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Archive for October, 2015

@CMSVoices

Thursday, October 29th, 2015

Building on the success of rotating Twitter accounts like @realscientists, which I participated in last year, the CMS experiment has a new account: @CMSVoices.  The idea is that it’s an account for talking to CMS members and hearing about their day-to-day work, in contrast with the official news from the @CMSexperiment account.  Of course, you can already hear from many individual CMS physicists on Twitter (I’m normally @sethzenz), but the account gives you the chance to interact with a new person each month, and it might even help us get some new tweeters started!  I also tried to explain things in more detail and start some more general discussions, for example:

There weren’t too many discussions or too many followers so far, but we’re just getting started, and I’m looking forward to others taking the account over and seeing what the do with it.  The next holder of the CMSVoices account, starting in November, will be @matt_bellis.  Please welcome him next week, and let us know if you have any questions or ideas!

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marcy

Quel soulagement d’apprendre la semaine dernière que le prix Nobel de Physique 2015 récompensait la découverte des oscillations de neutrinos et non pas celle d’exoplanètes, des planètes à l’extérieur du système solaire. Non pas que cette découverte ne le mérite pas, bien au contraire, mais parce que plusieurs pressentaient que Geoff Marcy pourrait recevoir ce prix avec Michel Mayor et Didier Queloz.

Geoff Marcy, professeur à l’Université de Californie à Berkeley, fait les manchettes des journaux depuis une semaine non pas en raison de sa notoriété en tant qu’astronome mais bien parce qu’une enquête interne conduite par l’Université l’a trouvé coupable de harcèlement sexuel envers plusieurs de ses étudiantes à Berkeley entre 2001 et 2010 suite à une plainte déposée par quatre de ses anciennes étudiantes. Mais ce qui ressort en ce moment n’est que la pointe de l’iceberg, car son comportement déplacé remonte à une trentaine d’années, alors qu’il enseignait à San Francisco State University.

C’est là que je l’ai connu en 1985 alors que j’étais étudiante à la maîtrise et chargée de cours au département de Physique et d’Astronomie. Déjà, à cette époque, il était bien connu pour entretenir des relations avec plusieurs de ses étudiantes. Mais à mon avis, ce n’est pas le seul manque au chapitre de la déontologie dont Marcy peut s’enorgueillir.

En 1987, sa collègue dans la recherche d’exoplanètes s’est rendu compte qu’il lui avait remis une copie modifiée de leur demande de subvention conjointe. Sur sa copie à elle, leur deux noms apparaissaient: lui était investigateur principal et elle, sa co-investigatrice.  Mais la copie officielle de Marcy, celle qu’il avait soumis à l’agence de financement, ne portait que son nom à lui.

Elle dénonça ce subterfuge au directeur du département, qui la congédia sur le champ. Marcy était le plus prometteur de son département. Elle logea alors une plainte formelle pour inconduite professionnelle contre Geoff Marcy. Mais elle ne pu retrouver son emploi et quitta le domaine de l’astronomie. Dans la foulée de ces évènements, quelques personnes tentèrent d’attirer l’attention de la direction de SFSU sur le comportement inapproprié de Geoff Marcy auprès de ses étudiantes.

Le Code de Conduite de l’époque interdisait formellement aux professeurs d’entretenir des relations intimes avec leurs étudiantes. Nous n’avons malheureusement pu convaincre aucune de ces femmes de porter plainte contre Marcy. L’une d’elle me confia plusieurs mois plus tard qu’à l’époque, elle sortait avec Marcy et pensait que j’étais folle de vouloir porter plainte. Mais avec du recul, une fois la relation terminée, elle avait compris comment elle s’était fait avoir. A ma connaissance, Marcy fut simplement avisé par l’Université que son comportement enfreignait le Code de Conduite et qu’il devait cesser. Mais c’est malheureusement encore la solution retenue par l’Université de Berkeley même si Marcy a été trouvé coupable de harcèlement sexuel, et même si 22 de ses collègues réclament sa démission.

Cette situation dépasse pourtant de beaucoup les propos tenu par le Professeur Tim Hunt. Ce biologiste, médaillé Nobel, avait affirmé qu’il était difficile de travailler en laboratoire avec des femmes car elles pleuraient tout le temps.

