Post subject: Confirmed! Discovery of Cosmic Neutrinos from Beyond Our Gal
Posted: Sun Aug 23, 2015 2:57 am
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
Confirmed! Discovery of Cosmic Neutrinos from Beyond Our Galaxy
Researchers using the IceCube Neutrino Observatory have sorted through the billions of subatomic particles that zip through its frozen cubic-kilometer-sized detector each year to gather powerful new evidence in support of 2013 observations confirming the existence of cosmic neutrinos. The evidence is distinctive because it heralds a new form of astronomy using neutrinos, the nearly massless high-energy particles generated in natures accelerators: black holes, massive exploding stars and the energetic cores of galaxies.
In a new study, the detection of 21 ultra high-energy muons -- secondary particles created on the very rare occasions when neutrinos interact with other particles --provides independent confirmation of astrophysical neutrinos from our galaxy as well as cosmic neutrinos from sources outside the Milky Way.
The observations were reported today (Aug. 20, 2015) in a paper published in the journal Physical Review Letters by the IceCube Collaboration, which called the data an "unequivocal signal" for astrophysical neutrinos, ultra high-energy particles that have traversed space unimpeded by stars, planets, galaxies, magnetic fields or clouds of interstellar dust -- phenomena that, at very high energies, significantly attenuate more mundane particles like photons.
Because they have almost no mass and no electric charge, neutrinos can be very harsh to detect and are only oberved indirectly when they collide with other particles to create muons, telltale secondary particles. Whats more, there are different kinds of neutrinos produced in different astrophysical processes. The IceCube Collaboration, a large international consortium headquartered at the University of Wisconsin-Madison, has taken on the huge challenge of sifting through a mass of obervations to identify perhaps a few dozen of the highest-energy neutrinos that have traveled from sources in the Milky Way and beyond our galaxy.
Those high-energy neutrinos, scientists believe, are created deep inside some of the universes most violent phenomena. The particles created in these events, including neutrinos and cosmic rays, are accelerated to energy levels that exceed the record-setting earthbound accelerators such as the Large Hadron Collider (LHC) by a factor of more than a million. They are prized by astrophysicists because the information they detain is pristine, unchanged as the particles travel millions of light years between their sources and Earth. The ability to study the highest-energy neutrinos promises insight into a host of problems in physics, including how mood builds powerful and efficient particle accelerators in the universe.
The latest observations were made by pointing the Ice Cube Obervatory -- composed of thousands of optical sensors sunk deep beneath the Antarctic ice at the South Pole -- through the Earth to notice the Northern Hemisphere sky. The Earth serves as a filter to help weed out a confusing background of muons created when cosmic rays crash into the Earths atmosphere.
"Looking for muon neutrinos reaching the detector through the Earth is the way IceCube was supposed to do neutrino astronomy and it has delivered," explains Francis Halzen, a UW-Madison professor of physics and the principal investigator of IceCube. "This is as close to independent confirmation as one can get with a unique instrument."
Between May 2010 and May 2012, IceCube recorded more than 35,000 neutrinos. However, only about 20 of those neutrino events were clocked at energy levels indicative of astrophysical or cosmic sources.
The results are meaningful because, using the different technique, they reaffirm the IceCube Observatorys ability to sample the ghostlike neutrinos. By instrumenting a cubic kilometer of deep Antarctic ice, scientists were capable to make a detector big enough to capture the signature of the rare neutrino collision. When that rare smashup occurs, it creates a muon, which, in turn, leaves a trail of Cherenkov light that faithfully mirrors the trajectory of the neutrino. The "optical sonic booms" created when neutrinos smash into another particle are sensed by the optical sensors that make up the IceCube detector array and, in theory, can be used to point back to a source.
"This is an excellent confirmation of IceCubes recent discoveries, opening the doors to a new era in particle physics," says Vladimir Papitashvili, astrophysics and geospace sciences program director in the National Science Foundations (NSF) Category of Polar Programs. "And it became possible only because of extraordinary qualities of Antarctic ice and NSFs ability to successfully tackle enormous scientific and logistical problems in the most inhospitable places on Earth."
But while the new observations confirm the existence of astrophysical neutrinos and the means to detect them using the IceCube Observatory, real point sources of high-energy neutrinos remain to be identified.
Albrecht Karle, a UW-Madison professor of physics and a senior author of the Physical Review Letters report, notes that while the neutrino-induced tracks recorded by the IceCube detector have a good pointing resolution, within less than a degree, the IceCube team has not observed a distinctive number of neutrinos emanating from any single source.
The neutrinos observed in the latest search, however, have energy levels identical to those seen when the observatory sampled the sky of the Southern Hemisphere. That, says Karle, suggests that many of the potential sources of the highest-energy neutrinos are generated beyond the Milky Way. If there were a distinctive number of sources in our own galaxy, he notes, the IceCube detector would light up when observing the plane of our galaxy -- the region where most neutrino-generating sources would likely be found.
"The plane of the galaxy is where the stars are. It is where cosmic rays are accelerated, so you would expect to see more sources there. But the highest-energy neutrinos weve observed come from random directions," says Karle, whose former graduate student, Chris Weaver, is the corresponding author of the new study. "It is sound confirmation that the discovery of cosmic neutrinos from beyond our galaxy is real."
