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Jelena Maricic | Drexel university, Philadelphia | USA

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A simple tip for explaining absense to toddlers

Wednesday, November 18th, 2009

My mom came up with a very bright (and simple) idea on how to explain to very small kids (toddler level) that mommy will not be back for days. And I would like to share it.

So I was absent from home more than half of a  month in the last month due to two collaboration meetings and a conference. Does not happen every month luckily. My mom, who was babysitting my children (2 and 4 years old) devised an ingenious way of telling them that there is no point in asking couple of times a day when is mommy coming back home. And here it is:

“Mommy went to work by airplane so she can not be back quickly (solid proof is a car left at home). Mommy only comes back quickly if she went to work by car! “

And it worked! Simple enough:).

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New face of LBNE

Wednesday, November 18th, 2009

The news is up. We had election results announced for the spokesperson for the Long Baseline Neutrino Experiment at DUSEL. This is the first time I witnessed proper elections. Three excellent candidates, extremely dedicated to the project. They came up with their vision and how they see project priorities and future.  It was interesting to tune into scientific elections. I am sure that all three will lead this longterm collaboration (read: results not likely before 2020) at some point or another. In the end collaborators decided for Bob Svoboda from UC Davis and I wish him good luck.

It is an unbeleivable challenge keeping motivated, dedicated collaboration for a decade at least. The physics promise is unsurpassed, but it is a long way getting there. We all want to know if  the lepton CP-violation phase is large enough to fit in the answer to matter dominance that we observe.  We all want to know which neutrino mass is the heaviest, but again, it is a long way getting there. Everyone would love to see some of the relic supernova neutrinos, of even a real supernova blast, but the road is long with a lot of hurdless.

So, in the meantime we concentrate on more down to Earth questions – some fun like choosing a more exciting name for the LBNE. Vote counting is underway between:

NuGOLD
Neutrino Galactic Observatory and Long baseline Detector

BISON
Black hills Illinois Supernova, Oscillation, and Nucleon decay detector

HND
Homestake Neutrino Detector

Which one do you like?

There are planty of technical design questions (a lot of fun too)  such as how one efficiently calibrates a 100 kton detector (size of just 1 of three modules!)?  What are the things that must be calibrated if we want to reliably answer above mentioned physics questions?

Generally, one can never calibrate too much to  better understand detector data, but what is the minimum, we wonder?

Since we will use water (most likely), it needs to be transparent – by hundreds of meters ! So there should be away that water clarity is checked regularly. Do organisms tend to grow in water?  Of course. Do they make water blurry?  Probably. So elaborate water purification system will be designed.

We may add gadolinium to water to get powerful neutron tagging ability (which I would really like to see happen since it opens doors for various several  MeV level physics). Will Gd stay in water? How do we put it back in after purification of everything else? We need to care about environment as well. So, more open questions…

On top of that we will need to get accurate timing and charge gain calibration for around 150,000 photomultiplier tubes (PMTs). Even at the speed of 10 per minute it would take a full month just for that (assume normal working days). We need to be clever.

And finally the part that I really like is calibrating detector energy scale – namely, when we gather all the PMT signals, we go back and figure out the energy of particle interaction that caused the signal. It is sort of like a detective game. We know when each PMT produced the signal and how big was it and then we trace back and figure out what particles and at what energy caused the signal and where in the detector it took place. Fun! As real detectives we first use the known (facts) which is calibration and based on it, figure out the unknown  which are all the other data collected from the PMTs. The first option for calibration are muons – they come in all energies from various direction, but it an uncontrolled fashion and no independent cross-check of their energy. One can build small accelerator and get fast electron of know energies to study detector nergy response. Part that we have started looking into are radioactive sources. Because it turns out that most of typical radioactive sources produce gammas and or other particles up to several MeV, but nothing above 10 MeV. And it is this reion of 10-20 MeV that would be really nice to understand well for supernova neutrnos. And getting a nice neutrino spectrum of fresh supernova would indeed be precious. So we started looking into fission fragments and if anything can be done with it. We may end up with some quite exsotic radioactive sources. Will keep you posted.

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Difficulty of defining oneself in one page

Tuesday, November 3rd, 2009

My student applied for Lindau fellowship last week and it took several iterations before his one page personal statement started to look more convincing and along the lines of what Lindau meeting organizers are looking for in their attendees.

By the way, Lindau meeting is an annual meeting with Nobel laureates every year that takes place in Lindau, Germany. This year the topics will be in physics, chemistry and related sciences. Another graduate student from Drexel attended the meeting 2 years ago and was thrilled with it. Highly recommended.

