Jobs – Page 222 of 521

A bright future for HERA physics

Combined H1 and ZEUS cross-sections versus exchanged photon virtuality, Q², at fixed Bjorken-x for inclusive e⁺p and e^–p deep-inelastic scattering using all of the HERA I and II data. Also shown are results from fixed-target experiments and the HERAPDF2.0 QCD fit at next-to-leading order. The data have a precision of about 1% up to Q² of around 400 GeV², and are well described by theory. Clearly visible are the steep rise of the cross-section at low x – scaling violations – and the electroweak effects at high Q² where the e⁺p and e^–p cross-sections diverge.

Even though HERA – the only electron–proton collider built so far – stopped running in mid-2007, analyses of the vast amounts of data from the Hermes, H1 and ZEUS experiments continue to produce important and high-impact measurements relevant to spin physics, the structure of the proton and other areas of QCD. Special efforts have been made to ensure that these unique data are safely preserved for future analyses for at least the next 10 years, within the framework of the Data Preservation in High-Energy Physics collaboration ( CERN Courier May 2009 p21).

In November 2014, DESY hosted a workshop on “Future Physics with the HERA Data for Current and Planned Experiments”, to pull together experts and ask questions about what the HERA data still have to say and how they are relevant to other facilities. The aim was, in effect, to create a list of subjects that are still to be investigated or exploited fully. Across two days, almost 30 presentations and lively discussions occupied around 70 participants, both experimentalists and theorists, from across the globe.

The most recent results from the collaborations and a perspective from theory were presented first in a special HERA symposium, starting with a presentation on recent results from Hermes by Charlotte Van Hulse of the University of the Basque Country. She highlighted the semi-inclusive deep-inelastic scattering (DIS) data collected on a transversely polarized hydrogen target that provides access to various transverse-momentum-dependent parton distribution functions (PDFs), which are sensitive to correlations between quark spin, proton spin, the transverse momentum of quarks and/or of final-state hadrons.

Two talks followed that showed results from H1 and ZEUS, the first on proton structure by Aharon Levy of Tel Aviv University and the second on diffraction and hadronic final states by Alice Valkárová of Charles University, Prague. All of the measurements of inclusive DIS from H1 and ZEUS have been combined recently and QCD fits to these data have been performed, providing a new set of PDFs of the proton (see figure). The 15 years of data taking at HERA have culminated in a combination of 3000 data points, and their impact on knowledge of the structure of the proton will last for years to come. Also, recent jet measurements at HERA have enabled the strong coupling constant to be extracted with an experimental precision of <1%. This has been achieved through the simultaneous measurement of inclusive-jet, dijet and trijet cross-sections.

Providing a theoretical perspective, Robert Thorne of University College London discussed the contribution that data from HERA have made to the understanding of electroweak physics, physics beyond the Standard Model and, in particular, QCD and the structure of the proton. With a crowded auditorium, the symposium went significantly over time because the results shown provoked much discussion that continued into the evening.

The workshop started with general talks from Elke Aschenauer of Brookhaven and Hannes Jung of DESY, both of whom highlighted the need to measure particle production – either inclusively or, even better, by tagging specific particle species – in electron–proton (ep) scattering, differential in four kinematic quantities. Such detailed measurements can be useful in model building and in tuning Monte Carlo simulations, but they can also pin down the transverse-momentum distributions of partons, which are more commonly considered in spin physics. Jung also stressed the contribution that HERA data can make to understanding the nature of multi-parton interactions, by virtue of the unique ability of being able to contrast events in which the colliding photon is either point-like or hadronic-like, thereby turning multi-parton interactions “off” and “on”, respectively, within the same experimental set-up.

Updates are needed to Monte Carlo simulations to include the more advanced models for underlying events in ep scattering, as has been done for pp interactions. Simon Plätzer of the Institute for Particle Physics Phenomenology, Durham, discussed recent advances made for the HERWIG++ event generator to include ep processes. He emphasized that the program is ready for comparison with DIS processes, even including the next-to-leading-order matrix elements. As well as a personal perspective, Achim Geiser of DESY provided an extensive list of topics yet to be covered, which anyone interested could look at to see what most excites them.

Given some tension seen between theory and the HERA inclusive data at low photon virtualities, Q², and low Bjorken-x, as presented by Levy, several talks, including those by Joachim Bartels of Hamburg University and Amanda Cooper-Sarkar of Oxford University, discussed this region as an avenue for future work. Clearly a joint H1 and ZEUS extraction of the longitudinal structure function, F_L, is needed. Also, the more precise combined data sets now available demand a phenomenological analysis in which the proton structure function, F₂, is parameterized in terms of x^–λ, where the dependence on –λ could reveal information on the Pomeron and the applicability of the parton-evolution schemes to describe the structure of the proton.

