On 21 May, the Korea Institute of Science & Technology Information–Global Science experimental Data hub Center (KISTI-GSDC) – the Korean Tier-1 site of the Worldwide LHC Computing Grid (WLCG) – completed the upgrade to 10 Gbps of the bandwidth of its optical-fibre link to CERN. The link is part of the LHC Optical Private Network (OPN) that is used for fast data replication from the Tier-0 at CERN to Tier-1 sites in the WLCG.
KISTI-GSDC was approved as a full Tier-1 site at the 24th WLCG Overview Board in November 2013, backed by the ALICE community’s appreciation of the effort to sustain the site’s reliability and the contribution to computing resources for the experiment. At the time, the bandwidth of the dedicated connection to CERN provided by KISTI-GSDC was below that required, but the road map for upgrading the bandwidth was accepted.
The original proposal was to provide the upgrade of the OPN link by October 2014. However, following an in-depth revision of the executive plan with the Ministry of Science, ICT and Future Planning – the funding agency – to find the most cost-effective way, the upgrade process did not start until the end of February this year. It was finally completed just before the scheduled start of the LHC’s Run 2 in May.
The OPN link between KISTI and CERN is composed of two sections: Daejeon–Chicago (operated by KISTI) and Chicago–Geneva (operated by SURFnet). An additional line to be switched on in case of any necessary intervention complements the link. The yearly budget is about CHF1.1 million.
The STAR collaboration at the Brookhaven National Laboratory (BNL) has published new evidence indicative of a “chiral magnetic wave” rippling through the quark–gluon plasma created in high-energy gold–gold collisions at the Relativistic Heavy Ion Collider (RHIC).
Heavy-ion collisions at RHIC and the LHC involve many spectators – nucleons that are not involved in any direct collision. The charged spectators – protons – have an important influence because they can produce a magnetic field of some 1014 T. In principle, this can lead to a collective excitation in the hot dense matter produced, the chiral magnetic wave. It results from the separation both of electric charge and of chiral charge, that is, right or left “handedness”, but only in a chirally symmetric phase. The phenomenon is predicted to manifest itself as an electric quadrupole moment of the collision system, where the “poles” and “equator” of the system acquire, respectively, additional positive and negative particles. This in turn influences differently the elliptic flow of positive and negative particles, decreasing the former and increasing the latter.
To look for this effect, STAR measured the elliptic flow, v2, of π+ and π– produced in gold–gold collisions at mid-rapidity, as a function of the event-by-event charge asymmetry, ACH, over a range of energies. The team found that v2 increased linearly with ACH for π–, but decreased for π+. At the highest energy, √sNN = 200 GeV, the slope of the difference in v2 between the π+ and π– as a function of ACH depends on the centrality of the collision in a manner consistent with calculations that incorporate the chiral magnetic wave. The team also found a similar result for energies down to √sNN = 27 GeV, with no obvious dependence on beam energy. The researchers note that none of the conventional models they have considered appear to explain the observations.
At the Flavor Physics and CP violation (FPCP) conference in Nagoya, the LHCb collaboration presented a measurement of the rate of B0 → D*+τ–ντ relative to the related decay B0→ D*+μ–νμ. The first measurement of any B → τX decay at a hadron collider, it also indicates a tantalizing anomaly.
In the Standard Model, the ratio of these two branching fractions differs from unity only as a result of effects related to the mass of the much heavier τ lepton. The ratio R(D*) = BR(B0 → D*+τ–ντ)/BR(B0 → D*+μ–νμ) is therefore precisely calculable in the Standard Model as equal to 0.252±0.003.
Lepton universality dictates that the electroweak coupling strength of the electron, muon and tau are identical, with the three flavours distinguished only by their respective masses. So the observation of decays with differing rates to each lepton flavour, after accounting for mass effects, would be a clear sign of physics beyond the Standard Model. Owing to the large τ mass, the semitauonic B0 → D*+τ–ντ decay rate is particularly sensitive to the charged Higgs bosons predicted by many extensions of the Standard Model. Previous measurements have consistently been above predictions, making new results hotly anticipated.
