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Jun 13, 2024

Physicists use machine learning techniques to search for exotic-looking collisions that could indicate new physics

Posted by in categories: particle physics, robotics/AI

One of the main goals of the LHC experiments is to look for signs of new particles, which could explain many of the unsolved mysteries in physics. Often, searches for new physics are designed to look for one specific type of new particle at a time, using theoretical predictions as a guide. But what about searching for unpredicted—and unexpected—new particles?

Jun 13, 2024

A first look inside radium’s solid-state chemistry

Posted by in categories: chemistry, particle physics

For the first time in history, scientists have measured radium’s bonding interactions with oxygen atoms in an organic molecule. Scientists have not measured this bonding before because radium-226 is available only in small amounts and it is highly radioactive (radium is one million times more radioactive than the same mass of uranium), making it challenging to work with.

Jun 13, 2024

Quantum Magic: How “Super Photons” Are Shaping the Future of Physics

Posted by in categories: particle physics, quantum physics

Researchers at the University of Bonn have demonstrated that super photons, or photon Bose-Einstein condensates, conform to fundamental physics theorems, enabling insights into properties that are often difficult to observe.

Under suitable conditions, thousands of particles of light can merge into a type of “super photon.” Physicists call such a state a photon Bose-Einstein condensate. Researchers at the University of Bonn have now shown that this exotic quantum state obeys a fundamental theorem of physics. This finding now allows one to measure properties of photon Bose-Einstein condensates which are usually difficult to access. The study was published on June 3 in the journal Nature Communications.

If many atoms are cooled to a very low temperature confined in a small volume, they can become indistinguishable and behave like a single “super particle.” Physicists also call this a Bose-Einstein condensate or quantum gas. Photons condense based on a similar principle and can be cooled using dye molecules. These molecules act like small refrigerators and swallow the “hot” light particles before spitting them out again at the right temperature.

Jun 12, 2024

A route to scalable Majorana qubits

Posted by in categories: particle physics, quantum physics

Researchers at QuTech have found a way to make Majorana particles in a two-dimensional plane. This was achieved by creating devices that exploit the combined material properties of superconductors and semiconductors. The inherent flexibility of this new 2D platform should allow one to perform experiments with Majoranas that were previously inaccessible. The results are published in Nature.

Jun 12, 2024

First Promethium ‘Complex’ Created, Revealing Mysterious Element’s Secrets

Posted by in categories: chemistry, nuclear energy, particle physics

Promethium, one of the rarest and most mysterious elements in the periodic table, has finally given up some crucial chemical secrets.

By Mark Peplow & Nature magazine

One of the rarest and most mysterious elements in the periodic table has finally given up some crucial chemical secrets, eight decades after its discovery. Researchers at Oak Ridge National Laboratory in Tennessee have become the first to use radioactive promethium to make a chemical ‘complex’ — a compound in which it is bound to a few surrounding molecules. This feat of synthesis enabled the team to study how the element bonds with other atoms in a solution with water. Published May 22 in Nature the findings fill a long-standing gap in chemistry textbooks, and could eventually lead to better methods for separating promethium from similar elements in nuclear waste, for example.

Jun 12, 2024

Wanted: advanced atomic vapor sensors for quantum information, imaging, communications, and RF electrometry

Posted by in categories: military, particle physics, quantum physics

ARLINGTON, Va. – U.S. military researchers are approaching industry to enhance atomic vapor sensors for electric field sensing, imaging, communications, and quantum information science (QIS).

Officials of the U.S. Defense Advanced research Projects Agency (DARPA) in Arlington, Va., have issued a broad agency announcement (HR001124S0031) for the Enhancing Quantum Sensor Technologies with Rydberg Atoms (EQSTRA) program.

EQSTRA seeks to enhance the performance, capabilities, and maturity of atomic vapor sensors for future compact, calibration-free, small, and lightweight devices with low drift, and quantum-limited accuracy and sensitivity.

Jun 12, 2024

Molecules in Motion: Advanced Spectroscopy Captures Molecular Dynamics in Real-Time

Posted by in categories: biological, chemistry, evolution, particle physics

Researchers have developed a new method that uses attosecond core-level spectroscopy to capture molecular dynamics in real time.

