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Posts Tagged ‘Minerva’

How to make a neutrino beam

Friday, December 12th, 2014

This article appeared in Fermilab Today on Dec. 11, 2014.

Ingredients for a neutrino beam: speedy protons, target, magnetic horn, decay pipe, absorbers. Image adapted from Fermilab

Ingredients for a neutrino beam: speedy protons, target, magnetic horn, decay pipe, absorbers. Image adapted from Fermilab

Fermilab is in the middle of expanding its neutrino program and is developing new detectors to study these ghostly particles. With its exquisite particle accelerator complex, Fermilab is capable of creating very intense beams of neutrinos.

Our neutrino recipe starts with a tank of hydrogen. The hydrogen atoms are fed an extra electron to make them negatively charged, allowing them to be accelerated. Once the charged atoms are accelerated, all of the electrons are ripped off, leaving a beam of positive protons. The protons are extracted into either the Booster Neutrino Beamline (BNB) or are further accelerated and extracted into the Neutrino Main Injector beamline (NuMI). Fermilab is the only laboratory with two neutrino beams. Our two beams have different energies, which allows us to study different properties of the neutrinos.

In the BNB, these protons smash into a target to break up the strong bonds of the quarks inside the proton. These collisions are so violent that they produce new quarks from their excess energy. These quarks immediately form together again into lighter composite short-lived particles called pions and kaons.

Since the pions and kaons emerge at different directions and speeds, they need to be herded together. As a bugle tunes your breath into musical notes, a horn of a different type rounds up and focuses the pions and kaons. The BNB horn looks roughly like the bell of a six-foot long bugle. It produces an electric field that in turn generates a funnel-like magnetic field, which directs all of the dispersed pions and kaons of positive electric charge straight ahead. Particles with negative charges get defocused. By switching the direction of the electric field, we can focus the negatively charged particles while defocusing the positive charges.

The focused particles in the BNB beam travel through a 50-meter long tunnel. This is where the magic happens. In this empty tunnel, the pions and kaons decay in flight into neutrinos, electrons and muons. At the end of the decay tunnel is a wall of steel and concrete to stop and absorb any particle that is not a neutrino. Because neutrinos interact so rarely, they easily whiz through the absorbers and on towards the experiments. And that’s the basic formula to make a beam of neutrinos!

A single neutrino beamline can support many experiments because the neutrinos interact too rarely to get “used up.” The BNB feeds neutrinos to MicroBooNE, and most of them go on through to the other side towards the MiniBooNE detector. Similarly, most of those go on through the other side as well and continue traveling to infinity and beyond. Detectors located in this beam measure neutrino oscillations and their interactions.

The NuMI beamline is designed similarly, but uses a different target material, two focusing horns, and a 675-meter decay pipe. The spacing between the two NuMI horns is adjustable, allowing fine-tuning of the neutrino beam energy. The NuMI beamline has higher-energy neutrinos than the BNB and thus studies different properties of neutrino oscillations.

The NuMI beamline feeds neutrinos to the MINERvA experiment and on through to the MINOS near detector. The NuMI beamline then continues about 450 miles through Earth on toward the MINOS far detector in the Soudan mine in Minnesota. By the time the beam reaches the far detector, it is about 20 miles in diameter! By having a near and far detector, we are able to observe neutrino flavor oscillations by measuring how much of the beam is electron neutrino flavor and muon neutrino flavor at each of these two detectors.

The last of the big Fermilab neutrino experiments is NOvA. Its near detector is off to the side of the NuMI beam and measures neutrinos only with a specific range of direction and energy. The NOvA far detector is positioned to measure the neutrinos with the same properties at a greater distance, about 500 miles away in Ash River, Minnesota. By placing the NOvA detectors 3 degrees to the side of the beam’s center, NOvA will get to make more precise oscillation measurements for a range of neutrino energies.

As more experiments are designed with more demanding requirements, Fermilab may expect to see more neutrino beamline R&D and the construction of new beamlines.

