Scientific American: Article: Cosmic Rays at the Energy Frontier: January 1997Cosmic Raysat the Energy Frontier These particles carry more energythanany others in the universe.Their originis unknown but may berelatively nearbySUBTOPICS:SIDEBAR:ILLUSTRATIONS:Roughly once a second, a subatomic particle enters the earth's atmosphere carrying as much energy as a well-thrown rock. Somewhere in the universe, that fact implies, there are forces that can impart to a single proton 100 million times the energy achievable by the most powerful earthbound accelerators. Where and how?Those questions have occupied physicists since were first discovered in 1912 (although the entities in question are now known to be particles, the name 'ray' persists). The contains atomic nuclei of every element in the periodic table, all moving under the influence of electrical and magnetic fields. Without the screening effect of the earth's atmosphere, cosmic rays would pose a significant health threat; indeed, people living in mountainous regions or making frequent airplane trips pick up a measurable extra radiation dose.Perhaps the most remarkable feature of this radiation is that investigators havenot yet found a natural end to the cosmic-ray spectrum. Most well-known sourcesof charged particles-such as the sun, with its -have acharacteristic energy limit; they simply do not produce particles with energiesabove this limit.

1. Introduction To Particle Physics Pdf

In contrast, cosmic rays appear, albeit in decreasing numbers,at energies as high as astrophysicists can measure. The data run out at levelsaround 300 billion times the rest-mass energy of a proton because there is atpresent no detector large enough to sample the very low number of incomingparticles predicted.Nevertheless, evidence of ultrahigh-energy cosmic rays has been seen atintervals of several years as particles hitting the atmosphere create myriadsecondary particles (which are easier to detect). On October 15, 1991, forexample, a cosmic-ray observatory in the Utah desert registered a from a 50-joule (3 x 10 20 electron volts)cosmic ray. Although the cosmic-ray flux decreases with higher energy, thisdecline levels off somewhat above about 10 16 eV, suggesting that themechanisms responsible for ultrahigh-energy cosmic rays are different from thosefor rays of more moderate energy.In 1960 Bernard Peters of the Tata Institute in Bombay suggested thatlower-energy cosmic rays are produced predominantly inside our own galaxy,whereas those of higher energy come from more distant sources.

One reason tothink so is that a cosmic-ray proton carrying more than 10 19 eV, forexample, would not be deflected significantly by any of thetypically generated by a galaxy, so it would travel more or less straight. Ifsuch particles came from inside our galaxy, we might expect to see differentnumbers coming from various directions because the galaxy is not arrangedsymmetrically around us. Instead the distribution is essentially isotropic, as isthat of the lower-energy rays, whose directions are scattered.Such tenuous inferences reveal how little is known for certain about theorigin of cosmic rays. Astrophysicists have plausible models for how they mightbe produced but no definitive answers. This state of affairs may be the result ofthe almost unimaginable difference between conditions on the earth and in theregions where cosmic rays are born. The contains only about one atom per cubic centimeter, a far lowerdensity than the best artificial vacuums we can create.

Furthermore, thesevolumes are filled with vast electrical and magnetic fields, intimately connectedto a diffuse population of charged particles even less numerous than the neutralatoms.This environment is far from the peaceful place one might expect: the lowdensities allow electrical and magnetic forces to operate over large distancesand timescales in a manner that would be quickly damped out in material ofterrestrial densities. Galactic space is therefore filled with an energetic andin a state of violent activity.

The motion is often hard toobserve on human timescales because astronomical distances are so large;nevertheless, those same distances allow even moderate forces to achieveimpressive results. A particle might zip through a terrestrial accelerator in afew microseconds, but it could spend years or even millennia in the accelerator'scosmic counterpart.

(The timescales are further complicated by the strange,relativity-distorted framework that ultrahigh-energy cosmic rays inhabit. If wecould observe such a particle for 10,000 years, that period would correspond toonly a single second as far as the particle is concerned.)Astronomers have long speculated that the bulk of galactic cosmic rays-thosewith energies below about 10 16 eV-originate with. A compellingreason for this theory is that the power required to maintain the observed supplyof cosmic-ray nuclei in our Milky Way galaxy is only slightly less than theaverage kinetic energy delivered to the galactic medium by the three supernovaexplosions that occur every century. There are few, if any, other sources of thisamount of power in our galaxy.When a massive star collapses, the outer parts of the star explode at speedsof up to 10,000 kilometers per second and more. A similar amount of energy isreleased when a star undergoes complete disintegration in a thermonuclear detonation.In both types of supernovae the ejected matter expands at supersonic velocities,driving a strong shock into the surrounding medium.

