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87-603: The ATLAS accelerator at Argonne should not be confused with the ATLAS experiment at the Large Hadron Collider at CERN . Stable ion beams at ATLAS are generated from one of two sources: the 9-MV electrostatic tandem Van de Graaff accelerator or the Positive Ion Injector, a 12-MV low-velocity linac and electron cyclotron resonance (ECR) ion source. The ions are sent from one of these two into

174-408: A gamma-ray facility , and particle detectors . In 2009, Argonne added a system called CARIBU (Californium Rare Ion Breeder Upgrade) to ATLAS. The system is capable of generating beams of rare isotopes, which can then be sent to the accelerator sections. ATLAS has since received additional upgrades with two enhancements: The Electron Beam Ion System (EBIS), which enables radioactive beams to match

261-455: A positron , each with a mass of 0.511 MeV/ c , can annihilate to yield 1.022 MeV of energy. A proton has a mass of 0.938 GeV/ c . In general, the masses of all hadrons are of the order of 1 GeV/ c , which makes the GeV/ c a convenient unit of mass for particle physics: The atomic mass constant ( m u ), one twelfth of the mass a carbon-12 atom, is close to

348-785: A unit of mass , effectively using a system of natural units with c set to 1. The kilogram equivalent of 1 eV/ c is: 1 eV / c 2 = ( 1.602   176   634 × 10 − 19 C ) × 1 V ( 299   792   458 m / s ) 2 = 1.782   661   92 × 10 − 36 kg . {\displaystyle 1\;{\text{eV}}/c^{2}={\frac {(1.602\ 176\ 634\times 10^{-19}\,{\text{C}})\times 1\,{\text{V}}}{(299\ 792\ 458\;\mathrm {m/s} )^{2}}}=1.782\ 661\ 92\times 10^{-36}\;{\text{kg}}.} For example, an electron and

435-525: A bus architecture cannot keep up with the data requirements of the LHC detectors, all the ATLAS data acquisition systems rely on high-speed point-to-point links and switching networks. Even with advanced electronics for data reading and storage, the ATLAS detector generates too much raw data to read out or store everything: about 25 MB per raw event, multiplied by 40 million beam crossings per second (40 MHz ) in

522-442: A current pulse (signal) in the wire. The wires with signals create a pattern of 'hit' straws that allow the path of the particle to be determined. Between the straws, materials with widely varying indices of refraction cause ultra-relativistic charged particles to produce transition radiation and leave much stronger signals in some straws. Xenon and argon gas is used to increase the number of straws with strong signals. Since

609-434: A few centimetres from the proton beam axis, extends to a radius of 1.2 metres, and is 6.2 metres in length along the beam pipe. Its basic function is to track charged particles by detecting their interaction with material at discrete points, revealing detailed information about the types of particles and their momentum. The Inner Detector has three parts, which are explained below. The magnetic field surrounding

696-517: A larger area practical. Each strip measures 80 micrometres by 12 centimetres. The SCT is the most critical part of the inner detector for basic tracking in the plane perpendicular to the beam, since it measures particles over a much larger area than the Pixel Detector, with more sampled points and roughly equal (albeit one-dimensional) accuracy. It is composed of four double layers of silicon strips, and has 6.3 million readout channels and

783-437: A particle with electric charge q gains an energy E = qV after passing through a voltage of V . An electronvolt is the amount of energy gained or lost by a single electron when it moves through an electric potential difference of one volt . Hence, it has a value of one volt , which is 1 J/C , multiplied by the elementary charge e  =  1.602 176 634 × 10  C . Therefore, one electronvolt

870-491: A photon are related by E = h ν = h c λ = 4.135   667   696 × 10 − 15 e V / H z × 299 792 458 m / s λ {\displaystyle E=h\nu ={\frac {hc}{\lambda }}={\frac {\mathrm {4.135\ 667\ 696\times 10^{-15}\;eV/Hz} \times \mathrm {299\,792\,458\;m/s} }{\lambda }}} where h

957-413: A system of natural units in which the speed of light in vacuum c and the reduced Planck constant ħ are dimensionless and equal to unity is widely used: c = ħ = 1 . In these units, both distances and times are expressed in inverse energy units (while energy and mass are expressed in the same units, see mass–energy equivalence ). In particular, particle scattering lengths are often presented using

