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103-478: The LHCb ( Large Hadron Collider beauty ) experiment is a particle physics detector experiment collecting data at the Large Hadron Collider at CERN . LHCb is a specialized b-physics experiment, designed primarily to measure the parameters of CP violation in the interactions of b- hadrons (heavy particles containing a bottom quark ). Such studies can help to explain the matter-antimatter asymmetry of

206-525: A centre-of-mass energy of 900 GeV were expected to take place before the end of September 2008, and the LHC was expected to be operating at 10 TeV by the end of 2008. However, owing to the delay caused by the incident, the collider was not operational until November 2009. Despite the delay, LHC was officially inaugurated on 21 October 2008, in the presence of political leaders, science ministers from CERN's 20 Member States, CERN officials, and members of

309-402: A hadron ( / ˈ h æ d r ɒ n / ; from Ancient Greek ἁδρός (hadrós)  'stout, thick') is a composite subatomic particle made of two or more quarks held together by the strong interaction . They are analogous to molecules , which are held together by the electric force . Most of the mass of ordinary matter comes from two hadrons: the proton and

412-487: A proton is composed of two up quarks (each with electric charge + + 2 ⁄ 3 , for a total of + 4 ⁄ 3 together) and one down quark (with electric charge − + 1 ⁄ 3 ). Adding these together yields the proton charge of +1. Although quarks also carry color charge , hadrons must have zero total color charge because of a phenomenon called color confinement . That is, hadrons must be "colorless" or "white". The simplest ways for this to occur are with

515-411: A beam, which travel in opposite directions around the ring. The beams intersect at four points around the ring, which is where the particle collisions take place. Some 1,232 dipole magnets keep the beams on their circular path (see image ), while an additional 392 quadrupole magnets are used to keep the beams focused, with stronger quadrupole magnets close to the intersection points in order to maximize

618-528: A combined energy of 13 TeV. On 3 June 2015, the LHC started delivering physics data after almost two years offline. In the following months, it was used for proton–proton collisions, while in November, the machine switched to collisions of lead ions and in December, the usual winter shutdown started. In 2016, the machine operators focused on increasing the luminosity for proton–proton collisions. The design value

721-409: A computer screen showing the protons travelled the full length of the collider. It took less than one hour to guide the stream of particles around its inaugural circuit. CERN next successfully sent a beam of protons in an anticlockwise direction, taking slightly longer at one and a half hours owing to a problem with the cryogenics , with the full circuit being completed at 14:59. On 19 September 2008,

824-431: A day, as the protons are accelerated from 450  GeV to 6.5  TeV , the field of the superconducting dipole magnets is increased from 0.54 to 7.7 teslas (T) . The protons each have an energy of 6.5 TeV, giving a total collision energy of 13 TeV. At this energy, the protons have a Lorentz factor of about 6,930 and move at about 0.999 999 990   c , or about 3.1 m/s (11 km/h) slower than

927-503: A first known baryon with two heavy quarks; and of the fully-charmed tetraquark T c c c c {\displaystyle \mathrm {T} _{\rm {cccc}}} in 2020, made of two charm quarks and two charm antiquarks. Studies of charge-parity (CP) violation in B-meson decays is the primary design goal of the LHCb experiment. As of 2021, LHCb measurements confirm with

1030-418: A further four tonnes leaked at lower pressure in the aftermath. A total of 53 magnets were damaged in the incident and were repaired or replaced during the winter shutdown. This accident was thoroughly discussed in a 22 February 2010 Superconductor Science and Technology article by CERN physicist Lucio Rossi . In the original schedule for LHC commissioning, the first "modest" high-energy collisions at

1133-554: A given decay to happen, was found to be 0.846 − 0.041 + 0.044 {\displaystyle 0.846_{-0.041}^{+0.044}} while the Standard Model predicts it to be very close to unity. In December 2022 improved measurements discarded this anomaly. In August 2023 joined searches in leptonic decays b → s ℓ + ℓ − {\displaystyle b\rightarrow s\ell ^{+}\ell ^{-}} by

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1236-427: A grid-based computer network infrastructure initially connecting 140 computing centres in 35 countries (over 170 in more than 40 countries as of 2012 ). It was designed by CERN to handle the significant volume of data produced by LHC experiments, incorporating both private fibre optic cable links and existing high-speed portions of the public Internet to enable data transfer from CERN to academic institutions around

1339-435: A magnet quench and liquid helium escape (inaugural testing, 2008). Because electricity costs are lower during the summer, the LHC normally does not operate over the winter months, although exceptions over the 2009/10 and 2012/2013 winters were made to make up for the 2008 start-up delays and to improve precision of measurements of the new particle discovered in 2012, respectively. With the 2022 Russian invasion of Ukraine ,

1442-424: A magnet quench occurred in about 100 bending magnets in sectors 3 and 4, where an electrical fault vented about six tonnes of liquid helium (the magnets' cryogenic coolant) into the tunnel. The escaping vapour expanded with explosive force, damaging 53 superconducting magnets and their mountings, and contaminating the vacuum pipe, which also lost vacuum conditions. Shortly after the incident, CERN reported that