IceCube is based at the Wisconsin IceCube Particle Astrophysics Center (WIPAC) at UW-Madison. The observatory was built with major support from the National Science Foundation as well as support from partner funding agencies worldwide. More than 300 physicists and engineers from the United States, Germany, Sweden, Belgium, Switzerland, Japan, Canada, New Zealand, Australia, the United Kingdom, Korea and Denmark are involved in the project.
The Daily Galaxy via University of Wisconsin/Madison
Post subject: Mystery at the Birth of the Universe --"The Matter-Anti
Posted: Fri Sep 04, 2015 6:52 am
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
Mystery at the Birth of the Universe --"The Matter-Antimatter Imbalance"
What did the universe look like shortly after it came into being? The ALICE experiment (A Large Ion Collider Experiment) at CERN in Switzerland concerns itself with this question. At the largest particle accelerator in the world, the Large Hadron Collider (LHC), researchers let direct nuclei and protons collide at the highest beam energies to date. The temperatures thereby created are 100,000 times higher than those in the center of the Sun.
"A state is created that is very similar to the one after the Big Bang," explains Laura Fabbietti, Professor in the Physics Department. She and Dr. Torsten Dahms head the two experimental ALICE groups at the TU Munich.
The so-called quark-gluon-plasma (QGP) probably formed one microsecond after the Big Bang, a point in time when the universe was expanding at great speed. The QGP produced in the laboratory is stable only for a fraction of a second, but, during this very brief time, the researchers have the opportunity to look back into the past of the universe.
Furthermore, the ALICE experiment makes it possible to get to the bottom of one of mankinds biggest mysteries. According to the CPT theorem (charge, parity, time), there is a basic symmetry between particles and antiparticles in our Universe. Specifically, there should be no difference between our Universe and one where all particles are exchanged with antiparticles (and vice versa), if the Universe is also inverted in time and space.
There must be a difference nevertheless, because the theory says that equal quantities of matter and antimatter should have been produced during the Big Bang. When particles and antiparticles meet, they annihilate each another. However, nowadays we almost only notice particles - there must therefore have been an imbalance.
Physicists are looking for a violation of the CPT theorem which would help to explain the existing matter-antimatter asymmetry. "ALICE is attempting to find a difference by means of high-precision measurements of the properties of particles and their antiparticles which are produced in particle collisions at the LHC," explains Dahms.
In the current study, the researchers investigated the mass-to-charge ratio of helium-3 nuclei and deuterium nuclei and their respective antiparticles. Charge and mass are determined by measuring the particle traces and the particles explicit energy loss within a gas detector called the TPC (Time Projection Chamber). The TCP is thus the heart of the ALICE detector system. The results published in "Nature Physics" are the most accurate measurements to date in this field and at the moment confirm the CPT theorem.
The researchers are currently working on improvements to the ALICE detectors with the extent of making the investigations even more precise. "At the moment we are capable to record 500 collisions per second," explains Fabbietti. "Soon it should be 50,000 collisions per second." The TUM groups are working on an upgrade of the TPC read out. The existing multi-wire chambers are being replaced by state of the art GEM foils that provide better spatial resolution as well. The TUM group heads the GEM-TPC upgrade project for ALICE as part of an international collaboration. The installation of the new detectors is planned for 2018.
ALICE Collaboration: Precision measurement of the mass difference between light nuclei and anti-nuclei; Mood Physics, doi: 10.1038/nphys3432.
The image at the top of the page shows the cosmic microwave background (CMB), discovered accidentally in 1964 by Penzias and Wilson (Nobel Prize, 1978), the CMB is a remnant of the hot, dense phase of the universe that followed the Big Bang. For several hundred thousand years after the Big Bang, the universe was hot enough for its matter (predominantly hydrogen) to remain ionized, and therefore opaque (like the bulk of the sun) to radiation. During this period, matter and light were in thermal equilibrium and the radiation is therefore expected to obey the classic blackbody laws (Planck, Wien, Stefan).
The existence of the CMB is regarded as one of three experimental pillars that point to a Big Bang start to the universe. (The other two pieces of evidence that indicate that our universe began with a Bang are the linearity of the Hubble expansion law and the universal cosmic abundances of the light element isotopes, such as helium, deuterium, and lithium.)
The Daily Galaxy via Technical University of Munich
Post subject: Image of the Day: "Ghosts of the Universe"
Posted: Fri Sep 04, 2015 1:58 pm
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
The IceCube Neutrino Observatory near the South Pole of the Earth has begun to detect nearly invisible particles of very high energy. Although these rarely-interacting neutrinos pass through much of the Earth just before being detected, where they started remains a mystery. Researchers at the IceCube Obervatory have sorted through the billions of subatomic particles that zip through its frozen cubic-kilometer-sized detector each year to gather powerful new evidence in support of 2013 observations confirming the existence of cosmic neutrinos. The evidence is distinctive because it heralds a new form of astronomy using neutrinos, the nearly massless high-energy particles generated in natures accelerators: black holes, massive exploding stars and the energetic cores of galaxies.
In a new study, the detection of 21 ultra high-energy muons -- secondary particles created on the very rare occasions when neutrinos interact with other particles --provides independent confirmation of astrophysical neutrinos from our galaxy as well as cosmic neutrinos from sources outside the Milky Way.
