# Applications from Elementary Particle Physics

Here we present a choice of impressive projects from elementary particle physics which have been carried out on GCS supercomputers.

## Toward the Anomalous Magnetic Moment of the Muon from 2+1‑Flavour Lattice QCD

Lattice Quantum Chromodynamics (Lattice QCD) is a first-principles, non-perturbative formulation of the theory of the strong interaction that allows for numerical simulations with systematic control of theoretical uncertainties, and which has a long and successful history of providing the information required for a quantitative understanding of strong interaction physics at low energies. Nevertheless, a number of quantities could not be studied so far with the desired level of control of statistical and systematic uncertainties; this includes the hadronic contribution to the anomalous magnetic moment of the muon, a precise determination of which is currently the most promising avenue in the search for physics beyond the Standard Model (SM) of particle physics. Here, reserachers investigate this quantity, among others, using lattice QCD simulations on fine and large lattices in order to control systematic uncertainties and enable a precise theoretical prediction.

**Principal Investigator: ** Georg von Hippel, Institut für Kernphysik, Johannes Gutenberg-Universität Mainz (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** March 2019 *(hmz23)*

**More: Toward the Anomalous Magnetic Moment of the Muon from 2+1‑Flavour Lattice QCD …**

## Multi-hadron States and String Breaking on Fine Lattices with Light Pions

Confinement is the observation that quarks cannot be seen in isolation in nature. As a consequence the static potential V(r), which is defined as the energy of of a system made of a static quark and a static anti-quark separated by a distance r, grows linearly with the separation r. When r is large enough, the potential V(r) flattens due to creation of a pair of light quarks, which combine into two static-light mesons. This so called “string breaking” phenomenon provides an intuitive example of a strong decay. It can be studied through the simulation of strong interactions between quarks and gluons on a supercomputer.

**Principal Investigator:** Francesco Knechtli, Fakultät für Mathematik und Naturwissenschaften, Bergische Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN and JURECA (JSC) -** Date published: **March 2019* (hwu21)*

**More: Multi-hadron States and String Breaking on Fine Lattices with Light Pions …**

## Atomic Nuclei as Laboratories for Quantum Physics

How do neutrons and protons bind to form atomic nuclei? Why do we observe alpha-particle clustering in light and medium-mass nuclei but not in heavy ones? These questions can be tackled in the framework of nuclear lattice effective field theory. These investigations have revealed some intriguing features of nuclei related to much discussed quantum phenomena such as entanglement and quantum phase transitions.

**Principal Investigator: ** Ulf-G. Meißner, Universität Bonn & Forschungszentrum Jülich (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** March 2019 *(hfz02)*

**More: Atomic Nuclei as Laboratories for Quantum Physics …**

## Charm Physics on Fine Lattices with Open Boundaries

In this project we compute the decay constants of the D and Ds mesons using numerical simulation (Lattice QCD). The decay constants are required in order to extract from experiment the CKM matrix elements, the parameters of the Standard Model of particle physics associated with weak decays. High precision determinations of the CKM matrix elements from a variety of processes are sought in order to uncover hints of physics beyond the Standard Model. A significant systematic arising in Lattice QCD simulations is that due to the finite lattice spacing. We reduce this systematic by simulating at a very fine lattice spacing.

**Principal Investigator:** Sara Collins, Institute for Theoretical Physics, Regensburg University (Germany)

**HPC Platform:** JUQUEEN (JSC) -** Date published: **March 2019* (hru29)*

**More: Charm Physics on Fine Lattices with Open Boundaries …**

## Distribution Amplitudes of the η and η' Mesons

In this project properties of two mesons, i.e. particles made up of a quark and an anti-quark, namely the η and the η', are studied by numerically simulating the underlying theory, QCD, on a four-dimensional spacetime lattice. The focus of previous studies was on establishing the masses of these particles, which are intricately related to the so-called axial anomaly. In this project, for the first time, the internal structure of these mesons was simulated too. This can be characterized in lightcone kinematics, which is relevant for collider experiments, by so-called distribution amplitudes (DAs). The normalization of a DA is also known as a decay constant. Four such previously unknown constants have been determined with full assessment of all systematics.

**Principal Investigator:** Andreas Schäfer, Institute for Theoretical Physics, Regensburg University (Germany)

**HPC Platform:** JUQUEEN (JSC) -** Date published: **February 2019* (hru28)*

**More: Distribution Amplitudes of the η and η' Mesons …**

## Disconnected Contributions to Generalized Form Factors (GPDs)

The main focus of high energy physics research is the search for signals of physics beyond the Standard Model. Many of the experiments built for this purpose involve protons or neutrons (collectively termed nucleons), either in the beam, such as at the Large Hadron Collider at CERN, or within the nuclei of the targets, such as those used for dark matter detection experiments. In order to extract information on the underlying interactions occurring in these experiments between quarks and other fundamental particles, one needs to know the distribution of the quarks within the nucleon. Lattice QCD simulations of the strong interactions between quarks and gluons can provide information on the momentum, spin and angular momentum of these particles within the nucleon. In general one distinguishes between elastic scattering processes where the nucleon is left intact and inelastic scattering where the nucleon is destroyed. Both aspects can be parameterized in terms of quark and gluon generalized parton distributions (GPDs). These will be measured at the proposed Electron Ion Collider (EIC) in the US. This project computes the moments of the GPDs, the so called generalised form factors. Disconnected contributions must be evaluated in order to access the moments for the individual quark flavours.

