Proton Definition and 835 Threads

A proton is a subatomic particle, symbol p or p+, with a positive electric charge of +1e elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are jointly referred to as "nucleons" (particles present in atomic nuclei).
One or more protons are present in the nucleus of every atom; they are a necessary part of the nucleus. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol Z). Since each element has a unique number of protons, each element has its own unique atomic number.
The word proton is Greek for "first", and this name was given to the hydrogen nucleus by Ernest Rutherford in 1920. In previous years, Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by atomic collisions. Protons were therefore a candidate to be a fundamental particle, and hence a building block of nitrogen and all other heavier atomic nuclei.
Although protons were originally considered fundamental or elementary particles, in the modern Standard Model of particle physics, protons are classified as hadrons, like neutrons, the other nucleon. Protons are composite particles composed of three valence quarks: two up quarks of charge +2/3e and one down quark of charge −1/3e. The rest masses of quarks contribute only about 1% of a proton's mass. The remainder of a proton's mass is due to quantum chromodynamics binding energy, which includes the kinetic energy of the quarks and the energy of the gluon fields that bind the quarks together. Because protons are not fundamental particles, they possess a measurable size; the root mean square charge radius of a proton is about 0.84–0.87 fm (or 0.84×10−15 to 0.87×10−15 m). In 2019, two different studies, using different techniques, have found the radius of the proton to be 0.833 fm, with an uncertainty of ±0.010 fm.Free protons occur occasionally on Earth: thunderstorms can produce protons with energies of up to several tens of MeV. At sufficiently low temperatures and kinetic energies, free protons will bind to electrons. However, the character of such bound protons does not change, and they remain protons. A fast proton moving through matter will slow by interactions with electrons and nuclei, until it is captured by the electron cloud of an atom. The result is a protonated atom, which is a chemical compound of hydrogen. In vacuum, when free electrons are present, a sufficiently slow proton may pick up a single free electron, becoming a neutral hydrogen atom, which is chemically a free radical. Such "free hydrogen atoms" tend to react chemically with many other types of atoms at sufficiently low energies. When free hydrogen atoms react with each other, they form neutral hydrogen molecules (H2), which are the most common molecular component of molecular clouds in interstellar space.
Free protons are routinely used for accelerators for proton therapy or various particle physics experiments, with the most powerful example being the Large Hadron Collider.

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  1. S

    I The ever-increasing proton lifetime

    I was reading this article discussing how experiments have been able to observe proton decay: https://www.economist.com/news/science-and-technology/21734379-no-guts-no-glory-fundamental-physics-frustrating-physicists It states that after concluding that there has been any evidence of proton...
  2. V

    Applying a time-dependent force to a proton

    Homework Statement A proton is initially located at the origin of some coordinate system (at rest), when a time-dependent force, $$F(t)=F_0\sin{(\omega t)},$$ is applied to it, where ##F_0## and ##\omega## are constants. a) Find the velocity and displacement of the proton as functions of...
  3. A

    Electron and proton penetration

    Homework Statement Which, of an electron and a proton (of a few Mev), is more likely to penetrate further into matter if they both have: a) The same energy b) The same speed Homework Equations Bethe-Bloch formula. Total stopping power = collision loss + radiation loss (de/dx)t = (de/dx)c +...
  4. eigenmax

    How to calculate the Coulomb barrier between a proton and a lithium nucleus

    Homework Statement How to calculate the Coulomb barrier between a proton and a lithium nucleus. The variable is r (interaction radius). The known data is Z1, Z2, k (Coulomb constant), and e (elementary charge). Homework Equations The equation is UCoul = kZ1Z2e2/r The Attempt at a Solution I...
  5. Pushoam

    Frequency of a proton moving in a circular orbit

    Homework Statement Homework EquationsThe Attempt at a Solution [/B]Assuming that the relation ## v = \omega r ## is valid in relativistic calculation. As the speed is greater for higher kinetic energy, ## \omega_2 ## is greater. This is shown by only (d). So, I think (d) should...
  6. Ranku

    I Grand Unified Theory and proton decay

    How far ahead are we in Grand Unified Theory? Are we still searching for proton decay?
  7. C

    Force between two charged particle beams -- proton and electron beams

    Homework Statement A proton beam is going from north to south and an electron beam is going from south to north, so in which direction is the electron beam deflected Homework EquationsThe Attempt at a Solution . [/B] I thought an electron...
  8. K

