Author Archives: Julie Haffner

First light for pioneering SESAME light source

SESAME,users,Jordan
Inside the SESAME ring. Image: Noemi Caraban Gonzalez/CERN

On behalf of SESAME

 

Allan, Jordan, 23 November 2017. At 10:50 yesterday morning scientists at the pioneering SESAME light source saw First Monochromatic Light through the XAFS/XRF (X-ray absorption fine structure/X-ray fluorescence) spectroscopy beamline, signalling the start of the laboratory’s experimental programme. This beamline, SESAME’s first to come on stream, delivers X-ray light that will be used to carry out research in areas ranging from solid state physics to environmental science and archaeology.

“After years of preparation, it’s great to see light on target,” said XAFS/XRF beamline scientist Messaoud Harfouche. “We have a fantastic experimental programme ahead of us, starting with an experiment to investigate heavy metals contaminating soils in the region.”

The initial research programme will be carried out at two beamlines, the XAFS/XRF beamline and the Infrared (IR) spectromicroscopy beamline that is scheduled to join the XAFS/XRF beamline this year. Both have specific characteristics that make them appropriate for various areas of research. A third beamline, devoted to materials science, will come on stream in 2018.

“Our first three beamlines already give SESAME a wide range of research options to fulfil the needs of our research community,” said SESAME Scientific Director Giorgio Paolucci, “the future for light source research in the Middle East and neighbouring countries is looking very bright!”

First Light is an important step in the commissioning process of a new synchrotron light source, but it is nevertheless just one step on the way to full operation. The SESAME synchrotron is currently operating with a beam current of just over 80 milliamps, while the design value is 400 milliamps. Over the coming weeks and months as experiments get underway, the current will be gradually increased.

SESAME is a major scientific and technological addition to research and education in the Middle East and beyond,” said Director of SESAME, Khaled Toukan. “Jordan supported the project financially and politically since its inception in 2004 for the benefit of science and peace in the region. The young scientists, physicists, engineers and administrators who have built SESAME, come for the first time from this part of the world.

Among the subjects likely to be studied in early experiments are environmental pollution with a view to improving public health, as well as studies aimed at identifying new drugs for cancer therapy, and cultural heritage studies ranging from bioarcheology – the study of our ancestors – to investigations of ancient manuscripts.

“On behalf of the SESAME Council, I’d like to congratulate the SESAME staff on this wonderful milestone,” said President of the Council, Rolf Heuer. “SESAME is a great addition to the region’s research infrastructure, allowing scientists from the region access to the kind of facility that they previously had to travel to Europe or the US to use.”

Contact:

James Gillies: James.Gillies@cern.ch +41 75 411 4555
Clarissa Formosa-Gauci: cfg@sesame.org.jo

SESAME XAFS/XRF beamline scientist, Messaoud Harfouche, points out SESAME’s first monochromatic light. Image: SESAME

The SESAME laboratory in Allan, Jordan. Image: Jacques Herve Fichet/CERN

Footnote(s)

1. CERN, the European Organization for Nuclear Research, is one of the world's leading laboratories for particle physics. The Organization is located on the French-Swiss border, with its headquarters in Geneva. Its Member States are: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Spain, Sweden, Switzerland and United Kingdom. Cyprus, Serbia and Slovenia are Associate Member States in the pre-stage to Membership. India, Pakistan, Turkey and Ukraine are Associate Member States. The European Union, Japan, JINR, the Russian Federation, UNESCO and the United States of America currently have Observer status.

Lithuania to become Associate Member of CERN

CERN Director General, Fabiola Gianotti, and the Minister of Foreign Affairs of the Republic of Lithuania, Linas Linkevičius, in the presence of the President of the Republic of Lithuania, Dalia Grybauskaitė, signed the Agreement admitting Lithuania as an Associate Member of CERN. (Image © Official Office of the President of the Republic of Lithuania - photo by Robertas Dačkus)

Vilnius, 27 June 2017. Today, in Vilnius, Lithuania, CERN Director General, Fabiola Gianotti, and the Minister of Foreign Affairs of the Republic of Lithuania, Linas Linkevičius, in the presence of the President of the Republic of Lithuania, Dalia Grybauskaitė, signed the Agreement admitting Lithuania as an Associate Member of CERN. The last step for the Agreement to enter into force requires final approval by the Government of Lithuania.

