I feel it mine

This is a reblog from Quantum Diaries

By Andrea Signori, Nikhef researcher (Theory)

On Saturday, 4 October, Nikhef – the Dutch National Institute for Subatomic Physics where I spend long days and efforts – opened its doors, labs and facilities to the public. In addition to Nikhef, all the other institutes located in the so-called “Science Park” – the scientific district located in the east part of Amsterdam – welcomed people all day long.

It’s the second “Open Day” that I’ve attended, both as a guest and as guide. Together with my fellow theoreticians we provided answers and explanations to people’s questions and curiosities, standing in the “Big Bang Theory Corner” of the main hall. Each department in Nikhef arranged its own stand and activities, and there were plenty of things to be amazed at to cover the entire day.

The research institutes in Science Park (and outside it) offer a good overview of the concept of research, looking for what is beyond the current status of knowledge. “Verder kijken”, or looking further, is the motto of Vrije Universiteit Amsterdam, my Dutch alma mater.

I deeply like this attitude of research, the willingness to investigating what’s around the corner. As they like to define themselves, Dutch people are “future oriented”: this is manifest in several things, from the way they read the clock (“half past seven” becomes “half before eight” in Dutch) to some peculiarities of the city itself, like the presence of a lot of cultural and research institutes.

This abundance of institutes, museums, exhibitions, public libraries, music festivals, art spaces, and independent cinemas makes me feel this city as cultural place. People interact with culture in its many manifestations and are connected to it in a more dynamic way than if they were only surrounded by historical and artistic.

Back to the Open Day and Nikhef, I was pleased to see lots of people, families with kids running here and there, checking out delicate instruments with their curious hands, and groups of guys and girls (also someone who looked like he had come straight from a skate-park) stopping by and looking around as if it were their own courtyard.

The following pictures give some examples of the ongoing activities:


We had a model of the ATLAS detector built with Legos: amazing!








And not only toy-models. We had also true detectors, like a cloud chamber that allowed visitors to see the traces of particles passing by!

And not only toy-models. We had also true detectors, like a cloud chamber that allowed visitors to see the traces of particles passing by!









Weak force and anti-matter are also cool, right?






The majority of people here (not me) are blond and/or tall, but not tall enough to see cosmic rays with just their eyes… So, please ask the experts!











I think I can summarize the huge impact and the benefit of such a cool day with the words of one man who stopped by one of the experimental setups. He listened to the careful (but a bit fuzzy) explanation provided by one of the students, and said “Thanks. Now I feel it mine too.”

Why pure research?

This is a reblog from Quantum Diaries!

By Andrea Signori, Nikhef researcher (Theory)

With my first post on Quantum Diaries I will not address a technical topic; instead, I would like to talk about the act (or art) of “studying” itself. In particular, why do we care about fundamental research, pure knowledge without any practical purpose or immediate application?

A. Flexner in 1939 authored a contribution to Harper’s Magazine (issue 179) named “The usefulness of useless knowledge”. He opens the discussion with an interesting question: “Is it not a curios fact that in a world steeped in irrational hatreds which threaten civilization itself, men and women – old and young – detach themselves wholly or partly from the angry current of daily life to devote themselves to the cultivation of beauty, to the extension of knowledge […] ?”

Nowadays this interrogative is still present, and probably the need for a satisfactory answer is even stronger.

From a pragmatic point of view, we can argue that there are many important applications and spin-offs of theoretical investigations into the deep structure of Nature that did not arise immediately after the scientific discoveries. This is, for example, the case of QED and antimatter, the theories for which date back to the 1920s and are nowadays exploited in hospitals for imaging purposes (like in PET, positron emission tomography). The most important discoveries affecting our everyday life, from electricity to the energy bounded in the atom, came from completely pure and theoretical studies: electricity and magnetism, summarized in Maxwell’s equations, and quantum mechanics are shining examples.

Books, the source of my knowledge

Books, the source of my knowledge

It may seem that it is just a matter of time: “Wait enough, and something useful will eventually pop out of these abstract studies!” True. But that would not be the most important answer. To me this is: “Pure research is important because it generates knowledge and education”. It is our own contribution to the understanding of Nature, a short but important step in a marvelous challenge set up by the human mind.

Personally, I find that research into the yet unknown aspects of Nature responds to some partly conscious and partly unconscious desires. Intellectual achievements provide a genuine ‘spiritual’ satisfaction, peculiar to the art of studying. For sake of truth I must say that there are also a lot of dark sides: frustration, stress, graduate-depression effects, geographical and economic instability and so on. But leaving for a while all these troubles aside, I think I am pretty lucky in doing this job.

During difficult times from the economic point of view, it is legitimate to ask also “Why spend a lot of money on expensive experiments like the Large Hadron Collider?” or “Why fund abstract research in labs and universities instead of investing in more socially useful studies?”