LHCb has analysed 3 fb–1 of data from Run 1 of the LHC to measure R(D*) using the τ → μνμντ decay, which allows both the semitauonic and semimuonic mode to be reconstructed in the same final state. The two decays are distinguished via a fit to the decay kinematics, reconstructed using the visible decay products and an approximation for the rest frame of the B (see figure). In addition to the B0 → D*+τ–ντ and B0 → D*+μ–νμ decays, the D*+μ–X final state also receives large contributions from several background processes. The modelling of these backgrounds in LHCb is constrained using control samples in data, strongly controlling uncertainties due to theoretical models. The result presented of 0.336±0.027±0.033 is in close agreement with a result from BaBar in 2012, and is 2.1σ away from the Standard Model prediction.
Between the results from LHCb, BaBar and the Belle collaboration – which also presented updated results at the conference – a tantalizing picture is emerging in this channel. LHCb already has plans for complementary measurements in the decays B– → D0τ–ντ and Λ0b → Λ+c τ–ντ with the LHC Run 1 data set, and data from Run 2 is expected to allow for exciting improvements.
Studies of the production of top quarks in the forward region at the LHC are potentially of great interest in terms of new physics. Not only does the process have an enhanced sensitivity to physics beyond the Standard Model (owing to sizable contributions from quark–antiquark and gluon–quark scattering), but measurements of the forward production of top-quark pairs (tt) can be used to constrain the gluon parton distribution function (PDF) at large momentum fraction. Reducing the uncertainty on this PDF will increase the precision of many Standard Model predictions, especially those that serve as backgrounds to searches for new high-mass particles.
Top quarks decay almost exclusively to a W boson and a b-quark jet. The LHCb collaboration has already made high-precision measurements of W-boson production, and recently demonstrated the ability to identify, or tag, jets originating from b and c quarks (LHCb 2015a). Now, the collaboration had combined these two abilities in a study of W-boson production in association with b and c jets (LHCb 2015b), using a subset of these data samples to observe top-quark production for the first time in the forward region (LHCb 2015c). The data show a large excess of events compared with the Standard Model’s W+b-jet prediction in the absence of top-quark production (see figure).
LHCb measured the top-quark production cross-sections in a reduced fiducial region chosen to enhance the relative top-quark content of the W+b-jet final state. Within this region, the inclusive top-quark production cross-sections, which include contributions from both tt and single-top production, are σ(top) [7 TeV] = 239±53(stat.)±38(syst.) fb and σ(top) [8 TeV] = 289±43(stat.)±46(syst.) fb. These values are in agreement with the Standard Model predictions of 180+51–41 (312+83–68) fb at 7(8) TeV obtained at next-to-leading order using MCFM, the Monte Carlo programme for femtobarn processes.
In the LHC’s Run 2, the higher beam energy should lead to a greatly increased cross-section and acceptance for top-quark production. This will allow LHCb to measure precisely both tt and single-top production, and so provide important constraints on the gluon PDF as well as potential signs for physics beyond the Standard Model.
When searching for new particles in ATLAS, it is often assumed that they will either decay to observable Standard Model particles at the centre of the detector, or escape undetected, in which case their presence can be inferred by measuring an imbalance of the total transverse momentum. This assumption was a guiding principle in designing the layout of the ATLAS detector.
However, another possibility exists: what if new particles are long lived? Many models of new physics include heavy particles with lifetimes large enough to allow them to travel measurable distances before decaying. Heavy particles typically decay quickly into lighter particles, unless the decay is suppressed by some mechanism. Suppression could occur if couplings are small, if the decaying particle is only slightly heavier than the only possible decay products, or if the decay is mediated by very heavy virtual exchange particles. Looking for signatures of these models in the LHC data implies exploiting the ATLAS detector in ways it was not necessarily designed for.
These models can give rise to a broad range of possible signatures, depending on the lifetime, charge, velocity and decay channels of the long-lived particle. Decays to charged particles within the ATLAS detector volume can be detected as “displaced vertices”. Heavy charged particles that traverse the detector will move more slowly than their Standard Model counterparts, and will leave a trail of large ionization-energy deposits. Particles with very long lifetimes could even stop in the dense material of the calorimeter and decay at a later time. The ATLAS collaboration has performed dedicated searches to explore all of these spectacular – and challenging – signatures.
