Ukraine, Russia and Astrophysics

My posts about scientists' response to the Russian invasion of Ukraine have been mostly focused on particle physics, since CERN has notably struggled to craft an appropriate response.  Nowhere else is the conflict between science as a driver of international cooperation, and the need to stand up against an immoral invasion so stark.    

But, other physicists have also faced conflicts over this.  In high-energy neutrino astrophysics, there was less collaboration between Russian and Western scientists, but there were still many discussions about appropriate responses.  

IceCube had no members whose primary affiliation was Russian.  Two IceCube physicists had secondary affiliations with Moscow Engineering Physics Institute, but they both dropped these connections shortly after the invasion.   

The Baikal-GVD experiment (in Lake Baikal) was almost entirely Russian collaborators.  Some long-time collaborators from what used to be East Germany dropped out.   Both the Baikal-GVD and IceCube responses were made relatively quietly. 

In contrast, the mostly-European KM3NeT collaboration (building two arrays in the Mediterranean) has taken a public stance.  They have had Russian collaborators in past years, but do not appear to do so now.  Nevertheless, they made a clear statement to #StandwithUkraine, suspending all institutional cooperation with science organizations in Russia.   Their statement, highlighted on their main web page is nicely nuanced, continuing "We deeply believe that science is to serve peace and understanding, and we therefore leave private communication channels open to our colleagues with Russian affiliation, of whom many have stood up against the war." 

 

 Photo: a KM3NeT string, waiting for deployment.  Credit: KM3NeT Collaboration.

 

The Global Neutrino Networks newsletter, edited by Christian Spiering (from DESY-Zeuthen, near Berlin)  has done a very nice job of covering the astrophysicists response to the Russian invasion.  Back issues of the newsletter are available here.

CERN and Russia break up

 At this week's meeting, the CERN Council did what many people expected: effectively ejected Russia and Belarus.  This was done somewhat more softly than had been expected, since, rather than acting immediately, the Council would not extend their cooperation agreements when they expire in 2024.   This was a compromise, since many people had been pushing for faster action.   2024 is far off.   The statement was accompanied by the expected text denouncing the Russian invasion, but it still seems like an attempt to put off any real action.   

It will also not solve the authorship problems faced by the large LHC Collaborations (and likely by smaller groups), where some European funding agencies (most notably the Germans and the Poles - see my previous posts) have told their grantees to stop collaboration with Russian institutions.   And, of course Ukrainian scientists are generally doing this of their own volition.  There may have been some quiet agreement with the European funding agencies, but this will still feel like a slap in the face to the Ukrainian scientists who work at CERN.   As I noted in a previous post, I have enormous sympathy for my Russian colleagues, many of whom expressed their opposition to the war when they could legally do so.  But still, if it comes down to a decision between accommodating scientists from the invaded country or those from the invaders country, my sympathy is clearly with the invaded country.  

On the other hand, scientific ethics require giving appropriate scientific credit to the people who did the work. In large collaborations, this is rule-based - when you join an experiment you have to contribute a certain amount of service work (work to keep the experiment running), take data-collection shifts, etc., and, after a certain amount of time, you are added to the author list for all papers, along with 900-3,000 of your closest colleagues.   For example, the ALICE experiment (at the LHC) experiment rules are available here.  Usually, 6 months or a year after you leave the collaboration, you are removed from the author list.   Neither the general principles of scientific ethics nor these collaboration-based rules contain exceptions for cases when the workers employers behave unacceptably. 

Authorship questions are likely to come up again as the CERN Council decision rattles down to the four LHC experiments, who will need to decide how to handle their author lists.   This will also likely result in a compromise of some sort.  One possibility which I like would be to list the scientists from Russian institutions on the author list, but not list their institutional affiliations. 

Reactions to Ukraine from the world of science

The Russian invasion of Ukraine has now continued for more than two months, and no end is in sight.  Instead of ending the war on May 9th, Putin seems likely to expand it.   'Wait and see' is becoming increasingly untenable.  Two main paradigms drive scientific worlds responses to the invasion:

One paradigm, followed by most of the Western world, is that the Russian invasion is a brutal unprovoked attack that must be punished; we should not associate with the attackers.  Continuing scientific cooperation is 'business as usual,' tantamount to ignoring the invasion.