**Principal Investigator:** Andreas Schäfer, Institute for Theoretical Physics, Regensburg University (Germany)

**HPC Platform:** SuperMUC (LRZ) -** Date published: **January 2019* (pr74po, pr48gi, pr84qe)*

**More: Disconnected Contributions to Generalized Form Factors (GPDs) …**

## Viscosity Estimate with Staggered Fermions

Lattice QCD has played a crucial role in the determination of the true equation of state. It is a numerical approach to solve the theory of strong interactions, quantum chromodynamics (QCD), which provides first principles access to the physics of QGP. Lattice QCD assumes thermal equilibrium, where also the equation of state is defined. Researchers calculated this input to hydrodynamics in a succession of projects with the goal to investigate, whether such first principle determination of the (shear) viscosity parameter is possible from lattice QCD.

**Principal Investigator:** Szabolcs Borsanyi, University of Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published: **December 2018 *(hwu30)*

**More: Viscosity Estimate with Staggered Fermions …**

## The Search for the *H* Dibaryon in Lattice QCD

All visible matter around us is made from nuclei, each consisting of protons and neutrons. One of the triumphs of 20th century particle physics is the realisation that protons and neutrons are made from even smaller building blocks, the so-called quarks, which are now regarded as the fundamental constituents of matter. Particles such as the proton and neutron (collectively referred to as baryons) are considered bound states of three quarks. The theory of Quantum Chromodynamics (QCD) describes with very high accuracy the forces that act between these elementary building blocks. However, it remains a great challenge to provide a quantitative description of particles such as the proton and nuclear matter in terms of the underlying interaction between quarks. In this project scientists study bound states of two baryons (so-called dibaryons) as prototypes of more complex systems such as light nuclei. The formulation of QCD on a space-time grid is employed, which makes the theory amenable to a numerical treatment. More specifically, the focus is on the so-called *H* dibaryon, whose existence has been predicted 40 years ago. These studies show that such a state may actually exist.

**Principal Investigator:** Hartmut Wittig, Institute for Nuclear Physics and PRISMA Cluster of Excellence, Johannes Gutenberg University of Mainz (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published: **October 2018 *(hmz21)*

**More: The Search for the H Dibaryon in Lattice QCD …**

## Thermodynamics with Overlap Fermions

The Universe soon after the Big Bang was hot and full of massless particles, so called fermions and bosons. As it expanded and cooled down particles become massive. They acquired mass from several kinds of mechanisms, which are investigated in detail in heavy-ion collision experiments, and also in theory. Ab-initio theoretical calculations require simulating massless particles on a supercomputer. This is a difficult problem, fortunately with an existing solution, the so-called overlap discretization of fermions. Here we make simulations with overlap fermions using supercomputing power.

**Principal Investigator:** Balint Toth, Bergische Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN (JSC) - **Date published: **April 2018 *(hwu26)*

**More: Thermodynamics with Overlap Fermions …**

## Exploring the QCD Phase Diagram Using the Complex Langevin Equation

The simulation of nuclear matter at nonzero baryon density presents a notoriously hard problem in lattice QCD. The usual simulation strategies depend on the exploration of the configuration space by interpreting the weight of each configuration in an average as a probability, which is however not valid here as the weight is non positive. This is called the ‘sign problem’ of nonzero density QCD. In this project, the researchers use a method based on the Complex Langevin equation evading the sign problem to map out the phase diagram of nuclear matter.

**Principal Investigator:** Dénes Sexty, Bergische Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN (JSC) - **Date published: **March 2018 *(hwu22)*

**More: Exploring the QCD Phase Diagram Using the Complex Langevin Equation …**

## Hadronic Corrections to the Muon Anomalous Magnetic Moment

Supercomputing resources are used to investigate a long standing discrepancy between theoretical calculation and experiment in the case of an elementary particle called muon. This muon magnetic moment puzzle is considered by many as a smoking gun for new physics, ie. something that cannot t into the current framework of particle physics.

**Principal Investigator:** Kálmán Szabó, Forschungszentrum Jülich GmbH (Germany)

**HPC Platform:** JUQUEEN (JSC) - **Date published: **March 2018 *(hfz00)*

**More: Hadronic Corrections to the Muon Anomalous Magnetic Moment …**

## Study of Strong Decays and Resonances at the Physical Pion Mass in Lattice QCD

In the quark model mesons are made up of a quark and an antiquark and baryons of three quarks. The theory of the strong interactions, QCD, however, suggests that more complicated structures are possible. New experimental results strongly point at the possibility of tetraquarks, close to strong decay thresholds into two mesons. To understand these structures, simulations are necessary that include these scattering states. For the first time such as study was performed in Lattice QCD, with nearly physical quark masses. First the well-known ρ-resonance was investigated and then the Tetraquark candidate states D*_{s0}(2317) and D_{s1}(2460).

**Principal Investigator:** Gunnar Bali, Institut für Theoretische Physik, Universität Regensburg (Germany)

**HPC Platform:** SuperMUC (LRZ) - **Date published: **March 2018 *(pr94ni)*

**More: Study of Strong Decays and Resonances at the Physical Pion Mass in Lattice QCD …**

## Hadron Scattering and Resonance Properties from Lattice QCD

It is a long lasting dream in nuclear physics to study nuclei like, for instance, carbon directly from Quantum Chromodynamics (QCD), the underlying fundamental theory of strong interactions. Such an endeavor is very challenging both, methodically and numerically. Towards this goal physicists from the European Twisted Mass Collaboration and in particular the University of Bonn have started to investigate two hadron systems using the approach of Lattice QCD.

**Principal Investigator:** Carsten Urbach, Helmholtz Institut für Strahlen und Kernphysik (Theorie), Rheinische Friedrich-Wilhelms-Universität Bonn (Germany)

**HPC Platform:** JUQUEEN/JSC and Hazel Hen/HLRS

**Date published: **February 2018 *(hbn28/GCS_hsrp)*

**More: Hadron Scattering and Resonance Properties from Lattice QCD …**

## The Conformal Window and Technicolour Theories with Adjoint Fermions

In this project, a multi-instutional team of researchers investigated new strongly interacting theories beyond the Standard Model of particle physics. These theories share fascinating but still puzzling features with the strong interaction of nuclear forces. In addition, they offer new phenomena and exotic properties that make them interesting for a more general understanding of the foundations of particle physics.