Standard reconstruction algorithms are not optimal for such unconventional signatures, so the ATLAS collaboration has used detailed knowledge of the experiment’s sub-detectors to develop dedicated algorithms; for example, to reconstruct charged-particle tracks from displaced decays or to measure the ionization-charge deposited by long-lived charged particles. A class of specialized triggers for picking up these signatures has also been designed and deployed.
These searches generally have very low background, but it is nevertheless essential to estimate the level because some of the signatures could be faked by instrumental effects that are not well-modelled in the simulation. Sophisticated data-driven background estimation techniques have therefore been developed.
One postulated type of long-lived particle is the “R hadron” – a supersymmetric particle with colour-charge combined with Standard Model quarks and gluons. Several ATLAS searches are sensitive to R hadrons, and between them they cover a wide range of lifetimes, as the figure (top right) shows (ATLAS Collaboration 2013 and 2015a). Other analyses have searched for a long-lived hidden-sector pion (“v pion”) by looking for displaced vertices in different ATLAS sub-detectors (ATLAS Collaboration 2015b and 2015c). Exotic Higgs-boson decays to long-lived neutral particles that decay to jets were constrained to a branching ratio smaller than 1% at the 95% confidence level, for a range of lifetime values, as in the figure (right).
With 13-TeV collisions under way at the LHC, the probability of producing heavy new particles has increased enormously, revitalizing the searches for new physics. ATLAS experimentalists are rising to the challenge of exploring as many new physics signatures as possible, including those related to long-lived particles.
The search for particles that could constitute dark matter in the universe relies on detecting their interplay with the Standard Model particles through a three-pronged approach: via direct-detection experiments, via indirect-detection experiments, and with hermetic detectors at colliders, covering the full 4π-phase space. Because dark matter behaves as a weakly interacting neutral particle, it escapes the detectors without interacting, so in collider experiments its production is inferred by measuring the imbalance in transverse momentum left in the detector. At the LHC, a search for the pair production of dark-matter particles can be performed by looking for events with a large momentum imbalance in association with initial-state radiation of either a jet or a photon – the “monojet” or “monophoton” searches.
The CMS collaboration now has results based on proton–proton collision data collected at a centre-of-mass energy of 8 TeV, amounting to 20 fb–1 of integrated luminosity. In the analysis, both monojet and monophoton searches employ a “cut-and-count” approach. A set of cuts is applied to select potential dark-matter events and, at the same time, to reduce the contamination from Standard Model processes.
One of the dominant and irreducible backgrounds for both searches is the decay of the Z boson into neutrinos, which accounts for roughly 60–70% of the total monojet/monophoton events. The searches look for an excess of events above those expected from the Standard Model processes. In the absence of an excess, limits can be placed on the pair production of dark-matter particles. The results are presented within the framework of an effective field theory where a contact interaction is assumed between the dark-matter and Standard Model particles. Because the effective field theory is not valid for the full parameter space probed at the LHC, the searches are also interpreted in the context of a simplified model with an s-channel mediator. Both assumptions are depicted in the Feynman diagrams in figure 1.
The results (see figure 2) show that CMS extends the sensitivity to spin-independent dark-matter–Standard Model interactions including a vector operator to dark-matter masses that are lower (below 5 GeV) than is currently accessible to the direct-detection experiments. For spin-dependent interactions that include an axial-vector operator, the sensitivity of CMS (not shown here) extends down to dark-matter–nucleon cross-sections of 10–41 cm2. If the particle mediating the dark-matter–Standard Model interaction is accessible at LHC energies, CMS has the opportunity to search for the mediator itself. Figure 3 shows the constraints placed on the mass and coupling strengths of vector-mediator interactions in the monophoton analysis.
The LHC plays a significant role in the search for dark matter and complements well the searches by the direct-detection experiments. The CMS collaboration is now looking forward to intensifying the search with data at 13 TeV and opening up a completely new energy regime to spot hints of dark-matter particles.
EuroCirCol, the EC-funded part of the Future Circular Collider (FCC) study that will develop the conceptual design of an energy-frontier hadron collider, officially started on 1 June. The “kick-off” event at CERN on 2–4 June brought together 62 participants to constitute governance bodies, commit to the project plan and align the organization, structures and processes of 16 institutions from 10 countries. The goal of the project is to conceive a post-LHC research infrastructure around a 100-km circular hadron collider capable of reaching 100-TeV collisions. The project will run for four years, with a total estimated budget of €11.2 million, which includes a €2.99 million contribution from the European Commission’s Horizon 2020 programme on developing new world-class research infrastructures.
