Showing posts with label Atlas. Show all posts
Showing posts with label Atlas. Show all posts

Friday, August 16, 2013

The Commissioning of the ATLAS

Atlas Experiment :Tile Calorimeter Barrel

The commissioning of the ATLAS detector with physics data started more than three years ago with cosmic rays. This has enabled us to put in place the full operation chain, from the trigger and data acquisition up to the analysis all over the world. Thanks to this intense commissioning campaign, ATLAS was ready to collect data already during the first day of LHC single beam operations on the 10th of September in 2008. Commissioning of the ATLAS detector with cosmic rays and first LHC beams
 There is no doubt that I would move fast forward to the culmination of everything that is a part of the atlas experiment to have said the final result is what is to be gained by measure. The Calorimeter view just seemed natural as the going on of Glast,  now called Fermi would have shown it's own construction as a necessary element of that measure in calorimeter design. So of course jumping ahead one needed to carry certain assumptions, and for me this was about the cosmic particle events that lay at the foundation of the universe in it's informative style as reductionist in nature.

"Black Hole" event superimposed over a classic image of the ATLAS detector.

There is a little confusion on my part here about the simultaneous view that what is in the pipeline has a strong correlation to what we seek of,  in cosmic particle collisions. The energies involved,  as decay products. So as I looked at this article and the phenomenological correspondence necessary I needed to understand that effects of such operations,  current in the cosmos could have somehow contaminated the results they were seeking through controlled processes. So how was this done is the issue here and how such data cannot be influenced by what is currently happening in the cosmos.

Neutrino Events-A compilation of some cool and unique neutrino events captured by the IceCube Neutrino Observatory.

As a layman it was of interest that my developing perspective about the cosmos at this scale sought some kind of revelation in the way research would have been done experimentally. So this was a challenge to me that I could see the scale at which the cosmos picture was developing microscopically on a large scale could have been part and parcel exemplified in this research as the cosmological view. It just seemed natural to me the effect of what was happening on earth was somehow translated in how the earth itself sat in the cosmos as a participant bathed in the cosmos glory.

webcast of seminar with ATLAS and CMS latest results from ICHEP

In a sense I have felt belittled by the idea that my seeking of the workings of the cosmos would have fell to such materialistic views. Of course I want to know how it all works.  But truly this is the way I am sure that would lead to the understanding of something very important about the way in which we can view the universe. At some point,  there is an exchange taking pace about how such matters form, and there is no other way in which to derive this but to further dissect the nature of particulate expression but by energy disposition?

COSMOS:AIRES Cosmic Ray Showers

Throughout the course of my research there has been a connecting thread that has brought me to certain conclusions about matter states as they exist in the cosmos, but by identifying the particulates of the realty in which we live. So in a way it is necessary to observe that nature we are seeing as so obvious in our observation on a fundamental level, can go much deeper as we implored the the use and need of the spectrum in this wider view of the cosmos. The backdrops necessary in determining what the energy is saying as we record the events in the calorimetry design,  how ever this is constructed.

In this same way as cosmic particle collisions are derivative of the events in the cosmos, for Atlas research,  CMS serves to support Atlas, and vice versa?? :)

See Also:

Friday, January 27, 2012

The dimensionality and geometry of the extra dimensions

We investigate possible signatures of black hole events at the LHC in the hypothesis that such objects will not evaporate completely, but leave a stable remnant. For the purpose of de fining a reference scenario, we have employed the publicly available Monte Carlo generator CHARYBDIS2, in which the remnant's behavior is mostly determined by kinematic constraints and conservation of some quantum numbers, such as the baryon charge. Our fi ndings show that electrically neutral remnants are highly favored and a signifi cantly larger amount of missing transverse momentum is to be expected with respect to the case of complete decay. See: Black Hole Remnants at the LHC by L. Bellagambab, R. Casadioa;by, R. Di Sipioa;bz and V. Viventiax 16 Jan 2012

ATLAS Experiment © 2011 CERN  "Black Hole" event superimposed over a classic image of the ATLAS detector.