1545-442: A more detailed report on 5 December 2008. The analysis of the incident by CERN confirmed that an electrical fault had indeed been the cause. The faulty electrical connection had led (correctly) to a failsafe power abort of the electrical systems powering the superconducting magnets, but had also caused an electric arc (or discharge) which damaged the integrity of the supercooled helium's enclosure and vacuum insulation, causing

1648-527: A new category term: Notwithstanding the fact that this report deals with weak interactions, we shall frequently have to speak of strongly interacting particles. These particles pose not only numerous scientific problems, but also a terminological problem. The point is that " strongly interacting particles " is a very clumsy term which does not yield itself to the formation of an adjective. For this reason, to take but one instance, decays into strongly interacting particles are called "non- leptonic ". This definition

1751-489: A powerful research tool because they reach a much higher center of mass energy than fixed target setups. Analysis of the byproducts of these collisions gives scientists good evidence of the structure of the subatomic world and the laws of nature governing it. Many of these byproducts are produced only by high-energy collisions, and they decay after very short periods of time. Thus many of them are hard or nearly impossible to study in other ways. Many physicists hope that

1854-425: A quark of one color and an antiquark of the corresponding anticolor, or three quarks of different colors. Hadrons with the first arrangement are a type of meson , and those with the second arrangement are a type of baryon . Massless virtual gluons compose the overwhelming majority of particles inside hadrons, as well as the major constituents of its mass (with the exception of the heavy charm and bottom quarks ;

1957-551: A reduction in CERN's budget, pushed the completion date from 2005 to April 2007. The superconducting magnets were responsible for SFr 180M of the cost increase. There were also further costs and delays owing to engineering difficulties encountered while building the cavern for the Compact Muon Solenoid , and also due to magnet supports which were insufficiently strongly designed and failed their initial testing (2007) and damage from

2060-467: A remarkable precision the picture described by the CKM unitarity triangle . The angle γ ( α 3 ) {\displaystyle \gamma \,\,(\alpha _{3})} of the unitarity triangle is now known to about 4°, and is in agreement with indirect determinations. In 2019, LHCb announced discovery of CP violation in decays of charm mesons. This is the first time CP violation

2163-416: A roadmap document that formed the core physics programme for the first high energy LHC running in 2010–2012. They include: The fact that the two b-hadrons are predominantly produced in the same forward cone is exploited in the layout of the LHCb detector. The LHCb detector is a single arm forward spectrometer with a polar angular coverage from 10 to 300 milliradians (mrad) in the horizontal and 250 mrad in

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2266-468: A series of systems that successively increase their energy. The first system is the linear particle accelerator Linac4 generating 160 MeV negative hydrogen ions (H ions), which feeds the Proton Synchrotron Booster (PSB). There, both electrons are stripped from the hydrogen ions leaving only the nucleus containing one proton. Protons are then accelerated to 2 GeV and injected into

2369-504: Is because massive superconducting magnets require considerable magnet training to handle the high currents involved without losing their superconducting ability , and the high currents are necessary to allow a high proton energy. The "training" process involves repeatedly running the magnets with lower currents to provoke any quenches or minute movements that may result. It also takes time to cool down magnets to their operating temperature of around 1.9 K (close to absolute zero ). Over time

2472-490: Is contained in a circular tunnel, with a circumference of 26.7 kilometres (16.6 mi), at a depth ranging from 50 to 175 metres (164 to 574 ft) underground. The variation in depth was deliberate, to reduce the amount of tunnel that lies under the Jura Mountains to avoid having to excavate a vertical access shaft there. A tunnel was chosen to avoid having to purchase expensive land on the surface and to take advantage of

2575-642: Is expected to continue until 2026. In addition to a higher energy the LHC is expected to reach a higher luminosity, which is expected to increase even further with the upgrade to the HL-LHC after Run 3. An initial focus of research was to investigate the possible existence of the Higgs boson , a key part of the Standard Model of physics which was predicted by theory, but had not yet been observed before due to its high mass and elusive nature. CERN scientists estimated that, if

2678-835: Is known as asymptotic freedom , has been experimentally confirmed in the energy range between 1  GeV (gigaelectronvolt) and 1  TeV (teraelectronvolt). All free hadrons except ( possibly ) the proton and antiproton are unstable . Baryons are hadrons containing an odd number of valence quarks (at least 3). Most well-known baryons such as the proton and neutron have three valence quarks, but pentaquarks with five quarks—three quarks of different colors, and also one extra quark-antiquark pair—have also been proven to exist. Because baryons have an odd number of quarks, they are also all fermions , i.e. , they have half-integer spin . As quarks possess baryon number B  =  1 ⁄ 3 , baryons have baryon number B  = 1. Pentaquarks also have B  = 1, since

