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Topic: Proton decay

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In the News (Mon 17 Jun 19)

  Protons and neutrons
Decay of the proton would violate the conservation of baryon number, and in doing so would be the only known process in nature which does so.
The decay of the neutron is associated with a quark transformation in which a down quark is converted to an up by the weak interaction.
The decay of the neutron is a good example of the observations which led to the discovery of the neutrino.
hyperphysics.phy-astr.gsu.edu /hbase/particles/proton.html   (1196 words)

  Proton - MSN Encarta
Proton, elementary particle that carries a positive electric charge and, along with the electron and the neutron, is one of the building blocks of all atoms.
Protons and neutrons are the building blocks of the atomic nucleus, the center of the atom.
Protons are affected by all four of the fundamental forces that govern all interactions between particles and energy in the universe.
encarta.msn.com /encyclopedia_761577976/Proton.html   (1393 words)

 Proton - Printer-friendly - MSN Encarta
Elements heavier than hydrogen usually contain about the same number of protons and neutrons in their nuclei, so the atomic mass, or the mass of one atom, is usually about twice the atomic number.
It is possible that protons may break up again, but this type of event, called proton decay, would be extremely rare.
Some protons live for a much shorter time than the average value, however, and scientists are constructing large experiments with thousands of tons of material, hoping to see a proton decay.
encarta.msn.com /text_761577976___2/Proton.html   (650 words)

 Theory: Decays (SLAC VVC)
When a nucleus decays radioactively, some of the decay products are constituents that were present before the decay, but others, such as photons or electrons, are entirely new objects produced by the decay process.
When a fundamental particle decays, all the produced particles are new objects that were not present before the decay.
Decay rates depend on the type of interaction and on the amount of energy "released," that is, energy converted from mass energy to kinetic energy.
www2.slac.stanford.edu /vvc/theory/decays.html   (537 words)

 Proton decay
For a long time, Protons were thought to be stable - that the laws of physics would not allow for a proton (which is baryonic matter) to spontaneously decay into positron and photon (non-baryonic matter) because of conservation of the baryon number.
However, it has been recently determined that the predominance of matter over antimatter in the universe is the result of a very slight imbalance in the ratio that occurred very early in its formation.
This means that in essence, rather than breaking the law of conservation of the baryon number, proton decay is actually the inevitable mechanism for bringing the baryon number back to equilibrium - correcting, if you will, the original imbalance that made all current matter in our universe possible.
www.ebroadcast.com.au /lookup/encyclopedia/pr/Proton_decay.html   (281 words)

 The Dispatch - Serving the Lexington, NC - News   (Site not responding. Last check: )
Protons and neutrons are both nucleons, which may be bound by the nuclear force into atomic nuclei.
The number of protons in the nucleus determines the chemical properties of the atom and which chemical element it is.
Due to their stability and large mass (compared to electrons), protons are well suited to use in particle colliders such as the Large Hadron Collider at CERN and the Tevatron at Fermilab.
www.the-dispatch.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=proton   (771 words)

 Beta Decay
Beta decay occurs when, in a nucleus with too many protons or too many neutrons, one of the protons or neutrons is transformed into the other.
Proton decay, neutron decay, and electron capture are three ways in which protons can be changed into neutrons or vice-versa; in each decay there is a change in the atomic number, so that the parent and daughter atoms are different elements.
In beta decay the change in binding energy appears as the mass energy and kinetic energy of the beta particle, the energy of the neutrino, and the kinetic energy of the recoiling daughter nucleus.
www.lbl.gov /abc/wallchart/chapters/03/2.html   (445 words)

 Modeling the Probability for Proton Decay
The experimental search for proton decay was undertaken because of the implications of the grand unification theories.
The probability for observing a proton decay can be estimated from the nature of particle decay and the application of Poisson statistics.
For a small sample, the observation of a proton decay is infinitesmal, but suppose we consider the volume of protons represented by the Super Kameokande neutrino detector in Japan.
hyperphysics.phy-astr.gsu.edu /hbase/particles/protondec.html   (312 words)

 Glossary Item - Beta Decay
During beta-minus decay, a neutron in an atom's nucleus turns into a proton, an electron and an antineutrino.
For example, after undergoing beta-minus decay, an atom of carbon (with 6 protons) becomes an atom of nitrogen (with 7 protons).
During beta-plus decay, a proton in an atom's nucleus turns into a neutron, a positron and a neutrino.
education.jlab.org /glossary/betadecay.html   (198 words)