Tia Miceli

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This article appeared in Fermilab Today on Sept. 16, 2014.

Summer intern Sheri Lopez, here with son Dominic, pursues her love of physics as a student at the University of New Mexico-Los Alamos. She spent this summer at Fermilab as a summer intern. Photo courtesy of Sheri Lopez

Summer intern Sheri Lopez, here with son Dominic, pursues her love of physics as a student at the University of New Mexico-Los Alamos. She spent this summer at Fermilab as a summer intern. Photo courtesy of Sheri Lopez

Dominic is two. He is obsessed with “Despicable Me” and choo-choos. His mom Sheri Lopez is 29, obsessed with physics, and always wanted to be an astronaut.

But while Dominic’s future is full of possibilities, his mom’s options are narrower. Lopez is a single mother and a sophomore at the University of New Mexico-Los Alamos, where she is double majoring in physics and mechanical engineering. Her future is focused on providing for her son, and that plan recently included 10 weeks spent at Fermilab for a Summer Undergraduate Laboratories Internship (SULI).

“Being at Fermilab was beautiful, and it really made me realize how much I love physics,” Lopez said. “On the other end of the spectrum, it made me realize that I have to think of my future in a tangible way.”

Instead of being an astronaut, now she plans on building the next generation of particle detectors. Lopez is reaching that goal by coupling her love of physics with practical trade skills such as coding, which she picked up at Fermilab as part of her research developing new ways to visualize data for the MINERvA neutrino experiment.

“The main goal of it was to try to make the data that the MINERvA project was getting a lot easier to read and more presentable for a web-based format,” Lopez said. Interactive, user-friendly data may be one way to generate interest in particle physics from a more diverse audience. Lopez had no previous coding experience but quickly realized at Fermilab that it would allow her to make a bigger difference in the field.

Dominic, meanwhile, spent the summer with his grandparents in New Mexico. That was hard, Lopez said, but she received a lot of support from Internship Program Administrator Tanja Waltrip.

“I was determined to not let her miss this opportunity, which she worked so hard to acquire,” Waltrip said. Waltrip coordinates support services for interns like Lopez in 11 different programs hosted by Fermilab.

Less than 10 percent of applicants were accepted into Fermilab’s summer program. SULI is funded by the U.S. Department of Energy, so many national labs host these internships, and applicants choose which labs to apply to.

“There was never a moment when anyone doubted or said I couldn’t do it,” Lopez said. Dominic doesn’t understand why his mom was gone this summer, but he made sure to give her the longest hug of her life when she came back. For her part, Lopez was happy to bring back a brighter future for her son.

Troy Rummler

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Fermilab planning a busy 2012

Tuesday, January 3rd, 2012

This column by Fermilab Director Pier Oddone first appeared in Fermilab Today Jan. 3 .

We have a mountain of exciting work coming our way!

In accelerator operations, we need to give enough neutrinos to MINERvA to complete their low-energy run, enough anti-neutrinos to MiniBooNE to complete their run and enough neutrinos to MINOS to enable their independent neutrino velocity measurement that will follow up on last year’s OPERA results. We need to provide test beams to several technology development projects and overcome setbacks due to an aging infrastructure to deliver beam to the SeaQuest nuclear physics experiment. And we need to do all of this in the first few months of the year before a year-long shutdown starts. During the shutdown, we will modify the accelerator complex for the NOvA era and begin the campaign to double the number of protons from the Booster to deliver simultaneous beams to various experiments.

In parallel with accelerator modifications, we will push forward on many new experiments. The NOvA detector is in full construction mode, and we face challenges in the very large number of detector elements and large mechanical systems. Any project of this scale requires a huge effort to achieve the full promise of its design. We have the resources in our FY2012 budget to make a lot of progress toward MicroBooNE, Mu2e and LBNE. We will continue to work with DOE to advance Muon g-2. All these experiments are at an important stage in their development and need to be firmly established this year.

