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Showing posts with label AMS. Show all posts
Showing posts with label AMS. Show all posts

Sunday, January 26, 2014

Gravitational Waves, as Quantum Flunctuations

"According to modern understanding, even if all matter could be removed from a volume, it would still not be "empty" due to vacuum fluctuations, dark energy, transiting gamma- and cosmic rays, neutrinos, along with other phenomena in quantum physics. In modern particle physics, the vacuum state is considered as the ground state of matter." See: Vacuum
Bold added by me for emphasis.

While covering long distances(cosmic particles) what is examined that differences could have been determined in AMSII Calorimeter devices have been implored to be defined in configuration spaces. See Glast/Fermi. Use of calorimeter devices against the backdrop of LHC.


When cosmic particle meet earth's boundary with space, forward faster then light effects are generated. It is important to me that space be given it proper context in relation too, what is actually being transmitted across distances. Speed of light is medium dependent. So energy depenence value is necessary for those forward measure faster then light measure, exemplified in ICECUBE.

The idea then, that these space fluctuation as vacua are in expression and are sensitive aside what else is also being transmitted across those long distances. This, in relation with cosmic particles that were also created in events.

The most important thing is to be motivated by your own intellectual curiosity.
KIP THORNE

Dr. Kip Thorne, Caltech 01-Relativity-The First 20th Century Revolution


In my mind Kip Thorne's determinations as to the length of measure and value of LiGO arms, also seen as beam of light very sensitive to those vacuum fluctuations.


Nearly a century after Einstein first predicted the existence of gravitational waves, a global network of Earth-based gravitational wave observatories1–4 is seeking to directly detect this faint radiation using precision laser interferometry. Photon shot noise, due to the quantum nature of light, imposes a fundamental limit on the attometre-level sensitivity of the kilometre-scale Michelson interferometers deployed for this task. Here, we inject squeezed states to improve the performance of one of the detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) beyond the quantum noise limit, most notably in the frequency region down to 150 Hz, critically important for several astrophysical sources, with no deterioration of performance observed at any frequency. With the injection of squeezed states, this LIGO detector demonstrated the best broadband sensitivity to gravitational waves ever achieved, with important implications for observing the gravitational-wave Universe with unprecedented sensitivity. A fundamental limit to the sensitivitySee: Enhanced sensitivity of the LIGO gravitational wave detector by using squeezed states of lightPUBLISHED ONLINE: 21 JULY 2013 | DOI: 10.1038/NPHOTON.2013.177

Sunday, October 20, 2013

Gravity The Movie and the Expanse of Space



Went and saw the movie yesterday. I must say it had a crazy effect on me seeing the movie in 3d.

It seem to capture some of my fears about having lost some constraint on how one is attach to the matters with which we are held bound. The grasping continuously,  of trying to grab onto and hold too, as if the need exists for all humanity to be grounded.

Effectively as a participant once fully engaged, it showed me a glimpse into the future, one way or another, of being involved in the process. While being to old to ever consider such a process now in space exploration, if there is a future life,  I have already glimpsed it,  and seen some of the work I was going to do.

Wishful thinking on my part perhaps, but equally real that the fear of being lost in space, ever so real as to the understanding of what we may call home to many of us. It is as fragile to realize that what we call home here on earth could have ever lost such bounds as to what we all remain attached too. In that moment of realization perhaps to see all around, us, as no longer being held to Earth as the mass between us somehow looses it gravitational hold.

You must forgive me for my layman pondering. How is it that we can change this gravitational connect between the masses without altering the mass of one? It seems to me that there is a  link  to mind somehow in what I come to believe to be true, is an ability to change how that mass is viewed? Is there any scientific proof for this that we can change the laws of gravity, by either injecting something into the space between these masses, or,  by altering the nature of the mass itself?

As Sandra Bullock is shown on the shore,  we find we are safe again.



Such a feeling had been deeply entrenched in my mind as I moved closer to the edge of a viewing point over looking  the Grand Canyon. That such an expanse of space was to have been found with such familiarity,  as in the movie just seen.

So in a way this idea of releasing the matters is a strange thing in my mind as to have ever considered it beyond the materialistic binds with which this process is viewed. That there are other and thought provoking ideas about what the spirit of ourselves can ever be held so tightly so as to see the way in which we are connected to the experiences in life.

What would it mean to have found that the attachments of life can be so easily held in perspective that we can release those things which keep us grounded. Not that we feel safe, but to realize that there is another kind of gravity that holds us to the materialistic binds which make our lives human here on earth.



See Also:

Friday, October 18, 2013

CERN Courier: AMS-02 provides a precise measure of cosmic rays

Fig. 1. AMS, far left, was installed by NASA on the International Space Station on 19 May 2011, where it is the only major physical science experiment. It will operate there for the station's lifetime of approximately 20 years.
Image credit: NASA.

AMS-02 is a large particle detector by space standards and built using the concepts and technologies developed for experiments at particle accelerators but adapted to the extremely hostile environment of space. Measuring 5 × 4 × 3 m3, it weighs 7.5 tonnes. Reliability, performance and redundancy are the key features for the safe and successful operation of this instrument in space (CERN Courier July/August 2011 p18 and p23). See: AMS-02 provides a precise measure of cosmic rays





It's important I think to see the context of particle  reductionism in the proper light  as we examine what goes on in LHC. Doing AMSII work on space station at the same time, we see from space those energies which help us  to understand the naturalness of the work being done.