 Nuclear Science Glossary
A drawing depicting the decay of a parent nucleus to a daughter nucleus.
Gamma rays emission is a decay mode by which excited state of a nucleus de-excite to lower (more stable) state in the same nucleus.
The proton is found in the nucleus and has a positive electrical charge equivalent to the negative charge of an electron and a mass similar to that of a neutron.
ie.lbl.gov /education/glossary/Glossary.htm   (1718 words)

 Proton decay - Definition, explanation
The standard model of particle physics states that protons are stable, i.e., that the laws of physics do not allow a proton (which is baryonic matter) to spontaneously decay into a positron and photons (non-baryonic matter) because of conservation of the baryon number.
This means that in essence, rather than breaking the law of conservation of the baryon number, proton decay could actually be the inevitable mechanism for bringing the baryon number back to equilibrium—in a sense correcting the original imbalance that made all current matter in our universe possible.
Although the phenomenon is referred to as "proton decay", the effect would also be seen in neutrons bound inside atomic nuclei.
www.calsky.com /lexikon/en/txt/p/pr/proton_decay.php   (0 words)

 Proton decay Summary
In particle physics, proton decay is an unobserved radioactive decay in which the proton decays into lighter subatomic particles, usually a neutral pion and a positron.
Proton decay is one of the few observable effects of the various proposed GUTs, the other major one being magnetic monopoles.
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.
www.bookrags.com /Proton_decay   (1134 words)

 Wikinfo | Proton
The number of protons in the nucleus determines the chemical properties of the atom and what chemical element it is.
Protons are classified as baryons and are composed of two up quarks and one down quark, which are also held together by the strong nuclear force, mediated by gluons.
In this context, a proton donor is an acid and a proton acceptor a base (see acid-base reaction theories).
www.wikinfo.org /wiki.php?title=proton   (337 words)

 The Half-Life of Proton Decay and its Relation to the "Heat Death" of the Universe
The ultimate form of this temporal decay of matter is "proton decay", whose extremely long half-life (unknown, but at least 35 powers of ten (10(35) years) is related to the extreme weakness of the gravitational force.
The significance of proton decay is that it is the end-point of temporal entropy for matter, in much the same way we might say the fl hole is the end-point of spatial entropy for light.
Hence the ratio of force strengths is directly related to gravitationally induced proton decay and therefore also to the energetic relationship between spatial and temporal entropy, since c and G are the fundamental gauges of these entropic drives and domains.
people.cornell.edu /pages/jag8/proton.html   (4579 words)

 The Weak Force: Identity or Number Charge
(a tau decays to a muon, tau neutrino, and muon antineutrino)
A neutron (or proton) is composed of 3 quarks: the quark composition of a neutron is (ddu); that of the proton is (uud).
The proton is slightly lighter than the neutron, so the proton is the "ground state" or lowest energy state of the baryons (the class of particles containing 3 quarks).
home.earthlink.net /~johngowan/identity.html   (3003 words)

 NuDat 2 Glossary
Branching ratios for this decay tend to be very small, due to the large Coulomb barrier encountered by the cluster and its very small pre-formation factor, that is, the probability of finding the cluster formed inside the nucleus.
The probability of undergoing a given nuclear decay is often indicated using the percent sign followed by the decay mode name and the probability per 100 decays.
The emission of a proton by a nucleus.
www.nndc.bnl.gov /nudat2/help/glossary.html   (2057 words)

 What's a Neutrino?
Pauli based his prediction on the fact that energy and momentum did not appear to be conserved in certain radioactive decays.
It is soon recognized to be a heavier version of the electron and muon, and its decay exhibits the same apparent imbalance of energy and momentum that led Pauli to predict the existence of the neutrino in 1931.
The existence of a third neutrino associated with the tau is hence inferred, although this neutrino has yet to be directly observed.
www.ps.uci.edu /~superk/neutrino.html   (946 words)

 Proton decay
Should these grand unified theory candidates be correct, the quark would be allowed to decay into a lepton -- a process which is held by the standard model to be forbidden.
The reason this decay mode is so unlikely, if it exists at all, is because of the enormous mass of the intermediary particle.
I might add that there are ongoing experiments being performed to detect proton decay in order to point us in the right direction.
www.physicsforums.com /showthread.php?t=1955   (0 words)

 Alternate View Column AV-01
It is possible for two of the quarks within a proton to simultaneously forget who they are and to trade places with their brothers or cousins.
This means that the proton abruptly becomes a positron and a pi-0 meson in loose association.
The "fuel" would then be atoms of normal matter caused to explode because their protons and neutrons undergo catalyzed decay as a flux of monopoles is passed through them.
www.npl.washington.edu /AV/altvw01.html   (2793 words)