If the fundamental Planck scale is of order a TeV, as the case in some extradimensions scenarios, future hadron colliders such as the Large Hadron Collider will be black hole factories. The non-perturbative process of black hole formation and decay by Hawking evaporation gives rise to spectacular events with up to many dozens of relatively hard jets and leptons, with a characteristic ratio of hadronic to leptonic activity of roughly 5:1. The total transverse energy of such events is typically a sizeable fraction of the beam energy. Perturbative hard scattering processes at energies well above the Planck scale are cloaked behind a horizon, thus limiting the ability to probe short distances. The high energy black hole cross section grows with energy at a rate determined by the dimensionality and geometry of the extra dimensions.See: High Energy Colliders as Black Hole Factories: The End of Short Distance Physics

Trackbacks for hep-ph/0106219

Wednesday, January 18, 2012

Atlas Experiment Simulated Black Hole Photos

ATLAS Experiment © 2011 CERN  A new view of a black hole event. ATLAS collision events. In some theories, microscopic black holes may be produced in particle collisions that occur when very-high-energy cosmic rays hit particles in our atmosphere. These microscopic-black-holes would decay into ordinary particles in a tiny fraction of a second and would be very difficult to observe in our atmosphere.
The ATLAS Experiment offers the exciting possibility to study them in the lab (if they exist). The simulated collision event shown is viewed along the beampipe. The event is one in which a microscopic-black-hole was produced in the collision of two protons (not shown). The microscopic-black-hole decayed immediately into many particles. The colors of the tracks show different types of particles emerging from the collision (at the center).
Photo #: black-hole-event-wide

ATLAS Experiment © 2011 CERN  "Black Hole" event superimposed over a classic image of the ATLAS detector.

See: Atlas Photos

Tuesday, January 03, 2012

ATLAS discovers its first new particle

String theory isn't just another quantum field theory, another particular finite list of elementary particles with some interactions. It's an intellectually and literally multi-dimensional reservoir of wisdom that has taught us many things of completely new kinds that we couldn't foresee. The Reference Frame: LHC: is a new particle?: LHC: is χb(3P) a new particle?

When you hold a particular point of view about nature it is important in my mind to know where the search is going and what this means overall. How we look at reality and how we look at nature.

The spectrum of the b states: the leftmost peak is the b(1P), the middle one the b(2P), and the rightmost the new b(3P). The upper plot shows the spectrum for decays involving unconverted photons, while th lower plot shows the spectra for decays involving converted photons. In the lower plot, the upper (red) curve shows the spectrum for b decays to (1S), while the lower (brown) curve shows the spectrum for decays to (2S). (Only the b(3P) peak appears distinctly in the lower spectrum because it is the only b state with decays involving enough energy to be detected in this study.) See: Atlas News

Also See: LHC heads into new year with first particle discovery

I understand how my own life can be changed from experiencing an anomaly in the everyday world? It is not proof enough. All scientists know this.

Is it better then for those who visit to know that such a thing in a condense matter view can can govern the matter states? This is part of recognizing the geometrical structure that Plato sought to establish as an underlying reality to nature? While it does not all define the matter states so successful we could attribute the universe to a soccer ball? No. For those of you who need more proof seek to find the subject of allotrope or polytopes here and you will understand what I mean.
How it can have such an impact, and to search, where our sciences have gone. I hope one day it offers up an answer. I suspect that the research in science experimentally will most likely lead the way.  I believe we will discover something quite dramatic in the coming years that seems now very unlikely.

The lure to write my experience as a truth and to offer it up as a question, is on my mind. I believe we are much closely attached to the depth of reality then we currently know. I can only write it up as fiction then.

This is part of the idea I have about the move into the cosmos as part of our education as civilians of a new cultural thematic that we will make our home out in the stars as a result of this.

Clearly I speak of the elemental nature and gravity, and this too is a pursuit in today's science that is underway. So while I speak in advance of such things, clearly it must be highlighted that this has not been accomplished yet either.

Of course there are theories out there and using them provide for a better perspective about our cosmos and the birth of it. In theory then, there is much that makes sense. In theory, it has to be experimentally proven. In theory, we construct the parameters?

