The neutron is a subatomic particle,symbol
n
or
n0
,which has a neutral charge,and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave similarly within the nucleus,and each has a mass of approximately one atomic mass unit,they are both referred to as nucleons. Their properties and interactions are described by nuclear physics. Protons and neutrons are not elementary particles;each is composed of three quarks.
In physics and chemistry,a nucleon is either a proton or a neutron,considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number.
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions and bosons. There are three generations of fermions,but ordinary matter is made only from the first fermion generation. The first generation consists of up and down quarks which form protons and neutrons,and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism,the weak interaction,and the strong interaction.
A proton is a stable subatomic particle,symbol
p
,H+,or 1H+ with a positive electric charge of +1 e elementary charge. Its mass is slightly less than that of a neutron and 1836 times the mass of an electron (the proton–electron mass ratio). Protons and neutrons,each with masses of approximately one atomic mass unit,are jointly referred to as "nucleons" (particles present in atomic nuclei).
A pentaquark is a human-made subatomic particle,consisting of four quarks and one antiquark bound together;they are not known to occur naturally,or exist outside of experiments specifically carried out to create them.
The Relativistic Heavy Ion Collider is the first and one of only two operating heavy-ion colliders,and the only spin-polarized proton collider ever built. Located at Brookhaven National Laboratory (BNL) in Upton,New York,and used by an international team of researchers,it is the only operating particle collider in the US. By using RHIC to collide ions traveling at relativistic speeds,physicists study the primordial form of matter that existed in the universe shortly after the Big Bang. By colliding spin-polarized protons,the spin structure of the proton is explored.
A hypernucleus is similar to a conventional atomic nucleus,but contains at least one hyperon in addition to the normal protons and neutrons. Hyperons are a category of baryon particles that carry non-zero strangeness quantum number,which is conserved by the strong and electromagnetic interactions.
Thomas Jefferson National Accelerator Facility (TJNAF),commonly called Jefferson Lab or JLab,is a US National Laboratory located in Newport News,Virginia. Its stated mission is "to provide forefront scientific facilities,opportunities and leadership essential for discovering the fundamental structure of nuclear matter;to partner in industry to apply its advanced technology;and to serve the nation and its communities through education and public outreach."
GlueX is a particle physics experiment located at the Thomas Jefferson National Accelerator Facility (JLab) accelerator. Its primary purpose is to better understand the nature of confinement in quantum chromodynamics (QCD) by identifying a spectrum of hybrid and exotic mesons generated by the excitation of the gluonic field binding the quarks. Such mesonic states are predicted to exist outside of the well-established quark model,but none have been definitively identified by previous experiments. A broad high-statistics survey of known light mesons up to and including the is also underway.
T2K is a particle physics experiment studying the oscillations of the accelerator neutrinos. The experiment is conducted in Japan by the international cooperation of about 500 physicists and engineers with over 60 research institutions from several countries from Europe,Asia and North America and it is a recognized CERN experiment (RE13). T2K collected data within its first phase of operation from 2010 till 2021. The second phase of data taking (T2K-II) is expected to start in 2023 and last until commencement of the successor of T2K –the Hyper-Kamiokande experiment in 2027.
The lambda baryons (Λ) are a family of subatomic hadron particles containing one up quark,one down quark,and a third quark from a higher flavour generation,in a combination where the quantum wave function changes sign upon the flavour of any two quarks being swapped. They are thus baryons,with total isospin of 0,and have either neutral electric charge or the elementary charge +1.
The Roper resonance,also known as P11(1440) or N(1440)1/2+,is an unstable nucleon resonance with a mass of about 1,440 MeV/c2 and with a relatively wide full Breit-Wigner width Γ≈300 MeV/c2. It contains three quarks (up (u) or down (d)) with total spin J = 1/2 and total isospin I = 1/2. In the quark model it is considered to be a radially excited three-quark state with radial quantum number N = 2 and positive parity. The Roper Resonance has been a subject of many studies because its mass is actually lower than three-quark states with radial quantum number N = 1. Only in the late 2000s was the lower-than-expected mass explained by theoretical calculations,revealing a quark core shielded by a dense cloud of mesons.
The NA58 experiment,or COMPASS is a 60-metre-long fixed-target experiment at the M2 beam line of the SPS at CERN. The experimental hall is located at the CERN North Area,close to the French village of Prévessin-Moëns. The experiment is a two-staged spectrometer with numerous tracking detectors,particle identification and calorimetry. The physics results are extracted by recording and analysing the final states of the scattering processes. The versatile set-up,the use of different targets and particle beams allow the investigation of various processes. The main physics goals are the investigation of the nucleon spin structure and hadron spectroscopy. The collaboration consists of 220 physicists from 13 different countries,involving 28 universities and research institutes.
CEBAF Large Acceptance Spectrometer (CLAS) is a nuclear and particle physics detector located in the experimental Hall B at Jefferson Laboratory in Newport News,Virginia,United States. It is used to study the properties of the nuclear matter by the collaboration of over 200 physicists from many countries all around the world.
The EMC effect is the surprising observation that the cross section for deep inelastic scattering from an atomic nucleus is different from that of the same number of free protons and neutrons. From this observation,it can be inferred that the quark momentum distributions in nucleons bound inside nuclei are different from those of free nucleons. This effect was first observed in 1983 at CERN by the European Muon Collaboration,hence the name "EMC effect". It was unexpected,since the average binding energy of protons and neutrons inside nuclei is insignificant when compared to the energy transferred in deep inelastic scattering reactions that probe quark distributions. While over 1000 scientific papers have been written on the topic and numerous hypotheses have been proposed,no definitive explanation for the cause of the effect has been confirmed. Determining the origin of the EMC effect is one of the major unsolved problems in the field of nuclear physics.
The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is a proposed water Cherenkov detector experiment designed to examine the nature of neutrino interactions. This experiment will study phenomena like proton decay,and neutrino oscillations,by analyzing neutrino interactions in gadolinium-loaded water and measuring their neutron yield. Neutron Tagging plays an important role in background rejection from atmospheric neutrinos. By implementing early prototypes of LAPPDs,high precision timing is possible. The suggested location for ANNIE is the SciBooNE hall on the Booster Neutrino Beam associated with the MiniBooNE experiment. The neutrino beam originates in Fermilab where The Booster delivers 8 GeV protons to a beryllium target producing secondary pions and kaons. These secondary mesons decay to produce a neutrino beam with an average energy of around 800 MeV. ANNIE will begin installation in the summer of 2015. Phase I of ANNIE,mapping the neutron background,completed in 2017. The detector is being upgraded for full science operation which is expected to begin late 2018.
When embedded in an atomic nucleus,neutrons are (usually) stable particles. Outside the nucleus,free neutrons are unstable and have a mean lifetime of 879.6±0.8 s. Therefore,the half-life for this process is 611±1 s. .
Joel Marshall Moss is an American experimental nuclear physicist.
The nucleon magnetic moments are the intrinsic magnetic dipole moments of the proton and neutron,symbols μp and μn. Protons and neutrons,both nucleons,comprise the nucleus of atoms,and both nucleons behave as small magnets whose strengths are measured by their magnetic moments. The nucleons interact with normal matter through either the nuclear force or their magnetic moments,with the charged proton also interacting by the Coulomb force.