EuroCirCol will deliver a design for a hadron collider as part of the broader FCC study (CERN Courier April 2014 p16). It will provide input to an accelerator-infrastructure road map, taking into account European and global interests by the time of the next update of the European Strategy for Particle Physics in 2018. It was the only one of 39 submissions to receive the maximum points from reviewers, a clear sign that high-energy physics remains a top priority for the European Commission.
EuroCirCol is organized around four technical work packages. The first two are to develop the collider’s lattice and beam optics, including the experimental regions. A third develops prototypes and tests a novel cryogenics beam-vacuum system that can respond to the challenges of the high levels of synchrotron radiation expected at such a collider. This work also pioneers collaboration between the particle-physics and light-source communities, with opportunities to improve existing synchrotron-radiation facilities and to reduce cost and performance of fourth- or fifth-generation light sources. The fourth work package will study a viable design for a 16-T accelerator magnet, as part of a worldwide study of conductor R&D for the High-Luminosity LHC project and the FCC.
The EuroCirCol project is set to create opportunities for doctoral and postdoctoral assignments in the areas of beam optics and accelerator technologies, in the participating institutes. It will also provide excellent training opportunities for the next generation of accelerator physicists, under the guidance of world-renowned experts in the field.
As a building block in the globally co-ordinated strategy of the FCC study to produce a global design for a global machine, EuroCirCol’s main outcome will be to lay the foundations for subsequent research-infrastructure development that will strengthen Europe as a leader in global research co-operation over the coming decades.
Astronomers using ESO’s Very Large Telescope (VLT) have discovered a very bright galaxy in the early universe, and found strong evidence that it contains first-generation stars. These massive luminous stars – previously purely theoretical – are made of primordial material from the Big Bang, and produced the first heavy elements. The newly found galaxy is three times brighter than the brightest distant galaxy known up to now.
Astronomers have long theorized the existence of a first generation of stars – known as Population III stars – born out of hydrogen, helium and trace amounts of lithium, the only elements produced by Big Bang nucleosynthesis. All of the heavier chemical elements, such as oxygen, nitrogen, carbon and iron, were forged by nuclear fusion in the cores of stars. The Population III stars would have been enormous – several hundred or even a thousand times more massive than the Sun. They would have exploded as supernovae after only about 2 million years, which is less than a thousandth of the Sun’s lifetime.
A team led by David Sobral, of the University of Lisbon and Leiden Observatory, has used the VLT to peer back into the ancient universe, to a period known as re-ionization, approximately 800 million years after the Big Bang. Instead of conducting a narrow and deep study of a small area of the sky, they broadened their scope to produce the widest survey of very distant galaxies ever attempted. Their expansive study was made using the VLT, with help from the W M Keck Observatory and the Subaru Telescope, as well as the NASA/ESA Hubble Space Telescope. The team discovered and confirmed a number of surprisingly bright, very young galaxies at a redshift, z, of around seven. One of these, labelled CR7 – for COSMOS Redshift 7, but also as an allusion to the footballer Cristiano Ronaldo, who is known as CR7 – is by far the brightest galaxy ever observed so early in the history of the universe.
The X-shooter and SINFONI instruments on the VLT found strong ionized-helium emission in CR7 but, crucially and surprisingly, no sign of any heavier elements in a bright area of the galaxy. This suggests that the team has discovered the first evidence for clusters of Population III stars that had ionized gas within a galaxy in the early universe. Bluer and somewhat redder clusters of stars were found within CR7, indicating that the formation of Population III stars had occurred in waves, as had been predicted. What the team directly observed was the last wave of Population III stars, suggesting that such stars should be easier to find than previously thought: they reside among regular stars, in brighter galaxies, not just in the earliest, smallest and dimmest galaxies, which are so faint as to be extremely difficult to study.