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1044-479: A total area of 12,000 square meters. The ATLAS detector uses two large superconducting magnet systems to bend the trajectory of charged particles, so that their momenta can be measured. This bending is due to the Lorentz force , whose modulus is proportional to the electric charge q {\displaystyle q} of the particle, to its speed v {\displaystyle v} and to

1131-430: A total area of 61 square meters. The Transition Radiation Tracker (TRT), the outermost component of the inner detector, is a combination of a straw tracker and a transition radiation detector . The detecting elements are drift tubes (straws), each four millimetres in diameter and up to 144 centimetres long. The uncertainty of track position measurements (position resolution) is about 200 micrometres. This

1218-686: A unit of inverse particle mass. Outside this system of units, the conversion factors between electronvolt, second, and nanometer are the following: ℏ = 1.054   571   817   646 × 10 − 34   J ⋅ s = 6.582   119   569   509 × 10 − 16   e V ⋅ s . {\displaystyle \hbar =1.054\ 571\ 817\ 646\times 10^{-34}\ \mathrm {J{\cdot }s} =6.582\ 119\ 569\ 509\times 10^{-16}\ \mathrm {eV{\cdot }s} .} The above relations also allow expressing

1305-403: A wavelength of 532 nm (green light) would have an energy of approximately 2.33 eV . Similarly, 1 eV would correspond to an infrared photon of wavelength 1240 nm or frequency 241.8 THz . In a low-energy nuclear scattering experiment, it is conventional to refer to the nuclear recoil energy in units of eVr, keVr, etc. This distinguishes the nuclear recoil energy from

1392-399: Is a Pythagorean equation . When a relatively high energy is applied to a particle with relatively low rest mass , it can be approximated as E ≃ p {\displaystyle E\simeq p} in high-energy physics such that an applied energy with expressed in the unit eV conveniently results in a numerically approximately equivalent change of momentum when expressed with

1479-434: Is a pixel (50 by 400 micrometres); there are roughly 47,000 pixels per module. The minute pixel size is designed for extremely precise tracking very close to the interaction point. In total, the Pixel Detector has over 92 million readout channels, which is about 50% of the total readout channels of the whole detector. Having such a large count created a considerable design and engineering challenge. Another challenge

1566-431: Is an extremely large tracking system, consisting of three parts: The extent of this sub-detector starts at a radius of 4.25 m close to the calorimeters out to the full radius of the detector (11 m). Its tremendous size is required to accurately measure the momentum of muons, which first go through all the other elements of the detector before reaching the muon spectrometer. It was designed to measure, standalone,

1653-794: Is convenient to use the electronvolt to express temperature. The electronvolt is divided by the Boltzmann constant to convert to the Kelvin scale : 1 e V / k B = 1.602   176   634 × 10 − 19  J 1.380   649 × 10 − 23  J/K = 11   604.518   12  K , {\displaystyle {1\,\mathrm {eV} /k_{\text{B}}}={1.602\ 176\ 634\times 10^{-19}{\text{ J}} \over 1.380\ 649\times 10^{-23}{\text{ J/K}}}=11\ 604.518\ 12{\text{ K}},} where k B

1740-507: Is designed to detect these particles, namely their masses, momentum , energies , lifetime, charges, and nuclear spins . Experiments at earlier colliders, such as the Tevatron and Large Electron–Positron Collider , were also designed for general-purpose detection. However, the beam energy and extremely high rate of collisions require ATLAS to be significantly larger and more complex than previous experiments, presenting unique challenges of

1827-421: Is equal to 1.602 176 634 × 10  J . The electronvolt (eV) is a unit of energy, but is not an SI unit . It is a commonly used unit of energy within physics, widely used in solid state , atomic , nuclear and particle physics, and high-energy astrophysics . It is commonly used with SI prefixes milli- (10 ), kilo- (10 ), mega- (10 ), giga- (10 ), tera- (10 ), peta- (10 ) or exa- (10 ),

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1914-416: Is large and comprises a huge amount of construction material: the main part of the calorimeter – the tile calorimeter – is 8 metres in diameter and covers 12 metres along the beam axis. The far-forward sections of the hadronic calorimeter are contained within the forward EM calorimeter's cryostat, and use liquid argon as well, while copper and tungsten are used as absorbers. The Muon Spectrometer

