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In the summer of 2012, a great discovery emerged at the Large Hadron Collider (LHC) at CERN in Geneva. A plethora of new precision data had already by then been collected by the ATLAS and CMS experiments at LHC, providing further extensive support for the validity of the Standard Model of particle physics. But what now appeared was the first evidence for what was not only the last unverified prediction of the Standard Model, but also perhaps the most decisive one: the prediction made already in 1964 of a unique scalar boson required by the theory of François Englert and Peter Higgs on how fundamental particles acquire mass. At that moment in 2012, it seemed particularly appropriate to start planning a gathering of world experts in particle physics to take stock of the situation and try to answer the challenging question: what next?

By May 2013, when the LHC Nobel Symposium was held at the Krusenberg Mansion outside Uppsala in Sweden, the first signs of a great discovery had already turned into fully convincing experimental evidence for the existence of a scalar boson of mass about 125 GeV, having properties compatible with the 50-year-old prediction. And in October 2013, the evidence was deemed so convincing that the Swedish Royal Academy of Sciences awarded the Nobel Prize in Physics to Englert and Higgs for their pioneering work.

At the same time the search at the LHC for other particles, beyond those predicted by the Standard Model, with heavier masses up to—and in some cases beyond—1 TeV, had provided no positive result. The triumph of the Standard Model seems resounding, in particular because the mass of the discovered scalar boson is such that, when identified with the Higgs boson, the Standard Model is able to provide predictions at energies as high as the Planck mass, although at the price of accepting that the vacuum would be metastable. However, even if there were some feelings of triumph, the ambience at the LHC Nobel Symposium was more one of puzzlement. The apparent absence of hints in the LHC experimental data of new phenomena that could relate to dark matter, dark energy, the dominance of matter over antimatter in the Universe, the unification of the strong and the electroweak interactions and their further unification with gravity left the Symposium with no guidance as to how to answer the question: what next? And in experimental fundamental science it is not the confirmation of already established theories that thrills the most; it is the appearance of the unexpected that creates the greatest excitement.

However, the LHC is only at the beginning of its voyage into the uncharted territories of higher energies and smaller dimensions that it was built for, so the possibilities for unexpected discoveries are only starting to be explored. The LHC will start up again in 2015 with nearly twice its previous energy and with increased luminosity—new discoveries might then appear sooner than we even dare hope for!

The LHC Nobel Symposium was attended by about 60 invited participants and lasted four days. The program was divided into seven sessions; QCD and Heavy Ion Physics, B Physics, Electroweak Physics, The Higgs Boson, Connections to Neutrino Physics and Astroparticle Physics, Beyond the Standard Model and Forward Look. There were 27 plenary invited talks given by participants, each followed by lively discussions. All but one of the speakers have submitted write-ups of their talks for these proceedings. We are hopeful that the remaining talk will be published in a forthcoming issue of Physica Scripta .

I am gratified that Professor Roland Allen has agreed to write a paper on the essence of the Higgs boson discovery to be published in Physica Scripta , intended for undergraduate students and educated physicists, regardless of their field of research.

I wish to express my deep gratitude to all Speakers and Participants in the Symposium, to the Members of the Local and International Organizing Committees, to the referees of these Proceedings and to the staff at Uppsala University, in particular my Administrative Assistant for the Symposium, Marja Fahlander, at the Royal Swedish Academy of Sciences, at the Nobel Foundation and at the Institute of Physics Publishing Company for Physica Scripta for realizing this enlightening Symposium at its proceedings.

The Nobel Symposium was financed by the Nobel Foundation.

Tord EkelöfChair of the LHC Nobel Symposium Local Organizing Committee and LHC Nobel Guest Editor for the Symposium Proceedings

Members of the Local Organizing Committee of the LHC Nobel Symposium

Tord Ekelöf (Uppsala University, Chair)

Kerstin Jon-And (Stockholms University)

Bengt Lund-Jensen (Royal Institute of Technology)

Anders Oskarsson (Lunds University)

Torsten Åkesson (Lund University)

Barbro Åsman (Swedish Royal Academy of Sciences)

Members of the International Advisory Committee of the LHC Nobel Symposium

Pierluigi Campana (INFN Frascati)

Fabiola Gianotti (CERN)

Paolo Giubellino (INFN-Torino)

Joe Incandela (UC Santa Barbara)

Young-Kee Kim (FNAL)

Michelangelo Mangano (CERN)