We could answer by stressing again the fact that many of the best innovations came from the fuzziest studies. But in my mind the ultimate answer, once for all, relies in the power of generating culture, and education through its diffusion. Everything occurs within our possibilities and limitations. A willingness to learn, a passion for teaching, blackboards, books and (super)computers: these are our tools.

Citing again Flexner’s paper: “The mere fact spiritual and intellectual freedoms bring satisfaction to an individual soul bent upon its own purification and elevation is all the justification that they need. […] A poem, a symphony, a painting, a mathematical truth, a new scientific fact, all bear in themselves all the justification that universities, colleges and institutes of research need or require.”

Last but not least, it is remarkable to think about how many people from different parts of the world may have met and collaborated while questing together after knowledge. This may seem a drop in the ocean, but research daily contributes in generating a culture of peace and cooperation among people with different cultural backgrounds. And that is for sure one of the more important practical spin-offs.

HCP in Kyoto over Higgs en Susy

Door Nicolo de Groot

Het Hadron Collider Physics Symposium wordt van 12 tot 16 November in Kyoto gehouden. Het wordt gevolgd door de Higgs coupling workshop. Nu worden er wel meer conferenties in ons vakgebied gehouden, maar deze is interessant omdat ATLAS en CMS updates zullen presenteren van hun Higgs resultaten in juli. De LHC heeft prima gedraaid en voor de vlaggeschip analyses is ruwweg twee keer zoveel data beschikbaar als voor de ontdekking in juli.

Wat kunnen we verwachten ?

De Higgs kan op verschillende manieren uiteenvallen. Deze zomer is de Higgs ondekt in het verval naar twee fotonen of lichtdeeltjes en het verval naar W en Z deeltjes, de dragers van de zwakker kernkracht. Bij de laatste twee kanalen was ook mijn groep betrokken. Dit zijn allemaal ijkbosonen, deeltjes die dragers van de fundamentele krachten zijn. De Higgs zou ook moeten vervallen naar fermionen, materiedeeltjes. Dat hebben we nog niet gezien en ik verwacht nieuwe resultaten van ATLAS en CMS over Higgs naar b quarks of naar tau leptonen. Voor het laatste vervalkanaal presenteerde CMS in de zomer resultaten. De meting was gevoelig genoeg om een hint te zien, maar wonderlijk genoeg was er geen zichtbaar signaal. Het wordt interessant om de nieuwe getallen van beide experimenten te zien en te weten of dit een fluctuatie is, of dat de Higgs zich misschien een beetje anders gedraagt.

Verder staan de kwantumgetallen op de agenda. Dat zijn de eigenschappen van het deeltje. We mogen dan wel een nieuw deeltje gevonden hebben terwijl we naar de Higgs zochten, zeker weten dat het een Higgs is doen we pas als we de eigenschappen gemeten hebben. Het gaat hier om de spin, hoe snel het deeltje draait om de eigen as en de pariteit, het gedrag bij spiegeling. Van de spin weten we dat het 0 of 2 kan zijn. Het Higgs deeltje hoort 0 te hebben. De van de Higgs hoort positief te zijn. Door te kijken naar de hoeken waaronder de vervalsproducten van de Higgs geproduceerd worden, kun je hier iets over zeggen. Daar zijn we in het geval van WW en ZZ druk mee bezig. De dataset van vandaag is te klein om een definitief antwoord te geven, maar kan al
wel een duidelijke voorkeur laten zien.

Er zijn nog een hoop vragen open over dit nieuwe deeltje. Is het alleen of zijn er meerdere ? Is het fundamenteel of samengesteld uit andere deeltjes en is het een pure vorm of een mengsel van twee toestanden. Ook, en het meest interessant, kan dit deeltje ons iets laten zien van de fysica die achter het Standaard Model ligt. Immers, het Standaard Model dat zo indrukwekkend precies de metingen beschrijft moet incompleet zijn. Zwaarte kracht ontbreekt erin en ook is een geen deeltje wat de donkere materie kan beschrijven. We verwachten dat er een uitbreiding van het Standaar Model nodig is en dat ergens bij een hogere energie de zware deeltjes van die uitbreiding zichtbaar worden. Het Higgsdeeltje koppelt aan deeltjes met een sterkte die afhangt van de massa en is bij uistek gevoelig voor die deeltjes. Deze deeltjes veranderen de koppeling van de Higgs aan gewone deeltjes door kwantum effecten. Dit is de reden dat er een aparte workshop aan Higgs koppelingen is gewijd. Door de koppelingen in verschillende kanalen goed te bestuderen en te zoeken naar afwijkingen van het Standaard Model kan de Higgs een poort vormen naar nieuwe fysica. De resultaten van afgelopen waren met net genoeg data voor een ontdekking, maar toen werd al opgemerkt dat Higgs naar twee fotonen in zowel ATLAS als CMS te vaak voorkomt. Of dat effect blijft bestaan met meer data is de vraag, maar wel iets om in het oog te houden. Mijn favoriete kanaal in dit opzicht is dat waar een Higgs boson samen met een paar top quarks wordt gemaakt en dan vervalt naar een paar b quarks. Het is heel gevoelig voor effecten van nieuwe deeltjes, maar moet nog even wachten tot 2014 als de LHC naar hoge energie gaat om gebruikt te kunnen worden.