2001-399: Is not as precise as those for the other two detectors, but it was necessary to reduce the cost of covering a larger volume and to have transition radiation detection capability. Each straw is filled with gas that becomes ionized when a charged particle passes through. The straws are held at about −1,500 V, driving the negative ions to a fine wire down the centre of each straw, producing

2088-422: Is not uniform, because a solenoid magnet of sufficient size would be prohibitively expensive to build. It varies between 2 and 8 Teslameters. The ATLAS detector is complemented by a set of four sub-detectors in the forward region to measure particles at very small angles. Earlier particle detector read-out and event detection systems were based on parallel shared buses such as VMEbus or FASTBUS . Since such

2175-441: Is the Boltzmann constant . The k B is assumed when using the electronvolt to express temperature, for example, a typical magnetic confinement fusion plasma is 15 keV (kiloelectronvolt), which is equal to 174 MK (megakelvin). As an approximation: k B T is about 0.025 eV (≈ ⁠ 290 K / 11604 K/eV ⁠ ) at a temperature of 20 °C . The energy E , frequency ν , and wavelength λ of

2262-663: Is the Planck constant , c is the speed of light . This reduces to E = 4.135   667   696 × 10 − 15 e V / H z × ν = 1   239.841   98 e V ⋅ n m λ . {\displaystyle {\begin{aligned}E&=4.135\ 667\ 696\times 10^{-15}\;\mathrm {eV/Hz} \times \nu \\[4pt]&={\frac {1\ 239.841\ 98\;\mathrm {eV{\cdot }nm} }{\lambda }}.\end{aligned}}} A photon with

2349-564: Is the largest general-purpose particle detector experiment at the Large Hadron Collider (LHC), a particle accelerator at CERN (the European Organization for Nuclear Research) in Switzerland. The experiment is designed to take advantage of the unprecedented energy available at the LHC and observe phenomena that involve highly massive particles which were not observable using earlier lower- energy accelerators. ATLAS

2436-411: Is the primary metal used to construct the tubes [1] in the individual in-line resonators. Niobium is used because it is relatively cheap, yet it is a superconductor at relatively high temperatures. Niobium has poor malleability, which makes it difficult to construct the shapes needed for the resonators. The machinists working at ATLAS are some of the only people in the world able to work with niobium to

2523-608: The Grand Unified Theories (GUTs) including Supersymmetry (SUSY), predicts the existence of new particles with masses greater than those of Standard Model . Most of the currently proposed theories predict new higher-mass particles, some of which may be light enough to be observed by ATLAS. Models of supersymmetry involve new, highly massive particles. In many cases these decay into high-energy quarks and stable heavy particles that are very unlikely to interact with ordinary matter. The stable particles would escape

2610-443: The Lorentz force is equal to where p = γ m v {\displaystyle p=\gamma \,m\,v} is the relativistic momentum of the particle. As a result, high-momentum particles curve very little (large r {\displaystyle r} ), while low-momentum particles curve significantly (small r {\displaystyle r} ). The amount of curvature can be quantified and

2697-459: The Standard model is believed to be theoretically self-consistent and has demonstrated huge successes in providing experimental predictions , it leaves some phenomena unexplained and falls short of being a complete theory of fundamental interactions . It does not fully explain baryon asymmetry , incorporate the full theory of gravitation as described by general relativity , or account for

Argonne Tandem Linear Accelerator System - Misplaced Pages Continue

2784-417: The Standard model . The Standard model of particle physics is the theory describing three of the four known fundamental forces (the electromagnetic , weak , and strong interactions, while omitting gravity ) in the universe , as well as classifying all known elementary particles . It was developed in stages throughout the latter half of the 20th century, through the work of many scientists around