    I New scientist SU(5) Unification without Proton Decay

    new scientist latest issue covers this paper SU(5) Unification without Proton Decay Bartosz Fornal, Benjamin Grinstein (Submitted on 26 Jun 2017 (v1), last revised 13 Nov 2017 (this version, v2)) We construct a four-dimensional SU(5) grand unified theory in which the proton is stable. The...
  9. S

    B Explaination of beta + decay in layman language

    QUESTION: I read in book that in beta + decay proton decays to neutron But i can't understand how it is possible if proton mass is less than neutron mass.I read on net but it says 'quarks' and 'd u p' things which i don't study about currently. Also why it only happen inside nucleus?What...
  10. A

    MCNPX Mesh Tally Problem: Offset of proton flux at surfaces

    Dear all, we are using MCNPX for the simulation of proton beam interactions at our proton therapy facility. But now we found a very strange behavior within a RMESH1:h flux tally: In an even very simple geometry we see a constriction or rather offset of the Proton flux at surfaces (surface 1118...
  11. M

    Mass of Hydrogen needed to determine lifetime of proton

    Homework Statement The current limit on the proton’s lifetime is determined by observing a large body of water for a long time and noticing that no one of the hydrogen nuclei in H2O have decayed. Assuming that the experiment making this measurement has been going on for 10 years, how many tons...
  12. P

    B Why is there no proton degeneracy pressure?

    Hello. I usually heard about electron degeneracy pressure and neutron degeneracy pressure. But I´ve never heard about a proton degeneracy pressure. Why is this?
  13. M

    A Proton anti-proton pair and CP eigenstate

    p\bar{p} pair is a CP eigenstate? As p and \bar{p} are fermions (the pair is assumed to be at S-state), the pair seems to be C's eigenstate with eigenvalue of -1. As they have opposite intrinsic parity, the pair state seems to be P's eigenstate with eigenvalue -1. Then isn't it CP eigenstate...
  14. P

    What is the impact speed of the proton in a 4850V capacitor?

    Homework Statement A parallel-plate capacitor is charged to 4850 V. A proton is fired into the center of the capacitor at a speed of v0=2.81 * 10^5 m/s. The proton is deflected while inside the capacitor, and the plates are long enough that the proton will hit one of them before emerging from...
  15. S

    B Collision of photon and proton

    In what condition does a photon hit a proton? What happens to the energy of the photon in that case? Does proton emit another photon and goes down to the initial energy state?
  16. B

    I Neutron/proton nucleon destruction by acceleration

    A nucleon that consists entirely of two or more protons, would be accelerated evenly, as each proton would see the same force (barring any collisions or other extraneous events.) Each should experience the same force of repulsion or attraction that is causing them to accelerate, so they should...
  17. B

    B Removing a proton from mercury

    Why are there no gold companies that produce gold by removing a proton from mercury? Is it because mercury is expensive or lack of facilities to remove the proton. Given a lot of budget (like billions).. what would it take to remove a proton from mercury to produce gold?
  18. R

    A Momentum transfer perpendicular to velocity of proton?

    An assumption in deducing the Bethe equation is that the momentum transfer is perpendicular to the direction of the particle. ALSO In Allison & Cobb (1980), just after eq. 28, they state that the first two terms of the Photoabsorption Ionization model arise from the magnetic vector potential...
  19. Y

    I Particle calculation during a solar proton event

    Trying to figure out how many particles would bombard an astronaut during a solar proton event. Given that the most possible is around 43,000 particle flux units (pfu) according to NASA. First calculating steradians, assuming a person is 1m^2, 1/(1E9)^2=1E-18. My calculation yields (43000...
  20. K

    I Deep Underground Neutrino Experiment proton decay

    is there a reason that Deep Underground Neutrino Experiment which uses 70, 000 tons of liquid Argon doesn't also do double duty work as a proton decay experiment? Argon has plenty of protons and 70, 0000 tons is a lot of material to work with it costs several billion dollars so why not use...
  21. MetinErsin

    Can Electrons Avoid Proton Attraction at Long Distances?

    Firstly sorry for my english . I don't know how i should search this question this is why i am asking here. while i am thinking about charges,i think consider a positive charge. And put an electron very far from it. Is there any posiblity for electron don't affect from positive charge
  22. bubsir

    Can proton mass be measured without assuming inertia?

    Direct gravitational measurements of subatomic particles seems impossible. Has it been done/tried? The mass of the proton as I know it is always "indirectly" determined by (for example) bending a beam of charged protons in a magnetic field.
  23. A

    I Is a Photon Emitted in the Proton-Proton Chain Reaction?