Dan is er ook nog supersymmetrie. De zoektochten op 7TeV data in 2011 leverden niets op. Ook heeft de Higgs ontdekking een ware slachting aangericht onder de mogelijk modellen van supersymmetrie. Ik verwacht op HCP in ieder geval een aantal resultaten met de 2012 data op 8TeV en die zouden gevoeliger moeten zijn. Als we nog steeds niets zien, hebben we in ieder geval betere limieten. Ook de Higgs koppelingen zullen het mogelijke Susy gebied steeds verder inperken. Kortom het werk is nu pas echt begonnen.

(Vandaag geblogt op het persoonlijke blog van Nicolo de Groot)

Het Tevatron ziet ook een glimp van de Higgs

Door: Nicolo de Groot.

Vandaag heeft het Tevatron, de versneller van het Fermilab in Chicago de laatste resultaten over de zoektocht naar het Higgs deeltje gepresenteerd. Aanvankelijk was het de bedoeling dat de resultaten gewoon op de ICHEP conferentie gepresenteerd zouden worden, maar nu CERN de presentatie van de LHC Higgs resultaten naar 4 Juli heeft gehaald, heeft Fermilab besloten CERN voor te zijn en nog een keer te vlammen.

De analyses van 27 verschillende kanalen worden door de D0 en CDF experimenten gecombineerd om tot deze meting te komen. Afzonderlijk zijn deze metingen niet heel gevoelig, maar bij elkaar opgeteld is het wel mogelijk om een uitspraak te doen over het al dan niet bestaan van een Higgs deeltje.

De conclusies: er wordt een mogelijk Higgs signaal gezien dat van 3 sigma. Sigma is de onzekerheid van de meting en dit betekent dat de data een overschot aan Higgs-achtige botsingen heeft van 3x die onzekerheid. Dit was ongeveer de situatie waar de LHC experimenten in december 2011 en wordt typisch beschouwd als een hint. Vier sigma is bewijs voor en vijf sigma een ontdekking. Een ontdekking is het dus niet, maar wel een stevige hint, te vergelijken met wat de LHC in december zag. Ook kunnen zij de massa van het mogelijke Higgs deeltje bepalen. Deze is 125 GeV met een onzekerheid van 7 GeV, ongeveer 130x de massa van een waterstofatoom. Dit is precies waar de ATLAS en CMS experimenten in 2011 ook een hint zagen en maakt het aannemelijk dat het om een echt signaal gaat.

Over twee dagen presenteren ATLAS en CMS hun resultaten. De experimenten hebben twee jaar net zoveel data verzameld als D0 en CDF in meer dan 10 jaar. Omdat de energie van de LHC veel hoger is, zullen zij met veel grotere precisie iets over de Higgs kunnen zeggen. Toch zijn de metingen van D0 en CDF belangrijk. Zij zien een Higgs signaal waarbij de Higgs vooral vervalt naar twee b-quarks. Dit verval is bij de LHC moeilijk waar te nemen. Daar wordt naar de Higgs gezocht in het verval naar twee fotonen, Z-deeltjes of W-deeltjes. Als er een nieuw deeltje gevonden wordt, is de eerste vraag of het wel een Higgs is, en zo ja of het de Higgs van het minimale Standaard Model is of misschien andere variant. Het vergelijken van de kanalen met b-quarks met die in fotonen, W en Z deeltjes is een belangrijke stap om deze vraag te beantwoorden.

Onze groep aan de Radboud Universiteit Nijmegen doet al jaren mee aan het D0 experiment op Fermilab en het ATLAS experiment op CERN. In D0 hebben we ons vooral gespecialiseerd in het identificeren van b-quarks. Vorige week promoveerde Melvin Meijer, onze laatste D0 promovendus, op een zoektocht naar het Higgsdeeltje. Met de LHC presentaties over twee dagen is het voor ons deze week dubbel druk en dubbel spannend. Het Tevatron heefthiermee een waardig slot gekregen en geeft nu definitief de fakkel over aan de LHC.