In the process of helping my student write his one page statement, it became strikingly obvious how difficult it is to express oneself effectively in one page, with strong arguments and without excessive words. Because saying that the Lindau is a great meeting and it would be great to go, will not do. That is common to everyone. On the other hand it is not easy to bring all the things from ones past that are significant, but seem unimportant and trivial because they have already been done. He ended with a pretty good statement and we’ll see if he gets selected. But one way or another, it was an excellent lesson in writing and bringing out the right facts and effective arguments that make the strong application.

Conclusion – it is all about practice and help from the more experienced once. More often you apply to various fellowships and grants the better you get. Ability to adequately explain scientific work and findings is no less important than the exciting science itself.

Recommendation – start early, apply to many places, and seek help and criticism from people around you.

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Discovering kindness

Tuesday, October 27th, 2009

The most peculiar thing happened to me on Saturday. Together with a bunch of my Double Chooz colleagues I waited for the train to arrive at the train station in Reims, France. We were coming back after the Double Chooz meeting. Since the train was delayed, I took a seat kindly offered by my DC colleague Maury and we started chatting about fun ways to explore Paris later that afternoon. I naively put my backpack next to me, but leaning forward to look closer at the map, the backpack ended behind my back. An that is when the thief seized the opportunity and took it. Everything really important for my trip was there – my passport, all of my documents, money and credit cards, my laptop, my cell phone and other minor things. In a few moments I realized that my backpack vanished! It was a horrific feeling. I was in shock for a moment. Maury and his wife Sharon started looking for it with me, but it was nowhere to be found. Still hoping that the thief may have just took the money and left the backpack laying around, I quickly went to the group of my colleagues to ask for help. Everyone started looking, but no luck. They were all very disturbed by the news. Guillaume and Michel asked at the information desk hoping it is there, but it was not. So, my last hope to find my documents at least was gone. I knew that I had to wait until Monday in Paris to get to the US embassy and ask for a new passport and I knew that I need a police report to show that the passport was stolen. I also knew that it will take several days to do it. It was bad. But  it would be much, much worse, if the kindness and care of my DC colleagues did not instantly start pouring on me. Maury gave me cash and offered to pay for my hotel stay in Paris. Guillaume took cash from the ATM machine and gave it to me. Both him and Michel offered to go with me to the police station to file a report, which I could never do by myself, since I do not speak French. Michel missed his train and a non-refundable ticket in order to help me with the police report. Thierry offered me to stay with his family in Paris until things get resolved and notified my husband back in US about the event. They all gave me their cell phone numbers and addresses to contact them in Paris if I need anything else. All this care and kindness that my collaborators showed HELPED immensely. Instead of feeling alone and desperate with no money, documents and place to stay, this looked like a solvable straightforward inconvenience that will just take a few extra days. AND THIS IS A DIFFERENCE THAT ONLY TRUE FRIENDS CAN MAKE! At that point I was not even seriously upset, and only thing that I still felt really bad about was the fact that my children Una and Luka will have to wait even longer to see mommy again in spite of my promise that they would see me in just one more day. Deceiving children is a very bitter feeling even when it is not your fault.

And then things turned around. While sitting in the police office and listening to Michel describing to the police officer the unfortunate event, and appreciating his presence even more (I understood almost nothing and police officer spoke no English at all), Michel’s phone rang. It was Guillaume calling from the train. He was just notified by the lady at the information desk at train station that my backpack was found with everything in it. We rushed back and it was there indeed! I was so happy and grateful that my lucky star shown on me that day so strongly. The rest of the afternoon, Michel and I spent in a pleasant chat while waiting for the next train to Paris.

In the end, the only way I can explain things is that all of my colleagues (10+ of them) looking for the backpack at once scared the thief and he decided to leave it rather than risking to get caught. I will never find out, but I do not wish to question my luck. I was so fortunate that day: fortunate to get all of my things back and fortunate to have such great friends and collaborators on Double Chooz  that  cared and helped me when it was really needed. It seems, that sometimes it takes being in trouble to discover all the greatness and kindness of the people  you know.

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Talking about neutrinos to non-physics women scientists

Thursday, October 22nd, 2009
Profile of the Earth seen by geo-neutrinos observed with KamLAND experiment
Profile of the Earth seen by geo-neutrinos   observed with KamLAND experiment

I just love public talks – to sparkle curiosity with our little neutrinos. These pople actually remind how cool is the particle I have been chasing for the last ten years.  It is definitely the coolest around – by my standards at least.

So I was invited to give a lecture to the AWIS (association of women in science). I sincerely support any e ffort that will promote women in science and that will help offset the gap created by  millenniums of   discrimination, but I was a bit reluctant to talk about neutrinos and geo-neutrinos to this group of mostly biologists and chemists (surprise, surprise! – this is where one can find women in science (not physics yet!)), involved in the cancer research, genetics and other areas that have very humane and direct applications. But, I decided to give my best and see what happens. And the weather did not help – it was a cold and rainy Thirsday night.