“Signing an agreement with CERN means recognition of Lithuanian science and talents as well as our common efforts in strengthening research, innovation and centres of excellence in the Baltic region,” said Dalia Grybauskaitė, President of the Republic of Lithuania. “We are proud of this Associate Membership - cooperation with CERN gives a new impetus for economic growth, provides an opportunity for us to take part in global research and opens a wide horizon for our youth.”

 “The involvement of Lithuanian scientists at CERN has been growing steadily over the past decade, and Associate Membership can now serve as a catalyst to further strengthen particle physics and fundamental research in the country,” said Fabiola Gianotti. “We warmly welcome Lithuania into the CERN family, and look forward to enhancing our partnership in science, technology development and education and training.”

Lithuania’s relationship with CERN dates back to 2004, when an International Cooperation Agreement was signed between the Organization and the government of the Republic of Lithuania. This set priorities for the further development of scientific and technical cooperation between CERN and Lithuania in high-energy physics. One year later, in 2005, a Protocol to this Agreement was signed, paving the way for the participation of Lithuanian universities and scientific institutions in high-energy particle physics experiments at CERN.

Lithuania has contributed to the CMS experiment since 2007 when a Memorandum of Understanding (MoU) was signed marking the beginning of Lithuanian scientists’ involvement in the CMS collaboration. Lithuania has also played an important role in database development at CERN for CMS data mining and data quality analysis. Lithuania actively promoted the BalticGrid in 2005.

In addition to its involvement in the CMS experiment, Lithuania is part of two collaborations that aim to develop detector technologies to address the challenging upgrades needed for the High-Luminosity LHC.

Since 2004, CERN and Lithuania have also successfully collaborated on many educational activities aimed at strengthening the Lithuanian particle physics community. Lithuania has been participating in the CERN Summer Student programme and 53 Lithuanian teachers have taken part in CERN’s high-school teachers programme.

Associate Membership will allow Lithuania to take part in meetings of the CERN Council and its committees (Finance Committee and Scientific Policy Committee). It will also make Lithuanian nationals eligible for limited-duration staff appointments. Last but not least, Lithuanian industry will be entitled to bid for CERN contracts, opening up opportunities for industrial collaboration in areas of advanced technology.

Footnote(s)

1. CERN, the European Organization for Nuclear Research, is one of the world's leading laboratories for particle physics. The Organization is located on the French-Swiss border, with its headquarters in Geneva. Its Member States are: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Spain, Sweden, Switzerland and United Kingdom. Cyprus and Serbia are Associate Member States in the pre-stage to Membership. India, Pakistan, Turkey and Ukraine are Associate Member States. The European Union, Japan, JINR, the Russian Federation, UNESCO and the United States of America currently have Observer status.

CERN celebrates completion of Linac 4, its brand new linear particle accelerator

Linac 4
Linac 4, CERN's newest accelerator acquisition since the Large Hadron Collider (LHC), was inaugurated today. (Image: M.Brice/CERN)

Geneva, 9 May 2017. At a ceremony today, CERN1 inaugurated its linear accelerator, Linac 4, the newest accelerator acquisition since the Large Hadron Collider (LHC). Linac 4 is due to feed the CERN accelerator complex with particle beams of higher energy, which will allow the LHC to reach higher luminosity by 2021. After an extensive testing period, Linac 4 will be connected to CERN’s accelerator complex during the upcoming long technical shut down in 2019-20. Linac 4 will replace Linac 2, which has been in service since 1978. It will become the first step in CERN’s accelerator chain, delivering proton beams to a wide range of experiments.

“We are delighted to celebrate this remarkable accomplishment. Linac 4 is a modern injector and the first key element of our ambitious upgrade programme, leading up to the High-Luminosity LHC. This high-luminosity phase will considerably increase the potential of the LHC experiments for discovering new physics and measuring the properties of the Higgs particle in more detail,” said CERN Director General Fabiola Gianotti.

“This is an achievement not only for CERN, but also for the partners from many countries who contributed to designing and building this new machine,” said CERN Director for Accelerators and Technology Frédérick Bordry. “Today, we also celebrate and thank the wide international collaboration that led this project, demonstrating once again what can be accomplished by bringing together the efforts of many nations.”

The linear accelerator is the first essential element of an accelerator chain. In the linear accelerator, the particles are produced and receive the initial acceleration; the density and intensity of the particle beams are also shaped in the linac. Linac 4 is an almost 90-metre-long machine sitting 12 metres below the ground. It took nearly 10 years to build.