Origineel gepost op: http://nicolodegroot.wordpress.com/2012/07/02/het-tevatron-ziet-ook-een-glimp-van-de-higgs-2-2/


Higgs Forecast

By Frank Linde, Nikhef-director

89-94 kg is what I, much to my chagrin, read every Sunday morning when I step on my scale. And if you think about it: all this is the fault of the Higgs particle (denoted H), the generator of mass[1]. At least if the symmetry breaking mechanism (the Higgs mechanism, as implemented and first hypothesized by Higgs, Brout and Englert in 1964) in the Standard Model of elementary particle physics is correct. The Higgs mechanism is an ingenuous (and, very important, mathematically consistent) way to ‘explain’ a fundamental difference (i.e. symmetry breaking) between two of the forces in nature incorporated in the Standard Model: the long range of the electromagnetic force versus the short range of the weak nuclear force. In particle physics terminology[2] this boils down to:

Why is the mediator of the electromagnetic force (the photon, γ) massless i.e.
y=0 GeV/c2 while the mediators of the weak nuclear force (the W- and Z-bosons) are massive i.e. mW80 GeV/c2 and mZ91 GeV/c2?

The Higgs mechanism requires the entire Universe to be filled by a field (the Higgs field) in a peculiar ground state thereby rendering mass to the W- and Z-bosons while keeping the photon strictly massless. I admit this sounds very tricky and technical, but in essence similar symmetry breaking events happen in phenomena like ferromagnetism, superconductivity and the ordinary buckling of a compressed needle i.e. the transition from an a-priori (rotational) symmetric environment to a state with a preferred direction in space with lower energy. A bonus of the Higgs mechanism is that it can also be used to render mass to the elementary matter particles i.e. the so-called leptons: electron (e), muon (μ) and tau (τ) and their corresponding neutrinos (electron-neutrino, muon-neutrino and tau-neutrino) as well as the so-called quarks up (u), charm (c), top (t) and down (d), strange (s) and bottom (b). In the absence of the Higgs mechanism all these matter particles would also be massless; in flagrant contradiction with my weekly Sunday morning experience! Last but not least: the Higgs mechanism predicts the existence of a new and unique particle: the Higgs particle! To be clear, the Higgs is not yet another matter particle like the electron, neutrino or quark. Neither is the Higgs a force mediating particles like the photon, gluon or W- and Z-boson. But, once discovered, the Higgs will be the first particle in an entirely new league! Within the Standard Model all properties of the Higgs particle are known with the exception of its mass. To date the Higgs particle is the only ingredient of the Standard Model lacking experimental observation. As such it is not surprising that the quest for the Higgs particle discovery is the main trust of experimental elementary particle physics as best exemplified by the gigantic scale of CERN’s Large Hadron Collider (LHC) project with its primary aim of concluding the Higgs hypothesis. Preferentially by the unambiguous discovery of the Higgs particle or, if all else fails, by the exclusion of the existence of the Standard Model Higgs particle.

So leaving the theory aside: What is the experimental status of the Higgs?

The Higgs created a lot of excitement in the final days of CERN’s previous flagship accelerator: the Large Electron Positron collider or in short LEP. A few LEP events matched the hunted after e+e-→ZH topology[3] hinting at a Higgs mass of around 114.5 GeV/c2; just about the kinematic limit set by the highest LEP center-of-mass energies achieved. However, the signal was too marginal to claim a discovery. Imagine if people had listened more intently to Dutch Nobel laureate Martinus Veltman who already in the 1970s advocated that LEP should reach 300 GeV center-of-mass energies! Instead all LEP could finally conclude about the mass of the Higgs was that it must exceed 114 GeV/c2 and that, within the context of the Standard Model, a light Higgs (i.e. a Higgs mass well below about 185 GeV/c2) is favoured. These LEP constraints are shown as the green exclusion bands in the figure below.
After the closure of LEP in the year 2000, Fermilab’s Tevatron (USA) took over the Higgs hunt. The Tevatron is a 2 TeV center-of-mass proton–antiproton collider. At such a machine the dominant Higgs production process is through quark–antiquark annihilation into a W- or Z-boson with subsequent radiation of a Higgs i.e. a final state including a WH or ZH pair. The analysis of these final states in the presence of the debris of the proton and antiproton is infinitely more difficult than the super clean Higgs production signature at LEP. So difficult in fact that the final result is not yet public even though the Tevatron already shut down in 2011. What is clear is that the Tevatron results corroborate the LEP findings in favour of a light Standard Model Higgs and that a bit more of the Higgs mass range allowed by LEP can be excluded as sketched in orange in the above figure (the final Tevatron result will exclude a bit more and possibly even show a hint of Higgs production).