**Principal Investigator:** Georg Bergner, Theoretisch-Physikalisches Institut, Universität Jena (Germany)

**HPC Platform:** JUQUEEN/JURECA (JSC) - **Date published: **January 2018 *(hfu08)*

**More: The Conformal Window and Technicolour Theories with Adjoint Fermions …**

## Flavor Singlet Physics with Background Fields

The calculation of sea quark and gluon content of hadrons, which can be traced back to flavour singlet hadron matrix elements, is one of the greatest technical challenges left in lattice QCD. This is due to the fact that the lattice calculation of so-called "disconnected diagrams" is extremely noisy and gives a poor signal. An improved determination of these disconnected contributions was the main aim of this project. For that, physicists of the QCDSF collaboration have proposed an alternative to the conventional three-point function technique (3-pt) for the study of hadron matrix elements in lattice QCD.

**Principal Investigator:** Arwed Schiller, Institut für Theoretische Physik, Leipzig University, Germany (QCDSF collaboration)

**HPC Platform:** JUQUEEN of JSC - **Date published:** December 2017* (hlz22)*

**More: Flavor Singlet Physics with Background Fields …**

## Phenomenology of Strange Resonances

The phenomenology of freeze-out and hadronization in heavy ion collision experiments greatly benefits from the availability of the Hadron Resonance Gas model. This, however, assumes the complete knowledge of the particle spectrum in a broad range. Alas, many of the bound states have not been found yet. In this project, researchers narrow down on the missing states using large scale lattice QCD computations.

**Principal Investigator:** Zoltán Fodor, Bergische Universität Wuppertal (Germany)

**HPC Platforms:** JUQUEEN of JSC and Hazel Hen of HLRS - **Date published:** November 2017 *(hwu08, GCS-posr)*

**More: Phenomenology of Strange Resonances …**

## Non-Zero Density Simulations in Full QCD

The simulation of nuclear matter at nonzero baryon density presents a notoriously hard problem in lattice QCD. The usual simulation strategies depend on the exploration of the configuration space by interpreting the weight of each configuration in an average as a probability, which is however not valid here as the weight is non positive. This is called the ‘sign problem’ of nonzero density QCD. In this project the researchers compare two different simulation strategies which evade the sign problem with very different methods.

**Principal Investigator:** Dénes Sexty, Heisenberg Fellow, Bergische Universität Wuppertal (Germany)

**HPC Platform:** SuperMUC of LRZ - **Date published:** October 2017 *(pr84to)*

**More: Non-Zero Density Simulations in Full QCD …**

## The Calculation of the Axion Mass from Lattice QCD

A large part of the universe consists of the so called dark matter. This is a form of matter, that interacts only very weakly with the every day, baryonic matter. A candidate for a dark matter particle is the axion. To increase the chances of detecting such a particle, the knowledge of its properties is important. In this project Lattice QCD is used to determine a mass estimate of the axion. This requires the use of supercomputers as well as the invention of new techniques to reduce the computational cost.

**Principal Investigator:** Zoltán Fodor, Bergische Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** October 2017 *(hwu16)*

**More: The Calculation of the Axion Mass from Lattice QCD …**

## Transport in the Gluon Plasma

The viscosity of a fluid is a measure of its resistance to deformation by shear stress. One of the least viscous fluids ever observed is that of the quark gluon plasma, created in heavy ion collisions. Nevertheless reliably calculating the equilibrium viscosity of the quark gluon plasma remains to be one of the big open challenges in heavy ion physics. In this project, researchers perform simulations to improve on previous estimates of this important quantity.

**Principal Investigator:** Dénes Sexty, Heisenberg Fellow, Bergische Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** October 2017 *(hwu25)*

**More: Transport in the Gluon Plasma …**

## The Beta Function of Strongly Coupled Gauge Theories near the Non-perturbative Conformal Edge

Strongly Coupled Gauge Theories (SCGTs) play an important role in High Energy Physics. Certain SCGTs are nearly conformal, which is a desired property in the search of new physics. The search of such theories requires the study of the beta function. In this project, the Lattice Higgs Collaboration investigates the beta function of SCGTs which are similar to QCD and observed that the beta function decreases with increasing number of fermion flavors. It also provides a quantitative estimate of how close to conformality these theories are, which is crucial in the search of viable models of new physics.

**Principal Investigator:** Chik Him Wong, University of Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** July 2017 (hwu23)

**More: The Beta Function of Strongly Coupled Gauge Theories near the Non-perturbative Conformal Edge …**

## Fluctuations of Conserved Charges in High-Temperature QCD

Researchers studying subatomic particles that govern our world have long been interested in describing phenomena that happen to the constituents of matter called protons and neutrons, called quarks and gluons, under extreme conditions. Using GCS computing resources, scientists were able to use quantum chromodynamics simulations to reveal that exotic “strange” and “charm” quarks freeze out at roughly the same temperature as the light quarks. In addition, it was found that more strange and charmed bound states should exist than have been detected experimentally thus far.

**Principal Investigator:** Edwin Laermann, Fakultät für Physik, Universität Bielefeld (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** June 2017 *(hbi08)*

**More: Fluctuations of Conserved Charges in High-Temperature QCD …**

## The Strangeness Content of the Nucleon

At the Large Hadron Collider at CERN protons are collided at extremely high energies in an effort to detect New Physics, i.e. deviations from Standard Model expectations. These depend on the structure of the colliding protons, and this is largely determined by quantum fluctuations, e.g., by how much of the proton is made up of short lived quark-antiquark pairs. At present the mass fractions are controversial both for light (up, down) and for strange quarks. These (and related) quantities are calculated within Quantum Chromodynamics. The partial results obtained so far hint at inconsistencies of present parametrizations.