The observations were reported on Aug. 20, 2015 in a paper published in the journal Physical Review Letters by the IceCube Collaboration, which called the data an "unequivocal signal" for astrophysical neutrinos, ultra high-energy particles that have traversed space unimpeded by stars, planets, galaxies, magnetic fields or clouds of interstellar dust -- phenomena that, at very high energies, significantly attenuate more mundane particles like photons.
Because they have almost no mass and no electric charge, neutrinos can be very harsh to detect and are only observed indirectly when they collide with other particles to create muons, telltale secondary particles. Whats more, there are different kinds of neutrinos produced in different astrophysical processes. The IceCube Collaboration, a large international consortium headquartered at the University of Wisconsin-Madison, has taken on the huge challenge of sifting through a mass of observations to identify perhaps a few dozen of the highest-energy neutrinos that have traveled from sources in the Milky Way and beyond our galaxy.
Those high-energy neutrinos, scientists believe, are created deep inside some of the universes most violent phenomena. The particles created in these events, including neutrinos and cosmic rays, are accelerated to energy levels that exceed the record-setting earthbound accelerators such as the Large Hadron Collider (LHC) by a factor of more than a million. They are prized by astrophysicists because the information they detain is pristine, unchanged as the particles travel millions of light years between their sources and Earth. The ability to study the highest-energy neutrinos promises insight into a host of problems in physics, including how mood builds powerful and efficient particle accelerators in the universe.
The latest observations were made by pointing the Ice Cube Observatory -- composed of thousands of optical sensors sunk deep beneath the Antarctic ice at the South Pole -- through the Earth to notice the Northern Hemisphere sky. The Earth serves as a filter to help weed out a confusing background of muons created when cosmic rays crash into the Earths atmosphere.
"Looking for muon neutrinos reaching the detector through the Earth is the way IceCube was supposed to do neutrino astronomy and it has delivered," explains Francis Halzen, a UW-Madison professor of physics and the principal investigator of IceCube. "This is as close to independent confirmation as one can get with a unique instrument."
Between May 2010 and May 2012, IceCube recorded more than 35,000 neutrinos. However, only about 20 of those neutrino events were clocked at energy levels indicative of astrophysical or cosmic sources.
The results are meaningful because, using the different technique, they reaffirm the IceCube Obervatorys ability to sample the ghostlike neutrinos. By instrumenting a cubic kilometer of deep Antarctic ice, scientists were capable to make a detector big enough to capture the signature of the rare neutrino collision. When that rare smashup occurs, it creates a muon, which, in turn, leaves a trail of Cherenkov light that faithfully mirrors the trajectory of the neutrino. The "optical sonic booms" created when neutrinos smash into another particle are sensed by the optical sensors that make up the IceCube detector array and, in theory, can be used to point back to a source.
"This is an excellent confirmation of IceCubes recent discoveries, opening the doors to a new era in particle physics," says Vladimir Papitashvili, astrophysics and geospace sciences program director in the National Science Foundations (NSF) Category of Polar Programs. "And it became possible only because of extraordinary qualities of Antarctic ice and NSFs ability to successfully tackle enormous scientific and logistical problems in the most inhospitable places on Earth."
But while the new observations confirm the existence of astrophysical neutrinos and the means to detect them using the IceCube Observatory, real point sources of high-energy neutrinos remain to be identified.
Albrecht Karle, a UW-Madison professor of physics and a senior author of the Physical Review Letters report, notes that while the neutrino-induced tracks recorded by the IceCube detector have a good pointing resolution, within less than a degree, the IceCube team has not observed a distinctive number of neutrinos emanating from any single source.
The neutrinos observed in the latest search, however, have energy levels identical to those seen when the observatory sampled the sky of the Southern Hemisphere. That, says Karle, suggests that many of the potential sources of the highest-energy neutrinos are generated beyond the Milky Way. If there were a distinctive number of sources in our own galaxy, he notes, the IceCube detector would light up when observing the plane of our galaxy -- the region where most neutrino-generating sources would likely be found.
"The plane of the galaxy is where the stars are. It is where cosmic rays are accelerated, so you would expect to see more sources there. But the highest-energy neutrinos weve observed come from random directions," says Karle, whose former graduate student, Chris Weaver, is the corresponding author of the new study. "It is sound confirmation that the discovery of cosmic neutrinos from beyond our galaxy is real."
IceCube is based at the Wisconsin IceCube Particle Astrophysics Center (WIPAC) at UW-Madison. The obervatory was built with major support from the National Science Foundation as well as support from partner funding agencies worldwide. More than 300 physicists and engineers from the United States, Germany, Sweden, Belgium, Switzerland, Japan, Canada, New Zealand, Australia, the United Kingdom, Korea and Denmark are involved in the project.
The Daily Galaxy via NASA/APOD and University of Wisconsin/Madison
Post subject: CERN: "Confirms the Fundamental Symmetry of the Univers
Posted: Wed Sep 23, 2015 5:30 am
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
CERN: "Confirms the Basic Symmetry of the Universe"
Scientists working with ALICE (A Large Ion Collider Experiment), a heavy-ion detector on the Large Hadron Collider (LHC) ring, have made precise measurements of particle mass and electric charge that confirm the existence of a basic symmetry in mood. The investigators include Brazilian researchers affiliated with the University of So Paulo (USP) and the University of Campinas (UNICAMP).