The LHC is designed to conclude the Standard Model Higgs saga. This means that irrespective of its mass the LHC will be able to either discover or refute the Standard Model Higgs. As opposed to Higgs production at the Tevatron, the dominant LHC Higgs production mechanism is through gluon–gluon fusion (the gluon is the mediator of the strong nuclear force) i.e. two gluons produce (via an intermediate top quark-pair) a Higgs particle. The Higgs particle immediately decays and, depending on the Higgs mass, very clean signatures can be isolated. In the Higgs mass range of interest, i.e. the light Higgs mass scenario 115-150 GeV/c2, two Higgs decay channels are favored:

H→ZZ→eeee, eeµµ or µµµµ; and

Higgs simulation

In here “µ” represents the muon, a heavy replica of the electron. Particles like electrons, muons and photons can be recognized and measured by the LHC detectors with excellent precision and hence allow precise reconstruction of the Higgs mass. In the adjacent figure this is shown for simulated data for a hypothetical Higgs mass of 130 GeV/c2 and on a ten times larger data sample than available to date (June 2012). The Higgs mass peak (in red) clearly stands out above the continuous γγ background.

Now for real LHC data: The first excitement came in on 13 December 2011 when during a joint ATLAS and CMS colloquium at CERN the two main LHC experiments reported their Higgs results to a packed auditorium at CERN and simultaneously to people all over the world. The message was clear: with the exception of a tiny window in the vicinity of 125 GeV/c2 the Standard Model Higgs was excluded! To raise the excitement, several Higgs candidate events were found near 125 GeV/c2 by the two experiments but their significance fell short to claim a discovery (the so-called 5-sigma criterion which basically rules out a background fluctuation mimicking the signal by 1 in 10 million). Next week CERN again organizes a joint ATLAS and CMS colloquium. Each collaboration doubled its 2011 data sample. Stay tuned and meanwhile you can admire Nikhef’s annual report 2011 cover shown on top and wonder whether or not (future Nobel laureate?) Peter Higgs is right about the outcome of the quest for the Higgs particle!

[1] Strictly speaking this is only true for the electrons i.e. a meager per mille of our body mass. The bulk of our body mass is due to the atomic nuclei i.e. the protons and neutrons which in turn are composed of quarks: up-up-down (‘uud’) for the proton and up-down-down (‘udd’) for the neutron. Even though the Higgs gives mass to the u- and  d-quarks, the actual mass of protons and neutrons stems from the binding energy of the quarks composing protons and neutrons via E=mc2!   

[2] In elementary particle physics masses are quoted in units of GeV/c2=109 eV/c2 with 1 eV/c2 being the energy an electron gains if accelerated by a 1 V battery and c the velocity of light in vacuum.

[3] In here e+ and e- represent the positron and the electron, respectively. The reaction e+e-→ZH means in words: the positron and electron annihilate one another creating a Z-boson which radiates a Higgs particle i.e. creating the “ZH” final state.

On the 4th of July, CERN is to give an update on the Higgs search as a curtain raiser to the ICHEP conference. For more information about the seminar and press conference, go to:



Een stapje dichter bij de Higgs?

Blogpost  (van zijn persoonlijke blog) door Nicolo De Groot, Nikhef-onderzoeker en hoogleraar natuurkunde aan de Radboud Universiteit Nijmegen.

Binnenkort gaat de belangrijkste zomerconferentie in de deeltjesfysica van start. De International Conference of High Energy Physics of ICHEP is van 4-11 Juli in Melbourne.

In December 2011 lieten zowel mijn eigen ATLAS experiment als de concurrent CMS de voorlopige resultaten zien van de zoektocht naar het Higgs deeltje.Beiden zagen een aantal kandidaten boven de achtergrond uitsteken zo rond een massa van 125 GeV. Het was niet genoeg om een ontdekking te claimen, maar interessant en hoopgevend was het zeken. Wat kunnen we op ICHEP verwachten ?

De LHC draait in 2012 met een hogere energie, 8 i.p.v. 7 TeV. Hierdoor zou de productie van Higgs deeltjes ruim 25% sneller moeten gaan. Helaas geldt dit ook voor de meeste achtergronden, zodat het netto effect hiervan kleiner is. De LHC draait erg goed dit jaar en de nieuwe dataset voor ICHEP is nu al 25% groter dan die van heel 2011.

Het Higgs deeltje wordt zelf niet gezien, alleen de deeltjes waarin het uiteenvalt. Voor een massa van 125 GeV zijn er drie vervalskanalen belangrijk. Het kanaal waarin een Higgs deeltje twee Z-deeltjes maakt die vervolgens weer in elektronen of muonen vervallen wordt het gouden kanaal genoemd omdat er heel weinig achtergrond zit. Met onze promovendus Antonio, die op CERN zit, werk ik met mijn Nijmeegse en Amsterdamse collega’s druk aan de verbetering van de muon identificatie en het begrijpen van de achtergronden.

In een ander kanaal gaat de Higgs naar twee W deeltjes die naar elektronen of muonen en twee neutrinos vervallen. Ook hier zijn we zeer actief. Dit kanaal is met de onzichtbare neutrinos experimenteel veel moeilijker. Omdat het wel veel vaker voorkomt speelde het een belangrijke rol bij het uitsluiten van een zwaardere Higgs van 130 GeV of meer.

