Blogging ICHEP 2010

A collective forum about the 35th edition of
the International Conference on High Energy Physics (Paris, July 2010)

Wednesday, June 30, 2010

Not a sound name for a physics software program

Through a casual browsing of the Arxiv's hep-ph section, I got to read the following title:

"CAMORRA: A C++ Library for Recursive Computation of Particle Scattering Amplitudes"

Authors are R.Kleiss and G. van den Oord. None of which appears Italian by name, so my first reaction to the title (are these people stupid or what?) got tempered by the fact that they may just be ignorant.

Camorra is the name of one of the three main criminal organizations operating in southern Italy. From wikipedia, even a computer-illiterate could learn that

The Camorra is a mafia-like criminal organization [...] It finances itself through drug trafficking/distribution, cigarette
smuggling, people smuggling, kidnapping, blackmail, bribery,
prostitution, toxic waste disposal, construction, counterfeiting, loan
sharking, money laundering, illegal gambling, robbery, arms smuggling,
extortion, protection, political corruption, and racketeering and its
activities have led to high levels of murder in the areas in which it
operates. It is the oldest and largest criminal organization in Italy.

Giving that name to a software package is a really bad idea, like calling "scrotum" a soft ice cream, "gonorrhea" a lipstick, or "pedophile" a theme park for toddlers. But as I said, the authors are probably just unaware of the issue.

In the paper, one learns that the name "CAMORRA" comes from "CAravaglios-MORetti Recursive Algorithm". Fine, but then why not call it MOCARA or CARMORA ? None of the latter would sound offensive to the ear. Unless, of course, in southern Bali CARMORA is an association of satanists, or the like... One never knows!

I look forward to hearing what you think about this. In the meantime, I sent an email to the authors, suggesting alternative names...

Saturday, June 19, 2010

On and off (stage)

As you might have noticed reading the posts by Mu-Chun and Georg, summer is a the heyday season for physics conferences and workshops. This is not only because we like to gather in gorgeous places that we can enjoy where the sun shines (Athens, Sardinia... or, yes, Paris), but also for a more mundane reason : many physicists lecture at university, and summer is the only time of the year where they can leave the classroom and travel to week-long international conferences without messing up their teaching schedule -- or their colleagues'.

I like to think of conferences as theatre plays, or operas. After all, they are all cultural events, aren't they ? You have the stage (the conference rooms), the actors (the speakers, with their share of drama kings and queens, happy jesters and uninspired declamatory comedians), the spectators (the good-humoured or bad-tempered participants), the director and conductor (the lucky organisers)... and the technicians taking care of everything basically, from the curtains to the lighting, passing through the costume and the make-up (the administrative and technical staff). And quite often, feelings are quite different on which side of the curtain you stand. At best, the innocent participant can sit and relax, enjoying the happy spectacle of a smoothly-run conference. But off-stage, eveybody jumps up and down like madmen to check minute details of costumes (or microphones) or to prevent major disasters looming (like the crash of the computer network).

Inasmuch as some plays become experiences of a lifetime, and some shows remain just a pleasant evening out, a thin line exists between run-of-the-mill conferences and truly memorable ones. Part of the job of the organising committee consists in gathering the right people talking on the right subjects at the right moment, and another part to propose the right social events with the right mood... Well, you need a bit of luck too. But no matter how outstanding the speakers are, and how exciting the topics turn out to be, the organising committee must also take care of another essential aspect : infrastructure. The best play in the world needs the theater to be open and working in full order.

Murphy's law being unfortunately well obeyed in real life, bad things happen on that side, but you should solve them before they affect the participants. This is a tough lesson that I learned taking part in the organisation of conferences before the ICHEP one. My more personal version is : never organise a conference in Paris in october or november. Or you will be in the same nightmare as Mu-Chun, because autumn is the heyday season for strikes in France as much as summer is for physics conferences. Fortunately (or thoughtfully) ICHEP takes place in July... At the same time as many theater and opera festivals taking place in Southern France like Avignon or Aix-en-Provence, but I do not expect a harsh competition from that side.

Another key element that cannot go astray under any circumstance : computers. Obviously, you need a good internet connection for the participants to check out mails and papers regularly (in Paris, if not in Sardinia, as mentionned by Georg). But with more than 900 participants and almost 600 talks and posters to be presented, you need a powerful tool to manage the huge data-base of people, title, places, times... and slides required by our very dense program (we have only 3 days of parallel sessions !). And for particle physics, all this rhymes with Integrated Digital Conference, or Indico, born at CERN, like so many great computer inventions. The CERN computer team has been incredibly efficient in designing and improving the Indico system that we use, Actually, by its size and its length, ICHEP is a good benchmark to test their new version of the software, and we spent a bit of time helping them to tune the system to our own needs.

Therefore, for physics as much as for many other aspects, ICHEP as a true première... And like for all premieres, both the participants and the organisers look forward to seing the play, that is, the results that will be presented for the first time in summertime Paris !