Lisa Randall (Harvard University)

This review gives a flavour of experimental quantum chromo dynamics (QCD) results obtained at the Large Hadron Collider (LHC) during the first run period in the years 2010–2012. The results cover selected aspects of soft low-p_T phenomena, typically described by phenomenological models, as well as high-p_T processes which can be studied theoretically with perturbative techniques. In general the phenomenological models required tuning to describe the data in the new energy region of 7–8 TeV, while perturbative QCD (pQCD) is found to work generally quite well for most of the phase space currently studied. The strong force will remain a main topic of research at colliders such as the LHC also in future, with the large data samples allowing for more detailed studies and in particular when the next energy level of 13–14 TeV will be reached.

At the LHC all processes are QCD ones, whether 'signal' or 'background'. In this review the frontiers of current QCD research are addressed, towards increased understanding, improved calculational precision, and role in potential future discoveries. Issues raised include:

• the limits of perturbative QCD calculations and parton distribution usage,

• the nature of multiparton interactions,

• the impact of colour reconnection on physical observables,

• the need for progress on hadronization modelling,

• the improvements of parton showers and their combination with the matrix-element description,

• the use of QCD concepts in Beyond-the-Standard-Model scenarios and

• the key position of event generators and other software in the successful exploration of LHC physics.

On the way, several questions are posed, where further studies are needed.

Towards the end of 2010, some 25 years after the very first collisions of ultra-relativistic heavy ions at fixed target energies, and some 10 years after the start of operation of the Relativistic Heavy Ion Collider, the Large Hadron Collider (LHC) opened a new era in heavy ion physics with lead on lead collisions at $\sqrt {s_{NN}} = 2.76\,{\mathrm {TeV}}$. After a short reminder of the main results from lower energies, this review highlights a few selected areas where significant progress has been made during the first three years of ion operation at the LHC.

This lecture presents an overview of the status of the investigation of the properties of the quark–gluon plasma using relativistic heavy ion collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider. It focuses on the insights that have been obtained by the comparison between experimental data from both facilities and theoretical calculations.

Heavy flavour physics provides a crucial role in the validation of the Standard Model of particle physics and in the search for new phenomena beyond. This review provides a personal summary of the headline results as of May 2013 from the Large Hadron Collider heavy flavour community in the subject areas of heavy flavour production and spectroscopy, mixing and charge parity violation and rare decays.

This paper discusses the impact of B factories in the era of Large Hadron Collider (LHC) experiments. It presents the advantages of experiments at a B factory and at a super B factory, and their complementarity to the studies at the LHC. As examples, some selected recent results from B factories are presented; precision measurements of the unitarity triangle, studies of rare B decays, full reconstruction of events in D meson decays and searches for lepton violating τ lepton decays. The paper also reviews the status of the preparation of the next step, a super B factory at KEK, with the SuperKEKB high luminosity asymmetric electron–positron collider and the detector Belle II. Finally a summary and an outlook are given.

In recent years, huge progress in flavor physics and in the physics of CP violation has been achieved by the BaBar, Belle, CDF, D0 and LHCb experiments. This led to a significant theoretical progress. In particular, the Kobayashi–Maskawa mechanism has been proven to be the dominant source of the observed CP violation, and the Cabibbo–Kobayashi–Maskawa mechanism has been proven to be a major player in the observed flavor changing neutral current (FCNC) processes. Two major questions in flavor physics remain however open. Firstly, the Standard Model flavor puzzle is the question of what is the source of the structure—smallness and hierarchy—in the charged fermion flavor parameters. The measurement of neutrino related flavor parameters only added to the complexity of this puzzle. Secondly, the New Physics flavor puzzle is the following question: if there is new physics at the TeV scale, why and how are its contributions to FCNC so strongly suppressed? The high p_T experiments at the LHC, ATLAS and CMS, are likely to solve the latter puzzle, and may even provide hints to the solution of the former.

I summarize the status of the electroweak interactions after the first phase of the Large Hadron Collider and give an outlook on its possible developments.

Top quark physics is one of the pillars of fundamental research in the field of high energy physics. It not only gives access to precision measurements for constraining the Standard Model of particles and interactions but also it represents a privileged domain for new physics searches. This contribution summarizes the main results in top quark physics obtained with the two general-purpose detectors ATLAS and CMS during the first two years of operations of the Large Hadron Collider (LHC) at CERN. It covers the 2010 and 2011 data taking periods, where the LHC ran at a centre-of-mass energy of 7 TeV.

