Tag Archives: particle

One tiny particle has the potential to alter our understanding of gravity

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Gravity is one of the four fundamental forces that bind matter in the universe. The other three forces (electromagnetic, weak nuclear, and strong nuclear) are explained through the exchange of force-carrying elementary particles, leading theorists to believe there is a similar quantum explanation for gravity.

The force carriers for the electromagnetic force are photons, while the weak nuclear force has W-, W+, and Z0 bosons as force carriers, and the strong nuclear force has eight types of gluons. On the other hand, the hypothetical carrier of gravitational force is known as the graviton.

The properties of the graviton are deducible in quantum theory. The amount of energy required to summon a force-carrying particle from the vacuum determines how quickly it must be recovered. Since gravity has an infinite range and does not require energy to create a graviton, the mass of the graviton must be zero.

Additionally, gravitons are expected to have a spin of 2, as only spin 2 particles interact with all matter, which is characteristic of universal gravity. This is in contrast to quarks and leptons, which have a spin of 1/2, and the non-gravitational force carriers, which have a spin of 1.

While gravity may not be fully explained by the exchange of gravitons, most physicists believe it can be quantized. String theory offers a potential framework where fundamental particles are envisioned as vibrations of mass-energy strings, with each vibrating string having the properties of a graviton.

However, string theory faces challenges due to its complexity and inability to make testable predictions. Detecting gravitons is difficult due to the extremely weak nature of gravity and the rare interactions gravitons have with matter.

Despite the challenges in detecting gravitons, recent advancements in experimental exploration, such as the discovery of spin-2 particle properties in a liquid analogue system, provide hope for a better understanding of gravitons and the eventual unification of fundamental forces into a single theory.

About our experts

Tony Rothman: A theoretical physicist who has taught at Princeton and Harvard Universities, he has published non-fiction and fiction novels and written various stage plays outside of his academic career. He has contributed to publications like Physics Basics, European Journal of Physics, and Astrophysics and Space Sciences.

Source: www.sciencefocus.com

Researchers Nearing Discovery of Elusive ‘Chameleon’ Particle Associated with Dark Energy

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A team of physicists at the University of California, Berkeley has developed the most sophisticated instrument ever designed to search for dark energy, the mysterious force that is accelerating the expansion of the universe.

The results of their experiment were published today in a prestigious journal. Nature – targets a hypothetical particle known as the chameleon, which could hold the key to unlocking this mysterious cosmic force.

First identified in 1998, dark energy makes up about 70 percent of all matter and energy in the universe, and despite many theories, its true nature remains a mystery.

One leading hypothesis is that there is a fifth force that is distinct from the four fundamental forces known in nature (gravity, electromagnetism, and the strong and weak nuclear forces).

This power is thought to be mediated by particles known as chameleons due to their ability to hide in plain sight.

In an experiment at the University of California, Berkeley, Professor Holger Muller utilizes an advanced atom interferometer combined with an optical lattice.

If that sounds technical, it is. Essentially, this setup allows for precise gravity measurements by holding free-falling atoms in place for a set period of time.

Physicists at UC Berkeley have clamped a small cluster of cesium atoms (the pink blob) in a vertical vacuum chamber and split each atom into a quantum state where half of the atom is close to the tungsten weight (the shiny cylinder) and the other half (the split sphere below the tungsten) is close to the tungsten weight. – Image credit: Cristian Panda/UC Berkeley

The longer we can keep the atoms there, the greater our chances of finding (or not finding) a trace of the chameleon.

“Atom interferometry is the technology and science that exploits the quantum properties of particles – their properties as both particles and waves. We split the waves so that the particles take two paths at the same time, and then we interfere with them at the end,” Muller said.

“The waves are either in phase and add, or out of phase and cancel each other out. The key is that whether they are in phase or out of phase depends very sensitively on the quantities you want to measure, such as acceleration, gravity, rotation, or fundamental constants.”

Whereas previous experiments have only been able to move atoms for a few milliseconds at a time, the new device can keep them in motion for much longer periods – from seconds to tens of seconds – a major improvement that improves the most precise measurements by a factor of five.

In a recent paper published in the journal Natural Physics Muller and his colleagues extended the hold time to a whopping 70 seconds.