Lattice 2010, Day Five

The day started with plenary sessions again. The first plenary speaker was Chris Sachrajda on the topic of phenomenology from the lattice. Referring to the talks on heavy and light quarks, spectroscopy and hadron structure for those topics, he covered a mix of various phenomenologically interesting quantities, starting from those that have been measured to good accuracy on the lattice and progressing to those that still pose serious or perhaps even unsurmountable problems. The accurate determination of Vus/Vud from fK/fπ and of Vus from the Kl3 form factor f+(0), where both the precision and the agreement with the Standard Model are very good, clearly fell into the first category. The determination of BK is less precise and there is a 2σ tension in the resulting value of K|. Even more challenging is the decay K --> ππ, for which however progress is being made, whereas the yet greater challenge of nonleptonic B-decays cannot be tackled with presently known methods. Chris closed his talk by reminding the audience that at another lattice conference held in Italy, namely that of 1989 (i.e. when I was just a teenager), Ken Wilson had predicted that it would take 30 years until precise results could be attained from lattice QCD, and that given that we still have nine years we are well on our way.

The next plenary talk was given by Jochen Heitger, who spoke about heavy flavours on the lattice. Flavour physics is an important ingredient in the search for new physics, because essentially all extensions to the Standard Model have some kind of flavour structure that could be used to find them from their contributions to flavour processes. On the lattice, "gold-plated" processes with no or one hadron in the final state and a well-controlled chiral behaviour play a crucial role because they can be treated accurately. Still, treating heavy quarks on the lattice is difficult, because on needs to maintain a multiscale hierarchy of 1/L << mπ << mQ << 1/a. A variety of methods are currently in use, and Jochen nicely summarised results from most of them, including, but not limited to, the current-current correlators used by HPQCD, ETMC's interpolation of ratios between the static limit and dynamical masses, and the Fermilab approach, paying special attention to the programme of non-perturbative HQET pursued by the ALPHA collaboration.
The second plenary session started with a talk by Mike Peardon about improved design of hadron creation operators. The method in question is the "distillation" method that has been talked about a lot for about a year now. The basic insight at its root is that we generally use smeared operators to improve the signal-to-noise ratio, and that smearing tends to wipe out contributions from high-frequency modes of the Laplacian. If one then defines a novel smearing operator by projecting on the lowest few modes of the (spatial) Laplacian, this operator can be used to re-express the large traces appearing in correlation functions with smaller traces over the space spanned by the low-modes. If the smearing or "distillation" operator is D(t)=V(t)V(t)+, one defines the "perambulator" τ(t,t')=V(t)+M-1(t,t')V(t') that takes the place of the propagator, and reduced operators Φ(t)=V(t)+ΓV(t), in terms of which to write the small traces. Insertions needed for three-point functions can be treated similarly by defining a generalised perambulator. Unfortunately, this method as it stands has a serious problem in that it scales very badly with the spatial volume -- the number of low-modes needed for a given accuracy scales with the volume, and so the method scales at least like the volume squared. However, this problem can be solved by using a stochastic estimator that is defined in the low-mode space, and the resulting stochastic method appears to perform much better than the usual "dilution" method.

The last speaker of the morning was Michele Pepe with a talk on string effects in Yang-Mills theory. The subject of the talk was the measurement of the width of the effective string and the observation of the decay of unstable k-strings in SU(2) gauge theory. By using a multilevel simulation technique proposed by Lüscher and Weisz, Pepe and collaborators have been able to perform these very challenging measurements. The results for the string width agree with theoretical expectations from the Nambu-Goto action, and the expected pattern of k-string decays (1 --> 0, 3/2 --> 1/2, and 2 --> 1 --> 0) could be nicely seen in the plots.

The plenary session was closed by the announcement that LATTICE 2011 will be held from 10-16th July 2011 at the Squaw Valley Resort in Lake Tahoe, California, USA.

In the afternoon there were again parallel sessions.

Friday, June 18, 2010

Hello World from Athens, Greece!

Greetings from Athens where I have been for the Neutrino 2010 Conference! As this is my first post, let me just briefly introduce myself. I am a particle theorist working on beyond the standard model physics. Particularly I have been interested in the origin of fermion masses and mixing (including the neutrinos, of course!) and have been trying to gain some insights into this problem by constructing models utilizing a variety kinds of new physics (grand unification, extra dimensions, Z'...).

Getting back to the Neutrino 2010 Conference. Some of the highlights of the conference were the new results from MINOS and MiniBoone. The MINOS Collaboration updated their results on the neutrino mode with more than double the data from their previous update in 2008. Updated results on the antineutrino mode were also presented. What is puzzling is the fact that the best fit value for the mass square difference extracted from the antineutrino mode is 3.36 x 10(-3) eV^2, which is far higher than the value determined using the neutrino mode data, 2.35 x 10^(-3) eV^2. One should note that the result for the neutrino mode was based on 7 x 10^(20) POT while the antineutrino mode result was based on significantly low statistics of 1.71 x 10^(20) POT. If the results turn out to be correct, it could mean CPT violation or the existence of new neutrino interaction. Clearly these data are still very preliminary and we should wait and see how this discrepancy disolve when more data becomes available.

MiniBoone also presented the results for both the neutrino and antineutrino modes. For both modes, an excess in the electron-like events was found in the low energy region. For the neutrino mode, there is an unexplained 3 sigma electron-like excess in the region of energy > 475 MeV, while in the region below 475 MeV the fit does not agree with LSND. For the anti-neutrino mode, there is a small excess above 475 MeV and the fit below 475 MeV agree with LSND result. It would be interesting to see if the low energy excess is still present when more statistics have been accumulated and when we have a better understanding of the background in the low energy region.