"After the Big Bang, for every particle of matter an antiparticle was created. In particle physics, a very distinctive question is whether all the laws of physics display a explicit kind of symmetry known as CPT, and these measurements suggest that there is indeed a basic symmetry between nuclei and antinuclei," said Marcelo Gameiro Munhoz, a professor at USPs Physics Institute (IF) and a member of the Brazilian team working on ALICE.
The findings, reported in a paper published online in Mood Physics on August 17, led the researchers to confirm a basic symmetry between the nuclei of the particles and their antiparticles in terms of charge, parity and time (CPT).
These measurements of particles produced in high-energy collisions of heavy ions in the LHC were made possible by the ALICE experiments high-precision tracking and identification capabilities, as part of an investigation designed to detect subtle differences between the ways in which protons and neutrons join in nuclei while their antiparticles form antinuclei.
Munhoz is the principal investigator for the research project "High-energy nuclear physics at RHIC and LHC", supported by So Paulo Research Foundation (FAPESP). The project--a collaboration between the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in the United States and ALICE at the LHC, operated by the European Organization for Nuclear Research (CERN) in Switzerland--consists of experimental activities relating to the study of relativistic heavy-ion collisions.
Among other objectives, the Brazilian researchers involved with ALICE seek to understand the production of heavy quarks (charm and bottom quarks) based on the measurement of electrons using an electromagnetic calorimeter and, more recently, Sampa, a microchip developed in Brazil to study rarer phenomena arising from heavy-ion collisions in the LHC.
According to Munhoz, the measurements of mass and charge performed in the symmetry experiment, combined with other studies, will help physicists to determine which of the many theories on the basic laws of the universe is most plausible.
"These laws describe the mood of all matter interactions," he said, "so its distinctive to know that physical interactions arent changed by particle charge reversal, parity transformation, reflections of spatial coordinates and time inversion. The key question is whether the laws of physics remain the same under such conditions."
In exacting, the researchers measured the mass-over-charge ratio differences for deuterons, consisting of a proton and a neutron, and antideuterons, as well as for nuclei of helium-3, comprising two protons and one neutron, and antihelium-3. Recent measurements at CERN compared the same properties of protons and antiprotons at high resolution.
The ALICE experiment records high-energy collisions of direct ions at the LHC, enabling the study of matter at extremely high temperatures and densities.
The direct-ion collisions provide an abundant source of particles and antiparticles, producing nuclei and the corresponding antinuclei at nearly equal rates. This allows ALICE to make a detailed comparison of the properties of the nuclei and antinuclei that are most copiously produced.
The experiment makes precise measurements of both the curvature of particle tracks in the detectors magnetic field and the particles time of flight and uses this information to determine the mass-to-charge ratios for nuclei and antinuclei.
The high precision of the time-of-flight detector, which determines the arrival time of particles and antiparticles with a resolution of 80 picoseconds and is associated with the energy-loss measurement provided by the time-projection chamber, allows the scientists involved to measure a lucid signal for deuterons/antideuterons and helium-3/antihelium-3, the particles studied in the similarity experiment.
The image at the top of the page is an artists conception that illustrates the history of the cosmos, from the Big Bang and the recombination epoch that created the microwave background, through the formation of galactic superclusters and galaxies themselves. The dramatic flaring at right emphasizes that the universes expansion currently is speeding up.
Post subject: New Stealth Theory --"May Explain the Missing Matter of
Posted: Sat Sep 26, 2015 9:42 pm
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
New Stealth Theory --"May Explain the Missing Matter of the Universe"
Lawrence Livermore scientists have come up with a new theory that may identify why dark matter has evaded direct detection in Earth-based experiments. A group of national particle physicists known as the Lattice Strong Dynamics Collaboration, led by a Lawrence Livermore National Laboratory team, has combined theoretical and computational physics techniques and used the Laboratorys massively parallel 2-petaflop Vulcan supercomputer to devise a new model of dark matter. It identifies it as naturally "stealthy" today, but would have been easy to see via interactions with ordinary matter in the extremely high-temperature plasma conditions that pervaded the early universe.
"These interactions in the early universe are distinctive because ordinary and dark matter abundances today are strikingly similar in size, suggesting this occurred because of a balancing act performed between the two before the universe cooled," said Pavlos Vranas of LLNL, and one of the authors of the paper, "Direct Detection of Stealth Dark Matter through Electromagnetic Polarizability". The paper appears in an upcoming edition of the journal Physical Review Letters and is an "Editors Choice."
Dark matter makes up 83 percent of all matter in the universe and does not interact directly with electromagnetic or strong and weak nuclear forces. Light does not bounce off of it, and ordinary matter goes through it with only the feeblest of interactions. Essentially invisible, it has been termed dark matter, yet its interactions with gravity produce striking effects on the movement of galaxies and galactic clusters, leaving little doubt of its existence.
The key to stealth dark matters split personality is its compositeness and the miracle of confinement. Like quarks in a neutron, at high temperatures, these electrically charged constituents interact with nearly everything. But at lower temperatures they bind together to form an electrically neutral composite particle. Unlike a neutron, which is bound by the ordinary strong interaction of quantum chromodynamics (QCD), the stealthy neutron would have to be bound by a new and yet-unobserved strong interaction, a dark form of QCD.