Linac 4 will send negative hydrogen ions, consisting of a hydrogen atom with two electrons, to CERN’s Proton Synchrotron Booster (PSB), which further accelerates the negative ions and removes the electrons. Linac 4 will bring the beam up to 160 MeV energy, more than three times the energy of its predecessor. The increase in energy, together with the use of hydrogen ions, will enable double the beam intensity to be delivered to the LHC, thus contributing to an increase in the luminosity of the LHC.

Luminosity is a parameter indicating the number of particles colliding within a defined amount of time. The peak luminosity of the LHC is planned to be increased by a factor of five by 2025. This will make it possible for the experiments to accumulate about 10 times more data over the period 2025 to 2035 than before. The High-Luminosity LHC will therefore provide more accurate measurements of fundamental particles than today, as well as the possibility of observing rare processes that occur beyond the machine’s present sensitivity level.

You can download recent photos of the Linac4 here and also a set of 2015 (from the Photowalk competition), and click here for video footage.

Footnote(s)

1.CERN, the European Organization for Nuclear Research, is one of the world's leading laboratories for particle physics. The Organization is located on the French-Swiss border, with its headquarters in Geneva. Its Member States are: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Spain, Sweden, Switzerland and United Kingdom. Cyprus and Serbia are Associate Member States in the pre-stage to Membership. India, Pakistan, Turkey and Ukraine are Associate Member States. The European Union, Japan, JINR, the Russian Federation, UNESCO and the United States of America currently have Observer status.

Pioneering SESAME light source circulates first beam

On behalf of SESAME

 

Allan, Jordan, 12 January 2017. A beam circulated for the first time in the pioneering SESAME synchrotron at 18:12 (UTC+2) yesterday. Following the first single turn, the next steps will be to achieve multi-turns, store and then accelerate a beam.

This is an important milestone on the way to research getting underway at the first light-source laboratory in the Middle East. SESAME was established under the auspices of UNESCO before becoming a fully independent intergovernmental organisation in its own right in 2004. SESAME’s Members are Bahrain, Cyprus, Egypt, Iran, Israel, Jordan, Pakistan, the Palestinian Authority and Turkey. Its mission is to provide a world-class research facility for the region, while fostering international scientific cooperation. The first call for proposals to carry out research at SESAME was recently issued.

“This is a very proud moment for the entire SESAME community,” said Professor Khaled Toukan, SESAME Director. “SESAME is now opening for business.”

SESAME, which stands for Synchrotron-light for Experimental Science and Applications in the Middle East, is a light-source; a particle accelerator-based facility that uses electromagnetic radiation emitted by circulating electron beams to study a range of properties of matter. Experiments at SESAME will enable research in fields ranging from medicine and biology, through materials science, physics and chemistry to healthcare, the environment, agriculture and archaeology.

Today’s milestone follows a series of key events, including the establishment of a Middle East Scientific Collaboration group in the mid-1990s. This was followed by the donation of the BESSY1 accelerator by the BESSY laboratory in Berlin. Refurbished and upgraded components of BESSY1 now serve as the injector for the completely new SESAME main ring, which is a competitive third-generation light source built by SESAME with support from the SESAME Members themselves, the European Commission, CERN and Italy.

“This is a great day for SESAME,” said Professor Sir Chris Llewellyn-Smith, President of the SESAME Council. “It’s a tribute to the skill and devotion of the scientists and decision-makers from the region who have worked tirelessly to make scientific collaboration between countries in the Middle East and neighbouring regions a reality.”

The first circulating beam is an important step on the way to first light, which marks the start of the research programme at any new synchrotron light-source facility, but there is much to be done before experiments can get underway. Beams have to be accelerated to SESAME’s operating energy of 2.5 GeV. Then the light emitted as the beams circulate has to be channelled along SESAME’s two day-one beam lines and optimised for the experiments that will take place there. This process is likely to take around six months, leading to first experiments in the summer of 2017.

In the meantime, scientists wishing to carry out research at SESAME are encouraged to submit their proposals following the procedure described here.

 

Resources

SESAME Press Release available here.