For the Neutrino Conference series, it has been the case that there are plenary sessions only. One thing that has been started since Neutrino 2008 in Christ Church, New Zealand, is the poster session. This is not uncommon in physics conferences, but what is special is the 3 min talks that enable the poster presenters to advertise their posters. Given that there are more than one hundred of them, the execution of the "3 min talk sessions" was quite an operation! Fortunately, the sessions went very smoothly, and since the talks were only for 3 min duration each, the speakers really had to get to the point right away making it an efficient way to learn numerous new results.

In addition to the exciting physics, life in Athens has been quite an experience. As you all know, there have been several protests and riots in Athens due to the economic crisis. Today is the third day since the Metro has gone on strike. This has posted a big problem for conference participants as most of us are staying quite far from the Megaron conference center and the Metro is the best way to get there from the hotels especially given that it is extrememly hard to get a taxis in central Athens. Hopefully the strike will end soon, or at the very least that it will not be extended to the airport in the next few days when everyone will be flying out of Athens.

This is it for this post. In the next one, I will report on the theoretical developments and additional experimental updates that I have learned at the conference as well as my overall impressions. So stay tuned.

Lattice 2010, Day Four

Today's first plenary session was started by Kazuyuki Kanaya with a talk on finite-temperature QCD. Many groups are looking for the transition temperature between the confined and deconfined phases, but since in the neighbourhood of the physical point, the transition is most likely a crossover, the value of the "critical" temperature found may be dependent on the observable studied. There was further some disagreement even between different studies using the same observables, but those discrepancies seem to have gone mostly away.

Next was Luigi Del Debbio speaking about the conformal window on the lattice. The motivation for those kinds of studies is the hope that the physics of electroweak symmetry breaking by originate not from a fundamental scalar Higgs, but from a fermionic condensate similar to the chiral condensate in QCD arising from a gauge theory ("technicolor") living at higher energy scales, perhaps around 1 TeV. One is then motivated to look for gauge theories having an infrared fixed point. Lattice simulations can help studying the question which combinations of Nc, the number of colours, and Nf, the number of fermion flavours, actually exhibit such behaviour. The Schrödinger functional can be used to study such questions, but while there are a number of results, no very clear picture appears to have emerged yet.

The second plenary session of the morning was opened with a talk on finite-density QCD by Sourendu Gupta. QCD at finite density, i.e. finite chemical potential, is plagued by a sign problem because the fermionic determinant can no longer be real in general. A number of ways around this problem have been proposed. The most straightforward is reweighting, the most ambitious a reformulation of the theory that manages to eliminate the sign problem entirely. On the latter front, there has been progress in that the 3D XY model, which also has a sign problem, has been successfully reformulated in different variables in which it does no longer suffer from its sign problem; whether something similar might be possible for QCD remains to be seen. Other approaches try to exploit analyticity to evade the sign problem, either by Taylor-expanding around zero chemical potential and measuring the Taylor coefficients as susceptibilities at zero chemical potential, or by simulating at purely imaginary chemical potential (where there is no sign problem) and extrapolating to real chemical potential. In this way, various determinations of the critical point of QCD have been performed, which agree more or less with each other. All of them lie in a region through which the freeze-out curve of heavy-ion experiments is expected to pass, so the question of the location of the critical point may become accessible experimentally.

The last plenary talk of the morning was Takeshi Yamazaki talking on a determination of the binding energy of helium nuclei in quenched QCD. The effort involved is considerable (there are more than 1000 different contractions for 4He, and the lattices considered have to be very large to be able to accommodate a helium nucleus and to distinguish between true bound states and attractive scattering states), even though the simulations were quenched and the valence quarks used corresponded to a pion mass of about 800 MeV. The study found that helium nuclei are indeed bound.

In the afternoon there were parallel sessions.

Thursday, June 17, 2010

Lattice 2010, Days Two and Three

Yesterday was an all-parallels day, so there are no plenary talks to summarise. In the evening there was the poster session.

The internet connection at the resort does not really have the capacity to deal with 360 computational physicist all reading their email, checking on their running computer jobs, browsing the hep-lat arXiv or writing their blog at the same time; this may lead to late updates from me, so please be patient.

Today's first plenary session was the traditional non-lattice plenary. The first talk was by Eytan Domany, who spoke about the challenges posed to computational science by the task of understanding the human genome. A large part of his talk was an introduction to the biological concepts involved, such as DNA, chromosomes, genes, RNA, transcription, transcription factors, ribosomes, gene expression, exons, introns, "junk" DNA, regulation networks and epigenetics. These days, it is possible to analyse the expression of thousands of genes in a sample by means of a single chip, and the data obtained by performing this kind of analysis on large numbers of samples (e.g. from different kinds of cells or from different patients) can be seen as an expression matrix with rows for genes and columns for samples. The difficult task is then to use this kind of large data matrix to infer regulation networks or connections between gene expression and phenotypes. Apparently, there are physicists working in this area together with the biologists, bringing in their computational expertise.

The second plenary talk was an LHC status summary given by Slawek Tkaczyk. The history of the LHC is of course well known to readers of this blog; so far, the first data are being analysed to "rediscover" the Standard Model with the aim of discovering new physics in the not too distant future, but there was no evidence of e.g. the Higgs or SUSY shown (yet?).