2781-403: Is located directly after the vertex detector. It is used for particle identification of low- momentum tracks. The main tracking system is placed before and after the dipole magnet. It is used to reconstruct the trajectories of charged particles and to measure their momenta. The tracker consists of three subdetectors: Following the tracking system is RICH-2. It allows the identification of

2884-547: Is not exact because "non-leptonic" may also signify photonic. In this report I shall call strongly interacting particles "hadrons", and the corresponding decays "hadronic" (the Greek ἁδρός signifies "large", "massive", in contrast to λεπτός which means "small", "light"). I hope that this terminology will prove to be convenient. — L. B. Okun (1962) According to the quark model , the properties of hadrons are primarily determined by their so-called valence quarks . For example,

2987-402: Is not meaningful to ask which quark is real and which virtual; only the small excess is apparent from the outside in the form of a hadron. Therefore, when a hadron or anti-hadron is stated to consist of (typically) two or three quarks, this technically refers to the constant excess of quarks versus antiquarks. Like all subatomic particles , hadrons are assigned quantum numbers corresponding to

3090-449: Is seen in decays of particles other than kaons or B mesons. The rate of the observed CP asymmetry is at the upper edge of existing theoretical predictions, which triggered some interest among particle theorists regarding possible impact of physics beyond the Standard Model. In 2020, LHCb announced discovery of time-dependent CP violation in decays of B s mesons. The oscillation frequency of B s mesons to its antiparticle and vice versa

3193-692: Is the world's largest and highest-energy particle accelerator . It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundreds of universities and laboratories across more than 100 countries. It lies in a tunnel 27 kilometres (17 mi) in circumference and as deep as 175 metres (574 ft) beneath the France–Switzerland border near Geneva . The first collisions were achieved in 2010 at an energy of 3.5  tera electronvolts (TeV) per beam, about four times

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3296-430: Is usually referred to as "SMOG". These datasets allow the collaboration to carry out the physics programme of precision Standard Model tests with many additional measurements. As of 2021, LHCb has published more than 500 scientific papers. LHCb is designed to study beauty and charm hadrons . In addition to precision studies of the known particles such as mysterious X(3872) , a number of new hadrons have been discovered by

3399-515: The LHCb collaboration. Mesons are hadrons containing an even number of valence quarks (at least two). Most well known mesons are composed of a quark-antiquark pair, but possible tetraquarks (four quarks) and hexaquarks (six quarks, comprising either a dibaryon or three quark-antiquark pairs) may have been discovered and are being investigated to confirm their nature. Several other hypothetical types of exotic meson may exist which do not fall within

3502-519: The LHCb collaboration. There are several more exotic hadron candidates and other colour-singlet quark combinations that may also exist. Almost all "free" hadrons and antihadrons (meaning, in isolation and not bound within an atomic nucleus ) are believed to be unstable and eventually decay into other particles. The only known possible exception is free protons, which appear to be stable , or at least, take immense amounts of time to decay (order of 10  years). By way of comparison, free neutrons are

3605-599: The Low Energy Ion Ring (LEIR) is used as an ion storage and cooler unit. The ions are then further accelerated by the PS and SPS before being injected into LHC ring, where they reach an energy of 2.3 TeV per nucleon (or 522 TeV per ion), higher than the energies reached by the Relativistic Heavy Ion Collider . The aim of the heavy-ion programme is to investigate quark–gluon plasma , which existed in

3708-567: The Proton Synchrotron (PS), where they are accelerated to 26 GeV. Finally, the Super Proton Synchrotron (SPS) is used to increase their energy further to 450 GeV before they are at last injected (over a period of several minutes) into the main ring. Here, the proton bunches are accumulated, accelerated (over a period of 20 minutes ) to their peak energy, and finally circulated for 5 to 24 hours while collisions occur at

3811-462: The Standard Model and Higgsless model required high-energy particle experiment data to validate their predictions and allow further theoretical development. The Standard Model was completed by detection of the Higgs boson by the LHC in 2012. LHC collisions have explored other questions, including: Other open questions that may be explored using high-energy particle collisions include: The collider

3914-401: The baryons such as protons and neutrons ; hadrons also include mesons such as the pion and kaon , which were discovered during cosmic ray experiments in the late 1940s and early 1950s. A collider is a type of a particle accelerator that brings two opposing particle beams together such that the particles collide. In particle physics , colliders, though harder to construct, are

4017-498: The early universe . Nine detectors have been built in large caverns excavated at the LHC's intersection points. Two of them, the ATLAS experiment and the Compact Muon Solenoid (CMS), are large general-purpose particle detectors . ALICE and LHCb have more specialized roles, while the other five— TOTEM , MoEDAL , LHCf , SND and FASER —are much smaller and are for very specialized research. The ATLAS and CMS experiments discovered

4120-415: The longest-lived unstable particle , and decay with a half-life of about 611 seconds, and have a mean lifetime of 879 seconds, see free neutron decay . Hadron physics is studied by colliding hadrons, e.g. protons, with each other or the nuclei of dense, heavy elements , such as lead (Pb) or gold (Au), and detecting the debris in the produced particle showers . A similar process occurs in