We review the special role that the top sector is playing in the context of electroweak (EW) symmetry breaking within and beyond the Standard Model. We briefly report on the current status of the Large Hadron Collider (LHC) 'battle of naturalness' related to top partner searches. The notion of 'mini' intensity and energy frontiers at the LHC is then explained with an example given for each of these fronts. The phase diagram of the Standard Model obtained by extrapolating the relevant basic parameters, in particular the top-Higgs Yukawa coupling to high scales is also mentioned. We finally address some interesting aspects of top physics that are not related to EW physics. In particular, the impressive progress made recently on the next-to-next-to leading order evaluation of the top pair production cross-section is described and the status of the forward–backward top asymmetry is also summarized.

The discovery of a Higgs-like boson with a mass of approximately 125 GeV by the ATLAS and CMS experiments at the Large Hadron Collider was announced at CERN on 4 July 2012. The data-set of 5 fb⁻¹ of proton–proton collisions with $\sqrt {s}=7\,{\mathrm { TeV}}$ collected during 2011 and 6 fb⁻¹ with $\sqrt {s}=8\,{\mathrm { TeV}}$ collected in 2012 up to the July discovery was supplemented by an additional 15 fb⁻¹ of data with $\sqrt {s}=8\,{\mathrm { TeV}}$ collected during the rest of 2012. The measurements of the properties of the new boson with the combined data-set have substantially strengthened the evidence that this new particle is indeed the Higgs boson predicted to exist as a consequence of the Brout–Englert–Higgs-mechanism that takes responsibility for generating masses of fundamental particles and for the electroweak symmetry breaking.

Searches for a Higgs boson in models beyond the Standard Model at the ATLAS and CMS experiments at the Large Hadron Collider are discussed. No sign of new physics is present in the data collected at 7 and 8 TeV proton center of mass energies. Limits on model parameters are set. Future studies at higher energy are presented.

We present a concise outlook of particle physics after the first Large Hadron Collider (LHC) results at 7–8 TeV. The discovery of the Higgs boson at 126 GeV will remain as one of the major physics discoveries of our time. But also the surprising absence of any signals of new physics, if confirmed in the continuation of the LHC experiments, is going to drastically change our vision of the field. At present the indication is that nature does not too much care about our notion of naturalness. Still the argument for naturalness is a solid one and we are facing a puzzling situation. We review the established facts so far and present a tentative assessment of the open problems.

This paper explores some of the questions that connect the Large Hadron Collider (LHC) and neutrino experiments. What is the origin of mass? What is the meaning of flavor? Is there direct evidence of new forces or particles? The neutrino program investigating these questions is large and diverse. The strategy here, to narrow the discussion, is to focus on relatively new ideas for experiments that may be less known within the LHC community.

The theory and phenomenology of neutrinos will be addressed, especially that relating to the observation of neutrino flavor transformations. The current status and implications for future experiments will be discussed with special emphasis on the experiments that will determine the neutrino mass ordering, the dominant flavor content of the neutrino mass eigenstate with the smallest electron neutrino content and the size of CP violation in the neutrino sector. Beyond the neutrino standard model, the evidence for and a possible definitive experiment to confirm or refute the existence of light sterile neutrinos will be briefly discussed.

Astroparticle physics is a rapidly developing field that has a high degree of overlap with particle physics and astronomy. This paper summarizes recent results and leading experiments in two selected areas: very high energy astrophysics and dark matter. Both areas have made great progress in the last 5 years due to improved instrumentation and a growing community. In very high energy astrophysics, many sources of GeV and TeV radiation have been detected and the challenge now is to fully understand the processes involved at these sites of extreme particle acceleration. In the area of dark matter, there is a close scientific connection between astroparticle experiments and the Large Hadron Collider (LHC). The combination of the LHC, direct-detection and indirect-detection experiments provide critical complementarity and unprecedented sensitivity in the quest to understand this deep mystery.

A brief overview is given about some issues in current astroparticle physics, focusing on the dark matter (DM) problem, where the connection to Large Hadron Collider (LHC) physics is particularly strong. New data from the Planck satellite has made the evidence in favour of the existence of DM even stronger. The favourite, though not the only, candidates for cosmological DM, weakly interacting massive particles, are being probed by a variety of experiments—direct detection through scattering in terrestrial detectors, indirect detection by observing products of annihilation of DM in the Galaxy and finally searches at accelerators such as the LHC. The field is in the interesting situation that all of these search methods are reaching sensitivities where signals of DM may plausibly soon be found, and a vast array of models will be probed in the next few years. Of course, expectations for a positive signature are high, which calls for caution regarding 'false alarms'. Some of the presently puzzling and partly conflicting pieces of evidence for DM detection are discussed as well as expectations for the future.