Wednesday, April 24, 2013

DarkSide-50

Pictorial image showing, superimposed to an optical image, the spatial distributions of ordinary matter (pink) and the one assigned to dark matter (blue) estimated studying the merging of two clusters of galaxies (Bullet Cluster)

The DarkSide collaboration is an international affiliation of universities and labs seeking to directly detect dark matter in the form of Weakly Interacting Massive Particles (WIMPs). The collaboration is building a series of noble liquid time projection chambers (TPCs) that are designed to be employed at the Gran Sasso National Laboratory in Assergi, Italy. The technique is based on liquid argon depleted in radioactive isotope 39Ar which is common for the atmospheric argon.

Dark-matter seekers get help from the DarkSide




Darkside

As part of the DarkSide program of direct dark matter searches using liquid argon TPCs, a prototype detector with an active volume containing 10 kg of liquid argon, DarkSide-10, was built and operated underground in the Gran Sasso National Laboratory in Italy. A critically important parameter for such devices is the scintillation light yield, as photon statistics limits the rejection of electron-recoil backgrounds by pulse shape discrimination. We have measured the light yield of DarkSide-10 using the readily-identifiable full-absorption peaks from gamma ray sources combined with single-photoelectron calibrations using low-occupancy laser pulses. For gamma lines of energies in the range 122-1275 keV, we get consistent light yields averaging 8.887\pm0.003(stat)\pm0.444(sys) p.e./keV_ee. With additional purification, the light yield measured at 511 keV increased to 9.142\pm0.006(stat) p.e./keV_ee. See:
Light Yield in DarkSide-10: a Prototype Two-phase Liquid Argon TPC for Dark Matter Searches

Saturday, March 30, 2013

Recent results from the AMS experiment


http://cds.cern.ch/record/1537419/linkbacks/sendtrackback by Prof. Samuel Ting (Massachusetts Inst. of Technology (US))

Wednesday, April 3, 2013 from 17:00 to 18:00 (Europe/Zurich) at CERN ( 500-1-001 - Main Auditorium )

 Cern Webcast






See Also:

Thank you Lubos Motl for the Update.

Thursday, February 21, 2013

What Will AMS-02 Reveal?


23% of the matter/energy balance of the universe is the form of dark matter, mysterious type of particles 6 times more abundant than normal matter which shape gravitationally all galaxies and dominates the evolution of the visible universe.Alpha Magnetic Spectrometer


One would always be curious as to what motivations help to drive the expansionary process of the universe as it is unfolding. What events in the cosmos allow us to reveal constituents entities of such expansionary process as dark energy/matter particles? Well hopefully such driven place in the cosmos is revealing of such motivational  process.

See Also:

Wednesday, February 20, 2013

Cosmic Particle Creation


The husks of exploded stars produce some of the fastest particles in the cosmos. New findings by NASA's Fermi show that two supernova remnants accelerate protons to near the speed of light. The protons interact with nearby interstellar gas clouds, which then emit gamma rays. Credit: NASA's Goddard Space Flight Center See:Fermi Proves Supernova Remnants Make Cosmic Rays



See Also:

Tuesday, February 19, 2013

Supernova Remnant W49B

Credits: X-ray: NASA/CXC/MIT/L.Lopez et al; Infrared: Palomar; Radio: NSF/NRAO/VLA 

The highly distorted supernova remnant shown in this image may contain the most recent black hole formed in the Milky Way galaxy. The image combines X-rays from NASA's Chandra X-ray Observatory in blue and green, radio data from the NSF's Very Large Array in pink, and infrared data from Caltech's Palomar Observatory in yellow.

The remnant, called W49B, is about a thousand years old, as seen from Earth, and is at a distance about 26,000 light years away.

The supernova explosions that destroy massive stars are generally symmetrical, with the stellar material blasting away more or less evenly in all directions. However, in the W49B supernova, material near the poles of the doomed rotating star was ejected at a much higher speed than material emanating from its equator. Jets shooting away from the star's poles mainly shaped the supernova explosion and its aftermath.

By tracing the distribution and amounts of different elements in the stellar debris field, researchers were able to compare the Chandra data to theoretical models of how a star explodes. For example, they found iron in only half of the remnant while other elements such as sulfur and silicon were spread throughout. This matches predictions for an asymmetric explosion. Also, W49B is much more barrel-shaped than most other remnants in X-rays and several other wavelengths, pointing to an unusual demise for this star.......
See:Supernova Remnant W49B
 



 See Also:


Thursday, August 11, 2011

The Alpha Magnetic Spectrometer Experiment )02

Credit: NASA/JSC, NASA

During the 14-day mission, Endeavour delivered the Alpha Magnetic Spectrometer (AMS) and spare parts including two S-band communications antennas, a high-pressure gas tank and additional spare parts for Dextre. This was the 36th shuttle mission to the International Space Station. STS-134 Mission Information



See:

HOW LONG – THE STORY OF AMS-02

July 31st, 2011 
In this video 16 years of preparation of AMS-02 become few blinks. The construction of AMS-02 is the result of a  worldwide effort undertaken by scientists from 16 different countries who now started analyzing the wealth of data downlinked from the ISS, looking for new, unexpected phenomena.

For me, following the story "on land"  by our own  innovators to understanding the energy valuations outputs and the many tree designs as Feynman pathways of particulate expressions has been very interesting. The pathways are designated motivation-ally and expressively, to see and reveal the level of experimental verification needed in looking at the results for confirm hypothesis and theoretical expectations. Proposals on what we might find. In AMS case and in Fermi,  we are counting these motivations from not only our sun , but from deep space as well.

See: BaBar: evidence for a charged Higgs boson

So in a sense should one also collaborate with what one can evaluate out in space with what one is evaluating on the ground with regard to Babar and LHC?