The second plenary session was devoted to non-QCD lattice simulations. The first talk was Renate Loll speaking on Lattice Quantum Gravity, specifically on causal dynamical triangulations. This approach to Quantum Gravity starts from the path integral for the Einstein-Hilbert action of General Relativity and regularises it by replacing continuous spacetime with a discrete triangulation. The discrete spacetime is then a simplicial complex satisfying certain additional requirements, and the Wick-rotated path integral can be treated using Monte Carlo techniques. In one phase of the (three-parameter) theory, the macroscopic structure of the resulting spacetime has been found to agree with de Sitter-space. Another surprising and interesting result of this approach has been that the spectral dimension associated with the diffusion of particles on the discrete spacetime is continuously going from around 2 at short (Plackian) to 4 at large distances.

Next was a talk on exact lattice SUSY by Simon Catterall. Normally, a lattice regularisation completely ruins supersymmetry, but theorists have found a way to formulate certain classes of supersymmetric theories (including N=4 Super-Yang-Mills) on a special kind of lattice, giving a local, gauge-invariant action with a doubler-free fermion formulation. This may offer a chance to study quantum gravity by simulations of lattice SUSY via the AdS/CFT correspondence.

In the afternoon there were excursions. I had signed up to the only excursion for which places were still available, which was a tour of a Sardinian winery with a wine tasting. The tour was not too interesting, as everything was very technologically modern, and as somebody said, we can go and look at the LHC if we want to see modern technology. The wines tasted were very nice, though.

Wednesday, June 16, 2010

Social programming

Ever attended a physics conference before? Then you should know that the most important moments are neither the plenary nor the parallel sessions, but... coffee breaks! Presentations at plenary sessions are often funny and entertaining; talks at parallel sessions is where one can really learn the details of any remote analysis. But for the gory details, the internal gossips, the questions one does not dare to ask in public, and everything that cannot be said in front of a formal audience but that is important to get to know, coffee-break-chats are what one needs. Alternatively, one can similarly profit of being seated at the right table during the conference dinner, or to participate to the right social events.

Now, this year ICHEP is proposing an impressive social program: apart for the usual welcome reception, we will get a concert in the Salon of the "Hôtel de Ville" of Paris on Friday, we can choose among several different visits of Paris on Sunday, we will be able to visit the Grande Galerie de l'Évolution on Tuesday and have dinner there, not to speak of the Nuit des particules. The conference secretariat just emailed me, asking to choose two of the different visits scheduled on Sunday. I have been in Paris more than once and already visited all the locations the program is proposing, so I guess I should instead choose according to a conference-coffee-break criterion. Where would I be able to come across the most succulent gossips? Where will I most likely learn the most by informally chatting during the visit? What would be the spot to attract the conference VIP's? Tour Eiffel? Opéra de Paris? The Jacquemart-André Museum? The "Cité des Sciences"? The Marais neighborhood? The Panthéon? Where do you plan to go?

Monday, June 14, 2010

Lattice 2010, Day One

Hello from the Atahotel Tanka Village Resort in Villasimius, Sardinia, Italy, where I am at the Lattice 2010 conference. I know that this blog is called "Blogging ICHEP 2010", but that doesn't mean I can't blog from another conference, does it?

The conference started this morning with a talk by Martin Lüscher about "Topology, the Wilson flow and the HMC algorithm". It is by now well known in the lattice community that Monte Carlo simulations of lattice QCD suffer from a severy problem with long autocorrelations of the topological charge of the gauge field. This problem affects the HMC algorithm and its variants that are used in lattice simulations with dynamical fermions just as well as the simple link updating schemes (Metropolis, heat bath) that can be used for pure gauge or quenched calculations. The autocorrelation time of the topological charge grows roughly like the fifth power of the inverse lattice spacing a as a is taken to zero. This is a real problem because it indicates the presence in the system being simulated of modes that are updates only very slowly, and as a consequence the statistical errors of observables measured from Monte Carlo simulations may be seriously underestimated, because the contribution to the error coming from the long tails of the autocorrelation function that stem from those modes are not properly taken into account. Martin Lüscher then introduced the Wilson flow, which is an evolution in field space generated by the Wilson plaquette action, and which can in some sense be seen as consisting of a sequence of infinitesimal stout link smearings. For the case of an abelian gauge theory, the flow equation can be solved exactly via the heat kernel, and it can be shown that it gives renormalised smooth solutions. For QCD, the same can be seen to be true numerically. Defining a transformed field V(U) by running with the Wilson flow for a specified time t0, it can then be shown that the path integral over U is the same as the path integral over V(U) with an additional term in the action that comes from the Jacobian of the transformation and is proportional to g0/a times the integral of the Wilson plaquette action along the flow trajectory. As a goes to zero, the latter term will act to suppress large value of the plaquette. An old theorem of Lüscher shows that the submanifold of field space with a plaquette values less than 0.067 divides into topological sectors, and hence the probability to be "between" topological sectors decays in line with the suppression of large plaquettes by the g0/a term. This explains the problem seen, but also offers hope for a solution, since one might now try to develop algorithms that make progress by making large changes to the smooth fields V.

This was followed by two review talks. The first was a review of the state of the art in hadron spectroscopy and light pseudoscalar decay constants by Christian Hölbling emphasizing the reduction of systematic errors achieved by decreasing lattice spacings and pion masses and increasing simulation volumes.

The second review talk of the morning was given by Constantia Alexandrou, who reviewed hadron structure and form factor calculations from the lattice, drawing attention to the many remaining uncertainties in this important area, where in particular the axial charge gA of the nucleon is consistently measured to be significantly lower on the lattice than in nature.