To reveal whether chameleon particles are indeed the dark energy mastermind, scientists would need to find holes in the outcomes predicted by the accepted theory of gravity — something no one has managed to do since Isaac Newton formulated it 400 years ago.

Muller and his team found no deviations from Newtonian gravity in their recent tests, suggesting that if chameleons exist, their effects are quite subtle.

Still, the researchers are optimistic: The improved precision of their instruments means future experiments may provide the evidence needed to confirm or disprove the existence of chameleons and other hypothesized particles that contribute to dark energy.

About the Experts

Holger Muller At the age of 14, he successfully filed his first patent. He then wrote his undergraduate thesis under the supervision of Jürgen Mullinek at the University of Konstanz in Germany. He graduated from the Humboldt University in Berlin with Achim Peters as his supervisor. Müller received a fellowship from the Alexander von Humboldt Foundation and joined Steven Chu’s group at Stanford University as a postdoctoral researcher. In July 2008, he joined the Physics Department at the University of California, Berkeley, where he is currently a Professor of Physics and Principal Investigator. He is currently the Principal Investigator of his research group, the Müller Group.

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Source: www.sciencefocus.com

CERN Scientists Aim to Produce Enigmatic Higgs Particle Duplicates

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Physicists from the ATLAS Collaboration at the Large Hadron Collider (LHC) at CERN have announced the results of the most sensitive search to date for double Higgs production and self-coupling, achieved by combining five double Higgs studies from LHC Run 2 data.

Event display of a double Higgs candidate event, photographed in 2017. Image courtesy of ATLAS Collaboration / CERN.

Remember how hard it was to find one Higgs boson? Now try and find two of them in the same place at the same time.

This intriguing process, known as double Higgs production, can teach scientists about the Higgs particle's self-interaction.

By studying it, physicists can measure the strength of the Higgs particle's self-binding, a fundamental aspect of the Standard Model that links the Higgs mechanism to the stability of the universe.

Searching for the creation of double Higgs particles is a particularly challenging task.

This is an extremely rare process, about 1,000 times rarer than the creation of a single Higgs particle.

While LHC Run 2 produced 40 million collisions per second, ATLAS is expected to produce just a few thousand double Higgs events.

So how can physicists find these rare needles in a mountain of data?

One way to make it easier to find double Higgs production is to search in multiple locations.

By investigating the different ways in which the double Higgs decay (decay modes) and combining them, physicists can maximise their chances of discovering and studying the creation of the double Higgs.

The new results from the ATLAS collaboration are the most comprehensive search to date, covering more than half of all possible double Higgs events with ATLAS.

Each of the five individual studies in this combination focuses on a different mode of damping, each with its own strengths and weaknesses.

For example, the most likely double-Higgs decay mode is the decay into four bottom quarks.

However, the Standard Model QCD process likely also produces four bottom quarks, making it difficult to distinguish this background process from a double Higgs event.

The double-Higgs decay into two bottom quarks and two tau leptons involves moderate background contamination, but it occurs five times less frequently and there are neutrinos that escape undetected, complicating physicists' efforts to recreate the decay.

Decays into multiple leptons are not uncommon, but they have complex characteristics.

Other double Higgs decays are even rarer, such as the decay into two bottom quarks and two photons.

This final state accounts for only 0.3% of all double Higgs decays, but has a cleaner signature and much smaller background contamination.

Combining their findings for each of these decays, ATLAS physicists were able to find that the probability of producing two Higgs particles rules out more than 2.9 times the Standard Model prediction.

This result has a confidence level of 95% and an expected sensitivity of 2.4 (assuming this process does not exist in nature).

They were also able to provide constraints on the strength of the Higgs particle's self-coupling, achieving the highest sensitivity to date for this important observable.

They found that the magnitude of the Higgs self-coupling constant and the strength of the interaction between two Higgs particles and two vector particles are consistent with the Standard Model predictions.

“This overall result marks a milestone in the study of double Higgs particle production,” the researchers said.

their result will be published in journal Physics Review Letter.

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ATLAS Collaboration. 2024. Combined search for Higgs pair production in pp collisions at s√=13 TeV with the ATLAS detector. Physiotherapy Rev Lett,in press; arXiv:2406.09971

Source: www.sci.news

Physicists at CERN release data on the discovery of the Higgs particle

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Physicist from CMS cooperation at CERN just published the combination of CMS measurements that helped establish the discovery of the Higgs boson in 2012.