The team considered two alternative theories: that the source of the light was either an active galactic nuclei, or Wolf–Rayet stars. The lack of heavy elements, together with other evidence, strongly refutes both these theories. The team also considered that the source may be a direct-collapse black hole, which would itself be an exotic, so far purely theoretical, object. The lack of a broad emission line, and the fact that the hydrogen and helium luminosities are much greater than what has been predicted for such a black hole, indicates that this scenario is also rather unlikely.
Synchrotron-light sources have become an essential tool in many branches of medicine, biology, physics, chemistry, materials science, environmental studies and even archaeology. There are some 50 storage-ring-based synchrotron-light sources in the world, including a few in developing countries, but none in the Middle East. SESAME is a 2.5-GeV, third-generation light source under construction near Amman. When it is commissioned in 2016, it will not only be the first light source in the Middle East, but arguably also the region’s first true international centre of excellence.
The members of SESAME are currently Bahrain, Cyprus, Egypt, Iran, Israel, Jordan, Pakistan, the Palestinian Authority and Turkey (others are being sought). Brazil, China, the European Union, France, Germany, Greece, Italy, Japan, Kuwait, Portugal, the Russian Federation, Spain, Sweden, Switzerland, the UK and the US are observers.
SESAME will: foster scientific and technological capacities and excellence in the Middle East and neighbouring regions, and help prevent or reverse the brain drain; build scientific links and foster better understanding and a culture of peace through collaboration between peoples with different creeds and political systems.
The origins of SESAME
The need for an international synchrotron light-source in the Middle East was recognized by the Pakistani Nobel laureate Abdus Salam, one of the fathers of the Standard Model of particle physics, more than 30 years ago. This need was also felt by the CERN-and-Middle-East-based Middle East Scientific Co-operation group (MESC), headed by Sergio Fubini. MESC’s efforts to promote regional co-operation in science, and also solidarity and peace, started in 1995 with the organization in Dahab, Egypt, of a meeting at which the Egyptian minister of higher education, Venice Gouda, and Eliezer Rabinovici of MESC and the Hebrew University in Israel – and now a delegate to the CERN and SESAME councils – took an official stand in support of Arab–Israeli co-operation.
At the request of Fubini and Herwig Schopper, the German government agreed to donate the components of BESSY I to SESAME
In 1997, Herman Winick of SLAC and the late Gustav-Adolf Voss of DESY suggested building a light source in the Middle East using components of the soon-to-be decommissioned BESSY I facility in Berlin. This brilliant proposal fell on fertile ground when it was presented and pursued during workshops organized in Italy (1997) and Sweden (1998) by MESC and Tord Ekelof, of MESC and Uppsala University. At the request of Fubini and Herwig Schopper, a former director-general of CERN, the German government agreed to donate the components of BESSY I to SESAME, provided that the dismantling and transport – eventually funded by UNESCO – were taken care of by SESAME.
The plan was brought to the attention of Federico Mayor, then director-general of UNESCO, who called a meeting of delegates from the Middle East and neighbouring regions at the organization’s headquarters in Paris in June 1999. The meeting launched the project by setting up an International Interim Council with Schopper as chair. Jordan was selected to host SESAME, in a competition with five other countries from the region. It has provided the land and funded the construction of the building.
In May 2002, the Executive Board of UNESCO unanimously approved the establishment of the new centre under UNESCO’s auspices. SESAME formally came into existence in April 2004, when the permanent council was established, and ratified the appointments of Schopper as president and of the first vice-presidents, Dincer Ülkü of Turkey and Khaled Toukan of Jordan. A year later, Toukan stepped down as vice-president and became director of SESAME.
Meanwhile, the ground-breaking ceremony was held in January 2003, and construction work began the following August. Since February 2008, SESAME has been working from its own premises, which were formally opened in November 2008 in a ceremony held under the auspices of King Abdullah II of Jordan, and with the participation of Prince Ghazi Ben Mohammed of Jordan and Koïchiro Matsuura, then director-general of UNESCO. In November 2008, Schopper stepped down as president of the Council and was replaced by Chris Llewellyn Smith, who is also a former director-general of CERN. In 2014, Rabinovici and Kamal Araj of Jordan became vice-presidents, replacing Tarek Hussein of Egypt and Seyed Aghamiri of Iran.