The second paradigm is that international science is an important way to maintain lines of communication and cooperation.  Maintaining scientific interchange is important for the scientists involved, and keeps the other side from being a nameless, faceless entity.   In the long term, this might influence governments to be less antagonistic toward each other.  

There are of course many slightly more nuanced approaches, mostly focused on punishing the relevant governments and government entities, while protecting the individual Russian and Belarusian scientists to the extent possible.

Both of these approaches have much merit, but they point in different directions.  Different scientists and scientific organizations have emphasized these two paradigms differently.   My personal view is that where they conflict, I will support the invadees over the invaders, and support the Ukrainian point of view, which is clearly that this is not a time for business as usual.  This approach has limits - scientific contact during the cold war clearly had significant benefits for all, but the invasion of Ukraine seems closer to Hitler in 1938 than the cold war.

Germany's Facility for Antiproton and Ion Research (FAIR) has condemned the invasion, and suspended all cooperation with Russian institutions, even at a cost of a several year delay in their new accelerator.    The CALICE Collaboration (a coalition that is developing new methods of calorimetry for high-energy physics experiments) has issued a similar condemnation, suspending Russian institutions from the Institution Board, prohibiting CALICE presentation by scientists from Russian institutions, and also banning CALICE presentations at conferences in Russia.  

Other large projects have taken much less action.  For example, the International Thermonuclear Experimental Reactor (ITER) has not visibly reacted to the invasion.   Similarly, U. S. Dept. of Energy laboratories have not said anything, although some experiments involving both Russian and European collaborators have had intense discussions about the way forward. 

As noted below, CERN has taken a somewhat middle view, issuing a statement of solidarity with Ukraine, suspending much cooperation with Russia, and, although not expelling Russian scientists, stopping new collaboration with Russia.  Further action may be taken at the next CERN Council meeting in June, possibly including expelling Russia.    This would be a major shift for CERN, since it was founded to improve cooperation in Europe in the aftermath of World War II - exactly per the second thrust above.

None of these decisions deal explicitly with scientific authorship for work that is already complete, or largely complete.  Scientific ethics rules require giving authorship credit to the people who did the work.   These rules do not include exceptions for changing rules from funding agencies that require (in the case of Germany, Poland and Finland, at least) an immediate end to collaboration.  

For now,  the large CERN LHC collaborations are posting their papers on the Cornell arXiv, authored by 'the XXX Collaboration', without individual names.  This may buy time, but it is not a long-term solution, since author lists are required before the papers are published in scientific journals.   Some papers from smaller collaborations have come out listing Russian authors, but without their Russian institutional affiliation.   To me, this seems like the least bad solution to a very difficult solution - we properly recognize the work of our Russian colleagues, but avoid giving credit to the institutions that are on record as supporting the war.

 

 

Science in the age of Ukraine: update

 One additional item regarding Russian involvement in world science:  According to a tweet by Robyn Dixon,  the Moscow Bureau Chief of the Washington Post, Russia has now barred university staff from publishing in international (presumably non-Russian) scientific journals or attending international conferences. 

If this is enforced, this will essentially bar all collaborative publications, since I can't imagine non-Russians being willing to publish in Russian journals.  All of the LHC experiments (and many many other international collaborations) have a long pipeline of papers at various stages in the analyzing/writing/editing/publication process.  What will happen to these papers?    

There may be a precedent from the height of the cold war, when the West and the Soviet Union had parallel journal structures, and cross-publishing was uncommon.   A. B. Migda published his' 1956 quantum mechanical calculation of Landau-Pomeranchuk-Migdal suppression of bremsstrahlung and pair production  in both the American Physical Review and the Soviet Doklady Akad Nauk SSR.  Now, the Physical Review article is well known and  still heavily cited, while the Doklady Akad Nauk SSR article is mostly forgotten.  

If all better solutions fall through, one could imagine a solution where the Russian part of a collaboration publishes a result in Russian journals, while the Western part publishes in a Western journal.   I am sure that many readers will be slightly outraged by this idea.  I do not claim that it is a good idea, but it may be the least-bad route forward if the Russian-Western estrangement drags on for longer than different collaboration can hold off on publications in the hope that the author list problem will resolve itself.

Science in the age of Ukraine

 

Watching the news the past two weeks has been difficult – the scenes from Ukraine are reminiscent of World War II, and the brutal unprovoked invasion by Putin’s Russia has few parallels in more recent history.     The one bright spot has been the U. S. and international reaction, where a consensus in support of Ukraine has developed, coupled with an active resupply of weapons and strong sanctions on Russia. 