The mechanisms behind chemical reactions are complex, involving many dynamic processes that affect both the electrons and the nuclei of the involved atoms. Frequently, the strongly coupled electron and nuclear dynamics trigger radiation-less relaxation processes known as conical intersections. These dynamics underpin many significant biological and chemical functions but are notoriously difficult to detect experimentally.

The challenge in studying these dynamics stems from the difficulty of tracing the nuclear and electronic motion simultaneously. Their dynamics are intertwined and occur on ultrafast timescales, which has made capturing the molecular dynamical evolution in real time a major challenge for both physicists and chemists in recent years.

Jun 12, 2024

A Close Look at the Dynamics of an Ion–Neutral Reaction

Posted by in categories: chemistry, nuclear energy, particle physics

A detailed study of a reaction between a molecular ion and a neutral atom has implications for both atmospheric and interstellar chemistry.

Reactions between ions and neutral atoms or molecules occur in various settings, from planetary atmospheres to plasmas. They are also the driving force behind rich reaction chains at play in the interstellar medium (ISM)—the giant clouds of gas and dust occupying the space between stars. The ISM is cold, highly dilute, and abundant with ionizing radiation [1]. These conditions are usually unfavorable for chemistry. Yet, more than 300 molecular species have been detected in the ISM to date, of which about 80% contain carbon [2]. Now Florian Grussie at the Max Planck Institute for Nuclear Physics (MPIK) in Germany and collaborators report an experimental and theoretical study of an ion–neutral reaction: that between a neutral carbon atom and a molecular ion (HD+), made of a hydrogen and a deuterium (heavy hydrogen) atom [3, 4]. The study’s findings could improve our understanding of the chemistry of the ISM.

Ion–neutral reactions are fundamentally different from those involving only neutral species. Unlike typical neutral–neutral reactions, ion–neutral reactions often do not need to overcome an activation energy barrier and proceed efficiently even if the temperature approaches absolute zero. The reason for this difference is that, in ion–neutral reactions, the ion strongly polarizes the neutral atom or molecule, causing attractive long-range interactions that bring the reactants together.

Jun 11, 2024

A chain of copper and carbon atoms may be the thinnest metallic wire

Posted by in categories: computing, information science, nanotechnology, particle physics

While carbon nanotubes are the materials that have received most of the attention so far, they have proved very difficult to manufacture and control, so scientists are eager to find other compounds that could be used to create nanowires and nanotubes with equally interesting properties, but easier to handle.

So, Chiara Cignarella, Davide Campi and Nicola Marzari thought to use to parse known three-dimensional crystals, looking for those that—based on their structural and —look like they could be easily “exfoliated,” essentially peeling away from them a stable 1-D structure. The same method has been successfully used in the past to study 2D materials, but this is the first application to their 1-D counterparts.

The researchers started from a collection of over 780,000 crystals, taken from various databases found in the literature and held together by van der Waals forces, the sort of weak interactions that happen when atoms are close enough for their electrons to overlap. Then they applied an algorithm that considered the spatial organization of their atoms looking for the ones that incorporated wire-like structures, and calculated how much energy would be necessary to separate that 1-D structure from the rest of the crystal.

Jun 10, 2024

ATLAS chases long-lived particles with the Higgs boson

Posted by in categories: cosmology, information science, particle physics, robotics/AI