Combien de femmes ont quitté les sciences à cause de Geoff Marcy ou un de ses semblables? Je me réjouis donc de voir que plusieurs astronomes (Katie Mack, Ruth Murray-Kay, John Johnson) osent dénoncer Marcy. Je me réjouis aussi de voir que malgré tout, plusieurs des victimes de Geoff Marcy, parmi celles qui ont osé parler et d’autres, sont désormais des astronomes réputées, loin de son emprise. Au lendemain de la journée Ada Lovelace, où on célèbrait les accomplissements des femmes en sciences, je salue la résilience et la détermination de ces femmes.

Pauline Gagnon

Pour recevoir un avis lors de la parution de nouveaux blogs, suivez-moi sur Twitter: @GagnonPauline ou par e-mail en ajoutant votre nom à cette liste de distribution. Vous pouvez aussi visiter mon site web.

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marcy

What a relief it was for me to hear last week that the Nobel Prize in Physics 2015 rewarded the discovery of neutrino oscillations and not exoplanets – planets outside the Solar system. Not that the discovery of exoplanets does not deserve it, on the contrary. But many people anticipated that Geoff Marcy could share the prize with Michel Mayor and Didier Queloz.

Geoff Marcy, an astronomy professor at the University of California Berkeley, makes the headlines right now not because of his fame as an astronomer but rather because an internal University investigation found him guilty of sexual harassment against several of his female students at Berkeley between 2001 and 2010 after four of his former students filed a complaint. But I suspect that what has come out so far is only the tip of the iceberg. His inappropriate behaviour goes back a good thirty years, when he was teaching at San Francisco State University.

This is where I met him in 1985 when we both worked in the Physics and Astronomy Department while I was a Master’s student and a lecturer. It was well known that he had intimate relationships with several of his female students. But it is not the only aspect where I felt Marcy’s ethics were questionable.

In 1987, Marcy’s colleague in the search for exoplanets realized that he had handed her a revised copy of their joint grant proposal. On the copy Marcy had given her, both their names appeared, his as main investigator and hers, as co-investigator. But Marcy’s official copy, the one he had submitted to the funding agency, bore only his name.

She reported this to the department head, who fired her on the spot. Marcy was the rising star of his department. She then filed a formal complaint for professional misconduct against Marcy. But she was unable to recover her position and she left the field of astronomy. Following these events, a few people tried to draw the University’s attention to Geoff Marcy’s inappropriate behaviour with his female students.

The Code of Conduct at the time strictly forbade professors to engage in intimate relationships with their students. We were unfortunately unable to convince some of the women to lodge a complaint against him. One woman told me several months later that at the time, she was dating Marcy and thought that I was crazy to want to file a complaint. But with hindsight, once the relationship had ended, she understood how she had been had. To my knowledge, Marcy was simply notified by the University that his behaviour violated the Code of Conduct and that it had to stop. Unfortunately, this is again the option chosen by UC Berkeley, even though he was found guilty of sexual harassment and even though 22 of his colleagues are now asking for his dismissal.

This situation is far in excess of the comments made by Professor Tim Hunt who had to resign from University College London. This biologist, a Nobel laureate, had asserted that it was difficult to work in a laboratory with women because they cried all the time.

How many women left science because of Geoff Marcy and the like? I am so delighted to see many astronomers (Katie Mack, Ruth Murray-Kay, John Johnson) dared to denounce him. I am also pleased to see that despite the abuse they sustained, several of Geoff Marcy’s victims, some who dared speak up, some who feared to, are now well-established astronomers far from his influence. Yesterday was Ada Lovelace Day, a time to celebrate the accomplishments of women in science. It’s a great opportunity to salute the resilience and determination of these women.

Pauline Gagnon

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A measurement to watch

Monday, October 12th, 2015

This article appeared in symmetry on Oct. 7, 2015.

Finding a small discrepancy in measurements of the properties of neutrinos could show us how they fit into the bigger picture.

Finding a small discrepancy in measurements of the properties of neutrinos could show us how they fit into the bigger picture.

Physics, perhaps more so than any other science, relies on measuring the same thing in multiple ways. Different experiments let scientists narrow in on right answers that satisfy all parties—a scientific system of checks and balances.

That’s why it’s exciting when a difference, even a minute one, appears. It can teach physicists something about their current model – or physics that extends beyond it. It’s possible that just such a discrepancy exists between a certain measurement of neutrinos coming out of accelerator experiments and reactor-based experiments.

Neutrinos are minuscule, neutral particles that don’t interact with much of anything. They can happily pass through a light-year of lead without a peep. Trillions pass through you every second. In fact, they are the most abundant massive particle in the universe—and something scientists are, naturally, quite keen to understand.