 

The Russian invasion also affect science.  Science is international, and most large collaborations include Russian and/or Ukrainian colleagues.    Naturally, there has been much talk about if/how to sanction Russian scientists, with many groups favoring their immediate ouster. 

 

Many of these scientific collaborations are long-standing.  The ALICE Collaboration (of which I am a member) at CERN’s [in English: European Organization for Nuclear Research] Large Hadron Collider has roots that go back more than 20 years, and much of the data now being published was taken in the mid 2010’s, with significant Russian involvement in both detector construction, data taking, and calibration and software.   The analysis connected with a single paper typically extends over more than a year, and involves people from multiple institutions.  

 

When a paper is written, there are clear standards for the required level of involvement to merit authorship.   This is true in both the broader scientific world, and, with more specific standards, within ALICE and other large collaborations.   Omitting deserving contributor from the author list can be considered either scientific misconduct (failing to give credit) or plagiarism (if the contributed actually wrote some of the text).   Per these rules, is unethical to rob Russian scientists of scientific credit for the work that they have done.

 

But, people are rightly outraged by Russian behavior. Ukrainian scientists very rightfully do not want to collaborate with Russian scientists, and have called for Russia’s ouster from CERN.  Some European funding agencies have banned collaboration with Russian authors, including joint publications. This extends to scientific journal operations.

 

On the other hand, during the first ~ week of the war, before it became illegal for them, many Russian scientists spoke out against the war. It feels wrong to sanction people who spoke up, at some personal risk.   Now, the scientists have been forced into silence, and their institutions are speaking out in favor of the invasion.   So, one goal would be to sanction the institutes, but not individual scientists.  This is unfortunately easier said than done.

 

Finding the right direction is not easy.  CERN, and most other international organizations) took no action during previous Russian invasions, such as Hungary in 1956, Czechoslovakia in 1968, Afghanistan in 1979 or Crimea and Donbass in 2014. The CERN Council recently decided to suspend Russia’s status as an observer at CERN.  They are not currently ousting the Russian scientists who are already working at CERN, but are also not expanding any ties.  This was clearly an attempt to find a middle ground, and it may be suitable short-term.    Other organizations have taken a range of actions, ranging from nothing (at least so far, such as International Thermonuclear Experimental Reactor (ITER)) to suspending Russian membership (Nuclear Physics European CollaborationCommittee (NuPECC)).  And, many institutions are taking steps to support their Ukrainian colleagues who have been affected by the invasion. 

 

Medium and long term, this solution is not enough, due to some nagging problems. One involves publications.   If Ukrainians and other European scientists will not or cannot (due to funding restrictions) publish with Russians, what do we do with ready-for-submission manuscripts with authors from both groups?   It seems wrong to drop the Russian authors, and at least equally wrong to let the presence of Russian authors keep other scientists from signing these papers.     So, what to do?  One possibility that has been circulating would be to allow the Russian authors to sign the papers, but as individuals, without their Russian institutional affiliations.  Whether that will satisfy everyone remains to be seen. 

 

Disclaimer:  The opinions expressed here are solely my own, and do not represent my employer or any other institutions or collaborations.  

 

Do sterile neutrinos exist?

Sterile neutrinos are among the most intriguing BSM (beyond-standard-model) ideas around, with a long history of data hinting that something unusual is going on.  The idea that neutrinos might oscillate into  a new type of invisible (or nearly invisible) neutrinos has attracted much theoretical interest, along with a large number of experiments.  Unfortunately, even after 25 years of study, we still don't know if sterile neutrinos exist or not.

The  sterile neutrino story starts in the mid 1990s, when the LSND (liquid Scintillator Neutrino Detector) studied neutrinos produced by the decay-at-rest of pions from LAMPF (the Los Alamos Meson Production Facility).  They observed a significant excess of electron-flavored neutrinos (henceforth electron-neutrinos) over the expectations.   The excess could naturally be explained via neutrino oscillations, but the oscillation parameters required to explain the data were inconsistent with the known neutrino masses and mixing.   It could, however, be explained by positing a fourth neutrino flavor (beyond those connected with the electron, muon and tau leptons).   These models are sometimes called 3+1 models, denoting three conventional neutrinos plus one sterile neutrino.