Images available at:
http://cds.cern.ch/record/2237478
http://cds.cern.ch/record/2201539
http://cds.cern.ch/record/2227099
http://cds.cern.ch/record/2238520
http://cds.cern.ch/record/2009159
http://cds.cern.ch/record/1995397

Contact

James Gillies: James.Gillies@cern.ch +41 75 411 4555

Clarissa Formosa-Gauci: c.formosa-gauci@unesco.org

 

The bright red spot on this display shows the passage of the first beam to circulate in the SESAME main ring. Image © SESAME

Footnote(s)

1. CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. Its headquarters are in Geneva. Its Member States are: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Spain, Sweden, Switzerland and United Kingdom. Cyprus and Serbia are Associate Member States in the pre-stage to Membership. Pakistan, Turkey and Ukraine are Associate Member States. The European Union, India, Japan, JINR, the Russian Federation, UNESCO and the United States of America currently have Observer status.

ALPHA experiment observes the light spectrum of antimatter for the first time

Geneva, 19 December 2016. In a paper published today in the journal Nature, the ALPHA collaboration reports the first ever measurement on the optical spectrum of an antimatter atom. This achievement features technological developments that open up a completely new era in high-precision antimatter research. It is the result of over 20 years of work by the CERN1 antimatter community.

“Using a laser to observe a transition in antihydrogen and comparing it to hydrogen to see if they obey the same laws of physics has always been a key goal of antimatter research,” said Jeffrey Hangst, Spokesperson of the ALPHA collaboration.

Atoms consist of electrons orbiting a nucleus. When the electrons move from one orbit to another they absorb or emit light at specific wavelengths, forming the atom's spectrum. Each element has a unique spectrum. As a result, spectroscopy is a commonly used tool in many areas of physics, astronomy and chemistry. It helps to characterise atoms and molecules and their internal states. For example, in astrophysics, analysing the light spectrum of remote stars allows scientists to determine their composition.

With its single proton and single electron, hydrogen is the most abundant, simple and well-understood atom in the Universe. Its spectrum has been measured to very high precision. Antihydrogen atoms, on the other hand are poorly understood. Because the Universe appears to consist entirely of matter, the constituents of antihydrogen atoms – antiprotons and positrons – have to be produced and assembled into atoms before the antihydrogen spectrum can be measured. It’s a painstaking process, but well worth the effort since any measurable difference between the spectra of hydrogen and antihydrogen would break basic principles of physics and possibly help understand the puzzle of the matter-antimatter imbalance in the Universe.

Today’s ALPHA result is the first observation of a spectral line in an antihydrogen atom, allowing the light spectrum of matter and antimatter to be compared for the first time. Within experimental limits, the result shows no difference compared to the equivalent spectral line in hydrogen. This is consistent with the Standard Model of particle physics, the theory that best describes particles and the forces at work between them, which predicts that hydrogen and antihydrogen should have identical spectroscopic characteristics.

The ALPHA collaboration expects to improve the precision of its measurements in the future. Measuring the antihydrogen spectrum with high-precision offers an extraordinary new tool to test whether matter behaves differently from antimatter and thus to further test the robustness of the Standard Model.

ALPHA is a unique experiment at CERN’s Antiproton Decelerator facility, able to produce antihydrogen atoms and hold them in a specially-designed magnetic trap, manipulating antiatoms a few at a time. Trapping antihydrogen atoms allows them to be studied using lasers or other radiation sources.

“Moving and trapping antiprotons or positrons is easy because they are charged particles,” said Hangst. “But when you combine the two you get neutral antihydrogen, which is far more difficult to trap, so we have designed a very special magnetic trap that relies on the fact that antihydrogen is a little bit magnetic.”

Antihydrogen is made by mixing plasmas of about 90 000 antiprotons from the Antiproton Decelerator with positrons, resulting in the production of about 25 000 antihydrogen atoms per attempt. Antihydrogen atoms can be trapped if they are moving slowly enough when they are created.  Using a new technique in which the collaboration stacks anti-atoms resulting from two successive mixing cycles, it is possible to trap on average 14 anti-atoms per trial, compared to just 1.2 with earlier methods. By illuminating the trapped atoms with a laser beam at a precisely tuned frequency, scientists can observe the interaction of the beam with the internal states of antihydrogen. The measurement was done by observing the so-called 1S-2S transition. The 2S state in atomic hydrogen is long-lived, leading to a narrow natural line width, so it is particularly suitable for precision measurement. 

