by Mark Bowen
Although Francis doesn’t remember that exchange, he points out that phenomenologists often know what is needed from a measurement better than experimentalists do: “I mean, I knew what data I needed.… Nygren knew how to get it.”
Jakob and Claudio went to an astonishing level of detail: They used the properties of the ice that had been elucidated by Buford Price’s group—and even the properties of the refrozen ice in the holes around the DOMs!—to simulate how light would have traveled to each of them. They used the waveforms at every single DOM that was involved in an event—354 in Ernie’s case—and rotated hypothetical showers around in every possible direction until they found the one that gave the best match to the multitude of pulse shapes. In the end, they could nail down the direction of a cascade to within about ten degrees—nowhere near as good as a muon track, which they could resolve to less than half a degree, but still very helpful.
This effort also gobbled up an impressive amount of computer time. Technology had long since left the Cray supercomputers in Berkeley behind. The current state of the art was the so-called Linux cluster, a bank of personal computers, aka central processing units or CPUs, running on the Linux operating system. After they had determined the directions of the twenty-one cascades, Claudio looked into the “cluster statistics” and found that they had used about sixty-two CPU-years’ worth of computing time—three years for each event! In other words, it would have taken that long if the calculations had been carried out on one computer. Since the computers in the cluster worked in parallel, it only took only a couple of weeks to a month.
* * *
In mid-February 2013, they un-blinded the times and hence directions to produce their first-ever map of the extraterrestrial neutrino sky. It looked as though there were “hot-spots”—hints of point sources.
Francis, Albrecht, and the then spokesperson of the collaboration, Maryland’s Greg Sullivan, had scheduled a phone conference with their NSF managers to discuss an important but mundane funding issue. When they shared the news, they were summoned to Washington. (The NSF folks were greatly relieved: they had two multi-hundred-million-dollar projects going at the time, the other being LIGO, and neither had much to show for it.) It was over a wine-infused dinner on the evening of the meeting, evidently, that the bureaucrats and scientists together decided to fast-track a letter to Nature. (It might have been Francis who mooted the idea: he had asked Nathan to begin drafting such a letter about a month earlier.)
It wasn’t a bad idea. The results were important, perhaps explosively so, and the news had already snuck out. Outsiders and popular science magazines had begun inquiring by e-mail, and theorists, a febrile lot, tend to jump on every new experimental result. Several had revealed Nathan’s “non-discovery” of GRB neutrinos on the arXiv before the Cubists had announced it themselves. They didn’t want to be scooped again.
The next morning (too early perhaps, considering the excitement and wine of the previous evening) Greg informed the rest of the collaboration of a plan to submit a letter within one or two weeks and get it published, hopefully, within a month. Unfortunately, he neglected to include a draft.
Panic ensued. E-mails flew. Even the proposed title, “Evidence for Extraterrestrial Sources of High-Energy Neutrinos,” provoked heated arguments—“sources” being the main sticking point. Not far below the surface, there was not only fear but considerable resentment. There were now about 220 people in the collaboration, many of whom had no idea what had been going on in Madison. Some suspected they were being sold a bill of goods by the “Evil Empire.” Some had petty personal concerns like getting tenure or their next round of funding. Some (the usual suspects) were so fundamentally pessimistic that they would never be convinced. And some, to be honest, couldn’t understand it all, even when it was explained to them. But most simply wanted the time to review the paper thoroughly and carefully, which was undoubtedly a good idea.
The dark cloud hanging over this drama was the knowledge that several years earlier, the Pierre Auger collaboration, which ran an enormous cosmic ray detector in western Argentina, had announced to great fanfare that they were 99 percent sure they had found the source of ultrahigh-energy cosmic rays: active galactic nuclei—and had then had to retract their claim when more data, that is, better statistics, washed their preliminary finding away.
The veneer of bureaucracy notwithstanding, when it got right down to it, IceCube was as anarchistic as AMANDA was. They still worked by consensus. Everyone had to agree—or at least not disagree too strenuously—before the new results could go public. And that meant there was plenty of emotion involved. People needed to be heard.
Francis did not engage in argument. He worked behind the scenes, pulling from the front end, while numerous others dug in their heels and dragged along behind. “This is the real thing, except to some of us of course who fear that a discovery may affect their lifestyle,” he wrote to me on the day of Greg’s announcement. “I showed our results privately to a friend at Goddard [Space Flight Center in Maryland] today. She had no doubt about what she was seeing. This is a vicious loop when you are conservative. The next step is that you can never see anything. No matter how you turn this, it is a discovery.”
He may have been overcorrecting a bit on the positive side, but that was his role. The skeptical role was also important, and beneath his frustration he knew that. IceCube was also in the luxurious position of having no competition, so there was no need to hurry.
Luckily, they had a steady hand in the chair of their publications committee, Olga Botner, who had been Kurt Woschnagg’s doctoral adviser in Uppsala before both had migrated from the accelerators to what was then AMANDA. Olga had been a force of quiet reason in the collaboration ever since she’d joined in 1998. Not only does she possess a formidable intelligence, she strikes a good balance between optimism and conservatism, she’s soft-spoken, she exudes trustworthiness, and she’s had plenty of experience. She sits on the Nobel physics committee. Also, and appropriately at this important moment, this capable and self-effacing woman was elected spokesperson of the collaboration less than a week after Greg’s announcement, although he remained in the post for the time being.