**Principal Investigator:** Andreas Schäfer, Institut für Theoretische Physik, Universität Regensburg (Germany)

**HPC Platform:** SuperMUC of LRZ - **Date published:** January 2017 *(pr84qe)*

**More: The Strangeness Content of the Nucleon …**

## Nucleon Observables as Probes for Physics Beyond the Standard Model

Utilizing the approach of lattice QCD, physicists computed key observables with the goal to better understand the inner structure of nucleons. This project addressed in particular the quark and gluon contributions to the spin, the angular momentum, and the momentum of the nucleon while a special focus was laid on the calculation of the scalar quark content of the proton. Such calculations will aid research of physical processes in particle physics and the as yet unknown nature of dark matter.

**Principal Investigator:** Dr. Karl Jansen, Deutsches Elektronen-Synchrotron/DESY, Zeuthen (Germany)

**HPC Platform:** Hazel Hen of HLRS - **Date published:** January 2017 *(GCS-nops)*

**More: Nucleon Observables as Probes for Physics Beyond the Standard Model …**

## Advanced Accelerator Concepts for Strong Field Interaction Simulated with the Plasma-Simulation-Code (Aacsfi-PSC)

Researchers of the Faculty of Physics at the Ludwig-Maximilians-Universität München leveraged HPC system SuperMUC to a) investigate the proton driven laser-wakefield acceleration of electrons, and b) simulate the interaction of ultra-intense laser pulses with ultra-thin foils. The applied highly sophisticated Particle-In-Cell computer simulations were meant to contribute to new insights into laser driven proton acceleration. Further findings in this area could help to significantly cut costs for cancer therapy centers.

**Principal Investigator:** Hartmut Ruhl, Faculty of Physics, University of Munich (Germany)

**HPC Platform:** SuperMUC (LRZ) - **Date published:** November 2016 *(pr84me)*

**More: Advanced Accelerator Concepts for Strong Field Interaction Simulated with the Plasma-Simulation-Code (Aacsfi-PSC) …**

## Unraveling the Mysteries of Element Generation

Lattice simulations of nuclear reactions that are relevant to nucleosynthesis in stars have recently become possible. As a first step, researchers from the Nuclear Lattice Effective Field Theory Collaboration have performed an *ab initio* calculation of the low-energy scattering of two alpha particles. This paves the way for a deeper understanding of the element generation and the limits of nuclear stability.

**Principal Investigator: ** Ulf-G. Meißner, Universität Bonn and Forschungszentrum Jülich

**HPC Platform:** JUQUEEN of JSC - **Date published:** October 2016 *(hfz02)*

**More: Unraveling the Mysteries of Element Generation …**

## 2+1+1 Lattice QCD Calculations With HEX Smeared Clover Fermions

The theories of Dark Matter (DM) are formulated in terms of couplings between DM particles and quarks, the elementary particles that build up protons and neutrons. To calculate the prediction of these theories and aid the experimental searches, one has to know the "quark content" of the nucleon, which is roughly speaking the probability of finding quarks in the nucleon. To calculate the nucleon quark content, an international team of researchers performed highly demanding computations on HPC system JUQUEEN of JSC.

**Principal Investigator:** Kálmán Szabó, Forschungszentrum Jülich, Institute for Advanced Simulation, Jülich Supercomputing Centre

**HPC Platform:** JUQUEEN of JSC - **Date published:** October 2016 *(hwu11)*

**More: 2+1+1 Lattice QCD Calculations With HEX Smeared Clover Fermions …**

## The Quantum Mechanical Structure of Protons and Other Hadrons

(To improve the understanding of the quark gluon structure of hadrons extremely demanding (ongoing and planned) experiments have to be complemented by equally demanding numerical simulations. Researchers from the University of Regensburg leveraged the computing power of HPC systems JUQUEEN and SuperMUC for challenging Lattice Quantum Chromodynamics (QCD) simulations for the "Generalized Parton Distributions" (GPDs) of the nucleon.

**Principal Investigator:** Andreas Schäfer, Institut für Theoretische Physik, Universität Regensburg (Germany)

**HPC Platform:** JUQUEEN of JSC and SuperMUC of LRZ - **Date published:** October 2016 *(GCS_13)*

**More: The Quantum Mechanical Structure of Protons and Other Hadrons …**

## Charm Loop Effects: Decoupling and Charmonium

In a joint project of scientists of the Universities of Wuppertal, Berlin, Cambridge and Münster, and of DESY, Zeuthen researchers investigate the effects that the inclusion of a dynamical charm quark in the simulations of lattice quantum chromodynamics has on observables like the charmonium spectrum, the mass of the charm quark and the strong coupling.

**Principal Investigator:** Francesco Knechtli, Fakultät für Mathematik und Naturwissenschaften, Bergische Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN and JURECA of JSC - **Date published:** September 2016 *(hwu17)*

**More: Charm Loop Effects: Decoupling and Charmonium …**

## Composite Higgs Theory Beyond the Standard Model

Despite the remarkable success of the Standard Model (SM), it is generally believed that there are phenomena beyond it. One class of Beyond Standard Model (BSM) theories postulates that the observed Higgs boson is indeed a composite particle composed of new subatomic particles bounded by new interactions. In this project, the Lattice Higgs Collaboration (LatHC) investigates the properties of the Sextet model including hadron spectroscopy and how interaction strength varies with probing energy. These findings have recently made the Sextet model one of the highly interesting BSM models.

