## Glimpses of Higgs

13/12/2011

Finally, after some frantic waiting filled with rumors, we heard the truth from people at CERN. And we discovered that rumors were just right. Evidence is mounting for a Higgs particle at around 120-130 GeV, after new data were accounted for. All these evidences point toward a Standard Model Higgs. But some caution words are needed (see Matt Strassler’s post) as a discovery cannot be claimed yet. ATLAS sees a 3.6 sigma overall evidence but, accounting for look elsewhere effect, this go down to 2.5 sigma while CMS has a similar 2.6 sigma going down to 1.9 with look elsewhere effect. This is not enough to rule out a fluctuations but, anyhow, a strong indication where to point researchers attention for the near future. All the matter will be pinned down later next year. From my side, I just note a possible contradiction between the two experiments as ATLAS keeps on claiming an excess around 500-600 GeV, also with increasing number of data and indeed evidence now goes beyond 2 sigma, while, as for today, CMS claims this range ruled out. It is possible that this is another glimpse for a Higgs multiplet as required by supersymmetry. I think that also this matter will be fixed soon next year.

The conference raised a lot of enthusiasm (see here) to some caution (see here) or skepticism (see here).

Fabiola Gianotti, Rolf Heuer and Guido Tonelli

What makes these hints striking is the fact that both experiments see the excess in the same region where the particle was expected and with the proper rates. It should also be said that, with these data and energy, people at CERN have done an excellent work with the analysis of them. But, of course, it is still possible that we are coping with a fluctuation and the particle is hiding elsewhere or is something else. For sure, next year the puzzle will be completed and also this part of the Standard Model will be part of our textbooks in the right way. What we have here is a completely new situation holding the premises for a clear understanding of one of the greatest question of mankind ever. So, when a child will ask to you: “Mom, what are we made of?” this question will have an answer, an answer arising from the work of a lot of smart people running one of the greatest technological achievement of our history: LHC.

## Galileo’s abjuration

06/07/2011

Next year there will be a great chance in Rome to take a look to an important part of Vatican Secret Archives. These archives span almost two thousand years of history with the most part of them being part of the build up of Western civilization. Vatican made available a hundred documents that will be exposed from February to September 2012 at Musei Capitolini. You can see a correspondence between the Church of England and the Pope at the time of Henry the Eighth but what is more interesting for us as physicists is the Galileo’s signature in the abjure document. I give you here the picture of this fundamental aspect of the History and I hope it will convey you some of the feelings I experienced. Of course, being here in Rome, I will take the chance to visit this museum and see directly this exceptional witness.

## Gian Giudice and Lisa Randall in Rome

24/01/2011

As usual, also for this year there has been the Festival delle Scienze (Festival of the Sciences) in Rome. This lasted for all the last week and ended this sunday. This is the chance to hear from leading scientists the status of forefront research. This year’s theme was “The End of the World – Instructions for the Use”. Two leading theoretical physicists were present in different events: Lisa Randall and Gian Francesco Giudice. I have had not the chance to listen Lisa Randall but something she said come out in Italian newspapers. Lisa declared that KK particles are spies of other dimensions and that these are in the reach of LHC. I think that readers of the blogosphere already know what we are talking about. Indeed, KK stays for Kaluza-Klein and these particles generally arise as an effect of compactification of the other dimensions beyond the four we everyday experience. Lisa has written a paper, in collaboration with Ben Lillie and Lian-Tao Wang, providing an expectation of mass for a KK particle arising as an excitation of gluons at LHC. Some hints in this direction appeared with the measurement of charge asymmetry at Tevatron. I would like to remember that the Randall-Sundrum scenario to explain the hierarchy problem between interactions is one of the most successful ones devised so far due to the real cleverness of the idea. I regret to have missed the opportunity to listen from Lisa due to my very few time, being her present on Friday evening.

Of course, on Saturday I have much more time to spend and so I have had the opportunity to hear from Gian Francesco Giudice from CERN Theoretical Division. His talk was scheduled on Saturday evening at 19 o’clock. The talk was addressed to a non-specialist public so it was also a good opportunity to take my thirteen year’s old boy to listen. The title was “Black holes, accelerators and the end of the World”. I think you have already heard of the fine book Gian Giudice wrote recently in Tommaso Dorigo’s blog. The talk was in-line with the content of the book trying to make common people aware of what are the endeavors we physicists are pursuing with such an enormous enterprise. What makes me hope for the better has been to see a really crowded room such that the saturation point was promptly achieved and the talk started ten minutes in advance with respect to the scheduled time.