The ghostly particles come in three flavors: electron, muon and tau. They transition between these three flavors as they travel. This means that a muon neutrino leaving an accelerator at Fermi National Accelerator Laboratory in Illinois can show up as an electron neutrino in an underground detector in South Dakota.

Not complicated enough for you? These neutrino flavors are made of mixtures of three different “mass states” of neutrinos, masses 1, 2 and 3.

At the end of the day, neutrinos are weird. They hang out in the quantum realm, a land of probabilities and mixing matrices and other shenanigans. But here’s what you should know. There are lots of different things we can measure about neutrinos—and one of them is a parameter called theta13 (pronounced theta one three). Theta13 relates deeply to how neutrinos mix together, and it’s here that scientists have seen the faintest hint of disagreement from different experiments.

Accelerators vs. reactors

There are lots of different ways to learn about neutrinos and things like theta13. Two of the most popular involve particle accelerators and nuclear reactors.

The best measurements of theta13 come from nuclear reactor experiments such as Double Chooz, RENO and Daya Bay Reactor Neutrino Experiment based in China (which released the best measurement to date a few weeks ago).

Detectors located near nuclear reactors provide such wonderful readings of theta13 because reactors produce an extremely pure fountain of electron antineutrinos, and theta13 is closely tied to how electron neutrinos mix. Researchers can calculate theta13 based on the number of electron antineutrinos that disappear as they travel from a near detector to the far detector, transforming into other types.

Accelerators, on the other hand, typically start with a beam of muon neutrinos. And while that beam is fairly pure, it can have a bit of contamination in the form of electron neutrinos. Far detectors can look for both muon neutrinos that have disappeared and electron neutrinos that have appeared, but that variety comes with a price.

“Both the power and the curse of long-baseline neutrino oscillation is that it’s sensitive to all of neutrino oscillation, not just theta13,” says Dan Dwyer, a scientist at Lawrence Berkeley National Laboratory and researcher on Daya Bay.

With that in mind, we come to the source of the disagreement. The results coming out of accelerator-based experiments, such as the United States-based NOvA and Japan-based T2K, see just a few more electron neutrinos than researchers would predict based on what the reactor experiments are saying.

“The theta13 value that fits the beam experiments, that really describes how much electron neutrino you get, is somewhat larger than what Daya Bay, RENO and Double Chooz measure,” says Kate Scholberg, professor of physics at Duke University and researcher on T2K. “So there’s a little bit of tension.”

Many grains of salt

Data coming out of the accelerator experiments is still very young compared to the strong readings from reactor experiments, and it is complicated by the nature of the beam. No one is jumping on the discrepancy yet because it can be explained in different ways. Most importantly, the accelerator experiments just don’t have enough information.

“We have to wait for T2K and NOvA to get sufficient statistics, and that’s going to take a while,” says Stephen Parke, head of the Theoretical Physics Department at Fermilab. Parke, Scholberg and Dwyer all estimated that about five more years of data collection will be required before researchers are able to start saying anything substantial.

“There’s been a lot of pressure on Daya Bay to try to eke out as precise a measurement as we possibly can,” Dwyer says. “Every bit of increased precision we provide further improves the ability of NOvA and T2K and eventually [proposed neutrino experiment] DUNE to measure the other parameters.”

Finding meaning in neutrinos

If the accelerator experiments gather more data and if a clear discrepancy emerges—a big if—what does it mean?

Turns out there are lots of reasons to love theta13. It’s one of the fundamental parameters that can define our universe. From a practical standpoint, it helps design future experiments to better understand neutrinos. And it could help physicists learn something new.

“We don’t expect things not to agree, but we kind of hope that they won’t,” says André de Gouvêa, professor of physics at Northwestern University. “It means that we’re missing something.”

That something could be CP violation, evidence that neutrinos and antineutrinos behave differently. CP violation has never been seen in neutrinos before, but if researchers observed it with accelerator experiments, it could help explain why our universe is made of matter rather than equal parts of matter and antimatter.

Figuring out if CP violation is occurring means nailing down all of the different neutrino mixing parameters, which in turn means building more powerful, next-generation experiments such as Hyper-K in Japan, JUNO in China and the Deep Underground Neutrino Experiment in the United States. DUNE will build on oscillation experiments like NOvA but will be able to better separate background noise from neutrino events, see a broader energy spectrum of neutrinos and find other neutrino characteristics.

DUNE, which will be built in a repurposed gold mine in South Dakota and detect neutrinos passed 800 miles through the Earth from Fermilab in Illinois, will be one of the best ways to see CP violation and rely on expertise gained from smaller neutrino experiments.