    In the proton chain, a deuteron and proton fuse to make a nucleus of helium 3, releasing 5.493 MeV by E=mc^2. To have the same total momentum before and after fusion, at least two particles must be emitted, right? That way they can "cancel out" some momentum by having roughly opposite...
  24. S

    I Proton- Proton Fusion on Earth?

    Hi, I have been doing my own personal fusion research for almost a year now and I recently began looking into the various fusion fuel cycles other than D-T and D-D. The cycle that I'm interested in is P-P fusion, I'm aware that this method is inefficient for energy production, however, it seems...
  25. A

    B Fusion and Alpha Particle Emission: Neutron vs Proton

    When two deuterons fuse, I understand they form an alpha particle in an excited state. Based on mass differences the fusion releases 23.85MeV, which is enough to eject a proton (19.81MeV) or a neutron (20.58MeV) from the alpha particle. It seems to prefer neutron emission, as this fusion is used...
  26. M

    Physics 12: Acceleration of Proton in B-Field

    Homework Statement [/B] A proton is accelerated from rest at the positive plate of two charged parallel plates with a potential difference of 2000 v. After leaving the plates through a small hole in the negative plate, it enters a uniform magnetic field of 0.50 T in a direction perpendicular to...
  27. P

    I Calculating Antimatter Portion in Protons

    Hi! I am asked to calculete the portion of antimatter present in protons. I am sayed that this portion is given by: r=(3R-1)/(3-R), where R is R=σ(antineutrino)/σ(neutrino). Another definition of r is r=∫x*Q'(x)dx/∫x*Q(x)dx, where Q(x) are partonic densities Q(x)=d(x)+u(x) (d is down quark and...
  28. E

    NMR Diastereotopic Proton Splitting

    This is one of those questions that probably has a very simple answer, but I can't find it anywhere, and as much as I think about it, the more confused I get. Can diastererotopic protons have different number of split peaks in their overall signal like on a CH2R group, for example, one proton...
  29. Quantum Velocity

    B How to change electron and proton charge

    To make antimatter you have to change the charge of proton and electron. So how do you do it
  30. Sebastiaan

    I Anti Proton - Non Proton reaction

    Alright, I have a basic understanding about anti hydrogen - hydrogen annihilation reaction. But what exactly happens if an anti hydrogen atom stumbles into anything else like a deuterium, tritium of helium atom? From my limited understanding, antimatter can only react with its anti-particle...
  31. I

    Calculating Speed of Protons in a Linear Accelerator: 530 MeV Kinetic Energy

    Homework Statement In a proton linear accelerator, protons are accelerated to have a kinetic energy of 530 MeV. What is the speed of these protons? (The rest mass of a proton is 1.67 × 10-27 kg.) Homework Equations E0=m0c^2 E=E0/√1-(v^2)/(c^2) E = KE + E0 The Attempt at a Solution Recognize...
  32. A

    What fraction of its energy does accelerating proton shed?

    Homework Statement If a proton with a kinetic energy of 6 MeV is traveling in a particle accelerator in a circular orbit of radius 0.75m, what fraction of its energy does it radiate per second? m = 1.67 * 10^-27 epsilon_0 = 8.854 * 10^-12 c = 3 * 10^8 Homework Equations dE/dt = (q^2 a^2) /...
  33. P

    I Why do protons and nuclei of light elements not ionize solid objects like metal?

    When protons or nuclei of light elements like Helium passes through gas, it ionises the molecules on it path. But that's not the case when proton or nuclei of light elements pass through solid objects like metal. What's the reason behind that?
  34. H

    Error: no plot because it would be empty, using mcnpx

    Hello everyone! I would like to ask you if anyone can help me solving my Problem with mcnpx. I created a file with a watertank, a nozzle and a slit blend on the surface. I also inserted a protonbeam and would like to plot the dose and fluence for examplte with Moritz. But when I execute the...
  35. L

    What is the kinetic energy of a proton when neutron decays?

    Homework Statement What is the kinetic energy given to the proton in the decay of a neutron when: a) The electron has negligibly small kinetic energy b) The neutrino has negligibly small kinetic energy Homework Equations Q = (mn - mp - me - mv ) c2 = .782MeV Where T is kinetic energy, and...
  36. T

    Proton trajectory grazing a charged sphere

    Homework Statement Homework Equations potential energy = -kQq/r potenial = kQ/rThe Attempt at a Solution i am not quite sure how does l play a part in this experiment since it is far away l is insignificant and the only initial energy is kinetic energy and final is kinetic and electric...
  37. Kmol6

    Parallel plate capacitor: Proton vs Electron

    Homework Statement A proton is released from rest at the positive plate of a parallel-plate capacitor. It crosses the capacitor and reaches the negative plate with a speed of 51000 m/s . What will be the final speed of an electron released from rest at the negative plate? Homework Equations...
  38. Vanessa Avila

    Solve Proton Homework: Min Speed to Miss Lower Plate

    Homework Statement In the figure, a proton, mass 1.67×10^−27 kg, is projected horizontally midway between two parallel plates that are separated by 0.20cm, with an electrical field with magnitude 7.8×10^5N/C between the plates. If the plates are 5.40cm long, find the minimum speed of the proton...
  39. mpolo

    I Has anyone ever determined at what rate quarks move?