At the Cosmic Frontier, we will commission and start operation of the Dark Energy Survey at the Blanco Telescope in Chile, where the camera has arrived and is being tested. In the dark matter arena we will commission and operate the 60 kg COUPP detector at Canada’s SNOLAB and continue the run of the CDMS 15 kg detector in the Soudan Mine while carrying out R&D on future projects. We continue to have a major role in the operation of the Pierre Auger cosmic-ray observatory. In addition we should complete the first phase of the Fermilab Holometer, which will study the properties of space-time at the Planck scale.

At the Energy Frontier, we play a major role in the LHC detector operations and analysis. It should be a fabulously exciting year at the LHC as we push on the hints that we already see in the data.

Beyond construction and operation of facilities we continue our R&D efforts on the superconducting RF technology necessary for Project X and other future accelerators. We will be building the Illinois Accelerator Research Center and moving forward to connect our advanced accelerator program with industry and universities. Our rich program on theory, computation and detector technology will continue to support our laboratory and the particle physics community.

If we accomplish all that is ahead of us for 2012, it will be a year to remember and celebrate when we hit New Year’s Day 2013!

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Illustration: Fermilab/Diana Canzone

Two weeks ago, my Aunt and Grand mom (G-Mom) came from New Jersey to visit me at Fermilab.  The first thing they wanted to see was the house in Fermilab Village where my bride-to-be and I would be living for the rest of my graduate career.  G-Mom was impressed: “They hung pictures on the walls for you!”

Then it got complicated. G-Mom asked me what I do.

”I do nuclear physics with the MINERvA, a neutrino interactions experiment.  This detector has an array of nuclear targets that vary in size.  By looking at events that occur in nuclei of different size, we can discover things about those nuclei.” (See notation ** below)

Her follow-up question was: “How is it you find that interesting?”

I told her that what we do in nuclear/particle physics is try to solve mysteries and puzzles, and I like doing that.  Being an avid reader of mystery novels and voracious solver of cross-word puzzles, G-Mom was on-board with this reasoning.  So, I tried to explain the mysteries of nuclear physics that MINERvA will investigate in the style of a Sam Spade or Philip Marlowe private detective novel…

MINERvA, Intra-Nuclear Detective”

MINERvA was starting to lose her cool.  Of all the detectors in all the world, this proton walked into her’s.

After 23 hours of interrogating this proton about what he was doing at the time of the boson exchange, he wasn’t revealing sign one  The had detector picked up the proton in the vicinity of the incident.  His usual accomplice, the muon, was seen fleeing north, where he was apprehended by MINOS, the adjacent detector.  Even with the proton refusing to talk, the greenest rookie could spot a muon and a proton in the final state and tell you this was a case of charged-current quasi-elastic neutrino scattering.

It happens all the time at these energies.  A neutrino with a few GeV of kinetic energy flies deep into some back-alley nucleus and meets up with a neutron.  The deal goes down quickly: a W+ is exchanged; the neutron, fed its fix of charge, is now a proton; the neutrino flies away as a muon, thanked for its troubles with a charge of his own.  This is textbook quasi-elastic scattering.

But this was not a textbook case.  MINERvA had in her custody not one, but two protons!  Only after she drained the last drop of espresso would MINERvA allow her weary legs to drag her back to the interrogation room.  The questioning was fast and direct.

A diagram of "textbook" quasi-elastic scattering.

“Listen Proton, we know you and the muon came out of a carbon nucleus.  Was it quasi-elastic scattering?”

“Sure, but it wasn’t me.  It was the other proton.”

“The other proton told us the same thing.  Then what were you doing fleeing the nucleus?”

“I already told you: I watched the neutrino come in and scatter off a neutron.  Guy turns into a proton and runs right into me!”

“That’s what they all say.  We think both of you protons were directly involved in the scattering.”

“Oh, yeah? How are you going to prove it?  You don’t have jurisdiction inside the nucleus!

The proton was right.  Experiments are not able to see inside the nucleus.  It could not be proven that the protons were involved directly in the neutrino interaction.