“Developing these types of experiments is very complicated,” de Gouvêa says. One of the major challenges of physics experiments is making sure you are measuring what you think you are measuring. “That’s part of the reason why we have a significant number of neutrino oscillation experiments.”

Ultimately, the neutrino puzzle is still missing many pieces. A variety of experiments are ramping up to fill in the gaps, making it an exciting time to be a neutrino physicist.

“We have to untangle the mysteries of the neutrino, and it’s not easy,” Parke says. “The neutrino doesn’t give up her secrets very easily.”

Lauren Biron

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Nobel Prize in Physics 2015

Tuesday, October 6th, 2015

So, the Nobel Prize in Physics 2015 has been announced. To much surprise of many (including the author), it was awarded jointly to Takaaki Kajita and Arthur B. McDonald “for the discovery of neutrino oscillations, which shows that neutrinos have mass.” Well deserved Nobel Prize for a fantastic discovery.

What is this Nobel prize all about? Some years ago (circa 1997) there were a couple of “deficit” problems in physics. First, it appeared that the detected number of (electron) neutrinos coming form the Sun was measured to be less than expected. This could be explained in a number of ways. First, neutrino could oscillate — that is, neutrinos produced as electron neutrinos in nuclear reactions in the Sun could turn into muon or tau neutrinos and thus not be detected by existing experiments, which were sensitive to electron neutrinos. This was the most exciting possibility that ultimately turned out to be correct! But it was by far not the only one! For example, one could say that the Standard Solar Model (SSM) predicted the fluxes wrong — after all, the flux of solar neutrinos is proportional to core temperature to a very high power (~T25 for 8B neutrinos, for example). So it is reasonable to say that neutrino flux is not so well known because the temperature is not well measured (this might be disputed by solar physicists). Or something more exotic could happen — like the fact that neutrinos could have large magnetic moment and thus change its helicity while propagating in the Sun to turn into a right-handed neutrino that is sterile.

The solution to this is rather ingenious — measure neutrino flux in two ways — sensitive to neutrino flavor (using “charged current (CC) interactions”) and insensitive to neutrino flavor (using “neutral current (NC) interactions”)! Choosing heavy water — which contains deuterium — is then ideal for this detection. This is exactly what SNO collaboration, led by A. McDonald did

Screen Shot 2015-10-06 at 2.51.27 PM

As it turned out, the NC flux was exactly what SSM predicted, while the CC flux was smaller. Hence the conclusion that electron neutrinos would oscillate into other types of neutrinos!

Another “deficit problem” was associated with the ratio of “atmospheric” muon and electron neutrinos. Cosmic rays hit Earth’s atmosphere and create pions that subsequently decay into muons and muon neutrinos. Muons would also eventually decay, mainly into an electron, muon (anti)neutrino and an electron neutrino, as

Screen Shot 2015-10-06 at 2.57.37 PM

As can be seen from the above figure, one would expect to have 2 muon-flavored neutrinos per one electron-flavored one.

This is not what Super K experiment (T. Kajita) saw — the ratio really changed with angle — that is, the ratio of neutrino fluxes from above would differ substantially from the ratio from below (this would describe neutrinos that went through the Earth and then got into the detector). The solution was again neutrino oscillations – this time, muon neutrinos oscillated into the tau ones.

The presence of neutrino oscillations imply that they have (tiny) masses — something that is not predicted by minimal Standard Model. So one can say that this is the first indication of physics beyond the Standard Model. And this is very exciting.

I think it is interesting to note that this Nobel prize might help the situation with funding of US particle physics research (if anything can help…). It shows that physics has not ended with the discovery of the Higgs boson — and Fermilab might be on the right track to uncover other secrets of the Universe.

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Nobel Week 2015

Monday, October 5th, 2015

So, once again, the Nobel week is upon us. And one of the topics of conversations for the “water cooler chat” in physics departments around the world is speculations on who (besides the infamous Hungarian “physicist” — sorry for the insider joke, I can elaborate on that if asked) would get the Nobel Prize in physics this year. What is your prediction?

With invention of various metrics for “measuring scientific performance” one can make some educated guesses — and even put the predictions on the industrial footage — see Thomson Reuters predictions based on a number of citations (they did get the Englert-Higgs prize right, but are almost always off). Or even try your luck with on-line betting (sorry, no link here — I don’t encourage this). So there is a variety of ways to make you interested.

My predictions for 2015: Vera Rubin for Dark Matter or Deborah Jin for fermionic condensates. But you must remember that my record is no better than that of Thomson Reuters.

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