If you have a particle that travels a distance and you use a calorimeter instrument to measure it's identity, then can you not seek to find a representative of calorimeter design that would suit the "time differences of something that would amount to a faster then light"....other then recognize existing mediums as a sure sign of Cerenkov?

You use the space station then? If you follow the history of high energy particles from space this left you with no alternative but to leave the domain of earth to establish some insight into the applicability of the AMS program and particle research? Dark matter research?

Tuesday, December 13, 2011

Higgs Update Today


Guido Tonelli(CMS spokesperson) Higgs update English 1404258

Fabiola Gianotti (ATLAS spokesperson) Higgs update English 1403055

Heuer with Gianotti and Tonelli

See Also:

    Fermilab scientist Don Lincoln describes the concept of how the search for the Higgs boson is accomplished. The latest data is revealed! Several large experimental groups are ht on the trail of this elusive subatomic particle which is thought to explain the origins of particle mass.

    Friday, December 09, 2011

    Tools For Cern Public Annoucement


     Tuesday, December 13, 2011 from to (Europe/Zurich)
    at CERN ( Main Auditorium )

    Tuesday, December 13, 2011
    • 14:00 - 14:30 Update on the Standard Model Higgs searches in ATLAS 30'
      Speaker: Fabiola Gianotti
    • 14:30 - 15:00 Update on the Standard Model Higgs searches in CMS 30'
      Speaker: Guido TONELLI
    • 15:00 - 16:00 Joint question session 1h0' 
    Located at Indico Cern Conference



    See Also:

    Sunday, November 06, 2011

    LHC trials proton–lead collisions

    Juggling magnetic fields to collide protons and lead

    Physicists at CERN's Large Hadron Collider (LHC) are analysing the results of their first attempt at colliding protons and lead ions. Further attempts at proton–lead collisions are expected over the next few weeks. If these trials are successful, a full-blown experimental programme could run in 2012.

    Since the Geneva lab began experiments with the LHC in 2009, it has mostly been used to send two beams of protons in opposite directions around the 27 km accelerator, with the hope of spotting, among other things, the Higgs boson in the resulting collisions. Two beams of lead ions have also been smashed into each other in order to recreate the hot dense matter, known as a quark–gluon plasma, that was present in the early universe.

    But to fully understand the results of such collisions, physicists need to know the properties of the lead ions before they collide. That is, their "cold state" before vast amounts of heat are released by the collisions. One way to do this, according to Urs Wiedemann at CERN, is to collide protons with lead ions.See:LHC trials proton–lead collisions
    A lead-ion collision as recorded by the CMS detector at the LHC. © CERN for the benefit of the CMS collaboration.

     The LHC has been smashing lead ions since Sunday, and physicists from the ALICE, ATLAS and CMS experiments are working around the clock to analyze the aftermath of these heavy-ion collisions at record energies and temperatures.* Last week we walked you through the process of creating, accelerating and colliding lead ions. Now we’ll talk about the big question: Why spend one month each year colliding heavy ions in the LHC?See:LHC basics: What we can learn from lead-ion collisions


    LHC finishes 2011 proton run

    Saturday, November 05, 2011

    Reflections on LHC experiments present latest results at Mumbai conference

    Just following up on ole news to keep abreast of what is going on with CERN.

    LHC experiments present latest results at Mumbai conference

     Geneva, 22 August 2011. Results from the ATLAS and CMS collaborations, presented at the biennial Lepton-Photon conference in Mumbai, India today, show that the elusive Higgs particle, if it exists, is running out of places to hide. Proving or disproving the existence the Higgs boson, which was postulated in the 1960s as part of a mechanism that would confer mass on fundamental particles, is among the main goals of the LHC scientific programme. ATLAS and CMS have excluded the existence of a Higgs over most of the mass region 145 to 466 GeV with 95 percent certainty.

    As well as the Higgs search results, the LHC experiments will be presenting new results across a wide range of physics. Thanks to the outstanding performance of the LHC, the experiments and the Worldwide LHC Computing Grid, some of the current analyses are based on roughly twice the data sample presented at the last major particle physics conference in July.