SESAME users
As at CERN, the users of SESAME will be based in universities and research institutes in the region. They will visit the laboratory periodically to carry out experiments, generally in collaboration. The potential user-community, which is growing rapidly, already numbers some 300, and is expected eventually to grow to between 1000 and 1500. It is being fostered by a series of Users’ Meetings – the 12th, in late 2014, attracted more than 240 applications, of which only 100 could be accepted. The training programme, which is supported by the International Atomic Energy Agency, various governments and many of the world’s synchrotron laboratories, and which includes working visits to operational light sources, is already bringing significant benefits to the region.
In 2002, the decision was taken to build a completely new main storage ring, with an energy of 2.5 GeV – compared with the 1 GeV that would have been provided by upgrading the main BESSY 1 ring – while retaining refurbished elements of the BESSY I microtron to provide the first stage of acceleration and the booster synchrotron. As a result, SESAME will not only be able to probe shorter distances, but will also be a third-generation light source, i.e. one that can accommodate insertion devices – wigglers and undulators – to produce enhanced synchrotron radiation. There are light sources with higher energy and greater brightness, but SESAME’s performance (see table) will be good enough to allow users – with the right ideas – to win Nobel prizes.
Progress has not been as rapid as had been hoped, owing mainly to lack of funding, as discussed below. The collapse of the roof under an unprecedented snowfall in December 2013, when it even snowed in Cairo, has not helped. Nevertheless, despite working under the open sky throughout 2014, the SESAME team successfully commissioned the booster synchrotron in September 2014. The beam was brought to the full energy of 800 MeV, essentially without loss, and the booster is now the highest-energy accelerator in the Middle East (CERN Courier November 2014 p5).
The final design of the magnets for the main ring and for the powering scheme was carried out by CERN in collaboration with SESAME. Construction of the magnets is being managed by CERN using funds provided by the European Commission. The first of 16 cells was assembled and successfully tested at CERN at the end of March, and installation will begin later this year (CERN Courier May 2015 p6). If all goes well, commissioning of the whole facility – initially with only two of the four accelerating cavities – should begin in June next year.
The scientific programme
SESAME will nominally have four “day-one” beamlines in Phase 1a, although to speed things up and save money, it will actually start with just two. Three more beamlines will be added in Phase 1b.
One of the beamlines that will be available next year will produce photons with energies of 0.01–1 eV for infrared spectromicroscopy, which is a powerful tool for non-invasive studies of chemical components in cells, tissues and inorganic materials. A Fourier transform infrared microscope, which will be adapted to this beamline, has already been purchased. Meanwhile, 11 proposals from the region to use it with a conventional thermal infrared source have been approved. The microscope has been in use since last year, and the first results include a study of breast cancer by Fatemeh Elmi of the University of Mazandaran, Iran, with Randa Mansour and Nisreen Dahshan, who are PhD students in the Faculty of Pharmacy, University of Jordan. When SESAME is in operation, the infrared beamline will be used in biological applications, environmental studies, materials and archaeological sciences.
An X-ray absorption fine-structure and X-ray fluorescence beamline, with photon energies of 3–30 keV, will also be in operation next year. It will have potential applications in materials and environmental sciences, providing information on chemical states and local atomic structure that can be used for designing new materials and improving catalysts (e.g. for the petrochemical industries). Other applications include the non-invasive identification of the chemical composition of fossils and of valuable paintings.
It is hoped that macro-molecular crystallography and material-science beamlines, with photon energies of 4–14 keV and 3–25 keV, respectively, will be added in the next two years, once the necessary funding is available. The former will be used for structural molecular biology, aimed at elucidating the structures of proteins and other types of biological macromolecules at the atomic level, to gain insight into mechanisms of diseases to guide drug design (as used by pharmaceutical and biotech companies). The latter will use powder diffraction for studies of disordered/amorphous material on the atomic scale. The use of powder diffraction to study the evolution of nanoscale structures and materials in extreme conditions of pressure and temperature has become a core technique for developing and characterizing new smart materials.
In Phase 1b, soft X-ray (0.05–2 keV), small and wide-angle X-ray scattering (8–12 keV) and extreme-ultraviolet (10–200 eV) beamlines will be added. They will be used, respectively, for atomic, molecular and condensed-matter physics; structural molecular biology and materials sciences; and atomic and molecular physics, in a spectral range that provides a window on the behaviour of atmospheric gases, and enables characterization of the electrical and mechanical properties of materials, surfaces and interfaces.