Gian started the talk discussing with a lot of irony the question of the LHC and the end of the World. He cited Nostradamus, Apocalypse by S. Giovanni and the date when the construction of the LHC started that sums up to a worrisome 666, the number of the devil. But he pointed out how a fine report to which he collaborated shows that no black hole could possibly form swallowing Earth and its neighborhood. The idea is that cosmic rays already produced even larger energies than LHC and corresponding collisions without ever producing such an effect. In this way, the probability of an unknown event can be evaluated and the event itself ruled out.

He then showed the extraordinary numbers of LHC that prompted a former NASA engineer participating to Apollo project to say that the latter was just a game for children with respect to the machine that was assembling.

Gian clarified that the mass arising from the Higgs field is not the same seen at a macroscopic level. Indeed, this is due to other reasons explained more and more in this blog and gives also another strong motivation to understand the behavior of Yang-Mills theory at low energies. To explain Higgs field, Gian used the example of a fish moving in the water. The fish cannot say there is a medium but if some excitations like waves are perceived these are an evidence in this sense. So, in the same way, we need LHC to get such excitations for the Higgs field and prove its existence. A small boy, claiming to be a physics amateur and well aware of quantum mechanics, asked if such a “Higgs fluid” could slow down particles as happens for normal fluids. Of course, we are talking of different things as relative motion is perceived in a case but not in the other. Higgs vacuum is absolutely indifferent to motion but not in the way it couples to different particles.

A question that naturally arose was if the fact that we have such a fixed space-time stage does not implies a resurrection of Newton’s absolute space. Gian explained with the example of general relativity that this idea is well dead and buried.

An important point Gian made was to note how, starting with a simple field, this field can give the seeds for fluctuations in an otherwise homogeneous space-time producing the galaxies and the large scale structures we observe today in the Universe. So, LHC is an essential starting point to understand our Universe and to answer fundamental questions by observing the particles that are the excitations of this kind of fields. Indeed, he said that are already several years that fields like cosmology, astrophysics and particle physics are going entangled inextricably together. He also pointed out how there are recurring ages in physics when some fields seem to have more results than other but this is just due to the fact that research goes through hits rather than with continuity.

Gian presented the contents with beautiful slides and animations keeping always alive the attention of the public. This was confirmed by the large number of questions people asked. What I have found interesting was the numbers Gian declared for “brains at work” for the LHC at CERN. He said that 4500 experimental physicists are involved against a mere 80 theoretical physicists! But the point that appeared to me more exciting was his declaration that the Higgs sector in the Standard Model appears somehow misplaced in an otherwise very beautiful theory and we, the theorists, all suspect that here is hidden the new physics that LHC will uncover for sure. Supersymmetry was in the air more and more, sometime just whispered but it was clear, at least to me, that this is the next actor due to appear on the scene. I strongly agree with this view from my humble side. The fear is that the only finding of LHC will be the Higgs boson and nothing more. This would decree the end of particle physics as devised since now. In any case, due to the needed long times, it is today that we are already doing feasibility studies for the accelerator of the next generation. Gian pointed out that the fact that the LHC will uncover something for sure is inside the Standard Model that seems to fail exactly at the order of energies the LHC works. A fine description of the Higgs particle was also given and this prompted several questions from the public. Indeed, it is easy to think that we are back to ether again but this is easily seen not the case as the Higgs vacuum is invariant by Lorentz transformations. Some people in the public seemed really informed about the experiments at CERN and a question arrived about the heavy ion collisions. Gian was very able to explain what are the aims and the reasons why humankind should keep on pursuing research like this.

The journalist Claudia Di Giorgio of the editorial office of Italian version of Scientific American (“Le Scienze”) was the host. She asked some recurring questions that surely was helpful for the public to be answered. A nice moment was when Gian clarified the question of the name “God particle” given to the Higgs boson by Leon Lederman and that Claudia used frequently asking for a reaction. Indeed, Gian explained that he asked the question to Lederman that claimed that the real title of his book was “The God damn particle” but the editor of the book did not like it and removed the word “damn”.