But MINERvA was getting close to connecting the dots enough to figure out what this gang of particles was doing inside the nucleus. They couldn’t hide forever. Soon MINERvA would unravel their pattern and tell all the detectors in the world what was going on.

MINERvA collaboration. Credit: Fermilab/Reidar Hahn

** When an interaction happens inside of a large nucleus, the particles involved in the neutrino interaction (“primary particles”) must travel through a sea of protons and neutrons to get outside the nucleus, where they can be detected.  Primary particles may interact with the other protons and neutrons on their way out.  For example, a primary proton can knock out another proton from the nucleus.  Then the experiment will observe two protons coming out of the nucleus (“final state particles”).  The messiness of primary particles interacting on their way out of the nucleus is called Final State Interactions (FSI).  MINERvA will measure FSI in its wide range of nuclei, thus revealing clues about the mysterious inner-workings of the nucleus.

 

— Brian Tice

Related posts:

• MINERvA model for building research bridge with Latin American
• Meet MINERvA: a blend of particle and nuclear physics
• MINERvA Decathlon
MINERvA sees its first neutrinos!

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Neutrinos could tell us why matter formed in the early universe.

The Japan-based experiment T2K Tuesday gave scores of U.S. particle hunters a license to ready their detectors and take aim at the biggest question in the universe: How everything we see came to exist.

“It’s our hunting license,” said Fermilab physicist and University of Rochester professor Kevin McFarland, who works on T2K and neutrino experiments at Fermilab.

The observation by T2K affects what the Fermilab neutrino experiments NOvA and the proposed Long Baseline Neutrino Experiment, LBNE, can expect to discover and how quickly. It also makes the experiment McFarland serves as co-spokesman on, MINERvA, more important than ever in the international neutrino-research field.

Physicists working with T2K recorded six muon neutrinos changing into electron neutrinos across a long distance, a transformation called theta 13 in physics circles. Physicists had predicted that they should observe only 1.5 of these transformations as background events rather than the six they did observe, so the probability of the existence of an electron neutrino appearance is estimated to be 99.3 percent. While the T2K observation doesn’t rise to the level of “discovery” in the science community, it is far enough beyond the expected statistical error bar to make people shout for joy and start revising plans for their own particle hunts.

“Because neutrino science is so hard, scientist don’t get a lot of exciting days,” McFarland said the day of the T2K announcement. “But this is a very exciting day.”

The T2K observation also was statistically large enough that it quells a long-standing fear that this transformation would be statistically too small, much less than one percent, to observe. At that level, modern technology wouldn’t be able to use the observation as a stepping stone to move to the next research phase in figure out how matter came to dominate antimatter in the universe.

The quarry:

Something, possibly neutrinos, tipped the scales to have more matter than antimatter in the universe allowing for life. Credit: symmetry magazine

Physics predicts that the three types of neutrino particles can change back and forth into one another across long distances. Previous solar and reactor neutrino experiments had observed two types doing just that, but the third switch – muon neutrino into electron neutrino – had remained elusive.

T2K’s recording of this transformation, the first of its kind, means that physicists will have the tools to track down the next two potential discoveries on the path to the ultimate trophy. After the Big Bang, equal amounts of matter and antimatter should have annihilated each other leaving nothing but free-floating energy. But we’re here and antimatter isn’t, so that didn’t happen. Something tipped the scales in matter’s favor, allowing particles to join together and form planets, plants and people. Physicists think neutrinos could be that tipping-point particle.

Following the tracks:

The first step in finding out if they are right is T2K’s observation. Plugging this observation into the research equation, physicists on NOvA, an experiment under construction in Minnesota, will be able to tease out the details of what is called the neutrino mass hierarchy. The pattern of this hierarchy essentially will tell physicist if neutrinos behave like other particles, in a pattern of light, heavy and very heavy, or neutrinos behave oddly in a pattern of light, heavy and heavy.