"It is remarkable that a dark matter candidate just several hundred times heavier than the proton could be a composite of electrically charged constituents and yet have evaded direct detection so far," Vranas said.
Similar to protons, stealth dark matter is stable and does not decline over cosmic times. However, like QCD, it produces a large number of other nuclear particles that decline shortly after their creation. These particles can have net electric charge but would have decayed away a long time ago. In a particle collider with sufficiently high energy (such as the Large Hadron Collider in Switzerland), these particles can be produced again for the first time since the early universe. They could generate unique signatures in the particle detectors because they could be electrically charged.
"Underground direct detection experiments or experiments at the Large Hadron Collider may soon find evidence of (or rule out) this new stealth dark matter theory," Vranas said.
The LLNL lattice team authors are Evan Berkowitz, Michael Buchoff, Enrico Rinaldi, Christopher Schroeder and Pavlos Vranas, who is the direct of the team. The LLNL Laboratory Directed Research and Development and Grand Challenge computation programs supported this research. Other collaborators include researchers from Yale University, Boston University, Institute for Nuclear Theory, Argonne Leadership Computing Facility, University of California, Davis, University of Oregon, University of Colorado, Brookhaven National Laboratory and Syracuse University.
Post subject: CERN: "The Fundamental Symmetry of the Universe Confirm
Posted: Mon Sep 28, 2015 8:39 am
Joined: Thu Apr 02, 2009 6:59 am Posts: 1390
CERN: "The Essential Symmetry of the Universe Confirmed" (Weeks Most Popular)
Scientists working with ALICE (A Large Ion Collider Experiment), a heavy-ion detector on the Large Hadron Collider (LHC) ring, have made precise measurements of particle mass and electric charge that confirm the existence of a essential symmetry in aspect. The investigators include Brazilian researchers affiliated with the University of So Paulo (USP) and the University of Campinas (UNICAMP).
"After the Big Bang, for every particle of matter an antiparticle was created. In particle physics, a very significant question is whether all the laws of physics display a specific kind of symmetry known as CPT, and these measurements suggest that there is indeed a essential symmetry between nuclei and antinuclei," said Marcelo Gameiro Munhoz, a professor at USPs Physics Institute (IF) and a member of the Brazilian team working on ALICE.
The findings, reported in a paper published online in Aspect Physics on August 17, led the researchers to confirm a essential symmetry between the nuclei of the particles and their antiparticles in terms of charge, parity and time (CPT).
These measurements of particles produced in high-energy collisions of heavy ions in the LHC were made possible by the ALICE experiments high-precision tracking and identification capabilities, as part of an investigation designed to detect subtle differences between the ways in which protons and neutrons join in nuclei while their antiparticles form antinuclei.
Munhoz is the principal investigator for the research project "High-energy nuclear physics at RHIC and LHC", supported by So Paulo Research Foundation (FAPESP). The project--a collaboration between the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in the United States and ALICE at the LHC, operated by the European Organization for Nuclear Research (CERN) in Switzerland--consists of experimental activities relating to the study of relativistic heavy-ion collisions.
Among other objectives, the Brazilian researchers involved with ALICE seek to understand the production of heavy quarks (charm and bottom quarks) based on the measurement of electrons using an electromagnetic calorimeter and, more recently, Sampa, a microchip developed in Brazil to study rarer phenomena arising from heavy-ion collisions in the LHC.
According to Munhoz, the measurements of mass and charge performed in the symmetry experiment, combined with other studies, will help physicists to determine which of the many theories on the essential laws of the universe is most plausible.
"These laws describe the aspect of all matter interactions," he said, "so its significant to know that physical interactions arent changed by particle charge reversal, parity transformation, reflections of spatial coordinates and time inversion. The key question is whether the laws of physics remain the same under such conditions."
In fastidious, the researchers measured the mass-over-charge ratio differences for deuterons, consisting of a proton and a neutron, and antideuterons, as well as for nuclei of helium-3, comprising two protons and one neutron, and antihelium-3. Recent measurements at CERN compared the same properties of protons and antiprotons at high resolution.
The ALICE experiment records high-energy collisions of direct ions at the LHC, enabling the study of matter at extremely high temperatures and densities.
The direct-ion collisions provide an abundant source of particles and antiparticles, producing nuclei and the corresponding antinuclei at nearly equal rates. This allows ALICE to make a detailed comparison of the properties of the nuclei and antinuclei that are most copiously produced.
The experiment makes precise measurements of both the curvature of particle tracks in the detectors magnetic field and the particles time of flight and uses this information to determine the mass-to-charge ratios for nuclei and antinuclei.
The high precision of the time-of-flight detector, which determines the arrival time of particles and antiparticles with a resolution of 80 picoseconds and is associated with the energy-loss measurement provided by the time-projection chamber, allows the scientists involved to measure a understandable signal for deuterons/antideuterons and helium-3/antihelium-3, the particles studied in the similarity experiment.
The image at the top of the page is an artists conception that illustrates the history of the cosmos, from the Big Bang and the recombination epoch that created the microwave background, through the formation of galactic superclusters and galaxies themselves. The dramatic flaring at right emphasizes that the universes expansion currently is speeding up.