It was a very pleasant crowd of 30+.  I started after the dinner on slow note with some neutrino properties and neutrino fun trivia and emphasized harmless nature of neutrinos  (I have set this as sort of a personal goal: whenever I talk about neutrinos in public, I will make sure that everyone learns that neutrinos are harmless for humans and environment, even when coming as strong beams from accelerators and trveling thousands of kilometers). So far  so good! Everyone was happy to learn that neutrinos are no danger for health and they were wide awake after 10 slides at 7 pm at night. This encouraged me to go farther and I managed to show them the detection of geo-neutrinos and how we could get thousands of  geo-neutrinos with giant deetctors.

But there is an additional reson why this event deserves to end in this blog and these are the questions I was asked after the talk by the crowd that was pretty much clueless about neutrinos just one hour earlier!

Question 1 (chemist): “It bothers me with neutrinos – why did you look for them in the first place, when they are so difficult to observe. Were there unexplained points in the data? Wrong shape?”. So this woman just retold the whole Pauli neutrino story in front of my eyes.

Question 2 (biologist): “You said that neutrinos have no charge.  Then, how do you know that they are different from anti-neutrinos?” – Majorana here we come, ha!

Question 3(biologist): “You said that neutrinos do not change the direction and stream through the universe. Has anyone though about using them to learn about distant universe?” – here you go Ice Cube, Anaters, Nestor, Anita…

I was amazed how the fresh open minds can point in the write direction right away.

I felt really good even the whole next day. Enthusism can cary you far…

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Choosing a new name for an experiment and other things

Wednesday, October 21st, 2009

Exciting week behind me. Just after coming from South Dakota we had my son’s 2nd birthday party followed by a frantic week of preparation for the conference in Reims, France and reports for the Double Chooz Collaboration meeting in Reims, too. The wonderful events that made me even busier are 2 graduate students and one undergraduate that would like to do research in the neutrino physics group. I was thrilled but it also took time to explain them their projects. Alex is an undergraduate looking for a senior thesis project and I had a right thing for him. He will evaluate light concentrators for the LBNE DUSEL, first by simulation and then by building a prototype and testing. He likes project a lot. I think this will be a lot of fun and timeline of October to June seems realistic. As for the other two, Frank likes the idea about building his own light ray tracing simulation for LBNE, while Ally will do some simple software analysis to get her started. We’ll see how it works.

So I was also preparing a talk for the LowNu meeting in France and was in terrible doubt how detailed introduction should I make since the speaker before me was speaking on closely related issue with geo-neutrinos. I ended simply asking him a day before the presentation, we sorted things out and voila – it worked like a charm for both of us. There was no repetition of facts.
As an exercise I calculated the geo-neutrino event rate for LBNE (part of my talk) if it was filled with liquid scintillator and the numbers are huge! Thousands of events per year as opposed to 75 for 4 years in KamLAND! I love big detectors. Although LBNE will probably never be a liquid scintillator detector it felt good to see such a high event rate. Well, if they put enough PMTs inside and add some gadolinium, anything is possible.
On another note, the meeting in Reims is just wonderful. I met some very interesting people working on Borexino experiment and SNO. We had a wonderful dinner in a vine cellar from nineteenth century with 18 km of tunnels filled with unbelievable number of champagne bottles. What a place! They gave us a tour of the vine cellar, explained how they make their exquisite champagne that they export in more than 50 countries and then fed us like kings. The champagne was amazing and they served us a couple of kinds with dinner.

As for the blog title, it is about choosing a new name for LBNE. Although some people think that Long baseline Neutrino Experiment is a perfectly good name, a number of people think we should find something more catchy. I happen to agree – while the name shouldn’t be cheesy or dull, LBNE is really a boring name. There is a bunch of alternatives at:
https://wiki.bnl.gov/dusel/index.php/Proposed_Names

People couldn’t decide at the meeting, so we will vote by email on the narrow choice of three most popular once.
I can’t wait to see the results. Some of the names are BISON, nuGOLD, ANNIE, HOME, CANON…

I will let you know in the few weeks.
Cheers.
Tomorrow we will start a Double Chooz meeting. Everyone is getting anxious for two reasons: we will get data within 6 moths from now and we are competing not with two other experiments. I have never been in the science “race” before. It is interesting.