CMS event display showing a Higgs boson candidate decaying into two photons. It is one of two decay channels that were key to the particle’s discovery. Image credit: CERN.

“Physical measurements based on data from CERN’s Large Hadron Collider (LHC) are typically reported as central values and corresponding uncertainties,” the CMS physicists said.

“For example, shortly after observing the Higgs boson in the LHC’s proton-proton collision data, CMS determined its mass to be 125.3 plus or minus 0.6 GeV (the mass of a proton is about 1 GeV).”

“But this figure is just a quick summary of the measurements, and is like the title of a book.”

In measurement, the complete information extracted from the data is encoded into a mathematical function known as a likelihood function. This function includes measurements of quantities and dependence on external factors.

“For CMS measurements, these factors include the calibration of the CMS detector, the accuracy of the CMS detector simulation used to facilitate the measurements, and other systematic effects,” the researchers said.

“To fully understand the nasty collisions that occur at the LHC, many aspects need to be determined, so the likelihood function for measurements based on LHC data can be complex.”

“For example, the likelihood function for the combined CMS Higgs boson discovery measurement that CMS just released in electronic form has nearly 700 parameters for a fixed value of the Higgs boson mass.”

“Only one of these, the number of Higgs bosons found in the data, is an important physical parameter, and the rest model systematic uncertainties.”

“Each of these parameters corresponds to a dimension of a multidimensional abstract space in which the likelihood function can be drawn.”

“It is difficult for humans to visualize spaces that contain multiple dimensions, much less spaces that contain many dimensions.”

The new release of the CMS Higgs boson discovery measurement likelihood function, the first publicly available likelihood function from this collaboration, allows researchers to avoid this problem.

Using a publicly accessible likelihood function, physicists outside the CMS Collaboration can now accurately incorporate CMS Higgs boson discovery measurements into their studies.

“The release of this likelihood function and the Combine software used to model likelihood and fit data marks another milestone in CMS’s 10-year commitment to fully open science.” said the people.

“This joins hundreds of open access publications, the release of nearly 5 petabytes of CMS data on the CERN Open Data Portal, and the publication of the entire software framework on GitHub.”

Source: www.sci.news

Graviton: An Insight into a Particle with Gravitational Behavior

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Have you found any traces of gravitons?

zf L/Getty Images

For decades, physicists have been searching for gravitons, the hypothetical particles thought to carry gravity. Although they had never been detected in space, particles like gravitons have now been observed in semiconductors. Using these to understand the behavior of gravitons could help unify general relativity and quantum mechanics, which have long been at odds.

“This is a needle in a haystack. [finding]. And the paper that started all this goes back to 1993. ” lauren pfeiffer at Princeton University. He wrote the paper with several colleagues. Aaron Pinchukdied in 2022 before finding any hint of the elusive particle.

Pinchuk's students and collaborators, including Pfeiffer, have completed the experiment they began discussing 30 years ago. They focused on electrons within a flat piece of the semiconductor gallium arsenide, which they placed in a powerful refrigerator and exposed to a strong magnetic field. Under these conditions, quantum effects cause electrons to behave in strange ways. The electrons interact strongly with each other, forming an unusual incompressible liquid.

Although this liquid is not gentle, it is characterized by collective motion in which all the electrons move in unison, which can lead to particle-like excitations. To investigate these excitations, the team illuminated the semiconductor with a carefully tuned laser and analyzed the light scattered from the semiconductor.

This revealed that the excitation contains a type of quantum spin that had previously been theorized to exist only in gravitons. This isn't a graviton itself, but it's the closest thing we've ever seen.

Liu Ziyu The professor at Columbia University in New York who worked on the experiment said he and his colleagues knew that graviton-like excitations could exist in semiconductors, but they needed to make the experiment precise enough to detect it. He said it took many years. “From a theoretical side, the story was kind of complete, but the experiments weren't really convincing,” he says.

This experiment is not a true analog of space-time. Electrons are confined in flat, two-dimensional space and move more slowly than objects governed by the theory of relativity.