4223-413: The neutron , while most of the mass of the protons and neutrons is in turn due to the binding energy of their constituent quarks, due to the strong force. Hadrons are categorized into two broad families: baryons , made of an odd number of quarks (usually three) and mesons , made of an even number of quarks (usually two: one quark and one antiquark ). Protons and neutrons (which make the majority of

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4326-472: The representations of the Poincaré group : J ( m ), where J is the spin quantum number, P the intrinsic parity (or P-parity ), C the charge conjugation (or C-parity ), and m is the particle's mass . Note that the mass of a hadron has very little to do with the mass of its valence quarks; rather, due to mass–energy equivalence , most of the mass comes from the large amount of energy associated with

4429-506: The speed of light ( c ). It takes less than 90 microseconds (μs) for a proton to travel 26.7 km around the main ring. This results in 11,245 revolutions per second for protons whether the particles are at low or high energy in the main ring, since the speed difference between these energies is beyond the fifth decimal. Rather than having continuous beams, the protons are bunched together, into up to 2,808 bunches , with 115 billion protons in each bunch so that interactions between

4532-718: The strong interaction . Hadrons may also carry flavor quantum numbers such as isospin ( G-parity ), and strangeness . All quarks carry an additive, conserved quantum number called a baryon number ( B ), which is + + 1 ⁄ 3 for quarks and − + 1 ⁄ 3 for antiquarks. This means that baryons (composite particles made of three, five or a larger odd number of quarks) have B  = 1 whereas mesons have B  = 0. Hadrons have excited states known as resonances . Each ground state hadron may have several excited states; several hundred different resonances have been observed in experiments. Resonances decay extremely quickly (within about 10   seconds ) via

4635-484: The top quark vanishes before it has time to bind into a hadron). The strength of the strong-force gluons which bind the quarks together has sufficient energy ( E ) to have resonances composed of massive ( m ) quarks ( E ≥ mc ). One outcome is that short-lived pairs of virtual quarks and antiquarks are continually forming and vanishing again inside a hadron. Because the virtual quarks are not stable wave packets (quanta), but an irregular and transient phenomenon, it

4738-424: The vacuum pipe . During its first run (2010–2013), the LHC collided two opposing particle beams of either protons at up to 4  teraelectronvolts (4 TeV or 0.64 microjoules ) , or lead nuclei (574 TeV per nucleus, or 2.76 TeV per nucleon ). Its first run discoveries included the long-sought Higgs boson, several composite particles ( hadrons ) like the χ b (3P) bottomonium state,

4841-507: The Big Bang. CERN originally planned that the LHC would run through to the end of 2012, with a short break at the end of 2011 to allow for an increase in beam energy from 3.5 to 4 TeV per beam. At the end of 2012, the LHC was planned to be temporarily shut down until around 2015 to allow upgrade to a planned beam energy of 7 TeV per beam. In late 2012, in light of the July 2012 discovery of

4944-793: The Higgs boson, the shutdown was postponed for some weeks into early 2013, to allow additional data to be obtained before shutdown. The LHC was shut down on 13 February 2013 for its two-year upgrade called Long Shutdown 1 (LS1), which was to touch on many aspects of the LHC: enabling collisions at 14 TeV, enhancing its detectors and pre-accelerators (the Proton Synchrotron and Super Proton Synchrotron), as well as replacing its ventilation system and 100 km (62 mi) of cabling impaired by high-energy collisions from its first run. The upgraded collider began its long start-up and testing process in June 2014, with

5047-436: The Higgs boson, which is strong evidence that the Standard Model has the correct mechanism of giving mass to elementary particles. Data produced by LHC, as well as LHC-related simulation, were estimated at 200 petabytes per year. The LHC Computing Grid was constructed as part of the LHC design, to handle the massive amounts of data expected for its collisions. It is an international collaborative project that consists of

5150-545: The LHC beam. This implies an enormous flux of particles; VELO has been designed to withstand integrated fluences of more than 10 p/cm per year for a period of about three years. The detector operates in vacuum and is cooled to approximately −25 °C (−13 °F) using a biphase CO 2 system. The data of the VELO detector are amplified and read out by the Beetle ASIC . The RICH-1 detector ( Ring imaging Cherenkov detector )

5253-580: The LHC the largest cryogenic facility in the world at liquid helium temperature. LHC uses 470 tonnes of Nb–Ti superconductor. During LHC operations, the CERN site draws roughly 200  MW of electrical power from the French electrical grid , which, for comparison, is about one-third the energy consumption of the city of Geneva; the LHC accelerator and detectors draw about 120 MW thereof. Each day of its operation generates 140 terabytes of data. When running an energy of 6.5 TeV per proton, once or twice