Such shocks are expected toaccelerate nuclei from the material they pass through, turning them into cosmicrays. Because cosmic rays are charged, they follow complicated paths through. As a result, their directions as observed from the earth yield noinformation about the location of their original source.By looking at the sometimes associated with supernova remnants, researchers havefound more direct evidence that supernovae can act as accelerators. Synchrotronradiation is characteristic of high-energy electrons moving in an intensemagnetic field of the kind that might act as a cosmic-ray accelerator, and thepresence of synchrotron x-rays in some supernova remnants suggests particularlyhigh energies. (In earthbound devices, synchrotron emission limits a particle'senergy because the emission rate increases as a particle goes faster; at somepoint, the radiation bleeds energy out of an accelerating particle as fast as itcan be pumped in.) Recently the Japanese x-ray satellite made imagesof the shell of Supernova 1006, which exploded 990 years ago. Unlike theradiation from the interior of the remnant, the x-radiation from the shell hasthe features characteristic of synchrotron radiation. Astrophysicists havededuced that electrons are being accelerated there at up to 10 14 eV(100 TeV).Theon the has also been used to study point sources of gamma raysidentified with supernova remnants.

The observed intensities and spectra (up to abillion electron volts) are consistent with an origin from the decay of particlescalled neutral pions, which could be produced by cosmic rays from the explodingstar's remnants colliding with nearby interstellar gas. Interestingly, however,searches made by the ground-based for gammarays of much higher energies from some of the same remnants have not seen signalsat the levels that would be expected if the supernovae were acceleratingparticles to 10 14 eV or more.A complementary method for testing the association of with supernovae involves the elemental composition of cosmic-raynuclei. The size of the orbit of a charged particle in a magnetic field isproportional to its total momentum per unit charge, so heavier nuclei havegreater total energy for a given orbit size. Any process that limits the particleacceleration on the basis of orbit size (such as an accelerating region oflimited extent) will thus lead to an excess of heavier nuclei at high energies.Eventually we would like to be able to go further and look for elementalsignatures of acceleration in specific types of supernovae. For example, thesupernova of a white dwarf detonation would accelerate whatever nuclei populatethe local interstellar medium. A supernova that followed the collapse of amassive star, in contrast, would accelerate the surrounding stellar wind, whichis characteristic of the outer layers of the progenitor star at earlier stages ofits evolution. In some cases, the wind could include an increased fraction ofhelium, carbon or even heavier nuclei.The identity of high-energy cosmic rays is all but lost when they interactwith atoms in the earth's atmosphere and form a.

Hence, to be absolutely sure of the nuclear composition,measurements must be made before the cosmic rays reach dense atmosphere.Unfortunately, to collect 100 cosmic rays of energies near 10 14 eV, a10-square-meter detector would have to be in orbit for three years. Typicalexposures at present are more like the equivalent of one square meter for threedays.Researchers are attacking this problem with some ingenious experiments.

Forexample, the National Aeronautics and Space Administration has developedtechniques to loft large payloads (about three tons) withfor many days. These cost a tinyfraction of what an equivalent satellite detector would. The most successfulflights of this type have taken place in Antarctica, where the upper atmospherewinds blow in an almost constant circle around the South Pole.A payload launched at McMurdo Sound on the coast of Antarctica will travel ata nearly constant radius from the Pole and return eventually to near the launchsite. Some balloons have circled the continent for 10 days. One of us (Swordy) iscollaborating with and ofthe University of Chicago on a 10-square-meter detector that could measure heavycosmic rays of up to 10 15 eV on such a flight.

There are efforts toextend the exposure times to roughly 100 days with similar flights nearer theequator.Studying even higher-energy cosmic rays-those produced by sources as yetunknown-requires large ground-based detectors, which overcome the problem of lowflux by watching enormous effective areas for months or years. The information,however, must be extracted from cascades of secondary particles-electrons,and gamma rays-initiated high in the atmosphere by an incoming cosmic-raynucleus. Such indirect methods can only suggest general features of thecomposition of a cosmic ray on a statistical basis, rather than identifying theatomic number of each incoming nucleus.At ground level, the millions of secondary particles unleashed by one cosmicray are spread over a radius of hundreds of meters. Because it is impractical toblanket such a large area with detectors, the detectors typically sample theseair showers at a few hundred or so discrete locations.Technical improvements have enabled such devices to collect increasinglysophisticated data sets, thus refining the conclusions we can draw from eachshower.