But he says it is “hugely important” and bridges various previously underappreciated areas of physics, such as materials physics and the theory of gravity. Kun Yan from Florida State University was not involved in this study.

but, Zlatko Papik Researchers at the University of Leeds in the UK cautioned against equating the new discovery with the detection of gravitons in space. He said the two are equivalent enough for electronic systems like the one in the new experiment to serve as a testing ground for theories of quantum gravity, but they are not equivalent for all quantum phenomena that occur in space-time on a cosmic scale. It says no.

This connection between particle-like excitations and theoretical gravitons also yields new ideas about exotic electronic states, team members say. de Linjie At Nanjing University, China.

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Source: www.newscientist.com

CERN’s New 91km-Long Particle Accelerator May Soon Unveil the End of the Universe

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Officials at CERN, the world’s leading particle physics research institute, have announced plans to build the world’s largest particle accelerator. The machine is designed to smash molecules at near the speed of light, marking a significant step forward.

The proposed super collider, called the Future Circular Collider (FCC), will be a massive 91 km in length, three times the size of the Large Hadron Collider (LHC). This new machine will allow scientists to collide particles with greater precision and energy than ever before, potentially unraveling some of the universe’s biggest mysteries. These include the existence of more matter than antimatter, the nature of dark matter and energy, the presence of hidden extra dimensions, and the existence of the universe as a whole.

This step forward is significant because scientists hope the FCC will deepen their understanding of particle physics, aiming to explain why particles have specific masses and forces, and to uncover the nature of dark matter and dark energy, which account for 95% of the mass-energy of the universe. If approved, construction is expected to start by the mid-2030s, with the first stage operating around 2045, followed by a second phase extending research into the 2070s, establishing the FCC as a multigenerational scientific research effort.

Is bigger always better?

The importance of building larger particle accelerators lies in the fact that they can achieve higher collision energies. The goal is to put in enough energy to create new particles, such as the Higgs boson. The FCC aims to eventually reach seven times the collision energy of the LHC, offering a new and more complete understanding of physics.

The FCC will be capable of creating millions of Higgs particles, providing scientists with the opportunity to study them in great detail to understand how they interact with other particles. The Higgs boson is a carrier particle of the Higgs field that permeates space and gives mass to other particles, challenging previously held concepts about matter and mass.

CERN’s proposed super collider would be 91 km long and would be the largest particle collider ever built. The hope is that its increased precision and higher collision energies will eventually allow physicists to understand the nature of the Higgs boson, and perhaps even reality itself. – Image credit: CERN

god particle

In addition to providing deeper insight into the Higgs boson, the FCC will also aim to uncover the mechanisms by which the Higgs boson interacts and its significance in the universe. It is thought to have played a crucial role in the very beginning of the universe, nanoseconds after the big bang, by giving mass to matter as the universe grew and cooled. The influence of the Higgs boson is also relevant in understanding how the universe will end, as it affects the stability of the universe itself.

The FCC is expected to contribute to our understanding of whether the universe is in a stable or unstable state, providing the key to answering fundamental questions about the universe’s fate.

the beginning and end of the universe

The FCC will play a crucial role in answering questions about the beginning and the end of the universe, with the expertise of notable scientists like Marcus Chown, professor Andy Parker, and Matthew McCullough. The expectation is that this new accelerator will contribute to an in-depth understanding of the fundamental physics that govern the universe and our place within it.

About our experts

Marcus Chown is an award-winning author, broadcaster, and former radio astronomer. He is the author of Breakthrough: The Spectacle of Scientific Discovery His Story from the Higgs Boson to the Black Hole (Faber & Faber, 2021). Professor Andy Parker is a British physicist and professor of high-energy physics at the University of Cambridge. He is a member and chair of the CERN Science Policy Committee and the Scientific Advisory Committee on Future Circular Colliders, among other notable positions. Matthew McCullough is a theoretical physicist and researcher at CERN, focused on areas of interest including collisional physics, cosmology, astroparticle physics, and quantum field theory, involved in FCC feasibility studies.

Source: www.sciencefocus.com

Unknown source of ultra-high energy extraterrestrial particle detected by telescope array

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An artist’s illustration of an extremely high-energy cosmic ray, named the “Amaterasu particle,” observed by the surface detector array of the Telescope Array experiment.Credit: Osaka Metropolitan University/L-INSIGHT, Kyoto University/Ryuunosuke Takeshige

A groundbreaking detection of extremely high-energy cosmic rays by a telescope array experiment points to a void in the universe and casts doubt on current theories about the origin and high-energy physics of cosmic rays. It raises questions about its source.