She and Francis worked together to tamp down the noise. They took the review of the paper private, and the review panel began to pound it into shape, sharing drafts with the rest of the collaboration as appropriate, a good way to bring them along.
The collaboration had inadvertently put themselves in the spotlight by inviting the world to an IceCube Particle Astrophysics Symposium to take place on the heels of their next collaboration meeting, scheduled for Madison in early May. As Greg told them all by e-mail, “At some point our very credibility is at stake, since … the community knows that we are doing (have done) [another] search, and obviously wonder[s] if we are competent enough to perform and report on a follow-up analysis with funding for over 200 people and a $270M detector.” (Francis put it more succinctly: “The whole world knows. That’s why we have to release this.”)
The pressure increased when Aya submitted her paper on Bert and Ernie to Physical Review Letters and posted it simultaneously on the arXiv. (PRL publishes breaking physics news. They don’t insist on embargos until press time, as Science and Nature do.) This attracted a flurry of international press coverage and won Aya the annual Young Scientist Prize from the cosmic ray physics division of the International Union of Pure and Applied Physics, the preeminent global umbrella organization. The first neutrino astrophysicist ever so honored, she would accept the prize at the International Cosmic Ray Conference in Rio de Janeiro the following summer.
Part of the problem was that the story of the twenty-eight events was too complicated to tell in the brief format of a Nature letter. It was like trying to fit a large woman into a tiny corset. Even some members of the collaboration had a hard time following the argument, as it relied extensively on so-called supplemental material, which would need to be published on the journal’s Web site when the l
etter appeared. But Nathan was fixated on getting another paper into this respected journal, and he and Claudio, the other primary author, were not converging with the rest of the collaboration. It also turned out that the collaboration’s internal review panel was a bit too large and included a couple of intransigent skeptics. About a week before the collaboration meeting, Francis, the political master, broke the logjam by working diplomatically with Nathan and Claudio to rewrite the paper in a normal physics format. He shared the resulting draft privately with Olga, and after some back and forth the two agreed that “this was the right paper.” The spokesperson and principal investigator make a powerful pair. (Interestingly, neither has been to Pole. “IceCube is like a space experiment,” Olga tells me. “You don’t have to go to lead the project.”)
On the first day of the collaboration meeting, the seventh of May, Olga went out on a limb and announced that the paper was almost ready for collaboration-wide review, the last step before journal submission, and proposed that they present the results publicly at the following week’s symposium.
Part of the reason she was willing to take this step was that they had caught a break a day or two earlier, when the traditionally skeptical Spencer Klein had presented a spectacular new cascade in a “pre-meeting” before the full meeting began. “Big Bird” was born right in the center of the detector and fully contained, and came in at about two PeV, twice the energy of Ernie, the previous record holder. Francis called this “our life insurance.” “If you didn’t believe anything, you cannot explain three PeV events as something coming from the atmosphere.” He also pointed out that this was yet another accident in what was becoming “an accumulation of accidents.” Bert and Ernie had snuck into Aya’s hands by chance, of course, and one of Spencer’s students had stumbled upon Big Bird in the burn sample from 2012, 10 percent of the data, which she had been allowed to un-blind for a preliminary study. Since the rest of that year’s data was still under wraps, there was a ten-to-one chance that she would have missed it.
Although Big Bird turned Spencer and several others into believers, many others still held out—and they had a point. When a harried Olga graciously gave me a moment of her time during the collaboration meeting, she showed me the crucial graph from the paper and pointed out that if you ignored Bert and Ernie (Big Bird could not be included in a study from the previous year), the other twenty-six events weren’t that far from the atmospheric background. “We have to make sure we’re not just seeing what we want to see,” she said.
She was holding endless side meetings to fine-tune the message and perfect the graphs that Claudio, Nathan, and Naoko were hoping to present at the symposium.
* * *
In addition to the feeling of a threshold being crossed, there was an air of poignancy at this gathering. The old guard was leaving. Buford Price was not there, having long since shifted his focus from the astrophysics aspect to the glaciology and climatology. Per Olof was absent for medical reasons. Christian Spiering was there, voicing his usual skepticism, but he had retired the previous week, having reached the mandatory age in Germany. Over dinner at a sushi place near the capitol building, he told me he’d probably attend the fall collaboration meeting in Munich, but not many more in the United States.
At the traditional banquet, I sat at one end of a square table, two people on a side, next to Tom Gaisser, the main cosmic ray theorist in the collaboration and the motivating force behind IceTop. Greg Sullivan and the newly elected deputy spokesperson, Ty DeYoung, sat perpendicular to us on our right. Albrecht sat to our left next to Allan Hallgren, a stalwart of the Swedish contingent since 1992. At Allan’s shoulder, directly across the table from me, sat his wife, Olga, and Francis sat next to her, across from Tom. Tom and I were both moved at the sight of Olga and Francis speaking softly and amiably together. They looked older than they had when we’d first met them, much longer ago in Tom’s case than in mine. He had first met Francis in the mid-seventies. Olga wore an understated black dress lined with thin horizontal ruffles. Francis had removed his suit jacket to reveal a black vest over a light blue collarless shirt with thin vertical ribbing. He wore round horn-rimmed glasses. The two were oddly reminiscent of the farm couple in the painting American Gothic. Tom borrowed Albrecht’s camera and took a shot (see photograph 33).