Tenslotte is er het kanaal waar de Higgs naar twee lichtdeeltjes oftewel fotonen vervalt. Daar is veel achtergrond waarboven een klein piekje uitsteekt. Het is experimenteel minder moeilijk omdat er maar een soort deeltjes, de fotonen, goed geïdentificeerd moeten worden. Dit kanaal liet in 2011 de sterkste hint zien.

In de deeltjesfysica hanteren we bepaalde regels. Als een signaal 3x boven de achtergrond uitsteekt noemen we het een hint. Bij 4x is het bewijs voor en bij 5x is het een ontdekking. De december resultaten van de experimenten waren een hint, niet meer. In 2011 zagen beide experimenten nog iets minder dan 3x de achtergrond, dus een kleine hint. Omdat ze dit op ongeveer dezelfde plaats zagen, kun je de data samen nemen en dan is er sprake van een duidelijke hint. Met meer dan een verdubbeling van de data zou, als het om een echt signaal gaat, de combinatie van de experimenten ditmaal “bewijs voor” kunnen opleveren. Als de hint van 2011 vals alarm was, zouden we het signaal zwakker moeten zien worden. Op het ogenblik zijn we in een heel hectische periode om alles af te krijgen voor ICHEP. Wat het resultaat zal zijn kan ik nog niet zeggen. We hebben afgesproken daarover vooraf niet te lekken. Dat geldt ongetwijfeld ook voor het CMS experiment. Maar Higgs of geen Higgs, ICHEP belooft interessant te worden.

Inflation @ Stanford II: Eternal Physics Summer Camp

By Sander Mooij

It has been almost two months now that I’m visiting Stanford University, time for a new update. I like the life in the theory group a lot. Many discussions, many talks, a continuous flow. At the moment there’s some reconstruction going on, and one of the goals seems to be to fit in as many blackboards as possible.

These talks, by the way, always begin with some context background information, but that is a tricky thing here. Usually some of the people who initiated the whole field are actually in the audience. This can lead to interesting historical debates on who has exactly done what first…

Campus life continues to intrigue me. If you live here (I don’t) there seems to be no reason to leave the campus. Cheap sandwiches, Thai, Mexican or whatever food you look for is available. Soccer pitches, tennis courts, athletic tracks, swimming pools, it is all there. The campus stadium has a capacity of 50,000. It was used in the 1994 soccer World Cup and has hosted a Super Bowl.

My roommate Joris (former Nikhef master student, in the R&D group) has joined the Stanford campus band. Having all notes right is not most important, knowing when to throw your saxophone up in the air (and catch it again) is. Last week they played standing around one of the fountains on campus, with their cheerleaders inside.

Furthermore there is an enormous book store, a museum for modern arts, places for concerts and for plays, and there’s probably a lot more that I haven’t discovered yet. It really is like an eternal summer university camp. Last Saturday I passed the church on campus and there was a wedding going on.

In the meantime I have visited UC Santa Cruz for one day to give a seminar. Studying physics at the Santa Cruz campus is really like studying nature in nature. The campus is on a hill overlooking the ocean, covered in a forest. “Covered” has to be taken literally here: the buildings are not allowed to exceed the trees. Halfway up the hill there is an organic farm. After the talk I made it just in time to the “Strawberry Justice Festival” held there, with bands playing and experimental berry drinks.

There was also a short and surprising Nikhef-visit this last week. Mark Beker and Eric Hennes were just returning from a workshop in Hawaii and visited the campus for one day to give a talk. So that was nice to walk over the campus with our small Nikhef team!


Cruising the Rhine

The poem 'Die Lorelei' by Heinrich Heine

By Frank Linde

Having often spent days, weeks and even months on board of huge ocean liners as a sailor’s son, I never imagined myself signing up for a cruise on the Rhine. To make matters worse: I already get seasick on the 30 minutes ferry ride from Den Helder to Texel. Nevertheless, Thursday April 12 I boarded the ms Amacello opposite the Amsterdam central railway station for a Rhine cruise. I had an excellent excuse: I was asked to entertain the passengers with a lecture series covering: The quantum world; past & present at CERN; Why particle physics matters!; and Astroparticle physics. And the real clincher: I could take my lovely wife along as well!

The service onboard can be summarized in one word: excellent. I now even fancy pasta. Not to mention foie gras. And did you know you really can have smoked salmon with champagne for breakfast? It will probably cost me and my wife at least a month to get back to our regular weight. Culturally, our fabulous cruise master showed us, in his words, numerous ABCs, i.e. “Another Bloody Church”. Some of them and notably the ones in Cologne and Strasbourg were indeed very nice. Certainly much nicer than the modern art museum in Strasbourg which I now rank as the worst museum I ever visited (admittedly, I did miss a Kandinsky). For this I cannot blame the cruise master because we toured Strasbourg on our own on bikes provided by the ms Amacello crew. We had to sign a disclaimer (apparently an earlier passenger is still suing after a touring bus just about failed to knock him/her of his/her bike …). After signing, the receptionist almost fainted when we informed her we did not want the bike helmets. Only after we had explicitly added in handwriting on the disclaimer that we declined to use the offered helmets, we were allowed to take the bikes … Strasbourg by bike is really marvelous, in particular the “Petit France” quarter. Another Rhine valley gemstone turned out to be the town of Colmar. Certainly a place we plan to visit again and I even like (some, Gewürztraminer) German white wine now.