2871-955: The W and Z bosons mass while leaving the photon massless. On July 4, 2012, ATLAS — together with CMS, its sister experiment at the LHC — reported evidence for the existence of a particle consistent with the Higgs boson at a confidence level of 5 sigma , with a mass around 125 GeV, or 133 times the proton mass. This new "Higgs-like" particle was detected by its decay into two photons ( H → γ γ {\displaystyle H\rightarrow \gamma \gamma } ) and its decay to four leptons ( H → Z Z ∗ → 4 l {\displaystyle H\rightarrow ZZ^{*}\rightarrow 4l} and H → W W ∗ → e ν μ ν {\displaystyle H\rightarrow WW^{*}\rightarrow e\nu \mu \nu } ). In March 2013, in

2958-529: The accelerating expansion of the universe as possibly described by dark energy . The model does not contain any viable dark matter particle that possesses all of the required properties deduced from observational cosmology . It also does not incorporate neutrino oscillations and their non-zero masses. With the important exception of the Higgs boson , detected by the ATLAS and the CMS experiments in 2012, all of

3045-399: The center of mass of the collision. Since then, the LHC energy has been increasing: 1.8 TeV at the end of 2009, 7 TeV for the whole of 2010 and 2011, then 8 TeV in 2012. The first data-taking period performed between 2010 and 2012 is referred to as Run I. After a long shutdown (LS1) in 2013 and 2014, in 2015 ATLAS saw 13 TeV collisions. The second data-taking period, Run II,

3132-410: The mean lifetime τ of an unstable particle (in seconds) in terms of its decay width Γ (in eV) via Γ = ħ / τ . For example, the B meson has a lifetime of 1.530(9)  picoseconds , mean decay length is cτ = 459.7 μm , or a decay width of 4.302(25) × 10  eV . Conversely, the tiny meson mass differences responsible for meson oscillations are often expressed in

3219-499: The photon . Instead, neutrinos have mass . In 1998 research results at detector Super-Kamiokande determined that neutrinos can oscillate from one flavor to another, which dictates that they have a mass other than zero. For these and other reasons, many particle physicists believe it is possible that the Standard Model will break down at energies at the teraelectronvolt (TeV) scale or higher. Most alternative theories,

3306-505: The pseudorapidity ) and its angle within the perpendicular plane are both measured to within roughly 0.025  radians . The barrel EM calorimeter has accordion shaped electrodes and the energy-absorbing materials are lead and stainless steel , with liquid argon as the sampling material, and a cryostat is required around the EM calorimeter to keep it sufficiently cool. The hadron calorimeter absorbs energy from particles that pass through

3393-483: The "electron equivalent" recoil energy (eVee, keVee, etc.) measured by scintillation light. For example, the yield of a phototube is measured in phe/keVee ( photoelectrons per keV electron-equivalent energy). The relationship between eV, eVr, and eVee depends on the medium the scattering takes place in, and must be established empirically for each material. One mole of particles given 1 eV of energy each has approximately 96.5 kJ of energy – this corresponds to

3480-436: The 20-MV 'booster' linac, then to the 20-MV 'ATLAS' linac section. The ATLAS linac is constructed with seven different superconducting resonator designs, each one creating an electromagnetic wave of a different velocity. The ions in the ATLAS linac are aligned into a beam which exits the linac into one of three experimental areas. The experiment areas contain scattering chambers, spectrometers and spectrographs , beamlines ,

3567-425: The ATLAS experiment pit starting in 2003. Construction was completed in 2008 and the experiment detected its first single proton beam events on 10 September of that year. Data-taking was then interrupted for over a year due to an LHC magnet quench incident . On 23 November 2009, the first proton–proton collisions occurred at the LHC and were recorded by ATLAS, at a relatively low injection energy of 900 GeV in

Argonne Tandem Linear Accelerator System - Misplaced Pages Continue

3654-404: The EM calorimeter, but do interact via the strong force ; these particles are primarily hadrons. It is less precise, both in energy magnitude and in the localization (within about 0.1 radians only). The energy-absorbing material is steel, with scintillating tiles that sample the energy deposited. Many of the features of the calorimeter are chosen for their cost-effectiveness; the instrument

3741-592: The Inner Detector, with muons curving so that their momentum can be measured, albeit with a different magnetic field configuration, lower spatial precision, and a much larger volume. It also serves the function of simply identifying muons – very few particles of other types are expected to pass through the calorimeters and subsequently leave signals in the Muon Spectrometer. It has roughly one million readout channels, and its layers of detectors have