 World Science
A drawing depicting the decay of a parent nucleus to a daughter nucleus.
Hydrogen burning is the fusion of four hydrogen nuclei (protons) into a single helium nucleus (two protons and neutrons.) The process is a series of reactions.
The proton is found in the nucleus and has a positive electrical charge equivalent to the negative charge of an electron and a mass similar to that of a neutron.
www.world-science.net /z03.htm   (1581 words)

 Dyson Newton
I discuss the predictions for the proton decay and show how they depend crucially on the fermion (and sfermion) masses and mixings.
An analysis of proton lifetime requires that one first address properly the fermion mass and mixing issues to predict in a realistic fashion proton lifetime.
In these models it is possible to control proton decay via the use of extra symmetries that might arise in models with universal extra dimensions...
www.valdostamuseum.org /hamsmith/DPFNov06SU5.html   (729 words)

 Theory of the angular distribution of beta-delayed protons from oriented nuclei   (Site not responding. Last check: )
Recent measurements of alpha decay from oriented nuclei have shown clearly that quantum tunneling through the Coulomb barrier is not generally the dominant factor in determining the angular distribution of alpha emission.
Nd the proton Coulomb barrier is 14.4 MeV and the centrifugal barrier 3.4 MeV for a partial wave with angular momentum L=2, whilst for alphas the equivalent values are 28.8 MeV and 0.86 MeV.
We have explored beta-delayed proton and neutron emission theoretically in detail, building on theory of the process for randomly oriented precursors [6,7] with coverage of the angular distribution properties examining the dependence of the energy spectra and angular distribution upon all variables involved.
www-nog.physics.ox.ac.uk /www/quantum/quantum.htm   (2115 words)

 The ICARUS first 600-ton module
Proton accelerators provide essentially nu_mu beams from the decay of pi's and K's, produced when the extracted proton beam hits a target.
These 'parent' particles are focused towards the detector and left to decay in a tunnel to produce muons and nu_mu's.
For most of these decays the background in ICARUS is expected to be negligible, hence one single event could be sufficient for discovery.
www.aquila.infn.it /dipartimento/programmi/fis_nucleare/icarus_text.html   (1986 words)

 Searches for Nucleon Decay at Super-Kamiokande
But consider the proton, which is a collection of three quarks not a single particle, one might expect it to decay to, say, a charged lepton and a neutral meson or a neutral lepton and a charged meson by having one of the quarks turn in to a lepton.
This decay (which is actually a scattering when one looks at the level of quarks) would conserve charge.
Second, the 80% of the protons in water are inside the oxygen nucleous and the pions from the decay of these protons must risk passage though the oxygen nucleous.
superk.physics.sunysb.edu /superk/physics/nucleon-decay   (916 words)

 proton decay concept from the Astronomy knowledge base   (Site not responding. Last check: )
proton decay concept from the Astronomy knowledge base
abstraction > theory related concept > prediction > proton decay
has definition Spontaneous disintegration of the proton, predicted by grand unified theory but never observed experimentally.
www.site.uottawa.ca:4321 /astronomy/protondecay.html   (34 words)

 Straddling a Speeding Proton
An observer atop an accelerating proton will be immersed in a thermal bath of particles--even though a stationary observer would measure a perfect vacuum.
Protons undergoing acceleration either decay or collide, depending on your perspective, according to a paper in the
From that perspective, Vanzella explains, the proton would appear to be standing still and should not decay.
focus.aps.org /story/v8/st19   (464 words)

 Elementary Particles Today
If the proton lifetime is indeed 10**30 years, and we watch 10**30 protons for one year, we would expect to observe one proton decay.
The problem with observing such a rare decay is that other events, such as a cosmic ray particle, or the decay of a radioactive nucleus, could trigger the detector and give a false signal.
The only way an experimenter could hope to observe a proton decay would be to put the detector deep underground, where the earth would shield it from all but the most energetic cosmic rays.
www.davidparker.com /janine/epntoday.html   (1647 words)

 Two-proton decay
Indeed, in the emission process the two-protons may leave the nucleus in various final states, ranging from a quasi-bound diproton to anticorrelated protons emitted in opposite directions, while in transfer reactions they are absorbed from a given initial state.
Therefore, one has to look for nuclei in which one-proton decay is energetically impossible (which limits the selection to even-Z elements), and where the two-proton decay energy is sufficiently large.
Indeed, in order to differentiate between various two-proton decay scenarios one has to perform the full three-body calculations, where the two protons and the daughter nucleus are allowed to develop arbitrary correlations, and the full three-body wave function is obtained.
www.fuw.edu.pl /~dobaczew/inpc28w/node3.html   (699 words)

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