In particle physics, proton decay is a hypothetical form of radioactive decay in which the proton decays into lighter subatomic particles, usually a neutral pion and a positron. Proton decay has not been observed. Thousands of particles explode from the collision point of two relativistic (100 GeV per ion) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... OK : Radioactive and Radioactivity redirect here. ... // Properties [1][2] In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... A subatomic particle is a particle smaller than an atom: it may be elementary or composite. ... In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: Ï€0, Ï€+ and π−. Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ...

In the Standard Model, protons, a type of baryon, are theoretically stable because baryon number is approximately conserved. That is, they will not decay perturbatively into other particles on their own because they are the lightest (and therefore least energetic) baryon. The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... In particle physics, the baryons are a family of subatomic particles including the proton and the neutron (collectively called nucleons), as well as a number of unstable, heavier particles (called hyperons). ... In particle physics, the baryon number is an approximate conserved quantum number. ... In particle physics, the baryon number is an approximate conserved quantum number of a system. ... In quantum mechanics, perturbation theory is a set of approximation schemes for describing a complicated quantum system in terms of a simpler one. ...

Beyond-the-Standard Model grand unified theories (GUTs) explicitly break the baryon number symmetry, allowing protons to decay via new X bosons. Proton decay is one of the few observable effects of the various proposed GUTs. To date, all attempts to observe these events have failed. Grand unification, grand unified theory, or GUT is a theory in physics that unifies the strong interaction and electroweak interaction. ... In particle physics, the baryon number is an approximate conserved quantum number. ... In physics, the term X boson is used in various different contexts. ...

Baryogenesis

Unsolved problems in physics: Do protons decay? If so, then what is the half-life?

One of the outstanding problems in modern physics is the predominance of matter over antimatter in the universe. The universe, as a whole, has a nonzero baryon number density — that is, matter exists. Since it is assumed in cosmology that the particles we see were created using the same physics we measure today, it would normally be expected that the overall baryon number should be zero, as matter and antimatter should have been created in roughly equal amounts. This has led to a number of proposed mechanisms for symmetry breaking that favour the creation of normal matter (as opposed to antimatter) under certain conditions. This imbalance would have been exceptionally small, on the order of 1 in every 10,000,000,000 (10¹⁰) particles a split second after the Big Bang, but after most of the matter and antimatter annihilated, what was left over was all the baryonic matter in the current universe, along with a much greater number of bosons. See baryogenesis. Image File history File links No higher resolution available. ... This is a list of some of the unsolved problems in physics. ... OK : Radioactive and Radioactivity redirect here. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... This article or section does not adequately cite its references or sources. ... In particle physics, antimatter extends the concept of the antiparticle to matter, whereby a particle of antimatter is composed of antiparticles in the same way that normal matter is. ... Universe is a word derived from the Old French univers, which in turn comes from the Latin roots unus (one) and versus (a form of vertere, to turn). Based on observations of the observable universe, physicists attempt to describe the whole of space-time, including all matter and energy and... Physical cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. ... Promotional picture Symmetry Breaking is a rock band from Northern New Jersey, in the United States. ... In particle physics, bosons, named after Satyendra Nath Bose, are particles having integer spin. ... Baryogenesis is the generic designation for the physical processes that generate matter (more specifically, a class of fundamental particle called baryon) from an otherwise matter-empty state (such as it is generally believed to be the state of the Universe at its onset, the so-called Big Bang). ...

Most grand unified theories (GUTs) explicitly break the baryon number symmetry, which would account for this discrepancy, typically invoking reactions mediated by very massive X bosons (X below) or massive Higgs bosons (T). The rate that these events occur is governed largely by the mass of the intermediate X or T particles, so by assuming these reactions are responsible for the majority of the baryon number seen today, a maximum mass can be calculated, above which the rate would be too slow to explain the presence of matter today. These estimates predict that a large volume of material will periodically exhibit spontaneous proton decay even given the much reduced energies available today. Grand unification, grand unified theory, or GUT is a theory in physics that unifies the strong interaction and electroweak interaction. ... In particle physics, the baryon number is an approximate conserved quantum number. ... In physics, the term X boson is used in various different contexts. ... The Higgs boson is a hypothetical massive scalar elementary particle predicted to exist by the Standard Model of particle physics. ...

Proton decay is one of the few observable effects of the various proposed GUTs, the other major one being magnetic monopoles. Both became the focus of major experimental physics efforts starting in the early 1980s. Proton decay was, for a time, an extremely exciting area of experimental physics research. To date, all attempts to observe these events have failed. In physics, a magnetic monopole is a hypothetical particle that may be loosely described as a magnet with only one pole (see electromagnetic theory for more on magnetic poles). ...

Experimental evidence

Recent experiments at the Super-Kamiokande water Cherenkov radiation detector in Japan indicate that if protons decay at all, their half-life must be at least 10³⁵ years. That is, the proposal that the mechanisms that also give rise to proton decay are responsible for baryogenesis appears to be the null result experimentally. Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ... Cherenkov radiation glowing in the core of a TRIGA reactor Cherenkov radiation (also spelled Cerenkov or sometimes ÄŒerenkov) is electromagnetic radiation emitted when a charged particle passes through an insulator at a speed greater than the speed of light in that medium. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... To help compare orders of magnitude of different times, this page lists times longer than 1019 seconds (317 billion years) See also times of other orders of magnitude. ... Generally, a null result is a result which is null (nothing): that is, the absence of an observable result. ...