The last plenary speaker of the day was Gregorio Herdoiza, who spoke about the progress being made towards 2+1+1 flavour simulations. The collaborations currently pursuing the ambitious goal of including a fully dynamic charm quark in their simulations are ETMC and MILC. MILC is using the Highly Improved Staggered Quark (HISQ) action to reduce discretisation errors, whereas ETMC is relying on a variant of twisted mass fermions with an explicit breaking of the mass degeneracy for the strange/charm doublet. In the former case, the effects of reduced lattice artifacts are clearly seen, while in the latter case the O(a2) mass splitting between the neutral and charged pion increases with the number of flavours. In either case, a significant effort is necessary to tune the strange and charm quark masses to their physical values, but the effort is definitely well-spent if it leads to Nf=2+1+1 predictions from lattice QCD that include all effects of an active charm quark.

In the afternoon there were parallel talks. Two that I'd like to highlight were the talk of Bastian Knipschild from Mainz, who presented an efficient method to strongly reduce the systematic error on nucleon form factors coming from excited state contributions, and David Adam's talk in which he presented a generalisation of the overlap operator to staggered fermions that gives a chiral two-flavour theory.

Saturday, June 12, 2010

A Zeptospace Odyssey: Gian Francesco Giudice's Brilliant New Book

Today rather than discussing what ICHEP 2010 will bring us I have something better to do, which will have a much more sizable positive effect for the diffusion of particle physics than a wish-list of measurements and findings. In fact, I hold in my hands a brand new copy of Gian Francesco Giudice's book, "A Zeptospace Odyssey - A Journey into the Physics of the LHC". All I have to do is to explain to you why you really should buy, read, and give as a present this book to all your friends.

Gian Francesco Giudice

First of all, a word on the author. Gian Francesco Giudice is a brilliant theoretical physicist who has worked at the CERN laboratories in the Theory Division since 1993. His scientific career brought him in many places before that, but it originated in Padova University, the place where I myself studied and now work. He is only five years older than me, but together with my slow academic career they were enough to get me to enjoy him as a teacher in a course on Group Theory during my Ph.D. studies in Padova. Since then, there is respect and friendship among us, although I see him rarely.

Giudice is a clear thinker and the Physics Department in Padova University aches for his escape, but he is always greeted warmly when he visits us. His last visit was two weeks ago, when he gave a very insightful lecture. It was only then that I learned about his book, silly me.

Giudice has authored dozens of important scientific publications. Before I describe his book, let me cite here a few recent ones. To make the list very short, I only pick papers with more than 50 citations produced in the last six years.

- "Towards a complete theory of thermal leptogenesis in the SM and MSSM", with A. Notari, M. Raidal, A. Riotto, A. Strumia . 56pp. Published in Nucl.Phys.B685:89-149,2004, cited 333 times.

- "Split supersymmetry", with A. Romanino. 28 pp.
Published in Nucl.Phys.B699:65-89,2004, cited 319 times.

- "Aspects of split supersymmetry", with N. Arkani-Hamed, S. Dimopoulos, A. Romanino. 51pp. Published in Nucl.Phys.B709:3-46,2005, cited 235 times.

- "The Well-tempered neutralino", with N. Arkani-Hamed, A. Delgado. 29pp.
Published in Nucl.Phys.B741:108-130,2006, cited 68 times.

- "The Strongly-Interacting Light Higgs", with C. Grojean, A. Pomarol, R. Rattazzi. 45pp. Published in JHEP 0706:045,2007, cited 95 times.

The Book: first impressions

The book is a nice-looking hardcover volume, published by Oxford University Press earlier this year. It is not thick enough to scare you away, and once you open it and start turning its pages, you get a feeling of the clean, tidily typeset and clearly readable text. You soon find dozen of beautiful pictures in black and white, few graphs all looking simple to understand, and absolutely no mathematical formulas. This is a book for everybody! But can it, given the subject ?

Yes, the subject: this is a book about the journey that the Large Hadron Collider at CERN has undertaken, a journey inside the smallest distance scales which will hopefully bring us to find new riches, and make humanity wealthier of knowledge on the physical world. Divided in three parts ("A matter of particles", "The starship of zeptospace", and "Missions in zeptospace"), it contains 13 sections whose titles appear indeed arcane: forces of nature, dealing with naturalness, supersymmetry, from extra dimensions to new forces. Can this be a book for everybody after all ?

Of course it can! As I recently argued here, no scientific concept is too hard to explain to a reader willing to make a sincere effort. Only, it takes the most capable writer to do the trick. And Gian Francesco is a sublimely capable writer!

I am probably not the best of judges for what concerns the English prose of the book -I am Italian, just as Giudice is-, but I must say that I find the text exceedingly clear and well written. The author makes a real effort to not only explain in the simplest way, and with plenty of spot-on analogies, all the concepts that he believes are necessary in order to perform this journey, but he manages to make the reading quite enjoyable in the meantime! The book is a real mine of anecdotes intertwined with physics explanations, such that it reads very easily and you absorb a wealth of knowledge in the process almost without realizing it.