Now the real surprise of this cruise: the passengers. Being Dutch (or perhaps just stupid), I always thought Rhine cruises were targeted at not exactly my favorite public (to state it mildly). How wrong can one be, at least with this American-dominated group! I think I have  rarely given a public lecture for a more science-interested audience than on the ms Amacello. These people not only listened almost daily to my 1½ hour lecture, but as well to lectures on: antiquities (Egyptians, Greeks and Romans); the inner workings of our Sun; and biology even my daughter, a bio-medical student, could learn from. And if that is not sufficient, some even took part in the parallel running so called MacMania lecture series on iPad, iCloud, iPhone, photography and other interesting IT topics! (Not to mention of course the trips to e.g. the Max Planck institute for astrophysics in Heidelberg …).

For instance, I learned interesting things about Hannibal crossing the Alps and I learned things I really disliked entirely (it made me very queasy) on how the Egyptian “doctors” improved the eye sight of those suffering from cataract. During lunch and dinner we not only enjoyed the great food, but even more the excellent discussions on many diverse topics: volcanoes, the early days of computers, Feynman, dinosaur digs, nuclear energy policy, digital photo editing- and archive software, politics, etc. In summary: this turned out to be one of the most entertaining workshops I ever went to! As a result I might even track Hannibal on bike across the alps and/or go to a dinosaur dig in the Rocky Mountains. And I guess I will avoid Yellowstone Park as long as that huge volcano remains looming underneath it.

Also nice things come to an end: Thursday April 19th at 10:30 sharp (Swiss timing) our taxi picked us up to drop us at the Basel SBB railway station to start our eight hour return trip to Almere. One thing in common between our house and our cabin: they both are below the waterline …

P.S. I
And indeed me and my wife also participated in a sixties dance session (with some Elvis Presley look-a-likes) and we did rather well.
And of course I do hope that those passengers who went on to CERN, enjoyed an unforgettable experience at, in my opinion, the world’s nicest research facility!

Inflation @ Stanford

By Sander Mooij

Now that I am in my fourth year as a PhD student, I thought it would be interesting to work in another institute for some time. And see: after collecting some money at Nikhef and sending a couple of emails back and forth (and surviving a lengthy conversation with US customs), here I am at the Stanford Institute for Theoretical Physics!

First I have to write something about the Stanford campus. Being used to Science Park dimensions, I am extremely impressed. I did expect many institutes, libraries and student housings, but not such an entire organism. Why can’t there be a Nikhef Football Stadium? Or a Science Park golf course? Or a nursery and an elementary school? Well, probably because we lack some millionaires donating to Nikhef to have their name on a building (“see you at William Gates”). Besides I guess it’s also the Stanford brand (there is a dedicated clothing store here) that generates substantial income. And, oh yes, we don’t ask 26000 dollars per semester from our students. Anyway: this is enormous. The eternal blue sky above all of this doesn’t hurt either. (By the way: I should mention that my colleague-PhD students are most proud of the fact that the Stanford campus needs TWO zip codes.)

In the institute I mainly work with Russian Andrei Linde, who – just before my birth – was one of the founders of the paradigm of cosmological inflation, which is exactly what my PhD is about. About three times a week we have lengthy discussions in which one is mainly talking and the other is mainly taking notes. Needless to say that I profit a lot. Most often Andrei’s wife, supergravity expert Renata Kallosh, joins the conversation as well. All offices have blackboards reaching up to the ceiling. Being two meters tall this gives me a whole private space to write.

I share a visitor’s office with Taiwanese professor Kim W. Ng. The Stanford PhDs work either in some large mixed space, or in a small office with three or four, or – for those who are finishing – in an extremely small private space. No, that could never beat my good old H321b at Nikhef! Especially because the hierarchy here is such that only postdocs and staff (and visitors) have windows in their offices.

The atmosphere in the institute is quite OK. People are pretty accessible – also the big shots. I know that this sounds like a brochure but it is exactly what I would call “an inspiring and interacting work atmosphere”. Many talks and seminars are organized (last week we had Gerard ‘t Hooft). Lenny Susskind, the head of the group, sits in front and explains, when discussions take too long, in one phrase what the confusion is all about, and that the speaker should continue.