**Principal Investigator:** Chik Him Wong, Bergische Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** September 2016 *(hwu15)*

**More: Composite Higgs Theory Beyond the Standard Model …**

## The Spectrum of Supersymmetric Yang-Mills Theory

In a joint project of scientists of the Universities of Münster, Bern and Regensburg, and of DESY, Hamburg, researchers investigate the properties of the N = 1 supersymmetric Yang-Mills theory, a theory which has supersymmetry and is part of many models for the physics beyond the Standard Model.

**Principal Investigator:** Gernot Münster, Institut für Theoretische Physik, Universität Münster (Germany)

**HPC Platform:** JUQUEEN and JURECA of JSC - **Date published:** July 2016 *(hhh04)*

**More: The Spectrum of Supersymmetric Yang-Mills Theory …**

## Leading Hadronic Contribution to the Anomalous Magnetic Moment of the Muon

The Standard Model of particle physics is one of the great scientific achievements of the 20^{th }century. After confirmation of the existence of the Higgs boson in 2013, physicists are now keen to see whether there is anything beyond the theory. Scientists of CNRS and Aix-Marseille University have been been using lattice QCD to see whether a certain experimental measurement is indeed a glimpse of new fundamental physics.

**Principal Investigator:** Laurent Lellouch, National Center for Scientific Research/CNRS & Aix-Marseille University (France)

**HPC Platform:** JUQUEEN of JSC - **Date published:** June 2016* (PRA-yy1)*

**More: Leading Hadronic Contribution to the Anomalous Magnetic Moment of the Muon …**

## Nucleon Structure Using Lattice QCD Simulation with Physical Pion Mass

Scientists are leveraging HPC system SuperMUC for state-of-the-art lattice Quantum Chromodynamics (QCD) simulations. Using these Tier-0 computational resources, the team of international researchers has pioneered the calculation of key observables that characterize the structure of protons and neutrons, collectively referred to as nucleons.

**Principal Investigator:** Constantia Alexandrou, University of Cyprus and The Cyprus Institute (Cyprus)

**HPC Platform:** SuperMUC of LRZ - **Date published:** April 2016 *(PRA_xx1)*

**More: Nucleon Structure Using Lattice QCD Simulation with Physical Pion Mass …**

## Pair-Dominated Plasmas and Radiation in Ultra Intense Fields

Leveraging the petascale computing power of SuperMUC, an international team of researchers performed 2D/3D simulations of laser absorption in dense electron-positron plasmas self-consistently created via electromagnetic cascades. Their numerical findings provide a set of laser parameters to optimize the conversion of optical photons into pairs and gamma rays allowing to mimic extreme astrophysical scenarios and their radiation signatures.

**Principal Investigator:** Thomas Grismayer, GoLP/IPFN, Instituto Superior Técnico, Lisboa (Portugal)

**HPC Platform:** SuperMUC of LRZ - **Date published:** March 2016 *(pr84yi)*

**More: Pair-Dominated Plasmas and Radiation in Ultra Intense Fields …**

## Lattice QCD + QED: Towards a Quantitative Understanding of the Stability of Matter

Leveraging the petascale computing power of HPC system JUQUEEN, scientists at Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany, included for the first time both Quantum Chromodynamics (QCD) and Quantum Electrodynamics (QED) in a nonperturbative calculation. This allowed the physicists to predict isospin breaking effects in the meson, baryon and quark sectors from first principles, and in particular the n - p mass difference.

**Principal Investigator: **Gerrit Schierholz, DESY Hamburg (Germany)

**HPC-Platform: **JUQUEEN of JSC – **Date published:** February 2016 *(hde07)*

**More: Lattice QCD + QED: Towards a Quantitative Understanding of the Stability of Matter …**

## Full Scale Modelling of the Proton Driven Plasma Wakefield Accelerator

Leveraging high performance computing system SuperMUC, an international team of researchers performed 3D simulations of scenarios relevant to The Proton Driven Plasma Wakefield Acceleration Experiment framed by AWAKE, an accelerator R&D project based at CERN. Their numerical findings provide a set of conditions for which the long proton bunches could propagate stably over arbitrarily long distances, and explore possible experimental configurations that could be relevant to investigate astrophysical scenarios in the lab.

**Principal Investigator:** Jorge Vieira, Instituto Superior Técnico, Lisboa (Portugal)

**HPC Platform:** SuperMUC of LRZ - **Date published:** February 2016 *(pr89wo)*

**More: Full Scale Modelling of the Proton Driven Plasma Wakefield Accelerator …**

## Exploring the Quark Mass Plane with Open Boundaries

An international team of researchers leveraged the computing power of supercomputer JUQUEEN in the context of a very large international effort in Lattice quantum chromodynamics (QCD). The project addressed important aspects of hadron physics for the very first time respectively with unprecedented accuracy, which would not have been possible without superior high performance computing (HPC) power.

**Principal Investigator:** Andreas Schäfer, Institut für Theoretische Physik, Universität Regensburg (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** January 2016 *(hru26)*

**More: Exploring the Quark Mass Plane with Open Boundaries …**

## Electron-Injection Techniques in Plasma-Wakefield Accelerators for Driving Free-Electron Lasers

Researchers from the Deutsches Elektronen-Synchrotron Hamburg (Germany) study and design electron-injection techniques in plasma-wakefield accelerators for the production of high-quality beams suitable for application as free-electron lasers. Since the physics involved in the process cannot be treated analytically in most of the cases of interest, particle-in-cell simulations are required which allow to calculate the response of the plasma electrons to the passage of charged beams and/or high-intensity lasers.

**Principal Investigators:** Jens Osterhoff and Alberto Martinez de la Ossa, Deutsches Elektronen-Synchrotron - DESY, Hamburg (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** January 2016 *(hhh23)*

**More: Electron-Injection Techniques in Plasma-Wakefield Accelerators for Driving Free-Electron Lasers …**

## Gluonic Scale Setting With √t_{0} and w_{0}

Physicists at the University of Wuppertal harness the supercomputer power of the JSC HPC system JUQUEEN to carry out a computation of the gluonic scales √t_{0} and w_{0} in QCD with 2+1+1 dynamical quarks where each of them is taken at its respective physical mass.