Any thoughts or opinions on that?

Sunday, June 12, 2011

Oh My God Particles

"The soul is awestruck and shudders at the sight of the beautiful." Plato

Leon Max Lederman (born July 15, 1922) is an American experimental physicist and Nobel Prize in Physics laureate for his work with neutrinos. He is Director Emeritus of Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. He founded the Illinois Mathematics and Science Academy, in Aurora, Illinois in 1986, and has served in the capacity of Resident Scholar since 1998.


 The lessons of history are clear. The more exotic, the more abstract the knowledge, the more profound will be its consequences." Leon Lederman, from an address to the Franklin Institute, 1995
***





Centaurus A - one of the closest galaxies with an active galactic nucleus - although it is over 10 million light years away. If you are looking for a likely source of ultra-high-energy cosmic rays - you may not need to look further. Credit: ESO.

Recent observations by the Pierre Auger Observatory have found a strong correlation between extragalactic cosmic rays patterns and the distribution of nearby galaxies with active galactic nuclei. Biermann and Souza have now come up with an evidence-based model for the origin of galactic and extragalactic cosmic rays – which has a number of testable predictions.


They propose that extragalactic cosmic rays are spun up in supermassive black hole accretion disks, which are the basis of active galactic nuclei. Furthermore, they estimate that nearly all extragalactic cosmic rays that reach Earth come from Centaurus A. So, no huge mystery – indeed a rich area for further research. Particles from an active supermassive black hole accretion disk in another galaxy are being delivered to our doorstep. See:Universe Today: Astronomy Without A Telescope – Oh-My-God Particles
***
The links that follow below are dated and may be open to corrections with current data.


Oh-My-God particle
On the evening of October 15, 1991, an ultra-high energy cosmic particle was observed over Salt Lake City, Utah. Dubbed the "Oh-My-God particle" (a play on the nickname "God particle" for the Higgs boson), it was estimated to have an energy of approximately 3 × 1020 electronvolts, equivalent to about 50 joules—in other words, it was a subatomic particle with macroscopic kinetic energy, comparable to that of a fastball, or to the mass-energy of a microbe. It was most likely a proton travelling with almost the speed of light (in the case that it was a proton its speed was approximately (1 - 4.9 × 10-24)c – after traveling one light year the particle would be only 46 nanometres behind a photon that left at the same time) and its observation was a shock to astrophysicists.

Since the first observation, by the University of Utah's Fly's Eye 2, at least fifteen similar events have been recorded, confirming the phenomenon. The source of such high energy particles remains a mystery, especially since interactions with blue-shifted cosmic microwave background radiation limit the distance that these particles can travel before losing energy (the Greisen-Zatsepin-Kuzmin limit).

Because of its mass the Oh-My-God particle would have experienced very little influence from cosmic electromagnetic and gravitational fields, and so its trajectory should be easily calculable. However, nothing of note was found in the estimated direction of its origin.

***

If some of physicists' favourite theories about extra dimensions are correct, it would also be possible for high-energy cosmic-ray particles from space to create black holes when they collide with molecules in the Earth's atmosphere. These black holes would be invisibly small, with a mass of only 10 micrograms or so. And they would be so unstable that they would explode in a burst of particles within around a billion-billion-billionth of a second.




One of the mysterious "Centauro" events seen by the Brazil ­Japan collaboration operating X-ray emulsion chambers at an altitude of 5200 m on Mt Chacaltaya in the Bolivian Andes. Given the number of hadrons seen in the lower chamber (left) physicists are intrigued by the relative lack of corresponding electromagnetic effects in the upper chamber (right).


Can Centauros or Chirons be the first observations
of evaporating mini Black Holes?



Among the various extensions of the Standard Model to energies beyond 1 TeV, one of the most attractive alternatives to the (Supersymmetric?) Great Desert Scenario is the TeV-gravity hypothesis with large extra dimensions [1]. According to it, matter particles and vector gauge bosons are open-string excitations, attached to a 3-brane (our world), which is embedded into compactified D-dimensional bulk space, where the closed-string excitations, including gravity, can propagate. This is the simplest possibility. Specific realizations of this idea and alternative scenaria may be found in [2]. Apart from a certain philosophic and aesthetic attraction of such models, they lead to the exciting possibility of experimental discovery of unification of the Standard Model with Quantum Gravity within the next few years, in the forthcoming accelerator, neutrino and cosmic-ray experiments [3, 4, 5].

Moreover, one could even claim that Quantum Gravity phenomena are already present in existing cosmic-ray data [6]. In the present paper we shall argue that the long-known Centauro-like events (CLEs) may be due to the formation and subsequent evaporation of mini black holes (MBHs), predicted in TeV-gravity models.

See:

Saturday, April 30, 2011

Space Shuttle Endeavour

Space Shuttle Endeavour

By recording the traces cosmic rays make as they pass through, the AMS might uncover a universe that is now invisible. Although Ting is hesitant to make predictions about what the instrument will find, he said the instrument was designed with dark matter and antimatter in mind. Very little is known about dark matter although it makes up an estimated 90 percent of the mass in the universe.

Although Earth-based facilities have been built to create powerful streams of subatomic particles, Ting said their limits are more than 14 million times weaker than the power produced by cosmic rays in space.

"No matter how large an accelerator you build, you're not going to compete with space," Ting told reporters recently. Ting offered the news media a close look at the AMS before it was packed for loading into Endeavour's cargo bay for launch.

See: AMS to Focus on Invisible Universe

Thursday, March 10, 2011

NASA's Fermi Catches Thunderstorms Hurling Antimatter into Space

How thunderstorms launch particle beams into space

Scientists using NASA's Fermi Gamma-ray Space Telescope have detected beams of antimatter produced above thunderstorms on Earth, a phenomenon never seen before.