A highlight of the workshop was the status of next-to-next-to-leading-order (NNLO) QCD predictions of jet production at HERA, presented by Thomas Gehrmann of Zurich University. The use of such predictions will allow more precise comparisons with data and, for example, reduced uncertainties on the extractions of PDFs and the strong coupling constant. The first full predictions and comparison to data for the production of dijets in DIS will be the first NNLO final-state prediction at HERA, and is expected during 2015.

In a wide-ranging talk on diffractive processes, Marta Ruspa of the University of Piemonte Orientale highlighted the crucial questions still to be answered, which relate to the consistency and combination of the H1 and ZEUS data for measurements of inclusive diffraction in DIS. These data allow the extraction of diffractive PDFs (DPDFs) in analogy to the conventional PDFs for inclusive DIS. Using DPDFs, and because factorization should hold, predictions can be made for other processes. The experimental results on the holding of factorization are not conclusive, however, and further investigation of the HERA data would help to clarify this issue and give a better understanding of the mechanism at the LHC, as Bartels indicated.

Ronan McNulty of University College Dublin discussed the overlaps in physics from HERA and the LHCb experiment at CERN, in particular the complementary information on extraction of proton PDFs and the measurement of vector-meson production, particularly J/ψ production, and its sensitivity to the gluon distribution in the proton. Similarly, Sasha Glazov of DESY proposed ideas for common HERA–LHC analyses in the area of PDF extractions and jet physics, where HERA has particularly precise measurements.

Alessandro Bacchetta of the University of Pavia and Emanuele Nocera of the University of Genova highlighted the many pioneering measurements made by the Hermes collaboration in mapping out the helicity and 3D structure of the proton. Open issues include the strange-quark spin content of the proton, electroweak structure functions, etc. These speakers also discussed how the final Hermes analyses, together with results from experiments such as COMPASS at CERN and others at Jefferson Lab and at a future electron–ion collider, could lead to a greater understanding of the complete picture of the structure of the proton.

In a presentation that was relatively technical but very important for this workshop, Dirk Kruecker of DESY outlined the status of the long-term and safe preservation of the HERA data. To ensure that the most is made of this data legacy, the collaborations are open to people outside of the traditional institutes who are interested in analysing the data. To gain access to the data and work on a publication along with a collaboration, interested people should contact the respective spokesperson. A summary document of the workshop will be published in early 2015, and should act as a useful reference for anyone interested in future analyses with the HERA data.

A summary talk by John Dainton of the University of Liverpool provided a thought-provoking and entertaining résumé of some of the highlights of HERA physics, and how they relate to other facilities and fit into the broad context of particle physics. After two intense days, the talks and discussions gave the workshop delegates renewed vigour with which to exploit the HERA data fully during the years to come, and push back the understanding of a rich and wide variety of QCD processes, such as the nature of diffraction and the structure of the proton.

A luminous future for the LHC

A prototype Roebel cable to be used to wind a high-temperature superconductor demonstration dipole magnet.
Image credit: CERN-PHOTO-201407-151-3.

To maintain scientific progress and exploit the full capacity of the LHC, the collider will need to operate at higher luminosity. Like shining a brighter light on an object, this will allow more accurate measurements of new particles, the observation of rarer processes, and increase the discovery reach with rare events at the high-energy frontier. The High-Luminosity LHC (HL-LHC) project began in 2011 under the framework of a European Union (EU) grant as a conceptual study, with the aim to increase its luminosity by a factor of 5–10 beyond the original design value and provide 3000 fb^–1 in 10 to 12 years.

The HL-LHC timeline as of 24 September 2014.

Two years later, CERN Council recognized the project as the top priority for CERN and for Europe (CERN Courier July/August 2013 p9), and then confirmed its priority status in CERN’s scientific and financial programme in 2014 by approving the laboratory’s medium-term plan for 2014–2019. Since this approval, new activities have started up to deliver key technologies that are needed for the upgrade. The latest results and recommendations by the various reviews that took place in 2014 were the main topics for discussion at the 4th Joint HiLumi LHC/LARP Annual Meeting, which was hosted by KEK in Tsukuba in November.

The latest updates

The event began with plenary sessions where members of the collaboration management – from CERN, KEK, the US LHC Accelerator Research Program (LARP) and the US Department of Energy – gave invited talks. The first plenary session closed with an update on the status of HL-LHC by the project leader, CERN’s Lucio Rossi, who also officially announced the new HL-LHC timeline. The plenary was followed by expert talks on residual dose-rate studies, layout and integration, optics and operation modes and progress on cooling, quench and assembly (together known as QXF). Akira Yamamoto of KEK presented the important results and recommendations of the recent superconducting cable review.