**Principal Investigator:** Stephan Dürr, Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

**HPC Platform: **JUQUEEN of JSC - **Date published:** December 2015

**More: Gluonic Scale Setting With √t0 and w0 …**

## Precise Relation Between Quark Masses in Different Renormalization Schemes

Leveraging the HPC platform of the HLRS, an international team of researchers of the Karlsruhe Institute of Technology, the Deutsches Elektronen-Synchrotron (DESY), and the Moscow State University have computed a precise relation between heavy quark masses defined in the two most commonly used renormalization schemes, the minimal subtraction (MS) and on-shell scheme.

**Principal Investigator:** Matthias Steinhauser, Institut für Theoretische Teilchenphysik, Karlsruhe Institute of Technology/KIT (Germany)

**HPC Platform: **Hornet and Hermit of HLRS - **Date published:** September 2015

**More: Precise Relation Between Quark Masses in Different Renormalization Schemes …**

## Lattice QCD Investigations of Nuclear and Hadronic Properties

The typical scale of Quantum Chromodynamics (QCD) is on the level of GeV (giga electron volt), but QCD should also describe nuclear physics, with has a typical scale of MeV (mega electron volt). This three orders of magnitude difference is a precision challenge, which scientists now were able to tackle in the proton-neutron system.

**Principal Investigator:** Zoltán Fodor, Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** March 2015

**More: Lattice QCD Investigations of Nuclear and Hadronic Properties …**

## Calculation of Tunneling Splittings of Vibrational Eigenstates of Malonaldehyde

Using the Heidelberg MCTDH package (Multi Configuration Time Dependent Hartree), Heidelberg based scientists investigated the spectral properties of malonaldehyde. The HPC resources of HLRS in Stuttgart served as computing platform for this project.

**Principal Investigator:** Hans-Dieter Meyer, Institute of Physical Chemistry, Universität Heidelberg (Germany)

**HPC Platform: **Hermit of HLRS - **Date published:** March 2015

**More: Calculation of Tunneling Splittings of Vibrational Eigenstates of Malonaldehyde …**

## Numerical Determination of the Phase Diagram of Nuclear Matter

Using GCS HPC system resources, scientists of the Institute for Theoretical Physics of the Goethe-Universität in Frankfurt/Germany are performing extensive simulations to theoretically predict the properties of the phase transition from nuclear matter to a quark gluon plasma state.

**Principal Investigator:** Owe Philipsen, Universität Frankfurt, ITP (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** February 2015

**More: Numerical Determination of the Phase Diagram of Nuclear Matter …**

## A Lattice QCD Calculation of Vector Meson Decay Constants

Leveraging the computing power of HPC system JUQUEEN of Jülich Supercomputing Centre, researchers from Bergische Universität Wuppertal (BUW) are using lattice quantumchromodynamics (QCD) to calculate vector meson decay constants f_{V} , where V represents a vector meson such as ρ, ω, φ, etc.

**Principal Investigator:** Eric B. Gregory, Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** January 2015

**More: A Lattice QCD Calculation of Vector Meson Decay Constants …**

## Petascale Computations for Atomic and Molecular Collisions

Research efforts of an international group of scientists from Germany, the UK, and the US focus on the development of computational methods to obtain quantities that can be measured from the equations of motion that arise for atoms and molecules interacting with electrons or light within a fully quantum description.

**Principal Investigator:** Alfred Müller, Institut für Atom- und Molekühlphysik, Universität Giessen (Germany)

**HPC Platform:** Hermit of HLRS - **Date published:** November 2014

**More: Petascale Computations for Atomic and Molecular Collisions …**

## Chiral Symmetry and Topological Properties in Lattice QCD With Wilson Twisted Mass Quarks

Quantum Chromodynamics (QCD) represents the nowadays widely accepted theory describing the interaction of quarks and gluons. QCD is expected to show a very similar phenomenon like the magnetisation of a ferromagnet, just that the magnetisation is called chiral condensate and the equivalent of the external magnetic field is a finite quark mass. Theoretical physicists of the Deutsches Elektronen-Synchrotron (DESY) and the Rheinische Friedrich-Wilhelms-Universität Bonn evaluated for the first time the chiral condensate using lattice QCD with dynamical up, down, strange and charm quarks and, therefore, confirm the expectation.

**Principal Investigator:** Carsten Urbach, Universität Bonn (Germany)

**HPC-Platform:** SuperMUC of LRZ - **Date published:** October 2014

**More: Chiral Symmetry and Topological Properties in Lattice QCD With Wilson Twisted Mass Quarks …**

## Extreme Plasma Acceleration: From the Laboratory to Astrophysics

A team of scientists investigated novel positron and ion acceleration schemes towards a future plasma based linear collider and medical applications, novel magnetic field generation mechanisms relevant in astrophysical scenarios, and laser-plasma interaction studies for fusion applications.

**Principal Investigator:** Jorge Vieira, Instituto Superior Técnico, Universidade de Lisboa (Portugal)

**HPC Platform: **SuperMUC of LRZ - **Date published:** September 2014

**More: Extreme Plasma Acceleration: From the Laboratory to Astrophysics …**

## QCDpQED--QCD Plus QED and the Stability of Matter

The mass of our visible universe is to a very large part provided by the strong nuclear interaction between elementary quarks, as described by the theory of quantum chromodynamics (QCD). In order to understand more deeply not only the origin of the mass of the visible universe but also its composition, tiny differences in the particle masses, especially those of protons and neutrons, are essential.

