Event with Four Muons

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

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

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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

• Backreaction: Micro Black Holes [Backreaction @ backreaction.blogspot.com/2006] [trackback posted Fri Sep 22 15:38:00 2006]

• Backreaction: Dangerous Implications? [Backreaction @ backreaction.blogspot.com/2008] [trackback posted Mon Mar 10 19:10:33 2008]

• Hawking radiation - Wikipedia, the free encyclopedia [Wikipedia @ en.wikipedia.org/wiki] [trackback posted Wed May 20 12:44:11 2009]

• Black hole - Wikipedia, the free encyclopedia [Wikipedia @ en.wikipedia.org/wiki] [trackback posted Wed Oct 15 03:57:08 2008]

• Safety of particle collisions at the Large Hadron Collider - Wikipedia, the free encyclopedia [Wikipedia @ en.wikipedia.org/wiki] [trackback posted Sat Feb 21 21:42:47 2009]

• Micro black hole - Wikipedia, the free encyclopedia [Wikipedia @ en.wikipedia.org/wiki] [trackback posted Mon Dec 22 03:02:39 2008]

• Top Cited Articles of All Time (2009 edition) in hep-ph [slac-spires @ www.slac.stanford.edu/spires] [trackback posted Mon Mar 8 05:02:01 2010]

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

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?

Higgs Update Today

Backgrounder:

Guido Tonelli(CMS spokesperson) Higgs update English 1404258

Fabiola Gianotti (ATLAS spokesperson) Higgs update English 1403055

Heuer with Gianotti and Tonelli

See:

• Higgs Update Today: Inconclusive, As Expected

• Firm Evidence Of A Higgs Boson At Last!

See Also:

• Possible Hints of the Higgs Remain in Latest Analyses

• Possible signs of the Higgs remain in latest analyses

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.

Tools For Cern Public Annoucement

CERN PUBLIC SEMINAR

 Tuesday, December 13, 2011 from 14:00 to 16:00 (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

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See:

• Article #1 on Standard Model Higgs: How It Is Produced at the LHC
•  Fundamental Glossary For The Higgs Broadcast
• Higgs boson
  

See Also:

• What is a Higgs boson?
• How do we search for Higgs bosons?

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

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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

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LHC finishes 2011 proton run

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.

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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 August 22, 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

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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. 

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Tscan

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:

• Picture of the Week

Update

See Also:

• CMS Physics Results
• The Plot Of The Week - Z Plus Jets
• B-Quark Jets: Keys To New Discoveries
• CMS Bosons!
• Two Jets, Two Protons, Nothing Else
• A Short Story Of Dijet Resonances
• New CMS Results On Dijet Resonances

2010 ion run: completed!

What Does the Higgs Jet Energy Sound Like?

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 (p_T). These particles are produced via fragmentation of energetic partons. The yields of these high-p_T 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-p_T 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

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.

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

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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

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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.

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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

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?

Author(s)
Alex Buche-University of Western Ontario / Perimeter Institute

Robert Myers-Perimeter Institute

Aninda Sinha-Perimeter Institute

 

Quark Soup: Applied Superstring Theory

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.

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"

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:

• the trigger system - selecting 100 interesting events per second out of 1000 million others
• the data acquisition system - channeling the data from the detectors to the storage
• the computing system - analysing 1000 Million events recorded per year

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!

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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

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.

Contents 1 Background 2 Physics goals 3 Detector summary 4 CMS by layers 4.1 The interaction point 4.2 Layer 1 – The tracker 4.3 Layer 2 – The Electromagnetic Calorimeter 4.4 Layer 3 – The Hadronic Calorimeter 4.5 Layer 4 – The magnet 4.6 Layer 5 – The muon detectors and return yoke 5 Collecting and collating the data 5.1 Pattern recognition 5.2 Trigger system 5.3 Data analysis 6 Milestones 7 See also 8 References 9 External links

Background

Recent collider experiments such as the now-dismantled Large Electron-Positron Collider at CERN and the (as of 2010^[update]) 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:

• to explore physics at the TeV scale
• to discover the Higgs boson
• to look for evidence of physics beyond the standard model, such as supersymmetry, or extra dimensions
• to study aspects of heavy ion collisions

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.

Preparing lead tungstate crystals for the ECAL

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.

The Hadron Calorimeter Barrel (in the foreground, on the yellow frame) waits to be inserted into the superconducting magnet (the silver cylinder in the centre of the red magnet yoke).

A part of the Magnet Yoke, with drift tubes and resistive-plate chambers in the barrel region.

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.

The insertion of the vacuum tank, June 2002

Add cYE+1, a component of CMS weighing 1,270 tonnes, finishes its 100 m descent into the CMS cavern, January 2007aption YE+2 descent into the cavern

Computer-generated event display of protons hitting a tungsten block just upstream of CMS on the first beam day, September 2008

See also

	Book:Large Hadron Collider
Books are collections of articles that can be downloaded or ordered in print.

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

• Della Negra, Michel; Petrilli, Achille; Herve, Alain; Foa, Lorenzo; (2006) (PDF). CMS Physics Technical Design Report Volume I: Software and Detector Performance. CERN. http://doc.cern.ch//archive/electronic/cern/preprints/lhcc/public/lhcc-2006-001.pdf. 

External links

Wikimedia Commons has media related to: Compact Muon Solenoid

• CMS home page
• CMS Outreach
• CMS Times
• CMS section from US/LHC Website
• http://petermccready.com/portfolio/07041601.html Panoramic view - click and drag to look around the experiment under construction (with sound!) (requires Quicktime)
• The assembly of the CMS detector, step by step, through a 3D animation
• The CMS Collaboration, S Chatrchyan et al. (2008-08-14). "The CMS experiment at the CERN LHC". Journal of Instrumentation 3: S08004. doi:10.1088/1748-0221/3/08/S08004. http://www.iop.org/EJ/journal/-page=extra.lhc/jinst. Retrieved 2008-08-26  (Full design documentation)