The main challenges
The main challenge has been – and continues to be – obtaining funding. Most of the SESAME members have tiny science budgets, many are in financial difficulties, and some have faced additional problems, such as floods in Pakistan and the huge influx of refugees in Jordan. Not surprisingly, they do not find it easy to pay their contributions to the operational costs, which are rising rapidly as more staff are recruited, and will increase even faster when SESAME comes into operation and is faced with paying large electricity bills at $0.36/kWh and rising. Nevertheless, increasing budgets have been approved by the SESAME Council. As soon as the funding can be found, a solar-power plant, which would soon pay for itself and ease the burden of paying the electricity bill, will be constructed. And SESAME has always been open to new members, who are being sought primarily to share the benefits but also to share the costs.
So far, $65 million has been invested, including the value to SESAME of in-kind contributions of equipment (from Jordan, Germany, the UK, France, Italy, the US and Switzerland), cash contributions to the capital budget (from the EU, Jordan, Israel, Turkey and Italy), and manpower and other operational costs that are paid by the members (but not including important in-kind contributions of manpower, especially from CERN and the French light source, SOLEIL).
SESAME is a working example of Arab–Israeli–Iranian–Turkish–Cypriot–Pakistani collaboration.
Thanks to the contributions already made and additional funding to come from Iran, Israel, Jordan and Turkey, which have each pledged voluntary contributions totalling $5 million, most of the funds that are required simply to bring SESAME into operation next year are now available. At the SESAME Council meeting in May, Egypt announced that it will also make a voluntary contribution, which will narrow the immediate funding gap. More will, however, be needed, to provide additional beamlines and a properly equipped laboratory, and additional funds are being sought from a variety of governments and philanthropic organizations.
The ongoing turbulence in the Middle East has only had two direct effects on SESAME. First, sanctions are making it impossible for Iran to pay its capital and operational contributions, which are much needed. Second, discussions of Egypt joining other members in making voluntary contributions were interrupted several times by changes in the government.
Outlook
SESAME is a working example of Arab–Israeli–Iranian–Turkish–Cypriot–Pakistani collaboration. Senior scientists and administrators from the region are working together to govern SESAME through the Council, with input from scientists from around the world through its advisory committees. Young and senior scientists from the region are collaborating in preparing the scientific programme at Users’ Meetings and workshops. And the extensive training programme of fellowships, visits and schools is already building scientific and technical capacity in the region.
According to the Italian political theorist Antonio Gramsci, there is a perpetual battle between the optimism of the will and the pessimism of the brain. Several times during its history, SESAME has faced seemingly impossible odds, and pessimists might have given up. Luckily, however, the will prevailed, and SESAME is now close to coming into operation. There are still huge challenges, but we are confident that thanks to the enthusiasm of all those involved they will be met and SESAME will fulfil its founders’ ambitious aims.
In early April, members of the Baikal collaboration deployed and started operation of the first cluster of the Gigaton Volume Detector (Baikal-GVD). Named “Dubna”, the cluster comprises 192 optical modules arranged at depths down to 1300 m. The modules are glass spheres that house photomultiplier tubes to detect Cherenkov light from the charged particles emerging from neutrino interactions in the water of the lake. By 2020, GVD is set to consist of 10–12 clusters covering a total volume of about 0.4 km3 (GVD phase-1). This is about half the size of the present world leader – the IceCube Neutrino Observatory at the South Pole (CERN Courier December 2014 p30). A planned further extension should then lead towards a second stage containing 27 clusters in a telescope with a total volume of about 1.5 km3.
Neutrino detection in Lake Baikal will be an important part of the effort to understand better the high-energy processes that occur in far-distant astrophysical sources, to determine the origin of cosmic particles of the highest energies ever registered, to search for dark matter, to study properties of elementary particles, and to learn a great deal of new information about the structure and evolution of the universe as a whole. Together with KM3NeT in the Mediterranean Sea, the other future Northern-hemisphere neutrino telescope (CERN Courier July/August 2012 p31), GVD will allow an optimal view to the central parts of the Galaxy.