Scientists think the antimatter particles were formed in a terrestrial gamma-ray flash (TGF), a brief burst produced inside thunderstorms and shown to be associated with lightning. It is estimated that about 500 TGFs occur daily worldwide, but most go undetected.

"These signals are the first direct evidence that thunderstorms make antimatter particle beams," said Michael Briggs, a member of Fermi's Gamma-ray Burst Monitor (GBM) team at the University of Alabama in Huntsville (UAH). He presented the findings Monday, during a news briefing at the American Astronomical Society meeting in Seattle.
See:NASA's Fermi Catches Thunderstorms Hurling Antimatter into Space

Sunday, December 12, 2010

The Compact Muon Solenoid......

Coordinates: 46°18′34″N 6°4′37″E / 46.30944°N 6.07694°E / 46.30944; 6.07694
Large Hadron Collider (LHC)
LHC.svg
LHC experiments
ATLAS A Toroidal LHC Apparatus
CMS Compact Muon Solenoid
LHCb LHC-beauty
ALICE A Large Ion Collider Experiment
TOTEM Total Cross Section, Elastic Scattering and Diffraction Dissociation
LHCf LHC-forward
MoEDAL Monopole and Exotics Detector At the LHC
LHC preaccelerators
p and Pb Linear accelerators for protons (Linac 2) and Lead (Linac 3)
(not marked) Proton Synchrotron Booster
PS Proton Synchrotron
SPS Super Proton Synchrotron

View of the CMS endcap through the barrel sections. The ladder to the lower right gives an impression of scale.
......(CMS) experiment is one of two large general-purpose particle physics detectors built on the proton-proton Large Hadron Collider (LHC) at CERN in Switzerland and France. Approximately 3,600 people from 183 scientific institutes, representing 38 countries form the CMS collaboration who built and now operate the detector.[1] It is located in an underground cavern at Cessy in France, just across the border from Geneva.

Contents

Background

Recent collider experiments such as the now-dismantled Large Electron-Positron Collider at CERN and the (as of 2010) still running Tevatron at Fermilab have provided remarkable insights into, and precision tests of the Standard Model of Particle Physics. However, a number of questions remain unanswered.

A principal concern is the lack of any direct evidence for the Higgs Boson, the particle resulting from the Higgs mechanism which provides an explanation for the masses of elementary particles. Other questions include uncertainties in the mathematical behaviour of the Standard Model at high energies, the lack of any particle physics explanation for dark matter and the reasons for the imbalance of matter and antimatter observed in the Universe.

The Large Hadron Collider and the associated experiments are designed to address a number of these questions.

Physics goals

The main goals of the experiment are:
The ATLAS experiment, at the other side of the LHC ring is designed with similar goals in mind, and the two experiments are designed to complement each other both to extend reach and to provide corroboration of findings.

Detector summary

CMS is designed as a general-purpose detector, capable of studying many aspects of proton collisions at 14 TeV, the center-of-mass energy of the LHC particle accelerator. It contains subsystems which are designed to measure the energy and momentum of photons, electrons, muons, and other products of the collisions. The innermost layer is a silicon-based tracker. Surrounding it is a scintillating crystal electromagnetic calorimeter, which is itself surrounded with a sampling calorimeter for hadrons. The tracker and the calorimetry are compact enough to fit inside the CMS solenoid which generates a powerful magnetic field of 3.8 T. Outside the magnet are the large muon detectors, which are inside the return yoke of the magnet.




The set up of the CMS. In the middle, under the so-called barrel there is a man for scale. (HCAL=hadron calorimeter, ECAL=electromagnetic calorimeter)

CMS by layers


A slice of the CMS detector.
For full technical details about the CMS detector, please see the Technical Design Report.

The interaction point

This is the point in the centre of the detector at which proton-proton collisions occur between the two counter-rotating beams of the LHC. At each end of the detector magnets focus the beams into the interaction point. At collision each beam has a radius of 17 μm and the crossing angle between the beams is 285 μrad.
At full design luminosity each of the two LHC beams will contain 2,808 bunches of 1.15×1011 protons. The interval between crossings is 25 ns, although the number of collisions per second is only 31.6 million due to gaps in the beam as injector magnets are activated and deactivated.

At full luminosity each collision will produce an average of 20 proton-proton interactions. The collisions occur at a centre of mass energy of 14 TeV. It is worth noting that the actual interactions occur between quarks rather than protons, and so the actual energy involved in each collision will be lower, as determined by the parton distribution functions.

The first which ran in September 2008 was expected to operate at a lower collision energy of 10 TeV but this was prevented by the 19 September 2008 shutdown. When at this target level, the LHC will have a significantly reduced luminosity, due to both fewer proton bunches in each beam and fewer protons per bunch. The reduced bunch frequency does allow the crossing angle to be reduced to zero however, as bunches are far enough spaced to prevent secondary collisions in the experimental beampipe.

Layer 1 – The tracker


The silicon strip tracker of CMS.
Immediately around the interaction point the inner tracker serves to identify the tracks of individual particles and match them to the vertices from which they originated. The curvature of charged particle tracks in the magnetic field allows their charge and momentum to be measured.