Collaboration members at the 4th Joint HiLumi LHC-LARP Annual Meeting.
Image credit: KEK.

There were invited talks on the LHC Injectors Upgrade (LIU) by project leader Malika Meddahi from CERN, and on the outcomes of the 2nd ECFA HL-LHC Experiments Workshop held in October – an indication of the close collaboration with the experimentalists. One of the highlights of the plenaries was the status update on the Preliminary Design Report – the main deliverable of the project, which is to be published soon. There were three days of parallel sessions reviewing the progress in design and R&D in the various work packages – named in terms of activities – both with and without EU funding.

Refined optics and layout of the high-luminosity insertions have been provided by the activity on accelerator physics and performance, in collaboration with the other work packages. This new baseline takes into account the updated design of the magnets (in particular those of the matching section), the results of the energy deposition and collimation studies, and the constraints resulting from the integration of the components in the tunnel. The work towards the definition of the specifications for the magnets and their field quality has progressed, with an emphasis on the matching section for which a first iteration based on the requirements resulting from studies of beam dynamics has been completed. The outcomes include an updated impedance model of the LHC and a preliminary estimate of the resulting intensity limits and beam–beam effects. The studies confirmed the need for low-impedance collimators. In addition, an updated set of beam parameters consistent through all of the injectors and the LHC has been defined in collaboration with the LIU team.

Progress with magnets

The 20-m-long electrical transmission line containing two 20 kA MgB₂ cables.
Image credit: CERN.

The main efforts of the activity on magnets for insertion regions (IRs) in the past 18 months focused on the exploration of different options for the layout of the interaction region. The main parameters of the magnet lattice, such as operational field/gradients, apertures, lengths and magnet technology, have been chosen as a result of the worldwide collaboration, including US LARP and KEK. A baseline for the layout of the new interaction region is one of the main results of this work. There is now a coherent layout, agreed with the beam dynamics, energy deposition, cooling and vacuum teams, covering the whole interaction region.

The engineering design of most of the IR magnets has now started and the first hardware tests are expected in 2015. There was also good news from the quench-protection side, which can meet all of the key requirements based on the results from tests performed on the magnets. In addition, there is a solution for cooling the inner triplet (IT) quadrupoles and the separation dipole, D1. It relies on two heat exchangers for the IT quadrupole/orbit correctors assembly, with a separate system for the D1 dipole and the high-order corrector magnets. Besides these results, considerable effort was devoted to selecting the technologies and the design for the other magnets required in the lattice, namely the orbit correctors, the high-order correctors and the recombination dipole, D2.

Crabs and collimators

A crystal target for advanced collimation under test in CERN’s HiRadMat facility.
Image credit: CERN.

The crab-cavities activity delivered designs for three prototype crab cavities, based on four-rod, RF-dipole (RFD) and double quarter-wave (DQW) structures. They were all tested successfully against the design gradient with higher-than-expected surface resistance. Further design improvements to the initial prototypes were made to comply with the strict requirements for higher-order-mode damping, while maintaining the deflecting field performance. There was significant progress on the engineering design of the dressed cavities and the two-cavity cryomodule conceptual design for tests at CERN’s Super Proton Synchrotron (SPS).

Full design studies, including thermal and mechanical analysis, were done for all three cavities, culminating in a major international design review where the three designs were assessed by a panel of independent leading superconducting RF experts. As an outcome of this review, the activity will focus the design effort for the SPS beam tests on the RFD and DQW cavities, with development of the 4-rod cavity continuing at a lower priority and not foreseen for the SPS tests. A key milestone – to freeze the cavity designs and interfaces – has also been met. In addition, a detailed road map to follow the fabrication and installation in the SPS has been prepared to meet the deadline of the extended year-end technical stop of 2016–2017.

Nb₃Sn coil for the 11-T dipole-model tests.
Image credit: CERN.

The wrap-up talk on the IR-collimation activity also reviewed the work of related non-EU-funded work packages, namely machine protection (WP7), energy deposition and absorber co-ordination (WP10), and beam transfer and kickers (WP14). The activity has reached several significant milestones, following the recommendations of the collimation-project external review, which took place in spring 2013. Highlights include important progress towards the finalization of the layouts for the IR collimation. A solid baseline solution has been proposed for the two most challenging cleaning requirements: proton losses around the betatron-cleaning insertion and losses from ion collisions. The solution is based on new collimators – the target collimator long dispersion suppressor, or TCLD – to be integrated into the cold dispersion suppressors. Thanks to the use of shorter 11 T dipoles that will replace the existing 15-m-long dipoles, there will be sufficient space for the installation of warm collimators between two cold magnets. This collimation solution is elegant and modular because it can be applied, in principle, at any “old” dipole location. As one of the most challenging and urgent upgrades for the high-luminosity era, solid baselines for the collimation upgrade in the dispersion suppressors around IR7 and IR2 were also defined. In addition, simulations have continued for advanced collimation layouts in the matching sections of IR1 and IR5, improving significantly the cleaning of “debris” from collisions downstream around the high-luminosity experiments.