For example, the CASA-MIA-DICE experiment in Utah, in which two of us(Cronin and Swordy) are involved, measures the distributions of electrons andmuons at ground level. It also detects (a type of optical shock wave produced by particles moving faster thanthe speed of light in their surrounding medium) generated by the shower particlesat various levels in the atmosphere. These data enable us to reconstruct theshape of the shower more reliably and thus take a better guess at the energy andidentity of the cosmic ray that initiated it.The third one of us (Gaisser) is working with an array that measures showersreaching the surface at the South Pole. This experiment works in conjunction with, which detectsenergetic muons produced in the same showers by observing Cerenkov radiationproduced deep in the ice cap.

The primary goal of AMANDA is to catch traces ofneutrinos produced in cosmic accelerators, which may generate upward-streamingshowers after passing through the earth.In addition to gathering better data, researchers are also improving detailedcomputer simulations that model how air showers develop. These simulations helpus to understand both the capabilities and the limitations of ground-basedmeasurements. The extension to higher energies of direct cosmic-ray detectionexperiments, which allows both ground-based and airborne detectors to observe thesame kinds of cosmic rays, will also help calibrate our ground-based data.Cosmic rays with energies above 10 20 eV strike the earth'satmosphere at a rate of only about one per square kilometer a year. As a result,studying them requires an air-shower detector of truly gigantic proportions. Inaddition to the 1991 event in Utah, particles with energies above 10 20eV have been seen by groups elsewhere in the U.S., in Akeno, Japan, in, U.K., and inYakutsk, Siberia.Particles of such high energy pose a conundrum. On the one hand, they arelikely to come from outside our galaxy because no known acceleration mechanismcould produce them and because they approach from all directions even though agalactic magnetic field is insufficient to bend their path.

✏Book Title: Cosmic Rays at Earth✏Author: P.K.F. Grieder✏Publisher: Gulf Professional Publishing✏Release Date: 2001-08-10✏Pages: 1093✏ISBN: ✏Available Language: English, Spanish, And French✏Cosmic Rays at Earth Book Summary: In 1912 Victor Franz Hess made the revolutionary discovery that ionizing radiation is incident upon the Earth from outer space. He showed with ground-based and balloon-borne detectors that the intensity of the radiation did not change significantly between day and night. Consequently, the sun could not be regarded as the sources of this radiation and the question of its origin remained unanswered. Today, almost one hundred years later the question of the origin of the cosmic radiation still remains a mystery.

Hess' discovery has given an enormous impetus to large areas of science, in particular to physics, and has played a major role in the formation of our current understanding of universal evolution. For example, the development of new fields of research such as elementary particle physics, modern astrophysics and cosmology are direct consequences of this discovery. Over the years the field of cosmic ray research has evolved in various directions: Firstly, the field of particle physics that was initiated by the discovery of many so-called elementary particles in the cosmic radiation. There is a strong trend from the accelerator physics community to reenter the field of cosmic ray physics, now under the name of astroparticle physics.

Secondly, an important branch of cosmic ray physics that has rapidly evolved in conjunction with space exploration concerns the low energy portion of the cosmic ray spectrum. Thirdly, the branch of research that is concerned with the origin, acceleration and propagation of the cosmic radiation represents a great challenge for astrophysics, astronomy and cosmology. Presently very popular fields of research have rapidly evolved, such as high-energy gamma ray and neutrino astronomy.

In addition, high-energy neutrino astronomy may soon initiate as a likely spin-off neutrino tomography of the Earth and thus open a unique new branch of geophysical research of the interior of the Earth. Finally, of considerable interest are the biological and medical aspects of the cosmic radiation because of it ionizing character and the inevitable irradiation to which we are exposed. This book is a reference manual for researchers and students of cosmic ray physics and associated fields and phenomena. It is not intended to be a tutorial. However, the book contains an adequate amount of background materials that its content should be useful to a broad community of scientists and professionals.