Let me make a few examples to explain what I mean here. If you are a reader of this blog you must know that I appreciate analogy as a powerful means to make tough physics concepts understandable; if you are not one, you might get a proof of that by reading my recent explanation of electroweak unification using a cup of chocolate, for instance. Being fond of analogies, I could not help appreciating the witty and fun way Gian Francesco explains complicated mathematics such as renormalization, one of the toughest hurdles in making sense of the theory of quantum electrodynamics:

"Imagine that tomorrow is St Valentine's Day. You and your friend David Beckham go out shopping to buy presents for your respective wives. You enter a store an David chooses for Victoria 30 diamong chokers, 50 emerald bracelets, 60 fur coats plus some other expensive items. He keeps careful track of his expenditures, which total some megabillion zillion euros. You pick up a small bouquet of flowers, whose price isn't marked. In the confusion at the checkout counter, all your purchases are rung up together and the total bill aounts to some megabillion zillion euros. Must you really pay some megabillion zillion euros for a bouquet ? Of course not: all you have to do is take the difference between the total bill and David's share, and you find that you must pay only 19 euros and 99 cents.

Something similar happens in calculations of QED. Most of the results of these calculations are equal to colossal numbers (actually infinity). However, these results do not correspond to measurable physical quantities, as much as the total bill above does not refer to what you must actually pay. Once the result of a physical quantity is appropriately expressed in terms of other physical quantities, colossal numbers are subtracted from each other and the result is a perfectly reasonable small number [...]"

The book contains countless quotes from the actors of the play of XXth century physics. I am also a collector of quotes, yet I was happy to find several that I had never heard before. And Gian is quick also to explain things that other authors overlook, oftentimes by using quotations, some of which are of true historical importance. Take this introduction to the neutrino:

"The name "neutrino" was coined jokingly by Enrico Fermi [...] when, during a seminar in Rome, he was asked if the two particles were the same. "No," replied Fermi, "Chadwick's neutrons are large and heavy. Pauli's neutrons are small and light; they must be called neutrinos." Of course the pun is lost in the English translation: in Italian "neutrino" is the diminutive of "neutron" - "little neutron".

How many of you non-Italian speakers knew this ?

To end this section, I need to mention an accident, which I hope will clarify just how accurate this book is. I wanted to write a paragraph here where I would say that incomplete explanations are a problem of any book which attempts the arduous task of explaining tough science to outsiders. I wanted to make the point that it is virtually impossible to stop and make sense of ALL the crucial concepts that arise in an explanation of physical concepts needed to read back-to-back a 250-page-long book. I had spotted one early on: on page 24, one reads that "... general relativity is not just a reformulation of Newton's theory. It predicted new effects - like the anomalous precession of Mercury perihelion[...]".

Aha! Gian fails to explain what this is here. What the heck is the anomalous precession of the perihelion of Mercury ? A non-physicist reading this sentence might be rightfully upset! ...But does he ? He doesn't. A glance at the Index under "Mercury" will reveal that later in the book, on page 224-225, the mysterious planet is mentioned again. And there, eventually, the diligent reader will finally find an answer to his doubt!

So, I owe apologies to Gian Francesco for having doubted of the completeness of this lean but self-sufficient book.


No review of a book would be complete without at least an attempt at criticizing its contents. I have read the book, and as I already said I found it clean, well written, and remarkably precise. I have nothing to say about the topics: the book covers the history of physics which lead to today's accelerators, the construction of the monster apparata, all the important goals of the LHC, not sparing even the most complex, cutting-edge theories of new physics. However, as they say "there's always one more bug". So let me have a shot at it. My list will be exceedingly short.

1. On page 27, talking of protons accelerated by the Bevatron in 1955, Gian says that "The proton energy was enormous for those days, but is actually less than a thousandth of the energy of a single LHC beam." Of course, he means "the energy of a proton in a LHC beam". The energy of a single LHC beam is trillions of times larger, being contributed by billions of protons.

2. It feels bad to criticize a very well-compiled Index, which is 20-pages long and is a quite useful addition to such a quotation-full book. However, the duty of the reviewer forces me. On page 276 the Index cites a "Wiloczek, Frank" which three lines above is correctly reported to reference two different pages as "Wilczek, Frank". The reference to page 71 should be thus added three lines before, and this line deleted. To be frank (with a lowercase f), the page-71 reference to Wilczek is correctly appearing on page 268, in the reference to "Nobel Prize".

3. As I already mentioned, the English in the text is quite correct and flowing. This is not surprising, given that if you heard Gian Francesco talk you might well exchange him for a Brit (the lack of typical Italian straggling of words in his pronunciation is remarkable). Even commas are used appropriately, following the so-called "Harvard comma" rule for serial lists (a comma is due before the last "and"). However, I found an inconsistent use of British versus American English spelling. On page 10 we read the word "color" and just one line below the word "odour". Who cares, you might ask! True, who cares. But since even 2000-strong scientific collaboration end up arguing at such level of detail on their drafts of scientific publications, I thought I would mention it...

A short interview with the author

Gian was kind enough to answer a few questions on his book for this blog. Here are five questions I posed, and his answers (in Italics):

1 - I am curious to know what brought you to the idea of this book, because I had no previous recollection of popularization activities on your part. What played a major role in deciding to write it: opportunity (being the right person in the right place and with the right means to write a very good account of the LHC adventure), desire to involve more people in the science we do, a challenge with yourself ? Or something else ?

It all started with some public lectures I gave on LHC physics. It was a surprise for me to see first hand how so many people, even those with no physics background, are sincerely fascinated by this wonderful scientific adventure. But at the same time I was really taken aback to see how the media coverage and newspaper articles were grossly misrepresenting the real aims of the LHC, feeding wrong information to the public. Explaining our research activity in simple and accessible terms does not necessarily require being scientifically inaccurate. So I decided to tell the story from a physicist's point of view. Any tale is more enticing when narrated by someone who is participating in the story.