**Principal Investigator:** Zoltán Fodor, Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date Published:** September 2014

**More: QCDpQED--QCD Plus QED and the Stability of Matter …**

## Baryon Structure Using Dynamical QCD Simulations With Physical Values of the Light, Strange and Charm Quark Masses

A team of international scientists, cooperating under the name European Twisted Mass Collaboration (ETMC), uses supercomputer JUQUEEN of JSC in their efforts to understand the properties of elementary particles such as the proton, which forms most of the ordinary matter around us.

**Principal Investigator:** Constantia Alexandrou, University of Cyprus (Cyprus)

**HPC Platform:** JUQUEEN of JSC - **Date published:** September 2014

**More: Baryon Structure Using Dynamical QCD Simulations With Physical Values of the Light, Strange and Charm Quark Masses …**

## Excited State Artefacts in Calculations of Hadron 3-Point Functions

Lattice QCD (Quantum Chromodynamics) allows to calculate properties of states which are composed of quarks and gluons, called hadrons. The most important hadrons are proton and neutron, i.e. the nucleons. To obtain this information from Lattice QCD one has to calculate what is called “3-point- functions”. With large computer resources provided such as by SuperMUC scientists were able to do this much more precisely. Furthermore, physical quark masses could be simulated rather than scientists having to rely on extrapolations from simulations with larger than physical quark masses.

**Principal Investigator:** Andreas Schäfer, Institut für Theoretische Physik, Universität Regensburg (Germany)

**HPC Platform: **SuperMUC of LRZ - **Date published:** July 2014

**More: Excited State Artefacts in Calculations of Hadron 3-Point Functions …**

## Kaon Semi-Leptonic Form Factor

The CKM-matrix (Cabibbo-Kobayashi-Maskawa) describes the mixing between the mass eigenstates and electro-weak eigenstates of the different quark flavors in the Standard Model of Particle Physics. Scientists leverage the computing power of HPC system SuperMUC for tests of the unitarity of the CKM matrix and therefore also probe the Standard Model of Particle Physics.

**Principal Investigator:** Enno E. Scholz, Institut für Theoretische Physik, Universität Regensburg (Germany)

**HPC Platform:** SuperMUC of LRZ - **Date published:** July 2014

**More: Kaon Semi-Leptonic Form Factor …**

## Nucleon and Meson Matrix Elements Close to the Physical Point

The validity of Quantum Field Theory (QFT) is proven beyond any reasonable doubt, but at the same time it is clear that the Standard Model is incomplete in many respects. Also, there are many aspects of the Standard Model, in particular of the QCD (Quantum Chromodynamics) sector, which are not yet understood. It is hoped that the combination of dedicated new experiments and Lattice QFT will allow to improve the understanding of these aspects.

**Principal Investigator:** Andreas Schäfer, Institut für Theoretische Physik, Universität Regensburg (Germany)

**HPC Platform:** SuperMUC of LRZ - **Date Published:** May 2014

**More: Nucleon and Meson Matrix Elements Close to the Physical Point …**

## Next Generation Lattice QCD Simulations of the First Two Quark Generations at the Physical Point

An international team of scientists leverages the computing power of supercomputers for a very ambitious project which is embedded in the area of elementary particle interactions and in particular the strong interaction of quarks and gluons which is described theoretically by quantum chromodynamics (QCD), a relativistic quantum field theory.

**Principal Investigator:** Karl Jansen, Deutsches Elektronen-Synchrotron/DESY, Zeuthen (Germany)

**HPC Platforms:** SuperMUC (LRZ) and JUQUEEN (JSC) - **Date pub.:** May 2014

**More: Next Generation Lattice QCD Simulations of the First Two Quark Generations at the Physical Point …**

## Controlled Electron-Beam Injection into Plasma Waves for Tailored Betatron-Radiation Generation

Researchers study few-femtosecond, phase-space-tailored electron bunches inside plasma wakefields. These bunches are generated by means of external injection of conventionally accelerated electron beams or by controlled, plasma-internal injection schemes.

**Principal Investigator:** Jens Osterhoff, Deutsches Elektronen-Synchrotron/DESY, Hamburg (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** April 2014

**More: Controlled Electron-Beam Injection into Plasma Waves for Tailored Betatron-Radiation Generation …**

## First Lattice QCD Study of B-physics With Four Flavors of Dynamical Quarks

Researchers from the three universities of Rome, the universities of Valencia, Paris XI, Groningen, Bonn, and Berlin have formed a team to carry out an extensive study of the physics of mesons containing a beauty quark. The results of this study will allow to address issues relevant for the phenomenology of the so-called flavor sector of the Standard Model and its possible extensions to New Physics.

**Principal Investigator:** Silvano Simula, Istituto Nazionale di Fisica Nucleare (INFN) - Sezione Roma Tre (Italy)

**HPC Platform:** JUGENE/JUQUEEN of JSC - ** Date published:** April 2014

**More: First Lattice QCD Study of B-physics With Four Flavors of Dynamical Quarks …**

## The Spectrum of Supersymmetric Yang-Mills Theory

In a joint project of scientists of the Universitiy of Münster, the University of Frankfurt, and of DESY, Hamburg, researchers investigate the properties of the N = 1 supersymmetric Yang-Mills theory, a theory which has supersymmetry and is part of many models for the physics beyond the Standard Model.

**Principal Investigator:** Gernot Münster, Institut für Theoretische Physik, FB-C, Universität Münster (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** March 2014

**More: The Spectrum of Supersymmetric Yang-Mills Theory …**

## Quantum Monte Carlo Simulation of Hydrogen at High Pressure

An international team of physicists used GCS supercomputer Hermit to elucidate important aspects of the hydrogen phase diagram related to the pressure-induced molecular dissociation and metallization and to improve the treatment of electronic correlation by developing algorithms based on Quantum Monte Carlo (QMC) methods.