3828-545: The Large Hadron Collider. In order to identify all particles produced at the interaction point where the particle beams collide, the detector is designed in layers made up of detectors of different types, each of which is designed to observe specific types of particles. The different traces that particles leave in each layer of the detector allow for effective particle identification and accurate measurements of energy and momentum. (The role of each layer in

3915-623: The Standard Model in equal numbers and leaving an unequivocal signature in the ATLAS detector. The ATLAS detector is 46 metres long, 25 metres in diameter, and weighs about 7,000 tonnes; it contains some 3,000 km of cable. At 27 km in circumference , the Large Hadron Collider (LHC) at CERN collides two beams of protons together, with each proton carrying up to 6.8  TeV of energy – enough to produce particles with masses significantly greater than any particles currently known, if these particles exist. When

4002-540: The accelerating structures by increasing the ion beam’s positive charge, and the Argonne In-Flight Radioactive Ion Separator (RAISOR), which helps to improve beam purity by separating out specific isotopes. The enhancements of ATLAS with EBIS and RAISOR help scientists probe the structures of exotic elements, study the nature of the nuclear forces, and better understand the production of elements in stars and supernovae. Niobium

4089-471: The amount of transition radiation is greatest for highly relativistic particles (those with a speed very near the speed of light ), and because particles of a particular energy have a higher speed the lighter they are, particle paths with many very strong signals can be identified as belonging to the lightest charged particles: electrons and their antiparticles, positrons . The TRT has about 298,000 straws in total. The calorimeters are situated outside

4176-495: The behavior of matter and antimatter , known as CP violation , is also being investigated. Recent experiments dedicated to measurements of CP violation, such as BaBar and Belle , have not detected sufficient CP violation in the Standard Model to explain the lack of detectable antimatter in the universe. It is possible that new models of physics will introduce additional CP violation, shedding light on this problem. Evidence supporting these models might either be detected directly by

4263-459: The center of the detector. This produces a total of 1 petabyte of raw data per second. By avoiding to write empty segments of each event (zero suppression), which do not contain physical information, the average size of an event is reduced to 1.6 MB , for a total of 64 terabyte of data per second. The trigger system uses fast event reconstruction to identify, in real time, the most interesting events to retain for detailed analysis. In

4350-876: The conversion to MKS system of units can be achieved by: p = 1 GeV / c = ( 1 × 10 9 ) × ( 1.602   176   634 × 10 − 19 C ) × ( 1 V ) 2.99   792   458 × 10 8 m / s = 5.344   286 × 10 − 19 kg ⋅ m / s . {\displaystyle p=1\;{\text{GeV}}/c={\frac {(1\times 10^{9})\times (1.602\ 176\ 634\times 10^{-19}\;{\text{C}})\times (1\;{\text{V}})}{2.99\ 792\ 458\times 10^{8}\;{\text{m}}/{\text{s}}}}=5.344\ 286\times 10^{-19}\;{\text{kg}}{\cdot }{\text{m}}/{\text{s}}.} In particle physics ,

4437-450: The decay of a hadron with a bottom quark (see b-tagging ). The Pixel Detector, the innermost part of the detector, contains four concentric layers and three disks on each end-cap, with a total of 1,744  modules , each measuring 2 centimetres by 6 centimetres. The detecting material is 250 μm thick silicon . Each module contains 16 readout chips and other electronic components. The smallest unit that can be read out

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4524-661: The degree necessary for construction and repair of the ATLAS parts. The energy levels of the ions produced by ATLAS are ideal to study the properties of the nucleus . Specifically, scientists use ATLAS to understand reactions between nuclei from very low energies (typically encountered in burning stars) to the very highest energies (encountered soon after the Big Bang). Nuclei with specific properties can be studied to understand fundamental interactions. ATLAS experiment 46°14′8″N 6°3′19″E  /  46.23556°N 6.05528°E  / 46.23556; 6.05528 ATLAS

4611-428: The details of the Standard Model, with the possibility of revealing inconsistencies that point to new physics. While the Standard Model predicts that quarks , leptons and neutrinos should exist, it does not explain why the masses of these particles are so different (they differ by orders of magnitude ). Furthermore, the mass of the neutrinos should be, according to the Standard Model , exactly zero as that of