Theoretical motivation

Despite the lack of observational evidence for proton decay, some grand unification theories require it. According to some such theories, the proton would have a half-life of 10³⁶ years, and would decay into a positron and a neutral pion that itself immediately decays into photons in the range of gamma radiation: It has been suggested that this article or section be merged into Unified field theory. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... To help compare orders of magnitude of different times, this page lists times longer than 1019 seconds (317 billion years) See also times of other orders of magnitude. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: Ï€0, Ï€+ and π−. Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force. ... The word light is defined here as electromagnetic radiation of any wavelength; thus, X-rays, gamma rays, ultraviolet light, microwaves, radio waves, and visible light are all forms of light. ... This article is about electromagnetic radiation. ...

Though this process has not been observed experimentally, it is within the realm of experimental testability for future planned very large-scale detectors on the megaton scale. Such detectors include the Hyper-Kamiokande. The Kamioka Observatory, Institute for Cosmic Ray Research ) is a neutrino physics laboratory located underground in the Mozumi Mine of the Kamioka Mining and Smelting Co. ...

Early grand unification theories, which were the first consistent theories to suggest proton decay postulated that the proton's half-life would be at least 10³¹ years. As further experiments and calculations were performed in the 1990s, it became clear that the proton half-life could not lie below 10³² years. Many books from that period refer to this figure for the possible decay time for baryonic matter. It has been suggested that this article or section be merged into Unified field theory. ... For the band, see 1990s (band). ...

Although the phenomenon is referred to as "proton decay", the effect would also be seen in neutrons bound inside atomic nuclei. Free neutrons—those not inside an atomic nucleus—are already known to decay into protons (and an electron and an anti-neutrino) in a process called Beta decay. Free neutrons have a half life of about 10 minutes due to the weak interaction. This article or section does not adequately cite its references or sources. ... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... Half-Life, often abbreviated as HL or HL1, is a sci-fi first-person shooter computer game developed by Valve Software, first released by Sierra Studios on November 19, 1998. ... The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four fundamental interactions of nature. ...

Decay operators

Dimension-6 proton decay operators

They are , , and where Λ is the cutoff scale for the Standard Model. All of these operators violate both baryon number and lepton number but not the combination B−L. This article is about physics. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... In particle physics, the baryon number is an approximate conserved quantum number. ... In high energy physics, the lepton number is the number of leptons minus the number of antileptons. ... In high energy physics, B−L (pronounced bee minus ell) is the baryon number minus the lepton number. ...

In GUT models, the exchange of an X or Y boson with the mass Λ_GUT can lead to the last two operators suppressed by . The exchange of a triplet Higgs with mass M can lead to all of the operators suppressed by 1/M². See doublet-triplet splitting problem. In physics, the term X boson is used in various different contexts. ... the y bosen like the x is a very hevy partical like the x not much is understood about it the bosen it self may nolonger exit the y and x were created in the high engery of the bigbang once the universe cooled thought the particals decaye though they... In particle physics, the doublet-triplet (splitting) problem is a problem of some Grand Unified Theories, such as SU(5), SO(10), . Grand unified theories predict Higgs bosons (doublets of ) arise from representations of the unified group that contain other states, in particular, states that are triplets of color. ...

Image File history File links Proton_decay2. ... Image File history File links Proton_decay3. ... Image File history File links Download high resolution version (492x674, 325 KB) Summary I created these diagrams. ...

Dimension-5 proton decay operators

In supersymmetric extensions (such as the MSSM), we can also have dimension-5 operators involving two fermions and two sfermions caused by the exchange of a tripletino of mass M. The sfermions will then exchange a gaugino or Higgsino or gravitino leaving two fermions. The overall Feynman diagram has a loop (and other complications due to strong interaction physics). This decay rate is suppressed by where M_SUSY is the mass scale of the superpartners. This article or section is in need of attention from an expert on the subject. ... A Minimal Supersymmetric Standard Model is a class of proposed supersymmetric extensions to the Standard Model. ... In particle physics, a sfermion is any of the class of spin-0 superpartners of ordinary fermions appearing in supersymmetric extensions to the Standard Model. ... In particle physics, a gaugino is the hypothetical superpartner of a gauge boson, as predicted by gauge theory combined with supersymmetry. ... In particle physics, a higgsino is the hypothetical superpartner of the Higgs boson, as predicted by supersymmetry. ... The gravitino is the hypothetical supersymmetric partner of the graviton, as predicted by theories combining general relativity and supersymmetry, i. ... In supersymmetry, it is proposed that every fermion should have a partner boson, known as its Superpartner. ...

Dimension-4 proton decay operators

In the absence of matter parity, supersymmetric extensions of the Standard Model can give rise to the last operator suppressed by the inverse square of sdown quark mass. This is due to the dimension-4 operators Image File history File links RPD.png‎ Author: Maliz R-parity violating rapid proton decay in MSSM I, the creator of this work, hereby release it into the public domain. ... R-parity is a concept in particle physics. ...

and

The proton decay rate is only suppressed by which is far too fast unless the couplings are very small.

In Pop-Culture

An experiment that proved protons decay was a central plot to an episode of the television legal drama Law and Order. Law and Order may refer to: Law and order (politics), a term common in political debate and discussion, generally indicating support of a strict criminal justice system Law and Order Offensive Party, a minor German political party In entertainment: Law & Order franchise, a number of related NBC television shows created...

Further reading

• Particle Data Group current best estimates of proton lifetime;
  • http://pdg.lbl.gov/2002/bxxxn.pdf - K. Hagiwara et al., Phys. Rev. D 66, 010001 (2002)
• Adams, Fred and Laughlin, Greg The Five Ages of the Universe : Inside the Physics of Eternity ISBN 0-684-86576-9
• Krauss, Lawrence M. Atom : An Odyssey from the Big Bang to Life on Earth ISBN 0-316-49946-3