 The result was immediately controversial, even within the LSND collaboration. The concern was that there could be some type of unmodelled background, such as neutrons sneaking into the detector.    The KARMEN experiment at Rutherford Appleton Laboratory (in England) searched for similar oscillations, but did not find anything anomalous.

LSND was followed by the MiniBoone experiment at Fermilab, which ran from 2002 to about 2008.  MiniBoone was designed to confirm or refuse the LSND excess.  Unfortunately, it also found an anomalous result, but one which was in some tension with the LSND result, at least within a 3+1 model.; their 2013 paper used the phrases 'have some overlap with' and 'marginally compatible.'  This led to a profusion of more complex models, with a 3+2 model, with two sterile flavors gaining some popularity.   Of course, one expects that a model with more free parameters to do a better job of fitting the data.  Models with unstable (decaying) sterile neutrinos were also proposed.  

By now, a good number of experiments were in position to search for sterile neutrinos.  Unfortunately, they found a wide spectrum of results, with some favoring sterile neutrinos, and some not.   IceCube was in the latter category, reporting results consistent with the standard model.

There were also dedicated experiments, most notably MicroBoone at Fermilab.  MicroBoone is a liquid argon time projection chamber, a follow-on to MiniBoone.   The collaboration recently released their results late this year, with four analyses (of the same data) finding that their data was consistent with the standard model.   

Of course, many theorists have pointed out ways that the MicroBoone null results could be compatible with the previous LSND and MiniBoone positive results.  So, we still don't really know if sterile neutrinos exist or not.  However, MicroBoone is a strong experiment, designed to avoid MicroBoone's weak spots (e. g. the ability to distinguish photons and electrons).  It did not, however, cover exactly the same range of parameters that MiniBoone did.   It would be a bit of a coincidence that nature provided sterile neutrinos with the right characteristics to elude MicroBoone.  So, although sterile neutrinos are not impossible, but they seem less likely than they did on New Years Day in 2021.

Seeing antineutrinos in a new way - the Glashow resonance

 Recently, IceCube made its first definitive observation of an antineutrino, as it interacts with an atomic electron.  The result was published in Nature, and is now available publicly on the arXiv preprint server, as arXiv:2110.15051.

The reaction is very different from the usual Deep Inelastic Scattering interactions, where a neutrino or antineutrino interacts with an atomic nucleus.   In this process, known as the Glashow Resonance, an antineutrino and an electron annihilate each other, producing a W boson, as is shown in the diagram to the right     The W boson is heavy (weighing about 85 times the mass of a proton), so it decays essentially immediately, usually into a quark and an antiquark which then fragment producing two jets of particles. In IceCube, this leads to a cascade of particles, which looks like (nearly) a point source of light.   For antineutrinos with the right energy (about 6.3 PeV), the interaction probability is very high - antineutrinos near the peak of the Glashow resonance only have a range in ice of about 100 km, only about 1% of the range for neutrinos of the same energy.

This reaction is of great interest because it only happens with antineutrinos.  Its not a big surprise that there are astrophysical antineutrinos, but it is nice to have clear confirmation.  Later, with enough statistics (this will take a while), we can measure the neutrino:antineutrino ratio, which will tell us something about how the neutrinos are produced.  

 

There were some interesting technical aspects of the event.  The event display (above) shows a large cascade near the edge of the instrumented volume.   In fact, the most likely location of the actual interaction is outside the detector, but close enough that we can reconstruct it well.   However, closer examination shows some interesting features.  

The bottom two parts of the graphic show the signals recorded in two of the optical modules, as a function of time.  The blue curves show the expected light profile from a pure cascade at the reconstructed interaction point.  The red curves show unexpected 'early' light.   We believe that this light came from muons produced in the cascade.  

The muons travelled at nearly the speed of light, while the light moves more slowly.  This may sound surprising but in dense materials like ice, the light interacts with the medium (one way to think about is as if the light bounces around as it moves), and so only moves at about 3/4 of the speed of light.  So, the muons will reach the vicinity of the optical sensors first, emitting early light which will reach the sensors before the light from the rest of the cascade.   This early light signals the presence of muons, which show that the cascade was a hadronic shower, rather than purely electromagnetic.  So, the cascade was not due to an electron-neutrino charged-current interaction.  By eliminating the electron-neutrino hypothesis, we strengthen the case that this is indeed the Glashow resonance.  Which, in turn, strengthens the case that we have observed an antineutrino.