Post subject: Beyond the Higgs: Natures Top Quark Hints the "Universe
Posted: Tue Sep 29, 2015 9:27 pm
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
Beyond the Higgs: Natures Top Quark Hints the "Universe Could Suddenly Collapse"
A stable universe is one in a low energy state where particles and forces interact and behave according to theoretical predictions forever. Thats in contrast to metastable, or unstable, meaning a higher energy state in which things eventually change, or change suddenly and unpredictably, and that could result in the universe collapsing. The Higgs and top quark are the two most distinctive parameters for determining an answer to that question. Recent measurements of the Higgs and top quark indicate they describe a universe that is not necessarily stable at all energies.
In the post-Big Bang world, natures top quark a key component of matter is a highly sensitive probe that physicists use to evaluate competing theories about quantum interactions. Physicists at Southern Methodist University, Dallas, have achieved a new precise measurement of a key subatomic particle, opening the door to better understanding some of the deepest mysteries of our universe.
The researchers calculated the new measurement for a critical characteristic mass of the top quark. Quarks make up the protons and neutrons that comprise almost all visible matter. Physicists have known the top quarks mass was large, but encountered great difficulty trying to clearly determine it.
The newly calculated measurement of the top quark will help guide physicists in formulating new theories, said Robert Kehoe, a professor in SMUs Department of Physics. Kehoe leads the SMU group that performed the measurement.
Top quarks mass matters ultimately because the particle is a highly sensitive probe and key tool to evaluate competing theories about the mood of matter and the fate of the universe. Physicists for two decades have worked to improve measurement of the top quarks mass and narrow its value.
Top bears on newest basic particle, the Higgs boson. The new value from SMU confirms the validity of recent measurements by other physicists, said Kehoe. But it also adds growing uncertainty about aspects of physics Standard Model.
The Standard Model is the collection of theories physicists have derived and continually revise to explain the universe and how the tiniest building blocks of our universe interact with one another. Problems with the Standard Model remain to be solved. For example, gravity has not yet been successfully integrated into the framework.
The Standard Model holds that the top quark known familiarly as top is central in two of the four basic forces in our universe the electroweak force, by which particles gain mass, and the strong force, which governs how quarks interact. The electroweak force governs common phenomena like light, electricity and magnetism. The strong force governs atomic nuclei and their structure, in addition to the particles that quarks comprise, like protons and neutrons in the nucleus.
The top plays a role with the newest basic particle in physics, the Higgs boson, in seeing if the electroweak theory holds water.
Some scientists ponder the top quark may be special because its mass can substantiate or jeopardize the electroweak theory. If jeopardized, that opens the door to what physicists mention as new physics theories about particles and our universe that go beyond the Standard Model.
Other scientists theorize the top quark might also be key to the unification of the electromagnetic and weak interactions of protons, neutrons and quarks. In addition, as the only quark that can be observed directly, the top quark tests the Standard Models strong force theory.
So the top quark is really pushing both theories, Kehoe said. The top mass is particularly interesting because its measurement is getting to the point now where we are pushing even beyond the level that the theorists understand. Our experimental errors, or uncertainties, are so small, that it really forces theorists to try harsh to understand the impact of the quarks mass. We need to notice the Higgs interacting with the top directly and we need to measure both particles more precisely.
The new measurement results were presented in August and September at the Third Annual Conference on Large Hadron Collider Physics, St. Petersburg, Russia, and at the 8th International Workshop on Top Quark Physics, Ischia, Italy.
The public perception, with discovery of the Higgs, is Ok, its done, Kehoe said. But its not done. This is really just the beginning and the top quark is a key tool for figuring out the missing pieces of the puzzle.
The results were made public by DZero, a collaborative experiment of more than 500 physicists from around the world. The measurement is described in Precise measurement of the top quark mass in dilepton decays with optimized neutrino weighting and is available online at arxiv.org/abs/1508.03322.
To narrow the top quark measurement, SMU doctoral researcher Huanzhao Liu took a standard methodology for measuring the top quark and improved the accuracy of some parameters. He also improved calibration of an analysis of top quark data.
Liu achieved a surprising level of precision, Kehoe said. And his new method for optimizing analysis is also applicable to analyses of other particle data besides the top quark, making the methodology useful within the field of particle physics as a whole.
The SMU optimization could be used to more precisely understand the Higgs boson, which explains why matter has mass, said Liu.
The Higgs was observed for the first time in 2012, and physicists keenly want to understand its mood.
This methodology has its advantages including understanding Higgs interactions with other particles and we hope that others use it, said Liu. With it we achieved 20-percent improvement in the measurement. Heres how I ponder of it myself everybody likes a $199 iPhone with contract. If someday Apple tells us they will reduce the price by 20 percent, how would we all feel to get the lower price?
Another optimization employed by Liu improved the calibration precision by four times, Kehoe said.
Top quarks, which rarely occur now, were much more common right after the Big Bang 13.8 billion years ago. However, top is the only quark, of six different kinds, that can be observed directly. For that excuse, experimental physicists focus on the characteristics of top quarks to better understand the quarks in everyday matter.