This pattern of masses is important to know because it provides a clue to help physicists understand what causes neutrinos to have masses that are so much lighter than other particles and why neutrinos aren’t massless as predicted by the Standard Model, the playbook for how the world works at the subatomic level.

Physicists think the origins of neutrino masses are closely tied to subatomic processes that took place right after the big bang. Determining which neutrino types are heaviest and lightest—the neutrino mass ordering—is a first step toward revealing these processes. Credit: symmetry magazine

NOvA is ideally situated to do discern this pattern because its particle beam will travel three times as farther than T2K’s, allowing researchers see how the material in the Earth alters the change from muon to electron neutrinos. T2K’s observation of half a dozen muon neutrino to electron neutrino changes points to the relatively high rate of the change, so NOvA should have a lot of data to work with to speed up the discovery of the mass hierarchy.

Step three is combining what NOvA learns about the mass hierarchy with more precise data from the LBNE experiment to look for differences in the neutrino and antineutrino probabilities of changing from muon to electron neutrino types. After accounting for the effect of the earth and the mass hierarchy, any remaining difference would point to a fundamental difference between matter and antimatter neutrinos. Differences between matter and anti-matter are nearly non-existent in nature and these differences are precious clues about why matter dominated antimatter to survive in today’s universe.

The three types of neutrinos mix across long distances enabling physicists to see them to change type if the distance is long enough. Credit: symmetry magazine

LBNE, proposed for South Dakota, sits even farther away from the Fermilab neutrino source, making it well-suited to make this comparison of antineutrinos, which are rarer and harder to detect than neutrinos. T2K’s observation of a large change signal means LBNE will have better statistics to create precise comparisons.
The level of precision could mean the difference between getting an answer or not, depending on how subtle the difference is between neutrinos and antineutrinos.

Bringing out the rifle scope:

Short-baseline experiments can’t compete in the hunt for why matter dominated antimatter, which requires tracking neutrinos across great distances, but they can provide the precision measurements that work like a rifle scope for the particle hunters. MINERvA at Fermilab and the neutrino reactor experiments Daya Bay in China and Double Chooz in France will provide the data to allow NOvA and LBNE to zoom in on the minute details of mass hierarchy and how neutrinos change types.

The reactor-based experiments with detectors near to neutrino spewing reactors were designed to be experts at finding the neutrino change T2K found. Ideally, they will find a cleaner neutrino transformation signal, without the data complications, such as the effects of Earth material on the transformation that come with T2K and NOvA being multi-purpose experiments. Cleaner reactor experiment measurements provide a baseline for the measurements of NOvA and LBNE.

MINERvA will provide data to help NOvA and LBNE map the type and amount of background events that can obscure their search. This will enable physicists to put the trophy deer-like potential discovery in their analysis cross-hairs and discount the imposter trees and hunters dressed in brown that cloud the view of their data. While MINERvA was built for this job and currently aids neutrino experiments across the globe, including T2K, with this variable-removing research information, T2K’s observation makes MINERvA’s unique skill more important. The large T2K signal means a lot of data and the ability to do precision analysis if MINERvA can tell researchers what variables to discount.

“There is always an exchange of data, and one experiment builds on another,” McFarland says.

Previously data from the MINOS experiment at Fermilab told T2K how to tune the energy of its particle beam. Now T2K is returning the favor with an observation that will help Fermilab experiments.

“Experiments building on one another,” he says, “that is what makes it exciting.”

Related information:

Symmetry breaking: Japan’s T2K experiment observes electrion neutrino appearance

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The number of Latin Americans working on the MINERvA experiment is unusual for a high-energy physics experiment. Among our Latin American collaborators, you’ll find professors, postdocs, graduate students and undergraduate students from countries such as Mexico, Brazil, Peru and Chile.

Cristian Pena in front of the MINERvA detector. Credit: Fermilab/Reidar Hahn

Being part of MINERvA offers many opportunities. For example, graduate students can complete their Ph.D. theses using MINERvA data, and many also have the opportunity to work at Fermilab, where they share ideas and knowledge with other students, postdocs, and professors from around the world. Working on MINERvA provides Latin American scientists the opportunity to perform research at the frontiers of experimental high-energy physics. The projects and studies on which we work are crucial for the experiment and for the neutrino physics program worldwide.