The Higgs boson has an extremely short lifespan, living for about 10–22 seconds before quickly decaying into other particles. For comparison, in that brief time, light can only travel about the width of a small atomic nucleus. Scientists study the Higgs boson by detecting its decay products in particle collisions at the Large Hadron Collider. But what if the Higgs boson could also decay into unexpected new particles that are long-lived? What if these particles can travel a few centimeters through the detector before they decay? These long-lived particles (LLPs) could shed light on some of the universe’s biggest mysteries, such as the reason matter prevailed over antimatter in the early universe and the nature of dark matter. Searching for LLPs is extremely challenging because they rarely interact with matter, making them difficult to observe in a particle detector. However, their unusual signatures provide exciting prospects for discovery. Unlike particles that leave a continuous track, LLPs result in noticeable displacements between their production and decay points within the detector. Identifying such a signature requires dedicated algorithms. In a new study submitted to Physical Review Letters, ATLAS scientists used a new algorithm to search for LLPs produced in the decay of Higgs bosons. Boosting sensitivity with a new algorithm Figure 1: A comparison of the radial distributions of reconstructed displaced vertices in a simulated long-lived particle (LLP) sample using the legacy and new (updated) track reconstruction configurations. The circular markers represent reconstructed vertices that are matched to LLP decay vertices and the dashed lines represent reconstructed vertices from background decay vertices (non-LLP). (Image: ATLAS Collaboration/CERN) Despite being critical to the LLP searches, dedicated reconstruction algorithms were previously so resource intensive that they could only be applied to less than 10% of all recorded ATLAS data. Recently, however, ATLAS scientists implemented a new “Large-Radius Tracking” algorithm (LRT), which significantly speeds up the reconstruction of charged particle trajectories in the ATLAS Inner Detector that do not point back to the primary proton-proton collision point, while drastically reducing backgrounds and random combinations of detector signals. The LRT algorithm is executed after the primary tracking iteration using exclusively the detector hits (energy deposits from charged particles recorded in individual detector elements) not already assigned to primary tracks. As a result, ATLAS saw an enormous increase in the efficiency of identifying LLP decays (see Figure 1). The new algorithm also improved CPU processing time more than tenfold compared to the legacy implementation, and the disk space usage per event was reduced by more than a factor of 50. These improvements enabled physicists to fully integrate the LRT algorithm into the standard ATLAS event reconstruction chain. Now, every recorded collision event can be scrutinized for the presence of new LLPs, greatly enhancing the discovery potential of such signatures. Physicists are searching for Higgs bosons decaying into new long-lived particles, which may leave a ‘displaced’ signature in the ATLAS detector. Exploring the dark with the Higgs boson Figure 2: Observed 95% confidence-limit on the decay of the Higgs boson to a pair of long-lived s particles that decay back to Standard-Model particles shown as a function of the mean proper decay length ( of the long-lived particle. The observed limits for the Higgs Portal model from the previous ATLAS search are shown with the dotted lines. (Image: ATLAS Collaboration/CERN) In their new result, ATLAS scientists employed the LRT algorithm to search for LLPs that decay hadronically, leaving a distinct signature of one or more hadronic “jets” of particles originating at a significantly displaced position from the proton–proton collision point (a displaced vertex). Physicists also focused on the Higgs “portal” model, in which the Higgs boson mediates interactions with dark-matter particles through its coupling to a neutral boson s, resulting in exotic decays of the Higgs boson to a pair of long-lived s particles that decay into Standard-Model particles. The ATLAS team studied collision events with unique characteristics consistent with the production of the Higgs boson. The background processes that mimic the LLP signature are complex and challenging to model. To achieve good discrimination between signal and background processes, ATLAS physicists used a machine learning algorithm trained to isolate events with jets arising from LLP decays. Complementary to this, a dedicated displaced vertex reconstruction algorithm was used to pinpoint the origin of hadronic jets originating from the decay of LLPs. This new search did not uncover any events featuring Higgs-boson decays to LLPs. It improves bounds on Higgs-boson decays to LLPs by a factor of 10 to 40 times compared to the previous search using the exact same dataset (see Figure 2)! For the first time at the LHC, bounds on exotic decays of the Higgs boson for low LLP masses (less than 16 GeV) have surpassed results for direct searches of exotic Higgs-boson decays to undetected states. About the event display: A 13 TeV collision event recorded by the ATLAS experiment containing two displaced decay vertices (blue circles) significantly displaced from the beam line showing “prompt” non displaced decay vertices (pink circles). The event characteristics are compatible with what would be expected if a Higgs boson is produced in association with a Z boson (decaying to two electrons indicated by green towers), and decayed into two LLPs (decaying into two b-quarks each). Tracks shown in yellow and jets are indicated by cones. The green and yellow blocks correspond to energy deposition in the electromagnetic and hadronic calorimeters, respectively. (Image: ATLAS Collaboration/CERN) Learn more Search for light long-lived particles in proton-proton collisions at 13 TeV using displaced vertices in the ATLAS inner detector (Submitted to PRL, arXiv:2403.15332, see figures) Performance of the reconstruction of large impact parameter tracks in the inner detector of ATLAS (Eur. Phys. J. C 83 (2023) 1,081, arXiv:2304.12867, see figures) Search for exotic decays of the Higgs boson into long-lived particles in proton-proton collisions at 13 TeV using displaced vertices in the ATLAS inner detector (JHEP 11 (2021) 229, arXiv:2107.06092, see figures)

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