The CMS silicon tracker consists of 13 layers in the central region and 14 layers in the endcaps. The innermost three layers (up to 11 cm radius) consist of 100×150 μm pixels, 66 million in total.
The next four layers (up to 55 cm radius) consist of 10 cm × 180 μm silicon strips, followed by the remaining six layers of 25 cm × 180 μm strips, out to a radius of 1.1 m. There are 9.6 million strip channels in total.
During full luminosity collisions the occupancy of the pixel layers per event is expected to be 0.1%, and 1–2% in the strip layers. The expected SLHC upgrade will increase the number of interactions to the point where over-occupancy may significantly reduce trackfinding effectiveness.

This part of the detector is the world's largest silicon detector. It has 205 m2 of silicon sensors (approximately the area of a tennis court) comprising 76 million channels.[2]

Layer 2 – The Electromagnetic Calorimeter

The Electromagnetic Calorimeter (ECAL) is designed to measure with high accuracy the energies of electrons and photons.

The ECAL is constructed from crystals of lead tungstate, PbWO4. This is an extremely dense but optically clear material, ideal for stopping high energy particles. It has a radiation length of χ0 = 0.89 cm, and has a rapid light yield, with 80% of light yield within one crossing time (25 ns). This is balanced however by a relatively low light yield of 30 photons per MeV of incident energy.

The crystals used have a front size of 22 mm × 22 mm and a depth of 230 mm. They are set in a matrix of carbon fibre to keep them optically isolated, and backed by silicon avalanche photodiodes for readout. The barrel region consists of 61,200 crystals, with a further 7,324 in each of the endcaps.

At the endcaps the ECAL inner surface is covered by the preshower subdetector, consisting of two layers of lead interleaved with two layers of silicon strip detectors. Its purpose is to aid in pion-photon discrimination.

Layer 3 – The Hadronic Calorimeter


Half of the Hadron Calorimeter
The purpose of the Hadronic Calorimeter (HCAL) is both to measure the energy of individual hadrons produced in each event, and to be as near to hermetic around the interaction region as possible to allow events with missing energy to be identified.

The HCAL consists of layers of dense material (brass or steel) interleaved with tiles of plastic scintillators, read out via wavelength-shifting fibres by hybrid photodiodes. This combination was determined to allow the maximum amount of absorbing material inside of the magnet coil.

The high pseudorapidity region (3.0 < | η | < 5.0) is instrumented by the Hadronic Forward detector. Located 11 m either side of the interaction point, this uses a slightly different technology of steel absorbers and quartz fibres for readout, designed to allow better separation of particles in the congested forward region.
The brass used in the endcaps of the HCAL used to be Russian artillery shells.[3]

Layer 4 – The magnet

Like most particle physics detectors, CMS has a large solenoid magnet. This allows the charge/mass ratio of particles to be determined from the curved track that they follow in the magnetic field. It is 13 m long and 6 m in diameter, and its refrigerated superconducting niobium-titanium coils were originally intended to produce a 4 T magnetic field. It was recently announced that the magnet will run at 3.8 T instead of the full design strength in order to maximize longevity.[4]

The inductance of the magnet is 14 Η and the nominal current for 4 T is 19,500 A, giving a total stored energy of 2.66 GJ, equivalent to about half-a-tonne of TNT. There are dump circuits to safely dissipate this energy should the magnet quench. The circuit resistance (essentially just the cables from the power converter to the cryostat) has a value of 0.1 mΩ which leads to a circuit time constant of nearly 39 hours. This is the longest time constant of any circuit at CERN. The operating current for 3.8 T is 18,160 A, giving a stored energy of 2.3 GJ.

Layer 5 – The muon detectors and return yoke

To identify muons and measure their momenta, CMS uses three types of detector: drift tubes (DT), cathode strip chambers (CSC) and resistive plate chambers (RPC). The DTs are used for precise trajectory measurements in the central barrel region, while the CSCs are used in the end caps. The RPCs provide a fast signal when a muon passes through the muon detector, and are installed in both the barrel and the end caps.

Collecting and collating the data

Pattern recognition


Testing the data read-out electronics for the tracker.
New particles discovered in CMS will be typically unstable and rapidly transform into a cascade of lighter, more stable and better understood particles. Particles travelling through CMS leave behind characteristic patterns, or ‘signatures’, in the different layers, allowing them to be identified. The presence (or not) of any new particles can then be inferred.

Trigger system

To have a good chance of producing a rare particle, such as a Higgs boson, a very large number of collisions are required. Most collision events in the detector are "soft" and do not produce interesting effects. The amount of raw data from each crossing is approximately 1 MB, which at the 40 MHz crossing rate would result in 40 TB of data a second, an amount that the experiment cannot hope to store or even process properly. The trigger system reduces the rate of interesting events down to a manageable 100 per second.
To accomplish this, a series of "trigger" stages are employed. All the data from each crossing is held in buffers within the detector while a small amount of key information is used to perform a fast, approximate calculation to identify features of interest such as high energy jets, muons or missing energy. This "Level 1" calculation is completed in around 1 µs, and event rate is reduced by a factor of about thousand down to 50 kHz. All these calculations are done on fast, custom hardware using reprogrammable FPGAs.

If an event is passed by the Level 1 trigger all the data still buffered in the detector is sent over fibre-optic links to the "High Level" trigger, which is software (mainly written in C++) running on ordinary computer servers. The lower event rate in the High Level trigger allows time for much more detailed analysis of the event to be done than in the Level 1 trigger. The High Level trigger reduces the event rate by a further factor of about a thousand down to around 100 events per second. These are then stored on tape for future analysis.