In my particular case, I am from Universidad Técnica Federico Santa María in Valparaíso, Chile. I recently had the opportunity and honor to be at Fermilab for five months working on two different projects. This experience was really exciting and challenging. I really learned a lot of physics and programming, understood more deeply how the experiment works, improved my English, and had the opportunity to meet and work directly with many experienced people in the field.

In terms of my personal life, it was a bit difficult to get accustomed to all the changes, such as language, food and geographical distances (my commute in Chile is just a five-minute walk). And once I got used to these, it started snowing. When I was first told about the weather at Fermilab, I said, “Oh come on. You must be exaggerating”, but clearly I was wrong. I really enjoyed meeting all the people in the collaboration and was interested to find out that Spanish from other Latin American countries is quite different – most people were not able to understand me when I used my spoken Chilean-Spanish. But now all those difficulties are just memories, thanks to the help Guiliano (my Chilean partner and roommate) and I received from the other Latin American folks at Fermilab.

MINERvA detector construction. Credit: Fermilab

When I returned to Chile a month ago, I realized that it would have been much more difficult to have this opportunity 10 years ago. I am really thankful for the efforts of Fermilab and the MINERvA experiment to make this possible, as well as the joint efforts that the Latin American Universities and their governments have made.

The fact that the number of Latin Americans in the MINERvA experiment is large is evidence of the science development which has started in our region. It also reinforces the importance of the efforts that institutions and governments are making to achieve the altruistic goal of developing science in their countries.

I would like to thank Jorge Morfin, who is working really hard to make collaborations like this possible; William Brooks, who is the leader of the experimental high-energy group of Universidad Técnica Federico Santa María and who keeps working to maintain and give the same opportunity to other Latin American students; and Deborah Harris and Kevin McFarland, the spokespersons of the experiment. I also want to thank the whole MINERvA collaboration who is doing a really nice job and pushing really hard to obtain the results the physics community is waiting for.

— Cristian Peña

Related information:
*Read about Cristian earning the Fulbright award

*From Peru to MINERvA

*Fermilab helps increase Mexican high-energy physics research

*Fermilab helps increase Brazilian high-energy physics research

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Dave Schmitz in front of the MINERvA detector at Fermilab. Credit: Fermilab

This story appeared April 7 in the DOE blog energy.gov. Dave Schmitz often posts on Quantum Diaries.

Particle physicist Dave Schmitz works on the MINERvA experiment at Fermi National Accelerator Lab — he took some time to tell us why neutrinos (electrically neutral, subatomic particles) are important to the universe and why the time 1:32am has special meaning for his experiment. And, check out Dr. Schmitz’s talk  — “In One Ear and Out the Other: A Talk about Neutrino”  — as part of Fermilab’s ‘Physics for Everyone’ lecture series.

Question: What sparked your interest in pursuing a career in science?

I started my career in science relatively late. I originally started as an architectural engineering student in college. I didn’t change to physics until late in my fourth year as an undergraduate. I had read several physics books for a public audience and became interested in learning more. I decided to enroll in a Physics III course as an elective towards my engineering degree. I remember my advisor thinking that I was completely nuts and only reluctantly signing my enrollment card. Maybe he was so hesitant because he feared I would not return to architecture.  
 
That semester, the class touched on the concepts of relativity and quantum mechanics for the first time. My professor was very enthusiastic and would happily spend extra time out of class discussing anything I wanted. At the end of that semester I joined a research group studying neutrinos produced by distant cosmological sources that interacted in the polar ice cap at the South Pole. In December 2000, I had the thrill of traveling to the experiment for two weeks to deploy some new equipment. If I wasn’t already hooked on a career in science, a trip to the bottom of the earth sealed the deal.   
 
Q: You’re a physicist and a neutrino expert. Why did you choose this field?
 