    The Latest Word on the Higgs from the Mumbai Conference

     Restructured the post: My preliminary discussion is first, the updates from the talks are now at the end.  The take-away message from the LHC talks: Conversations About Science with Theoretical Physicist Matt Strassler-Posted on

    Tuesday, November 01, 2011

    The Developmental Jet Process

    As a layman I have been going through the research of those better educated then I in order to construct a accurate syntactically written developed scientific process as I have become aware of it. This is what I have been doing for the last number of years so as to get some idea of the scientific process experimentally driven to this point.

    Theoretical development is important to myself,  as well as,   the underlying quest for a foundational perspective of how we can push back perspective with regard to the timeline of the universe in expression.

    This has to be experimentally written in the processes we now use to help formulate an understanding of how the universe came into being by examining local events with the distribution of the cosmological data we are accumulating. A Spherical Cow anyone?

    Jets: Article Updated An update here as well, "Two-Photons: Data and Theory Disagree"

    I do appreciate all those scientist who have been giving their time to educating the public. This is a big thank you for that devotion to the ideal of bringing society forward as to what we as a public are not privy too. As too, being not part of that 3% of the population who are far removed from the work being done in particle research.

    Almost a year ago, I had an e-mail exchange, and planned a phone call, with Maria Spiropulu of CMS. She looked particularly excited about something and the mortals may be learning what the cause was today.

    CMS turned out to be much more "aggressive" relatively to the "conservative" ATLAS detector and it has already provided us with some hints. But what they published today, in the paper called: See:
    CMS: a very large excess of diphotons

    Measurement of the Production Cross Section for Pairs of Isolated Photons in pp collisions at sqrt(s) = 7 TeV
    The integrated and differential cross sections for the production of pairs of isolated photons is measured in proton-proton collisions at a centre-of-mass energy of 7 TeV with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 36 inverse picobarns is analysed. A next-to-leading-order perturbative QCD calculation is compared to the measurements. A discrepancy is observed for regions of the phase space where the two photons have an azimuthal angle difference, Delta(phi), less than approximately 2.8. 


    Tscan ("Trivial Scanner") is an event display, traditionally called a scanner, which I developed. It is a program that shows events graphically on the computer screen.

    It was designed to be simple ("trivial") internally, and to have a simple user interface. A lot of importance was given to giving the user a large choice of options to display events in many different ways.

    Tscan proved to be a very useful tool for the development of fitters. A particularly useful feature is the ability to show custom data for every photpmultiplier tube (PMT). Instead of the usual time and charge, it can show expected charge, scattered light, likelihood, chi-squared difference, patches, and any other data that can be prepared in a text format.
    See:Trivial Scanner

    Credit: Super-Kamiokande/Tomasz Barszczak Three (or more?) Cerenkov rings

    Multiple rings of Cerenkov light brighten up this display of an event found in the Super-Kamiokande - neutrino detector in Japan. The pattern of rings - produced when electrically charged particles travel faster through the water in the detector than light does - is similar to the result if a proton had decayed into a positron and a neutral pion. The pion would decay immediately to two gamma-ray photons that would produce fuzzy rings, while the positron would shoot off in the opposite direction to produce a clearer ring. Such kinds of decay have been predicted by "grand unified theories" that link three of nature's fundamental forces - the strong, weak and electromagnetic forces. However, there is so far no evidence for such decays; this event, for example, did not stand up to closer scrutiny.


    See Also:

  • 2010 ion run: completed!
  • What Does the Higgs Jet Energy Sound Like?
  • Monday, July 11, 2011

    ALICE Enters New Territory

    A computer screen in the ALICE control room shows an event display on the night of the first heavy-ion collisions in the LHC in November 2010.
    A basic process in QCD is the energy loss of a fast parton in a medium composed of colour charges. This phenomenon, "jet quenching", is especially useful in the study of the QGP, using the naturally occurring products (jets) of the hard scattering of quarks and gluons from the incoming nuclei. A highly energetic parton (a colour charge) probes the coloured medium rather like an X-ray probes ordinary matter. The production of these partonic probes in hadronic collisions is well understood within perturbative QCD. The theory also shows that a parton traversing the medium will lose a fraction of its energy in emitting many soft (low energy) gluons. The amount of the radiated energy is proportional to the density of the medium and to the square of the path length travelled by the parton in the medium. Theory also predicts that the energy loss depends on the flavour of the parton.