My son was very enthusiastic about Gian’s presentation and, at the end of the talk, I took him to greet Gian. It was also my chance to shake his hand and to cite him Tommaso Dorigo… Gian Giudice represents a great example of what means following a right track and surely he was one of the right people for my son to be known.

Lillie, B., Randall, L., & Wang, L. (2007). The Bulk RS KK-gluon at the LHC Journal of High Energy Physics, 2007 (09), 74-74 DOI: 10.1088/1126-6708/2007/09/074

## Edward Witten

23/03/2009

Today I was at the Festival of Mathematics 2009 in Rome to listen a talk by Edward Witten. Witten is one of the greatest living physicists and his contributions to mathematics were so relevant that he was awarded a Fields medal. This was for me a great chance to see him personally and hear at his way of doing physics for everybody. This is a challenging task for anyone and mostly for the most relevant personalities of our community. I was there with my eleven years old son and two of his friends. Before the start of the talk, John Nash come out near our row of seats and my son and his friends suggested to go to him asking for an autograph. Indeed, he seemed in real difficulty as some people was around him asking for an handshaking or something else. Somebody took him away and this was a significant help.

I showed Witten immediately at my company. He was there speaking and greeting people around. He appeared a tall and a very cordial man.

Marco Cattaneo, deputy director of the Italian edition of Scientific American (Le Scienze), introduced Witten with a very beautiful and well deserved presentation. Witten of course speaks Italian being his wife Chiara Nappi, an Italian physicist. Witten started to talk in Italian saying that he was very happy to be in Italy to meet his wife parents but his Italian was not enough to sustain a talk like the one he was giving.

The talk was addressed to a generic public. It was very well presented and my company found it very interesting. Witten did not use any formulas rather than Einstein’s $E=mc^2$ and the parabola $y=x^2$ and this is enough to keep up the attention of the public for all the time.

Witten pointed out that quantum field theory represents the greatest achievement ever for physicists. This theory is so deep and complex that mathematicians still fail to go through it fully and most of these results, widely used by physicists, are presently out of reach for mathematical proofs. He also said clearly, showing it explicitly, that the problem implied in the vertexes of ordinary Feynman diagrams are removed by string theory making all the machinery less singular.

He did a historical excursus starting from Einstein and arriving to string theory. He showed the famous Anderson’s photograph blatantly proving the very existence of antimatter. A great success of the wedding between special relativity and quantum mechanics. This wedding produced such a great triumph as quantum field theory. Witten showed this with the muon magnetic moment, emphasizing the precise agreement between theory and experiment, but saying that the small discrepancy may be or not real new physics being just at $1\sigma$.

He emphasized the long path it takes to physicists to achieve our present understanding of quantum field theory and cited several Nobel prize winners that gave key contributions for this goal. He pointed out the relevance of the seventies of the last century that become a cornerstone moment for our current view.

Starting from Gabriele Veneziano‘s insight, Witten arrived to our current view about string theory. He said that this theory has had some frailty aspects that put it, sometime, on the border of a gulch. But, as we know, recoveries happened. He said that strings set the rules and not the other way round as happens with the Standard Model. He gave the example of the Veneziano’s model for strong interactions that was there pretending spin two excitations. This made the model better suited for other aims as indeed happened.

Witten hopes that LHC will unveil supersymmetry. He showed a detector of this great accelerator that we will see at work at the end of this year. Discovery of supersymmetry will be a great achievement for humankind as it will be the first evidence for a world with more than four dimensions. Anyhow, Witten said, string theory put out several elements, quantum gravity and supersymmetry are two of them, that make this theory compelling.

After the talk, some questions by the public were about ten or eleven dimensions in string theory. Witten avoided to be too technical. But the most interesting question was the one by Marco Cattaneo. He asked about critics of string theory and its present inability to do predictions. Witten’s answer was quite unexpected. He said that it is a good fact that a theory has critics. It is some kind of praise for it. But he also said, and his answer was quite similar to the one of Nicola Cabibbo, that there are a lot of things to be understood yet but such a richness physicists run into cannot be just a matter of chance with no significance.