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5356-551: The LHC to discover. The first physics results from the LHC, involving 284 collisions which took place in the ALICE detector, were reported on 15 December 2009. The results of the first proton–proton collisions at energies higher than Fermilab's Tevatron proton–antiproton collisions were published by the CMS collaboration in early February 2010, yielding greater-than-predicted charged-hadron production. Hadron In particle physics ,

5459-401: The LHC was shut down for upgrades, with a restart currently planned for early 2022. For the LHCb detector, almost all subdetectors are to be modernised or replaced. It will get a fully new tracking system composed of a modernised vertex locator, upstream tracker (UT) and scintillator fibre tracker (SciFi). The RICH detectors will also be updated, as well as the whole detector electronics. However,

5562-522: The LHCb and semileptonic decays b → s ℓ ν {\displaystyle b\rightarrow s\ell \nu } by Belle II (with ℓ = e , μ {\displaystyle \ell =e,\mu } ) set new limits for universality violations. LHCb has contributed to studies of quantum chromodynamics, electroweak physics, and provided cross-section measurements for astroparticle physics. Large Hadron Collider The Large Hadron Collider ( LHC )

5665-496: The Large Hadron Collider will help answer some of the fundamental open questions in physics, which concern the basic laws governing the interactions and forces among elementary particles and the deep structure of space and time, particularly the interrelation between quantum mechanics and general relativity . These high-energy particle experiments can provide data to support different scientific models. For example,

5768-479: The Proton Synchrotron Booster starting on 2 June 2014, the final interconnection between magnets completing and the Proton Synchrotron circulating particles on 18 June 2014, and the first section of the main LHC supermagnet system reaching operating temperature of 1.9 K (−271.25 °C), a few days later. Due to the slow progress with "training" the superconducting magnets, it was decided to start

5871-470: The Standard Model was correct, the LHC would produce several Higgs bosons every minute, allowing physicists to finally confirm or disprove the Higgs boson's existence. In addition, the LHC allowed the search for supersymmetric particles and other hypothetical particles as possible unknown areas of physics. Some extensions of the Standard Model predict additional particles, such as the heavy W' and Z' gauge bosons , which are also estimated to be within reach of

5974-533: The Ukrainian contribution to CERN for 2022 to the amount already remitted to the Organization, thereby waiving the second installment of the contribution. In both of its runs (2010 to 2012 and 2015), the LHC was initially run at energies below its planned operating energy, and ramped up to just 2 x 4 TeV energy on its first run and 2 x 6.5 TeV on its second run, below the design energy of 2 x 7 TeV. This

6077-483: The Universe. The detector is also able to perform measurements of production cross sections, exotic hadron spectroscopy, charm physics and electroweak physics in the forward region. The LHCb collaborators, who built, operate and analyse data from the experiment, are composed of approximately 1650 people from 98 scientific institutes, representing 22 countries. Vincenzo Vagnoni succeeded on July 1, 2023 as spokesperson for

6180-426: The accelerated particles collide. Nine detectors , each designed to detect different phenomena, are positioned around the crossing points. The LHC primarily collides proton beams, but it can also accelerate beams of heavy ions , such as in lead –lead collisions and proton –lead collisions. The LHC's goal is to allow physicists to test the predictions of different theories of particle physics , including measuring

6283-403: The accelerator and 1.16bn (SFr) (about $ 1.1bn, €0.8bn, or £0.7bn as of January 2010 ) for the CERN contribution to the experiments. The construction of LHC was approved in 1995 with a budget of SFr 2.6bn, with another SFr 210M toward the experiments. However, cost overruns, estimated in a major review in 2001 at around SFr 480M for the accelerator, and SFr 50M for the experiments, along with

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6386-471: The beam pipes contain 1.0×10 gram of hydrogen, which, in standard conditions for temperature and pressure , would fill the volume of one grain of fine sand. With a budget of €7.5 billion (about $ 9bn or £6.19bn as of June 2010 ), the LHC is one of the most expensive scientific instruments ever built. The total cost of the project is expected to be of the order of 4.6bn Swiss francs (SFr) (about $ 4.4bn, €3.1bn, or £2.8bn as of January 2010 ) for

6489-484: The beam pipes. With this information, the scientists are able to determine how the magnets should be calibrated to gain the most stable "orbit" of the beams in the ring. In August 2011, a second application (Test4Theory) went live which performs simulations against which to compare actual test data, to determine confidence levels of the results. By 2012, data from over 6 quadrillion ( 6 × 10 ) LHC proton–proton collisions had been analysed. The LHC Computing Grid had become

6592-408: The bending magnets were upgraded to safely handle the current required for 7 TeV per beam (14 TeV collision energy). However, the bending magnets were only trained to handle up to 6.5 TeV per beam (13 TeV collision energy), which became the operating energy for 2015 to 2018. The energy was first reached on 10 April 2015. The upgrades culminated in colliding protons together with