**Principal Investigator:** Carlo Pierleoni, Universita' dell'Aquila (Italy)

**HPC Platform:** Hermit of HLRS - **Date published:** March 2014

**More: Quantum Monte Carlo Simulation of Hydrogen at High Pressure …**

## A lattice QCD Calculation of the Leading Order Hadronic corrections to g − 2 of the Muon

Researchers from Wuppertal and Marseilles are using lattice quantum chromodynamics (QCD) to calculate contributions of the strong force to the anomalous magnetic moment of the muon, a heavier cousin of the electron.

**Principal Investigator:** Zoltán Fodor, Institut für Theoretische Physik, FB-C, Universität Münster (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date Published:** February 2014

**More: A lattice QCD Calculation of the Leading Order Hadronic corrections to g − 2 of the Muon …**

## Heavy Ion Phenomenology Form Lattice Simulations

A team of physicists used JSC supercomputer JUQUEEN to study the energy density, entropy, specific heat and pressure of quark gluon plasma, starting from a high temperature at its creation to a low temperature where the plasma actually freezes. Their goal: to identify the plasma's break-up point, i. e. the point when the plasma freezes and its matter is transformed into subatomic particles.

**Principal Investigator:** Szabolcs Borsányi, Institut für Theoretische Physik, FB-C, Universität Münster (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** February 2014

**More: Heavy Ion Phenomenology Form Lattice Simulations …**

## 2+1+1 Lattice QCD Calculations With HEX Smeared Clover Fermions

Supercomputer resources of GCS enable physicists to solve the equations of QCD on a large enough and simultaneously fine enough lattice to accurately compute the effects of the charm quark and predict the masses of short-lived particles it is contained in.

**Principal Investigator:** Christian Hölbling, Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** February 2014

**More: 2+1+1 Lattice QCD Calculations With HEX Smeared Clover Fermions …**

## Fluctuations of Conserved Charges in the Quark Gluon Plasma

Leveraging the vast computing power of HPC system JUQUEEN of JSC, an international team of physicists aims on a model independent determination of the freeze-out temperature and density of Quark Gluon Plasma (QGP), based on the fundamental equations of the theory of strongly interacting matter, Quantum Chromodynamics (QCD).

**Principal Investigator:** Christian Schmidt, Physics Department, University of Bielefeld (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** February 2014

**More: Fluctuations of Conserved Charges in the Quark Gluon Plasma …**

## Lattice QCD with Wilson Quarks at zero and non-zero Temperature

A team of researchers, led by Prof. Hartmut Wittig of the University of Mainz, investigates the many facets of QCD in the low-energy regime using GCS supercomputing resources.

**Principal Investigator:** Hartmut Wittig, Institut für Kernphysik, Universität Mainz (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** November 2013

**More: Lattice QCD with Wilson Quarks at zero and non-zero Temperature …**

## Precision Computation of f_{K}/f_{π} from Staggered 2+1+1 Flavor Simulations

A a team of scientists of the University of Wuppertal under leadership of Dr. Stephan Duerr uses GCS supercomputers for precision tests of the first-row unitarity relation of the Cabibbo-Kobayashi-Maskawa (CKM) matrix.

**Principal Investigator:** Stephan Duerr, Wuppertal University and IAS/JSC at Forschungszentrum Jülich

**HPC Platform:** JUQUEEN of JSC - **Date published:** October 2013

**More: Precision Computation of fK/fπ from Staggered 2+1+1 Flavor Simulations …**

## Flavor Physics of Up, Down and Strange Quarks from Simulations of Dynamical QCD + QED

In the a. m. project, an international team of scientists under leadership of particle physicist Prof. Dr. Gerrit Schierholz from DESY (Deutsches Elektronen-Synchrotron) run a fully dynamical simulation of QCD + QED on GCS supercomputers.

**Principal Investigator:** Gerrit Schierholz, DESY, Hamburg (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** October 2013

**More: Flavor Physics of Up, Down and Strange Quarks from Simulations of Dynamical QCD + QED …**

## Matter-Antimatter Asymmetry

The dominance of matter over antimatter in our universe is one of the unsolved riddles of present day physics. During the early phases of our universe, matter must have been produced predominantly over antimatter, but the only such process we currently know only affects quarks, the fundamental constituents of the atomic nucleus, and does not provide enough matter dominance.

**Principal Investigator:** Christian Hölbling, Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** October 2013

**More: Matter-Antimatter Asymmetry …**

## Finite Temperature Lattice QCD with Wilson Quarks

Theoretical investigation of matter at extreme high temperatures and densities has a huge importance since this kind of matter is produced in heavy-ion collision experiments.

**Principal Investigator:** Kálmán Szabó, Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

**HPC Platform: **JUQUEEN of JSC - **Date published:** October 2013

**More: Finite Temperature Lattice QCD with Wilson Quarks …**

## Pseudoscalar Decay Constants at the Physical Mass Point

With the help of supercomputing, scientists from the University of Wuppertal tackle a key component of Elementary Particle Physics: The fundamental forces of nature.

**Principal Investigator:** Christian Hölbling, Institut für Theoretische Physik, FB-C, Universität Wuppertal (Germany)

**HPC Platform:** JUQUEEN of JSC - **Date published:** July 2013

**More: Pseudoscalar Decay Constants at the Physical Mass Point …**

## The Synthesis of the Elements, in Particular Carbon

Life on Earth is based on carbon that was generated in stars. A special role in the synthesis of carbon is played by a particular excited state of carbon, the socalled Hoyle state.

**Principal Investigator: ** Ulf-G. Meißner, Universität Bonn (HISKP) und FZ Jülich (IAS & IKP)

**HPC Platform:** JUQUEEN of JSC - **Date published:** July 2013

**More: The Synthesis of the Elements, in Particular Carbon …**