Surely, this has been a very well paid waiting!

## Nicola Cabibbo and Arno Penzias

21/03/2009

Today I have been at Festival della Matematica 2009 here in Rome to listen at a discussion with Arno Penzias and Nicola Cabibbo.  The moderator was Riccardo Chiaberge, a journalist of the italian newspaper Il Sole 24 Ore. Chiaberge wrote a book with an interview to George Coyne and Arno Penzias (in Italian, see here). Cabibbo is currently the President of the Pontificia Accademia delle Scienze and is a believer. This evening he took the role Coyne had in the book in a confrontation between scientists with different beliefs. Asked by Chiaberge if the Pope listens Accademia, Cabibbo said “Sometime.” and cited the case of cerebral death.

Penzias has been put by Chiaberge on the Einstein side, a “non-believer deeply religious”. But what Penzias said has been sometime astonishing revealing a kind of faith elevating humankind well above its nature. Of course, themes like string theory and multiverse were also touched upon in the discussion. Cabibbo said that we should give time to the theory to develop before to conclude anything about, being now too early to draw any conclusion. Stringists will say but surely “mathematics is truly beautiful”. When he said so I thought to Perelman that, copying a functional from string theory, achieved one of the greatest goals of modern mathematics. Penzias is more skeptical about and does not think it should be considered science yet and, on the same line, multiverse is not falsifiable and so to be dismissed. Cabibbo said “till now!” letting us think that the future will deserve some surprise about as always happened in matters like these.

This point was quite entertaining as Cabibbo defended multiverse as the most elegant idea to explain the foundations of quantum mechanics but, as Chiaberge emphasized, this is an escape for atheist to claim the non-existence of God. On the other side, Penzias said that our current understanding of Universe and all this nice fine tuning of its constants appears a serious support for believers.

Galileo, Copernico and Kepler were discussed and the Galileo question, with his trial and abjure, was declared by Cabibbo as a severe error by the Catholic Church that cost too much to Italian science. He said that “Bellarmino, notwithstanding was a fine cultured man, failed to recognize that these were completely new matters” and should have been carefully treated.

About the question of intelligent design and Darwinism, Penzias put forward a nice metaphor. He remembered the last scene of The Wizard of Oz where a dog moves a curtain unveiling the wizard pushing around buttons all the time and this appears to be the god of intelligent design. On the other side, human beings are really cousins of chimpanzees but there is something more, that kind of inexplicable that makes us believe that something like love and free will are real as the rest of our physical world. Cabibbo added that the idea of evolution should enter into the certainties accepted by the Catholic Church as the Copernican system and all that. Evolution is an assessed fact but still some embarrassment is seen from clerics, the same that happens when one talks about the possibility of intelligent life in other solar systems. Giordano Bruno has not been fully digested by Catholic Church yet.

Cabibbo also put forward a nice analogy between phase transitions and the appearance of  intelligence in human beings that completely overwhelmed previous animal species, a threshold effect.

Chiaberge gave a nice summary of the discussion by saying:”Science has limits but no authority should impose limits on it”. All agreed about this but Penzias remembered horrors of some experiments and Cabibbo emphasized that for medicine some kind of limits should be eventually considered or, better, self-imposed.

Tomorrow I will be there to listen Edward Witten. Stay tuned!

## Festival of Mathematics 2009

01/03/2009

In this month will be held at New York and Rome the Festival of Mathematics (Festival della Matematica) 2009. It is an opportunity to hear Nobelists and Fields medalists talking about physics and mathematics. In New York there will be Shelly Glashow, Benoit Mandelbrot and Brian Greene. In Rome there will be John Nash, Arno Penzias and Edward Witten. I will take my chance to hear Witten talking. The argument of his talk is “Geometry and Quanta”. Penzias and Nicola Cabibbo will talk about “Thinking with Mathematics”.

The festival  is organized each year by Piergiorgio Odifreddi, an italian mathematician, to give the opportunity for people to get acquainted with mathematics listening some of the most relevant thinkers working in this field. This is the third edition.

Last year I listened John Nash and Robert Aumann and it was the chance to let my son know such great personalities in the history of mathematics and economy.