The “SUSY Bet” event in Copenhagen took place today, with video available for a while at this site. It appears to be gone for the moment, will put up a better link if it becomes available. An expensive bottle of cognac was presented by Nima Arkani-Hamed to Poul Damgaard, conceding loss of the bet. On the larger question of the significance of the negative LHC results, a recorded statement by Gerard ‘t Hooft (who had bet against SUSY), and a statement by Stephen Hawking (not in on the bet, but in the audience) claimed that if arguments for SUSY were correct, the LHC should have seen something, so they think nature has spoken and there’s something wrong with the idea.
The losers of the bet who spoke, (Arkani-Hamed, David Gross and David Shih) demonstrated the lesson about science that supersymmetry and superstring theory have taught us: particle theorists backing these ideas won’t give up on them, no matter what. They all took the position that they still weren’t giving up on SUSY, despite losing the bet. In more detail:
- Arkani-Hamed was not a signatory of the original bet in 2000, but signed on to the later 2011 version. He explained today that at the time he thought chances of SUSY visible early on at the LHC were just 50/50 (with his 2004 work on split SUSY motivated by realizing that pre-LHC the conventional picture of SUSY at the electroweak scale was already ruled out). He attributed his decision to take the pro-SUSY side of a 50/50 bet to “optimism”, implying that this took place at a conference dinner where there may have been too much to drink. In his split-SUSY scenario, SUSY may yet show up at the LHC, or it could even be invisible there, requiring a higher energy accelerator. So, he’s not giving up on SUSY based on LHC results.
- David Gross also is not giving up, arguing that fine tuning of a factor of 100 or 1000 is not a problem (invoking the large ratios that appear in the fundamental Yukawa couplings). He did say that young people might want to take this as reason to look for new ideas, but, for himself, felt “I’m too old for that”.
- David Shih isn’t giving up either, arguing that there still was lots of data to come, plenty of room for SUSY to appear at the LHC, still believes we’ll discover SUSY, at the LHC or elsewhere.
One piece of misinformation promoted by several of the speakers was the idea that “everyone” back around 2000 believed in SUSY as the next new physics to be found. In my book (written in 2002-3) I wrote a long section about the evidence against SUSY, and, of course, if you look at the bet under discussion, in 2000 many more people (16 vs. 7) were taking the anti-SUSY vs. pro-SUSY side (at least in Copenhagen, but I think this reflects the general range of opinions).
No one today asked the obvious question “Is there any forseeable experimental data that would cause you to decide that SUSY was an idea that should be abandoned?”. I’m now not seeing any prospect in my lifetime of anything that would cause these or other SUSY proponents to give up (John Ellis has also announced that no matter what the LHC says, he’s not giving up). Unfortunately “Not Ever Wrong” is clearly the slogan of the (minority) segment of the particle theory community that long ago signed up for the vision of fundamental physics in which SUSY plays a critical part.
Update: There’s a blog entry from Natalie Wolchover about this. She has more detail about the final remarks from Gross that I mentioned:
“In the absence of any positive experimental evidence for supersymmetry,” Gross said, “it’s a good time to scare the hell out of the young people in the audience and tell them: ‘Don’t follow your elders. … Go out and look for something new and crazy and powerful and different. Different, especially.’ That’s definitely a good lesson. But I’m too old for that.”
Update: Video of the Copenhagen event is available here.
Update: I happened to be looking at Michael Dine’s 2007 Physics Today article on string theory and the LHC, noticed the side remark that “The Large Hadron Collider will either make a spectacular discovery or rule out supersymmetry entirely.” I wonder if he still thinks this, and whether we’ll ever see Physics Today publishing something updating its readers.
Update: Yet another news story about this, from Science News.