Data analysis

Data that has passed the triggering stages and been stored on tape is duplicated using the Grid to additional sites around the world for easier access and redundancy. Physicists are then able to use the Grid to access and run their analyses on the data.
Some possible analyses might be:
  • Looking at events with large amounts of apparently missing energy, which implies the presence of particles that have passed through the detector without leaving a signature, such as neutrinos.
  • Looking at the kinematics of pairs of particles produced by the decay of a parent, such as the Z boson decaying to a pair of electrons or the Higgs boson decaying to a pair of tau leptons or photons, to determine the properties and mass of the parent.
  • Looking at jets of particles to study the way the quarks in the collided protons have interacted.

Milestones

1998 Construction of surface buildings for CMS begins.
2000 LEP shut down, construction of cavern begins.
2004 Cavern completed.
10 September 2008 First beam in CMS.
23 November 2009 First collisions in CMS.
30 March 2010 First 7 TeV collisions in CMS.

See also


References

  1. ^ [1]
  2. ^ CMS installs the world's largest silicon detector, CERN Courier, Feb 15, 2008
  3. ^ CMS HCAL history - CERN
  4. ^ http://iopscience.iop.org/1748-0221/5/03/T03021/pdf/1748-0221_5_03_T03021.pdf Precise mapping of the magnetic field in the CMS barrel yoke using cosmic rays

External links

Thursday, December 09, 2010

Muon










The Moon's cosmic ray shadow, as seen in secondary muons generated by cosmic rays in the atmosphere, and detected 700 meters below ground, at the Soudan II detector.
Composition: Elementary particle
Particle statistics: Fermionic
Group: Lepton
Generation: Second
Interaction: Gravity, Electromagnetic,
Weak
Symbol(s): μ
Antiparticle: Antimuon (μ+)
Theorized:
Discovered: Carl D. Anderson (1936)
Mass: 105.65836668(38) MeV/c2
Mean lifetime: 2.197034(21)×10−6 s[1]
Electric charge: −1 e
Color charge: None
Spin: 12


The muon (from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with a negative electric charge and a spin of ½. Together with the electron, the tau, and the three neutrinos, it is classified as a lepton. It is an unstable subatomic particle with the second longest mean lifetime (2.2 µs), exceeded only by that of the free neutron (~15 minutes). Like all elementary particles, the muon has a corresponding antiparticle of opposite charge but equal mass and spin: the antimuon (also called a positive muon). Muons are denoted by μ and antimuons by μ+. Muons were previously called mu mesons, but are not classified as mesons by modern particle physicists (see History).

Muons have a mass of 105.7 MeV/c2, which is about 200 times the mass of an electron. Since the muon's interactions are very similar to those of the electron, a muon can be thought of as a much heavier version of the electron. Due to their greater mass, muons are not as sharply accelerated when they encounter electromagnetic fields, and do not emit as much bremsstrahlung radiation. Thus muons of a given energy penetrate matter far more deeply than electrons, since the deceleration of electrons and muons is primarily due to energy loss by this mechanism. So-called "secondary muons", generated by cosmic rays hitting the atmosphere, can penetrate to the Earth's surface and into deep mines.

As with the case of the other charged leptons, the muon has an associated muon neutrino. Muon neutrinos are denoted by νμ.

Contents

History

Muons were discovered by Carl D. Anderson and Seth Neddermeyer at Caltech in 1936, while studying cosmic radiation. Anderson had noticed particles that curved differently from electrons and other known particles when passed through a magnetic field. They were negatively charged but curved less sharply than electrons, but more sharply than protons, for particles of the same velocity. It was assumed that the magnitude of their negative electric charge was equal to that of the electron, and so to account for the difference in curvature, it was supposed that their mass was greater than an electron but smaller than a proton. Thus Anderson initially called the new particle a mesotron, adopting the prefix meso- from the Greek word for "mid-". Shortly thereafter, additional particles of intermediate mass were discovered, and the more general term meson was adopted to refer to any such particle. To differentiate between different types of mesons, the mesotron was in 1947 renamed the mu meson (the Greek letter μ (mu) corresponds to m).
It was soon found that the mu meson significantly differed from other mesons: for example, its decay products included a neutrino and an antineutrino, rather than just one or the other, as was observed with other mesons. Other mesons were eventually understood to be hadrons—that is, particles made of quarks—and thus subject to the residual strong force. In the quark model, a meson is composed of exactly two quarks (a quark and antiquark) unlike baryons, which are composed of three quarks. Mu mesons, however, were found to be fundamental particles (leptons) like electrons, with no quark structure. Thus, mu mesons were not mesons at all (in the new sense and use of the term meson), and so the term mu meson was abandoned, and replaced with the modern term muon.

Another particle (the pion, with which the muon was initially confused) had been predicted by theorist Hideki Yukawa:[2]

"It seems natural to modify the theory of Heisenberg and Fermi in the following way. The transition of a heavy particle from neutron state to proton state is not always accompanied by the mission of light particles. The transition is sometimes taken up by another heavy particle."

The existence of the muon was confirmed in 1937 by J. C. Street and E. C. Stevenson's cloud chamber experiment.[3] The discovery of the muon seemed so incongruous and surprising at the time that Nobel laureate I. I. Rabi famously quipped, "Who ordered that?"

In a 1941 experiment on Mount Washington in New Hampshire, muons were used to observe the time dilation predicted by special relativity for the first time.[4]

Muon sources

Since the production of muons requires an available center of momentum frame energy of 105.7 MeV, neither ordinary radioactive decay events nor nuclear fission and fusion events (such as those occurring in nuclear reactors and nuclear weapons) are energetic enough to produce muons. Only nuclear fission produces single-nuclear-event energies in this range, but do not produce muons as the production of a single muon would violate the conservation of quantum numbers (see under "muon decay" below).