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Reflections – LBNE meeting at DUSEL

Thursday, October 8th, 2009

October 6, 2009

This is my first post and I am quite excited about it. I am an assistant level professor at Drexel University in Philadelphia. We study neutrinos, their properties, and especially features related to the fact that neutrinos oscillate – peculiar feature that we learned about more in the last decade. In short, neutrinos come in three different types that are clearly distinct from each other. Nevertheless, they oscillate between different types as they fly. And neutrinos, just to make it clear, always viz around close to the speed of light. Neutrino oscillations are as striking as if you would see an eagle soaring over the sky rapidly turn into a parrot, continue flying, then turn into a duck, and after more flying turn BACK into an eagle soaring in the sky! Neutrino oscillations also told us that neutrinos have mass, and even better, that they maybe hold the key to the question of why we have more matter than antimatter in the universe (and we know we have!). So it is a puzzle that many, many people would like to see solved. However, it is also a tough one, and luckily there are quite a few physicists that are on the enthusiastic quest for it. And as of recently, I am one of them too.

This year I got involved in the project called Long Baseline Neutrino Experiment (LBNE – boring name, but temporary; we are about to name it). Along looking to see if protons can decay (major prediction of Standard Model of particle physics) it will observe (detect) neutrinos and anti-neutrinos from various sources like: accelerator neutrinos and antineutrinos sent from Fermi lab 1300 km away (to search for neutrino-antineutrino asymmetry), neutrinos from the Sun, neutrinos and antineutrinos from galactic supernovae, neutrinos and antineutrinos from past supernovae streaming through our Universe and maybe even antineutrinos from the Earth. That is A LOT OF different neutrinos and it will be FUN, BUT we need to build our neutrino detector first.

So, I am just out of the meeting for the LBNE that is all about planning this giant 300 kton Water Cherenkov neutrino detector . It will be built in the abandoned old goldmine called Homestake in the town of Lead in South Dakota. 300 ktons is a lot of water and no one has ever built a water Cherenkov detector of this size. The largest up to date is SuperKamiokande water Cherenkov neutrino detector in Japan and that one is 30 kton (still huge, but significantly smaller). The detector is envisioned to be made out of three 100 kton tanks or maybe even two 150 kton tanks (take a look at the picture).

Long Baseline Neutrino Oscillation Experiment at Homestake mine in South Dakota

Long Baseline Neutrino Oscillation Experiment at Homestake mine in South Dakota

Did I mention that they will be placed very deep in the mine at 4850 feet (1479 m) depth? This is to use all the 1.5 km dirt above, as a sort of umbrella to shield the detector and get much fewer cosmic ray muons that interact in the detector and make it noisy. Just the size of the caverns one needs to place the detectors is enormous. A cavern that can fit a single tank needs to be 55 m high and around 60 m wide cylindrical hole (like a 20 floor high-rise building). So we need to dig out a total of 60 floors high buildings of rock! Therefore, at this meeting, there was a whole set of reports and plans presented how to excavate such large caverns, evaluate the rock hardness in the mine at that depth, make sure that there is enough electricity, air, working elevators, wide enough, completely vertical shafts and many of other things. Huge work! And expensive!

The whole plethora of detector elements and aspects of detector building were addressed. There were people talking about producing a neutrino beam at Fermi lab, small near to the beam detector, alternative liquid argon detector and accompanying details. There were more than 100 people at the meeting, while whole collaboration has more than 180 members which is huge for the neutrino experiment. But this time I will focus on one important part of Water Cherenkov detectors and these are PMTs, and also something that I got involved in.

To “see” neutrinos we will use very sensitive photomultiplier tubes (PMTs) that can observe a single visible photon that hits, and produce measurable electric signal on the order of mili volts. And here is a picture of one PMT.

Single photomultiplier tube

Single photomultiplier tube

Such sensitivity to light is crucial for us. Using a large number of PMTs mounted on detector walls, floor and ceiling and looking inward we can observe light coming from the particles interacting inside the detector to help us determine what type of particle interacted in the detector, how much energy it carried and where the interaction took place. In this way we detect neutrinos as well! For such huge detector modules we will need about 150,000 PMTs that are 25 cm (10 inch) in diameter. Not only that the PMTs are expensive, but that many PMTs will require 13,000 km of cables and accompanying electronic modules which makes it twice as much expensive. So is there a way around that? This is a question that my group at Drexel will try to answer. So, at the meeting we discussed using light concentrators which are basically non-imaging light collectors that gather the photons that would otherwise miss the PMTs. So, we can collect even more light or use fewer PMTs and keep the light level unchanged! Light concentrators look like bottomless, shallow, shiny metallic bowls that are placed on the PMT face (top part) to funnel the photons efficiently to the PMTs. So, we discussed how to optimize their shape, what to make them from and compare to experience of other experiments like SNO and Borexino where similar devices produced 50%-60% increase in light collection. It is promising that with a right design we can make a real difference. So, I am looking forward to some simulation work with my postdoc Karim and collaborators at Duke. I will also offer a new graduate student Frank to work on it since he expressed a strong preference to simulation work. We also choose materials and see if they can withstand ultrapure water that these kind of detectors use. A lot of interesting work ahead!

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