And then at 7 I take my beautiful race bike (169 dollars at the Walmart supermarket) and leave the “Stanford Bubble”. I live about seven kilometres away, with an Indian guy and another Dutch physicist, Joris van Heijningen, who has just finished a one-year internship at our R&D group. It is a small world!

The most frequently asked question

By: Frank Linde, director Nikhef

A guaranteed question after all (ok, almost all) of my public lectures is: “What is the societal impact of …?” In Tuesday night’s Dutch talkshow “Pauw & Witteman” Jolande Sap (member of Dutch parliament) asked Robbert Dijkgraaf (chairman of the KNAW, the Royal Netherlands Academy of Arts and Sciences) exactly this question. I already saw it on Jolande’s face while Robbert was giving his excellent explanation (and that for a theorist who, as far as I know, never dealt with the practicalities of experimental (particle) physics) on the impact of the events which took place earlier that day at CERN: the joint announcement of the ATLAS and CMS collaborations that first hints of the Higgs particle had been observed.

What Higgs? – What can we do with the Higgs?

How to answer this question properly? My first reaction is often: “What is the use of (classical) music, art, making love, theatre, etc.?” I.e. many things in life we simply do for relaxation, pleasure and fun. Personally, I think that is exactly what differentiates mankind from animals. And incidentally: it is probably also why we evolved over history to what we are today: a highly sophisticated society.

I fear, for many this is not sufficient and certainly not in today’s economic climate. So let me try better.

Somewhere around 1881 James Clerk Maxwell published an integrated theory of electricity and magnetism. This was the culmination of more than a century of experimental and theoretical research by numerous people. Maxwell’s new theoretical framework predicted the existence of “electro-magnetic waves”: an oscillatory phenomenon traveling at the speed of light, even in vacuum. Maxwell’s prediction’s societal impact was instant throughout the decades after: radio, television, microwaves, radar, mobile phones, optical communications, etc. Incidentally: ordinary light is also an electro-magnetic wave.

Who can imagine our society without all this?
Maxwell initiated a concept we particle physicists now call unification: a desire to incorporate the fundamental forces of Nature into a single unified theory i.e. formula.

Another example: in 1905 Albert Einstein published his theory of relativity. This time the societal impact took much longer. But thanks to Einstein: our GPS works properly; we have sufficient electrical power (albeit, since Fukushima I cease to be an advocate of nuclear power …); we have a plethora of nuclear-based healthcare machinery and treatment; etc. I cannot resist also mentioning the impact of the initially purely theoretical concept of antimatter (Paul Dirac, 1928): the so-called PET (positron emission tomography) which makes use of the anti-electron, coined positron, to visualize transport inside the human body. I can add: most (all?) non-invasive tools in medicine go back to nuclear physics (roentgen, NMRI, CT, SPECT, PET, …).
And last but not least: the World Wide Web, the biggest economic boom (and bust), in mankind was launched at CERN in 1989. And there is more.

But is this enough to guarantee future societal impact of ingenuity-driven research like CERN’s hunt for the Higgs particle?

Future will tell. Meanwhile, our universities and institutes like Nikhef train numerous, and often incredibly smart, youngsters to become original, independent researchers. Many of them opted for physics because of the challenges and progress in the quest for the fundamental building blocks of our Universe and their interactions! About 50% of Nikhef’s PhD students eventually pursue a career in private industries like Philips, ASML, Shell, finance and consulting companies to directly boost the Dutch economic activity. If that is still insufficient, the income tax paid by Nikhef graduates working in private industry alone corresponds more-or-less to Nikhef’s gross annual budget!

Finally: Are endeavors like CERN’s Large Hadron Collider (LHC) project expensive? Surely with an investment tag in the multibillion Euro range, the LHC machine isn’t cheap. But is it expensive? The LHC design started in the eighties of the last century. It was built between 1994-2008 (re-using the old LEP underground tunnel!). First turned on in September 2008 with a major incident soon after. As of November 2009 the LHC is operating smoothly at ½ of its design energy. In 2014 the LHC is expected to reach its design specifications. At present “standard” LHC operations are expected to continue until 2030. Around that time one of the options is to double the LHC energy and to run it for at least another decade. Hence we are talking about an one-of-a-kind worldwide 50-year project. Can one do research more efficiently than that? I do not think so. LHC investment costs amount to about 20 k€ per physicist per year, similar to the instrumentation expenses of many other experimenters. Of course there is a price to pay: particle physicists have to collaborate, to work incredibly hard to secure funding even in harsh economic times, to have the endurance to patiently work towards that fabulous moment that the facility is switched on and hopefully starts to deliver the physics it was built for. And in my opinion it is more than worth it: the first Z-events (1989) and WW-events (1994) at LEP or the first hints of the Higgs at the LHC (2011). And for you?

Finally: Robbert’s answer in response to Jolande’s question also boldly referred to nuclear power (a reality these days, even for those, like me, who dislike it).