    Jet quenching was first observed at RHIC by measuring the yields of hadrons with high transverse momentum (pT). These particles are produced via fragmentation of energetic partons. The yields of these high-pT particles in central nucleus–nucleus collisions were found to be a factor of five lower than expected from the measurements in proton–proton reactions. ALICE has recently published the measurement of charged particles in central heavy-ion collisions at the LHC. As at RHIC, the production of high-pT hadrons at the LHC is strongly suppressed. However, the observations at the LHC show qualitatively new features (see box). The observation from ALICE is consistent with reports from the ATLAS and CMS collaborations on direct evidence for parton energy loss within heavy-ion collisions using fully reconstructed back-to-back jets of particles associated with hard parton scatterings (CERN Courier January/February 2011 p6 and March 2011 p6). The latter two experiments have shown a strong energy imbalance between the jet and its recoiling partner (G Aad et al. 2010 and CMS collaboration 2011). This imbalance is thought to arise because one of the jets traversed the hot and dense matter, transferring a substantial fraction of its energy to the medium in a way that is not recovered by the reconstruction of the jets.See: ALICE enters new territory in heavy-ion collisions

    Click no Image for larger viewing

    Thursday, July 07, 2011

    Atlas Experiment :Tile Calorimeter Barrel

    Atlas Photos

    The tile calorimeter will collect the energy released in the LHC's proton-proton collisions. Special plastic manufacturing techniques have been adapted to mass produce the ATLAS elements.

    Tuesday, June 21, 2011

    The Sound The Universe Makes

    As most know who have come to visit here at this Blog site, my fascination with the ways in which "sensationally" and internally one might look at the universe. So of course as long as the science is there in terms of how we are interpreting events. Then,  using the underlying mechanism of that interpretation,  so that it is universally applied,  then you get to see nature in different ways.

    For example, in 1704 Sir Isaac Newton struggled to devise mathematical formulas to equate the vibrational frequency of sound waves with a corresponding wavelength of light. He failed to find his hoped-for translation algorithm, but the idea of correspondence took root, and the first practical application of it appears to be the clavecin oculaire, an instrument that played sound and light simultaneously. It was invented in 1725. Charles Darwin’s grandfather, Erasmus, achieved the same effect with a harpsichord and lanterns in 1790, although many others were built in the intervening years, on the same principle, where by a keyboard controlled mechanical shutters from behind which colored lights shne. By 1810 even Goethe was expounding correspondences between color and other senses in his book, Theory of Color. Pg 53, The Man Who Tasted Shapes, by Richard E. Cytowic, M.D.

    As a reader,  you will also see if you look deeper into this blog the historical relation of humanity always seeking to define the way we can look at nature whether it is expressed musicianly or artistically. Is to identify this deep seated need to understand the cosmos in ways that we might not of considered.

    5 types of ATLAS event shape data
    The data is first processed using the vast and all-powerful ATLAS software framework. This allows raw data (streams of ones and zeroes) to be converted step-by-step into ‘objects’ such as silicon detector hits and energy deposits. We can reconstruct particles using these objects. The next step is to convert the information into a file containing two or three columns of numbers known as a "breakpoint file". It can also be used as a "note list". This kind of file can be read by compositional software such as the Composers Desktop Project (CDP) and Csound software used for this project. See: How is Data Converted into Sounds

    Janna Levin

    I want to ask you all to consider for a second the very simple fact that, by far, most of what we know about the universe comes to us from light. We can stand on the Earth and look up at the night sky and see stars with our bare eyes. The Sun burns our peripheral vision, we see light reflected off the Moon, and in the time since Galileo pointed that rudimentary telescope at the celestial bodies, the known universe has come to us through light, across vast eras in cosmic history. And with all of our modern telescopes, we've been able to collect this stunning silent movie of the universe -- these series of snapshots that go all the way back to the Big Bang.
    And yet, the universe is not a silent movie, because the universe isn't silent. I'd like to convince you that the universe has a soundtrack, and that soundtrack is played on space itself. Because space can wobble like a drum. It can ring out a kind of recording throughout the universe of some of the most dramatic events as they unfold. Now we'd like to be able to add to a kind glorious visual composition that we have of the universe a sonic composition. And while we've never heard the sounds from space, we really should, in the next few years, start to turn up the volume on what's going on out there. See: Janna Levin: The sound the universe makes

    Radar echos from Titan's surface

    This recording was produced by converting into audible sounds some of the radar echoes received by Huygens during the last few kilometers of its descent onto Titan. As the probe approaches the ground, both the pitch and intensity increase. Scientists will use intensity of the echoes to speculate about the nature of the surface.