Cold powering

The cold-powering activity has seen the world-record current of 20 kA at 24 K in an electrical transmission line consisting of two 20-m-long MgB₂ superconducting cables. Another achievement was with the novel design of the part of the cold-powering system that transfers the current from room temperature to the superconducting link. Following further elaboration, this was adopted as the baseline. The idea is that high-temperature superconducting (HTS) current-leads will be modular components that are connected via a flexible HTS cable to a compact cryostat, where the electrical joints between the HTS and MgB₂ parts of the superconducting link are made. Simulation studies were also made to evaluate the electromagnetic and thermal behaviour of the MgB₂ cables contained in the cold mass of the superconducting link, under static and transient conditions.

Computer-generated image of Fermilab’s 1-m-long 11-T dipole model and a pair of CERN coils.
Image credit: Don Mitchell/Fermilab.

The final configuration has tens of high-current cables packed in a compact envelope to transfer a total current of about 150 kA feeding different magnet circuits. Cryogenic-flow schemes were also elaborated for the cold-powering systems at points 7, 1 and 5 on the LHC. An experimental study performed in the 20-m-long superconducting line at CERN was launched to understand quench propagation in the MgB₂ superconducting cables operated in helium gas. In addition, integration studies of the cold-powering systems in the LHC were also done, with priority given to the system at point 7.

The meeting also covered updates on other topics such as machine protection, cryogenics, vacuum and beam instrumentation. Delicate arbitration took place between the needs of crab-cavity tests in the SPS at long straight section 4 and the requirements for the continuing study and tests of electron-cloud mitigation of those working on vacuum aspects (see Old machine to validate new technology below).

Summaries of the EU-funded work packages closed the meeting, showing “excellent technical progress thanks to the hard and smart work of many, including senior and junior”, as project leader Rossi concluded in his wrap-up talk.

Upcoming meetings will be the LARP/HiLumi LHC meeting on 11–13 May at Fermilab and the final FP7 HiLumi LHC/LARP collaboration meeting on 26–30 October at CERN. As a contribution to the UNESCO International Year of Light, special events celebrating this occasion will be organized by HL-LHC throughout the year – see cern.ch/go/light. (See also Viewpoint )

Old machine to validate new technology

Crab cavities have never been tested on hadron beams. So for the recently selected HL-LHC crab cavities (RFD and DQW, see main text), tests in the SPS beam are considered to be crucial. The goals are to validate the cavities with beam in terms of, for example, electric field, ramping, RF controls and impedance, and to study other parameters such as cavity transparency, RF noise, emittance growth and nonlinearities.

Long straight section 4 (LSS4) of the SPS already has a cold section, which was set up for the cold-bore experiment (COLDEX). Originally designed to measure synchrotron-radiation-induced gas release, COLDEX has become a key tool for evaluating electron-cloud effects. It mimics the cold bore and beam screen of the LHC for electron-cloud studies. Installed in the bypass line of the beam pipe, COLDEX is assembled on a moving table so that beam can pass either through the experiment during machine development runs or through the standard SPS beam pipe during normal operation. It has been running again since the SPS started up again last year after the first long shutdown, providing key information on new materials and technology to reduce or suppress severe electron-cloud effects that would otherwise be detrimental to LHC beams with 25 ns bunch spacing – as planned for Run 2.

Naturally, SPS LSS4 would be the right place to put the crab-cavity prototypes for the beam test. The goal was originally to install them during the extended year-end technical stop of 2016–2017, to validate the cavities in 2017, the year in which series construction must be launched. However, installing the cavities together with their powering and cryogenic infrastructure in an access time of 11–12 weeks is a real challenge. So at the meeting in Tsukuba, the idea of bringing forward part of the installation to 2015–2016 was discussed. However, in view of the severe electron-cloud effects that were computed in 2014 for LHC beam at high intensity, and the consequent need for a longer and deeper study to validate various solutions, COLDEX needs to run beyond 2015.

