Proton-neutron mass difference, electroproduction, and photoabsorption in an analytic model of the virtual Compton amplitude

1975 ◽  
Vol 12 (9) ◽  
pp. 2709-2724 ◽  
Author(s):  
B. B. Deo ◽  
B. P. Mahapatra
2020 ◽  
Vol 80 (12) ◽  
Author(s):  
J. Gasser ◽  
H. Leutwyler ◽  
A. Rusetsky

AbstractThe Cottingham formula expresses the leading contribution of the electromagnetic interaction to the proton-neutron mass difference as an integral over the forward Compton amplitude. Since quarks and gluons reggeize, the dispersive representation of this amplitude requires a subtraction. We assume that the asymptotic behaviour is dominated by Reggeon exchange. This leads to a sum rule that expresses the subtraction function in terms of measurable quantities. The evaluation of this sum rule leads to $$m_{\mathrm{QED}}^{p-n}=0.58\pm 0.16\,\text {MeV}$$ m QED p - n = 0.58 ± 0.16 MeV .


NASPA Journal ◽  
1999 ◽  
Vol 36 (4) ◽  
Author(s):  
Ellen Lavelle ◽  
Bill Rickford

Models of college student development have demonstrated an insensitivity to the differences that exist among various students, although such differences are very important in a world where student bodies in higher education are increasingly diverse. The authors present a model based on The Dakota Inventory of Student Orientations, which may be useful for program developmen that fosters reflection, self discovery, perspective-taking, and collaboration among students with varying orientations towards learning.


Author(s):  
Steven E. Vigdor

Chapter 4 deals with the stability of the proton, hence of hydrogen, and how to reconcile that stability with the baryon number nonconservation (or baryon conservation) needed to establish a matter–antimatter imbalance in the infant universe. Sakharov’s three conditions for establishing a matter–antimatter imbalance are presented. Grand unified theories and experimental searches for proton decay are described. The concept of spontaneous symmetry breaking is introduced in describing the electroweak phase transition in the infant universe. That transition is treated as the potential site for introducing the imbalance between quarks and antiquarks, via either baryogenesis or leptogenesis models. The up–down quark mass difference is presented as essential for providing the stability of hydrogen and of the deuteron, which serves as a crucial stepping stone in stellar hydrogen-burning reactions that generate the energy and elements needed for life. Constraints on quark masses from lattice QCD calculations and violations of chiral symmetry are discussed.


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