2 - The text is quite clean and devoid of complications - there are no formulas, no graphs, and even the use of scientific notation for numbers is introduced by an apology. When you wrote your book did you aim at the widest possible audience, or was your choice of material rather driven by a specific target (such as, by means of example, high-school students) ?

The book is directed to anyone who is curious about the world of particle physics and the LHC. I made an effort to avoid technical terms and make sure that readers with no physics background could follow the story. But hopefully even physicists (especially young physicists) working at the LHC might find in the book elements that can help them broaden their views on their experiment and their field.

3 - Did anybody help you find and choose the dozens of appropriate quotations that are used in the book to introduce chapters and even subsections ? Their breadth is remarkable.

I like to read and this helped me. The quotations I collected from various authors and disciplines are mostly meant to bring a touch of irony in the presentation of a scientific field that most people believe to be high-browed and arcane. But they are also meant to show how physics is intertwined with other creative, artistic and speculative human activities.

4 - I know very well that you are a busy scientist, and your time is precious. Decreasing your involvement in your studies is probably out of the question, even for a noble goal like that of writing a popularization book on particle physics. How long did it take you to write this book ? Did you take a leave from work to finish it, or did you overburden your summer vacations, or did you instead proceed slowly by using your spare time in tiny bits ?

Finding the time to write was the most serious difficulty I had to face. The project took me about a year, and nights and weekends were my favourite writing periods. My family has been very kind and patient during that time.

5 - Although any book like yours is one of a kind, there always exist similarities in the way they are constructed, or in some choices like the material covered or the depth with which topics are discussed. Did you find inspiration in any previous book by particle physicists? Is there a model you followed ?

I read many books related to particle physics before and during the writing, and I learned much from them. Many of these great books have certainly influenced the way I view the development of our field and the meaning of the LHC. I absorbed this material, but I don't think I followed one particular book or author as a model. Instead I tried to adopt a writing style which is just a crossover from the style of my seminars and public lectures. I like to link ideas and developments in science with their historical context and to present advanced concepts in theoretical physics using simple and familiar analogies.

What others think

If you got this down in my review, you will no doubt have gotten the impression that I was paid very well for my lip service! No kidding: the fact is, my salary was a copy of the book, and my reward in writing the review was ... writing the review! I did not need to lie in the least. But to show you that I am in good company in appreciating Giudice's work, below I attach a short list of reviews on Giudice's book by unsuspectable arbiters.

"Gian Giudice has, as one would expect from such a clear and original thinker, produced a book which both challenges and excites, providing fresh insights into the domain of particles and their interactions. " - Ken Peach, University of Oxford and Royal Holloway University of London.

"This fascinating book is entertaining and comprehensible, leading the reader to the world of extremes: the high technology of the Large Hadron Collider at CERN and its huge particle detectors, the quest for the Higgs particle and the mysterious Dark Matter, and the theories of superstrings and extra dimensions at the verge of human imagination." - Thomas Lohse, Humboldt University, Berlin, Germany.

"I enjoyed this book tremendously. The weaving of important information with fun facts and anecdotes was awesome." - Savas Dimopoulos, Stanford University.

"This book shows that it is possible to describe to non-experts the frontiers of modern physics, in a way which is both faithful and comprehensible. I almost envy the author his right-on-the-bull's-eye explanatory metaphors. I believe that this book will become required reading for anyone interested in the reality of our world and in scientific human endeavour." - Riccardo Barbieri, Scuola Normale Superiore, Pisa, Italy.

"Gian Giudice provides a comprehensive introduction to the LHC as only a physicist working in the field could do." - Lisa Randall, Harvard University.

"Gian Giudice has given us a charming, comprehensive, and deep yet easily readable description of the history, technology, and scientific aspirations of the Large Hadron Collider, perhaps the greatest scientific experiment ever." - Gordon Kane, University of Michigan.

"This book, written by one of the leaders of the field, has a number of outstanding qualities: it is brilliant, original, comprehensive, entertaining and clear. It is a must for cultivated, non specialist readers who want to get an introduction to contemporary particle physics and to the exciting programme of the Large Hadron Collider of CERN." - Guido Altarelli, University of Rome and CERN.

"Gian Giudice has drawn on his deep understanding of physics to write a wonderful book, presenting the central ideas underlying the grand intellectual adventure of particle physics in an engaging and thought-provoking way. A must read for anyone who wants to understand the big questions we face in fundamental physics, and the ways we are tackling them." - Nima Arkani-Hamed, Institute for Advanced Study, Princeton.

A final advice

Buy the book. Read it, appreciate it, and then buy more copies as a gift for friends and relative of yours who think they would not understand particle physics for the life of them. They will be grateful!

Wednesday, June 9, 2010

Physics at the LHC – What did Guido mean!?

My summer has started. And the first stop is the conference Physics at the LHC 2010 conference (or pLHC as it has been known internally by the experiments).

As Barbara already mentioned, this conference, occurring this week in Hamburg, Germany, is a preview of results we might expect at ICHEP.

It is Wednesday morning and all the LHC experiments have big plenary talks discussing overviews of their physics current results. One of the CMS results has already been discussed by Tommaso. The results all show the first time the experiments are gingerly dipping their foot into the pool of physics. Ok, so it is the shallow end right now. Observation of many quark-onia bumps, but some real new measurements not done at the LHC’s new higher-than-ever energy, 7 TeV. But they also include the first observation of the W boson and the Z boson at the LHC. Now we’re talking!