The status of searches for physics beyond the Standard Model is reviewed, in the light of the data from the Large Hadron Collider runs at 7 and 8 TeV centre-of-mass energy.

I discuss the central challenges to fundamental physics raised by the discovery of the Higgs, revolving around 'naturalness' and its discontents.

This talk was given at a special place and on a special occasion for a special audience. It describes the results, magic and doubts that an attempt to construct a theory based on the idea that the basic constituents of matter can also be extended objects has led to. The emphasis is on the spirit behind the ideas.

The discovery of a new particle, the properties of which are compatible with the expected Brout–Englert–Higgs scalar field in the Standard Model (SM), is the starting point of an intense program for studying its couplings. With this particle, all the components of the SM have now been unraveled. Yet, the existence of dark matter, baryon asymmetry of the Universe and neutrino mass call for new physics at an energy scale, which is not determined so far. Therefore, new large scale accelerators are needed to investigate these mysteries through ultra-high precision measurements and/or the exploration of higher energy frontiers. In the following, we discuss the various accelerator projects aimed at the achievement of the above objectives. The physics reach of these facilities will be briefly described as well as their main technical features and related challenges, highlighting the importance of accelerator R&D not only for the benefit of particle physics but also for other fields of research, and more generally for the society.

Development of novel detector concepts has always played a major role in supporting and enabling scientific research. In the forthcoming phase of high energy physics (HEP), the design and development of new detectors and detector concepts will be even more important than it was in the past owing to the harsh environmental conditions and the challenging requests imposed by the physicists' needs for: improved spatial and time resolution, innovative functions, acquisition speed, radiation tolerance, minimal power consumption, robustness and reliability, minimal material and more. This overview addresses the challenges that upgrades and future projects in HEP will impose in terms of novel technologies and stresses the detectors' potential and limitations in attempting to achieve the scientific goals. In addition the increasingly strong dependence on large-scale industrial production and industrial development, especially in the area of integrated electronics, sensors and large complex systems will be addressed.

I was asked to discuss future experimental programs even though I am a theorist. As a result, I present my own personal views on where the field is, and where it is going, based on what I myself have been working on. In particular, I discuss why we need expeditions into high energies to find clues to where the relevant energy scale is for dark matter, baryon asymmetry and neutrino mass. I also argue that the next energy frontier machine should be justified on the basis of what we know, namely the mass of the Higgs boson, so that we will learn what energy we should aim at once we nail the Higgs sector. Finally, I make remarks on dark energy.

This paper presents the role of big laboratories in their function as research infrastructures. Starting from the general definition and features of big laboratories, the paper goes on to present the key ingredients and issues, based on scientific excellence, for the successful realization of large-scale science projects at such facilities. The paper concludes by taking the example of scientific research in the field of particle physics and describing the structures and methods required to be implemented for the way forward.

This paper describes the process which led to the update of the European strategy for particle physics in 2013. A large number of proposals for new facilities and projects were submitted to the Strategy Group and their physics potential and technological feasibility were carefully analyzed. An overview of these projects is given, followed by a summary of the main points of the approved European Strategy Update. The official text, which was approved at a special session of the CERN Council in 30 May 2013 is reproduced in the appendix.

This is a personal summary of points made during, and arising from the symposium, drawing largely from the talks presented there. The standard model is doing fine, including QCD, the electroweak sector and flavour physics. The good news is that a standard model-like Higgs boson has appeared with the predicted mass, but the bad news is that the Large Hadron Collider (LHC) has provided no hint of other new physics. On the other hand, physics beyond the standard model is needed to explain neutrino masses and mixing, and we look forward to experiments revealing their mass hierarchy and CP violation. Cosmology and astrophysics also require new physics to explain the origin of matter, dark matter, dark energy and the CMB fluctuations. I still think that supersymmetry is the best-motivated extension of the standard model, and look forward to the next phases of LHC operation at higher energy and luminosity. In the mean time, ideas abound for a new accelerator to study the Higgs boson in detail and/or whatever else the LHC may reveal in its next run.

The full text of this article is available in the PDF provided.