They are civilized enough not to give long speeches at these banquets. During the gala in 2010, Francis had set the tone by opening with, “I’m from Belgium, where we take food seriously” and speaking for less than a minute. As this banquet came to a close, Greg stood up to pass the baton to Olga. Making light of his failed attempt to fast-track the paper, he said that the experience of being spokesperson had taken him back to his early interest in Buddhism and Taoism. He’d learned that “the harder I push, the slower things go.”
He handed the microphone to Olga, who thanked them all for the honor of serving as spokesperson and expressed her confidence in their present findings and future promise.
Francis spoke last, the longest-running of the old-timers. It had been twenty-five years since he had presented the paper in Lodz, Poland, that had formed the basis for AMANDA’s letter of intent. He wasn’t going anywhere. “IceCube is my joy, every night,” he said.
* * *
These meetings traditionally end with a collaboration report delivered by the spokesperson. Olga had to leave early for some business in Europe, so Greg took her place. This was fitting. After delivering his “State of the Collaboration Address,” he presented a plan to reveal their new results at the symposium in several days and follow it up with a journal article—not, most likely, in Nature. They would claim “evidence” for the first extraterrestrial neutrinos ever detected, what astronomers call “first light” in the nascent field of neutrino astronomy. They would present their map of the high-energy neutrino sky, but they would make no claims as to hotspots, point sources, “neutrino stars” or anything of the like—a sensible and conservative tack. Press releases would accompany both the talks, which would be given by Claudio, Nathan, and Naoko, and the journal article. Since their main goal was to get the greatest possible impact out of the latter, Greg expressed misgivings about this double-press-release strategy. Then he did a wise thing. He invited discussion.
It seemed that everyone had been waiting for this moment, whether they realized it or not. Several people griped about the lack of transparency in producing the paper. Some doubted the results. Hardly anyone was happy with the publicity plan. But no one objected strenuously, even though quite a few shuffled out of the room looking down at their feet or shaking their heads, once those who wanted to speak had spoken and the conversation had come to a natural end.
They seemed thrilled at their discovery and scared at the same time. They were in uncharted territory.
Epilogue: The Dawn of Multi-Messenger Astronomy
People think science converges. It doesn’t converge. It answers questions that raise more questions that are usually more interesting but also more difficult.
—FRANCIS
The paper appeared in Science the following November, about nine months behind Greg’s original plan. A dramatic muon event made the cover, superimposed upon an elegant white background. (“Mr. Snuffleupagus,” though the journal disregarded this whimsy.)
Francis, Olga, and the three young authors were inundated with phone calls. The New York Times featured the story at the top of its Web page for about a day, under a photograph of the IceCube Laboratory standing in blue- and violet-hued isolation on the wind-carved and manifestly frigid ice sheet. (Sven Lidström had taken the photograph, probably in the “time of the long shadows,” sunrise or sunset, during one of his winterovers.) Stories were carried by the BBC, Time, NBC, National Public Radio, and other prominent outlets worldwide.
In mid-December, Physics World, the members’ magazine of the British Institute of Physics, named the “first observations of high-energy cosmic neutrinos” its breakthrough of the year. This made even Francis nervous.
When he accepted the award he kept thinking, “What are we going to do if this is wrong?” There was an extremely remote possibility that their twenty-eight high-energy neutrinos actually were atmospheric, born from the decay of charm particles produced by cosmic rays in the atmosphere. It wasn’t a particularly realistic possibility, but Francis found himself obsessing about it anyway. For the next several years, he spent much of his “physics time” working on charm, and finally, in 2016, demonstrated conclusively that it could not explain their results.
The accolades continued. In February, Nathan Whitehorn was named a “Young Star” by the Astrophysics Division of the American Physical Society. The following year, 2015, Francis received the Giuseppe and Vanna Cocconi Prize from the European Physical Society, “for his visionary and leading role in the detection of very high-energy extraterrestrial neutrinos, opening a new observational window on the Universe,” and the prestigious Balzan Prize.
The International Balzan Foundation awards four prizes each year, “two in literature, the moral sciences and the arts, and two in the physical, mathematical and natural sciences and medicine,” but the specific subject areas change year to year. In science disciplines that don’t receive a Nobel, the Balzan is considered the equivalent. In its citation, the Foundation wrote, “Francis Halzen is an inspiring example of a scientist who, though coming from a different research discipline, had the foresight to see where the next breakthrough in our understanding of the universe is likely be found, and who has the energy and leadership to realize this vision.” While this assessment was probably true, Francis noted at the beginning of his acceptance speech that he was “humbly aware that I receive this Prize thanks to the talent and dedication of the technicians, engineers, scientists and administrators who made the IceCube project a reality.”