So what other options are there for testing the crab cavities? A preliminary look at possible locations for an additional cold section in the SPS led to LSS5. This would result in having two permanent “super” facilities to test equipment with proton beams. The hope is that these facilities would not only be available for testing crab cavities for the HL-LHC project, but would also provide a world facility for testing superconducting RF-accelerating structures in intense, high-energy proton beams. With the installation of adequate cryogenics and power infrastructure, a facility in LSS5 could further evolve and possibly also allow tests of beam damage and other beam effects for future superconducting magnets, for example for the Future Circular Collider study (CERN Courier April 2014 p16). This new idea raises many questions, but the experts are confident that these can be solved with suitable design and imagination.

Spin goes Chinese

Lecture hall at Peking University — The lecture hall at Peking University provided an attractive setting for many sessions.
Image credits: SPIN2014 organizers.

The biannual series of international symposia on spin physics plays a leading role at the interface of nuclear and particle physics on one hand, and the study of spin-dependent phenomena in experiment and theory on the other. The series grew from the merger of the five-yearly symposia on polarization phenomena in nuclear reactions, first held in Basel in 1960, and the symposia on high-energy spin, which started in 1974 and had reached the 13th edition by 1998. The joint meetings began as the 14th International Symposium on Spin Physics in 2000. The 21st International Symposium on Spin Physics (SPIN2014) is the first in the series that China has hosted – taking place on the 40th anniversary of the first high-energy spin meeting at Argonne National Laboratory in 1974.

The scientific programme of the symposium series today is based on physics with photons and leptons, spin phenomena in nuclei and nuclear reactions, and new physics beyond the Standard Model. It also includes new technologies related to accelerators, storage rings, polarized targets and polarized beams, and spin physics in medicine is also included. In addition, SPIN2014 extended the topics to incorporate spin in condensed matter, quantum communication and their related applications.

Hosted by Peking University, Beijing, and supported by many renowned research institutions and universities, both inside and outside of China, SPIN2014 took place on 20–24 October 2014. Nearly 300 participants attended from more than 20 countries. With 28 plenary talks and 177 parallel talks, the symposium provided a platform to communicate new results in the field of spin physics and to reinforce academic collaborations with colleagues. It was also an important platform to advertise the academic achievements of Chinese researchers, and to strengthen the importance of Chinese involvement in spin physics. The following gives an overview of the scientific programme.

Hadrons, nucleons and symmetries

A key highlight was the excellent opening plenary talk on the spin structure of the nucleon by Xiangdong Ji of Shanghai Jiao Tong University and the University of Maryland. The quest to determine the origin of nucleon spin challenges the understanding of QCD. There is a worldwide experimental programme underway using spin observables to gain insight into this fundamental question in hadronic physics. The conference also heard more than 50 reports from experiments carried out at Brookhaven, CERN, DESY, Jefferson Lab and KEK on measurements that included inclusive lepton scattering (quark and gluon contributions), proton–proton scattering (gluon contribution, quark flavour decomposition using W-boson production), semi-inclusive deep-inelastic scattering (quark flavour decomposition, transverse-momentum distributions), deeply virtual Compton scattering (quark orbital angular momentum) and fragmentation in electron–positron collisions. There were also discussions on future possible experiments, including polarized Drell–Yan scattering, at Fermilab, the Japan Proton Accelerator Research Complex, the Nuclotron-based Ion Collider fAcility (NICA) in Dubna, and Brookhaven’s Relativistic Heavy-Ion Collider (RHIC). Keh-Fei Liu of the University of Kentucky gave an overview of the exciting developments in lattice QCD in a plenary talk. This was followed by more than 20 presentations on theoretical research into the spin structure of hadrons.

Co-chair Haiyan Gao opening the conference.

The plenary programme on “Spin Physics in Nuclear Reactions and Nuclei” included a report by Andro Kacharava from the Forschungszentrum Jülich on results from the Cooler Synchrotron (COSY) on nucleon–nucleon scattering using polarization degrees of freedom to probe nuclear forces. Mohammad Ahmed of North Caroline Central University described the latest results on few-body reactions from the High Intensity Gamma-Ray Source Facility at the Triangle Universities Nuclear Laboratory, where both polarized beam and polarized targets were employed, as well as results on Compton scattering from ⁶Li and ¹⁶O. Fifteen talks in the parallel programme were related to spin physics in nuclear reactions and nuclei.

Spin physics plays an important role in studies of fundamental symmetries

Spin physics plays an important role in studies of fundamental symmetries and searches for new physics beyond the Standard Model of particle physics. Plenary talks included reports on the latest result on the weak charge of the proton from parity-violating electron scattering by Dave Mack of Jefferson Lab. Mike Snow of Indiana University presented recent results on hadronic parity-violating experiments such as np → dγ, while Brad Filippone of Caltech provided an overview of the worldwide effort on searches for particle electric-dipole moments (EMDs). Frank Maas described the latest results on dark-photon searches from the University of Mainz and elsewhere. From China, Wei-Tou Ni of National Tsinghua University discussed the role of spin experiments in probing the structure and origin of gravity. Thirteen talks relating to fundamental symmetries were presented in the associated parallel sessions.