On Earth, most naturally occurring muons are created by cosmic rays, which consist mostly of protons, many arriving from deep space at very high energy[5]

About 10,000 muons reach every square meter of the earth's surface a minute; these charged particles form as by-products of cosmic rays colliding with molecules in the upper atmosphere. Travelling at relativistic speeds, muons can penetrate tens of meters into rocks and other matter before attenuating as a result of absorption or deflection by other atoms.

When a cosmic ray proton impacts atomic nuclei of air atoms in the upper atmosphere, pions are created. These decay within a relatively short distance (meters) into muons (the pion's preferred decay product), and neutrinos. The muons from these high energy cosmic rays generally continue in about the same direction as the original proton, at a very high velocity. Although their lifetime without relativistic effects would allow a half-survival distance of only about 0.66 km (660 meters) at most (as seen from Earth) the time dilation effect of special relativity (from the viewpoint of the Earth) allows cosmic ray secondary muons to survive the flight to the Earth's surface, since in the Earth frame, the muons have a longer half-life due to their velocity. From the viewpoint (inertial frame) of the muon, on the other hand, it is the length contraction effect of special relativity which allows this penetration, since in the muon frame, its lifetime is unaffected, but the distance through the atmosphere and earth appears far shorter than these distances in the Earth rest-frame. Both are equally valid ways of explaining the fast muon's unusual survival over distances.

Since muons are unusually penetrative of ordinary matter, like neutrinos, they are also detectable deep underground (700 meters at the Soudan II detector) and underwater, where they form a major part of the natural background ionizing radiation. Like cosmic rays, as noted, this secondary muon radiation is also directional.

The same nuclear reaction described above (i.e. hadron-hadron impacts to produce pion beams, which then quickly decay to muon beams over short distances) is used by particle physicists to produce muon beams, such as the beam used for the muon g − 2 experiment.[6]

Muon decay


The most common decay of the muon
Muons are unstable elementary particles and are heavier than electrons and neutrinos but lighter than all other matter particles. They decay via the weak interaction. Because lepton numbers must be conserved, one of the product neutrinos of muon decay must be a muon-type neutrino and the other an electron-type antineutrino (antimuon decay produces the corresponding antiparticles, as detailed below). Because charge must be conserved, one of the products of muon decay is always an electron of the same charge as the muon (a positron if it is a positive muon). Thus all muons decay to at least an electron, and two neutrinos. Sometimes, besides these necessary products, additional other particles that have a net charge and spin of zero (i.e. a pair of photons, or an electron-positron pair), are produced.

The dominant muon decay mode (sometimes called the Michel decay after Louis Michel) is the simplest possible: the muon decays to an electron, an electron-antineutrino, and a muon-neutrino. Antimuons, in mirror fashion, most often decay to the corresponding antiparticles: a positron, an electron-neutrino, and a muon-antineutrino. In formulaic terms, these two decays are:
\mu^-\to e^- + \bar\nu_e + \nu_\mu,~~~\mu^+\to e^+ + \nu_e + \bar\nu_\mu.
The mean lifetime of the (positive) muon is 2.197 019 ± 0.000 021 μs[7]. The equality of the muon and anti-muon lifetimes has been established to better than one part in 104.

The tree-level muon decay width is
\Gamma=\frac{G_F^2 m_\mu^5}{192\pi^3}I\left(\frac{m_e^2}{m_\mu^2}\right),
where I(x) = 1 − 8x − 12x2lnx + 8x3x4;  G_F^2 is the Fermi coupling constant.
The decay distributions of the electron in muon decays have been parameterised using the so-called Michel parameters. The values of these four parameters are predicted unambiguously in the Standard Model of particle physics, thus muon decays represent a good test of the space-time structure of the weak interaction. No deviation from the Standard Model predictions has yet been found.

Certain neutrino-less decay modes are kinematically allowed but forbidden in the Standard Model. Examples forbidden by lepton flavour conservation are
\mu^-\to e^- + \gamma and \mu^-\to e^- + e^+ + e^-.
Observation of such decay modes would constitute clear evidence for physics beyond the Standard Model (BSM). Current experimental upper limits for the branching fractions of such decay modes are in the range 10−11 to 10−12.

Muonic atoms

The muon was the first elementary particle discovered that does not appear in ordinary atoms. Negative muons can, however, form muonic atoms (also called mu-mesic atoms), by replacing an electron in ordinary atoms. Muonic hydrogen atoms are much smaller than typical hydrogen atoms because the much larger mass of the muon gives it a much smaller ground-state wavefunction than is observed for the electron. In multi-electron atoms, when only one of the electrons is replaced by a muon, the size of the atom continues to be determined by the other electrons, and the atomic size is nearly unchanged. However, in such cases the orbital of the muon continues to be smaller and far closer to the nucleus than the atomic orbitals of the electrons.

A positive muon, when stopped in ordinary matter, can also bind an electron and form an exotic atom known as muonium (Mu) atom, in which the muon acts as the nucleus. The positive muon, in this context, can be considered a pseudo-isotope of hydrogen with one ninth of the mass of the proton. Because the reduced mass of muonium, and hence its Bohr radius, is very close to that of hydrogen[clarification needed], this short-lived "atom" behaves chemically — to a first approximation — like hydrogen, deuterium and tritium.