6695-462: The chances of interaction where the two beams cross. Magnets of higher multipole orders are used to correct smaller imperfections in the field geometry. In total, about 10,000 superconducting magnets are installed, with the dipole magnets having a mass of over 27 tonnes. About 96 tonnes of superfluid helium-4 is needed to keep the magnets, made of copper-clad niobium-titanium , at their operating temperature of 1.9 K (−271.25 °C), making

6798-504: The collaboration from Chris Parkes (spokesperson 2020–2023). The experiment is located at point 8 on the LHC tunnel close to Ferney-Voltaire , France just over the border from Geneva . The (small) MoEDAL experiment shares the same cavern. The experiment has wide physics program covering many important aspects of heavy flavour (both beauty and charm), electroweak and quantum chromodynamics (QCD) physics. Six key measurements have been identified involving B mesons. These are described in

6901-461: The coolant's temperature and pressure to rapidly rise beyond the ability of the safety systems to contain it, and leading to a temperature rise of about 100 degrees Celsius in some of the affected magnets. Energy stored in the superconducting magnets and electrical noise induced in other quench detectors also played a role in the rapid heating. Around two tonnes of liquid helium escaped explosively before detectors triggered an emergency stop, and

7004-948: The decays in question are very rare, a larger dataset needs to be analysed in order to make definitive conclusions. In March 2021, LHCb announced that the anomaly in lepton universality crossed the "3 sigma " statistical significance threshold, which translates to a p-value of 0.1%. The measured value of R K = B ( B + → K + μ + μ − ) B ( B + → K + e + e − ) {\displaystyle R_{\rm {K}}={\frac {{\mathcal {B}}(\mathrm {B} ^{+}\to \mathrm {K} ^{+}\mu ^{+}\mu ^{-})}{{\mathcal {B}}(\mathrm {B} ^{+}\to \mathrm {K} ^{+}\mathrm {e} ^{+}\mathrm {e} ^{-})}}} , where symbol B {\displaystyle {\mathcal {B}}} denotes probability of

7107-518: The experiment. As of 2021, all four LHC experiments have discovered about 60 new hadrons in total, vast majority of which by LHCb. In 2015, analysis of the decay of bottom lambda baryons (Λ b ) in the LHCb experiment revealed the apparent existence of pentaquarks , in what was described as an "accidental" discovery. Other notable discoveries are those of the "doubly charmed" baryon Ξ c c + + {\displaystyle \Xi _{\rm {cc}}^{++}} in 2017, being

7210-488: The extra quark's and antiquark's baryon numbers cancel. Each type of baryon has a corresponding antiparticle (antibaryon) in which quarks are replaced by their corresponding antiquarks. For example, just as a proton is made of two up quarks and one down quark, its corresponding antiparticle, the antiproton, is made of two up antiquarks and one down antiquark. As of August 2015, there are two known pentaquarks, P c (4380) and P c (4450) , both discovered in 2015 by

7313-413: The first creation of a quark–gluon plasma, and the first observations of the very rare decay of the B s meson into two muons (B s → μ μ ), which challenged the validity of existing models of supersymmetry . The size of the LHC constitutes an exceptional engineering challenge with unique operational issues on account of the amount of energy stored in the magnets and the beams. While operating,

7416-431: The four intersection points. The LHC physics programme is mainly based on proton–proton collisions. However, during shorter running periods, typically one month per year, heavy-ion collisions are included in the programme. While lighter ions are considered as well, the baseline scheme deals with lead ions (see A Large Ion Collider Experiment ). The lead ions are first accelerated by the linear accelerator LINAC 3 , and

7519-402: The latter have sizeable uncertainties. In the Standard Model, couplings of charged leptons (electron, muon and tau lepton) to the gauge bosons are expected to be identical, with the only difference emerging from the lepton masses. This postulate is referred to as "lepton flavour universality". As a consequence, in decays of b hadrons, electrons and muons should be produced at similar rates, and

7622-452: The luminosity by a factor of 10. LS2 ended in April 2022. The Long Shutdown 3 (LS3) in the 2020s will take place before the HL-LHC project is done. LHC became operational again on 22 April 2022 with a new maximum beam energy of 6.8 TeV (13.6 TeV collision energy), which was first achieved on 25 April. It officially commenced its run 3 physics season on 5 July 2022. This round

7725-470: The magnet "beds in" and ceases to quench at these lesser currents and can handle the full design current without quenching; CERN media describe the magnets as "shaking out" the unavoidable tiny manufacturing imperfections in their crystals and positions that had initially impaired their ability to handle their planned currents. The magnets, over time and with training, gradually become able to handle their full planned currents without quenching. The first beam

7828-596: The mass of an atom ) are examples of baryons; pions are an example of a meson. "Exotic" hadrons , containing more than three valence quarks, have been discovered in recent years. A tetraquark state (an exotic meson ), named the Z(4430) , was discovered in 2007 by the Belle Collaboration and confirmed as a resonance in 2014 by the LHCb collaboration. Two pentaquark states ( exotic baryons ), named P c (4380) and P c (4450) , were discovered in 2015 by