Current tools and future facilities

The methods to study spin-dependent effects are fundamental for the spin-physics community. At SPIN2014, the two main areas of interest were acceleration, storage and polarimetry of polarized beams, and sources of polarized ion and lepton beams and polarized targets. Nearly all of these disciplines formed part of the exciting plenary of Annika Vauth of DESY, who discussed the status of beam polarization and the International Linear Collider that could be built in Japan. Nearly 20 parallel talks were devoted to accelerator aspects, among them studies in the US and in China on electron–ion colliders (EICs), at JINR on the use of NICA as a polarized-ion collider, on storage rings for searches for ion EDMs, and on the new tools to be developed to meet these challenges. The operation of existing rings with polarized beams and the steady improvement of their operational parameters were also covered, with RHIC and its amazing performance as the only double-polarized ion collider built so far, and with COSY, which is famous for its stored polarized beams in the medium-energy range and the variety of internal targets.

More than a dozen parallel talks on sources and targets were presented, introduced by Dmitriy Toporkov of the Budker Institute of Nuclear Physics in his plenary on experiments with polarized targets in storage rings, in which he showed the potential of this technique. The review on polarized sources by Anatoli Zelenski of Brookhaven and other parallel talks covered a wide span of polarized beams, from high-intensity electrons for an EIC, to protons, as in H^– ions for RHIC, to deuterons for COSY and ³He ions for eRHIC. Chris Keith of Jefferson Lab and other speakers in the parallel sessions covered solid targets polarized by dynamic nuclear polarization or by the brute-force method in several lepton-scattering experiments. Gas targets for H, D and ³He atoms were also discussed.

The poster session presented new research results.

The conference heard reports on major upgrades of spin capabilities at existing facilities. The status and plans for Jefferson Lab’s 12 GeV upgrade were presented in a plenary talk by associate director Rolf Ent, and Wolfgang Lorenzon of the University of Michigan described the possibility of polarizing the Fermilab proton beam and mounting a programme of polarized Drell–Yan measurements. In Europe, the Mainz Energy-Recovering Superconducting Accelerator provides a high-intensity low-energy polarized electron facility, while COSY has embarked on a major development of new polarized proton- and deuteron-beam capabilities, motivated by experiments to look for nonzero EDMs in light nuclei.

In the US, the QCD community is pursuing a high-luminosity polarized EIC

Alexander Nagaytsev of JINR described the new accelerator NICA under construction in Dubna, together with the planned spin-physics programme, including measurements of polarized Drell–Yan and J/ψ production. In the US, the QCD community is pursuing a high-luminosity polarized EIC. This could be implemented at Brookhaven or Jefferson Lab. The concept has driven R&D in both high-intensity polarized electron guns and a polarized ³He source. In the European Physical Journal A plenary lecture, Zein-Eddine Mezziani of Temple University gave a compelling presentation on the spin science that motivates this new machine. Physicists in China have recently become interested in a similar facility.

Further features

As a novelty, SPIN2014 included a significant programme on spintronics – low-dimensional solid-spin systems exhibiting different quantum effects that can be employed, for example, in quantum computers, metrology, information technology and more. This ambitious field of research and technology is being pursued actively at Tsinghua and Peking Universities, and many other Chinese institutes, and was presented in a public lecture (see below) as well as in parallel sessions that included 20 talks. Apart from spintronics themes, medical applications such as imaging were discussed, a highlight being the beautiful talk by Warren Warren of Duke University on “Imaging with Highly Spin-Polarized Molecules”. There were also two talks on the application of polarized fuel for fusion reactors.

Besides the communication of recent results at the physics frontier, SPIN2014 also organized a lecture on popular science by Qi-Kun Xue from Tsinghua University on “Quantum Anomalous Hall Effect and Information Technology”, attended by more than 100 people from Peking University, Tsinghua University, Beijing University of Posts and Telecommunications, Beihang University and others. A memorial session devoted to the memory of CERN’s Michel Borghini was organized by Alan Krisch of Michigan and Akira Massike of Kyoto, highlighting Borghini’s contributions to the development of solid polarized targets.