One fascinating conversation occured right at the start of the meeting. It was a discussion that occurred during the introductory talk by Guido Tonelli, the spokesperson for CMS (video available). Sitting in the audience was Steven Myers from CERN, who runs the LHC (who also gave a talk on the present and near future of the LHC machine). Both Guido and Fabiola Gianotti (ATLAS spokesperson) pleaded with Steve to give them more luminosity. Guido went one step further and said that if they can give CMS enough luminosity in the next month they will measure the Standard Model for ICHEP.

What does that mean? Both experiments have observed the W boson now. Does that mean measuring its cross section? Or an observation of top quark production? Is there any reasonable plan for the LHC that would give it enough luminosity to observe top quark production!? Or was it just a flashy statement made to urge Steve to give the experiments more data? Does CMS have something up their sleeve? I guess time will tell… And both CMS and ATLAS will do push their data as far as they can.

Update: at the end of the CMS talk, slide 54, there is the statement “100 nb-1, 380 W and 35 Z”, and the speaker said “this we can be sure of.” So, that gives the scale of the CMS plans. And lets hope the LHC can actually give us that 100 np-1 of data!

Late to the party…

Hi all! We are now about 6 weeks out from the start of ICHEP, and this is my first blog post. So introductions are in order. I’m a professor at the University of Washington, located in fantastic Seattle (we only tell people it is raining…). I’m an experimentalist working on the DZERO experiment at the Tevatron and the ATLAS experiment at the LHC.

I maintain another blog (sporadically). If you read through it you’ll quickly discover my main interests. I love high-pT physics. DZERO’s recent B’s mixing result (see Jester’s earlier posts on it here and here) is fascinating, but sadly aren’t things I work on. I tend to be more interested in top, Higgs physics, and, recently exotic physics. On the flip side I’ve long been fascinated with computing in HEP, having started in high school programming a LeCroy FASTBUS microcontroller (yeah, yeah, tell me about it, I didn’t get out much).

This year’s ICHEP should be special for the LHC and the Tevatron experiments. I know this because of how busy everyone is in the experiments… More on that in a future post.

Monday, June 7, 2010

Physics at LHC

This week some 270 people are getting a taster of what ICHEP may (or may not) be like: at Physics at LHC, a conference that started today at DESY in Hamburg, Germany, about, well... physics at the LHC. I've heard some hints that different results will be available for the summer conferences, seen many interesting talks and heard many excited scientists getting pure bliss out of the fact that they can finally present real data from real collisions at a really remarkable LHC.

If you're not in Hamburg you can still follow the action -- the talks are webcast and also recorded and put up on the conference's indico page along with the slides.


Friday, June 4, 2010

News From The Third World Of Research - Italy

Economy, and all the more so politics, should be of no interest to a focused researcher in fundamental Physics, in an ideal world. But we do not live in an ideal world.

After two years spent saying that Italy has a strong economy and is doing better than the rest of Europe, and strongly criticizing whomever tried to warn that the economical crisis was not over yet, the Italian government led by Silvio Berlusconi has made a sharp turn. The buzzword is now "avert the Greek risk", and while painting dreadful scenarios Berlusconi and his ministers have crafted a finance law that drags over 30 billion euros mostly from salaries. The anti-Robin-Hood strikes again.

The thing would be sad by itself, but some of the ancillary rules contained in the new law will have a devastating effect on basic research. I can only speak for particle physics, where I know how funds are spent. For the most part, funds in particle physics research are administered quite well in Italy, a result of the narrow margin within which researchers have to manouver; there are cases of abuse, but these are rare. Let us take the case of the participation to CERN and its experiments.

In order to participate in the large experiments at the CERN laboratory, over 1000 researchers based in Italian universities need to periodically travel to Geneva. Actually, the participation to the experiments forces researchers to make themselves available for week-long shifts at the data-taking, plus of course performing maintenance to the detector components they themselves built. Then there are meetings, working groups, etcetera -but these are not crucial activities, since they can be performed through remote videoconferencing.

Now, what does the new finance law says ? It says that effective June 1st, the per-diem compensation of researchers traveling abroad (some 120 euros per day, with which one should pay for lodging, meals, and all the rest) is zeroed. Only lodging expenses are refunded, and we do not yet know whether meals will be in some way paid back. Furthermore, the law states that the total expense of institutes such as INFN -the Italian Institute of Nuclear Physics that hired me- for missions abroad cannot exceed 50% of what was spent last year. Since we are in June, you can well understand how narrow a margin this leaves for travel abroad in 2010!

Now, since without Italian researchers the CERN experiments cannot run safely, unless they overburden with shifts the scientists from other countries, the matter poses a urgent problem. In principle, one might think that physicists do not work for a salary, but for the beauty of science: this would not be far from the truth in the case of Italian physicists, since their salary is about a third of that of our colleagues from the US, Germany, or many other countries. So we can expect that Italian researchers will bow their head and continue working abroad even if they spend more than what they earn. But I have my doubts.

The matter is made complicated by the fact that INFN promised quite a bit of support, in terms of available manpower, to the CERN experiments. These agreements will go unattended if the Italian government does not repair the awkward situation.

UPDATE: two links.
The first link is to Peppe Liberti's blog, who translates in Italian part of the text above in a post on the same topic.
The second is the original text of the law (in Italian only, sorry). You can find the part of relevance to researchers traveling abroad in section 6, subparagraph 12.