The start of the Baikal neutrino experiment dates back to 1 October 1980, when a laboratory of high-energy neutrino astrophysics was established at the Institute for Nuclear Research of the former Academy of Sciences of the USSR in Moscow – now the Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS). This laboratory later became the core of the Baikal collaboration, including at various times the Joint Institute for Nuclear Research (JINR) in Dubna, Irkutsk State University, Moscow State University, DESY-Zeuthen, the Nizhni Novgorod State Technical University, the Saint Petersburg State Marine Technical University, and other scientific research organizations in Russia, Hungary and Germany. At present, the participation of institutes from the Czech Republic, Slovakia and Poland is under discussion.
The idea to register neutrinos in large-scale Cherenkov detectors in natural water was expressed for the first time by Moisey Markov, then at Dubna, at the 10th International Conference on High-Energy Physics, in 1960. Two decades later, Alexander Chudakov, of INR, proposed using Lake Baikal as a site both for tests and for future large-scale neutrino telescopes. The choice of this lake – the largest and deepest freshwater reservoir in the world – was determined by the high transparency of its water, its depth, and the ice cover that allows the installation of deep-water equipment during two months in winter.
The predecessor of GVD was constructed during 1993–1998. Named NT200, it comprised 192 photodetectors placed on eight vertical strings at a depth of 1100–1200 m. NT200 covered some 100,000 m3 of fresh water (an order of magnitude less than the present Dubna cluster). Already in 1994, data taken with only 36 of the final 192 photodetectors showed two neutrino events. These two events were the first of several-hundred-thousand atmospheric neutrinos since recorded by deep-underwater and under-ice experiments. Scientific research with NT200 covered a wide programme, most notably the search for a cosmic diffuse neutrino flux leading to tight limits on that flux (CERN Courier July/August 2005 p24). Moreover, limits were derived on the flux of magnetic monopoles and on muons from dark-matter annihilation in the centre of the Earth and the Sun. Last but not least, the NT200 infrastructure was used for innovative environmental studies.
A notable breakthrough in the field came in 2012, when IceCube detected the first high-energy “astrophysical” neutrinos, i.e. high-energy neutrinos generated beyond the solar system (CERN Courier July/August 2013 p35). That marked the birth of high-energy neutrino astronomy, and underlined the need to develop neutrino telescopes of similar capacity in the Northern hemisphere, to be able to study high-energy neutrino sources across the whole celestial sphere. JINR, with many years of experience as a participant in the Baikal neutrino project, recognized this opportunity and decided to treat activities related to Baikal-GVD as a scientific priority.
Baikal-GVD will have a modular structure formed from functionally independent clusters of vertical strings of optical modules. This modular structure will allow data acquisition at early stages in the construction of the facility. The choice of the telescope structure will also allow adjustment of its configuration in response to changes in scientific priorities at different times.
Prototypes of all of the basic elements of the GVD telescope system were designed, manufactured and tested during 2006–2010. The final stage of complex in-situ testing started in 2011 and finished in 2015 with the development of the Dubna cluster. Its 192 optical modules are arranged down to depths of 1300 m on eight vertical strings, each 345-m long. Different from NT200, the optical modules are not grouped in pairs, resulting in 192 space points per cluster (instead of only 96 for NT200). Moreover, the former custom-made, hybrid QUASAR phototube has been replaced by a conventional 10-inch photomultiplier with a high-sensitivity photocathode. The mechanical structure has been simplified compared with NT200, and a totally new system for front-end and trigger electronics and for data acquisition has been designed and implemented.
Deployment of the Dubna cluster is an exciting step towards a next-generation neutrino telescope in Lake Baikal. Such a telescope will be a cornerstone of a future worldwide neutrino observatory, with detectors at the South Pole, in the Mediterranean Sea and in Lake Baikal. The Baikal collaboration pioneered this technology in the 1980s and 1990s, and measured neutrinos generated in the Earth’s atmosphere. Two decades later, the long-awaited discovery by IceCube of the first high-energy neutrinos from far beyond the Earth and the solar system has given increased motivation to projects for similar large detectors in the Northern hemisphere. IceCube has lifted the curtain that hides the high-energy neutrino universe, but just by a little. In the future, Baikal-GVD will help to chart this new cosmic territory fully.
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