The present book contains chiefly a data collection in compact form that covers the cosmic radiation in the vicinity of the Earth, in the Earth's atmosphere, at sea level and underground. Included are predominantly experimental but also theoretical data. In addition the book contains related data, definitions and important relations. The aim of this book is to offer the reader in a single volume a readily available comprehensive set of data that will save him the need of frequent time consuming literature searches. ✏Book Title: Cosmic Radiations From Astronomy to Particle Physics✏Author: Giorgio Giacomelli✏Publisher: Springer Science & Business Media✏Release Date: 2001-11-30✏Pages: 354✏ISBN: ✏Available Language: English, Spanish, And French✏Cosmic Radiations From Astronomy to Particle Physics Book Summary: Non-accelerator particle physicists, especially those studying neutrino oscillation experiments, will read with profit the in-depth discussions of new results and their interpretations. New guidelines are also set out for new developments in this and related fields. Discussions are presented of neutrino oscillations, neutrino astronomy, high energy cosmic rays, gravitational waves, magnetic monopoles and dark matter.

The future large-scale research projects discussed include the experiments on long baseline neutrino beams from CERN to Gran Sasso and Fermilab to the Soudan mine; large underwater and under-ice experiments; the highest energy cosmic rays; gravitational waves; and the search for new particles and new phenomena. ✏Book Title: Cosmic Rays for Particle and Astroparticle Physics✏Author: S.

Giani✏Publisher: World Scientific✏Release Date: 2011✏Pages: 668✏ISBN: 033✏Available Language: English, Spanish, And French✏Cosmic Rays for Particle and Astroparticle Physics Book Summary: The conference was aimed at promoting contacts between scientists involved in solar-terrestrial physics, space physics, astroparticle physics and cosmology both from the theoretical and the experimental approach. The conference was devoted to physics and physics requirements, survey of theoretical models and performances of detectors employed (or to be employed) in experiments for fundamental physics, astroparticle physics, astrophysics research and space environment OCo including Earth magnetosphere and heliosphere and solar-terrestrial physics. Furthermore, cosmic rays have been used to extend the scientific research experience to teachers and students with air shower arrays and other techniques.

Presentations included the following subjects: advances in physics from present and next generation ground and space experiments, dark matter, double beta decay, high-energy astrophysics, space environment, trapped particles, propagation of cosmic rays in the Earth atmosphere, Heliosphere, Galaxy and broader impact activities in cosmic rays science. The open and flexible format of the Conference was conducive to fruitful exchanges of points of view among participants and permitted the evaluation of the progresses made and indicated future research directions.

Introduction To Particle Physics Pdf

The participants were experienced researchers but also graduate students (MSc and PhD) and recent postdoctoral fellows.' ✏Book Title: High Energy Cosmic Rays✏Author: Todor Stanev✏Publisher: Springer Science & Business Media✏Release Date: 2010-03-10✏Pages: 333✏ISBN: 486✏Available Language: English, Spanish, And French✏High Energy Cosmic Rays Book Summary: Offers an accessible text and reference (a cosmic-ray manual) for graduate students entering the field and high-energy astrophysicists will find this an accessible cosmic-ray manual Easy to read for the general astronomer, the first part describes the standard model of cosmic rays based on our understanding of modern particle physics. Presents the acceleration scenario in some detail in supernovae explosions as well as in the passage of cosmic rays through the Galaxy. Compares experimental data in the atmosphere as well as underground are compared with theoretical models. ✏Book Title: Particle Detectors✏Author: Claus Grupen✏Publisher: Cambridge University Press✏Release Date: 2008-03-13✏Pages:✏ISBN: 531✏Available Language: English, Spanish, And French✏Particle Detectors Book Summary: The scope of the detection techniques in particle detectors is very wide, depending on the aim of the measurement. Detectors cover the measurement of energies from the very low to the highest of energies observed in cosmic rays.

Describing the instrumentation for experiments in high energy physics and astroparticle physics, this edition describes track detectors, calorimeters, particle identification, neutrino detectors, momentum measurement, electronics, and data analysis. It also discusses applications of these detectors in other fields such as nuclear medicine, radiation protection and environmental science. Problem sets have been added to each chapter and additional instructive material has been provided, making this an excellent reference for graduate students and researchers in particle physics. ✏Book Title: A Thin Cosmic Rain✏Author: Michael W. Friedlander✏Publisher: Harvard University Press✏Release Date: 2002-11-01✏Pages: 241✏ISBN: 899✏Available Language: English, Spanish, And French✏A Thin Cosmic Rain Book Summary: A scientific history of 'cosmic rays' chronicles the discovery of a steady 'rain' of atomic nuclei, beginning with the birth of subatomic particle physics in the 1890s and moving through the subsequent uncovering of muons, pions, kaons, hyperons, and other particles.