7931-418: The most important change is the switch to the fully software trigger of the experiment, which means that every recorded collision will be analysed by sophisticated software programmes without an intermediate hardware filtering step (which was found to be a bottleneck in the past). During the 2011 proton-proton run, LHCb recorded an integrated luminosity of 1 fb at a collision energy of 7 TeV. In 2012, about 2 fb

8034-399: The most likely cause of the problem was a faulty electrical connection between two magnets. It estimated that repairs would take at least two months, owing to the time needed to warm up the affected sectors and then cool them back down to operating temperature. CERN released an interim technical report and preliminary analysis of the incident on 15 and 16 October 2008 respectively, and

8137-401: The natural environment, in the extreme upper-atmosphere, where muons and mesons such as pions are produced by the collisions of cosmic rays with rarefied gas particles in the outer atmosphere. The term "hadron" is a new Greek word introduced by L. B. Okun in a plenary talk at the 1962 International Conference on High Energy Physics at CERN . He opened his talk with the definition of

8240-505: The participation of Russians with CERN was called into question. About 8% of the workforce are of Russian nationality. In June 2022, CERN said the governing council "intends to terminate" CERN's cooperation agreements with Belarus and Russia when they expire, respectively in June and December 2024. CERN said it would monitor developments in Ukraine and remains prepared to take additional steps as warranted. CERN further said that it would reduce

8343-400: The particle type of high-momentum tracks. The electromagnetic and hadronic calorimeters provide measurements of the energy of electrons , photons , and hadrons . These measurements are used at trigger level to identify the particles with large transverse momentum (high-Pt particles). The muon system is used to identify and trigger on muons in the events. At the end of 2018,

8446-423: The previous world record. The discovery of the Higgs boson at the LHC was announced in 2012. Between 2013 and 2015, the LHC was shut down and upgraded; after those upgrades it reached 6.5 TeV per beam (13.0 TeV total collision energy). At the end of 2018, it was shut down for maintenance and further upgrades, reopened over three years later in April 2022. The collider has four crossing points where

8549-444: The properties of the Higgs boson , searching for the large family of new particles predicted by supersymmetric theories , and studying other unresolved questions in particle physics . The term hadron refers to subatomic composite particles composed of quarks held together by the strong force (analogous to the way that atoms and molecules are held together by the electromagnetic force ). The best-known hadrons are

8652-447: The quark model of classification. These include glueballs and hybrid mesons (mesons bound by excited gluons ). Because mesons have an even number of quarks, they are also all bosons , with integer spin , i.e. , 0, +1, or −1. They have baryon number B = ⁠ 1 / 3 ⁠ − ⁠ 1 / 3 ⁠ = 0 . Examples of mesons commonly produced in particle physics experiments include pions and kaons . Pions also play

8755-454: The second run with a lower energy of 6.5 TeV per beam, corresponding to a current in the magnet of 11,000 amperes . The first of the main LHC magnets were reported to have been successfully trained by 9 December 2014, while training the other magnet sectors was finished in March 2015. On 5 April 2015, the LHC restarted after a two-year break, during which the electrical connectors between

8858-744: The shielding against background radiation that the Earth's crust provides. The 3.8-metre (12 ft) wide concrete-lined tunnel, constructed between 1983 and 1988, was formerly used to house the Large Electron–Positron Collider . The tunnel crosses the border between Switzerland and France at four points, with most of it in France. Surface buildings hold ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants. The collider tunnel contains two adjacent parallel beamlines (or beam pipes ) each containing

8961-631: The small difference due to the lepton masses is precisely calculable. LHCb has found deviations from this predictions by comparing the rate of the decay B + → K + μ + μ − {\displaystyle \mathrm {B} ^{+}\to \mathrm {K} ^{+}\mu ^{+}\mu ^{-}} to that of B + → K + e + e − {\displaystyle \mathrm {B} ^{+}\to \mathrm {K} ^{+}\mathrm {e} ^{+}\mathrm {e} ^{-}} , and in similar processes. However, as

9064-416: The strong nuclear force. In other phases of matter the hadrons may disappear. For example, at very high temperature and high pressure, unless there are sufficiently many flavors of quarks, the theory of quantum chromodynamics (QCD) predicts that quarks and gluons will no longer be confined within hadrons, "because the strength of the strong interaction diminishes with energy ". This property, which

9167-499: The total energy stored in the magnets is 10 GJ (2,400 kilograms of TNT) and the total energy carried by the two beams reaches 724 MJ (173 kilograms of TNT). Loss of only one ten-millionth part (10 ) of the beam is sufficient to quench a superconducting magnet, while each of the two beam dumps must absorb 362 MJ (87 kilograms of TNT). These energies are carried by very little matter: under nominal operating conditions (2,808 bunches per beam, 1.15×10 protons per bunch),