    I am wondering if anyone has determined by experiment or calculation at what rate or even better what frequency the quarks move around at inside a neutron and proton? Do neutrons or protons vibrate at a specific frequency.
  40. A

    Proton transport problem using MCNP

    Hello everyone ! I wanted to ask you if anyone ever encountered problems with proton transport using MCNP. In particular, the production of electrons when protons interact with matter. I have been trying to figure it out modifying the different physics cards (phys, lca, ...) with no result...
  41. J

    I Is proton decay considered in neutron star models (and LHC)?

    Although it is definitely not simple, there are many reasons to consider that baryon number can be violated, for example: - while baryogenesis there was created more matter than antimatter, - hypothetical Hawking radiation can finally turn any matter (mainly baryons) into massless radiation...
  42. jlmccart03

    Find the electric field on a proton by an electron

    Homework Statement A proton is at the origin and an electron is at the point x = 0.36 nm , y = 0.34 nm. Find the x- and y-components of the electric force on the proton. Homework Equations E = kQ/r2 The Attempt at a Solution So I found that E = 9.38 * 10-28, but my problem is that I do not...
  43. Ian Baughman

    Electron in orbit of around a single proton

    Today I was doing some reading and I came across this topic. If we have a stationary hydrogen atom with a single electron in orbit around the nucleus and want to calculate the kinetic energy of the electron we would take the following approach. 1) Using Newton's second law: F = ma ⇒ FE = mac...
  44. Sentosa

    I Does an H proton weigh more than an He proton?

    In his book https://www.amazon.com/dp/0385477058/?tag=pfamazon01-20, Michio Kaku is discussing hydrogen fusion and states that, "the protons in hydrogen weigh more than the protons in helium". Is this correct? I understand that atoms and nuclei will weigh different amounts, but I thought a...
  45. K

    I Implications of no proton decay, simplest GUT ruled out

    Search for Proton Decay via p→e+π0 and p→μ+π0 in 0.31 megaton⋅years exposure of the Super-Kamiokande Water Cherenkov Detector M. Miura (The Super-Kamiokande Collaboration) (Submitted on 12 Oct 2016) We have searched for proton decay via p→e+π0 and p→μ+π0 using Super-Kamiokande data from April...
  46. A

    B Free Proton verses Nucleus Proton rest mass

    The energy associated with the mass of a free proton in the center of momentum frame where the proton’s momentum is zero is 938.272 (with more decimals). What is the rest energy of a single proton inside a Uranium atom? (It could be any other radioactive or fissionable element but I took...
  47. niveda

    Proton is moving at an alpha particle, distance when it stops

    Homework Statement an alpha particle with a charge of 2e is fixed at the origin. a proton is aimed at the alpha particle and shot from a distance of 2.00 m at a speed of 3.46x10^6 m/s. How close will the proton come to the alpha particle before coming to a stop? Homework Equations Please help...
  48. H

    B Is a single (naked) proton atomic/elemental Hydrogen

    Okay ... some "simple" questions (I think): If a single baryonic proton magically appears in a pure vacuum container (which is otherwise completely empty), can that proton be considered a positive Hydrogen ion? Or must a Hydrogen atom lose an electron first (so we just end up with a single...
  49. P

    Electron to Stationary Proton Collision

    Homework Statement A 2 GeV electron is incident on proton (m_p * C^2 = 0.938 GeV) target at rest. Calculate the invariant mass of the electron-proton pair in the Center of Mass(CM) frame. Neglect the mass of electron which is much less than the proton mass.Homework Equations M = [P1 + P2)][/2]...
  50. Anchovy

    A Why lower limits on proton decay lifetimes depend on channel

    If I look at the lower limits on the proton decay lifetime \tau set by, say, Super-Kamiokande, I'll see different lower limits depending on what the proton could decay into, eg. \tau_{min}(p \rightarrow K^{+} \overline{\nu}) < \tau_{min}(p \rightarrow \mu^{+} \pi^{0}) < \tau_{min}(p \rightarrow...
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