Measurement of flavor asymmetry of the light-quark sea in the proton with Drell-Yan dimuon production in p + p and p + d collisions at 120 GeV
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Engineering topics
Miyachi, Y.
Publications and source records attributed to Miyachi, Y..
Publisher Correction: The asymmetry of antimatter in the proton
The fundamental building blocks of the proton—quarks and gluons—have been known for decades. However, we still have an incomplete theoretical and experimental understanding of how these particles and their dynamics give rise to the quantum bound state of the proton and its physical properties, such as its spin1. The two up quarks and the single down quark that comprise the proton in the simplest picture account only for a few per cent of the proton mass, the bulk of which is in the form of quark kinetic and potential energy and gluon energy from the strong force2. An essential feature of this force, as described by quantum chromodynamics, is its ability to create matter–antimatter quark pairs inside the proton that exist only for a very short time. Their fleeting existence makes the antimatter quarks within protons difficult to study, but their existence is discernible in reactions in which a matter–antimatter quark pair annihilates. In this picture of quark–antiquark creation by the strong force, the probability distributions as a function of momentum for the presence of up and down antimatter quarks should be nearly identical, given that their masses are very similar and small compared to the mass of the proton3. Here we provide evidence from muon pair production measurements that these distributions are considerably different, with more abundant down antimatter quarks than up antimatter quarks over a wide range of momenta. These results are expected to revive interest in several proposed mechanisms for the origin of this antimatter asymmetry in the proton that had been disfavoured by previous results4, and point to future measurements that can distinguish between these mechanisms.
Dove, J.↗
The asymmetry of antimatter in the proton
The fundamental building blocks of the proton—quarks and gluons—have been known for decades. However, we still have an incomplete theoretical and experimental understanding of how these particles and their dynamics give rise to the quantum bound state of the proton and its physical properties, such as its spin1. The two up quarks and the single down quark that comprise the proton in the simplest picture account only for a few per cent of the proton mass, the bulk of which is in the form of quark kinetic and potential energy and gluon energy from the strong force2. An essential feature of this force, as described by quantum chromodynamics, is its ability to create matter–antimatter quark pairs inside the proton that exist only for a very short time. Their fleeting existence makes the antimatter quarks within protons difficult to study, but their existence is discernible in reactions in which a matter–antimatter quark pair annihilates. In this picture of quark–antiquark creation by the strong force, the probability distributions as a function of momentum for the presence of up and down antimatter quarks should be nearly identical, given that their masses are very similar and small compared to the mass of the proton. Here we provide evidence from muon pair production measurements that these distributions are considerably different, with more abundant down antimatter quarks than up antimatter quarks over a wide range of momenta. These results are expected to revive interest in several proposed mechanisms for the origin of this antimatter asymmetry in the proton that had been disfavoured by previous results, and point to future measurements that can distinguish between these mechanisms.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Azimuthal single- and double-spin asymmetries in semi-inclusive deep-inelastic lepton scattering by transversely polarized protons
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos ( Φ–Φ S ) modulations provide evidence for a sizable worm-gear (II) distribution, ${g}_{1\mathrm{T}}^q\left(x,{\mathrm{p}}_T^2\right)$. Most of the other modulations are found to be consistent with zero with the notable exception of large sin ( Φ S ) modulations for charged pions and K + .
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Fermilab Test Beam Facility Annual Report: FY19
This Technical Memorandum (TM) summarizes the Fermilab Test Beam Faciltiy (FTBF) operations for FY2019. It is one of a series of annual publications intended to gather information in one place. This TM discusses the experiments performed at the Test Beam from November 2018 to July 2019. The experiments are listed in Table 1. Each experiment wrote a summary that was edited for clarity and is included in this report.
43 PARTICLE ACCELERATORS↗