    Gravity is talking. LISA will listen.

    The Cosmos sings with many strong gravitational voices, causing ripples in the fabric of space and time that carry the message of tremendous astronomical events: the rapid dances of closely orbiting stellar remnants, the mergers of massive black holes millions of times heavier than the Sun, the aftermath of the Big Bang. These ripples are the gravitational waves predicted by Albert Einstein's 1915 general relativity; nearly one century later, it is now possible to detect them. Gravitational waves will give us an entirely new way to observe and understand the Universe, enhancing and complementing the insights of conventional astronomy.
    See:What Does Gravity Sound Like?

           Gravitational Wave Detectors are Best Described as "Sounds.

    See Also: LHC sound

    Wednesday, March 09, 2011

    Are There Extra Dimensions of Space?

    Are there Extra Dimensions of Space?

    A QGP is formed at the collision point of two relativistically accelerated gold ions in the center of the STAR detector at the relativistic heavy ion collider at the Brookhaven national laboratory.

    Some of these issues in relation to the LHC are what I tried to explain to Searosa.

    Brookhaven National Laboratory

    HOT A computer rendition of 4-trillion-degree Celsius quark-gluon plasma created in a demonstration of what scientists suspect shaped cosmic history.

    Here's what has to be considered. There is a calculated energy value to the collision process. You add that up as all the constituents of that process, and what's left is,  so much energy left to be discerned as particulate expressions as beyond that collision point. This may not be truly an accurate portrayal yet it is one that allows perspective to consider the spaces at such microscopic levels for consideration.

    The perspective of valuations with regard to the LHC is whether or not there is sufficient energy within the confines of LHC experiments in which to satisfy the questions about extra those dimensions. It seems the parameters of those decisions seem to be sufficient?

    Alex Buche-University of Western Ontario / Perimeter Institute

    Robert Myers-Perimeter Institute
    Aninda Sinha-Perimeter Institute


    It is believed that in the first few microseconds after the Big Bang, our universe was dominated by a strongly interacting phase of nuclear matter at extreme temperatures. An impressive experimental program at the Brookhaven National Laboratory on Long Island has been studying the properties of this nuclear plasma with some rather surprising results. We outline how there may be a deep connection between extra-dimensional gravity of String Theory and the fundamental theories of subatomic particles can solve the mystery of the near-ideal fluid properties of the strongly coupled nuclear plasma.

    The QGP has directed attention to a method of expression with regard to that collision point.

    First direct observation of jet quenching.


    At the recent seminar, the LHC’s dedicated heavy-ion experiment, ALICE, confirmed that QGP behaves like an ideal liquid, a phenomenon earlier observed at the US Brookhaven Laboratory’s RHIC facility. This question was indeed one of the main points of this first phase of data analysis, which also included the analysis of secondary particles produced in the lead-lead collisions. ALICE's results already rule out many of the existing theoretical models describing the physics of heavy-ions.

    See: 2010 ion run: completed!

    The equations of string theory specify the arrangement of the manifold configuration, along with their associated branes (green) and lines of force known as flux lines (orange). The physics that is observed in the three large dimensions depends on the size and the structure of the manifold: how many doughnut-like "handles" it has, the length and circumference of each handle, the number and locations of its branes, and the number of flux lines wrapped around each doughnut.

    Early on looking at spaces, it was a struggle for me to understand how extra dimensions would be explained. It was easy using a coordinated frame of reference as x,y,z, yet,  how much did you have to go toward seeing that rotation around each of those arrows of direction would add greater depth of perception about such spaces?

    It's easier if you just draw the picture.