4698-401: The detector is discussed below .) As the energy of the particles produced by the accelerator increases, the detectors attached to it must grow to effectively measure and stop higher-energy particles. As of 2022, the ATLAS detector is the largest ever built at a particle collider. The ATLAS detector consists of a series of ever-larger concentric cylinders around the interaction point where

4785-562: The detector must be " hermetic ", meaning it must detect all non-neutrinos produced, with no blind spots. The installation of all the above detector systems was finished in August 2008. The detectors collected millions of cosmic rays during the magnet repairs which took place between fall 2008 and fall 2009, prior to the first proton collisions. The detector operated with close to 100% efficiency and provided performance characteristics very close to its design values. The Inner Detector begins

4872-511: The detector, leaving as a signal one or more high-energy quark jets and a large amount of "missing" momentum . Other hypothetical massive particles, like those in the Kaluza–Klein theory , might leave a similar signature. The data collected up to the end of LHC Run II do not show evidence of supersymmetric or unexpected particles, the research of which will continue in the data that will be collected from Run III onwards. The asymmetry between

4959-575: The detector, was formed in 1992 when the proposed EAGLE (Experiment for Accurate Gamma, Lepton and Energy Measurements) and ASCOT (Apparatus with Super Conducting Toroids) collaborations merged their efforts to build a single, general-purpose particle detector for a new particle accelerator , the Large Hadron Collider . At present, the ATLAS Collaboration involves 6,003 members, out of which 3,822 are physicists (last update: June 26, 2022) from 257 institutions in 42 countries. The design

5046-436: The electronvolt as a product with fundamental constants of importance in the theory are often used. By mass–energy equivalence , the electronvolt corresponds to a unit of mass . It is common in particle physics , where units of mass and energy are often interchanged, to express mass in units of eV/ c , where c is the speed of light in vacuum (from E = mc ). It is common to informally express mass in terms of eV as

5133-417: The energy of the original particle from this measurement. The electromagnetic (EM) calorimeter absorbs energy from particles that interact electromagnetically , which include charged particles and photons. It has high precision, both in the amount of energy absorbed and in the precise location of the energy deposited. The angle between the particle's trajectory and the detector's beam axis (or more precisely

5220-416: The entire inner detector causes charged particles to curve; the direction of the curve reveals a particle's charge and the degree of curvature reveals its momentum. The starting points of the tracks yield useful information for identifying particles ; for example, if a group of tracks seem to originate from a point other than the original proton–proton collision, this may be a sign that the particles came from

5307-566: The field and most likely not be measured; however, this energy is very small compared to the several TeV of energy released in each proton collision. The outer toroidal magnetic field is produced by eight very large air-core superconducting barrel loops and two smaller end-caps air toroidal magnets, for a total of 24 barrel loops all situated outside the calorimeters and within the muon system. This magnetic field extends in an area 26 metres long and 20 metres in diameter, and it stores 1.6  gigajoules of energy. Its magnetic field

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5394-491: The field of particle physics , ATLAS studies different types of processes detected or detectable in energetic collisions at the Large Hadron Collider (LHC). For the processes already known, it is a matter of measuring more and more accurately the properties of known particles or finding quantitative confirmations of the Standard model . Processes not observed so far would allow, if detected, to discover new particles or to have confirmation of physical theories that go beyond

5481-505: The intensity B {\displaystyle B} of the magnetic field: Since all particles produced in the LHC's proton collisions are traveling at very close to the speed of light in vacuum ( v ≃ c ) {\displaystyle (v\simeq c)} , the Lorentz force is about the same for all the particles with same electric charge q {\displaystyle q} : The radius of curvature r {\displaystyle r} due to

5568-475: The light of the updated ATLAS and CMS results, CERN announced that the new particle was indeed a Higgs boson. The experiments were also able to show that the properties of the particle as well as the ways it interacts with other particles were well-matched with those of a Higgs boson, which is expected to have spin 0 and positive parity . Analysis of more properties of the particle and data collected in 2015 and 2016 confirmed this further. In October 2013, two of

5655-438: The mass [(80,370±19) MeV ] of the W boson , one of the two mediators of the weak interaction , with a measurement uncertainty of ±2.4 ‰ . One of the most important goals of ATLAS was to investigate a missing piece of the Standard Model, the Higgs boson . The Higgs mechanism , which includes the Higgs boson, gives mass to elementary particles, leading to differences between the weak force and electromagnetism by giving