9270-400: The two beams take place at discrete intervals, mainly 25 nanoseconds (ns) apart, providing a bunch collision rate of 40 MHz. It was operated with fewer bunches in the first years. The design luminosity of the LHC is 10 cm s , which was first reached in June 2016. By 2017, twice this value was achieved. Before being injected into the main accelerator, the particles are prepared by

9373-472: The vertical plane. The asymmetry between the horizontal and vertical plane is determined by a large dipole magnet with the main field component in the vertical direction. [REDACTED] The Vertex Locator (VELO) is built around the proton interaction region. It is used to measure the particle trajectories close to the interaction point in order to precisely separate primary and secondary vertices. The detector operates at 7 millimetres (0.28 in) from

9476-469: The world's highest-energy particle accelerator, beating the Tevatron 's previous record of 0.98 TeV per beam held for eight years. The early part of 2010 saw the continued ramp-up of beam in energies and early physics experiments towards 3.5 TeV per beam and on 30 March 2010, LHC set a new record for high-energy collisions by colliding proton beams at a combined energy level of 7 TeV. The attempt

9579-416: The world's largest computing grid in 2012, comprising over 170 computing facilities in a worldwide network across more than 40 countries. The LHC first went operational on 10 September 2008, but initial testing was delayed for 14 months from 19 September 2008 to 20 November 2009, following a magnet quench incident that caused extensive damage to over 50 superconducting magnets , their mountings, and

9682-541: The world. The LHC Computing Grid consists of global federations across Europe, Asia Pacific and the Americas. The distributed computing project LHC@home was started to support the construction and calibration of the LHC. The project uses the BOINC platform, enabling anybody with an Internet connection and a computer running Mac OS X , Windows or Linux to use their computer's idle time to simulate how particles will travel in

9785-444: The worldwide scientific community. Most of 2009 was spent on repairs and reviews from the damage caused by the quench incident, along with two further vacuum leaks identified in July 2009; this pushed the start of operations to November of that year. On 20 November 2009, low-energy beams circulated in the tunnel for the first time since the incident, and shortly after, on 30 November, the LHC achieved 1.18 TeV per beam to become

9888-399: Was circulated through the collider on the morning of 10 September 2008. CERN successfully fired the protons around the tunnel in stages, three kilometres at a time. The particles were fired in a clockwise direction into the accelerator and successfully steered around it at 10:28 local time. The LHC successfully completed its major test: after a series of trial runs, two white dots flashed on

9991-470: Was collected at an energy of 8 TeV. During 2015–2018 (Run 2 of the LHC), about 6 fb was collected at a center-of-mass energy of 13 TeV. In addition, small samples were collected in proton-lead, lead-lead, and xenon-xenon collisions. The LHCb design also allowed the study of collisions of particle beams with a gas (helium or neon) injected inside the VELO volume, making it similar to a fixed-target experiment; this setup

10094-416: Was first reached 29 June, and further improvements increased the collision rate to 40% above the design value. The total number of collisions in 2016 exceeded the number from Run 1 – at a higher energy per collision. The proton–proton run was followed by four weeks of proton–lead collisions. In 2017, the luminosity was increased further and reached twice the design value. The total number of collisions

10197-515: Was found close to the Standard Model predictions. This measurement has harshly limited the possible parameter space of supersymmetry theories, which have predicted a large enhancement in rate. Since then, LHCb has published several papers with more precise measurements in this decay mode. Anomalies were found in several rare decays of B mesons. The most famous example in the so-called P 5 ′ {\displaystyle \mathrm {P} _{5}^{'}} angular observable

10300-427: Was found in the decay B 0 → K ∗ 0 μ + μ − {\displaystyle \mathrm {B} ^{0}\to \mathrm {K} ^{*0}\mu ^{+}\mu ^{-}} , where the deviation between the data and theoretical prediction has persisted for years. The decay rates of several rare decays also differ from the theoretical predictions, though

10403-488: Was higher than in 2016 as well. The 2018 physics run began on 17 April and stopped on 3 December, including four weeks of lead–lead collisions. Long Shutdown 2 (LS2) started on 10 December 2018. The LHC and the whole CERN accelerator complex was maintained and upgraded. The goal of the upgrades was to implement the High Luminosity Large Hadron Collider (HL-LHC) project that will increase

10506-582: Was measured to a great precision in 2021. Rare decays are the decay modes harshly suppressed in the Standard Model, which makes them sensitive to potential effects from yet unknown physics mechanisms. In 2014, LHCb and CMS experiments published a joint paper in Nature announcing the discovery of the very rare decay B s 0 → μ + μ − {\displaystyle \mathrm {B} _{\rm {s}}^{0}\to \mu ^{+}\mu ^{-}} , rate of which

10609-438: Was the third that day, after two unsuccessful attempts in which the protons had to be "dumped" from the collider and new beams had to be injected. This also marked the start of the main research programme. The first proton run ended on 4 November 2010. A run with lead ions started on 8 November 2010, and ended on 6 December 2010, allowing the ALICE experiment to study matter under extreme conditions similar to those shortly after

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