A poster session for presenting new research results included Outstanding Poster Awards, sponsored by the Hanscom endowment from Duke University. From 14 posters, three young researchers from the China Institute of Atomic Energy, Tsinghua University and the Institute of Modern Physics of the Chinese Academy of Sciences received awards. The hope is that the poster session and awards will inspire young researchers to work with passion in the area of spin physics. A reception and banquet, and a visit to the nearby Summer Palace, served to bring all of the participants together, enhancing close discussions. They will surely remember SPIN2014 as a stimulating meeting that demonstrated the beauty and vitality of the field – and look forward to the next in the series, which will take place on 26–30 September 2016 at the University of Illinois Urbana-Champaign.

• For more about the organizers and sponsors of SPIN2014, and details of the full programme, visit www.phy.pku.edu.cn/spin2014/.

Seeing is believing

Lucio Rossi, CERN, is leader of the High-Luminosity LHC project.
Image credit: CERN-HI-0806018-05.

Seeing has always been a trigger for curiosity – the desire to know reality – and light is a means for bridging reality with our minds. It is not the only means, but probably the most important. Sight conveys the most information, the most detail about the world around us. Think, for example, of the richness of detail in today’s high-definition (HD) or 3D images. Now, to remind us of light’s importance and how useful it is in our lives, the UN has declared 2015 as the International Year of Light.

From Euclid, who first put down the principles of geometric optics in 300 BC, to Alhazen, whose first real theory of light and sight around 1000 AD was so influential in Europe, to Francesco Maurolico who in the 16th century developed a modern theory of sight and the functioning of the eyes – light and sight have long fascinated scientists. Indeed, light is fundamentally linked to the birth of modern science. In 1609–1610, Galileo Galilei was able to perfect the lens and telescope, making the first modern scientific instrument. The “canone occhiale” or “spectacles cannon” – the words at the root of the Italian for telescope – allowed him to see “things never seen beforehand”, as he wrote in his “instant book” Sidereus Nuncius. Thanks to an instrument based on light, he was able to discover the moons of Jupiter and make the Empyrean Heaven a place where change happens, and therefore worthy of investigation by physicists.

Later in the 17th century, Francesco Grimaldi first observed diffraction – soon formalized by Christiaan Huygens in a complete physics theory – and in 1873 Ernst Abbe showed that this limits the detail of what we can see. The resolution of our vision depends on the wavelength of the light or any other wave used for detection, such as sound waves, as in bats, or electromagnetic waves of different wavelengths. So, if we use millimetre-range infrared waves, the image is inevitably less well resolved than with submicrometre visible light. That is why our vision is so good and we can appreciate the splendour of HD images.

For more than a century, physicists have been able to see with finer wavelength “light” – for example, X-rays with wavelengths 100–1000 times shorter – and today, being able to “see” atoms at the nanometre scale, daily life is invaded by “nanotechnology”. Nevertheless, we can peer down to much smaller scales. Just 90 years ago, Louis de Broglie put forward the unimaginable idea that a particle can behave like a wave, with a wavelength inversely proportional to its momentum. This completed the particle–wave duality initiated by Albert Einstein in his annus mirabilis, when he realized that waves behave like particles and introduced the concept of light quanta, the photons.

The High-Luminosity LHC project is already on the starting blocks to be ready 10 years from now

In this way, particle accelerators can generate the finest “light”. The cyclotrons and synchrotrons of the 1950s and 1960s were capable of illuminating entities such as protons, but were limited by diffraction in the femtometre range. Each new, more powerful accelerator joined the race for the finest light, allowing the best resolving power. Most recently, with the LHC, the simple relation λ = h/p tells us that at 1 TeV (the average collision energy of a quark–quark interaction) we can resolve the attometre, or 10^–18 m, scale. However, thanks to higher energy in some collisions and to sophisticated experimental techniques, the LHC has shown that quarks are point-like at the level of 5 × 10^–20 m, or 50 zeptometres.

But light is only a means, a bridge between reality and our minds, where the image is formed and vision occurs. Indeed the light generated by the LHC would be useless without “eyes” – the LHC detectors that collect the collision events to record the detail illuminated by the light. As with the eyes, the collected information is then transmitted to the mind for image formation. At the LHC, the computers, the physics theory, the brains of the experimentalists and theoretical physicists – all of these form the “mind” where the wonderful images of, for example, the Higgs boson, are formed and, finally, known. Exactly as with sight, some signals (most of them, in fact) are first treated “unconsciously” (by the trigger) and only a selected part is treated consciously on a longer time scale.

Now the LHC is restarting and we will be able to generate light almost as twice as fine, thanks to the 13 TeV collision energy. Moreover, the High-Luminosity LHC project is already on the starting blocks to be ready 10 years from now (see A Luminous future for the LHC). Why high luminosity? Just as in a room where we might ask for more light to investigate finer details and measure the properties of objects more precisely, with the LHC we are planning to increase luminosity by a factor of five (instantaneous) or 10 (integrated) to make more precise measurements and so extend our sight, i.e., the physics reach of the collider and the detectors.