Use in measurement of the proton charge radius

The recent culmination of a twelve year experiment investigating the proton's charge radius involved the use of muonic hydrogen. This form of hydrogen is composed of a muon orbiting a proton[8]. The Lamb shift in muonic hydrogen was measured by driving the muon from the from its 2s state up to an excited 2p state using a laser. The frequency of the photon required to induce this transition was revealed to be 50 terahertz which, according to present theories of quantum electrodynamics, yields a value of 0.84184 ± 0.00067 femtometres for the charge radius of the proton.[9]

Anomalous magnetic dipole moment

The anomalous magnetic dipole moment is the difference between the experimentally observed value of the magnetic dipole moment and the theoretical value predicted by the Dirac equation. The measurement and prediction of this value is very important in the precision tests of QED (quantum electrodynamics). The E821 experiment at Brookhaven National Laboratory (BNL) studied the precession of muon and anti-muon in a constant external magnetic field as they circulated in a confining storage ring. The E821 Experiment reported the following average value (from the July 2007 review by Particle Data Group)
a = \frac{g-2}{2} = 0.00116592080(54)(33)
where the first errors are statistical and the second systematic.

The difference between the g-factors of the muon and the electron is due to their difference in mass. Because of the muon's larger mass, contributions to the theoretical calculation of its anomalous magnetic dipole moment from Standard Model weak interactions and from contributions involving hadrons are important at the current level of precision, whereas these effects are not important for the electron. The muon's anomalous magnetic dipole moment is also sensitive to contributions from new physics beyond the Standard Model, such as supersymmetry. For this reason, the muon's anomalous magnetic moment is normally used as a probe for new physics beyond the Standard Model rather than as a test of QED (Phys.Lett. B649, 173 (2007)).

See also

References

  1. ^ K. Nakamura et al. (Particle Data Group), J. Phys. G 37, 075021 (2010), URL: http://pdg.lbl.gov
  2. ^ Yukaya Hideka, On the Interaction of Elementary Particles 1, Proceedings of the Physico-Mathematical Society of Japan (3) 17, 48, pp 139-148 (1935). (Read 17 November 1934)
  3. ^ New Evidence for the Existence of a Particle Intermediate Between the Proton and Electron", Phys. Rev. 52, 1003 (1937).
  4. ^ David H. Frisch and James A. Smith, "Measurement of the Relativistic Time Dilation Using Muons", American Journal of Physics, 31, 342, 1963, cited by Michael Fowler, "Special Relativity: What Time is it?"
  5. ^ S. Carroll (2004). Spacetime and Geometry: An Introduction to General Relativity. Addison Wesly. p. 204
  6. ^ Brookhaven National Laboratory (30 July 2002). "Physicists Announce Latest Muon g-2 Measurement". Press release. http://www.bnl.gov/bnlweb/pubaf/pr/2002/bnlpr073002.htm. Retrieved 2009-11-14. 
  7. ^ [1]
  8. ^ TRIUMF Muonic Hydrogen collaboration. "A brief description of Muonic Hydrogen research". Retrieved 2010-11-7
  9. ^ Pohl, Randolf et al. "The Size of the Proton" Nature 466, 213-216 (8 July 2010)

External links


***
Comment on Backreaction made to Steven

Hi Steven

Would we not be correct to say that unification with the small would be most apropos indeed with the large?

Pushing through that veil.

My interest with the QGP is well documented, as it presented itself "with an interesting location" with which to look at during the collision process.

Natural Microscopic blackhole creations? Are such conditions possible in the natural way of things? Although quickly dissipative, they leave their mark as Cerenkov effects.

As one looks toward the cosmos this reductionist process is how one might look at the cosmos at large, as to some of it's "motivations displayed" in the cosmos?

What conditions allow such reductionism at play to consider the end result of geometrical propensity as a message across the vast distance of space, so as to "count these effects" here on earth?

Let's say cosmos particle collisions and LHC are hand in hand "as to decay of the original particles in space" as they leave their imprint noticeably in the measures of SNO or Icecube, but help us discern further effects of that decay chain as to the constitutions of LHC energy progressions of particles in examination?

Emulating the conditions in LHC progression, adaptability seen then from such progressions, working to produce future understandings. Muon detections through the earth?

So "modeled experiments" in which "distillation of thought" are helped to be reduced too, in kind, lead to matter forming ideas with which to progress? Measure. Self evident.

You see the view has to be on two levels, maybe as a poet using words to describe, or as a artist, trying to explain the natural world. The natural consequence, of understanding of our humanity and it's continuations expressed as abstract thought of our interactions with the world at large, unseen, and miscomprehended?

Do you think Superstringy has anything to do with what I just told you here?:)

Best,

    Hi Steven,

    Maybe the following will help, and then I will lead up to a modern version for consideration, so you understand the relation.

    Keep Gran Sasso in your mind as you look at what I am giving you.

    The underground laboratory, which opened in 1989, with its low background radiation is used for experiments in particle and nuclear physics,including the study of neutrinos, high-energy cosmic rays, dark matter, nuclear decay, as well as geology, and biology-wiki


    Neutrinos, get set, go!

    This summer, CERN gave the starting signal for the long-distance neutrino race to Italy. The CNGS facility (CERN Neutrinos to Gran Sasso), embedded in the laboratory's accelerator complex, produced its first neutrino beam. For the first time, billions of neutrinos were sent through the Earth's crust to the Gran Sasso laboratory, 732 kilometres away in Italy, a journey at almost the speed of light which they completed in less than 2.5 milliseconds. The OPERA experiment at the Gran Sasso laboratory was then commissioned, recording the first neutrino tracks.

    Because I am a layman, does not reduce the understanding that I can have, that a scientist may have.

    Now for the esoteric :)

    Secrets of the Pyramids In a boon for archaeology, particle physicists plan to probe ancient structures for tombs and other hidden chambers. The key to the technology is the muon, a cousin of the electron that rains harmlessly from the sky.

    What kind of result would they get from using the muon. What will it tell them?:)

    Best,