Discovery of an exceptional extraterrestrial particle

Researchers involved in the telescope array experiment announced that they had detected cosmic rays with unusual energy. This particle originates outside our galaxy and has an incredible energy level of more than 240 exaelectronvolts (EeV). Despite this remarkable discovery, its exact source remains elusive, as its direction of arrival does not point to any known celestial body.

The mystery of ultra-high energy cosmic rays

Cosmic rays are subatomic charged particles that come from space, and ultra-high energy cosmic rays (UHECRs) are a rare and extremely powerful type. These UHECRs have energies in excess of 1 EeV, which is about a million times the energy reached by man-made particle accelerators. These are thought to originate from the most energetic phenomena in the universe, such as black holes, gamma-ray bursts, and active galactic nuclei. However, its exact physics and acceleration mechanisms are still not fully understood. These high-energy cosmic rays occur infrequently, estimated at less than one particle per square kilometer per century, making their detection a rare event and requiring instruments with large collection areas. .

An artist’s illustration of ultra-high energy cosmic ray astronomy, which elucidates highly energetic phenomena as opposed to weak cosmic rays that are affected by electromagnetic fields.Credit: Osaka Metropolitan University/Kyoto University/Ryuunosuke Takeshige

A unique discovery of telescope arrays

The Telescope Array (TA) experiment, a large-scale surface detector array in Utah with an effective detection area of ​​700 square kilometers, successfully detected UHECR on May 27, 2021 at a breakthrough energy of approximately 244 EeV.

Given the very high energy of this particle, it should experience only a relatively small deflection by the foreground magnetic field, and therefore its direction of arrival should be expected to be more closely correlated with its source. Researchers point out that there is. However, our results show that the direction of arrival does not indicate an obvious source galaxy or other known objects that could be potential sources of UHECRs.

Instead, its direction of arrival points to a cavity in the large-scale structure of the universe, a region where galaxies are almost absent. Scientists believe this indicates a much larger magnetic deflection than predicted by galactic magnetic field models, an unidentified source in the local extragalactic neighborhood, or an incomplete understanding of the high-energy particle physics involved. This suggests that there is a possibility that

For more information on this discovery, see:

Reference: “Extremely high-energy cosmic rays observed by surface detector arrays”*†, RU Abbasi, MG Allen, R. Arimura, JW Belz, DR Bergman, SA Blake, BK Shin, IJ Buckland, BG Cheon, Tetsuya Fujii, Kazuya Fujisue, Kazuya Fujita, Masaki Fukushima, GD Furlich, ZR Gerber, N. Globus, Kazuto Hibino, Tatsuya Higuchi, Kazuya Honda, Daisho Ikeda, Hiroshi Ito, Akira Iwasaki, S. Jeong, HM Jeong, CH Jui, K. Kadota, F. Kakimoto, OE Kalashev, K. Kasahara, K. Kawata, I. Kharuk, E. Kido, SW Kim, HB Kim, JH Kim, JH Kim, I. Komae, Y. Kubota, MY Kuznetsov, KH Lee, BK Rubsandrjiev, JP Lundquist, JN Matthews, S. Nagataki, T. nakamara, A. Nakazawa, T. Nonaka, S. Ogio, M. Ono, H. Oshima, IH Park. , M. Potts, S. Pushilkov, JR Remington, DC Rodriguez, C. Lott, GI Rubtsov, D. Liu, H. Sagawa, N. Sakaki, T. Sako, N. Sakurai, H. Shin, JD Smith, P Sokolsky, BT Stokes, TS Stroman, K. Takahashi, M. Takeda, A. Takeda, Y. Tameda, S. Thomas, GB Thomson, PG Tyniakov, I. Tkachev, T. Tomita, SV Troitsky, Y. Tsunesada, S. Udo, FR Urban, T. Wong, K. Yamazaki, Y. Yuma, YV Zeser, Z. Zunder, November 23, 2023. science.
DOI: 10.1126/science.abo5095

Source: scitechdaily.com