With our accelerators, detectors, computing facilities, physics analysis and theory, we really do reproduce the act of sight, generating the finest light and therefore perceiving a reality that is unimaginable to our normal senses: the frontier of the infinitely small.

Symmetries in Nature: The Scientific Heritage of Louis Michel

By Thibault Damour, Ivan Todorov and Boris Zhilinskii (eds)
World Scientific
Hardback: £83

Reflecting the oeuvre of “a man of two cultures: the culture of pure mathematics and the culture of theoretical physics”, this volume is centred around the notion of symmetry and its breaking. Starting with particle physics, the content proceeds to symmetries of matter, defects and crystals. The mathematics of group extensions, non-linear group action, critical orbits and phase transitions is developed along the way. The symmetry principles and general mathematical tools provide unity in the treatment of different topics. The papers and lecture notes are preceded by a lively biography of Louis Michel, and a commentary that relates his selected works both to the physics of his time and to contemporary trends.

The Bethe Wavefunction

By Michel Gaudin (translated by Jean-Sébastien Caux)
Cambridge University Press
Hardback: £70 $110
E-book: $88

Available in English for the first time, this translation of Michel Gaudin’s book La fonction d’onde de Bethe brings this classic work on exactly solvable models of quantum mechanics and statistical physics to a new generation of graduate students and researchers in physics. The book begins with the Heisenberg spin chain, starting from the co-ordinate Bethe ansatz and culminating in a discussion of its thermodynamic properties. Delta-interacting bosons (the Lieb–Liniger model) are then explored, and extended to exactly solvable models associated to a reflection group. After discussing the continuum limit of spin chains, the book covers six- and eight-vertex models in extensive detail, while later chapters examine advanced topics such as multi-component delta-interacting systems and Gaudin magnets.

Proceedings of the Conference in Honour of the 90th Birthday of Freeman Dyson

By K K Phua, L C Kwek, N P Chang and A H Chan (eds)
World Scientific
Hardback: £56
Paperback: £29
E-book: £22

As a tribute to Freeman Dyson on the occasion of his 90th birthday, and to celebrate his lifelong contributions in physics, mathematics, astronomy, nuclear engineering and global warming, a conference covering a range of topics was held in Singapore in August 2013. This memorial volume brings together an interesting lecture by Professor Dyson, “Is a Graviton Detectable?”, contributions by speakers at the conference, as well as guest contributions by colleagues who celebrated Dyson’s birthday at Rutgers University and the Institute for Advanced Study in Princeton.

Astroparticle, Particle, Space Physics and Detectors for Physics Applications: Proceedings of the 14th ICATPP Conference

By S Giani, C Leroy, L Price, P-G Rancoita and R Ruchti (eds)
World Scientific
Hardback: £117
E-book: £88

Exploration of the subnuclear world is done through increasingly complex experiments covering a range of energy in diverse environments, from particle accelerators and underground detectors to satellites in space. These research programmes call for new techniques, materials and instrumentation to be used in detectors, often of large scale. The reports from this conference review topics that range from cosmic-ray observations through high-energy physics experiments to advanced detector techniques.

What We Would Like LHC to Give Us

By Antonino Zichichi (ed.)
World Scientific
Hardback: £104
E-book: £78

This book is the proceedings of the International School of Subnuclear Physics, ISSP 2012, 50th Course, held in Erice on 23 June–2 July 2012. The course was devoted to celebrations of the 50th anniversary of the subnuclear-physics school, started in 1961 by Antonino Zichichi with John Bell at CERN, and formally established in 1962 by Bell, Blackett, Weisskopf, Rabi and Zichichi in Geneva (at CERN). The lectures cover the latest, most significant achievements in theoretical and experimental subnuclear physics.

Next Generation Experiments to Measure the Neutron Lifetime: Proceedings of the 2012 Workshop

By Susan J Seestrom (ed.)
World Scientific
Hardback: £63
E-book: £47

The neutron lifetime is an important fundamental quantity, as well as a parameter influencing important processes such as nucleosynthesis and the rate of energy production in the Sun, so there is great interest in improving the limits of its value to a precision level of 0.1 s. This workshop, held in November 2012, aimed to create a road map of R&D for a next-generation neutron-lifetime experiment that can be endorsed by the North American neutron community. The focus was on experiments using traps with ultracold neutrons and confinement by a combination of magnetic and/or gravitational interaction to avoid systematic uncertainties introduced by neutron interactions with material walls.

Topics

Reset your password

Registration complete