5742-404: The mass of a proton. To convert to electronvolt mass-equivalent, use the formula: By dividing a particle's kinetic energy in electronvolts by the fundamental constant c (the speed of light), one can describe the particle's momentum in units of eV/ c . In natural units in which the fundamental velocity constant c is numerically 1, the c may be informally be omitted to express momentum using

5829-406: The momentum of 100 GeV muons with 3% accuracy and of 1 TeV muons with 10% accuracy. It was vital to go to the lengths of putting together such a large piece of equipment because a number of interesting physical processes can only be observed if one or more muons are detected, and because the total energy of particles in an event could not be measured if the muons were ignored. It functions similarly to

5916-985: The more convenient inverse picoseconds. Energy in electronvolts is sometimes expressed through the wavelength of light with photons of the same energy: 1 eV h c = 1.602   176   634 × 10 − 19 J ( 2.99   792   458 × 10 11 mm / s ) × ( 6.62   607   015 × 10 − 34 J ⋅ s ) ≈ 806.55439 mm − 1 . {\displaystyle {\frac {1\;{\text{eV}}}{hc}}={\frac {1.602\ 176\ 634\times 10^{-19}\;{\text{J}}}{(2.99\ 792\ 458\times 10^{11}\;{\text{mm}}/{\text{s}})\times (6.62\ 607\ 015\times 10^{-34}\;{\text{J}}{\cdot }{\text{s}})}}\thickapprox 806.55439\;{\text{mm}}^{-1}.} In certain fields, such as plasma physics , it

6003-430: The muon system makes additional measurements of highly penetrating muons. The two magnet systems bend charged particles in the Inner Detector and the Muon Spectrometer, allowing their electric charges and momenta to be measured. The only established stable particles that cannot be detected directly are neutrinos ; their presence is inferred by measuring a momentum imbalance among detected particles. For this to work,

6090-460: The numerical value of 1 eV in joules (symbol J) is equal to the numerical value of the charge of an electron in coulombs (symbol C). Under the 2019 revision of the SI , this sets 1 eV equal to the exact value 1.602 176 634 × 10  J . Historically, the electronvolt was devised as a standard unit of measure through its usefulness in electrostatic particle accelerator sciences, because

6177-469: The particle momentum can be determined from this value. The inner solenoid produces a two tesla magnetic field surrounding the Inner Detector. This high magnetic field allows even very energetic particles to curve enough for their momentum to be determined, and its nearly uniform direction and strength allow measurements to be made very precisely. Particles with momenta below roughly 400 MeV will be curved so strongly that they will loop repeatedly in

6264-429: The particles predicted by the Standard Model had been observed by previous experiments. In this field, in addition to the discovery of the Higgs boson , the experimental work of ATLAS has focused on precision measurements, aimed at determining with ever greater accuracy the many physical parameters of theory. In particular for ATLAS measures: For example, the data collected by ATLAS made it possible in 2018 to measure

6351-477: The production of new particles, or indirectly by measurements of the properties of B- and D- mesons . LHCb , an LHC experiment dedicated to B-mesons, is likely to be better suited to the latter. Some hypotheses, based on the ADD model , involve large extra dimensions and predict that micro black holes could be formed by the LHC. These would decay immediately by means of Hawking radiation , producing all particles in

6438-522: The proton beams produced by the Large Hadron Collider interact in the center of the detector, a variety of different particles with a broad range of energies are produced. The ATLAS detector is designed to be general-purpose. Rather than focusing on a particular physical process, ATLAS is designed to measure the broadest possible range of signals. This is intended to ensure that whatever form any new physical processes or particles might take, ATLAS will be able to detect them and measure their properties. ATLAS

6525-437: The proton beams from the LHC collide. Maintaining detector performance in the high radiation areas immediately surrounding the proton beams is a significant engineering challenge. The detector can be divided into four major systems: Each of these is in turn made of multiple layers. The detectors are complementary: the Inner Detector tracks particles precisely, the calorimeters measure the energy of easily stopped particles, and