The current result, along with recent limits on the ratio of the antiproton-electron mass established by the ASACUSA collaboration, and antiproton charge-to-mass ratio determined by the BASE collaboration, demonstrate that tests of fundamental symmetries with antimatter at CERN are maturing rapidly.

 

Ressources:

Video: https://cds.cern.ch/record/2239266

Footage available at: https://cds.cern.ch/record/2239283 and https://cds.cern.ch/record/2239263

Photos available at: http://cds.cern.ch/record/2121303 and https://cds.cern.ch/record/2238961

 

ALPHA spokesperson, Jeffrey Hangst, explains the latest results. (Video: Jacques Herve Fichet/CERN)

Footnote(s)

1. CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. Its headquarters are in Geneva. Its Member States are: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Spain, Sweden, Switzerland and United Kingdom. Cyprus and Serbia are Associate Member States in the pre-stage to Membership. Pakistan, Turkey and Ukraine are Associate Member States. The European Union, India, Japan, JINR, the Russian Federation, UNESCO and the United States of America have Observer status.

The LHC collides ions at new record energy

Geneva, 25 November 2015. After the successful restart of the Large Hadron Collider and its first months of data taking with proton collisions at a new energy frontier, the LHC is moving to a new phase, with the first lead-ion collisions of season 2 at an energy about twice as high as that of any previous collider experiment. Following a period of intense activity to re-configure the LHC and its chain of accelerators for heavy ion beams, CERN1’s accelerator specialists put the beams into collision for the first time in the early morning of 17 November 2015 and ‘stable beams’ were declared at 10.59am today, marking the start of a one-month run with positively charged lead ions: lead atoms stripped of electrons. The four large LHC experiments will all take data over this campaign, including LHCb, which will record this kind of collision for the first time. Colliding lead ions allows the LHC experiments to study a state of matter that existed shortly after the big bang, reaching a temperature of several trillion degrees.

“It is a tradition to collide ions over one month every year as part of our diverse research programme at the LHC,” said CERN Director General Rolf Heuer. “This year however is special as we reach a new energy and will explore matter at an even earlier stage of our universe.”

Early in the life of our universe, for a few millionths of a second, matter was a very hot and very dense medium – a kind of primordial ‘soup’ of particles, mainly composed of fundamental particles known as quarks and gluons. In today’s cold Universe, the gluons “glue” quarks together into the protons and neutrons that form bulk matter, including us, as well as other kinds of particles.

There are many very dense and very hot questions to be addressed with the ion run for which our experiment was specifically designed and further improved during the shutdown,” said ALICE collaboration spokesperson Paolo Giubellino. “For instance, we are eager to learn how the increase in energy will affect charmonium production, and to probe heavy flavour and jet quenching with higher statistics. The whole collaboration is enthusiastically preparing for a new journey of discovery.”

 

Collision between lead ions seen within the ALICE detector (Image: ALICE ©CERN)

Increasing the energy of collisions will increase the volume and the temperature of the quark and gluon plasma, allowing for significant advances in understanding the strongly-interacting medium formed in lead-ion collisions at the LHC. As an example, in season 1 the LHC experiments confirmed the perfect liquid nature of the quark-gluon plasma and the existence of “jet quenching” in ion collisions, a phenomenon in which generated particles lose energy through the quark-gluon plasma. The high abundance of such phenomena will provide the experiments with tools to characterize the behaviour of this quark-gluon plasma. Measurements to higher jet energies will thus allow new and more detailed characterization of this very interesting state of matter.

The heavy-ion run will provide a great complement to the proton-proton data we've taken this year," said ATLAS collaboration spokesperson Dave Charlton. "We are looking forward to extending ATLAS' studies of how energetic objects such as jets and W and Z bosons behave in the quark gluon plasma.”

 

Collision between lead ions seen within the ATLAS detector (Image: ATLAS ©CERN)

The LHC detectors were substantially improved during the LHC’s first long shutdown. With higher statistics expected, physicists will be able to look deeper at the tantalising signals observed in season 1.

"Heavy flavour particles will be produced at high rate in Season 2, opening up unprecedented opportunities to study hadronic matter in extreme conditions,” said CMS collaboration spokesperson Tiziano Camporesi. « CMS is ideally suited to trigger on these rare probes and to measure them with high precision. »

 

Collision between lead ions seen within the CMS detector (Image: CMS ©CERN)

For the very first time, the LHCb collaboration will join the club of experiments taking data with ion-ion collisions.