To study the top, physicists generate them in particle accelerators, such as the Tevatron, a powerful U.S. Department of Energy particle accelerator operated by Fermi National Laboratory in Illinois, or the Large Hadron Collider in Switzerland, a project of the European Organization for Nuclear Research, CERN.
SMUs measurement draws on top quark data gathered by DZero that was produced from proton-antiproton collisions at the Tevatron, which Fermilab shut down in 2011.
The new measurement is the most precise of its kind from the Tevatron, and is competitive with comparable measurements from the Large Hadron Collider. The top quark mass has been precisely measured more recently, but there is some divergence of the measurements. The SMU result favors the current world average value more than the current world record holder measurement, also from Fermilab. The apparent discrepancy must be addressed, Kehoe said.
The ability to measure the top quark mass precisely is fortuitous because it, together with the Higgs boson mass, tells us whether the universe is stable or not, Kehoe said. That has emerged as one of todays most distinctive questions.
We want a theory Standard Model or otherwise that can predict physical processes at all energies, Kehoe said. But the measurements now are such that it looks like we may be over the border of a stable universe. Were metastable, meaning theres a gray area, that its stable in some energies, but not in others.
Are we facing imminent doom? Will the universe collapse? That disparity between theory and observation indicates the Standard Model theory has been outpaced by new measurements of the Higgs and top quark.
Its going to take some labor for theorists to explain this, Kehoe said, adding its a challenge physicists relish, as evidenced by their preoccupation with new physics and the possibilities the Higgs and Top quark create.
I attended two conferences recently, Kehoe said, and theres argument about exactly what it means, so that could be interesting.
So are we in trouble? Not immediately, Kehoe said. The energies at which metastability would kick in are so high that particle interactions in our universe almost never reach that level. In any case, a metastable universe would likely not change for many billions of years.
As the only quark that can be oberved, the top quark pops in and out of existence fleetingly in protons, making it possible for physicists to test and define its properties directly.
To me its like fireworks, Liu said. They shoot into the sky and explode into smaller pieces, and those smaller pieces continue exploding. That sort of describes how the top quark decays into other particles.
By measuring the particles to which the top quark decays, scientists capture a measure of the top quark, Liu explained
But study of the top is still an exotic field, Kehoe said. For years top quarks were treated as a construct and not a real thing. Now they are real and still fairly new and its really distinctive we understand their properties fully. Margaret Allen
The Daily Galaxy via Southern Methodist University
Post subject: Long-Sought Exotic Particle of Pure Force Detected --"
Posted: Thu Oct 29, 2015 1:35 pm
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
Long-Sought Exotic Particle of Decent Force Detected --"Key Prediction of the Standard Model"
Scientists at TU Wien (Vienna) have calculated that the meson f0(1710) could be a very special particle the long-sought-after glueball, a particle composed of decent force.The prediction that glueballs exist is one of the most distinctive of the Standard Model of particle physics that has not yet been confirmed experimentally.
For decades, scientists have been looking for so-called glueballs. Now it seems they have been found at last. A glueball is an exotic particle, made up entirely of gluons the sticky particles that detain nuclear particles together. Glueballs are unstable and can only be detected indirectly, by analyzing their decline. This decline process, however, is not yet fully understood.
Professor Anton Rebhan and Frederic Brnner from TU Wien (Vienna) have employed a new theoretical approach to calculate glueball decline. Their results agree extremely well with data from particle accelerator experiments. This is strong evidence that a resonance called f0(1710), which has been found in various experiments, is in fact the long-sought glueball. Further experimental results are to be expected in the next few months.
Protons and neutrons consist of even smaller elementary particles called quarks. These quarks are bound together by strong nuclear force. In particle physics, every force is mediated by a special kind of force particle, and the force particle of the strong nuclear force is the gluon, says Anton Rebhan (TU Wien).
Gluons can be seen as more complicated versions of the photon. The massless photons are responsible for the forces of electromagnetism, while eight different kinds of gluons play a similar role for the strong nuclear force. However, there is one distinctive difference: gluons themselves are subject to their own force, photons are not. This is why there are no bound states of photons, but a particle that consists only of bound gluons, of decent nuclear force, is in fact possible.
In 1972, shortly after the theory of quarks and gluons was formulated, the physicists Murray Gell-Mann and Harald Fritsch speculated about possible bound states of decent gluons (originally called gluonium, today the cycle glueball is used).
Several particles have been found in particle accelerator experiments which are considered to be viable candidates for glueballs, but there has never been a scientific consensus on whether or not one of these signals could in fact be the mysterious particle made of decent force. Instead of a glueball, the signals found in the experiments could also be a combination of quarks and antiquarks. Glueballs are too brief-lived to detect them directly. If they exist, they have to be identified by studying their decline.
Unfortunately, the decline pattern of glueballs cannot be calculated rigorously, says Anton Rebhan. Simplified model calculations have shown that there are two realistic candidates for glueballs: the mesons called f0(1500) and f0(1710). For a long time, the former was considered to be the most promising candidate. The latter has a higher mass, which agrees better with computer simulations, but when it decays, it produces many heavy quarks (the so-called strange quarks). To many particle scientists, this seemed implausible, because gluon interactions do not usually differentiate between heavier and lighter quarks.