    A section of the quintic Calabi–Yau three-fold (3D projection)

    In superstring theory the extra dimensions of spacetime are sometimes conjectured to take the form of a 6-dimensional Calabi–Yau manifold, which led to the idea of mirror symmetry.


    The benefit of phenomenological approaches in experimental processes to attempt to answer these theoretical points of views.


    The first results on supersymmetry from the Large Hadron Collider (LHC) have been analysed by physicists and some are suggesting that the theory may be in trouble. Data from proton collisions in both the Compact Muon Solenoid (CMS) and ATLAS experiments have shown no evidence for supersymmetric particles – or sparticles – that are predicted by this extension to the Standard Model of particle physics. Will the LHC find supersymmetry Kate McAlpine ?

    Thank you Tommaso Dorigo


    Also see:


    Beautiful theory collides with smashing particle data."

    Implications of Initial LHC Searches for Supersymmetry"

    More SUSY limits"

    Tuesday, February 22, 2011

    Keeping it Real

    The first results on supersymmetry from the Large Hadron Collider (LHC) have been analysed by physicists and some are suggesting that the theory may be in trouble. Data from proton collisions in both the Compact Muon Solenoid (CMS) and ATLAS experiments have shown no evidence for supersymmetric particles – or sparticles – that are predicted by this extension to the Standard Model of particle physics. Will the LHC find supersymmetry Kate McAlpine ?

    Thank you Tommaso Dorigo

    If such propositions are ever moved to the project of LHC confirmations then the ideals of those who proposed should never be conceived as rats as a commentator writes. It's just not polite.

    I would comment at your blog article but like Cosmic Variance I have been blocked. Oh well:)

    This information is a form of responsible action toward experimental fundamentalism we take as one moves forward.

    Atlas Experiment

    Link on Title and internal "color reference links" will highlight links to subject locations. Well worth the visit.

     The ATLAS detector consists of four major components
    (place your cursor over the links below to identify the location of the components):
    • inner detector (yellow) - measures the momentum of each charged particle
    • calorimeter (orange and green) - measures the energies carried by the particles
    • muon spectrometer (blue) - identifies and measures muons
    • magnet system (grey) - bending charged particles for momentum measurement
    The interactions in the ATLAS detectors will create an enormous dataflow. To digest this data we need:

    Monday, December 13, 2010

    2010 ion run: completed!

    First direct observation of jet quenching.

    At the recent seminar, the LHC’s dedicated heavy-ion experiment, ALICE, confirmed that QGP behaves like an ideal liquid, a phenomenon earlier observed at the US Brookhaven Laboratory’s RHIC facility. This question was indeed one of the main points of this first phase of data analysis, which also included the analysis of secondary particles produced in the lead-lead collisions. ALICE's results already rule out many of the existing theoretical models describing the physics of heavy-ions.
    See: 2010 ion run: completed!


    After a very fast switchover from protons to lead ions, the LHC has achieved performances that allowed the machine to exceed both peak and integrated luminosity by a factor of three. Thanks to this, experiments have been able to produce high-profile results on ion physics almost immediately, confirming that the LHC was able to keep its promises for ions as well as for protons.

    A seminar on 2 December was the opportunity for the ALICE, ATLAS and CMS collaborations to present their first results on ion physics in front of a packed auditorium. These results are important and are already having a major impact on the understanding of the physics processes that involve the basic constituents of matter at high energies.

    In the ion-ion collisions, the temperature is so high that partons (quarks and gluons), which are usually constrained inside the nucleons, are deconfined to form a highly dense and hot soup known as quark-gluon plasma (QGP). This type of matter existed about 1 millionth of a second after the Big Bang. By studying it, scientists hope to understand the processes that led to the formation of nucleons, which in turn became the nuclei of atoms. See:LHC completes first heavy-ion run

    See Also: Jets: Article Updated

    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 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.



    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.


    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


    1. ^ [1]
    2. ^ CMS installs the world's largest silicon detector, CERN Courier, Feb 15, 2008
    3. ^ CMS HCAL history - CERN
    4. ^ Precise mapping of the magnetic field in the CMS barrel yoke using cosmic rays

    External links