"This is an exciting step into the unknown for LHCb, which has very precise particle identification capabilities. Our detector will enable us to perform measurements that are highly complementary to those of our friends elsewhere around the ring,” said LHCb collaboration spokesperson Guy Wilkinson.

 

Collision between lead ions seen within the LHCb detector (Image: LHCb ©CERN)

 

For more information:
Update: LHC: A proton 'reference' run to prepare for lead

Footnote(s)

1. CERN, the European Organization for Nuclear Research, is the world’s leading particle physics research laboratory. Its headquarters are in Geneva. Its Member States are currently: Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, the Slovak Republic, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession and Serbia is an Associate Member State in the Pre-stage to Membership. Pakistan and Turkey are Associate Members. The United States of America, the Russian Federation, India, Japan, the Joint Institute for Nuclear Research (JINR), UNESCO and the European Union have Observer status.

The ALICE experiment at CERN makes precise comparison of light nuclei and antinuclei

Measurements of energy loss in the time-projection chamber enable the ALICE experiment to identify antinuclei (upper curves on the left) and nuclei (upper curves on the right) produced in the lead-ion collisions at the LHC.

Geneva 17 August 2015. The ALICE experiment at the Large Hadron Collider (LHC) at CERN1 has made a precise measurement of the difference between ratios of the mass and electric charge of light nuclei and antinuclei. The result, published today in Nature Physics, confirms a fundamental symmetry of nature to an unprecedented precision for light nuclei. The measurements are based on the ALICE experiment’s abilities to track and identify particles produced in high-energy heavy-ion collisions at the LHC.

The ALICE collaboration has measured the difference between mass-to-charge ratios for deuterons (a proton, or hydrogen nucleus, with an additional neutron) and antideuterons, as well as for helium-3 nuclei (two protons plus a neutron) and antihelium-3 nuclei. Measurements at CERN, most recently by the BASE experiment, have already compared the same properties of protons and antiprotons to high precision. The study by ALICE takes this research further as it probes the possibility of subtle differences between the way that protons and neutrons bind together in nuclei compared with how their antiparticle counterparts form antinuclei.

The measurements by ALICE and by BASE have taken place at the highest and lowest energies available at CERN, at the LHC and the Antiproton Decelerator, respectively,” said CERN Director-General Rolf Heuer. “This is a perfect illustration of the diversity in the laboratory’s research programme.”

The measurement by ALICE comparing the mass-to-charge ratios in deuterons/antideuterons and in helium-3/antihelium-3 confirms the fundamental symmetry known as CPT in these light nuclei. This symmetry of nature implies that all of the laws of physics are the same under the simultaneous reversal of charges (charge conjugation C), reflection of spatial coordinates (parity transformation P) and time inversion (T). The new result, which comes exactly 50 years after the discovery of the antideuteron at CERN and in the US, improves on existing measurements by a factor of 10-100.

The ALICE experiment records high-energy collisions of lead ions at the LHC, enabling it to study matter at extremely high temperatures and densities. The lead-ion collisions provide a copious source of particles and antiparticles, and nuclei and the corresponding antinuclei are produced at nearly equal rates. This allows ALICE to make a detailed comparison of the properties of the nuclei and antinuclei that are most abundantly produced. The experiment makes precise measurements of the curvature of particle tracks in the detector’s magnetic field and of the particles’ time of flight, and uses this information to determine the mass-to-charge ratios for the nuclei and antinuclei.

“The high precision of our time-of-flight detector, which determines the arrival time of particles and antiparticles with a resolution of 80 picoseconds, associated with the energy-loss measurement provided by our time-projection chamber, allows us to measure a clear signal for deuterons/antideuterons and helium-3/antihelium-3 over a wide range of momentum”, said ALICE spokesperson Paolo Giubellino.

The measured differences in the mass-to-charge ratios are compatible with zero within the estimated uncertainties, in agreement with expectations for CPT symmetry. These measurements, as well as those that compare protons with antiprotons, may further constrain theories that go beyond the existing Standard Model of particles and the forces through which they interact.

 

Pictures of the ALICE experiment.

 

Footnote(s)

1. CERN, the European Organization for Nuclear Research, is the world's leading laboratory for particle physics. It has its headquarters in Geneva. At present, its member states are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. Pakistan and Turkey are Associate Members. India, Japan, the Russian Federation, the United States of America, the European Union, JINR and UNESCO have observer status.