SBND collaboration. “This initial data represents a very promising beginning to our search for new physics, something that all of us have been working toward for years. “.”.
In addition to being the last component of Fermilab’s Short-Baseline Neutrino (SBN) Program, SBND will be essential in resolving a long-standing puzzle in particle physics. It has taken a global effort to get SBND to this point. A multinational team comprising 250 physicists and engineers from Brazil, Spain, Switzerland, the United Kingdom, and the United States constructed the detector.
The most comprehensive explanation of how the universe functions at its most basic level is provided by the Standard Model. When calculating anything from high-intensity particle collisions in particle accelerators to extremely rare decays, particle physicists turn to this gold standard. The Standard Model, however, is not perfect, even though it is a well-tested theory. Additionally, anomalies that may indicate the existence of a novel kind of neutrino have been detected by several experiments over the past 30 years.
In the universe, neutrinos are the second most common particle. Even though they are very common, they are very challenging to study because they rarely appear in detectors and only interact through gravity and the weak nuclear force.
There are three flavors or types of neutrinos: tau, electron, and muon. The fact that these particles oscillate between these flavors—from muon to electron to tau—may be the strangest thing about them.
It is fairly well known to scientists how many of each type of neutrino should be present at various separations from a neutrino source. However, the results of a few earlier neutrino experiments did not match those predictions’ observations.
The scientist at Fermilab, Anne Schukraft, explained, “That could mean that there are more than the three known neutrino flavors.”. This new kind of neutrino would not interact through the weak force, in contrast to the three known types. We would only notice them if there was an anomaly in the measurement of the tau, electron, and muon neutrino counts. “.”.
At Fermilab, searches for neutrino oscillation and evidence suggesting the existence of this fourth neutrino will be conducted by the Short Baseline Neutrino Program. For the Short Baseline Neutrino Program, SBND is the near detector and ICARUS, which began data collection in 2021, is the far detector. That year also saw the completion of particle collision recordings with the same neutrino beamline using a third detector, MicroBooNE.
Unlike earlier short-baseline measurements using accelerator-made neutrinos, Fermilab’s Short Baseline Neutrino Program has a near detector in addition to a far detector. While ICARUS measures the neutrinos after they may have oscillated, SBND measures them as they are produced in the Fermilab beam. Accordingly, the SBN Program will provide an absolute determination of the original neutrino beam composition, whereas earlier experiments had to rely on conjecture.
“For the past 25 years, one of the main goals in the field has been to understand the anomalies seen by previous experiments,” Schmitz stated. “ICARUS and SBND working together will provide exceptional capability to verify the presence of these novel neutrinos. “. .
Past the search for novel neutrinos.
Besides collaborating with ICARUS to hunt for a fourth neutrino, SBND has an interesting physics program of its own.
More neutrinos than any other detector of its type, SBND will witness 7,000 interactions every day due to its close proximity to the neutrino beam. Researchers will be able to examine neutrino interactions with previously unheard-of precision thanks to the large data sample. Future experiments, like the long-baseline Deep Underground Neutrino Experiment, or DUNE, that use liquid argon to detect neutrinos, will heavily rely on the physics of these interactions.
The interaction of a neutrino with an atom’s nucleus causes a spray of particles to fly through the detector. In order to deduce the characteristics of the spectral neutrinos, physicists must take into consideration every particle generated during that interaction, both visible and invisible.
Simple nuclei, such as hydrogen and helium, are relatively simple to model, but argon is used in SBND, as in many other contemporary neutrino experiments, to trap neutrinos. Because an argon atom has 40 nucleons in its nucleus, interactions with argon are more complicated and challenging to comprehend.
Ornella Palamara, a scientist at Fermilab and a co-speaker for SBND, stated, “We will gather 10 times more data on how neutrinos interact with argon than all previous experiments combined.”. As a result, DUNE will greatly benefit from the analyses we perform. “.
However, scientists at SBND will be watching for other particles besides neutrinos. Given the proximity of the detector to the particle beam, it is plausible that additional surprises could be observed by the collaboration.
“The detector would be able to detect things that are produced as a byproduct of the beam that have nothing to do with neutrinos and are outside of the Standard Model,” Schukraft said.
Dark matter remains one of the most significant unanswered questions of the Standard Model. SBND would only be sensitive to light particles, but those hypothetical particles might offer an initial look at a “dark sector.”. “.
Andrzej Szelc, co-coordinator of SBND physics and professor at the University of Edinburgh, stated that “direct” dark matter searches for massive particles have not yet produced any results. Many dark sector models of lightweight dark particles that could be created in a neutrino beam have been proposed by theorists; SBND will be able to verify the veracity of these models. “.”.
For SBND, these neutrino signatures are merely the start. Over the course of the next few years, the collaboration will keep running the detector and examining the millions of neutrino interactions that have been recorded.
As Palamara put it, “We have been working towards this long process for years, and seeing these first neutrinos is the start of it.”. “This marks the start of a new chapter in the partnership. “.
