 Publication Date:
 NSFPAR ID:
 10345333
 Journal Name:
 Journal of High Energy Physics
 Volume:
 2021
 Issue:
 8
 ISSN:
 10298479
 Sponsoring Org:
 National Science Foundation
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A bstract We report on the measurement of the Central Exclusive Production of charged particle pairs h + h − ( h = π, K, p ) with the STAR detector at RHIC in protonproton collisions at $$ \sqrt{s} $$ s = 200 GeV. The charged particle pairs produced in the reaction pp → p ′ + h + h − + p ′ are reconstructed from the tracks in the central detector and identified using the specific energy loss and the time of flight method, while the forwardscattered protons are measured in the Roman Pot system. Exclusivity of the event is guaranteed by requiring the transverse momentum balance of all four finalstate particles. Differential cross sections are measured as functions of observables related to the central hadronic final state and to the forwardscattered protons. They are measured in a fiducial region corresponding to the acceptance of the STAR detector and determined by the central particles’ transverse momenta and pseudorapidities as well as by the forwardscattered protons’ momenta. This fiducial region roughly corresponds to the square of the fourmomentum transfers at the proton vertices in the range 0 . 04 GeV 2 < −t 1 , −t 2 < 0more »

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Abstract The matter in an accretion disk must lose angular momentum when moving radially inwards but how this works has long been a mystery. By calculating the trajectories of individual colliding neutrals, ions, and electrons in a weakly ionized 2D plasma containing gravitational and magnetic fields, we numerically simulate accretion disk dynamics at the particle level. As predicted by Lagrangian mechanics, the fundamental conserved global quantity is the total canonical angular momentum, not the ordinary angular momentum. When the Kepler angular velocity and the magnetic field have opposite polarity, collisions between neutrals and charged particles cause: (i) ions to move radially inwards, (ii) electrons to move radially outwards, (iii) neutrals to lose ordinary angular momentum, and (iv) charged particles to gain canonical angular momentum. Neutrals thus spiral inward due to their decrease of ordinary angular momentum while the accumulation of ions at small radius and accumulation of electrons at large radius produces a radially outward electric field. In 3D, this radial electric field would drive an outofplane poloidal current that produces the magnetic forces that drive bidirectional astrophysical jets. Because this neutral angular momentum loss depends only on neutrals colliding with charged particles, it should be ubiquitous. Quantitative scaling ofmore »

Mathematical analysis of the well known model of a piezoelectric energy harvester is presented. The harvester is designed as a cantilever Timoshenko beam with piezoelectric layers attached to its top and bottom faces. Thin, perfectly conductive electrodes are covering the top and bottom faces of the piezoelectric layers. These electrodes are connected to a resistive load. The model is governed by a system of three partial differential equations. The first two of them are the equations of the Timoshenko beam model and the third one represents Kirchhoff’s law for the electric circuit. All equations are coupled due to the piezoelectric effect. We represent the system as a single operator evolution equation in the Hilbert state space of the system. The dynamics generator of this evolution equation is a nonselfadjoint matrix differential operator with compact resolvent. The paper has two main results. Both results are explicit asymptotic formulas for eigenvalues of this operator, i.e., the modal analysis for the electrically loaded system is performed. The first set of the asymptotic formulas has remainder terms of the order O ( 1 n ) , where n is the number of an eigenvalue. These formulas are derived for the model with variable physicalmore »

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