6612-435: The respective symbols being meV, keV, MeV, GeV, TeV, PeV and EeV. The SI unit of energy is the joule (J). In some older documents, and in the name Bevatron , the symbol BeV is used, where the B stands for billion . The symbol BeV is therefore equivalent to GeV , though neither is an SI unit. In the fields of physics in which the electronvolt is used, other quantities are typically measured using units derived from

6699-409: The second data-taking period of the LHC, Run-2, there were two distinct trigger levels: Electron volt#MeV In physics , an electronvolt (symbol eV ), also written electron-volt and electron volt , is the measure of an amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt in vacuum . When used as a unit of energy ,

6786-412: The solenoidal magnet that surrounds the Inner Detector. Their purpose is to measure the energy from particles by absorbing it. There are two basic calorimeter systems: an inner electromagnetic calorimeter and an outer hadronic calorimeter. Both are sampling calorimeters ; that is, they absorb energy in high-density metal and periodically sample the shape of the resulting particle shower , inferring

6873-725: The theoretical physicists who predicted the existence of the Standard Model Higgs boson, Peter Higgs and François Englert , were awarded the Nobel Prize in Physics . The properties of the top quark , discovered at Fermilab in 1995, had been measured approximately. With much greater energy and greater collision rates, the LHC produces a tremendous number of top quarks, allowing ATLAS to make much more precise measurements of its mass and interactions with other particles. These measurements provide indirect information on

6960-441: The unit electronvolt. The energy–momentum relation E 2 = p 2 c 2 + m 0 2 c 4 {\displaystyle E^{2}=p^{2}c^{2}+m_{0}^{2}c^{4}} in natural units (with c = 1 {\displaystyle c=1} ) E 2 = p 2 + m 0 2 {\displaystyle E^{2}=p^{2}+m_{0}^{2}}

7047-404: The unit eV/ c . The dimension of momentum is T L M . The dimension of energy is T L M . Dividing a unit of energy (such as eV) by a fundamental constant (such as the speed of light) that has the dimension of velocity ( T L ) facilitates the required conversion for using a unit of energy to quantify momentum. For example, if the momentum p of an electron is 1 GeV/ c , then

7134-446: The world, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks . Since then, confirmation of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard model . In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy. Although

7221-697: Was a combination of two previous projects for LHC, EAGLE and ASCOT, and also benefitted from the detector research and development that had been done for the Superconducting Super Collider , a US project interrupted in 1993. The ATLAS experiment was proposed in its current form in 1994, and officially funded by the CERN member countries in 1995. Additional countries, universities , and laboratories have joined in subsequent years. Construction work began at individual institutions, with detector components then being shipped to CERN and assembled in

7308-502: Was built by Ernest O. Lawrence in 1931, with a radius of just a few centimetres and a particle energy of 1 megaelectronvolt (MeV) . Since then, accelerators have grown enormously in the quest to produce new particles of greater and greater mass . As accelerators have grown, so too has the list of known particles that they might be used to investigate. The ATLAS Collaboration, the international group of physicists belonging to different universities and research centres who built and run

7395-506: Was completed, always at 13 TeV energy, at the end of 2018 with a recorded integrated luminosity of nearly 140 fb (inverse femtobarn ). A second long shutdown (LS2) in 2019-22 with upgrades to the ATLAS detector was followed by Run III, which started in July 2022. The ATLAS Collaboration is currently led by Spokesperson Andreas Hoecker and Deputy Spokespersons Marumi Kado and Manuella Vincter . Former Spokespersons have been: In

7482-437: Was one of the two LHC experiments involved in the discovery of the Higgs boson in July 2012. It was also designed to search for evidence of theories of particle physics beyond the Standard Model . The experiment is a collaboration involving 6,003 members, out of which 3,822 are physicists (last update: June 26, 2022) from 257 institutions in 42 countries. The first cyclotron , an early type of particle accelerator,

7569-440: Was the radiation to which the Pixel Detector is exposed because of its proximity to the interaction point, requiring that all components be radiation hardened in order to continue operating after significant exposures. The Semi-Conductor Tracker (SCT) is the middle component of the inner detector. It is similar in concept and function to the Pixel Detector but with long, narrow strips rather than small pixels, making coverage of

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