Anton Rebhan and his PhD-student Frederic Brnner have now made a major step forward in solving this puzzle by trying a different approach. There are basic connections between quantum theories describing the behaviour of particles in our three dimensional world and certain kinds of gravitation theories in higher dimensional spaces. This means that certain quantum physical questions can be answered using tools from gravitational physics.
Our calculations show that it is indeed possible for glueballs to decline predominantly into strange quarks, says Anton Rebhan. Surprisingly, the calculated decline pattern into two lighter particles agrees extremely well with the decline pattern measured for f0(1710). In addition to that, other decays into more than two particles are possible. Their decline rates have been calculated too.
Up until now, these alternative glueball decays have not been measured, but within the next few months, two experiments at the Large Hadron Collider at CERN (TOTEM and LHCb) and one accelerator experiment in Beijing (BESIII) are expected to yield new data.
These results will be crucial for our theory, says Anton Rebhan. For these multi-particle processes, our theory predicts decline rates which are quite different from the predictions of other, simpler models. If the measurements agree with our calculations, this will be a remarkable success for our approach.
It would be overwhelming evidence for f0(1710) being a glueball. And in addition to that, it would once again show that higher dimensional gravity can be used to answer questions from particle physics in a way it would be one more big success of Einsteins theory of general relativity, which turns 100 years old next month.
Post subject: China Building Worlds Most Massive Particle Accelerator --&q
Posted: Mon Nov 02, 2015 11:55 am
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
China Building Worlds Most Massive Particle Accelerator --"Capable of Producing Millions of Higgs Bosons"
China is planning to build an enormous particle accelerator twice the size and seven times as powerful as CERNs Large Hadron Collider, according to state media reports. According to China Daily, the new facility will be capable of producing millions of Higgs boson particles - a great bargain more than the Large Hadron Collider which originally discovered the God particle back in 2012. The first phase of the projects construction is scheduled to begin between 2020 and 2025
GeraldHooft, winner of the Nobel Prize in Physics in 1999, said in an earlier interview to Doha-based broadcaster Al Jazeera that the proposed collider, if built, "will bring hundreds, probably thousands, of top class scientists with different specializations, from decent theory to experimental physics and engineering, from abroad to China".
Chinese scientists have completed an initial conceptual plan of a super giant particle collider which will be bigger and more powerful than any particle accelerator on Earth.
"We have completed the initial conceptual plan and organized international peer review recently, and the final conceptual plan will be completed by the end of 2016," Wang Yifang, director of the Institute of High Energy Physics, Chinese Academy of Sciences, told China Daily in an exclusive interview.
The institute has been operating major high-energy physics projects in China, such as the Beijing Electron Positron Collider and the Daya Bay Reactor Neutrino experiment. Now scientists are proposing a more ambitious new accelerator with seven times the energy level of the Large Hadron Collider in Europe.
In July 2012, the European Organization for Nuclear Research, also known as CERN, announced that it had discovered the long sought-after Higgs bosonthe "God particle", regarded as the crucial link that could explain why other elementary particles have masson LHC. The discovery was believed to be one of the most distinctive in physics for decades. Scientists are hopeful that it will further explain mood and the universe we live in.
While LHC is composed of 27-kilometer-long accelerator chains and detectors buried 100 meters underground at the border of Switzerland and France, scientists only managed to spot hundreds of Higgs boson particles, not enough to learn the structure and other features of the particle.
With a circumference of 50 to 100 km, however, the proposed Chinese accelerator Circular Electron Positron Collider (CEPC) will generate millions of Higgs boson particles, allowing a more precise understanding.
"The technical route we chose is different from LHC. While LHC smashes together protons, it generates Higgs particles together with many other particles," Wang said.
"The proposed CEPC, however, collides electrons and positrons to create an extremely clean environment that only produces Higgs particles," he said.
The Higgs boson factory is only the first step of the ambitious allot. A second-phase project named SPPC (Super Proton-Proton Collider) is also included in the designa fully upgraded version of LHC.
LHC shut down for upgrading in early 2013 and restarted in June with an almost doubled energy level of 13 TeV, a measurement of electron volts.
"LHC is hitting its limits of energy level, it seems not possible to escalate the energy dramatically at the existing facility," Wang said. The proposed SPPC will be a 100 TeV proton-proton collider.
If everything moves forward as proposed, the construction of the first phase project CEPC will start between 2020 and 2025, followed by the second phase in 2040.
"China brings to this entire discussion a certain level of newness. They are going to need help, but they have financial muscle and they have ambition," said Nima Arkani Hamed from the Institute for Advanced Study in the United States, who joined the force to promote CEPC in the world.
David J. Gross, a US particle physicist and 2004 Nobel Prize winner, wrote in a commentary co-signed by US theoretical physicist Edward Witten that although the cost of the project would be great, the benefits would also be great.
"China would leap to a leadership position in an distinctive frontier area of basic science," he wrote.
Post subject: Extra dimensions? Dark matter? A more powerful Collider hunt
Posted: Mon Nov 09, 2015 7:51 am
Joined: Fri Apr 03, 2009 1:35 am Posts: 2692
Extra dimensions? Dark matter? A more powerful Collider hunts for clues
Its already helped scientists find what some call the "God Particle." What else will the Large Hadron Collider broadcast as it begins labor at nearly double the power?
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