DS: Neutrinos first sparked my interest as an undergraduate. The idea that neutrinos could be used to tell us something new and exciting about an object on the other side of the universe was pretty incredible to me. Then in graduate school I had the opportunity to work on an experiment that was searching for a completely new kind of neutrino that we had never even seen before. I worked on the MiniBooNE experiment at Fermilab which was searching for evidence of “sterile” neutrinos, a new type that did not interact via any of the currently known forces. It turns out there remain many interesting unanswered questions about the fundamental nature of the neutrino. We now know that neutrinos do have a tiny mass, but we have not been able to measure its value — we only know that it isn’t zero. There is also the possibility that neutrinos and their antiparticles (simply called antineutrinos) may behave differently in very subtle ways. We are planning experiments now to search for such differences, which could be a big part of the explanation for why the universe we live in is dominated by matter with little to no antimatter. In this way, neutrinos could fill in a critical piece to our understanding of how the universe has evolved into the amazing (and, thankfully, hospitable!) place we see around us.

See the rest of the article at energy.gov.

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When I say I work at Fermilab, most people assume I work on one of the Tevatron experiments. When I tell them that I work with neutrinos instead, a lot of people still aren’t familiar with the MINERvA experiment. So, since this is our collaboration’s first official contribution to Fermilab’s blog on Quantum Diaries this year, I’d like to introduce you to our small but awesome experiment.

MINERvA is a neutrino detector the sits in the NuMI beam — the most intense beam of neutrinos in the world and the same beam that’s currently used by MINOS and that will soon be used by NOvA.  In fact, MINERvA sits right in front of the MINOS near detector, in a cavern about 330 feet below ground.  The detector itself is, among other things (See paragraph five), basically a big hunk of plastic — many thousands of long thin strips of a special kind of plastic that generates light when charged particles pass through it.  When neutrinos from the NuMI beam enter MINERvA, a few of them interact with the nuclei that make up the MINERvA and we detect the products of these interactions through the light they produce.

MINERvA is what’s called a neutrino-scattering experiment.  Basically, this means our goal is to understand how neutrinos interact with ordinary matter.  Because neutrinos interact so weakly, this is much less understood than you might think — it’s really hard to get enough neutrino interactions to make precise measurements.  But thanks to the huge numbers of neutrinos from the NuMI beam and the precision of the detector, MINERvA is part of a new era of neutrino physics when precise measurements are becoming possible. 

So, why do we want to better understand neutrino interactions?  There are lots of neutrinos in the universe, and understanding what happens when they collide with matter is interesting in its own right, but there are also a lot of other reasons we’d like to understand neutrino scattering.  For instance, experiments looking for exotic neutrino phenomena such as mass oscillations are plagued by large uncertainties associated with how likely neutrinos are to interact with nuclei.  Input from MINERvA will decrease those uncertainties, and because the energy of the NuMI beam is near the optimum for studying neutrino oscillations, our measurements will be particularly useful to oscillation experiments.

To tell you about another cool aspect of MINERvA, I have to explain that I lied a little bit above.  The detector is not just a big hunk of plastic — it’s actually plastic interspersed with a few other materials, including our nuclear targets.  Made of  iron, lead, water and helium the targets allow us to study how neutrino interactions differ depending on what kind of nuclei they are interacting with.  Neutrino scattering experiments in the past have attempted to study this, but because we’ll be able to analyze several different nuclei using the same beam and same detector, MINERvA will have a lot to say on this subject.   Also, it turns out that studying neutrino-nuclei interactions is not just useful for understanding the properties of neutrinos, but can also tell you a lot about nuclei.  So, while the majority of the physicists who work on MINERvA would call themselves particle physicists, we have quite a few collaborators who are nuclear physicists.  

We started taking data with the full MINERvA detector early last year, and we are now really hard at work trying to understand that data.  There will definitely be a lot of interesting results from MINERvA soon — so stay tuned to this space, where we hope to tell you all about it.

–Laura Fields

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